[llvm] [GVN] Teach GVN simple masked load/store forwarding (PR #157689)

[David Sherwood via llvm-commits]

https://github.com/david-arm commented:

It's looking pretty good now, thanks for addressing all the previous comments! I just have a few more minor comments, then I think it's ready to go.

https://github.com/llvm/llvm-project/pull/157689