// Copyright 2017 The Abseil Authors. // // 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 // // https://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. // The implementation of CycleClock::Frequency. // // NOTE: only i386 and x86_64 have been well tested. // PPC, sparc, alpha, and ia64 are based on // http://peter.kuscsik.com/wordpress/?p=14 // with modifications by m3b. See also // https://setisvn.ssl.berkeley.edu/svn/lib/fftw-3.0.1/kernel/cycle.h #include "absl/base/internal/cycleclock.h" #include #include // NOLINT(build/c++11) #include "absl/base/attributes.h" #include "absl/base/internal/unscaledcycleclock.h" namespace absl { ABSL_NAMESPACE_BEGIN namespace base_internal { #if ABSL_USE_UNSCALED_CYCLECLOCK constexpr int32_t CycleClock::kShift; constexpr double CycleClock::kFrequencyScale; ABSL_CONST_INIT std::atomic CycleClock::cycle_clock_source_{nullptr}; void CycleClockSource::Register(CycleClockSourceFunc source) { // Corresponds to the load(std::memory_order_acquire) in LoadCycleClockSource. CycleClock::cycle_clock_source_.store(source, std::memory_order_release); } #ifdef _WIN32 int64_t CycleClock::Now() { auto fn = LoadCycleClockSource(); if (fn == nullptr) { return base_internal::UnscaledCycleClock::Now() >> kShift; } return fn() >> kShift; } #endif #else int64_t CycleClock::Now() { return std::chrono::duration_cast( std::chrono::steady_clock::now().time_since_epoch()) .count(); } double CycleClock::Frequency() { return 1e9; } #endif } // namespace base_internal ABSL_NAMESPACE_END } // namespace absl