[polly] r238088 - Enable scalar and PHI code generation for Polly

[Johannes Doerfert]

This looks really good, but I agree we might just exclude some SCoPs
now. However, even if we do it shouldn't be a general problem.

Thanks again for summarizing the effects nicely!

On 05/23, Tobias Grosser wrote:
> On 05/23/2015 05:34 AM, Tobias Grosser wrote:
> >Author: grosser
> >Date: Fri May 22 22:34:41 2015
> >New Revision: 238088
> >
> >URL: http://llvm.org/viewvc/llvm-project?rev=238088&view=rev
> >Log:
> >Enable scalar and PHI code generation for Polly
> >
> >The feature itself has been committed by Johannes in r238070. As this is the
> >way forward, we now enable it to ensure we get test coverage.
> >
> >Thank you Johannes for this nice work!
> 
> And here the performance results:
> 
> A) clang -O3 -mllvm -polly (before vs. after this commit):
> 
> http://llvm.org/perf/db_default/v4/nts/27114?num_comparison_runs=0&test_filter=&test_min_value_filter=&aggregation_fn=median&MW_confidence_lv=0.01&compare_to=27106&submit=Update
> 
> B1) clang O3 vs clang -O3 -polly (after the change)
> 
> http://llvm.org/perf/db_default/v4/nts/27114?num_comparison_runs=0&test_filter=&test_min_value_filter=&aggregation_fn=median&MW_confidence_lv=0.01&compare_to=27113&submit=Update
> 
> B2) clang O3 vs clang -O3 -polly (before the change)
> 
> http://llvm.org/perf/db_default/v4/nts/27106?num_comparison_runs=0&test_filter=&test_min_value_filter=&aggregation_fn=median&MW_confidence_lv=0.01&compare_to=27113&submit=Update
> 
> Chart A shows 114 performance improvements vs just 7 performance regressions
> (mostly compile-time performance) with around 30 test cases
> reducing compile time between 10 and 30%. Most of these are short running
> test cases, but with MultiSource/Applications/sgefa/sgefa we also have a
> test case where we save over 500ms.
> 
> Comparing chart B1 and B2 we see that number of performance regressions
> compared to clang -O3 is reduced from 254 to just 185. This again mostly
> affects compile time, but also several run-time numbers have been improved.
> 
> The run-time performance benefits enabled by Polly are not negatively
> affected.
> 
> The primary goals of this change where to make Polly useful as an
> analysis as well as to avoid spurious modifications to the code. Seeing
> performance improvements is a nice side-effect, but we should keep our eyes
> open to verify they do not (in-parts) come from a reduced number of detected
> scops.
> 
> Overall I am very happy with this change. Thanks Johannes for putting it in!
> 
> Best,
> Tobias

-- 

Johannes Doerfert
Researcher / PhD Student

Compiler Design Lab (Prof. Hack)
Saarland University, Computer Science
Building E1.3, Room 4.31

Tel. +49 (0)681 302-57521 : doerfert at cs.uni-saarland.de
Fax. +49 (0)681 302-3065  : http://www.cdl.uni-saarland.de/people/doerfert
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