[llvm] [VPlan] Don't rely on region check in isUniformAfterVectorization. (PR #137883)

[via llvm-commits]

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@@ -39,18 +39,37 @@ const SCEV *getSCEVExprForVPValue(VPValue *V, ScalarEvolution &SE);
 
 /// Returns true if \p VPV is uniform after vectorization.
 inline bool isUniformAfterVectorization(const VPValue *VPV) {
+  auto IsKnownUniformOpcode = [](auto *R) -> bool {
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ayalz wrote:

Pass R's opcode instead of R?

Can the lambda's name be more accurate, say `PreservesUniformity/SingleScalar(opcode)`? I.e., given uniform/single-scalar operands produces a uniform/single-scalar result.

https://github.com/llvm/llvm-project/pull/137883