[llvm-dev] Enable STATISTIC all the time again?

[Matthias Braun via llvm-dev]

Last time I measured 0.5%-1% slowdown with statistics enabled in a release build. Also see my last thread about this: https://groups.google.com/forum/#!topic/llvm-dev/xZVBNg5bsSk <https://groups.google.com/forum/#!topic/llvm-dev/xZVBNg5bsSk>
We also had plans to push statistics (probably newly introduced one rather than retrofitting the existing ones) through the optimization remark system to allow some context like per-function statistics. But there is nothing concrete yet.

- Matthias

> On May 31, 2017, at 7:39 AM, Daniel Berlin via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> Right now, the LLVM Statistic class does not increment values if we are in non-debug mode, unless you define LLVM_ENABLE_STATS (which, sadly, is also not available from cmake).
> 
> Before i go and add it to cmake, i ran numbers.
> 
> I can't find a single testcase, large or small, where enabling statistics all the time isn't completely noise.
> 
> It looks like it was disabled in march  2013.
> https://reviews.llvm.org/D486 <https://reviews.llvm.org/D486>
> 
> The only discussion i can find in the same time period is around fastisel using a lot of per-instruction stats, and it causing some slow-down.
> 
> However, I can't find any actual data/testcases in this discussion at all, and disabling stats globally is actually fairly annoying for performance work.
> :(
> 
> Does anyone have any testcases where it is actually slow that i can look at?
> 
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