SLP/Loop vectorizer pass ordering

[Zinovy Nis]

Hi.

Did you have a chance to look at my reproducer?

2014-10-07 21:34 GMT+04:00 Zinovy Nis <zinovy.nis at gmail.com>:
> Hi.
>
> I attached a reduced sample, based on https://code.google.com/p/aobench/.
>
> Run it first with an old SLP order:
>
> 1) clang -c -Ofast -static -march=core-avx2 aobench.cpp -Rpass=.
> -mllvm -debug-only=loop-vectorize -mllvm
> -run-slp-after-loop-vectorization=0
>
> and then with a new order:
>
> 2) clang -c -Ofast -static -march=core-avx2 aobench.cpp -Rpass=.
> -debug-only=loop-vectorize -mllvm -run-slp-after-loop-vectorization=1
>
> and see the logs:
>
> 1) aobench.cpp:59:9: remark: vectorized loop (vectorization factor: 8,
> unrolling interleave factor: 1) [-Rpass=loop-vectorize]
> 2) aobench.cpp:59:9: remark: loop ***not*** vectorized: use
> -Rpass-analysis=loop-vectorize for more info
> [-Rpass-missed=loop-vectorize]
>
> LV: Found an unidentified PHI.  %occlusion.017 = phi float [
> 1.000000e+00, %entry ], [ %phitmp, %for.inc.for.body_crit_edge ]
> LV: Can't vectorize the instructions or CFG
> LV: Not vectorizing: Cannot prove legality.
>
> 2014-10-06 17:46 GMT+04:00 Hal Finkel <hfinkel at anl.gov>:
>> ----- Original Message -----
>>> From: "Zinovy Nis" <zinovy.nis at gmail.com>
>>> To: "Hal Finkel" <hfinkel at anl.gov>
>>> Cc: "LLVM Commits" <llvm-commits at cs.uiuc.edu>, "Tobias Grosser" <tobias at grosser.es>, "Chandler Carruth"
>>> <chandlerc at google.com>, "Nadav Rotem" <nrotem at apple.com>, "Arnold Schwaighofer" <aschwaighofer at apple.com>
>>> Sent: Monday, October 6, 2014 8:44:28 AM
>>> Subject: Re: SLP/Loop vectorizer pass ordering
>>>
>>> A bit later. At least GVN creates critical edges which are not
>>> handled
>>> by loop vectorizer then.
>>
>> Okay, please do (this is fairly important) -- if you can extract some relevant IR, filing a bug report would be great. Are you saying that running SLP early inhibits GVN from creating critical edges that the loop vectorizer does not understand?
>>
>> Thanks again,
>> Hal
>>
>>>
>>> 2014-10-06 17:33 GMT+04:00 Hal Finkel <hfinkel at anl.gov>:
>>> > ----- Original Message -----
>>> >> From: "Zinovy Nis" <zinovy.nis at gmail.com>
>>> >> To: "Chandler Carruth" <chandlerc at google.com>
>>> >> Cc: "LLVM Commits" <llvm-commits at cs.uiuc.edu>, "Tobias Grosser"
>>> >> <tobias at grosser.es>
>>> >> Sent: Monday, October 6, 2014 8:19:24 AM
>>> >> Subject: Re: SLP/Loop vectorizer pass ordering
>>> >>
>>> >> Please wait a while, I'm using it to revert the new order as it
>>> >> introduces regression in our internal benchmark: SLP was creating
>>> >> loop
>>> >> vectorization opportunities when was called before LV. Now no such
>>> >> opportunities are available, so we've got a regression.
>>> >
>>> > Interesting. Can you provide any further details?
>>> >
>>> >  -Hal
>>> >
>>> >>
>>> >> 2014-10-06 3:28 GMT+04:00 Chandler Carruth <chandlerc at google.com>:
>>> >> >
>>> >> > On Thu, Sep 4, 2014 at 6:32 AM, James Molloy
>>> >> > <james at jamesmolloy.co.uk>
>>> >> > wrote:
>>> >> >>
>>> >> >> Hi Hal, Chandler,
>>> >> >>
>>> >> >> r217144.
>>> >> >
>>> >> >
>>> >> > Is anyone still using the option to disable this? If I don't
>>> >> > hear
>>> >> > anything,
>>> >> > I'll remove this option entirely in the next week.
>>> >> >
>>> >> > _______________________________________________
>>> >> > llvm-commits mailing list
>>> >> > llvm-commits at cs.uiuc.edu
>>> >> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>> >> >
>>> >> _______________________________________________
>>> >> llvm-commits mailing list
>>> >> llvm-commits at cs.uiuc.edu
>>> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>> >>
>>> >
>>> > --
>>> > Hal Finkel
>>> > Assistant Computational Scientist
>>> > Leadership Computing Facility
>>> > Argonne National Laboratory
>>>
>>
>> --
>> Hal Finkel
>> Assistant Computational Scientist
>> Leadership Computing Facility
>> Argonne National Laboratory