tsan: removing redundant loop in ThreadClock::release()

[dfava]

Summary

The removed loop clears reused for entries at the tail of a SyncClock. The loop is redundant since those entries were already cleared by the immediately preceding loop, which iterates over all entries in the SyncClock (including the tail entries).

[dvyukov]

LGTM. Thanks!
Do you have commit access? Or do you want me to merge this?

[dfava]

Please merge it for me. I don't have commit access. Thanks!

[dvyukov]

Merged in https://github.com/llvm/llvm-project/commit/9b91bcf6c6187afb488ef6e12b8ef245b6635fd2

lib/tsan/rtl/tsan_clock.cpp

void ThreadClock::release(ClockCache *c, SyncClock *dst) {
   for (ClockElem &ce : *dst) {
     ce.epoch = max(ce.epoch, clk_[i]);
     ce.reused = 0;
     i++;
   }
   // Clear 'acquired' flag in the remaining elements.
   if (nclk_ < dst->size_)
     CPP_STAT_INC(StatClockReleaseClearTail);
-  for (uptr i = nclk_; i < dst->size_; i++)
-    dst->elem(i).reused = 0;
   dst->release_store_tid_ = kInvalidTid;
   dst->release_store_reused_ = 0;
   // If we've acquired dst, remember this fact,
   // so that we don't need to acquire it on next acquire.
   if (acquired)
     dst->elem(tid_).reused = reused_;
 }