[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:

> For now, I've implemented what I have in mind for Strong SIV. If you still see any issues, please let me know.
> 
> [kasuga-fj/llvm-project at c0a7b15...f579161](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.

1- looking at strong SIV code, you have removed 24 lines of code and added 36 lines of code. So your code is more complex. 

2- How do you know nsw is valid for first or last iteration of the loop?

3- This is more compile time intensive than previous approach. Just a quick look at the SCEV related computations in your approach it seems more expensive than the previous approach


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