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 optimizre
  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 patched with the 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. It is hoped that the patch will be integrated into the Perl core at some point soon. This patch is 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 usefull 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.

AUTHOR

Simon Cozens, simon@cpan.org

Extended functionality and current maintainer.

Arthur Bergman, abergman@cpan.org

SEE ALSO

B::Generate, optimize