[llvm] [GlobalISel] Avoid redundant copy for zero-offset GEPs (PR #203029)

[Nikita Popov via llvm-commits]

nikic wrote:

> Where do these come from? Can we fold such GEPs in the IRBuilder folder to prevent them from being emitted by Clang in the first place? (Is there already some precedent for things like this? cc @nikic)

IRBuilder supports this if you use InstSimplifyFolder.

https://github.com/llvm/llvm-project/pull/203029