add a compiler.h to libcutils. it's intended to define compiler-dependent macros.

currently, it defines CC_LIKELY and CC_UNLIKELY.

include/cutils/compiler.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2007 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#ifndef ANDROID_CUTILS_COMPILER_H
+#define ANDROID_CUTILS_COMPILER_H
+
+/*
+ * helps the compiler's optimizer predicting branches
+ */
+
+#ifdef __cplusplus
+#   define CC_LIKELY( exp )    (__builtin_expect( !!(exp), true ))
+#   define CC_UNLIKELY( exp )  (__builtin_expect( !!(exp), false ))
+#else
+#   define CC_LIKELY( exp )    (__builtin_expect( !!(exp), 1 ))
+#   define CC_UNLIKELY( exp )  (__builtin_expect( !!(exp), 0 ))
+#endif
+
+#endif // ANDROID_CUTILS_COMPILER_H