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

[Ehsan Amiri via llvm-commits]

================

----------------
amehsan wrote:

> > In an earlier discussion before, you were not even clear about the concept of UB and I mentioned it right there.
> 
> Which one?

Once you presented a pair of example in IR and I explained to you that one of your examples has UB. Let's stop this. Let's focus on the current technical discussion. 

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