2 * Copyright 2015 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 #ifndef FOLLY_BASE_ASSUME_H_
18 #define FOLLY_BASE_ASSUME_H_
20 #include <folly/Portability.h>
21 #include <glog/logging.h>
26 * Inform the compiler that the argument can be assumed true. It is
27 * undefined behavior if the argument is not actually true, so use
30 * Implemented as a function instead of a macro because
31 * __builtin_assume does not evaluate its argument at runtime, so it
32 * cannot be used with expressions that have side-effects.
35 FOLLY_ALWAYS_INLINE void assume(bool cond) {
38 #elif defined(__clang__) // Must go first because Clang also defines __GNUC__.
39 __builtin_assume(cond);
40 #elif defined(__GNUC__)
41 if (!cond) { __builtin_unreachable(); }