diff -r 000000000000 -r 6474c204b198 mfbt/Likely.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mfbt/Likely.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,23 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * MOZ_LIKELY and MOZ_UNLIKELY macros to hint to the compiler how a
+ * boolean predicate should be branch-predicted.
+ */
+
+#ifndef mozilla_Likely_h
+#define mozilla_Likely_h
+
+#if defined(__clang__) || defined(__GNUC__)
+#  define MOZ_LIKELY(x)   (__builtin_expect(!!(x), 1))
+#  define MOZ_UNLIKELY(x) (__builtin_expect(!!(x), 0))
+#else
+#  define MOZ_LIKELY(x)   (!!(x))
+#  define MOZ_UNLIKELY(x) (!!(x))
+#endif
+
+#endif /* mozilla_Likely_h */