[PATCH] D87877: [InstCombine] Fix errno bug in pow expansion to sqrt

[Hubert Tong via Phabricator via llvm-commits]

hubert.reinterpretcast marked 2 inline comments as done.
hubert.reinterpretcast added inline comments.


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Comment at: llvm/test/Transforms/InstCombine/pow-sqrt.ll:31
 
-; This makes no difference, but FMF are propagated.
+; This makes no difference, but FMF are propagated/retained.
 
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spatel wrote:
> This comment should be more like above:
>   ; The transform to sqrt is not allowed if we risk setting errno due to -INF.
> 
> Although that raises a question: if the user has allowed an approximation of pow(), do they really expect that errno would be set accurately? Similarly, if they allowed 'reassoc'...
Given NaN propagation, if the `sqrt` was okay, then the result here should be NaN. That is, I think the question is more "can we just do the transform and omit the select"?


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  https://reviews.llvm.org/D87877/new/

https://reviews.llvm.org/D87877