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

[Sameer Sahasrabuddhe via llvm-commits]

ssahasra wrote:

I don't see why uniformity should be mentioned anywhere in this patch at all. If the result of a ballot is "-1", then its operand is "1" in every lane of the wave. But that's all that is needed. The further implication that the operand is uniform is not relevant to this optimization. It's an unnecessary conflation between the facts implied by an assume on the one hand and uniformity implied by those facts on the other hand. The latter is not needed and should be removed from this patch.

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