NAME

optimizer - Write your own Perl optimizer, in Perl

SYNOPSIS

  # Use Perl's default optimizer
  use optimizer 'C';

  # Use a Perl implementation of the default optimizer
  use optimizer 'perl';

  # Use an extension of the default optimizer
  use optimizer extend => sub {
        warn "goto considered harmful" if $_[0]-1>name eq "goto"
  }

  # Use a simple optimizer with callbacks for each op
  use optimizer callback => sub { .. }

  # Completely implement your own optimizer
  use optimizer mine => sub { ... }

  # use the standard optimizer with an extra callback
  # this is the most compatible optimizer version
  use optimizer 'extend-c' => sub { print $_[0]->name() };

  # don't provide a peep optimizer, rather get a callback
  # after we are finished with every code block
  use optimizer 'sub-detect' => sub { print $_[0]->name() };

  no optimizer; # Use the simplest working optimizer

DESCRIPTION

This module allows you to replace the default Perl optree optimizer, peep, with a Perl function of your own devising.

It requires a Perl > 5.8 or patched with the plugpeep patch supplied with the module distribution; this patch allows the optimizer to be pluggable and replaceable with a C function pointer. This module provides the glue between the C function and a Perl subroutine. This patch was integrated as of perl 5.8.

Your optimizer subroutine will be handed a B::OP-derived object representing the first (NOT the root) op in the program. You are expected to be fluent with the B module to know what to do with this. You can use B::Generate to fiddle around with the optree you are given, while traversing it in execution order.

If you choose complete control over your optimizer, you must assign sequence numbers to operations. This can be done via the optimizer::op_seqmax_inc function, which supplies a new incremented sequence number. Do something like this:

    while ($$op) {
        $op->seq(optimizer::op_seqmax_inc);

        ... more optimizations ...

        $op = $op->next;
        last unless $op->can("next"); # Shouldn't get here
    }

The callback option to this module will essentially do the above, calling your given subroutine with each op.

If you just want to use this function to get a callback after every code block is compiled so you can do any arbitrary work on it use the sub-detect option, you will be passed LEAVE* ops after the standard peep optimizer has been run, this minimises the risk for bugs as we use the standard one. The op tree you are handed is also stable so you are free to work on it. This is useful if you are limited by CHECK and INIT blocks as this works with string eval and require aswell. Only one callback per package is allowed.

PERL_DL_NONLAZY and B::Generate

Note that optimizer do works fine on most platforms and perl versions, only on Windows some libperl functions are not exported anymore, which B::Generate needs.

OPTIONS

C

Use Perl's default optimizer.

  use optimizer 'C';

perl

Use a Perl implementation of Perl's default optimizer.

  use optimizer 'perl';

extend

Use an extension of the default optimizer. The callback is called for every visited op.

  use optimizer extend => sub {
        warn "goto considered harmful" if $_[0]->name eq "goto"
  }

callback

Use a simple optimizer with callbacks for each op.

  use optimizer callback => sub { .. }

mine

Completely implement your own optimizer. You have to provide your own walker and peep.

  use optimizer mine => sub { ... }

extend-c

Use the standard optimizer with an extra callback. This is the most compatible optimizer version.

  use optimizer 'extend-c' => sub { print $_[0]->name() };

sub-detect

Don't provide a peep optimizer, rather get a callback after we are finished with every code block (sub). You will be passed LEAVE* ops after the standard peep optimizer has been run, this minimises the risk for bugs as we use the standard one.

  use optimizer 'sub-detect' => sub { print $_[0]->name() };

HELPER FUNCTIONS

callbackoptimizer (this, callback)

The helper function for the option callback.

peepextend (this, callback)

The helper function for the option extend.

->import('perl') uses peepextend with an empty callback.

c_extend_install

The helper function for the option extend-c. It uses the longish XS function c_extend_peep as experimental peeper, and calls the user-side perl callback for each OP.

c_sub_detect_install

The XS helper function for the option sub-detect. It installs c_sub_detect as PL_peep. c_sub_detect calls all perl-side callbacks at any LEAVE op.

unimport

Override with an empty callbackoptimizer, effectively disabling any installed optimizer.

STATUS

relocatetopad fails with threaded perls.

5.10 Changes

Since Perl 5.10 there are no op_seqmax and op_seq numbers in CORE anymore, so we add a package global op_seqmax for the op-tree numbering, for $B::OP::seq also. This is not thread-safe.

AUTHOR

  Simon Cozens, C<simon@cpan.org>

Extended functionality:

  Artur Bergman, C<abergman@cpan.org>

5.10 support and current maintainer Reini Urban:

  Reini Urban, C<rurban@cpan.org>

SEE ALSO

B::Generate, optimize