[llvm] [WIP][Uniformity Analysis][Assume] Generic assume-based uniformity optimization (PR #160670)

[Sameer Sahasrabuddhe via llvm-commits]

ssahasra wrote:

> > Isn't the ballot result anded with exec? Such that this assume is only correct for full dispatches at the entry to the kernel?
> 
> AMDGPU backend only cares about uniformity within the active lanes of a wave. I didn't really understand the second sentence.

On second thought, I think I know what you mean. Inside a divergent branch, if the program wants to check if a value is uniform for the active lanes, the result of the ballot will be checked against execmask and not "-1". That pattern should also be added to this patch.

https://github.com/llvm/llvm-project/pull/160670