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

[Jay Foad via llvm-commits]

jayfoad wrote:

Do you have realistic examples of cases where we do want the execz branch, and cases where we do not want the execz branch?

I am sceptical that you can effectively distinguish these categories with a generic analysis of the IR (but maybe I'm wrong). I think it's more likely that you would have to pattern-match some examples of one category, and assume that everything else is in the other category.

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