llvm/lib/Target/Hexagon/HexagonISelLoweringHVX.cpp

//===-- HexagonISelLoweringHVX.cpp --- Lowering HVX operations ------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "HexagonISelLowering.h"
#include "HexagonRegisterInfo.h"
#include "HexagonSubtarget.h"

using namespace llvm;

SDValue
HexagonTargetLowering::getInt(unsigned IntId, MVT ResTy, ArrayRef<SDValue> Ops,
                              const SDLoc &dl, SelectionDAG &DAG) const {
  SmallVector<SDValue,4> IntOps;
  IntOps.push_back(DAG.getConstant(IntId, dl, MVT::i32));
  for (const SDValue &Op : Ops)
    IntOps.push_back(Op);
  return DAG.getNode(ISD::INTRINSIC_WO_CHAIN, dl, ResTy, IntOps);
}

MVT
HexagonTargetLowering::typeJoin(const TypePair &Tys) const {
  assert(Tys.first.getVectorElementType() == Tys.second.getVectorElementType());

  MVT ElemTy = Tys.first.getVectorElementType();
  return MVT::getVectorVT(ElemTy, Tys.first.getVectorNumElements() +
                                  Tys.second.getVectorNumElements());
}

HexagonTargetLowering::TypePair
HexagonTargetLowering::typeSplit(MVT VecTy) const {
  assert(VecTy.isVector());
  unsigned NumElem = VecTy.getVectorNumElements();
  assert((NumElem % 2) == 0 && "Expecting even-sized vector type");
  MVT HalfTy = MVT::getVectorVT(VecTy.getVectorElementType(), NumElem/2);
  return { HalfTy, HalfTy };
}

MVT
HexagonTargetLowering::typeExtElem(MVT VecTy, unsigned Factor) const {
  MVT ElemTy = VecTy.getVectorElementType();
  MVT NewElemTy = MVT::getIntegerVT(ElemTy.getSizeInBits() * Factor);
  return MVT::getVectorVT(NewElemTy, VecTy.getVectorNumElements());
}

MVT
HexagonTargetLowering::typeTruncElem(MVT VecTy, unsigned Factor) const {
  MVT ElemTy = VecTy.getVectorElementType();
  MVT NewElemTy = MVT::getIntegerVT(ElemTy.getSizeInBits() / Factor);
  return MVT::getVectorVT(NewElemTy, VecTy.getVectorNumElements());
}

SDValue
HexagonTargetLowering::opCastElem(SDValue Vec, MVT ElemTy,
                                  SelectionDAG &DAG) const {
  if (ty(Vec).getVectorElementType() == ElemTy)
    return Vec;
  MVT CastTy = tyVector(Vec.getValueType().getSimpleVT(), ElemTy);
  return DAG.getBitcast(CastTy, Vec);
}

SDValue
HexagonTargetLowering::opJoin(const VectorPair &Ops, const SDLoc &dl,
                              SelectionDAG &DAG) const {
  return DAG.getNode(ISD::CONCAT_VECTORS, dl, typeJoin(ty(Ops)),
                     Ops.second, Ops.first);
}

HexagonTargetLowering::VectorPair
HexagonTargetLowering::opSplit(SDValue Vec, const SDLoc &dl,
                               SelectionDAG &DAG) const {
  TypePair Tys = typeSplit(ty(Vec));
  return DAG.SplitVector(Vec, dl, Tys.first, Tys.second);
}

bool
HexagonTargetLowering::isHvxSingleTy(MVT Ty) const {
  return Subtarget.isHVXVectorType(Ty) &&
         Ty.getSizeInBits() == 8 * Subtarget.getVectorLength();
}

bool
HexagonTargetLowering::isHvxPairTy(MVT Ty) const {
  return Subtarget.isHVXVectorType(Ty) &&
         Ty.getSizeInBits() == 16 * Subtarget.getVectorLength();
}

SDValue
HexagonTargetLowering::convertToByteIndex(SDValue ElemIdx, MVT ElemTy,
                                          SelectionDAG &DAG) const {
  if (ElemIdx.getValueType().getSimpleVT() != MVT::i32)
    ElemIdx = DAG.getBitcast(MVT::i32, ElemIdx);

  unsigned ElemWidth = ElemTy.getSizeInBits();
  if (ElemWidth == 8)
    return ElemIdx;

  unsigned L = Log2_32(ElemWidth/8);
  const SDLoc &dl(ElemIdx);
  return DAG.getNode(ISD::SHL, dl, MVT::i32,
                     {ElemIdx, DAG.getConstant(L, dl, MVT::i32)});
}

SDValue
HexagonTargetLowering::getIndexInWord32(SDValue Idx, MVT ElemTy,
                                        SelectionDAG &DAG) const {
  unsigned ElemWidth = ElemTy.getSizeInBits();
  assert(ElemWidth >= 8 && ElemWidth <= 32);
  if (ElemWidth == 32)
    return Idx;

  if (ty(Idx) != MVT::i32)
    Idx = DAG.getBitcast(MVT::i32, Idx);
  const SDLoc &dl(Idx);
  SDValue Mask = DAG.getConstant(32/ElemWidth - 1, dl, MVT::i32);
  SDValue SubIdx = DAG.getNode(ISD::AND, dl, MVT::i32, {Idx, Mask});
  return SubIdx;
}

SDValue
HexagonTargetLowering::getByteShuffle(const SDLoc &dl, SDValue Op0,
                                      SDValue Op1, ArrayRef<int> Mask,
                                      SelectionDAG &DAG) const {
  MVT OpTy = ty(Op0);
  assert(OpTy == ty(Op1));

  MVT ElemTy = OpTy.getVectorElementType();
  if (ElemTy == MVT::i8)
    return DAG.getVectorShuffle(OpTy, dl, Op0, Op1, Mask);
  assert(ElemTy.getSizeInBits() >= 8);

  MVT ResTy = tyVector(OpTy, MVT::i8);
  unsigned ElemSize = ElemTy.getSizeInBits() / 8;

  SmallVector<int,128> ByteMask;
  for (int M : Mask) {
    if (M < 0) {
      for (unsigned I = 0; I != ElemSize; ++I)
        ByteMask.push_back(-1);
    } else {
      int NewM = M*ElemSize;
      for (unsigned I = 0; I != ElemSize; ++I)
        ByteMask.push_back(NewM+I);
    }
  }
  assert(ResTy.getVectorNumElements() == ByteMask.size());
  return DAG.getVectorShuffle(ResTy, dl, opCastElem(Op0, MVT::i8, DAG),
                              opCastElem(Op1, MVT::i8, DAG), ByteMask);
}

SDValue
HexagonTargetLowering::buildHvxVectorReg(ArrayRef<SDValue> Values,
                                         const SDLoc &dl, MVT VecTy,
                                         SelectionDAG &DAG) const {
  unsigned VecLen = Values.size();
  MachineFunction &MF = DAG.getMachineFunction();
  MVT ElemTy = VecTy.getVectorElementType();
  unsigned ElemWidth = ElemTy.getSizeInBits();
  unsigned HwLen = Subtarget.getVectorLength();

  unsigned ElemSize = ElemWidth / 8;
  assert(ElemSize*VecLen == HwLen);
  SmallVector<SDValue,32> Words;

  if (VecTy.getVectorElementType() != MVT::i32) {
    assert((ElemSize == 1 || ElemSize == 2) && "Invalid element size");
    unsigned OpsPerWord = (ElemSize == 1) ? 4 : 2;
    MVT PartVT = MVT::getVectorVT(VecTy.getVectorElementType(), OpsPerWord);
    for (unsigned i = 0; i != VecLen; i += OpsPerWord) {
      SDValue W = buildVector32(Values.slice(i, OpsPerWord), dl, PartVT, DAG);
      Words.push_back(DAG.getBitcast(MVT::i32, W));
    }
  } else {
    Words.assign(Values.begin(), Values.end());
  }

  unsigned NumWords = Words.size();
  bool IsSplat = true, IsUndef = true;
  SDValue SplatV;
  for (unsigned i = 0; i != NumWords && IsSplat; ++i) {
    if (isUndef(Words[i]))
      continue;
    IsUndef = false;
    if (!SplatV.getNode())
      SplatV = Words[i];
    else if (SplatV != Words[i])
      IsSplat = false;
  }
  if (IsUndef)
    return DAG.getUNDEF(VecTy);
  if (IsSplat) {
    assert(SplatV.getNode());
    auto *IdxN = dyn_cast<ConstantSDNode>(SplatV.getNode());
    if (IdxN && IdxN->isNullValue())
      return getZero(dl, VecTy, DAG);
    MVT WordTy = MVT::getVectorVT(MVT::i32, HwLen/4);
    SDValue SV = DAG.getNode(HexagonISD::VSPLAT, dl, WordTy, SplatV);
    return DAG.getBitcast(VecTy, SV);
  }

  // Delay recognizing constant vectors until here, so that we can generate
  // a vsplat.
  SmallVector<ConstantInt*, 128> Consts(VecLen);
  bool AllConst = getBuildVectorConstInts(Values, VecTy, DAG, Consts);
  if (AllConst) {
    ArrayRef<Constant*> Tmp((Constant**)Consts.begin(),
                            (Constant**)Consts.end());
    Constant *CV = ConstantVector::get(Tmp);
    unsigned Align = HwLen;
    SDValue CP = LowerConstantPool(DAG.getConstantPool(CV, VecTy, Align), DAG);
    return DAG.getLoad(VecTy, dl, DAG.getEntryNode(), CP,
                       MachinePointerInfo::getConstantPool(MF), Align);
  }

  // Construct two halves in parallel, then or them together.
  assert(4*Words.size() == Subtarget.getVectorLength());
  SDValue HalfV0 = getInstr(Hexagon::V6_vd0, dl, VecTy, {}, DAG);
  SDValue HalfV1 = getInstr(Hexagon::V6_vd0, dl, VecTy, {}, DAG);
  SDValue S = DAG.getConstant(4, dl, MVT::i32);
  for (unsigned i = 0; i != NumWords/2; ++i) {
    SDValue N = DAG.getNode(HexagonISD::VINSERTW0, dl, VecTy,
                            {HalfV0, Words[i]});
    SDValue M = DAG.getNode(HexagonISD::VINSERTW0, dl, VecTy,
                            {HalfV1, Words[i+NumWords/2]});
    HalfV0 = DAG.getNode(HexagonISD::VROR, dl, VecTy, {N, S});
    HalfV1 = DAG.getNode(HexagonISD::VROR, dl, VecTy, {M, S});
  }

  HalfV0 = DAG.getNode(HexagonISD::VROR, dl, VecTy,
                       {HalfV0, DAG.getConstant(HwLen/2, dl, MVT::i32)});
  SDValue DstV = DAG.getNode(ISD::OR, dl, VecTy, {HalfV0, HalfV1});
  return DstV;
}

SDValue
HexagonTargetLowering::createHvxPrefixPred(SDValue PredV, const SDLoc &dl,
      unsigned BitBytes, bool ZeroFill, SelectionDAG &DAG) const {
  MVT PredTy = ty(PredV);
  unsigned HwLen = Subtarget.getVectorLength();
  MVT ByteTy = MVT::getVectorVT(MVT::i8, HwLen);

  if (Subtarget.isHVXVectorType(PredTy, true)) {
    // Move the vector predicate SubV to a vector register, and scale it
    // down to match the representation (bytes per type element) that VecV
    // uses. The scaling down will pick every 2nd or 4th (every Scale-th
    // in general) element and put them at the front of the resulting
    // vector. This subvector will then be inserted into the Q2V of VecV.
    // To avoid having an operation that generates an illegal type (short
    // vector), generate a full size vector.
    //
    SDValue T = DAG.getNode(HexagonISD::Q2V, dl, ByteTy, PredV);
    SmallVector<int,128> Mask(HwLen);
    // Scale = BitBytes(PredV) / Given BitBytes.
    unsigned Scale = HwLen / (PredTy.getVectorNumElements() * BitBytes);
    unsigned BlockLen = PredTy.getVectorNumElements() * BitBytes;

    for (unsigned i = 0; i != HwLen; ++i) {
      unsigned Num = i % Scale;
      unsigned Off = i / Scale;
      Mask[BlockLen*Num + Off] = i;
    }
    SDValue S = DAG.getVectorShuffle(ByteTy, dl, T, DAG.getUNDEF(ByteTy), Mask);
    if (!ZeroFill)
      return S;
    // Fill the bytes beyond BlockLen with 0s.
    MVT BoolTy = MVT::getVectorVT(MVT::i1, HwLen);
    SDValue Q = getInstr(Hexagon::V6_pred_scalar2, dl, BoolTy,
                         {DAG.getConstant(BlockLen, dl, MVT::i32)}, DAG);
    SDValue M = DAG.getNode(HexagonISD::Q2V, dl, ByteTy, Q);
    return DAG.getNode(ISD::AND, dl, ByteTy, S, M);
  }

  // Make sure that this is a valid scalar predicate.
  assert(PredTy == MVT::v2i1 || PredTy == MVT::v4i1 || PredTy == MVT::v8i1);

  unsigned Bytes = 8 / PredTy.getVectorNumElements();
  SmallVector<SDValue,4> Words[2];
  unsigned IdxW = 0;

  auto Lo32 = [&DAG, &dl] (SDValue P) {
    return DAG.getTargetExtractSubreg(Hexagon::isub_lo, dl, MVT::i32, P);
  };
  auto Hi32 = [&DAG, &dl] (SDValue P) {
    return DAG.getTargetExtractSubreg(Hexagon::isub_hi, dl, MVT::i32, P);
  };

  SDValue W0 = isUndef(PredV)
                  ? DAG.getUNDEF(MVT::i64)
                  : DAG.getNode(HexagonISD::P2D, dl, MVT::i64, PredV);
  Words[IdxW].push_back(Hi32(W0));
  Words[IdxW].push_back(Lo32(W0));

  while (Bytes < BitBytes) {
    IdxW ^= 1;
    Words[IdxW].clear();

    if (Bytes < 4) {
      for (const SDValue &W : Words[IdxW ^ 1]) {
        SDValue T = expandPredicate(W, dl, DAG);
        Words[IdxW].push_back(Hi32(T));
        Words[IdxW].push_back(Lo32(T));
      }
    } else {
      for (const SDValue &W : Words[IdxW ^ 1]) {
        Words[IdxW].push_back(W);
        Words[IdxW].push_back(W);
      }
    }
    Bytes *= 2;
  }

  assert(Bytes == BitBytes);

  SDValue Vec = ZeroFill ? getZero(dl, ByteTy, DAG) : DAG.getUNDEF(ByteTy);
  SDValue S4 = DAG.getConstant(HwLen-4, dl, MVT::i32);
  for (const SDValue &W : Words[IdxW]) {
    Vec = DAG.getNode(HexagonISD::VROR, dl, ByteTy, Vec, S4);
    Vec = DAG.getNode(HexagonISD::VINSERTW0, dl, ByteTy, Vec, W);
  }

  return Vec;
}

SDValue
HexagonTargetLowering::buildHvxVectorPred(ArrayRef<SDValue> Values,
                                          const SDLoc &dl, MVT VecTy,
                                          SelectionDAG &DAG) const {
  // Construct a vector V of bytes, such that a comparison V >u 0 would
  // produce the required vector predicate.
  unsigned VecLen = Values.size();
  unsigned HwLen = Subtarget.getVectorLength();
  assert(VecLen <= HwLen || VecLen == 8*HwLen);
  SmallVector<SDValue,128> Bytes;
  bool AllT = true, AllF = true;

  auto IsTrue = [] (SDValue V) {
    if (const auto *N = dyn_cast<ConstantSDNode>(V.getNode()))
      return !N->isNullValue();
    return false;
  };
  auto IsFalse = [] (SDValue V) {
    if (const auto *N = dyn_cast<ConstantSDNode>(V.getNode()))
      return N->isNullValue();
    return false;
  };

  if (VecLen <= HwLen) {
    // In the hardware, each bit of a vector predicate corresponds to a byte
    // of a vector register. Calculate how many bytes does a bit of VecTy
    // correspond to.
    assert(HwLen % VecLen == 0);
    unsigned BitBytes = HwLen / VecLen;
    for (SDValue V : Values) {
      AllT &= IsTrue(V);
      AllF &= IsFalse(V);

      SDValue Ext = !V.isUndef() ? DAG.getZExtOrTrunc(V, dl, MVT::i8)
                                 : DAG.getUNDEF(MVT::i8);
      for (unsigned B = 0; B != BitBytes; ++B)
        Bytes.push_back(Ext);
    }
  } else {
    // There are as many i1 values, as there are bits in a vector register.
    // Divide the values into groups of 8 and check that each group consists
    // of the same value (ignoring undefs).
    for (unsigned I = 0; I != VecLen; I += 8) {
      unsigned B = 0;
      // Find the first non-undef value in this group.
      for (; B != 8; ++B) {
        if (!Values[I+B].isUndef())
          break;
      }
      SDValue F = Values[I+B];
      AllT &= IsTrue(F);
      AllF &= IsFalse(F);

      SDValue Ext = (B < 8) ? DAG.getZExtOrTrunc(F, dl, MVT::i8)
                            : DAG.getUNDEF(MVT::i8);
      Bytes.push_back(Ext);
      // Verify that the rest of values in the group are the same as the
      // first.
      for (; B != 8; ++B)
        assert(Values[I+B].isUndef() || Values[I+B] == F);
    }
  }

  if (AllT)
    return DAG.getNode(HexagonISD::QTRUE, dl, VecTy);
  if (AllF)
    return DAG.getNode(HexagonISD::QFALSE, dl, VecTy);

  MVT ByteTy = MVT::getVectorVT(MVT::i8, HwLen);
  SDValue ByteVec = buildHvxVectorReg(Bytes, dl, ByteTy, DAG);
  return DAG.getNode(HexagonISD::V2Q, dl, VecTy, ByteVec);
}

SDValue
HexagonTargetLowering::extractHvxElementReg(SDValue VecV, SDValue IdxV,
      const SDLoc &dl, MVT ResTy, SelectionDAG &DAG) const {
  MVT ElemTy = ty(VecV).getVectorElementType();

  unsigned ElemWidth = ElemTy.getSizeInBits();
  assert(ElemWidth >= 8 && ElemWidth <= 32);
  (void)ElemWidth;

  SDValue ByteIdx = convertToByteIndex(IdxV, ElemTy, DAG);
  SDValue ExWord = DAG.getNode(HexagonISD::VEXTRACTW, dl, MVT::i32,
                               {VecV, ByteIdx});
  if (ElemTy == MVT::i32)
    return ExWord;

  // Have an extracted word, need to extract the smaller element out of it.
  // 1. Extract the bits of (the original) IdxV that correspond to the index
  //    of the desired element in the 32-bit word.
  SDValue SubIdx = getIndexInWord32(IdxV, ElemTy, DAG);
  // 2. Extract the element from the word.
  SDValue ExVec = DAG.getBitcast(tyVector(ty(ExWord), ElemTy), ExWord);
  return extractVector(ExVec, SubIdx, dl, ElemTy, MVT::i32, DAG);
}

SDValue
HexagonTargetLowering::extractHvxElementPred(SDValue VecV, SDValue IdxV,
      const SDLoc &dl, MVT ResTy, SelectionDAG &DAG) const {
  // Implement other return types if necessary.
  assert(ResTy == MVT::i1);

  unsigned HwLen = Subtarget.getVectorLength();
  MVT ByteTy = MVT::getVectorVT(MVT::i8, HwLen);
  SDValue ByteVec = DAG.getNode(HexagonISD::Q2V, dl, ByteTy, VecV);

  unsigned Scale = HwLen / ty(VecV).getVectorNumElements();
  SDValue ScV = DAG.getConstant(Scale, dl, MVT::i32);
  IdxV = DAG.getNode(ISD::MUL, dl, MVT::i32, IdxV, ScV);

  SDValue ExtB = extractHvxElementReg(ByteVec, IdxV, dl, MVT::i32, DAG);
  SDValue Zero = DAG.getTargetConstant(0, dl, MVT::i32);
  return getInstr(Hexagon::C2_cmpgtui, dl, MVT::i1, {ExtB, Zero}, DAG);
}

SDValue
HexagonTargetLowering::insertHvxElementReg(SDValue VecV, SDValue IdxV,
      SDValue ValV, const SDLoc &dl, SelectionDAG &DAG) const {
  MVT ElemTy = ty(VecV).getVectorElementType();

  unsigned ElemWidth = ElemTy.getSizeInBits();
  assert(ElemWidth >= 8 && ElemWidth <= 32);
  (void)ElemWidth;

  auto InsertWord = [&DAG,&dl,this] (SDValue VecV, SDValue ValV,
                                     SDValue ByteIdxV) {
    MVT VecTy = ty(VecV);
    unsigned HwLen = Subtarget.getVectorLength();
    SDValue MaskV = DAG.getNode(ISD::AND, dl, MVT::i32,
                                {ByteIdxV, DAG.getConstant(-4, dl, MVT::i32)});
    SDValue RotV = DAG.getNode(HexagonISD::VROR, dl, VecTy, {VecV, MaskV});
    SDValue InsV = DAG.getNode(HexagonISD::VINSERTW0, dl, VecTy, {RotV, ValV});
    SDValue SubV = DAG.getNode(ISD::SUB, dl, MVT::i32,
                               {DAG.getConstant(HwLen, dl, MVT::i32), MaskV});
    SDValue TorV = DAG.getNode(HexagonISD::VROR, dl, VecTy, {InsV, SubV});
    return TorV;
  };

  SDValue ByteIdx = convertToByteIndex(IdxV, ElemTy, DAG);
  if (ElemTy == MVT::i32)
    return InsertWord(VecV, ValV, ByteIdx);

  // If this is not inserting a 32-bit word, convert it into such a thing.
  // 1. Extract the existing word from the target vector.
  SDValue WordIdx = DAG.getNode(ISD::SRL, dl, MVT::i32,
                                {ByteIdx, DAG.getConstant(2, dl, MVT::i32)});
  SDValue Ext = extractHvxElementReg(opCastElem(VecV, MVT::i32, DAG), WordIdx,
                                     dl, MVT::i32, DAG);

  // 2. Treating the extracted word as a 32-bit vector, insert the given
  //    value into it.
  SDValue SubIdx = getIndexInWord32(IdxV, ElemTy, DAG);
  MVT SubVecTy = tyVector(ty(Ext), ElemTy);
  SDValue Ins = insertVector(DAG.getBitcast(SubVecTy, Ext),
                             ValV, SubIdx, dl, ElemTy, DAG);

  // 3. Insert the 32-bit word back into the original vector.
  return InsertWord(VecV, Ins, ByteIdx);
}

SDValue
HexagonTargetLowering::insertHvxElementPred(SDValue VecV, SDValue IdxV,
      SDValue ValV, const SDLoc &dl, SelectionDAG &DAG) const {
  unsigned HwLen = Subtarget.getVectorLength();
  MVT ByteTy = MVT::getVectorVT(MVT::i8, HwLen);
  SDValue ByteVec = DAG.getNode(HexagonISD::Q2V, dl, ByteTy, VecV);

  unsigned Scale = HwLen / ty(VecV).getVectorNumElements();
  SDValue ScV = DAG.getConstant(Scale, dl, MVT::i32);
  IdxV = DAG.getNode(ISD::MUL, dl, MVT::i32, IdxV, ScV);
  ValV = DAG.getNode(ISD::SIGN_EXTEND, dl, MVT::i32, ValV);

  SDValue InsV = insertHvxElementReg(ByteVec, IdxV, ValV, dl, DAG);
  return DAG.getNode(HexagonISD::V2Q, dl, ty(VecV), InsV);
}

SDValue
HexagonTargetLowering::extractHvxSubvectorReg(SDValue VecV, SDValue IdxV,
      const SDLoc &dl, MVT ResTy, SelectionDAG &DAG) const {
  MVT VecTy = ty(VecV);
  unsigned HwLen = Subtarget.getVectorLength();
  unsigned Idx = cast<ConstantSDNode>(IdxV.getNode())->getZExtValue();
  MVT ElemTy = VecTy.getVectorElementType();
  unsigned ElemWidth = ElemTy.getSizeInBits();

  // If the source vector is a vector pair, get the single vector containing
  // the subvector of interest. The subvector will never overlap two single
  // vectors.
  if (isHvxPairTy(VecTy)) {
    unsigned SubIdx;
    if (Idx * ElemWidth >= 8*HwLen) {
      SubIdx = Hexagon::vsub_hi;
      Idx -= VecTy.getVectorNumElements() / 2;
    } else {
      SubIdx = Hexagon::vsub_lo;
    }
    VecTy = typeSplit(VecTy).first;
    VecV = DAG.getTargetExtractSubreg(SubIdx, dl, VecTy, VecV);
    if (VecTy == ResTy)
      return VecV;
  }

  // The only meaningful subvectors of a single HVX vector are those that
  // fit in a scalar register.
  assert(ResTy.getSizeInBits() == 32 || ResTy.getSizeInBits() == 64);

  MVT WordTy = tyVector(VecTy, MVT::i32);
  SDValue WordVec = DAG.getBitcast(WordTy, VecV);
  unsigned WordIdx = (Idx*ElemWidth) / 32;

  SDValue W0Idx = DAG.getConstant(WordIdx, dl, MVT::i32);
  SDValue W0 = extractHvxElementReg(WordVec, W0Idx, dl, MVT::i32, DAG);
  if (ResTy.getSizeInBits() == 32)
    return DAG.getBitcast(ResTy, W0);

  SDValue W1Idx = DAG.getConstant(WordIdx+1, dl, MVT::i32);
  SDValue W1 = extractHvxElementReg(WordVec, W1Idx, dl, MVT::i32, DAG);
  SDValue WW = DAG.getNode(HexagonISD::COMBINE, dl, MVT::i64, {W1, W0});
  return DAG.getBitcast(ResTy, WW);
}

SDValue
HexagonTargetLowering::extractHvxSubvectorPred(SDValue VecV, SDValue IdxV,
      const SDLoc &dl, MVT ResTy, SelectionDAG &DAG) const {
  MVT VecTy = ty(VecV);
  unsigned HwLen = Subtarget.getVectorLength();
  MVT ByteTy = MVT::getVectorVT(MVT::i8, HwLen);
  SDValue ByteVec = DAG.getNode(HexagonISD::Q2V, dl, ByteTy, VecV);
  // IdxV is required to be a constant.
  unsigned Idx = cast<ConstantSDNode>(IdxV.getNode())->getZExtValue();

  unsigned ResLen = ResTy.getVectorNumElements();
  unsigned BitBytes = HwLen / VecTy.getVectorNumElements();
  unsigned Offset = Idx * BitBytes;
  SDValue Undef = DAG.getUNDEF(ByteTy);
  SmallVector<int,128> Mask;

  if (Subtarget.isHVXVectorType(ResTy, true)) {
    // Converting between two vector predicates. Since the result is shorter
    // than the source, it will correspond to a vector predicate with the
    // relevant bits replicated. The replication count is the ratio of the
    // source and target vector lengths.
    unsigned Rep = VecTy.getVectorNumElements() / ResLen;
    assert(isPowerOf2_32(Rep) && HwLen % Rep == 0);
    for (unsigned i = 0; i != HwLen/Rep; ++i) {
      for (unsigned j = 0; j != Rep; ++j)
        Mask.push_back(i + Offset);
    }
    SDValue ShuffV = DAG.getVectorShuffle(ByteTy, dl, ByteVec, Undef, Mask);
    return DAG.getNode(HexagonISD::V2Q, dl, ResTy, ShuffV);
  }

  // Converting between a vector predicate and a scalar predicate. In the
  // vector predicate, a group of BitBytes bits will correspond to a single
  // i1 element of the source vector type. Those bits will all have the same
  // value. The same will be true for ByteVec, where each byte corresponds
  // to a bit in the vector predicate.
  // The algorithm is to traverse the ByteVec, going over the i1 values from
  // the source vector, and generate the corresponding representation in an
  // 8-byte vector. To avoid repeated extracts from ByteVec, shuffle the
  // elements so that the interesting 8 bytes will be in the low end of the
  // vector.
  unsigned Rep = 8 / ResLen;
  // Make sure the output fill the entire vector register, so repeat the
  // 8-byte groups as many times as necessary.
  for (unsigned r = 0; r != HwLen/ResLen; ++r) {
    // This will generate the indexes of the 8 interesting bytes.
    for (unsigned i = 0; i != ResLen; ++i) {
      for (unsigned j = 0; j != Rep; ++j)
        Mask.push_back(Offset + i*BitBytes);
    }
  }

  SDValue Zero = getZero(dl, MVT::i32, DAG);
  SDValue ShuffV = DAG.getVectorShuffle(ByteTy, dl, ByteVec, Undef, Mask);
  // Combine the two low words from ShuffV into a v8i8, and byte-compare
  // them against 0.
  SDValue W0 = DAG.getNode(HexagonISD::VEXTRACTW, dl, MVT::i32, {ShuffV, Zero});
  SDValue W1 = DAG.getNode(HexagonISD::VEXTRACTW, dl, MVT::i32,
                           {ShuffV, DAG.getConstant(4, dl, MVT::i32)});
  SDValue Vec64 = DAG.getNode(HexagonISD::COMBINE, dl, MVT::v8i8, {W1, W0});
  return getInstr(Hexagon::A4_vcmpbgtui, dl, ResTy,
                  {Vec64, DAG.getTargetConstant(0, dl, MVT::i32)}, DAG);
}

SDValue
HexagonTargetLowering::insertHvxSubvectorReg(SDValue VecV, SDValue SubV,
      SDValue IdxV, const SDLoc &dl, SelectionDAG &DAG) const {
  MVT VecTy = ty(VecV);
  MVT SubTy = ty(SubV);
  unsigned HwLen = Subtarget.getVectorLength();
  MVT ElemTy = VecTy.getVectorElementType();
  unsigned ElemWidth = ElemTy.getSizeInBits();

  bool IsPair = isHvxPairTy(VecTy);
  MVT SingleTy = MVT::getVectorVT(ElemTy, (8*HwLen)/ElemWidth);
  // The two single vectors that VecV consists of, if it's a pair.
  SDValue V0, V1;
  SDValue SingleV = VecV;
  SDValue PickHi;

  if (IsPair) {
    V0 = DAG.getTargetExtractSubreg(Hexagon::vsub_lo, dl, SingleTy, VecV);
    V1 = DAG.getTargetExtractSubreg(Hexagon::vsub_hi, dl, SingleTy, VecV);

    SDValue HalfV = DAG.getConstant(SingleTy.getVectorNumElements(),
                                    dl, MVT::i32);
    PickHi = DAG.getSetCC(dl, MVT::i1, IdxV, HalfV, ISD::SETUGT);
    if (isHvxSingleTy(SubTy)) {
      if (const auto *CN = dyn_cast<const ConstantSDNode>(IdxV.getNode())) {
        unsigned Idx = CN->getZExtValue();
        assert(Idx == 0 || Idx == VecTy.getVectorNumElements()/2);
        unsigned SubIdx = (Idx == 0) ? Hexagon::vsub_lo : Hexagon::vsub_hi;
        return DAG.getTargetInsertSubreg(SubIdx, dl, VecTy, VecV, SubV);
      }
      // If IdxV is not a constant, generate the two variants: with the
      // SubV as the high and as the low subregister, and select the right
      // pair based on the IdxV.
      SDValue InLo = DAG.getNode(ISD::CONCAT_VECTORS, dl, VecTy, {SubV, V1});
      SDValue InHi = DAG.getNode(ISD::CONCAT_VECTORS, dl, VecTy, {V0, SubV});
      return DAG.getNode(ISD::SELECT, dl, VecTy, PickHi, InHi, InLo);
    }
    // The subvector being inserted must be entirely contained in one of
    // the vectors V0 or V1. Set SingleV to the correct one, and update
    // IdxV to be the index relative to the beginning of that vector.
    SDValue S = DAG.getNode(ISD::SUB, dl, MVT::i32, IdxV, HalfV);
    IdxV = DAG.getNode(ISD::SELECT, dl, MVT::i32, PickHi, S, IdxV);
    SingleV = DAG.getNode(ISD::SELECT, dl, SingleTy, PickHi, V1, V0);
  }

  // The only meaningful subvectors of a single HVX vector are those that
  // fit in a scalar register.
  assert(SubTy.getSizeInBits() == 32 || SubTy.getSizeInBits() == 64);
  // Convert IdxV to be index in bytes.
  auto *IdxN = dyn_cast<ConstantSDNode>(IdxV.getNode());
  if (!IdxN || !IdxN->isNullValue()) {
    IdxV = DAG.getNode(ISD::MUL, dl, MVT::i32, IdxV,
                       DAG.getConstant(ElemWidth/8, dl, MVT::i32));
    SingleV = DAG.getNode(HexagonISD::VROR, dl, SingleTy, SingleV, IdxV);
  }
  // When inserting a single word, the rotation back to the original position
  // would be by HwLen-Idx, but if two words are inserted, it will need to be
  // by (HwLen-4)-Idx.
  unsigned RolBase = HwLen;
  if (VecTy.getSizeInBits() == 32) {
    SDValue V = DAG.getBitcast(MVT::i32, SubV);
    SingleV = DAG.getNode(HexagonISD::VINSERTW0, dl, SingleTy, V);
  } else {
    SDValue V = DAG.getBitcast(MVT::i64, SubV);
    SDValue R0 = DAG.getTargetExtractSubreg(Hexagon::isub_lo, dl, MVT::i32, V);
    SDValue R1 = DAG.getTargetExtractSubreg(Hexagon::isub_hi, dl, MVT::i32, V);
    SingleV = DAG.getNode(HexagonISD::VINSERTW0, dl, SingleTy, SingleV, R0);
    SingleV = DAG.getNode(HexagonISD::VROR, dl, SingleTy, SingleV,
                          DAG.getConstant(4, dl, MVT::i32));
    SingleV = DAG.getNode(HexagonISD::VINSERTW0, dl, SingleTy, SingleV, R1);
    RolBase = HwLen-4;
  }
  // If the vector wasn't ror'ed, don't ror it back.
  if (RolBase != 4 || !IdxN || !IdxN->isNullValue()) {
    SDValue RolV = DAG.getNode(ISD::SUB, dl, MVT::i32,
                               DAG.getConstant(RolBase, dl, MVT::i32), IdxV);
    SingleV = DAG.getNode(HexagonISD::VROR, dl, SingleTy, SingleV, RolV);
  }

  if (IsPair) {
    SDValue InLo = DAG.getNode(ISD::CONCAT_VECTORS, dl, VecTy, {SingleV, V1});
    SDValue InHi = DAG.getNode(ISD::CONCAT_VECTORS, dl, VecTy, {V0, SingleV});
    return DAG.getNode(ISD::SELECT, dl, VecTy, PickHi, InHi, InLo);
  }
  return SingleV;
}

SDValue
HexagonTargetLowering::insertHvxSubvectorPred(SDValue VecV, SDValue SubV,
      SDValue IdxV, const SDLoc &dl, SelectionDAG &DAG) const {
  MVT VecTy = ty(VecV);
  MVT SubTy = ty(SubV);
  assert(Subtarget.isHVXVectorType(VecTy, true));
  // VecV is an HVX vector predicate. SubV may be either an HVX vector
  // predicate as well, or it can be a scalar predicate.

  unsigned VecLen = VecTy.getVectorNumElements();
  unsigned HwLen = Subtarget.getVectorLength();
  assert(HwLen % VecLen == 0 && "Unexpected vector type");

  unsigned Scale = VecLen / SubTy.getVectorNumElements();
  unsigned BitBytes = HwLen / VecLen;
  unsigned BlockLen = HwLen / Scale;

  MVT ByteTy = MVT::getVectorVT(MVT::i8, HwLen);
  SDValue ByteVec = DAG.getNode(HexagonISD::Q2V, dl, ByteTy, VecV);
  SDValue ByteSub = createHvxPrefixPred(SubV, dl, BitBytes, false, DAG);
  SDValue ByteIdx;

  auto *IdxN = dyn_cast<ConstantSDNode>(IdxV.getNode());
  if (!IdxN || !IdxN->isNullValue()) {
    ByteIdx = DAG.getNode(ISD::MUL, dl, MVT::i32, IdxV,
                          DAG.getConstant(BitBytes, dl, MVT::i32));
    ByteVec = DAG.getNode(HexagonISD::VROR, dl, ByteTy, ByteVec, ByteIdx);
  }

  // ByteVec is the target vector VecV rotated in such a way that the
  // subvector should be inserted at index 0. Generate a predicate mask
  // and use vmux to do the insertion.
  MVT BoolTy = MVT::getVectorVT(MVT::i1, HwLen);
  SDValue Q = getInstr(Hexagon::V6_pred_scalar2, dl, BoolTy,
                       {DAG.getConstant(BlockLen, dl, MVT::i32)}, DAG);
  ByteVec = getInstr(Hexagon::V6_vmux, dl, ByteTy, {Q, ByteSub, ByteVec}, DAG);
  // Rotate ByteVec back, and convert to a vector predicate.
  if (!IdxN || !IdxN->isNullValue()) {
    SDValue HwLenV = DAG.getConstant(HwLen, dl, MVT::i32);
    SDValue ByteXdi = DAG.getNode(ISD::SUB, dl, MVT::i32, HwLenV, ByteIdx);
    ByteVec = DAG.getNode(HexagonISD::VROR, dl, ByteTy, ByteVec, ByteXdi);
  }
  return DAG.getNode(HexagonISD::V2Q, dl, VecTy, ByteVec);
}

SDValue
HexagonTargetLowering::extendHvxVectorPred(SDValue VecV, const SDLoc &dl,
      MVT ResTy, bool ZeroExt, SelectionDAG &DAG) const {
  // Sign- and any-extending of a vector predicate to a vector register is
  // equivalent to Q2V. For zero-extensions, generate a vmux between 0 and
  // a vector of 1s (where the 1s are of type matching the vector type).
  assert(Subtarget.isHVXVectorType(ResTy));
  if (!ZeroExt)
    return DAG.getNode(HexagonISD::Q2V, dl, ResTy, VecV);

  assert(ty(VecV).getVectorNumElements() == ResTy.getVectorNumElements());
  SDValue True = DAG.getNode(HexagonISD::VSPLAT, dl, ResTy,
                             DAG.getConstant(1, dl, MVT::i32));
  SDValue False = getZero(dl, ResTy, DAG);
  return DAG.getSelect(dl, ResTy, VecV, True, False);
}

SDValue
HexagonTargetLowering::LowerHvxBuildVector(SDValue Op, SelectionDAG &DAG)
      const {
  const SDLoc &dl(Op);
  MVT VecTy = ty(Op);

  unsigned Size = Op.getNumOperands();
  SmallVector<SDValue,128> Ops;
  for (unsigned i = 0; i != Size; ++i)
    Ops.push_back(Op.getOperand(i));

  if (VecTy.getVectorElementType() == MVT::i1)
    return buildHvxVectorPred(Ops, dl, VecTy, DAG);

  if (VecTy.getSizeInBits() == 16*Subtarget.getVectorLength()) {
    ArrayRef<SDValue> A(Ops);
    MVT SingleTy = typeSplit(VecTy).first;
    SDValue V0 = buildHvxVectorReg(A.take_front(Size/2), dl, SingleTy, DAG);
    SDValue V1 = buildHvxVectorReg(A.drop_front(Size/2), dl, SingleTy, DAG);
    return DAG.getNode(ISD::CONCAT_VECTORS, dl, VecTy, V0, V1);
  }

  return buildHvxVectorReg(Ops, dl, VecTy, DAG);
}

SDValue
HexagonTargetLowering::LowerHvxConcatVectors(SDValue Op, SelectionDAG &DAG)
      const {
  // This should only be called for vectors of i1. The "scalar" vector
  // concatenation does not need special lowering (assuming that only
  // two vectors are concatenated at a time).
  MVT VecTy = ty(Op);
  assert(VecTy.getVectorElementType() == MVT::i1);

  const SDLoc &dl(Op);
  unsigned HwLen = Subtarget.getVectorLength();
  unsigned NumOp = Op.getNumOperands();
  assert(isPowerOf2_32(NumOp) && HwLen % NumOp == 0);
  (void)NumOp;

  // Count how many bytes (in a vector register) each bit in VecTy
  // corresponds to.
  unsigned BitBytes = HwLen / VecTy.getVectorNumElements();

  SmallVector<SDValue,8> Prefixes;
  for (SDValue V : Op.getNode()->op_values()) {
    SDValue P = createHvxPrefixPred(V, dl, BitBytes, true, DAG);
    Prefixes.push_back(P);
  }

  unsigned InpLen = ty(Op.getOperand(0)).getVectorNumElements();
  MVT ByteTy = MVT::getVectorVT(MVT::i8, HwLen);
  SDValue S = DAG.getConstant(InpLen*BitBytes, dl, MVT::i32);
  SDValue Res = getZero(dl, ByteTy, DAG);
  for (unsigned i = 0, e = Prefixes.size(); i != e; ++i) {
    Res = DAG.getNode(HexagonISD::VROR, dl, ByteTy, Res, S);
    Res = DAG.getNode(ISD::OR, dl, ByteTy, Res, Prefixes[e-i-1]);
  }
  return DAG.getNode(HexagonISD::V2Q, dl, VecTy, Res);
}

SDValue
HexagonTargetLowering::LowerHvxExtractElement(SDValue Op, SelectionDAG &DAG)
      const {
  // Change the type of the extracted element to i32.
  SDValue VecV = Op.getOperand(0);
  MVT ElemTy = ty(VecV).getVectorElementType();
  const SDLoc &dl(Op);
  SDValue IdxV = Op.getOperand(1);
  if (ElemTy == MVT::i1)
    return extractHvxElementPred(VecV, IdxV, dl, ty(Op), DAG);

  return extractHvxElementReg(VecV, IdxV, dl, ty(Op), DAG);
}

SDValue
HexagonTargetLowering::LowerHvxInsertElement(SDValue Op, SelectionDAG &DAG)
      const {
  const SDLoc &dl(Op);
  SDValue VecV = Op.getOperand(0);
  SDValue ValV = Op.getOperand(1);
  SDValue IdxV = Op.getOperand(2);
  MVT ElemTy = ty(VecV).getVectorElementType();
  if (ElemTy == MVT::i1)
    return insertHvxElementPred(VecV, IdxV, ValV, dl, DAG);

  return insertHvxElementReg(VecV, IdxV, ValV, dl, DAG);
}

SDValue
HexagonTargetLowering::LowerHvxExtractSubvector(SDValue Op, SelectionDAG &DAG)
      const {
  SDValue SrcV = Op.getOperand(0);
  MVT SrcTy = ty(SrcV);
  MVT DstTy = ty(Op);
  SDValue IdxV = Op.getOperand(1);
  unsigned Idx = cast<ConstantSDNode>(IdxV.getNode())->getZExtValue();
  assert(Idx % DstTy.getVectorNumElements() == 0);
  (void)Idx;
  const SDLoc &dl(Op);

  MVT ElemTy = SrcTy.getVectorElementType();
  if (ElemTy == MVT::i1)
    return extractHvxSubvectorPred(SrcV, IdxV, dl, DstTy, DAG);

  return extractHvxSubvectorReg(SrcV, IdxV, dl, DstTy, DAG);
}

SDValue
HexagonTargetLowering::LowerHvxInsertSubvector(SDValue Op, SelectionDAG &DAG)
      const {
  // Idx does not need to be a constant.
  SDValue VecV = Op.getOperand(0);
  SDValue ValV = Op.getOperand(1);
  SDValue IdxV = Op.getOperand(2);

  const SDLoc &dl(Op);
  MVT VecTy = ty(VecV);
  MVT ElemTy = VecTy.getVectorElementType();
  if (ElemTy == MVT::i1)
    return insertHvxSubvectorPred(VecV, ValV, IdxV, dl, DAG);

  return insertHvxSubvectorReg(VecV, ValV, IdxV, dl, DAG);
}

SDValue
HexagonTargetLowering::LowerHvxMul(SDValue Op, SelectionDAG &DAG) const {
  MVT ResTy = ty(Op);
  assert(ResTy.isVector());
  const SDLoc &dl(Op);
  SmallVector<int,256> ShuffMask;

  MVT ElemTy = ResTy.getVectorElementType();
  unsigned VecLen = ResTy.getVectorNumElements();
  SDValue Vs = Op.getOperand(0);
  SDValue Vt = Op.getOperand(1);

  switch (ElemTy.SimpleTy) {
    case MVT::i8: {
      // For i8 vectors Vs = (a0, a1, ...), Vt = (b0, b1, ...),
      // V6_vmpybv Vs, Vt produces a pair of i16 vectors Hi:Lo,
      // where Lo = (a0*b0, a2*b2, ...), Hi = (a1*b1, a3*b3, ...).
      MVT ExtTy = typeExtElem(ResTy, 2);
      unsigned MpyOpc = ElemTy == MVT::i8 ? Hexagon::V6_vmpybv
                                          : Hexagon::V6_vmpyhv;
      SDValue M = getInstr(MpyOpc, dl, ExtTy, {Vs, Vt}, DAG);

      // Discard high halves of the resulting values, collect the low halves.
      for (unsigned I = 0; I < VecLen; I += 2) {
        ShuffMask.push_back(I);         // Pick even element.
        ShuffMask.push_back(I+VecLen);  // Pick odd element.
      }
      VectorPair P = opSplit(opCastElem(M, ElemTy, DAG), dl, DAG);
      SDValue BS = getByteShuffle(dl, P.first, P.second, ShuffMask, DAG);
      return DAG.getBitcast(ResTy, BS);
    }
    case MVT::i16:
      // For i16 there is V6_vmpyih, which acts exactly like the MUL opcode.
      // (There is also V6_vmpyhv, which behaves in an analogous way to
      // V6_vmpybv.)
      return getInstr(Hexagon::V6_vmpyih, dl, ResTy, {Vs, Vt}, DAG);
    case MVT::i32: {
      // Use the following sequence for signed word multiply:
      // T0 = V6_vmpyiowh Vs, Vt
      // T1 = V6_vaslw T0, 16
      // T2 = V6_vmpyiewuh_acc T1, Vs, Vt
      SDValue S16 = DAG.getConstant(16, dl, MVT::i32);
      SDValue T0 = getInstr(Hexagon::V6_vmpyiowh, dl, ResTy, {Vs, Vt}, DAG);
      SDValue T1 = getInstr(Hexagon::V6_vaslw, dl, ResTy, {T0, S16}, DAG);
      SDValue T2 = getInstr(Hexagon::V6_vmpyiewuh_acc, dl, ResTy,
                            {T1, Vs, Vt}, DAG);
      return T2;
    }
    default:
      break;
  }
  return SDValue();
}

SDValue
HexagonTargetLowering::LowerHvxMulh(SDValue Op, SelectionDAG &DAG) const {
  MVT ResTy = ty(Op);
  assert(ResTy.isVector());
  const SDLoc &dl(Op);
  SmallVector<int,256> ShuffMask;

  MVT ElemTy = ResTy.getVectorElementType();
  unsigned VecLen = ResTy.getVectorNumElements();
  SDValue Vs = Op.getOperand(0);
  SDValue Vt = Op.getOperand(1);
  bool IsSigned = Op.getOpcode() == ISD::MULHS;

  if (ElemTy == MVT::i8 || ElemTy == MVT::i16) {
    // For i8 vectors Vs = (a0, a1, ...), Vt = (b0, b1, ...),
    // V6_vmpybv Vs, Vt produces a pair of i16 vectors Hi:Lo,
    // where Lo = (a0*b0, a2*b2, ...), Hi = (a1*b1, a3*b3, ...).
    // For i16, use V6_vmpyhv, which behaves in an analogous way to
    // V6_vmpybv: results Lo and Hi are products of even/odd elements
    // respectively.
    MVT ExtTy = typeExtElem(ResTy, 2);
    unsigned MpyOpc = ElemTy == MVT::i8
        ? (IsSigned ? Hexagon::V6_vmpybv : Hexagon::V6_vmpyubv)
        : (IsSigned ? Hexagon::V6_vmpyhv : Hexagon::V6_vmpyuhv);
    SDValue M = getInstr(MpyOpc, dl, ExtTy, {Vs, Vt}, DAG);

    // Discard low halves of the resulting values, collect the high halves.
    for (unsigned I = 0; I < VecLen; I += 2) {
      ShuffMask.push_back(I+1);         // Pick even element.
      ShuffMask.push_back(I+VecLen+1);  // Pick odd element.
    }
    VectorPair P = opSplit(opCastElem(M, ElemTy, DAG), dl, DAG);
    SDValue BS = getByteShuffle(dl, P.first, P.second, ShuffMask, DAG);
    return DAG.getBitcast(ResTy, BS);
  }

  assert(ElemTy == MVT::i32);
  SDValue S16 = DAG.getConstant(16, dl, MVT::i32);

  if (IsSigned) {
    // mulhs(Vs,Vt) =
    //   = [(Hi(Vs)*2^16 + Lo(Vs)) *s (Hi(Vt)*2^16 + Lo(Vt))] >> 32
    //   = [Hi(Vs)*2^16 *s Hi(Vt)*2^16 + Hi(Vs) *su Lo(Vt)*2^16
    //      + Lo(Vs) *us (Hi(Vt)*2^16 + Lo(Vt))] >> 32
    //   = [Hi(Vs) *s Hi(Vt)*2^32 + Hi(Vs) *su Lo(Vt)*2^16
    //      + Lo(Vs) *us Vt] >> 32
    // The low half of Lo(Vs)*Lo(Vt) will be discarded (it's not added to
    // anything, so it cannot produce any carry over to higher bits),
    // so everything in [] can be shifted by 16 without loss of precision.
    //   = [Hi(Vs) *s Hi(Vt)*2^16 + Hi(Vs)*su Lo(Vt) + Lo(Vs)*Vt >> 16] >> 16
    //   = [Hi(Vs) *s Hi(Vt)*2^16 + Hi(Vs)*su Lo(Vt) + V6_vmpyewuh(Vs,Vt)] >> 16
    // Denote Hi(Vs) = Vs':
    //   = [Vs'*s Hi(Vt)*2^16 + Vs' *su Lo(Vt) + V6_vmpyewuh(Vt,Vs)] >> 16
    //   = Vs'*s Hi(Vt) + (V6_vmpyiewuh(Vs',Vt) + V6_vmpyewuh(Vt,Vs)) >> 16
    SDValue T0 = getInstr(Hexagon::V6_vmpyewuh, dl, ResTy, {Vt, Vs}, DAG);
    // Get Vs':
    SDValue S0 = getInstr(Hexagon::V6_vasrw, dl, ResTy, {Vs, S16}, DAG);
    SDValue T1 = getInstr(Hexagon::V6_vmpyiewuh_acc, dl, ResTy,
                          {T0, S0, Vt}, DAG);
    // Shift by 16:
    SDValue S2 = getInstr(Hexagon::V6_vasrw, dl, ResTy, {T1, S16}, DAG);
    // Get Vs'*Hi(Vt):
    SDValue T2 = getInstr(Hexagon::V6_vmpyiowh, dl, ResTy, {S0, Vt}, DAG);
    // Add:
    SDValue T3 = DAG.getNode(ISD::ADD, dl, ResTy, {S2, T2});
    return T3;
  }

  // Unsigned mulhw. (Would expansion using signed mulhw be better?)

  auto LoVec = [&DAG,ResTy,dl] (SDValue Pair) {
    return DAG.getTargetExtractSubreg(Hexagon::vsub_lo, dl, ResTy, Pair);
  };
  auto HiVec = [&DAG,ResTy,dl] (SDValue Pair) {
    return DAG.getTargetExtractSubreg(Hexagon::vsub_hi, dl, ResTy, Pair);
  };

  MVT PairTy = typeJoin({ResTy, ResTy});
  SDValue P = getInstr(Hexagon::V6_lvsplatw, dl, ResTy,
                       {DAG.getConstant(0x02020202, dl, MVT::i32)}, DAG);
  // Multiply-unsigned halfwords:
  //   LoVec = Vs.uh[2i] * Vt.uh[2i],
  //   HiVec = Vs.uh[2i+1] * Vt.uh[2i+1]
  SDValue T0 = getInstr(Hexagon::V6_vmpyuhv, dl, PairTy, {Vs, Vt}, DAG);
  // The low halves in the LoVec of the pair can be discarded. They are
  // not added to anything (in the full-precision product), so they cannot
  // produce a carry into the higher bits.
  SDValue T1 = getInstr(Hexagon::V6_vlsrw, dl, ResTy, {LoVec(T0), S16}, DAG);
  // Swap low and high halves in Vt, and do the halfword multiplication
  // to get products Vs.uh[2i] * Vt.uh[2i+1] and Vs.uh[2i+1] * Vt.uh[2i].
  SDValue D0 = getInstr(Hexagon::V6_vdelta, dl, ResTy, {Vt, P}, DAG);
  SDValue T2 = getInstr(Hexagon::V6_vmpyuhv, dl, PairTy, {Vs, D0}, DAG);
  // T2 has mixed products of halfwords: Lo(Vt)*Hi(Vs) and Hi(Vt)*Lo(Vs).
  // These products are words, but cannot be added directly because the
  // sums could overflow. Add these products, by halfwords, where each sum
  // of a pair of halfwords gives a word.
  SDValue T3 = getInstr(Hexagon::V6_vadduhw, dl, PairTy,
                        {LoVec(T2), HiVec(T2)}, DAG);
  // Add the high halfwords from the products of the low halfwords.
  SDValue T4 = DAG.getNode(ISD::ADD, dl, ResTy, {T1, LoVec(T3)});
  SDValue T5 = getInstr(Hexagon::V6_vlsrw, dl, ResTy, {T4, S16}, DAG);
  SDValue T6 = DAG.getNode(ISD::ADD, dl, ResTy, {HiVec(T0), HiVec(T3)});
  SDValue T7 = DAG.getNode(ISD::ADD, dl, ResTy, {T5, T6});
  return T7;
}

SDValue
HexagonTargetLowering::LowerHvxSetCC(SDValue Op, SelectionDAG &DAG) const {
  MVT ResTy = ty(Op);
  MVT VecTy = ty(Op.getOperand(0));
  assert(VecTy == ty(Op.getOperand(1)));
  unsigned HwLen = Subtarget.getVectorLength();
  const SDLoc &dl(Op);

  SDValue Cmp = Op.getOperand(2);
  ISD::CondCode CC = cast<CondCodeSDNode>(Cmp)->get();

  if (VecTy.getSizeInBits() == 16*HwLen) {
    VectorPair P0 = opSplit(Op.getOperand(0), dl, DAG);
    VectorPair P1 = opSplit(Op.getOperand(1), dl, DAG);
    MVT HalfTy = typeSplit(ResTy).first;

    SDValue V0 = DAG.getSetCC(dl, HalfTy, P0.first, P1.first, CC);
    SDValue V1 = DAG.getSetCC(dl, HalfTy, P0.second, P1.second, CC);
    return DAG.getNode(ISD::CONCAT_VECTORS, dl, ResTy, V1, V0);
  }

  return SDValue();
}

SDValue
HexagonTargetLowering::LowerHvxExtend(SDValue Op, SelectionDAG &DAG) const {
  // Sign- and zero-extends are legal.
  assert(Op.getOpcode() == ISD::ANY_EXTEND_VECTOR_INREG);
  return DAG.getZeroExtendVectorInReg(Op.getOperand(0), SDLoc(Op), ty(Op));
}

SDValue
HexagonTargetLowering::LowerHvxShift(SDValue Op, SelectionDAG &DAG) const {
  return Op;
}