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

[Adam Nemet via llvm-dev]

> On May 31, 2017, at 10:57 AM, Matthias Braun via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> 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.

And just to elaborate, this originated form the observation that there are many cases where we issue a debug message, emit an optimization remark and also increment a statistic within a few lines of code.  Having a single way of feeding all these use cases would be nice code-readability and usability improvement.

Adam

> 
> - Matthias
> 
>> On May 31, 2017, at 7:39 AM, Daniel Berlin via llvm-dev <llvm-dev at lists.llvm.org <mailto: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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