[llvm] [polly] [delinearize] Extract array dimensions from alloca and global declarations (PR #156342)

[Ryotaro Kasuga via llvm-commits]

kasuga-fj wrote:

> I don't know yet: we will know if `delinearizeFixedSizeArray` is sufficient once we have a way to delinearize all the use-cases we have in the testsuite in DA + delinearize and in Polly. The current implementation of `delinearizeFixedSizeArray` needs some more work to recover the info currently read from GEPs.

What do you mean by "all the use-cases in the test suite"? I think it’s impractical to fully reproduce the current GEP-based delinearization behavior without relying on GEP’s type information. While `delinearizeFixedSizeArray` still has room for improvement (I've not checked the details of failed tests, though), there will probably be some limitations, and we’ll have to make compromises at some point. If you’re referring to the regression tests, I don’t think we need to be constrained by them -- especially since I believe we agreed to remove functionality from DA. 

Polly shouldn’t be relevant here, even if it uses GEP-based delinearization as well.

https://github.com/llvm/llvm-project/pull/156342