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-rw-r--r--src/common/x64/native_clock.cpp69
-rw-r--r--src/common/x64/native_clock.h7
2 files changed, 71 insertions, 5 deletions
diff --git a/src/common/x64/native_clock.cpp b/src/common/x64/native_clock.cpp
index eb8a7782f..e246432d0 100644
--- a/src/common/x64/native_clock.cpp
+++ b/src/common/x64/native_clock.cpp
@@ -2,12 +2,17 @@
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
+#include <array>
#include <chrono>
+#include <limits>
#include <mutex>
#include <thread>
#ifdef _MSC_VER
#include <intrin.h>
+
+#pragma intrinsic(__umulh)
+#pragma intrinsic(_udiv128)
#else
#include <x86intrin.h>
#endif
@@ -15,6 +20,55 @@
#include "common/uint128.h"
#include "common/x64/native_clock.h"
+namespace {
+
+[[nodiscard]] u64 GetFixedPoint64Factor(u64 numerator, u64 divisor) {
+#ifdef __SIZEOF_INT128__
+ const auto base = static_cast<unsigned __int128>(numerator) << 64ULL;
+ return static_cast<u64>(base / divisor);
+#elif defined(_M_X64) || defined(_M_ARM64)
+ std::array<u64, 2> r = {0, numerator};
+ u64 remainder;
+#if _MSC_VER < 1923
+ return udiv128(r[1], r[0], divisor, &remainder);
+#else
+ return _udiv128(r[1], r[0], divisor, &remainder);
+#endif
+#else
+ // This one is bit more inaccurate.
+ return MultiplyAndDivide64(std::numeric_limits<u64>::max(), numerator, divisor);
+#endif
+}
+
+[[nodiscard]] u64 MultiplyHigh(u64 a, u64 b) {
+#ifdef __SIZEOF_INT128__
+ return (static_cast<unsigned __int128>(a) * static_cast<unsigned __int128>(b)) >> 64;
+#elif defined(_M_X64) || defined(_M_ARM64)
+ return __umulh(a, b); // MSVC
+#else
+ // Generic fallback
+ const u64 a_lo = u32(a);
+ const u64 a_hi = a >> 32;
+ const u64 b_lo = u32(b);
+ const u64 b_hi = b >> 32;
+
+ const u64 a_x_b_hi = a_hi * b_hi;
+ const u64 a_x_b_mid = a_hi * b_lo;
+ const u64 b_x_a_mid = b_hi * a_lo;
+ const u64 a_x_b_lo = a_lo * b_lo;
+
+ const u64 carry_bit = (static_cast<u64>(static_cast<u32>(a_x_b_mid)) +
+ static_cast<u64>(static_cast<u32>(b_x_a_mid)) + (a_x_b_lo >> 32)) >>
+ 32;
+
+ const u64 multhi = a_x_b_hi + (a_x_b_mid >> 32) + (b_x_a_mid >> 32) + carry_bit;
+
+ return multhi;
+#endif
+}
+
+} // namespace
+
namespace Common {
u64 EstimateRDTSCFrequency() {
@@ -50,6 +104,11 @@ NativeClock::NativeClock(u64 emulated_cpu_frequency_, u64 emulated_clock_frequen
_mm_mfence();
last_measure = __rdtsc();
accumulated_ticks = 0U;
+ ns_rtsc_factor = GetFixedPoint64Factor(1000000000, rtsc_frequency);
+ us_rtsc_factor = GetFixedPoint64Factor(1000000, rtsc_frequency);
+ ms_rtsc_factor = GetFixedPoint64Factor(1000, rtsc_frequency);
+ clock_rtsc_factor = GetFixedPoint64Factor(emulated_clock_frequency, rtsc_frequency);
+ cpu_rtsc_factor = GetFixedPoint64Factor(emulated_cpu_frequency, rtsc_frequency);
}
u64 NativeClock::GetRTSC() {
@@ -75,27 +134,27 @@ void NativeClock::Pause(bool is_paused) {
std::chrono::nanoseconds NativeClock::GetTimeNS() {
const u64 rtsc_value = GetRTSC();
- return std::chrono::nanoseconds{MultiplyAndDivide64(rtsc_value, 1000000000, rtsc_frequency)};
+ return std::chrono::nanoseconds{MultiplyHigh(rtsc_value, ns_rtsc_factor)};
}
std::chrono::microseconds NativeClock::GetTimeUS() {
const u64 rtsc_value = GetRTSC();
- return std::chrono::microseconds{MultiplyAndDivide64(rtsc_value, 1000000, rtsc_frequency)};
+ return std::chrono::microseconds{MultiplyHigh(rtsc_value, us_rtsc_factor)};
}
std::chrono::milliseconds NativeClock::GetTimeMS() {
const u64 rtsc_value = GetRTSC();
- return std::chrono::milliseconds{MultiplyAndDivide64(rtsc_value, 1000, rtsc_frequency)};
+ return std::chrono::milliseconds{MultiplyHigh(rtsc_value, ms_rtsc_factor)};
}
u64 NativeClock::GetClockCycles() {
const u64 rtsc_value = GetRTSC();
- return MultiplyAndDivide64(rtsc_value, emulated_clock_frequency, rtsc_frequency);
+ return MultiplyHigh(rtsc_value, clock_rtsc_factor);
}
u64 NativeClock::GetCPUCycles() {
const u64 rtsc_value = GetRTSC();
- return MultiplyAndDivide64(rtsc_value, emulated_cpu_frequency, rtsc_frequency);
+ return MultiplyHigh(rtsc_value, cpu_rtsc_factor);
}
} // namespace X64
diff --git a/src/common/x64/native_clock.h b/src/common/x64/native_clock.h
index 6d1e32ac8..a7b1ee9e0 100644
--- a/src/common/x64/native_clock.h
+++ b/src/common/x64/native_clock.h
@@ -41,6 +41,13 @@ private:
u64 last_measure{};
u64 accumulated_ticks{};
u64 rtsc_frequency;
+
+ // factors
+ u64 ns_rtsc_factor{};
+ u64 us_rtsc_factor{};
+ u64 ms_rtsc_factor{};
+ u64 clock_rtsc_factor{};
+ u64 cpu_rtsc_factor{};
};
} // namespace X64