[PATCH] D96648: [InstCombine] fold fdiv with pow divisor (PR49147)

Sat Feb 13 08:36:38 PST 2021

spatel added a comment.

In D96648#2561792 <https://reviews.llvm.org/D96648#2561792>, @lebedev.ri wrote:

> Hm, alive2 doesn't support fast-math flags still?
> Filed https://github.com/AliveToolkit/alive2/issues/667

Thanks! Yes, I think Alive2 knows how to handle the "special value" FMF (ninf, nnan, nsz), but not these math properties.

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Comment at: llvm/test/Transforms/InstCombine/fdiv.ll:698
   %p = call fast float @llvm.pow.f32(float %x, float %y)
   %r = fdiv reassoc float %z, %p
   ret float %r
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lebedev.ri wrote:
> Might be worth duplicating the test with `reassoc` missing instead?
Yes, good point - or I can just have both variants (only reassoc and only arcp). If we change our FMF fdiv constraints in the future, we'll have coverage in either direction.

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  https://reviews.llvm.org/D96648/new/

https://reviews.llvm.org/D96648