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BenchmarkUtil.h
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BenchmarkUtil.h
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/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* 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.
*/
#pragma once
#include <folly/Portability.h>
#include <folly/lang/Hint.h>
namespace folly {
/**
* Call doNotOptimizeAway(var) to ensure that var will be computed even
* post-optimization. Use it for variables that are computed during
* benchmarking but otherwise are useless. The compiler tends to do a
* good job at eliminating unused variables, and this function fools it
* into thinking var is in fact needed.
*
* Call makeUnpredictable(var) when you don't want the optimizer to use
* its knowledge of var to shape the following code. This is useful
* when constant propagation or power reduction is possible during your
* benchmark but not in real use cases.
*/
template <class T>
FOLLY_ALWAYS_INLINE void doNotOptimizeAway(const T& datum) {
compiler_must_not_elide(datum);
}
template <typename T>
FOLLY_ALWAYS_INLINE void makeUnpredictable(T& datum) {
compiler_must_not_predict(datum);
}
} // namespace folly