[llvm] [VPlan] Introduce VPSingleDefRecipe. (PR #77023)

[via llvm-commits]

================
@@ -1433,6 +1493,9 @@ class VPHeaderPHIRecipe : public VPRecipeBase, public VPValue {
     return B && B->getVPDefID() >= VPRecipeBase::VPFirstHeaderPHISC &&
            B->getVPDefID() <= VPRecipeBase::VPLastHeaderPHISC;
   }
+  static inline bool classof(const VPSingleDefRecipe *R) {
+    return classof(cast<VPRecipeBase>(R));
+  }
----------------
ayalz wrote:

Is this needed, or inherited from VPRecipeBase?

https://github.com/llvm/llvm-project/pull/77023