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

[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);
+  }
+};
+/// Support casting from VPRecipeBase -> VPPhiAccessors, by down-casting to the
+/// recipe types implementing VPPhiAccessors.
+template <>
+struct CastInfo<VPPhiAccessors, const VPRecipeBase *>
+    : public CastIsPossible<VPPhiAccessors, const VPRecipeBase *> {
+
+  using Self = CastInfo<VPPhiAccessors, const VPRecipeBase *>;
+
+  using CastReturnType =
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ayalz wrote:

Where is CastReturnType used?

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