[PATCH] D74066: [ValueTracking] usub(a, b) cannot overflow if a >= b.

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

My only concern here is compile-time impact. Keep in mind that this function is not just being called for `usub.with.overflow`, but for every `sub` in the IR, trying to infer the `nuw` flag. As `isImpliedByDomCondition()` only inspects the direct predecessor, that's probably fine though.

Generally we're missing a pass that can propagate conditions and assumes with non-constant operands (CVP mostly covers the constant operand case)...


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https://reviews.llvm.org/D74066