[llvm] [LAA] Support different strides & non constant dep distances using SCEV. (PR #88039)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

The latest comments should be addressed/responded to, thanks!

I also added a missing check that the strides must have the same direction for now (extra tests added in 5138ccd0e479d1702c2adefe1cd611e1aebe2f8b). Without this check, we would at least try to vectorize with runtime checks in cases where the runtime checks would always be false.

https://github.com/llvm/llvm-project/pull/88039