diff options
Diffstat (limited to 'base/time/time_win.cc')
| -rw-r--r-- | base/time/time_win.cc | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/base/time/time_win.cc b/base/time/time_win.cc index cf7be68..5fa899d 100644 --- a/base/time/time_win.cc +++ b/base/time/time_win.cc @@ -393,11 +393,14 @@ class HighResNowSingleton { int64 QPCValueToMicroseconds(LONGLONG qpc_value) { if (!ticks_per_second_) return 0; - - // Intentionally calculate microseconds in a round about manner to avoid - // overflow and precision issues. Think twice before simplifying! + // If the QPC Value is below the overflow threshold, we proceed with + // simple multiply and divide. + if (qpc_value < Time::kQPCOverflowThreshold) + return qpc_value * Time::kMicrosecondsPerSecond / ticks_per_second_; + // Otherwise, calculate microseconds in a round about manner to avoid + // overflow and precision issues. int64 whole_seconds = qpc_value / ticks_per_second_; - int64 leftover_ticks = qpc_value % ticks_per_second_; + int64 leftover_ticks = qpc_value - (whole_seconds * ticks_per_second_); int64 microseconds = (whole_seconds * Time::kMicrosecondsPerSecond) + ((leftover_ticks * Time::kMicrosecondsPerSecond) / ticks_per_second_); @@ -447,7 +450,8 @@ NowFunction now_function = RolloverProtectedNow; bool CPUReliablySupportsHighResTime() { base::CPU cpu; - if (!cpu.has_non_stop_time_stamp_counter()) + if (!cpu.has_non_stop_time_stamp_counter() || + !GetHighResNowSingleton()->IsUsingHighResClock()) return false; if (IsBuggyAthlon(cpu)) |