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

[Ehsan Amiri via llvm-commits]

amehsan wrote:

> If you intend to continue this one, I'd strongly recommend creating a new PR/Issue and moving the discussion there. It seems this is no longer closely related to the original issue I raised. I'd like to go back to the original topic.

But I agree that the situation now is very different and our understanding has changed quite deeply about how these tests work.  There were a couple of very critical points that was missed before.

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