[llvm] [InstCombine] Move alignment assumptions to the base of a gep if alignment is preserved (PR #203032)

[Yingwei Zheng via llvm-commits]

https://github.com/dtcxzyw requested changes to this pull request.

A correctness issue was identified by [llvm-hackme](https://github.com/dtcxzyw/llvm-hackme). Please see the [issue comment](https://github.com/llvm/llvm-project/pull/203032#issuecomment-4672209454) for details.

https://github.com/llvm/llvm-project/pull/203032