65 lines
1.7 KiB
C++
65 lines
1.7 KiB
C++
/*
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* Copyright 2016-present Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <folly/Portability.h>
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#include <chrono>
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#include <cstdint>
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#ifdef _MSC_VER
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#include <intrin.h>
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#endif
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namespace folly {
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inline void asm_volatile_memory() {
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#if defined(__clang__) || defined(__GNUC__)
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asm volatile("" : : : "memory");
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#elif defined(_MSC_VER)
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::_ReadWriteBarrier();
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#endif
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}
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inline void asm_volatile_pause() {
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#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
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::_mm_pause();
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#elif defined(__i386__) || FOLLY_X64
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asm volatile("pause");
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#elif FOLLY_AARCH64 || defined(__arm__)
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asm volatile("yield");
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#elif FOLLY_PPC64
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asm volatile("or 27,27,27");
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#endif
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}
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inline std::uint64_t asm_rdtsc() {
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#if _MSC_VER
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return (uint64_t)__rdtsc();
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#elif defined(__i386__) || FOLLY_X64
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// read the timestamp counter on x86
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auto hi = std::uint32_t{};
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auto lo = std::uint32_t{};
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asm volatile("rdtsc" : "=a"(lo), "=d"(hi));
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return (((std::uint64_t)lo) + (((std::uint64_t)hi) << 32));
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#else
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// use steady_clock::now() as an approximation for the timestamp counter on
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// non-x86 systems
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return std::chrono::steady_clock::now().time_since_epoch().count();
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#endif
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}
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} // namespace folly
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