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B::Bytecode

Section: Perl Programmers Reference Guide (3pm)
Updated: perl v5.6.1
Index

NAME

B::Bytecode - Perl compiler's bytecode backend

SYNOPSIS

        perl -MO=Bytecode[,OPTIONS] foo.pl

DESCRIPTION

This compiler backend takes Perl source and generates aplatform-independent bytecode encapsulating code to load theinternal structures perl uses to run your program. When thegenerated bytecode is loaded in, your program is ready to run,reducing the time which perl would have taken to load and parseyour program into its internal semi-compiled form. That means thatcompiling with this backend will not help improve the runtimeexecution speed of your program but may improve the start-up time.Depending on the environment in which your program runs this mayor may not be a help.

The resulting bytecode can be run with a special byteperl executableor (for non-main programs) be loaded via the "byteload_fh" functionin the B module.

OPTIONS

If there are any non-option arguments, they are taken to be names ofobjects to be saved (probably doesn't work properly yet). Withoutextra arguments, it saves the main program.

-ofilename: Output to filename instead of STDOUT.
-afilename: Append output to filename.
--: Force end of options.
-f: Force optimisations on or off one at a time. Each can be precededby no- to turn the option off (e.g. -fno-compress-nullops).
-fcompress-nullops: Only fills in the necessary fields of ops which havebeen optimised away by perl's internal compiler.
-fomit-sequence-numbers: Leaves out code to fill in the op_seq field of all opswhich is only used by perl's internal compiler.
-fbypass-nullops: If op->op_next ever points to a NULLOP, replaces the op_next fieldwith the first non-NULLOP in the path of execution.
-On: Optimisation level (n = 0, 1, 2, ...). -O means -O1.-O1 sets -fcompress-nullops -fomit-sequence numbers.-O2 adds -fbypass-nullops.
-D: Debug options (concatenated or separate flags like "perl -D").
-Do: Prints each OP as it's processed.
-Db: Print debugging information about bytecompiler progress.
-Da: Tells the (bytecode) assembler to include source assembler linesin its output as bytecode comments.
-DC: Prints each CV taken from the final symbol tree walk.
-S: Output (bytecode) assembler source rather than piping itthrough the assembler and outputting bytecode.
-upackage: Stores package in the output.

EXAMPLES

    perl -MO=Bytecode,-O6,-ofoo.plc,-umain foo.pl

    perl -MO=Bytecode,-S,-umain foo.pl > foo.S    assemble foo.S > foo.plc

Note that "assemble" lives in the "B" subdirectory of your perllibrary directory. The utility called perlcc may also be used to help make use of this compiler.

    perl -MO=Bytecode,-uFoo,-oFoo.pmc Foo.pm

BUGS

Output is still huge and there are still occasional crashes duringeither compilation or ByteLoading. Current status: experimental.

AUTHORS

Malcolm Beattie, "mbeattieAATTsable.ox.ac.uk"Benjamin Stuhl, "sho_piAATThotmail.com"

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