[llvm] [NaryReassociate] Teach NaryReassociate about UniformityAnalysis (PR #175167)

[Jay Foad via llvm-commits]

jayfoad wrote:

> > There is still the problem that UniformityAnalysis unconditionally requires CycleAnalysis, which causes a measurable performance impact on targets that don't care about divergence: [#99878 (comment)](https://github.com/llvm/llvm-project/pull/99878#issuecomment-2243179679)
> 
> Right, let me guard the fetch with hasBranchDivergence.

I think the suggestion was to change UniformityAnalysis to guard the fetch of CycleAnalysis with hasBranchDivergence. That would potentially benefit all passes that use UI.

https://github.com/llvm/llvm-project/pull/175167