[PATCH] D63390: [Codegen] TargetLowering::SimplifySetCC(): omit urem when possible

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

Thank you for the reviews.

In D63390#1546676 <https://reviews.llvm.org/D63390#1546676>, @spatel wrote:

> LGTM. I have no idea if it's worth the trade-off, but we could do this sooner in IR (instcombine) instead of or in addition to SDAG?


Indeed, this fold is missed in middle-end too, but the regression at hand is in back-end test,
so i'm not sure if we should just hand-wave and only fix it in middle-end.
Also, where should the middle-end fix be? Again InstCombine?

I'm also not sure if this is the best approach, the fold doesn't care *where* those bits are,
it only cares about the *count* of ones, and is thus easily defeated by shift operations,
as it is seen from tests.


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  rL LLVM

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