cli: Avoid large intermediates in the windows get_time_nanos

By multiplicating the performance counter value (within its own
time base) by the intended target time base, and only then dividing,
we reduce the available numeric range by the factor of the
original time base times the new time base.

On Windows 10 on ARM64, the performance counter frequency is
19200000 (on x86_64 in a virtual machine, it's 10000000), making
the calculation overflow every (1 << 64) / (19200000 * 1000000000)
= 960 seconds, i.e. 16 minutes - long before the actual uint64_t
nanosecond return value wraps around.

1 files changed, 3 insertions, 1 deletions

diff --git a/tools/dav1d.c b/tools/dav1d.c
index 129375a..4b97a9f 100644
--- a/tools/dav1d.c
+++ b/tools/dav1d.c
@@ -63,7 +63,9 @@ static uint64_t get_time_nanos(void) {
     QueryPerformanceFrequency(&frequency);
     LARGE_INTEGER t;
     QueryPerformanceCounter(&t);
-    return 1000000000 * t.QuadPart / frequency.QuadPart;
+    uint64_t seconds = t.QuadPart / frequency.QuadPart;
+    uint64_t fractions = t.QuadPart % frequency.QuadPart;
+    return 1000000000 * seconds + 1000000000 * fractions / frequency.QuadPart;
 #elif defined(HAVE_CLOCK_GETTIME)
     struct timespec ts;
     clock_gettime(CLOCK_MONOTONIC, &ts);