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

/*

 * 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