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

[Ryotaro Kasuga via llvm-commits]

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kasuga-fj wrote:

> I thought today SCEV won't prove nsw for conditional statements.

This is exactly the problem I am pointing out. In the end, you failed to realize by yourself that Strong SIV is buggy. This is absolutely not a "proof".
Also, you are still misunderstanding. SCEV does not infer `nsw` from conditional memory load/store.

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