[llvm] [UniformityAnalysis] Replace DivergentValues with UniformValues for conservative divergence queries (PR #180509)

[Pankaj Dwivedi via llvm-commits]

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PankajDwivedi-25 wrote:

To handle locally we need to iterates over all arguments and block definitions, and then the main body of print() iterates over them again. However, this is specifically to decide whether to print "ALL VALUES UNIFORM" and return early. Several tests use CHECK-NEXT: ALL VALUES UNIFORM right after the function label, so it must appear at the top, before any block output.

The original code achieved this in O(1) via DivergentValues.empty(). Since we removed DivergentValues, the local scan is the cost of computing it locally.

https://github.com/llvm/llvm-project/pull/180509