[llvm] [ValueTracking] Add support for `sub` in `isKnownNonEqual` (PR #87704)

[via llvm-commits]

goldsteinn wrote:

> Looks like there is essentially no impact, and the impact there is does not look positive (? not entirely sure on that). As such, I don't think we should add this.

Okay, ill put this on hold unless a motivating case can be found.
I might push the comment in the `isNonZeroSub` helper.

https://github.com/llvm/llvm-project/pull/87704