Avoid 64-bit divide when sampling timestamp

base/time/time_posix.cc

Index: base/time/time_posix.cc
diff --git a/base/time/time_posix.cc b/base/time/time_posix.cc
index dcbd83cd54e4fb7b769ded532b2ed9b5bf626f47..ad00c513685c2ce4891c7f958520543e167a7f6c 100644
--- a/base/time/time_posix.cc
+++ b/base/time/time_posix.cc
@@ -98,7 +98,7 @@ base::TimeTicks ClockNow(clockid_t clk_id) {
 
   absolute_micro =
       (static_cast<int64>(ts.tv_sec) * base::Time::kMicrosecondsPerSecond) +
-      (static_cast<int64>(ts.tv_nsec) / base::Time::kNanosecondsPerMicrosecond);
+      (static_cast<int64>(ts.tv_nsec / base::Time::kNanosecondsPerMicrosecond));

[jamesr, 2014/09/29 23:37:31]

i'm pretty sure this doesn't actually help, since kNanosecondsPerMicrosecond is:

static const int64 kNanosecondsPerMicrosecond = 1000;

so thanks to type promotion this is still a 64 bit divide.

[Peter Kasting, 2014/09/30 00:22:15]

This.  I'm in the process of cleaning up our 64-bit math around time constants
in various places in the codebase and frankly the right change here is probably
to simply remove both casts entirely.  Neither one will have any effect on the
generated code, no matter how you parenthesize things.

 
   return base::TimeTicks::FromInternalValue(absolute_micro);
 }