[llvm] [Delinearization] Add function for fixed size array without relying on GEP (PR #145050)

[Ryotaro Kasuga via llvm-commits]

kasuga-fj wrote:

I generally agree with the overall direction. Adding an option like `-use-old-type-based-gep-delinearization` seems a practical way at this moment (though I feel it's ideal to erase the GEP source element type driven heuristics entirely and literally from DA, if possible). Here are my thoughts regarding the minor points:

- We should submit another PR to replace the old function with the new one. Since their signatures differ, this change will require more than just a simple renaming the calls to the old function in DA. I'd also prefer to keep commits as functionally separated as possible.
- Instead of marking tests as XFAIL, I think it’s better to verify behavior with and without the -use-old-type-based-gep-delinearization option. This can be done using FileCheck's `--check-prefix` argument.
- Before adding such an option, I'd like to fix the issue where `DependenceAnalysisPrinter` prints either `0` or `=` depending on the situation. This is not a correctness issue, but makes tests fragile. I'll work on it.

https://github.com/llvm/llvm-project/pull/145050