[LLVMdev] Performance regression on ARM

[Hal Finkel]

----- Original Message -----
> From: "Renato Golin" <renato.golin at linaro.org>
> To: "LLVM Dev" <llvmdev at cs.uiuc.edu>
> Sent: Thursday, October 16, 2014 2:47:11 AM
> Subject: [LLVMdev] Performance regression on ARM
> 
> Folks,
> 
> First win of the benchmark buildbot!
> 
> http://llvm.org/perf/db_default/v4/nts/graph?plot.0=49.128.2&highlight_run=31861
> 
> It seems mandel-2 had a huge regression a few commits ago, and based
> on a quick look, it may have to do with the inst combine changes. I
> haven't investigated yet, but this is the first time I spot
> regressions on test-suite, so I'd like to first congratulate the
> people that worked on making that a reality!

Interesting. Looks like the problem is in (219545, 219569].

Based on the commit logs, it does seem like the best candidates are:
  r219566, r219567, r219568 - InstCombine bug fixes re: no-wrap flags
  r219550, r219562 - Fixes to trip-count computations in the vectorizer/unroller

and given the magnitude of the change, I think that the trip-count changes are more likely. Of course, all of these things are bug fixes :( -- So how do we follow-up on this?

 -Hal

> 
> Now, I'd like to have been warned of that automatically, by email,
> based on some simple heuristics... But that's a topic for the
> Performance/Benchmarking BoF in a few weeks... :)
> 
> cheers,
> --renato
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory