win, util: rearrange uv_hrtime

Rearrange math operations in uv_hrtime. This is a workaround for a
probable compiler bug in VS2019.

Fixes: #1633

PR-URL: #2866
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

Author: bzoz

src/win/internal.h

@@ -266,7 +266,7 @@ void uv__fs_poll_endgame(uv_loop_t* loop, uv_fs_poll_t* handle);
  */
 void uv__util_init(void);
 
-uint64_t uv__hrtime(double scale);
+uint64_t uv__hrtime(unsigned int scale);
 __declspec(noreturn) void uv_fatal_error(const int errorno, const char* syscall);
 int uv__getpwuid_r(uv_passwd_t* pwd);
 int uv__convert_utf16_to_utf8(const WCHAR* utf16, int utf16len, char** utf8);

src/win/util.c

@@ -67,8 +67,8 @@ extern BOOLEAN NTAPI SystemFunction036(PVOID Buffer, ULONG BufferLength);
 static char *process_title;
 static CRITICAL_SECTION process_title_lock;
 
-/* Interval (in seconds) of the high-resolution clock. */
-static double hrtime_interval_ = 0;
+/* Frequency of the high-resolution clock. */
+static uint64_t hrtime_frequency_ = 0;
 
 
 /*
@@ -84,9 +84,9 @@ void uv__util_init(void) {
    * and precompute its reciprocal.
    */
   if (QueryPerformanceFrequency(&perf_frequency)) {
-    hrtime_interval_ = 1.0 / perf_frequency.QuadPart;
+    hrtime_frequency_ = perf_frequency.QuadPart;
   } else {
-    hrtime_interval_= 0;
+    uv_fatal_error(GetLastError(), "QueryPerformanceFrequency");
   }
 }
 
@@ -490,23 +490,23 @@ uint64_t uv_hrtime(void) {
   return uv__hrtime(UV__NANOSEC);
 }
 
-uint64_t uv__hrtime(double scale) {
+uint64_t uv__hrtime(unsigned int scale) {
   LARGE_INTEGER counter;
 
-  /* If the performance interval is zero, there's no support. */
-  if (hrtime_interval_ == 0) {
-    return 0;
-  }
-
+  assert(hrtime_frequency_ != 0);
+  assert(scale != 0);
   if (!QueryPerformanceCounter(&counter)) {
-    return 0;
+    uv_fatal_error(GetLastError(), "QueryPerformanceCounter");
   }
+  assert(counter.QuadPart != 0);
 
   /* Because we have no guarantee about the order of magnitude of the
    * performance counter interval, integer math could cause this computation
    * to overflow. Therefore we resort to floating point math.
    */
-  return (uint64_t) ((double) counter.QuadPart * hrtime_interval_ * scale);
+  double scaled_freq = (double)hrtime_frequency_ / scale;
+  double result = (double) counter.QuadPart / scaled_freq;
+  return (uint64_t) result;
 }