[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 don't expect the area team to assist even at this level of detail...

I'm crafting a prototype to show my approach. I'll share it once it's ready. If you still have any objections, please say so. I honestly have no idea what you are disagreeing with.

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