Merge pull request #7809 from Morph1984/clock-constants

common: wall_clock: Utilize constants for ms, us, and ns ratios

src/common/wall_clock.cpp

@@ -65,16 +65,20 @@ private:
 
 #ifdef ARCHITECTURE_x86_64
 
-std::unique_ptr<WallClock> CreateBestMatchingClock(u32 emulated_cpu_frequency,
-                                                   u32 emulated_clock_frequency) {
+std::unique_ptr<WallClock> CreateBestMatchingClock(u64 emulated_cpu_frequency,
+                                                   u64 emulated_clock_frequency) {
     const auto& caps = GetCPUCaps();
     u64 rtsc_frequency = 0;
     if (caps.invariant_tsc) {
         rtsc_frequency = EstimateRDTSCFrequency();
     }
 
-    // Fallback to StandardWallClock if rtsc period is higher than a nano second
-    if (rtsc_frequency <= 1000000000) {
+    // Fallback to StandardWallClock if the hardware TSC does not have the precision greater than:
+    // - A nanosecond
+    // - The emulated CPU frequency
+    // - The emulated clock counter frequency (CNTFRQ)
+    if (rtsc_frequency <= WallClock::NS_RATIO || rtsc_frequency <= emulated_cpu_frequency ||
+        rtsc_frequency <= emulated_clock_frequency) {
         return std::make_unique<StandardWallClock>(emulated_cpu_frequency,
                                                    emulated_clock_frequency);
     } else {
@@ -85,8 +89,8 @@ std::unique_ptr<WallClock> CreateBestMatchingClock(u32 emulated_cpu_frequency,
 
 #else
 
-std::unique_ptr<WallClock> CreateBestMatchingClock(u32 emulated_cpu_frequency,
-                                                   u32 emulated_clock_frequency) {
+std::unique_ptr<WallClock> CreateBestMatchingClock(u64 emulated_cpu_frequency,
+                                                   u64 emulated_clock_frequency) {
     return std::make_unique<StandardWallClock>(emulated_cpu_frequency, emulated_clock_frequency);
 }
 

src/common/wall_clock.h

@@ -13,6 +13,10 @@ namespace Common {
 
 class WallClock {
 public:
+    static constexpr u64 NS_RATIO = 1'000'000'000;
+    static constexpr u64 US_RATIO = 1'000'000;
+    static constexpr u64 MS_RATIO = 1'000;
+
     virtual ~WallClock() = default;
 
     /// Returns current wall time in nanoseconds
@@ -49,7 +53,7 @@ private:
     bool is_native;
 };
 
-[[nodiscard]] std::unique_ptr<WallClock> CreateBestMatchingClock(u32 emulated_cpu_frequency,
-                                                                 u32 emulated_clock_frequency);
+[[nodiscard]] std::unique_ptr<WallClock> CreateBestMatchingClock(u64 emulated_cpu_frequency,
+                                                                 u64 emulated_clock_frequency);
 
 } // namespace Common

src/common/x64/native_clock.cpp

@@ -47,9 +47,9 @@ NativeClock::NativeClock(u64 emulated_cpu_frequency_, u64 emulated_clock_frequen
     _mm_mfence();
     time_point.inner.last_measure = __rdtsc();
     time_point.inner.accumulated_ticks = 0U;
-    ns_rtsc_factor = GetFixedPoint64Factor(1000000000, rtsc_frequency);
-    us_rtsc_factor = GetFixedPoint64Factor(1000000, rtsc_frequency);
-    ms_rtsc_factor = GetFixedPoint64Factor(1000, rtsc_frequency);
+    ns_rtsc_factor = GetFixedPoint64Factor(NS_RATIO, rtsc_frequency);
+    us_rtsc_factor = GetFixedPoint64Factor(US_RATIO, rtsc_frequency);
+    ms_rtsc_factor = GetFixedPoint64Factor(MS_RATIO, rtsc_frequency);
     clock_rtsc_factor = GetFixedPoint64Factor(emulated_clock_frequency, rtsc_frequency);
     cpu_rtsc_factor = GetFixedPoint64Factor(emulated_cpu_frequency, rtsc_frequency);
 }