Define the behavior if passed param is VP intrinsic.

Author: Mel-Chen

llvm/include/llvm/IR/IntrinsicInst.h

@@ -569,8 +569,9 @@ class VPIntrinsic : public IntrinsicInst {
   /// The llvm.vp.* intrinsics for this instruction Opcode
   static Intrinsic::ID getForOpcode(unsigned OC);
 
-  /// The llvm.vp.* intrinsics for this intrinsic ID.
-  static Intrinsic::ID getForIntrinsic(Intrinsic::ID);
+  /// The llvm.vp.* intrinsics for this intrinsic ID \p Id. Return \p Id if it
+  /// is already a VP intrinsic.
+  static Intrinsic::ID getForIntrinsic(Intrinsic::ID Id);
 
   // Whether \p ID is a VP intrinsic ID.
   static bool isVPIntrinsic(Intrinsic::ID);

llvm/lib/IR/IntrinsicInst.cpp

@@ -600,6 +600,9 @@ Intrinsic::ID VPIntrinsic::getForOpcode(unsigned IROPC) {
 }
 
 Intrinsic::ID VPIntrinsic::getForIntrinsic(Intrinsic::ID Id) {
+  if (isVPIntrinsic(Id))
+    return Id;
+
   switch (Id) {
   default:
     break;