[llvm] [ValueTracking] Recognize `X op (X != 0)` as non-zero (PR #88579)

[via llvm-commits]

goldsteinn wrote:

> Pretty sure that this will miscompile if X is undef and isKnownNonZero() is used in a transform that retains the original expression.

Hmm? The proofs allow for `undef`.

https://github.com/llvm/llvm-project/pull/88579