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src/common/x64/rdtsc.cpp
39 строк
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Morph
x64: Deduplicate RDTSC usage
08 июн 2023, 04:44
08 июн 2023, 04:44
dd12dd4
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// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project // SPDX-License-Identifier: GPL-2.0-or-later #include <thread> #include "common/steady_clock.h" #include "common/uint128.h" #include "common/x64/rdtsc.h" namespace Common::X64 { template <u64 Nearest> static u64 RoundToNearest(u64 value) { const auto mod = value % Nearest; return mod >= (Nearest / 2) ? (value - mod + Nearest) : (value - mod); } u64 EstimateRDTSCFrequency() { // Discard the first result measuring the rdtsc. FencedRDTSC(); std::this_thread::sleep_for(std::chrono::milliseconds{1}); FencedRDTSC(); // Get the current time. const auto start_time = RealTimeClock::Now(); const u64 tsc_start = FencedRDTSC(); // Wait for 100 milliseconds. std::this_thread::sleep_for(std::chrono::milliseconds{100}); const auto end_time = RealTimeClock::Now(); const u64 tsc_end = FencedRDTSC(); // Calculate differences. const u64 timer_diff = static_cast<u64>( std::chrono::duration_cast<std::chrono::nanoseconds>(end_time - start_time).count()); const u64 tsc_diff = tsc_end - tsc_start; const u64 tsc_freq = MultiplyAndDivide64(tsc_diff, 1000000000ULL, timer_diff); return RoundToNearest<100'000>(tsc_freq); } } // namespace Common::X64