[RISCV][NFC] Add getVLOperand for RVV intrinsics.

Use the VLOperand information to get the VL.

Differential Revision: https://reviews.llvm.org/D118156

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -1547,6 +1547,19 @@ bool RISCVTargetLowering::isLegalElementTypeForRVV(Type *ScalarTy) const {
   return false;
 }
 
+static SDValue getVLOperand(SDValue Op) {
+  assert((Op.getOpcode() == ISD::INTRINSIC_WO_CHAIN ||
+          Op.getOpcode() == ISD::INTRINSIC_W_CHAIN) &&
+         "Unexpected opcode");
+  bool HasChain = Op.getOpcode() == ISD::INTRINSIC_W_CHAIN;
+  unsigned IntNo = Op.getConstantOperandVal(HasChain ? 1 : 0);
+  const RISCVVIntrinsicsTable::RISCVVIntrinsicInfo *II =
+      RISCVVIntrinsicsTable::getRISCVVIntrinsicInfo(IntNo);
+  if (!II)
+    return SDValue();
+  return Op.getOperand(II->VLOperand + 1 + HasChain);
+}
+
 static bool useRVVForFixedLengthVectorVT(MVT VT,
                                          const RISCVSubtarget &Subtarget) {
   assert(VT.isFixedLengthVector() && "Expected a fixed length vector type!");
@@ -4372,7 +4385,7 @@ static SDValue lowerVectorIntrinsicSplats(SDValue Op, SelectionDAG &DAG,
   // We need to convert the scalar to a splat vector.
   // FIXME: Can we implicitly truncate the scalar if it is known to
   // be sign extended?
-  SDValue VL = Op.getOperand(II->VLOperand + 1 + HasChain);
+  SDValue VL = getVLOperand(Op);
   assert(VL.getValueType() == XLenVT);
   ScalarOp = splatSplitI64WithVL(DL, VT, ScalarOp, VL, DAG);
   return DAG.getNode(Op->getOpcode(), DL, Op->getVTList(), Operands);
@@ -4460,7 +4473,7 @@ SDValue RISCVTargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op,
     //   vmerge.vvm vDest, vSrc, vVal, mMask
     MVT VT = Op.getSimpleValueType();
     SDValue Vec = Op.getOperand(1);
-    SDValue VL = Op.getOperand(3);
+    SDValue VL = getVLOperand(Op);
 
     SDValue SplattedVal = splatSplitI64WithVL(DL, VT, Scalar, VL, DAG);
     SDValue SplattedIdx = DAG.getNode(RISCVISD::VMV_V_X_VL, DL, VT,
@@ -4506,7 +4519,7 @@ SDValue RISCVTargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op,
                                    DAG.getConstant(1, DL, XLenVT));
 
     // Double the VL since we halved SEW.
-    SDValue VL = Op.getOperand(NumOps - (1 + OpOffset));
+    SDValue VL = getVLOperand(Op);
     SDValue I32VL =
         DAG.getNode(ISD::SHL, DL, XLenVT, VL, DAG.getConstant(1, DL, XLenVT));