[llvm] AMDGPU: Fix temporal divergence introduced by machine-sink and performance regression introduced by D155343 (PR #67456)

[Nicolai Hähnle via llvm-commits]

https://github.com/nhaehnle commented:

You didn't yet update the tests, did you?

Anyway, this already looks much better, thanks! Still some issues with the logic and compile time, please see inline.

https://github.com/llvm/llvm-project/pull/67456