[llvm] [UniformityAnalysis] Track uniform values for conservative divergence queries at IR level (PR #180509)

[Juan Manuel Martinez Caamaño via llvm-commits]

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@@ -417,6 +434,10 @@ template <typename ContextT> class GenericUniformityAnalysisImpl {
   DenseSet<ConstValueRefT> DivergentValues;
   SmallPtrSet<const BlockT *, 32> DivergentTermBlocks;
 
+  // Known uniform values (populated after analysis by finalizeUniformValues).
+  // Values NOT in this set are conservatively treated as divergent.
+  DenseSet<ConstValueRefT> UniformValues;
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jmmartinez wrote:

> What i feel would be more convenient as of now is: "Use CallbackVH for the IR case." It keeps the current "unknown = divergent" behavior safe against address reuse? Full mutable uniformity info for the reason of divergence propagation will require more effort that can be planned later.

I agree. Sounds like a step in the right direction.

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