[llvm] [DA] Add tests for nsw doesn't hold on entier iteration (PR #162281)

[Michael Kruse via llvm-commits]

Meinersbur wrote:

> I think we can make DA more precise by taking context such as branch conditions into account. For example, simply replacing `isKnownPredicate` with `isKnownPredicateAt` may improve the result in some cases. However, I'd like to work on such improvements after fixing the existing correctness issues.

Wow, I didn't know about `isKnownPredicateAt`. It is indeed what I had in mind. For monotonicity, we would need a `isMonotonicAt` function that takes a `CtxI`.

https://github.com/llvm/llvm-project/pull/162281