[PATCH] D79078: [VectorCombine] Leave reduction operation to SLP

Wed Apr 29 05:51:46 PDT 2020

lebedev.ri added a comment.

In D79078#2009883 <https://reviews.llvm.org/D79078#2009883>, @junparser wrote:

> In D79078#2009814 <https://reviews.llvm.org/D79078#2009814>, @lebedev.ri wrote:
>
> > This needs a phase-ordering test.
>
>
> For now vector-combine is executed before slp in both legacy pm and new pm with O2 <https://reviews.llvm.org/owners/package/2/>, so either we handle it here or slp can handle this kind of pattern.

I'm not really sure what you mean.
We clearly have phase-ordering issue, and we should have a test that shows it.

>> Why shouldn't SLPVectorizer be taught about that pattern instead?
> 
> I think we can handle this in SLP, however it may much hard than doing here? I'm not sure.

It would be best to enhance SLP rather than adding potentially-numerous semi-arbitrarily bailout elsewhere, i think.

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  https://reviews.llvm.org/D79078/new/

https://reviews.llvm.org/D79078