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Use C++11 atomic_signal_fence for ClobberMemory (#1190)

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* Use C++11 atomic_signal_fence for ClobberMemory

* include

* Conditionally using std::atomic_signal_fence when C++11 is available
This commit is contained in:
Mircea Trofin 2021-06-28 09:03:26 -07:00 committed by GitHub
parent 38b767e58a
commit 40d2069d84
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1 changed files with 14 additions and 3 deletions
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17
include/benchmark/benchmark.h
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@ -187,6 +187,7 @@ BENCHMARK(BM_test)->Unit(benchmark::kMillisecond);
#include <vector>
#if defined(BENCHMARK_HAS_CXX11)
#include <atomic>
#include <initializer_list>
#include <type_traits>
#include <utility>
@ -327,6 +328,14 @@ BENCHMARK_UNUSED static int stream_init_anchor = InitializeStreams();
#define BENCHMARK_HAS_NO_INLINE_ASSEMBLY
#endif
// Force the compiler to flush pending writes to global memory. Acts as an
// effective read/write barrier
#ifdef BENCHMARK_HAS_CXX11
inline BENCHMARK_ALWAYS_INLINE void ClobberMemory() {
std::atomic_signal_fence(std::memory_order_acq_rel);
}
#endif
// The DoNotOptimize(...) function can be used to prevent a value or
// expression from being optimized away by the compiler. This function is
// intended to add little to no overhead.
@ -346,11 +355,11 @@ inline BENCHMARK_ALWAYS_INLINE void DoNotOptimize(Tp& value) {
#endif
}
// Force the compiler to flush pending writes to global memory. Acts as an
// effective read/write barrier
#ifndef BENCHMARK_HAS_CXX11
inline BENCHMARK_ALWAYS_INLINE void ClobberMemory() {
asm volatile("" : : : "memory");
}
#endif
#elif defined(_MSC_VER)
template <class Tp>
inline BENCHMARK_ALWAYS_INLINE void DoNotOptimize(Tp const& value) {
@ -358,13 +367,15 @@ inline BENCHMARK_ALWAYS_INLINE void DoNotOptimize(Tp const& value) {
_ReadWriteBarrier();
}
#ifndef BENCHMARK_HAS_CXX11
inline BENCHMARK_ALWAYS_INLINE void ClobberMemory() { _ReadWriteBarrier(); }
#endif
#else
template <class Tp>
inline BENCHMARK_ALWAYS_INLINE void DoNotOptimize(Tp const& value) {
internal::UseCharPointer(&reinterpret_cast<char const volatile&>(value));
}
// FIXME Add ClobberMemory() for non-gnu and non-msvc compilers
// FIXME Add ClobberMemory() for non-gnu and non-msvc compilers, before C++11.
#endif
// This class is used for user-defined counters.