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-rw-r--r--EmulatorPkg/Unix/Host/EmuThunk.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/EmulatorPkg/Unix/Host/EmuThunk.c b/EmulatorPkg/Unix/Host/EmuThunk.c
index 52875c3bce..a7b12b14e5 100644
--- a/EmulatorPkg/Unix/Host/EmuThunk.c
+++ b/EmulatorPkg/Unix/Host/EmuThunk.c
@@ -259,18 +259,26 @@ QueryPerformanceCounter (
{
#if __APPLE__
UINT64 Start;
- Nanoseconds elapsedNano;
+ static mach_timebase_info_data_t sTimebaseInfo;
+
Start = mach_absolute_time ();
// Convert to nanoseconds.
- // Have to do some pointer fun because AbsoluteToNanoseconds
- // works in terms of UnsignedWide, which is a structure rather
- // than a proper 64-bit integer.
- elapsedNano = AbsoluteToNanoseconds (*(AbsoluteTime *) &Start);
+ // If this is the first time we've run, get the timebase.
+ // We can use denom == 0 to indicate that sTimebaseInfo is
+ // uninitialised because it makes no sense to have a zero
+ // denominator is a fraction.
+
+ if ( sTimebaseInfo.denom == 0 ) {
+ (void) mach_timebase_info(&sTimebaseInfo);
+ }
+
+ // Do the maths. We hope that the multiplication doesn't
+ // overflow; the price you pay for working in fixed point.
- return *(uint64_t *) &elapsedNano;
+ return (Start * sTimebaseInfo.numer) / sTimebaseInfo.denom;
#else
// Need to figure out what to do for Linux?
return 0;