[PATCH] D18164: [tsan] Do not instrument reads/writes to instruction profile counters.

Dmitry Vyukov via llvm-commits llvm-commits at lists.llvm.org
Wed Mar 16 01:21:30 PDT 2016

dvyukov added a comment.

Anna reported that there is in fact some degradation if we use monotonic atomics. I am fine if we ignore the counters during tsan instrumentation, but also file bugs on optimizer (there must be no performance difference). This whole discussion has little to do with profiler, we are discussing that llvm does not permit users to have fast and correct code at the same time.

I don't that switch to atomic RMWs under tsan is a good idea: having precise counters only in tsan build does not make sense. That could be a separate option (if user wants precise counters), but it is orthogonal to this discussion.


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