[llvm] Feat/sink gep constant offset (PR #140027)

[via llvm-commits]

StevenYangCC wrote:

> Needs new tests that show the transformation (preferably precommitted so the diff easily shows what this did)

@john Thanks for catching these! I have fixed this, could you please verify the change?

https://github.com/llvm/llvm-project/pull/140027