[llvm] [ValueTracking] Add support for `usub.sat` in `isKnownNonZero (PR #87700)

[Nikita Popov via llvm-commits]

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@@ -882,11 +882,7 @@ define i1 @usub_sat_nonzero(i8 %xx, i8 %yy, i8 %ind) {
 ; CHECK-LABEL: @usub_sat_nonzero(
 ; CHECK-NEXT:    [[Y_ULT_31:%.*]] = icmp ult i8 [[YY:%.*]], 31
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[Y_ULT_31]])
-; CHECK-NEXT:    [[XO:%.*]] = or i8 [[XX:%.*]], 34
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nikic wrote:

Ah yes, good point. Actually, now that you mention it, I'm pretty sure that @goldsteinn already submitted a patch along these lines on phabricator and we reached the same conclusion there... Maybe we should leave a comment so we don't get a third implementation :)

https://github.com/llvm/llvm-project/pull/87700