[PATCH] D159190: [RISCV]Combine to make the fixed vector vadd of splats are scalarized

Wed Aug 30 07:19:05 PDT 2023

luke added a comment.

In D159190#4628357 <https://reviews.llvm.org/D159190#4628357>, @luke wrote:

> In D159190#4628284 <https://reviews.llvm.org/D159190#4628284>, @liaolucy wrote:
>
>> In D159190#4628179 <https://reviews.llvm.org/D159190#4628179>, @luke wrote:
>>
>>> Thanks for the patch. Did you take a look at scalarizeBinOpOfSplats in DAGCombiner? I think that might be more generic, it's the combine that kicks in for the scalable vector test case in that issue. I was wondering if it would be possible to get it to work on fixed vectors too.
>>
>> I have a question, this ir has been optimized in the opt phase. https://godbolt.org/z/MPvvTG5dT  Maybe we don't need another combine in codegen?
>
> Good point, I didn't realise opt already took care of this. I guess it depends if this pattern is introduced during codegen at all

I originally noticed this when looking at the code generated whilst expanding ISD::ROT{L,R}, e.g. https://godbolt.org/z/Wh99EPbja
So it can be introduced after the middle-end (but it might not be that common)

Repository:
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https://reviews.llvm.org/D159190