1 files changed, 142 insertions, 0 deletions
diff --git a/lib/B/Bblock.pm b/lib/B/Bblock.pm
new file mode 100644
index 0000000000..125c8a3c65
--- /dev/null
+++ b/lib/B/Bblock.pm
@@ -0,0 +1,142 @@
+package B::Bblock;
+use Exporter ();
+@ISA = "Exporter";
+@EXPORT_OK = qw(find_leaders);
+
+use B qw(peekop walkoptree walkoptree_exec
+	 main_root main_start svref_2object);
+use B::Terse;
+use strict;
+
+my $bblock;
+my @bblock_ends;
+
+sub mark_leader {
+    my $op = shift;
+    if ($$op) {
+	$bblock->{$$op} = $op;
+    }
+}
+
+sub find_leaders {
+    my ($root, $start) = @_;
+    $bblock = {};
+    mark_leader($start);
+    walkoptree($root, "mark_if_leader");
+    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 != $$lastop; $op = $op->next) {
+	    printf "    %s\n", peekop($op);
+	}
+	printf "    %s\n", peekop($lastop);
+    }
+    print "-------\n";
+    walkoptree_exec($start, "terse");
+}
+
+sub walk_bblocks_obj {
+    my $cvref = shift;
+    my $cv = svref_2object($cvref);
+    walk_bblocks($cv->ROOT, $cv->START);
+}
+
+sub B::OP::mark_if_leader {}
+
+sub B::COP::mark_if_leader {
+    my $op = shift;
+    if ($op->label) {
+	mark_leader($op);
+    }
+}
+
+sub B::LOOP::mark_if_leader {
+    my $op = shift;
+    mark_leader($op->next);
+    mark_leader($op->nextop);
+    mark_leader($op->redoop);
+    mark_leader($op->lastop->next);
+}
+
+sub B::LOGOP::mark_if_leader {
+    my $op = shift;
+    my $ppaddr = $op->ppaddr;
+    mark_leader($op->next);
+    if ($ppaddr eq "pp_entertry") {
+	mark_leader($op->other->next);
+    } else {
+	mark_leader($op->other);
+    }
+}
+
+sub B::CONDOP::mark_if_leader {
+    my $op = shift;
+    mark_leader($op->next);
+    mark_leader($op->true);
+    mark_leader($op->false);
+}
+
+sub B::PMOP::mark_if_leader {
+    my $op = shift;
+    if ($op->ppaddr ne "pp_pushre") {
+	my $replroot = $op->pmreplroot;
+	if ($$replroot) {
+	    mark_leader($replroot);
+	    mark_leader($op->next);
+	    mark_leader($op->pmreplstart);
+	}
+    }
+}
+
+# PMOP stuff omitted
+
+sub compile {
+    my @options = @_;
+    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 ops pointed at by op_true and op_false of a CONDOP
+#     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;