package B::Bblock; our $VERSION = '1.00'; use Exporter (); @ISA = "Exporter"; @EXPORT_OK = qw(find_leaders); use B qw(peekop walkoptree walkoptree_exec main_root main_start svref_2object OPf_SPECIAL OPf_STACKED ); use B::Terse; use strict; my $bblock; my @bblock_ends; sub mark_leader { my $op = shift; if ($$op) { $bblock->{$$op} = $op; } } sub remove_sortblock{ foreach (keys %$bblock){ my $leader=$$bblock{$_}; delete $$bblock{$_} if( $leader == 0); } } sub find_leaders { my ($root, $start) = @_; $bblock = {}; mark_leader($start) if ( ref $start ne "B::NULL" ); walkoptree($root, "mark_if_leader") if ((ref $root) ne "B::NULL") ; remove_sortblock(); return $bblock; } # Debugging sub walk_bblocks { my ($root, $start) = @_; my ($op, $lastop, $leader, $bb); $bblock = {}; mark_leader($start); walkoptree($root, "mark_if_leader"); my @leaders = values %$bblock; while ($leader = shift @leaders) { $lastop = $leader; $op = $leader->next; while ($$op && !exists($bblock->{$$op})) { $bblock->{$$op} = $leader; $lastop = $op; $op = $op->next; } push(@bblock_ends, [$leader, $lastop]); } foreach $bb (@bblock_ends) { ($leader, $lastop) = @$bb; printf "%s .. %s\n", peekop($leader), peekop($lastop); for ($op = $leader; $$op != $$lastop; $op = $op->next) { printf " %s\n", peekop($op); } printf " %s\n", peekop($lastop); } print "-------\n"; walkoptree_exec($start, "terse"); } sub walk_bblocks_obj { my $cvref = shift; my $cv = svref_2object($cvref); walk_bblocks($cv->ROOT, $cv->START); } sub B::OP::mark_if_leader {} sub B::COP::mark_if_leader { my $op = shift; if ($op->label) { mark_leader($op); } } sub B::LOOP::mark_if_leader { my $op = shift; mark_leader($op->next); mark_leader($op->nextop); mark_leader($op->redoop); mark_leader($op->lastop->next); } sub B::LOGOP::mark_if_leader { my $op = shift; my $opname = $op->name; mark_leader($op->next); if ($opname eq "entertry") { mark_leader($op->other->next); } else { mark_leader($op->other); } } sub B::LISTOP::mark_if_leader { my $op = shift; my $first=$op->first; $first=$first->next while ($first->name eq "null"); mark_leader($op->first) unless (exists( $bblock->{$$first})); mark_leader($op->next); if ($op->name eq "sort" and $op->flags & OPf_SPECIAL and $op->flags & OPf_STACKED){ my $root=$op->first->sibling->first; my $leader=$root->first; $bblock->{$$leader} = 0; } } sub B::PMOP::mark_if_leader { my $op = shift; if ($op->name ne "pushre") { my $replroot = $op->pmreplroot; if ($$replroot) { mark_leader($replroot); mark_leader($op->next); mark_leader($op->pmreplstart); } } } # PMOP stuff omitted sub compile { my @options = @_; B::clearsym(); if (@options) { return sub { my $objname; foreach $objname (@options) { $objname = "main::$objname" unless $objname =~ /::/; eval "walk_bblocks_obj(\\&$objname)"; die "walk_bblocks_obj(\\&$objname) failed: $@" if $@; } } } else { return sub { walk_bblocks(main_root, main_start) }; } } # Basic block leaders: # Any COP (pp_nextstate) with a non-NULL label # [The op after a pp_enter] Omit # [The op after a pp_entersub. Don't count this one.] # The ops pointed at by nextop, redoop and lastop->op_next of a LOOP # The ops pointed at by op_next and op_other of a LOGOP, except # for pp_entertry which has op_next and op_other->op_next # The op pointed at by op_pmreplstart of a PMOP # The op pointed at by op_other->op_pmreplstart of pp_substcont? # [The op after a pp_return] Omit 1; __END__ =head1 NAME B::Bblock - Walk basic blocks =head1 SYNOPSIS # External interface perl -MO=Bblock[,OPTIONS] foo.pl # Programmatic API use B::Bblock qw(find_leaders); my $leaders = find_leaders($root_op, $start_op); =head1 DESCRIPTION This module is used by the B::CC back end. It walks "basic blocks". A basic block is a series of operations which is known to execute from start to finish, with no possiblity of branching or halting. It can be used either stand alone or from inside another program. =for _private Somebody who understands the stand-alone options document them, please. =head2 Functions =over 4 =item B my $leaders = find_leaders($root_op, $start_op); Given the root of the op tree and an op from which to start processing, it will return a hash ref representing all the ops which start a block. =for _private The above description may be somewhat wrong. The values of %$leaders are the op objects themselves. Keys are $$op addresses. =for _private Above cribbed from B::CC's comments. What's a $$op address? =back =head1 AUTHOR Malcolm Beattie, C =cut