[PATCH] D87972: [OldPM] Pass manager: run SROA after (simple) loop unrolling

[Roman Lebedev via Phabricator via cfe-commits]

lebedev.ri added a comment.

In D87972#2294614 <https://reviews.llvm.org/D87972#2294614>, @lebedev.ri wrote:

> In D87972#2294488 <https://reviews.llvm.org/D87972#2294488>, @xbolva00 wrote:
>
>>>> Does that sound reasonable?
>>
>> Yes IMHO.
>>
>>>> What are the next suggested steps?
>>
>> It would be great to isolate and check the cases which regressed a bit.
>
> I've rerun my benchmark, and while the results are still the same (runtime geomean -0.53%/-0.40%,
> but that obviously depends on the benchmarks), there are some obvious outliers:
> F13059172: image.png <https://reviews.llvm.org/F13059172>
> F13059175: rsbench.txt <https://reviews.llvm.org/F13059175>
> I'll try to take a look at that, assuming it's not noise.

Hmm. So i did just take a look, manually re-benchmarking each of these, and while i still see a few small improvements,
the regressions there are all appear to be basically noise. Not what i was hoping for :/

In D87972#2284060 <https://reviews.llvm.org/D87972#2284060>, @MaskRay wrote:

> I have tested this patch internally and seen gains and losses. On one document search related benchmark 3~5% improvement. One zippy (snappy) there is 3~5% regression. Perhaps we do need a conditional extra SROA run.

Does it look like one of the scary "branch predictor got confused"/"code layout changed causing different alignment"?

I'm not really sure what are my potential next steps here.


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