X86ISelLowering.cpp

/// specifies a shuffle of elements that is suitable for input to MOVSS,
/// MOVSD, and MOVD, i.e. setting the lowest element.
static bool isMOVLMask(const SmallVectorImpl<int> &Mask, EVT VT) {
  if (VT.getVectorElementType().getSizeInBits() < 32)
    return false;

  int NumElts = VT.getVectorNumElements();

  if (!isUndefOrEqual(Mask[0], NumElts))
    return false;

  for (int i = 1; i < NumElts; ++i)
    if (!isUndefOrEqual(Mask[i], i))
      return false;

  return true;
}

bool X86::isMOVLMask(ShuffleVectorSDNode *N) {
  SmallVector<int, 8> M;
  N->getMask(M);
  return ::isMOVLMask(M, N->getValueType(0));
}

/// isCommutedMOVL - Returns true if the shuffle mask is except the reverse
/// of what x86 movss want. X86 movs requires the lowest  element to be lowest
/// element of vector 2 and the other elements to come from vector 1 in order.
static bool isCommutedMOVLMask(const SmallVectorImpl<int> &Mask, EVT VT,
                               bool V2IsSplat = false, bool V2IsUndef = false) {
  int NumOps = VT.getVectorNumElements();
  if (NumOps != 2 && NumOps != 4 && NumOps != 8 && NumOps != 16)
    return false;

  if (!isUndefOrEqual(Mask[0], 0))
    return false;

  for (int i = 1; i < NumOps; ++i)
    if (!(isUndefOrEqual(Mask[i], i+NumOps) ||
          (V2IsUndef && isUndefOrInRange(Mask[i], NumOps, NumOps*2)) ||
          (V2IsSplat && isUndefOrEqual(Mask[i], NumOps))))
      return false;

  return true;
}

static bool isCommutedMOVL(ShuffleVectorSDNode *N, bool V2IsSplat = false,
                           bool V2IsUndef = false) {
  SmallVector<int, 8> M;
  N->getMask(M);
  return isCommutedMOVLMask(M, N->getValueType(0), V2IsSplat, V2IsUndef);
}

/// isMOVSHDUPMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to MOVSHDUP.
bool X86::isMOVSHDUPMask(ShuffleVectorSDNode *N) {
  if (N->getValueType(0).getVectorNumElements() != 4)
    return false;

  // Expect 1, 1, 3, 3
  for (unsigned i = 0; i < 2; ++i) {
    int Elt = N->getMaskElt(i);
    if (Elt >= 0 && Elt != 1)
      return false;
  }

  bool HasHi = false;
  for (unsigned i = 2; i < 4; ++i) {
    int Elt = N->getMaskElt(i);
    if (Elt >= 0 && Elt != 3)
      return false;
    if (Elt == 3)
      HasHi = true;
  }
  // Don't use movshdup if it can be done with a shufps.
  // FIXME: verify that matching u, u, 3, 3 is what we want.
  return HasHi;
}

/// isMOVSLDUPMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to MOVSLDUP.
bool X86::isMOVSLDUPMask(ShuffleVectorSDNode *N) {
  if (N->getValueType(0).getVectorNumElements() != 4)
    return false;

  // Expect 0, 0, 2, 2
  for (unsigned i = 0; i < 2; ++i)
    if (N->getMaskElt(i) > 0)
      return false;

  bool HasHi = false;
  for (unsigned i = 2; i < 4; ++i) {
    int Elt = N->getMaskElt(i);
    if (Elt >= 0 && Elt != 2)
      return false;
    if (Elt == 2)
      HasHi = true;
  }
  // Don't use movsldup if it can be done with a shufps.
  return HasHi;
}

/// isMOVDDUPMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to MOVDDUP.
bool X86::isMOVDDUPMask(ShuffleVectorSDNode *N) {
  int e = N->getValueType(0).getVectorNumElements() / 2;

  for (int i = 0; i < e; ++i)
    if (!isUndefOrEqual(N->getMaskElt(i), i))
      return false;
  for (int i = 0; i < e; ++i)
    if (!isUndefOrEqual(N->getMaskElt(e+i), i))
      return false;
  return true;
}

/// getShuffleSHUFImmediate - Return the appropriate immediate to shuffle
/// the specified VECTOR_SHUFFLE mask with PSHUF* and SHUFP* instructions.
unsigned X86::getShuffleSHUFImmediate(SDNode *N) {
  ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(N);
  int NumOperands = SVOp->getValueType(0).getVectorNumElements();

  unsigned Shift = (NumOperands == 4) ? 2 : 1;
  unsigned Mask = 0;
  for (int i = 0; i < NumOperands; ++i) {
    int Val = SVOp->getMaskElt(NumOperands-i-1);
    if (Val < 0) Val = 0;
    if (Val >= NumOperands) Val -= NumOperands;
    Mask |= Val;
    if (i != NumOperands - 1)
      Mask <<= Shift;
  }
  return Mask;
}

/// getShufflePSHUFHWImmediate - Return the appropriate immediate to shuffle
/// the specified VECTOR_SHUFFLE mask with the PSHUFHW instruction.
unsigned X86::getShufflePSHUFHWImmediate(SDNode *N) {
  ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(N);
  unsigned Mask = 0;
  // 8 nodes, but we only care about the last 4.
  for (unsigned i = 7; i >= 4; --i) {
    int Val = SVOp->getMaskElt(i);
    if (Val >= 0)
      Mask |= (Val - 4);
    if (i != 4)
      Mask <<= 2;
  }
  return Mask;
}

/// getShufflePSHUFLWImmediate - Return the appropriate immediate to shuffle
/// the specified VECTOR_SHUFFLE mask with the PSHUFLW instruction.
unsigned X86::getShufflePSHUFLWImmediate(SDNode *N) {
  ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(N);
  unsigned Mask = 0;
  // 8 nodes, but we only care about the first 4.
  for (int i = 3; i >= 0; --i) {
    int Val = SVOp->getMaskElt(i);
    if (Val >= 0)
      Mask |= Val;
    if (i != 0)
      Mask <<= 2;
  }
  return Mask;
}

/// getShufflePALIGNRImmediate - Return the appropriate immediate to shuffle
/// the specified VECTOR_SHUFFLE mask with the PALIGNR instruction.
unsigned X86::getShufflePALIGNRImmediate(SDNode *N) {
  ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(N);
  EVT VVT = N->getValueType(0);
  unsigned EltSize = VVT.getVectorElementType().getSizeInBits() >> 3;
  int Val = 0;

  unsigned i, e;
  for (i = 0, e = VVT.getVectorNumElements(); i != e; ++i) {
    Val = SVOp->getMaskElt(i);
    if (Val >= 0)
      break;
  }
  return (Val - i) * EltSize;
}

/// isZeroNode - Returns true if Elt is a constant zero or a floating point
/// constant +0.0.
bool X86::isZeroNode(SDValue Elt) {
  return ((isa<ConstantSDNode>(Elt) &&
           cast<ConstantSDNode>(Elt)->isNullValue()) ||
          (isa<ConstantFPSDNode>(Elt) &&
           cast<ConstantFPSDNode>(Elt)->getValueAPF().isPosZero()));
}

/// CommuteVectorShuffle - Swap vector_shuffle operands as well as values in
/// their permute mask.
static SDValue CommuteVectorShuffle(ShuffleVectorSDNode *SVOp,
                                    SelectionDAG &DAG) {
  EVT VT = SVOp->getValueType(0);
  unsigned NumElems = VT.getVectorNumElements();
  SmallVector<int, 8> MaskVec;

  for (unsigned i = 0; i != NumElems; ++i) {
    int idx = SVOp->getMaskElt(i);
    if (idx < 0)
      MaskVec.push_back(idx);
    else if (idx < (int)NumElems)
      MaskVec.push_back(idx + NumElems);
    else
      MaskVec.push_back(idx - NumElems);
  }
  return DAG.getVectorShuffle(VT, SVOp->getDebugLoc(), SVOp->getOperand(1),
                              SVOp->getOperand(0), &MaskVec[0]);
}

/// CommuteVectorShuffleMask - Change values in a shuffle permute mask assuming
/// the two vector operands have swapped position.
static void CommuteVectorShuffleMask(SmallVectorImpl<int> &Mask, EVT VT) {
  unsigned NumElems = VT.getVectorNumElements();
  for (unsigned i = 0; i != NumElems; ++i) {
    int idx = Mask[i];
    if (idx < 0)
      continue;
    else if (idx < (int)NumElems)
      Mask[i] = idx + NumElems;
    else
      Mask[i] = idx - NumElems;
  }
}

/// ShouldXformToMOVHLPS - Return true if the node should be transformed to
/// match movhlps. The lower half elements should come from upper half of
/// V1 (and in order), and the upper half elements should come from the upper
/// half of V2 (and in order).
static bool ShouldXformToMOVHLPS(ShuffleVectorSDNode *Op) {
  if (Op->getValueType(0).getVectorNumElements() != 4)
    return false;
  for (unsigned i = 0, e = 2; i != e; ++i)
    if (!isUndefOrEqual(Op->getMaskElt(i), i+2))
      return false;
  for (unsigned i = 2; i != 4; ++i)
    if (!isUndefOrEqual(Op->getMaskElt(i), i+4))
      return false;
  return true;
}

/// isScalarLoadToVector - Returns true if the node is a scalar load that
/// is promoted to a vector. It also returns the LoadSDNode by reference if
/// required.
static bool isScalarLoadToVector(SDNode *N, LoadSDNode **LD = NULL) {
  if (N->getOpcode() != ISD::SCALAR_TO_VECTOR)
    return false;
  N = N->getOperand(0).getNode();
  if (!ISD::isNON_EXTLoad(N))
    return false;
  if (LD)
    *LD = cast<LoadSDNode>(N);
  return true;
}

/// ShouldXformToMOVLP{S|D} - Return true if the node should be transformed to
/// match movlp{s|d}. The lower half elements should come from lower half of
/// V1 (and in order), and the upper half elements should come from the upper
/// half of V2 (and in order). And since V1 will become the source of the
/// MOVLP, it must be either a vector load or a scalar load to vector.
static bool ShouldXformToMOVLP(SDNode *V1, SDNode *V2,
                               ShuffleVectorSDNode *Op) {
  if (!ISD::isNON_EXTLoad(V1) && !isScalarLoadToVector(V1))
    return false;
  // Is V2 is a vector load, don't do this transformation. We will try to use
  // load folding shufps op.
  if (ISD::isNON_EXTLoad(V2))
    return false;

  unsigned NumElems = Op->getValueType(0).getVectorNumElements();

  if (NumElems != 2 && NumElems != 4)
    return false;
  for (unsigned i = 0, e = NumElems/2; i != e; ++i)
    if (!isUndefOrEqual(Op->getMaskElt(i), i))
      return false;
  for (unsigned i = NumElems/2; i != NumElems; ++i)
    if (!isUndefOrEqual(Op->getMaskElt(i), i+NumElems))
      return false;
  return true;
}

/// isSplatVector - Returns true if N is a BUILD_VECTOR node whose elements are
/// all the same.
static bool isSplatVector(SDNode *N) {
  if (N->getOpcode() != ISD::BUILD_VECTOR)
    return false;

  SDValue SplatValue = N->getOperand(0);
  for (unsigned i = 1, e = N->getNumOperands(); i != e; ++i)
    if (N->getOperand(i) != SplatValue)
      return false;
  return true;
}

/// isZeroShuffle - Returns true if N is a VECTOR_SHUFFLE that can be resolved
/// to an zero vector.
/// FIXME: move to dag combiner / method on ShuffleVectorSDNode
static bool isZeroShuffle(ShuffleVectorSDNode *N) {
  SDValue V1 = N->getOperand(0);
  SDValue V2 = N->getOperand(1);
  unsigned NumElems = N->getValueType(0).getVectorNumElements();
  for (unsigned i = 0; i != NumElems; ++i) {
    int Idx = N->getMaskElt(i);
    if (Idx >= (int)NumElems) {
      unsigned Opc = V2.getOpcode();
      if (Opc == ISD::UNDEF || ISD::isBuildVectorAllZeros(V2.getNode()))
        continue;
      if (Opc != ISD::BUILD_VECTOR ||
          !X86::isZeroNode(V2.getOperand(Idx-NumElems)))
        return false;
    } else if (Idx >= 0) {
      unsigned Opc = V1.getOpcode();
      if (Opc == ISD::UNDEF || ISD::isBuildVectorAllZeros(V1.getNode()))
        continue;
      if (Opc != ISD::BUILD_VECTOR ||
          !X86::isZeroNode(V1.getOperand(Idx)))
        return false;
    }
  }
  return true;
}

/// getZeroVector - Returns a vector of specified type with all zero elements.
///
static SDValue getZeroVector(EVT VT, bool HasSSE2, SelectionDAG &DAG,
                             DebugLoc dl) {
  assert(VT.isVector() && "Expected a vector type");

  // Always build zero vectors as <4 x i32> or <2 x i32> bitcasted to their dest
  // type.  This ensures they get CSE'd.
  SDValue Vec;
  if (VT.getSizeInBits() == 64) { // MMX
    SDValue Cst = DAG.getTargetConstant(0, MVT::i32);
    Vec = DAG.getNode(ISD::BUILD_VECTOR, dl, MVT::v2i32, Cst, Cst);
  } else if (HasSSE2) {  // SSE2
    SDValue Cst = DAG.getTargetConstant(0, MVT::i32);
    Vec = DAG.getNode(ISD::BUILD_VECTOR, dl, MVT::v4i32, Cst, Cst, Cst, Cst);
  } else { // SSE1
    SDValue Cst = DAG.getTargetConstantFP(+0.0, MVT::f32);
    Vec = DAG.getNode(ISD::BUILD_VECTOR, dl, MVT::v4f32, Cst, Cst, Cst, Cst);
  }
  return DAG.getNode(ISD::BIT_CONVERT, dl, VT, Vec);
}

/// getOnesVector - Returns a vector of specified type with all bits set.
///
static SDValue getOnesVector(EVT VT, SelectionDAG &DAG, DebugLoc dl) {
  assert(VT.isVector() && "Expected a vector type");

  // Always build ones vectors as <4 x i32> or <2 x i32> bitcasted to their dest
  // type.  This ensures they get CSE'd.
  SDValue Cst = DAG.getTargetConstant(~0U, MVT::i32);
  SDValue Vec;
  if (VT.getSizeInBits() == 64)  // MMX
    Vec = DAG.getNode(ISD::BUILD_VECTOR, dl, MVT::v2i32, Cst, Cst);
  else                                              // SSE
    Vec = DAG.getNode(ISD::BUILD_VECTOR, dl, MVT::v4i32, Cst, Cst, Cst, Cst);
  return DAG.getNode(ISD::BIT_CONVERT, dl, VT, Vec);
}


/// NormalizeMask - V2 is a splat, modify the mask (if needed) so all elements
/// that point to V2 points to its first element.
static SDValue NormalizeMask(ShuffleVectorSDNode *SVOp, SelectionDAG &DAG) {
  EVT VT = SVOp->getValueType(0);
  unsigned NumElems = VT.getVectorNumElements();

  bool Changed = false;
  SmallVector<int, 8> MaskVec;
  SVOp->getMask(MaskVec);

  for (unsigned i = 0; i != NumElems; ++i) {
    if (MaskVec[i] > (int)NumElems) {
      MaskVec[i] = NumElems;
      Changed = true;
    }
  }
  if (Changed)
    return DAG.getVectorShuffle(VT, SVOp->getDebugLoc(), SVOp->getOperand(0),
                                SVOp->getOperand(1), &MaskVec[0]);
  return SDValue(SVOp, 0);
}

/// getMOVLMask - Returns a vector_shuffle mask for an movs{s|d}, movd
/// operation of specified width.
static SDValue getMOVL(SelectionDAG &DAG, DebugLoc dl, EVT VT, SDValue V1,
                       SDValue V2) {
  unsigned NumElems = VT.getVectorNumElements();
  SmallVector<int, 8> Mask;
  Mask.push_back(NumElems);
  for (unsigned i = 1; i != NumElems; ++i)
    Mask.push_back(i);
  return DAG.getVectorShuffle(VT, dl, V1, V2, &Mask[0]);
}

/// getUnpackl - Returns a vector_shuffle node for an unpackl operation.
static SDValue getUnpackl(SelectionDAG &DAG, DebugLoc dl, EVT VT, SDValue V1,
                          SDValue V2) {
  unsigned NumElems = VT.getVectorNumElements();
  SmallVector<int, 8> Mask;
  for (unsigned i = 0, e = NumElems/2; i != e; ++i) {
    Mask.push_back(i);
    Mask.push_back(i + NumElems);
  }
  return DAG.getVectorShuffle(VT, dl, V1, V2, &Mask[0]);
}

/// getUnpackhMask - Returns a vector_shuffle node for an unpackh operation.
static SDValue getUnpackh(SelectionDAG &DAG, DebugLoc dl, EVT VT, SDValue V1,
                          SDValue V2) {
  unsigned NumElems = VT.getVectorNumElements();
  unsigned Half = NumElems/2;
  SmallVector<int, 8> Mask;
  for (unsigned i = 0; i != Half; ++i) {
    Mask.push_back(i + Half);
    Mask.push_back(i + NumElems + Half);
  }
  return DAG.getVectorShuffle(VT, dl, V1, V2, &Mask[0]);
}

/// PromoteSplat - Promote a splat of v4f32, v8i16 or v16i8 to v4i32.
static SDValue PromoteSplat(ShuffleVectorSDNode *SV, SelectionDAG &DAG,
                            bool HasSSE2) {
  if (SV->getValueType(0).getVectorNumElements() <= 4)
    return SDValue(SV, 0);

  EVT PVT = MVT::v4f32;
  EVT VT = SV->getValueType(0);
  DebugLoc dl = SV->getDebugLoc();
  SDValue V1 = SV->getOperand(0);
  int NumElems = VT.getVectorNumElements();
  int EltNo = SV->getSplatIndex();

  // unpack elements to the correct location
  while (NumElems > 4) {
    if (EltNo < NumElems/2) {
      V1 = getUnpackl(DAG, dl, VT, V1, V1);
    } else {
      V1 = getUnpackh(DAG, dl, VT, V1, V1);
      EltNo -= NumElems/2;
    }
    NumElems >>= 1;
  }

  // Perform the splat.
  int SplatMask[4] = { EltNo, EltNo, EltNo, EltNo };
  V1 = DAG.getNode(ISD::BIT_CONVERT, dl, PVT, V1);
  V1 = DAG.getVectorShuffle(PVT, dl, V1, DAG.getUNDEF(PVT), &SplatMask[0]);
  return DAG.getNode(ISD::BIT_CONVERT, dl, VT, V1);
}

/// getShuffleVectorZeroOrUndef - Return a vector_shuffle of the specified
/// vector of zero or undef vector.  This produces a shuffle where the low
/// element of V2 is swizzled into the zero/undef vector, landing at element
/// Idx.  This produces a shuffle mask like 4,1,2,3 (idx=0) or  0,1,2,4 (idx=3).
static SDValue getShuffleVectorZeroOrUndef(SDValue V2, unsigned Idx,
                                             bool isZero, bool HasSSE2,
                                             SelectionDAG &DAG) {
  EVT VT = V2.getValueType();
  SDValue V1 = isZero
    ? getZeroVector(VT, HasSSE2, DAG, V2.getDebugLoc()) : DAG.getUNDEF(VT);
  unsigned NumElems = VT.getVectorNumElements();
  SmallVector<int, 16> MaskVec;
  for (unsigned i = 0; i != NumElems; ++i)
    // If this is the insertion idx, put the low elt of V2 here.
    MaskVec.push_back(i == Idx ? NumElems : i);
  return DAG.getVectorShuffle(VT, V2.getDebugLoc(), V1, V2, &MaskVec[0]);
}

/// getNumOfConsecutiveZeros - Return the number of elements in a result of
/// a shuffle that is zero.
static
unsigned getNumOfConsecutiveZeros(ShuffleVectorSDNode *SVOp, int NumElems,
                                  bool Low, SelectionDAG &DAG) {
  unsigned NumZeros = 0;
  for (int i = 0; i < NumElems; ++i) {
    unsigned Index = Low ? i : NumElems-i-1;
    int Idx = SVOp->getMaskElt(Index);
    if (Idx < 0) {
      ++NumZeros;
      continue;
    }
    SDValue Elt = DAG.getShuffleScalarElt(SVOp, Index);
    if (Elt.getNode() && X86::isZeroNode(Elt))
      ++NumZeros;
    else
      break;
  }
  return NumZeros;
}

/// isVectorShift - Returns true if the shuffle can be implemented as a
/// logical left or right shift of a vector.
/// FIXME: split into pslldqi, psrldqi, palignr variants.
static bool isVectorShift(ShuffleVectorSDNode *SVOp, SelectionDAG &DAG,
                          bool &isLeft, SDValue &ShVal, unsigned &ShAmt) {
  unsigned NumElems = SVOp->getValueType(0).getVectorNumElements();

  isLeft = true;
  unsigned NumZeros = getNumOfConsecutiveZeros(SVOp, NumElems, true, DAG);
  if (!NumZeros) {
    isLeft = false;
    NumZeros = getNumOfConsecutiveZeros(SVOp, NumElems, false, DAG);
    if (!NumZeros)
      return false;
  }
  bool SeenV1 = false;
  bool SeenV2 = false;
  for (unsigned i = NumZeros; i < NumElems; ++i) {
    unsigned Val = isLeft ? (i - NumZeros) : i;
    int Idx_ = SVOp->getMaskElt(isLeft ? i : (i - NumZeros));
    if (Idx_ < 0)
      continue;
    unsigned Idx = (unsigned) Idx_;
    if (Idx < NumElems)
      SeenV1 = true;
    else {
      Idx -= NumElems;
      SeenV2 = true;
    }
    if (Idx != Val)
      return false;
  }
  if (SeenV1 && SeenV2)
    return false;

  ShVal = SeenV1 ? SVOp->getOperand(0) : SVOp->getOperand(1);
  ShAmt = NumZeros;
  return true;
}


/// LowerBuildVectorv16i8 - Custom lower build_vector of v16i8.
///
static SDValue LowerBuildVectorv16i8(SDValue Op, unsigned NonZeros,
                                       unsigned NumNonZero, unsigned NumZero,
                                       SelectionDAG &DAG,
                                       const TargetLowering &TLI) {
  if (NumNonZero > 8)
    return SDValue();

  DebugLoc dl = Op.getDebugLoc();
  SDValue V(0, 0);
  bool First = true;
  for (unsigned i = 0; i < 16; ++i) {
    bool ThisIsNonZero = (NonZeros & (1 << i)) != 0;
    if (ThisIsNonZero && First) {
      if (NumZero)
        V = getZeroVector(MVT::v8i16, true, DAG, dl);
      else
        V = DAG.getUNDEF(MVT::v8i16);
      First = false;
    }

    if ((i & 1) != 0) {
      SDValue ThisElt(0, 0), LastElt(0, 0);
      bool LastIsNonZero = (NonZeros & (1 << (i-1))) != 0;
      if (LastIsNonZero) {
        LastElt = DAG.getNode(ISD::ZERO_EXTEND, dl,
                              MVT::i16, Op.getOperand(i-1));
      }
      if (ThisIsNonZero) {
        ThisElt = DAG.getNode(ISD::ZERO_EXTEND, dl, MVT::i16, Op.getOperand(i));
        ThisElt = DAG.getNode(ISD::SHL, dl, MVT::i16,
                              ThisElt, DAG.getConstant(8, MVT::i8));
        if (LastIsNonZero)
          ThisElt = DAG.getNode(ISD::OR, dl, MVT::i16, ThisElt, LastElt);
      } else
        ThisElt = LastElt;

      if (ThisElt.getNode())
        V = DAG.getNode(ISD::INSERT_VECTOR_ELT, dl, MVT::v8i16, V, ThisElt,
                        DAG.getIntPtrConstant(i/2));
    }
  }

  return DAG.getNode(ISD::BIT_CONVERT, dl, MVT::v16i8, V);
}

/// LowerBuildVectorv8i16 - Custom lower build_vector of v8i16.
///
static SDValue LowerBuildVectorv8i16(SDValue Op, unsigned NonZeros,
                                     unsigned NumNonZero, unsigned NumZero,
                                     SelectionDAG &DAG,
                                     const TargetLowering &TLI) {
  if (NumNonZero > 4)
    return SDValue();

  DebugLoc dl = Op.getDebugLoc();
  SDValue V(0, 0);
  bool First = true;
  for (unsigned i = 0; i < 8; ++i) {
    bool isNonZero = (NonZeros & (1 << i)) != 0;
    if (isNonZero) {
      if (First) {
        if (NumZero)
          V = getZeroVector(MVT::v8i16, true, DAG, dl);
        else
          V = DAG.getUNDEF(MVT::v8i16);
        First = false;
      }
      V = DAG.getNode(ISD::INSERT_VECTOR_ELT, dl,
                      MVT::v8i16, V, Op.getOperand(i),
                      DAG.getIntPtrConstant(i));
    }
  }

  return V;
}

/// getVShift - Return a vector logical shift node.
///
static SDValue getVShift(bool isLeft, EVT VT, SDValue SrcOp,
                         unsigned NumBits, SelectionDAG &DAG,
                         const TargetLowering &TLI, DebugLoc dl) {
  bool isMMX = VT.getSizeInBits() == 64;
  EVT ShVT = isMMX ? MVT::v1i64 : MVT::v2i64;
  unsigned Opc = isLeft ? X86ISD::VSHL : X86ISD::VSRL;
  SrcOp = DAG.getNode(ISD::BIT_CONVERT, dl, ShVT, SrcOp);
  return DAG.getNode(ISD::BIT_CONVERT, dl, VT,
                     DAG.getNode(Opc, dl, ShVT, SrcOp,
                             DAG.getConstant(NumBits, TLI.getShiftAmountTy())));
}

SDValue
X86TargetLowering::LowerAsSplatVectorLoad(SDValue SrcOp, EVT VT, DebugLoc dl,
                                          SelectionDAG &DAG) const {
  
  // Check if the scalar load can be widened into a vector load. And if
  // the address is "base + cst" see if the cst can be "absorbed" into
  // the shuffle mask.
  if (LoadSDNode *LD = dyn_cast<LoadSDNode>(SrcOp)) {
    SDValue Ptr = LD->getBasePtr();
    if (!ISD::isNormalLoad(LD) || LD->isVolatile())
      return SDValue();
    EVT PVT = LD->getValueType(0);
    if (PVT != MVT::i32 && PVT != MVT::f32)
      return SDValue();

    int FI = -1;
    int64_t Offset = 0;
    if (FrameIndexSDNode *FINode = dyn_cast<FrameIndexSDNode>(Ptr)) {
      FI = FINode->getIndex();
      Offset = 0;
    } else if (Ptr.getOpcode() == ISD::ADD &&
               isa<ConstantSDNode>(Ptr.getOperand(1)) &&
               isa<FrameIndexSDNode>(Ptr.getOperand(0))) {
      FI = cast<FrameIndexSDNode>(Ptr.getOperand(0))->getIndex();
      Offset = Ptr.getConstantOperandVal(1);
      Ptr = Ptr.getOperand(0);
    } else {
      return SDValue();
    }

    SDValue Chain = LD->getChain();
    // Make sure the stack object alignment is at least 16.
    MachineFrameInfo *MFI = DAG.getMachineFunction().getFrameInfo();
    if (DAG.InferPtrAlignment(Ptr) < 16) {
      if (MFI->isFixedObjectIndex(FI)) {
        // Can't change the alignment. FIXME: It's possible to compute
        // the exact stack offset and reference FI + adjust offset instead.
        // If someone *really* cares about this. That's the way to implement it.
        return SDValue();
      } else {
        MFI->setObjectAlignment(FI, 16);
      }
    }

    // (Offset % 16) must be multiple of 4. Then address is then
    // Ptr + (Offset & ~15).
    if (Offset < 0)
      return SDValue();
    if ((Offset % 16) & 3)
      return SDValue();
    int64_t StartOffset = Offset & ~15;
    if (StartOffset)
      Ptr = DAG.getNode(ISD::ADD, Ptr.getDebugLoc(), Ptr.getValueType(),
                        Ptr,DAG.getConstant(StartOffset, Ptr.getValueType()));

    int EltNo = (Offset - StartOffset) >> 2;
    int Mask[4] = { EltNo, EltNo, EltNo, EltNo };
    EVT VT = (PVT == MVT::i32) ? MVT::v4i32 : MVT::v4f32;
    SDValue V1 = DAG.getLoad(VT, dl, Chain, Ptr,LD->getSrcValue(),0,
                             false, false, 0);
    // Canonicalize it to a v4i32 shuffle.
    V1 = DAG.getNode(ISD::BIT_CONVERT, dl, MVT::v4i32, V1);
    return DAG.getNode(ISD::BIT_CONVERT, dl, VT,
                       DAG.getVectorShuffle(MVT::v4i32, dl, V1,
                                            DAG.getUNDEF(MVT::v4i32), &Mask[0]));
  }

  return SDValue();
}

/// EltsFromConsecutiveLoads - Given the initializing elements 'Elts' of a 
/// vector of type 'VT', see if the elements can be replaced by a single large 
/// load which has the same value as a build_vector whose operands are 'elts'.
///
/// Example: <load i32 *a, load i32 *a+4, undef, undef> -> zextload a
/// 
/// FIXME: we'd also like to handle the case where the last elements are zero
/// rather than undef via VZEXT_LOAD, but we do not detect that case today.
/// There's even a handy isZeroNode for that purpose.
static SDValue EltsFromConsecutiveLoads(EVT VT, SmallVectorImpl<SDValue> &Elts,
                                        DebugLoc &dl, SelectionDAG &DAG) {
  EVT EltVT = VT.getVectorElementType();
  unsigned NumElems = Elts.size();
  
  LoadSDNode *LDBase = NULL;
  unsigned LastLoadedElt = -1U;
  
  // For each element in the initializer, see if we've found a load or an undef.
  // If we don't find an initial load element, or later load elements are 
  // non-consecutive, bail out.
  for (unsigned i = 0; i < NumElems; ++i) {
    SDValue Elt = Elts[i];
    
    if (!Elt.getNode() ||
        (Elt.getOpcode() != ISD::UNDEF && !ISD::isNON_EXTLoad(Elt.getNode())))
      return SDValue();
    if (!LDBase) {
      if (Elt.getNode()->getOpcode() == ISD::UNDEF)
        return SDValue();
      LDBase = cast<LoadSDNode>(Elt.getNode());
      LastLoadedElt = i;
      continue;
    }
    if (Elt.getOpcode() == ISD::UNDEF)
      continue;

    LoadSDNode *LD = cast<LoadSDNode>(Elt);
    if (!DAG.isConsecutiveLoad(LD, LDBase, EltVT.getSizeInBits()/8, i))
      return SDValue();
    LastLoadedElt = i;
  }

  // If we have found an entire vector of loads and undefs, then return a large
  // load of the entire vector width starting at the base pointer.  If we found
  // consecutive loads for the low half, generate a vzext_load node.
  if (LastLoadedElt == NumElems - 1) {
    if (DAG.InferPtrAlignment(LDBase->getBasePtr()) >= 16)
      return DAG.getLoad(VT, dl, LDBase->getChain(), LDBase->getBasePtr(),
                         LDBase->getSrcValue(), LDBase->getSrcValueOffset(),
                         LDBase->isVolatile(), LDBase->isNonTemporal(), 0);
    return DAG.getLoad(VT, dl, LDBase->getChain(), LDBase->getBasePtr(),
                       LDBase->getSrcValue(), LDBase->getSrcValueOffset(),
                       LDBase->isVolatile(), LDBase->isNonTemporal(),
                       LDBase->getAlignment());
  } else if (NumElems == 4 && LastLoadedElt == 1) {
    SDVTList Tys = DAG.getVTList(MVT::v2i64, MVT::Other);
    SDValue Ops[] = { LDBase->getChain(), LDBase->getBasePtr() };
    SDValue ResNode = DAG.getNode(X86ISD::VZEXT_LOAD, dl, Tys, Ops, 2);
    return DAG.getNode(ISD::BIT_CONVERT, dl, VT, ResNode);
  }
  return SDValue();
}

SDValue
X86TargetLowering::LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const {
  DebugLoc dl = Op.getDebugLoc();
  // All zero's are handled with pxor, all one's are handled with pcmpeqd.
  if (ISD::isBuildVectorAllZeros(Op.getNode())
      || ISD::isBuildVectorAllOnes(Op.getNode())) {
    // Canonicalize this to either <4 x i32> or <2 x i32> (SSE vs MMX) to
    // 1) ensure the zero vectors are CSE'd, and 2) ensure that i64 scalars are
    // eliminated on x86-32 hosts.
    if (Op.getValueType() == MVT::v4i32 || Op.getValueType() == MVT::v2i32)
      return Op;

    if (ISD::isBuildVectorAllOnes(Op.getNode()))
      return getOnesVector(Op.getValueType(), DAG, dl);
    return getZeroVector(Op.getValueType(), Subtarget->hasSSE2(), DAG, dl);
  }

  EVT VT = Op.getValueType();
  EVT ExtVT = VT.getVectorElementType();
  unsigned EVTBits = ExtVT.getSizeInBits();

  unsigned NumElems = Op.getNumOperands();
  unsigned NumZero  = 0;
  unsigned NumNonZero = 0;
  unsigned NonZeros = 0;
  bool IsAllConstants = true;
  SmallSet<SDValue, 8> Values;
  for (unsigned i = 0; i < NumElems; ++i) {
    SDValue Elt = Op.getOperand(i);
    if (Elt.getOpcode() == ISD::UNDEF)
      continue;
    Values.insert(Elt);
    if (Elt.getOpcode() != ISD::Constant &&
        Elt.getOpcode() != ISD::ConstantFP)
      IsAllConstants = false;
    if (X86::isZeroNode(Elt))
      NumZero++;
    else {
      NonZeros |= (1 << i);
      NumNonZero++;
    }
  }

  if (NumNonZero == 0) {
    // All undef vector. Return an UNDEF.  All zero vectors were handled above.
    return DAG.getUNDEF(VT);
  }

  // Special case for single non-zero, non-undef, element.
  if (NumNonZero == 1) {
    unsigned Idx = CountTrailingZeros_32(NonZeros);
    SDValue Item = Op.getOperand(Idx);

    // If this is an insertion of an i64 value on x86-32, and if the top bits of
    // the value are obviously zero, truncate the value to i32 and do the
    // insertion that way.  Only do this if the value is non-constant or if the
    // value is a constant being inserted into element 0.  It is cheaper to do
    // a constant pool load than it is to do a movd + shuffle.
    if (ExtVT == MVT::i64 && !Subtarget->is64Bit() &&
        (!IsAllConstants || Idx == 0)) {
      if (DAG.MaskedValueIsZero(Item, APInt::getBitsSet(64, 32, 64))) {
        // Handle MMX and SSE both.
        EVT VecVT = VT == MVT::v2i64 ? MVT::v4i32 : MVT::v2i32;
        unsigned VecElts = VT == MVT::v2i64 ? 4 : 2;

        // Truncate the value (which may itself be a constant) to i32, and
        // convert it to a vector with movd (S2V+shuffle to zero extend).
        Item = DAG.getNode(ISD::TRUNCATE, dl, MVT::i32, Item);
        Item = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, VecVT, Item);
        Item = getShuffleVectorZeroOrUndef(Item, 0, true,
                                           Subtarget->hasSSE2(), DAG);

        // Now we have our 32-bit value zero extended in the low element of
        // a vector.  If Idx != 0, swizzle it into place.
        if (Idx != 0) {
          SmallVector<int, 4> Mask;
          Mask.push_back(Idx);
          for (unsigned i = 1; i != VecElts; ++i)
            Mask.push_back(i);
          Item = DAG.getVectorShuffle(VecVT, dl, Item,
                                      DAG.getUNDEF(Item.getValueType()),
                                      &Mask[0]);
        }
        return DAG.getNode(ISD::BIT_CONVERT, dl, Op.getValueType(), Item);
      }
    }

    // If we have a constant or non-constant insertion into the low element of
    // a vector, we can do this with SCALAR_TO_VECTOR + shuffle of zero into
    // the rest of the elements.  This will be matched as movd/movq/movss/movsd
    // depending on what the source datatype is.
    if (Idx == 0) {
      if (NumZero == 0) {
        return DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, VT, Item);
      } else if (ExtVT == MVT::i32 || ExtVT == MVT::f32 || ExtVT == MVT::f64 ||
          (ExtVT == MVT::i64 && Subtarget->is64Bit())) {
        Item = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, VT, Item);
        // Turn it into a MOVL (i.e. movss, movsd, or movd) to a zero vector.
        return getShuffleVectorZeroOrUndef(Item, 0, true, Subtarget->hasSSE2(),
                                           DAG);
      } else if (ExtVT == MVT::i16 || ExtVT == MVT::i8) {
        Item = DAG.getNode(ISD::ZERO_EXTEND, dl, MVT::i32, Item);
        EVT MiddleVT = VT.getSizeInBits() == 64 ? MVT::v2i32 : MVT::v4i32;
        Item = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, MiddleVT, Item);
        Item = getShuffleVectorZeroOrUndef(Item, 0, true,
                                           Subtarget->hasSSE2(), DAG);
        return DAG.getNode(ISD::BIT_CONVERT, dl, VT, Item);
      }
    }

    // Is it a vector logical left shift?
    if (NumElems == 2 && Idx == 1 &&
        X86::isZeroNode(Op.getOperand(0)) &&
        !X86::isZeroNode(Op.getOperand(1))) {
      unsigned NumBits = VT.getSizeInBits();
      return getVShift(true, VT,
                       DAG.getNode(ISD::SCALAR_TO_VECTOR, dl,
                                   VT, Op.getOperand(1)),
                       NumBits/2, DAG, *this, dl);
    }

    if (IsAllConstants) // Otherwise, it's better to do a constpool load.
      return SDValue();

    // Otherwise, if this is a vector with i32 or f32 elements, and the element
    // is a non-constant being inserted into an element other than the low one,
    // we can't use a constant pool load.  Instead, use SCALAR_TO_VECTOR (aka
    // movd/movss) to move this into the low element, then shuffle it into
    // place.
    if (EVTBits == 32) {
      Item = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, VT, Item);

      // Turn it into a shuffle of zero and zero-extended scalar to vector.
      Item = getShuffleVectorZeroOrUndef(Item, 0, NumZero > 0,
                                         Subtarget->hasSSE2(), DAG);
      SmallVector<int, 8> MaskVec;
      for (unsigned i = 0; i < NumElems; i++)
        MaskVec.push_back(i == Idx ? 0 : 1);
      return DAG.getVectorShuffle(VT, dl, Item, DAG.getUNDEF(VT), &MaskVec[0]);
    }
  }

  // Splat is obviously ok. Let legalizer expand it to a shuffle.
  if (Values.size() == 1) {
    if (EVTBits == 32) {
      // Instead of a shuffle like this:
      // shuffle (scalar_to_vector (load (ptr + 4))), undef, <0, 0, 0, 0>
      // Check if it's possible to issue this instead.
      // shuffle (vload ptr)), undef, <1, 1, 1, 1>
      unsigned Idx = CountTrailingZeros_32(NonZeros);
      SDValue Item = Op.getOperand(Idx);
      if (Op.getNode()->isOnlyUserOf(Item.getNode()))
        return LowerAsSplatVectorLoad(Item, VT, dl, DAG);
    }
    return SDValue();
  }

  // A vector full of immediates; various special cases are already
  // handled, so this is best done with a single constant-pool load.
  if (IsAllConstants)
    return SDValue();

  // Let legalizer expand 2-wide build_vectors.
  if (EVTBits == 64) {
    if (NumNonZero == 1) {
      // One half is zero or undef.
      unsigned Idx = CountTrailingZeros_32(NonZeros);
      SDValue V2 = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, VT,
                                 Op.getOperand(Idx));
      return getShuffleVectorZeroOrUndef(V2, Idx, true,
                                         Subtarget->hasSSE2(), DAG);
    }
    return SDValue();
  }

  // If element VT is < 32 bits, convert it to inserts into a zero vector.
  if (EVTBits == 8 && NumElems == 16) {
    SDValue V = LowerBuildVectorv16i8(Op, NonZeros,NumNonZero,NumZero, DAG,
                                        *this);
    if (V.getNode()) return V;
  }

  if (EVTBits == 16 && NumElems == 8) {
    SDValue V = LowerBuildVectorv8i16(Op, NonZeros,NumNonZero,NumZero, DAG,
                                        *this);
    if (V.getNode()) return V;
  }

  // If element VT is == 32 bits, turn it into a number of shuffles.
  SmallVector<SDValue, 8> V;
  V.resize(NumElems);
  if (NumElems == 4 && NumZero > 0) {
    for (unsigned i = 0; i < 4; ++i) {
      bool isZero = !(NonZeros & (1 << i));
      if (isZero)
        V[i] = getZeroVector(VT, Subtarget->hasSSE2(), DAG, dl);
      else
        V[i] = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, VT, Op.getOperand(i));
    }

    for (unsigned i = 0; i < 2; ++i) {
      switch ((NonZeros & (0x3 << i*2)) >> (i*2)) {
        default: break;
        case 0:
          V[i] = V[i*2];  // Must be a zero vector.
          break;
        case 1:
          V[i] = getMOVL(DAG, dl, VT, V[i*2+1], V[i*2]);
          break;
        case 2:
          V[i] = getMOVL(DAG, dl, VT, V[i*2], V[i*2+1]);
          break;
        case 3:
          V[i] = getUnpackl(DAG, dl, VT, V[i*2], V[i*2+1]);
          break;
      }
    }

    SmallVector<int, 8> MaskVec;
    bool Reverse = (NonZeros & 0x3) == 2;
    for (unsigned i = 0; i < 2; ++i)
      MaskVec.push_back(Reverse ? 1-i : i);
    Reverse = ((NonZeros & (0x3 << 2)) >> 2) == 2;
    for (unsigned i = 0; i < 2; ++i)
      MaskVec.push_back(Reverse ? 1-i+NumElems : i+NumElems);
    return DAG.getVectorShuffle(VT, dl, V[0], V[1], &MaskVec[0]);
  }

  if (Values.size() > 1 && VT.getSizeInBits() == 128) {
    // Check for a build vector of consecutive loads.
    for (unsigned i = 0; i < NumElems; ++i)
      V[i] = Op.getOperand(i);
    
    // Check for elements which are consecutive loads.
    SDValue LD = EltsFromConsecutiveLoads(VT, V, dl, DAG);
    if (LD.getNode())
      return LD;
    
    // For SSE 4.1, use inserts into undef.