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GCC(1)				      GNU				GCC(1)

NAME
       gcc - GNU project C and C++ compiler

SYNOPSIS
       gcc [-c|-S|-E] [-std=standard]
	   [-g]	[-pg] [-Olevel]
	   [-Wwarn...] [-pedantic]
	   [-Idir...] [-Ldir...]
	   [-Dmacro[=defn]...] [-Umacro]
	   [-foption...] [-mmachine-option...]
	   [-o outfile]	[@file]	infile...

       Only the	most useful options are	listed here; see below for the remain-
       der.  g++ accepts mostly	the same options as gcc.

DESCRIPTION
       When you	invoke GCC, it normally	does preprocessing, compilation,
       assembly	and linking.  The "overall options" allow you to stop this
       process at an intermediate stage.  For example, the -c option says not
       to run the linker.  Then	the output consists of object files output by
       the assembler.

       Other options are passed	on to one stage	of processing.	Some options
       control the preprocessor	and others the compiler	itself.	 Yet other
       options control the assembler and linker; most of these are not docu-
       mented here, since you rarely need to use any of	them.

       Most of the command line	options	that you can use with GCC are useful
       for C programs; when an option is only useful with another language
       (usually	C++), the explanation says so explicitly.  If the description
       for a particular	option does not	mention	a source language, you can use
       that option with	all supported languages.

       The gcc program accepts options and file	names as operands.  Many
       options have multi-letter names;	therefore multiple single-letter
       options may not be grouped: -dr is very different from -d -r.

       You can mix options and other arguments.	 For the most part, the	order
       you use doesn't matter.	Order does matter when you use several options
       of the same kind; for example, if you specify -L	more than once,	the
       directories are searched	in the order specified.

       Many options have long names starting with -f or	with -W---for example,
       -fmove-loop-invariants, -Wformat	and so on.  Most of these have both
       positive	and negative forms; the	negative form of -ffoo would be
       -fno-foo.  This manual documents	only one of these two forms, whichever
       one is not the default.

OPTIONS
       Option Summary

       Here is a summary of all	the options, grouped by	type.  Explanations
       are in the following sections.

       Overall Options
	   -c  -S  -E  -o file	-combine -pipe	-pass-exit-codes -x language
	   -v  -###  --help  --target-help  --version @file

       C Language Options
	   -ansi  -std=standard	 -fgnu89-inline	-aux-info filename -fno-asm
	   -fno-builtin	 -fno-builtin-function -fhosted	 -ffreestanding
	   -fopenmp -fms-extensions -trigraphs	-no-integrated-cpp  -tradi-
	   tional  -traditional-cpp -fallow-single-precision  -fcond-mismatch
	   -fsigned-bitfields  -fsigned-char -funsigned-bitfields  -fun-
	   signed-char

       C++ Language Options
	   -fabi-version=n  -fno-access-control	 -fcheck-new -fconserve-space
	   -ffriend-injection -fno-elide-constructors -fno-enforce-eh-specs
	   -ffor-scope	-fno-for-scope	-fno-gnu-keywords -fno-implicit-tem-
	   plates -fno-implicit-inline-templates -fno-implement-inlines
	   -fms-extensions -fno-nonansi-builtins  -fno-operator-names
	   -fno-optional-diags	-fpermissive -frepo  -fno-rtti	-fstats
	   -ftemplate-depth-n -fno-threadsafe-statics -fuse-cxa-atexit
	   -fno-weak  -nostdinc++ -fno-default-inline  -fvisibil-
	   ity-inlines-hidden -Wabi  -Wctor-dtor-privacy -Wnon-virtual-dtor
	   -Wreorder -Weffc++  -Wno-deprecated	-Wstrict-null-sentinel
	   -Wno-non-template-friend  -Wold-style-cast -Woverloaded-virtual
	   -Wno-pmf-conversions	-Wsign-promo

       Language	Independent Options
	   -fmessage-length=n -fdiagnostics-show-location=[once|every-line]
	   -fdiagnostics-show-option

       Warning Options
	   -fsyntax-only  -pedantic  -pedantic-errors -w  -Wextra  -Wall
	   -Waddress  -Waggregate-return -Wno-attributes -Wc++-compat
	   -Wcast-align	 -Wcast-qual  -Wchar-subscripts	 -Wcomment -Wconver-
	   sion	 -Wno-deprecated-declarations -Wdisabled-optimization
	   -Wno-div-by-zero  -Wno-endif-labels -Werror	-Werror=* -Wer-
	   ror-implicit-function-declaration -Wfatal-errors  -Wfloat-equal
	   -Wformat  -Wformat=2	-Wno-format-extra-args -Wformat-nonliteral
	   -Wformat-security  -Wformat-y2k -Wimplicit  -Wimplicit-func-
	   tion-declaration  -Wimplicit-int -Wimport  -Wno-import  -Winit-self
	   -Winline -Wno-int-to-pointer-cast -Wno-invalid-offsetof  -Win-
	   valid-pch -Wlarger-than-len	-Wunsafe-loop-optimizations
	   -Wlong-long -Wmain  -Wmissing-braces	 -Wmissing-field-initializers
	   -Wmissing-format-attribute  -Wmissing-include-dirs -Wmissing-nore-
	   turn	-Wno-multichar	-Wnonnull  -Wno-overflow -Woverlength-strings
	   -Wpacked  -Wpadded -Wparentheses  -Wpointer-arith
	   -Wno-pointer-to-int-cast -Wredundant-decls -Wreturn-type  -Wse-
	   quence-point	 -Wshadow -Wsign-compare  -Wstack-protector
	   -Wstrict-aliasing -Wstrict-aliasing=2 -Wstrict-overflow
	   -Wstrict-overflow=n -Wswitch	 -Wswitch-default  -Wswitch-enum
	   -Wsystem-headers  -Wtrigraphs  -Wundef  -Wuninitialized -Wun-
	   known-pragmas  -Wno-pragmas -Wunreachable-code -Wunused
	   -Wunused-function  -Wunused-label  -Wunused-parameter
	   -Wunused-value  -Wunused-variable  -Wvariadic-macros
	   -Wvolatile-register-var  -Wwrite-strings

       C-only Warning Options
	   -Wbad-function-cast	-Wmissing-declarations -Wmissing-prototypes
	   -Wnested-externs  -Wold-style-definition -Wstrict-prototypes
	   -Wtraditional -Wdeclaration-after-statement -Wpointer-sign

       Debugging Options
	   -dletters  -dumpspecs  -dumpmachine	-dumpversion -fdump-noaddr
	   -fdump-unnumbered  -fdump-translation-unit[-n] -fdump-class-hierar-
	   chy[-n] -fdump-ipa-all -fdump-ipa-cgraph -fdump-tree-all
	   -fdump-tree-original[-n] -fdump-tree-optimized[-n]
	   -fdump-tree-inlined[-n] -fdump-tree-cfg -fdump-tree-vcg
	   -fdump-tree-alias -fdump-tree-ch -fdump-tree-ssa[-n]
	   -fdump-tree-pre[-n] -fdump-tree-ccp[-n] -fdump-tree-dce[-n]
	   -fdump-tree-gimple[-raw] -fdump-tree-mudflap[-n]
	   -fdump-tree-dom[-n] -fdump-tree-dse[-n] -fdump-tree-phiopt[-n]
	   -fdump-tree-forwprop[-n] -fdump-tree-copyrename[-n] -fdump-tree-nrv
	   -fdump-tree-vect -fdump-tree-sink -fdump-tree-sra[-n]
	   -fdump-tree-salias -fdump-tree-fre[-n] -fdump-tree-vrp[-n]
	   -ftree-vectorizer-verbose=n -fdump-tree-storeccp[-n]	-felimi-
	   nate-dwarf2-dups -feliminate-unused-debug-types -felimi-
	   nate-unused-debug-symbols -femit-class-debug-always -fmem-report
	   -fprofile-arcs -frandom-seed=string -fsched-verbose=n -ftest-cover-
	   age	-ftime-report -fvar-tracking -g	 -glevel  -gcoff -gdwarf-2
	   -ggdb  -gstabs  -gstabs+  -gvms  -gxcoff  -gxcoff+ -p  -pg
	   -print-file-name=library  -print-libgcc-file-name
	   -print-multi-directory  -print-multi-lib -print-prog-name=program
	   -print-search-dirs  -Q -save-temps  -time

       Optimization Options
	   -falign-functions=n	-falign-jumps=n	-falign-labels=n
	   -falign-loops=n -fbounds-check -fmudflap -fmudflapth	-fmudflapir
	   -fbranch-probabilities -fprofile-values -fvpt -fbranch-tar-
	   get-load-optimize -fbranch-target-load-optimize2 -fbtr-bb-exclusive
	   -fcaller-saves  -fcprop-registers  -fcse-follow-jumps
	   -fcse-skip-blocks  -fcx-limited-range  -fdata-sections -fde-
	   layed-branch	 -fdelete-null-pointer-checks -fearly-inlining -fex-
	   pensive-optimizations  -ffast-math  -ffloat-store -fforce-addr
	   -ffunction-sections -fgcse  -fgcse-lm  -fgcse-sm  -fgcse-las
	   -fgcse-after-reload -fcrossjumping  -fif-conversion	-fif-conver-
	   sion2 -finline-functions  -finline-functions-called-once -fin-
	   line-limit=n	 -fkeep-inline-functions -fkeep-static-consts
	   -fmerge-constants  -fmerge-all-constants -fmodulo-sched
	   -fno-branch-count-reg -fno-default-inline  -fno-defer-pop
	   -fmove-loop-invariants -fno-function-cse  -fno-guess-branch-proba-
	   bility -fno-inline  -fno-math-errno	-fno-peephole  -fno-peephole2
	   -funsafe-math-optimizations	-funsafe-loop-optimizations  -ffi-
	   nite-math-only -fno-toplevel-reorder	-fno-trapping-math
	   -fno-zero-initialized-in-bss	-fomit-frame-pointer  -foptimize-reg-
	   ister-move -foptimize-sibling-calls	-fprefetch-loop-arrays -fpro-
	   file-generate -fprofile-use -fregmove  -frename-registers -fre-
	   order-blocks	 -freorder-blocks-and-partition	-freorder-functions
	   -frerun-cse-after-loop -frounding-math -frtl-abstract-sequences
	   -fschedule-insns  -fschedule-insns2 -fno-sched-interblock
	   -fno-sched-spec  -fsched-spec-load -fsched-spec-load-dangerous
	   -fsched-stalled-insns=n -fsched-stalled-insns-dep=n
	   -fsched2-use-superblocks -fsched2-use-traces	-fsee -fresched-
	   ule-modulo-scheduled-loops -fsection-anchors	 -fsignaling-nans
	   -fsingle-precision-constant -fstack-protector  -fstack-protec-
	   tor-all -fstrict-aliasing  -fstrict-overflow	 -ftracer
	   -fthread-jumps -funroll-all-loops  -funroll-loops  -fpeel-loops
	   -fsplit-ivs-in-unroller -funswitch-loops -fvariable-expan-
	   sion-in-unroller -ftree-pre	-ftree-ccp  -ftree-dce
	   -ftree-loop-optimize	-ftree-loop-linear -ftree-loop-im
	   -ftree-loop-ivcanon -fivopts	-ftree-dominator-opts -ftree-dse
	   -ftree-copyrename -ftree-sink -ftree-ch -ftree-sra -ftree-ter
	   -ftree-lrs -ftree-fre -ftree-vectorize -ftree-vect-loop-version
	   -ftree-salias -fipa-pta -fweb -ftree-copy-prop -ftree-store-ccp
	   -ftree-store-copy-prop -fwhole-program --param name=value -O	 -O0
	   -O1	-O2  -O3  -Os

       Preprocessor Options
	   -Aquestion=answer -A-question[=answer] -C  -dD  -dI	-dM  -dN
	   -Dmacro[=defn]  -E  -H -idirafter dir -include file	-imacros file
	   -iprefix file  -iwithprefix dir -iwithprefixbefore dir  -isystem
	   dir -imultilib dir -isysroot	dir -M	-MM  -MF  -MG  -MP  -MQ	 -MT
	   -nostdinc -P	 -fworking-directory  -remap -trigraphs	 -undef
	   -Umacro  -Wp,option -Xpreprocessor option

       Assembler Option
	   -Wa,option  -Xassembler option

       Linker Options
	   object-file-name  -llibrary -nostartfiles  -nodefaultlibs  -nost-
	   dlib	-pie -rdynamic -s  -static  -static-libgcc  -shared
	   -shared-libgcc  -symbolic -Wl,option	 -Xlinker option -u symbol

       Directory Options
	   -Bprefix  -Idir  -iquotedir	-Ldir -specs=file  -I- --sysroot=dir

       Target Options
	   -V version  -b machine

       Machine Dependent Options
	   ARC Options -EB  -EL	-mmangle-cpu  -mcpu=cpu	 -mtext=text-section
	   -mdata=data-section	-mrodata=readonly-data-section

	   ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name
	   -mapcs-stack-check  -mno-apcs-stack-check -mapcs-float
	   -mno-apcs-float -mapcs-reentrant  -mno-apcs-reentrant -msched-pro-
	   log	-mno-sched-prolog -mlittle-endian  -mbig-endian	 -mwords-lit-
	   tle-endian -mfloat-abi=name	-msoft-float  -mhard-float  -mfpe
	   -mthumb-interwork  -mno-thumb-interwork -mcpu=name  -march=name
	   -mfpu=name -mstructure-size-boundary=n -mabort-on-noreturn
	   -mlong-calls	 -mno-long-calls -msingle-pic-base  -mno-sin-
	   gle-pic-base	-mpic-register=reg -mnop-fun-dllimport -mcir-
	   rus-fix-invalid-insns -mno-cirrus-fix-invalid-insns -mpoke-func-
	   tion-name -mthumb  -marm -mtpcs-frame  -mtpcs-leaf-frame
	   -mcaller-super-interworking	-mcallee-super-interworking -mtp=name

	   AVR Options -mmcu=mcu  -msize  -minit-stack=n  -mno-interrupts
	   -mcall-prologues  -mno-tablejump  -mtiny-stack  -mint8

	   Blackfin Options -momit-leaf-frame-pointer
	   -mno-omit-leaf-frame-pointer	-mspecld-anomaly -mno-specld-anomaly
	   -mcsync-anomaly -mno-csync-anomaly -mlow-64k	-mno-low64k
	   -mid-shared-library -mno-id-shared-library -mshared-library-id=n
	   -mlong-calls	 -mno-long-calls

	   CRIS	Options	-mcpu=cpu  -march=cpu  -mtune=cpu -mmax-stack-frame=n
	   -melinux-stacksize=n	-metrax4  -metrax100  -mpdebug	-mcc-init
	   -mno-side-effects -mstack-align  -mdata-align  -mconst-align
	   -m32-bit  -m16-bit  -m8-bit	-mno-prologue-epilogue	-mno-gotplt
	   -melf  -maout  -melinux  -mlinux  -sim  -sim2 -mmul-bug-workaround
	   -mno-mul-bug-workaround

	   CRX Options -mmac -mpush-args

	   Darwin Options -all_load  -allowable_client	-arch
	   -arch_errors_fatal -arch_only  -bind_at_load	 -bundle  -bun-
	   dle_loader -client_name  -compatibility_version  -current_version
	   -dead_strip -dependency-file	 -dylib_file  -dylinker_install_name
	   -dynamic  -dynamiclib  -exported_symbols_list -filelist
	   -flat_namespace  -force_cpusubtype_ALL -force_flat_namespace
	   -headerpad_max_install_names	-image_base  -init  -install_name
	   -keep_private_externs -multi_module	-multiply_defined  -multi-
	   ply_defined_unused -noall_load   -no_dead_strip_inits_and_terms
	   -nofixprebinding -nomultidefs  -noprebind  -noseglinkedit
	   -pagezero_size  -prebind  -prebind_all_twolevel_modules -pri-
	   vate_bundle	-read_only_relocs  -sectalign -sectobjectsymbols
	   -whyload  -seg1addr -sectcreate  -sectobjectsymbols	-sectorder
	   -segaddr -segs_read_only_addr -segs_read_write_addr -seg_addr_table
	   -seg_addr_table_filename  -seglinkedit -segprot
	   -segs_read_only_addr	 -segs_read_write_addr -single_module  -static
	   -sub_library	 -sub_umbrella -twolevel_namespace  -umbrella  -unde-
	   fined -unexported_symbols_list  -weak_reference_mismatches -what-
	   sloaded -F -gused -gfull -mmacosx-version-min=version -mkernel
	   -mone-byte-bool

	   DEC Alpha Options -mno-fp-regs  -msoft-float	 -malpha-as  -mgas
	   -mieee  -mieee-with-inexact	-mieee-conformant -mfp-trap-mode=mode
	   -mfp-rounding-mode=mode -mtrap-precision=mode  -mbuild-constants
	   -mcpu=cpu-type  -mtune=cpu-type -mbwx  -mmax	 -mfix	-mcix
	   -mfloat-vax	-mfloat-ieee -mexplicit-relocs	-msmall-data
	   -mlarge-data	-msmall-text  -mlarge-text -mmemory-latency=time

	   DEC Alpha/VMS Options -mvms-return-codes

	   FRV Options -mgpr-32	 -mgpr-64  -mfpr-32  -mfpr-64 -mhard-float
	   -msoft-float	-malloc-cc  -mfixed-cc	-mdword	 -mno-dword -mdouble
	   -mno-double -mmedia	-mno-media  -mmuladd  -mno-muladd -mfdpic
	   -minline-plt	-mgprel-ro  -multilib-library-pic -mlinked-fp
	   -mlong-calls	 -malign-labels	-mlibrary-pic  -macc-4	-macc-8	-mpack
	   -mno-pack  -mno-eflags  -mcond-move	-mno-cond-move -moptimize-mem-
	   bar -mno-optimize-membar -mscc  -mno-scc  -mcond-exec
	   -mno-cond-exec -mvliw-branch	 -mno-vliw-branch -mmulti-cond-exec
	   -mno-multi-cond-exec	 -mnested-cond-exec -mno-nested-cond-exec
	   -mtomcat-stats -mTLS	-mtls -mcpu=cpu

	   GNU/Linux Options -muclibc

	   H8/300 Options -mrelax  -mh	-ms  -mn  -mint32  -malign-300

	   HPPA	Options	-march=architecture-type -mbig-switch  -mdis-
	   able-fpregs	-mdisable-indexing -mfast-indirect-calls  -mgas
	   -mgnu-ld   -mhp-ld -mfixed-range=register-range -mjump-in-delay
	   -mlinker-opt	-mlong-calls -mlong-load-store	-mno-big-switch
	   -mno-disable-fpregs -mno-disable-indexing  -mno-fast-indirect-calls
	   -mno-gas -mno-jump-in-delay	-mno-long-load-store -mno-porta-
	   ble-runtime	-mno-soft-float	-mno-space-regs	 -msoft-float
	   -mpa-risc-1-0 -mpa-risc-1-1	-mpa-risc-2-0  -mportable-runtime
	   -mschedule=cpu-type	-mspace-regs  -msio  -mwsio -munix=unix-std
	   -nolibdld  -static  -threads

	   i386	and x86-64 Options -mtune=cpu-type  -march=cpu-type -mfp-
	   math=unit -masm=dialect  -mno-fancy-math-387	-mno-fp-ret-in-387
	   -msoft-float	 -msvr3-shlib -mno-wide-multiply  -mrtd	 -malign-dou-
	   ble -mpreferred-stack-boundary=num -mmmx  -msse  -msse2 -msse3
	   -mssse3 -m3dnow -mthreads  -mno-align-stringops  -min-
	   line-all-stringops -mpush-args  -maccumulate-outgoing-args
	   -m128bit-long-double	-m96bit-long-double  -mregparm=num  -mssereg-
	   parm	-mstackrealign -momit-leaf-frame-pointer  -mno-red-zone
	   -mno-tls-direct-seg-refs -mcmodel=code-model	-m32  -m64
	   -mlarge-data-threshold=num

	   IA-64 Options -mbig-endian  -mlittle-endian	-mgnu-as  -mgnu-ld
	   -mno-pic -mvolatile-asm-stop	 -mregister-names  -mno-sdata -mcon-
	   stant-gp  -mauto-pic	 -minline-float-divide-min-latency -min-
	   line-float-divide-max-throughput -minline-int-divide-min-latency
	   -minline-int-divide-max-throughput -minline-sqrt-min-latency	-min-
	   line-sqrt-max-throughput -mno-dwarf2-asm -mearly-stop-bits
	   -mfixed-range=register-range	-mtls-size=tls-size -mtune=cpu-type
	   -mt -pthread	-milp32	-mlp64 -mno-sched-br-data-spec
	   -msched-ar-data-spec	-mno-sched-control-spec
	   -msched-br-in-data-spec -msched-ar-in-data-spec -msched-in-con-
	   trol-spec -msched-ldc -mno-sched-control-ldc	-mno-sched-spec-ver-
	   bose	-mno-sched-prefer-non-data-spec-insns -mno-sched-pre-
	   fer-non-control-spec-insns -mno-sched-count-spec-in-critical-path

	   M32R/D Options -m32r2 -m32rx	-m32r -mdebug -malign-loops
	   -mno-align-loops -missue-rate=number	-mbranch-cost=number
	   -mmodel=code-size-model-type	-msdata=sdata-type -mno-flush-func
	   -mflush-func=name -mno-flush-trap -mflush-trap=number -G num

	   M32C	Options	-mcpu=cpu -msim	-memregs=number

	   M680x0 Options -m68000  -m68020  -m68020-40	-m68020-60  -m68030
	   -m68040 -m68060  -mcpu32  -m5200  -mcfv4e -m68881  -mbitfield
	   -mc68000  -mc68020 -mnobitfield  -mrtd  -mshort  -msoft-float
	   -mpcrel -malign-int	-mstrict-align	-msep-data  -mno-sep-data
	   -mshared-library-id=n  -mid-shared-library  -mno-id-shared-library

	   M68hc1x Options -m6811  -m6812  -m68hc11  -m68hc12	-m68hcs12
	   -mauto-incdec  -minmax  -mlong-calls	 -mshort
	   -msoft-reg-count=count

	   MCore Options -mhardlit  -mno-hardlit  -mdiv	 -mno-div  -mre-
	   lax-immediates -mno-relax-immediates	 -mwide-bitfields
	   -mno-wide-bitfields -m4byte-functions  -mno-4byte-functions
	   -mcallgraph-data -mno-callgraph-data	 -mslow-bytes  -mno-slow-bytes
	   -mno-lsim -mlittle-endian  -mbig-endian  -m210  -m340
	   -mstack-increment

	   MIPS	Options	-EL  -EB  -march=arch  -mtune=arch -mips1  -mips2
	   -mips3  -mips4  -mips32  -mips32r2  -mips64 -mips16	-mno-mips16
	   -mabi=abi  -mabicalls  -mno-abicalls	-mshared  -mno-shared  -mxgot
	   -mno-xgot  -mgp32  -mgp64 -mfp32  -mfp64  -mhard-float
	   -msoft-float	-msingle-float	-mdouble-float	-mdsp  -mpaired-single
	   -mips3d -mlong64  -mlong32  -msym32	-mno-sym32 -Gnum  -membed-
	   ded-data  -mno-embedded-data	-muninit-const-in-rodata
	   -mno-uninit-const-in-rodata -msplit-addresses  -mno-split-addresses
	   -mexplicit-relocs  -mno-explicit-relocs -mcheck-zero-division
	   -mno-check-zero-division -mdivide-traps  -mdivide-breaks -mmemcpy
	   -mno-memcpy	-mlong-calls  -mno-long-calls -mmad  -mno-mad
	   -mfused-madd	 -mno-fused-madd  -nocpp -mfix-r4000  -mno-fix-r4000
	   -mfix-r4400	-mno-fix-r4400 -mfix-vr4120  -mno-fix-vr4120
	   -mfix-vr4130	-mfix-sb1  -mno-fix-sb1	-mflush-func=func
	   -mno-flush-func -mbranch-likely  -mno-branch-likely -mfp-exceptions
	   -mno-fp-exceptions -mvr4130-align -mno-vr4130-align

	   MMIX	Options	-mlibfuncs  -mno-libfuncs  -mepsilon  -mno-epsilon
	   -mabi=gnu -mabi=mmixware  -mzero-extend  -mknuthdiv	-mto-
	   plevel-symbols -melf	 -mbranch-predict  -mno-branch-predict
	   -mbase-addresses -mno-base-addresses	 -msingle-exit	-mno-sin-
	   gle-exit

	   MN10300 Options -mmult-bug  -mno-mult-bug -mam33  -mno-am33
	   -mam33-2  -mno-am33-2 -mreturn-pointer-on-d0	-mno-crt0  -mrelax

	   MT Options -mno-crt0	-mbacc -msim -march=cpu-type

	   PDP-11 Options -mfpu	 -msoft-float  -mac0  -mno-ac0	-m40  -m45
	   -m10	-mbcopy	 -mbcopy-builtin  -mint32  -mno-int16 -mint16
	   -mno-int32  -mfloat32  -mno-float64 -mfloat64  -mno-float32	-mab-
	   shi	-mno-abshi -mbranch-expensive  -mbranch-cheap -msplit
	   -mno-split  -munix-asm  -mdec-asm

	   PowerPC Options See RS/6000 and PowerPC Options.

	   RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type -mpower
	   -mno-power  -mpower2	 -mno-power2 -mpowerpc	-mpowerpc64  -mno-pow-
	   erpc	-maltivec  -mno-altivec	-mpowerpc-gpopt	 -mno-powerpc-gpopt
	   -mpowerpc-gfxopt  -mno-powerpc-gfxopt -mmfcrf  -mno-mfcrf  -mpopc-
	   ntb	-mno-popcntb  -mfprnd  -mno-fprnd -mnew-mnemonics
	   -mold-mnemonics -mfull-toc	-mminimal-toc  -mno-fp-in-toc
	   -mno-sum-in-toc -m64	 -m32  -mxl-compat  -mno-xl-compat  -mpe
	   -malign-power  -malign-natural -msoft-float	-mhard-float  -mmulti-
	   ple	-mno-multiple -mstring	-mno-string  -mupdate  -mno-update
	   -mfused-madd	 -mno-fused-madd  -mbit-align  -mno-bit-align
	   -mstrict-align  -mno-strict-align  -mrelocatable -mno-relocatable
	   -mrelocatable-lib  -mno-relocatable-lib -mtoc  -mno-toc  -mlittle
	   -mlittle-endian  -mbig  -mbig-endian	-mdynamic-no-pic  -maltivec
	   -mswdiv -mprioritize-restricted-insns=priority
	   -msched-costly-dep=dependence_type -minsert-sched-nops=scheme
	   -mcall-sysv	-mcall-netbsd -maix-struct-return
	   -msvr4-struct-return	-mabi=abi-type -msecure-plt -mbss-plt -misel
	   -mno-isel -misel=yes	 -misel=no -mspe -mno-spe -mspe=yes  -mspe=no
	   -mvrsave -mno-vrsave	-mmulhw	-mno-mulhw -mdlmzb -mno-dlmzb
	   -mfloat-gprs=yes  -mfloat-gprs=no -mfloat-gprs=single
	   -mfloat-gprs=double -mprototype  -mno-prototype -msim  -mmvme
	   -mads  -myellowknife	 -memb	-msdata	-msdata=opt  -mvxworks
	   -mwindiss  -G num  -pthread

	   S/390 and zSeries Options -mtune=cpu-type  -march=cpu-type
	   -mhard-float	 -msoft-float -mlong-double-64 -mlong-double-128
	   -mbackchain	-mno-backchain -mpacked-stack  -mno-packed-stack
	   -msmall-exec	 -mno-small-exec  -mmvcle -mno-mvcle -m64  -m31	 -mde-
	   bug	-mno-debug  -mesa  -mzarch -mtpf-trace -mno-tpf-trace
	   -mfused-madd	 -mno-fused-madd -mwarn-framesize  -mwarn-dynamicstack
	   -mstack-size	-mstack-guard

	   Score Options -meb -mel -mnhwloop -muls -mmac -mscore5 -mscore5u
	   -mscore7 -mscore7d

	   SH Options -m1  -m2	-m2e  -m3  -m3e	-m4-nofpu  -m4-single-only
	   -m4-single  -m4 -m4a-nofpu -m4a-single-only -m4a-single -m4a	-m4al
	   -m5-64media	-m5-64media-nofpu -m5-32media  -m5-32media-nofpu
	   -m5-compact	-m5-compact-nofpu -mb  -ml  -mdalign  -mrelax
	   -mbigtable  -mfmovd	-mhitachi -mrenesas -mno-renesas -mnomacsave
	   -mieee  -misize  -mpadstruct	 -mspace -mprefergot  -musermode
	   -multcost=number -mdiv=strategy -mdivsi3_libfunc=name -mad-
	   just-unroll -mindexed-addressing -mgettrcost=number -mpt-fixed
	    -minvalid-symbols

	   SPARC Options -mcpu=cpu-type	-mtune=cpu-type	-mcmodel=code-model
	   -m32	 -m64  -mapp-regs  -mno-app-regs -mfaster-structs
	   -mno-faster-structs -mfpu  -mno-fpu	-mhard-float  -msoft-float
	   -mhard-quad-float  -msoft-quad-float	-mimpure-text
	   -mno-impure-text  -mlittle-endian -mstack-bias  -mno-stack-bias
	   -munaligned-doubles	-mno-unaligned-doubles -mv8plus	 -mno-v8plus
	   -mvis  -mno-vis -threads -pthreads -pthread

	   System V Options -Qy	 -Qn  -YP,paths	 -Ym,dir

	   TMS320C3x/C4x Options -mcpu=cpu  -mbig  -msmall  -mregparm  -mmem-
	   parm	-mfast-fix  -mmpyi  -mbk  -mti	-mdp-isr-reload	-mrpts=count
	   -mrptb  -mdb	 -mloop-unsigned -mparallel-insns  -mparallel-mpy
	   -mpreserve-float

	   V850	Options	-mlong-calls  -mno-long-calls  -mep  -mno-ep -mpro-
	   log-function	 -mno-prolog-function  -mspace -mtda=n	-msda=n
	   -mzda=n -mapp-regs  -mno-app-regs -mdisable-callt  -mno-dis-
	   able-callt -mv850e1 -mv850e -mv850  -mbig-switch

	   VAX Options -mg  -mgnu  -munix

	   x86-64 Options See i386 and x86-64 Options.

	   Xstormy16 Options -msim

	   Xtensa Options -mconst16 -mno-const16 -mfused-madd  -mno-fused-madd
	   -mtext-section-literals  -mno-text-section-literals -mtarget-align
	   -mno-target-align -mlongcalls  -mno-longcalls

	   zSeries Options See S/390 and zSeries Options.

       Code Generation Options
	   -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexceptions
	   -fnon-call-exceptions  -funwind-tables -fasynchronous-unwind-tables
	   -finhibit-size-directive  -finstrument-functions -fno-common
	   -fno-ident -fpcc-struct-return  -fpic  -fPIC	-fpie -fPIE
	   -fno-jump-tables -freg-struct-return	 -fshort-enums -fshort-double
	   -fshort-wchar -fverbose-asm	-fpack-struct[=n]  -fstack-check
	   -fstack-limit-register=reg  -fstack-limit-symbol=sym	-fargu-
	   ment-alias  -fargument-noalias -fargument-noalias-global  -fargu-
	   ment-noalias-anything -fleading-underscore  -ftls-model=model
	   -ftrapv  -fwrapv  -fbounds-check -fvisibility

       Options Controlling the Kind of Output

       Compilation can involve up to four stages: preprocessing, compilation
       proper, assembly	and linking, always in that order.  GCC	is capable of
       preprocessing and compiling several files either	into several assembler
       input files, or into one	assembler input	file; then each	assembler
       input file produces an object file, and linking combines	all the	object
       files (those newly compiled, and	those specified	as input) into an exe-
       cutable file.

       For any given input file, the file name suffix determines what kind of
       compilation is done:

       file.c
	   C source code which must be preprocessed.

       file.i
	   C source code which should not be preprocessed.

       file.ii
	   C++ source code which should	not be preprocessed.

       file.h
	   C, or C++ header file to be turned into a precompiled header.

       file.cc
       file.cp
       file.cxx
       file.cpp
       file.CPP
       file.c++
       file.C
	   C++ source code which must be preprocessed.	Note that in .cxx, the
	   last	two letters must both be literally x.  Likewise, .C refers to
	   a literal capital C.

       file.hh
       file.H
	   C++ header file to be turned	into a precompiled header.

       file.f
       file.for
       file.FOR
	   Fixed form Fortran source code which	should not be preprocessed.

       file.F
       file.fpp
       file.FPP
	   Fixed form Fortran source code which	must be	preprocessed (with the
	   traditional preprocessor).

       file.f90
       file.f95
	   Free	form Fortran source code which should not be preprocessed.

       file.F90
       file.F95
	   Free	form Fortran source code which must be preprocessed (with the
	   traditional preprocessor).

       file.ads
	   Ada source code file	which contains a library unit declaration (a
	   declaration of a package, subprogram, or generic, or	a generic
	   instantiation), or a	library	unit renaming declaration (a package,
	   generic, or subprogram renaming declaration).  Such files are also
	   called specs.

       file.adb
	   Ada source code file	containing a library unit body (a subprogram
	   or package body).  Such files are also called bodies.

       file.s
	   Assembler code.

       file.S
	   Assembler code which	must be	preprocessed.

       other
	   An object file to be	fed straight into linking.  Any	file name with
	   no recognized suffix	is treated this	way.

       You can specify the input language explicitly with the -x option:

       -x language
	   Specify explicitly the language for the following input files
	   (rather than	letting	the compiler choose a default based on the
	   file	name suffix).  This option applies to all following input
	   files until the next	-x option.  Possible values for	language are:

		   c  c-header	c-cpp-output
		   c++	c++-header  c++-cpp-output
		   assembler  assembler-with-cpp
		   ada
		   f95	f95-cpp-input
		   java
		   treelang

       -x none
	   Turn	off any	specification of a language, so	that subsequent	files
	   are handled according to their file name suffixes (as they are if
	   -x has not been used	at all).

       -pass-exit-codes
	   Normally the	gcc program will exit with the code of 1 if any	phase
	   of the compiler returns a non-success return	code.  If you specify
	   -pass-exit-codes, the gcc program will instead return with numeri-
	   cally highest error produced	by any phase that returned an error
	   indication.	The C, C++, and	Fortran	frontends return 4, if an
	   internal compiler error is encountered.

       If you only want	some of	the stages of compilation, you can use -x (or
       filename	suffixes) to tell gcc where to start, and one of the options
       -c, -S, or -E to	say where gcc is to stop.  Note	that some combinations
       (for example, -x	cpp-output -E) instruct	gcc to do nothing at all.

       -c  Compile or assemble the source files, but do	not link.  The linking
	   stage simply	is not done.  The ultimate output is in	the form of an
	   object file for each	source file.

	   By default, the object file name for	a source file is made by
	   replacing the suffix	.c, .i,	.s, etc., with .o.

	   Unrecognized	input files, not requiring compilation or assembly,
	   are ignored.

       -S  Stop	after the stage	of compilation proper; do not assemble.	 The
	   output is in	the form of an assembler code file for each non-assem-
	   bler	input file specified.

	   By default, the assembler file name for a source file is made by
	   replacing the suffix	.c, .i,	etc., with .s.

	   Input files that don't require compilation are ignored.

       -E  Stop	after the preprocessing	stage; do not run the compiler proper.
	   The output is in the	form of	preprocessed source code, which	is
	   sent	to the standard	output.

	   Input files which don't require preprocessing are ignored.

       -o file
	   Place output	in file	file.  This applies regardless to whatever
	   sort	of output is being produced, whether it	be an executable file,
	   an object file, an assembler	file or	preprocessed C code.

	   If -o is not	specified, the default is to put an executable file in
	   a.out, the object file for source.suffix in source.o, its assembler
	   file	in source.s, a precompiled header file in source.suffix.gch,
	   and all preprocessed	C source on standard output.

       -v  Print (on standard error output) the	commands executed to run the
	   stages of compilation.  Also	print the version number of the	com-
	   piler driver	program	and of the preprocessor	and the	compiler
	   proper.

       -###
	   Like	-v except the commands are not executed	and all	command	argu-
	   ments are quoted.  This is useful for shell scripts to capture the
	   driver-generated command lines.

       -pipe
	   Use pipes rather than temporary files for communication between the
	   various stages of compilation.  This	fails to work on some systems
	   where the assembler is unable to read from a	pipe; but the GNU
	   assembler has no trouble.

       -combine
	   If you are compiling	multiple source	files, this option tells the
	   driver to pass all the source files to the compiler at once (for
	   those languages for which the compiler can handle this).  This will
	   allow intermodule analysis (IMA) to be performed by the compiler.
	   Currently the only language for which this is supported is C.  If
	   you pass source files for multiple languages	to the driver, using
	   this	option,	the driver will	invoke the compiler(s) that support
	   IMA once each, passing each compiler	all the	source files appropri-
	   ate for it.	For those languages that do not	support	IMA this
	   option will be ignored, and the compiler will be invoked once for
	   each	source file in that language.  If you use this option in con-
	   junction with -save-temps, the compiler will	generate multiple pre-
	   processed files (one	for each source	file), but only	one (combined)
	   .o or .s file.

       --help
	   Print (on the standard output) a description	of the command line
	   options understood by gcc.  If the -v option	is also	specified then
	   --help will also be passed on to the	various	processes invoked by
	   gcc,	so that	they can display the command line options they accept.
	   If the -Wextra option is also specified then	command	line options
	   which have no documentation associated with them will also be dis-
	   played.

       --target-help
	   Print (on the standard output) a description	of target specific
	   command line	options	for each tool.

       --version
	   Display the version number and copyrights of	the invoked GCC.

       @file
	   Read	command-line options from file.	 The options read are inserted
	   in place of the original @file option.  If file does	not exist, or
	   cannot be read, then	the option will	be treated literally, and not
	   removed.

	   Options in file are separated by whitespace.	 A whitespace charac-
	   ter may be included in an option by surrounding the entire option
	   in either single or double quotes.  Any character (including	a
	   backslash) may be included by prefixing the character to be
	   included with a backslash.  The file	may itself contain additional
	   @file options; any such options will	be processed recursively.

       Compiling C++ Programs

       C++ source files	conventionally use one of the suffixes .C, .cc,	.cpp,
       .CPP, .c++, .cp,	or .cxx; C++ header files often	use .hh	or .H; and
       preprocessed C++	files use the suffix .ii.  GCC recognizes files	with
       these names and compiles	them as	C++ programs even if you call the com-
       piler the same way as for compiling C programs (usually with the	name
       gcc).

       However,	the use	of gcc does not	add the	C++ library.  g++ is a program
       that calls GCC and treats .c, .h	and .i files as	C++ source files
       instead of C source files unless	-x is used, and	automatically speci-
       fies linking against the	C++ library.  This program is also useful when
       precompiling a C	header file with a .h extension	for use	in C++ compi-
       lations.	 On many systems, g++ is also installed	with the name c++.

       When you	compile	C++ programs, you may specify many of the same com-
       mand-line options that you use for compiling programs in	any language;
       or command-line options meaningful for C	and related languages; or
       options that are	meaningful only	for C++	programs.

       Options Controlling C Dialect

       The following options control the dialect of C (or languages derived
       from C, such as C++) that the compiler accepts:

       -ansi
	   In C	mode, support all ISO C90 programs.  In	C++ mode, remove GNU
	   extensions that conflict with ISO C++.

	   This	turns off certain features of GCC that are incompatible	with
	   ISO C90 (when compiling C code), or of standard C++ (when compiling
	   C++ code), such as the "asm"	and "typeof" keywords, and predefined
	   macros such as "unix" and "vax" that	identify the type of system
	   you are using.  It also enables the undesirable and rarely used ISO
	   trigraph feature.  For the C	compiler, it disables recognition of
	   C++ style //	comments as well as the	"inline" keyword.

	   The alternate keywords "__asm__", "__extension__", "__inline__" and
	   "__typeof__"	continue to work despite -ansi.	 You would not want to
	   use them in an ISO C	program, of course, but	it is useful to	put
	   them	in header files	that might be included in compilations done
	   with	-ansi.	Alternate predefined macros such as "__unix__" and
	   "__vax__" are also available, with or without -ansi.

	   The -ansi option does not cause non-ISO programs to be rejected
	   gratuitously.  For that, -pedantic is required in addition to
	   -ansi.

	   The macro "__STRICT_ANSI__" is predefined when the -ansi option is
	   used.  Some header files may	notice this macro and refrain from
	   declaring certain functions or defining certain macros that the ISO
	   standard doesn't call for; this is to avoid interfering with	any
	   programs that might use these names for other things.

	   Functions which would normally be built in but do not have seman-
	   tics	defined	by ISO C (such as "alloca" and "ffs") are not built-in
	   functions with -ansi	is used.

       -std=
	   Determine the language standard.  This option is currently only
	   supported when compiling C or C++.  A value for this	option must be
	   provided; possible values are

	   c89
	   iso9899:1990
	       ISO C90 (same as	-ansi).

	   iso9899:199409
	       ISO C90 as modified in amendment	1.

	   c99
	   c9x
	   iso9899:1999
	   iso9899:199x
	       ISO C99.	 Note that this	standard is not	yet fully supported;
	       see <http://gcc.gnu.org/gcc-4.2/c99status.html> for more	infor-
	       mation.	The names c9x and iso9899:199x are deprecated.

	   gnu89
	       Default,	ISO C90	plus GNU extensions (including some C99	fea-
	       tures).

	   gnu99
	   gnu9x
	       ISO C99 plus GNU	extensions.  When ISO C99 is fully implemented
	       in GCC, this will become	the default.  The name gnu9x is	depre-
	       cated.

	   c++98
	       The 1998	ISO C++	standard plus amendments.

	   gnu++98
	       The same	as -std=c++98 plus GNU extensions.  This is the
	       default for C++ code.

	   Even	when this option is not	specified, you can still use some of
	   the features	of newer standards in so far as	they do	not conflict
	   with	previous C standards.  For example, you	may use	"__restrict__"
	   even	when -std=c99 is not specified.

	   The -std options specifying some version of ISO C have the same
	   effects as -ansi, except that features that were not	in ISO C90 but
	   are in the specified	version	(for example, // comments and the
	   "inline" keyword in ISO C99)	are not	disabled.

       -fgnu89-inline
	   The option -fgnu89-inline tells GCC to use the traditional GNU
	   semantics for "inline" functions when in C99	mode.
	     Using this	option is roughly equivalent to	adding the
	   "gnu_inline"	function attribute to all inline functions.

	   This	option is accepted by GCC versions 4.1.3 and up.  In GCC ver-
	   sions prior to 4.3, C99 inline semantics are	not supported, and
	   thus	this option is effectively assumed to be present regardless of
	   whether or not it is	specified; the only effect of specifying it
	   explicitly is to disable warnings about using inline	functions in
	   C99 mode.  Likewise,	the option -fno-gnu89-inline is	not supported
	   in versions of GCC before 4.3.  It will be supported	only in	C99 or
	   gnu99 mode, not in C89 or gnu89 mode.

	   The preprocesor macros "__GNUC_GNU_INLINE__"	and
	   "__GNUC_STDC_INLINE__" may be used to check which semantics are in
	   effect for "inline" functions.

       -aux-info filename
	   Output to the given filename	prototyped declarations	for all	func-
	   tions declared and/or defined in a translation unit,	including
	   those in header files.  This	option is silently ignored in any lan-
	   guage other than C.

	   Besides declarations, the file indicates, in	comments, the origin
	   of each declaration (source file and	line), whether the declaration
	   was implicit, prototyped or unprototyped (I,	N for new or O for
	   old,	respectively, in the first character after the line number and
	   the colon), and whether it came from	a declaration or a definition
	   (C or F, respectively, in the following character).	In the case of
	   function definitions, a K&R-style list of arguments followed	by
	   their declarations is also provided,	inside comments, after the
	   declaration.

       -fno-asm
	   Do not recognize "asm", "inline" or "typeof"	as a keyword, so that
	   code	can use	these words as identifiers.  You can use the keywords
	   "__asm__", "__inline__" and "__typeof__" instead.  -ansi implies
	   -fno-asm.

	   In C++, this	switch only affects the	"typeof" keyword, since	"asm"
	   and "inline"	are standard keywords.	You may	want to	use the
	   -fno-gnu-keywords flag instead, which has the same effect.  In C99
	   mode	(-std=c99 or -std=gnu99), this switch only affects the "asm"
	   and "typeof"	keywords, since	"inline" is a standard keyword in ISO
	   C99.

       -fno-builtin
       -fno-builtin-function
	   Don't recognize built-in functions that do not begin	with
	   __builtin_ as prefix.

	   GCC normally	generates special code to handle certain built-in
	   functions more efficiently; for instance, calls to "alloca" may
	   become single instructions that adjust the stack directly, and
	   calls to "memcpy" may become	inline copy loops.  The	resulting code
	   is often both smaller and faster, but since the function calls no
	   longer appear as such, you cannot set a breakpoint on those calls,
	   nor can you change the behavior of the functions by linking with a
	   different library.  In addition, when a function is recognized as a
	   built-in function, GCC may use information about that function to
	   warn	about problems with calls to that function, or to generate
	   more	efficient code,	even if	the resulting code still contains
	   calls to that function.  For	example, warnings are given with
	   -Wformat for	bad calls to "printf", when "printf" is	built in, and
	   "strlen" is known not to modify global memory.

	   With	the -fno-builtin-function option only the built-in function
	   function is disabled.  function must	not begin with __builtin_.  If
	   a function is named this is not built-in in this version of GCC,
	   this	option is ignored.  There is no	corresponding -fbuiltin-func-
	   tion	option;	if you wish to enable built-in functions selectively
	   when	using -fno-builtin or -ffreestanding, you may define macros
	   such	as:

		   #define abs(n)	   __builtin_abs ((n))
		   #define strcpy(d, s)	   __builtin_strcpy ((d), (s))

       -fhosted
	   Assert that compilation takes place in a hosted environment.	 This
	   implies -fbuiltin.  A hosted	environment is one in which the	entire
	   standard library is available, and in which "main" has a return
	   type	of "int".  Examples are	nearly everything except a kernel.
	   This	is equivalent to -fno-freestanding.

       -ffreestanding
	   Assert that compilation takes place in a freestanding environment.
	   This	implies	-fno-builtin.  A freestanding environment is one in
	   which the standard library may not exist, and program startup may
	   not necessarily be at "main".  The most obvious example is an OS
	   kernel.  This is equivalent to -fno-hosted.

       -fopenmp
	   Enable handling of OpenMP directives	"#pragma omp" in C/C++ and
	   "!$omp" in Fortran.	When -fopenmp is specified, the	compiler gen-
	   erates parallel code	according to the OpenMP	Application Program
	   Interface v2.5 <http://www.openmp.org/>.

       -fms-extensions
	   Accept some non-standard constructs used in Microsoft header	files.

	   Some	cases of unnamed fields	in structures and unions are only
	   accepted with this option.

       -trigraphs
	   Support ISO C trigraphs.  The -ansi option (and -std	options	for
	   strict ISO C	conformance) implies -trigraphs.

       -no-integrated-cpp
	   Performs a compilation in two passes: preprocessing and compiling.
	   This	option allows a	user supplied "cc1", "cc1plus",	or "cc1obj"
	   via the -B option.  The user	supplied compilation step can then add
	   in an additional preprocessing step after normal preprocessing but
	   before compiling.  The default is to	use the	integrated cpp (inter-
	   nal cpp)

	   The semantics of this option	will change if "cc1", "cc1plus", and
	   "cc1obj" are	merged.

       -traditional
       -traditional-cpp
	   Formerly, these options caused GCC to attempt to emulate a pre-
	   standard C compiler.	 They are now only supported with the -E
	   switch.  The	preprocessor continues to support a pre-standard mode.
	   See the GNU CPP manual for details.

       -fcond-mismatch
	   Allow conditional expressions with mismatched types in the second
	   and third arguments.	 The value of such an expression is void.
	   This	option is not supported	for C++.

       -funsigned-char
	   Let the type	"char" be unsigned, like "unsigned char".

	   Each	kind of	machine	has a default for what "char" should be.  It
	   is either like "unsigned char" by default or	like "signed char" by
	   default.

	   Ideally, a portable program should always use "signed char" or
	   "unsigned char" when	it depends on the signedness of	an object.
	   But many programs have been written to use plain "char" and expect
	   it to be signed, or expect it to be unsigned, depending on the
	   machines they were written for.  This option, and its inverse, let
	   you make such a program work	with the opposite default.

	   The type "char" is always a distinct	type from each of "signed
	   char" or "unsigned char", even though its behavior is always	just
	   like	one of those two.

       -fsigned-char
	   Let the type	"char" be signed, like "signed char".

	   Note	that this is equivalent	to -fno-unsigned-char, which is	the
	   negative form of -funsigned-char.  Likewise,	the option
	   -fno-signed-char is equivalent to -funsigned-char.

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
	   These options control whether a bit-field is	signed or unsigned,
	   when	the declaration	does not use either "signed" or	"unsigned".
	   By default, such a bit-field	is signed, because this	is consistent:
	   the basic integer types such	as "int" are signed types.

       Options Controlling C++ Dialect

       This section describes the command-line options that are	only meaning-
       ful for C++ programs; but you can also use most of the GNU compiler
       options regardless of what language your	program	is in.	For example,
       you might compile a file	"firstClass.C" like this:

	       g++ -g -frepo -O	-c firstClass.C

       In this example,	only -frepo is an option meant only for	C++ programs;
       you can use the other options with any language supported by GCC.

       Here is a list of options that are only for compiling C++ programs:

       -fabi-version=n
	   Use version n of the	C++ ABI.  Version 2 is the version of the C++
	   ABI that first appeared in G++ 3.4.	Version	1 is the version of
	   the C++ ABI that first appeared in G++ 3.2.	Version	0 will always
	   be the version that conforms	most closely to	the C++	ABI specifica-
	   tion.  Therefore, the ABI obtained using version 0 will change as
	   ABI bugs are	fixed.

	   The default is version 2.

       -fno-access-control
	   Turn	off all	access checking.  This switch is mainly	useful for
	   working around bugs in the access control code.

       -fcheck-new
	   Check that the pointer returned by "operator	new" is	non-null
	   before attempting to	modify the storage allocated.  This check is
	   normally unnecessary	because	the C++	standard specifies that	"oper-
	   ator	new" will only return 0	if it is declared tthhrrooww(()), in which
	   case	the compiler will always check the return value	even without
	   this	option.	 In all	other cases, when "operator new" has a non-
	   empty exception specification, memory exhaustion is signalled by
	   throwing "std::bad_alloc".  See also	new (nothrow).

       -fconserve-space
	   Put uninitialized or	runtime-initialized global variables into the
	   common segment, as C	does.  This saves space	in the executable at
	   the cost of not diagnosing duplicate	definitions.  If you compile
	   with	this flag and your program mysteriously	crashes	after "main()"
	   has completed, you may have an object that is being destroyed twice
	   because two definitions were	merged.

	   This	option is no longer useful on most targets, now	that support
	   has been added for putting variables	into BSS without making	them
	   common.

       -ffriend-injection
	   Inject friend functions into	the enclosing namespace, so that they
	   are visible outside the scope of the	class in which they are
	   declared.  Friend functions were documented to work this way	in the
	   old Annotated C++ Reference Manual, and versions of G++ before 4.1
	   always worked that way.  However, in	ISO C++	a friend function
	   which is not	declared in an enclosing scope can only	be found using
	   argument dependent lookup.  This option causes friends to be
	   injected as they were in earlier releases.

	   This	option is for compatibility, and may be	removed	in a future
	   release of G++.

       -fno-elide-constructors
	   The C++ standard allows an implementation to	omit creating a	tempo-
	   rary	which is only used to initialize another object	of the same
	   type.  Specifying this option disables that optimization, and
	   forces G++ to call the copy constructor in all cases.

       -fno-enforce-eh-specs
	   Don't generate code to check	for violation of exception specifica-
	   tions at runtime.  This option violates the C++ standard, but may
	   be useful for reducing code size in production builds, much like
	   defining NDEBUG.  This does not give	user code permission to	throw
	   exceptions in violation of the exception specifications; the	com-
	   piler will still optimize based on the specifications, so throwing
	   an unexpected exception will	result in undefined behavior.

       -ffor-scope
       -fno-for-scope
	   If -ffor-scope is specified,	the scope of variables declared	in a
	   for-init-statement is limited to the	for loop itself, as specified
	   by the C++ standard.	 If -fno-for-scope is specified, the scope of
	   variables declared in a for-init-statement extends to the end of
	   the enclosing scope,	as was the case	in old versions	of G++,	and
	   other (traditional) implementations of C++.

	   The default if neither flag is given	to follow the standard,	but to
	   allow and give a warning for	old-style code that would otherwise be
	   invalid, or have different behavior.

       -fno-gnu-keywords
	   Do not recognize "typeof" as	a keyword, so that code	can use	this
	   word	as an identifier.  You can use the keyword "__typeof__"
	   instead.  -ansi implies -fno-gnu-keywords.

       -fno-implicit-templates
	   Never emit code for non-inline templates which are instantiated
	   implicitly (i.e. by use); only emit code for	explicit instantia-
	   tions.

       -fno-implicit-inline-templates
	   Don't emit code for implicit	instantiations of inline templates,
	   either.  The	default	is to handle inlines differently so that com-
	   piles with and without optimization will need the same set of
	   explicit instantiations.

       -fno-implement-inlines
	   To save space, do not emit out-of-line copies of inline functions
	   controlled by #pragma implementation.  This will cause linker
	   errors if these functions are not inlined everywhere	they are
	   called.

       -fms-extensions
	   Disable pedantic warnings about constructs used in MFC, such	as
	   implicit int	and getting a pointer to member	function via non-stan-
	   dard	syntax.

       -fno-nonansi-builtins
	   Disable built-in declarations of functions that are not mandated by
	   ANSI/ISO C.	These include "ffs", "alloca", "_exit",	"index",
	   "bzero", "conjf", and other related functions.

       -fno-operator-names
	   Do not treat	the operator name keywords "and", "bitand", "bitor",
	   "compl", "not", "or"	and "xor" as synonyms as keywords.

       -fno-optional-diags
	   Disable diagnostics that the	standard says a	compiler does not need
	   to issue.  Currently, the only such diagnostic issued by G++	is the
	   one for a name having multiple meanings within a class.

       -fpermissive
	   Downgrade some diagnostics about nonconformant code from errors to
	   warnings.  Thus, using -fpermissive will allow some nonconforming
	   code	to compile.

       -frepo
	   Enable automatic template instantiation at link time.  This option
	   also	implies	-fno-implicit-templates.

       -fno-rtti
	   Disable generation of information about every class with virtual
	   functions for use by	the C++	runtime	type identification features
	   (dynamic_cast and typeid).  If you don't use	those parts of the
	   language, you can save some space by	using this flag.  Note that
	   exception handling uses the same information, but it	will generate
	   it as needed. The dynamic_cast operator can still be	used for casts
	   that	do not require runtime type information, i.e. casts to "void
	   *" or to unambiguous	base classes.

       -fstats
	   Emit	statistics about front-end processing at the end of the	compi-
	   lation.  This information is	generally only useful to the G++
	   development team.

       -ftemplate-depth-n
	   Set the maximum instantiation depth for template classes to n.  A
	   limit on the	template instantiation depth is	needed to detect end-
	   less	recursions during template class instantiation.	 ANSI/ISO C++
	   conforming programs must not	rely on	a maximum depth	greater	than
	   17.

       -fno-threadsafe-statics
	   Do not emit the extra code to use the routines specified in the C++
	   ABI for thread-safe initialization of local statics.	 You can use
	   this	option to reduce code size slightly in code that doesn't need
	   to be thread-safe.

       -fuse-cxa-atexit
	   Register destructors	for objects with static	storage	duration with
	   the "__cxa_atexit" function rather than the "atexit"	function.
	   This	option is required for fully standards-compliant handling of
	   static destructors, but will	only work if your C library supports
	   "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
	   Don't use the "__cxa_get_exception_ptr" runtime routine.  This will
	   cause "std::uncaught_exception" to be incorrect, but	is necessary
	   if the runtime routine is not available.

       -fvisibility-inlines-hidden
	   This	switch declares	that the user does not attempt to compare
	   pointers to inline methods where the	addresses of the two functions
	   were	taken in different shared objects.

	   The effect of this is that GCC may, effectively, mark inline	meth-
	   ods with "__attribute__ ((visibility	("hidden")))" so that they do
	   not appear in the export table of a DSO and do not require a	PLT
	   indirection when used within	the DSO.  Enabling this	option can
	   have	a dramatic effect on load and link times of a DSO as it	mas-
	   sively reduces the size of the dynamic export table when the
	   library makes heavy use of templates.

	   The behaviour of this switch	is not quite the same as marking the
	   methods as hidden directly, because it does not affect static vari-
	   ables local to the function or cause	the compiler to	deduce that
	   the function	is defined in only one shared object.

	   You may mark	a method as having a visibility	explicitly to negate
	   the effect of the switch for	that method.  For example, if you do
	   want	to compare pointers to a particular inline method, you might
	   mark	it as having default visibility.  Marking the enclosing	class
	   with	explicit visibility will have no effect.

	   Explicitly instantiated inline methods are unaffected by this
	   option as their linkage might otherwise cross a shared library
	   boundary.

       -fno-weak
	   Do not use weak symbol support, even	if it is provided by the
	   linker.  By default,	G++ will use weak symbols if they are avail-
	   able.  This option exists only for testing, and should not be used
	   by end-users; it will result	in inferior code and has no benefits.
	   This	option may be removed in a future release of G++.

       -nostdinc++
	   Do not search for header files in the standard directories specific
	   to C++, but do still	search the other standard directories.	(This
	   option is used when building	the C++	library.)

       In addition, these optimization,	warning, and code generation options
       have meanings only for C++ programs:

       -fno-default-inline
	   Do not assume inline	for functions defined inside a class scope.
	     Note that these functions will have linkage like inline func-
	   tions; they just won't be inlined by	default.

       -Wabi (C++ only)
	   Warn	when G++ generates code	that is	probably not compatible	with
	   the vendor-neutral C++ ABI.	Although an effort has been made to
	   warn	about all such cases, there are	probably some cases that are
	   not warned about, even though G++ is	generating incompatible	code.
	   There may also be cases where warnings are emitted even though the
	   code	that is	generated will be compatible.

	   You should rewrite your code	to avoid these warnings	if you are
	   concerned about the fact that code generated	by G++ may not be
	   binary compatible with code generated by other compilers.

	   The known incompatibilities at this point include:

	   *   Incorrect handling of tail-padding for bit-fields.  G++ may
	       attempt to pack data into the same byte as a base class.	 For
	       example:

		       struct A	{ virtual void f(); int	f1 : 1;	};
		       struct B	: public A { int f2 : 1; };

	       In this case, G++ will place "B::f2" into the same byte
	       as"A::f1"; other	compilers will not.  You can avoid this	prob-
	       lem by explicitly padding "A" so	that its size is a multiple of
	       the byte	size on	your platform; that will cause G++ and other
	       compilers to layout "B" identically.

	   *   Incorrect handling of tail-padding for virtual bases.  G++ does
	       not use tail padding when laying	out virtual bases.  For	exam-
	       ple:

		       struct A	{ virtual void f(); char c1; };
		       struct B	{ B(); char c2;	};
		       struct C	: public A, public virtual B {};

	       In this case, G++ will not place	"B" into the tail-padding for
	       "A"; other compilers will.  You can avoid this problem by
	       explicitly padding "A" so that its size is a multiple of	its
	       alignment (ignoring virtual base	classes); that will cause G++
	       and other compilers to layout "C" identically.

	   *   Incorrect handling of bit-fields	with declared widths greater
	       than that of their underlying types, when the bit-fields	appear
	       in a union.  For	example:

		       union U { int i : 4096; };

	       Assuming	that an	"int" does not have 4096 bits, G++ will	make
	       the union too small by the number of bits in an "int".

	   *   Empty classes can be placed at incorrect	offsets.  For example:

		       struct A	{};

		       struct B	{
			 A a;
			 virtual void f	();
		       };

		       struct C	: public B, public A {};

	       G++ will	place the "A" base class of "C"	at a nonzero offset;
	       it should be placed at offset zero.  G++	mistakenly believes
	       that the	"A" data member	of "B" is already at offset zero.

	   *   Names of	template functions whose types involve "typename" or
	       template	template parameters can	be mangled incorrectly.

		       template	<typename Q>
		       void f(typename Q::X) {}

		       template	<template <typename> class Q>
		       void f(typename Q<int>::X) {}

	       Instantiations of these templates may be	mangled	incorrectly.

       -Wctor-dtor-privacy (C++	only)
	   Warn	when a class seems unusable because all	the constructors or
	   destructors in that class are private, and it has neither friends
	   nor public static member functions.

       -Wnon-virtual-dtor (C++ only)
	   Warn	when a class appears to	be polymorphic,	thereby	requiring a
	   virtual destructor, yet it declares a non-virtual one.  This	warn-
	   ing is also enabled if -Weffc++ is specified.

       -Wreorder (C++ only)
	   Warn	when the order of member initializers given in the code	does
	   not match the order in which	they must be executed.	For instance:

		   struct A {
		     int i;
		     int j;
		     A(): j (0), i (1) { }
		   };

	   The compiler	will rearrange the member initializers for i and j to
	   match the declaration order of the members, emitting	a warning to
	   that	effect.	 This warning is enabled by -Wall.

       The following -W... options are not affected by -Wall.

       -Weffc++	(C++ only)
	   Warn	about violations of the	following style	guidelines from	Scott
	   Meyers' Effective C++ book:

	   *   Item 11:	 Define	a copy constructor and an assignment operator
	       for classes with	dynamically allocated memory.

	   *   Item 12:	 Prefer	initialization to assignment in	constructors.

	   *   Item 14:	 Make destructors virtual in base classes.

	   *   Item 15:	 Have "operator=" return a reference to	*this.

	   *   Item 23:	 Don't try to return a reference when you must return
	       an object.

	   Also	warn about violations of the following style guidelines	from
	   Scott Meyers' More Effective	C++ book:

	   *   Item 6:	Distinguish between prefix and postfix forms of	incre-
	       ment and	decrement operators.

	   *   Item 7:	Never overload "&&", "||", or ",".

	   When	selecting this option, be aware	that the standard library
	   headers do not obey all of these guidelines;	use grep -v to filter
	   out those warnings.

       -Wno-deprecated (C++ only)
	   Do not warn about usage of deprecated features.

       -Wstrict-null-sentinel (C++ only)
	   Warn	also about the use of an uncasted "NULL" as sentinel.  When
	   compiling only with GCC this	is a valid sentinel, as	"NULL" is
	   defined to "__null".	 Although it is	a null pointer constant	not a
	   null	pointer, it is guaranteed to of	the same size as a pointer.
	   But this use	is not portable	across different compilers.

       -Wno-non-template-friend	(C++ only)
	   Disable warnings when non-templatized friend	functions are declared
	   within a template.  Since the advent	of explicit template specifi-
	   cation support in G++, if the name of the friend is an unqualified-
	   id (i.e., friend foo(int)), the C++ language	specification demands
	   that	the friend declare or define an	ordinary, nontemplate func-
	   tion.  (Section 14.5.3).  Before G++	implemented explicit specifi-
	   cation, unqualified-ids could be interpreted	as a particular	spe-
	   cialization of a templatized	function.  Because this	non-conforming
	   behavior is no longer the default behavior for G++, -Wnon-tem-
	   plate-friend	allows the compiler to check existing code for poten-
	   tial	trouble	spots and is on	by default.  This new compiler behav-
	   ior can be turned off with -Wno-non-template-friend which keeps the
	   conformant compiler code but	disables the helpful warning.

       -Wold-style-cast	(C++ only)
	   Warn	if an old-style	(C-style) cast to a non-void type is used
	   within a C++	program.  The new-style	casts (dynamic_cast,
	   static_cast,	reinterpret_cast, and const_cast) are less vulnerable
	   to unintended effects and much easier to search for.

       -Woverloaded-virtual (C++ only)
	   Warn	when a function	declaration hides virtual functions from a
	   base	class.	For example, in:

		   struct A {
		     virtual void f();
		   };

		   struct B: public A {
		     void f(int);
		   };

	   the "A" class version of "f"	is hidden in "B", and code like:

		   B* b;
		   b->f();

	   will	fail to	compile.

       -Wno-pmf-conversions (C++ only)
	   Disable the diagnostic for converting a bound pointer to member
	   function to a plain pointer.

       -Wsign-promo (C++ only)
	   Warn	when overload resolution chooses a promotion from unsigned or
	   enumerated type to a	signed type, over a conversion to an unsigned
	   type	of the same size.  Previous versions of	G++ would try to pre-
	   serve unsignedness, but the standard	mandates the current behavior.

		   struct A {
		     operator int ();
		     A&	operator = (int);
		   };

		   main	()
		   {
		     A a,b;
		     a = b;
		   }

	   In this example, G++	will synthesize	a default A& operator =	(const
	   A&);, while cfront will use the user-defined	operator =.

       Options to Control Diagnostic Messages Formatting

       Traditionally, diagnostic messages have been formatted irrespective of
       the output device's aspect (e.g.	its width, ...).  The options
       described below can be used to control the diagnostic messages format-
       ting algorithm, e.g. how	many characters	per line, how often source
       location	information should be reported.	 Right now, only the C++ front
       end can honor these options.  However it	is expected, in	the near
       future, that the	remaining front	ends would be able to digest them cor-
       rectly.

       -fmessage-length=n
	   Try to format error messages	so that	they fit on lines of about n
	   characters.	The default is 72 characters for g++ and 0 for the
	   rest	of the front ends supported by GCC.  If	n is zero, then	no
	   line-wrapping will be done; each error message will appear on a
	   single line.

       -fdiagnostics-show-location=once
	   Only	meaningful in line-wrapping mode.  Instructs the diagnostic
	   messages reporter to	emit once source location information; that
	   is, in case the message is too long to fit on a single physical
	   line	and has	to be wrapped, the source location won't be emitted
	   (as prefix) again, over and over, in	subsequent continuation	lines.
	   This	is the default behavior.

       -fdiagnostics-show-location=every-line
	   Only	meaningful in line-wrapping mode.  Instructs the diagnostic
	   messages reporter to	emit the same source location information (as
	   prefix) for physical	lines that result from the process of breaking
	   a message which is too long to fit on a single line.

       -fdiagnostics-show-option
	   This	option instructs the diagnostic	machinery to add text to each
	   diagnostic emitted, which indicates which command line option
	   directly controls that diagnostic, when such	an option is known to
	   the diagnostic machinery.

       Options to Request or Suppress Warnings

       Warnings	are diagnostic messages	that report constructions which	are
       not inherently erroneous	but which are risky or suggest there may have
       been an error.

       You can request many specific warnings with options beginning -W, for
       example -Wimplicit to request warnings on implicit declarations.	 Each
       of these	specific warning options also has a negative form beginning
       -Wno- to	turn off warnings; for example,	-Wno-implicit.	This manual
       lists only one of the two forms,	whichever is not the default.

       The following options control the amount	and kinds of warnings produced
       by GCC; for further, language-specific options also refer to C++
       Dialect Options.

       -fsyntax-only
	   Check the code for syntax errors, but don't do anything beyond
	   that.

       -pedantic
	   Issue all the warnings demanded by strict ISO C and ISO C++;	reject
	   all programs	that use forbidden extensions, and some	other programs
	   that	do not follow ISO C and	ISO C++.  For ISO C, follows the ver-
	   sion	of the ISO C standard specified	by any -std option used.

	   Valid ISO C and ISO C++ programs should compile properly with or
	   without this	option (though a rare few will require -ansi or	a -std
	   option specifying the required version of ISO C).  However, without
	   this	option,	certain	GNU extensions and traditional C and C++ fea-
	   tures are supported as well.	 With this option, they	are rejected.

	   -pedantic does not cause warning messages for use of	the alternate
	   keywords whose names	begin and end with __.	Pedantic warnings are
	   also	disabled in the	expression that	follows	"__extension__".  How-
	   ever, only system header files should use these escape routes;
	   application programs	should avoid them.

	   Some	users try to use -pedantic to check programs for strict	ISO C
	   conformance.	 They soon find	that it	does not do quite what they
	   want: it finds some non-ISO practices, but not all---only those for
	   which ISO C requires	a diagnostic, and some others for which	diag-
	   nostics have	been added.

	   A feature to	report any failure to conform to ISO C might be	useful
	   in some instances, but would	require	considerable additional	work
	   and would be	quite different	from -pedantic.	 We don't have plans
	   to support such a feature in	the near future.

	   Where the standard specified	with -std represents a GNU extended
	   dialect of C, such as gnu89 or gnu99, there is a corresponding base
	   standard, the version of ISO	C on which the GNU extended dialect is
	   based.  Warnings from -pedantic are given where they	are required
	   by the base standard.  (It would not	make sense for such warnings
	   to be given only for	features not in	the specified GNU C dialect,
	   since by definition the GNU dialects	of C include all features the
	   compiler supports with the given option, and	there would be nothing
	   to warn about.)

       -pedantic-errors
	   Like	-pedantic, except that errors are produced rather than warn-
	   ings.

       -w  Inhibit all warning messages.

       -Wno-import
	   Inhibit warning messages about the use of #import.

       -Wchar-subscripts
	   Warn	if an array subscript has type "char".	This is	a common cause
	   of error, as	programmers often forget that this type	is signed on
	   some	machines.  This	warning	is enabled by -Wall.

       -Wcomment
	   Warn	whenever a comment-start sequence /* appears in	a /* comment,
	   or whenever a Backslash-Newline appears in a	// comment.  This
	   warning is enabled by -Wall.

       -Wfatal-errors
	   This	option causes the compiler to abort compilation	on the first
	   error occurred rather than trying to	keep going and printing	fur-
	   ther	error messages.

       -Wformat
	   Check calls to "printf" and "scanf",	etc., to make sure that	the
	   arguments supplied have types appropriate to	the format string
	   specified, and that the conversions specified in the	format string
	   make	sense.	This includes standard functions, and others specified
	   by format attributes, in the	"printf", "scanf", "strftime" and
	   "strfmon" (an X/Open	extension, not in the C	standard) families (or
	   other target-specific families).  Which functions are checked with-
	   out format attributes having	been specified depends on the standard
	   version selected, and such checks of	functions without the
	   attribute specified are disabled by -ffreestanding or -fno-builtin.

	   The formats are checked against the format features supported by
	   GNU libc version 2.2.  These	include	all ISO	C90 and	C99 features,
	   as well as features from the	Single Unix Specification and some BSD
	   and GNU extensions.	Other library implementations may not support
	   all these features; GCC does	not support warning about features
	   that	go beyond a particular library's limitations.  However,	if
	   -pedantic is	used with -Wformat, warnings will be given about for-
	   mat features	not in the selected standard version (but not for
	   "strfmon" formats, since those are not in any version of the	C
	   standard).

	   Since -Wformat also checks for null format arguments	for several
	   functions, -Wformat also implies -Wnonnull.

	   -Wformat is included	in -Wall.  For more control over some aspects
	   of format checking, the options -Wformat-y2k, -Wno-for-
	   mat-extra-args, -Wno-format-zero-length, -Wformat-nonliteral,
	   -Wformat-security, and -Wformat=2 are available, but	are not
	   included in -Wall.

       -Wformat-y2k
	   If -Wformat is specified, also warn about "strftime"	formats	which
	   may yield only a two-digit year.

       -Wno-format-extra-args
	   If -Wformat is specified, do	not warn about excess arguments	to a
	   "printf" or "scanf" format function.	 The C standard	specifies that
	   such	arguments are ignored.

	   Where the unused arguments lie between used arguments that are
	   specified with $ operand number specifications, normally warnings
	   are still given, since the implementation could not know what type
	   to pass to "va_arg" to skip the unused arguments.  However, in the
	   case	of "scanf" formats, this option	will suppress the warning if
	   the unused arguments	are all	pointers, since	the Single Unix	Speci-
	   fication says that such unused arguments are	allowed.

       -Wno-format-zero-length
	   If -Wformat is specified, do	not warn about zero-length formats.
	   The C standard specifies that zero-length formats are allowed.

       -Wformat-nonliteral
	   If -Wformat is specified, also warn if the format string is not a
	   string literal and so cannot	be checked, unless the format function
	   takes its format arguments as a "va_list".

       -Wformat-security
	   If -Wformat is specified, also warn about uses of format functions
	   that	represent possible security problems.  At present, this	warns
	   about calls to "printf" and "scanf" functions where the format
	   string is not a string literal and there are	no format arguments,
	   as in "printf (foo);".  This	may be a security hole if the format
	   string came from untrusted input and	contains %n.  (This is cur-
	   rently a subset of what -Wformat-nonliteral warns about, but	in
	   future warnings may be added	to -Wformat-security that are not
	   included in -Wformat-nonliteral.)

       -Wformat=2
	   Enable -Wformat plus	format checks not included in -Wformat.	 Cur-
	   rently equivalent to	-Wformat -Wformat-nonliteral -Wformat-security
	   -Wformat-y2k.

       -Wnonnull
	   Warn	about passing a	null pointer for arguments marked as requiring
	   a non-null value by the "nonnull" function attribute.

	   -Wnonnull is	included in -Wall and -Wformat.	 It can	be disabled
	   with	the -Wno-nonnull option.

       -Winit-self (C, C++ only)
	   Warn	about uninitialized variables which are	initialized with them-
	   selves.  Note this option can only be used with the -Wuninitialized
	   option, which in turn only works with -O1 and above.

	   For example,	GCC will warn about "i"	being uninitialized in the
	   following snippet only when -Winit-self has been specified:

		   int f()
		   {
		     int i = i;
		     return i;
		   }

       -Wimplicit-int
	   Warn	when a declaration does	not specify a type.  This warning is
	   enabled by -Wall.

       -Wimplicit-function-declaration
       -Werror-implicit-function-declaration
	   Give	a warning (or error) whenever a	function is used before	being
	   declared.  The form -Wno-error-implicit-function-declaration	is not
	   supported.  This warning is enabled by -Wall	(as a warning, not an
	   error).

       -Wimplicit
	   Same	as -Wimplicit-int and -Wimplicit-function-declaration.	This
	   warning is enabled by -Wall.

       -Wmain
	   Warn	if the type of main is suspicious.  main should	be a function
	   with	external linkage, returning int, taking	either zero arguments,
	   two,	or three arguments of appropriate types.  This warning is
	   enabled by -Wall.

       -Wmissing-braces
	   Warn	if an aggregate	or union initializer is	not fully bracketed.
	   In the following example, the initializer for a is not fully	brack-
	   eted, but that for b	is fully bracketed.

		   int a[2][2] = { 0, 1, 2, 3 };
		   int b[2][2] = { { 0,	1 }, { 2, 3 } };

	   This	warning	is enabled by -Wall.

       -Wmissing-include-dirs (C and C++ only)
	   Warn	if a user-supplied include directory does not exist.

       -Wparentheses
	   Warn	if parentheses are omitted in certain contexts,	such as	when
	   there is an assignment in a context where a truth value is
	   expected, or	when operators are nested whose	precedence people
	   often get confused about.  Only the warning for an assignment used
	   as a	truth value is supported when compiling	C++; the other warn-
	   ings	are only supported when	compiling C.

	   Also	warn if	a comparison like x<=y<=z appears; this	is equivalent
	   to (x<=y ? 1	: 0) <=	z, which is a different	interpretation from
	   that	of ordinary mathematical notation.

	   Also	warn about constructions where there may be confusion to which
	   "if"	statement an "else" branch belongs.  Here is an	example	of
	   such	a case:

		   {
		     if	(a)
		       if (b)
			 foo ();
		     else
		       bar ();
		   }

	   In C, every "else" branch belongs to	the innermost possible "if"
	   statement, which in this example is "if (b)".  This is often	not
	   what	the programmer expected, as illustrated	in the above example
	   by indentation the programmer chose.	 When there is the potential
	   for this confusion, GCC will	issue a	warning	when this flag is
	   specified.  To eliminate the	warning, add explicit braces around
	   the innermost "if" statement	so there is no way the "else" could
	   belong to the enclosing "if".  The resulting	code would look	like
	   this:

		   {
		     if	(a)
		       {
			 if (b)
			   foo ();
			 else
			   bar ();
		       }
		   }

	   This	warning	is enabled by -Wall.

       -Wsequence-point
	   Warn	about code that	may have undefined semantics because of	viola-
	   tions of sequence point rules in the	C and C++ standards.

	   The C and C++ standards defines the order in	which expressions in a
	   C/C++ program are evaluated in terms	of sequence points, which rep-
	   resent a partial ordering between the execution of parts of the
	   program: those executed before the sequence point, and those	exe-
	   cuted after it.  These occur	after the evaluation of	a full expres-
	   sion	(one which is not part of a larger expression),	after the
	   evaluation of the first operand of a	"&&", "||", "? :" or ","
	   (comma) operator, before a function is called (but after the	evalu-
	   ation of its	arguments and the expression denoting the called func-
	   tion), and in certain other places.	Other than as expressed	by the
	   sequence point rules, the order of evaluation of subexpressions of
	   an expression is not	specified.  All	these rules describe only a
	   partial order rather	than a total order, since, for example,	if two
	   functions are called	within one expression with no sequence point
	   between them, the order in which the	functions are called is	not
	   specified.  However,	the standards committee	have ruled that	func-
	   tion	calls do not overlap.

	   It is not specified when between sequence points modifications to
	   the values of objects take effect.  Programs	whose behavior depends
	   on this have	undefined behavior; the	C and C++ standards specify
	   that	"Between the previous and next sequence	point an object	shall
	   have	its stored value modified at most once by the evaluation of an
	   expression.	Furthermore, the prior value shall be read only	to
	   determine the value to be stored.".	If a program breaks these
	   rules, the results on any particular	implementation are entirely
	   unpredictable.

	   Examples of code with undefined behavior are	"a = a++;", "a[n] =
	   b[n++]" and "a[i++] = i;".  Some more complicated cases are not
	   diagnosed by	this option, and it may	give an	occasional false posi-
	   tive	result,	but in general it has been found fairly	effective at
	   detecting this sort of problem in programs.

	   The standard	is worded confusingly, therefore there is some debate
	   over	the precise meaning of the sequence point rules	in subtle
	   cases.  Links to discussions	of the problem,	including proposed
	   formal definitions, may be found on the GCC readings	page, at
	   <http://gcc.gnu.org/readings.html>.

	   This	warning	is enabled by -Wall for	C and C++.

       -Wreturn-type
	   Warn	whenever a function is defined with a return-type that
	   defaults to "int".  Also warn about any "return" statement with no
	   return-value	in a function whose return-type	is not "void".

	   For C, also warn if the return type of a function has a type	quali-
	   fier	such as	"const".  Such a type qualifier	has no effect, since
	   the value returned by a function is not an lvalue.  ISO C prohibits
	   qualified "void" return types on function definitions, so such
	   return types	always receive a warning even without this option.

	   For C++, a function without return type always produces a diagnos-
	   tic message,	even when -Wno-return-type is specified.  The only
	   exceptions are main and functions defined in	system headers.

	   This	warning	is enabled by -Wall.

       -Wswitch
	   Warn	whenever a "switch" statement has an index of enumerated type
	   and lacks a "case" for one or more of the named codes of that enu-
	   meration.  (The presence of a "default" label prevents this warn-
	   ing.)  "case" labels	outside	the enumeration	range also provoke
	   warnings when this option is	used.  This warning is enabled by
	   -Wall.

       -Wswitch-default
	   Warn	whenever a "switch" statement does not have a "default"	case.

       -Wswitch-enum
	   Warn	whenever a "switch" statement has an index of enumerated type
	   and lacks a "case" for one or more of the named codes of that enu-
	   meration.  "case" labels outside the	enumeration range also provoke
	   warnings when this option is	used.

       -Wtrigraphs
	   Warn	if any trigraphs are encountered that might change the meaning
	   of the program (trigraphs within comments are not warned about).
	   This	warning	is enabled by -Wall.

       -Wunused-function
	   Warn	whenever a static function is declared but not defined or a
	   non-inline static function is unused.  This warning is enabled by
	   -Wall.

       -Wunused-label
	   Warn	whenever a label is declared but not used.  This warning is
	   enabled by -Wall.

	   To suppress this warning use	the unused attribute.

       -Wunused-parameter
	   Warn	whenever a function parameter is unused	aside from its decla-
	   ration.

	   To suppress this warning use	the unused attribute.

       -Wunused-variable
	   Warn	whenever a local variable or non-constant static variable is
	   unused aside	from its declaration.  This warning is enabled by
	   -Wall.

	   To suppress this warning use	the unused attribute.

       -Wunused-value
	   Warn	whenever a statement computes a	result that is explicitly not
	   used.  This warning is enabled by -Wall.

	   To suppress this warning cast the expression	to void.

       -Wunused
	   All the above -Wunused options combined.

	   In order to get a warning about an unused function parameter, you
	   must	either specify -Wextra -Wunused	(note that -Wall implies
	   -Wunused), or separately specify -Wunused-parameter.

       -Wuninitialized
	   Warn	if an automatic	variable is used without first being initial-
	   ized	or if a	variable may be	clobbered by a "setjmp"	call.

	   These warnings are possible only in optimizing compilation, because
	   they	require	data flow information that is computed only when opti-
	   mizing.  If you do not specify -O, you will not get these warnings.
	   Instead, GCC	will issue a warning about -Wuninitialized requiring
	   -O.

	   If you want to warn about code which	uses the uninitialized value
	   of the variable in its own initializer, use the -Winit-self option.

	   These warnings occur	for individual uninitialized or	clobbered ele-
	   ments of structure, union or	array variables	as well	as for vari-
	   ables which are uninitialized or clobbered as a whole.  They	do not
	   occur for variables or elements declared "volatile".	 Because these
	   warnings depend on optimization, the	exact variables	or elements
	   for which there are warnings	will depend on the precise optimiza-
	   tion	options	and version of GCC used.

	   Note	that there may be no warning about a variable that is used
	   only	to compute a value that	itself is never	used, because such
	   computations	may be deleted by data flow analysis before the	warn-
	   ings	are printed.

	   These warnings are made optional because GCC	is not smart enough to
	   see all the reasons why the code might be correct despite appearing
	   to have an error.  Here is one example of how this can happen:

		   {
		     int x;
		     switch (y)
		       {
		       case 1: x = 1;
			 break;
		       case 2: x = 4;
			 break;
		       case 3: x = 5;
		       }
		     foo (x);
		   }

	   If the value	of "y" is always 1, 2 or 3, then "x" is	always ini-
	   tialized, but GCC doesn't know this.	 Here is another common	case:

		   {
		     int save_y;
		     if	(change_y) save_y = y, y = new_y;
		     ...
		     if	(change_y) y = save_y;
		   }

	   This	has no bug because "save_y" is used only if it is set.

	   This	option also warns when a non-volatile automatic	variable might
	   be changed by a call	to "longjmp".  These warnings as well are pos-
	   sible only in optimizing compilation.

	   The compiler	sees only the calls to "setjmp".  It cannot know where
	   "longjmp" will be called; in	fact, a	signal handler could call it
	   at any point	in the code.  As a result, you may get a warning even
	   when	there is in fact no problem because "longjmp" cannot in	fact
	   be called at	the place which	would cause a problem.

	   Some	spurious warnings can be avoided if you	declare	all the	func-
	   tions you use that never return as "noreturn".

	   This	warning	is enabled by -Wall.

       -Wunknown-pragmas
	   Warn	when a #pragma directive is encountered	which is not under-
	   stood by GCC.  If this command line option is used, warnings	will
	   even	be issued for unknown pragmas in system	header files.  This is
	   not the case	if the warnings	were only enabled by the -Wall command
	   line	option.

       -Wno-pragmas
	   Do not warn about misuses of	pragmas, such as incorrect parameters,
	   invalid syntax, or conflicts	between	pragmas.  See also -Wun-
	   known-pragmas.

       -Wstrict-aliasing
	   This	option is only active when -fstrict-aliasing is	active.	 It
	   warns about code which might	break the strict aliasing rules	that
	   the compiler	is using for optimization.  The	warning	does not catch
	   all cases, but does attempt to catch	the more common	pitfalls.  It
	   is included in -Wall.

       -Wstrict-aliasing=2
	   This	option is only active when -fstrict-aliasing is	active.	 It
	   warns about code which might	break the strict aliasing rules	that
	   the compiler	is using for optimization.  This warning catches more
	   cases than -Wstrict-aliasing, but it	will also give a warning for
	   some	ambiguous cases	that are safe.

       -Wstrict-overflow
       -Wstrict-overflow=n
	   This	option is only active when -fstrict-overflow is	active.	 It
	   warns about cases where the compiler	optimizes based	on the assump-
	   tion	that signed overflow does not occur.  Note that	it does	not
	   warn	about all cases	where the code might overflow: it only warns
	   about cases where the compiler implements some optimization.	 Thus
	   this	warning	depends	on the optimization level.

	   An optimization which assumes that signed overflow does not occur
	   is perfectly	safe if	the values of the variables involved are such
	   that	overflow never does, in	fact, occur.  Therefore	this warning
	   can easily give a false positive: a warning about code which	is not
	   actually a problem.	To help	focus on important issues, several
	   warning levels are defined.	No warnings are	issued for the use of
	   undefined signed overflow when estimating how many iterations a
	   loop	will require, in particular when determining whether a loop
	   will	be executed at all.

	   @option<-Wstrict-overflow=1>
	       Warn about cases	which are both questionable and	easy to	avoid.
	       For example: "x + 1 > x"; with -fstrict-overflow, the compiler
	       will simplify this to 1.	 This level of -Wstrict-overflow is
	       enabled by -Wall; higher	levels are not,	and must be explicitly
	       requested.

	   @option<-Wstrict-overflow=2>
	       Also warn about other cases where a comparison is simplified to
	       a constant.  For	example: "abs (x) >= 0".  This can only	be
	       simplified when -fstrict-overflow is in effect, because "abs
	       (INT_MIN)" overflows to "INT_MIN", which	is less	than zero.
	       -Wstrict-overflow (with no level) is the	same as	-Wstrict-over-
	       flow=2.

	   @option<-Wstrict-overflow=3>
	       Also warn about other cases where a comparison is simplified.
	       For example: "x + 1 > 1"	will be	simplified to "x > 0".

	   @option<-Wstrict-overflow=4>
	       Also warn about other simplifications not covered by the	above
	       cases.  For example: "(x	* 10) /	5" will	be simplified to "x *
	       2".

	   @option<-Wstrict-overflow=5>
	       Also warn about cases where the compiler	reduces	the magnitude
	       of a constant involved in a comparison.	For example: "x	+ 2 >
	       y" will be simplified to	"x + 1 >= y".  This is reported	only
	       at the highest warning level because this simplification
	       applies to many comparisons, so this warning level will give a
	       very large number of false positives.

       -Wall
	   All of the above -W options combined.  This enables all the warn-
	   ings	about constructions that some users consider questionable, and
	   that	are easy to avoid (or modify to	prevent	the warning), even in
	   conjunction with macros.  This also enables some language-specific
	   warnings described in C++ Dialect Options.

       The following -W... options are not implied by -Wall.  Some of them
       warn about constructions	that users generally do	not consider question-
       able, but which occasionally you	might wish to check for; others	warn
       about constructions that	are necessary or hard to avoid in some cases,
       and there is no simple way to modify the	code to	suppress the warning.

       -Wextra
	   (This option	used to	be called -W.  The older name is still sup-
	   ported, but the newer name is more descriptive.)  Print extra warn-
	   ing messages	for these events:

	   *   A function can return either with or without a value.  (Falling
	       off the end of the function body	is considered returning	with-
	       out a value.)  For example, this	function would evoke such a
	       warning:

		       foo (a)
		       {
			 if (a > 0)
			   return a;
		       }

	   *   An expression-statement or the left-hand	side of	a comma
	       expression contains no side effects.  To	suppress the warning,
	       cast the	unused expression to void.  For	example, an expression
	       such as x[i,j] will cause a warning, but	x[(void)i,j] will not.

	   *   An unsigned value is compared against zero with < or >=.

	   *   Storage-class specifiers	like "static" are not the first	things
	       in a declaration.  According to the C Standard, this usage is
	       obsolescent.

	   *   If -Wall	or -Wunused is also specified, warn about unused argu-
	       ments.

	   *   A comparison between signed and unsigned	values could produce
	       an incorrect result when	the signed value is converted to
	       unsigned.  (But don't warn if -Wno-sign-compare is also speci-
	       fied.)

	   *   An aggregate has	an initializer which does not initialize all
	       members.	 This warning can be independently controlled by
	       -Wmissing-field-initializers.

	   *   An initialized field without side effects is overridden when
	       using designated	initializers.  This warning can	be indepen-
	       dently controlled by -Woverride-init.

	   *   A function parameter is declared	without	a type specifier in
	       K&R-style functions:

		       void foo(bar) { }

	   *   An empty	body occurs in an if or	else statement.

	   *   A pointer is compared against integer zero with <, <=, >, or
	       >=.

	   *   A variable might	be changed by longjmp or vfork.

	   *<(C++ only)>
	       An enumerator and a non-enumerator both appear in a conditional
	       expression.

	   *<(C++ only)>
	       A non-static reference or non-static const member appears in a
	       class without constructors.

	   *<(C++ only)>
	       Ambiguous virtual bases.

	   *<(C++ only)>
	       Subscripting an array which has been declared register.

	   *<(C++ only)>
	       Taking the address of a variable	which has been declared	regis-
	       ter.

	   *<(C++ only)>
	       A base class is not initialized in a derived class' copy	con-
	       structor.

       -Wno-div-by-zero
	   Do not warn about compile-time integer division by zero.  Floating
	   point division by zero is not warned	about, as it can be a legiti-
	   mate	way of obtaining infinities and	NaNs.

       -Wsystem-headers
	   Print warning messages for constructs found in system header	files.
	   Warnings from system	headers	are normally suppressed, on the
	   assumption that they	usually	do not indicate	real problems and
	   would only make the compiler	output harder to read.	Using this
	   command line	option tells GCC to emit warnings from system headers
	   as if they occurred in user code.  However, note that using -Wall
	   in conjunction with this option will	not warn about unknown pragmas
	   in system headers---for that, -Wunknown-pragmas must	also be	used.

       -Wfloat-equal
	   Warn	if floating point values are used in equality comparisons.

	   The idea behind this	is that	sometimes it is	convenient (for	the
	   programmer) to consider floating-point values as approximations to
	   infinitely precise real numbers.  If	you are	doing this, then you
	   need	to compute (by analyzing the code, or in some other way) the
	   maximum or likely maximum error that	the computation	introduces,
	   and allow for it when performing comparisons	(and when producing
	   output, but that's a	different problem).  In	particular, instead of
	   testing for equality, you would check to see	whether	the two	values
	   have	ranges that overlap; and this is done with the relational
	   operators, so equality comparisons are probably mistaken.

       -Wtraditional (C	only)
	   Warn	about certain constructs that behave differently in tradi-
	   tional and ISO C.  Also warn	about ISO C constructs that have no
	   traditional C equivalent, and/or problematic	constructs which
	   should be avoided.

	   *   Macro parameters	that appear within string literals in the
	       macro body.  In traditional C macro replacement takes place
	       within string literals, but does	not in ISO C.

	   *   In traditional C, some preprocessor directives did not exist.
	       Traditional preprocessors would only consider a line to be a
	       directive if the	# appeared in column 1 on the line.  Therefore
	       -Wtraditional warns about directives that traditional C under-
	       stands but would	ignore because the # does not appear as	the
	       first character on the line.  It	also suggests you hide direc-
	       tives like #pragma not understood by traditional	C by indenting
	       them.  Some traditional implementations would not recognize
	       #elif, so it suggests avoiding it altogether.

	   *   A function-like macro that appears without arguments.

	   *   The unary plus operator.

	   *   The U integer constant suffix, or the F or L floating point
	       constant	suffixes.  (Traditional	C does support the L suffix on
	       integer constants.)  Note, these	suffixes appear	in macros
	       defined in the system headers of	most modern systems, e.g. the
	       _MIN/_MAX macros	in "<limits.h>".  Use of these macros in user
	       code might normally lead	to spurious warnings, however GCC's
	       integrated preprocessor has enough context to avoid warning in
	       these cases.

	   *   A function declared external in one block and then used after
	       the end of the block.

	   *   A "switch" statement has	an operand of type "long".

	   *   A non-"static" function declaration follows a "static" one.
	       This construct is not accepted by some traditional C compilers.

	   *   The ISO type of an integer constant has a different width or
	       signedness from its traditional type.  This warning is only
	       issued if the base of the constant is ten.  I.e.	hexadecimal or
	       octal values, which typically represent bit patterns, are not
	       warned about.

	   *   Usage of	ISO string concatenation is detected.

	   *   Initialization of automatic aggregates.

	   *   Identifier conflicts with labels.  Traditional C	lacks a	sepa-
	       rate namespace for labels.

	   *   Initialization of unions.  If the initializer is	zero, the
	       warning is omitted.  This is done under the assumption that the
	       zero initializer	in user	code appears conditioned on e.g.
	       "__STDC__" to avoid missing initializer warnings	and relies on
	       default initialization to zero in the traditional C case.

	   *   Conversions by prototypes between fixed/floating	point values
	       and vice	versa.	The absence of these prototypes	when compiling
	       with traditional	C would	cause serious problems.	 This is a
	       subset of the possible conversion warnings, for the full	set
	       use -Wconversion.

	   *   Use of ISO C style function definitions.	 This warning inten-
	       tionally	is not issued for prototype declarations or variadic
	       functions because these ISO C features will appear in your code
	       when using libiberty's traditional C compatibility macros,
	       "PARAMS"	and "VPARAMS".	This warning is	also bypassed for
	       nested functions	because	that feature is	already	a GCC exten-
	       sion and	thus not relevant to traditional C compatibility.

       -Wdeclaration-after-statement (C	only)
	   Warn	when a declaration is found after a statement in a block.
	   This	construct, known from C++, was introduced with ISO C99 and is
	   by default allowed in GCC.  It is not supported by ISO C90 and was
	   not supported by GCC	versions before	GCC 3.0.

       -Wundef
	   Warn	if an undefined	identifier is evaluated	in an #if directive.

       -Wno-endif-labels
	   Do not warn whenever	an #else or an #endif are followed by text.

       -Wshadow
	   Warn	whenever a local variable shadows another local	variable,
	   parameter or	global variable	or whenever a built-in function	is
	   shadowed.

       -Wlarger-than-len
	   Warn	whenever an object of larger than len bytes is defined.

       -Wunsafe-loop-optimizations
	   Warn	if the loop cannot be optimized	because	the compiler could not
	   assume anything on the bounds of the	loop indices.  With -fun-
	   safe-loop-optimizations warn	if the compiler	made such assumptions.

       -Wpointer-arith
	   Warn	about anything that depends on the "size of" a function	type
	   or of "void".  GNU C	assigns	these types a size of 1, for conve-
	   nience in calculations with "void *"	pointers and pointers to func-
	   tions.

       -Wbad-function-cast (C only)
	   Warn	whenever a function call is cast to a non-matching type.  For
	   example, warn if "int malloc()" is cast to "anything	*".

       -Wc++-compat
	   Warn	about ISO C constructs that are	outside	of the common subset
	   of ISO C and	ISO C++, e.g. request for implicit conversion from
	   "void *" to a pointer to non-"void" type.

       -Wcast-qual
	   Warn	whenever a pointer is cast so as to remove a type qualifier
	   from	the target type.  For example, warn if a "const	char *"	is
	   cast	to an ordinary "char *".

       -Wcast-align
	   Warn	whenever a pointer is cast such	that the required alignment of
	   the target is increased.  For example, warn if a "char *" is	cast
	   to an "int *" on machines where integers can	only be	accessed at
	   two-	or four-byte boundaries.

       -Wwrite-strings
	   When	compiling C, give string constants the type "const
	   char[length]" so that copying the address of	one into a non-"const"
	   "char *" pointer will get a warning;	when compiling C++, warn about
	   the deprecated conversion from string literals to "char *".	This
	   warning, by default,	is enabled for C++ programs.  These warnings
	   will	help you find at compile time code that	can try	to write into
	   a string constant, but only if you have been	very careful about
	   using "const" in declarations and prototypes.  Otherwise, it	will
	   just	be a nuisance; this is why we did not make -Wall request these
	   warnings.

       -Wconversion
	   Warn	if a prototype causes a	type conversion	that is	different from
	   what	would happen to	the same argument in the absence of a proto-
	   type.  This includes	conversions of fixed point to floating and
	   vice	versa, and conversions changing	the width or signedness	of a
	   fixed point argument	except when the	same as	the default promotion.

	   Also, warn if a negative integer constant expression	is implicitly
	   converted to	an unsigned type.  For example,	warn about the assign-
	   ment	"x = -1" if "x"	is unsigned.  But do not warn about explicit
	   casts like "(unsigned) -1".

       -Wsign-compare
	   Warn	when a comparison between signed and unsigned values could
	   produce an incorrect	result when the	signed value is	converted to
	   unsigned.  This warning is also enabled by -Wextra; to get the
	   other warnings of -Wextra without this warning, use -Wextra
	   -Wno-sign-compare.

       -Waddress
	   Warn	about suspicious uses of memory	addresses. These include using
	   the address of a function in	a conditional expression, such as
	   "void func(void); if	(func)", and comparisons against the memory
	   address of a	string literal,	such as	"if (x == "abc")".  Such uses
	   typically indicate a	programmer error: the address of a function
	   always evaluates to true, so	their use in a conditional usually
	   indicate that the programmer	forgot the parentheses in a function
	   call; and comparisons against string	literals result	in unspecified
	   behavior and	are not	portable in C, so they usually indicate	that
	   the programmer intended to use "strcmp".  This warning is enabled
	   by -Wall.

       -Waggregate-return
	   Warn	if any functions that return structures	or unions are defined
	   or called.  (In languages where you can return an array, this also
	   elicits a warning.)

       -Wno-attributes
	   Do not warn if an unexpected	"__attribute__"	is used, such as
	   unrecognized	attributes, function attributes	applied	to variables,
	   etc.	 This will not stop errors for incorrect use of	supported
	   attributes.

       -Wstrict-prototypes (C only)
	   Warn	if a function is declared or defined without specifying	the
	   argument types.  (An	old-style function definition is permitted
	   without a warning if	preceded by a declaration which	specifies the
	   argument types.)

       -Wold-style-definition (C only)
	   Warn	if an old-style	function definition is used.  A	warning	is
	   given even if there is a previous prototype.

       -Wmissing-prototypes (C only)
	   Warn	if a global function is	defined	without	a previous prototype
	   declaration.	 This warning is issued	even if	the definition itself
	   provides a prototype.  The aim is to	detect global functions	that
	   fail	to be declared in header files.

       -Wmissing-declarations (C only)
	   Warn	if a global function is	defined	without	a previous declara-
	   tion.  Do so	even if	the definition itself provides a prototype.
	   Use this option to detect global functions that are not declared in
	   header files.

       -Wmissing-field-initializers
	   Warn	if a structure's initializer has some fields missing.  For
	   example, the	following code would cause such	a warning, because
	   "x.h" is implicitly zero:

		   struct s { int f, g,	h; };
		   struct s x =	{ 3, 4 };

	   This	option does not	warn about designated initializers, so the
	   following modification would	not trigger a warning:

		   struct s { int f, g,	h; };
		   struct s x =	{ .f = 3, .g = 4 };

	   This	warning	is included in -Wextra.	 To get	other -Wextra warnings
	   without this	one, use -Wextra -Wno-missing-field-initializers.

       -Wmissing-noreturn
	   Warn	about functions	which might be candidates for attribute	"nore-
	   turn".  Note	these are only possible	candidates, not	absolute ones.
	   Care	should be taken	to manually verify functions actually do not
	   ever	return before adding the "noreturn" attribute, otherwise sub-
	   tle code generation bugs could be introduced.  You will not get a
	   warning for "main" in hosted	C environments.

       -Wmissing-format-attribute
	   Warn	about function pointers	which might be candidates for "format"
	   attributes.	Note these are only possible candidates, not absolute
	   ones.  GCC will guess that function pointers	with "format"
	   attributes that are used in assignment, initialization, parameter
	   passing or return statements	should have a corresponding "format"
	   attribute in	the resulting type.  I.e. the left-hand	side of	the
	   assignment or initialization, the type of the parameter variable,
	   or the return type of the containing	function respectively should
	   also	have a "format"	attribute to avoid the warning.

	   GCC will also warn about function definitions which might be	candi-
	   dates for "format" attributes.  Again, these	are only possible can-
	   didates.  GCC will guess that "format" attributes might be appro-
	   priate for any function that	calls a	function like "vprintf"	or
	   "vscanf", but this might not	always be the case, and	some functions
	   for which "format" attributes are appropriate may not be detected.

       -Wno-multichar
	   Do not warn if a multicharacter constant ('FOOF') is	used.  Usually
	   they	indicate a typo	in the user's code, as they have implementa-
	   tion-defined	values,	and should not be used in portable code.

       -Wnormalized=<none|id|nfc|nfkc>
	   In ISO C and	ISO C++, two identifiers are different if they are
	   different sequences of characters.  However,	sometimes when charac-
	   ters	outside	the basic ASCII	character set are used,	you can	have
	   two different character sequences that look the same.  To avoid
	   confusion, the ISO 10646 standard sets out some normalization rules
	   which when applied ensure that two sequences	that look the same are
	   turned into the same	sequence.  GCC can warn	you if you are using
	   identifiers which have not been normalized; this option controls
	   that	warning.

	   There are four levels of warning that GCC supports.	The default is
	   -Wnormalized=nfc, which warns about any identifier which is not in
	   the ISO 10646 "C" normalized	form, NFC.  NFC	is the recommended
	   form	for most uses.

	   Unfortunately, there	are some characters which ISO C	and ISO	C++
	   allow in identifiers	that when turned into NFC aren't allowable as
	   identifiers.	 That is, there's no way to use	these symbols in por-
	   table ISO C or C++ and have all your	identifiers in NFC.  -Wnormal-
	   ized=id suppresses the warning for these characters.	 It is hoped
	   that	future versions	of the standards involved will correct this,
	   which is why	this option is not the default.

	   You can switch the warning off for all characters by	writing	-Wnor-
	   malized=none.  You would only want to do this if you	were using
	   some	other normalization scheme (like "D"), because otherwise you
	   can easily create bugs that are literally impossible	to see.

	   Some	characters in ISO 10646	have distinct meanings but look	iden-
	   tical in some fonts or display methodologies, especially once for-
	   matting has been applied.  For instance "\u207F", "SUPERSCRIPT
	   LATIN SMALL LETTER N", will display just like a regular "n" which
	   has been placed in a	superscript.  ISO 10646	defines	the NFKC nor-
	   malization scheme to	convert	all these into a standard form as
	   well, and GCC will warn if your code	is not in NFKC if you use
	   -Wnormalized=nfkc.  This warning is comparable to warning about
	   every identifier that contains the letter O because it might	be
	   confused with the digit 0, and so is	not the	default, but may be
	   useful as a local coding convention if the programming environment
	   is unable to	be fixed to display these characters distinctly.

       -Wno-deprecated-declarations
	   Do not warn about uses of functions,	variables, and types marked as
	   deprecated by using the "deprecated"	attribute.

       -Wno-overflow
	   Do not warn about compile-time overflow in constant expressions.

       -Woverride-init
	   Warn	if an initialized field	without	side effects is	overridden
	   when	using designated initializers.

	   This	warning	is included in -Wextra.	 To get	other -Wextra warnings
	   without this	one, use -Wextra -Wno-override-init.

       -Wpacked
	   Warn	if a structure is given	the packed attribute, but the packed
	   attribute has no effect on the layout or size of the	structure.
	   Such	structures may be mis-aligned for little benefit.  For
	   instance, in	this code, the variable	"f.x" in "struct bar" will be
	   misaligned even though "struct bar" does not	itself have the	packed
	   attribute:

		   struct foo {
		     int x;
		     char a, b,	c, d;
		   } __attribute__((packed));
		   struct bar {
		     char z;
		     struct foo	f;
		   };

       -Wpadded
	   Warn	if padding is included in a structure, either to align an ele-
	   ment	of the structure or to align the whole structure.  Sometimes
	   when	this happens it	is possible to rearrange the fields of the
	   structure to	reduce the padding and so make the structure smaller.

       -Wredundant-decls
	   Warn	if anything is declared	more than once in the same scope, even
	   in cases where multiple declaration is valid	and changes nothing.

       -Wnested-externs	(C only)
	   Warn	if an "extern" declaration is encountered within a function.

       -Wunreachable-code
	   Warn	if the compiler	detects	that code will never be	executed.

	   This	option is intended to warn when	the compiler detects that at
	   least a whole line of source	code will never	be executed, because
	   some	condition is never satisfied or	because	it is after a proce-
	   dure	that never returns.

	   It is possible for this option to produce a warning even though
	   there are circumstances under which part of the affected line can
	   be executed,	so care	should be taken	when removing apparently-
	   unreachable code.

	   For instance, when a	function is inlined, a warning may mean	that
	   the line is unreachable in only one inlined copy of the function.

	   This	option is not made part	of -Wall because in a debugging	ver-
	   sion	of a program there is often substantial	code which checks cor-
	   rect	functioning of the program and is, hopefully, unreachable
	   because the program does work.  Another common use of unreachable
	   code	is to provide behavior which is	selectable at compile-time.

       -Winline
	   Warn	if a function can not be inlined and it	was declared as
	   inline.  Even with this option, the compiler	will not warn about
	   failures to inline functions	declared in system headers.

	   The compiler	uses a variety of heuristics to	determine whether or
	   not to inline a function.  For example, the compiler	takes into
	   account the size of the function being inlined and the amount of
	   inlining that has already been done in the current function.
	   Therefore, seemingly	insignificant changes in the source program
	   can cause the warnings produced by -Winline to appear or disappear.

       -Wno-invalid-offsetof (C++ only)
	   Suppress warnings from applying the offsetof	macro to a non-POD
	   type.  According to the 1998	ISO C++	standard, applying offsetof to
	   a non-POD type is undefined.	 In existing C++ implementations, how-
	   ever, offsetof typically gives meaningful results even when applied
	   to certain kinds of non-POD types. (Such as a simple	struct that
	   fails to be a POD type only by virtue of having a constructor.)
	   This	flag is	for users who are aware	that they are writing non-
	   portable code and who have deliberately chosen to ignore the	warn-
	   ing about it.

	   The restrictions on offsetof	may be relaxed in a future version of
	   the C++ standard.

       -Wno-int-to-pointer-cast	(C only)
	   Suppress warnings from casts	to pointer type	of an integer of a
	   different size.

       -Wno-pointer-to-int-cast	(C only)
	   Suppress warnings from casts	from a pointer to an integer type of a
	   different size.

       -Winvalid-pch
	   Warn	if a precompiled header	is found in the	search path but	can't
	   be used.

       -Wlong-long
	   Warn	if long	long type is used.  This is default.  To inhibit the
	   warning messages, use -Wno-long-long.  Flags	-Wlong-long and
	   -Wno-long-long are taken into account only when -pedantic flag is
	   used.

       -Wvariadic-macros
	   Warn	if variadic macros are used in pedantic	ISO C90	mode, or the
	   GNU alternate syntax	when in	pedantic ISO C99 mode.	This is
	   default.  To	inhibit	the warning messages, use -Wno-vari-
	   adic-macros.

       -Wvolatile-register-var
	   Warn	if a register variable is declared volatile.  The volatile
	   modifier does not inhibit all optimizations that may	eliminate
	   reads and/or	writes to register variables.

       -Wdisabled-optimization
	   Warn	if a requested optimization pass is disabled.  This warning
	   does	not generally indicate that there is anything wrong with your
	   code; it merely indicates that GCC's	optimizers were	unable to han-
	   dle the code	effectively.  Often, the problem is that your code is
	   too big or too complex; GCC will refuse to optimize programs	when
	   the optimization itself is likely to	take inordinate	amounts	of
	   time.

       -Wpointer-sign
	   Warn	for pointer argument passing or	assignment with	different
	   signedness.	This option is only supported for C.  It is implied by
	   -Wall and by	-pedantic, which can be	disabled with
	   -Wno-pointer-sign.

       -Werror
	   Make	all warnings into errors.

       -Werror=
	   Make	the specified warning into an errors.  The specifier for a
	   warning is appended,	for example -Werror=switch turns the warnings
	   controlled by -Wswitch into errors.	This switch takes a negative
	   form, to be used to negate -Werror for specific warnings, for exam-
	   ple -Wno-error=switch makes -Wswitch	warnings not be	errors,	even
	   when	-Werror	is in effect.  You can use the -fdiagnos-
	   tics-show-option option to have each	controllable warning amended
	   with	the option which controls it, to determine what	to use with
	   this	option.

	   Note	that specifying	-Werror=foo automatically implies -Wfoo.  How-
	   ever, -Wno-error=foo	does not imply anything.

       -Wstack-protector
	   This	option is only active when -fstack-protector is	active.	 It
	   warns about functions that will not be protected against stack
	   smashing.

       -Woverlength-strings
	   Warn	about string constants which are longer	than the "minimum max-
	   imum" length	specified in the C standard.  Modern compilers gener-
	   ally	allow string constants which are much longer than the stan-
	   dard's minimum limit, but very portable programs should avoid using
	   longer strings.

	   The limit applies after string constant concatenation, and does not
	   count the trailing NUL.  In C89, the	limit was 509 characters; in
	   C99,	it was raised to 4095.	C++98 does not specify a normative
	   minimum maximum, so we do not diagnose overlength strings in	C++.

	   This	option is implied by -pedantic,	and can	be disabled with
	   -Wno-overlength-strings.

       Options for Debugging Your Program or GCC

       GCC has various special options that are	used for debugging either your
       program or GCC:

       -g  Produce debugging information in the	operating system's native for-
	   mat (stabs, COFF, XCOFF, or DWARF 2).  GDB can work with this
	   debugging information.

	   On most systems that	use stabs format, -g enables use of extra
	   debugging information that only GDB can use;	this extra information
	   makes debugging work	better in GDB but will probably	make other
	   debuggers crash or refuse to	read the program.  If you want to con-
	   trol	for certain whether to generate	the extra information, use
	   -gstabs+, -gstabs, -gxcoff+,	-gxcoff, or -gvms (see below).

	   GCC allows you to use -g with -O.  The shortcuts taken by optimized
	   code	may occasionally produce surprising results: some variables
	   you declared	may not	exist at all; flow of control may briefly move
	   where you did not expect it;	some statements	may not	be executed
	   because they	compute	constant results or their values were already
	   at hand; some statements may	execute	in different places because
	   they	were moved out of loops.

	   Nevertheless	it proves possible to debug optimized output.  This
	   makes it reasonable to use the optimizer for	programs that might
	   have	bugs.

	   The following options are useful when GCC is	generated with the
	   capability for more than one	debugging format.

       -ggdb
	   Produce debugging information for use by GDB.  This means to	use
	   the most expressive format available	(DWARF 2, stabs, or the	native
	   format if neither of	those are supported), including	GDB extensions
	   if at all possible.

       -gstabs
	   Produce debugging information in stabs format (if that is sup-
	   ported), without GDB	extensions.  This is the format	used by	DBX on
	   most	BSD systems.  On MIPS, Alpha and System	V Release 4 systems
	   this	option produces	stabs debugging	output which is	not understood
	   by DBX or SDB.  On System V Release 4 systems this option requires
	   the GNU assembler.

       -feliminate-unused-debug-symbols
	   Produce debugging information in stabs format (if that is sup-
	   ported), for	only symbols that are actually used.

       -femit-class-debug-always
	   Instead of emitting debugging information for a C++ class in	only
	   one object file, emit it in all object files	using the class.  This
	   option should be used only with debuggers that are unable to	handle
	   the way GCC normally	emits debugging	information for	classes
	   because using this option will increase the size of debugging
	   information by as much as a factor of two.

       -gstabs+
	   Produce debugging information in stabs format (if that is sup-
	   ported), using GNU extensions understood only by the	GNU debugger
	   (GDB).  The use of these extensions is likely to make other debug-
	   gers	crash or refuse	to read	the program.

       -gcoff
	   Produce debugging information in COFF format	(if that is sup-
	   ported).  This is the format	used by	SDB on most System V systems
	   prior to System V Release 4.

       -gxcoff
	   Produce debugging information in XCOFF format (if that is sup-
	   ported).  This is the format	used by	the DBX	debugger on IBM
	   RS/6000 systems.

       -gxcoff+
	   Produce debugging information in XCOFF format (if that is sup-
	   ported), using GNU extensions understood only by the	GNU debugger
	   (GDB).  The use of these extensions is likely to make other debug-
	   gers	crash or refuse	to read	the program, and may cause assemblers
	   other than the GNU assembler	(GAS) to fail with an error.

       -gdwarf-2
	   Produce debugging information in DWARF version 2 format (if that is
	   supported).	This is	the format used	by DBX on IRIX 6.  With	this
	   option, GCC uses features of	DWARF version 3	when they are useful;
	   version 3 is	upward compatible with version 2, but may still	cause
	   problems for	older debuggers.

       -gvms
	   Produce debugging information in VMS	debug format (if that is sup-
	   ported).  This is the format	used by	DEBUG on VMS systems.

       -glevel
       -ggdblevel
       -gstabslevel
       -gcofflevel
       -gxcofflevel
       -gvmslevel
	   Request debugging information and also use level to specify how
	   much	information.  The default level	is 2.

	   Level 1 produces minimal information, enough	for making backtraces
	   in parts of the program that	you don't plan to debug.  This
	   includes descriptions of functions and external variables, but no
	   information about local variables and no line numbers.

	   Level 3 includes extra information, such as all the macro defini-
	   tions present in the	program.  Some debuggers support macro expan-
	   sion	when you use -g3.

	   -gdwarf-2 does not accept a concatenated debug level, because GCC
	   used	to support an option -gdwarf that meant	to generate debug
	   information in version 1 of the DWARF format	(which is very differ-
	   ent from version 2),	and it would have been too confusing.  That
	   debug format	is long	obsolete, but the option cannot	be changed
	   now.	 Instead use an	additional -glevel option to change the	debug
	   level for DWARF2.

       -feliminate-dwarf2-dups
	   Compress DWARF2 debugging information by eliminating	duplicated
	   information about each symbol.  This	option only makes sense	when
	   generating DWARF2 debugging information with	-gdwarf-2.

       -p  Generate extra code to write	profile	information suitable for the
	   analysis program prof.  You must use	this option when compiling the
	   source files	you want data about, and you must also use it when
	   linking.

       -pg Generate extra code to write	profile	information suitable for the
	   analysis program gprof.  You	must use this option when compiling
	   the source files you	want data about, and you must also use it when
	   linking.

       -Q  Makes the compiler print out	each function name as it is compiled,
	   and print some statistics about each	pass when it finishes.

       -ftime-report
	   Makes the compiler print some statistics about the time consumed by
	   each	pass when it finishes.

       -fmem-report
	   Makes the compiler print some statistics about permanent memory
	   allocation when it finishes.

       -fprofile-arcs
	   Add code so that program flow arcs are instrumented.	 During	execu-
	   tion	the program records how	many times each	branch and call	is
	   executed and	how many times it is taken or returns.	When the com-
	   piled program exits it saves	this data to a file called aux-
	   name.gcda for each source file.  The	data may be used for profile-
	   directed optimizations (-fbranch-probabilities), or for test	cover-
	   age analysis	(-ftest-coverage).  Each object	file's auxname is gen-
	   erated from the name	of the output file, if explicitly specified
	   and it is not the final executable, otherwise it is the basename of
	   the source file.  In	both cases any suffix is removed (e.g.
	   foo.gcda for	input file dir/foo.c, or dir/foo.gcda for output file
	   specified as	-o dir/foo.o).

       --coverage
	   This	option is used to compile and link code	instrumented for cov-
	   erage analysis.  The	option is a synonym for	-fprofile-arcs
	   -ftest-coverage (when compiling) and	-lgcov (when linking).	See
	   the documentation for those options for more	details.

	   *   Compile the source files	with -fprofile-arcs plus optimization
	       and code	generation options.  For test coverage analysis, use
	       the additional -ftest-coverage option.  You do not need to pro-
	       file every source file in a program.

	   *   Link your object	files with -lgcov or -fprofile-arcs (the lat-
	       ter implies the former).

	   *   Run the program on a representative workload to generate	the
	       arc profile information.	 This may be repeated any number of
	       times.  You can run concurrent instances	of your	program, and
	       provided	that the file system supports locking, the data	files
	       will be correctly updated.  Also	"fork" calls are detected and
	       correctly handled (double counting will not happen).

	   *   For profile-directed optimizations, compile the source files
	       again with the same optimization	and code generation options
	       plus -fbranch-probabilities.

	   *   For test	coverage analysis, use gcov to produce human readable
	       information from	the .gcno and .gcda files.  Refer to the gcov
	       documentation for further information.

	   With	-fprofile-arcs,	for each function of your program GCC creates
	   a program flow graph, then finds a spanning tree for	the graph.
	   Only	arcs that are not on the spanning tree have to be instru-
	   mented: the compiler	adds code to count the number of times that
	   these arcs are executed.  When an arc is the	only exit or only
	   entrance to a block,	the instrumentation code can be	added to the
	   block; otherwise, a new basic block must be created to hold the
	   instrumentation code.

       -ftest-coverage
	   Produce a notes file	that the gcov code-coverage utility can	use to
	   show	program	coverage.  Each	source file's note file	is called aux-
	   name.gcno.  Refer to	the -fprofile-arcs option above	for a descrip-
	   tion	of auxname and instructions on how to generate test coverage
	   data.  Coverage data	will match the source files more closely, if
	   you do not optimize.

       -dletters
       -fdump-rtl-pass
	   Says	to make	debugging dumps	during compilation at times specified
	   by letters.	  This is used for debugging the RTL-based passes of
	   the compiler.  The file names for most of the dumps are made	by
	   appending a pass number and a word to the dumpname.	dumpname is
	   generated from the name of the output file, if explicitly specified
	   and it is not an executable,	otherwise it is	the basename of	the
	   source file.

	   Most	debug dumps can	be enabled either passing a letter to the -d
	   option, or with a long -fdump-rtl switch; here are the possible
	   letters for use in letters and pass,	and their meanings:

	   -dA Annotate	the assembler output with miscellaneous	debugging
	       information.

	   -dB
	   -fdump-rtl-bbro
	       Dump after block	reordering, to file.148r.bbro.

	   -dc
	   -fdump-rtl-combine
	       Dump after instruction combination, to the file file.129r.com-
	       bine.

	   -dC
	   -fdump-rtl-ce1
	   -fdump-rtl-ce2
	       -dC and -fdump-rtl-ce1 enable dumping after the first if	con-
	       version,	to the file file.117r.ce1.  -dC	and -fdump-rtl-ce2
	       enable dumping after the	second if conversion, to the file
	       file.130r.ce2.

	   -dd
	   -fdump-rtl-btl
	   -fdump-rtl-dbr
	       -dd and -fdump-rtl-btl enable dumping after branch target load
	       optimization, to	file.31.btl.  -dd and -fdump-rtl-dbr enable
	       dumping after delayed branch scheduling,	to file.36.dbr.

	   -dD Dump all	macro definitions, at the end of preprocessing,	in
	       addition	to normal output.

	   -dE
	   -fdump-rtl-ce3
	       Dump after the third if conversion, to file.146r.ce3.

	   -df
	   -fdump-rtl-cfg
	   -fdump-rtl-life
	       -df and -fdump-rtl-cfg enable dumping after control and data
	       flow analysis, to file.116r.cfg.	 -df and -fdump-rtl-cfg	enable
	       dumping dump after life analysis, to file.128r.life1 and
	       file.135r.life2.

	   -dg
	   -fdump-rtl-greg
	       Dump after global register allocation, to file.139r.greg.

	   -dG
	   -fdump-rtl-gcse
	   -fdump-rtl-bypass
	       -dG and -fdump-rtl-gcse enable dumping after GCSE, to
	       file.114r.gcse.	-dG and	-fdump-rtl-bypass enable dumping after
	       jump bypassing and control flow optimizations, to
	       file.115r.bypass.

	   -dh
	   -fdump-rtl-eh
	       Dump after finalization of EH handling code, to file.02.eh.

	   -di
	   -fdump-rtl-sibling
	       Dump after sibling call optimizations, to file.106r.sibling.

	   -dj
	   -fdump-rtl-jump
	       Dump after the first jump optimization, to file.112r.jump.

	   -dk
	   -fdump-rtl-stack
	       Dump after conversion from registers to stack, to
	       file.152r.stack.

	   -dl
	   -fdump-rtl-lreg
	       Dump after local	register allocation, to	file.138r.lreg.

	   -dL
	   -fdump-rtl-loop2
	       -dL and -fdump-rtl-loop2	enable dumping after the loop opti-
	       mization	pass, to file.119r.loop2, file.120r.loop2_init,
	       file.121r.loop2_invariant, and file.125r.loop2_done.

	   -dm
	   -fdump-rtl-sms
	       Dump after modulo scheduling, to	file.136r.sms.

	   -dM
	   -fdump-rtl-mach
	       Dump after performing the machine dependent reorganization
	       pass, to	file.155r.mach.

	   -dn
	   -fdump-rtl-rnreg
	       Dump after register renumbering,	to file.147r.rnreg.

	   -dN
	   -fdump-rtl-regmove
	       Dump after the register move pass, to file.132r.regmove.

	   -do
	   -fdump-rtl-postreload
	       Dump after post-reload optimizations, to	file.24.postreload.

	   -dr
	   -fdump-rtl-expand
	       Dump after RTL generation, to file.104r.expand.

	   -dR
	   -fdump-rtl-sched2
	       Dump after the second scheduling	pass, to file.150r.sched2.

	   -ds
	   -fdump-rtl-cse
	       Dump after CSE (including the jump optimization that sometimes
	       follows CSE), to	file.113r.cse.

	   -dS
	   -fdump-rtl-sched
	       Dump after the first scheduling pass, to	file.21.sched.

	   -dt
	   -fdump-rtl-cse2
	       Dump after the second CSE pass (including the jump optimization
	       that sometimes follows CSE), to file.127r.cse2.

	   -dT
	   -fdump-rtl-tracer
	       Dump after running tracer, to file.118r.tracer.

	   -dV
	   -fdump-rtl-vpt
	   -fdump-rtl-vartrack
	       -dV and -fdump-rtl-vpt enable dumping after the value profile
	       transformations,	to file.10.vpt.	 -dV and -fdump-rtl-vartrack
	       enable dumping after variable tracking, to file.154r.vartrack.

	   -dw
	   -fdump-rtl-flow2
	       Dump after the second flow pass,	to file.142r.flow2.

	   -dz
	   -fdump-rtl-peephole2
	       Dump after the peephole pass, to	file.145r.peephole2.

	   -dZ
	   -fdump-rtl-web
	       Dump after live range splitting,	to file.126r.web.

	   -da
	   -fdump-rtl-all
	       Produce all the dumps listed above.

	   -dH Produce a core dump whenever an error occurs.

	   -dm Print statistics	on memory usage, at the	end of the run,	to
	       standard	error.

	   -dp Annotate	the assembler output with a comment indicating which
	       pattern and alternative was used.  The length of	each instruc-
	       tion is also printed.

	   -dP Dump the	RTL in the assembler output as a comment before	each
	       instruction.  Also turns	on -dp annotation.

	   -dv For each	of the other indicated dump files (either with -d or
	       -fdump-rtl-pass), dump a	representation of the control flow
	       graph suitable for viewing with VCG to file.pass.vcg.

	   -dx Just generate RTL for a function	instead	of compiling it.  Usu-
	       ally used with r	(-fdump-rtl-expand).

	   -dy Dump debugging information during parsing, to standard error.

       -fdump-noaddr
	   When	doing debugging	dumps (see -d option above), suppress address
	   output.  This makes it more feasible	to use diff on debugging dumps
	   for compiler	invocations with different compiler binaries and/or
	   different text / bss	/ data / heap /	stack /	dso start locations.

       -fdump-unnumbered
	   When	doing debugging	dumps (see -d option above), suppress instruc-
	   tion	numbers, line number note and address output.  This makes it
	   more	feasible to use	diff on	debugging dumps	for compiler invoca-
	   tions with different	options, in particular with and	without	-g.

       -fdump-translation-unit (C++ only)
       -fdump-translation-unit-options (C++ only)
	   Dump	a representation of the	tree structure for the entire transla-
	   tion	unit to	a file.	 The file name is made by appending .tu	to the
	   source file name.  If the -options form is used, options controls
	   the details of the dump as described	for the	-fdump-tree options.

       -fdump-class-hierarchy (C++ only)
       -fdump-class-hierarchy-options (C++ only)
	   Dump	a representation of each class's hierarchy and virtual func-
	   tion	table layout to	a file.	 The file name is made by appending
	   .class to the source	file name.  If the -options form is used,
	   options controls the	details	of the dump as described for the
	   -fdump-tree options.

       -fdump-ipa-switch
	   Control the dumping at various stages of inter-procedural analysis
	   language tree to a file.  The file name is generated	by appending a
	   switch specific suffix to the source	file name.  The	following
	   dumps are possible:

	   all Enables all inter-procedural analysis dumps; currently the only
	       produced	dump is	the cgraph dump.

	   cgraph
	       Dumps information about call-graph optimization,	unused func-
	       tion removal, and inlining decisions.

       -fdump-tree-switch
       -fdump-tree-switch-options
	   Control the dumping at various stages of processing the intermedi-
	   ate language	tree to	a file.	 The file name is generated by append-
	   ing a switch	specific suffix	to the source file name.  If the
	   -options form is used, options is a list of - separated options
	   that	control	the details of the dump.  Not all options are applica-
	   ble to all dumps, those which are not meaningful will be ignored.
	   The following options are available

	   address
	       Print the address of each node.	Usually	this is	not meaningful
	       as it changes according to the environment and source file.
	       Its primary use is for tying up a dump file with	a debug	envi-
	       ronment.

	   slim
	       Inhibit dumping of members of a scope or	body of	a function
	       merely because that scope has been reached.  Only dump such
	       items when they are directly reachable by some other path.
	       When dumping pretty-printed trees, this option inhibits dumping
	       the bodies of control structures.

	   raw Print a raw representation of the tree.	By default, trees are
	       pretty-printed into a C-like representation.

	   details
	       Enable more detailed dumps (not honored by every	dump option).

	   stats
	       Enable dumping various statistics about the pass	(not honored
	       by every	dump option).

	   blocks
	       Enable showing basic block boundaries (disabled in raw dumps).

	   vops
	       Enable showing virtual operands for every statement.

	   lineno
	       Enable showing line numbers for statements.

	   uid Enable showing the unique ID ("DECL_UID") for each variable.

	   all Turn on all options, except raw,	slim and lineno.

	   The following tree dumps are	possible:

	   original
	       Dump before any tree based optimization,	to file.original.

	   optimized
	       Dump after all tree based optimization, to file.optimized.

	   inlined
	       Dump after function inlining, to	file.inlined.

	   gimple
	       Dump each function before and after the gimplification pass to
	       a file.	The file name is made by appending .gimple to the
	       source file name.

	   cfg Dump the	control	flow graph of each function to a file.	The
	       file name is made by appending .cfg to the source file name.

	   vcg Dump the	control	flow graph of each function to a file in VCG
	       format.	The file name is made by appending .vcg	to the source
	       file name.  Note	that if	the file contains more than one	func-
	       tion, the generated file	cannot be used directly	by VCG.	 You
	       will need to cut	and paste each function's graph	into its own
	       separate	file first.

	   ch  Dump each function after	copying	loop headers.  The file	name
	       is made by appending .ch	to the source file name.

	   ssa Dump SSA	related	information to a file.	The file name is made
	       by appending .ssa to the	source file name.

	   salias
	       Dump structure aliasing variable	information to a file.	This
	       file name is made by appending .salias to the source file name.

	   alias
	       Dump aliasing information for each function.  The file name is
	       made by appending .alias	to the source file name.

	   ccp Dump each function after	CCP.  The file name is made by append-
	       ing .ccp	to the source file name.

	   storeccp
	       Dump each function after	STORE-CCP.  The	file name is made by
	       appending .storeccp to the source file name.

	   pre Dump trees after	partial	redundancy elimination.	 The file name
	       is made by appending .pre to the	source file name.

	   fre Dump trees after	full redundancy	elimination.  The file name is
	       made by appending .fre to the source file name.

	   copyprop
	       Dump trees after	copy propagation.  The file name is made by
	       appending .copyprop to the source file name.

	   store_copyprop
	       Dump trees after	store copy-propagation.	 The file name is made
	       by appending .store_copyprop to the source file name.

	   dce Dump each function after	dead code elimination.	The file name
	       is made by appending .dce to the	source file name.

	   mudflap
	       Dump each function after	adding mudflap instrumentation.	 The
	       file name is made by appending .mudflap to the source file
	       name.

	   sra Dump each function after	performing scalar replacement of
	       aggregates.  The	file name is made by appending .sra to the
	       source file name.

	   sink
	       Dump each function after	performing code	sinking.  The file
	       name is made by appending .sink to the source file name.

	   dom Dump each function after	applying dominator tree	optimizations.
	       The file	name is	made by	appending .dom to the source file
	       name.

	   dse Dump each function after	applying dead store elimination.  The
	       file name is made by appending .dse to the source file name.

	   phiopt
	       Dump each function after	optimizing PHI nodes into straightline
	       code.  The file name is made by appending .phiopt to the	source
	       file name.

	   forwprop
	       Dump each function after	forward	propagating single use vari-
	       ables.  The file	name is	made by	appending .forwprop to the
	       source file name.

	   copyrename
	       Dump each function after	applying the copy rename optimization.
	       The file	name is	made by	appending .copyrename to the source
	       file name.

	   nrv Dump each function after	applying the named return value	opti-
	       mization	on generic trees.  The file name is made by appending
	       .nrv to the source file name.

	   vect
	       Dump each function after	applying vectorization of loops.  The
	       file name is made by appending .vect to the source file name.

	   vrp Dump each function after	Value Range Propagation	(VRP).	The
	       file name is made by appending .vrp to the source file name.

	   all Enable all the available	tree dumps with	the flags provided in
	       this option.

       -ftree-vectorizer-verbose=n
	   This	option controls	the amount of debugging	output the vectorizer
	   prints.  This information is	written	to standard error, unless
	   -fdump-tree-all or -fdump-tree-vect is specified, in	which case it
	   is output to	the usual dump listing file, .vect.  For n=0 no	diag-
	   nostic information is reported.  If n=1 the vectorizer reports each
	   loop	that got vectorized, and the total number of loops that	got
	   vectorized.	If n=2 the vectorizer also reports non-vectorized
	   loops that passed the first analysis	phase (vect_analyze_loop_form)
	   - i.e. countable, inner-most, single-bb, single-entry/exit loops.
	   This	is the same verbosity level that -fdump-tree-vect-stats	uses.
	   Higher verbosity levels mean	either more information	dumped for
	   each	reported loop, or same amount of information reported for more
	   loops: If n=3, alignment related information	is added to the
	   reports.  If	n=4, data-references related information (e.g. memory
	   dependences,	memory access-patterns)	is added to the	reports.  If
	   n=5,	the vectorizer reports also non-vectorized inner-most loops
	   that	did not	pass the first analysis	phase (i.e. may	not be count-
	   able, or may	have complicated control-flow).	 If n=6, the vector-
	   izer	reports	also non-vectorized nested loops.  For n=7, all	the
	   information the vectorizer generates	during its analysis and	trans-
	   formation is	reported.  This	is the same verbosity level that
	   -fdump-tree-vect-details uses.

       -frandom-seed=string
	   This	option provides	a seed that GCC	uses when it would otherwise
	   use random numbers.	It is used to generate certain symbol names
	   that	have to	be different in	every compiled file.  It is also used
	   to place unique stamps in coverage data files and the object	files
	   that	produce	them.  You can use the -frandom-seed option to produce
	   reproducibly	identical object files.

	   The string should be	different for every file you compile.

       -fsched-verbose=n
	   On targets that use instruction scheduling, this option controls
	   the amount of debugging output the scheduler	prints.	 This informa-
	   tion	is written to standard error, unless -dS or -dR	is specified,
	   in which case it is output to the usual dump	listing	file, .sched
	   or .sched2 respectively.  However for n greater than	nine, the out-
	   put is always printed to standard error.

	   For n greater than zero, -fsched-verbose outputs the	same informa-
	   tion	as -dRS.  For n	greater	than one, it also output basic block
	   probabilities, detailed ready list information and unit/insn	info.
	   For n greater than two, it includes RTL at abort point, control-
	   flow	and regions info.  And for n over four,	-fsched-verbose	also
	   includes dependence info.

       -save-temps
	   Store the usual "temporary" intermediate files permanently; place
	   them	in the current directory and name them based on	the source
	   file.  Thus,	compiling foo.c	with -c	-save-temps would produce
	   files foo.i and foo.s, as well as foo.o.  This creates a prepro-
	   cessed foo.i	output file even though	the compiler now normally uses
	   an integrated preprocessor.

	   When	used in	combination with the -x	command	line option,
	   -save-temps is sensible enough to avoid over	writing	an input
	   source file with the	same extension as an intermediate file.	 The
	   corresponding intermediate file may be obtained by renaming the
	   source file before using -save-temps.

       -time
	   Report the CPU time taken by	each subprocess	in the compilation
	   sequence.  For C source files, this is the compiler proper and
	   assembler (plus the linker if linking is done).  The	output looks
	   like	this:

		   # cc1 0.12 0.01
		   # as	0.00 0.01

	   The first number on each line is the	"user time", that is time
	   spent executing the program itself.	The second number is "system
	   time", time spent executing operating system	routines on behalf of
	   the program.	 Both numbers are in seconds.

       -fvar-tracking
	   Run variable	tracking pass.	It computes where variables are	stored
	   at each position in code.  Better debugging information is then
	   generated (if the debugging information format supports this	infor-
	   mation).

	   It is enabled by default when compiling with	optimization (-Os, -O,
	   -O2,	...), debugging	information (-g) and the debug info format
	   supports it.

       -print-file-name=library
	   Print the full absolute name	of the library file library that would
	   be used when	linking---and don't do anything	else.  With this
	   option, GCC does not	compile	or link	anything; it just prints the
	   file	name.

       -print-multi-directory
	   Print the directory name corresponding to the multilib selected by
	   any other switches present in the command line.  This directory is
	   supposed to exist in	GCC_EXEC_PREFIX.

       -print-multi-lib
	   Print the mapping from multilib directory names to compiler
	   switches that enable	them.  The directory name is separated from
	   the switches	by ;, and each switch starts with an @}	instead	of the
	   @samp{-, without spaces between multiple switches.  This is sup-
	   posed to ease shell-processing.

       -print-prog-name=program
	   Like	-print-file-name, but searches for a program such as cpp.

       -print-libgcc-file-name
	   Same	as -print-file-name=libgcc.a.

	   This	is useful when you use -nostdlib or -nodefaultlibs but you do
	   want	to link	with libgcc.a.	You can	do

		   gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

       -print-search-dirs
	   Print the name of the configured installation directory and a list
	   of program and library directories gcc will search---and don't do
	   anything else.

	   This	is useful when gcc prints the error message installation prob-
	   lem,	cannot exec cpp0: No such file or directory.  To resolve this
	   you either need to put cpp0 and the other compiler components where
	   gcc expects to find them, or	you can	set the	environment variable
	   GCC_EXEC_PREFIX to the directory where you installed	them.  Don't
	   forget the trailing /.

       -dumpmachine
	   Print the compiler's	target machine (for example,
	   i686-pc-linux-gnu)---and don't do anything else.

       -dumpversion
	   Print the compiler version (for example, 3.0)---and don't do	any-
	   thing else.

       -dumpspecs
	   Print the compiler's	built-in specs---and don't do anything else.
	   (This is used when GCC itself is being built.)

       -feliminate-unused-debug-types
	   Normally, when producing DWARF2 output, GCC will emit debugging
	   information for all types declared in a compilation unit, regard-
	   less	of whether or not they are actually used in that compilation
	   unit.  Sometimes this is useful, such as if,	in the debugger, you
	   want	to cast	a value	to a type that is not actually used in your
	   program (but	is declared).  More often, however, this results in a
	   significant amount of wasted	space.	With this option, GCC will
	   avoid producing debug symbol	output for types that are nowhere used
	   in the source file being compiled.

       Options That Control Optimization

       These options control various sorts of optimizations.

       Without any optimization	option,	the compiler's goal is to reduce the
       cost of compilation and to make debugging produce the expected results.
       Statements are independent: if you stop the program with	a breakpoint
       between statements, you can then	assign a new value to any variable or
       change the program counter to any other statement in the	function and
       get exactly the results you would expect	from the source	code.

       Turning on optimization flags makes the compiler	attempt	to improve the
       performance and/or code size at the expense of compilation time and
       possibly	the ability to debug the program.

       The compiler performs optimization based	on the knowledge it has	of the
       program.	 Optimization levels -O	and above, in particular, enable unit-
       at-a-time mode, which allows the	compiler to consider information
       gained from later functions in the file when compiling a	function.
       Compiling multiple files	at once	to a single output file	in unit-at-a-
       time mode allows	the compiler to	use information	gained from all	of the
       files when compiling each of them.

       Not all optimizations are controlled directly by	a flag.	 Only opti-
       mizations that have a flag are listed.

       -O
       -O1 Optimize.  Optimizing compilation takes somewhat more time, and a
	   lot more memory for a large function.

	   With	-O, the	compiler tries to reduce code size and execution time,
	   without performing any optimizations	that take a great deal of com-
	   pilation time.

	   -O turns on the following optimization flags: -fdefer-pop -fde-
	   layed-branch	-fguess-branch-probability -fcprop-registers -fif-con-
	   version -fif-conversion2 -ftree-ccp -ftree-dce -ftree-domina-
	   tor-opts -ftree-dse -ftree-ter -ftree-lrs -ftree-sra	-ftree-copyre-
	   name	-ftree-fre -ftree-ch -funit-at-a-time -fmerge-constants

	   -O also turns on -fomit-frame-pointer on machines where doing so
	   does	not interfere with debugging.

       -O2 Optimize even more.	GCC performs nearly all	supported optimiza-
	   tions that do not involve a space-speed tradeoff.  The compiler
	   does	not perform loop unrolling or function inlining	when you spec-
	   ify -O2.  As	compared to -O,	this option increases both compilation
	   time	and the	performance of the generated code.

	   -O2 turns on	all optimization flags specified by -O.	 It also turns
	   on the following optimization flags:	-fthread-jumps -fcrossjumping
	   -foptimize-sibling-calls -fcse-follow-jumps	-fcse-skip-blocks
	   -fgcse  -fgcse-lm -fexpensive-optimizations -frerun-cse-after-loop
	   -fcaller-saves -fpeephole2 -fschedule-insns	-fschedule-insns2
	   -fsched-interblock  -fsched-spec -fregmove -fstrict-aliasing
	   -fstrict-overflow -fdelete-null-pointer-checks -freorder-blocks
	   -freorder-functions -falign-functions  -falign-jumps	-falign-loops
	   -falign-labels -ftree-vrp -ftree-pre

	   Please note the warning under -fgcse	about invoking -O2 on programs
	   that	use computed gotos.

	   -O2 doesn't turn on -ftree-vrp for the Ada compiler.	 This option
	   must	be explicitly specified	on the command line to be enabled for
	   the Ada compiler.

       -O3 Optimize yet	more.  -O3 turns on all	optimizations specified	by -O2
	   and also turns on the -finline-functions, -funswitch-loops and
	   -fgcse-after-reload options.

       -O0 Do not optimize.  This is the default.

       -Os Optimize for	size.  -Os enables all -O2 optimizations that do not
	   typically increase code size.  It also performs further optimiza-
	   tions designed to reduce code size.

	   -Os disables	the following optimization flags: -falign-functions
	   -falign-jumps  -falign-loops	-falign-labels	-freorder-blocks
	   -freorder-blocks-and-partition -fprefetch-loop-arrays
	   -ftree-vect-loop-version

	   If you use multiple -O options, with	or without level numbers, the
	   last	such option is the one that is effective.

       Options of the form -fflag specify machine-independent flags.  Most
       flags have both positive	and negative forms; the	negative form of -ffoo
       would be	-fno-foo.  In the table	below, only one	of the forms is
       listed---the one	you typically will use.	 You can figure	out the	other
       form by either removing no- or adding it.

       The following options control specific optimizations.  They are either
       activated by -O options or are related to ones that are.	 You can use
       the following flags in the rare cases when "fine-tuning"	of optimiza-
       tions to	be performed is	desired.

       -fno-default-inline
	   Do not make member functions	inline by default merely because they
	   are defined inside the class	scope (C++ only).  Otherwise, when you
	   specify -O, member functions	defined	inside class scope are com-
	   piled inline	by default; i.e., you don't need to add	inline in
	   front of the	member function	name.

       -fno-defer-pop
	   Always pop the arguments to each function call as soon as that
	   function returns.  For machines which must pop arguments after a
	   function call, the compiler normally	lets arguments accumulate on
	   the stack for several function calls	and pops them all at once.

	   Disabled at levels -O, -O2, -O3, -Os.

       -fforce-mem
	   Force memory	operands to be copied into registers before doing
	   arithmetic on them.	This produces better code by making all	memory
	   references potential	common subexpressions.	When they are not com-
	   mon subexpressions, instruction combination should eliminate	the
	   separate register-load. This	option is now a	nop and	will be
	   removed in 4.3.

       -fforce-addr
	   Force memory	address	constants to be	copied into registers before
	   doing arithmetic on them.

       -fomit-frame-pointer
	   Don't keep the frame	pointer	in a register for functions that don't
	   need	one.  This avoids the instructions to save, set	up and restore
	   frame pointers; it also makes an extra register available in	many
	   functions.  It also makes debugging impossible on some machines.

	   On some machines, such as the VAX, this flag	has no effect, because
	   the standard	calling	sequence automatically handles the frame
	   pointer and nothing is saved	by pretending it doesn't exist.	 The
	   machine-description macro "FRAME_POINTER_REQUIRED" controls whether
	   a target machine supports this flag.

	   Enabled at levels -O, -O2, -O3, -Os.

       -foptimize-sibling-calls
	   Optimize sibling and	tail recursive calls.

	   Enabled at levels -O2, -O3, -Os.

       -fno-inline
	   Don't pay attention to the "inline" keyword.	 Normally this option
	   is used to keep the compiler	from expanding any functions inline.
	   Note	that if	you are	not optimizing,	no functions can be expanded
	   inline.

       -finline-functions
	   Integrate all simple	functions into their callers.  The compiler
	   heuristically decides which functions are simple enough to be worth
	   integrating in this way.

	   If all calls	to a given function are	integrated, and	the function
	   is declared "static", then the function is normally not output as
	   assembler code in its own right.

	   Enabled at level -O3.

       -finline-functions-called-once
	   Consider all	"static" functions called once for inlining into their
	   caller even if they are not marked "inline".	 If a call to a	given
	   function is integrated, then	the function is	not output as assem-
	   bler	code in	its own	right.

	   Enabled if -funit-at-a-time is enabled.

       -fearly-inlining
	   Inline functions marked by "always_inline" and functions whose body
	   seems smaller than the function call	overhead early before doing
	   -fprofile-generate instrumentation and real inlining	pass.  Doing
	   so makes profiling significantly cheaper and	usually	inlining
	   faster on programs having large chains of nested wrapper functions.

	   Enabled by default.

       -finline-limit=n
	   By default, GCC limits the size of functions	that can be inlined.
	   This	flag allows the	control	of this	limit for functions that are
	   explicitly marked as	inline (i.e., marked with the inline keyword
	   or defined within the class definition in c++).  n is the size of
	   functions that can be inlined in number of pseudo instructions (not
	   counting parameter handling).  The default value of n is 600.
	   Increasing this value can result in more inlined code at the	cost
	   of compilation time and memory consumption.	Decreasing usually
	   makes the compilation faster	and less code will be inlined (which
	   presumably means slower programs).  This option is particularly
	   useful for programs that use	inlining heavily such as those based
	   on recursive	templates with C++.

	   Inlining is actually	controlled by a	number of parameters, which
	   may be specified individually by using --param name=value.  The
	   -finline-limit=n option sets	some of	these parameters as follows:

	   max-inline-insns-single
		is set to I<n>/2.

	   max-inline-insns-auto
		is set to I<n>/2.

	   min-inline-insns
		is set to 130 or I<n>/4, whichever is smaller.

	   max-inline-insns-rtl
		is set to I<n>.

	   See below for a documentation of the	individual parameters control-
	   ling	inlining.

	   Note: pseudo	instruction represents,	in this	particular context, an
	   abstract measurement	of function's size.  In	no way does it repre-
	   sent	a count	of assembly instructions and as	such its exact meaning
	   might change	from one release to an another.

       -fkeep-inline-functions
	   In C, emit "static" functions that are declared "inline" into the
	   object file,	even if	the function has been inlined into all of its
	   callers.  This switch does not affect functions using the "extern
	   inline" extension in	GNU C.	In C++,	emit any and all inline	func-
	   tions into the object file.

       -fkeep-static-consts
	   Emit	variables declared "static const" when optimization isn't
	   turned on, even if the variables aren't referenced.

	   GCC enables this option by default.	If you want to force the com-
	   piler to check if the variable was referenced, regardless of
	   whether or not optimization is turned on, use the
	   -fno-keep-static-consts option.

       -fmerge-constants
	   Attempt to merge identical constants	(string	constants and floating
	   point constants) across compilation units.

	   This	option is the default for optimized compilation	if the assem-
	   bler	and linker support it.	Use -fno-merge-constants to inhibit
	   this	behavior.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fmerge-all-constants
	   Attempt to merge identical constants	and identical variables.

	   This	option implies -fmerge-constants.  In addition to -fmerge-con-
	   stants this considers e.g. even constant initialized	arrays or ini-
	   tialized constant variables with integral or	floating point types.
	   Languages like C or C++ require each	non-automatic variable to have
	   distinct location, so using this option will	result in non-conform-
	   ing behavior.

       -fmodulo-sched
	   Perform swing modulo	scheduling immediately before the first	sched-
	   uling pass.	This pass looks	at innermost loops and reorders	their
	   instructions	by overlapping different iterations.

       -fno-branch-count-reg
	   Do not use "decrement and branch" instructions on a count register,
	   but instead generate	a sequence of instructions that	decrement a
	   register, compare it	against	zero, then branch based	upon the
	   result.  This option	is only	meaningful on architectures that sup-
	   port	such instructions, which include x86, PowerPC, IA-64 and
	   S/390.

	   The default is -fbranch-count-reg.

       -fno-function-cse
	   Do not put function addresses in registers; make each instruction
	   that	calls a	constant function contain the function's address
	   explicitly.

	   This	option results in less efficient code, but some	strange	hacks
	   that	alter the assembler output may be confused by the optimiza-
	   tions performed when	this option is not used.

	   The default is -ffunction-cse

       -fno-zero-initialized-in-bss
	   If the target supports a BSS	section, GCC by	default	puts variables
	   that	are initialized	to zero	into BSS.  This	can save space in the
	   resulting code.

	   This	option turns off this behavior because some programs explic-
	   itly	rely on	variables going	to the data section.  E.g., so that
	   the resulting executable can	find the beginning of that section
	   and/or make assumptions based on that.

	   The default is -fzero-initialized-in-bss.

       -fbounds-check
	   For front-ends that support it, generate additional code to check
	   that	indices	used to	access arrays are within the declared range.
	   This	is currently only supported by the Java	and Fortran
	   front-ends, where this option defaults to true and false respec-
	   tively.

       -fmudflap -fmudflapth -fmudflapir
	   For front-ends that support it (C and C++), instrument all risky
	   pointer/array dereferencing operations, some	standard library
	   string/heap functions, and some other associated constructs with
	   range/validity tests.  Modules so instrumented should be immune to
	   buffer overflows, invalid heap use, and some	other classes of C/C++
	   programming errors.	The instrumentation relies on a	separate run-
	   time	library	(libmudflap), which will be linked into	a program if
	   -fmudflap is	given at link time.  Run-time behavior of the instru-
	   mented program is controlled	by the MUDFLAP_OPTIONS environment
	   variable.  See "env MUDFLAP_OPTIONS=-help a.out" for	its options.

	   Use -fmudflapth instead of -fmudflap	to compile and to link if your
	   program is multi-threaded.  Use -fmudflapir,	in addition to -fmud-
	   flap	or -fmudflapth,	if instrumentation should ignore pointer
	   reads.  This	produces less instrumentation (and therefore faster
	   execution) and still	provides some protection against outright mem-
	   ory corrupting writes, but allows erroneously read data to propa-
	   gate	within a program.

       -fthread-jumps
	   Perform optimizations where we check	to see if a jump branches to a
	   location where another comparison subsumed by the first is found.
	   If so, the first branch is redirected to either the destination of
	   the second branch or	a point	immediately following it, depending on
	   whether the condition is known to be	true or	false.

	   Enabled at levels -O2, -O3, -Os.

       -fcse-follow-jumps
	   In common subexpression elimination,	scan through jump instructions
	   when	the target of the jump is not reached by any other path.  For
	   example, when CSE encounters	an "if"	statement with an "else"
	   clause, CSE will follow the jump when the condition tested is
	   false.

	   Enabled at levels -O2, -O3, -Os.

       -fcse-skip-blocks
	   This	is similar to -fcse-follow-jumps, but causes CSE to follow
	   jumps which conditionally skip over blocks.	When CSE encounters a
	   simple "if" statement with no else clause, -fcse-skip-blocks	causes
	   CSE to follow the jump around the body of the "if".

	   Enabled at levels -O2, -O3, -Os.

       -frerun-cse-after-loop
	   Re-run common subexpression elimination after loop optimizations
	   has been performed.

	   Enabled at levels -O2, -O3, -Os.

       -fgcse
	   Perform a global common subexpression elimination pass.  This pass
	   also	performs global	constant and copy propagation.

	   Note: When compiling	a program using	computed gotos,	a GCC exten-
	   sion, you may get better runtime performance	if you disable the
	   global common subexpression elimination pass	by adding -fno-gcse to
	   the command line.

	   Enabled at levels -O2, -O3, -Os.

       -fgcse-lm
	   When	-fgcse-lm is enabled, global common subexpression elimination
	   will	attempt	to move	loads which are	only killed by stores into
	   themselves.	This allows a loop containing a	load/store sequence to
	   be changed to a load	outside	the loop, and a	copy/store within the
	   loop.

	   Enabled by default when gcse	is enabled.

       -fgcse-sm
	   When	-fgcse-sm is enabled, a	store motion pass is run after global
	   common subexpression	elimination.  This pass	will attempt to	move
	   stores out of loops.	 When used in conjunction with -fgcse-lm,
	   loops containing a load/store sequence can be changed to a load
	   before the loop and a store after the loop.

	   Not enabled at any optimization level.

       -fgcse-las
	   When	-fgcse-las is enabled, the global common subexpression elimi-
	   nation pass eliminates redundant loads that come after stores to
	   the same memory location (both partial and full redundancies).

	   Not enabled at any optimization level.

       -fgcse-after-reload
	   When	-fgcse-after-reload is enabled,	a redundant load elimination
	   pass	is performed after reload.  The	purpose	of this	pass is	to
	   cleanup redundant spilling.

       -funsafe-loop-optimizations
	   If given, the loop optimizer	will assume that loop indices do not
	   overflow, and that the loops	with nontrivial	exit condition are not
	   infinite.  This enables a wider range of loop optimizations even if
	   the loop optimizer itself cannot prove that these assumptions are
	   valid.  Using -Wunsafe-loop-optimizations, the compiler will	warn
	   you if it finds this	kind of	loop.

       -fcrossjumping
	   Perform cross-jumping transformation.  This transformation unifies
	   equivalent code and save code size.	The resulting code may or may
	   not perform better than without cross-jumping.

	   Enabled at levels -O2, -O3, -Os.

       -fif-conversion
	   Attempt to transform	conditional jumps into branch-less equiva-
	   lents.  This	include	use of conditional moves, min, max, set	flags
	   and abs instructions, and some tricks doable	by standard arith-
	   metics.  The	use of conditional execution on	chips where it is
	   available is	controlled by "if-conversion2".

	   Enabled at levels -O, -O2, -O3, -Os.

       -fif-conversion2
	   Use conditional execution (where available) to transform condi-
	   tional jumps	into branch-less equivalents.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fdelete-null-pointer-checks
	   Use global dataflow analysis	to identify and	eliminate useless
	   checks for null pointers.  The compiler assumes that	dereferencing
	   a null pointer would	have halted the	program.  If a pointer is
	   checked after it has	already	been dereferenced, it cannot be	null.

	   In some environments, this assumption is not	true, and programs can
	   safely dereference null pointers.  Use
	   -fno-delete-null-pointer-checks to disable this optimization	for
	   programs which depend on that behavior.

	   Enabled at levels -O2, -O3, -Os.

       -fexpensive-optimizations
	   Perform a number of minor optimizations that	are relatively expen-
	   sive.

	   Enabled at levels -O2, -O3, -Os.

       -foptimize-register-move
       -fregmove
	   Attempt to reassign register	numbers	in move	instructions and as
	   operands of other simple instructions in order to maximize the
	   amount of register tying.  This is especially helpful on machines
	   with	two-operand instructions.

	   Note	-fregmove and -foptimize-register-move are the same optimiza-
	   tion.

	   Enabled at levels -O2, -O3, -Os.

       -fdelayed-branch
	   If supported	for the	target machine,	attempt	to reorder instruc-
	   tions to exploit instruction	slots available	after delayed branch
	   instructions.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fschedule-insns
	   If supported	for the	target machine,	attempt	to reorder instruc-
	   tions to eliminate execution	stalls due to required data being
	   unavailable.	 This helps machines that have slow floating point or
	   memory load instructions by allowing	other instructions to be
	   issued until	the result of the load or floating point instruction
	   is required.

	   Enabled at levels -O2, -O3, -Os.

       -fschedule-insns2
	   Similar to -fschedule-insns,	but requests an	additional pass	of
	   instruction scheduling after	register allocation has	been done.
	   This	is especially useful on	machines with a	relatively small num-
	   ber of registers and	where memory load instructions take more than
	   one cycle.

	   Enabled at levels -O2, -O3, -Os.

       -fno-sched-interblock
	   Don't schedule instructions across basic blocks.  This is normally
	   enabled by default when scheduling before register allocation, i.e.
	   with	-fschedule-insns or at -O2 or higher.

       -fno-sched-spec
	   Don't allow speculative motion of non-load instructions.  This is
	   normally enabled by default when scheduling before register alloca-
	   tion, i.e.  with -fschedule-insns or	at -O2 or higher.

       -fsched-spec-load
	   Allow speculative motion of some load instructions.	This only
	   makes sense when scheduling before register allocation, i.e.	with
	   -fschedule-insns or at -O2 or higher.

       -fsched-spec-load-dangerous
	   Allow speculative motion of more load instructions.	This only
	   makes sense when scheduling before register allocation, i.e.	with
	   -fschedule-insns or at -O2 or higher.

       -fsched-stalled-insns=n
	   Define how many insns (if any) can be moved prematurely from	the
	   queue of stalled insns into the ready list, during the second
	   scheduling pass.

       -fsched-stalled-insns-dep=n
	   Define how many insn	groups (cycles)	will be	examined for a depen-
	   dency on a stalled insn that	is candidate for premature removal
	   from	the queue of stalled insns.  Has an effect only	during the
	   second scheduling pass, and only if -fsched-stalled-insns is	used
	   and its value is not	zero.

       -fsched2-use-superblocks
	   When	scheduling after register allocation, do use superblock	sched-
	   uling algorithm.  Superblock	scheduling allows motion across	basic
	   block boundaries resulting on faster	schedules.  This option	is
	   experimental, as not	all machine descriptions used by GCC model the
	   CPU closely enough to avoid unreliable results from the algorithm.

	   This	only makes sense when scheduling after register	allocation,
	   i.e.	with -fschedule-insns2 or at -O2 or higher.

       -fsched2-use-traces
	   Use -fsched2-use-superblocks	algorithm when scheduling after	regis-
	   ter allocation and additionally perform code	duplication in order
	   to increase the size	of superblocks using tracer pass.  See
	   -ftracer for	details	on trace formation.

	   This	mode should produce faster but significantly longer programs.
	   Also	without	-fbranch-probabilities the traces constructed may not
	   match the reality and hurt the performance.	This only makes	sense
	   when	scheduling after register allocation, i.e. with	-fsched-
	   ule-insns2 or at -O2	or higher.

       -fsee
	   Eliminates redundant	extension instructions and move	the non	redun-
	   dant	ones to	optimal	placement using	LCM.

       -freschedule-modulo-scheduled-loops
	   The modulo scheduling comes before the traditional scheduling, if a
	   loop	was modulo scheduled we	may want to prevent the	later schedul-
	   ing passes from changing its	schedule, we use this option to	con-
	   trol	that.

       -fcaller-saves
	   Enable values to be allocated in registers that will	be clobbered
	   by function calls, by emitting extra	instructions to	save and
	   restore the registers around	such calls.  Such allocation is	done
	   only	when it	seems to result	in better code than would otherwise be
	   produced.

	   This	option is always enabled by default on certain machines, usu-
	   ally	those which have no call-preserved registers to	use instead.

	   Enabled at levels -O2, -O3, -Os.

       -ftree-pre
	   Perform Partial Redundancy Elimination (PRE)	on trees.  This	flag
	   is enabled by default at -O2	and -O3.

       -ftree-fre
	   Perform Full	Redundancy Elimination (FRE) on	trees.	The difference
	   between FRE and PRE is that FRE only	considers expressions that are
	   computed on all paths leading to the	redundant computation.	This
	   analysis faster than	PRE, though it exposes fewer redundancies.
	   This	flag is	enabled	by default at -O and higher.

       -ftree-copy-prop
	   Perform copy	propagation on trees.  This pass eliminates unneces-
	   sary	copy operations.  This flag is enabled by default at -O	and
	   higher.

       -ftree-store-copy-prop
	   Perform copy	propagation of memory loads and	stores.	 This pass
	   eliminates unnecessary copy operations in memory references (struc-
	   tures, global variables, arrays, etc).  This	flag is	enabled	by
	   default at -O2 and higher.

       -ftree-salias
	   Perform structural alias analysis on	trees.	This flag is enabled
	   by default at -O and	higher.

       -fipa-pta
	   Perform interprocedural pointer analysis.

       -ftree-sink
	   Perform forward store motion	 on trees.  This flag is enabled by
	   default at -O and higher.

       -ftree-ccp
	   Perform sparse conditional constant propagation (CCP) on trees.
	   This	pass only operates on local scalar variables and is enabled by
	   default at -O and higher.

       -ftree-store-ccp
	   Perform sparse conditional constant propagation (CCP) on trees.
	   This	pass operates on both local scalar variables and memory	stores
	   and loads (global variables,	structures, arrays, etc).  This	flag
	   is enabled by default at -O2	and higher.

       -ftree-dce
	   Perform dead	code elimination (DCE) on trees.  This flag is enabled
	   by default at -O and	higher.

       -ftree-dominator-opts
	   Perform a variety of	simple scalar cleanups (constant/copy propaga-
	   tion, redundancy elimination, range propagation and expression sim-
	   plification)	based on a dominator tree traversal.  This also	per-
	   forms jump threading	(to reduce jumps to jumps). This flag is
	   enabled by default at -O and	higher.

       -ftree-ch
	   Perform loop	header copying on trees.  This is beneficial since it
	   increases effectiveness of code motion optimizations.  It also
	   saves one jump.  This flag is enabled by default at -O and higher.
	   It is not enabled for -Os, since it usually increases code size.

       -ftree-loop-optimize
	   Perform loop	optimizations on trees.	 This flag is enabled by
	   default at -O and higher.

       -ftree-loop-linear
	   Perform linear loop transformations on tree.	 This flag can improve
	   cache performance and allow further loop optimizations to take
	   place.

       -ftree-loop-im
	   Perform loop	invariant motion on trees.  This pass moves only
	   invariants that would be hard to handle at RTL level	(function
	   calls, operations that expand to nontrivial sequences of insns).
	   With	-funswitch-loops it also moves operands	of conditions that are
	   invariant out of the	loop, so that we can use just trivial invari-
	   antness analysis in loop unswitching.  The pass also	includes store
	   motion.

       -ftree-loop-ivcanon
	   Create a canonical counter for number of iterations in the loop for
	   that	determining number of iterations requires complicated analy-
	   sis.	 Later optimizations then may determine	the number easily.
	   Useful especially in	connection with	unrolling.

       -fivopts
	   Perform induction variable optimizations (strength reduction,
	   induction variable merging and induction variable elimination) on
	   trees.

       -ftree-sra
	   Perform scalar replacement of aggregates.  This pass	replaces
	   structure references	with scalars to	prevent	committing structures
	   to memory too early.	 This flag is enabled by default at -O and
	   higher.

       -ftree-copyrename
	   Perform copy	renaming on trees.  This pass attempts to rename com-
	   piler temporaries to	other variables	at copy	locations, usually
	   resulting in	variable names which more closely resemble the origi-
	   nal variables.  This	flag is	enabled	by default at -O and higher.

       -ftree-ter
	   Perform temporary expression	replacement during the SSA->normal
	   phase.  Single use/single def temporaries are replaced at their use
	   location with their defining	expression.  This results in non-GIM-
	   PLE code, but gives the expanders much more complex trees to	work
	   on resulting	in better RTL generation.  This	is enabled by default
	   at -O and higher.

       -ftree-lrs
	   Perform live	range splitting	during the SSA->normal phase.  Dis-
	   tinct live ranges of	a variable are split into unique variables,
	   allowing for	better optimization later.  This is enabled by default
	   at -O and higher.

       -ftree-vectorize
	   Perform loop	vectorization on trees.

       -ftree-vect-loop-version
	   Perform loop	versioning when	doing loop vectorization on trees.
	   When	a loop appears to be vectorizable except that data alignment
	   or data dependence cannot be	determined at compile time then	vec-
	   torized and non-vectorized versions of the loop are generated along
	   with	runtime	checks for alignment or	dependence to control which
	   version is executed.	 This option is	enabled	by default except at
	   level -Os where it is disabled.

       -ftree-vrp
	   Perform Value Range Propagation on trees.  This is similar to the
	   constant propagation	pass, but instead of values, ranges of values
	   are propagated.  This allows	the optimizers to remove unnecessary
	   range checks	like array bound checks	and null pointer checks.  This
	   is enabled by default at -O2	and higher.  Null pointer check	elimi-
	   nation is only done if -fdelete-null-pointer-checks is enabled.

       -ftracer
	   Perform tail	duplication to enlarge superblock size.	 This trans-
	   formation simplifies	the control flow of the	function allowing
	   other optimizations to do better job.

       -funroll-loops
	   Unroll loops	whose number of	iterations can be determined at	com-
	   pile	time or	upon entry to the loop.	 -funroll-loops	implies	-fre-
	   run-cse-after-loop.	This option makes code larger, and may or may
	   not make it run faster.

       -funroll-all-loops
	   Unroll all loops, even if their number of iterations	is uncertain
	   when	the loop is entered.  This usually makes programs run more
	   slowly.  -funroll-all-loops implies the same	options	as -fun-
	   roll-loops,

       -fsplit-ivs-in-unroller
	   Enables expressing of values	of induction variables in later	itera-
	   tions of the	unrolled loop using the	value in the first iteration.
	   This	breaks long dependency chains, thus improving efficiency of
	   the scheduling passes.

	   Combination of -fweb	and CSE	is often sufficient to obtain the same
	   effect.  However in cases the loop body is more complicated than a
	   single basic	block, this is not reliable.  It also does not work at
	   all on some of the architectures due	to restrictions	in the CSE
	   pass.

	   This	optimization is	enabled	by default.

       -fvariable-expansion-in-unroller
	   With	this option, the compiler will create multiple copies of some
	   local variables when	unrolling a loop which can result in superior
	   code.

       -fprefetch-loop-arrays
	   If supported	by the target machine, generate	instructions to
	   prefetch memory to improve the performance of loops that access
	   large arrays.

	   This	option may generate better or worse code; results are highly
	   dependent on	the structure of loops within the source code.

	   Disabled at level -Os.

       -fno-peephole
       -fno-peephole2
	   Disable any machine-specific	peephole optimizations.	 The differ-
	   ence	between	-fno-peephole and -fno-peephole2 is in how they	are
	   implemented in the compiler;	some targets use one, some use the
	   other, a few	use both.

	   -fpeephole is enabled by default.  -fpeephole2 enabled at levels
	   -O2,	-O3, -Os.

       -fno-guess-branch-probability
	   Do not guess	branch probabilities using heuristics.

	   GCC will use	heuristics to guess branch probabilities if they are
	   not provided	by profiling feedback (-fprofile-arcs).	 These heuris-
	   tics	are based on the control flow graph.  If some branch probabil-
	   ities are specified by __builtin_expect, then the heuristics	will
	   be used to guess branch probabilities for the rest of the control
	   flow	graph, taking the __builtin_expect info	into account.  The
	   interactions	between	the heuristics and __builtin_expect can	be
	   complex, and	in some	cases, it may be useful	to disable the heuris-
	   tics	so that	the effects of __builtin_expect	are easier to under-
	   stand.

	   The default is -fguess-branch-probability at	levels -O, -O2,	-O3,
	   -Os.

       -freorder-blocks
	   Reorder basic blocks	in the compiled	function in order to reduce
	   number of taken branches and	improve	code locality.

	   Enabled at levels -O2, -O3.

       -freorder-blocks-and-partition
	   In addition to reordering basic blocks in the compiled function, in
	   order to reduce number of taken branches, partitions	hot and	cold
	   basic blocks	into separate sections of the assembly and .o files,
	   to improve paging and cache locality	performance.

	   This	optimization is	automatically turned off in the	presence of
	   exception handling, for linkonce sections, for functions with a
	   user-defined	section	attribute and on any architecture that does
	   not support named sections.

       -freorder-functions
	   Reorder functions in	the object file	in order to improve code
	   locality.  This is implemented by using special subsections
	   ".text.hot" for most	frequently executed functions and
	   ".text.unlikely" for	unlikely executed functions.  Reordering is
	   done	by the linker so object	file format must support named sec-
	   tions and linker must place them in a reasonable way.

	   Also	profile	feedback must be available in to make this option
	   effective.  See -fprofile-arcs for details.

	   Enabled at levels -O2, -O3, -Os.

       -fstrict-aliasing
	   Allows the compiler to assume the strictest aliasing	rules applica-
	   ble to the language being compiled.	For C (and C++), this acti-
	   vates optimizations based on	the type of expressions.  In particu-
	   lar,	an object of one type is assumed never to reside at the	same
	   address as an object	of a different type, unless the	types are
	   almost the same.  For example, an "unsigned int" can	alias an
	   "int", but not a "void*" or a "double".  A character	type may alias
	   any other type.

	   Pay special attention to code like this:

		   union a_union {
		     int i;
		     double d;
		   };

		   int f() {
		     a_union t;
		     t.d = 3.0;
		     return t.i;
		   }

	   The practice	of reading from	a different union member than the one
	   most	recently written to (called "type-punning") is common.	Even
	   with	-fstrict-aliasing, type-punning	is allowed, provided the mem-
	   ory is accessed through the union type.  So,	the code above will
	   work	as expected.  However, this code might not:

		   int f() {
		     a_union t;
		     int* ip;
		     t.d = 3.0;
		     ip	= &t.i;
		     return *ip;
		   }

	   Every language that wishes to perform language-specific alias anal-
	   ysis	should define a	function that computes,	given an "tree"	node,
	   an alias set	for the	node.  Nodes in	different alias	sets are not
	   allowed to alias.  For an example, see the C	front-end function
	   "c_get_alias_set".

	   Enabled at levels -O2, -O3, -Os.

       -fstrict-overflow
	   Allow the compiler to assume	strict signed overflow rules, depend-
	   ing on the language being compiled.	For C (and C++)	this means
	   that	overflow when doing arithmetic with signed numbers is unde-
	   fined, which	means that the compiler	may assume that	it will	not
	   happen.  This permits various optimizations.	 For example, the com-
	   piler will assume that an expression	like "i	+ 10 > i" will always
	   be true for signed "i".  This assumption is only valid if signed
	   overflow is undefined, as the expression is false if	"i + 10" over-
	   flows when using twos complement arithmetic.	 When this option is
	   in effect any attempt to determine whether an operation on signed
	   numbers will	overflow must be written carefully to not actually
	   involve overflow.

	   See also the	-fwrapv	option.	 Using -fwrapv means that signed over-
	   flow	is fully defined: it wraps.  When -fwrapv is used, there is no
	   difference between -fstrict-overflow	and -fno-strict-overflow.
	   With	-fwrapv	certain	types of overflow are permitted.  For example,
	   if the compiler gets	an overflow when doing arithmetic on con-
	   stants, the overflowed value	can still be used with -fwrapv,	but
	   not otherwise.

	   The -fstrict-overflow option	is enabled at levels -O2, -O3, -Os.

       -falign-functions
       -falign-functions=n
	   Align the start of functions	to the next power-of-two greater than
	   n, skipping up to n bytes.  For instance, -falign-functions=32
	   aligns functions to the next	32-byte	boundary, but -falign-func-
	   tions=24 would align	to the next 32-byte boundary only if this can
	   be done by skipping 23 bytes	or less.

	   -fno-align-functions	and -falign-functions=1	are equivalent and
	   mean	that functions will not	be aligned.

	   Some	assemblers only	support	this flag when n is a power of two; in
	   that	case, it is rounded up.

	   If n	is not specified or is zero, use a machine-dependent default.

	   Enabled at levels -O2, -O3.

       -falign-labels
       -falign-labels=n
	   Align all branch targets to a power-of-two boundary,	skipping up to
	   n bytes like	-falign-functions.  This option	can easily make	code
	   slower, because it must insert dummy	operations for when the	branch
	   target is reached in	the usual flow of the code.

	   -fno-align-labels and -falign-labels=1 are equivalent and mean that
	   labels will not be aligned.

	   If -falign-loops or -falign-jumps are applicable and	are greater
	   than	this value, then their values are used instead.

	   If n	is not specified or is zero, use a machine-dependent default
	   which is very likely	to be 1, meaning no alignment.

	   Enabled at levels -O2, -O3.

       -falign-loops
       -falign-loops=n
	   Align loops to a power-of-two boundary, skipping up to n bytes like
	   -falign-functions.  The hope	is that	the loop will be executed many
	   times, which	will make up for any execution of the dummy opera-
	   tions.

	   -fno-align-loops and	-falign-loops=1	are equivalent and mean	that
	   loops will not be aligned.

	   If n	is not specified or is zero, use a machine-dependent default.

	   Enabled at levels -O2, -O3.

       -falign-jumps
       -falign-jumps=n
	   Align branch	targets	to a power-of-two boundary, for	branch targets
	   where the targets can only be reached by jumping, skipping up to n
	   bytes like -falign-functions.  In this case,	no dummy operations
	   need	be executed.

	   -fno-align-jumps and	-falign-jumps=1	are equivalent and mean	that
	   loops will not be aligned.

	   If n	is not specified or is zero, use a machine-dependent default.

	   Enabled at levels -O2, -O3.

       -funit-at-a-time
	   Parse the whole compilation unit before starting to produce code.
	   This	allows some extra optimizations	to take	place but consumes
	   more	memory (in general).  There are	some compatibility issues with
	   unit-at-a-time mode:

	   *   enabling	unit-at-a-time mode may	change the order in which
	       functions, variables, and top-level "asm" statements are	emit-
	       ted, and	will likely break code relying on some particular
	       ordering.  The majority of such top-level "asm" statements,
	       though, can be replaced by "section" attributes.	 The fno-
	       toplevel-reorder	option may be used to keep the ordering	used
	       in the input file, at the cost of some optimizations.

	   *   unit-at-a-time mode removes unreferenced	static variables and
	       functions.  This	may result in undefined	references when	an
	       "asm" statement refers directly to variables or functions that
	       are otherwise unused.  In that case either the variable/func-
	       tion shall be listed as an operand of the "asm" statement oper-
	       and or, in the case of top-level	"asm" statements the attribute
	       "used" shall be used on the declaration.

	   *   Static functions	now can	use non-standard passing conventions
	       that may	break "asm" statements calling functions directly.
	       Again, attribute	"used" will prevent this behavior.

	   As a	temporary workaround, -fno-unit-at-a-time can be used, but
	   this	scheme may not be supported by future releases of GCC.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fno-toplevel-reorder
	   Do not reorder top-level functions, variables, and "asm" state-
	   ments.  Output them in the same order that they appear in the input
	   file.  When this option is used, unreferenced static	variables will
	   not be removed.  This option	is intended to support existing	code
	   which relies	on a particular	ordering.  For new code, it is better
	   to use attributes.

       -fweb
	   Constructs webs as commonly used for	register allocation purposes
	   and assign each web individual pseudo register.  This allows	the
	   register allocation pass to operate on pseudos directly, but	also
	   strengthens several other optimization passes, such as CSE, loop
	   optimizer and trivial dead code remover.  It	can, however, make
	   debugging impossible, since variables will no longer	stay in	a
	   "home register".

	   Enabled by default with -funroll-loops.

       -fwhole-program
	   Assume that the current compilation unit represents whole program
	   being compiled.  All	public functions and variables with the	excep-
	   tion	of "main" and those merged by attribute	"externally_visible"
	   become static functions and in a affect gets	more aggressively
	   optimized by	interprocedural	optimizers.  While this	option is
	   equivalent to proper	use of "static"	keyword	for programs consist-
	   ing of single file, in combination with option --combine this flag
	   can be used to compile most of smaller scale	C programs since the
	   functions and variables become local	for the	whole combined compi-
	   lation unit,	not for	the single source file itself.

       -fno-cprop-registers
	   After register allocation and post-register allocation instruction
	   splitting, we perform a copy-propagation pass to try	to reduce
	   scheduling dependencies and occasionally eliminate the copy.

	   Disabled at levels -O, -O2, -O3, -Os.

       -fprofile-generate
	   Enable options usually used for instrumenting application to	pro-
	   duce	profile	useful for later recompilation with profile feedback
	   based optimization.	You must use -fprofile-generate	both when com-
	   piling and when linking your	program.

	   The following options are enabled: "-fprofile-arcs",	"-fpro-
	   file-values", "-fvpt".

       -fprofile-use
	   Enable profile feedback directed optimizations, and optimizations
	   generally profitable	only with profile feedback available.

	   The following options are enabled: "-fbranch-probabilities",
	   "-fvpt", "-funroll-loops", "-fpeel-loops", "-ftracer"

       The following options control compiler behavior regarding floating
       point arithmetic.  These	options	trade off between speed	and correct-
       ness.  All must be specifically enabled.

       -ffloat-store
	   Do not store	floating point variables in registers, and inhibit
	   other options that might change whether a floating point value is
	   taken from a	register or memory.

	   This	option prevents	undesirable excess precision on	machines such
	   as the 68000	where the floating registers (of the 68881) keep more
	   precision than a "double" is	supposed to have.  Similarly for the
	   x86 architecture.  For most programs, the excess precision does
	   only	good, but a few	programs rely on the precise definition	of
	   IEEE	floating point.	 Use -ffloat-store for such programs, after
	   modifying them to store all pertinent intermediate computations
	   into	variables.

       -ffast-math
	   Sets	-fno-math-errno, -funsafe-math-optimizations, -fno-trap-
	   ping-math, -ffinite-math-only, -fno-rounding-math, -fno-signal-
	   ing-nans and	fcx-limited-range.

	   This	option causes the preprocessor macro "__FAST_MATH__" to	be
	   defined.

	   This	option should never be turned on by any	-O option since	it can
	   result in incorrect output for programs which depend	on an exact
	   implementation of IEEE or ISO rules/specifications for math func-
	   tions.

       -fno-math-errno
	   Do not set ERRNO after calling math functions that are executed
	   with	a single instruction, e.g., sqrt.  A program that relies on
	   IEEE	exceptions for math error handling may want to use this	flag
	   for speed while maintaining IEEE arithmetic compatibility.

	   This	option should never be turned on by any	-O option since	it can
	   result in incorrect output for programs which depend	on an exact
	   implementation of IEEE or ISO rules/specifications for math func-
	   tions.

	   The default is -fmath-errno.

	   On Darwin systems, the math library never sets "errno".  There is
	   therefore no	reason for the compiler	to consider the	possibility
	   that	it might, and -fno-math-errno is the default.

       -funsafe-math-optimizations
	   Allow optimizations for floating-point arithmetic that (a) assume
	   that	arguments and results are valid	and (b)	may violate IEEE or
	   ANSI	standards.  When used at link-time, it may include libraries
	   or startup files that change	the default FPU	control	word or	other
	   similar optimizations.

	   This	option should never be turned on by any	-O option since	it can
	   result in incorrect output for programs which depend	on an exact
	   implementation of IEEE or ISO rules/specifications for math func-
	   tions.

	   The default is -fno-unsafe-math-optimizations.

       -ffinite-math-only
	   Allow optimizations for floating-point arithmetic that assume that
	   arguments and results are not NaNs or +-Infs.

	   This	option should never be turned on by any	-O option since	it can
	   result in incorrect output for programs which depend	on an exact
	   implementation of IEEE or ISO rules/specifications.

	   The default is -fno-finite-math-only.

       -fno-trapping-math
	   Compile code	assuming that floating-point operations	cannot gener-
	   ate user-visible traps.  These traps	include	division by zero,
	   overflow, underflow,	inexact	result and invalid operation.  This
	   option implies -fno-signaling-nans.	Setting	this option may	allow
	   faster code if one relies on	"non-stop" IEEE	arithmetic, for	exam-
	   ple.

	   This	option should never be turned on by any	-O option since	it can
	   result in incorrect output for programs which depend	on an exact
	   implementation of IEEE or ISO rules/specifications for math func-
	   tions.

	   The default is -ftrapping-math.

       -frounding-math
	   Disable transformations and optimizations that assume default
	   floating point rounding behavior.  This is round-to-zero for	all
	   floating point to integer conversions, and round-to-nearest for all
	   other arithmetic truncations.  This option should be	specified for
	   programs that change	the FP rounding	mode dynamically, or that may
	   be executed with a non-default rounding mode.  This option disables
	   constant folding of floating	point expressions at compile-time
	   (which may be affected by rounding mode) and	arithmetic transforma-
	   tions that are unsafe in the	presence of sign-dependent rounding
	   modes.

	   The default is -fno-rounding-math.

	   This	option is experimental and does	not currently guarantee	to
	   disable all GCC optimizations that are affected by rounding mode.
	   Future versions of GCC may provide finer control of this setting
	   using C99's "FENV_ACCESS" pragma.  This command line	option will be
	   used	to specify the default state for "FENV_ACCESS".

       -frtl-abstract-sequences
	   It is a size	optimization method. This option is to find identical
	   sequences of	code, which can	be turned into pseudo-procedures  and
	   then	 replace  all  occurrences with	 calls to  the	newly created
	   subroutine. It is kind of an	opposite of -finline-functions.	 This
	   optimization	runs at	RTL level.

       -fsignaling-nans
	   Compile code	assuming that IEEE signaling NaNs may generate user-
	   visible traps during	floating-point operations.  Setting this
	   option disables optimizations that may change the number of excep-
	   tions visible with signaling	NaNs.  This option implies -ftrap-
	   ping-math.

	   This	option causes the preprocessor macro "__SUPPORT_SNAN__"	to be
	   defined.

	   The default is -fno-signaling-nans.

	   This	option is experimental and does	not currently guarantee	to
	   disable all GCC optimizations that affect signaling NaN behavior.

       -fsingle-precision-constant
	   Treat floating point	constant as single precision constant instead
	   of implicitly converting it to double precision constant.

       -fcx-limited-range
       -fno-cx-limited-range
	   When	enabled, this option states that a range reduction step	is not
	   needed when performing complex division.  The default is
	   -fno-cx-limited-range, but is enabled by -ffast-math.

	   This	option controls	the default setting of the ISO C99 "CX_LIM-
	   ITED_RANGE" pragma.	Nevertheless, the option applies to all	lan-
	   guages.

       The following options control optimizations that	may improve perfor-
       mance, but are not enabled by any -O options.  This section includes
       experimental options that may produce broken code.

       -fbranch-probabilities
	   After running a program compiled with -fprofile-arcs, you can com-
	   pile	it a second time using -fbranch-probabilities, to improve
	   optimizations based on the number of	times each branch was taken.
	   When	the program compiled with -fprofile-arcs exits it saves	arc
	   execution counts to a file called sourcename.gcda for each source
	   file	 The information in this data file is very dependent on	the
	   structure of	the generated code, so you must	use the	same source
	   code	and the	same optimization options for both compilations.

	   With	-fbranch-probabilities,	GCC puts a REG_BR_PROB note on each
	   JUMP_INSN and CALL_INSN.  These can be used to improve optimiza-
	   tion.  Currently, they are only used	in one place: in reorg.c,
	   instead of guessing which path a branch is mostly to	take, the
	   REG_BR_PROB values are used to exactly determine which path is
	   taken more often.

       -fprofile-values
	   If combined with -fprofile-arcs, it adds code so that some data
	   about values	of expressions in the program is gathered.

	   With	-fbranch-probabilities,	it reads back the data gathered	from
	   profiling values of expressions and adds REG_VALUE_PROFILE notes to
	   instructions	for their later	usage in optimizations.

	   Enabled with	-fprofile-generate and -fprofile-use.

       -fvpt
	   If combined with -fprofile-arcs, it instructs the compiler to add a
	   code	to gather information about values of expressions.

	   With	-fbranch-probabilities,	it reads back the data gathered	and
	   actually performs the optimizations based on	them.  Currently the
	   optimizations include specialization	of division operation using
	   the knowledge about the value of the	denominator.

       -frename-registers
	   Attempt to avoid false dependencies in scheduled code by making use
	   of registers	left over after	register allocation.  This optimiza-
	   tion	will most benefit processors with lots of registers.  Depend-
	   ing on the debug information	format adopted by the target, however,
	   it can make debugging impossible, since variables will no longer
	   stay	in a "home register".

	   Enabled by default with -funroll-loops.

       -ftracer
	   Perform tail	duplication to enlarge superblock size.	 This trans-
	   formation simplifies	the control flow of the	function allowing
	   other optimizations to do better job.

	   Enabled with	-fprofile-use.

       -funroll-loops
	   Unroll loops	whose number of	iterations can be determined at	com-
	   pile	time or	upon entry to the loop.	 -funroll-loops	implies	-fre-
	   run-cse-after-loop, -fweb and -frename-registers.  It also turns on
	   complete loop peeling (i.e. complete	removal	of loops with small
	   constant number of iterations).  This option	makes code larger, and
	   may or may not make it run faster.

	   Enabled with	-fprofile-use.

       -funroll-all-loops
	   Unroll all loops, even if their number of iterations	is uncertain
	   when	the loop is entered.  This usually makes programs run more
	   slowly.  -funroll-all-loops implies the same	options	as -fun-
	   roll-loops.

       -fpeel-loops
	   Peels the loops for that there is enough information	that they do
	   not roll much (from profile feedback).  It also turns on complete
	   loop	peeling	(i.e. complete removal of loops	with small constant
	   number of iterations).

	   Enabled with	-fprofile-use.

       -fmove-loop-invariants
	   Enables the loop invariant motion pass in the RTL loop optimizer.
	   Enabled at level -O1

       -funswitch-loops
	   Move	branches with loop invariant conditions	out of the loop, with
	   duplicates of the loop on both branches (modified according to
	   result of the condition).

       -ffunction-sections
       -fdata-sections
	   Place each function or data item into its own section in the	output
	   file	if the target supports arbitrary sections.  The	name of	the
	   function or the name	of the data item determines the	section's name
	   in the output file.

	   Use these options on	systems	where the linker can perform optimiza-
	   tions to improve locality of	reference in the instruction space.
	   Most	systems	using the ELF object format and	SPARC processors run-
	   ning	Solaris	2 have linkers with such optimizations.	 AIX may have
	   these optimizations in the future.

	   Only	use these options when there are significant benefits from
	   doing so.  When you specify these options, the assembler and	linker
	   will	create larger object and executable files and will also	be
	   slower.  You	will not be able to use	"gprof"	on all systems if you
	   specify this	option and you may have	problems with debugging	if you
	   specify both	this option and	-g.

       -fbranch-target-load-optimize
	   Perform branch target register load optimization before prologue /
	   epilogue threading.	The use	of target registers can	typically be
	   exposed only	during reload, thus hoisting loads out of loops	and
	   doing inter-block scheduling	needs a	separate optimization pass.

       -fbranch-target-load-optimize2
	   Perform branch target register load optimization after prologue /
	   epilogue threading.

       -fbtr-bb-exclusive
	   When	performing branch target register load optimization, don't re-
	   use branch target registers in within any basic block.

       -fstack-protector
	   Emit	extra code to check for	buffer overflows, such as stack	smash-
	   ing attacks.	 This is done by adding	a guard	variable to functions
	   with	vulnerable objects.  This includes functions that call alloca,
	   and functions with buffers larger than 8 bytes.  The	guards are
	   initialized when a function is entered and then checked when	the
	   function exits.  If a guard check fails, an error message is
	   printed and the program exits.

       -fstack-protector-all
	   Like	-fstack-protector except that all functions are	protected.

       -fsection-anchors
	   Try to reduce the number of symbolic	address	calculations by	using
	   shared "anchor" symbols to address nearby objects.  This transfor-
	   mation can help to reduce the number	of GOT entries and GOT
	   accesses on some targets.

	   For example,	the implementation of the following function "foo":

		   static int a, b, c;
		   int foo (void) { return a + b + c; }

	   would usually calculate the addresses of all	three variables, but
	   if you compile it with -fsection-anchors, it	will access the	vari-
	   ables from a	common anchor point instead.  The effect is similar to
	   the following pseudocode (which isn't valid C):

		   int foo (void)
		   {
		     register int *xr =	&x;
		     return xr[&a - &x]	+ xr[&b	- &x] +	xr[&c -	&x];
		   }

	   Not all targets support this	option.

       --param name=value
	   In some places, GCC uses various constants to control the amount of
	   optimization	that is	done.  For example, GCC	will not inline	func-
	   tions that contain more that	a certain number of instructions.  You
	   can control some of these constants on the command-line using the
	   --param option.

	   The names of	specific parameters, and the meaning of	the values,
	   are tied to the internals of	the compiler, and are subject to
	   change without notice in future releases.

	   In each case, the value is an integer.  The allowable choices for
	   name	are given in the following table:

	   salias-max-implicit-fields
	       The maximum number of fields in a variable without direct
	       structure accesses for which structure aliasing will consider
	       trying to track each field.  The	default	is 5

	   salias-max-array-elements
	       The maximum number of elements an array can have	and its	ele-
	       ments still be tracked individually by structure	aliasing. The
	       default is 4

	   sra-max-structure-size
	       The maximum structure size, in bytes, at	which the scalar
	       replacement of aggregates (SRA) optimization will perform block
	       copies.	The default value, 0, implies that GCC will select the
	       most appropriate	size itself.

	   sra-field-structure-ratio
	       The threshold ratio (as a percentage) between instantiated
	       fields and the complete structure size.	We say that if the
	       ratio of	the number of bytes in instantiated fields to the num-
	       ber of bytes in the complete structure exceeds this parameter,
	       then block copies are not used.	The default is 75.

	   max-crossjump-edges
	       The maximum number of incoming edges to consider	for crossjump-
	       ing.  The algorithm used	by -fcrossjumping is O(N^2) in the
	       number of edges incoming	to each	block.	Increasing values mean
	       more aggressive optimization, making the	compile	time increase
	       with probably small improvement in executable size.

	   min-crossjump-insns
	       The minimum number of instructions which	must be	matched	at the
	       end of two blocks before	crossjumping will be performed on
	       them.  This value is ignored in the case	where all instructions
	       in the block being crossjumped from are matched.	 The default
	       value is	5.

	   max-grow-copy-bb-insns
	       The maximum code	size expansion factor when copying basic
	       blocks instead of jumping.  The expansion is relative to	a jump
	       instruction.  The default value is 8.

	   max-goto-duplication-insns
	       The maximum number of instructions to duplicate to a block that
	       jumps to	a computed goto.  To avoid O(N^2) behavior in a	number
	       of passes, GCC factors computed gotos early in the compilation
	       process,	and unfactors them as late as possible.	 Only computed
	       jumps at	the end	of a basic blocks with no more than max-goto-
	       duplication-insns are unfactored.  The default value is 8.

	   max-delay-slot-insn-search
	       The maximum number of instructions to consider when looking for
	       an instruction to fill a	delay slot.  If	more than this arbi-
	       trary number of instructions is searched, the time savings from
	       filling the delay slot will be minimal so stop searching.
	       Increasing values mean more aggressive optimization, making the
	       compile time increase with probably small improvement in	exe-
	       cutable run time.

	   max-delay-slot-live-search
	       When trying to fill delay slots,	the maximum number of instruc-
	       tions to	consider when searching	for a block with valid live
	       register	information.  Increasing this arbitrarily chosen value
	       means more aggressive optimization, increasing the compile
	       time.  This parameter should be removed when the	delay slot
	       code is rewritten to maintain the control-flow graph.

	   max-gcse-memory
	       The approximate maximum amount of memory	that will be allocated
	       in order	to perform the global common subexpression elimination
	       optimization.  If more memory than specified is required, the
	       optimization will not be	done.

	   max-gcse-passes
	       The maximum number of passes of GCSE to run.  The default is 1.

	   max-pending-list-length
	       The maximum number of pending dependencies scheduling will
	       allow before flushing the current state and starting over.
	       Large functions with few	branches or calls can create exces-
	       sively large lists which	needlessly consume memory and
	       resources.

	   max-inline-insns-single
	       Several parameters control the tree inliner used	in gcc.	 This
	       number sets the maximum number of instructions (counted in
	       GCC's internal representation) in a single function that	the
	       tree inliner will consider for inlining.	 This only affects
	       functions declared inline and methods implemented in a class
	       declaration (C++).  The default value is	450.

	   max-inline-insns-auto
	       When you	use -finline-functions (included in -O3), a lot	of
	       functions that would otherwise not be considered	for inlining
	       by the compiler will be investigated.  To those functions, a
	       different (more restrictive) limit compared to functions
	       declared	inline can be applied.	The default value is 90.

	   large-function-insns
	       The limit specifying really large functions.  For functions
	       larger than this	limit after inlining inlining is constrained
	       by --param large-function-growth.  This parameter is useful
	       primarily to avoid extreme compilation time caused by non-lin-
	       ear algorithms used by the backend.  This parameter is ignored
	       when -funit-at-a-time is	not used.  The default value is	2700.

	   large-function-growth
	       Specifies maximal growth	of large function caused by inlining
	       in percents.  This parameter is ignored when -funit-at-a-time
	       is not used.  The default value is 100 which limits large func-
	       tion growth to 2.0 times	the original size.

	   large-unit-insns
	       The limit specifying large translation unit.  Growth caused by
	       inlining	of units larger	than this limit	is limited by --param
	       inline-unit-growth.  For	small units this might be too tight
	       (consider unit consisting of function A that is inline and B
	       that just calls A three time.  If B is small relative to	A, the
	       growth of unit is 300\% and yet such inlining is	very sane.
	       For very	large units consisting of small	inlininable functions
	       however the overall unit	growth limit is	needed to avoid	expo-
	       nential explosion of code size.	Thus for smaller units,	the
	       size is increased to --param large-unit-insns before applying
	       --param inline-unit-growth.  The	default	is 10000

	   inline-unit-growth
	       Specifies maximal overall growth	of the compilation unit	caused
	       by inlining.  This parameter is ignored when -funit-at-a-time
	       is not used.  The default value is 50 which limits unit growth
	       to 1.5 times the	original size.

	   max-inline-insns-recursive
	   max-inline-insns-recursive-auto
	       Specifies maximum number	of instructions	out-of-line copy of
	       self recursive inline function can grow into by performing
	       recursive inlining.

	       For functions declared inline --param max-inline-insns-recur-
	       sive is taken into account.  For	function not declared inline,
	       recursive inlining happens only when -finline-functions
	       (included in -O3) is enabled and	--param	max-inline-insns-
	       recursive-auto is used.	The default value is 450.

	   max-inline-recursive-depth
	   max-inline-recursive-depth-auto
	       Specifies maximum recursion depth used by the recursive inlin-
	       ing.

	       For functions declared inline --param max-inline-recursive-
	       depth is	taken into account.  For function not declared inline,
	       recursive inlining happens only when -finline-functions
	       (included in -O3) is enabled and	--param	max-inline-recursive-
	       depth-auto is used.  The	default	value is 450.

	   min-inline-recursive-probability
	       Recursive inlining is profitable	only for function having deep
	       recursion in average and	can hurt for function having little
	       recursion depth by increasing the prologue size or complexity
	       of function body	to other optimizers.

	       When profile feedback is	available (see -fprofile-generate) the
	       actual recursion	depth can be guessed from probability that
	       function	will recurse via given call expression.	 This parame-
	       ter limits inlining only	to call	expression whose probability
	       exceeds given threshold (in percents).  The default value is
	       10.

	   inline-call-cost
	       Specify cost of call instruction	relative to simple arithmetics
	       operations (having cost of 1).  Increasing this cost disquali-
	       fies inlining of	non-leaf functions and at the same time
	       increases size of leaf function that is believed	to reduce
	       function	size by	being inlined.	In effect it increases amount
	       of inlining for code having large abstraction penalty (many
	       functions that just pass	the arguments to other functions) and
	       decrease	inlining for code with low abstraction penalty.	 The
	       default value is	16.

	   max-unrolled-insns
	       The maximum number of instructions that a loop should have if
	       that loop is unrolled, and if the loop is unrolled, it deter-
	       mines how many times the	loop code is unrolled.

	   max-average-unrolled-insns
	       The maximum number of instructions biased by probabilities of
	       their execution that a loop should have if that loop is
	       unrolled, and if	the loop is unrolled, it determines how	many
	       times the loop code is unrolled.

	   max-unroll-times
	       The maximum number of unrollings	of a single loop.

	   max-peeled-insns
	       The maximum number of instructions that a loop should have if
	       that loop is peeled, and	if the loop is peeled, it determines
	       how many	times the loop code is peeled.

	   max-peel-times
	       The maximum number of peelings of a single loop.

	   max-completely-peeled-insns
	       The maximum number of insns of a	completely peeled loop.

	   max-completely-peel-times
	       The maximum number of iterations	of a loop to be	suitable for
	       complete	peeling.

	   max-unswitch-insns
	       The maximum number of insns of an unswitched loop.

	   max-unswitch-level
	       The maximum number of branches unswitched in a single loop.

	   lim-expensive
	       The minimum cost	of an expensive	expression in the loop invari-
	       ant motion.

	   iv-consider-all-candidates-bound
	       Bound on	number of candidates for induction variables below
	       that all	candidates are considered for each use in induction
	       variable	optimizations.	Only the most relevant candidates are
	       considered if there are more candidates,	to avoid quadratic
	       time complexity.

	   iv-max-considered-uses
	       The induction variable optimizations give up on loops that con-
	       tain more induction variable uses.

	   iv-always-prune-cand-set-bound
	       If number of candidates in the set is smaller than this value,
	       we always try to	remove unnecessary ivs from the	set during its
	       optimization when a new iv is added to the set.

	   scev-max-expr-size
	       Bound on	size of	expressions used in the	scalar evolutions ana-
	       lyzer.  Large expressions slow the analyzer.

	   vect-max-version-checks
	       The maximum number of runtime checks that can be	performed when
	       doing loop versioning in	the vectorizer.	 See option ftree-
	       vect-loop-version for more information.

	   max-iterations-to-track
	       The maximum number of iterations	of a loop the brute force
	       algorithm for analysis of # of iterations of the	loop tries to
	       evaluate.

	   hot-bb-count-fraction
	       Select fraction of the maximal count of repetitions of basic
	       block in	program	given basic block needs	to have	to be consid-
	       ered hot.

	   hot-bb-frequency-fraction
	       Select fraction of the maximal frequency	of executions of basic
	       block in	function given basic block needs to have to be consid-
	       ered hot

	   max-predicted-iterations
	       The maximum number of loop iterations we	predict	statically.
	       This is useful in cases where function contain single loop with
	       known bound and other loop with unknown.	 We predict the	known
	       number of iterations correctly, while the unknown number	of
	       iterations average to roughly 10.  This means that the loop
	       without bounds would appear artificially	cold relative to the
	       other one.

	   tracer-dynamic-coverage
	   tracer-dynamic-coverage-feedback
	       This value is used to limit superblock formation	once the given
	       percentage of executed instructions is covered.	This limits
	       unnecessary code	size expansion.

	       The tracer-dynamic-coverage-feedback is used only when profile
	       feedback	is available.  The real	profiles (as opposed to	stati-
	       cally estimated ones) are much less balanced allowing the
	       threshold to be larger value.

	   tracer-max-code-growth
	       Stop tail duplication once code growth has reached given	per-
	       centage.	 This is rather	hokey argument,	as most	of the dupli-
	       cates will be eliminated	later in cross jumping,	so it may be
	       set to much higher values than is the desired code growth.

	   tracer-min-branch-ratio
	       Stop reverse growth when	the reverse probability	of best	edge
	       is less than this threshold (in percent).

	   tracer-min-branch-ratio
	   tracer-min-branch-ratio-feedback
	       Stop forward growth if the best edge do have probability	lower
	       than this threshold.

	       Similarly to tracer-dynamic-coverage two	values are present,
	       one for compilation for profile feedback	and one	for compila-
	       tion without.  The value	for compilation	with profile feedback
	       needs to	be more	conservative (higher) in order to make tracer
	       effective.

	   max-cse-path-length
	       Maximum number of basic blocks on path that cse considers.  The
	       default is 10.

	   max-cse-insns
	       The maximum instructions	CSE process before flushing. The
	       default is 1000.

	   global-var-threshold
	       Counts the number of function calls (n) and the number of call-
	       clobbered variables (v).	 If nxv	is larger than this limit, a
	       single artificial variable will be created to represent all the
	       call-clobbered variables	at function call sites.	 This artifi-
	       cial variable will then be made to alias	every call-clobbered
	       variable.  (done	as "int	* size_t" on the host machine; beware
	       overflow).

	   max-aliased-vops
	       Maximum number of virtual operands allowed to represent aliases
	       before triggering the alias grouping heuristic.	Alias grouping
	       reduces compile times and memory	consumption needed for alias-
	       ing at the expense of precision loss in alias information.

	   ggc-min-expand
	       GCC uses	a garbage collector to manage its own memory alloca-
	       tion.  This parameter specifies the minimum percentage by which
	       the garbage collector's heap should be allowed to expand
	       between collections.  Tuning this may improve compilation
	       speed; it has no	effect on code generation.

	       The default is 30% + 70%	* (RAM/1GB) with an upper bound	of
	       100% when RAM >=	1GB.  If "getrlimit" is	available, the notion
	       of "RAM"	is the smallest	of actual RAM and "RLIMIT_DATA"	or
	       "RLIMIT_AS".  If	GCC is not able	to calculate RAM on a particu-
	       lar platform, the lower bound of	30% is used.  Setting this
	       parameter and ggc-min-heapsize to zero causes a full collection
	       to occur	at every opportunity.  This is extremely slow, but can
	       be useful for debugging.

	   ggc-min-heapsize
	       Minimum size of the garbage collector's heap before it begins
	       bothering to collect garbage.  The first	collection occurs
	       after the heap expands by ggc-min-expand% beyond	ggc-min-heap-
	       size.  Again, tuning this may improve compilation speed,	and
	       has no effect on	code generation.

	       The default is the smaller of RAM/8, RLIMIT_RSS,	or a limit
	       which tries to ensure that RLIMIT_DATA or RLIMIT_AS are not
	       exceeded, but with a lower bound	of 4096	(four megabytes) and
	       an upper	bound of 131072	(128 megabytes).  If GCC is not	able
	       to calculate RAM	on a particular	platform, the lower bound is
	       used.  Setting this parameter very large	effectively disables
	       garbage collection.  Setting this parameter and ggc-min-expand
	       to zero causes a	full collection	to occur at every opportunity.

	   max-reload-search-insns
	       The maximum number of instruction reload	should look backward
	       for equivalent register.	 Increasing values mean	more aggres-
	       sive optimization, making the compile time increase with	proba-
	       bly slightly better performance.	 The default value is 100.

	   max-cselib-memory-locations
	       The maximum number of memory locations cselib should take into
	       account.	 Increasing values mean	more aggressive	optimization,
	       making the compile time increase	with probably slightly better
	       performance.  The default value is 500.

	   max-flow-memory-locations
	       Similar as max-cselib-memory-locations but for dataflow live-
	       ness.  The default value	is 100.

	   reorder-blocks-duplicate
	   reorder-blocks-duplicate-feedback
	       Used by basic block reordering pass to decide whether to	use
	       unconditional branch or duplicate the code on its destination.
	       Code is duplicated when its estimated size is smaller than this
	       value multiplied	by the estimated size of unconditional jump in
	       the hot spots of	the program.

	       The reorder-block-duplicate-feedback is used only when profile
	       feedback	is available and may be	set to higher values than
	       reorder-block-duplicate since information about the hot spots
	       is more accurate.

	   max-sched-ready-insns
	       The maximum number of instructions ready	to be issued the
	       scheduler should	consider at any	given time during the first
	       scheduling pass.	 Increasing values mean	more thorough
	       searches, making	the compilation	time increase with probably
	       little benefit.	The default value is 100.

	   max-sched-region-blocks
	       The maximum number of blocks in a region	to be considered for
	       interblock scheduling.  The default value is 10.

	   max-sched-region-insns
	       The maximum number of insns in a	region to be considered	for
	       interblock scheduling.  The default value is 100.

	   min-spec-prob
	       The minimum probability (in percents) of	reaching a source
	       block for interblock speculative	scheduling.  The default value
	       is 40.

	   max-sched-extend-regions-iters
	       The maximum number of iterations	through	CFG to extend regions.
	       0 - disable region extension, N - do at most N iterations.  The
	       default value is	0.

	   max-sched-insn-conflict-delay
	       The maximum conflict delay for an insn to be considered for
	       speculative motion.  The	default	value is 3.

	   sched-spec-prob-cutoff
	       The minimal probability of speculation success (in percents),
	       so that speculative insn	will be	scheduled.  The	default	value
	       is 40.

	   max-last-value-rtl
	       The maximum size	measured as number of RTLs that	can be
	       recorded	in an expression in combiner for a pseudo register as
	       last known value	of that	register.  The default is 10000.

	   integer-share-limit
	       Small integer constants can use a shared	data structure,	reduc-
	       ing the compiler's memory usage and increasing its speed.  This
	       sets the	maximum	value of a shared integer constant's.  The
	       default value is	256.

	   min-virtual-mappings
	       Specifies the minimum number of virtual mappings	in the incre-
	       mental SSA updater that should be registered to trigger the
	       virtual mappings	heuristic defined by virtual-mappings-ratio.
	       The default value is 100.

	   virtual-mappings-ratio
	       If the number of	virtual	mappings is virtual-mappings-ratio
	       bigger than the number of virtual symbols to be updated,	then
	       the incremental SSA updater switches to a full update for those
	       symbols.	 The default ratio is 3.

	   ssp-buffer-size
	       The minimum size	of buffers (i.e. arrays) that will receive
	       stack smashing protection when -fstack-protection is used.

	   max-jump-thread-duplication-stmts
	       Maximum number of statements allowed in a block that needs to
	       be duplicated when threading jumps.

	   max-fields-for-field-sensitive
	       Maximum number of fields	in a structure we will treat in	a
	       field sensitive manner during pointer analysis.

       Options Controlling the Preprocessor

       These options control the C preprocessor, which is run on each C	source
       file before actual compilation.

       If you use the -E option, nothing is done except	preprocessing.	Some
       of these	options	make sense only	together with -E because they cause
       the preprocessor	output to be unsuitable	for actual compilation.

	   You can use -Wp,option to bypass the	compiler driver	and pass
	   option directly through to the preprocessor.	 If option contains
	   commas, it is split into multiple options at	the commas.  However,
	   many	options	are modified, translated or interpreted	by the com-
	   piler driver	before being passed to the preprocessor, and -Wp
	   forcibly bypasses this phase.  The preprocessor's direct interface
	   is undocumented and subject to change, so whenever possible you
	   should avoid	using -Wp and let the driver handle the	options
	   instead.

       -Xpreprocessor option
	   Pass	option as an option to the preprocessor.  You can use this to
	   supply system-specific preprocessor options which GCC does not know
	   how to recognize.

	   If you want to pass an option that takes an argument, you must use
	   -Xpreprocessor twice, once for the option and once for the argu-
	   ment.

       -D name
	   Predefine name as a macro, with definition 1.

       -D name=definition
	   The contents	of definition are tokenized and	processed as if	they
	   appeared during translation phase three in a	#define	directive.  In
	   particular, the definition will be truncated	by embedded newline
	   characters.

	   If you are invoking the preprocessor	from a shell or	shell-like
	   program you may need	to use the shell's quoting syntax to protect
	   characters such as spaces that have a meaning in the	shell syntax.

	   If you wish to define a function-like macro on the command line,
	   write its argument list with	surrounding parentheses	before the
	   equals sign (if any).  Parentheses are meaningful to	most shells,
	   so you will need to quote the option.  With sh and csh,
	   -D'name(args...)=definition'	works.

	   -D and -U options are processed in the order	they are given on the
	   command line.  All -imacros file and	-include file options are pro-
	   cessed after	all -D and -U options.

       -U name
	   Cancel any previous definition of name, either built	in or provided
	   with	a -D option.

       -undef
	   Do not predefine any	system-specific	or GCC-specific	macros.	 The
	   standard predefined macros remain defined.

       -I dir
	   Add the directory dir to the	list of	directories to be searched for
	   header files.  Directories named by -I are searched before the
	   standard system include directories.	 If the	directory dir is a
	   standard system include directory, the option is ignored to ensure
	   that	the default search order for system directories	and the	spe-
	   cial	treatment of system headers are	not defeated .

       -o file
	   Write output	to file.  This is the same as specifying file as the
	   second non-option argument to cpp.  gcc has a different interpreta-
	   tion	of a second non-option argument, so you	must use -o to specify
	   the output file.

       -Wall
	   Turns on all	optional warnings which	are desirable for normal code.
	   At present this is -Wcomment, -Wtrigraphs, -Wmultichar and a	warn-
	   ing about integer promotion causing a change	of sign	in "#if"
	   expressions.	 Note that many	of the preprocessor's warnings are on
	   by default and have no options to control them.

       -Wcomment
       -Wcomments
	   Warn	whenever a comment-start sequence /* appears in	a /* comment,
	   or whenever a backslash-newline appears in a	// comment.  (Both
	   forms have the same effect.)

       -Wtrigraphs
	   Most	trigraphs in comments cannot affect the	meaning	of the pro-
	   gram.  However, a trigraph that would form an escaped newline (??/
	   at the end of a line) can, by changing where	the comment begins or
	   ends.  Therefore, only trigraphs that would form escaped newlines
	   produce warnings inside a comment.

	   This	option is implied by -Wall.  If	-Wall is not given, this
	   option is still enabled unless trigraphs are	enabled.  To get tri-
	   graph conversion without warnings, but get the other	-Wall warn-
	   ings, use -trigraphs	-Wall -Wno-trigraphs.

       -Wtraditional
	   Warn	about certain constructs that behave differently in tradi-
	   tional and ISO C.  Also warn	about ISO C constructs that have no
	   traditional C equivalent, and problematic constructs	which should
	   be avoided.

       -Wimport
	   Warn	the first time #import is used.

       -Wundef
	   Warn	whenever an identifier which is	not a macro is encountered in
	   an #if directive, outside of	defined.  Such identifiers are
	   replaced with zero.

       -Wunused-macros
	   Warn	about macros defined in	the main file that are unused.	A
	   macro is used if it is expanded or tested for existence at least
	   once.  The preprocessor will	also warn if the macro has not been
	   used	at the time it is redefined or undefined.

	   Built-in macros, macros defined on the command line,	and macros
	   defined in include files are	not warned about.

	   Note: If a macro is actually	used, but only used in skipped condi-
	   tional blocks, then CPP will	report it as unused.  To avoid the
	   warning in such a case, you might improve the scope of the macro's
	   definition by, for example, moving it into the first	skipped	block.
	   Alternatively, you could provide a dummy use	with something like:

		   #if defined the_macro_causing_the_warning
		   #endif

       -Wendif-labels
	   Warn	whenever an #else or an	#endif are followed by text.  This
	   usually happens in code of the form

		   #if FOO
		   ...
		   #else FOO
		   ...
		   #endif FOO

	   The second and third	"FOO" should be	in comments, but often are not
	   in older programs.  This warning is on by default.

       -Werror
	   Make	all warnings into hard errors.	Source code which triggers
	   warnings will be rejected.

       -Wsystem-headers
	   Issue warnings for code in system headers.  These are normally
	   unhelpful in	finding	bugs in	your own code, therefore suppressed.
	   If you are responsible for the system library, you may want to see
	   them.

       -w  Suppress all	warnings, including those which	GNU CPP	issues by
	   default.

       -pedantic
	   Issue all the mandatory diagnostics listed in the C standard.  Some
	   of them are left out	by default, since they trigger frequently on
	   harmless code.

       -pedantic-errors
	   Issue all the mandatory diagnostics,	and make all mandatory diag-
	   nostics into	errors.	 This includes mandatory diagnostics that GCC
	   issues without -pedantic but	treats as warnings.

       -M  Instead of outputting the result of preprocessing, output a rule
	   suitable for	make describing	the dependencies of the	main source
	   file.  The preprocessor outputs one make rule containing the	object
	   file	name for that source file, a colon, and	the names of all the
	   included files, including those coming from -include	or -imacros
	   command line	options.

	   Unless specified explicitly (with -MT or -MQ), the object file name
	   consists of the basename of the source file with any	suffix
	   replaced with object	file suffix.  If there are many	included files
	   then	the rule is split into several lines using \-newline.  The
	   rule	has no commands.

	   This	option does not	suppress the preprocessor's debug output, such
	   as -dM.  To avoid mixing such debug output with the dependency
	   rules you should explicitly specify the dependency output file with
	   -MF,	or use an environment variable like DEPENDENCIES_OUTPUT.
	   Debug output	will still be sent to the regular output stream	as
	   normal.

	   Passing -M to the driver implies -E,	and suppresses warnings	with
	   an implicit -w.

       -MM Like	-M but do not mention header files that	are found in system
	   header directories, nor header files	that are included, directly or
	   indirectly, from such a header.

	   This	implies	that the choice	of angle brackets or double quotes in
	   an #include directive does not in itself determine whether that
	   header will appear in -MM dependency	output.	 This is a slight
	   change in semantics from GCC	versions 3.0 and earlier.

       -MF file
	   When	used with -M or	-MM, specifies a file to write the dependen-
	   cies	to.  If	no -MF switch is given the preprocessor	sends the
	   rules to the	same place it would have sent preprocessed output.

	   When	used with the driver options -MD or -MMD, -MF overrides	the
	   default dependency output file.

       -MG In conjunction with an option such as -M requesting dependency gen-
	   eration, -MG	assumes	missing	header files are generated files and
	   adds	them to	the dependency list without raising an error.  The
	   dependency filename is taken	directly from the "#include" directive
	   without prepending any path.	 -MG also suppresses preprocessed out-
	   put,	as a missing header file renders this useless.

	   This	feature	is used	in automatic updating of makefiles.

       -MP This	option instructs CPP to	add a phony target for each dependency
	   other than the main file, causing each to depend on nothing.	 These
	   dummy rules work around errors make gives if	you remove header
	   files without updating the Makefile to match.

	   This	is typical output:

		   test.o: test.c test.h

		   test.h:

       -MT target
	   Change the target of	the rule emitted by dependency generation.  By
	   default CPP takes the name of the main input	file, including	any
	   path, deletes any file suffix such as .c, and appends the plat-
	   form's usual	object suffix.	The result is the target.

	   An -MT option will set the target to	be exactly the string you
	   specify.  If	you want multiple targets, you can specify them	as a
	   single argument to -MT, or use multiple -MT options.

	   For example,	-MT '$(objpfx)foo.o' might give

		   $(objpfx)foo.o: foo.c

       -MQ target
	   Same	as -MT,	but it quotes any characters which are special to
	   Make.  -MQ '$(objpfx)foo.o' gives

		   $$(objpfx)foo.o: foo.c

	   The default target is automatically quoted, as if it	were given
	   with	-MQ.

       -MD -MD is equivalent to	-M -MF file, except that -E is not implied.
	   The driver determines file based on whether an -o option is given.
	   If it is, the driver	uses its argument but with a suffix of .d,
	   otherwise it	take the basename of the input file and	applies	a .d
	   suffix.

	   If -MD is used in conjunction with -E, any -o switch	is understood
	   to specify the dependency output file, but if used without -E, each
	   -o is understood to specify a target	object file.

	   Since -E is not implied, -MD	can be used to generate	a dependency
	   output file as a side-effect	of the compilation process.

       -MMD
	   Like	-MD except mention only	user header files, not system header
	   files.

       -fpch-deps
	   When	using precompiled headers, this	flag will cause	the depen-
	   dency-output	flags to also list the files from the precompiled
	   header's dependencies.  If not specified only the precompiled
	   header would	be listed and not the files that were used to create
	   it because those files are not consulted when a precompiled header
	   is used.

       -fpch-preprocess
	   This	option allows use of a precompiled header together with	-E.
	   It inserts a	special	"#pragma", "#pragma GCC	pch_preprocess "<file-
	   name>"" in the output to mark the place where the precompiled
	   header was found, and its filename.	When -fpreprocessed is in use,
	   GCC recognizes this "#pragma" and loads the PCH.

	   This	option is off by default, because the resulting	preprocessed
	   output is only really suitable as input to GCC.  It is switched on
	   by -save-temps.

	   You should not write	this "#pragma" in your own code, but it	is
	   safe	to edit	the filename if	the PCH	file is	available in a differ-
	   ent location.  The filename may be absolute or it may be relative
	   to GCC's current directory.

       -x c
       -x c++
       -x assembler-with-cpp
	   Specify the source language:	C, C++,	or assembly.  This has nothing
	   to do with standards	conformance or extensions; it merely selects
	   which base syntax to	expect.	 If you	give none of these options,
	   cpp will deduce the language	from the extension of the source file:
	   .c, .cc, .m,	or .S.	Some other common extensions for C++ and
	   assembly are	also recognized.  If cpp does not recognize the	exten-
	   sion, it will treat the file	as C; this is the most generic mode.

	   Note: Previous versions of cpp accepted a -lang option which
	   selected both the language and the standards	conformance level.
	   This	option has been	removed, because it conflicts with the -l
	   option.

       -std=standard
       -ansi
	   Specify the standard	to which the code should conform.  Currently
	   CPP knows about C and C++ standards;	others may be added in the
	   future.

	   standard may	be one of:

	   "iso9899:1990"
	   "c89"
	       The ISO C standard from 1990.  c89 is the customary shorthand
	       for this	version	of the standard.

	       The -ansi option	is equivalent to -std=c89.

	   "iso9899:199409"
	       The 1990	C standard, as amended in 1994.

	   "iso9899:1999"
	   "c99"
	   "iso9899:199x"
	   "c9x"
	       The revised ISO C standard, published in	December 1999.	Before
	       publication, this was known as C9X.

	   "gnu89"
	       The 1990	C standard plus	GNU extensions.	 This is the default.

	   "gnu99"
	   "gnu9x"
	       The 1999	C standard plus	GNU extensions.

	   "c++98"
	       The 1998	ISO C++	standard plus amendments.

	   "gnu++98"
	       The same	as -std=c++98 plus GNU extensions.  This is the
	       default for C++ code.

       -I- Split the include path.  Any	directories specified with -I options
	   before -I- are searched only	for headers requested with
	   "#include "file""; they are not searched for	"#include <file>".  If
	   additional directories are specified	with -I	options	after the -I-,
	   those directories are searched for all #include directives.

	   In addition,	-I- inhibits the use of	the directory of the current
	   file	directory as the first search directory	for "#include "file"".
	   This	option has been	deprecated.

       -nostdinc
	   Do not search the standard system directories for header files.
	   Only	the directories	you have specified with	-I options (and	the
	   directory of	the current file, if appropriate) are searched.

       -nostdinc++
	   Do not search for header files in the C++-specific standard direc-
	   tories, but do still	search the other standard directories.	(This
	   option is used when building	the C++	library.)

       -include	file
	   Process file	as if "#include	"file""	appeared as the	first line of
	   the primary source file.  However, the first	directory searched for
	   file	is the preprocessor's working directory	instead	of the direc-
	   tory	containing the main source file.  If not found there, it is
	   searched for	in the remainder of the	"#include "..."" search	chain
	   as normal.

	   If multiple -include	options	are given, the files are included in
	   the order they appear on the	command	line.

       -imacros	file
	   Exactly like	-include, except that any output produced by scanning
	   file	is thrown away.	 Macros	it defines remain defined.  This
	   allows you to acquire all the macros	from a header without also
	   processing its declarations.

	   All files specified by -imacros are processed before	all files
	   specified by	-include.

       -idirafter dir
	   Search dir for header files,	but do it after	all directories	speci-
	   fied	with -I	and the	standard system	directories have been
	   exhausted.  dir is treated as a system include directory.

       -iprefix	prefix
	   Specify prefix as the prefix	for subsequent -iwithprefix options.
	   If the prefix represents a directory, you should include the	final
	   /.

       -iwithprefix dir
       -iwithprefixbefore dir
	   Append dir to the prefix specified previously with -iprefix,	and
	   add the resulting directory to the include search path.  -iwithpre-
	   fixbefore puts it in	the same place -I would; -iwithprefix puts it
	   where -idirafter would.

       -isysroot dir
	   This	option is like the --sysroot option, but applies only to
	   header files.  See the --sysroot option for more information.

       -imultilib dir
	   Use dir as a	subdirectory of	the directory containing target-spe-
	   cific C++ headers.

       -isystem	dir
	   Search dir for header files,	after all directories specified	by -I
	   but before the standard system directories.	Mark it	as a system
	   directory, so that it gets the same special treatment as is applied
	   to the standard system directories.

       -iquote dir
	   Search dir only for header files requested with "#include "file"";
	   they	are not	searched for "#include <file>",	before all directories
	   specified by	-I and before the standard system directories.

       -fdollars-in-identifiers
	   Accept $ in identifiers.

       -fextended-identifiers
	   Accept universal character names in identifiers.  This option is
	   experimental; in a future version of	GCC, it	will be	enabled	by
	   default for C99 and C++.

       -fpreprocessed
	   Indicate to the preprocessor	that the input file has	already	been
	   preprocessed.  This suppresses things like macro expansion, tri-
	   graph conversion, escaped newline splicing, and processing of most
	   directives.	The preprocessor still recognizes and removes com-
	   ments, so that you can pass a file preprocessed with	-C to the com-
	   piler without problems.  In this mode the integrated	preprocessor
	   is little more than a tokenizer for the front ends.

	   -fpreprocessed is implicit if the input file	has one	of the exten-
	   sions .i, .ii or .mi.  These	are the	extensions that	GCC uses for
	   preprocessed	files created by -save-temps.

       -ftabstop=width
	   Set the distance between tab	stops.	This helps the preprocessor
	   report correct column numbers in warnings or	errors,	even if	tabs
	   appear on the line.	If the value is	less than 1 or greater than
	   100,	the option is ignored.	The default is 8.

       -fexec-charset=charset
	   Set the execution character set, used for string and	character con-
	   stants.  The	default	is UTF-8.  charset can be any encoding sup-
	   ported by the system's "iconv" library routine.

       -fwide-exec-charset=charset
	   Set the wide	execution character set, used for wide string and
	   character constants.	 The default is	UTF-32 or UTF-16, whichever
	   corresponds to the width of "wchar_t".  As with -fexec-charset,
	   charset can be any encoding supported by the	system's "iconv"
	   library routine; however, you will have problems with encodings
	   that	do not fit exactly in "wchar_t".

       -finput-charset=charset
	   Set the input character set,	used for translation from the charac-
	   ter set of the input	file to	the source character set used by GCC.
	   If the locale does not specify, or GCC cannot get this information
	   from	the locale, the	default	is UTF-8.  This	can be overridden by
	   either the locale or	this command line option.  Currently the com-
	   mand	line option takes precedence if	there's	a conflict.  charset
	   can be any encoding supported by the	system's "iconv" library rou-
	   tine.

       -fworking-directory
	   Enable generation of	linemarkers in the preprocessor	output that
	   will	let the	compiler know the current working directory at the
	   time	of preprocessing.  When	this option is enabled,	the preproces-
	   sor will emit, after	the initial linemarker,	a second linemarker
	   with	the current working directory followed by two slashes.	GCC
	   will	use this directory, when it's present in the preprocessed
	   input, as the directory emitted as the current working directory in
	   some	debugging information formats.	This option is implicitly
	   enabled if debugging	information is enabled,	but this can be	inhib-
	   ited	with the negated form -fno-working-directory.  If the -P flag
	   is present in the command line, this	option has no effect, since no
	   "#line" directives are emitted whatsoever.

       -fno-show-column
	   Do not print	column numbers in diagnostics.	This may be necessary
	   if diagnostics are being scanned by a program that does not under-
	   stand the column numbers, such as dejagnu.

       -A predicate=answer
	   Make	an assertion with the predicate	predicate and answer answer.
	   This	form is	preferred to the older form -A predicate(answer),
	   which is still supported, because it	does not use shell special
	   characters.

       -A -predicate=answer
	   Cancel an assertion with the	predicate predicate and	answer answer.

       -dCHARS
	   CHARS is a sequence of one or more of the following characters, and
	   must	not be preceded	by a space.  Other characters are interpreted
	   by the compiler proper, or reserved for future versions of GCC, and
	   so are silently ignored.  If	you specify characters whose behavior
	   conflicts, the result is undefined.

	   M   Instead of the normal output, generate a	list of	#define	direc-
	       tives for all the macros	defined	during the execution of	the
	       preprocessor, including predefined macros.  This	gives you a
	       way of finding out what is predefined in	your version of	the
	       preprocessor.  Assuming you have	no file	foo.h, the command

		       touch foo.h; cpp	-dM foo.h

	       will show all the predefined macros.

	   D   Like M except in	two respects: it does not include the prede-
	       fined macros, and it outputs both the #define directives	and
	       the result of preprocessing.  Both kinds	of output go to	the
	       standard	output file.

	   N   Like D, but emit	only the macro names, not their	expansions.

	   I   Output #include directives in addition to the result of prepro-
	       cessing.

       -P  Inhibit generation of linemarkers in	the output from	the preproces-
	   sor.	 This might be useful when running the preprocessor on some-
	   thing that is not C code, and will be sent to a program which might
	   be confused by the linemarkers.

       -C  Do not discard comments.  All comments are passed through to	the
	   output file,	except for comments in processed directives, which are
	   deleted along with the directive.

	   You should be prepared for side effects when	using -C; it causes
	   the preprocessor to treat comments as tokens	in their own right.
	   For example,	comments appearing at the start	of what	would be a
	   directive line have the effect of turning that line into an ordi-
	   nary	source line, since the first token on the line is no longer a
	   #.

       -CC Do not discard comments, including during macro expansion.  This is
	   like	-C, except that	comments contained within macros are also
	   passed through to the output	file where the macro is	expanded.

	   In addition to the side-effects of the -C option, the -CC option
	   causes all C++-style	comments inside	a macro	to be converted	to
	   C-style comments.  This is to prevent later use of that macro from
	   inadvertently commenting out	the remainder of the source line.

	   The -CC option is generally used to support lint comments.

       -traditional-cpp
	   Try to imitate the behavior of old-fashioned	C preprocessors, as
	   opposed to ISO C preprocessors.

       -trigraphs
	   Process trigraph sequences.	These are three-character sequences,
	   all starting	with ??, that are defined by ISO C to stand for	single
	   characters.	For example, ??/ stands	for \, so '??/n' is a charac-
	   ter constant	for a newline.	By default, GCC	ignores	trigraphs, but
	   in standard-conforming modes	it converts them.  See the -std	and
	   -ansi options.

	   The nine trigraphs and their	replacements are

		   Trigraph:	   ??(	??)  ??<  ??>  ??=  ??/	 ??'  ??!  ??-
		   Replacement:	     [	  ]    {    }	 #    \	   ^	|    ~

       -remap
	   Enable special code to work around file systems which only permit
	   very	short file names, such as MS-DOS.

       --help
       --target-help
	   Print text describing all the command line options instead of pre-
	   processing anything.

       -v  Verbose mode.  Print	out GNU	CPP's version number at	the beginning
	   of execution, and report the	final form of the include path.

       -H  Print the name of each header file used, in addition	to other nor-
	   mal activities.  Each name is indented to show how deep in the
	   #include stack it is.  Precompiled header files are also printed,
	   even	if they	are found to be	invalid; an invalid precompiled	header
	   file	is printed with	...x and a valid one with ...! .

       -version
       --version
	   Print out GNU CPP's version number.	With one dash, proceed to pre-
	   process as normal.  With two	dashes,	exit immediately.

       Passing Options to the Assembler

       You can pass options to the assembler.

       -Wa,option
	   Pass	option as an option to the assembler.  If option contains com-
	   mas,	it is split into multiple options at the commas.

       -Xassembler option
	   Pass	option as an option to the assembler.  You can use this	to
	   supply system-specific assembler options which GCC does not know
	   how to recognize.

	   If you want to pass an option that takes an argument, you must use
	   -Xassembler twice, once for the option and once for the argument.

       Options for Linking

       These options come into play when the compiler links object files into
       an executable output file.  They	are meaningless	if the compiler	is not
       doing a link step.

       object-file-name
	   A file name that does not end in a special recognized suffix	is
	   considered to name an object	file or	library.  (Object files	are
	   distinguished from libraries	by the linker according	to the file
	   contents.)  If linking is done, these object	files are used as
	   input to the	linker.

       -c
       -S
       -E  If any of these options is used, then the linker is not run,	and
	   object file names should not	be used	as arguments.

       -llibrary
       -l library
	   Search the library named library when linking.  (The	second alter-
	   native with the library as a	separate argument is only for POSIX
	   compliance and is not recommended.)

	   It makes a difference where in the command you write	this option;
	   the linker searches and processes libraries and object files	in the
	   order they are specified.  Thus, foo.o -lz bar.o searches library z
	   after file foo.o but	before bar.o.  If bar.o	refers to functions in
	   z, those functions may not be loaded.

	   The linker searches a standard list of directories for the library,
	   which is actually a file named liblibrary.a.	 The linker then uses
	   this	file as	if it had been specified precisely by name.

	   The directories searched include several standard system directo-
	   ries	plus any that you specify with -L.

	   Normally the	files found this way are library files---archive files
	   whose members are object files.  The	linker handles an archive file
	   by scanning through it for members which define symbols that	have
	   so far been referenced but not defined.  But	if the file that is
	   found is an ordinary	object file, it	is linked in the usual fash-
	   ion.	 The only difference between using an -l option	and specifying
	   a file name is that -l surrounds library with lib and .a and
	   searches several directories.

       -nostartfiles
	   Do not use the standard system startup files	when linking.  The
	   standard system libraries are used normally,	unless -nostdlib or
	   -nodefaultlibs is used.

       -nodefaultlibs
	   Do not use the standard system libraries when linking.  Only	the
	   libraries you specify will be passed	to the linker.	The standard
	   startup files are used normally, unless -nostartfiles is used.  The
	   compiler may	generate calls to "memcmp", "memset", "memcpy" and
	   "memmove".  These entries are usually resolved by entries in	libc.
	   These entry points should be	supplied through some other mechanism
	   when	this option is specified.

       -nostdlib
	   Do not use the standard system startup files	or libraries when
	   linking.  No	startup	files and only the libraries you specify will
	   be passed to	the linker.  The compiler may generate calls to	"mem-
	   cmp", "memset", "memcpy" and	"memmove".  These entries are usually
	   resolved by entries in libc.	 These entry points should be supplied
	   through some	other mechanism	when this option is specified.

	   One of the standard libraries bypassed by -nostdlib and -nodefault-
	   libs	is libgcc.a, a library of internal subroutines that GCC	uses
	   to overcome shortcomings of particular machines, or special needs
	   for some languages.

	   In most cases, you need libgcc.a even when you want to avoid	other
	   standard libraries.	In other words,	when you specify -nostdlib or
	   -nodefaultlibs you should usually specify -lgcc as well.  This
	   ensures that	you have no unresolved references to internal GCC
	   library subroutines.	 (For example, __main, used to ensure C++ con-
	   structors will be called.)

       -pie
	   Produce a position independent executable on	targets	which support
	   it.	For predictable	results, you must also specify the same	set of
	   options that	were used to generate code (-fpie, -fPIE, or model
	   suboptions) when you	specify	this option.

       -rdynamic
	   Pass	the flag -export-dynamic to the	ELF linker, on targets that
	   support it. This instructs the linker to add	all symbols, not only
	   used	ones, to the dynamic symbol table. This	option is needed for
	   some	uses of	"dlopen" or to allow obtaining backtraces from within
	   a program.

       -s  Remove all symbol table and relocation information from the exe-
	   cutable.

       -static
	   On systems that support dynamic linking, this prevents linking with
	   the shared libraries.  On other systems, this option	has no effect.

       -shared
	   Produce a shared object which can then be linked with other objects
	   to form an executable.  Not all systems support this	option.	 For
	   predictable results,	you must also specify the same set of options
	   that	were used to generate code (-fpic, -fPIC, or model suboptions)
	   when	you specify this option.[1]

       -shared-libgcc
       -static-libgcc
	   On systems that provide libgcc as a shared library, these options
	   force the use of either the shared or static	version	respectively.
	   If no shared	version	of libgcc was built when the compiler was con-
	   figured, these options have no effect.

	   There are several situations	in which an application	should use the
	   shared libgcc instead of the	static version.	 The most common of
	   these is when the application wishes	to throw and catch exceptions
	   across different shared libraries.  In that case, each of the
	   libraries as	well as	the application	itself should use the shared
	   libgcc.

	   Therefore, the G++ and GCJ drivers automatically add	-shared-libgcc
	   whenever you	build a	shared library or a main executable, because
	   C++ and Java	programs typically use exceptions, so this is the
	   right thing to do.

	   If, instead,	you use	the GCC	driver to create shared	libraries, you
	   may find that they will not always be linked	with the shared
	   libgcc.  If GCC finds, at its configuration time, that you have a
	   non-GNU linker or a GNU linker that does not	support	option
	   --eh-frame-hdr, it will link	the shared version of libgcc into
	   shared libraries by default.	 Otherwise, it will take advantage of
	   the linker and optimize away	the linking with the shared version of
	   libgcc, linking with	the static version of libgcc by	default.  This
	   allows exceptions to	propagate through such shared libraries, with-
	   out incurring relocation costs at library load time.

	   However, if a library or main executable is supposed	to throw or
	   catch exceptions, you must link it using the	G++ or GCJ driver, as
	   appropriate for the languages used in the program, or using the
	   option -shared-libgcc, such that it is linked with the shared
	   libgcc.

       -symbolic
	   Bind	references to global symbols when building a shared object.
	   Warn	about any unresolved references	(unless	overridden by the link
	   editor option -Xlinker -z -Xlinker defs).  Only a few systems sup-
	   port	this option.

       -Xlinker	option
	   Pass	option as an option to the linker.  You	can use	this to	supply
	   system-specific linker options which	GCC does not know how to rec-
	   ognize.

	   If you want to pass an option that takes an argument, you must use
	   -Xlinker twice, once	for the	option and once	for the	argument.  For
	   example, to pass -assert definitions, you must write	-Xlinker
	   -assert -Xlinker definitions.  It does not work to write -Xlinker
	   "-assert definitions", because this passes the entire string	as a
	   single argument, which is not what the linker expects.

       -Wl,option
	   Pass	option as an option to the linker.  If option contains commas,
	   it is split into multiple options at	the commas.

       -u symbol
	   Pretend the symbol symbol is	undefined, to force linking of library
	   modules to define it.  You can use -u multiple times	with different
	   symbols to force loading of additional library modules.

       Options for Directory Search

       These options specify directories to search for header files, for
       libraries and for parts of the compiler:

       -Idir
	   Add the directory dir to the	head of	the list of directories	to be
	   searched for	header files.  This can	be used	to override a system
	   header file,	substituting your own version, since these directories
	   are searched	before the system header file directories.  However,
	   you should not use this option to add directories that contain ven-
	   dor-supplied	system header files (use -isystem for that).  If you
	   use more than one -I	option,	the directories	are scanned in left-
	   to-right order; the standard	system directories come	after.

	   If a	standard system	include	directory, or a	directory specified
	   with	-isystem, is also specified with -I, the -I option will	be
	   ignored.  The directory will	still be searched but as a system
	   directory at	its normal position in the system include chain.  This
	   is to ensure	that GCC's procedure to	fix buggy system headers and
	   the ordering	for the	include_next directive are not inadvertently
	   changed.  If	you really need	to change the search order for system
	   directories,	use the	-nostdinc and/or -isystem options.

       -iquotedir
	   Add the directory dir to the	head of	the list of directories	to be
	   searched for	header files only for the case of #include "file";
	   they	are not	searched for #include <file>, otherwise	just like -I.

       -Ldir
	   Add directory dir to	the list of directories	to be searched for -l.

       -Bprefix
	   This	option specifies where to find the executables,	libraries,
	   include files, and data files of the	compiler itself.

	   The compiler	driver program runs one	or more	of the subprograms
	   cpp,	cc1, as	and ld.	 It tries prefix as a prefix for each program
	   it tries to run, both with and without machine/version/.

	   For each subprogram to be run, the compiler driver first tries the
	   -B prefix, if any.  If that name is not found, or if	-B was not
	   specified, the driver tries two standard prefixes, which are
	   /usr/lib/gcc/ and /usr/local/lib/gcc/.  If neither of those results
	   in a	file name that is found, the unmodified	program	name is
	   searched for	using the directories specified	in your	PATH environ-
	   ment	variable.

	   The compiler	will check to see if the path provided by the -B
	   refers to a directory, and if necessary it will add a directory
	   separator character at the end of the path.

	   -B prefixes that effectively	specify	directory names	also apply to
	   libraries in	the linker, because the	compiler translates these
	   options into	-L options for the linker.  They also apply to
	   includes files in the preprocessor, because the compiler translates
	   these options into -isystem options for the preprocessor.  In this
	   case, the compiler appends include to the prefix.

	   The run-time	support	file libgcc.a can also be searched for using
	   the -B prefix, if needed.  If it is not found there,	the two	stan-
	   dard	prefixes above are tried, and that is all.  The	file is	left
	   out of the link if it is not	found by those means.

	   Another way to specify a prefix much	like the -B prefix is to use
	   the environment variable GCC_EXEC_PREFIX.

	   As a	special	kludge,	if the path provided by	-B is [dir/]stageN/,
	   where N is a	number in the range 0 to 9, then it will be replaced
	   by [dir/]include.  This is to help with boot-strapping the com-
	   piler.

       -specs=file
	   Process file	after the compiler reads in the	standard specs file,
	   in order to override	the defaults that the gcc driver program uses
	   when	determining what switches to pass to cc1, cc1plus, as, ld,
	   etc.	 More than one -specs=file can be specified on the command
	   line, and they are processed	in order, from left to right.

       --sysroot=dir
	   Use dir as the logical root directory for headers and libraries.
	   For example,	if the compiler	would normally search for headers in
	   /usr/include	and libraries in /usr/lib, it will instead search
	   dir/usr/include and dir/usr/lib.

	   If you use both this	option and the -isysroot option, then the
	   --sysroot option will apply to libraries, but the -isysroot option
	   will	apply to header	files.

	   The GNU linker (beginning with version 2.16)	has the	necessary sup-
	   port	for this option.  If your linker does not support this option,
	   the header file aspect of --sysroot will still work,	but the
	   library aspect will not.

       -I- This	option has been	deprecated.  Please use	-iquote	instead	for -I
	   directories before the -I- and remove the -I-.  Any directories you
	   specify with	-I options before the -I- option are searched only for
	   the case of #include	"file";	they are not searched for #include
	   <file>.

	   If additional directories are specified with	-I options after the
	   -I-,	these directories are searched for all #include	directives.
	   (Ordinarily all -I directories are used this	way.)

	   In addition,	the -I-	option inhibits	the use	of the current direc-
	   tory	(where the current input file came from) as the	first search
	   directory for #include "file".  There is no way to override this
	   effect of -I-.  With	-I. you	can specify searching the directory
	   which was current when the compiler was invoked.  That is not
	   exactly the same as what the	preprocessor does by default, but it
	   is often satisfactory.

	   -I- does not	inhibit	the use	of the standard	system directories for
	   header files.  Thus,	-I- and	-nostdinc are independent.

       Specifying Target Machine and Compiler Version

       The usual way to	run GCC	is to run the executable called	gcc, or
       _machine_-gcc when cross-compiling, or _machine_-gcc-_version_ to run a
       version other than the one that was installed last.  Sometimes this is
       inconvenient, so	GCC provides options that will switch to another
       cross-compiler or version.

       -b machine
	   The argument	machine	specifies the target machine for compilation.

	   The value to	use for	machine	is the same as was specified as	the
	   machine type	when configuring GCC as	a cross-compiler.  For exam-
	   ple,	if a cross-compiler was	configured with	configure arm-elf,
	   meaning to compile for an arm processor with	elf binaries, then you
	   would specify -b arm-elf to run that	cross compiler.	 Because there
	   are other options beginning with -b,	the configuration must contain
	   a hyphen.

       -V version
	   The argument	version	specifies which	version	of GCC to run.	This
	   is useful when multiple versions are	installed.  For	example, ver-
	   sion	might be 4.0, meaning to run GCC version 4.0.

       The -V and -b options work by running the _machine_-gcc-_version_ exe-
       cutable,	so there's no real reason to use them if you can just run that
       directly.

       Hardware	Models and Configurations

       Earlier we discussed the	standard option	-b which chooses among differ-
       ent installed compilers for completely different	target machines, such
       as VAX vs. 68000	vs. 80386.

       In addition, each of these target machine types can have	its own	spe-
       cial options, starting with -m, to choose among various hardware	models
       or configurations---for example,	68010 vs 68020,	floating coprocessor
       or none.	 A single installed version of the compiler can	compile	for
       any model or configuration, according to	the options specified.

       Some configurations of the compiler also	support	additional special
       options,	usually	for compatibility with other compilers on the same
       platform.

       ARC Options

       These options are defined for ARC implementations:

       -EL Compile code	for little endian mode.	 This is the default.

       -EB Compile code	for big	endian mode.

       -mmangle-cpu
	   Prepend the name of the cpu to all public symbol names.  In multi-
	   ple-processor systems, there	are many ARC variants with different
	   instruction and register set	characteristics.  This flag prevents
	   code	compiled for one cpu to	be linked with code compiled for
	   another.  No	facility exists	for handling variants that are "almost
	   identical".	This is	an all or nothing option.

       -mcpu=cpu
	   Compile code	for ARC	variant	cpu.  Which variants are supported
	   depend on the configuration.	 All variants support -mcpu=base, this
	   is the default.

       -mtext=text-section
       -mdata=data-section
       -mrodata=readonly-data-section
	   Put functions, data,	and readonly data in text-section, data-sec-
	   tion, and readonly-data-section respectively	by default.  This can
	   be overridden with the "section" attribute.

       ARM Options

       These -m	options	are defined for	Advanced RISC Machines (ARM) architec-
       tures:

       -mabi=name
	   Generate code for the specified ABI.	 Permissible values are: apcs-
	   gnu,	atpcs, aapcs, aapcs-linux and iwmmxt.

       -mapcs-frame
	   Generate a stack frame that is compliant with the ARM Procedure
	   Call	Standard for all functions, even if this is not	strictly nec-
	   essary for correct execution	of the code.  Specifying
	   -fomit-frame-pointer	with this option will cause the	stack frames
	   not to be generated for leaf	functions.  The	default	is
	   -mno-apcs-frame.

       -mapcs
	   This	is a synonym for -mapcs-frame.

       -mthumb-interwork
	   Generate code which supports	calling	between	the ARM	and Thumb
	   instruction sets.  Without this option the two instruction sets
	   cannot be reliably used inside one program.	The default is
	   -mno-thumb-interwork, since slightly	larger code is generated when
	   -mthumb-interwork is	specified.

       -mno-sched-prolog
	   Prevent the reordering of instructions in the function prolog, or
	   the merging of those	instruction with the instructions in the func-
	   tion's body.	 This means that all functions will start with a rec-
	   ognizable set of instructions (or in	fact one of a choice from a
	   small set of	different function prologues), and this	information
	   can be used to locate the start if functions	inside an executable
	   piece of code.  The default is -msched-prolog.

       -mhard-float
	   Generate output containing floating point instructions.  This is
	   the default.

       -msoft-float
	   Generate output containing library calls for	floating point.	 Warn-
	   ing:	the requisite libraries	are not	available for all ARM targets.
	   Normally the	facilities of the machine's usual C compiler are used,
	   but this cannot be done directly in cross-compilation.  You must
	   make	your own arrangements to provide suitable library functions
	   for cross-compilation.

	   -msoft-float	changes	the calling convention in the output file;
	   therefore, it is only useful	if you compile all of a	program	with
	   this	option.	 In particular,	you need to compile libgcc.a, the
	   library that	comes with GCC,	with -msoft-float in order for this to
	   work.

       -mfloat-abi=name
	   Specifies which ABI to use for floating point values.  Permissible
	   values are: soft, softfp and	hard.

	   soft	and hard are equivalent	to -msoft-float	and -mhard-float
	   respectively.  softfp allows	the generation of floating point
	   instructions, but still uses	the soft-float calling conventions.

       -mlittle-endian
	   Generate code for a processor running in little-endian mode.	 This
	   is the default for all standard configurations.

       -mbig-endian
	   Generate code for a processor running in big-endian mode; the
	   default is to compile code for a little-endian processor.

       -mwords-little-endian
	   This	option only applies when generating code for big-endian	pro-
	   cessors.  Generate code for a little-endian word order but a	big-
	   endian byte order.  That is,	a byte order of	the form 32107654.
	   Note: this option should only be used if you	require	compatibility
	   with	code for big-endian ARM	processors generated by	versions of
	   the compiler	prior to 2.8.

       -mcpu=name
	   This	specifies the name of the target ARM processor.	 GCC uses this
	   name	to determine what kind of instructions it can emit when	gener-
	   ating assembly code.	 Permissible names are:	arm2, arm250, arm3,
	   arm6, arm60,	arm600,	arm610,	arm620,	arm7, arm7m, arm7d, arm7dm,
	   arm7di, arm7dmi, arm70, arm700, arm700i, arm710, arm710c, arm7100,
	   arm7500, arm7500fe, arm7tdmi, arm7tdmi-s, arm8, strongarm, stron-
	   garm110, strongarm1100, arm8, arm810, arm9, arm9e, arm920, arm920t,
	   arm922t, arm946e-s, arm966e-s, arm968e-s, arm926ej-s, arm940t,
	   arm9tdmi, arm10tdmi,	arm1020t, arm1026ej-s, arm10e, arm1020e,
	   arm1022e, arm1136j-s, arm1136jf-s, mpcore, mpcorenovfp,
	   arm1176jz-s,	arm1176jzf-s, xscale, iwmmxt, ep9312.

       -mtune=name
	   This	option is very similar to the -mcpu= option, except that
	   instead of specifying the actual target processor type, and hence
	   restricting which instructions can be used, it specifies that GCC
	   should tune the performance of the code as if the target were of
	   the type specified in this option, but still	choosing the instruc-
	   tions that it will generate based on	the cpu	specified by a -mcpu=
	   option.  For	some ARM implementations better	performance can	be
	   obtained by using this option.

       -march=name
	   This	specifies the name of the target ARM architecture.  GCC	uses
	   this	name to	determine what kind of instructions it can emit	when
	   generating assembly code.  This option can be used in conjunction
	   with	or instead of the -mcpu= option.  Permissible names are:
	   armv2, armv2a, armv3, armv3m, armv4,	armv4t,	armv5, armv5t,
	   armv5te, armv6, armv6j, iwmmxt, ep9312.

       -mfpu=name
       -mfpe=number
       -mfp=number
	   This	specifies what floating	point hardware (or hardware emulation)
	   is available	on the target.	Permissible names are: fpa, fpe2,
	   fpe3, maverick, vfp.	 -mfp and -mfpe	are synonyms for -mfpu=fpenum-
	   ber,	for compatibility with older versions of GCC.

	   If -msoft-float is specified	this specifies the format of floating
	   point values.

       -mstructure-size-boundary=n
	   The size of all structures and unions will be rounded up to a mul-
	   tiple of the	number of bits set by this option.  Permissible	values
	   are 8, 32 and 64.  The default value	varies for different
	   toolchains.	For the	COFF targeted toolchain	the default value is
	   8.  A value of 64 is	only allowed if	the underlying ABI supports
	   it.

	   Specifying the larger number	can produce faster, more efficient
	   code, but can also increase the size	of the program.	 Different
	   values are potentially incompatible.	 Code compiled with one	value
	   cannot necessarily expect to	work with code or libraries compiled
	   with	another	value, if they exchange	information using structures
	   or unions.

       -mabort-on-noreturn
	   Generate a call to the function "abort" at the end of a "noreturn"
	   function.  It will be executed if the function tries	to return.

       -mlong-calls
       -mno-long-calls
	   Tells the compiler to perform function calls	by first loading the
	   address of the function into	a register and then performing a sub-
	   routine call	on this	register.  This	switch is needed if the	target
	   function will lie outside of	the 64 megabyte	addressing range of
	   the offset based version of subroutine call instruction.

	   Even	if this	switch is enabled, not all function calls will be
	   turned into long calls.  The	heuristic is that static functions,
	   functions which have	the short-call attribute, functions that are
	   inside the scope of a #pragma no_long_calls directive and functions
	   whose definitions have already been compiled	within the current
	   compilation unit, will not be turned	into long calls.  The excep-
	   tion	to this	rule is	that weak function definitions,	functions with
	   the long-call attribute or the section attribute, and functions
	   that	are within the scope of	a #pragma long_calls directive,	will
	   always be turned into long calls.

	   This	feature	is not enabled by default.  Specifying -mno-long-calls
	   will	restore	the default behavior, as will placing the function
	   calls within	the scope of a #pragma long_calls_off directive.  Note
	   these switches have no effect on how	the compiler generates code to
	   handle function calls via function pointers.

       -mnop-fun-dllimport
	   Disable support for the "dllimport" attribute.

       -msingle-pic-base
	   Treat the register used for PIC addressing as read-only, rather
	   than	loading	it in the prologue for each function.  The run-time
	   system is responsible for initializing this register	with an	appro-
	   priate value	before execution begins.

       -mpic-register=reg
	   Specify the register	to be used for PIC addressing.	The default is
	   R10 unless stack-checking is	enabled, when R9 is used.

       -mcirrus-fix-invalid-insns
	   Insert NOPs into the	instruction stream to in order to work around
	   problems with invalid Maverick instruction combinations.  This
	   option is only valid	if the -mcpu=ep9312 option has been used to
	   enable generation of	instructions for the Cirrus Maverick floating
	   point co-processor.	This option is not enabled by default, since
	   the problem is only present in older	Maverick implementations.  The
	   default can be re-enabled by	use of the -mno-cir-
	   rus-fix-invalid-insns switch.

       -mpoke-function-name
	   Write the name of each function into	the text section, directly
	   preceding the function prologue.  The generated code	is similar to
	   this:

			t0
			    .ascii "arm_poke_function_name", 0
			    .align
			t1
			    .word 0xff000000 + (t1 - t0)
			arm_poke_function_name
			    mov	    ip,	sp
			    stmfd   sp!, {fp, ip, lr, pc}
			    sub	    fp,	ip, #4

	   When	performing a stack backtrace, code can inspect the value of
	   "pc"	stored at "fp +	0".  If	the trace function then	looks at loca-
	   tion	"pc - 12" and the top 8	bits are set, then we know that	there
	   is a	function name embedded immediately preceding this location and
	   has length "((pc[-3]) & 0xff000000)".

       -mthumb
	   Generate code for the 16-bit	Thumb instruction set.	The default is
	   to use the 32-bit ARM instruction set.

       -mtpcs-frame
	   Generate a stack frame that is compliant with the Thumb Procedure
	   Call	Standard for all non-leaf functions.  (A leaf function is one
	   that	does not call any other	functions.)  The default is
	   -mno-tpcs-frame.

       -mtpcs-leaf-frame
	   Generate a stack frame that is compliant with the Thumb Procedure
	   Call	Standard for all leaf functions.  (A leaf function is one that
	   does	not call any other functions.)	The default is
	   -mno-apcs-leaf-frame.

       -mcallee-super-interworking
	   Gives all externally	visible	functions in the file being compiled
	   an ARM instruction set header which switches	to Thumb mode before
	   executing the rest of the function.	This allows these functions to
	   be called from non-interworking code.

       -mcaller-super-interworking
	   Allows calls	via function pointers (including virtual functions) to
	   execute correctly regardless	of whether the target code has been
	   compiled for	interworking or	not.  There is a small overhead	in the
	   cost	of executing a function	pointer	if this	option is enabled.

       -mtp=name
	   Specify the access model for	the thread local storage pointer.  The
	   valid models	are soft, which	generates calls	to "__aeabi_read_tp",
	   cp15, which fetches the thread pointer from "cp15" directly (sup-
	   ported in the arm6k architecture), and auto,	which uses the best
	   available method for	the selected processor.	 The default setting
	   is auto.

       AVR Options

       These options are defined for AVR implementations:

       -mmcu=mcu
	   Specify ATMEL AVR instruction set or	MCU type.

	   Instruction set avr1	is for the minimal AVR core, not supported by
	   the C compiler, only	for assembler programs (MCU types: at90s1200,
	   attiny10, attiny11, attiny12, attiny15, attiny28).

	   Instruction set avr2	(default) is for the classic AVR core with up
	   to 8K program memory	space (MCU types: at90s2313, at90s2323,
	   attiny22, at90s2333,	at90s2343, at90s4414, at90s4433, at90s4434,
	   at90s8515, at90c8534, at90s8535).

	   Instruction set avr3	is for the classic AVR core with up to 128K
	   program memory space	(MCU types: atmega103, atmega603, at43usb320,
	   at76c711).

	   Instruction set avr4	is for the enhanced AVR	core with up to	8K
	   program memory space	(MCU types: atmega8, atmega83, atmega85).

	   Instruction set avr5	is for the enhanced AVR	core with up to	128K
	   program memory space	(MCU types: atmega16, atmega161, atmega163,
	   atmega32, atmega323,	atmega64, atmega128, at43usb355, at94k).

       -msize
	   Output instruction sizes to the asm file.

       -minit-stack=N
	   Specify the initial stack address, which may	be a symbol or numeric
	   value, __stack is the default.

       -mno-interrupts
	   Generated code is not compatible with hardware interrupts.  Code
	   size	will be	smaller.

       -mcall-prologues
	   Functions prologues/epilogues expanded as call to appropriate sub-
	   routines.  Code size	will be	smaller.

       -mno-tablejump
	   Do not generate tablejump insns which sometimes increase code size.

       -mtiny-stack
	   Change only the low 8 bits of the stack pointer.

       -mint8
	   Assume int to be 8 bit integer.  This affects the sizes of all
	   types: A char will be 1 byte, an int	will be	1 byte,	an long	will
	   be 2	bytes and long long will be 4 bytes.  Please note that this
	   option does not comply to the C standards, but it will provide you
	   with	smaller	code size.

       Blackfin	Options

       -momit-leaf-frame-pointer
	   Don't keep the frame	pointer	in a register for leaf functions.
	   This	avoids the instructions	to save, set up	and restore frame
	   pointers and	makes an extra register	available in leaf functions.
	   The option -fomit-frame-pointer removes the frame pointer for all
	   functions which might make debugging	harder.

       -mspecld-anomaly
	   When	enabled, the compiler will ensure that the generated code does
	   not contain speculative loads after jump instructions.  This	option
	   is enabled by default.

       -mno-specld-anomaly
	   Don't generate extra	code to	prevent	speculative loads from occur-
	   ring.

       -mcsync-anomaly
	   When	enabled, the compiler will ensure that the generated code does
	   not contain CSYNC or	SSYNC instructions too soon after conditional
	   branches.  This option is enabled by	default.

       -mno-csync-anomaly
	   Don't generate extra	code to	prevent	CSYNC or SSYNC instructions
	   from	occurring too soon after a conditional branch.

       -mlow-64k
	   When	enabled, the compiler is free to take advantage	of the knowl-
	   edge	that the entire	program	fits into the low 64k of memory.

       -mno-low-64k
	   Assume that the program is arbitrarily large.  This is the default.

       -mid-shared-library
	   Generate code that supports shared libraries	via the	library	ID
	   method.  This allows	for execute in place and shared	libraries in
	   an environment without virtual memory management.  This option
	   implies -fPIC.

       -mno-id-shared-library
	   Generate code that doesn't assume ID	based shared libraries are
	   being used.	This is	the default.

       -mshared-library-id=n
	   Specified the identification	number of the ID based shared library
	   being compiled.  Specifying a value of 0 will generate more compact
	   code, specifying other values will force the	allocation of that
	   number to the current library but is	no more	space or time effi-
	   cient than omitting this option.

       -mlong-calls
       -mno-long-calls
	   Tells the compiler to perform function calls	by first loading the
	   address of the function into	a register and then performing a sub-
	   routine call	on this	register.  This	switch is needed if the	target
	   function will lie outside of	the 24 bit addressing range of the
	   offset based	version	of subroutine call instruction.

	   This	feature	is not enabled by default.  Specifying -mno-long-calls
	   will	restore	the default behavior.  Note these switches have	no
	   effect on how the compiler generates	code to	handle function	calls
	   via function	pointers.

       CRIS Options

       These options are defined specifically for the CRIS ports.

       -march=architecture-type
       -mcpu=architecture-type
	   Generate code for the specified architecture.  The choices for
	   architecture-type are v3, v8	and v10	for respectively ETRAX 4,
	   ETRAX 100, and ETRAX	100 LX.	 Default is v0 except for
	   cris-axis-linux-gnu,	where the default is v10.

       -mtune=architecture-type
	   Tune	to architecture-type everything	applicable about the generated
	   code, except	for the	ABI and	the set	of available instructions.
	   The choices for architecture-type are the same as for -march=archi-
	   tecture-type.

       -mmax-stack-frame=n
	   Warn	when the stack frame of	a function exceeds n bytes.

       -melinux-stacksize=n
	   Only	available with the cris-axis-aout target.  Arranges for	indi-
	   cations in the program to the kernel	loader that the	stack of the
	   program should be set to n bytes.

       -metrax4
       -metrax100
	   The options -metrax4	and -metrax100 are synonyms for	-march=v3 and
	   -march=v8 respectively.

       -mmul-bug-workaround
       -mno-mul-bug-workaround
	   Work	around a bug in	the "muls" and "mulu" instructions for CPU
	   models where	it applies.  This option is active by default.

       -mpdebug
	   Enable CRIS-specific	verbose	debug-related information in the
	   assembly code.  This	option also has	the effect to turn off the
	   #NO_APP formatted-code indicator to the assembler at	the beginning
	   of the assembly file.

       -mcc-init
	   Do not use condition-code results from previous instruction;	always
	   emit	compare	and test instructions before use of condition codes.

       -mno-side-effects
	   Do not emit instructions with side-effects in addressing modes
	   other than post-increment.

       -mstack-align
       -mno-stack-align
       -mdata-align
       -mno-data-align
       -mconst-align
       -mno-const-align
	   These options (no-options) arranges (eliminate arrangements)	for
	   the stack-frame, individual data and	constants to be	aligned	for
	   the maximum single data access size for the chosen CPU model.  The
	   default is to arrange for 32-bit alignment.	ABI details such as
	   structure layout are	not affected by	these options.

       -m32-bit
       -m16-bit
       -m8-bit
	   Similar to the stack- data- and const-align options above, these
	   options arrange for stack-frame, writable data and constants	to all
	   be 32-bit, 16-bit or	8-bit aligned.	The default is 32-bit align-
	   ment.

       -mno-prologue-epilogue
       -mprologue-epilogue
	   With	-mno-prologue-epilogue,	the normal function prologue and epi-
	   logue that sets up the stack-frame are omitted and no return
	   instructions	or return sequences are	generated in the code.	Use
	   this	option only together with visual inspection of the compiled
	   code: no warnings or	errors are generated when call-saved registers
	   must	be saved, or storage for local variable	needs to be allocated.

       -mno-gotplt
       -mgotplt
	   With	-fpic and -fPIC, don't generate	(do generate) instruction
	   sequences that load addresses for functions from the	PLT part of
	   the GOT rather than (traditional on other architectures) calls to
	   the PLT.  The default is -mgotplt.

       -maout
	   Legacy no-op	option only recognized with the	cris-axis-aout target.

       -melf
	   Legacy no-op	option only recognized with the	cris-axis-elf and
	   cris-axis-linux-gnu targets.

       -melinux
	   Only	recognized with	the cris-axis-aout target, where it selects a
	   GNU/linux-like multilib, include files and instruction set for
	   -march=v8.

       -mlinux
	   Legacy no-op	option only recognized with the	cris-axis-linux-gnu
	   target.

       -sim
	   This	option,	recognized for the cris-axis-aout and cris-axis-elf
	   arranges to link with input-output functions	from a simulator
	   library.  Code, initialized data and	zero-initialized data are
	   allocated consecutively.

       -sim2
	   Like	-sim, but pass linker options to locate	initialized data at
	   0x40000000 and zero-initialized data	at 0x80000000.

       CRX Options

       These options are defined specifically for the CRX ports.

       -mmac
	   Enable the use of multiply-accumulate instructions. Disabled	by
	   default.

       -mpush-args
	   Push	instructions will be used to pass outgoing arguments when
	   functions are called. Enabled by default.

       Darwin Options

       These options are defined for all architectures running the Darwin
       operating system.

       FSF GCC on Darwin does not create "fat" object files; it	will create an
       object file for the single architecture that it was built to target.
       Apple's GCC on Darwin does create "fat" files if	multiple -arch options
       are used; it does so by running the compiler or linker multiple times
       and joining the results together	with lipo.

       The subtype of the file created (like ppc7400 or	ppc970 or i686)	is
       determined by the flags that specify the	ISA that GCC is	targetting,
       like -mcpu or -march.  The -force_cpusubtype_ALL	option can be used to
       override	this.

       The Darwin tools	vary in	their behavior when presented with an ISA mis-
       match.  The assembler, as, will only permit instructions	to be used
       that are	valid for the subtype of the file it is	generating, so you
       cannot put 64-bit instructions in an ppc750 object file.	 The linker
       for shared libraries, /usr/bin/libtool, will fail and print an error if
       asked to	create a shared	library	with a less restrictive	subtype	than
       its input files (for instance, trying to	put a ppc970 object file in a
       ppc7400 library).  The linker for executables, ld, will quietly give
       the executable the most restrictive subtype of any of its input files.

       -Fdir
	   Add the framework directory dir to the head of the list of directo-
	   ries	to be searched for header files.  These	directories are	inter-
	   leaved with those specified by -I options and are scanned in	a
	   left-to-right order.

	   A framework directory is a directory	with frameworks	in it.	A
	   framework is	a directory with a "Headers" and/or "PrivateHeaders"
	   directory contained directly	in it that ends	in ".framework".  The
	   name	of a framework is the name of this directory excluding the
	   ".framework".  Headers associated with the framework	are found in
	   one of those	two directories, with "Headers"	being searched first.
	   A subframework is a framework directory that	is in a	framework's
	   "Frameworks"	directory.  Includes of	subframework headers can only
	   appear in a header of a framework that contains the subframework,
	   or in a sibling subframework	header.	 Two subframeworks are sib-
	   lings if they occur in the same framework.  A subframework should
	   not have the	same name as a framework, a warning will be issued if
	   this	is violated.  Currently	a subframework cannot have subframe-
	   works, in the future, the mechanism may be extended to support
	   this.  The standard frameworks can be found in "/Sys-
	   tem/Library/Frameworks" and "/Library/Frameworks".  An example
	   include looks like "#include	<Framework/header.h>", where Framework
	   denotes the name of the framework and header.h is found in the
	   "PrivateHeaders" or "Headers" directory.

       -gused
	   Emit	debugging information for symbols that are used.  For STABS
	   debugging format, this enables -feliminate-unused-debug-symbols.
	   This	is by default ON.

       -gfull
	   Emit	debugging information for all symbols and types.

       -mmacosx-version-min=version
	   The earliest	version	of MacOS X that	this executable	will run on is
	   version.  Typical values of version include 10.1, 10.2, and 10.3.9.

	   The default for this	option is to make choices that seem to be most
	   useful.

       -mkernel
	   Enable kernel development mode.  The	-mkernel option	sets -static,
	   -fno-common,	-fno-cxa-atexit, -fno-exceptions, -fno-non-call-excep-
	   tions, -fapple-kext,	-fno-weak and -fno-rtti	where applicable.
	   This	mode also sets -mno-altivec, -msoft-float, -fno-builtin	and
	   -mlong-branch for PowerPC targets.

       -mone-byte-bool
	   Override the	defaults for bool so that sizeof(bool)==1.  By default
	   sizeof(bool)	is 4 when compiling for	Darwin/PowerPC and 1 when com-
	   piling for Darwin/x86, so this option has no	effect on x86.

	   Warning: The	-mone-byte-bool	switch causes GCC to generate code
	   that	is not binary compatible with code generated without that
	   switch.  Using this switch may require recompiling all other	mod-
	   ules	in a program, including	system libraries.  Use this switch to
	   conform to a	non-default data model.

       -mfix-and-continue
       -ffix-and-continue
       -findirect-data
	   Generate code suitable for fast turn	around development.  Needed to
	   enable gdb to dynamically load ".o" files into already running pro-
	   grams.  -findirect-data and -ffix-and-continue are provided for
	   backwards compatibility.

       -all_load
	   Loads all members of	static archive libraries.  See man ld(1) for
	   more	information.

       -arch_errors_fatal
	   Cause the errors having to do with files that have the wrong	archi-
	   tecture to be fatal.

       -bind_at_load
	   Causes the output file to be	marked such that the dynamic linker
	   will	bind all undefined references when the file is loaded or
	   launched.

       -bundle
	   Produce a Mach-o bundle format file.	 See man ld(1) for more	infor-
	   mation.

       -bundle_loader executable
	   This	option specifies the executable	that will be loading the build
	   output file being linked.  See man ld(1) for	more information.

       -dynamiclib
	   When	passed this option, GCC	will produce a dynamic library instead
	   of an executable when linking, using	the Darwin libtool command.

       -force_cpusubtype_ALL
	   This	causes GCC's output file to have the ALL subtype, instead of
	   one controlled by the -mcpu or -march option.

       -allowable_client  client_name
       -client_name
       -compatibility_version
       -current_version
       -dead_strip
       -dependency-file
       -dylib_file
       -dylinker_install_name
       -dynamic
       -exported_symbols_list
       -filelist
       -flat_namespace
       -force_flat_namespace
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -no_dead_strip_inits_and_terms
       -nofixprebinding
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -segaddr
       -segs_read_only_addr
       -segs_read_write_addr
       -seg_addr_table
       -seg_addr_table_filename
       -seglinkedit
       -segprot
       -segs_read_only_addr
       -segs_read_write_addr
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
	   These options are passed to the Darwin linker.  The Darwin linker
	   man page describes them in detail.

       DEC Alpha Options

       These -m	options	are defined for	the DEC	Alpha implementations:

       -mno-soft-float
       -msoft-float
	   Use (do not use) the	hardware floating-point	instructions for
	   floating-point operations.  When -msoft-float is specified, func-
	   tions in libgcc.a will be used to perform floating-point opera-
	   tions.  Unless they are replaced by routines	that emulate the
	   floating-point operations, or compiled in such a way	as to call
	   such	emulations routines, these routines will issue floating-point
	   operations.	 If you	are compiling for an Alpha without floating-
	   point operations, you must ensure that the library is built so as
	   not to call them.

	   Note	that Alpha implementations without floating-point operations
	   are required	to have	floating-point registers.

       -mfp-reg
       -mno-fp-regs
	   Generate code that uses (does not use) the floating-point register
	   set.	 -mno-fp-regs implies -msoft-float.  If	the floating-point
	   register set	is not used, floating point operands are passed	in
	   integer registers as	if they	were integers and floating-point
	   results are passed in $0 instead of $f0.  This is a non-standard
	   calling sequence, so	any function with a floating-point argument or
	   return value	called by code compiled	with -mno-fp-regs must also be
	   compiled with that option.

	   A typical use of this option	is building a kernel that does not
	   use,	and hence need not save	and restore, any floating-point	regis-
	   ters.

       -mieee
	   The Alpha architecture implements floating-point hardware optimized
	   for maximum performance.  It	is mostly compliant with the IEEE
	   floating point standard.  However, for full compliance, software
	   assistance is required.  This option	generates code fully IEEE com-
	   pliant code except that the inexact-flag is not maintained (see
	   below).  If this option is turned on, the preprocessor macro
	   "_IEEE_FP" is defined during	compilation.  The resulting code is
	   less	efficient but is able to correctly support denormalized	num-
	   bers	and exceptional	IEEE values such as not-a-number and
	   plus/minus infinity.	 Other Alpha compilers call this option
	   -ieee_with_no_inexact.

       -mieee-with-inexact
	   This	is like	-mieee except the generated code also maintains	the
	   IEEE	inexact-flag.  Turning on this option causes the generated
	   code	to implement fully-compliant IEEE math.	 In addition to
	   "_IEEE_FP", "_IEEE_FP_EXACT"	is defined as a	preprocessor macro.
	   On some Alpha implementations the resulting code may	execute	sig-
	   nificantly slower than the code generated by	default.  Since	there
	   is very little code that depends on the inexact-flag, you should
	   normally not	specify	this option.  Other Alpha compilers call this
	   option -ieee_with_inexact.

       -mfp-trap-mode=trap-mode
	   This	option controls	what floating-point related traps are enabled.
	   Other Alpha compilers call this option -fptm	trap-mode.  The	trap
	   mode	can be set to one of four values:

	   n   This is the default (normal) setting.  The only traps that are
	       enabled are the ones that cannot	be disabled in software	(e.g.,
	       division	by zero	trap).

	   u   In addition to the traps	enabled	by n, underflow	traps are
	       enabled as well.

	   su  Like u, but the instructions are	marked to be safe for software
	       completion (see Alpha architecture manual for details).

	   sui Like su,	but inexact traps are enabled as well.

       -mfp-rounding-mode=rounding-mode
	   Selects the IEEE rounding mode.  Other Alpha	compilers call this
	   option -fprm	rounding-mode.	The rounding-mode can be one of:

	   n   Normal IEEE rounding mode.  Floating point numbers are rounded
	       towards the nearest machine number or towards the even machine
	       number in case of a tie.

	   m   Round towards minus infinity.

	   c   Chopped rounding	mode.  Floating	point numbers are rounded
	       towards zero.

	   d   Dynamic rounding	mode.  A field in the floating point control
	       register	(fpcr, see Alpha architecture reference	manual)	con-
	       trols the rounding mode in effect.  The C library initializes
	       this register for rounding towards plus infinity.  Thus,	unless
	       your program modifies the fpcr, d corresponds to	round towards
	       plus infinity.

       -mtrap-precision=trap-precision
	   In the Alpha	architecture, floating point traps are imprecise.
	   This	means without software assistance it is	impossible to recover
	   from	a floating trap	and program execution normally needs to	be
	   terminated.	GCC can	generate code that can assist operating	system
	   trap	handlers in determining	the exact location that	caused a
	   floating point trap.	 Depending on the requirements of an applica-
	   tion, different levels of precisions	can be selected:

	   p   Program precision.  This	option is the default and means	a trap
	       handler can only	identify which program caused a	floating point
	       exception.

	   f   Function	precision.  The	trap handler can determine the func-
	       tion that caused	a floating point exception.

	   i   Instruction precision.  The trap	handler	can determine the
	       exact instruction that caused a floating	point exception.

	   Other Alpha compilers provide the equivalent	options	called
	   -scope_safe and -resumption_safe.

       -mieee-conformant
	   This	option marks the generated code	as IEEE	conformant.  You must
	   not use this	option unless you also specify -mtrap-precision=i and
	   either -mfp-trap-mode=su or -mfp-trap-mode=sui.  Its	only effect is
	   to emit the line .eflag 48 in the function prologue of the gener-
	   ated	assembly file.	Under DEC Unix,	this has the effect that IEEE-
	   conformant math library routines will be linked in.

       -mbuild-constants
	   Normally GCC	examines a 32- or 64-bit integer constant to see if it
	   can construct it from smaller constants in two or three instruc-
	   tions.  If it cannot, it will output	the constant as	a literal and
	   generate code to load it from the data segment at runtime.

	   Use this option to require GCC to construct all integer constants
	   using code, even if it takes	more instructions (the maximum is
	   six).

	   You would typically use this	option to build	a shared library
	   dynamic loader.  Itself a shared library, it	must relocate itself
	   in memory before it can find	the variables and constants in its own
	   data	segment.

       -malpha-as
       -mgas
	   Select whether to generate code to be assembled by the vendor-sup-
	   plied assembler (-malpha-as)	or by the GNU assembler	-mgas.

       -mbwx
       -mno-bwx
       -mcix
       -mno-cix
       -mfix
       -mno-fix
       -mmax
       -mno-max
	   Indicate whether GCC	should generate	code to	use the	optional BWX,
	   CIX,	FIX and	MAX instruction	sets.  The default is to use the
	   instruction sets supported by the CPU type specified	via -mcpu=
	   option or that of the CPU on	which GCC was built if none was	speci-
	   fied.

       -mfloat-vax
       -mfloat-ieee
	   Generate code that uses (does not use) VAX F	and G floating point
	   arithmetic instead of IEEE single and double	precision.

       -mexplicit-relocs
       -mno-explicit-relocs
	   Older Alpha assemblers provided no way to generate symbol reloca-
	   tions except	via assembler macros.  Use of these macros does	not
	   allow optimal instruction scheduling.  GNU binutils as of version
	   2.12	supports a new syntax that allows the compiler to explicitly
	   mark	which relocations should apply to which	instructions.  This
	   option is mostly useful for debugging, as GCC detects the capabili-
	   ties	of the assembler when it is built and sets the default accord-
	   ingly.

       -msmall-data
       -mlarge-data
	   When	-mexplicit-relocs is in	effect,	static data is accessed	via
	   gp-relative relocations.  When -msmall-data is used,	objects	8
	   bytes long or smaller are placed in a small data area (the ".sdata"
	   and ".sbss" sections) and are accessed via 16-bit relocations off
	   of the $gp register.	 This limits the size of the small data	area
	   to 64KB, but	allows the variables to	be directly accessed via a
	   single instruction.

	   The default is -mlarge-data.	 With this option the data area	is
	   limited to just below 2GB.  Programs	that require more than 2GB of
	   data	must use "malloc" or "mmap" to allocate	the data in the	heap
	   instead of in the program's data segment.

	   When	generating code	for shared libraries, -fpic implies
	   -msmall-data	and -fPIC implies -mlarge-data.

       -msmall-text
       -mlarge-text
	   When	-msmall-text is	used, the compiler assumes that	the code of
	   the entire program (or shared library) fits in 4MB, and is thus
	   reachable with a branch instruction.	 When -msmall-data is used,
	   the compiler	can assume that	all local symbols share	the same $gp
	   value, and thus reduce the number of	instructions required for a
	   function call from 4	to 1.

	   The default is -mlarge-text.

       -mcpu=cpu_type
	   Set the instruction set and instruction scheduling parameters for
	   machine type	cpu_type.  You can specify either the EV style name or
	   the corresponding chip number.  GCC supports	scheduling parameters
	   for the EV4,	EV5 and	EV6 family of processors and will choose the
	   default values for the instruction set from the processor you spec-
	   ify.	 If you	do not specify a processor type, GCC will default to
	   the processor on which the compiler was built.

	   Supported values for	cpu_type are

	   ev4
	   ev45
	   21064
	       Schedules as an EV4 and has no instruction set extensions.

	   ev5
	   21164
	       Schedules as an EV5 and has no instruction set extensions.

	   ev56
	   21164a
	       Schedules as an EV5 and supports	the BWX	extension.

	   pca56
	   21164pc
	   21164PC
	       Schedules as an EV5 and supports	the BWX	and MAX	extensions.

	   ev6
	   21264
	       Schedules as an EV6 and supports	the BWX, FIX, and MAX exten-
	       sions.

	   ev67
	   21264a
	       Schedules as an EV6 and supports	the BWX, CIX, FIX, and MAX
	       extensions.

       -mtune=cpu_type
	   Set only the	instruction scheduling parameters for machine type
	   cpu_type.  The instruction set is not changed.

       -mmemory-latency=time
	   Sets	the latency the	scheduler should assume	for typical memory
	   references as seen by the application.  This	number is highly
	   dependent on	the memory access patterns used	by the application and
	   the size of the external cache on the machine.

	   Valid options for time are

	   number
	       A decimal number	representing clock cycles.

	   L1
	   L2
	   L3
	   main
	       The compiler contains estimates of the number of	clock cycles
	       for "typical" EV4 & EV5 hardware	for the	Level 1, 2 & 3 caches
	       (also called Dcache, Scache, and	Bcache), as well as to main
	       memory.	Note that L3 is	only valid for EV5.

       DEC Alpha/VMS Options

       These -m	options	are defined for	the DEC	Alpha/VMS implementations:

       -mvms-return-codes
	   Return VMS condition	codes from main.  The default is to return
	   POSIX style condition (e.g. error) codes.

       FRV Options

       -mgpr-32
	   Only	use the	first 32 general purpose registers.

       -mgpr-64
	   Use all 64 general purpose registers.

       -mfpr-32
	   Use only the	first 32 floating point	registers.

       -mfpr-64
	   Use all 64 floating point registers

       -mhard-float
	   Use hardware	instructions for floating point	operations.

       -msoft-float
	   Use library routines	for floating point operations.

       -malloc-cc
	   Dynamically allocate	condition code registers.

       -mfixed-cc
	   Do not try to dynamically allocate condition	code registers,	only
	   use "icc0" and "fcc0".

       -mdword
	   Change ABI to use double word insns.

       -mno-dword
	   Do not use double word instructions.

       -mdouble
	   Use floating	point double instructions.

       -mno-double
	   Do not use floating point double instructions.

       -mmedia
	   Use media instructions.

       -mno-media
	   Do not use media instructions.

       -mmuladd
	   Use multiply	and add/subtract instructions.

       -mno-muladd
	   Do not use multiply and add/subtract	instructions.

       -mfdpic
	   Select the FDPIC ABI, that uses function descriptors	to represent
	   pointers to functions.  Without any PIC/PIE-related options,	it
	   implies -fPIE.  With	-fpic or -fpie,	it assumes GOT entries and
	   small data are within a 12-bit range	from the GOT base address;
	   with	-fPIC or -fPIE,	GOT offsets are	computed with 32 bits.

       -minline-plt
	   Enable inlining of PLT entries in function calls to functions that
	   are not known to bind locally.  It has no effect without -mfdpic.
	   It's	enabled	by default if optimizing for speed and compiling for
	   shared libraries (i.e., -fPIC or -fpic), or when an optimization
	   option such as -O3 or above is present in the command line.

       -mTLS
	   Assume a large TLS segment when generating thread-local code.

       -mtls
	   Do not assume a large TLS segment when generating thread-local
	   code.

       -mgprel-ro
	   Enable the use of "GPREL" relocations in the	FDPIC ABI for data
	   that	is known to be in read-only sections.  It's enabled by
	   default, except for -fpic or	-fpie: even though it may help make
	   the global offset table smaller, it trades 1	instruction for	4.
	   With	-fPIC or -fPIE,	it trades 3 instructions for 4,	one of which
	   may be shared by multiple symbols, and it avoids the	need for a GOT
	   entry for the referenced symbol, so it's more likely	to be a	win.
	   If it is not, -mno-gprel-ro can be used to disable it.

       -multilib-library-pic
	   Link	with the (library, not FD) pic libraries.  It's	implied	by
	   -mlibrary-pic, as well as by	-fPIC and -fpic	without	-mfdpic.  You
	   should never	have to	use it explicitly.

       -mlinked-fp
	   Follow the EABI requirement of always creating a frame pointer
	   whenever a stack frame is allocated.	 This option is	enabled	by
	   default and can be disabled with -mno-linked-fp.

       -mlong-calls
	   Use indirect	addressing to call functions outside the current com-
	   pilation unit.  This	allows the functions to	be placed anywhere
	   within the 32-bit address space.

       -malign-labels
	   Try to align	labels to an 8-byte boundary by	inserting nops into
	   the previous	packet.	 This option only has an effect	when VLIW
	   packing is enabled.	It doesn't create new packets; it merely adds
	   nops	to existing ones.

       -mlibrary-pic
	   Generate position-independent EABI code.

       -macc-4
	   Use only the	first four media accumulator registers.

       -macc-8
	   Use all eight media accumulator registers.

       -mpack
	   Pack	VLIW instructions.

       -mno-pack
	   Do not pack VLIW instructions.

       -mno-eflags
	   Do not mark ABI switches in e_flags.

       -mcond-move
	   Enable the use of conditional-move instructions (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-cond-move
	   Disable the use of conditional-move instructions.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mscc
	   Enable the use of conditional set instructions (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-scc
	   Disable the use of conditional set instructions.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mcond-exec
	   Enable the use of conditional execution (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-cond-exec
	   Disable the use of conditional execution.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mvliw-branch
	   Run a pass to pack branches into VLIW instructions (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-vliw-branch
	   Do not run a	pass to	pack branches into VLIW	instructions.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mmulti-cond-exec
	   Enable optimization of "&&" and "||"	in conditional execution
	   (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-multi-cond-exec
	   Disable optimization	of "&&"	and "||" in conditional	execution.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mnested-cond-exec
	   Enable nested conditional execution optimizations (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-nested-cond-exec
	   Disable nested conditional execution	optimizations.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -moptimize-membar
	   This	switch removes redundant "membar" instructions from the	com-
	   piler generated code.  It is	enabled	by default.

       -mno-optimize-membar
	   This	switch disables	the automatic removal of redundant "membar"
	   instructions	from the generated code.

       -mtomcat-stats
	   Cause gas to	print out tomcat statistics.

       -mcpu=cpu
	   Select the processor	type for which to generate code.  Possible
	   values are frv, fr550, tomcat, fr500, fr450,	fr405, fr400, fr300
	   and simple.

       GNU/Linux Options

       These -m	options	are defined for	GNU/Linux targets:

       -mglibc
	   Use the GNU C library instead of uClibc.  This is the default
	   except on *-*-linux-*uclibc*	targets.

       -muclibc
	   Use uClibc instead of the GNU C library.  This is the default on
	   *-*-linux-*uclibc* targets.

       H8/300 Options

       These -m	options	are defined for	the H8/300 implementations:

       -mrelax
	   Shorten some	address	references at link time, when possible;	uses
	   the linker option -relax.

       -mh Generate code for the H8/300H.

       -ms Generate code for the H8S.

       -mn Generate code for the H8S and H8/300H in the	normal mode.  This
	   switch must be used either with -mh or -ms.

       -ms2600
	   Generate code for the H8S/2600.  This switch	must be	used with -ms.

       -mint32
	   Make	"int" data 32 bits by default.

       -malign-300
	   On the H8/300H and H8S, use the same	alignment rules	as for the
	   H8/300.  The	default	for the	H8/300H	and H8S	is to align longs and
	   floats on 4 byte boundaries.	 -malign-300 causes them to be aligned
	   on 2	byte boundaries.  This option has no effect on the H8/300.

       HPPA Options

       These -m	options	are defined for	the HPPA family	of computers:

       -march=architecture-type
	   Generate code for the specified architecture.  The choices for
	   architecture-type are 1.0 for PA 1.0, 1.1 for PA 1.1, and 2.0 for
	   PA 2.0 processors.  Refer to	/usr/lib/sched.models on an HP-UX sys-
	   tem to determine the	proper architecture option for your machine.
	   Code	compiled for lower numbered architectures will run on higher
	   numbered architectures, but not the other way around.

       -mpa-risc-1-0
       -mpa-risc-1-1
       -mpa-risc-2-0
	   Synonyms for	-march=1.0, -march=1.1,	and -march=2.0 respectively.

       -mbig-switch
	   Generate code suitable for big switch tables.  Use this option only
	   if the assembler/linker complain about out of range branches	within
	   a switch table.

       -mjump-in-delay
	   Fill	delay slots of function	calls with unconditional jump instruc-
	   tions by modifying the return pointer for the function call to be
	   the target of the conditional jump.

       -mdisable-fpregs
	   Prevent floating point registers from being used in any manner.
	   This	is necessary for compiling kernels which perform lazy context
	   switching of	floating point registers.  If you use this option and
	   attempt to perform floating point operations, the compiler will
	   abort.

       -mdisable-indexing
	   Prevent the compiler	from using indexing address modes.  This
	   avoids some rather obscure problems when compiling MIG generated
	   code	under MACH.

       -mno-space-regs
	   Generate code that assumes the target has no	space registers.  This
	   allows GCC to generate faster indirect calls	and use	unscaled index
	   address modes.

	   Such	code is	suitable for level 0 PA	systems	and kernels.

       -mfast-indirect-calls
	   Generate code that assumes calls never cross	space boundaries.
	   This	allows GCC to emit code	which performs faster indirect calls.

	   This	option will not	work in	the presence of	shared libraries or
	   nested functions.

       -mfixed-range=register-range
	   Generate code treating the given register range as fixed registers.
	   A fixed register is one that	the register allocator can not use.
	   This	is useful when compiling kernel	code.  A register range	is
	   specified as	two registers separated	by a dash.  Multiple register
	   ranges can be specified separated by	a comma.

       -mlong-load-store
	   Generate 3-instruction load and store sequences as sometimes
	   required by the HP-UX 10 linker.  This is equivalent	to the +k
	   option to the HP compilers.

       -mportable-runtime
	   Use the portable calling conventions	proposed by HP for ELF sys-
	   tems.

       -mgas
	   Enable the use of assembler directives only GAS understands.

       -mschedule=cpu-type
	   Schedule code according to the constraints for the machine type
	   cpu-type.  The choices for cpu-type are 700 7100, 7100LC, 7200,
	   7300	and 8000.  Refer to /usr/lib/sched.models on an	HP-UX system
	   to determine	the proper scheduling option for your machine.	The
	   default scheduling is 8000.

       -mlinker-opt
	   Enable the optimization pass	in the HP-UX linker.  Note this	makes
	   symbolic debugging impossible.  It also triggers a bug in the HP-UX
	   8 and HP-UX 9 linkers in which they give bogus error	messages when
	   linking some	programs.

       -msoft-float
	   Generate output containing library calls for	floating point.	 Warn-
	   ing:	the requisite libraries	are not	available for all HPPA tar-
	   gets.  Normally the facilities of the machine's usual C compiler
	   are used, but this cannot be	done directly in cross-compilation.
	   You must make your own arrangements to provide suitable library
	   functions for cross-compilation.  The embedded target hppa1.1-*-pro
	   does	provide	software floating point	support.

	   -msoft-float	changes	the calling convention in the output file;
	   therefore, it is only useful	if you compile all of a	program	with
	   this	option.	 In particular,	you need to compile libgcc.a, the
	   library that	comes with GCC,	with -msoft-float in order for this to
	   work.

       -msio
	   Generate the	predefine, "_SIO", for server IO.  The default is
	   -mwsio.  This generates the predefines, "__hp9000s700",
	   "__hp9000s700__" and	"_WSIO", for workstation IO.  These options
	   are available under HP-UX and HI-UX.

       -mgnu-ld
	   Use GNU ld specific options.	 This passes -shared to	ld when	build-
	   ing a shared	library.  It is	the default when GCC is	configured,
	   explicitly or implicitly, with the GNU linker.  This	option does
	   not have any	affect on which	ld is called, it only changes what
	   parameters are passed to that ld.  The ld that is called is deter-
	   mined by the	--with-ld configure option, GCC's program search path,
	   and finally by the user's PATH.  The	linker used by GCC can be
	   printed using which `gcc -print-prog-name=ld`.  This	option is only
	   available on	the 64 bit HP-UX GCC, i.e. configured with
	   hppa*64*-*-hpux*.

       -mhp-ld
	   Use HP ld specific options.	This passes -b to ld when building a
	   shared library and passes +Accept TypeMismatch to ld	on all links.
	   It is the default when GCC is configured, explicitly	or implicitly,
	   with	the HP linker.	This option does not have any affect on	which
	   ld is called, it only changes what parameters are passed to that
	   ld.	The ld that is called is determined by the --with-ld configure
	   option, GCC's program search	path, and finally by the user's	PATH.
	   The linker used by GCC can be printed using which `gcc
	   -print-prog-name=ld`.  This option is only available	on the 64 bit
	   HP-UX GCC, i.e. configured with hppa*64*-*-hpux*.

       -mlong-calls
	   Generate code that uses long	call sequences.	 This ensures that a
	   call	is always able to reach	linker generated stubs.	 The default
	   is to generate long calls only when the distance from the call site
	   to the beginning of the function or translation unit, as the	case
	   may be, exceeds a predefined	limit set by the branch	type being
	   used.  The limits for normal	calls are 7,600,000 and	240,000	bytes,
	   respectively	for the	PA 2.0 and PA 1.X architectures.  Sibcalls are
	   always limited at 240,000 bytes.

	   Distances are measured from the beginning of	functions when using
	   the -ffunction-sections option, or when using the -mgas and
	   -mno-portable-runtime options together under	HP-UX with the SOM
	   linker.

	   It is normally not desirable	to use this option as it will degrade
	   performance.	 However, it may be useful in large applications, par-
	   ticularly when partial linking is used to build the application.

	   The types of	long calls used	depends	on the capabilities of the
	   assembler and linker, and the type of code being generated.	The
	   impact on systems that support long absolute	calls, and long	pic
	   symbol-difference or	pc-relative calls should be relatively small.
	   However, an indirect	call is	used on	32-bit ELF systems in pic code
	   and it is quite long.

       -munix=unix-std
	   Generate compiler predefines	and select a startfile for the speci-
	   fied	UNIX standard.	The choices for	unix-std are 93, 95 and	98.
	   93 is supported on all HP-UX	versions.  95 is available on HP-UX
	   10.10 and later.  98	is available on	HP-UX 11.11 and	later.	The
	   default values are 93 for HP-UX 10.00, 95 for HP-UX 10.10 though to
	   11.00, and 98 for HP-UX 11.11 and later.

	   -munix=93 provides the same predefines as GCC 3.3 and 3.4.
	   -munix=95 provides additional predefines for	"XOPEN_UNIX" and
	   "_XOPEN_SOURCE_EXTENDED", and the startfile unix95.o.  -munix=98
	   provides additional predefines for "_XOPEN_UNIX",
	   "_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE"	and
	   "_INCLUDE_XOPEN_SOURCE_500",	and the	startfile unix98.o.

	   It is important to note that	this option changes the	interfaces for
	   various library routines.  It also affects the operational behavior
	   of the C library.  Thus, extreme care is needed in using this
	   option.

	   Library code	that is	intended to operate with more than one UNIX
	   standard must test, set and restore the variable
	   __xpg4_extended_mask	as appropriate.	 Most GNU software doesn't
	   provide this	capability.

       -nolibdld
	   Suppress the	generation of link options to search libdld.sl when
	   the -static option is specified on HP-UX 10 and later.

       -static
	   The HP-UX implementation of setlocale in libc has a dependency on
	   libdld.sl.  There isn't an archive version of libdld.sl.  Thus,
	   when	the -static option is specified, special link options are
	   needed to resolve this dependency.

	   On HP-UX 10 and later, the GCC driver adds the necessary options to
	   link	with libdld.sl when the	-static	option is specified.  This
	   causes the resulting	binary to be dynamic.  On the 64-bit port, the
	   linkers generate dynamic binaries by	default	in any case.  The
	   -nolibdld option can	be used	to prevent the GCC driver from adding
	   these link options.

       -threads
	   Add support for multithreading with the dce thread library under
	   HP-UX.  This	option sets flags for both the preprocessor and
	   linker.

       Intel 386 and AMD x86-64	Options

       These -m	options	are defined for	the i386 and x86-64 family of comput-
       ers:

       -mtune=cpu-type
	   Tune	to cpu-type everything applicable about	the generated code,
	   except for the ABI and the set of available instructions.  The
	   choices for cpu-type	are:

	   generic
	       Produce code optimized for the most common IA32/AMD64/EM64T
	       processors.  If you know	the CPU	on which your code will	run,
	       then you	should use the corresponding -mtune option instead of
	       -mtune=generic.	But, if	you do not know	exactly	what CPU users
	       of your application will	have, then you should use this option.

	       As new processors are deployed in the marketplace, the behavior
	       of this option will change.  Therefore, if you upgrade to a
	       newer version of	GCC, the code generated	option will change to
	       reflect the processors that were	most common when that version
	       of GCC was released.

	       There is	no -march=generic option because -march	indicates the
	       instruction set the compiler can	use, and there is no generic
	       instruction set applicable to all processors.  In contrast,
	       -mtune indicates	the processor (or, in this case, collection of
	       processors) for which the code is optimized.

	   native
	       This selects the	CPU to tune for	at compilation time by deter-
	       mining the processor type of the	compiling machine.  Using
	       -mtune=native will produce code optimized for the local machine
	       under the constraints of	the selected instruction set.  Using
	       -march=native will enable all instruction subsets supported by
	       the local machine (hence	the result might not run on different
	       machines).

	   i386
	       Original	Intel's	i386 CPU.

	   i486
	       Intel's i486 CPU.  (No scheduling is implemented	for this
	       chip.)

	   i586, pentium
	       Intel Pentium CPU with no MMX support.

	   pentium-mmx
	       Intel PentiumMMX	CPU based on Pentium core with MMX instruction
	       set support.

	   pentiumpro
	       Intel PentiumPro	CPU.

	   i686
	       Same as "generic", but when used	as "march" option, PentiumPro
	       instruction set will be used, so	the code will run on all i686
	       family chips.

	   pentium2
	       Intel Pentium2 CPU based	on PentiumPro core with	MMX instruc-
	       tion set	support.

	   pentium3, pentium3m
	       Intel Pentium3 CPU based	on PentiumPro core with	MMX and	SSE
	       instruction set support.

	   pentium-m
	       Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2
	       instruction set support.	 Used by Centrino notebooks.

	   pentium4, pentium4m
	       Intel Pentium4 CPU with MMX, SSE	and SSE2 instruction set sup-
	       port.

	   prescott
	       Improved	version	of Intel Pentium4 CPU with MMX,	SSE, SSE2 and
	       SSE3 instruction	set support.

	   nocona
	       Improved	version	of Intel Pentium4 CPU with 64-bit extensions,
	       MMX, SSE, SSE2 and SSE3 instruction set support.

	   core2
	       Intel Core2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3
	       and SSSE3 instruction set support.

	   k6  AMD K6 CPU with MMX instruction set support.

	   k6-2, k6-3
	       Improved	versions of AMD	K6 CPU with MMX	and 3dNOW! instruction
	       set support.

	   athlon, athlon-tbird
	       AMD Athlon CPU with MMX,	3dNOW!,	enhanced 3dNOW!	and SSE
	       prefetch	instructions support.

	   athlon-4, athlon-xp,	athlon-mp
	       Improved	AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and
	       full SSE	instruction set	support.

	   k8, opteron,	athlon64, athlon-fx
	       AMD K8 core based CPUs with x86-64 instruction set support.
	       (This supersets MMX, SSE, SSE2, 3dNOW!, enhanced	3dNOW! and
	       64-bit instruction set extensions.)

	   k8-sse3, opteron-sse3, athlon64-sse3
	       Improved	versions of k8,	opteron	and athlon64 with SSE3
	       instruction set support.

	   winchip-c6
	       IDT Winchip C6 CPU, dealt in same way as	i486 with additional
	       MMX instruction set support.

	   winchip2
	       IDT Winchip2 CPU, dealt in same way as i486 with	additional MMX
	       and 3dNOW!  instruction set support.

	   c3  Via C3 CPU with MMX and 3dNOW! instruction set support.	(No
	       scheduling is implemented for this chip.)

	   c3-2
	       Via C3-2	CPU with MMX and SSE instruction set support.  (No
	       scheduling is implemented for this chip.)

	   geode
	       Embedded	AMD CPU	with MMX and 3dNOW! instruction	set support.

	   While picking a specific cpu-type will schedule things appropri-
	   ately for that particular chip, the compiler	will not generate any
	   code	that does not run on the i386 without the -march=cpu-type
	   option being	used.

       -march=cpu-type
	   Generate instructions for the machine type cpu-type.	 The choices
	   for cpu-type	are the	same as	for -mtune.  Moreover, specifying
	   -march=cpu-type implies -mtune=cpu-type.

       -mcpu=cpu-type
	   A deprecated	synonym	for -mtune.

       -m386
       -m486
       -mpentium
       -mpentiumpro
	   These options are synonyms for -mtune=i386, -mtune=i486,
	   -mtune=pentium, and -mtune=pentiumpro respectively.	These synonyms
	   are deprecated.

       -mfpmath=unit
	   Generate floating point arithmetics for selected unit unit.	The
	   choices for unit are:

	   387 Use the standard	387 floating point coprocessor present major-
	       ity of chips and	emulated otherwise.  Code compiled with	this
	       option will run almost everywhere.  The temporary results are
	       computed	in 80bit precision instead of precision	specified by
	       the type	resulting in slightly different	results	compared to
	       most of other chips.  See -ffloat-store for more	detailed
	       description.

	       This is the default choice for i386 compiler.

	   sse Use scalar floating point instructions present in the SSE
	       instruction set.	 This instruction set is supported by Pentium3
	       and newer chips,	in the AMD line	by Athlon-4, Athlon-xp and
	       Athlon-mp chips.	 The earlier version of	SSE instruction	set
	       supports	only single precision arithmetics, thus	the double and
	       extended	precision arithmetics is still done using 387.	Later
	       version,	present	only in	Pentium4 and the future	AMD x86-64
	       chips supports double precision arithmetics too.

	       For the i386 compiler, you need to use -march=cpu-type, -msse
	       or -msse2 switches to enable SSE	extensions and make this
	       option effective.  For the x86-64 compiler, these extensions
	       are enabled by default.

	       The resulting code should be considerably faster	in the major-
	       ity of cases and	avoid the numerical instability	problems of
	       387 code, but may break some existing code that expects tempo-
	       raries to be 80bit.

	       This is the default choice for the x86-64 compiler.

	   sse,387
	       Attempt to utilize both instruction sets	at once.  This effec-
	       tively double the amount	of available registers and on chips
	       with separate execution units for 387 and SSE the execution
	       resources too.  Use this	option with care, as it	is still
	       experimental, because the GCC register allocator	does not model
	       separate	functional units well resulting	in instable perfor-
	       mance.

       -masm=dialect
	   Output asm instructions using selected dialect.  Supported choices
	   are intel or	att (the default one).	Darwin does not	support	intel.

       -mieee-fp
       -mno-ieee-fp
	   Control whether or not the compiler uses IEEE floating point	com-
	   parisons.  These handle correctly the case where the	result of a
	   comparison is unordered.

       -msoft-float
	   Generate output containing library calls for	floating point.	 Warn-
	   ing:	the requisite libraries	are not	part of	GCC.  Normally the
	   facilities of the machine's usual C compiler	are used, but this
	   can't be done directly in cross-compilation.	 You must make your
	   own arrangements to provide suitable	library	functions for
	   cross-compilation.

	   On machines where a function	returns	floating point results in the
	   80387 register stack, some floating point opcodes may be emitted
	   even	if -msoft-float	is used.

       -mno-fp-ret-in-387
	   Do not use the FPU registers	for return values of functions.

	   The usual calling convention	has functions return values of types
	   "float" and "double"	in an FPU register, even if there is no	FPU.
	   The idea is that the	operating system should	emulate	an FPU.

	   The option -mno-fp-ret-in-387 causes	such values to be returned in
	   ordinary CPU	registers instead.

       -mno-fancy-math-387
	   Some	387 emulators do not support the "sin",	"cos" and "sqrt"
	   instructions	for the	387.  Specify this option to avoid generating
	   those instructions.	This option is the default on FreeBSD, OpenBSD
	   and NetBSD.	This option is overridden when -march indicates	that
	   the target cpu will always have an FPU and so the instruction will
	   not need emulation.	As of revision 2.6.1, these instructions are
	   not generated unless	you also use the -funsafe-math-optimizations
	   switch.

       -malign-double
       -mno-align-double
	   Control whether GCC aligns "double",	"long double", and "long long"
	   variables on	a two word boundary or a one word boundary.  Aligning
	   "double" variables on a two word boundary will produce code that
	   runs	somewhat faster	on a Pentium at	the expense of more memory.

	   On x86-64, -malign-double is	enabled	by default.

	   Warning: if you use the -malign-double switch, structures contain-
	   ing the above types will be aligned differently than	the published
	   application binary interface	specifications for the 386 and will
	   not be binary compatible with structures in code compiled without
	   that	switch.

       -m96bit-long-double
       -m128bit-long-double
	   These switches control the size of "long double" type.  The i386
	   application binary interface	specifies the size to be 96 bits, so
	   -m96bit-long-double is the default in 32 bit	mode.

	   Modern architectures	(Pentium and newer) would prefer "long double"
	   to be aligned to an 8 or 16 byte boundary.  In arrays or structures
	   conforming to the ABI, this would not be possible.  So specifying a
	   -m128bit-long-double	will align "long double" to a 16 byte boundary
	   by padding the "long	double"	with an	additional 32 bit zero.

	   In the x86-64 compiler, -m128bit-long-double	is the default choice
	   as its ABI specifies	that "long double" is to be aligned on 16 byte
	   boundary.

	   Notice that neither of these	options	enable any extra precision
	   over	the x87	standard of 80 bits for	a "long	double".

	   Warning: if you override the	default	value for your target ABI, the
	   structures and arrays containing "long double" variables will
	   change their	size as	well as	function calling convention for	func-
	   tion	taking "long double" will be modified.	Hence they will	not be
	   binary compatible with arrays or structures in code compiled	with-
	   out that switch.

       -mmlarge-data-threshold=number
	   When	-mcmodel=medium	is specified, the data greater than threshold
	   are placed in large data section.  This value must be the same
	   across all object linked into the binary and	defaults to 65535.

       -msvr3-shlib
       -mno-svr3-shlib
	   Control whether GCC places uninitialized local variables into the
	   "bss" or "data" segments.  -msvr3-shlib places them into "bss".
	   These options are meaningful	only on	System V Release 3.

       -mrtd
	   Use a different function-calling convention,	in which functions
	   that	take a fixed number of arguments return	with the "ret" num
	   instruction,	which pops their arguments while returning.  This
	   saves one instruction in the	caller since there is no need to pop
	   the arguments there.

	   You can specify that	an individual function is called with this
	   calling sequence with the function attribute	stdcall.  You can also
	   override the	-mrtd option by	using the function attribute cdecl.

	   Warning: this calling convention is incompatible with the one nor-
	   mally used on Unix, so you cannot use it if you need	to call
	   libraries compiled with the Unix compiler.

	   Also, you must provide function prototypes for all functions	that
	   take	variable numbers of arguments (including "printf"); otherwise
	   incorrect code will be generated for	calls to those functions.

	   In addition,	seriously incorrect code will result if	you call a
	   function with too many arguments.  (Normally, extra arguments are
	   harmlessly ignored.)

       -mregparm=num
	   Control how many registers are used to pass integer arguments.  By
	   default, no registers are used to pass arguments, and at most 3
	   registers can be used.  You can control this	behavior for a spe-
	   cific function by using the function	attribute regparm.

	   Warning: if you use this switch, and	num is nonzero,	then you must
	   build all modules with the same value, including any	libraries.
	   This	includes the system libraries and startup modules.

       -msseregparm
	   Use SSE register passing conventions	for float and double arguments
	   and return values.  You can control this behavior for a specific
	   function by using the function attribute sseregparm.

	   Warning: if you use this switch then	you must build all modules
	   with	the same value,	including any libraries.  This includes	the
	   system libraries and	startup	modules.

       -mstackrealign
	   Realign the stack at	entry.	On the Intel x86, the -mstackrealign
	   option will generate	an alternate prologue and epilogue that
	   realigns the	runtime	stack.	This supports mixing legacy codes that
	   keep	a 4-byte aligned stack with modern codes that keep a 16-byte
	   stack for SSE compatibility.	 The alternate prologue	and epilogue
	   are slower and bigger than the regular ones,	and the	alternate pro-
	   logue requires an extra scratch register; this lowers the number of
	   registers available if used in conjunction with the "regparm"
	   attribute.  The -mstackrealign option is incompatible with the
	   nested function prologue; this is considered	a hard error.  See
	   also	the attribute "force_align_arg_pointer", applicable to indi-
	   vidual functions.

       -mpreferred-stack-boundary=num
	   Attempt to keep the stack boundary aligned to a 2 raised to num
	   byte	boundary.  If -mpreferred-stack-boundary is not	specified, the
	   default is 4	(16 bytes or 128 bits).

	   On Pentium and PentiumPro, "double" and "long double" values	should
	   be aligned to an 8 byte boundary (see -malign-double) or suffer
	   significant run time	performance penalties.	On Pentium III,	the
	   Streaming SIMD Extension (SSE) data type "__m128" may not work
	   properly if it is not 16 byte aligned.

	   To ensure proper alignment of this values on	the stack, the stack
	   boundary must be as aligned as that required	by any value stored on
	   the stack.  Further,	every function must be generated such that it
	   keeps the stack aligned.  Thus calling a function compiled with a
	   higher preferred stack boundary from	a function compiled with a
	   lower preferred stack boundary will most likely misalign the	stack.
	   It is recommended that libraries that use callbacks always use the
	   default setting.

	   This	extra alignment	does consume extra stack space,	and generally
	   increases code size.	 Code that is sensitive	to stack space usage,
	   such	as embedded systems and	operating system kernels, may want to
	   reduce the preferred	alignment to -mpreferred-stack-boundary=2.

       -mmmx
       -mno-mmx
       -msse
       -mno-sse
       -msse2
       -mno-sse2
       -msse3
       -mno-sse3
       -mssse3
       -mno-ssse3
       -m3dnow
       -mno-3dnow
	   These switches enable or disable the	use of instructions in the
	   MMX,	SSE, SSE2, SSE3, SSSE3 or 3DNow! extended instruction sets.
	   These extensions are	also available as built-in functions: see X86
	   Built-in Functions, for details of the functions enabled and	dis-
	   abled by these switches.

	   To have SSE/SSE2 instructions generated automatically from float-
	   ing-point code (as opposed to 387 instructions), see	-mfpmath=sse.

	   These options will enable GCC to use	these extended instructions in
	   generated code, even	without	-mfpmath=sse.  Applications which per-
	   form	runtime	CPU detection must compile separate files for each
	   supported architecture, using the appropriate flags.	 In particu-
	   lar,	the file containing the	CPU detection code should be compiled
	   without these options.

       -mpush-args
       -mno-push-args
	   Use PUSH operations to store	outgoing parameters.  This method is
	   shorter and usually equally fast as method using SUB/MOV operations
	   and is enabled by default.  In some cases disabling it may improve
	   performance because of improved scheduling and reduced dependen-
	   cies.

       -maccumulate-outgoing-args
	   If enabled, the maximum amount of space required for	outgoing argu-
	   ments will be computed in the function prologue.  This is faster on
	   most	modern CPUs because of reduced dependencies, improved schedul-
	   ing and reduced stack usage when preferred stack boundary is	not
	   equal to 2.	The drawback is	a notable increase in code size.  This
	   switch implies -mno-push-args.

       -mthreads
	   Support thread-safe exception handling on Mingw32.  Code that
	   relies on thread-safe exception handling must compile and link all
	   code	with the -mthreads option.  When compiling, -mthreads defines
	   -D_MT; when linking,	it links in a special thread helper library
	   -lmingwthrd which cleans up per thread exception handling data.

       -mno-align-stringops
	   Do not align	destination of inlined string operations.  This	switch
	   reduces code	size and improves performance in case the destination
	   is already aligned, but GCC doesn't know about it.

       -minline-all-stringops
	   By default GCC inlines string operations only when destination is
	   known to be aligned at least	to 4 byte boundary.  This enables more
	   inlining, increase code size, but may improve performance of	code
	   that	depends	on fast	memcpy,	strlen and memset for short lengths.

       -momit-leaf-frame-pointer
	   Don't keep the frame	pointer	in a register for leaf functions.
	   This	avoids the instructions	to save, set up	and restore frame
	   pointers and	makes an extra register	available in leaf functions.
	   The option -fomit-frame-pointer removes the frame pointer for all
	   functions which might make debugging	harder.

       -mtls-direct-seg-refs
       -mno-tls-direct-seg-refs
	   Controls whether TLS	variables may be accessed with offsets from
	   the TLS segment register (%gs for 32-bit, %fs for 64-bit), or
	   whether the thread base pointer must	be added.  Whether or not this
	   is legal depends on the operating system, and whether it maps the
	   segment to cover the	entire TLS area.

	   For systems that use	GNU libc, the default is on.

       These -m	switches are supported in addition to the above	on AMD x86-64
       processors in 64-bit environments.

       -m32
       -m64
	   Generate code for a 32-bit or 64-bit	environment.  The 32-bit envi-
	   ronment sets	int, long and pointer to 32 bits and generates code
	   that	runs on	any i386 system.  The 64-bit environment sets int to
	   32 bits and long and	pointer	to 64 bits and generates code for
	   AMD's x86-64	architecture. For darwin only the -m64 option turns
	   off the -fno-pic and	-mdynamic-no-pic options.

       -mno-red-zone
	   Do not use a	so called red zone for x86-64 code.  The red zone is
	   mandated by the x86-64 ABI, it is a 128-byte	area beyond the	loca-
	   tion	of the stack pointer that will not be modified by signal or
	   interrupt handlers and therefore can	be used	for temporary data
	   without adjusting the stack pointer.	 The flag -mno-red-zone	dis-
	   ables this red zone.

       -mcmodel=small
	   Generate code for the small code model: the program and its symbols
	   must	be linked in the lower 2 GB of the address space.  Pointers
	   are 64 bits.	 Programs can be statically or dynamically linked.
	   This	is the default code model.

       -mcmodel=kernel
	   Generate code for the kernel	code model.  The kernel	runs in	the
	   negative 2 GB of the	address	space.	This model has to be used for
	   Linux kernel	code.

       -mcmodel=medium
	   Generate code for the medium	model: The program is linked in	the
	   lower 2 GB of the address space but symbols can be located anywhere
	   in the address space.  Programs can be statically or	dynamically
	   linked, but building	of shared libraries are	not supported with the
	   medium model.

       -mcmodel=large
	   Generate code for the large model: This model makes no assumptions
	   about addresses and sizes of	sections.  Currently GCC does not
	   implement this model.

       IA-64 Options

       These are the -m	options	defined	for the	Intel IA-64 architecture.

       -mbig-endian
	   Generate code for a big endian target.  This	is the default for
	   HP-UX.

       -mlittle-endian
	   Generate code for a little endian target.  This is the default for
	   AIX5	and GNU/Linux.

       -mgnu-as
       -mno-gnu-as
	   Generate (or	don't) code for	the GNU	assembler.  This is the
	   default.

       -mgnu-ld
       -mno-gnu-ld
	   Generate (or	don't) code for	the GNU	linker.	 This is the default.

       -mno-pic
	   Generate code that does not use a global pointer register.  The
	   result is not position independent code, and	violates the IA-64
	   ABI.

       -mvolatile-asm-stop
       -mno-volatile-asm-stop
	   Generate (or	don't) a stop bit immediately before and after
	   volatile asm	statements.

       -mregister-names
       -mno-register-names
	   Generate (or	don't) in, loc,	and out	register names for the stacked
	   registers.  This may	make assembler output more readable.

       -mno-sdata
       -msdata
	   Disable (or enable) optimizations that use the small	data section.
	   This	may be useful for working around optimizer bugs.

       -mconstant-gp
	   Generate code that uses a single constant global pointer value.
	   This	is useful when compiling kernel	code.

       -mauto-pic
	   Generate code that is self-relocatable.  This implies -mcon-
	   stant-gp.  This is useful when compiling firmware code.

       -minline-float-divide-min-latency
	   Generate code for inline divides of floating	point values using the
	   minimum latency algorithm.

       -minline-float-divide-max-throughput
	   Generate code for inline divides of floating	point values using the
	   maximum throughput algorithm.

       -minline-int-divide-min-latency
	   Generate code for inline divides of integer values using the	mini-
	   mum latency algorithm.

       -minline-int-divide-max-throughput
	   Generate code for inline divides of integer values using the	maxi-
	   mum throughput algorithm.

       -minline-sqrt-min-latency
	   Generate code for inline square roots using the minimum latency
	   algorithm.

       -minline-sqrt-max-throughput
	   Generate code for inline square roots using the maximum throughput
	   algorithm.

       -mno-dwarf2-asm
       -mdwarf2-asm
	   Don't (or do) generate assembler code for the DWARF2	line number
	   debugging info.  This may be	useful when not	using the GNU assem-
	   bler.

       -mearly-stop-bits
       -mno-early-stop-bits
	   Allow stop bits to be placed	earlier	than immediately preceding the
	   instruction that triggered the stop bit.  This can improve instruc-
	   tion	scheduling, but	does not always	do so.

       -mfixed-range=register-range
	   Generate code treating the given register range as fixed registers.
	   A fixed register is one that	the register allocator can not use.
	   This	is useful when compiling kernel	code.  A register range	is
	   specified as	two registers separated	by a dash.  Multiple register
	   ranges can be specified separated by	a comma.

       -mtls-size=tls-size
	   Specify bit size of immediate TLS offsets.  Valid values are	14,
	   22, and 64.

       -mtune=cpu-type
	   Tune	the instruction	scheduling for a particular CPU, Valid values
	   are itanium,	itanium1, merced, itanium2, and	mckinley.

       -mt
       -pthread
	   Add support for multithreading using	the POSIX threads library.
	   This	option sets flags for both the preprocessor and	linker.	 It
	   does	not affect the thread safety of	object code produced by	the
	   compiler or that of libraries supplied with it.  These are HP-UX
	   specific flags.

       -milp32
       -mlp64
	   Generate code for a 32-bit or 64-bit	environment.  The 32-bit envi-
	   ronment sets	int, long and pointer to 32 bits.  The 64-bit environ-
	   ment	sets int to 32 bits and	long and pointer to 64 bits.  These
	   are HP-UX specific flags.

       -mno-sched-br-data-spec
       -msched-br-data-spec
	   (Dis/En)able	data speculative scheduling before reload.  This will
	   result in generation	of the ld.a instructions and the corresponding
	   check instructions (ld.c / chk.a).  The default is 'disable'.

       -msched-ar-data-spec
       -mno-sched-ar-data-spec
	   (En/Dis)able	data speculative scheduling after reload.  This	will
	   result in generation	of the ld.a instructions and the corresponding
	   check instructions (ld.c / chk.a).  The default is 'enable'.

       -mno-sched-control-spec
       -msched-control-spec
	   (Dis/En)able	control	speculative scheduling.	 This feature is
	   available only during region	scheduling (i.e. before	reload).  This
	   will	result in generation of	the ld.s instructions and the corre-
	   sponding check instructions chk.s .	The default is 'disable'.

       -msched-br-in-data-spec
       -mno-sched-br-in-data-spec
	   (En/Dis)able	speculative scheduling of the instructions that	are
	   dependent on	the data speculative loads before reload.  This	is
	   effective only with -msched-br-data-spec enabled.  The default is
	   'enable'.

       -msched-ar-in-data-spec
       -mno-sched-ar-in-data-spec
	   (En/Dis)able	speculative scheduling of the instructions that	are
	   dependent on	the data speculative loads after reload.  This is
	   effective only with -msched-ar-data-spec enabled.  The default is
	   'enable'.

       -msched-in-control-spec
       -mno-sched-in-control-spec
	   (En/Dis)able	speculative scheduling of the instructions that	are
	   dependent on	the control speculative	loads.	This is	effective only
	   with	-msched-control-spec enabled.  The default is 'enable'.

       -msched-ldc
       -mno-sched-ldc
	   (En/Dis)able	use of simple data speculation checks ld.c .  If dis-
	   abled, only chk.a instructions will be emitted to check data	specu-
	   lative loads.  The default is 'enable'.

       -mno-sched-control-ldc
       -msched-control-ldc
	   (Dis/En)able	use of ld.c instructions to check control speculative
	   loads.  If enabled, in case of control speculative load with	no
	   speculatively scheduled dependent instructions this load will be
	   emitted as ld.sa and	ld.c will be used to check it.	The default is
	   'disable'.

       -mno-sched-spec-verbose
       -msched-spec-verbose
	   (Dis/En)able	printing of the	information about speculative motions.

       -mno-sched-prefer-non-data-spec-insns
       -msched-prefer-non-data-spec-insns
	   If enabled, data speculative	instructions will be chosen for	sched-
	   ule only if there are no other choices at the moment.  This will
	   make	the use	of the data speculation	much more conservative.	 The
	   default is 'disable'.

       -mno-sched-prefer-non-control-spec-insns
       -msched-prefer-non-control-spec-insns
	   If enabled, control speculative instructions	will be	chosen for
	   schedule only if there are no other choices at the moment.  This
	   will	make the use of	the control speculation	much more conserva-
	   tive.  The default is 'disable'.

       -mno-sched-count-spec-in-critical-path
       -msched-count-spec-in-critical-path
	   If enabled, speculative dependencies	will be	considered during com-
	   putation of the instructions	priorities.  This will make the	use of
	   the speculation a bit more conservative.  The default is 'disable'.

       M32C Options

       -mcpu=name
	   Select the CPU for which code is generated.	name may be one	of r8c
	   for the R8C/Tiny series, m16c for the M16C (up to /60) series,
	   m32cm for the M16C/80 series, or m32c for the M32C/80 series.

       -msim
	   Specifies that the program will be run on the simulator.  This
	   causes an alternate runtime library to be linked in which supports,
	   for example,	file I/O.  You must not	use this option	when generat-
	   ing programs	that will run on real hardware;	you must provide your
	   own runtime library for whatever I/O	functions are needed.

       -memregs=number
	   Specifies the number	of memory-based	pseudo-registers GCC will use
	   during code generation.  These pseudo-registers will	be used	like
	   real	registers, so there is a tradeoff between GCC's	ability	to fit
	   the code into available registers, and the performance penalty of
	   using memory	instead	of registers.  Note that all modules in	a pro-
	   gram	must be	compiled with the same value for this option.  Because
	   of that, you	must not use this option with the default runtime
	   libraries gcc builds.

       M32R/D Options

       These -m	options	are defined for	Renesas	M32R/D architectures:

       -m32r2
	   Generate code for the M32R/2.

       -m32rx
	   Generate code for the M32R/X.

       -m32r
	   Generate code for the M32R.	This is	the default.

       -mmodel=small
	   Assume all objects live in the lower	16MB of	memory (so that	their
	   addresses can be loaded with	the "ld24" instruction), and assume
	   all subroutines are reachable with the "bl" instruction.  This is
	   the default.

	   The addressability of a particular object can be set	with the
	   "model" attribute.

       -mmodel=medium
	   Assume objects may be anywhere in the 32-bit	address	space (the
	   compiler will generate "seth/add3" instructions to load their
	   addresses), and assume all subroutines are reachable	with the "bl"
	   instruction.

       -mmodel=large
	   Assume objects may be anywhere in the 32-bit	address	space (the
	   compiler will generate "seth/add3" instructions to load their
	   addresses), and assume subroutines may not be reachable with	the
	   "bl"	instruction (the compiler will generate	the much slower
	   "seth/add3/jl" instruction sequence).

       -msdata=none
	   Disable use of the small data area.	Variables will be put into one
	   of .data, bss, or .rodata (unless the "section" attribute has been
	   specified).	This is	the default.

	   The small data area consists	of sections .sdata and .sbss.  Objects
	   may be explicitly put in the	small data area	with the "section"
	   attribute using one of these	sections.

       -msdata=sdata
	   Put small global and	static data in the small data area, but	do not
	   generate special code to reference them.

       -msdata=use
	   Put small global and	static data in the small data area, and	gener-
	   ate special instructions to reference them.

       -G num
	   Put global and static objects less than or equal to num bytes into
	   the small data or bss sections instead of the normal	data or	bss
	   sections.  The default value	of num is 8.  The -msdata option must
	   be set to one of sdata or use for this option to have any effect.

	   All modules should be compiled with the same	-G num value.  Compil-
	   ing with different values of	num may	or may not work; if it doesn't
	   the linker will give	an error message---incorrect code will not be
	   generated.

       -mdebug
	   Makes the M32R specific code	in the compiler	display	some statis-
	   tics	that might help	in debugging programs.

       -malign-loops
	   Align all loops to a	32-byte	boundary.

       -mno-align-loops
	   Do not enforce a 32-byte alignment for loops.  This is the default.

       -missue-rate=number
	   Issue number	instructions per cycle.	 number	can only be 1 or 2.

       -mbranch-cost=number
	   number can only be 1	or 2.  If it is	1 then branches	will be	pre-
	   ferred over conditional code, if it is 2, then the opposite will
	   apply.

       -mflush-trap=number
	   Specifies the trap number to	use to flush the cache.	 The default
	   is 12.  Valid numbers are between 0 and 15 inclusive.

       -mno-flush-trap
	   Specifies that the cache cannot be flushed by using a trap.

       -mflush-func=name
	   Specifies the name of the operating system function to call to
	   flush the cache.  The default is _flush_cache, but a	function call
	   will	only be	used if	a trap is not available.

       -mno-flush-func
	   Indicates that there	is no OS function for flushing the cache.

       M680x0 Options

       These are the -m	options	defined	for the	68000 series.  The default
       values for these	options	depends	on which style of 68000	was selected
       when the	compiler was configured; the defaults for the most common
       choices are given below.

       -m68000
       -mc68000
	   Generate output for a 68000.	 This is the default when the compiler
	   is configured for 68000-based systems.

	   Use this option for microcontrollers	with a 68000 or	EC000 core,
	   including the 68008,	68302, 68306, 68307, 68322, 68328 and 68356.

       -m68020
       -mc68020
	   Generate output for a 68020.	 This is the default when the compiler
	   is configured for 68020-based systems.

       -m68881
	   Generate output containing 68881 instructions for floating point.
	   This	is the default for most	68020 systems unless --nfp was speci-
	   fied	when the compiler was configured.

       -m68030
	   Generate output for a 68030.	 This is the default when the compiler
	   is configured for 68030-based systems.

       -m68040
	   Generate output for a 68040.	 This is the default when the compiler
	   is configured for 68040-based systems.

	   This	option inhibits	the use	of 68881/68882 instructions that have
	   to be emulated by software on the 68040.  Use this option if	your
	   68040 does not have code to emulate those instructions.

       -m68060
	   Generate output for a 68060.	 This is the default when the compiler
	   is configured for 68060-based systems.

	   This	option inhibits	the use	of 68020 and 68881/68882 instructions
	   that	have to	be emulated by software	on the 68060.  Use this	option
	   if your 68060 does not have code to emulate those instructions.

       -mcpu32
	   Generate output for a CPU32.	 This is the default when the compiler
	   is configured for CPU32-based systems.

	   Use this option for microcontrollers	with a CPU32 or	CPU32+ core,
	   including the 68330,	68331, 68332, 68333, 68334, 68336, 68340,
	   68341, 68349	and 68360.

       -m5200
	   Generate output for a 520X "coldfire" family	cpu.  This is the
	   default when	the compiler is	configured for 520X-based systems.

	   Use this option for microcontroller with a 5200 core, including the
	   MCF5202, MCF5203, MCF5204 and MCF5202.

       -mcfv4e
	   Generate output for a ColdFire V4e family cpu (e.g. 547x/548x).
	   This	includes use of	hardware floating point	instructions.

       -m68020-40
	   Generate output for a 68040,	without	using any of the new instruc-
	   tions.  This	results	in code	which can run relatively efficiently
	   on either a 68020/68881 or a	68030 or a 68040.  The generated code
	   does	use the	68881 instructions that	are emulated on	the 68040.

       -m68020-60
	   Generate output for a 68060,	without	using any of the new instruc-
	   tions.  This	results	in code	which can run relatively efficiently
	   on either a 68020/68881 or a	68030 or a 68040.  The generated code
	   does	use the	68881 instructions that	are emulated on	the 68060.

       -msoft-float
	   Generate output containing library calls for	floating point.	 Warn-
	   ing:	the requisite libraries	are not	available for all m68k tar-
	   gets.  Normally the facilities of the machine's usual C compiler
	   are used, but this can't be done directly in	cross-compilation.
	   You must make your own arrangements to provide suitable library
	   functions for cross-compilation.  The embedded targets m68k-*-aout
	   and m68k-*-coff do provide software floating	point support.

       -mshort
	   Consider type "int" to be 16	bits wide, like	"short int".  Addi-
	   tionally, parameters	passed on the stack are	also aligned to	a
	   16-bit boundary even	on targets whose API mandates promotion	to
	   32-bit.

       -mnobitfield
	   Do not use the bit-field instructions.  The -m68000,	-mcpu32	and
	   -m5200 options imply	-mnobitfield.

       -mbitfield
	   Do use the bit-field	instructions.  The -m68020 option implies
	   -mbitfield.	This is	the default if you use a configuration
	   designed for	a 68020.

       -mrtd
	   Use a different function-calling convention,	in which functions
	   that	take a fixed number of arguments return	with the "rtd"
	   instruction,	which pops their arguments while returning.  This
	   saves one instruction in the	caller since there is no need to pop
	   the arguments there.

	   This	calling	convention is incompatible with	the one	normally used
	   on Unix, so you cannot use it if you	need to	call libraries com-
	   piled with the Unix compiler.

	   Also, you must provide function prototypes for all functions	that
	   take	variable numbers of arguments (including "printf"); otherwise
	   incorrect code will be generated for	calls to those functions.

	   In addition,	seriously incorrect code will result if	you call a
	   function with too many arguments.  (Normally, extra arguments are
	   harmlessly ignored.)

	   The "rtd" instruction is supported by the 68010, 68020, 68030,
	   68040, 68060	and CPU32 processors, but not by the 68000 or 5200.

       -malign-int
       -mno-align-int
	   Control whether GCC aligns "int", "long", "long long", "float",
	   "double", and "long double" variables on a 32-bit boundary
	   (-malign-int) or a 16-bit boundary (-mno-align-int).	 Aligning
	   variables on	32-bit boundaries produces code	that runs somewhat
	   faster on processors	with 32-bit busses at the expense of more mem-
	   ory.

	   Warning: if you use the -malign-int switch, GCC will	align struc-
	   tures containing the	above types  differently than most published
	   application binary interface	specifications for the m68k.

       -mpcrel
	   Use the pc-relative addressing mode of the 68000 directly, instead
	   of using a global offset table.  At present,	this option implies
	   -fpic, allowing at most a 16-bit offset for pc-relative addressing.
	   -fPIC is not	presently supported with -mpcrel, though this could be
	   supported for 68020 and higher processors.

       -mno-strict-align
       -mstrict-align
	   Do not (do) assume that unaligned memory references will be handled
	   by the system.

       -msep-data
	   Generate code that allows the data segment to be located in a dif-
	   ferent area of memory from the text segment.	 This allows for exe-
	   cute	in place in an environment without virtual memory management.
	   This	option implies -fPIC.

       -mno-sep-data
	   Generate code that assumes that the data segment follows the	text
	   segment.  This is the default.

       -mid-shared-library
	   Generate code that supports shared libraries	via the	library	ID
	   method.  This allows	for execute in place and shared	libraries in
	   an environment without virtual memory management.  This option
	   implies -fPIC.

       -mno-id-shared-library
	   Generate code that doesn't assume ID	based shared libraries are
	   being used.	This is	the default.

       -mshared-library-id=n
	   Specified the identification	number of the ID based shared library
	   being compiled.  Specifying a value of 0 will generate more compact
	   code, specifying other values will force the	allocation of that
	   number to the current library but is	no more	space or time effi-
	   cient than omitting this option.

       M68hc1x Options

       These are the -m	options	defined	for the	68hc11 and 68hc12 microcon-
       trollers.  The default values for these options depends on which	style
       of microcontroller was selected when the	compiler was configured; the
       defaults	for the	most common choices are	given below.

       -m6811
       -m68hc11
	   Generate output for a 68HC11.  This is the default when the com-
	   piler is configured for 68HC11-based	systems.

       -m6812
       -m68hc12
	   Generate output for a 68HC12.  This is the default when the com-
	   piler is configured for 68HC12-based	systems.

       -m68S12
       -m68hcs12
	   Generate output for a 68HCS12.

       -mauto-incdec
	   Enable the use of 68HC12 pre	and post auto-increment	and auto-
	   decrement addressing	modes.

       -minmax
       -nominmax
	   Enable the use of 68HC12 min	and max	instructions.

       -mlong-calls
       -mno-long-calls
	   Treat all calls as being far	away (near).  If calls are assumed to
	   be far away,	the compiler will use the "call" instruction to	call a
	   function and	the "rtc" instruction for returning.

       -mshort
	   Consider type "int" to be 16	bits wide, like	"short int".

       -msoft-reg-count=count
	   Specify the number of pseudo-soft registers which are used for the
	   code	generation.  The maximum number	is 32.	Using more pseudo-soft
	   register may	or may not result in better code depending on the pro-
	   gram.  The default is 4 for 68HC11 and 2 for	68HC12.

       MCore Options

       These are the -m	options	defined	for the	Motorola M*Core	processors.

       -mhardlit
       -mno-hardlit
	   Inline constants into the code stream if it can be done in two
	   instructions	or less.

       -mdiv
       -mno-div
	   Use the divide instruction.	(Enabled by default).

       -mrelax-immediate
       -mno-relax-immediate
	   Allow arbitrary sized immediates in bit operations.

       -mwide-bitfields
       -mno-wide-bitfields
	   Always treat	bit-fields as int-sized.

       -m4byte-functions
       -mno-4byte-functions
	   Force all functions to be aligned to	a four byte boundary.

       -mcallgraph-data
       -mno-callgraph-data
	   Emit	callgraph information.

       -mslow-bytes
       -mno-slow-bytes
	   Prefer word access when reading byte	quantities.

       -mlittle-endian
       -mbig-endian
	   Generate code for a little endian target.

       -m210
       -m340
	   Generate code for the 210 processor.

       MIPS Options

       -EB Generate big-endian code.

       -EL Generate little-endian code.	 This is the default for mips*el-*-*
	   configurations.

       -march=arch
	   Generate code that will run on arch,	which can be the name of a
	   generic MIPS	ISA, or	the name of a particular processor.  The ISA
	   names are: mips1, mips2, mips3, mips4, mips32, mips32r2, and
	   mips64.  The	processor names	are: 4kc, 4km, 4kp, 5kc, 5kf, 20kc,
	   24k,	24kc, 24kf, 24kx, m4k, orion, r2000, r3000, r3900, r4000,
	   r4400, r4600, r4650,	r6000, r8000, rm7000, rm9000, sb1, sr71000,
	   vr4100, vr4111, vr4120, vr4130, vr4300, vr5000, vr5400 and vr5500.
	   The special value from-abi selects the most compatible architecture
	   for the selected ABI	(that is, mips1	for 32-bit ABIs	and mips3 for
	   64-bit ABIs).

	   In processor	names, a final 000 can be abbreviated as k (for	exam-
	   ple,	-march=r2k).  Prefixes are optional, and vr may	be written r.

	   GCC defines two macros based	on the value of	this option.  The
	   first is _MIPS_ARCH,	which gives the	name of	target architecture,
	   as a	string.	 The second has	the form _MIPS_ARCH_foo, where foo is
	   the capitalized value of _MIPS_ARCH.	 For example, -march=r2000
	   will	set _MIPS_ARCH to "r2000" and define the macro
	   _MIPS_ARCH_R2000.

	   Note	that the _MIPS_ARCH macro uses the processor names given
	   above.  In other words, it will have	the full prefix	and will not
	   abbreviate 000 as k.	 In the	case of	from-abi, the macro names the
	   resolved architecture (either "mips1" or "mips3").  It names	the
	   default architecture	when no	-march option is given.

       -mtune=arch
	   Optimize for	arch.  Among other things, this	option controls	the
	   way instructions are	scheduled, and the perceived cost of arith-
	   metic operations.  The list of arch values is the same as for
	   -march.

	   When	this option is not used, GCC will optimize for the processor
	   specified by	-march.	 By using -march and -mtune together, it is
	   possible to generate	code that will run on a	family of processors,
	   but optimize	the code for one particular member of that family.

	   -mtune defines the macros _MIPS_TUNE	and _MIPS_TUNE_foo, which work
	   in the same way as the -march ones described	above.

       -mips1
	   Equivalent to -march=mips1.

       -mips2
	   Equivalent to -march=mips2.

       -mips3
	   Equivalent to -march=mips3.

       -mips4
	   Equivalent to -march=mips4.

       -mips32
	   Equivalent to -march=mips32.

       -mips32r2
	   Equivalent to -march=mips32r2.

       -mips64
	   Equivalent to -march=mips64.

       -mips16
       -mno-mips16
	   Generate (do	not generate) MIPS16 code.  If GCC is targetting a
	   MIPS32 or MIPS64 architecture, it will make use of the MIPS16e ASE.

       -mabi=32
       -mabi=o64
       -mabi=n32
       -mabi=64
       -mabi=eabi
	   Generate code for the given ABI.

	   Note	that the EABI has a 32-bit and a 64-bit	variant.  GCC normally
	   generates 64-bit code when you select a 64-bit architecture,	but
	   you can use -mgp32 to get 32-bit code instead.

	   For information about the O64 ABI, see
	   <http://gcc.gnu.org/projects/mipso64-abi.html>.

       -mabicalls
       -mno-abicalls
	   Generate (do	not generate) code that	is suitable for	SVR4-style
	   dynamic objects.  -mabicalls	is the default for SVR4-based systems.

       -mshared
       -mno-shared
	   Generate (do	not generate) code that	is fully position-independent,
	   and that can	therefore be linked into shared	libraries.  This
	   option only affects -mabicalls.

	   All -mabicalls code has traditionally been position-independent,
	   regardless of options like -fPIC and	-fpic.	However, as an exten-
	   sion, the GNU toolchain allows executables to use absolute accesses
	   for locally-binding symbols.	 It can	also use shorter GP initial-
	   ization sequences and generate direct calls to locally-defined
	   functions.  This mode is selected by	-mno-shared.

	   -mno-shared depends on binutils 2.16	or higher and generates
	   objects that	can only be linked by the GNU linker.  However,	the
	   option does not affect the ABI of the final executable; it only
	   affects the ABI of relocatable objects.  Using -mno-shared will
	   generally make executables both smaller and quicker.

	   -mshared is the default.

       -mxgot
       -mno-xgot
	   Lift	(do not	lift) the usual	restrictions on	the size of the	global
	   offset table.

	   GCC normally	uses a single instruction to load values from the GOT.
	   While this is relatively efficient, it will only work if the	GOT is
	   smaller than	about 64k.  Anything larger will cause the linker to
	   report an error such	as:

		   relocation truncated	to fit:	R_MIPS_GOT16 foobar

	   If this happens, you	should recompile your code with	-mxgot.	 It
	   should then work with very large GOTs, although it will also	be
	   less	efficient, since it will take three instructions to fetch the
	   value of a global symbol.

	   Note	that some linkers can create multiple GOTs.  If	you have such
	   a linker, you should	only need to use -mxgot	when a single object
	   file	accesses more than 64k's worth of GOT entries.	Very few do.

	   These options have no effect	unless GCC is generating position
	   independent code.

       -mgp32
	   Assume that general-purpose registers are 32	bits wide.

       -mgp64
	   Assume that general-purpose registers are 64	bits wide.

       -mfp32
	   Assume that floating-point registers	are 32 bits wide.

       -mfp64
	   Assume that floating-point registers	are 64 bits wide.

       -mhard-float
	   Use floating-point coprocessor instructions.

       -msoft-float
	   Do not use floating-point coprocessor instructions.	Implement
	   floating-point calculations using library calls instead.

       -msingle-float
	   Assume that the floating-point coprocessor only supports single-
	   precision operations.

       -mdouble-float
	   Assume that the floating-point coprocessor supports double-preci-
	   sion	operations.  This is the default.

       -mdsp
       -mno-dsp
	   Use (do not use) the	MIPS DSP ASE.

       -mpaired-single
       -mno-paired-single
	   Use (do not use) paired-single floating-point instructions.
	     This option can only be used when generating 64-bit code and
	   requires hardware floating-point support to be enabled.

       -mips3d
       -mno-mips3d
	   Use (do not use) the	MIPS-3D	ASE.  The option -mips3d implies
	   -mpaired-single.

       -mlong64
	   Force "long"	types to be 64 bits wide.  See -mlong32	for an expla-
	   nation of the default and the way that the pointer size is deter-
	   mined.

       -mlong32
	   Force "long", "int",	and pointer types to be	32 bits	wide.

	   The default size of "int"s, "long"s and pointers depends on the
	   ABI.	 All the supported ABIs	use 32-bit "int"s.  The	n64 ABI	uses
	   64-bit "long"s, as does the 64-bit EABI; the	others use 32-bit
	   "long"s.  Pointers are the same size	as "long"s, or the same	size
	   as integer registers, whichever is smaller.

       -msym32
       -mno-sym32
	   Assume (do not assume) that all symbols have	32-bit values, regard-
	   less	of the selected	ABI.  This option is useful in combination
	   with	-mabi=64 and -mno-abicalls because it allows GCC to generate
	   shorter and faster references to symbolic addresses.

       -G num
	   Put global and static items less than or equal to num bytes into
	   the small data or bss section instead of the	normal data or bss
	   section.  This allows the data to be	accessed using a single
	   instruction.

	   All modules should be compiled with the same	-G num value.

       -membedded-data
       -mno-embedded-data
	   Allocate variables to the read-only data section first if possible,
	   then	next in	the small data section if possible, otherwise in data.
	   This	gives slightly slower code than	the default, but reduces the
	   amount of RAM required when executing, and thus may be preferred
	   for some embedded systems.

       -muninit-const-in-rodata
       -mno-uninit-const-in-rodata
	   Put uninitialized "const" variables in the read-only	data section.
	   This	option is only meaningful in conjunction with -membedded-data.

       -msplit-addresses
       -mno-split-addresses
	   Enable (disable) use	of the "%hi()" and "%lo()" assembler reloca-
	   tion	operators.  This option	has been superseded by -mex-
	   plicit-relocs but is	retained for backwards compatibility.

       -mexplicit-relocs
       -mno-explicit-relocs
	   Use (do not use) assembler relocation operators when	dealing	with
	   symbolic addresses.	The alternative, selected by
	   -mno-explicit-relocs, is to use assembler macros instead.

	   -mexplicit-relocs is	the default if GCC was configured to use an
	   assembler that supports relocation operators.

       -mcheck-zero-division
       -mno-check-zero-division
	   Trap	(do not	trap) on integer division by zero.  The	default	is
	   -mcheck-zero-division.

       -mdivide-traps
       -mdivide-breaks
	   MIPS	systems	check for division by zero by generating either	a con-
	   ditional trap or a break instruction.  Using	traps results in
	   smaller code, but is	only supported on MIPS II and later.  Also,
	   some	versions of the	Linux kernel have a bug	that prevents trap
	   from	generating the proper signal ("SIGFPE").  Use -mdivide-traps
	   to allow conditional	traps on architectures that support them and
	   -mdivide-breaks to force the	use of breaks.

	   The default is usually -mdivide-traps, but this can be overridden
	   at configure	time using --with-divide=breaks.  Divide-by-zero
	   checks can be completely disabled using -mno-check-zero-division.

       -mmemcpy
       -mno-memcpy
	   Force (do not force)	the use	of "memcpy()" for non-trivial block
	   moves.  The default is -mno-memcpy, which allows GCC	to inline most
	   constant-sized copies.

       -mlong-calls
       -mno-long-calls
	   Disable (do not disable) use	of the "jal" instruction.  Calling
	   functions using "jal" is more efficient but requires	the caller and
	   callee to be	in the same 256	megabyte segment.

	   This	option has no effect on	abicalls code.	The default is
	   -mno-long-calls.

       -mmad
       -mno-mad
	   Enable (disable) use	of the "mad", "madu" and "mul" instructions,
	   as provided by the R4650 ISA.

       -mfused-madd
       -mno-fused-madd
	   Enable (disable) use	of the floating	point multiply-accumulate
	   instructions, when they are available.  The default is
	   -mfused-madd.

	   When	multiply-accumulate instructions are used, the intermediate
	   product is calculated to infinite precision and is not subject to
	   the FCSR Flush to Zero bit.	This may be undesirable	in some	cir-
	   cumstances.

       -nocpp
	   Tell	the MIPS assembler to not run its preprocessor over user
	   assembler files (with a .s suffix) when assembling them.

       -mfix-r4000
       -mno-fix-r4000
	   Work	around certain R4000 CPU errata:

	   -   A double-word or	a variable shift may give an incorrect result
	       if executed immediately after starting an integer division.

	   -   A double-word or	a variable shift may give an incorrect result
	       if executed while an integer multiplication is in progress.

	   -   An integer division may give an incorrect result	if started in
	       a delay slot of a taken branch or a jump.

       -mfix-r4400
       -mno-fix-r4400
	   Work	around certain R4400 CPU errata:

	   -   A double-word or	a variable shift may give an incorrect result
	       if executed immediately after starting an integer division.

       -mfix-vr4120
       -mno-fix-vr4120
	   Work	around certain VR4120 errata:

	   -   "dmultu"	does not always	produce	the correct result.

	   -   "div" and "ddiv"	do not always produce the correct result if
	       one of the operands is negative.

	   The workarounds for the division errata rely	on special functions
	   in libgcc.a.	 At present, these functions are only provided by the
	   "mips64vr*-elf" configurations.

	   Other VR4120	errata require a nop to	be inserted between certain
	   pairs of instructions.  These errata	are handled by the assembler,
	   not by GCC itself.

       -mfix-vr4130
	   Work	around the VR4130 "mflo"/"mfhi"	errata.	 The workarounds are
	   implemented by the assembler	rather than by GCC, although GCC will
	   avoid using "mflo" and "mfhi" if the	VR4130 "macc", "macchi",
	   "dmacc" and "dmacchi" instructions are available instead.

       -mfix-sb1
       -mno-fix-sb1
	   Work	around certain SB-1 CPU	core errata.  (This flag currently
	   works around	the SB-1 revision 2 "F1" and "F2" floating point
	   errata.)

       -mflush-func=func
       -mno-flush-func
	   Specifies the function to call to flush the I and D caches, or to
	   not call any	such function.	If called, the function	must take the
	   same	arguments as the common	"_flush_func()", that is, the address
	   of the memory range for which the cache is being flushed, the size
	   of the memory range,	and the	number 3 (to flush both	caches).  The
	   default depends on the target GCC was configured for, but commonly
	   is either _flush_func or __cpu_flush.

       -mbranch-likely
       -mno-branch-likely
	   Enable or disable use of Branch Likely instructions,	regardless of
	   the default for the selected	architecture.  By default, Branch
	   Likely instructions may be generated	if they	are supported by the
	   selected architecture.  An exception	is for the MIPS32 and MIPS64
	   architectures and processors	which implement	those architectures;
	   for those, Branch Likely instructions will not be generated by
	   default because the MIPS32 and MIPS64 architectures specifically
	   deprecate their use.

       -mfp-exceptions
       -mno-fp-exceptions
	   Specifies whether FP	exceptions are enabled.	 This affects how we
	   schedule FP instructions for	some processors.  The default is that
	   FP exceptions are enabled.

	   For instance, on the	SB-1, if FP exceptions are disabled, and we
	   are emitting	64-bit code, then we can use both FP pipes.  Other-
	   wise, we can	only use one FP	pipe.

       -mvr4130-align
       -mno-vr4130-align
	   The VR4130 pipeline is two-way superscalar, but can only issue two
	   instructions	together if the	first one is 8-byte aligned.  When
	   this	option is enabled, GCC will align pairs	of instructions	that
	   it thinks should execute in parallel.

	   This	option only has	an effect when optimizing for the VR4130.  It
	   normally makes code faster, but at the expense of making it bigger.
	   It is enabled by default at optimization level -O3.

       MMIX Options

       These options are defined for the MMIX:

       -mlibfuncs
       -mno-libfuncs
	   Specify that	intrinsic library functions are	being compiled,	pass-
	   ing all values in registers,	no matter the size.

       -mepsilon
       -mno-epsilon
	   Generate floating-point comparison instructions that	compare	with
	   respect to the "rE" epsilon register.

       -mabi=mmixware
       -mabi=gnu
	   Generate code that passes function parameters and return values
	   that	(in the	called function) are seen as registers $0 and up, as
	   opposed to the GNU ABI which	uses global registers $231 and up.

       -mzero-extend
       -mno-zero-extend
	   When	reading	data from memory in sizes shorter than 64 bits,	use
	   (do not use)	zero-extending load instructions by default, rather
	   than	sign-extending ones.

       -mknuthdiv
       -mno-knuthdiv
	   Make	the result of a	division yielding a remainder have the same
	   sign	as the divisor.	 With the default, -mno-knuthdiv, the sign of
	   the remainder follows the sign of the dividend.  Both methods are
	   arithmetically valid, the latter being almost exclusively used.

       -mtoplevel-symbols
       -mno-toplevel-symbols
	   Prepend (do not prepend) a :	to all global symbols, so the assembly
	   code	can be used with the "PREFIX" assembly directive.

       -melf
	   Generate an executable in the ELF format, rather than the default
	   mmo format used by the mmix simulator.

       -mbranch-predict
       -mno-branch-predict
	   Use (do not use) the	probable-branch	instructions, when static
	   branch prediction indicates a probable branch.

       -mbase-addresses
       -mno-base-addresses
	   Generate (do	not generate) code that	uses base addresses.  Using a
	   base	address	automatically generates	a request (handled by the
	   assembler and the linker) for a constant to be set up in a global
	   register.  The register is used for one or more base	address
	   requests within the range 0 to 255 from the value held in the reg-
	   ister.  The generally leads to short	and fast code, but the number
	   of different	data items that	can be addressed is limited.  This
	   means that a	program	that uses lots of static data may require
	   -mno-base-addresses.

       -msingle-exit
       -mno-single-exit
	   Force (do not force)	generated code to have a single	exit point in
	   each	function.

       MN10300 Options

       These -m	options	are defined for	Matsushita MN10300 architectures:

       -mmult-bug
	   Generate code to avoid bugs in the multiply instructions for	the
	   MN10300 processors.	This is	the default.

       -mno-mult-bug
	   Do not generate code	to avoid bugs in the multiply instructions for
	   the MN10300 processors.

       -mam33
	   Generate code which uses features specific to the AM33 processor.

       -mno-am33
	   Do not generate code	which uses features specific to	the AM33 pro-
	   cessor.  This is the	default.

       -mreturn-pointer-on-d0
	   When	generating a function which returns a pointer, return the
	   pointer in both "a0"	and "d0".  Otherwise, the pointer is returned
	   only	in a0, and attempts to call such functions without a prototype
	   would result	in errors.  Note that this option is on	by default;
	   use -mno-return-pointer-on-d0 to disable it.

       -mno-crt0
	   Do not link in the C	run-time initialization	object file.

       -mrelax
	   Indicate to the linker that it should perform a relaxation opti-
	   mization pass to shorten branches, calls and	absolute memory
	   addresses.  This option only	has an effect when used	on the command
	   line	for the	final link step.

	   This	option makes symbolic debugging	impossible.

       MT Options

       These -m	options	are defined for	Morpho MT architectures:

       -march=cpu-type
	   Generate code that will run on cpu-type, which is the name of a
	   system representing a certain processor type.  Possible values for
	   cpu-type are	ms1-64-001, ms1-16-002,	ms1-16-003 and ms2.

	   When	this option is not used, the default is	-march=ms1-16-002.

       -mbacc
	   Use byte loads and stores when generating code.

       -mno-bacc
	   Do not use byte loads and stores when generating code.

       -msim
	   Use simulator runtime

       -mno-crt0
	   Do not link in the C	run-time initialization	object file crti.o.
	   Other run-time initialization and termination files such as
	   startup.o and exit.o	are still included on the linker command line.

       PDP-11 Options

       These options are defined for the PDP-11:

       -mfpu
	   Use hardware	FPP floating point.  This is the default.  (FIS	float-
	   ing point on	the PDP-11/40 is not supported.)

       -msoft-float
	   Do not use hardware floating	point.

       -mac0
	   Return floating-point results in ac0	(fr0 in	Unix assembler syn-
	   tax).

       -mno-ac0
	   Return floating-point results in memory.  This is the default.

       -m40
	   Generate code for a PDP-11/40.

       -m45
	   Generate code for a PDP-11/45.  This	is the default.

       -m10
	   Generate code for a PDP-11/10.

       -mbcopy-builtin
	   Use inline "movmemhi" patterns for copying memory.  This is the
	   default.

       -mbcopy
	   Do not use inline "movmemhi"	patterns for copying memory.

       -mint16
       -mno-int32
	   Use 16-bit "int".  This is the default.

       -mint32
       -mno-int16
	   Use 32-bit "int".

       -mfloat64
       -mno-float32
	   Use 64-bit "float".	This is	the default.

       -mfloat32
       -mno-float64
	   Use 32-bit "float".

       -mabshi
	   Use "abshi2"	pattern.  This is the default.

       -mno-abshi
	   Do not use "abshi2" pattern.

       -mbranch-expensive
	   Pretend that	branches are expensive.	 This is for experimenting
	   with	code generation	only.

       -mbranch-cheap
	   Do not pretend that branches	are expensive.	This is	the default.

       -msplit
	   Generate code for a system with split I&D.

       -mno-split
	   Generate code for a system without split I&D.  This is the default.

       -munix-asm
	   Use Unix assembler syntax.  This is the default when	configured for
	   pdp11-*-bsd.

       -mdec-asm
	   Use DEC assembler syntax.  This is the default when configured for
	   any PDP-11 target other than	pdp11-*-bsd.

       PowerPC Options

       These are listed	under

       IBM RS/6000 and PowerPC Options

       These -m	options	are defined for	the IBM	RS/6000	and PowerPC:

       -mpower
       -mno-power
       -mpower2
       -mno-power2
       -mpowerpc
       -mno-powerpc
       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
       -mmfcrf
       -mno-mfcrf
       -mpopcntb
       -mno-popcntb
       -mfprnd
       -mno-fprnd
	   GCC supports	two related instruction	set architectures for the
	   RS/6000 and PowerPC.	 The POWER instruction set are those instruc-
	   tions supported by the rios chip set	used in	the original RS/6000
	   systems and the PowerPC instruction set is the architecture of the
	   Freescale MPC5xx, MPC6xx, MPC8xx microprocessors, and the IBM 4xx,
	   6xx,	and follow-on microprocessors.

	   Neither architecture	is a subset of the other.  However there is a
	   large common	subset of instructions supported by both.  An MQ reg-
	   ister is included in	processors supporting the POWER	architecture.

	   You use these options to specify which instructions are available
	   on the processor you	are using.  The	default	value of these options
	   is determined when configuring GCC.	Specifying the -mcpu=cpu_type
	   overrides the specification of these	options.  We recommend you use
	   the -mcpu=cpu_type option rather than the options listed above.

	   The -mpower option allows GCC to generate instructions that are
	   found only in the POWER architecture	and to use the MQ register.
	   Specifying -mpower2 implies -power and also allows GCC to generate
	   instructions	that are present in the	POWER2 architecture but	not
	   the original	POWER architecture.

	   The -mpowerpc option	allows GCC to generate instructions that are
	   found only in the 32-bit subset of the PowerPC architecture.	 Spec-
	   ifying -mpowerpc-gpopt implies -mpowerpc and	also allows GCC	to use
	   the optional	PowerPC	architecture instructions in the General Pur-
	   pose	group, including floating-point	square root.  Specifying
	   -mpowerpc-gfxopt implies -mpowerpc and also allows GCC to use the
	   optional PowerPC architecture instructions in the Graphics group,
	   including floating-point select.

	   The -mmfcrf option allows GCC to generate the move from condition
	   register field instruction implemented on the POWER4	processor and
	   other processors that support the PowerPC V2.01 architecture.  The
	   -mpopcntb option allows GCC to generate the popcount	and double
	   precision FP	reciprocal estimate instruction	implemented on the
	   POWER5 processor and	other processors that support the PowerPC
	   V2.02 architecture.	The -mfprnd option allows GCC to generate the
	   FP round to integer instructions implemented	on the POWER5+ proces-
	   sor and other processors that support the PowerPC V2.03 architec-
	   ture.

	   The -mpowerpc64 option allows GCC to	generate the additional	64-bit
	   instructions	that are found in the full PowerPC64 architecture and
	   to treat GPRs as 64-bit, doubleword quantities.  GCC	defaults to
	   -mno-powerpc64.

	   If you specify both -mno-power and -mno-powerpc, GCC	will use only
	   the instructions in the common subset of both architectures plus
	   some	special	AIX common-mode	calls, and will	not use	the MQ regis-
	   ter.	 Specifying both -mpower and -mpowerpc permits GCC to use any
	   instruction from either architecture	and to allow use of the	MQ
	   register; specify this for the Motorola MPC601.

       -mnew-mnemonics
       -mold-mnemonics
	   Select which	mnemonics to use in the	generated assembler code.
	   With	-mnew-mnemonics, GCC uses the assembler	mnemonics defined for
	   the PowerPC architecture.  With -mold-mnemonics it uses the assem-
	   bler	mnemonics defined for the POWER	architecture.  Instructions
	   defined in only one architecture have only one mnemonic; GCC	uses
	   that	mnemonic irrespective of which of these	options	is specified.

	   GCC defaults	to the mnemonics appropriate for the architecture in
	   use.	 Specifying -mcpu=cpu_type sometimes overrides the value of
	   these option.  Unless you are building a cross-compiler, you	should
	   normally not	specify	either -mnew-mnemonics or -mold-mnemonics, but
	   should instead accept the default.

       -mcpu=cpu_type
	   Set architecture type, register usage, choice of mnemonics, and
	   instruction scheduling parameters for machine type cpu_type.	 Sup-
	   ported values for cpu_type are 401, 403, 405, 405fp,	440, 440fp,
	   505,	601, 602, 603, 603e, 604, 604e,	620, 630, 740, 7400, 7450,
	   750,	801, 821, 823, 860, 970, 8540, ec603e, G3, G4, G5, power,
	   power2, power3, power4, power5, power5+, power6, common, powerpc,
	   powerpc64, rios, rios1, rios2, rsc, and rs64.

	   -mcpu=common	selects	a completely generic processor.	 Code gener-
	   ated	under this option will run on any POWER	or PowerPC processor.
	   GCC will use	only the instructions in the common subset of both
	   architectures, and will not use the MQ register.  GCC assumes a
	   generic processor model for scheduling purposes.

	   -mcpu=power,	-mcpu=power2, -mcpu=powerpc, and -mcpu=powerpc64 spec-
	   ify generic POWER, POWER2, pure 32-bit PowerPC (i.e., not MPC601),
	   and 64-bit PowerPC architecture machine types, with an appropriate,
	   generic processor model assumed for scheduling purposes.

	   The other options specify a specific	processor.  Code generated
	   under those options will run	best on	that processor,	and may	not
	   run at all on others.

	   The -mcpu options automatically enable or disable the following
	   options: -maltivec, -mfprnd,	-mhard-float, -mmfcrf, -mmultiple,
	   -mnew-mnemonics, -mpopcntb, -mpower,	-mpower2, -mpowerpc64, -mpow-
	   erpc-gpopt, -mpowerpc-gfxopt, -mstring, -mmulhw, -mdlmzb.  The par-
	   ticular options set for any particular CPU will vary	between	com-
	   piler versions, depending on	what setting seems to produce optimal
	   code	for that CPU; it doesn't necessarily reflect the actual	hard-
	   ware's capabilities.	 If you	wish to	set an individual option to a
	   particular value, you may specify it	after the -mcpu	option,	like
	   -mcpu=970 -mno-altivec.

	   On AIX, the -maltivec and -mpowerpc64 options are not enabled or
	   disabled by the -mcpu option	at present because AIX does not	have
	   full	support	for these options.  You	may still enable or disable
	   them	individually if	you're sure it'll work in your environment.

       -mtune=cpu_type
	   Set the instruction scheduling parameters for machine type
	   cpu_type, but do not	set the	architecture type, register usage, or
	   choice of mnemonics,	as -mcpu=cpu_type would.  The same values for
	   cpu_type are	used for -mtune	as for -mcpu.  If both are specified,
	   the code generated will use the architecture, registers, and
	   mnemonics set by -mcpu, but the scheduling parameters set by
	   -mtune.

       -mswdiv
       -mno-swdiv
	   Generate code to compute division as	reciprocal estimate and	itera-
	   tive	refinement, creating opportunities for increased throughput.
	   This	feature	requires: optional PowerPC Graphics instruction	set
	   for single precision	and FRE	instruction for	double precision,
	   assuming divides cannot generate user-visible traps,	and the	domain
	   values not include Infinities, denormals or zero denominator.

       -maltivec
       -mno-altivec
	   Generate code that uses (does not use) AltiVec instructions,	and
	   also	enable the use of built-in functions that allow	more direct
	   access to the AltiVec instruction set.  You may also	need to	set
	   -mabi=altivec to adjust the current ABI with	AltiVec	ABI enhance-
	   ments.

       -mvrsave
       -mno-vrsave
	   Generate VRSAVE instructions	when generating	AltiVec	code.

       -msecure-plt
	   Generate code that allows ld	and ld.so to build executables and
	   shared libraries with non-exec .plt and .got	sections.  This	is a
	   PowerPC 32-bit SYSV ABI option.

       -mbss-plt
	   Generate code that uses a BSS .plt section that ld.so fills in, and
	   requires .plt and .got sections that	are both writable and exe-
	   cutable.  This is a PowerPC 32-bit SYSV ABI option.

       -misel
       -mno-isel
	   This	switch enables or disables the generation of ISEL instruc-
	   tions.

       -misel=yes/no
	   This	switch has been	deprecated.  Use -misel	and -mno-isel instead.

       -mspe
       -mno-spe
	   This	switch enables or disables the generation of SPE simd instruc-
	   tions.

       -mspe=yes/no
	   This	option has been	deprecated.  Use -mspe and -mno-spe instead.

       -mfloat-gprs=yes/single/double/no
       -mfloat-gprs
	   This	switch enables or disables the generation of floating point
	   operations on the general purpose registers for architectures that
	   support it.

	   The argument	yes or single enables the use of single-precision
	   floating point operations.

	   The argument	double enables the use of single and double-precision
	   floating point operations.

	   The argument	no disables floating point operations on the general
	   purpose registers.

	   This	option is currently only available on the MPC854x.

       -m32
       -m64
	   Generate code for 32-bit or 64-bit environments of Darwin and SVR4
	   targets (including GNU/Linux).  The 32-bit environment sets int,
	   long	and pointer to 32 bits and generates code that runs on any
	   PowerPC variant.  The 64-bit	environment sets int to	32 bits	and
	   long	and pointer to 64 bits,	and generates code for PowerPC64, as
	   for -mpowerpc64.

       -mfull-toc
       -mno-fp-in-toc
       -mno-sum-in-toc
       -mminimal-toc
	   Modify generation of	the TOC	(Table Of Contents), which is created
	   for every executable	file.  The -mfull-toc option is	selected by
	   default.  In	that case, GCC will allocate at	least one TOC entry
	   for each unique non-automatic variable reference in your program.
	   GCC will also place floating-point constants	in the TOC.  However,
	   only	16,384 entries are available in	the TOC.

	   If you receive a linker error message that saying you have over-
	   flowed the available	TOC space, you can reduce the amount of	TOC
	   space used with the -mno-fp-in-toc and -mno-sum-in-toc options.
	   -mno-fp-in-toc prevents GCC from putting floating-point constants
	   in the TOC and -mno-sum-in-toc forces GCC to	generate code to cal-
	   culate the sum of an	address	and a constant at run-time instead of
	   putting that	sum into the TOC.  You may specify one or both of
	   these options.  Each	causes GCC to produce very slightly slower and
	   larger code at the expense of conserving TOC	space.

	   If you still	run out	of space in the	TOC even when you specify both
	   of these options, specify -mminimal-toc instead.  This option
	   causes GCC to make only one TOC entry for every file.  When you
	   specify this	option,	GCC will produce code that is slower and
	   larger but which uses extremely little TOC space.  You may wish to
	   use this option only	on files that contain less frequently executed
	   code.

       -maix64
       -maix32
	   Enable 64-bit AIX ABI and calling convention: 64-bit	pointers,
	   64-bit "long" type, and the infrastructure needed to	support	them.
	   Specifying -maix64 implies -mpowerpc64 and -mpowerpc, while -maix32
	   disables the	64-bit ABI and implies -mno-powerpc64.	GCC defaults
	   to -maix32.

       -mxl-compat
       -mno-xl-compat
	   Produce code	that conforms more closely to IBM XL compiler seman-
	   tics	when using AIX-compatible ABI.	Pass floating-point arguments
	   to prototyped functions beyond the register save area (RSA) on the
	   stack in addition to	argument FPRs.	Do not assume that most	sig-
	   nificant double in 128-bit long double value	is properly rounded
	   when	comparing values and converting	to double.  Use	XL symbol
	   names for long double support routines.

	   The AIX calling convention was extended but not initially docu-
	   mented to handle an obscure K&R C case of calling a function	that
	   takes the address of	its arguments with fewer arguments than
	   declared.  IBM XL compilers access floating point arguments which
	   do not fit in the RSA from the stack	when a subroutine is compiled
	   without optimization.  Because always storing floating-point	argu-
	   ments on the	stack is inefficient and rarely	needed,	this option is
	   not enabled by default and only is necessary	when calling subrou-
	   tines compiled by IBM XL compilers without optimization.

       -mpe
	   Support IBM RS/6000 SP Parallel Environment (PE).  Link an applica-
	   tion	written	to use message passing with special startup code to
	   enable the application to run.  The system must have	PE installed
	   in the standard location (/usr/lpp/ppe.poe/), or the	specs file
	   must	be overridden with the -specs= option to specify the appropri-
	   ate directory location.  The	Parallel Environment does not support
	   threads, so the -mpe	option and the -pthread	option are incompati-
	   ble.

       -malign-natural
       -malign-power
	   On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux,	the option
	   -malign-natural overrides the ABI-defined alignment of larger
	   types, such as floating-point doubles, on their natural size-based
	   boundary.  The option -malign-power instructs GCC to	follow the
	   ABI-specified alignment rules.  GCC defaults	to the standard	align-
	   ment	defined	in the ABI.

	   On 64-bit Darwin, natural alignment is the default, and
	   -malign-power is not	supported.

       -msoft-float
       -mhard-float
	   Generate code that does not use (uses) the floating-point register
	   set.	 Software floating point emulation is provided if you use the
	   -msoft-float	option,	and pass the option to GCC when	linking.

       -mmultiple
       -mno-multiple
	   Generate code that uses (does not use) the load multiple word
	   instructions	and the	store multiple word instructions.  These
	   instructions	are generated by default on POWER systems, and not
	   generated on	PowerPC	systems.  Do not use -mmultiple	on little
	   endian PowerPC systems, since those instructions do not work	when
	   the processor is in little endian mode.  The	exceptions are PPC740
	   and PPC750 which permit the instructions usage in little endian
	   mode.

       -mstring
       -mno-string
	   Generate code that uses (does not use) the load string instructions
	   and the store string	word instructions to save multiple registers
	   and do small	block moves.  These instructions are generated by
	   default on POWER systems, and not generated on PowerPC systems.  Do
	   not use -mstring on little endian PowerPC systems, since those
	   instructions	do not work when the processor is in little endian
	   mode.  The exceptions are PPC740 and	PPC750 which permit the
	   instructions	usage in little	endian mode.

       -mupdate
       -mno-update
	   Generate code that uses (does not use) the load or store instruc-
	   tions that update the base register to the address of the calcu-
	   lated memory	location.  These instructions are generated by
	   default.  If	you use	-mno-update, there is a	small window between
	   the time that the stack pointer is updated and the address of the
	   previous frame is stored, which means code that walks the stack
	   frame across	interrupts or signals may get corrupted	data.

       -mfused-madd
       -mno-fused-madd
	   Generate code that uses (does not use) the floating point multiply
	   and accumulate instructions.	 These instructions are	generated by
	   default if hardware floating	is used.

       -mmulhw
       -mno-mulhw
	   Generate code that uses (does not use) the half-word	multiply and
	   multiply-accumulate instructions on the IBM 405 and 440 processors.
	   These instructions are generated by default when targetting those
	   processors.

       -mdlmzb
       -mno-dlmzb
	   Generate code that uses (does not use) the string-search dlmzb
	   instruction on the IBM 405 and 440 processors.  This	instruction is
	   generated by	default	when targetting	those processors.

       -mno-bit-align
       -mbit-align
	   On System V.4 and embedded PowerPC systems do not (do) force	struc-
	   tures and unions that contain bit-fields to be aligned to the base
	   type	of the bit-field.

	   For example,	by default a structure containing nothing but 8
	   "unsigned" bit-fields of length 1 would be aligned to a 4 byte
	   boundary and	have a size of 4 bytes.	 By using -mno-bit-align, the
	   structure would be aligned to a 1 byte boundary and be one byte in
	   size.

       -mno-strict-align
       -mstrict-align
	   On System V.4 and embedded PowerPC systems do not (do) assume that
	   unaligned memory references will be handled by the system.

       -mrelocatable
       -mno-relocatable
	   On embedded PowerPC systems generate	code that allows (does not
	   allow) the program to be relocated to a different address at	run-
	   time.  If you use -mrelocatable on any module, all objects linked
	   together must be compiled with -mrelocatable	or -mrelocatable-lib.

       -mrelocatable-lib
       -mno-relocatable-lib
	   On embedded PowerPC systems generate	code that allows (does not
	   allow) the program to be relocated to a different address at	run-
	   time.  Modules compiled with	-mrelocatable-lib can be linked	with
	   either modules compiled without -mrelocatable and -mrelocatable-lib
	   or with modules compiled with the -mrelocatable options.

       -mno-toc
       -mtoc
	   On System V.4 and embedded PowerPC systems do not (do) assume that
	   register 2 contains a pointer to a global area pointing to the
	   addresses used in the program.

       -mlittle
       -mlittle-endian
	   On System V.4 and embedded PowerPC systems compile code for the
	   processor in	little endian mode.  The -mlittle-endian option	is the
	   same	as -mlittle.

       -mbig
       -mbig-endian
	   On System V.4 and embedded PowerPC systems compile code for the
	   processor in	big endian mode.  The -mbig-endian option is the same
	   as -mbig.

       -mdynamic-no-pic
	   On Darwin and Mac OS	X systems, compile code	so that	it is not
	   relocatable,	but that its external references are relocatable.  The
	   resulting code is suitable for applications,	but not	shared
	   libraries.

       -mprioritize-restricted-insns=priority
	   This	option controls	the priority that is assigned to dispatch-slot
	   restricted instructions during the second scheduling	pass.  The
	   argument priority takes the value 0/1/2 to assign no/highest/sec-
	   ond-highest priority	to dispatch slot restricted instructions.

       -msched-costly-dep=dependence_type
	   This	option controls	which dependences are considered costly	by the
	   target during instruction scheduling.  The argument dependence_type
	   takes one of	the following values: no: no dependence	is costly,
	   all:	all dependences	are costly, true_store_to_load:	a true depen-
	   dence from store to load is costly, store_to_load: any dependence
	   from	store to load is costly, number: any dependence	which latency
	   >= number is	costly.

       -minsert-sched-nops=scheme
	   This	option controls	which nop insertion scheme will	be used	during
	   the second scheduling pass.	The argument scheme takes one of the
	   following values: no: Don't insert nops.  pad: Pad with nops	any
	   dispatch group which	has vacant issue slots,	according to the
	   scheduler's grouping.  regroup_exact: Insert	nops to	force costly
	   dependent insns into	separate groups.  Insert exactly as many nops
	   as needed to	force an insn to a new group, according	to the esti-
	   mated processor grouping.  number: Insert nops to force costly
	   dependent insns into	separate groups.  Insert number	nops to	force
	   an insn to a	new group.

       -mcall-sysv
	   On System V.4 and embedded PowerPC systems compile code using call-
	   ing conventions that	adheres	to the March 1995 draft	of the System
	   V Application Binary	Interface, PowerPC processor supplement.  This
	   is the default unless you configured	GCC using powerpc-*-eabiaix.

       -mcall-sysv-eabi
	   Specify both	-mcall-sysv and	-meabi options.

       -mcall-sysv-noeabi
	   Specify both	-mcall-sysv and	-mno-eabi options.

       -mcall-solaris
	   On System V.4 and embedded PowerPC systems compile code for the
	   Solaris operating system.

       -mcall-linux
	   On System V.4 and embedded PowerPC systems compile code for the
	   Linux-based GNU system.

       -mcall-gnu
	   On System V.4 and embedded PowerPC systems compile code for the
	   Hurd-based GNU system.

       -mcall-netbsd
	   On System V.4 and embedded PowerPC systems compile code for the
	   NetBSD operating system.

       -maix-struct-return
	   Return all structures in memory (as specified by the	AIX ABI).

       -msvr4-struct-return
	   Return structures smaller than 8 bytes in registers (as specified
	   by the SVR4 ABI).

       -mabi=abi-type
	   Extend the current ABI with a particular extension, or remove such
	   extension.  Valid values are	altivec, no-altivec, spe, no-spe, ibm-
	   longdouble, ieeelongdouble.

       -mabi=spe
	   Extend the current ABI with SPE ABI extensions.  This does not
	   change the default ABI, instead it adds the SPE ABI extensions to
	   the current ABI.

       -mabi=no-spe
	   Disable Booke SPE ABI extensions for	the current ABI.

       -mabi=ibmlongdouble
	   Change the current ABI to use IBM extended precision	long double.
	   This	is a PowerPC 32-bit SYSV ABI option.

       -mabi=ieeelongdouble
	   Change the current ABI to use IEEE extended precision long double.
	   This	is a PowerPC 32-bit Linux ABI option.

       -mprototype
       -mno-prototype
	   On System V.4 and embedded PowerPC systems assume that all calls to
	   variable argument functions are properly prototyped.	 Otherwise,
	   the compiler	must insert an instruction before every	non prototyped
	   call	to set or clear	bit 6 of the condition code register (CR) to
	   indicate whether floating point values were passed in the floating
	   point registers in case the function	takes a	variable arguments.
	   With	-mprototype, only calls	to prototyped variable argument	func-
	   tions will set or clear the bit.

       -msim
	   On embedded PowerPC systems,	assume that the	startup	module is
	   called sim-crt0.o and that the standard C libraries are libsim.a
	   and libc.a.	This is	the default for	powerpc-*-eabisim.  configura-
	   tions.

       -mmvme
	   On embedded PowerPC systems,	assume that the	startup	module is
	   called crt0.o and the standard C libraries are libmvme.a and
	   libc.a.

       -mads
	   On embedded PowerPC systems,	assume that the	startup	module is
	   called crt0.o and the standard C libraries are libads.a and libc.a.

       -myellowknife
	   On embedded PowerPC systems,	assume that the	startup	module is
	   called crt0.o and the standard C libraries are libyk.a and libc.a.

       -mvxworks
	   On System V.4 and embedded PowerPC systems, specify that you	are
	   compiling for a VxWorks system.

       -mwindiss
	   Specify that	you are	compiling for the WindISS simulation environ-
	   ment.

       -memb
	   On embedded PowerPC systems,	set the	PPC_EMB	bit in the ELF flags
	   header to indicate that eabi	extended relocations are used.

       -meabi
       -mno-eabi
	   On System V.4 and embedded PowerPC systems do (do not) adhere to
	   the Embedded	Applications Binary Interface (eabi) which is a	set of
	   modifications to the	System V.4 specifications.  Selecting -meabi
	   means that the stack	is aligned to an 8 byte	boundary, a function
	   "__eabi" is called to from "main" to	set up the eabi	environment,
	   and the -msdata option can use both "r2" and	"r13" to point to two
	   separate small data areas.  Selecting -mno-eabi means that the
	   stack is aligned to a 16 byte boundary, do not call an initializa-
	   tion	function from "main", and the -msdata option will only use
	   "r13" to point to a single small data area.	The -meabi option is
	   on by default if you	configured GCC using one of the	pow-
	   erpc*-*-eabi* options.

       -msdata=eabi
	   On System V.4 and embedded PowerPC systems, put small initialized
	   "const" global and static data in the .sdata2 section, which	is
	   pointed to by register "r2".	 Put small initialized non-"const"
	   global and static data in the .sdata	section, which is pointed to
	   by register "r13".  Put small uninitialized global and static data
	   in the .sbss	section, which is adjacent to the .sdata section.  The
	   -msdata=eabi	option is incompatible with the	-mrelocatable option.
	   The -msdata=eabi option also	sets the -memb option.

       -msdata=sysv
	   On System V.4 and embedded PowerPC systems, put small global	and
	   static data in the .sdata section, which is pointed to by register
	   "r13".  Put small uninitialized global and static data in the .sbss
	   section, which is adjacent to the .sdata section.  The -msdata=sysv
	   option is incompatible with the -mrelocatable option.

       -msdata=default
       -msdata
	   On System V.4 and embedded PowerPC systems, if -meabi is used, com-
	   pile	code the same as -msdata=eabi, otherwise compile code the same
	   as -msdata=sysv.

       -msdata-data
	   On System V.4 and embedded PowerPC systems, put small global	data
	   in the .sdata section.  Put small uninitialized global data in the
	   .sbss section.  Do not use register "r13" to	address	small data
	   however.  This is the default behavior unless other -msdata options
	   are used.

       -msdata=none
       -mno-sdata
	   On embedded PowerPC systems,	put all	initialized global and static
	   data	in the .data section, and all uninitialized data in the	.bss
	   section.

       -G num
	   On embedded PowerPC systems,	put global and static items less than
	   or equal to num bytes into the small	data or	bss sections instead
	   of the normal data or bss section.  By default, num is 8.  The -G
	   num switch is also passed to	the linker.  All modules should	be
	   compiled with the same -G num value.

       -mregnames
       -mno-regnames
	   On System V.4 and embedded PowerPC systems do (do not) emit regis-
	   ter names in	the assembly language output using symbolic forms.

       -mlongcall
       -mno-longcall
	   By default assume that all calls are	far away so that a longer more
	   expensive calling sequence is required.  This is required for calls
	   further than	32 megabytes (33,554,432 bytes)	from the current loca-
	   tion.  A short call will be generated if the	compiler knows the
	   call	cannot be that far away.  This setting can be overridden by
	   the "shortcall" function attribute, or by "#pragma longcall(0)".

	   Some	linkers	are capable of detecting out-of-range calls and	gener-
	   ating glue code on the fly.	On these systems, long calls are
	   unnecessary and generate slower code.  As of	this writing, the AIX
	   linker can do this, as can the GNU linker for PowerPC/64.  It is
	   planned to add this feature to the GNU linker for 32-bit PowerPC
	   systems as well.

	   On Darwin/PPC systems, "#pragma longcall" will generate "jbsr
	   callee, L42", plus a	"branch	island"	(glue code).  The two target
	   addresses represent the callee and the "branch island".  The	Dar-
	   win/PPC linker will prefer the first	address	and generate a "bl
	   callee" if the PPC "bl" instruction will reach the callee directly;
	   otherwise, the linker will generate "bl L42"	to call	the "branch
	   island".  The "branch island" is appended to	the body of the	call-
	   ing function; it computes the full 32-bit address of	the callee and
	   jumps to it.

	   On Mach-O (Darwin) systems, this option directs the compiler	emit
	   to the glue for every direct	call, and the Darwin linker decides
	   whether to use or discard it.

	   In the future, we may cause GCC to ignore all longcall specifica-
	   tions when the linker is known to generate glue.

       -pthread
	   Adds	support	for multithreading with	the pthreads library.  This
	   option sets flags for both the preprocessor and linker.

       S/390 and zSeries Options

       These are the -m	options	defined	for the	S/390 and zSeries architec-
       ture.

       -mhard-float
       -msoft-float
	   Use (do not use) the	hardware floating-point	instructions and reg-
	   isters for floating-point operations.  When -msoft-float is speci-
	   fied, functions in libgcc.a will be used to perform floating-point
	   operations.	When -mhard-float is specified,	the compiler generates
	   IEEE	floating-point instructions.  This is the default.

       -mlong-double-64
       -mlong-double-128
	   These switches control the size of "long double" type. A size of
	   64bit makes the "long double" type equivalent to the	"double" type.
	   This	is the default.

       -mbackchain
       -mno-backchain
	   Store (do not store)	the address of the caller's frame as backchain
	   pointer into	the callee's stack frame.  A backchain may be needed
	   to allow debugging using tools that do not understand DWARF-2 call
	   frame information.  When -mno-packed-stack is in effect, the
	   backchain pointer is	stored at the bottom of	the stack frame; when
	   -mpacked-stack is in	effect,	the backchain is placed	into the top-
	   most	word of	the 96/160 byte	register save area.

	   In general, code compiled with -mbackchain is call-compatible with
	   code	compiled with -mmo-backchain; however, use of the backchain
	   for debugging purposes usually requires that	the whole binary is
	   built with -mbackchain.  Note that the combination of -mbackchain,
	   -mpacked-stack and -mhard-float is not supported.  In order to
	   build a linux kernel	use -msoft-float.

	   The default is to not maintain the backchain.

       -mpacked-stack
       -mno-packed-stack
	   Use (do not use) the	packed stack layout.  When -mno-packed-stack
	   is specified, the compiler uses the all fields of the 96/160	byte
	   register save area only for their default purpose; unused fields
	   still take up stack space.  When -mpacked-stack is specified, reg-
	   ister save slots are	densely	packed at the top of the register save
	   area; unused	space is reused	for other purposes, allowing for more
	   efficient use of the	available stack	space.	However, when
	   -mbackchain is also in effect, the topmost word of the save area is
	   always used to store	the backchain, and the return address register
	   is always saved two words below the backchain.

	   As long as the stack	frame backchain	is not used, code generated
	   with	-mpacked-stack is call-compatible with code generated with
	   -mno-packed-stack.  Note that some non-FSF releases of GCC 2.95 for
	   S/390 or zSeries generated code that	uses the stack frame backchain
	   at run time,	not just for debugging purposes.  Such code is not
	   call-compatible with	code compiled with -mpacked-stack.  Also, note
	   that	the combination	of -mbackchain,	-mpacked-stack and
	   -mhard-float	is not supported.  In order to build a linux kernel
	   use -msoft-float.

	   The default is to not use the packed	stack layout.

       -msmall-exec
       -mno-small-exec
	   Generate (or	do not generate) code using the	"bras" instruction to
	   do subroutine calls.	 This only works reliably if the total exe-
	   cutable size	does not exceed	64k.  The default is to	use the	"basr"
	   instruction instead,	which does not have this limitation.

       -m64
       -m31
	   When	-m31 is	specified, generate code compliant to the GNU/Linux
	   for S/390 ABI.  When	-m64 is	specified, generate code compliant to
	   the GNU/Linux for zSeries ABI.  This	allows GCC in particular to
	   generate 64-bit instructions.  For the s390 targets,	the default is
	   -m31, while the s390x targets default to -m64.

       -mzarch
       -mesa
	   When	-mzarch	is specified, generate code using the instructions
	   available on	z/Architecture.	 When -mesa is specified, generate
	   code	using the instructions available on ESA/390.  Note that	-mesa
	   is not possible with	-m64.  When generating code compliant to the
	   GNU/Linux for S/390 ABI, the	default	is -mesa.  When	generating
	   code	compliant to the GNU/Linux for zSeries ABI, the	default	is
	   -mzarch.

       -mmvcle
       -mno-mvcle
	   Generate (or	do not generate) code using the	"mvcle"	instruction to
	   perform block moves.	 When -mno-mvcle is specified, use a "mvc"
	   loop	instead.  This is the default unless optimizing	for size.

       -mdebug
       -mno-debug
	   Print (or do	not print) additional debug information	when compil-
	   ing.	 The default is	to not print debug information.

       -march=cpu-type
	   Generate code that will run on cpu-type, which is the name of a
	   system representing a certain processor type.  Possible values for
	   cpu-type are	g5, g6,	z900, and z990.	 When generating code using
	   the instructions available on z/Architecture, the default is
	   -march=z900.	 Otherwise, the	default	is -march=g5.

       -mtune=cpu-type
	   Tune	to cpu-type everything applicable about	the generated code,
	   except for the ABI and the set of available instructions.  The list
	   of cpu-type values is the same as for -march.  The default is the
	   value used for -march.

       -mtpf-trace
       -mno-tpf-trace
	   Generate code that adds (does not add) in TPF OS specific branches
	   to trace routines in	the operating system.  This option is off by
	   default, even when compiling	for the	TPF OS.

       -mfused-madd
       -mno-fused-madd
	   Generate code that uses (does not use) the floating point multiply
	   and accumulate instructions.	 These instructions are	generated by
	   default if hardware floating	point is used.

       -mwarn-framesize=framesize
	   Emit	a warning if the current function exceeds the given frame
	   size.  Because this is a compile time check it doesn't need to be a
	   real	problem	when the program runs.	It is intended to identify
	   functions which most	probably cause a stack overflow.  It is	useful
	   to be used in an environment	with limited stack size	e.g. the linux
	   kernel.

       -mwarn-dynamicstack
	   Emit	a warning if the function calls	alloca or uses dynamically
	   sized arrays.  This is generally a bad idea with a limited stack
	   size.

       -mstack-guard=stack-guard
       -mstack-size=stack-size
	   These arguments always have to be used in conjunction.  If they are
	   present the s390 back end emits additional instructions in the
	   function prologue which trigger a trap if the stack size is stack-
	   guard bytes above the stack-size (remember that the stack on	s390
	   grows downward).  These options are intended	to be used to help
	   debugging stack overflow problems.  The additionally	emitted	code
	   causes only little overhead and hence can also be used in produc-
	   tion	like systems without greater performance degradation.  The
	   given values	have to	be exact powers	of 2 and stack-size has	to be
	   greater than	stack-guard without exceeding 64k.  In order to	be
	   efficient the extra code makes the assumption that the stack	starts
	   at an address aligned to the	value given by stack-size.

       Score Options

       These options are defined for Score implementations:

       -meb
	   Compile code	for big	endian mode.  This is the default.

       -mel
	   Compile code	for little endian mode.

       -mnhwloop
	   Disable generate bcnz instruction.

       -muls
	   Enable generate unaligned load and store instruction.

       -mmac
	   Enable the use of multiply-accumulate instructions. Disabled	by
	   default.

       -mscore5
	   Specify the SCORE5 as the target architecture.

       -mscore5u
	   Specify the SCORE5U of the target architecture.

       -mscore7
	   Specify the SCORE7 as the target architecture. This is the default.

       -mscore7d
	   Specify the SCORE7D as the target architecture.

       SH Options

       These -m	options	are defined for	the SH implementations:

       -m1 Generate code for the SH1.

       -m2 Generate code for the SH2.

       -m2e
	   Generate code for the SH2e.

       -m3 Generate code for the SH3.

       -m3e
	   Generate code for the SH3e.

       -m4-nofpu
	   Generate code for the SH4 without a floating-point unit.

       -m4-single-only
	   Generate code for the SH4 with a floating-point unit	that only sup-
	   ports single-precision arithmetic.

       -m4-single
	   Generate code for the SH4 assuming the floating-point unit is in
	   single-precision mode by default.

       -m4 Generate code for the SH4.

       -m4a-nofpu
	   Generate code for the SH4al-dsp, or for a SH4a in such a way	that
	   the floating-point unit is not used.

       -m4a-single-only
	   Generate code for the SH4a, in such a way that no double-precision
	   floating point operations are used.

       -m4a-single
	   Generate code for the SH4a assuming the floating-point unit is in
	   single-precision mode by default.

       -m4a
	   Generate code for the SH4a.

       -m4al
	   Same	as -m4a-nofpu, except that it implicitly passes	-dsp to	the
	   assembler.  GCC doesn't generate any	DSP instructions at the
	   moment.

       -mb Compile code	for the	processor in big endian	mode.

       -ml Compile code	for the	processor in little endian mode.

       -mdalign
	   Align doubles at 64-bit boundaries.	Note that this changes the
	   calling conventions,	and thus some functions	from the standard C
	   library will	not work unless	you recompile it first with -mdalign.

       -mrelax
	   Shorten some	address	references at link time, when possible;	uses
	   the linker option -relax.

       -mbigtable
	   Use 32-bit offsets in "switch" tables.  The default is to use
	   16-bit offsets.

       -mfmovd
	   Enable the use of the instruction "fmovd".

       -mhitachi
	   Comply with the calling conventions defined by Renesas.

       -mrenesas
	   Comply with the calling conventions defined by Renesas.

       -mno-renesas
	   Comply with the calling conventions defined for GCC before the
	   Renesas conventions were available.	This option is the default for
	   all targets of the SH toolchain except for sh-symbianelf.

       -mnomacsave
	   Mark	the "MAC" register as call-clobbered, even if -mhitachi	is
	   given.

       -mieee
	   Increase IEEE-compliance of floating-point code.  At	the moment,
	   this	is equivalent to -fno-finite-math-only.	 When generating 16
	   bit SH opcodes, getting IEEE-conforming results for comparisons of
	   NANs	/ infinities incurs extra overhead in every floating point
	   comparison, therefore the default is	set to -ffinite-math-only.

       -misize
	   Dump	instruction size and location in the assembly code.

       -mpadstruct
	   This	option is deprecated.  It pads structures to multiple of 4
	   bytes, which	is incompatible	with the SH ABI.

       -mspace
	   Optimize for	space instead of speed.	 Implied by -Os.

       -mprefergot
	   When	generating position-independent	code, emit function calls
	   using the Global Offset Table instead of the	Procedure Linkage Ta-
	   ble.

       -musermode
	   Generate a library function call to invalidate instruction cache
	   entries, after fixing up a trampoline.  This	library	function call
	   doesn't assume it can write to the whole memory address space.
	   This	is the default when the	target is "sh-*-linux*".

       -multcost=number
	   Set the cost	to assume for a	multiply insn.

       -mdiv=strategy
	   Set the division strategy to	use for	SHmedia	code.  strategy	must
	   be one of: call, call2, fp, inv, inv:minlat,	inv20u,	inv20l,
	   inv:call, inv:call2,	inv:fp .  "fp" performs	the operation in
	   floating point.  This has a very high latency, but needs only a few
	   instructions, so it might be	a good choice if your code has enough
	   easily exploitable ILP to allow the compiler	to schedule the	float-
	   ing point instructions together with	other instructions.  Division
	   by zero causes a floating point exception.  "inv" uses integer
	   operations to calculate the inverse of the divisor, and then	multi-
	   plies the dividend with the inverse.	 This strategy allows cse and
	   hoisting of the inverse calculation.	 Division by zero calculates
	   an unspecified result, but does not trap.  "inv:minlat" is a	vari-
	   ant of "inv"	where if no cse	/ hoisting opportunities have been
	   found, or if	the entire operation has been hoisted to the same
	   place, the last stages of the inverse calculation are intertwined
	   with	the final multiply to reduce the overall latency, at the
	   expense of using a few more instructions, and thus offering fewer
	   scheduling opportunities with other code.  "call" calls a library
	   function that usually implements the	inv:minlat strategy.  This
	   gives high code density for m5-*media-nofpu compilations.  "call2"
	   uses	a different entry point	of the same library function, where it
	   assumes that	a pointer to a lookup table has	already	been set up,
	   which exposes the pointer load to cse / code	hoisting optimiza-
	   tions.  "inv:call", "inv:call2" and "inv:fp"	all use	the "inv"
	   algorithm for initial code generation, but if the code stays	unop-
	   timized, revert to the "call", "call2", or "fp" strategies, respec-
	   tively.  Note that the potentially-trapping side effect of division
	   by zero is carried by a separate instruction, so it is possible
	   that	all the	integer	instructions are hoisted out, but the marker
	   for the side	effect stays where it is.  A recombination to fp oper-
	   ations or a call is not possible in that case.  "inv20u" and
	   "inv20l" are	variants of the	"inv:minlat" strategy.	In the case
	   that	the inverse calculation	was nor	separated from the multiply,
	   they	speed up division where	the dividend fits into 20 bits (plus
	   sign	where applicable), by inserting	a test to skip a number	of
	   operations in this case; this test slows down the case of larger
	   dividends.  inv20u assumes the case of a such a small dividend to
	   be unlikely,	and inv20l assumes it to be likely.

       -mdivsi3_libfunc=name
	   Set the name	of the library function	used for 32 bit	signed divi-
	   sion	to name.  This only affect the name used in the	call and
	   inv:call division strategies, and the compiler will still expect
	   the same sets of input/output/clobbered registers as	if this	option
	   was not present.

       -madjust-unroll
	   Throttle unrolling to avoid thrashing target	registers.  This
	   option only has an effect if	the gcc	code base supports the TAR-
	   GET_ADJUST_UNROLL_MAX target	hook.

       -mindexed-addressing
	   Enable the use of the indexed addressing mode for SHmedia32/SHcom-
	   pact.  This is only safe if the hardware and/or OS implement	32 bit
	   wrap-around semantics for the indexed addressing mode.  The archi-
	   tecture allows the implementation of	processors with	64 bit MMU,
	   which the OS	could use to get 32 bit	addressing, but	since no cur-
	   rent	hardware implementation	supports this or any other way to make
	   the indexed addressing mode safe to use in the 32 bit ABI, the
	   default is -mno-indexed-addressing.

       -mgettrcost=number
	   Set the cost	assumed	for the	gettr instruction to number.  The
	   default is 2	if -mpt-fixed is in effect, 100	otherwise.

       -mpt-fixed
	   Assume pt* instructions won't trap.	This will generally generate
	   better scheduled code, but is unsafe	on current hardware.  The cur-
	   rent	architecture definition	says that ptabs	and ptrel trap when
	   the target anded with 3 is 3.  This has the unintentional effect of
	   making it unsafe to schedule	ptabs /	ptrel before a branch, or
	   hoist it out	of a loop.  For	example, __do_global_ctors, a part of
	   libgcc that runs constructors at program startup, calls functions
	   in a	list which is delimited	by -1.	With the -mpt-fixed option,
	   the ptabs will be done before testing against -1.  That means that
	   all the constructors	will be	run a bit quicker, but when the	loop
	   comes to the	end of the list, the program crashes because ptabs
	   loads -1 into a target register.  Since this	option is unsafe for
	   any hardware	implementing the current architecture specification,
	   the default is -mno-pt-fixed.  Unless the user specifies a specific
	   cost	with -mgettrcost, -mno-pt-fixed	also implies -mgettrcost=100;
	   this	deters register	allocation using target	registers for storing
	   ordinary integers.

       -minvalid-symbols
	   Assume symbols might	be invalid.  Ordinary function symbols gener-
	   ated	by the compiler	will always be valid to	load with
	   movi/shori/ptabs or movi/shori/ptrel, but with assembler and/or
	   linker tricks it is possible	to generate symbols that will cause
	   ptabs / ptrel to trap.  This	option is only meaningful when
	   -mno-pt-fixed is in effect.	It will	then prevent cross-basic-block
	   cse,	hoisting and most scheduling of	symbol loads.  The default is
	   -mno-invalid-symbols.

       SPARC Options

       These -m	options	are supported on the SPARC:

       -mno-app-regs
       -mapp-regs
	   Specify -mapp-regs to generate output using the global registers 2
	   through 4, which the	SPARC SVR4 ABI reserves	for applications.
	   This	is the default.

	   To be fully SVR4 ABI	compliant at the cost of some performance
	   loss, specify -mno-app-regs.	 You should compile libraries and sys-
	   tem software	with this option.

       -mfpu
       -mhard-float
	   Generate output containing floating point instructions.  This is
	   the default.

       -mno-fpu
       -msoft-float
	   Generate output containing library calls for	floating point.	 Warn-
	   ing:	the requisite libraries	are not	available for all SPARC	tar-
	   gets.  Normally the facilities of the machine's usual C compiler
	   are used, but this cannot be	done directly in cross-compilation.
	   You must make your own arrangements to provide suitable library
	   functions for cross-compilation.  The embedded targets sparc-*-aout
	   and sparclite-*-* do	provide	software floating point	support.

	   -msoft-float	changes	the calling convention in the output file;
	   therefore, it is only useful	if you compile all of a	program	with
	   this	option.	 In particular,	you need to compile libgcc.a, the
	   library that	comes with GCC,	with -msoft-float in order for this to
	   work.

       -mhard-quad-float
	   Generate output containing quad-word	(long double) floating point
	   instructions.

       -msoft-quad-float
	   Generate output containing library calls for	quad-word (long	dou-
	   ble)	floating point instructions.  The functions called are those
	   specified in	the SPARC ABI.	This is	the default.

	   As of this writing, there are no SPARC implementations that have
	   hardware support for	the quad-word floating point instructions.
	   They	all invoke a trap handler for one of these instructions, and
	   then	the trap handler emulates the effect of	the instruction.
	   Because of the trap handler overhead, this is much slower than
	   calling the ABI library routines.  Thus the -msoft-quad-float
	   option is the default.

       -mno-unaligned-doubles
       -munaligned-doubles
	   Assume that doubles have 8 byte alignment.  This is the default.

	   With	-munaligned-doubles, GCC assumes that doubles have 8 byte
	   alignment only if they are contained	in another type, or if they
	   have	an absolute address.  Otherwise, it assumes they have 4	byte
	   alignment.  Specifying this option avoids some rare compatibility
	   problems with code generated	by other compilers.  It	is not the
	   default because it results in a performance loss, especially	for
	   floating point code.

       -mno-faster-structs
       -mfaster-structs
	   With	-mfaster-structs, the compiler assumes that structures should
	   have	8 byte alignment.  This	enables	the use	of pairs of "ldd" and
	   "std" instructions for copies in structure assignment, in place of
	   twice as many "ld" and "st" pairs.  However,	the use	of this
	   changed alignment directly violates the SPARC ABI.  Thus, it's
	   intended only for use on targets where the developer	acknowledges
	   that	their resulting	code will not be directly in line with the
	   rules of the	ABI.

       -mimpure-text
	   -mimpure-text, used in addition to -shared, tells the compiler to
	   not pass -z text to the linker when linking a shared	object.	 Using
	   this	option,	you can	link position-dependent	code into a shared
	   object.

	   -mimpure-text suppresses the	"relocations remain against allocat-
	   able	but non-writable sections" linker error	message.  However, the
	   necessary relocations will trigger copy-on-write, and the shared
	   object is not actually shared across	processes.  Instead of using
	   -mimpure-text, you should compile all source	code with -fpic	or
	   -fPIC.

	   This	option is only available on SunOS and Solaris.

       -mcpu=cpu_type
	   Set the instruction set, register set, and instruction scheduling
	   parameters for machine type cpu_type.  Supported values for
	   cpu_type are	v7, cypress, v8, supersparc, sparclite,	f930, f934,
	   hypersparc, sparclite86x, sparclet, tsc701, v9, ultrasparc, ultra-
	   sparc3, and niagara.

	   Default instruction scheduling parameters are used for values that
	   select an architecture and not an implementation.  These are	v7,
	   v8, sparclite, sparclet, v9.

	   Here	is a list of each supported architecture and their supported
	   implementations.

		       v7:	       cypress
		       v8:	       supersparc, hypersparc
		       sparclite:      f930, f934, sparclite86x
		       sparclet:       tsc701
		       v9:	       ultrasparc, ultrasparc3,	niagara

	   By default (unless configured otherwise), GCC generates code	for
	   the V7 variant of the SPARC architecture.  With -mcpu=cypress, the
	   compiler additionally optimizes it for the Cypress CY7C602 chip, as
	   used	in the SPARCStation/SPARCServer	3xx series.  This is also
	   appropriate for the older SPARCStation 1, 2,	IPX etc.

	   With	-mcpu=v8, GCC generates	code for the V8	variant	of the SPARC
	   architecture.  The only difference from V7 code is that the com-
	   piler emits the integer multiply and	integer	divide instructions
	   which exist in SPARC-V8 but not in SPARC-V7.	 With -mcpu=super-
	   sparc, the compiler additionally optimizes it for the SuperSPARC
	   chip, as used in the	SPARCStation 10, 1000 and 2000 series.

	   With	-mcpu=sparclite, GCC generates code for	the SPARClite variant
	   of the SPARC	architecture.  This adds the integer multiply, integer
	   divide step and scan	("ffs")	instructions which exist in SPARClite
	   but not in SPARC-V7.	 With -mcpu=f930, the compiler additionally
	   optimizes it	for the	Fujitsu	MB86930	chip, which is the original
	   SPARClite, with no FPU.  With -mcpu=f934, the compiler additionally
	   optimizes it	for the	Fujitsu	MB86934	chip, which is the more	recent
	   SPARClite with FPU.

	   With	-mcpu=sparclet,	GCC generates code for the SPARClet variant of
	   the SPARC architecture.  This adds the integer multiply, multi-
	   ply/accumulate, integer divide step and scan	("ffs")	instructions
	   which exist in SPARClet but not in SPARC-V7.	 With -mcpu=tsc701,
	   the compiler	additionally optimizes it for the TEMIC	SPARClet chip.

	   With	-mcpu=v9, GCC generates	code for the V9	variant	of the SPARC
	   architecture.  This adds 64-bit integer and floating-point move
	   instructions, 3 additional floating-point condition code registers
	   and conditional move	instructions.  With -mcpu=ultrasparc, the com-
	   piler additionally optimizes	it for the Sun UltraSPARC I/II/IIi
	   chips.  With	-mcpu=ultrasparc3, the compiler	additionally optimizes
	   it for the Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+	chips.	With
	   -mcpu=niagara, the compiler additionally optimizes it for Sun
	   UltraSPARC T1 chips.

       -mtune=cpu_type
	   Set the instruction scheduling parameters for machine type
	   cpu_type, but do not	set the	instruction set	or register set	that
	   the option -mcpu=cpu_type would.

	   The same values for -mcpu=cpu_type can be used for -mtune=cpu_type,
	   but the only	useful values are those	that select a particular cpu
	   implementation.  Those are cypress, supersparc, hypersparc, f930,
	   f934, sparclite86x, tsc701, ultrasparc, ultrasparc3,	and niagara.

       -mv8plus
       -mno-v8plus
	   With	-mv8plus, GCC generates	code for the SPARC-V8+ ABI.  The dif-
	   ference from	the V8 ABI is that the global and out registers	are
	   considered 64-bit wide.  This is enabled by default on Solaris in
	   32-bit mode for all SPARC-V9	processors.

       -mvis
       -mno-vis
	   With	-mvis, GCC generates code that takes advantage of the Ultra-
	   SPARC Visual	Instruction Set	extensions.  The default is -mno-vis.

       These -m	options	are supported in addition to the above on SPARC-V9
       processors in 64-bit environments:

       -mlittle-endian
	   Generate code for a processor running in little-endian mode.	 It is
	   only	available for a	few configurations and most notably not	on
	   Solaris and Linux.

       -m32
       -m64
	   Generate code for a 32-bit or 64-bit	environment.  The 32-bit envi-
	   ronment sets	int, long and pointer to 32 bits.  The 64-bit environ-
	   ment	sets int to 32 bits and	long and pointer to 64 bits.

       -mcmodel=medlow
	   Generate code for the Medium/Low code model:	64-bit addresses, pro-
	   grams must be linked	in the low 32 bits of memory.  Programs	can be
	   statically or dynamically linked.

       -mcmodel=medmid
	   Generate code for the Medium/Middle code model: 64-bit addresses,
	   programs must be linked in the low 44 bits of memory, the text and
	   data	segments must be less than 2GB in size and the data segment
	   must	be located within 2GB of the text segment.

       -mcmodel=medany
	   Generate code for the Medium/Anywhere code model: 64-bit addresses,
	   programs may	be linked anywhere in memory, the text and data	seg-
	   ments must be less than 2GB in size and the data segment must be
	   located within 2GB of the text segment.

       -mcmodel=embmedany
	   Generate code for the Medium/Anywhere code model for	embedded sys-
	   tems: 64-bit	addresses, the text and	data segments must be less
	   than	2GB in size, both starting anywhere in memory (determined at
	   link	time).	The global register %g4	points to the base of the data
	   segment.  Programs are statically linked and	PIC is not supported.

       -mstack-bias
       -mno-stack-bias
	   With	-mstack-bias, GCC assumes that the stack pointer, and frame
	   pointer if present, are offset by -2047 which must be added back
	   when	making stack frame references.	This is	the default in 64-bit
	   mode.  Otherwise, assume no such offset is present.

       These switches are supported in addition	to the above on	Solaris:

       -threads
	   Add support for multithreading using	the Solaris threads library.
	   This	option sets flags for both the preprocessor and	linker.	 This
	   option does not affect the thread safety of object code produced by
	   the compiler	or that	of libraries supplied with it.

       -pthreads
	   Add support for multithreading using	the POSIX threads library.
	   This	option sets flags for both the preprocessor and	linker.	 This
	   option does not affect the thread safety of object code produced
	   by the compiler or that of libraries	supplied with it.

       -pthread
	   This	is a synonym for -pthreads.

       Options for System V

       These additional	options	are available on System	V Release 4 for	com-
       patibility with other compilers on those	systems:

       -G  Create a shared object.  It is recommended that -symbolic or
	   -shared be used instead.

       -Qy Identify the	versions of each tool used by the compiler, in a
	   ".ident" assembler directive	in the output.

       -Qn Refrain from	adding ".ident"	directives to the output file (this is
	   the default).

       -YP,dirs
	   Search the directories dirs,	and no others, for libraries specified
	   with	-l.

       -Ym,dir
	   Look	in the directory dir to	find the M4 preprocessor.  The assem-
	   bler	uses this option.

       TMS320C3x/C4x Options

       These -m	options	are defined for	TMS320C3x/C4x implementations:

       -mcpu=cpu_type
	   Set the instruction set, register set, and instruction scheduling
	   parameters for machine type cpu_type.  Supported values for
	   cpu_type are	c30, c31, c32, c40, and	c44.  The default is c40 to
	   generate code for the TMS320C40.

       -mbig-memory
       -mbig
       -msmall-memory
       -msmall
	   Generates code for the big or small memory model.  The small	memory
	   model assumed that all data fits into one 64K word page.  At	run-
	   time	the data page (DP) register must be set	to point to the	64K
	   page	containing the .bss and	.data program sections.	 The big mem-
	   ory model is	the default and	requires reloading of the DP register
	   for every direct memory access.

       -mbk
       -mno-bk
	   Allow (disallow) allocation of general integer operands into	the
	   block count register	BK.

       -mdb
       -mno-db
	   Enable (disable) generation of code using decrement and branch,
	   DBcond(D), instructions.  This is enabled by	default	for the	C4x.
	   To be on the	safe side, this	is disabled for	the C3x, since the
	   maximum iteration count on the C3x is 2^{23 + 1} (but who iterates
	   loops more than 2^{23} times	on the C3x?).  Note that GCC will try
	   to reverse a	loop so	that it	can utilize the	decrement and branch
	   instruction,	but will give up if there is more than one memory ref-
	   erence in the loop.	Thus a loop where the loop counter is decre-
	   mented can generate slightly	more efficient code, in	cases where
	   the RPTB instruction	cannot be utilized.

       -mdp-isr-reload
       -mparanoid
	   Force the DP	register to be saved on	entry to an interrupt service
	   routine (ISR), reloaded to point to the data	section, and restored
	   on exit from	the ISR.  This should not be required unless someone
	   has violated	the small memory model by modifying the	DP register,
	   say within an object	library.

       -mmpyi
       -mno-mpyi
	   For the C3x use the 24-bit MPYI instruction for integer multiplies
	   instead of a	library	call to	guarantee 32-bit results.  Note	that
	   if one of the operands is a constant, then the multiplication will
	   be performed	using shifts and adds.	If the -mmpyi option is	not
	   specified for the C3x, then squaring	operations are performed
	   inline instead of a library call.

       -mfast-fix
       -mno-fast-fix
	   The C3x/C4x FIX instruction to convert a floating point value to an
	   integer value chooses the nearest integer less than or equal	to the
	   floating point value	rather than to the nearest integer.  Thus if
	   the floating	point number is	negative, the result will be incor-
	   rectly truncated an additional code is necessary to detect and cor-
	   rect	this case.  This option	can be used to disable generation of
	   the additional code required	to correct the result.

       -mrptb
       -mno-rptb
	   Enable (disable) generation of repeat block sequences using the
	   RPTB	instruction for	zero overhead looping.	The RPTB construct is
	   only	used for innermost loops that do not call functions or jump
	   across the loop boundaries.	There is no advantage having nested
	   RPTB	loops due to the overhead required to save and restore the RC,
	   RS, and RE registers.  This is enabled by default with -O2.

       -mrpts=count
       -mno-rpts
	   Enable (disable) the	use of the single instruction repeat instruc-
	   tion	RPTS.  If a repeat block contains a single instruction,	and
	   the loop count can be guaranteed to be less than the	value count,
	   GCC will emit a RPTS	instruction instead of a RPTB.	If no value is
	   specified, then a RPTS will be emitted even if the loop count can-
	   not be determined at	compile	time.  Note that the repeated instruc-
	   tion	following RPTS does not	have to	be reloaded from memory	each
	   iteration, thus freeing up the CPU buses for	operands.  However,
	   since interrupts are	blocked	by this	instruction, it	is disabled by
	   default.

       -mloop-unsigned
       -mno-loop-unsigned
	   The maximum iteration count when using RPTS and RPTB	(and DB	on the
	   C40)	is 2^{31 + 1} since these instructions test if the iteration
	   count is negative to	terminate the loop.  If	the iteration count is
	   unsigned there is a possibility than	the 2^{31 + 1} maximum itera-
	   tion	count may be exceeded.	This switch allows an unsigned itera-
	   tion	count.

       -mti
	   Try to emit an assembler syntax that	the TI assembler (asm30) is
	   happy with.	This also enforces compatibility with the API employed
	   by the TI C3x C compiler.  For example, long	doubles	are passed as
	   structures rather than in floating point registers.

       -mregparm
       -mmemparm
	   Generate code that uses registers (stack) for passing arguments to
	   functions.  By default, arguments are passed	in registers where
	   possible rather than	by pushing arguments on	to the stack.

       -mparallel-insns
       -mno-parallel-insns
	   Allow the generation	of parallel instructions.  This	is enabled by
	   default with	-O2.

       -mparallel-mpy
       -mno-parallel-mpy
	   Allow the generation	of MPY||ADD and	MPY||SUB parallel instruc-
	   tions, provided -mparallel-insns is also specified.	These instruc-
	   tions have tight register constraints which can pessimize the code
	   generation of large functions.

       V850 Options

       These -m	options	are defined for	V850 implementations:

       -mlong-calls
       -mno-long-calls
	   Treat all calls as being far	away (near).  If calls are assumed to
	   be far away,	the compiler will always load the functions address up
	   into	a register, and	call indirect through the pointer.

       -mno-ep
       -mep
	   Do not optimize (do optimize) basic blocks that use the same	index
	   pointer 4 or	more times to copy pointer into	the "ep" register, and
	   use the shorter "sld" and "sst" instructions.  The -mep option is
	   on by default if you	optimize.

       -mno-prolog-function
       -mprolog-function
	   Do not use (do use) external	functions to save and restore regis-
	   ters	at the prologue	and epilogue of	a function.  The external
	   functions are slower, but use less code space if more than one
	   function saves the same number of registers.	 The -mprolog-function
	   option is on	by default if you optimize.

       -mspace
	   Try to make the code	as small as possible.  At present, this	just
	   turns on the	-mep and -mprolog-function options.

       -mtda=n
	   Put static or global	variables whose	size is	n bytes	or less	into
	   the tiny data area that register "ep" points	to.  The tiny data
	   area	can hold up to 256 bytes in total (128 bytes for byte refer-
	   ences).

       -msda=n
	   Put static or global	variables whose	size is	n bytes	or less	into
	   the small data area that register "gp" points to.  The small	data
	   area	can hold up to 64 kilobytes.

       -mzda=n
	   Put static or global	variables whose	size is	n bytes	or less	into
	   the first 32	kilobytes of memory.

       -mv850
	   Specify that	the target processor is	the V850.

       -mbig-switch
	   Generate code suitable for big switch tables.  Use this option only
	   if the assembler/linker complain about out of range branches	within
	   a switch table.

       -mapp-regs
	   This	option will cause r2 and r5 to be used in the code generated
	   by the compiler.  This setting is the default.

       -mno-app-regs
	   This	option will cause r2 and r5 to be treated as fixed registers.

       -mv850e1
	   Specify that	the target processor is	the V850E1.  The preprocessor
	   constants __v850e1__	and __v850e__ will be defined if this option
	   is used.

       -mv850e
	   Specify that	the target processor is	the V850E.  The	preprocessor
	   constant __v850e__ will be defined if this option is	used.

	   If neither -mv850 nor -mv850e nor -mv850e1 are defined then a
	   default target processor will be chosen and the relevant __v850*__
	   preprocessor	constant will be defined.

	   The preprocessor constants __v850 and __v851__ are always defined,
	   regardless of which processor variant is the	target.

       -mdisable-callt
	   This	option will suppress generation	of the CALLT instruction for
	   the v850e and v850e1	flavors	of the v850 architecture.  The default
	   is -mno-disable-callt which allows the CALLT	instruction to be
	   used.

       VAX Options

       These -m	options	are defined for	the VAX:

       -munix
	   Do not output certain jump instructions ("aobleq" and so on)	that
	   the Unix assembler for the VAX cannot handle	across long ranges.

       -mgnu
	   Do output those jump	instructions, on the assumption	that you will
	   assemble with the GNU assembler.

       -mg Output code for g-format floating point numbers instead of d-for-
	   mat.

       x86-64 Options

       These are listed	under

       Xstormy16 Options

       These options are defined for Xstormy16:

       -msim
	   Choose startup files	and linker script suitable for the simulator.

       Xtensa Options

       These options are supported for Xtensa targets:

       -mconst16
       -mno-const16
	   Enable or disable use of "CONST16" instructions for loading con-
	   stant values.  The "CONST16"	instruction is currently not a stan-
	   dard	option from Tensilica.	When enabled, "CONST16"	instructions
	   are always used in place of the standard "L32R" instructions.  The
	   use of "CONST16" is enabled by default only if the "L32R" instruc-
	   tion	is not available.

       -mfused-madd
       -mno-fused-madd
	   Enable or disable use of fused multiply/add and multiply/subtract
	   instructions	in the floating-point option.  This has	no effect if
	   the floating-point option is	not also enabled.  Disabling fused
	   multiply/add	and multiply/subtract instructions forces the compiler
	   to use separate instructions	for the	multiply and add/subtract
	   operations.	This may be desirable in some cases where strict IEEE
	   754-compliant results are required: the fused multiply add/subtract
	   instructions	do not round the intermediate result, thereby produc-
	   ing results with more bits of precision than	specified by the IEEE
	   standard.  Disabling	fused multiply add/subtract instructions also
	   ensures that	the program output is not sensitive to the compiler's
	   ability to combine multiply and add/subtract	operations.

       -mtext-section-literals
       -mno-text-section-literals
	   Control the treatment of literal pools.  The	default	is
	   -mno-text-section-literals, which places literals in	a separate
	   section in the output file.	This allows the	literal	pool to	be
	   placed in a data RAM/ROM, and it also allows	the linker to combine
	   literal pools from separate object files to remove redundant	liter-
	   als and improve code	size.  With -mtext-section-literals, the lit-
	   erals are interspersed in the text section in order to keep them as
	   close as possible to	their references.  This	may be necessary for
	   large assembly files.

       -mtarget-align
       -mno-target-align
	   When	this option is enabled,	GCC instructs the assembler to auto-
	   matically align instructions	to reduce branch penalties at the
	   expense of some code	density.  The assembler	attempts to widen den-
	   sity	instructions to	align branch targets and the instructions fol-
	   lowing call instructions.  If there are not enough preceding	safe
	   density instructions	to align a target, no widening will be per-
	   formed.  The	default	is -mtarget-align.  These options do not
	   affect the treatment	of auto-aligned	instructions like "LOOP",
	   which the assembler will always align, either by widening density
	   instructions	or by inserting	no-op instructions.

       -mlongcalls
       -mno-longcalls
	   When	this option is enabled,	GCC instructs the assembler to trans-
	   late	direct calls to	indirect calls unless it can determine that
	   the target of a direct call is in the range allowed by the call
	   instruction.	 This translation typically occurs for calls to	func-
	   tions in other source files.	 Specifically, the assembler trans-
	   lates a direct "CALL" instruction into an "L32R" followed by	a
	   "CALLX" instruction.	 The default is	-mno-longcalls.	 This option
	   should be used in programs where the	call target can	potentially be
	   out of range.  This option is implemented in	the assembler, not the
	   compiler, so	the assembly code generated by GCC will	still show
	   direct call instructions---look at the disassembled object code to
	   see the actual instructions.	 Note that the assembler will use an
	   indirect call for every cross-file call, not	just those that	really
	   will	be out of range.

       zSeries Options

       These are listed	under

       Options for Code	Generation Conventions

       These machine-independent options control the interface conventions
       used in code generation.

       Most of them have both positive and negative forms; the negative	form
       of -ffoo	would be -fno-foo.  In the table below,	only one of the	forms
       is listed---the one which is not	the default.  You can figure out the
       other form by either removing no- or adding it.

       -fbounds-check
	   For front-ends that support it, generate additional code to check
	   that	indices	used to	access arrays are within the declared range.
	   This	is currently only supported by the Java	and Fortran
	   front-ends, where this option defaults to true and false respec-
	   tively.

       -ftrapv
	   This	option generates traps for signed overflow on addition,	sub-
	   traction, multiplication operations.

       -fwrapv
	   This	option instructs the compiler to assume	that signed arithmetic
	   overflow of addition, subtraction and multiplication	wraps around
	   using twos-complement representation.  This flag enables some opti-
	   mizations and disables others.  This	option is enabled by default
	   for the Java	front-end, as required by the Java language specifica-
	   tion.

       -fexceptions
	   Enable exception handling.  Generates extra code needed to propa-
	   gate	exceptions.  For some targets, this implies GCC	will generate
	   frame unwind	information for	all functions, which can produce sig-
	   nificant data size overhead,	although it does not affect execution.
	   If you do not specify this option, GCC will enable it by default
	   for languages like C++ which	normally require exception handling,
	   and disable it for languages	like C that do not normally require
	   it.	However, you may need to enable	this option when compiling C
	   code	that needs to interoperate properly with exception handlers
	   written in C++.  You	may also wish to disable this option if	you
	   are compiling older C++ programs that don't use exception handling.

       -fnon-call-exceptions
	   Generate code that allows trapping instructions to throw excep-
	   tions.  Note	that this requires platform-specific runtime support
	   that	does not exist everywhere.  Moreover, it only allows trapping
	   instructions	to throw exceptions, i.e. memory references or float-
	   ing point instructions.  It does not	allow exceptions to be thrown
	   from	arbitrary signal handlers such as "SIGALRM".

       -funwind-tables
	   Similar to -fexceptions, except that	it will	just generate any
	   needed static data, but will	not affect the generated code in any
	   other way.  You will	normally not enable this option; instead, a
	   language processor that needs this handling would enable it on your
	   behalf.

       -fasynchronous-unwind-tables
	   Generate unwind table in dwarf2 format, if supported	by target
	   machine.  The table is exact	at each	instruction boundary, so it
	   can be used for stack unwinding from	asynchronous events (such as
	   debugger or garbage collector).

       -fpcc-struct-return
	   Return "short" "struct" and "union" values in memory	like longer
	   ones, rather	than in	registers.  This convention is less efficient,
	   but it has the advantage of allowing	intercallability between GCC-
	   compiled files and files compiled with other	compilers, particu-
	   larly the Portable C	Compiler (pcc).

	   The precise convention for returning	structures in memory depends
	   on the target configuration macros.

	   Short structures and	unions are those whose size and	alignment
	   match that of some integer type.

	   Warning: code compiled with the -fpcc-struct-return switch is not
	   binary compatible with code compiled	with the -freg-struct-return
	   switch.  Use	it to conform to a non-default application binary
	   interface.

       -freg-struct-return
	   Return "struct" and "union" values in registers when	possible.
	   This	is more	efficient for small structures than
	   -fpcc-struct-return.

	   If you specify neither -fpcc-struct-return nor -freg-struct-return,
	   GCC defaults	to whichever convention	is standard for	the target.
	   If there is no standard convention, GCC defaults to
	   -fpcc-struct-return,	except on targets where	GCC is the principal
	   compiler.  In those cases, we can choose the	standard, and we chose
	   the more efficient register return alternative.

	   Warning: code compiled with the -freg-struct-return switch is not
	   binary compatible with code compiled	with the -fpcc-struct-return
	   switch.  Use	it to conform to a non-default application binary
	   interface.

       -fshort-enums
	   Allocate to an "enum" type only as many bytes as it needs for the
	   declared range of possible values.  Specifically, the "enum"	type
	   will	be equivalent to the smallest integer type which has enough
	   room.

	   Warning: the	-fshort-enums switch causes GCC	to generate code that
	   is not binary compatible with code generated	without	that switch.
	   Use it to conform to	a non-default application binary interface.

       -fshort-double
	   Use the same	size for "double" as for "float".

	   Warning: the	-fshort-double switch causes GCC to generate code that
	   is not binary compatible with code generated	without	that switch.
	   Use it to conform to	a non-default application binary interface.

       -fshort-wchar
	   Override the	underlying type	for wchar_t to be short	unsigned int
	   instead of the default for the target.  This	option is useful for
	   building programs to	run under WINE.

	   Warning: the	-fshort-wchar switch causes GCC	to generate code that
	   is not binary compatible with code generated	without	that switch.
	   Use it to conform to	a non-default application binary interface.

       -fno-common
	   In C, allocate even uninitialized global variables in the data sec-
	   tion	of the object file, rather than	generating them	as common
	   blocks.  This has the effect	that if	the same variable is declared
	   (without "extern") in two different compilations, you will get an
	   error when you link them.  The only reason this might be useful is
	   if you wish to verify that the program will work on other systems
	   which always	work this way.

       -fno-ident
	   Ignore the #ident directive.

       -finhibit-size-directive
	   Don't output	a ".size" assembler directive, or anything else	that
	   would cause trouble if the function is split	in the middle, and the
	   two halves are placed at locations far apart	in memory.  This
	   option is used when compiling crtstuff.c; you should	not need to
	   use it for anything else.

       -fverbose-asm
	   Put extra commentary	information in the generated assembly code to
	   make	it more	readable.  This	option is generally only of use	to
	   those who actually need to read the generated assembly code (per-
	   haps	while debugging	the compiler itself).

	   -fno-verbose-asm, the default, causes the extra information to be
	   omitted and is useful when comparing	two assembler files.

       -fpic
	   Generate position-independent code (PIC) suitable for use in	a
	   shared library, if supported	for the	target machine.	 Such code
	   accesses all	constant addresses through a global offset table
	   (GOT).  The dynamic loader resolves the GOT entries when the	pro-
	   gram	starts (the dynamic loader is not part of GCC; it is part of
	   the operating system).  If the GOT size for the linked executable
	   exceeds a machine-specific maximum size, you	get an error message
	   from	the linker indicating that -fpic does not work;	in that	case,
	   recompile with -fPIC	instead.  (These maximums are 8k on the	SPARC
	   and 32k on the m68k and RS/6000.  The 386 has no such limit.)

	   Position-independent	code requires special support, and therefore
	   works only on certain machines.  For	the 386, GCC supports PIC for
	   System V but	not for	the Sun	386i.  Code generated for the IBM
	   RS/6000 is always position-independent.

	   When	this flag is set, the macros "__pic__" and "__PIC__" are
	   defined to 1.

       -fPIC
	   If supported	for the	target machine,	emit position-independent
	   code, suitable for dynamic linking and avoiding any limit on	the
	   size	of the global offset table.  This option makes a difference on
	   the m68k, PowerPC and SPARC.

	   Position-independent	code requires special support, and therefore
	   works only on certain machines.

	   When	this flag is set, the macros "__pic__" and "__PIC__" are
	   defined to 2.

       -fpie
       -fPIE
	   These options are similar to	-fpic and -fPIC, but generated posi-
	   tion	independent code can be	only linked into executables.  Usually
	   these options are used when -pie GCC	option will be used during
	   linking.

       -fno-jump-tables
	   Do not use jump tables for switch statements	even where it would be
	   more	efficient than other code generation strategies.  This option
	   is of use in	conjunction with -fpic or -fPIC	for building code
	   which forms part of a dynamic linker	and cannot reference the
	   address of a	jump table.  On	some targets, jump tables do not
	   require a GOT and this option is not	needed.

       -ffixed-reg
	   Treat the register named reg	as a fixed register; generated code
	   should never	refer to it (except perhaps as a stack pointer,	frame
	   pointer or in some other fixed role).

	   reg must be the name	of a register.	The register names accepted
	   are machine-specific	and are	defined	in the "REGISTER_NAMES"	macro
	   in the machine description macro file.

	   This	flag does not have a negative form, because it specifies a
	   three-way choice.

       -fcall-used-reg
	   Treat the register named reg	as an allocable	register that is clob-
	   bered by function calls.  It	may be allocated for temporaries or
	   variables that do not live across a call.  Functions	compiled this
	   way will not	save and restore the register reg.

	   It is an error to used this flag with the frame pointer or stack
	   pointer.  Use of this flag for other	registers that have fixed per-
	   vasive roles	in the machine's execution model will produce disas-
	   trous results.

	   This	flag does not have a negative form, because it specifies a
	   three-way choice.

       -fcall-saved-reg
	   Treat the register named reg	as an allocable	register saved by
	   functions.  It may be allocated even	for temporaries	or variables
	   that	live across a call.  Functions compiled	this way will save and
	   restore the register	reg if they use	it.

	   It is an error to used this flag with the frame pointer or stack
	   pointer.  Use of this flag for other	registers that have fixed per-
	   vasive roles	in the machine's execution model will produce disas-
	   trous results.

	   A different sort of disaster	will result from the use of this flag
	   for a register in which function values may be returned.

	   This	flag does not have a negative form, because it specifies a
	   three-way choice.

       -fpack-struct[=n]
	   Without a value specified, pack all structure members together
	   without holes.  When	a value	is specified (which must be a small
	   power of two), pack structure members according to this value, rep-
	   resenting the maximum alignment (that is, objects with default
	   alignment requirements larger than this will	be output potentially
	   unaligned at	the next fitting location.

	   Warning: the	-fpack-struct switch causes GCC	to generate code that
	   is not binary compatible with code generated	without	that switch.
	   Additionally, it makes the code suboptimal.	Use it to conform to a
	   non-default application binary interface.

       -finstrument-functions
	   Generate instrumentation calls for entry and	exit to	functions.
	   Just	after function entry and just before function exit, the	fol-
	   lowing profiling functions will be called with the address of the
	   current function and	its call site.	(On some platforms,
	   "__builtin_return_address" does not work beyond the current func-
	   tion, so the	call site information may not be available to the pro-
	   filing functions otherwise.)

		   void	__cyg_profile_func_enter (void *this_fn,
						  void *call_site);
		   void	__cyg_profile_func_exit	 (void *this_fn,
						  void *call_site);

	   The first argument is the address of	the start of the current func-
	   tion, which may be looked up	exactly	in the symbol table.

	   This	instrumentation	is also	done for functions expanded inline in
	   other functions.  The profiling calls will indicate where, concep-
	   tually, the inline function is entered and exited.  This means that
	   addressable versions	of such	functions must be available.  If all
	   your	uses of	a function are expanded	inline,	this may mean an addi-
	   tional expansion of code size.  If you use extern inline in your C
	   code, an addressable	version	of such	functions must be provided.
	   (This is normally the case anyways, but if you get lucky and	the
	   optimizer always expands the	functions inline, you might have got-
	   ten away without providing static copies.)

	   A function may be given the attribute "no_instrument_function", in
	   which case this instrumentation will	not be done.  This can be
	   used, for example, for the profiling	functions listed above,	high-
	   priority interrupt routines,	and any	functions from which the pro-
	   filing functions cannot safely be called (perhaps signal handlers,
	   if the profiling routines generate output or	allocate memory).

       -fstack-check
	   Generate code to verify that	you do not go beyond the boundary of
	   the stack.  You should specify this flag if you are running in an
	   environment with multiple threads, but only rarely need to specify
	   it in a single-threaded environment since stack overflow is auto-
	   matically detected on nearly	all systems if there is	only one
	   stack.

	   Note	that this switch does not actually cause checking to be	done;
	   the operating system	must do	that.  The switch causes generation of
	   code	to ensure that the operating system sees the stack being
	   extended.

       -fstack-limit-register=reg
       -fstack-limit-symbol=sym
       -fno-stack-limit
	   Generate code to ensure that	the stack does not grow	beyond a cer-
	   tain	value, either the value	of a register or the address of	a sym-
	   bol.	 If the	stack would grow beyond	the value, a signal is raised.
	   For most targets, the signal	is raised before the stack overruns
	   the boundary, so it is possible to catch the	signal without taking
	   special precautions.

	   For instance, if the	stack starts at	absolute address 0x80000000
	   and grows downwards,	you can	use the	flags -fstack-limit-sym-
	   bol=__stack_limit and -Wl,--defsym,__stack_limit=0x7ffe0000 to
	   enforce a stack limit of 128KB.  Note that this may only work with
	   the GNU linker.

       -fargument-alias
       -fargument-noalias
       -fargument-noalias-global
       -fargument-noalias-anything
	   Specify the possible	relationships among parameters and between
	   parameters and global data.

	   -fargument-alias specifies that arguments (parameters) may alias
	   each	other and may alias global storage.-fargument-noalias speci-
	   fies	that arguments do not alias each other,	but may	alias global
	   storage.-fargument-noalias-global specifies that arguments do not
	   alias each other and	do not alias global storage.  -fargu-
	   ment-noalias-anything specifies that	arguments do not alias any
	   other storage.

	   Each	language will automatically use	whatever option	is required by
	   the language	standard.  You should not need to use these options
	   yourself.

       -fleading-underscore
	   This	option and its counterpart, -fno-leading-underscore, forcibly
	   change the way C symbols are	represented in the object file.	 One
	   use is to help link with legacy assembly code.

	   Warning: the	-fleading-underscore switch causes GCC to generate
	   code	that is	not binary compatible with code	generated without that
	   switch.  Use	it to conform to a non-default application binary
	   interface.  Not all targets provide complete	support	for this
	   switch.

       -ftls-model=model
	   Alter the thread-local storage model	to be used.  The model argu-
	   ment	should be one of "global-dynamic", "local-dynamic", "ini-
	   tial-exec" or "local-exec".

	   The default without -fpic is	"initial-exec";	with -fpic the default
	   is "global-dynamic".

       -fvisibility=default|internal|hidden|protected
	   Set the default ELF image symbol visibility to the specified
	   option---all	symbols	will be	marked with this unless	overridden
	   within the code.  Using this	feature	can very substantially improve
	   linking and load times of shared object libraries, produce more
	   optimized code, provide near-perfect	API export and prevent symbol
	   clashes.  It	is strongly recommended	that you use this in any
	   shared objects you distribute.

	   Despite the nomenclature, "default" always means public ie; avail-
	   able	to be linked against from outside the shared object.  "pro-
	   tected" and "internal" are pretty useless in	real-world usage so
	   the only other commonly used	option will be "hidden".  The default
	   if -fvisibility isn't specified is "default", i.e., make every sym-
	   bol public---this causes the	same behavior as previous versions of
	   GCC.

	   A good explanation of the benefits offered by ensuring ELF symbols
	   have	the correct visibility is given	by "How	To Write Shared
	   Libraries" by Ulrich	Drepper	(which can be found at <http://peo-
	   ple.redhat.com/~drepper/>)---however	a superior solution made pos-
	   sible by this option	to marking things hidden when the default is
	   public is to	make the default hidden	and mark things	public.	 This
	   is the norm with DLL's on Windows and with -fvisibility=hidden and
	   "__attribute__ ((visibility("default")))" instead of
	   "__declspec(dllexport)" you get almost identical semantics with
	   identical syntax.  This is a	great boon to those working with
	   cross-platform projects.

	   For those adding visibility support to existing code, you may find
	   #pragma GCC visibility of use.  This	works by you enclosing the
	   declarations	you wish to set	visibility for with (for example)
	   #pragma GCC visibility push(hidden) and #pragma GCC visibility pop.
	   Bear	in mind	that symbol visibility should be viewed	as part	of the
	   API interface contract and thus all new code	should always specify
	   visibility when it is not the default ie; declarations only for use
	   within the local DSO	should always be marked	explicitly as hidden
	   as so to avoid PLT indirection overheads---making this abundantly
	   clear also aids readability and self-documentation of the code.
	   Note	that due to ISO	C++ specification requirements,	operator new
	   and operator	delete must always be of default visibility.

	   Be aware that headers from outside your project, in particular sys-
	   tem headers and headers from	any other library you use, may not be
	   expecting to	be compiled with visibility other than the default.
	   You may need	to explicitly say #pragma GCC visibility push(default)
	   before including any	such headers.

	   extern declarations are not affected	by -fvisibility, so a lot of
	   code	can be recompiled with -fvisibility=hidden with	no modifica-
	   tions.  However, this means that calls to extern functions with no
	   explicit visibility will use	the PLT, so it is more effective to
	   use __attribute ((visibility)) and/or #pragma GCC visibility	to
	   tell	the compiler which extern declarations should be treated as
	   hidden.

	   Note	that -fvisibility does affect C++ vague	linkage	entities. This
	   means that, for instance, an	exception class	that will be thrown
	   between DSOs	must be	explicitly marked with default visibility so
	   that	the type_info nodes will be unified between the	DSOs.

	   An overview of these	techniques, their benefits and how to use them
	   is at <http://gcc.gnu.org/wiki/Visibility>.

ENVIRONMENT
       This section describes several environment variables that affect	how
       GCC operates.  Some of them work	by specifying directories or prefixes
       to use when searching for various kinds of files.  Some are used	to
       specify other aspects of	the compilation	environment.

       Note that you can also specify places to	search using options such as
       -B, -I and -L.  These take precedence over places specified using envi-
       ronment variables, which	in turn	take precedence	over those specified
       by the configuration of GCC.

       LANG
       LC_CTYPE
       LC_MESSAGES
       LC_ALL
	   These environment variables control the way that GCC	uses localiza-
	   tion	information that allow GCC to work with	different national
	   conventions.	 GCC inspects the locale categories LC_CTYPE and
	   LC_MESSAGES if it has been configured to do so.  These locale cate-
	   gories can be set to	any value supported by your installation.  A
	   typical value is en_GB.UTF-8	for English in the United Kingdom
	   encoded in UTF-8.

	   The LC_CTYPE	environment variable specifies character classifica-
	   tion.  GCC uses it to determine the character boundaries in a
	   string; this	is needed for some multibyte encodings that contain
	   quote and escape characters that would otherwise be interpreted as
	   a string end	or escape.

	   The LC_MESSAGES environment variable	specifies the language to use
	   in diagnostic messages.

	   If the LC_ALL environment variable is set, it overrides the value
	   of LC_CTYPE and LC_MESSAGES;	otherwise, LC_CTYPE and	LC_MESSAGES
	   default to the value	of the LANG environment	variable.  If none of
	   these variables are set, GCC	defaults to traditional	C English
	   behavior.

       TMPDIR
	   If TMPDIR is	set, it	specifies the directory	to use for temporary
	   files.  GCC uses temporary files to hold the	output of one stage of
	   compilation which is	to be used as input to the next	stage: for
	   example, the	output of the preprocessor, which is the input to the
	   compiler proper.

       GCC_EXEC_PREFIX
	   If GCC_EXEC_PREFIX is set, it specifies a prefix to use in the
	   names of the	subprograms executed by	the compiler.  No slash	is
	   added when this prefix is combined with the name of a subprogram,
	   but you can specify a prefix	that ends with a slash if you wish.

	   If GCC_EXEC_PREFIX is not set, GCC will attempt to figure out an
	   appropriate prefix to use based on the pathname it was invoked
	   with.

	   If GCC cannot find the subprogram using the specified prefix, it
	   tries looking in the	usual places for the subprogram.

	   The default value of	GCC_EXEC_PREFIX	is prefix/lib/gcc/ where pre-
	   fix is the value of "prefix"	when you ran the configure script.

	   Other prefixes specified with -B take precedence over this prefix.

	   This	prefix is also used for	finding	files such as crt0.o that are
	   used	for linking.

	   In addition,	the prefix is used in an unusual way in	finding	the
	   directories to search for header files.  For	each of	the standard
	   directories whose name normally begins with /usr/local/lib/gcc
	   (more precisely, with the value of GCC_INCLUDE_DIR),	GCC tries
	   replacing that beginning with the specified prefix to produce an
	   alternate directory name.  Thus, with -Bfoo/, GCC will search
	   foo/bar where it would normally search /usr/local/lib/bar.  These
	   alternate directories are searched first; the standard directories
	   come	next.

       COMPILER_PATH
	   The value of	COMPILER_PATH is a colon-separated list	of directo-
	   ries, much like PATH.  GCC tries the	directories thus specified
	   when	searching for subprograms, if it can't find the	subprograms
	   using GCC_EXEC_PREFIX.

       LIBRARY_PATH
	   The value of	LIBRARY_PATH is	a colon-separated list of directories,
	   much	like PATH.  When configured as a native	compiler, GCC tries
	   the directories thus	specified when searching for special linker
	   files, if it	can't find them	using GCC_EXEC_PREFIX.	Linking	using
	   GCC also uses these directories when	searching for ordinary
	   libraries for the -l	option (but directories	specified with -L come
	   first).

       LANG
	   This	variable is used to pass locale	information to the compiler.
	   One way in which this information is	used is	to determine the char-
	   acter set to	be used	when character literals, string	literals and
	   comments are	parsed in C and	C++.  When the compiler	is configured
	   to allow multibyte characters, the following	values for LANG	are
	   recognized:

	   C-JIS
	       Recognize JIS characters.

	   C-SJIS
	       Recognize SJIS characters.

	   C-EUCJP
	       Recognize EUCJP characters.

	   If LANG is not defined, or if it has	some other value, then the
	   compiler will use mblen and mbtowc as defined by the	default	locale
	   to recognize	and translate multibyte	characters.

       Some additional environments variables affect the behavior of the pre-
       processor.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
	   Each	variable's value is a list of directories separated by a spe-
	   cial	character, much	like PATH, in which to look for	header files.
	   The special character, "PATH_SEPARATOR", is target-dependent	and
	   determined at GCC build time.  For Microsoft	Windows-based targets
	   it is a semicolon, and for almost all other targets it is a colon.

	   CPATH specifies a list of directories to be searched	as if speci-
	   fied	with -I, but after any paths given with	-I options on the com-
	   mand	line.  This environment	variable is used regardless of which
	   language is being preprocessed.

	   The remaining environment variables apply only when preprocessing
	   the particular language indicated.  Each specifies a	list of	direc-
	   tories to be	searched as if specified with -isystem,	but after any
	   paths given with -isystem options on	the command line.

	   In all these	variables, an empty element instructs the compiler to
	   search its current working directory.  Empty	elements can appear at
	   the beginning or end	of a path.  For	instance, if the value of
	   CPATH is ":/special/include", that has the same effect as
	   -I. -I/special/include.

       DEPENDENCIES_OUTPUT
	   If this variable is set, its	value specifies	how to output depen-
	   dencies for Make based on the non-system header files processed by
	   the compiler.  System header	files are ignored in the dependency
	   output.

	   The value of	DEPENDENCIES_OUTPUT can	be just	a file name, in	which
	   case	the Make rules are written to that file, guessing the target
	   name	from the source	file name.  Or the value can have the form
	   file	target,	in which case the rules	are written to file file using
	   target as the target	name.

	   In other words, this	environment variable is	equivalent to combin-
	   ing the options -MM and -MF,	with an	optional -MT switch too.

       SUNPRO_DEPENDENCIES
	   This	variable is the	same as	DEPENDENCIES_OUTPUT (see above),
	   except that system header files are not ignored, so it implies -M
	   rather than -MM.  However, the dependence on	the main input file is
	   omitted.

BUGS
       For instructions	on reporting bugs, see <http://gcc.gnu.org/bugs.html>.

FOOTNOTES
       1.  On some systems, gcc	-shared	needs to build supplementary stub code
	   for constructors to work.  On multi-libbed systems, gcc -shared
	   must	select the correct support libraries to	link against.  Failing
	   to supply the correct flags may lead	to subtle defects.  Supplying
	   them	in cases where they are	not necessary is innocuous.

SEE ALSO
       gpl(7), gfdl(7),	fsf-funding(7),	cpp(1),	gcov(1), as(1),	ld(1), gdb(1),
       adb(1), dbx(1), sdb(1) and the Info entries for gcc, cpp, as, ld, binu-
       tils and	gdb.

AUTHOR
       See the Info entry for gcc, or <http://gcc.gnu.org/onlinedocs/gcc/Con-
       tributors.html>,	for contributors to GCC.

COPYRIGHT
       Copyright (c) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
       1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software Founda-
       tion, Inc.

       Permission is granted to	copy, distribute and/or	modify this document
       under the terms of the GNU Free Documentation License, Version 1.2 or
       any later version published by the Free Software	Foundation; with the
       Invariant Sections being	"GNU General Public License" and "Funding Free
       Software", the Front-Cover texts	being (a) (see below), and with	the
       Back-Cover Texts	being (b) (see below).	A copy of the license is
       included	in the gfdl(7) man page.

       (a) The FSF's Front-Cover Text is:

	    A GNU Manual

       (b) The FSF's Back-Cover	Text is:

	    You	have freedom to	copy and modify	this GNU Manual, like GNU
	    software.  Copies published	by the Free Software Foundation	raise
	    funds for GNU development.

gcc-4.2.1			  2011-03-07				GCC(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | BUGS | FOOTNOTES | SEE ALSO | AUTHOR | COPYRIGHT

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