[llvm] [Delinearization] Remove tryDelinearizeFixedSizeImpl (PR #169046)

[Sjoerd Meijer via llvm-commits]

sjoerdmeijer wrote:

> Polly uses `getIndexExpressionsFromGEP`, which is different from `tryDelinearizeFixedSizeImpl`. So this PR should not affect Polly test cases. We also should remove `getIndexExpressionsFromGEP` in the future, and it needs to update Polly test cases, which Michael is working on ([#164798 (review)](https://github.com/llvm/llvm-project/pull/164798#pullrequestreview-3492677386))

Ok, great, then you can just go ahead and merge this I think.  

https://github.com/llvm/llvm-project/pull/169046