checkasm: Improve seed generation on Windows

GetTickCount() increases at a very low frequency, >10ms per tick.
When running multiple loops of checkasm instances in parallel
different instances regularly ends up using identical seeds.

Prefer the use of QueryPerformanceCounter() instead, which ticks at
a significantly higher rate, which in turn increases randomness.

1 files changed, 14 insertions, 14 deletions

diff --git a/tests/checkasm/checkasm.c b/tests/checkasm/checkasm.c
index e0aebaf..787ecbf 100644
--- a/tests/checkasm/checkasm.c
+++ b/tests/checkasm/checkasm.c
@@ -38,10 +38,6 @@
 #define COLOR_RED    FOREGROUND_RED
 #define COLOR_GREEN  FOREGROUND_GREEN
 #define COLOR_YELLOW (FOREGROUND_RED|FOREGROUND_GREEN)
-
-static unsigned get_seed(void) {
-    return GetTickCount();
-}
 #else
 #include <unistd.h>
 #include <signal.h>
@@ -52,16 +48,6 @@ static unsigned get_seed(void) {
 #define COLOR_RED    1
 #define COLOR_GREEN  2
 #define COLOR_YELLOW 3
-
-static unsigned get_seed(void) {
-#ifdef __APPLE__
-    return (unsigned) mach_absolute_time();
-#elif defined(HAVE_CLOCK_GETTIME)
-    struct timespec ts;
-    clock_gettime(CLOCK_MONOTONIC, &ts);
-    return (unsigned) (1000000000ULL * ts.tv_sec + ts.tv_nsec);
-#endif
-}
 #endif
 
 /* List of tests to invoke */
@@ -521,6 +507,20 @@ static void print_cpu_name(void) {
     }
 }
 
+static unsigned get_seed(void) {
+#ifdef _WIN32
+    LARGE_INTEGER i;
+    QueryPerformanceCounter(&i);
+    return i.LowPart;
+#elif defined(__APPLE__)
+    return (unsigned) mach_absolute_time();
+#else
+    struct timespec ts;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+    return (unsigned) (1000000000ULL * ts.tv_sec + ts.tv_nsec);
+#endif
+}
+
 int main(int argc, char *argv[]) {
     state.seed = get_seed();