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

[Ryotaro Kasuga via llvm-commits]

kasuga-fj wrote:

I didn't except to ask for opinions from others (including LLVM Area Team) on this one, because

- This thread alone lacks context
- Even the information within the thread isn't well-organized
- Nearly half of this thread is somewhat off-topic

I think summarizing the contents and issues is necessary before involving others.

> my suggestion is to start with a meeting on the issue

I'm very bad at speaking and listening in English, so I'm not sure if arranging a meeting is a good idea. That said, I don't mind joining the next loop opt meeting.

Anyway, I'll mark this PR as ready for review in a few days, as it's clear that either the definition of monotonicity or the result of its check needs to be corrected.

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