[Hexagon] Use isNullConstant (NFC)

Author: kazutakahirata

llvm/lib/Target/Hexagon/HexagonISelDAGToDAG.cpp

@@ -1028,15 +1028,11 @@ void HexagonDAGToDAGISel::ppSimplifyOrSelect0(std::vector<SDNode*> &&Nodes) {
     if (I->getOpcode() != ISD::OR)
       continue;
 
-    auto IsZero = [] (const SDValue &V) -> bool {
-      if (ConstantSDNode *SC = dyn_cast<ConstantSDNode>(V.getNode()))
-        return SC->isZero();
-      return false;
-    };
-    auto IsSelect0 = [IsZero] (const SDValue &Op) -> bool {
+    auto IsSelect0 = [](const SDValue &Op) -> bool {
       if (Op.getOpcode() != ISD::SELECT)
         return false;
-      return IsZero(Op.getOperand(1)) || IsZero(Op.getOperand(2));
+      return isNullConstant(Op.getOperand(1)) ||
+             isNullConstant(Op.getOperand(2));
     };
 
     SDValue N0 = I->getOperand(0), N1 = I->getOperand(1);
@@ -1050,11 +1046,11 @@ void HexagonDAGToDAGISel::ppSimplifyOrSelect0(std::vector<SDNode*> &&Nodes) {
       SDValue SX = SOp.getOperand(1);
       SDValue SY = SOp.getOperand(2);
       SDLoc DLS = SOp;
-      if (IsZero(SY)) {
+      if (isNullConstant(SY)) {
         SDValue NewOr = DAG.getNode(ISD::OR, DLS, VT, SX, VOp);
         SDValue NewSel = DAG.getNode(ISD::SELECT, DLS, VT, SC, NewOr, VOp);
         DAG.ReplaceAllUsesWith(I, NewSel.getNode());
-      } else if (IsZero(SX)) {
+      } else if (isNullConstant(SX)) {
         SDValue NewOr = DAG.getNode(ISD::OR, DLS, VT, SY, VOp);
         SDValue NewSel = DAG.getNode(ISD::SELECT, DLS, VT, SC, VOp, NewOr);
         DAG.ReplaceAllUsesWith(I, NewSel.getNode());

llvm/lib/Target/Hexagon/HexagonISelLowering.cpp

@@ -2717,12 +2717,11 @@ HexagonTargetLowering::extractVectorPred(SDValue VecV, SDValue IdxV,
   assert(VecWidth == 8 || VecWidth == 4 || VecWidth == 2);
 
   // Check if this is an extract of the lowest bit.
-  if (auto *IdxN = dyn_cast<ConstantSDNode>(IdxV)) {
+  if (isNullConstant(IdxV) && ValTy.getSizeInBits() == 1) {
     // Extracting the lowest bit is a no-op, but it changes the type,
     // so it must be kept as an operation to avoid errors related to
     // type mismatches.
-    if (IdxN->isZero() && ValTy.getSizeInBits() == 1)
-      return DAG.getNode(HexagonISD::TYPECAST, dl, MVT::i1, VecV);
+    return DAG.getNode(HexagonISD::TYPECAST, dl, MVT::i1, VecV);
   }
 
   // If the value extracted is a single bit, use tstbit.

llvm/lib/Target/Hexagon/HexagonISelLoweringHVX.cpp

@@ -829,8 +829,7 @@ HexagonTargetLowering::buildHvxVectorReg(ArrayRef<SDValue> Values,
     return DAG.getUNDEF(VecTy);
   if (IsSplat) {
     assert(SplatV.getNode());
-    auto *IdxN = dyn_cast<ConstantSDNode>(SplatV.getNode());
-    if (IdxN && IdxN->isZero())
+    if (isNullConstant(SplatV))
       return getZero(dl, VecTy, DAG);
     MVT WordTy = MVT::getVectorVT(MVT::i32, HwLen/4);
     SDValue S = DAG.getNode(ISD::SPLAT_VECTOR, dl, WordTy, SplatV);