[PATCH] D149413: [ValueTracking] Add logic for `isKnownNonZero(usub.sat X, Y)`

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added a comment.

In D149413#4304537 <https://reviews.llvm.org/D149413#4304537>, @nikic wrote:

> This case looks unnecessary. If `%x >= %y` we will fold the usub.sat to `sub nuw %x, %y` and not hit this pattern.

Most likely yeah. My feeling is it might exist outside of `InstCombine` and need to be analyzed. I.e if its analyzable in `InstSimplify`
it may enable further simplifications of patterns we don't want to have to duplicate in `InstCombine`.

But if you're not convinced ill abandon.


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