xref: /external/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

//===-- SelectionDAG.cpp - Implement the SelectionDAG data structures -----===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements the SelectionDAG class.
//
//===----------------------------------------------------------------------===//

#include "llvm/CodeGen/SelectionDAG.h"
#include "SDNodeDbgValue.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/DebugInfo.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Mutex.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetIntrinsicInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSelectionDAGInfo.h"
#include <algorithm>
#include <cmath>
using namespace llvm;

/// makeVTList - Return an instance of the SDVTList struct initialized with the
/// specified members.
static SDVTList makeVTList(const EVT *VTs, unsigned NumVTs) {
  SDVTList Res = {VTs, NumVTs};
  return Res;
}

// Default null implementations of the callbacks.
void SelectionDAG::DAGUpdateListener::NodeDeleted(SDNode*, SDNode*) {}
void SelectionDAG::DAGUpdateListener::NodeUpdated(SDNode*) {}

//===----------------------------------------------------------------------===//
//                              ConstantFPSDNode Class
//===----------------------------------------------------------------------===//

/// isExactlyValue - We don't rely on operator== working on double values, as
/// it returns true for things that are clearly not equal, like -0.0 and 0.0.
/// As such, this method can be used to do an exact bit-for-bit comparison of
/// two floating point values.
bool ConstantFPSDNode::isExactlyValue(const APFloat& V) const {
  return getValueAPF().bitwiseIsEqual(V);
}

bool ConstantFPSDNode::isValueValidForType(EVT VT,
                                           const APFloat& Val) {
  assert(VT.isFloatingPoint() && "Can only convert between FP types");

  // convert modifies in place, so make a copy.
  APFloat Val2 = APFloat(Val);
  bool losesInfo;
  (void) Val2.convert(SelectionDAG::EVTToAPFloatSemantics(VT),
                      APFloat::rmNearestTiesToEven,
                      &losesInfo);
  return !losesInfo;
}

//===----------------------------------------------------------------------===//
//                              ISD Namespace
//===----------------------------------------------------------------------===//

/// isBuildVectorAllOnes - Return true if the specified node is a
/// BUILD_VECTOR where all of the elements are ~0 or undef.
bool ISD::isBuildVectorAllOnes(const SDNode *N) {
  // Look through a bit convert.
  if (N->getOpcode() == ISD::BITCAST)
    N = N->getOperand(0).getNode();

  if (N->getOpcode() != ISD::BUILD_VECTOR) return false;

  unsigned i = 0, e = N->getNumOperands();

  // Skip over all of the undef values.
  while (i != e && N->getOperand(i).getOpcode() == ISD::UNDEF)
    ++i;

  // Do not accept an all-undef vector.
  if (i == e) return false;

  // Do not accept build_vectors that aren't all constants or which have non-~0
  // elements. We have to be a bit careful here, as the type of the constant
  // may not be the same as the type of the vector elements due to type
  // legalization (the elements are promoted to a legal type for the target and
  // a vector of a type may be legal when the base element type is not).
  // We only want to check enough bits to cover the vector elements, because
  // we care if the resultant vector is all ones, not whether the individual
  // constants are.
  SDValue NotZero = N->getOperand(i);
  unsigned EltSize = N->getValueType(0).getVectorElementType().getSizeInBits();
  if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(NotZero)) {
    if (CN->getAPIntValue().countTrailingOnes() < EltSize)
      return false;
  } else if (ConstantFPSDNode *CFPN = dyn_cast<ConstantFPSDNode>(NotZero)) {
    if (CFPN->getValueAPF().bitcastToAPInt().countTrailingOnes() < EltSize)
      return false;
  } else
    return false;

  // Okay, we have at least one ~0 value, check to see if the rest match or are
  // undefs. Even with the above element type twiddling, this should be OK, as
  // the same type legalization should have applied to all the elements.
  for (++i; i != e; ++i)
    if (N->getOperand(i) != NotZero &&
        N->getOperand(i).getOpcode() != ISD::UNDEF)
      return false;
  return true;
}


/// isBuildVectorAllZeros - Return true if the specified node is a
/// BUILD_VECTOR where all of the elements are 0 or undef.
bool ISD::isBuildVectorAllZeros(const SDNode *N) {
  // Look through a bit convert.
  if (N->getOpcode() == ISD::BITCAST)
    N = N->getOperand(0).getNode();

  if (N->getOpcode() != ISD::BUILD_VECTOR) return false;

  unsigned i = 0, e = N->getNumOperands();

  // Skip over all of the undef values.
  while (i != e && N->getOperand(i).getOpcode() == ISD::UNDEF)
    ++i;

  // Do not accept an all-undef vector.
  if (i == e) return false;

  // Do not accept build_vectors that aren't all constants or which have non-0
  // elements.
  SDValue Zero = N->getOperand(i);
  if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Zero)) {
    if (!CN->isNullValue())
      return false;
  } else if (ConstantFPSDNode *CFPN = dyn_cast<ConstantFPSDNode>(Zero)) {
    if (!CFPN->getValueAPF().isPosZero())
      return false;
  } else
    return false;

  // Okay, we have at least one 0 value, check to see if the rest match or are
  // undefs.
  for (++i; i != e; ++i)
    if (N->getOperand(i) != Zero &&
        N->getOperand(i).getOpcode() != ISD::UNDEF)
      return false;
  return true;
}

/// isScalarToVector - Return true if the specified node is a
/// ISD::SCALAR_TO_VECTOR node or a BUILD_VECTOR node where only the low
/// element is not an undef.
bool ISD::isScalarToVector(const SDNode *N) {
  if (N->getOpcode() == ISD::SCALAR_TO_VECTOR)
    return true;

  if (N->getOpcode() != ISD::BUILD_VECTOR)
    return false;
  if (N->getOperand(0).getOpcode() == ISD::UNDEF)
    return false;
  unsigned NumElems = N->getNumOperands();
  if (NumElems == 1)
    return false;
  for (unsigned i = 1; i < NumElems; ++i) {
    SDValue V = N->getOperand(i);
    if (V.getOpcode() != ISD::UNDEF)
      return false;
  }
  return true;
}

/// allOperandsUndef - Return true if the node has at least one operand
/// and all operands of the specified node are ISD::UNDEF.
bool ISD::allOperandsUndef(const SDNode *N) {
  // Return false if the node has no operands.
  // This is "logically inconsistent" with the definition of "all" but
  // is probably the desired behavior.
  if (N->getNumOperands() == 0)
    return false;

  for (unsigned i = 0, e = N->getNumOperands(); i != e ; ++i)
    if (N->getOperand(i).getOpcode() != ISD::UNDEF)
      return false;

  return true;
}

/// getSetCCSwappedOperands - Return the operation corresponding to (Y op X)
/// when given the operation for (X op Y).
ISD::CondCode ISD::getSetCCSwappedOperands(ISD::CondCode Operation) {
  // To perform this operation, we just need to swap the L and G bits of the
  // operation.
  unsigned OldL = (Operation >> 2) & 1;
  unsigned OldG = (Operation >> 1) & 1;
  return ISD::CondCode((Operation & ~6) |  // Keep the N, U, E bits
                       (OldL << 1) |       // New G bit
                       (OldG << 2));       // New L bit.
}

/// getSetCCInverse - Return the operation corresponding to !(X op Y), where
/// 'op' is a valid SetCC operation.
ISD::CondCode ISD::getSetCCInverse(ISD::CondCode Op, bool isInteger) {
  unsigned Operation = Op;
  if (isInteger)
    Operation ^= 7;   // Flip L, G, E bits, but not U.
  else
    Operation ^= 15;  // Flip all of the condition bits.

  if (Operation > ISD::SETTRUE2)
    Operation &= ~8;  // Don't let N and U bits get set.

  return ISD::CondCode(Operation);
}


/// isSignedOp - For an integer comparison, return 1 if the comparison is a
/// signed operation and 2 if the result is an unsigned comparison.  Return zero
/// if the operation does not depend on the sign of the input (setne and seteq).
static int isSignedOp(ISD::CondCode Opcode) {
  switch (Opcode) {
  default: llvm_unreachable("Illegal integer setcc operation!");
  case ISD::SETEQ:
  case ISD::SETNE: return 0;
  case ISD::SETLT:
  case ISD::SETLE:
  case ISD::SETGT:
  case ISD::SETGE: return 1;
  case ISD::SETULT:
  case ISD::SETULE:
  case ISD::SETUGT:
  case ISD::SETUGE: return 2;
  }
}

/// getSetCCOrOperation - Return the result of a logical OR between different
/// comparisons of identical values: ((X op1 Y) | (X op2 Y)).  This function
/// returns SETCC_INVALID if it is not possible to represent the resultant
/// comparison.
ISD::CondCode ISD::getSetCCOrOperation(ISD::CondCode Op1, ISD::CondCode Op2,
                                       bool isInteger) {
  if (isInteger && (isSignedOp(Op1) | isSignedOp(Op2)) == 3)
    // Cannot fold a signed integer setcc with an unsigned integer setcc.
    return ISD::SETCC_INVALID;

  unsigned Op = Op1 | Op2;  // Combine all of the condition bits.

  // If the N and U bits get set then the resultant comparison DOES suddenly
  // care about orderedness, and is true when ordered.
  if (Op > ISD::SETTRUE2)
    Op &= ~16;     // Clear the U bit if the N bit is set.

  // Canonicalize illegal integer setcc's.
  if (isInteger && Op == ISD::SETUNE)  // e.g. SETUGT | SETULT
    Op = ISD::SETNE;

  return ISD::CondCode(Op);
}

/// getSetCCAndOperation - Return the result of a logical AND between different
/// comparisons of identical values: ((X op1 Y) & (X op2 Y)).  This
/// function returns zero if it is not possible to represent the resultant
/// comparison.
ISD::CondCode ISD::getSetCCAndOperation(ISD::CondCode Op1, ISD::CondCode Op2,
                                        bool isInteger) {
  if (isInteger && (isSignedOp(Op1) | isSignedOp(Op2)) == 3)
    // Cannot fold a signed setcc with an unsigned setcc.
    return ISD::SETCC_INVALID;

  // Combine all of the condition bits.
  ISD::CondCode Result = ISD::CondCode(Op1 & Op2);

  // Canonicalize illegal integer setcc's.
  if (isInteger) {
    switch (Result) {
    default: break;
    case ISD::SETUO : Result = ISD::SETFALSE; break;  // SETUGT & SETULT
    case ISD::SETOEQ:                                 // SETEQ  & SETU[LG]E
    case ISD::SETUEQ: Result = ISD::SETEQ   ; break;  // SETUGE & SETULE
    case ISD::SETOLT: Result = ISD::SETULT  ; break;  // SETULT & SETNE
    case ISD::SETOGT: Result = ISD::SETUGT  ; break;  // SETUGT & SETNE
    }
  }

  return Result;
}

//===----------------------------------------------------------------------===//
//                           SDNode Profile Support
//===----------------------------------------------------------------------===//

/// AddNodeIDOpcode - Add the node opcode to the NodeID data.
///
static void AddNodeIDOpcode(FoldingSetNodeID &ID, unsigned OpC)  {
  ID.AddInteger(OpC);
}

/// AddNodeIDValueTypes - Value type lists are intern'd so we can represent them
/// solely with their pointer.
static void AddNodeIDValueTypes(FoldingSetNodeID &ID, SDVTList VTList) {
  ID.AddPointer(VTList.VTs);
}

/// AddNodeIDOperands - Various routines for adding operands to the NodeID data.
///
static void AddNodeIDOperands(FoldingSetNodeID &ID,
                              const SDValue *Ops, unsigned NumOps) {
  for (; NumOps; --NumOps, ++Ops) {
    ID.AddPointer(Ops->getNode());
    ID.AddInteger(Ops->getResNo());
  }
}

/// AddNodeIDOperands - Various routines for adding operands to the NodeID data.
///
static void AddNodeIDOperands(FoldingSetNodeID &ID,
                              const SDUse *Ops, unsigned NumOps) {
  for (; NumOps; --NumOps, ++Ops) {
    ID.AddPointer(Ops->getNode());
    ID.AddInteger(Ops->getResNo());
  }
}

static void AddNodeIDNode(FoldingSetNodeID &ID,
                          unsigned short OpC, SDVTList VTList,
                          const SDValue *OpList, unsigned N) {
  AddNodeIDOpcode(ID, OpC);
  AddNodeIDValueTypes(ID, VTList);
  AddNodeIDOperands(ID, OpList, N);
}

/// AddNodeIDCustom - If this is an SDNode with special info, add this info to
/// the NodeID data.
static void AddNodeIDCustom(FoldingSetNodeID &ID, const SDNode *N) {
  switch (N->getOpcode()) {
  case ISD::TargetExternalSymbol:
  case ISD::ExternalSymbol:
    llvm_unreachable("Should only be used on nodes with operands");
  default: break;  // Normal nodes don't need extra info.
  case ISD::TargetConstant:
  case ISD::Constant:
    ID.AddPointer(cast<ConstantSDNode>(N)->getConstantIntValue());
    break;
  case ISD::TargetConstantFP:
  case ISD::ConstantFP: {
    ID.AddPointer(cast<ConstantFPSDNode>(N)->getConstantFPValue());
    break;
  }
  case ISD::TargetGlobalAddress:
  case ISD::GlobalAddress:
  case ISD::TargetGlobalTLSAddress:
  case ISD::GlobalTLSAddress: {
    const GlobalAddressSDNode *GA = cast<GlobalAddressSDNode>(N);
    ID.AddPointer(GA->getGlobal());
    ID.AddInteger(GA->getOffset());
    ID.AddInteger(GA->getTargetFlags());
    ID.AddInteger(GA->getAddressSpace());
    break;
  }
  case ISD::BasicBlock:
    ID.AddPointer(cast<BasicBlockSDNode>(N)->getBasicBlock());
    break;
  case ISD::Register:
    ID.AddInteger(cast<RegisterSDNode>(N)->getReg());
    break;
  case ISD::RegisterMask:
    ID.AddPointer(cast<RegisterMaskSDNode>(N)->getRegMask());
    break;
  case ISD::SRCVALUE:
    ID.AddPointer(cast<SrcValueSDNode>(N)->getValue());
    break;
  case ISD::FrameIndex:
  case ISD::TargetFrameIndex:
    ID.AddInteger(cast<FrameIndexSDNode>(N)->getIndex());
    break;
  case ISD::JumpTable:
  case ISD::TargetJumpTable:
    ID.AddInteger(cast<JumpTableSDNode>(N)->getIndex());
    ID.AddInteger(cast<JumpTableSDNode>(N)->getTargetFlags());
    break;
  case ISD::ConstantPool:
  case ISD::TargetConstantPool: {
    const ConstantPoolSDNode *CP = cast<ConstantPoolSDNode>(N);
    ID.AddInteger(CP->getAlignment());
    ID.AddInteger(CP->getOffset());
    if (CP->isMachineConstantPoolEntry())
      CP->getMachineCPVal()->addSelectionDAGCSEId(ID);
    else
      ID.AddPointer(CP->getConstVal());
    ID.AddInteger(CP->getTargetFlags());
    break;
  }
  case ISD::TargetIndex: {
    const TargetIndexSDNode *TI = cast<TargetIndexSDNode>(N);
    ID.AddInteger(TI->getIndex());
    ID.AddInteger(TI->getOffset());
    ID.AddInteger(TI->getTargetFlags());
    break;
  }
  case ISD::LOAD: {
    const LoadSDNode *LD = cast<LoadSDNode>(N);
    ID.AddInteger(LD->getMemoryVT().getRawBits());
    ID.AddInteger(LD->getRawSubclassData());
    ID.AddInteger(LD->getPointerInfo().getAddrSpace());
    break;
  }
  case ISD::STORE: {
    const StoreSDNode *ST = cast<StoreSDNode>(N);
    ID.AddInteger(ST->getMemoryVT().getRawBits());
    ID.AddInteger(ST->getRawSubclassData());
    ID.AddInteger(ST->getPointerInfo().getAddrSpace());
    break;
  }
  case ISD::ATOMIC_CMP_SWAP:
  case ISD::ATOMIC_SWAP:
  case ISD::ATOMIC_LOAD_ADD:
  case ISD::ATOMIC_LOAD_SUB:
  case ISD::ATOMIC_LOAD_AND:
  case ISD::ATOMIC_LOAD_OR:
  case ISD::ATOMIC_LOAD_XOR:
  case ISD::ATOMIC_LOAD_NAND:
  case ISD::ATOMIC_LOAD_MIN:
  case ISD::ATOMIC_LOAD_MAX:
  case ISD::ATOMIC_LOAD_UMIN:
  case ISD::ATOMIC_LOAD_UMAX:
  case ISD::ATOMIC_LOAD:
  case ISD::ATOMIC_STORE: {
    const AtomicSDNode *AT = cast<AtomicSDNode>(N);
    ID.AddInteger(AT->getMemoryVT().getRawBits());
    ID.AddInteger(AT->getRawSubclassData());
    ID.AddInteger(AT->getPointerInfo().getAddrSpace());
    break;
  }
  case ISD::PREFETCH: {
    const MemSDNode *PF = cast<MemSDNode>(N);
    ID.AddInteger(PF->getPointerInfo().getAddrSpace());
    break;
  }
  case ISD::VECTOR_SHUFFLE: {
    const ShuffleVectorSDNode *SVN = cast<ShuffleVectorSDNode>(N);
    for (unsigned i = 0, e = N->getValueType(0).getVectorNumElements();
         i != e; ++i)
      ID.AddInteger(SVN->getMaskElt(i));
    break;
  }
  case ISD::TargetBlockAddress:
  case ISD::BlockAddress: {
    const BlockAddressSDNode *BA = cast<BlockAddressSDNode>(N);
    ID.AddPointer(BA->getBlockAddress());
    ID.AddInteger(BA->getOffset());
    ID.AddInteger(BA->getTargetFlags());
    break;
  }
  } // end switch (N->getOpcode())

  // Target specific memory nodes could also have address spaces to check.
  if (N->isTargetMemoryOpcode())
    ID.AddInteger(cast<MemSDNode>(N)->getPointerInfo().getAddrSpace());
}

/// AddNodeIDNode - Generic routine for adding a nodes info to the NodeID
/// data.
static void AddNodeIDNode(FoldingSetNodeID &ID, const SDNode *N) {
  AddNodeIDOpcode(ID, N->getOpcode());
  // Add the return value info.
  AddNodeIDValueTypes(ID, N->getVTList());
  // Add the operand info.
  AddNodeIDOperands(ID, N->op_begin(), N->getNumOperands());

  // Handle SDNode leafs with special info.
  AddNodeIDCustom(ID, N);
}

/// encodeMemSDNodeFlags - Generic routine for computing a value for use in
/// the CSE map that carries volatility, temporalness, indexing mode, and
/// extension/truncation information.
///
static inline unsigned
encodeMemSDNodeFlags(int ConvType, ISD::MemIndexedMode AM, bool isVolatile,
                     bool isNonTemporal, bool isInvariant) {
  assert((ConvType & 3) == ConvType &&
         "ConvType may not require more than 2 bits!");
  assert((AM & 7) == AM &&
         "AM may not require more than 3 bits!");
  return ConvType |
         (AM << 2) |
         (isVolatile << 5) |
         (isNonTemporal << 6) |
         (isInvariant << 7);
}

//===----------------------------------------------------------------------===//
//                              SelectionDAG Class
//===----------------------------------------------------------------------===//

/// doNotCSE - Return true if CSE should not be performed for this node.
static bool doNotCSE(SDNode *N) {
  if (N->getValueType(0) == MVT::Glue)
    return true; // Never CSE anything that produces a flag.

  switch (N->getOpcode()) {
  default: break;
  case ISD::HANDLENODE:
  case ISD::EH_LABEL:
    return true;   // Never CSE these nodes.
  }

  // Check that remaining values produced are not flags.
  for (unsigned i = 1, e = N->getNumValues(); i != e; ++i)
    if (N->getValueType(i) == MVT::Glue)
      return true; // Never CSE anything that produces a flag.

  return false;
}

/// RemoveDeadNodes - This method deletes all unreachable nodes in the
/// SelectionDAG.
void SelectionDAG::RemoveDeadNodes() {
  // Create a dummy node (which is not added to allnodes), that adds a reference
  // to the root node, preventing it from being deleted.
  HandleSDNode Dummy(getRoot());

  SmallVector<SDNode*, 128> DeadNodes;

  // Add all obviously-dead nodes to the DeadNodes worklist.
  for (allnodes_iterator I = allnodes_begin(), E = allnodes_end(); I != E; ++I)
    if (I->use_empty())
      DeadNodes.push_back(I);

  RemoveDeadNodes(DeadNodes);

  // If the root changed (e.g. it was a dead load, update the root).
  setRoot(Dummy.getValue());
}

/// RemoveDeadNodes - This method deletes the unreachable nodes in the
/// given list, and any nodes that become unreachable as a result.
void SelectionDAG::RemoveDeadNodes(SmallVectorImpl<SDNode *> &DeadNodes) {

  // Process the worklist, deleting the nodes and adding their uses to the
  // worklist.
  while (!DeadNodes.empty()) {
    SDNode *N = DeadNodes.pop_back_val();

    for (DAGUpdateListener *DUL = UpdateListeners; DUL; DUL = DUL->Next)
      DUL->NodeDeleted(N, 0);

    // Take the node out of the appropriate CSE map.
    RemoveNodeFromCSEMaps(N);

    // Next, brutally remove the operand list.  This is safe to do, as there are
    // no cycles in the graph.
    for (SDNode::op_iterator I = N->op_begin(), E = N->op_end(); I != E; ) {
      SDUse &Use = *I++;
      SDNode *Operand = Use.getNode();
      Use.set(SDValue());

      // Now that we removed this operand, see if there are no uses of it left.
      if (Operand->use_empty())
        DeadNodes.push_back(Operand);
    }

    DeallocateNode(N);
  }
}

void SelectionDAG::RemoveDeadNode(SDNode *N){
  SmallVector<SDNode*, 16> DeadNodes(1, N);

  // Create a dummy node that adds a reference to the root node, preventing
  // it from being deleted.  (This matters if the root is an operand of the
  // dead node.)
  HandleSDNode Dummy(getRoot());

  RemoveDeadNodes(DeadNodes);
}

void SelectionDAG::DeleteNode(SDNode *N) {
  // First take this out of the appropriate CSE map.
  RemoveNodeFromCSEMaps(N);

  // Finally, remove uses due to operands of this node, remove from the
  // AllNodes list, and delete the node.
  DeleteNodeNotInCSEMaps(N);
}

void SelectionDAG::DeleteNodeNotInCSEMaps(SDNode *N) {
  assert(N != AllNodes.begin() && "Cannot delete the entry node!");
  assert(N->use_empty() && "Cannot delete a node that is not dead!");

  // Drop all of the operands and decrement used node's use counts.
  N->DropOperands();

  DeallocateNode(N);
}

void SelectionDAG::DeallocateNode(SDNode *N) {
  if (N->OperandsNeedDelete)
    delete[] N->OperandList;

  // Set the opcode to DELETED_NODE to help catch bugs when node
  // memory is reallocated.
  N->NodeType = ISD::DELETED_NODE;

  NodeAllocator.Deallocate(AllNodes.remove(N));

  // If any of the SDDbgValue nodes refer to this SDNode, invalidate them.
  ArrayRef<SDDbgValue*> DbgVals = DbgInfo->getSDDbgValues(N);
  for (unsigned i = 0, e = DbgVals.size(); i != e; ++i)
    DbgVals[i]->setIsInvalidated();
}

/// RemoveNodeFromCSEMaps - Take the specified node out of the CSE map that
/// correspond to it.  This is useful when we're about to delete or repurpose
/// the node.  We don't want future request for structurally identical nodes
/// to return N anymore.
bool SelectionDAG::RemoveNodeFromCSEMaps(SDNode *N) {
  bool Erased = false;
  switch (N->getOpcode()) {
  case ISD::HANDLENODE: return false;  // noop.
  case ISD::CONDCODE:
    assert(CondCodeNodes[cast<CondCodeSDNode>(N)->get()] &&
           "Cond code doesn't exist!");
    Erased = CondCodeNodes[cast<CondCodeSDNode>(N)->get()] != 0;
    CondCodeNodes[cast<CondCodeSDNode>(N)->get()] = 0;
    break;
  case ISD::ExternalSymbol:
    Erased = ExternalSymbols.erase(cast<ExternalSymbolSDNode>(N)->getSymbol());
    break;
  case ISD::TargetExternalSymbol: {
    ExternalSymbolSDNode *ESN = cast<ExternalSymbolSDNode>(N);
    Erased = TargetExternalSymbols.erase(
               std::pair<std::string,unsigned char>(ESN->getSymbol(),
                                                    ESN->getTargetFlags()));
    break;
  }
  case ISD::VALUETYPE: {
    EVT VT = cast<VTSDNode>(N)->getVT();
    if (VT.isExtended()) {
      Erased = ExtendedValueTypeNodes.erase(VT);
    } else {
      Erased = ValueTypeNodes[VT.getSimpleVT().SimpleTy] != 0;
      ValueTypeNodes[VT.getSimpleVT().SimpleTy] = 0;
    }
    break;
  }
  default:
    // Remove it from the CSE Map.
    assert(N->getOpcode() != ISD::DELETED_NODE && "DELETED_NODE in CSEMap!");
    assert(N->getOpcode() != ISD::EntryToken && "EntryToken in CSEMap!");
    Erased = CSEMap.RemoveNode(N);
    break;
  }
#ifndef NDEBUG
  // Verify that the node was actually in one of the CSE maps, unless it has a
  // flag result (which cannot be CSE'd) or is one of the special cases that are
  // not subject to CSE.
  if (!Erased && N->getValueType(N->getNumValues()-1) != MVT::Glue &&
      !N->isMachineOpcode() && !doNotCSE(N)) {
    N->dump(this);
    dbgs() << "\n";
    llvm_unreachable("Node is not in map!");
  }
#endif
  return Erased;
}

/// AddModifiedNodeToCSEMaps - The specified node has been removed from the CSE
/// maps and modified in place. Add it back to the CSE maps, unless an identical
/// node already exists, in which case transfer all its users to the existing
/// node. This transfer can potentially trigger recursive merging.
///
void
SelectionDAG::AddModifiedNodeToCSEMaps(SDNode *N) {
  // For node types that aren't CSE'd, just act as if no identical node
  // already exists.
  if (!doNotCSE(N)) {
    SDNode *Existing = CSEMap.GetOrInsertNode(N);
    if (Existing != N) {
      // If there was already an existing matching node, use ReplaceAllUsesWith
      // to replace the dead one with the existing one.  This can cause
      // recursive merging of other unrelated nodes down the line.
      ReplaceAllUsesWith(N, Existing);

      // N is now dead. Inform the listeners and delete it.
      for (DAGUpdateListener *DUL = UpdateListeners; DUL; DUL = DUL->Next)
        DUL->NodeDeleted(N, Existing);
      DeleteNodeNotInCSEMaps(N);
      return;
    }
  }

  // If the node doesn't already exist, we updated it.  Inform listeners.
  for (DAGUpdateListener *DUL = UpdateListeners; DUL; DUL = DUL->Next)
    DUL->NodeUpdated(N);
}

/// FindModifiedNodeSlot - Find a slot for the specified node if its operands
/// were replaced with those specified.  If this node is never memoized,
/// return null, otherwise return a pointer to the slot it would take.  If a
/// node already exists with these operands, the slot will be non-null.
SDNode *SelectionDAG::FindModifiedNodeSlot(SDNode *N, SDValue Op,
                                           void *&InsertPos) {
  if (doNotCSE(N))
    return 0;

  SDValue Ops[] = { Op };
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, N->getOpcode(), N->getVTList(), Ops, 1);
  AddNodeIDCustom(ID, N);
  SDNode *Node = CSEMap.FindNodeOrInsertPos(ID, InsertPos);
  return Node;
}

/// FindModifiedNodeSlot - Find a slot for the specified node if its operands
/// were replaced with those specified.  If this node is never memoized,
/// return null, otherwise return a pointer to the slot it would take.  If a
/// node already exists with these operands, the slot will be non-null.
SDNode *SelectionDAG::FindModifiedNodeSlot(SDNode *N,
                                           SDValue Op1, SDValue Op2,
                                           void *&InsertPos) {
  if (doNotCSE(N))
    return 0;

  SDValue Ops[] = { Op1, Op2 };
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, N->getOpcode(), N->getVTList(), Ops, 2);
  AddNodeIDCustom(ID, N);
  SDNode *Node = CSEMap.FindNodeOrInsertPos(ID, InsertPos);
  return Node;
}


/// FindModifiedNodeSlot - Find a slot for the specified node if its operands
/// were replaced with those specified.  If this node is never memoized,
/// return null, otherwise return a pointer to the slot it would take.  If a
/// node already exists with these operands, the slot will be non-null.
SDNode *SelectionDAG::FindModifiedNodeSlot(SDNode *N,
                                           const SDValue *Ops,unsigned NumOps,
                                           void *&InsertPos) {
  if (doNotCSE(N))
    return 0;

  FoldingSetNodeID ID;
  AddNodeIDNode(ID, N->getOpcode(), N->getVTList(), Ops, NumOps);
  AddNodeIDCustom(ID, N);
  SDNode *Node = CSEMap.FindNodeOrInsertPos(ID, InsertPos);
  return Node;
}

#ifndef NDEBUG
/// VerifyNodeCommon - Sanity check the given node.  Aborts if it is invalid.
static void VerifyNodeCommon(SDNode *N) {
  switch (N->getOpcode()) {
  default:
    break;
  case ISD::BUILD_PAIR: {
    EVT VT = N->getValueType(0);
    assert(N->getNumValues() == 1 && "Too many results!");
    assert(!VT.isVector() && (VT.isInteger() || VT.isFloatingPoint()) &&
           "Wrong return type!");
    assert(N->getNumOperands() == 2 && "Wrong number of operands!");
    assert(N->getOperand(0).getValueType() == N->getOperand(1).getValueType() &&
           "Mismatched operand types!");
    assert(N->getOperand(0).getValueType().isInteger() == VT.isInteger() &&
           "Wrong operand type!");
    assert(VT.getSizeInBits() == 2 * N->getOperand(0).getValueSizeInBits() &&
           "Wrong return type size");
    break;
  }
  case ISD::BUILD_VECTOR: {
    assert(N->getNumValues() == 1 && "Too many results!");
    assert(N->getValueType(0).isVector() && "Wrong return type!");
    assert(N->getNumOperands() == N->getValueType(0).getVectorNumElements() &&
           "Wrong number of operands!");
    EVT EltVT = N->getValueType(0).getVectorElementType();
    for (SDNode::op_iterator I = N->op_begin(), E = N->op_end(); I != E; ++I) {
      assert((I->getValueType() == EltVT ||
             (EltVT.isInteger() && I->getValueType().isInteger() &&
              EltVT.bitsLE(I->getValueType()))) &&
            "Wrong operand type!");
      assert(I->getValueType() == N->getOperand(0).getValueType() &&
             "Operands must all have the same type");
    }
    break;
  }
  }
}

/// VerifySDNode - Sanity check the given SDNode.  Aborts if it is invalid.
static void VerifySDNode(SDNode *N) {
  // The SDNode allocators cannot be used to allocate nodes with fields that are
  // not present in an SDNode!
  assert(!isa<MemSDNode>(N) && "Bad MemSDNode!");
  assert(!isa<ShuffleVectorSDNode>(N) && "Bad ShuffleVectorSDNode!");
  assert(!isa<ConstantSDNode>(N) && "Bad ConstantSDNode!");
  assert(!isa<ConstantFPSDNode>(N) && "Bad ConstantFPSDNode!");
  assert(!isa<GlobalAddressSDNode>(N) && "Bad GlobalAddressSDNode!");
  assert(!isa<FrameIndexSDNode>(N) && "Bad FrameIndexSDNode!");
  assert(!isa<JumpTableSDNode>(N) && "Bad JumpTableSDNode!");
  assert(!isa<ConstantPoolSDNode>(N) && "Bad ConstantPoolSDNode!");
  assert(!isa<BasicBlockSDNode>(N) && "Bad BasicBlockSDNode!");
  assert(!isa<SrcValueSDNode>(N) && "Bad SrcValueSDNode!");
  assert(!isa<MDNodeSDNode>(N) && "Bad MDNodeSDNode!");
  assert(!isa<RegisterSDNode>(N) && "Bad RegisterSDNode!");
  assert(!isa<BlockAddressSDNode>(N) && "Bad BlockAddressSDNode!");
  assert(!isa<EHLabelSDNode>(N) && "Bad EHLabelSDNode!");
  assert(!isa<ExternalSymbolSDNode>(N) && "Bad ExternalSymbolSDNode!");
  assert(!isa<CondCodeSDNode>(N) && "Bad CondCodeSDNode!");
  assert(!isa<CvtRndSatSDNode>(N) && "Bad CvtRndSatSDNode!");
  assert(!isa<VTSDNode>(N) && "Bad VTSDNode!");
  assert(!isa<MachineSDNode>(N) && "Bad MachineSDNode!");

  VerifyNodeCommon(N);
}

/// VerifyMachineNode - Sanity check the given MachineNode.  Aborts if it is
/// invalid.
static void VerifyMachineNode(SDNode *N) {
  // The MachineNode allocators cannot be used to allocate nodes with fields
  // that are not present in a MachineNode!
  // Currently there are no such nodes.

  VerifyNodeCommon(N);
}
#endif // NDEBUG

/// getEVTAlignment - Compute the default alignment value for the
/// given type.
///
unsigned SelectionDAG::getEVTAlignment(EVT VT) const {
  Type *Ty = VT == MVT::iPTR ?
                   PointerType::get(Type::getInt8Ty(*getContext()), 0) :
                   VT.getTypeForEVT(*getContext());

  return TM.getTargetLowering()->getDataLayout()->getABITypeAlignment(Ty);
}

// EntryNode could meaningfully have debug info if we can find it...
SelectionDAG::SelectionDAG(const TargetMachine &tm, CodeGenOpt::Level OL)
  : TM(tm), TSI(*tm.getSelectionDAGInfo()), TTI(0), OptLevel(OL),
    EntryNode(ISD::EntryToken, 0, DebugLoc(), getVTList(MVT::Other)),
    Root(getEntryNode()), UpdateListeners(0) {
  AllNodes.push_back(&EntryNode);
  DbgInfo = new SDDbgInfo();
}

void SelectionDAG::init(MachineFunction &mf, const TargetTransformInfo *tti) {
  MF = &mf;
  TTI = tti;
  Context = &mf.getFunction()->getContext();
}

SelectionDAG::~SelectionDAG() {
  assert(!UpdateListeners && "Dangling registered DAGUpdateListeners");
  allnodes_clear();
  delete DbgInfo;
}

void SelectionDAG::allnodes_clear() {
  assert(&*AllNodes.begin() == &EntryNode);
  AllNodes.remove(AllNodes.begin());
  while (!AllNodes.empty())
    DeallocateNode(AllNodes.begin());
}

void SelectionDAG::clear() {
  allnodes_clear();
  OperandAllocator.Reset();
  CSEMap.clear();

  ExtendedValueTypeNodes.clear();
  ExternalSymbols.clear();
  TargetExternalSymbols.clear();
  std::fill(CondCodeNodes.begin(), CondCodeNodes.end(),
            static_cast<CondCodeSDNode*>(0));
  std::fill(ValueTypeNodes.begin(), ValueTypeNodes.end(),
            static_cast<SDNode*>(0));

  EntryNode.UseList = 0;
  AllNodes.push_back(&EntryNode);
  Root = getEntryNode();
  DbgInfo->clear();
}

SDValue SelectionDAG::getAnyExtOrTrunc(SDValue Op, SDLoc DL, EVT VT) {
  return VT.bitsGT(Op.getValueType()) ?
    getNode(ISD::ANY_EXTEND, DL, VT, Op) :
    getNode(ISD::TRUNCATE, DL, VT, Op);
}

SDValue SelectionDAG::getSExtOrTrunc(SDValue Op, SDLoc DL, EVT VT) {
  return VT.bitsGT(Op.getValueType()) ?
    getNode(ISD::SIGN_EXTEND, DL, VT, Op) :
    getNode(ISD::TRUNCATE, DL, VT, Op);
}

SDValue SelectionDAG::getZExtOrTrunc(SDValue Op, SDLoc DL, EVT VT) {
  return VT.bitsGT(Op.getValueType()) ?
    getNode(ISD::ZERO_EXTEND, DL, VT, Op) :
    getNode(ISD::TRUNCATE, DL, VT, Op);
}

SDValue SelectionDAG::getZeroExtendInReg(SDValue Op, SDLoc DL, EVT VT) {
  assert(!VT.isVector() &&
         "getZeroExtendInReg should use the vector element type instead of "
         "the vector type!");
  if (Op.getValueType() == VT) return Op;
  unsigned BitWidth = Op.getValueType().getScalarType().getSizeInBits();
  APInt Imm = APInt::getLowBitsSet(BitWidth,
                                   VT.getSizeInBits());
  return getNode(ISD::AND, DL, Op.getValueType(), Op,
                 getConstant(Imm, Op.getValueType()));
}

/// getNOT - Create a bitwise NOT operation as (XOR Val, -1).
///
SDValue SelectionDAG::getNOT(SDLoc DL, SDValue Val, EVT VT) {
  EVT EltVT = VT.getScalarType();
  SDValue NegOne =
    getConstant(APInt::getAllOnesValue(EltVT.getSizeInBits()), VT);
  return getNode(ISD::XOR, DL, VT, Val, NegOne);
}

SDValue SelectionDAG::getConstant(uint64_t Val, EVT VT, bool isT) {
  EVT EltVT = VT.getScalarType();
  assert((EltVT.getSizeInBits() >= 64 ||
         (uint64_t)((int64_t)Val >> EltVT.getSizeInBits()) + 1 < 2) &&
         "getConstant with a uint64_t value that doesn't fit in the type!");
  return getConstant(APInt(EltVT.getSizeInBits(), Val), VT, isT);
}

SDValue SelectionDAG::getConstant(const APInt &Val, EVT VT, bool isT) {
  return getConstant(*ConstantInt::get(*Context, Val), VT, isT);
}

SDValue SelectionDAG::getConstant(const ConstantInt &Val, EVT VT, bool isT) {
  assert(VT.isInteger() && "Cannot create FP integer constant!");

  EVT EltVT = VT.getScalarType();
  const ConstantInt *Elt = &Val;

  const TargetLowering *TLI = TM.getTargetLowering();

  // In some cases the vector type is legal but the element type is illegal and
  // needs to be promoted, for example v8i8 on ARM.  In this case, promote the
  // inserted value (the type does not need to match the vector element type).
  // Any extra bits introduced will be truncated away.
  if (VT.isVector() && TLI->getTypeAction(*getContext(), EltVT) ==
      TargetLowering::TypePromoteInteger) {
   EltVT = TLI->getTypeToTransformTo(*getContext(), EltVT);
   APInt NewVal = Elt->getValue().zext(EltVT.getSizeInBits());
   Elt = ConstantInt::get(*getContext(), NewVal);
  }

  assert(Elt->getBitWidth() == EltVT.getSizeInBits() &&
         "APInt size does not match type size!");
  unsigned Opc = isT ? ISD::TargetConstant : ISD::Constant;
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, Opc, getVTList(EltVT), 0, 0);
  ID.AddPointer(Elt);
  void *IP = 0;
  SDNode *N = NULL;
  if ((N = CSEMap.FindNodeOrInsertPos(ID, IP)))
    if (!VT.isVector())
      return SDValue(N, 0);

  if (!N) {
    N = new (NodeAllocator) ConstantSDNode(isT, Elt, EltVT);
    CSEMap.InsertNode(N, IP);
    AllNodes.push_back(N);
  }

  SDValue Result(N, 0);
  if (VT.isVector()) {
    SmallVector<SDValue, 8> Ops;
    Ops.assign(VT.getVectorNumElements(), Result);
    Result = getNode(ISD::BUILD_VECTOR, SDLoc(), VT, &Ops[0], Ops.size());
  }
  return Result;
}

SDValue SelectionDAG::getIntPtrConstant(uint64_t Val, bool isTarget) {
  return getConstant(Val, TM.getTargetLowering()->getPointerTy(), isTarget);
}


SDValue SelectionDAG::getConstantFP(const APFloat& V, EVT VT, bool isTarget) {
  return getConstantFP(*ConstantFP::get(*getContext(), V), VT, isTarget);
}

SDValue SelectionDAG::getConstantFP(const ConstantFP& V, EVT VT, bool isTarget){
  assert(VT.isFloatingPoint() && "Cannot create integer FP constant!");

  EVT EltVT = VT.getScalarType();

  // Do the map lookup using the actual bit pattern for the floating point
  // value, so that we don't have problems with 0.0 comparing equal to -0.0, and
  // we don't have issues with SNANs.
  unsigned Opc = isTarget ? ISD::TargetConstantFP : ISD::ConstantFP;
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, Opc, getVTList(EltVT), 0, 0);
  ID.AddPointer(&V);
  void *IP = 0;
  SDNode *N = NULL;
  if ((N = CSEMap.FindNodeOrInsertPos(ID, IP)))
    if (!VT.isVector())
      return SDValue(N, 0);

  if (!N) {
    N = new (NodeAllocator) ConstantFPSDNode(isTarget, &V, EltVT);
    CSEMap.InsertNode(N, IP);
    AllNodes.push_back(N);
  }

  SDValue Result(N, 0);
  if (VT.isVector()) {
    SmallVector<SDValue, 8> Ops;
    Ops.assign(VT.getVectorNumElements(), Result);
    // FIXME SDLoc info might be appropriate here
    Result = getNode(ISD::BUILD_VECTOR, SDLoc(), VT, &Ops[0], Ops.size());
  }
  return Result;
}

SDValue SelectionDAG::getConstantFP(double Val, EVT VT, bool isTarget) {
  EVT EltVT = VT.getScalarType();
  if (EltVT==MVT::f32)
    return getConstantFP(APFloat((float)Val), VT, isTarget);
  else if (EltVT==MVT::f64)
    return getConstantFP(APFloat(Val), VT, isTarget);
  else if (EltVT==MVT::f80 || EltVT==MVT::f128 || EltVT==MVT::ppcf128 ||
           EltVT==MVT::f16) {
    bool ignored;
    APFloat apf = APFloat(Val);
    apf.convert(EVTToAPFloatSemantics(EltVT), APFloat::rmNearestTiesToEven,
                &ignored);
    return getConstantFP(apf, VT, isTarget);
  } else
    llvm_unreachable("Unsupported type in getConstantFP");
}

SDValue SelectionDAG::getGlobalAddress(const GlobalValue *GV, SDLoc DL,
                                       EVT VT, int64_t Offset,
                                       bool isTargetGA,
                                       unsigned char TargetFlags) {
  assert((TargetFlags == 0 || isTargetGA) &&
         "Cannot set target flags on target-independent globals");

  // Truncate (with sign-extension) the offset value to the pointer size.
  unsigned BitWidth = TM.getTargetLowering()->getPointerTy().getSizeInBits();
  if (BitWidth < 64)
    Offset = SignExtend64(Offset, BitWidth);

  const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
  if (!GVar) {
    // If GV is an alias then use the aliasee for determining thread-localness.
    if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
      GVar = dyn_cast_or_null<GlobalVariable>(GA->resolveAliasedGlobal(false));
  }

  unsigned Opc;
  if (GVar && GVar->isThreadLocal())
    Opc = isTargetGA ? ISD::TargetGlobalTLSAddress : ISD::GlobalTLSAddress;
  else
    Opc = isTargetGA ? ISD::TargetGlobalAddress : ISD::GlobalAddress;

  FoldingSetNodeID ID;
  AddNodeIDNode(ID, Opc, getVTList(VT), 0, 0);
  ID.AddPointer(GV);
  ID.AddInteger(Offset);
  ID.AddInteger(TargetFlags);
  ID.AddInteger(GV->getType()->getAddressSpace());
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) GlobalAddressSDNode(Opc, DL.getIROrder(),
                                                      DL.getDebugLoc(), GV, VT,
                                                      Offset, TargetFlags);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getFrameIndex(int FI, EVT VT, bool isTarget) {
  unsigned Opc = isTarget ? ISD::TargetFrameIndex : ISD::FrameIndex;
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, Opc, getVTList(VT), 0, 0);
  ID.AddInteger(FI);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) FrameIndexSDNode(FI, VT, isTarget);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getJumpTable(int JTI, EVT VT, bool isTarget,
                                   unsigned char TargetFlags) {
  assert((TargetFlags == 0 || isTarget) &&
         "Cannot set target flags on target-independent jump tables");
  unsigned Opc = isTarget ? ISD::TargetJumpTable : ISD::JumpTable;
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, Opc, getVTList(VT), 0, 0);
  ID.AddInteger(JTI);
  ID.AddInteger(TargetFlags);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) JumpTableSDNode(JTI, VT, isTarget,
                                                  TargetFlags);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getConstantPool(const Constant *C, EVT VT,
                                      unsigned Alignment, int Offset,
                                      bool isTarget,
                                      unsigned char TargetFlags) {
  assert((TargetFlags == 0 || isTarget) &&
         "Cannot set target flags on target-independent globals");
  if (Alignment == 0)
    Alignment =
    TM.getTargetLowering()->getDataLayout()->getPrefTypeAlignment(C->getType());
  unsigned Opc = isTarget ? ISD::TargetConstantPool : ISD::ConstantPool;
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, Opc, getVTList(VT), 0, 0);
  ID.AddInteger(Alignment);
  ID.AddInteger(Offset);
  ID.AddPointer(C);
  ID.AddInteger(TargetFlags);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) ConstantPoolSDNode(isTarget, C, VT, Offset,
                                                     Alignment, TargetFlags);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}


SDValue SelectionDAG::getConstantPool(MachineConstantPoolValue *C, EVT VT,
                                      unsigned Alignment, int Offset,
                                      bool isTarget,
                                      unsigned char TargetFlags) {
  assert((TargetFlags == 0 || isTarget) &&
         "Cannot set target flags on target-independent globals");
  if (Alignment == 0)
    Alignment =
    TM.getTargetLowering()->getDataLayout()->getPrefTypeAlignment(C->getType());
  unsigned Opc = isTarget ? ISD::TargetConstantPool : ISD::ConstantPool;
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, Opc, getVTList(VT), 0, 0);
  ID.AddInteger(Alignment);
  ID.AddInteger(Offset);
  C->addSelectionDAGCSEId(ID);
  ID.AddInteger(TargetFlags);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) ConstantPoolSDNode(isTarget, C, VT, Offset,
                                                     Alignment, TargetFlags);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getTargetIndex(int Index, EVT VT, int64_t Offset,
                                     unsigned char TargetFlags) {
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, ISD::TargetIndex, getVTList(VT), 0, 0);
  ID.AddInteger(Index);
  ID.AddInteger(Offset);
  ID.AddInteger(TargetFlags);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) TargetIndexSDNode(Index, VT, Offset,
                                                    TargetFlags);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getBasicBlock(MachineBasicBlock *MBB) {
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, ISD::BasicBlock, getVTList(MVT::Other), 0, 0);
  ID.AddPointer(MBB);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) BasicBlockSDNode(MBB);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getValueType(EVT VT) {
  if (VT.isSimple() && (unsigned)VT.getSimpleVT().SimpleTy >=
      ValueTypeNodes.size())
    ValueTypeNodes.resize(VT.getSimpleVT().SimpleTy+1);

  SDNode *&N = VT.isExtended() ?
    ExtendedValueTypeNodes[VT] : ValueTypeNodes[VT.getSimpleVT().SimpleTy];

  if (N) return SDValue(N, 0);
  N = new (NodeAllocator) VTSDNode(VT);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getExternalSymbol(const char *Sym, EVT VT) {
  SDNode *&N = ExternalSymbols[Sym];
  if (N) return SDValue(N, 0);
  N = new (NodeAllocator) ExternalSymbolSDNode(false, Sym, 0, VT);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getTargetExternalSymbol(const char *Sym, EVT VT,
                                              unsigned char TargetFlags) {
  SDNode *&N =
    TargetExternalSymbols[std::pair<std::string,unsigned char>(Sym,
                                                               TargetFlags)];
  if (N) return SDValue(N, 0);
  N = new (NodeAllocator) ExternalSymbolSDNode(true, Sym, TargetFlags, VT);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getCondCode(ISD::CondCode Cond) {
  if ((unsigned)Cond >= CondCodeNodes.size())
    CondCodeNodes.resize(Cond+1);

  if (CondCodeNodes[Cond] == 0) {
    CondCodeSDNode *N = new (NodeAllocator) CondCodeSDNode(Cond);
    CondCodeNodes[Cond] = N;
    AllNodes.push_back(N);
  }

  return SDValue(CondCodeNodes[Cond], 0);
}

// commuteShuffle - swaps the values of N1 and N2, and swaps all indices in
// the shuffle mask M that point at N1 to point at N2, and indices that point
// N2 to point at N1.
static void commuteShuffle(SDValue &N1, SDValue &N2, SmallVectorImpl<int> &M) {
  std::swap(N1, N2);
  int NElts = M.size();
  for (int i = 0; i != NElts; ++i) {
    if (M[i] >= NElts)
      M[i] -= NElts;
    else if (M[i] >= 0)
      M[i] += NElts;
  }
}

SDValue SelectionDAG::getVectorShuffle(EVT VT, SDLoc dl, SDValue N1,
                                       SDValue N2, const int *Mask) {
  assert(N1.getValueType() == N2.getValueType() && "Invalid VECTOR_SHUFFLE");
  assert(VT.isVector() && N1.getValueType().isVector() &&
         "Vector Shuffle VTs must be a vectors");
  assert(VT.getVectorElementType() == N1.getValueType().getVectorElementType()
         && "Vector Shuffle VTs must have same element type");

  // Canonicalize shuffle undef, undef -> undef
  if (N1.getOpcode() == ISD::UNDEF && N2.getOpcode() == ISD::UNDEF)
    return getUNDEF(VT);

  // Validate that all indices in Mask are within the range of the elements
  // input to the shuffle.
  unsigned NElts = VT.getVectorNumElements();
  SmallVector<int, 8> MaskVec;
  for (unsigned i = 0; i != NElts; ++i) {
    assert(Mask[i] < (int)(NElts * 2) && "Index out of range");
    MaskVec.push_back(Mask[i]);
  }

  // Canonicalize shuffle v, v -> v, undef
  if (N1 == N2) {
    N2 = getUNDEF(VT);
    for (unsigned i = 0; i != NElts; ++i)
      if (MaskVec[i] >= (int)NElts) MaskVec[i] -= NElts;
  }

  // Canonicalize shuffle undef, v -> v, undef.  Commute the shuffle mask.
  if (N1.getOpcode() == ISD::UNDEF)
    commuteShuffle(N1, N2, MaskVec);

  // Canonicalize all index into lhs, -> shuffle lhs, undef
  // Canonicalize all index into rhs, -> shuffle rhs, undef
  bool AllLHS = true, AllRHS = true;
  bool N2Undef = N2.getOpcode() == ISD::UNDEF;
  for (unsigned i = 0; i != NElts; ++i) {
    if (MaskVec[i] >= (int)NElts) {
      if (N2Undef)
        MaskVec[i] = -1;
      else
        AllLHS = false;
    } else if (MaskVec[i] >= 0) {
      AllRHS = false;
    }
  }
  if (AllLHS && AllRHS)
    return getUNDEF(VT);
  if (AllLHS && !N2Undef)
    N2 = getUNDEF(VT);
  if (AllRHS) {
    N1 = getUNDEF(VT);
    commuteShuffle(N1, N2, MaskVec);
  }

  // If Identity shuffle, or all shuffle in to undef, return that node.
  bool AllUndef = true;
  bool Identity = true;
  for (unsigned i = 0; i != NElts; ++i) {
    if (MaskVec[i] >= 0 && MaskVec[i] != (int)i) Identity = false;
    if (MaskVec[i] >= 0) AllUndef = false;
  }
  if (Identity && NElts == N1.getValueType().getVectorNumElements())
    return N1;
  if (AllUndef)
    return getUNDEF(VT);

  FoldingSetNodeID ID;
  SDValue Ops[2] = { N1, N2 };
  AddNodeIDNode(ID, ISD::VECTOR_SHUFFLE, getVTList(VT), Ops, 2);
  for (unsigned i = 0; i != NElts; ++i)
    ID.AddInteger(MaskVec[i]);

  void* IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  // Allocate the mask array for the node out of the BumpPtrAllocator, since
  // SDNode doesn't have access to it.  This memory will be "leaked" when
  // the node is deallocated, but recovered when the NodeAllocator is released.
  int *MaskAlloc = OperandAllocator.Allocate<int>(NElts);
  memcpy(MaskAlloc, &MaskVec[0], NElts * sizeof(int));

  ShuffleVectorSDNode *N =
    new (NodeAllocator) ShuffleVectorSDNode(VT, dl.getIROrder(), dl.getDebugLoc(), N1, N2, MaskAlloc);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getConvertRndSat(EVT VT, SDLoc dl,
                                       SDValue Val, SDValue DTy,
                                       SDValue STy, SDValue Rnd, SDValue Sat,
                                       ISD::CvtCode Code) {
  // If the src and dest types are the same and the conversion is between
  // integer types of the same sign or two floats, no conversion is necessary.
  if (DTy == STy &&
      (Code == ISD::CVT_UU || Code == ISD::CVT_SS || Code == ISD::CVT_FF))
    return Val;

  FoldingSetNodeID ID;
  SDValue Ops[] = { Val, DTy, STy, Rnd, Sat };
  AddNodeIDNode(ID, ISD::CONVERT_RNDSAT, getVTList(VT), &Ops[0], 5);
  void* IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  CvtRndSatSDNode *N = new (NodeAllocator) CvtRndSatSDNode(VT, dl.getIROrder(), dl.getDebugLoc(), Ops, 5,
                                                           Code);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getRegister(unsigned RegNo, EVT VT) {
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, ISD::Register, getVTList(VT), 0, 0);
  ID.AddInteger(RegNo);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) RegisterSDNode(RegNo, VT);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getRegisterMask(const uint32_t *RegMask) {
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, ISD::RegisterMask, getVTList(MVT::Untyped), 0, 0);
  ID.AddPointer(RegMask);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) RegisterMaskSDNode(RegMask);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getEHLabel(SDLoc dl, SDValue Root, MCSymbol *Label) {
  FoldingSetNodeID ID;
  SDValue Ops[] = { Root };
  AddNodeIDNode(ID, ISD::EH_LABEL, getVTList(MVT::Other), &Ops[0], 1);
  ID.AddPointer(Label);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) EHLabelSDNode(dl.getIROrder(), dl.getDebugLoc(), Root, Label);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}


SDValue SelectionDAG::getBlockAddress(const BlockAddress *BA, EVT VT,
                                      int64_t Offset,
                                      bool isTarget,
                                      unsigned char TargetFlags) {
  unsigned Opc = isTarget ? ISD::TargetBlockAddress : ISD::BlockAddress;

  FoldingSetNodeID ID;
  AddNodeIDNode(ID, Opc, getVTList(VT), 0, 0);
  ID.AddPointer(BA);
  ID.AddInteger(Offset);
  ID.AddInteger(TargetFlags);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) BlockAddressSDNode(Opc, VT, BA, Offset,
                                                     TargetFlags);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

SDValue SelectionDAG::getSrcValue(const Value *V) {
  assert((!V || V->getType()->isPointerTy()) &&
         "SrcValue is not a pointer?");

  FoldingSetNodeID ID;
  AddNodeIDNode(ID, ISD::SRCVALUE, getVTList(MVT::Other), 0, 0);
  ID.AddPointer(V);

  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) SrcValueSDNode(V);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}

/// getMDNode - Return an MDNodeSDNode which holds an MDNode.
SDValue SelectionDAG::getMDNode(const MDNode *MD) {
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, ISD::MDNODE_SDNODE, getVTList(MVT::Other), 0, 0);
  ID.AddPointer(MD);

  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) MDNodeSDNode(MD);
  CSEMap.InsertNode(N, IP);
  AllNodes.push_back(N);
  return SDValue(N, 0);
}


/// getShiftAmountOperand - Return the specified value casted to
/// the target's desired shift amount type.
SDValue SelectionDAG::getShiftAmountOperand(EVT LHSTy, SDValue Op) {
  EVT OpTy = Op.getValueType();
  EVT ShTy = TM.getTargetLowering()->getShiftAmountTy(LHSTy);
  if (OpTy == ShTy || OpTy.isVector()) return Op;

  ISD::NodeType Opcode = OpTy.bitsGT(ShTy) ?  ISD::TRUNCATE : ISD::ZERO_EXTEND;
  return getNode(Opcode, SDLoc(Op), ShTy, Op);
}

/// CreateStackTemporary - Create a stack temporary, suitable for holding the
/// specified value type.
SDValue SelectionDAG::CreateStackTemporary(EVT VT, unsigned minAlign) {
  MachineFrameInfo *FrameInfo = getMachineFunction().getFrameInfo();
  unsigned ByteSize = VT.getStoreSize();
  Type *Ty = VT.getTypeForEVT(*getContext());
  const TargetLowering *TLI = TM.getTargetLowering();
  unsigned StackAlign =
  std::max((unsigned)TLI->getDataLayout()->getPrefTypeAlignment(Ty), minAlign);

  int FrameIdx = FrameInfo->CreateStackObject(ByteSize, StackAlign, false);
  return getFrameIndex(FrameIdx, TLI->getPointerTy());
}

/// CreateStackTemporary - Create a stack temporary suitable for holding
/// either of the specified value types.
SDValue SelectionDAG::CreateStackTemporary(EVT VT1, EVT VT2) {
  unsigned Bytes = std::max(VT1.getStoreSizeInBits(),
                            VT2.getStoreSizeInBits())/8;
  Type *Ty1 = VT1.getTypeForEVT(*getContext());
  Type *Ty2 = VT2.getTypeForEVT(*getContext());
  const TargetLowering *TLI = TM.getTargetLowering();
  const DataLayout *TD = TLI->getDataLayout();
  unsigned Align = std::max(TD->getPrefTypeAlignment(Ty1),
                            TD->getPrefTypeAlignment(Ty2));

  MachineFrameInfo *FrameInfo = getMachineFunction().getFrameInfo();
  int FrameIdx = FrameInfo->CreateStackObject(Bytes, Align, false);
  return getFrameIndex(FrameIdx, TLI->getPointerTy());
}

SDValue SelectionDAG::FoldSetCC(EVT VT, SDValue N1,
                                SDValue N2, ISD::CondCode Cond, SDLoc dl) {
  // These setcc operations always fold.
  switch (Cond) {
  default: break;
  case ISD::SETFALSE:
  case ISD::SETFALSE2: return getConstant(0, VT);
  case ISD::SETTRUE:
  case ISD::SETTRUE2:  return getConstant(1, VT);

  case ISD::SETOEQ:
  case ISD::SETOGT:
  case ISD::SETOGE:
  case ISD::SETOLT:
  case ISD::SETOLE:
  case ISD::SETONE:
  case ISD::SETO:
  case ISD::SETUO:
  case ISD::SETUEQ:
  case ISD::SETUNE:
    assert(!N1.getValueType().isInteger() && "Illegal setcc for integer!");
    break;
  }

  if (ConstantSDNode *N2C = dyn_cast<ConstantSDNode>(N2.getNode())) {
    const APInt &C2 = N2C->getAPIntValue();
    if (ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1.getNode())) {
      const APInt &C1 = N1C->getAPIntValue();

      switch (Cond) {
      default: llvm_unreachable("Unknown integer setcc!");
      case ISD::SETEQ:  return getConstant(C1 == C2, VT);
      case ISD::SETNE:  return getConstant(C1 != C2, VT);
      case ISD::SETULT: return getConstant(C1.ult(C2), VT);
      case ISD::SETUGT: return getConstant(C1.ugt(C2), VT);
      case ISD::SETULE: return getConstant(C1.ule(C2), VT);
      case ISD::SETUGE: return getConstant(C1.uge(C2), VT);
      case ISD::SETLT:  return getConstant(C1.slt(C2), VT);
      case ISD::SETGT:  return getConstant(C1.sgt(C2), VT);
      case ISD::SETLE:  return getConstant(C1.sle(C2), VT);
      case ISD::SETGE:  return getConstant(C1.sge(C2), VT);
      }
    }
  }
  if (ConstantFPSDNode *N1C = dyn_cast<ConstantFPSDNode>(N1.getNode())) {
    if (ConstantFPSDNode *N2C = dyn_cast<ConstantFPSDNode>(N2.getNode())) {
      APFloat::cmpResult R = N1C->getValueAPF().compare(N2C->getValueAPF());
      switch (Cond) {
      default: break;
      case ISD::SETEQ:  if (R==APFloat::cmpUnordered)
                          return getUNDEF(VT);
                        // fall through
      case ISD::SETOEQ: return getConstant(R==APFloat::cmpEqual, VT);
      case ISD::SETNE:  if (R==APFloat::cmpUnordered)
                          return getUNDEF(VT);
                        // fall through
      case ISD::SETONE: return getConstant(R==APFloat::cmpGreaterThan ||
                                           R==APFloat::cmpLessThan, VT);
      case ISD::SETLT:  if (R==APFloat::cmpUnordered)
                          return getUNDEF(VT);
                        // fall through
      case ISD::SETOLT: return getConstant(R==APFloat::cmpLessThan, VT);
      case ISD::SETGT:  if (R==APFloat::cmpUnordered)
                          return getUNDEF(VT);
                        // fall through
      case ISD::SETOGT: return getConstant(R==APFloat::cmpGreaterThan, VT);
      case ISD::SETLE:  if (R==APFloat::cmpUnordered)
                          return getUNDEF(VT);
                        // fall through
      case ISD::SETOLE: return getConstant(R==APFloat::cmpLessThan ||
                                           R==APFloat::cmpEqual, VT);
      case ISD::SETGE:  if (R==APFloat::cmpUnordered)
                          return getUNDEF(VT);
                        // fall through
      case ISD::SETOGE: return getConstant(R==APFloat::cmpGreaterThan ||
                                           R==APFloat::cmpEqual, VT);
      case ISD::SETO:   return getConstant(R!=APFloat::cmpUnordered, VT);
      case ISD::SETUO:  return getConstant(R==APFloat::cmpUnordered, VT);
      case ISD::SETUEQ: return getConstant(R==APFloat::cmpUnordered ||
                                           R==APFloat::cmpEqual, VT);
      case ISD::SETUNE: return getConstant(R!=APFloat::cmpEqual, VT);
      case ISD::SETULT: return getConstant(R==APFloat::cmpUnordered ||
                                           R==APFloat::cmpLessThan, VT);
      case ISD::SETUGT: return getConstant(R==APFloat::cmpGreaterThan ||
                                           R==APFloat::cmpUnordered, VT);
      case ISD::SETULE: return getConstant(R!=APFloat::cmpGreaterThan, VT);
      case ISD::SETUGE: return getConstant(R!=APFloat::cmpLessThan, VT);
      }
    } else {
      // Ensure that the constant occurs on the RHS.
      return getSetCC(dl, VT, N2, N1, ISD::getSetCCSwappedOperands(Cond));
    }
  }

  // Could not fold it.
  return SDValue();
}

/// SignBitIsZero - Return true if the sign bit of Op is known to be zero.  We
/// use this predicate to simplify operations downstream.
bool SelectionDAG::SignBitIsZero(SDValue Op, unsigned Depth) const {
  // This predicate is not safe for vector operations.
  if (Op.getValueType().isVector())
    return false;

  unsigned BitWidth = Op.getValueType().getScalarType().getSizeInBits();
  return MaskedValueIsZero(Op, APInt::getSignBit(BitWidth), Depth);
}

/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero.  We use
/// this predicate to simplify operations downstream.  Mask is known to be zero
/// for bits that V cannot have.
bool SelectionDAG::MaskedValueIsZero(SDValue Op, const APInt &Mask,
                                     unsigned Depth) const {
  APInt KnownZero, KnownOne;
  ComputeMaskedBits(Op, KnownZero, KnownOne, Depth);
  assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
  return (KnownZero & Mask) == Mask;
}

/// ComputeMaskedBits - Determine which of the bits specified in Mask are
/// known to be either zero or one and return them in the KnownZero/KnownOne
/// bitsets.  This code only analyzes bits in Mask, in order to short-circuit
/// processing.
void SelectionDAG::ComputeMaskedBits(SDValue Op, APInt &KnownZero,
                                     APInt &KnownOne, unsigned Depth) const {
  const TargetLowering *TLI = TM.getTargetLowering();
  unsigned BitWidth = Op.getValueType().getScalarType().getSizeInBits();

  KnownZero = KnownOne = APInt(BitWidth, 0);   // Don't know anything.
  if (Depth == 6)
    return;  // Limit search depth.

  APInt KnownZero2, KnownOne2;

  switch (Op.getOpcode()) {
  case ISD::Constant:
    // We know all of the bits for a constant!
    KnownOne = cast<ConstantSDNode>(Op)->getAPIntValue();
    KnownZero = ~KnownOne;
    return;
  case ISD::AND:
    // If either the LHS or the RHS are Zero, the result is zero.
    ComputeMaskedBits(Op.getOperand(1), KnownZero, KnownOne, Depth+1);
    ComputeMaskedBits(Op.getOperand(0), KnownZero2, KnownOne2, Depth+1);
    assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
    assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");

    // Output known-1 bits are only known if set in both the LHS & RHS.
    KnownOne &= KnownOne2;
    // Output known-0 are known to be clear if zero in either the LHS | RHS.
    KnownZero |= KnownZero2;
    return;
  case ISD::OR:
    ComputeMaskedBits(Op.getOperand(1), KnownZero, KnownOne, Depth+1);
    ComputeMaskedBits(Op.getOperand(0), KnownZero2, KnownOne2, Depth+1);
    assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
    assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");

    // Output known-0 bits are only known if clear in both the LHS & RHS.
    KnownZero &= KnownZero2;
    // Output known-1 are known to be set if set in either the LHS | RHS.
    KnownOne |= KnownOne2;
    return;
  case ISD::XOR: {
    ComputeMaskedBits(Op.getOperand(1), KnownZero, KnownOne, Depth+1);
    ComputeMaskedBits(Op.getOperand(0), KnownZero2, KnownOne2, Depth+1);
    assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
    assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");

    // Output known-0 bits are known if clear or set in both the LHS & RHS.
    APInt KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2);
    // Output known-1 are known to be set if set in only one of the LHS, RHS.
    KnownOne = (KnownZero & KnownOne2) | (KnownOne & KnownZero2);
    KnownZero = KnownZeroOut;
    return;
  }
  case ISD::MUL: {
    ComputeMaskedBits(Op.getOperand(1), KnownZero, KnownOne, Depth+1);
    ComputeMaskedBits(Op.getOperand(0), KnownZero2, KnownOne2, Depth+1);
    assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
    assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");

    // If low bits are zero in either operand, output low known-0 bits.
    // Also compute a conserative estimate for high known-0 bits.
    // More trickiness is possible, but this is sufficient for the
    // interesting case of alignment computation.
    KnownOne.clearAllBits();
    unsigned TrailZ = KnownZero.countTrailingOnes() +
                      KnownZero2.countTrailingOnes();
    unsigned LeadZ =  std::max(KnownZero.countLeadingOnes() +
                               KnownZero2.countLeadingOnes(),
                               BitWidth) - BitWidth;

    TrailZ = std::min(TrailZ, BitWidth);
    LeadZ = std::min(LeadZ, BitWidth);
    KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) |
                APInt::getHighBitsSet(BitWidth, LeadZ);
    return;
  }
  case ISD::UDIV: {
    // For the purposes of computing leading zeros we can conservatively
    // treat a udiv as a logical right shift by the power of 2 known to
    // be less than the denominator.
    ComputeMaskedBits(Op.getOperand(0), KnownZero2, KnownOne2, Depth+1);
    unsigned LeadZ = KnownZero2.countLeadingOnes();

    KnownOne2.clearAllBits();
    KnownZero2.clearAllBits();
    ComputeMaskedBits(Op.getOperand(1), KnownZero2, KnownOne2, Depth+1);
    unsigned RHSUnknownLeadingOnes = KnownOne2.countLeadingZeros();
    if (RHSUnknownLeadingOnes != BitWidth)
      LeadZ = std::min(BitWidth,
                       LeadZ + BitWidth - RHSUnknownLeadingOnes - 1);

    KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ);
    return;
  }
  case ISD::SELECT:
    ComputeMaskedBits(Op.getOperand(2), KnownZero, KnownOne, Depth+1);
    ComputeMaskedBits(Op.getOperand(1), KnownZero2, KnownOne2, Depth+1);
    assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
    assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");

    // Only known if known in both the LHS and RHS.
    KnownOne &= KnownOne2;
    KnownZero &= KnownZero2;
    return;
  case ISD::SELECT_CC:
    ComputeMaskedBits(Op.getOperand(3), KnownZero, KnownOne, Depth+1);
    ComputeMaskedBits(Op.getOperand(2), KnownZero2, KnownOne2, Depth+1);
    assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
    assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");

    // Only known if known in both the LHS and RHS.
    KnownOne &= KnownOne2;
    KnownZero &= KnownZero2;
    return;
  case ISD::SADDO:
  case ISD::UADDO:
  case ISD::SSUBO:
  case ISD::USUBO:
  case ISD::SMULO:
  case ISD::UMULO:
    if (Op.getResNo() != 1)
      return;
    // The boolean result conforms to getBooleanContents.  Fall through.
  case ISD::SETCC:
    // If we know the result of a setcc has the top bits zero, use this info.
    if (TLI->getBooleanContents(Op.getValueType().isVector()) ==
        TargetLowering::ZeroOrOneBooleanContent && BitWidth > 1)
      KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - 1);
    return;
  case ISD::SHL:
    // (shl X, C1) & C2 == 0   iff   (X & C2 >>u C1) == 0
    if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
      unsigned ShAmt = SA->getZExtValue();

      // If the shift count is an invalid immediate, don't do anything.
      if (ShAmt >= BitWidth)
        return;

      ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
      assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
      KnownZero <<= ShAmt;
      KnownOne  <<= ShAmt;
      // low bits known zero.
      KnownZero |= APInt::getLowBitsSet(BitWidth, ShAmt);
    }
    return;
  case ISD::SRL:
    // (ushr X, C1) & C2 == 0   iff  (-1 >> C1) & C2 == 0
    if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
      unsigned ShAmt = SA->getZExtValue();

      // If the shift count is an invalid immediate, don't do anything.
      if (ShAmt >= BitWidth)
        return;

      ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
      assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
      KnownZero = KnownZero.lshr(ShAmt);
      KnownOne  = KnownOne.lshr(ShAmt);

      APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt);
      KnownZero |= HighBits;  // High bits known zero.
    }
    return;
  case ISD::SRA:
    if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
      unsigned ShAmt = SA->getZExtValue();

      // If the shift count is an invalid immediate, don't do anything.
      if (ShAmt >= BitWidth)
        return;

      // If any of the demanded bits are produced by the sign extension, we also
      // demand the input sign bit.
      APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt);

      ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
      assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
      KnownZero = KnownZero.lshr(ShAmt);
      KnownOne  = KnownOne.lshr(ShAmt);

      // Handle the sign bits.
      APInt SignBit = APInt::getSignBit(BitWidth);
      SignBit = SignBit.lshr(ShAmt);  // Adjust to where it is now in the mask.

      if (KnownZero.intersects(SignBit)) {
        KnownZero |= HighBits;  // New bits are known zero.
      } else if (KnownOne.intersects(SignBit)) {
        KnownOne  |= HighBits;  // New bits are known one.
      }
    }
    return;
  case ISD::SIGN_EXTEND_INREG: {
    EVT EVT = cast<VTSDNode>(Op.getOperand(1))->getVT();
    unsigned EBits = EVT.getScalarType().getSizeInBits();

    // Sign extension.  Compute the demanded bits in the result that are not
    // present in the input.
    APInt NewBits = APInt::getHighBitsSet(BitWidth, BitWidth - EBits);

    APInt InSignBit = APInt::getSignBit(EBits);
    APInt InputDemandedBits = APInt::getLowBitsSet(BitWidth, EBits);

    // If the sign extended bits are demanded, we know that the sign
    // bit is demanded.
    InSignBit = InSignBit.zext(BitWidth);
    if (NewBits.getBoolValue())
      InputDemandedBits |= InSignBit;

    ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
    KnownOne &= InputDemandedBits;
    KnownZero &= InputDemandedBits;
    assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");

    // If the sign bit of the input is known set or clear, then we know the
    // top bits of the result.
    if (KnownZero.intersects(InSignBit)) {         // Input sign bit known clear
      KnownZero |= NewBits;
      KnownOne  &= ~NewBits;
    } else if (KnownOne.intersects(InSignBit)) {   // Input sign bit known set
      KnownOne  |= NewBits;
      KnownZero &= ~NewBits;
    } else {                              // Input sign bit unknown
      KnownZero &= ~NewBits;
      KnownOne  &= ~NewBits;
    }
    return;
  }
  case ISD::CTTZ:
  case ISD::CTTZ_ZERO_UNDEF:
  case ISD::CTLZ:
  case ISD::CTLZ_ZERO_UNDEF:
  case ISD::CTPOP: {
    unsigned LowBits = Log2_32(BitWidth)+1;
    KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - LowBits);
    KnownOne.clearAllBits();
    return;
  }
  case ISD::LOAD: {
    LoadSDNode *LD = cast<LoadSDNode>(Op);
    // If this is a ZEXTLoad and we are looking at the loaded value.
    if (ISD::isZEXTLoad(Op.getNode()) && Op.getResNo() == 0) {
      EVT VT = LD->getMemoryVT();
      unsigned MemBits = VT.getScalarType().getSizeInBits();
      KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - MemBits);
    } else if (const MDNode *Ranges = LD->getRanges()) {
      computeMaskedBitsLoad(*Ranges, KnownZero);
    }
    return;
  }
  case ISD::ZERO_EXTEND: {
    EVT InVT = Op.getOperand(0).getValueType();
    unsigned InBits = InVT.getScalarType().getSizeInBits();
    APInt NewBits   = APInt::getHighBitsSet(BitWidth, BitWidth - InBits);
    KnownZero = KnownZero.trunc(InBits);
    KnownOne = KnownOne.trunc(InBits);
    ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
    KnownZero = KnownZero.zext(BitWidth);
    KnownOne = KnownOne.zext(BitWidth);
    KnownZero |= NewBits;
    return;
  }
  case ISD::SIGN_EXTEND: {
    EVT InVT = Op.getOperand(0).getValueType();
    unsigned InBits = InVT.getScalarType().getSizeInBits();
    APInt InSignBit = APInt::getSignBit(InBits);
    APInt NewBits   = APInt::getHighBitsSet(BitWidth, BitWidth - InBits);

    KnownZero = KnownZero.trunc(InBits);
    KnownOne = KnownOne.trunc(InBits);
    ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);

    // Note if the sign bit is known to be zero or one.
    bool SignBitKnownZero = KnownZero.isNegative();
    bool SignBitKnownOne  = KnownOne.isNegative();
    assert(!(SignBitKnownZero && SignBitKnownOne) &&
           "Sign bit can't be known to be both zero and one!");

    KnownZero = KnownZero.zext(BitWidth);
    KnownOne = KnownOne.zext(BitWidth);

    // If the sign bit is known zero or one, the top bits match.
    if (SignBitKnownZero)
      KnownZero |= NewBits;
    else if (SignBitKnownOne)
      KnownOne  |= NewBits;
    return;
  }
  case ISD::ANY_EXTEND: {
    EVT InVT = Op.getOperand(0).getValueType();
    unsigned InBits = InVT.getScalarType().getSizeInBits();
    KnownZero = KnownZero.trunc(InBits);
    KnownOne = KnownOne.trunc(InBits);
    ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
    KnownZero = KnownZero.zext(BitWidth);
    KnownOne = KnownOne.zext(BitWidth);
    return;
  }
  case ISD::TRUNCATE: {
    EVT InVT = Op.getOperand(0).getValueType();
    unsigned InBits = InVT.getScalarType().getSizeInBits();
    KnownZero = KnownZero.zext(InBits);
    KnownOne = KnownOne.zext(InBits);
    ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
    assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
    KnownZero = KnownZero.trunc(BitWidth);
    KnownOne = KnownOne.trunc(BitWidth);
    break;
  }
  case ISD::AssertZext: {
    EVT VT = cast<VTSDNode>(Op.getOperand(1))->getVT();
    APInt InMask = APInt::getLowBitsSet(BitWidth, VT.getSizeInBits());
    ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
    KnownZero |= (~InMask);
    KnownOne  &= (~KnownZero);
    return;
  }
  case ISD::FGETSIGN:
    // All bits are zero except the low bit.
    KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - 1);
    return;

  case ISD::SUB: {
    if (ConstantSDNode *CLHS = dyn_cast<ConstantSDNode>(Op.getOperand(0))) {
      // We know that the top bits of C-X are clear if X contains less bits
      // than C (i.e. no wrap-around can happen).  For example, 20-X is
      // positive if we can prove that X is >= 0 and < 16.
      if (CLHS->getAPIntValue().isNonNegative()) {
        unsigned NLZ = (CLHS->getAPIntValue()+1).countLeadingZeros();
        // NLZ can't be BitWidth with no sign bit
        APInt MaskV = APInt::getHighBitsSet(BitWidth, NLZ+1);
        ComputeMaskedBits(Op.getOperand(1), KnownZero2, KnownOne2, Depth+1);

        // If all of the MaskV bits are known to be zero, then we know the
        // output top bits are zero, because we now know that the output is
        // from [0-C].
        if ((KnownZero2 & MaskV) == MaskV) {
          unsigned NLZ2 = CLHS->getAPIntValue().countLeadingZeros();
          // Top bits known zero.
          KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2);
        }
      }
    }
  }
  // fall through
  case ISD::ADD:
  case ISD::ADDE: {
    // Output known-0 bits are known if clear or set in both the low clear bits
    // common to both LHS & RHS.  For example, 8+(X<<3) is known to have the
    // low 3 bits clear.
    ComputeMaskedBits(Op.getOperand(0), KnownZero2, KnownOne2, Depth+1);
    assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
    unsigned KnownZeroOut = KnownZero2.countTrailingOnes();

    ComputeMaskedBits(Op.getOperand(1), KnownZero2, KnownOne2, Depth+1);
    assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
    KnownZeroOut = std::min(KnownZeroOut,
                            KnownZero2.countTrailingOnes());

    if (Op.getOpcode() == ISD::ADD) {
      KnownZero |= APInt::getLowBitsSet(BitWidth, KnownZeroOut);
      return;
    }

    // With ADDE, a carry bit may be added in, so we can only use this
    // information if we know (at least) that the low two bits are clear.  We
    // then return to the caller that the low bit is unknown but that other bits
    // are known zero.
    if (KnownZeroOut >= 2) // ADDE
      KnownZero |= APInt::getBitsSet(BitWidth, 1, KnownZeroOut);
    return;
  }
  case ISD::SREM:
    if (ConstantSDNode *Rem = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
      const APInt &RA = Rem->getAPIntValue().abs();
      if (RA.isPowerOf2()) {
        APInt LowBits = RA - 1;
        APInt Mask2 = LowBits | APInt::getSignBit(BitWidth);
        ComputeMaskedBits(Op.getOperand(0), KnownZero2,KnownOne2,Depth+1);

        // The low bits of the first operand are unchanged by the srem.
        KnownZero = KnownZero2 & LowBits;
        KnownOne = KnownOne2 & LowBits;

        // If the first operand is non-negative or has all low bits zero, then
        // the upper bits are all zero.
        if (KnownZero2[BitWidth-1] || ((KnownZero2 & LowBits) == LowBits))
          KnownZero |= ~LowBits;

        // If the first operand is negative and not all low bits are zero, then
        // the upper bits are all one.
        if (KnownOne2[BitWidth-1] && ((KnownOne2 & LowBits) != 0))
          KnownOne |= ~LowBits;
        assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
      }
    }
    return;
  case ISD::UREM: {
    if (ConstantSDNode *Rem = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
      const APInt &RA = Rem->getAPIntValue();
      if (RA.isPowerOf2()) {
        APInt LowBits = (RA - 1);
        KnownZero |= ~LowBits;
        ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne,Depth+1);
        assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
        break;
      }
    }

    // Since the result is less than or equal to either operand, any leading
    // zero bits in either operand must also exist in the result.
    ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
    ComputeMaskedBits(Op.getOperand(1), KnownZero2, KnownOne2, Depth+1);

    uint32_t Leaders = std::max(KnownZero.countLeadingOnes(),
                                KnownZero2.countLeadingOnes());
    KnownOne.clearAllBits();
    KnownZero = APInt::getHighBitsSet(BitWidth, Leaders);
    return;
  }
  case ISD::FrameIndex:
  case ISD::TargetFrameIndex:
    if (unsigned Align = InferPtrAlignment(Op)) {
      // The low bits are known zero if the pointer is aligned.
      KnownZero = APInt::getLowBitsSet(BitWidth, Log2_32(Align));
      return;
    }
    break;

  default:
    if (Op.getOpcode() < ISD::BUILTIN_OP_END)
      break;
    // Fallthrough
  case ISD::INTRINSIC_WO_CHAIN:
  case ISD::INTRINSIC_W_CHAIN:
  case ISD::INTRINSIC_VOID:
    // Allow the target to implement this method for its nodes.
    TLI->computeMaskedBitsForTargetNode(Op, KnownZero, KnownOne, *this, Depth);
    return;
  }
}

/// ComputeNumSignBits - Return the number of times the sign bit of the
/// register is replicated into the other bits.  We know that at least 1 bit
/// is always equal to the sign bit (itself), but other cases can give us
/// information.  For example, immediately after an "SRA X, 2", we know that
/// the top 3 bits are all equal to each other, so we return 3.
unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, unsigned Depth) const{
  const TargetLowering *TLI = TM.getTargetLowering();
  EVT VT = Op.getValueType();
  assert(VT.isInteger() && "Invalid VT!");
  unsigned VTBits = VT.getScalarType().getSizeInBits();
  unsigned Tmp, Tmp2;
  unsigned FirstAnswer = 1;

  if (Depth == 6)
    return 1;  // Limit search depth.

  switch (Op.getOpcode()) {
  default: break;
  case ISD::AssertSext:
    Tmp = cast<VTSDNode>(Op.getOperand(1))->getVT().getSizeInBits();
    return VTBits-Tmp+1;
  case ISD::AssertZext:
    Tmp = cast<VTSDNode>(Op.getOperand(1))->getVT().getSizeInBits();
    return VTBits-Tmp;

  case ISD::Constant: {
    const APInt &Val = cast<ConstantSDNode>(Op)->getAPIntValue();
    return Val.getNumSignBits();
  }

  case ISD::SIGN_EXTEND:
    Tmp = VTBits-Op.getOperand(0).getValueType().getScalarType().getSizeInBits();
    return ComputeNumSignBits(Op.getOperand(0), Depth+1) + Tmp;

  case ISD::SIGN_EXTEND_INREG:
    // Max of the input and what this extends.
    Tmp =
      cast<VTSDNode>(Op.getOperand(1))->getVT().getScalarType().getSizeInBits();
    Tmp = VTBits-Tmp+1;

    Tmp2 = ComputeNumSignBits(Op.getOperand(0), Depth+1);
    return std::max(Tmp, Tmp2);

  case ISD::SRA:
    Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1);
    // SRA X, C   -> adds C sign bits.
    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
      Tmp += C->getZExtValue();
      if (Tmp > VTBits) Tmp = VTBits;
    }
    return Tmp;
  case ISD::SHL:
    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
      // shl destroys sign bits.
      Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1);
      if (C->getZExtValue() >= VTBits ||      // Bad shift.
          C->getZExtValue() >= Tmp) break;    // Shifted all sign bits out.
      return Tmp - C->getZExtValue();
    }
    break;
  case ISD::AND:
  case ISD::OR:
  case ISD::XOR:    // NOT is handled here.
    // Logical binary ops preserve the number of sign bits at the worst.
    Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1);
    if (Tmp != 1) {
      Tmp2 = ComputeNumSignBits(Op.getOperand(1), Depth+1);
      FirstAnswer = std::min(Tmp, Tmp2);
      // We computed what we know about the sign bits as our first
      // answer. Now proceed to the generic code that uses
      // ComputeMaskedBits, and pick whichever answer is better.
    }
    break;

  case ISD::SELECT:
    Tmp = ComputeNumSignBits(Op.getOperand(1), Depth+1);
    if (Tmp == 1) return 1;  // Early out.
    Tmp2 = ComputeNumSignBits(Op.getOperand(2), Depth+1);
    return std::min(Tmp, Tmp2);

  case ISD::SADDO:
  case ISD::UADDO:
  case ISD::SSUBO:
  case ISD::USUBO:
  case ISD::SMULO:
  case ISD::UMULO:
    if (Op.getResNo() != 1)
      break;
    // The boolean result conforms to getBooleanContents.  Fall through.
  case ISD::SETCC:
    // If setcc returns 0/-1, all bits are sign bits.
    if (TLI->getBooleanContents(Op.getValueType().isVector()) ==
        TargetLowering::ZeroOrNegativeOneBooleanContent)
      return VTBits;
    break;
  case ISD::ROTL:
  case ISD::ROTR:
    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
      unsigned RotAmt = C->getZExtValue() & (VTBits-1);

      // Handle rotate right by N like a rotate left by 32-N.
      if (Op.getOpcode() == ISD::ROTR)
        RotAmt = (VTBits-RotAmt) & (VTBits-1);

      // If we aren't rotating out all of the known-in sign bits, return the
      // number that are left.  This handles rotl(sext(x), 1) for example.
      Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1);
      if (Tmp > RotAmt+1) return Tmp-RotAmt;
    }
    break;
  case ISD::ADD:
    // Add can have at most one carry bit.  Thus we know that the output
    // is, at worst, one more bit than the inputs.
    Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1);
    if (Tmp == 1) return 1;  // Early out.

    // Special case decrementing a value (ADD X, -1):
    if (ConstantSDNode *CRHS = dyn_cast<ConstantSDNode>(Op.getOperand(1)))
      if (CRHS->isAllOnesValue()) {
        APInt KnownZero, KnownOne;
        ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);

        // If the input is known to be 0 or 1, the output is 0/-1, which is all
        // sign bits set.
        if ((KnownZero | APInt(VTBits, 1)).isAllOnesValue())
          return VTBits;

        // If we are subtracting one from a positive number, there is no carry
        // out of the result.
        if (KnownZero.isNegative())
          return Tmp;
      }

    Tmp2 = ComputeNumSignBits(Op.getOperand(1), Depth+1);
    if (Tmp2 == 1) return 1;
    return std::min(Tmp, Tmp2)-1;

  case ISD::SUB:
    Tmp2 = ComputeNumSignBits(Op.getOperand(1), Depth+1);
    if (Tmp2 == 1) return 1;

    // Handle NEG.
    if (ConstantSDNode *CLHS = dyn_cast<ConstantSDNode>(Op.getOperand(0)))
      if (CLHS->isNullValue()) {
        APInt KnownZero, KnownOne;
        ComputeMaskedBits(Op.getOperand(1), KnownZero, KnownOne, Depth+1);
        // If the input is known to be 0 or 1, the output is 0/-1, which is all
        // sign bits set.
        if ((KnownZero | APInt(VTBits, 1)).isAllOnesValue())
          return VTBits;

        // If the input is known to be positive (the sign bit is known clear),
        // the output of the NEG has the same number of sign bits as the input.
        if (KnownZero.isNegative())
          return Tmp2;

        // Otherwise, we treat this like a SUB.
      }

    // Sub can have at most one carry bit.  Thus we know that the output
    // is, at worst, one more bit than the inputs.
    Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1);
    if (Tmp == 1) return 1;  // Early out.
    return std::min(Tmp, Tmp2)-1;
  case ISD::TRUNCATE:
    // FIXME: it's tricky to do anything useful for this, but it is an important
    // case for targets like X86.
    break;
  }

  // If we are looking at the loaded value of the SDNode.
  if (Op.getResNo() == 0) {
    // Handle LOADX separately here. EXTLOAD case will fallthrough.
    if (LoadSDNode *LD = dyn_cast<LoadSDNode>(Op)) {
      unsigned ExtType = LD->getExtensionType();
      switch (ExtType) {
        default: break;
        case ISD::SEXTLOAD:    // '17' bits known
          Tmp = LD->getMemoryVT().getScalarType().getSizeInBits();
          return VTBits-Tmp+1;
        case ISD::ZEXTLOAD:    // '16' bits known
          Tmp = LD->getMemoryVT().getScalarType().getSizeInBits();
          return VTBits-Tmp;
      }
    }
  }

  // Allow the target to implement this method for its nodes.
  if (Op.getOpcode() >= ISD::BUILTIN_OP_END ||
      Op.getOpcode() == ISD::INTRINSIC_WO_CHAIN ||
      Op.getOpcode() == ISD::INTRINSIC_W_CHAIN ||
      Op.getOpcode() == ISD::INTRINSIC_VOID) {
    unsigned NumBits = TLI->ComputeNumSignBitsForTargetNode(Op, Depth);
    if (NumBits > 1) FirstAnswer = std::max(FirstAnswer, NumBits);
  }

  // Finally, if we can prove that the top bits of the result are 0's or 1's,
  // use this information.
  APInt KnownZero, KnownOne;
  ComputeMaskedBits(Op, KnownZero, KnownOne, Depth);

  APInt Mask;
  if (KnownZero.isNegative()) {        // sign bit is 0
    Mask = KnownZero;
  } else if (KnownOne.isNegative()) {  // sign bit is 1;
    Mask = KnownOne;
  } else {
    // Nothing known.
    return FirstAnswer;
  }

  // Okay, we know that the sign bit in Mask is set.  Use CLZ to determine
  // the number of identical bits in the top of the input value.
  Mask = ~Mask;
  Mask <<= Mask.getBitWidth()-VTBits;
  // Return # leading zeros.  We use 'min' here in case Val was zero before
  // shifting.  We don't want to return '64' as for an i32 "0".
  return std::max(FirstAnswer, std::min(VTBits, Mask.countLeadingZeros()));
}

/// isBaseWithConstantOffset - Return true if the specified operand is an
/// ISD::ADD with a ConstantSDNode on the right-hand side, or if it is an
/// ISD::OR with a ConstantSDNode that is guaranteed to have the same
/// semantics as an ADD.  This handles the equivalence:
///     X|Cst == X+Cst iff X&Cst = 0.
bool SelectionDAG::isBaseWithConstantOffset(SDValue Op) const {
  if ((Op.getOpcode() != ISD::ADD && Op.getOpcode() != ISD::OR) ||
      !isa<ConstantSDNode>(Op.getOperand(1)))
    return false;

  if (Op.getOpcode() == ISD::OR &&
      !MaskedValueIsZero(Op.getOperand(0),
                     cast<ConstantSDNode>(Op.getOperand(1))->getAPIntValue()))
    return false;

  return true;
}


bool SelectionDAG::isKnownNeverNaN(SDValue Op) const {
  // If we're told that NaNs won't happen, assume they won't.
  if (getTarget().Options.NoNaNsFPMath)
    return true;

  // If the value is a constant, we can obviously see if it is a NaN or not.
  if (const ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Op))
    return !C->getValueAPF().isNaN();

  // TODO: Recognize more cases here.

  return false;
}

bool SelectionDAG::isKnownNeverZero(SDValue Op) const {
  // If the value is a constant, we can obviously see if it is a zero or not.
  if (const ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Op))
    return !C->isZero();

  // TODO: Recognize more cases here.
  switch (Op.getOpcode()) {
  default: break;
  case ISD::OR:
    if (const ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1)))
      return !C->isNullValue();
    break;
  }

  return false;
}

bool SelectionDAG::isEqualTo(SDValue A, SDValue B) const {
  // Check the obvious case.
  if (A == B) return true;

  // For for negative and positive zero.
  if (const ConstantFPSDNode *CA = dyn_cast<ConstantFPSDNode>(A))
    if (const ConstantFPSDNode *CB = dyn_cast<ConstantFPSDNode>(B))
      if (CA->isZero() && CB->isZero()) return true;

  // Otherwise they may not be equal.
  return false;
}

/// getNode - Gets or creates the specified node.
///
SDValue SelectionDAG::getNode(unsigned Opcode, SDLoc DL, EVT VT) {
  FoldingSetNodeID ID;
  AddNodeIDNode(ID, Opcode, getVTList(VT), 0, 0);
  void *IP = 0;
  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
    return SDValue(E, 0);

  SDNode *N = new (NodeAllocator) SDNode(Opcode, DL.getIROrder(), DL.getDebugLoc(), getVTList(VT));
  CSEMap.InsertNode(N, IP);

  AllNodes.push_back(N);
#ifndef NDEBUG
  VerifySDNode(N);
#endif
  return SDValue(N, 0);
}

SDValue SelectionDAG::getNode(unsigned Opcode, SDLoc DL,
                              EVT VT, SDValue Operand) {
  // Constant fold unary operations with an integer constant operand.
  if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Operand.getNode())) {
    const APInt &Val = C->getAPIntValue();
    switch (Opcode) {
    default: break;
    case ISD::SIGN_EXTEND:
      return getConstant(Val.sextOrTrunc(VT.getSizeInBits()), VT);
    case ISD::ANY_EXTEND:
    case ISD::ZERO_EXTEND:
    case ISD::TRUNCATE:
      return getConstant(Val.zextOrTrunc(VT.getSizeInBits()), VT);
    case ISD::UINT_TO_FP:
    case ISD::SINT_TO_FP: {
      APFloat apf(EVTToAPFloatSemantics(VT),
                  APInt::getNullValue(VT.getSizeInBits()));
      (void)apf.convertFromAPInt(Val,
                                 Opcode==ISD::SINT_TO_FP,
                                 APFloat::rmNearestTiesToEven);
      return getConstantFP(apf, VT);
    }
    case ISD::BITCAST:
      if (VT == MVT::f32 && C->getValueType(0) == MVT::i32)
        return getConstantFP(APFloat(APFloat::IEEEsingle, Val), VT);
      else if (VT == MVT::f64 && C->getValueType(0) == MVT::i64)
        return getConstantFP(APFloat(APFloat::IEEEdouble, Val), VT);
      break;
    case ISD::BSWAP:
      return getConstant(Val.byteSwap(), VT);
    case ISD::CTPOP:
      return getConstant(Val.countPopulation(), VT);
    case ISD::CTLZ:
    case ISD::CTLZ_ZERO_UNDEF:
      return getConstant(Val.countLeadingZeros(), VT);
    case ISD::CTTZ:
    case ISD::CTTZ_ZERO_UNDEF:
      return getConstant(Val.countTrailingZeros(), VT);
    }
  }

  // Constant fold unary operations with a floating point constant operand.
  if (ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Operand.getNode())) {
    APFloat V = C->getValueAPF();    // make copy
    switch (Opcode) {
    case ISD::FNEG:
      V.changeSign();
      return getConstantFP(V, VT);
    case ISD::FABS:
      V.clearSign();
      return getConstantFP(V, VT);
    case ISD::FCEIL: {
      APFloat::opStatus fs = V.roundToIntegral(APFloat::rmTowardPositive);
      if (fs == APFloat::opOK || fs == APFloat::opInexact)
        return getConstantFP(V, VT);
      break;
    }
    case ISD::FTRUNC: {
      APFloat::opStatus fs = V.roundToIntegral(APFloat::rmTowardZero);
      if (fs == APFloat::opOK || fs == APFloat::opInexact)
        return getConstantFP(V, VT);
      break;
    }
    case ISD::FFLOOR: {
      APFloat::opStatus fs = V.roundToIntegral(APFloat::rmTowardNegative);
      if (fs == APFloat::opOK || fs == APFloat::opInexact)
        return getConstantFP(V, VT);
      break;
    }
    case ISD::FP_EXTEND: {
      bool ignored;
      // This can return overflow, underflow, or inexact; we don't care.
      // FIXME need to be more flexible about rounding mode.
      (void)V.convert(EVTToAPFloatSemantics(VT),
                      APFloat::rmNearestTiesToEven, &ignored);
      return getConstantFP(V, VT);
    }
    case ISD::FP_TO_SINT:
    case ISD::FP_TO_UINT: {
      integerPart x[2];
      bool ignored;
      assert(integerPartWidth >= 64);
      // FIXME need to be more flexible about rounding mode.
      APFloat::opStatus s = V.convertToInteger(x, VT.getSizeInBits(),
                            Opcode==ISD::FP_TO_SINT,
                            APFloat::rmTowardZero, &ignored);
      if (s==APFloat::opInvalidOp)     // inexact is OK, in fact usual
        break;
      APInt api(VT.getSizeInBits(), x);
      return getConstant(api, VT);
    }
    case ISD::BITCAST:
      if (VT == MVT::i32 && C->getValueType(0) == MVT::f32)
        return getConstant((uint32_t)V.bitcastToAPInt().getZExtValue(), VT);
      else if (VT == MVT::i64 && C->getValueType(0) == MVT::f64)
        return getConstant(V.bitcastToAPInt().getZExtValue(), VT);
      break;
    }
  }

  unsigned OpOpcode = Operand.getNode()->getOpcode();
  switch (Opcode) {
  case ISD::TokenFactor:
  case ISD::MERGE_VALUES:
  case ISD::CONCAT_VECTORS:
    return Operand;         // Factor, merge or concat of one node?  No need.
  case ISD::FP_ROUND: llvm_unreachable("Invalid method to make FP_ROUND node");
  case ISD::FP_EXTEND:
    assert(VT.isFloatingPoint() &&
           Operand.getValueType().isFloatingPoint() && "Invalid FP cast!");
    if (Operand.getValueType() == VT) return Operand;  // noop conversion.
    assert((!VT.isVector() ||
            VT.getVectorNumElements() ==
            Operand.getValueType().getVectorNumElements()) &&
           "Vector element count mismatch!");
    if (Operand.getOpcode() == ISD::UNDEF)
      return getUNDEF(VT);
    break;
  case ISD::SIGN_EXTEND:
    assert(VT.isInteger() && Operand.getValueType().isInteger() &&
           "Invalid SIGN_EXTEND!");
    if (Operand.getValueType() == VT) return Operand;   // noop extension
    assert(Operand.getValueType().getScalarType().bitsLT(VT.getScalarType()) &&
           "Invalid sext node, dst < src!");
    assert((!VT.isVector() ||
            VT.getVectorNumElements() ==
            Operand.getValueType().getVectorNumElements()) &&
           "Vector element count mismatch!");
    if (OpOpcode == ISD::SIGN_EXTEND || OpOpcode == ISD::ZERO_EXTEND)
      return getNode(OpOpcode, DL, VT, Operand.getNode()->getOperand(0));
    else if (OpOpcode == ISD::UNDEF)
      // sext(undef) = 0, because the top bits will all be the same.
      return getConstant(0, VT);
    break;
  case ISD::ZERO_EXTEND:
    assert(VT.isInteger() && Operand.getValueType().isInteger() &&
           "Invalid ZERO_EXTEND!");
    if (Operand.getValueType() == VT) return Operand;   // noop extension
    assert(Operand.getValueType().getScalarType().bitsLT(VT.getScalarType()) &&
           "Invalid zext node, dst < src!");
    assert((!VT.isVector() ||
            VT.getVectorNumElements() ==
            Operand.getValueType().getVectorNumElements()) &&
           "Vector element count mismatch!");
    if (OpOpcode == ISD::ZERO_EXTEND)   // (zext (zext x)) -> (zext x)
      return getNode(ISD::ZERO_EXTEND, DL, VT,
                     Operand.getNode()->getOperand(0));
    else if (OpOpcode == ISD::UNDEF)
      // zext(undef) = 0, because the top bits will be zero.
      return getConstant(0, VT);
    break;
  case ISD::ANY_EXTEND:
    assert(VT.isInteger() && Operand.getValueType().isInteger() &&
           "Invalid ANY_EXTEND!");
    if (Operand.getValueType() == VT) return Operand;   // noop extension
    assert(Operand.getValueType().getScalarType().bitsLT(VT.getScalarType()) &&
           "Invalid anyext node, dst < src!");
    assert((!VT.isVector() ||
            VT.getVectorNumElements() ==
            Operand.getValueType().getVectorNumElements()) &&
           "Vector element count mismatch!");

    if (OpOpcode == ISD::ZERO_EXTEND || OpOpcode == ISD::SIGN_EXTEND ||
        OpOpcode == ISD::ANY_EXTEND)
      // (ext (zext x)) -> (zext x)  and  (ext (sext x)) -> (sext x)
      return getNode(OpOpcode, DL, VT, Operand.getNode()->getOperand(0));
    else if (OpOpcode == ISD::UNDEF)
      return getUNDEF(VT);

    // (ext (trunx x)) -> x
    if (OpOpcode == ISD::TRUNCATE) {
      SDValue OpOp = Operand.getNode()->getOperand(0);
      if (OpOp.getValueType() == VT)
        return OpOp;
    }
    break;
  case ISD::TRUNCATE:
    assert(VT.isInteger() && Operand.getValueType().isInteger() &&
           "Invalid TRUNCATE!");
    if (Operand.getValueType() == VT) return Operand;   // noop truncate
    assert(Operand.getValueType().getScalarType().bitsGT(VT.getScalarType()) &&
           "Invalid truncate node, src < dst!");
    assert((!VT.isVector() ||
            VT.getVectorNumElements() ==
            Operand.getValueType().getVectorNumElements()) &&
           "Vector element count mismatch!");
    if (OpOpcode == ISD::TRUNCATE)
      return getNode(ISD::TRUNCATE, DL, VT, Operand.getNode()->getOperand(0));
    if (OpOpcode == ISD::ZERO_EXTEND || OpOpcode == ISD::SIGN_EXTEND ||
        OpOpcode == ISD::ANY_EXTEND) {
      // If the source is smaller than the dest, we still need an extend.
      if (Operand.getNode()->getOperand(0).getValueType().getScalarType()
            .bitsLT(VT.getScalarType()))
        return getNode(OpOpcode, DL, VT, Operand.getNode()->getOperand(0));
      if (Operand.getNode()->getOperand(0).getValueType().bitsGT(VT))
        return getNode(ISD::TRUNCATE, DL, VT, Operand.getNode()->getOperand(0));
      return Operand.getNode()->getOperand(0);
    }
    if (OpOpcode == ISD::UNDEF)
      return getUNDEF(VT);
    break;
  case ISD::BITCAST:
    // Basic sanity checking.
    assert(VT.getSizeInBits() == Operand.getValueType().getSizeInBits()
           && "Cannot BITCAST between types of different sizes!");
    if (VT == Operand.getValueType()) return Operand;  // noop conversion.
    if (OpOpcode == ISD::BITCAST)  // bitconv(bitconv(x)) -> bitconv(x)
      return getNode(ISD::BITCAST, DL, VT, Operand.getOperand(0));
    if (OpOpcode == ISD::UNDEF)
      return getUNDEF(VT);
    break;
  case ISD::SCALAR_TO_VECTOR:
    assert(VT.isVector() && !Operand.getValueType().isVector() &&
           (VT.getVectorElementType() == Operand.getValueType() ||
            (VT.getVectorElementType().isInteger() &&
             Operand.getValueType().isInteger() &&
             VT.getVectorElementType().bitsLE(Operand.getValueType()))) &&
           "Illegal SCALAR_TO_VECTOR node!");
    if (OpOpcode == ISD::UNDEF)
      return getUNDEF(VT);
    // scalar_to_vector(extract_vector_elt V, 0) -> V, top bits are undefined.
    if (OpOpcode == ISD::EXTRACT_VECTOR_ELT &&
        isa<ConstantSDNode>(Operand.getOperand(1)) &&
        Operand.getConstantOperandVal(1) == 0 &&
        Operand.getOperand(0).getValueType() == VT)
      return Operand.getOperand(0);
    break;
  case ISD::FNEG:
    // -(X-Y) -> (Y-X) is unsafe because when X==Y, -0.0 != +0.0
    if (getTarget().Options.UnsafeFPMath && OpOpcode == ISD::FSUB)
      return getNode(ISD::FSUB, DL, VT, Operand.getNode()->getOperand(1),
                     Operand.getNode()->getOperand(0));
    if (OpOpcode == ISD::FNEG)  // --X -> X
      return Operand.getNode()->getOperand(0);
    break;
  case ISD::FABS:
    if (OpOpcode == ISD::FNEG)  // abs(-X) -> abs(X)
      return getNode(ISD::FABS, DL, VT, Operand.getNode()->getOperand(0));
    break;
  }

  SDNode *N;
  SDVTList VTs = getVTList(VT);
  if (VT != MVT::Glue) { // Don't CSE flag producing nodes
    FoldingSetNodeID ID;
    SDValue Ops[1] = { Operand };
    AddNodeIDNode(ID, Opcode, VTs, Ops, 1);
    void *IP = 0;
    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
      return SDValue(E, 0);

    N = new (NodeAllocator) UnarySDNode(Opcode, DL.getIROrder(), DL.getDebugLoc(), VTs, Operand);
    CSEMap.InsertNode(N, IP);
  } else {
    N = new (NodeAllocator) UnarySDNode(Opcode, DL.getIROrder(), DL.getDebugLoc(), VTs, Operand);
  }

  AllNodes.push_back(N);
#ifndef NDEBUG
  VerifySDNode(N);
#endif
  return SDValue(N, 0);
}

SDValue SelectionDAG::FoldConstantArithmetic(unsigned Opcode, EVT VT,
                                             SDNode *Cst1, SDNode *Cst2) {
  SmallVector<std::pair<ConstantSDNode *, ConstantSDNode *>, 4> Inputs;
  SmallVector<SDValue, 4> Outputs;
  EVT SVT = VT.getScalarType();

  ConstantSDNode *Scalar1 = dyn_cast<ConstantSDNode>(Cst1);
  ConstantSDNode *Scalar2 = dyn_cast<ConstantSDNode>(Cst2);
  if (Scalar1 && Scalar2) {
    // Scalar instruction.
    Inputs.push_back(std::make_pair(Scalar1, Scalar2));
  } else {
    // For vectors extract each constant element into Inputs so we can constant
    // fold them individually.
    BuildVectorSDNode *BV1 = dyn_cast<BuildVectorSDNode>(Cst1);
    BuildVectorSDNode *BV2 = dyn_cast<BuildVectorSDNode>(Cst2);
    if (!BV1 || !BV2)
      return SDValue();

    assert(BV1->getNumOperands() == BV2->getNumOperands() && "Out of sync!");

    for (unsigned I = 0, E = BV1->getNumOperands(); I != E; ++I) {
      ConstantSDNode *V1 = dyn_cast<ConstantSDNode>(BV1->getOperand(I));
      ConstantSDNode *V2 = dyn_cast<ConstantSDNode>(BV2->getOperand(I));
      if (!V1 || !V2) // Not a constant, bail.
        return SDValue();

      // Avoid BUILD_VECTOR nodes that perform implicit truncation.
      // FIXME: This is valid and could be handled by truncating the APInts.
      if (V1->getValueType(0) != SVT || V2->getValueType(0) != SVT)
        return SDValue();

      Inputs.push_back(std::make_pair(V1, V2));
    }
  }

  // We have a number of constant values, constant fold them element by element.
  for (unsigned I = 0, E = Inputs.size(); I != E; ++I) {
    const APInt &C1 = Inputs[I].first->getAPIntValue();
    const APInt &C2 = Inputs[I].second->getAPIntValue();

    switch (Opcode) {
    case ISD::ADD:
      Outputs.push_back(getConstant(C1 + C2, SVT));
      break;
    case ISD::SUB:
      Outputs.push_back(getConstant(C1 - C2, SVT));
      break;
    case ISD::MUL:
      Outputs.push_back(getConstant(C1 * C2, SVT));
      break;
    case ISD::UDIV:
      if (!C2.getBoolValue())
        return SDValue();
      Outputs.push_back(getConstant(C1.udiv(C2), SVT));
      break;
    case ISD::UREM:
      if (!C2.getBoolValue())
        return SDValue();
      Outputs.push_back(getConstant(C1.urem(C2), SVT));
      break;
    case ISD::SDIV:
      if (!C2.getBoolValue())
        return SDValue();
      Outputs.push_back(getConstant(C1.sdiv(C2), SVT));
      break;
    case ISD::SREM:
      if (!C2.getBoolValue())
        return SDValue();
      Outputs.push_back(getConstant(C1.srem(C2), SVT));
      break;
    case ISD::AND:
      Outputs.push_back(getConstant(C1 & C2, SVT));
      break;
    case ISD::OR:
      Outputs.push_back(getConstant(C1 | C2, SVT));
      break;
    case ISD::XOR:
      Outputs.push_back(getConstant(C1 ^ C2, SVT));
      break;
    case ISD::SHL:
      Outputs.push_back(getConstant(C1 << C2, SVT));
      break;
    case ISD::SRL:
      Outputs.push_back(getConstant(C1.lshr(C2), SVT));
      break;
    case ISD::SRA:
      Outputs.push_back(getConstant(C1.ashr(C2), SVT));
      break;
    case ISD::ROTL:
      Outputs.push_back(getConstant(C1.rotl(C2), SVT));
      break;
    case ISD::ROTR:
      Outputs.push_back(getConstant(C1.rotr(C2), SVT));
      break;
    default:
      return SDValue();
    }
  }

  // Handle the scalar case first.
  if (Scalar1 && Scalar2)
    return Outputs.back();

  // Otherwise build a big vector out of the scalar elements we generated.
  return getNode(ISD::BUILD_VECTOR, SDLoc(), VT, Outputs.data(),
                 Outputs.size());
}

SDValue SelectionDAG::getNode(unsigned Opcode, SDLoc DL, EVT VT, SDValue N1,
                              SDValue N2) {
  ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1.getNode());
  ConstantSDNode *N2C = dyn_cast<ConstantSDNode>(N2.getNode());
  switch (Opcode) {
  default: break;
  case ISD::TokenFactor:
    assert(VT == MVT::Other && N1.getValueType() == MVT::Other &&
           N2.getValueType() == MVT::Other && "Invalid token factor!");
    // Fold trivial token factors.
    if (N1.getOpcode() == ISD::EntryToken) return N2;
    if (N2.getOpcode() == ISD::EntryToken) return N1;
    if (N1 == N2) return N1;
    break;
  case ISD::CONCAT_VECTORS:
    // Concat of UNDEFs is UNDEF.
    if (N1.getOpcode() == ISD::UNDEF &&
        N2.getOpcode() == ISD::UNDEF)
      return getUNDEF(VT);

    // A CONCAT_VECTOR with all operands BUILD_VECTOR can be simplified to
    // one big BUILD_VECTOR.
    if (N1.getOpcode() == ISD::BUILD_VECTOR &&
        N2.getOpcode() == ISD::BUILD_VECTOR) {
      SmallVector<SDValue, 16> Elts(N1.getNode()->op_begin(),
                                    N1.getNode()->op_end());
      Elts.append(N2.getNode()->op_begin(), N2.getNode()->op_end());
      return getNode(ISD::BUILD_VECTOR, DL, VT, &Elts[0], Elts.size());
    }
    break;
  case ISD::AND:
    assert(VT.isInteger() && "This operator does not apply to FP types!");
    assert(N1.getValueType() == N2.getValueType() &&
           N1.getValueType() == VT && "Binary operator types must match!");
    // (X & 0) -> 0.  This commonly occurs when legalizing i64 values, so it's
    // worth handling here.
    if (N2C && N2C->isNullValue())
      return N2;
    if (N2C && N2C->isAllOnesValue())  // X & -1 -> X
      return N1;
    break;
  case ISD::OR:
  case ISD::XOR:
  case ISD::ADD:
  case ISD::SUB:
    assert(VT.isInteger() && "This operator does not apply to FP types!");
    assert(N1.getValueType() == N2.getValueType() &&
           N1.getValueType() == VT && "Binary operator types must match!");
    // (X ^|+- 0) -> X.  This commonly occurs when legalizing i64 values, so
    // it's worth handling here.
    if (N2C && N2C->isNullValue())
      return N1;
    break;
  case ISD::UDIV:
  case ISD::UREM:
  case ISD::MULHU:
  case ISD::MULHS:
  case ISD::MUL:
  case ISD::SDIV:
  case ISD::SREM:
    assert(VT.isInteger() && "This operator does not apply to FP types!");
    assert(N1.getValueType() == N2.getValueType() &&
           N1.getValueType() == VT && "Binary operator types must match!");
    break;
  case ISD::FADD:
  case ISD::FSUB:
  case ISD::FMUL:
  case ISD::FDIV:
  case ISD::FREM:
    if (getTarget().Options.UnsafeFPMath) {
      if (Opcode == ISD::FADD) {
        // 0+x --> x
        if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N1))
          if (CFP->getValueAPF().isZero())
            return N2;
        // x+0 --> x
        if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N2))
          if (CFP->getValueAPF().isZero())
            return N1;
      } else if (Opcode == ISD::FSUB) {
        // x-0 --> x
        if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N2))
          if (CFP->getValueAPF().isZero())
            return N1;
      } else if (Opcode == ISD::FMUL) {
        ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N1);
        SDValue V = N2;

        // If the first operand isn't the constant, try the second
        if (!CFP) {
          CFP = dyn_cast<ConstantFPSDNode>(N2);
          V = N1;
        }

        if (CFP) {
          // 0*x --> 0
          if (CFP->isZero())
            return SDValue(CFP,0);
          // 1*x --> x
          if (CFP->isExactlyValue(1.0))
            return V;
        }
      }
    }
    assert(VT.isFloatingPoint() && "This operator only applies to FP types!");
    assert(N1.getValueType() == N2.getValueType() &&
           N1.getValueType() == VT && "Binary operator types must match!");
    break;
  case ISD::FCOPYSIGN:   // N1 and result must match.  N1/N2 need not match.
    assert(N1.getValueType() == VT &&
           N1.getValueType().isFloatingPoint() &&
           N2.getValueType().isFloatingPoint() &&
           "Invalid FCOPYSIGN!");
    break;
  case ISD::SHL:
  case ISD::SRA:
  case ISD::SRL:
  case ISD::ROTL:
  case ISD::ROTR:
    assert(VT == N1.getValueType() &&
           "Shift operators return type must be the same as their first arg");
    assert(VT.isInteger() && N2.getValueType().isInteger() &&
           "Shifts only work on integers");
    assert((!VT.isVector() || VT == N2.getValueType()) &&
           "Vector shift amounts must be in the same as their first arg");
    // Verify that the shift amount VT is bit enough to hold valid shift
    // amounts.  This catches things like trying to shift an i1024 value by an
    // i8, which is easy to fall into in generic code that uses
    // TLI.getShiftAmount().
    assert(N2.getValueType().getSizeInBits() >=
                   Log2_32_Ceil(N1.getValueType().getSizeInBits()) &&
           "Invalid use of small shift amount with oversized value!");

    // Always fold shifts of i1 values so the code generator doesn't need to
    // handle them.  Since we know the size of the shift has to be less than the
    // size of the value, the shift/rotate count is guaranteed to be zero.
    if (