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

[Ehsan Amiri via llvm-commits]

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amehsan wrote:

I will post a PR on Friday. Have been busy with multiple issues and so I have some delay. I will post a minimal PR, to help focus on the point of disagreement.

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