[llvm] [AMDGPU] Eliminate likely-spurious execz checks (PR #117567)

[Fabian Ritter via llvm-commits]

ritter-x2a wrote:

> This feels like what I had in mind for the heuristic, but it seems like there's uncertainty there

Thanks for the confirmation! I'm currently still working on getting performance numbers for a variant of this heuristic; I think the further steps on this PR depend on those performance numbers.

https://github.com/llvm/llvm-project/pull/117567