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

[Ryotaro Kasuga via llvm-commits]

kasuga-fj wrote:

The change itself doesn't seem to be problematic, but as I mentioned in https://github.com/llvm/llvm-project/issues/159846#issuecomment-3434653586, I'm now skeptical of the approach that uses wider integer types. For the cases I provided, where overflows are triggered by large constant values, I don't think they are practical enough to justify the added complexity of using wider integer types. While it's certainly beneficial to provide more accurate results in such cases, I believe it's sufficient to simply return an unknown dependency.

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