[PATCH] D149742: [SLP]Improve isGatherShuffledEntry by trying per-register shuffle.

[Valeriy Dmitriev via Phabricator via llvm-commits]

vdmitrie added a comment.

In D149742#4460486 <https://reviews.llvm.org/D149742#4460486>, @ABataev wrote:

> In D149742#4401811 <https://reviews.llvm.org/D149742#4401811>, @vdmitrie wrote:
>
>> F27851102: test.ll <https://reviews.llvm.org/F27851102>
>>
>> command to reproduce: opt -passes=slp-vectorizer -mtriple=x86_64 -mcpu=core-avx2 -S test.ll
>
> HMM, llvm-mca shows that the code after patch is better than the code before (with the patch the throughput is 4.0, without - 5.0)
>
> https://godbolt.org/z/zvzTKedPd

It puzzled me too actually. It was the only vectorization candidate that changed behavior due to the patch in the test. I could not find any obvious flaw in handling subsequent vectorization sequences.
Eyeballing of generated code before/after also did not reveal any obvious issues.


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