X86ISelLowering.cpp

  // Check if the value doesn't reference the second vector.
  for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) continue;
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    if (cast<ConstantSDNode>(Arg)->getValue() >= 4)
      return false;
  }

  return true;
}

/// isPSHUFHWMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to PSHUFHW.
bool X86::isPSHUFHWMask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  if (N->getNumOperands() != 8)
    return false;

  // Lower quadword copied in order.
  for (unsigned i = 0; i != 4; ++i) {
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) continue;
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    if (cast<ConstantSDNode>(Arg)->getValue() != i)
      return false;
  }

  // Upper quadword shuffled.
  for (unsigned i = 4; i != 8; ++i) {
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) continue;
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
    if (Val < 4 || Val > 7)
      return false;
  }

  return true;
}

/// isPSHUFLWMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to PSHUFLW.
bool X86::isPSHUFLWMask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  if (N->getNumOperands() != 8)
    return false;

  // Upper quadword copied in order.
  for (unsigned i = 4; i != 8; ++i)
    if (!isUndefOrEqual(N->getOperand(i), i))
      return false;

  // Lower quadword shuffled.
  for (unsigned i = 0; i != 4; ++i)
    if (!isUndefOrInRange(N->getOperand(i), 0, 4))
      return false;

  return true;
}

/// isSHUFPMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to SHUFP*.
static bool isSHUFPMask(std::vector<SDOperand> &N) {
  unsigned NumElems = N.size();
  if (NumElems != 2 && NumElems != 4) return false;

  unsigned Half = NumElems / 2;
  for (unsigned i = 0; i < Half; ++i)
    if (!isUndefOrInRange(N[i], 0, NumElems))
      return false;
  for (unsigned i = Half; i < NumElems; ++i)
    if (!isUndefOrInRange(N[i], NumElems, NumElems*2))
      return false;

  return true;
}

bool X86::isSHUFPMask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);
  std::vector<SDOperand> Ops(N->op_begin(), N->op_end());
  return ::isSHUFPMask(Ops);
}

/// isCommutedSHUFP - Returns true if the shuffle mask is except
/// the reverse of what x86 shuffles want. x86 shuffles requires the lower
/// half elements to come from vector 1 (which would equal the dest.) and
/// the upper half to come from vector 2.
static bool isCommutedSHUFP(std::vector<SDOperand> &Ops) {
  unsigned NumElems = Ops.size();
  if (NumElems != 2 && NumElems != 4) return false;

  unsigned Half = NumElems / 2;
  for (unsigned i = 0; i < Half; ++i)
    if (!isUndefOrInRange(Ops[i], NumElems, NumElems*2))
      return false;
  for (unsigned i = Half; i < NumElems; ++i)
    if (!isUndefOrInRange(Ops[i], 0, NumElems))
      return false;
  return true;
}

static bool isCommutedSHUFP(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);
  std::vector<SDOperand> Ops(N->op_begin(), N->op_end());
  return isCommutedSHUFP(Ops);
}

/// isMOVHLPSMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to MOVHLPS.
bool X86::isMOVHLPSMask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  if (N->getNumOperands() != 4)
    return false;

  // Expect bit0 == 6, bit1 == 7, bit2 == 2, bit3 == 3
  return isUndefOrEqual(N->getOperand(0), 6) &&
         isUndefOrEqual(N->getOperand(1), 7) &&
         isUndefOrEqual(N->getOperand(2), 2) &&
         isUndefOrEqual(N->getOperand(3), 3);
}

/// isMOVLPMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to MOVLP{S|D}.
bool X86::isMOVLPMask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  unsigned NumElems = N->getNumOperands();
  if (NumElems != 2 && NumElems != 4)
    return false;

  for (unsigned i = 0; i < NumElems/2; ++i)
    if (!isUndefOrEqual(N->getOperand(i), i + NumElems))
      return false;

  for (unsigned i = NumElems/2; i < NumElems; ++i)
    if (!isUndefOrEqual(N->getOperand(i), i))
      return false;

  return true;
}

/// isMOVHPMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to MOVHP{S|D}
/// and MOVLHPS.
bool X86::isMOVHPMask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  unsigned NumElems = N->getNumOperands();
  if (NumElems != 2 && NumElems != 4)
    return false;

  for (unsigned i = 0; i < NumElems/2; ++i)
    if (!isUndefOrEqual(N->getOperand(i), i))
      return false;

  for (unsigned i = 0; i < NumElems/2; ++i) {
    SDOperand Arg = N->getOperand(i + NumElems/2);
    if (!isUndefOrEqual(Arg, i + NumElems))
      return false;
  }

  return true;
}

/// isUNPCKLMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to UNPCKL.
bool static isUNPCKLMask(std::vector<SDOperand> &N, bool V2IsSplat = false) {
  unsigned NumElems = N.size();
  if (NumElems != 2 && NumElems != 4 && NumElems != 8 && NumElems != 16)
    return false;

  for (unsigned i = 0, j = 0; i != NumElems; i += 2, ++j) {
    SDOperand BitI  = N[i];
    SDOperand BitI1 = N[i+1];
    if (!isUndefOrEqual(BitI, j))
      return false;
    if (V2IsSplat) {
      if (isUndefOrEqual(BitI1, NumElems))
        return false;
    } else {
      if (!isUndefOrEqual(BitI1, j + NumElems))
        return false;
    }
  }

  return true;
}

bool X86::isUNPCKLMask(SDNode *N, bool V2IsSplat) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);
  std::vector<SDOperand> Ops(N->op_begin(), N->op_end());
  return ::isUNPCKLMask(Ops, V2IsSplat);
}

/// isUNPCKHMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to UNPCKH.
bool static isUNPCKHMask(std::vector<SDOperand> &N, bool V2IsSplat = false) {
  unsigned NumElems = N.size();
  if (NumElems != 2 && NumElems != 4 && NumElems != 8 && NumElems != 16)
    return false;

  for (unsigned i = 0, j = 0; i != NumElems; i += 2, ++j) {
    SDOperand BitI  = N[i];
    SDOperand BitI1 = N[i+1];
    if (!isUndefOrEqual(BitI, j + NumElems/2))
      return false;
    if (V2IsSplat) {
      if (isUndefOrEqual(BitI1, NumElems))
        return false;
    } else {
      if (!isUndefOrEqual(BitI1, j + NumElems/2 + NumElems))
        return false;
    }
  }

  return true;
}

bool X86::isUNPCKHMask(SDNode *N, bool V2IsSplat) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);
  std::vector<SDOperand> Ops(N->op_begin(), N->op_end());
  return ::isUNPCKHMask(Ops, V2IsSplat);
}

/// isUNPCKL_v_undef_Mask - Special case of isUNPCKLMask for canonical form
/// of vector_shuffle v, v, <0, 4, 1, 5>, i.e. vector_shuffle v, undef,
/// <0, 0, 1, 1>
bool X86::isUNPCKL_v_undef_Mask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  unsigned NumElems = N->getNumOperands();
  if (NumElems != 4 && NumElems != 8 && NumElems != 16)
    return false;

  for (unsigned i = 0, j = 0; i != NumElems; i += 2, ++j) {
    SDOperand BitI  = N->getOperand(i);
    SDOperand BitI1 = N->getOperand(i+1);

    if (!isUndefOrEqual(BitI, j))
      return false;
    if (!isUndefOrEqual(BitI1, j))
      return false;
  }

  return true;
}

/// isMOVLMask - Return true if the specified VECTOR_SHUFFLE operand
/// specifies a shuffle of elements that is suitable for input to MOVSS,
/// MOVSD, and MOVD, i.e. setting the lowest element.
static bool isMOVLMask(std::vector<SDOperand> &N) {
  unsigned NumElems = N.size();
  if (NumElems != 2 && NumElems != 4 && NumElems != 8 && NumElems != 16)
    return false;

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

  for (unsigned i = 1; i < NumElems; ++i) {
    SDOperand Arg = N[i];
    if (!isUndefOrEqual(Arg, i))
      return false;
  }

  return true;
}

bool X86::isMOVLMask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);
  std::vector<SDOperand> Ops(N->op_begin(), N->op_end());
  return ::isMOVLMask(Ops);
}

/// 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 isCommutedMOVL(std::vector<SDOperand> &Ops, bool V2IsSplat = false,
                           bool V2IsUndef = false) {
  unsigned NumElems = Ops.size();
  if (NumElems != 2 && NumElems != 4 && NumElems != 8 && NumElems != 16)
    return false;

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

  for (unsigned i = 1; i < NumElems; ++i) {
    SDOperand Arg = Ops[i];
    if (!(isUndefOrEqual(Arg, i+NumElems) ||
          (V2IsUndef && isUndefOrInRange(Arg, NumElems, NumElems*2)) ||
          (V2IsSplat && isUndefOrEqual(Arg, NumElems))))
      return false;
  }

  return true;
}

static bool isCommutedMOVL(SDNode *N, bool V2IsSplat = false,
                           bool V2IsUndef = false) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);
  std::vector<SDOperand> Ops(N->op_begin(), N->op_end());
  return isCommutedMOVL(Ops, 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(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  if (N->getNumOperands() != 4)
    return false;

  // Expect 1, 1, 3, 3
  for (unsigned i = 0; i < 2; ++i) {
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) continue;
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
    if (Val != 1) return false;
  }

  bool HasHi = false;
  for (unsigned i = 2; i < 4; ++i) {
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) continue;
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
    if (Val != 3) return false;
    HasHi = true;
  }

  // Don't use movshdup if it can be done with a shufps.
  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(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  if (N->getNumOperands() != 4)
    return false;

  // Expect 0, 0, 2, 2
  for (unsigned i = 0; i < 2; ++i) {
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) continue;
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
    if (Val != 0) return false;
  }

  bool HasHi = false;
  for (unsigned i = 2; i < 4; ++i) {
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) continue;
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
    if (Val != 2) return false;
    HasHi = true;
  }

  // Don't use movshdup if it can be done with a shufps.
  return HasHi;
}

/// isSplatMask - Return true if the specified VECTOR_SHUFFLE operand specifies
/// a splat of a single element.
static bool isSplatMask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  // This is a splat operation if each element of the permute is the same, and
  // if the value doesn't reference the second vector.
  unsigned NumElems = N->getNumOperands();
  SDOperand ElementBase;
  unsigned i = 0;
  for (; i != NumElems; ++i) {
    SDOperand Elt = N->getOperand(i);
    if (ConstantSDNode *EltV = dyn_cast<ConstantSDNode>(Elt)) {
      ElementBase = Elt;
      break;
    }
  }

  if (!ElementBase.Val)
    return false;

  for (; i != NumElems; ++i) {
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) continue;
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    if (Arg != ElementBase) return false;
  }

  // Make sure it is a splat of the first vector operand.
  return cast<ConstantSDNode>(ElementBase)->getValue() < NumElems;
}

/// isSplatMask - Return true if the specified VECTOR_SHUFFLE operand specifies
/// a splat of a single element and it's a 2 or 4 element mask.
bool X86::isSplatMask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  // We can only splat 64-bit, and 32-bit quantities with a single instruction.
  if (N->getNumOperands() != 4 && N->getNumOperands() != 2)
    return false;
  return ::isSplatMask(N);
}

/// getShuffleSHUFImmediate - Return the appropriate immediate to shuffle
/// the specified isShuffleMask VECTOR_SHUFFLE mask with PSHUF* and SHUFP*
/// instructions.
unsigned X86::getShuffleSHUFImmediate(SDNode *N) {
  unsigned NumOperands = N->getNumOperands();
  unsigned Shift = (NumOperands == 4) ? 2 : 1;
  unsigned Mask = 0;
  for (unsigned i = 0; i < NumOperands; ++i) {
    unsigned Val = 0;
    SDOperand Arg = N->getOperand(NumOperands-i-1);
    if (Arg.getOpcode() != ISD::UNDEF)
      Val = cast<ConstantSDNode>(Arg)->getValue();
    if (Val >= NumOperands) Val -= NumOperands;
    Mask |= Val;
    if (i != NumOperands - 1)
      Mask <<= Shift;
  }

  return Mask;
}

/// getShufflePSHUFHWImmediate - Return the appropriate immediate to shuffle
/// the specified isShuffleMask VECTOR_SHUFFLE mask with PSHUFHW
/// instructions.
unsigned X86::getShufflePSHUFHWImmediate(SDNode *N) {
  unsigned Mask = 0;
  // 8 nodes, but we only care about the last 4.
  for (unsigned i = 7; i >= 4; --i) {
    unsigned Val = 0;
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() != ISD::UNDEF)
      Val = cast<ConstantSDNode>(Arg)->getValue();
    Mask |= (Val - 4);
    if (i != 4)
      Mask <<= 2;
  }

  return Mask;
}

/// getShufflePSHUFLWImmediate - Return the appropriate immediate to shuffle
/// the specified isShuffleMask VECTOR_SHUFFLE mask with PSHUFLW
/// instructions.
unsigned X86::getShufflePSHUFLWImmediate(SDNode *N) {
  unsigned Mask = 0;
  // 8 nodes, but we only care about the first 4.
  for (int i = 3; i >= 0; --i) {
    unsigned Val = 0;
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() != ISD::UNDEF)
      Val = cast<ConstantSDNode>(Arg)->getValue();
    Mask |= Val;
    if (i != 0)
      Mask <<= 2;
  }

  return Mask;
}

/// isPSHUFHW_PSHUFLWMask - true if the specified VECTOR_SHUFFLE operand
/// specifies a 8 element shuffle that can be broken into a pair of
/// PSHUFHW and PSHUFLW.
static bool isPSHUFHW_PSHUFLWMask(SDNode *N) {
  assert(N->getOpcode() == ISD::BUILD_VECTOR);

  if (N->getNumOperands() != 8)
    return false;

  // Lower quadword shuffled.
  for (unsigned i = 0; i != 4; ++i) {
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) continue;
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
    if (Val > 4)
      return false;
  }

  // Upper quadword shuffled.
  for (unsigned i = 4; i != 8; ++i) {
    SDOperand Arg = N->getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) continue;
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
    if (Val < 4 || Val > 7)
      return false;
  }

  return true;
}

/// CommuteVectorShuffle - Swap vector_shuffle operandsas well as
/// values in ther permute mask.
static SDOperand CommuteVectorShuffle(SDOperand Op, SelectionDAG &DAG) {
  SDOperand V1 = Op.getOperand(0);
  SDOperand V2 = Op.getOperand(1);
  SDOperand Mask = Op.getOperand(2);
  MVT::ValueType VT = Op.getValueType();
  MVT::ValueType MaskVT = Mask.getValueType();
  MVT::ValueType EltVT = MVT::getVectorBaseType(MaskVT);
  unsigned NumElems = Mask.getNumOperands();
  std::vector<SDOperand> MaskVec;

  for (unsigned i = 0; i != NumElems; ++i) {
    SDOperand Arg = Mask.getOperand(i);
    if (Arg.getOpcode() == ISD::UNDEF) {
      MaskVec.push_back(DAG.getNode(ISD::UNDEF, EltVT));
      continue;
    }
    assert(isa<ConstantSDNode>(Arg) && "Invalid VECTOR_SHUFFLE mask!");
    unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
    if (Val < NumElems)
      MaskVec.push_back(DAG.getConstant(Val + NumElems, EltVT));
    else
      MaskVec.push_back(DAG.getConstant(Val - NumElems, EltVT));
  }

  Mask = DAG.getNode(ISD::BUILD_VECTOR, MaskVT, &MaskVec[0], MaskVec.size());
  return DAG.getNode(ISD::VECTOR_SHUFFLE, VT, V2, V1, Mask);
}

/// 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(SDNode *Mask) {
  unsigned NumElems = Mask->getNumOperands();
  if (NumElems != 4)
    return false;
  for (unsigned i = 0, e = 2; i != e; ++i)
    if (!isUndefOrEqual(Mask->getOperand(i), i+2))
      return false;
  for (unsigned i = 2; i != 4; ++i)
    if (!isUndefOrEqual(Mask->getOperand(i), i+4))
      return false;
  return true;
}

/// isScalarLoadToVector - Returns true if the node is a scalar load that
/// is promoted to a vector.
static inline bool isScalarLoadToVector(SDNode *N) {
  if (N->getOpcode() == ISD::SCALAR_TO_VECTOR) {
    N = N->getOperand(0).Val;
    return (N->getOpcode() == ISD::LOAD);
  }
  return false;
}

/// 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 *Mask) {
  if (V1->getOpcode() != ISD::LOAD && !isScalarLoadToVector(V1))
    return false;

  unsigned NumElems = Mask->getNumOperands();
  if (NumElems != 2 && NumElems != 4)
    return false;
  for (unsigned i = 0, e = NumElems/2; i != e; ++i)
    if (!isUndefOrEqual(Mask->getOperand(i), i))
      return false;
  for (unsigned i = NumElems/2; i != NumElems; ++i)
    if (!isUndefOrEqual(Mask->getOperand(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;

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

/// isUndefShuffle - Returns true if N is a VECTOR_SHUFFLE that can be resolved
/// to an undef.
static bool isUndefShuffle(SDNode *N) {
  if (N->getOpcode() != ISD::BUILD_VECTOR)
    return false;

  SDOperand V1 = N->getOperand(0);
  SDOperand V2 = N->getOperand(1);
  SDOperand Mask = N->getOperand(2);
  unsigned NumElems = Mask.getNumOperands();
  for (unsigned i = 0; i != NumElems; ++i) {
    SDOperand Arg = Mask.getOperand(i);
    if (Arg.getOpcode() != ISD::UNDEF) {
      unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
      if (Val < NumElems && V1.getOpcode() != ISD::UNDEF)
        return false;
      else if (Val >= NumElems && V2.getOpcode() != ISD::UNDEF)
        return false;
    }
  }
  return true;
}

/// NormalizeMask - V2 is a splat, modify the mask (if needed) so all elements
/// that point to V2 points to its first element.
static SDOperand NormalizeMask(SDOperand Mask, SelectionDAG &DAG) {
  assert(Mask.getOpcode() == ISD::BUILD_VECTOR);

  bool Changed = false;
  std::vector<SDOperand> MaskVec;
  unsigned NumElems = Mask.getNumOperands();
  for (unsigned i = 0; i != NumElems; ++i) {
    SDOperand Arg = Mask.getOperand(i);
    if (Arg.getOpcode() != ISD::UNDEF) {
      unsigned Val = cast<ConstantSDNode>(Arg)->getValue();
      if (Val > NumElems) {
        Arg = DAG.getConstant(NumElems, Arg.getValueType());
        Changed = true;
      }
    }
    MaskVec.push_back(Arg);
  }

  if (Changed)
    Mask = DAG.getNode(ISD::BUILD_VECTOR, Mask.getValueType(),
                       &MaskVec[0], MaskVec.size());
  return Mask;
}

/// getMOVLMask - Returns a vector_shuffle mask for an movs{s|d}, movd
/// operation of specified width.
static SDOperand getMOVLMask(unsigned NumElems, SelectionDAG &DAG) {
  MVT::ValueType MaskVT = MVT::getIntVectorWithNumElements(NumElems);
  MVT::ValueType BaseVT = MVT::getVectorBaseType(MaskVT);

  std::vector<SDOperand> MaskVec;
  MaskVec.push_back(DAG.getConstant(NumElems, BaseVT));
  for (unsigned i = 1; i != NumElems; ++i)
    MaskVec.push_back(DAG.getConstant(i, BaseVT));
  return DAG.getNode(ISD::BUILD_VECTOR, MaskVT, &MaskVec[0], MaskVec.size());
}

/// getUnpacklMask - Returns a vector_shuffle mask for an unpackl operation
/// of specified width.
static SDOperand getUnpacklMask(unsigned NumElems, SelectionDAG &DAG) {
  MVT::ValueType MaskVT = MVT::getIntVectorWithNumElements(NumElems);
  MVT::ValueType BaseVT = MVT::getVectorBaseType(MaskVT);
  std::vector<SDOperand> MaskVec;
  for (unsigned i = 0, e = NumElems/2; i != e; ++i) {
    MaskVec.push_back(DAG.getConstant(i,            BaseVT));
    MaskVec.push_back(DAG.getConstant(i + NumElems, BaseVT));
  }
  return DAG.getNode(ISD::BUILD_VECTOR, MaskVT, &MaskVec[0], MaskVec.size());
}

/// getUnpackhMask - Returns a vector_shuffle mask for an unpackh operation
/// of specified width.
static SDOperand getUnpackhMask(unsigned NumElems, SelectionDAG &DAG) {
  MVT::ValueType MaskVT = MVT::getIntVectorWithNumElements(NumElems);
  MVT::ValueType BaseVT = MVT::getVectorBaseType(MaskVT);
  unsigned Half = NumElems/2;
  std::vector<SDOperand> MaskVec;
  for (unsigned i = 0; i != Half; ++i) {
    MaskVec.push_back(DAG.getConstant(i + Half,            BaseVT));
    MaskVec.push_back(DAG.getConstant(i + NumElems + Half, BaseVT));
  }
  return DAG.getNode(ISD::BUILD_VECTOR, MaskVT, &MaskVec[0], MaskVec.size());
}

/// getZeroVector - Returns a vector of specified type with all zero elements.
///
static SDOperand getZeroVector(MVT::ValueType VT, SelectionDAG &DAG) {
  assert(MVT::isVector(VT) && "Expected a vector type");
  unsigned NumElems = getVectorNumElements(VT);
  MVT::ValueType EVT = MVT::getVectorBaseType(VT);
  bool isFP = MVT::isFloatingPoint(EVT);
  SDOperand Zero = isFP ? DAG.getConstantFP(0.0, EVT) : DAG.getConstant(0, EVT);
  std::vector<SDOperand> ZeroVec(NumElems, Zero);
  return DAG.getNode(ISD::BUILD_VECTOR, VT, &ZeroVec[0], ZeroVec.size());
}

/// PromoteSplat - Promote a splat of v8i16 or v16i8 to v4i32.
///
static SDOperand PromoteSplat(SDOperand Op, SelectionDAG &DAG) {
  SDOperand V1 = Op.getOperand(0);
  SDOperand Mask = Op.getOperand(2);
  MVT::ValueType VT = Op.getValueType();
  unsigned NumElems = Mask.getNumOperands();
  Mask = getUnpacklMask(NumElems, DAG);
  while (NumElems != 4) {
    V1 = DAG.getNode(ISD::VECTOR_SHUFFLE, VT, V1, V1, Mask);
    NumElems >>= 1;
  }
  V1 = DAG.getNode(ISD::BIT_CONVERT, MVT::v4i32, V1);

  MVT::ValueType MaskVT = MVT::getIntVectorWithNumElements(4);
  Mask = getZeroVector(MaskVT, DAG);
  SDOperand Shuffle = DAG.getNode(ISD::VECTOR_SHUFFLE, MVT::v4i32, V1,
                                  DAG.getNode(ISD::UNDEF, MVT::v4i32), Mask);
  return DAG.getNode(ISD::BIT_CONVERT, VT, Shuffle);
}

/// isZeroNode - Returns true if Elt is a constant zero or a floating point
/// constant +0.0.
static inline bool isZeroNode(SDOperand Elt) {
  return ((isa<ConstantSDNode>(Elt) &&
           cast<ConstantSDNode>(Elt)->getValue() == 0) ||
          (isa<ConstantFPSDNode>(Elt) &&
           cast<ConstantFPSDNode>(Elt)->isExactlyValue(0.0)));
}

/// getShuffleVectorZeroOrUndef - Return a vector_shuffle of the specified
/// vector and zero or undef vector.
static SDOperand getShuffleVectorZeroOrUndef(SDOperand V2, MVT::ValueType VT,
                                             unsigned NumElems, unsigned Idx,
                                             bool isZero, SelectionDAG &DAG) {
  SDOperand V1 = isZero ? getZeroVector(VT, DAG) : DAG.getNode(ISD::UNDEF, VT);
  MVT::ValueType MaskVT = MVT::getIntVectorWithNumElements(NumElems);
  MVT::ValueType EVT = MVT::getVectorBaseType(MaskVT);
  SDOperand Zero = DAG.getConstant(0, EVT);
  std::vector<SDOperand> MaskVec(NumElems, Zero);
  MaskVec[Idx] = DAG.getConstant(NumElems, EVT);
  SDOperand Mask = DAG.getNode(ISD::BUILD_VECTOR, MaskVT,
                               &MaskVec[0], MaskVec.size());
  return DAG.getNode(ISD::VECTOR_SHUFFLE, VT, V1, V2, Mask);
}

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

  SDOperand 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, DAG);
      else
        V = DAG.getNode(ISD::UNDEF, MVT::v8i16);
      First = false;
    }

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

      if (ThisElt.Val)
        V = DAG.getNode(ISD::INSERT_VECTOR_ELT, MVT::v8i16, V, ThisElt,
                        DAG.getConstant(i/2, TLI.getPointerTy()));
    }
  }

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

/// LowerBuildVectorv16i8 - Custom lower build_vector of v8i16.
///
static SDOperand LowerBuildVectorv8i16(SDOperand Op, unsigned NonZeros,
                                       unsigned NumNonZero, unsigned NumZero,
                                       SelectionDAG &DAG, TargetLowering &TLI) {
  if (NumNonZero > 4)
    return SDOperand();

  SDOperand 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, DAG);
        else
          V = DAG.getNode(ISD::UNDEF, MVT::v8i16);
        First = false;
      }
      V = DAG.getNode(ISD::INSERT_VECTOR_ELT, MVT::v8i16, V, Op.getOperand(i),
                      DAG.getConstant(i, TLI.getPointerTy()));
    }
  }

  return V;
}

SDOperand
X86TargetLowering::LowerBUILD_VECTOR(SDOperand Op, SelectionDAG &DAG) {
  // All zero's are handled with pxor.
  if (ISD::isBuildVectorAllZeros(Op.Val))
    return Op;

  // All one's are handled with pcmpeqd.
  if (ISD::isBuildVectorAllOnes(Op.Val))
    return Op;

  MVT::ValueType VT = Op.getValueType();
  MVT::ValueType EVT = MVT::getVectorBaseType(VT);
  unsigned EVTBits = MVT::getSizeInBits(EVT);

  unsigned NumElems = Op.getNumOperands();
  unsigned NumZero  = 0;
  unsigned NumNonZero = 0;
  unsigned NonZeros = 0;
  std::set<SDOperand> Values;
  for (unsigned i = 0; i < NumElems; ++i) {
    SDOperand Elt = Op.getOperand(i);
    if (Elt.getOpcode() != ISD::UNDEF) {
      Values.insert(Elt);
      if (isZeroNode(Elt))
        NumZero++;
      else {
        NonZeros |= (1 << i);
        NumNonZero++;
      }
    }
  }

  if (NumNonZero == 0)
    // Must be a mix of zero and undef. Return a zero vector.
    return getZeroVector(VT, DAG);

  // Splat is obviously ok. Let legalizer expand it to a shuffle.
  if (Values.size() == 1)
    return SDOperand();

  // Special case for single non-zero element.
  if (NumNonZero == 1) {
    unsigned Idx = CountTrailingZeros_32(NonZeros);
    SDOperand Item = Op.getOperand(Idx);
    Item = DAG.getNode(ISD::SCALAR_TO_VECTOR, VT, Item);
    if (Idx == 0)
      // Turn it into a MOVL (i.e. movss, movsd, or movd) to a zero vector.
      return getShuffleVectorZeroOrUndef(Item, VT, NumElems, Idx,
                                         NumZero > 0, DAG);

    if (EVTBits == 32) {
      // Turn it into a shuffle of zero and zero-extended scalar to vector.
      Item = getShuffleVectorZeroOrUndef(Item, VT, NumElems, 0, NumZero > 0,
                                         DAG);
      MVT::ValueType MaskVT  = MVT::getIntVectorWithNumElements(NumElems);
      MVT::ValueType MaskEVT = MVT::getVectorBaseType(MaskVT);
      std::vector<SDOperand> MaskVec;
      for (unsigned i = 0; i < NumElems; i++)
        MaskVec.push_back(DAG.getConstant((i == Idx) ? 0 : 1, MaskEVT));
      SDOperand Mask = DAG.getNode(ISD::BUILD_VECTOR, MaskVT,
                                   &MaskVec[0], MaskVec.size());
      return DAG.getNode(ISD::VECTOR_SHUFFLE, VT, Item,
                         DAG.getNode(ISD::UNDEF, VT), Mask);
    }
  }

  // Let legalizer expand 2-widde build_vector's.
  if (EVTBits == 64)
    return SDOperand();

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

  if (EVTBits == 16) {
    SDOperand V = LowerBuildVectorv8i16(Op, NonZeros,NumNonZero,NumZero, DAG,
                                        *this);
    if (V.Val) return V;
  }

  // If element VT is == 32 bits, turn it into a number of shuffles.
  std::vector<SDOperand> V(NumElems);
  if (NumElems == 4 && NumZero > 0) {
    for (unsigned i = 0; i < 4; ++i) {
      bool isZero = !(NonZeros & (1 << i));
      if (isZero)
        V[i] = getZeroVector(VT, DAG);
      else
        V[i] = DAG.getNode(ISD::SCALAR_TO_VECTOR, 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] = DAG.getNode(ISD::VECTOR_SHUFFLE, VT, V[i*2+1], V[i*2],
                             getMOVLMask(NumElems, DAG));
          break;
        case 2:
          V[i] = DAG.getNode(ISD::VECTOR_SHUFFLE, VT, V[i*2], V[i*2+1],
                             getMOVLMask(NumElems, DAG));
          break;
        case 3:
          V[i] = DAG.getNode(ISD::VECTOR_SHUFFLE, VT, V[i*2], V[i*2+1],
                             getUnpacklMask(NumElems, DAG));
          break;
      }
    }

    // Take advantage of the fact GR32 to VR128 scalar_to_vector (i.e. movd)
    // clears the upper bits. 
    // FIXME: we can do the same for v4f32 case when we know both parts of
    // the lower half come from scalar_to_vector (loadf32). We should do
    // that in post legalizer dag combiner with target specific hooks.
    if (MVT::isInteger(EVT) && (NonZeros & (0x3 << 2)) == 0)
      return V[0];
    MVT::ValueType MaskVT = MVT::getIntVectorWithNumElements(NumElems);
    MVT::ValueType EVT = MVT::getVectorBaseType(MaskVT);
    std::vector<SDOperand> MaskVec;
    bool Reverse = (NonZeros & 0x3) == 2;
    for (unsigned i = 0; i < 2; ++i)
      if (Reverse)
        MaskVec.push_back(DAG.getConstant(1-i, EVT));
      else
        MaskVec.push_back(DAG.getConstant(i, EVT));
    Reverse = ((NonZeros & (0x3 << 2)) >> 2) == 2;
    for (unsigned i = 0; i < 2; ++i)
      if (Reverse)
        MaskVec.push_back(DAG.getConstant(1-i+NumElems, EVT));
      else
        MaskVec.push_back(DAG.getConstant(i+NumElems, EVT));
    SDOperand ShufMask = DAG.getNode(ISD::BUILD_VECTOR, MaskVT,
                                     &MaskVec[0], MaskVec.size());
    return DAG.getNode(ISD::VECTOR_SHUFFLE, VT, V[0], V[1], ShufMask);
  }

  if (Values.size() > 2) {
    // Expand into a number of unpckl*.
    // e.g. for v4f32
    //   Step 1: unpcklps 0, 2 ==> X: <?, ?, 2, 0>
    //         : unpcklps 1, 3 ==> Y: <?, ?, 3, 1>
    //   Step 2: unpcklps X, Y ==>    <3, 2, 1, 0>
    SDOperand UnpckMask = getUnpacklMask(NumElems, DAG);
    for (unsigned i = 0; i < NumElems; ++i)
      V[i] = DAG.getNode(ISD::SCALAR_TO_VECTOR, VT, Op.getOperand(i));
    NumElems >>= 1;
    while (NumElems != 0) {
      for (unsigned i = 0; i < NumElems; ++i)
        V[i] = DAG.getNode(ISD::VECTOR_SHUFFLE, VT, V[i], V[i + NumElems],
                           UnpckMask);
      NumElems >>= 1;
    }
    return V[0];
  }

  return SDOperand();
}

SDOperand
X86TargetLowering::LowerVECTOR_SHUFFLE(SDOperand Op, SelectionDAG &DAG) {
  SDOperand V1 = Op.getOperand(0);
  SDOperand V2 = Op.getOperand(1);
  SDOperand PermMask = Op.getOperand(2);
  MVT::ValueType VT = Op.getValueType();
  unsigned NumElems = PermMask.getNumOperands();
  bool V1IsUndef = V1.getOpcode() == ISD::UNDEF;
  bool V2IsUndef = V2.getOpcode() == ISD::UNDEF;

  if (isUndefShuffle(Op.Val))
    return DAG.getNode(ISD::UNDEF, VT);

  if (isSplatMask(PermMask.Val)) {
    if (NumElems <= 4) return Op;
    // Promote it to a v4i32 splat.
    return PromoteSplat(Op, DAG);
  }

  if (X86::isMOVLMask(PermMask.Val))
    return (V1IsUndef) ? V2 : Op;