Optimise mro_get_linear_isa_c3() when there is a single parent. 40% speed up.

Idea blatantly copied from chromatic's analogous change to parrot, r38477.

1 files changed, 69 insertions, 0 deletions

diff --git a/t/mro/isa_c3.t b/t/mro/isa_c3.t
new file mode 100644
index 0000000000..713d10ef3a
--- /dev/null
+++ b/t/mro/isa_c3.t
@@ -0,0 +1,69 @@
+#!perl -w
+
+BEGIN {
+    chdir 't' if -d 't';
+    @INC = '../lib';
+    require "./test.pl";
+}
+
+use strict;
+
+plan 'no_plan';
+
+# package klonk doesn't have a stash.
+
+package kapow;
+use mro 'c3';
+
+# No parents
+
+package urkkk;
+use mro 'c3';
+
+# 1 parent
+@urkkk::ISA = 'klonk';
+
+package kayo;
+use mro 'c3';
+
+# 2 parents
+@urkkk::ISA = ('klonk', 'kapow');
+
+package thwacke;
+use mro 'c3';
+
+# No parents, has @ISA
+@thwacke::ISA = ();
+
+package zzzzzwap;
+use mro 'c3';
+
+@zzzzzwap::ISA = ('thwacke', 'kapow');
+
+package whamm;
+use mro 'c3';
+
+@whamm::ISA = ('kapow', 'thwacke');
+
+package main;
+
+my %expect =
+    (
+     klonk => [qw(klonk)],
+     urkkk => [qw(urkkk klonk kapow)],
+     kapow => [qw(kapow)],
+     kayo => [qw(kayo)],
+     thwacke => [qw(thwacke)],
+     zzzzzwap => [qw(zzzzzwap thwacke kapow)],
+     whamm => [qw(whamm kapow thwacke)],
+    );
+
+foreach my $package (qw(klonk urkkk kapow kayo thwacke zzzzzwap whamm)) {
+    my $ref = bless [], $package;
+    my $isa = $expect{$package};
+    is("@{mro::get_linear_isa($package)}", "@$isa", "\@ISA for $package");
+
+    foreach my $class ($package, @$isa, 'UNIVERSAL') {
+	isa_ok($ref, $class, $package);
+    }
+}