[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:

For now, I've implemented what I have in mind for Strong SIV. If you still see any issues, please let me know.

https://github.com/kasuga-fj/llvm-project/compare/c0a7b15d0158a79786a38f5e94fa8315d4c9f0fe...f579161e477b647f031ca821fc93b023f6a4bca1

I believe this approach is better than inserting overflow checks everywhere as we don't need complex proofs.

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