annotation: add likely/unlikely functions

Makefile.am

@@ -32,6 +32,7 @@ UTIL_FILES   =			\
     alloc/null.hpp		\
     alloc/stack.cpp		\
     alloc/stack.hpp		\
+    annotation.hpp		\
     ascii.hpp			\
     backtrace.hpp   		\
     bezier.cpp			\

annotation.hpp

@@ -0,0 +1,33 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2011 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_ANNOTATION_HPP
+#define __UTIL_ANNOTATION_HPP
+
+template <typename T>
+constexpr inline
+bool
+likely (T &&t)
+{ return __builtin_expect (!!t, true); }
+
+
+template <typename T>
+constexpr inline
+bool
+unlikely (T &&t)
+{ return __builtin_expect (!!t, false); }
+
+#endif