try to avoid floating point conversion and mult via (hopefully well p…

…redicted) branch
Swiftb0y · Aug 29, 2023 · f90452c · f90452c
1 parent 45653b4
commit f90452c
Showing 1 changed file with 8 additions and 4 deletions.
diff --git a/src/util/highresolution_monotonic_clock.cpp b/src/util/highresolution_monotonic_clock.cpp
@@ -61,7 +61,7 @@
 
 // mac/unix code heavily copied from QElapsedTimer
 
-#if false
+#if defined(Q_OS_MAC)
 
 static double multiplier = 0.0;
 static double getMultiplier() {
@@ -74,15 +74,19 @@ static double getMultiplier() {
 }
 
 static std::chrono::nanoseconds absoluteToNSecs(qint64 cpuTime) {
-    return std::chrono::nanoseconds(static_cast<double>(cpuTime) * getMultiplier());
+    double mult = getMultiplier();
+    if (mult == 1.0) [[likely]] {
+        return std::chrono::nanoseconds(cpuTime);
+    } else {
+        return std::chrono::nanoseconds(static_cast<double>(cpuTime) * mult);
+    }
 }
 
 auto HighResolutionMonotonicClockFallback::now() noexcept -> time_point {
     return time_point(absoluteToNSecs(mach_absolute_time()));
 }
 
-#elif defined(Q_OS_UNIX) || defined(Q_OS_MAC)
-
+#elif defined(Q_OS_UNIX)
 // #if (_POSIX_MONOTONIC_CLOCK - 0 != 0)
 // static std::atomic<bool> monotonicClockChecked = true;
 // static std::atomic<bool> monotonicClockAvailable = _POSIX_MONOTONIC_CLOCK > 0;