[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:

> Again, monotonicity (and `nsw` of addrecs) don't imply `a * x` doesn't overflow in a signed sense.

Consider it a shortcut for saying that  addrec won't overflow for iteration `x` of the loop.

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