[llvm] [DA] Widening SCEV expressions in strong SIV test to prevent overflow (PR #164704)

[Alireza Torabian via llvm-commits]

1997alireza wrote:

@kasuga-fj This patch addresses the issue with the strong SIV test you referenced in [#164246](https://github.com/llvm/llvm-project/pull/164246). While strong SIV produces the correct result `consistent output [1]`, the DA result is `none!`. This reason is due to an overflow in the RDIV test, which causes the test to incorrectly disprove the dependency.

While we should resolve the bug in RDIV, I believe it may not be necessary for DA to perform the additional tests when strong SIV has already proved the dependency. Specifically, I’m referring to this [line](https://github.com/llvm/llvm-project/pull/164704/files#diff-2d5f1ae1260d47d458eaed38ae7d5d5e7d8782232c205b621355d07ee51fb084L2717). Even if `disproven` is false, we can determine whether strong SIV successfully proved the dependency or if the test failed to produce any results. Based on this outcome, we can then decide whether to proceed with the other tests.

https://github.com/llvm/llvm-project/pull/164704