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ARCH(7)		   FreeBSD Miscellaneous Information Manual	       ARCH(7)

     arch -- Architecture-specific details

     Differences between CPU architectures and platforms supported by FreeBSD.

     This document is a	quick reference	of key ABI details of FreeBSD archi-
     tecture ports.  For full details consult the processor-specific ABI sup-
     plement documentation.

     If	not explicitly mentioned, sizes	are in bytes.  The architecture
     details in	this document apply to FreeBSD 10.0 and	later, unless other-
     wise noted.

     FreeBSD uses a flat address space.	 Variables of types unsigned long,
     uintptr_t,	and size_t and pointers	all have the same representation.

     In	order to maximize compatibility	with future pointer integrity mecha-
     nisms, manipulations of pointers as integers should be performed via
     uintptr_t or intptr_t and no other	types.	In particular, long and
     ptrdiff_t should be avoided.

     On	some architectures, e.g.  sparc64, powerpc and AIM variants of
     powerpc64,	the kernel uses	a separate address space.  On other architec-
     tures, kernel and a user mode process share a single address space.  The
     kernel is located at the highest addresses.

     On	each architecture, the main user mode thread's stack starts near the
     highest user address and grows down.

     FreeBSD architecture support varies by release.  This table shows the
     first FreeBSD release to support each architecture, and, for discontinued
     architectures, the	final release.

	   Architecture	      Initial Release	    Final Release
	   alpha	      3.2		    6.4
	   amd64	      5.1
	   arm		      6.0
	   armeb	      8.0
	   armv6	      10.0
	   arm64	      11.0
	   ia64		      5.0		    10.x
	   i386		      1.0
	   mips		      8.0
	   mipsel	      9.0
	   mipselhf	      12.0
	   mipshf	      12.0
	   mipsn32	      9.0
	   mips64	      9.0
	   mips64el	      9.0
	   mips64elhf	      12.0
	   mips64hf	      12.0
	   pc98		      2.2		    11.x
	   powerpc	      6.0
	   powerpcspe	      12.0
	   powerpc64	      6.0
	   riscv64	      12.0
	   riscv64sf	      12.0
	   sparc64	      5.0

   Type	sizes
     All FreeBSD architectures use some	variant	of the ELF (see	elf(5))
     Application Binary	Interface (ABI)	for the	machine	processor.  All	sup-
     ported ABIs can be	divided	into two groups:

     ILP32     int, long, void * types machine representations all have	4-byte

     LP64      int type	machine	representation uses 4 bytes, while long	and
	       void * are 8 bytes.
     Compilers define the _LP64	symbol when compiling for an LP64 ABI.

     Some machines support more	that one FreeBSD ABI.  Typically these are
     64-bit machines, where the	``native'' LP64	execution environment is
     accompanied by the	``legacy'' ILP32 environment, which was	historical
     32-bit predecessor	for 64-bit evolution.  Examples	are:

	   LP64		   ILP32 counterpart
	   amd64	   i386
	   powerpc64	   powerpc
	   mips64*	   mips*
     arm64 currently does not support execution	of armv6 binaries, even	if the
     CPU implements AArch32 execution state.

     On	all supported architectures:

	    Type	 Size
	    short	 2
	    int		 4
	    long	 sizeof(void*)
	    long long	 8
	    float	 4
	    double	 8
     Integers are represented in two's complement.  Alignment of integer and
     pointer types is natural, that is,	the address of the variable must be
     congruent to zero modulo the type size.  Most ILP32 ABIs, except arm,
     require only 4-byte alignment for 64-bit integers.

     Machine-dependent type sizes:

	   Architecture	      void *	   long	double	     time_t
	   amd64	      8		   16		     8
	   arm		      4		   8		     8
	   armeb	      4		   8		     8
	   armv6	      4		   8		     8
	   arm64	      8		   16		     8
	   i386		      4		   12		     4
	   mips		      4		   8		     8
	   mipsel	      4		   8		     8
	   mipselhf	      4		   8		     8
	   mipshf	      4		   8		     8
	   mipsn32	      4		   8		     8
	   mips64	      8		   8		     8
	   mips64el	      8		   8		     8
	   mips64elhf	      8		   8		     8
	   mips64hf	      8		   8		     8
	   powerpc	      4		   8		     4
	   powerpcspe	      4		   8		     4
	   powerpc64	      8		   8		     8
	   riscv64	      8		   16		     8
	   riscv64sf	      8		   16		     8
	   sparc64	      8		   16		     8

     time_t is 8 bytes on all supported	architectures except i386 and 32-bit
     variants of powerpc.

   Endianness and Char Signedness
	   Architecture	      Endianness       char Signedness
	   amd64	      little	       signed
	   arm		      little	       unsigned
	   armeb	      big	       unsigned
	   armv6	      little	       unsigned
	   arm64	      little	       unsigned
	   i386		      little	       signed
	   mips		      big	       signed
	   mipsel	      little	       signed
	   mipselhf	      little	       signed
	   mipshf	      big	       signed
	   mipsn32	      big	       signed
	   mips64	      big	       signed
	   mips64el	      little	       signed
	   mips64elhf	      little	       signed
	   mips64hf	      big	       signed
	   powerpc	      big	       unsigned
	   powerpcspe	      big	       unsigned
	   powerpc64	      big	       unsigned
	   riscv64	      little	       signed
	   riscv64sf	      little	       signed
	   sparc64	      big	       signed

   Page	Size
	   Architecture	      Page Sizes
	   amd64	      4K, 2M, 1G
	   arm		      4K
	   armeb	      4K
	   armv6	      4K, 1M
	   arm64	      4K, 2M, 1G
	   i386		      4K, 2M (PAE), 4M
	   mips		      4K
	   mipsel	      4K
	   mipselhf	      4K
	   mipshf	      4K
	   mipsn32	      4K
	   mips64	      4K
	   mips64el	      4K
	   mips64elhf	      4K
	   mips64hf	      4K
	   powerpc	      4K
	   powerpcspe	      4K
	   powerpc64	      4K
	   riscv64	      4K
	   riscv64sf	      4K
	   sparc64	      8K

   Floating Point
	   Architecture	      float, double	  long double
	   amd64	      hard		  hard,	80 bit
	   arm		      soft		  soft,	double precision
	   armeb	      soft		  soft,	double precision
	   armv6	      hard(1)		  hard,	double precision
	   arm64	      hard		  soft,	quad precision
	   i386		      hard		  hard,	80 bit
	   mips		      soft		  identical to double
	   mipsel	      soft		  identical to double
	   mipselhf	      hard		  identical to double
	   mipshf	      hard		  identical to double
	   mipsn32	      soft		  identical to double
	   mips64	      soft		  identical to double
	   mips64el	      soft		  identical to double
	   mips64elhf	      hard		  identical to double
	   mips64hf	      hard		  identical to double
	   powerpc	      hard		  hard,	double precision
	   powerpcspe	      hard		  hard,	double precision
	   powerpc64	      hard		  hard,	double precision
	   riscv64	      hard		  hard,	double precision
	   riscv64sf	      soft		  soft,	double precision
	   sparc64	      hard		  hard,	quad precision

     (1) Prior to FreeBSD 11.0,	armv6 used the softfp ABI even though it sup-
     ported only processors with a floating point unit.

   Predefined Macros
     The compiler provides a number of predefined macros.  Some	of these pro-
     vide architecture-specific	details	and are	explained below.  Other
     macros, including those required by the language standard,	are not
     included here.

     The full set of predefined	macros can be obtained with this command:

	   cc -x c -dM -E /dev/null

     Common type size and endianness macros:

	   Macro	 Meaning
	   __LP64__	 64-bit	(8-byte) long and pointer, 32-bit (4-byte) int
	   __ILP32__	 32-bit	(4-byte) int, long and pointer
				       not used	on FreeBSD.

     Architecture-specific macros:

	   Architecture	      Predefined macros
	   amd64	      __amd64__, __x86_64__
	   arm		      __arm__
	   armeb	      __arm__
	   armv6	      __arm__, __ARM_ARCH >= 6
	   arm64	      __aarch64__
	   i386		      __i386__
	   mips		      __mips__,	__MIPSEB__, __mips_o32
	   mipsel	      __mips__,	__mips_o32
	   mipselhf	      __mips__,	__mips_o32
	   mipshf	      __mips__,	__MIPSEB__, __mips_o32
	   mipsn32	      __mips__,	__MIPSEB__, __mips_n32
	   mips64	      __mips__,	__MIPSEB__, __mips_n64
	   mips64el	      __mips__,	__mips_n64
	   mips64elhf	      __mips__,	__mips_n64
	   mips64hf	      __mips__,	__MIPSEB__, __mips_n64
	   powerpc	      __powerpc__
	   powerpcspe	      __powerpc__, __SPE__
	   powerpc64	      __powerpc__, __powerpc64__
	   riscv64	      __riscv__, __riscv64
	   riscv64sf	      __riscv__, __riscv64
	   sparc64	      __sparc64__

     src.conf(5), build(7)

     An	arch manual page appeared in FreeBSD 12.

FreeBSD	11.2			 May 16, 2017			  FreeBSD 11.2


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