[llvm] [AArch64] Remove redundant COPY from loadRegFromStackSlot (PR #107396)

[Amara Emerson via llvm-commits]

https://github.com/aemerson approved this pull request.

Assuming that this is really redundant, LGTM. Since this was found in the wild I'd also like to see the IR test added to make sure the original case is fixed too.

Definitely wanted for LLVM 19 if possible.

https://github.com/llvm/llvm-project/pull/107396