[llvm] [VPlan] Verify dominance for incoming values of phi-like recipes. (PR #124838)

[Florian Hahn via llvm-commits]

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@@ -3283,6 +3295,48 @@ class VPScalarIVStepsRecipe : public VPRecipeWithIRFlags,
   }
 };
 
+/// Casting from VPRecipeBase -> VPPhiAccessors is supported for all recipe
+/// types implementing VPPhiAccessors.
+template <> struct CastIsPossible<VPPhiAccessors, const VPRecipeBase *> {
+  static inline bool isPossible(const VPRecipeBase *f) {
+    return isa<VPIRPhi, VPHeaderPHIRecipe, VPWidenPHIRecipe, VPPhi>(f);
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fhahn wrote:

Yes, but I left it out for now because more work will be needed as there the operands also don't match the # of predecessors.

https://github.com/llvm/llvm-project/pull/124838