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

[Ehsan Amiri via llvm-commits]

amehsan wrote:

> I still think we need to handle loop guards properly in some way, and I believe the test case `@nsw_under_loop_guard0` illustrates why.

I'd like to look into this in detail, but I may not be able to do it today. Will get back to you on this asap.

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