[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:

> It looks to me that you still don't understand what `nsw` of addrecs means. `{c,+,a}<nsw>` does NOT say `a*i` doesn't overflow. It only says `(((c + a) + a) + ...)` doesn't overflow.

When you have enough `a` in that sequence,  you will have an overflow. that is the point.

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