[PATCH] D62341: [DAGCombine][X86][AArch64][AMDGPU][MIPS][PPC] (sub x, c) -> (add x, -c) vector edition.

Roman Lebedev via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Wed Aug 28 15:15:43 PDT 2019


lebedev.ri added a comment.

In D62341#1649924 <https://reviews.llvm.org/D62341#1649924>, @hfinkel wrote:

> In D62341#1647808 <https://reviews.llvm.org/D62341#1647808>, @lebedev.ri wrote:
>
> > @hfinkel should i be worried about PPC regressions here?
> >  Those are there regardless of the patch (instcombine already did this fold).
> >  I'm not yet sure how to handle them, in some of these patterns the constant
> >  is already constant-pool load, in some cases it's bitcasted, etc.
>
>
> Yeah, those don't look good. @nemanjai , are we just missing some patterns?


I believe you need something similar to https://reviews.llvm.org/D66805#change-JSdQ9NCYAb2i / D63558 <https://reviews.llvm.org/D63558>,
but i'm not sure how to do that for PPC, would be great if someone actually familiar with that backend could handle that..


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