core: core_timing_util: Optimize core timing math.

- Avoids a lot of unnecessary 128-bit math for imperceptible accuracy.

3 files changed, 48 insertions, 98 deletions

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 28196d26a..c6bdf72ec 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -19,7 +19,6 @@ add_library(core STATIC
     core.h
     core_timing.cpp
     core_timing.h
-    core_timing_util.cpp
     core_timing_util.h
     cpu_manager.cpp
     cpu_manager.h
diff --git a/src/core/core_timing_util.cpp b/src/core/core_timing_util.cpp
deleted file mode 100644
index 8ce8e602e..000000000
--- a/src/core/core_timing_util.cpp
+++ /dev/null
@@ -1,84 +0,0 @@
-// Copyright 2008 Dolphin Emulator Project / 2017 Citra Emulator Project
-// Licensed under GPLv2+
-// Refer to the license.txt file included.
-
-#include "core/core_timing_util.h"
-
-#include <cinttypes>
-#include <limits>
-#include "common/logging/log.h"
-#include "common/uint128.h"
-#include "core/hardware_properties.h"
-
-namespace Core::Timing {
-
-constexpr u64 MAX_VALUE_TO_MULTIPLY = std::numeric_limits<s64>::max() / Hardware::BASE_CLOCK_RATE;
-
-s64 msToCycles(std::chrono::milliseconds ms) {
-    if (static_cast<u64>(ms.count() / 1000) > MAX_VALUE_TO_MULTIPLY) {
-        LOG_ERROR(Core_Timing, "Integer overflow, use max value");
-        return std::numeric_limits<s64>::max();
-    }
-    if (static_cast<u64>(ms.count()) > MAX_VALUE_TO_MULTIPLY) {
-        LOG_DEBUG(Core_Timing, "Time very big, do rounding");
-        return Hardware::BASE_CLOCK_RATE * (ms.count() / 1000);
-    }
-    return (Hardware::BASE_CLOCK_RATE * ms.count()) / 1000;
-}
-
-s64 usToCycles(std::chrono::microseconds us) {
-    if (static_cast<u64>(us.count() / 1000000) > MAX_VALUE_TO_MULTIPLY) {
-        LOG_ERROR(Core_Timing, "Integer overflow, use max value");
-        return std::numeric_limits<s64>::max();
-    }
-    if (static_cast<u64>(us.count()) > MAX_VALUE_TO_MULTIPLY) {
-        LOG_DEBUG(Core_Timing, "Time very big, do rounding");
-        return Hardware::BASE_CLOCK_RATE * (us.count() / 1000000);
-    }
-    return (Hardware::BASE_CLOCK_RATE * us.count()) / 1000000;
-}
-
-s64 nsToCycles(std::chrono::nanoseconds ns) {
-    const u128 temporal = Common::Multiply64Into128(ns.count(), Hardware::BASE_CLOCK_RATE);
-    return Common::Divide128On32(temporal, static_cast<u32>(1000000000)).first;
-}
-
-u64 msToClockCycles(std::chrono::milliseconds ns) {
-    const u128 temp = Common::Multiply64Into128(ns.count(), Hardware::CNTFREQ);
-    return Common::Divide128On32(temp, 1000).first;
-}
-
-u64 usToClockCycles(std::chrono::microseconds ns) {
-    const u128 temp = Common::Multiply64Into128(ns.count(), Hardware::CNTFREQ);
-    return Common::Divide128On32(temp, 1000000).first;
-}
-
-u64 nsToClockCycles(std::chrono::nanoseconds ns) {
-    const u128 temp = Common::Multiply64Into128(ns.count(), Hardware::CNTFREQ);
-    return Common::Divide128On32(temp, 1000000000).first;
-}
-
-u64 CpuCyclesToClockCycles(u64 ticks) {
-    const u128 temporal = Common::Multiply64Into128(ticks, Hardware::CNTFREQ);
-    return Common::Divide128On32(temporal, static_cast<u32>(Hardware::BASE_CLOCK_RATE)).first;
-}
-
-std::chrono::milliseconds CyclesToMs(s64 cycles) {
-    const u128 temporal = Common::Multiply64Into128(cycles, 1000);
-    u64 ms = Common::Divide128On32(temporal, static_cast<u32>(Hardware::BASE_CLOCK_RATE)).first;
-    return std::chrono::milliseconds(ms);
-}
-
-std::chrono::nanoseconds CyclesToNs(s64 cycles) {
-    const u128 temporal = Common::Multiply64Into128(cycles, 1000000000);
-    u64 ns = Common::Divide128On32(temporal, static_cast<u32>(Hardware::BASE_CLOCK_RATE)).first;
-    return std::chrono::nanoseconds(ns);
-}
-
-std::chrono::microseconds CyclesToUs(s64 cycles) {
-    const u128 temporal = Common::Multiply64Into128(cycles, 1000000);
-    u64 us = Common::Divide128On32(temporal, static_cast<u32>(Hardware::BASE_CLOCK_RATE)).first;
-    return std::chrono::microseconds(us);
-}
-
-} // namespace Core::Timing
diff --git a/src/core/core_timing_util.h b/src/core/core_timing_util.h
index e4a046bf9..14c36a485 100644
--- a/src/core/core_timing_util.h
+++ b/src/core/core_timing_util.h
@@ -1,24 +1,59 @@
-// Copyright 2008 Dolphin Emulator Project / 2017 Citra Emulator Project
-// Licensed under GPLv2+
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
 #pragma once
 
 #include <chrono>
+
 #include "common/common_types.h"
+#include "core/hardware_properties.h"
 
 namespace Core::Timing {
 
-s64 msToCycles(std::chrono::milliseconds ms);
-s64 usToCycles(std::chrono::microseconds us);
-s64 nsToCycles(std::chrono::nanoseconds ns);
-u64 msToClockCycles(std::chrono::milliseconds ns);
-u64 usToClockCycles(std::chrono::microseconds ns);
-u64 nsToClockCycles(std::chrono::nanoseconds ns);
-std::chrono::milliseconds CyclesToMs(s64 cycles);
-std::chrono::nanoseconds CyclesToNs(s64 cycles);
-std::chrono::microseconds CyclesToUs(s64 cycles);
-
-u64 CpuCyclesToClockCycles(u64 ticks);
+namespace detail {
+constexpr u64 CNTFREQ_ADJUSTED = Hardware::CNTFREQ / 1000;
+constexpr u64 BASE_CLOCK_RATE_ADJUSTED = Hardware::BASE_CLOCK_RATE / 1000;
+} // namespace detail
+
+[[nodiscard]] constexpr s64 msToCycles(std::chrono::milliseconds ms) {
+    return ms.count() * detail::BASE_CLOCK_RATE_ADJUSTED;
+}
+
+[[nodiscard]] constexpr s64 usToCycles(std::chrono::microseconds us) {
+    return us.count() * detail::BASE_CLOCK_RATE_ADJUSTED / 1000;
+}
+
+[[nodiscard]] constexpr s64 nsToCycles(std::chrono::nanoseconds ns) {
+    return ns.count() * detail::BASE_CLOCK_RATE_ADJUSTED / 1000000;
+}
+
+[[nodiscard]] constexpr u64 msToClockCycles(std::chrono::milliseconds ms) {
+    return static_cast<u64>(ms.count()) * detail::CNTFREQ_ADJUSTED;
+}
+
+[[nodiscard]] constexpr u64 usToClockCycles(std::chrono::microseconds us) {
+    return us.count() * detail::CNTFREQ_ADJUSTED / 1000;
+}
+
+[[nodiscard]] constexpr u64 nsToClockCycles(std::chrono::nanoseconds ns) {
+    return ns.count() * detail::CNTFREQ_ADJUSTED / 1000000;
+}
+
+[[nodiscard]] constexpr u64 CpuCyclesToClockCycles(u64 ticks) {
+    return ticks * detail::CNTFREQ_ADJUSTED / detail::BASE_CLOCK_RATE_ADJUSTED;
+}
+
+[[nodiscard]] constexpr std::chrono::milliseconds CyclesToMs(s64 cycles) {
+    return std::chrono::milliseconds(cycles / detail::BASE_CLOCK_RATE_ADJUSTED);
+}
+
+[[nodiscard]] constexpr std::chrono::nanoseconds CyclesToNs(s64 cycles) {
+    return std::chrono::nanoseconds(cycles * 1000000 / detail::BASE_CLOCK_RATE_ADJUSTED);
+}
+
+[[nodiscard]] constexpr std::chrono::microseconds CyclesToUs(s64 cycles) {
+    return std::chrono::microseconds(cycles * 1000 / detail::BASE_CLOCK_RATE_ADJUSTED);
+}
 
 } // namespace Core::Timing