[PATCH] D111450: [FPEnv][InstSimplify] Fold fadd X, 0 ==> X, when we know X is not -0

[Kevin P. Neal via Phabricator via llvm-commits]

kpn added inline comments.


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Comment at: llvm/test/Transforms/InstSimplify/strictfp-fadd.ll:287
 ;
   %add = call nsz nnan float @llvm.experimental.constrained.fadd.f32(float %a, float 0.0, metadata !"round.tonearest", metadata !"fpexcept.strict") #0
   ret float %add
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spatel wrote:
> Don't we want a test without `nnan` where exceptions are ignored but is not the default FP env?
> 
> Ie, this should fold?
>   %add = call nsz float @llvm.experimental.constrained.fadd.f32(float %a, float 0.0, metadata !"round.downward", metadata !"fpexcept.ignore") #0
> 
Yes, that's a good idea. And, yes, I believe we do want this to fold. The "nsz" flag means (I think) that if "x" is zero the sign of "0 - 0" is insignificant. I think that's what that means, anyway.


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https://reviews.llvm.org/D111450