[PATCH] D100211: [InstCombine] Fold cmpeq/ne(and(~X,Y),0) --> cmpeq/ne(or(freeze(X),Y),X) (PR44136)

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D100211#2681777 <https://reviews.llvm.org/D100211#2681777>, @RKSimon wrote:

> The missing middle-end fold was noted on the ticket (PR44136) - this patch is to show what would be necessary.
>
> Limiting this to isGuaranteedNotToBeUndefOrPoison would be safer, although I'm not sure how common the case is tbh. Happy to abandon and close the ticket if this is pointless extra work.
>
> @lebedev.ri any thoughts?

I'm not sure, which is why i haven't posted any patches after originally replying to the bug.

Right now i don't quite understand why we are so afraid of using `freeze`.
Can we not teach instcombine to hoist it?

Ignoring the `freeze` question, i think this is an improvement.


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  https://reviews.llvm.org/D100211/new/

https://reviews.llvm.org/D100211