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B::Asmdata(3)	      User Contributed Perl Documentation	 B::Asmdata(3)

NAME
       B::Asmdata - Autogenerated data about Perl ops, used to generate
       bytecode

SYNOPSIS
	       use B::Asmdata qw(%insn_data @insn_name @optype @specialsv_name);

DESCRIPTION
       Provides	information about Perl ops in order to generate	bytecode via a
       bunch of	exported variables.  Its mostly	used by	B::Assembler and
       B::Disassembler.

       %insn_data
	     my($bytecode_num, $put_sub, $get_meth) = @$insn_data{$op_name};

	   For a given $op_name	(for example, 'cop_label', 'sv_flags', etc...)
	   you get an array ref	containing the bytecode	number of the op, a
	   reference to	the subroutine used to 'PUT' the op argument to	the
	   bytecode stream, and	the name of the	method used to 'GET' op
	   argument from the bytecode stream.

	   Most	ops require one	arg, in	fact all ops without the PUT/GET_none
	   methods, and	the GET	and PUT	methods	are used to en-/decode the arg
	   to binary bytecode.	The names are constructed from the GET/PUT
	   prefix and the argument type, such as U8, U16, U32, svindex,
	   opindex, pvindex, ...

	   The PUT method is used in the B::Bytecode compiler within
	   B::Assembler, the GET method	just for the B::Disassembler.  The GET
	   method is not used by the binary ByteLoader module.

	   A full "insn" table with version, opcode, name, lvalue, argtype and
	   flags is located as DATA in bytecode.pl.

	   An empty PUT	method,	the number 0, denotes an unsupported bytecode
	   for this perl.  It is there to support disassembling	older perl
	   bytecode. This was added with 1.02_02.

       @insn_name
	     my	$op_name = $insn_name[$bytecode_num];

	   A simple mapping of the bytecode number to the name of the op.
	   Suitable for	using with %insn_data like so:

	     my	$op_info = $insn_data{$insn_name[$bytecode_num]};

       @optype
	     my	$op_type = $optype[$op_type_num];

	   A simple mapping of the op type number to its type (like 'COP' or
	   'BINOP').

	   Since Perl version 5.10 defined in B.

       @specialsv_name
	     my	$sv_name = $specialsv_name[$sv_index];

	   Certain SV types are	considered 'special'.  They're represented by
	   B::SPECIAL and are referred to by a number from the specialsv_list.
	   This	array maps that	number back to the name	of the SV (like
	   'Nullsv' or '&PL_sv_undef').

	   Since Perl version 5.10 defined in B.

PORTABILITY
       All bytecode values are already portable.  Cross-platform portability
       is implemented, cross-version not yet.

       Cross-version portability will be very limited, cross-platform only for
       the same	threading model.

   CROSS-PLATFORM PORTABILITY
       For different endian-ness there are ByteLoader converters in effect.
       Header entry: byteorder.

       64int - 64all - 32int is	portable. Header entry:	ivsize

       ITHREADS	are unportable;	header entry: archflag - bitflag 1.
       MULTIPLICITY is also unportable;	header entry: archflag - bitflag 2

       TODO For	cross-version portability we will try to translate older
       bytecode	ops to the current perl	op via ByteLoader::Translate.  Asmdata
       already contains	the old	ops, all with the PUT method 0.	 Header	entry:
       perlversion

   CROSS-VERSION PORTABILITY (TODO - HARD)
       Bytecode	ops: We	can only reliably load bytecode	from previous versions
       and promise that	from 5.10.0 on future versions will only add new op
       numbers at the end, but will never replace old opcodes with
       incompatible arguments.	Unsupported insn's are supported by
       disassemble, and	if "force" in the ByteLoader is	set, it	is tried to
       load/set	them also, with	probably fatal consequences.  On the first
       unknown bytecode	op from	a future version - added to the	end - we will
       die.

       ByteLoader::BcVersions contains logic to	translate previous errors from
       this bytecode policy. E.g. 5.8 violated the 5.6 bytecode	order policy
       and began to juggle it around (similar to parrot), in detail removed
       various bytecodes, like ldspecsvx:7, xpv_cur, xpv_len, xiv64:26.	 So in
       theory it would have been possible to load 5.6 into 5.8 bytecode	as the
       underlying perl pp_code ops didn't change that much, but	it is risky.

       We have unused tables of	all bytecode ops for all version-specific
       changes to the bytecode table. This only	changed	with the ByteLoader
       version,	ithreads and major Perl	versions.

       Also special replacements in the	byteloader for all the unsupported
       ops, like xiv64,	cop_arybase.

AUTHOR
       Malcolm Beattie "MICB at	cpan.org" (retired), Reini Urban added the
       version logic, support >= 5.10, portability.

perl v5.32.0			  2020-08-11			 B::Asmdata(3)

NAME | SYNOPSIS | DESCRIPTION | PORTABILITY | AUTHOR

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