Fixup, reuse same function as select instruction

Author: ElvisWang123

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp

@@ -1132,11 +1132,10 @@ RISCVTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
     return getCmpSelInstrCost(*FOp, ICA.getReturnType(), ICA.getArgTypes()[0],
                               CmpInst::BAD_ICMP_PREDICATE, CostKind);
   }
-  case Intrinsic::vp_merge: {
-    auto LT = getTypeLegalizationCost(RetTy);
-    return LT.first *
-           getRISCVInstructionCost(RISCV::VMERGE_VVM, LT.second, CostKind);
-  }
+  case Intrinsic::vp_merge:
+    return getCmpSelInstrCost(Instruction::Select, ICA.getReturnType(),
+                              ICA.getArgTypes()[0], CmpInst::BAD_ICMP_PREDICATE,
+                              CostKind);
   }
 
   if (ST->hasVInstructions() && RetTy->isVectorTy()) {