[llvm] [VPlan] Use scalar VPPhi instead of VPWidenPHIRecipe in createPlainCFG. (PR #150847)

[via llvm-commits]

================
@@ -1243,8 +1243,20 @@ struct LLVM_ABI_FOR_TEST VPPhi : public VPInstruction, public VPPhiAccessors {
     return R && R->getOpcode() == Instruction::PHI;
   }
 
+  static inline bool classof(const VPValue *V) {
+    auto *VPI = dyn_cast<VPInstruction>(V);
+    return VPI && VPI->getOpcode() == Instruction::PHI;
----------------
ayalz wrote:

Also holds for above classof, for consistency.

https://github.com/llvm/llvm-project/pull/150847