lib/Target/X86/X86ISelPattern.cpp

//===-- X86ISelPattern.cpp - A pattern matching inst selector for X86 -----===//
// 
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
// 
//===----------------------------------------------------------------------===//
//
// This file defines a pattern matching instruction selector for X86.
//
//===----------------------------------------------------------------------===//

#include "X86.h"
#include "X86InstrBuilder.h"
#include "X86RegisterInfo.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/CodeGen/SSARegMap.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/ADT/Statistic.h"
#include <set>
using namespace llvm;

//===----------------------------------------------------------------------===//
//  X86TargetLowering - X86 Implementation of the TargetLowering interface
namespace {
  class X86TargetLowering : public TargetLowering {
    int VarArgsFrameIndex;            // FrameIndex for start of varargs area.
  public:
    X86TargetLowering(TargetMachine &TM) : TargetLowering(TM) {
      // Set up the TargetLowering object.
      addRegisterClass(MVT::i8, X86::R8RegisterClass);
      addRegisterClass(MVT::i16, X86::R16RegisterClass);
      addRegisterClass(MVT::i32, X86::R32RegisterClass);
      addRegisterClass(MVT::f64, X86::RFPRegisterClass);
      
      // FIXME: Eliminate these two classes when legalize can handle promotions
      // well.
      addRegisterClass(MVT::i1, X86::R8RegisterClass);
      addRegisterClass(MVT::f32, X86::RFPRegisterClass);
      
      computeRegisterProperties();
      
      setOperationUnsupported(ISD::MUL, MVT::i8);
      setOperationUnsupported(ISD::SELECT, MVT::i1);
      setOperationUnsupported(ISD::SELECT, MVT::i8);
      
      addLegalFPImmediate(+0.0); // FLD0
      addLegalFPImmediate(+1.0); // FLD1
      addLegalFPImmediate(-0.0); // FLD0/FCHS
      addLegalFPImmediate(-1.0); // FLD1/FCHS
    }

    /// LowerArguments - This hook must be implemented to indicate how we should
    /// lower the arguments for the specified function, into the specified DAG.
    virtual std::vector<SDOperand>
    LowerArguments(Function &F, SelectionDAG &DAG);

    /// LowerCallTo - This hook lowers an abstract call to a function into an
    /// actual call.
    virtual SDNode *LowerCallTo(const Type *RetTy, SDOperand Callee,
                                ArgListTy &Args, SelectionDAG &DAG);
  };
}


std::vector<SDOperand>
X86TargetLowering::LowerArguments(Function &F, SelectionDAG &DAG) {
  std::vector<SDOperand> ArgValues;

  // Add DAG nodes to load the arguments...  On entry to a function on the X86,
  // the stack frame looks like this:
  //
  // [ESP] -- return address
  // [ESP + 4] -- first argument (leftmost lexically)
  // [ESP + 8] -- second argument, if first argument is four bytes in size
  //    ... 
  //
  MachineFunction &MF = DAG.getMachineFunction();
  MachineFrameInfo *MFI = MF.getFrameInfo();
  
  unsigned ArgOffset = 0;   // Frame mechanisms handle retaddr slot
  for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I) {
    MVT::ValueType ObjectVT = getValueType(I->getType());
    unsigned ArgIncrement = 4;
    unsigned ObjSize;
    switch (ObjectVT) {
    default: assert(0 && "Unhandled argument type!");
    case MVT::i1:
    case MVT::i8:  ObjSize = 1;                break;
    case MVT::i16: ObjSize = 2;                break;
    case MVT::i32: ObjSize = 4;                break;
    case MVT::i64: ObjSize = ArgIncrement = 8; break;
    case MVT::f32: ObjSize = 4;                break;
    case MVT::f64: ObjSize = ArgIncrement = 8; break;
    }
    // Create the frame index object for this incoming parameter...
    int FI = MFI->CreateFixedObject(ObjSize, ArgOffset);
    
    // Create the SelectionDAG nodes corresponding to a load from this parameter
    SDOperand FIN = DAG.getFrameIndex(FI, MVT::i32);

    // Don't codegen dead arguments.  FIXME: remove this check when we can nuke
    // dead loads.
    SDOperand ArgValue;
    if (!I->use_empty())
      ArgValue = DAG.getLoad(ObjectVT, DAG.getEntryNode(), FIN);
    else {
      if (MVT::isInteger(ObjectVT))
        ArgValue = DAG.getConstant(0, ObjectVT);
      else
        ArgValue = DAG.getConstantFP(0, ObjectVT);
    }
    ArgValues.push_back(ArgValue);

    ArgOffset += ArgIncrement;   // Move on to the next argument...
  }

  // If the function takes variable number of arguments, make a frame index for
  // the start of the first vararg value... for expansion of llvm.va_start.
  if (F.isVarArg())
    VarArgsFrameIndex = MFI->CreateFixedObject(1, ArgOffset);

  return ArgValues;
}

SDNode *X86TargetLowering::LowerCallTo(const Type *RetTy, SDOperand Callee,
                                       ArgListTy &Args, SelectionDAG &DAG) {
  // Count how many bytes are to be pushed on the stack.
  unsigned NumBytes = 0;

  if (Args.empty()) {
    // Save zero bytes.
    DAG.setRoot(DAG.getNode(ISD::ADJCALLSTACKDOWN, MVT::Other, DAG.getRoot(),
                            DAG.getConstant(0, getPointerTy())));
  } else {
    for (unsigned i = 0, e = Args.size(); i != e; ++i)
      switch (getValueType(Args[i].second)) {
      default: assert(0 && "Unknown value type!");
      case MVT::i1:
      case MVT::i8:
      case MVT::i16:
      case MVT::i32:
      case MVT::f32:
        NumBytes += 4;
        break;
      case MVT::i64:
      case MVT::f64:
        NumBytes += 8;
        break;
      }

    DAG.setRoot(DAG.getNode(ISD::ADJCALLSTACKDOWN, MVT::Other, DAG.getRoot(), 
                            DAG.getConstant(NumBytes, getPointerTy())));

    // Arguments go on the stack in reverse order, as specified by the ABI.
    unsigned ArgOffset = 0;
    SDOperand StackPtr = DAG.getCopyFromReg(X86::ESP, MVT::i32);
    for (unsigned i = 0, e = Args.size(); i != e; ++i) {
      unsigned ArgReg;
      SDOperand PtrOff = DAG.getConstant(ArgOffset, getPointerTy());
      PtrOff = DAG.getNode(ISD::ADD, MVT::i32, StackPtr, PtrOff);

      switch (getValueType(Args[i].second)) {
      default: assert(0 && "Unexpected ValueType for argument!");
      case MVT::i1:
      case MVT::i8:
      case MVT::i16:
        // Promote the integer to 32 bits.  If the input type is signed use a
        // sign extend, otherwise use a zero extend.
        if (Args[i].second->isSigned())
          Args[i].first =DAG.getNode(ISD::SIGN_EXTEND, MVT::i32, Args[i].first);
        else
          Args[i].first =DAG.getNode(ISD::ZERO_EXTEND, MVT::i32, Args[i].first);

        // FALL THROUGH
      case MVT::i32:
      case MVT::f32:
        // FIXME: Note that all of these stores are independent of each other.
        DAG.setRoot(DAG.getNode(ISD::STORE, MVT::Other, DAG.getRoot(),
                                Args[i].first, PtrOff));
        ArgOffset += 4;
        break;
      case MVT::i64:
      case MVT::f64:
        // FIXME: Note that all of these stores are independent of each other.
        DAG.setRoot(DAG.getNode(ISD::STORE, MVT::Other, DAG.getRoot(),
                                Args[i].first, PtrOff));
        ArgOffset += 8;
        break;
      }
    }
  }

  std::vector<MVT::ValueType> RetVals;
  MVT::ValueType RetTyVT = getValueType(RetTy);
  if (RetTyVT != MVT::isVoid)
    RetVals.push_back(RetTyVT);
  RetVals.push_back(MVT::Other);

  SDNode *TheCall = DAG.getCall(RetVals, DAG.getRoot(), Callee);
  DAG.setRoot(SDOperand(TheCall, TheCall->getNumValues()-1));
  DAG.setRoot(DAG.getNode(ISD::ADJCALLSTACKUP, MVT::Other, DAG.getRoot(),
              DAG.getConstant(NumBytes, getPointerTy())));
  return TheCall;
}






namespace {
  Statistic<>
  NumFPKill("x86-codegen", "Number of FP_REG_KILL instructions added");

  //===--------------------------------------------------------------------===//
  /// ISel - X86 specific code to select X86 machine instructions for
  /// SelectionDAG operations.
  ///
  class ISel : public SelectionDAGISel {
    /// ContainsFPCode - Every instruction we select that uses or defines a FP
    /// register should set this to true.
    bool ContainsFPCode;

    /// X86Lowering - This object fully describes how to lower LLVM code to an
    /// X86-specific SelectionDAG.
    X86TargetLowering X86Lowering;


    /// ExprMap - As shared expressions are codegen'd, we keep track of which
    /// vreg the value is produced in, so we only emit one copy of each compiled
    /// tree.
    std::map<SDOperand, unsigned> ExprMap;
    std::set<SDOperand> LoweredTokens;

  public:
    ISel(TargetMachine &TM) : SelectionDAGISel(X86Lowering), X86Lowering(TM) {
    }

    /// InstructionSelectBasicBlock - This callback is invoked by
    /// SelectionDAGISel when it has created a SelectionDAG for us to codegen.
    virtual void InstructionSelectBasicBlock(SelectionDAG &DAG) {
      // While we're doing this, keep track of whether we see any FP code for
      // FP_REG_KILL insertion.
      ContainsFPCode = false;

      // Codegen the basic block.
      Select(DAG.getRoot());

      // Insert FP_REG_KILL instructions into basic blocks that need them.  This
      // only occurs due to the floating point stackifier not being aggressive
      // enough to handle arbitrary global stackification.
      //
      // Currently we insert an FP_REG_KILL instruction into each block that
      // uses or defines a floating point virtual register.
      //
      // When the global register allocators (like linear scan) finally update
      // live variable analysis, we can keep floating point values in registers
      // across basic blocks.  This will be a huge win, but we are waiting on
      // the global allocators before we can do this.
      //
      if (ContainsFPCode && BB->succ_size()) {
        BuildMI(*BB, BB->getFirstTerminator(), X86::FP_REG_KILL, 0);
        ++NumFPKill;
      }

      // Clear state used for selection.
      ExprMap.clear();
      LoweredTokens.clear();
    }

    void EmitCMP(SDOperand LHS, SDOperand RHS);
    bool EmitBranchCC(MachineBasicBlock *Dest, SDOperand Cond);
    unsigned SelectExpr(SDOperand N);
    bool SelectAddress(SDOperand N, X86AddressMode &AM);
    void Select(SDOperand N);
  };
}

/// SelectAddress - Add the specified node to the specified addressing mode,
/// returning true if it cannot be done.
bool ISel::SelectAddress(SDOperand N, X86AddressMode &AM) {
  switch (N.getOpcode()) {
  default: break;
  case ISD::FrameIndex:
    if (AM.BaseType == X86AddressMode::RegBase && AM.Base.Reg == 0) {
      AM.BaseType = X86AddressMode::FrameIndexBase;
      AM.Base.FrameIndex = cast<FrameIndexSDNode>(N)->getIndex();
      return false;
    }
    break;
  case ISD::GlobalAddress:
    if (AM.GV == 0) {
      AM.GV = cast<GlobalAddressSDNode>(N)->getGlobal();
      return false;
    }
    break;
  case ISD::Constant:
    AM.Disp += cast<ConstantSDNode>(N)->getValue();
    return false;
  case ISD::SHL:
    if (AM.IndexReg == 0 || AM.Scale == 1)
      if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.Val->getOperand(1))) {
        unsigned Val = CN->getValue();
        if (Val == 1 || Val == 2 || Val == 3) {
          AM.Scale = 1 << Val;
          AM.IndexReg = SelectExpr(N.Val->getOperand(0));
          return false;
        }
      }
    break;

  case ISD::ADD: {
    X86AddressMode Backup = AM;
    if (!SelectAddress(N.Val->getOperand(0), AM) &&
        !SelectAddress(N.Val->getOperand(1), AM))
      return false;
    AM = Backup;
    break;
  }
  }

  if (AM.BaseType != X86AddressMode::RegBase ||
      AM.Base.Reg)
    return true;

  // Default, generate it as a register.
  AM.BaseType = X86AddressMode::RegBase;
  AM.Base.Reg = SelectExpr(N);
  return false;
}

/// Emit2SetCCsAndLogical - Emit the following sequence of instructions,
/// assuming that the temporary registers are in the 8-bit register class.
///
///  Tmp1 = setcc1
///  Tmp2 = setcc2
///  DestReg = logicalop Tmp1, Tmp2
///
static void Emit2SetCCsAndLogical(MachineBasicBlock *BB, unsigned SetCC1,
                                  unsigned SetCC2, unsigned LogicalOp,
                                  unsigned DestReg) {
  SSARegMap *RegMap = BB->getParent()->getSSARegMap();
  unsigned Tmp1 = RegMap->createVirtualRegister(X86::R8RegisterClass);
  unsigned Tmp2 = RegMap->createVirtualRegister(X86::R8RegisterClass);
  BuildMI(BB, SetCC1, 0, Tmp1);
  BuildMI(BB, SetCC2, 0, Tmp2);
  BuildMI(BB, LogicalOp, 2, DestReg).addReg(Tmp1).addReg(Tmp2);
}

/// EmitSetCC - Emit the code to set the specified 8-bit register to 1 if the
/// condition codes match the specified SetCCOpcode.  Note that some conditions
/// require multiple instructions to generate the correct value.
static void EmitSetCC(MachineBasicBlock *BB, unsigned DestReg,
                      ISD::CondCode SetCCOpcode, bool isFP) {
  unsigned Opc;
  if (!isFP) {
    switch (SetCCOpcode) {
    default: assert(0 && "Illegal integer SetCC!");
    case ISD::SETEQ: Opc = X86::SETEr; break;
    case ISD::SETGT: Opc = X86::SETGr; break;
    case ISD::SETGE: Opc = X86::SETGEr; break;
    case ISD::SETLT: Opc = X86::SETLr; break;
    case ISD::SETLE: Opc = X86::SETLEr; break;
    case ISD::SETNE: Opc = X86::SETNEr; break;
    case ISD::SETULT: Opc = X86::SETBr; break;
    case ISD::SETUGT: Opc = X86::SETAr; break;
    case ISD::SETULE: Opc = X86::SETBEr; break;
    case ISD::SETUGE: Opc = X86::SETAEr; break;
    }
  } else {
    // On a floating point condition, the flags are set as follows:
    // ZF  PF  CF   op
    //  0 | 0 | 0 | X > Y
    //  0 | 0 | 1 | X < Y
    //  1 | 0 | 0 | X == Y
    //  1 | 1 | 1 | unordered
    //
    switch (SetCCOpcode) {
    default: assert(0 && "Invalid FP setcc!");
    case ISD::SETUEQ:
    case ISD::SETEQ:
      Opc = X86::SETEr;    // True if ZF = 1
      break;
    case ISD::SETOGT:
    case ISD::SETGT:
      Opc = X86::SETAr;    // True if CF = 0 and ZF = 0
      break;
    case ISD::SETOGE:
    case ISD::SETGE:
      Opc = X86::SETAEr;   // True if CF = 0
      break;
    case ISD::SETULT:
    case ISD::SETLT:
      Opc = X86::SETBr;    // True if CF = 1
      break;
    case ISD::SETULE:
    case ISD::SETLE:
      Opc = X86::SETBEr;   // True if CF = 1 or ZF = 1
      break;
    case ISD::SETONE:
    case ISD::SETNE:
      Opc = X86::SETNEr;   // True if ZF = 0
      break;
    case ISD::SETUO:
      Opc = X86::SETPr;    // True if PF = 1
      break;
    case ISD::SETO:
      Opc = X86::SETNPr;   // True if PF = 0
      break;
    case ISD::SETOEQ:      // !PF & ZF
      Emit2SetCCsAndLogical(BB, X86::SETNPr, X86::SETEr, X86::AND8rr, DestReg);
      return;
    case ISD::SETOLT:      // !PF & CF
      Emit2SetCCsAndLogical(BB, X86::SETNPr, X86::SETBr, X86::AND8rr, DestReg);
      return;
    case ISD::SETOLE:      // !PF & (CF || ZF)
      Emit2SetCCsAndLogical(BB, X86::SETNPr, X86::SETBEr, X86::AND8rr, DestReg);
      return;
    case ISD::SETUGT:      // PF | (!ZF & !CF)
      Emit2SetCCsAndLogical(BB, X86::SETPr, X86::SETAr, X86::OR8rr, DestReg);
      return;
    case ISD::SETUGE:      // PF | !CF
      Emit2SetCCsAndLogical(BB, X86::SETPr, X86::SETAEr, X86::OR8rr, DestReg);
      return;
    case ISD::SETUNE:      // PF | !ZF
      Emit2SetCCsAndLogical(BB, X86::SETPr, X86::SETNEr, X86::OR8rr, DestReg);
      return;
    }
  }
  BuildMI(BB, Opc, 0, DestReg);
}


/// EmitBranchCC - Emit code into BB that arranges for control to transfer to
/// the Dest block if the Cond condition is true.  If we cannot fold this
/// condition into the branch, return true.
///
bool ISel::EmitBranchCC(MachineBasicBlock *Dest, SDOperand Cond) {
  // FIXME: Evaluate whether it would be good to emit code like (X < Y) | (A >
  // B) using two conditional branches instead of one condbr, two setcc's, and
  // an or.
  if ((Cond.getOpcode() == ISD::OR ||
       Cond.getOpcode() == ISD::AND) && Cond.Val->hasOneUse()) {
    // And and or set the flags for us, so there is no need to emit a TST of the
    // result.  It is only safe to do this if there is only a single use of the
    // AND/OR though, otherwise we don't know it will be emitted here.
    SelectExpr(Cond);
    BuildMI(BB, X86::JNE, 1).addMBB(Dest);
    return false;
  }

  // Codegen br not C -> JE.
  if (Cond.getOpcode() == ISD::XOR)
    if (ConstantSDNode *NC = dyn_cast<ConstantSDNode>(Cond.Val->getOperand(1)))
      if (NC->isAllOnesValue()) {
        unsigned CondR = SelectExpr(Cond.Val->getOperand(0));
        BuildMI(BB, X86::TEST8rr, 2).addReg(CondR).addReg(CondR);
        BuildMI(BB, X86::JE, 1).addMBB(Dest);
        return false;
      }

  SetCCSDNode *SetCC = dyn_cast<SetCCSDNode>(Cond);
  if (SetCC == 0)
    return true;                       // Can only handle simple setcc's so far.

  unsigned Opc;

  // Handle integer conditions first.
  if (MVT::isInteger(SetCC->getOperand(0).getValueType())) {
    switch (SetCC->getCondition()) {
    default: assert(0 && "Illegal integer SetCC!");
    case ISD::SETEQ: Opc = X86::JE; break;
    case ISD::SETGT: Opc = X86::JG; break;
    case ISD::SETGE: Opc = X86::JGE; break;
    case ISD::SETLT: Opc = X86::JL; break;
    case ISD::SETLE: Opc = X86::JLE; break;
    case ISD::SETNE: Opc = X86::JNE; break;
    case ISD::SETULT: Opc = X86::JB; break;
    case ISD::SETUGT: Opc = X86::JA; break;
    case ISD::SETULE: Opc = X86::JBE; break;
    case ISD::SETUGE: Opc = X86::JAE; break;
    }
    EmitCMP(SetCC->getOperand(0), SetCC->getOperand(1));
    BuildMI(BB, Opc, 1).addMBB(Dest);
    return false;
  }

  ContainsFPCode = true;
  unsigned Opc2 = 0;  // Second branch if needed.

  // On a floating point condition, the flags are set as follows:
  // ZF  PF  CF   op
  //  0 | 0 | 0 | X > Y
  //  0 | 0 | 1 | X < Y
  //  1 | 0 | 0 | X == Y
  //  1 | 1 | 1 | unordered
  //
  switch (SetCC->getCondition()) {
  default: assert(0 && "Invalid FP setcc!");
  case ISD::SETUEQ:
  case ISD::SETEQ:   Opc = X86::JE;  break;     // True if ZF = 1
  case ISD::SETOGT:
  case ISD::SETGT:   Opc = X86::JA;  break;     // True if CF = 0 and ZF = 0
  case ISD::SETOGE:
  case ISD::SETGE:   Opc = X86::JAE; break;     // True if CF = 0
  case ISD::SETULT:
  case ISD::SETLT:   Opc = X86::JB;  break;     // True if CF = 1
  case ISD::SETULE:
  case ISD::SETLE:   Opc = X86::JBE; break;     // True if CF = 1 or ZF = 1
  case ISD::SETONE:
  case ISD::SETNE:   Opc = X86::JNE; break;     // True if ZF = 0
  case ISD::SETUO:   Opc = X86::JP;  break;     // True if PF = 1
  case ISD::SETO:    Opc = X86::JNP; break;     // True if PF = 0
  case ISD::SETUGT:      // PF = 1 | (ZF = 0 & CF = 0)
    Opc = X86::JA;       // ZF = 0 & CF = 0
    Opc2 = X86::JP;      // PF = 1
    break;
  case ISD::SETUGE:      // PF = 1 | CF = 0
    Opc = X86::JAE;      // CF = 0
    Opc2 = X86::JP;      // PF = 1
    break;
  case ISD::SETUNE:      // PF = 1 | ZF = 0
    Opc = X86::JNE;      // ZF = 0
    Opc2 = X86::JP;      // PF = 1
    break;
  case ISD::SETOEQ:      // PF = 0 & ZF = 1
    //X86::JNP, X86::JE
    //X86::AND8rr
    return true;    // FIXME: Emit more efficient code for this branch.
  case ISD::SETOLT:      // PF = 0 & CF = 1
    //X86::JNP, X86::JB
    //X86::AND8rr
    return true;    // FIXME: Emit more efficient code for this branch.
  case ISD::SETOLE:      // PF = 0 & (CF = 1 || ZF = 1)
    //X86::JNP, X86::JBE
    //X86::AND8rr
    return true;    // FIXME: Emit more efficient code for this branch.
  }

  EmitCMP(SetCC->getOperand(0), SetCC->getOperand(1));
  BuildMI(BB, Opc, 1).addMBB(Dest);
  if (Opc2)
    BuildMI(BB, Opc2, 1).addMBB(Dest);
  return false;
}

void ISel::EmitCMP(SDOperand LHS, SDOperand RHS) {
  unsigned Tmp1 = SelectExpr(LHS), Opc;
  if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(RHS)) {
    Opc = 0;
    switch (RHS.getValueType()) {
    default: break;
    case MVT::i1:
    case MVT::i8:  Opc = X86::CMP8ri;  break;
    case MVT::i16: Opc = X86::CMP16ri; break;
    case MVT::i32: Opc = X86::CMP32ri; break;
    }
    if (Opc) {
      BuildMI(BB, Opc, 2).addReg(Tmp1).addImm(CN->getValue());
      return;
    }
  }

  switch (LHS.getValueType()) {
  default: assert(0 && "Cannot compare this value!");
  case MVT::i1:
  case MVT::i8:  Opc = X86::CMP8rr;  break;
  case MVT::i16: Opc = X86::CMP16rr; break;
  case MVT::i32: Opc = X86::CMP32rr; break;
  case MVT::f32:
  case MVT::f64: Opc = X86::FUCOMIr; ContainsFPCode = true; break;
  }
  unsigned Tmp2 = SelectExpr(RHS);
  BuildMI(BB, Opc, 2).addReg(Tmp1).addReg(Tmp2);
}

unsigned ISel::SelectExpr(SDOperand N) {
  unsigned Result;
  unsigned Tmp1, Tmp2, Tmp3;
  unsigned Opc = 0;

  if (N.getOpcode() == ISD::CopyFromReg)
    // Just use the specified register as our input.
    return dyn_cast<CopyRegSDNode>(N)->getReg();

  // If there are multiple uses of this expression, memorize the
  // register it is code generated in, instead of emitting it multiple
  // times.
  // FIXME: Disabled for our current selection model.
  if (1 || !N.Val->hasOneUse()) {
    unsigned &Reg = ExprMap[N];
    if (Reg) return Reg;

    if (N.getOpcode() != ISD::CALL)
      Reg = Result = (N.getValueType() != MVT::Other) ?
                         MakeReg(N.getValueType()) : 1;
    else {
      // If this is a call instruction, make sure to prepare ALL of the result
      // values as well as the chain.
      if (N.Val->getNumValues() == 1)
        Reg = Result = 1;  // Void call, just a chain.
      else {
        Result = MakeReg(N.Val->getValueType(0));
        ExprMap[SDOperand(N.Val,0)] = Result;
        for (unsigned i = 1, e = N.Val->getNumValues()-1; i != e; ++i)
          ExprMap[SDOperand(N.Val, i)] = MakeReg(N.Val->getValueType(i));
        ExprMap[SDOperand(N.Val, N.Val->getNumValues()-1)] = 1;
      }
    }
  } else {
    Result = MakeReg(N.getValueType());
  }

  switch (N.getOpcode()) {
  default:
    N.Val->dump();
    assert(0 && "Node not handled!\n");
  case ISD::FrameIndex:
    Tmp1 = cast<FrameIndexSDNode>(N)->getIndex();
    addFrameReference(BuildMI(BB, X86::LEA32r, 4, Result), (int)Tmp1);
    return Result;
  case ISD::ConstantPool:
    Tmp1 = cast<ConstantPoolSDNode>(N)->getIndex();
    addConstantPoolReference(BuildMI(BB, X86::LEA32r, 4, Result), Tmp1);
    return Result;
  case ISD::ConstantFP:
    ContainsFPCode = true;
    Tmp1 = Result;   // Intermediate Register
    if (cast<ConstantFPSDNode>(N)->getValue() < 0.0 ||
        cast<ConstantFPSDNode>(N)->isExactlyValue(-0.0))
      Tmp1 = MakeReg(MVT::f64);

    if (cast<ConstantFPSDNode>(N)->isExactlyValue(+0.0) ||
        cast<ConstantFPSDNode>(N)->isExactlyValue(-0.0))
      BuildMI(BB, X86::FLD0, 0, Tmp1);
    else if (cast<ConstantFPSDNode>(N)->isExactlyValue(+1.0) ||
             cast<ConstantFPSDNode>(N)->isExactlyValue(-1.0))
      BuildMI(BB, X86::FLD1, 0, Tmp1);
    else
      assert(0 && "Unexpected constant!");
    if (Tmp1 != Result)
      BuildMI(BB, X86::FCHS, 1, Result).addReg(Tmp1);
    return Result;
  case ISD::Constant:
    switch (N.getValueType()) {
    default: assert(0 && "Cannot use constants of this type!");
    case MVT::i1:
    case MVT::i8:  Opc = X86::MOV8ri;  break;
    case MVT::i16: Opc = X86::MOV16ri; break;
    case MVT::i32: Opc = X86::MOV32ri; break;
    }
    BuildMI(BB, Opc, 1,Result).addImm(cast<ConstantSDNode>(N)->getValue());
    return Result;
  case ISD::GlobalAddress: {
    GlobalValue *GV = cast<GlobalAddressSDNode>(N)->getGlobal();
    BuildMI(BB, X86::MOV32ri, 1, Result).addGlobalAddress(GV);
    return Result;
  }
  case ISD::ExternalSymbol: {
    const char *Sym = cast<ExternalSymbolSDNode>(N)->getSymbol();
    BuildMI(BB, X86::MOV32ri, 1, Result).addExternalSymbol(Sym);
    return Result;
  }
  case ISD::FP_EXTEND:
    Tmp1 = SelectExpr(N.getOperand(0));
    BuildMI(BB, X86::FpMOV, 1, Result).addReg(Tmp1);
    ContainsFPCode = true;
    return Result;
  case ISD::ZERO_EXTEND: {
    int DestIs16 = N.getValueType() == MVT::i16;
    int SrcIs16  = N.getOperand(0).getValueType() == MVT::i16;

    static const unsigned Opc[3] = {
      X86::MOVZX32rr8, X86::MOVZX32rr16, X86::MOVZX16rr8
    };
    Tmp1 = SelectExpr(N.getOperand(0));
    BuildMI(BB, Opc[SrcIs16+DestIs16*2], 1, Result).addReg(Tmp1);
    return Result;
  }    
  case ISD::SIGN_EXTEND: {
    int DestIs16 = N.getValueType() == MVT::i16;
    int SrcIs16  = N.getOperand(0).getValueType() == MVT::i16;

    static const unsigned Opc[3] = {
      X86::MOVSX32rr8, X86::MOVSX32rr16, X86::MOVSX16rr8
    };
    Tmp1 = SelectExpr(N.getOperand(0));
    BuildMI(BB, Opc[SrcIs16+DestIs16*2], 1, Result).addReg(Tmp1);
    return Result;
  }
  case ISD::TRUNCATE:
    // Handle cast of LARGER int to SMALLER int using a move to EAX followed by
    // a move out of AX or AL.
    switch (N.getOperand(0).getValueType()) {
    default: assert(0 && "Unknown truncate!");
    case MVT::i8:  Tmp2 = X86::AL;  Opc = X86::MOV8rr;  break;
    case MVT::i16: Tmp2 = X86::AX;  Opc = X86::MOV16rr; break;
    case MVT::i32: Tmp2 = X86::EAX; Opc = X86::MOV32rr; break;
    }
    Tmp1 = SelectExpr(N.getOperand(0));
    BuildMI(BB, Opc, 1, Tmp2).addReg(Tmp1);

    switch (N.getValueType()) {
    default: assert(0 && "Unknown truncate!");
    case MVT::i1:
    case MVT::i8:  Tmp2 = X86::AL;  Opc = X86::MOV8rr;  break;
    case MVT::i16: Tmp2 = X86::AX;  Opc = X86::MOV16rr; break;
    }
    BuildMI(BB, Opc, 1, Result).addReg(Tmp2);
    return Result;

  case ISD::FP_ROUND:
    // Truncate from double to float by storing to memory as float,
    // then reading it back into a register.

    // Create as stack slot to use.
    Tmp1 = TLI.getTargetData().getFloatAlignment();
    Tmp2 = BB->getParent()->getFrameInfo()->CreateStackObject(4, Tmp1);

    // Codegen the input.
    Tmp1 = SelectExpr(N.getOperand(0));

    // Emit the store, then the reload.
    addFrameReference(BuildMI(BB, X86::FST32m, 5), Tmp2).addReg(Tmp1);
    addFrameReference(BuildMI(BB, X86::FLD32m, 5, Result), Tmp2);
    ContainsFPCode = true;
    return Result;

  case ISD::ADD:
    // See if we can codegen this as an LEA to fold operations together.
    if (N.getValueType() == MVT::i32) {
      X86AddressMode AM;
      if (!SelectAddress(N.getOperand(0), AM) &&
          !SelectAddress(N.getOperand(1), AM)) {
	// If this is not just an add, emit the LEA.  For a simple add (like
	// reg+reg or reg+imm), we just emit an add.  If might be a good idea to
	// leave this as LEA, then peephole it to 'ADD' after two address elim
	// happens.
        if (AM.Scale != 1 || AM.BaseType == X86AddressMode::FrameIndexBase ||
            AM.Base.Reg && AM.IndexReg && (AM.Disp || AM.GV)) {
          addFullAddress(BuildMI(BB, X86::LEA32r, 4, Result), AM);
          return Result;
        }
      }
    }
    Tmp1 = SelectExpr(N.getOperand(0));
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      Opc = 0;
      if (CN->getValue() == 1) {   // add X, 1 -> inc X
        switch (N.getValueType()) {
        default: assert(0 && "Cannot integer add this type!");
        case MVT::i8:  Opc = X86::INC8r; break;
        case MVT::i16: Opc = X86::INC16r; break;
        case MVT::i32: Opc = X86::INC32r; break;
        }
      } else if (CN->isAllOnesValue()) { // add X, -1 -> dec X
        switch (N.getValueType()) {
        default: assert(0 && "Cannot integer add this type!");
        case MVT::i8:  Opc = X86::DEC8r; break;
        case MVT::i16: Opc = X86::DEC16r; break;
        case MVT::i32: Opc = X86::DEC32r; break;
        }
      }

      if (Opc) {
        BuildMI(BB, Opc, 1, Result).addReg(Tmp1);
        return Result;
      }

      switch (N.getValueType()) {
      default: assert(0 && "Cannot add this type!");
      case MVT::i8:  Opc = X86::ADD8ri; break;
      case MVT::i16: Opc = X86::ADD16ri; break;
      case MVT::i32: Opc = X86::ADD32ri; break;
      }
      if (Opc) {
        BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(CN->getValue());
        return Result;
      }
    }

    Tmp2 = SelectExpr(N.getOperand(1));
    switch (N.getValueType()) {
    default: assert(0 && "Cannot add this type!");
    case MVT::i8:  Opc = X86::ADD8rr; break;
    case MVT::i16: Opc = X86::ADD16rr; break;
    case MVT::i32: Opc = X86::ADD32rr; break;
    case MVT::f32: 
    case MVT::f64: Opc = X86::FpADD; ContainsFPCode = true; break;
    }
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;
  case ISD::SUB:
    if (MVT::isInteger(N.getValueType()))
      if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(0)))
        if (CN->isNullValue()) {   // 0 - N -> neg N
          switch (N.getValueType()) {
          default: assert(0 && "Cannot sub this type!");
          case MVT::i1:
          case MVT::i8:  Opc = X86::NEG8r;  break;
          case MVT::i16: Opc = X86::NEG16r; break;
          case MVT::i32: Opc = X86::NEG32r; break;
          }
          Tmp1 = SelectExpr(N.getOperand(1));
          BuildMI(BB, Opc, 1, Result).addReg(Tmp1);
          return Result;
        }

    Tmp1 = SelectExpr(N.getOperand(0));
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      switch (N.getValueType()) {
      default: assert(0 && "Cannot sub this type!");
      case MVT::i1:
      case MVT::i8:  Opc = X86::SUB8ri;  break;
      case MVT::i16: Opc = X86::SUB16ri; break;
      case MVT::i32: Opc = X86::SUB32ri; break;
      }
      BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(CN->getValue());
      return Result;
    }
    Tmp2 = SelectExpr(N.getOperand(1));
    switch (N.getValueType()) {
    default: assert(0 && "Cannot add this type!");
    case MVT::i1:
    case MVT::i8:  Opc = X86::SUB8rr; break;
    case MVT::i16: Opc = X86::SUB16rr; break;
    case MVT::i32: Opc = X86::SUB32rr; break;
    case MVT::f32:
    case MVT::f64: Opc = X86::FpSUB; ContainsFPCode = true; break;
    }
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;

  case ISD::AND:
    Tmp1 = SelectExpr(N.getOperand(0));
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      switch (N.getValueType()) {
      default: assert(0 && "Cannot add this type!");
      case MVT::i1:
      case MVT::i8:  Opc = X86::AND8ri;  break;
      case MVT::i16: Opc = X86::AND16ri; break;
      case MVT::i32: Opc = X86::AND32ri; break;
      }
      BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(CN->getValue());
      return Result;
    }
    Tmp2 = SelectExpr(N.getOperand(1));
    switch (N.getValueType()) {
    default: assert(0 && "Cannot add this type!");
    case MVT::i1:
    case MVT::i8:  Opc = X86::AND8rr; break;
    case MVT::i16: Opc = X86::AND16rr; break;
    case MVT::i32: Opc = X86::AND32rr; break;
    }
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;
  case ISD::OR:
    Tmp1 = SelectExpr(N.getOperand(0));
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      switch (N.getValueType()) {
      default: assert(0 && "Cannot add this type!");
      case MVT::i1:
      case MVT::i8:  Opc = X86::OR8ri;  break;
      case MVT::i16: Opc = X86::OR16ri; break;
      case MVT::i32: Opc = X86::OR32ri; break;
      }
      BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(CN->getValue());
      return Result;
    }
    Tmp2 = SelectExpr(N.getOperand(1));
    switch (N.getValueType()) {
    default: assert(0 && "Cannot add this type!");
    case MVT::i1:
    case MVT::i8:  Opc = X86::OR8rr; break;
    case MVT::i16: Opc = X86::OR16rr; break;
    case MVT::i32: Opc = X86::OR32rr; break;
    }
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;
  case ISD::XOR:
    Tmp1 = SelectExpr(N.getOperand(0));
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      switch (N.getValueType()) {
      default: assert(0 && "Cannot add this type!");
      case MVT::i1:
      case MVT::i8:  Opc = X86::XOR8ri;  break;
      case MVT::i16: Opc = X86::XOR16ri; break;
      case MVT::i32: Opc = X86::XOR32ri; break;
      }
      BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(CN->getValue());
      return Result;
    }
    Tmp2 = SelectExpr(N.getOperand(1));
    switch (N.getValueType()) {
    default: assert(0 && "Cannot add this type!");
    case MVT::i1:
    case MVT::i8:  Opc = X86::XOR8rr; break;
    case MVT::i16: Opc = X86::XOR16rr; break;
    case MVT::i32: Opc = X86::XOR32rr; break;
    }
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;

  case ISD::MUL:
    Tmp1 = SelectExpr(N.getOperand(0));
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      Opc = 0;
      switch (N.getValueType()) {
      default: assert(0 && "Cannot multiply this type!");
      case MVT::i8:  break;
      case MVT::i16: Opc = X86::IMUL16rri; break;
      case MVT::i32: Opc = X86::IMUL32rri; break;
      }
      if (Opc) {
        BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(CN->getValue());
        return Result;
      }
    }
    Tmp2 = SelectExpr(N.getOperand(1));
    switch (N.getValueType()) {
    default: assert(0 && "Cannot add this type!");
    case MVT::i8: assert(0 && "FIXME: MUL i8 not implemented yet!");
    case MVT::i16: Opc = X86::IMUL16rr; break;
    case MVT::i32: Opc = X86::IMUL32rr; break;
    case MVT::f32: 
    case MVT::f64: Opc = X86::FpMUL; ContainsFPCode = true; break;
    }
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;

  case ISD::SELECT:
    // FIXME: implement folding of setcc into select.
    if (N.getValueType() != MVT::i1 && N.getValueType() != MVT::i8) {
      Tmp2 = SelectExpr(N.getOperand(1));
      Tmp3 = SelectExpr(N.getOperand(2));
      Tmp1 = SelectExpr(N.getOperand(0));

      switch (N.getValueType()) {
      default: assert(0 && "Cannot select this type!");
      case MVT::i16: Opc = X86::CMOVE16rr; break;
      case MVT::i32: Opc = X86::CMOVE32rr; break;
      case MVT::f32:
      case MVT::f64: Opc = X86::FCMOVE; ContainsFPCode = true; break;
      }

      // Get the condition into the zero flag.
      BuildMI(BB, X86::TEST8rr, 2).addReg(Tmp1).addReg(Tmp1);
      BuildMI(BB, Opc, 2, Result).addReg(Tmp2).addReg(Tmp3);
      return Result;
    } else {
      // FIXME: This should not be implemented here, it should be in the generic
      // code!
      Tmp2 = SelectExpr(CurDAG->getNode(ISD::ZERO_EXTEND, MVT::i16,
                                        N.getOperand(1)));
      Tmp3 = SelectExpr(CurDAG->getNode(ISD::ZERO_EXTEND, MVT::i16,
                                        N.getOperand(2)));
      Tmp1 = SelectExpr(N.getOperand(0));
      BuildMI(BB, X86::TEST8rr, 2).addReg(Tmp1).addReg(Tmp1);
      // FIXME: need subregs to do better than this!
      unsigned TmpReg = MakeReg(MVT::i16);
      BuildMI(BB, X86::CMOVE16rr, 2, TmpReg).addReg(Tmp2).addReg(Tmp3);
      BuildMI(BB, X86::MOV16rr, 1, X86::AX).addReg(TmpReg);
      BuildMI(BB, X86::MOV8rr, 1, Result).addReg(X86::AL);
      return Result;
    }

  case ISD::SDIV:
  case ISD::UDIV:
  case ISD::SREM:
  case ISD::UREM: {
    Tmp1 = SelectExpr(N.getOperand(0));

    if (N.getOpcode() == ISD::SDIV)
      if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
        // FIXME: These special cases should be handled by the lowering impl!
        unsigned RHS = CN->getValue();
        bool isNeg = false;
        if ((int)RHS < 0) {
          isNeg = true;
          RHS = -RHS;
        }
        if (RHS && (RHS & (RHS-1)) == 0) {   // Signed division by power of 2?
          unsigned Log = log2(RHS);
          unsigned TmpReg = MakeReg(N.getValueType());
          unsigned SAROpc, SHROpc, ADDOpc, NEGOpc;
          switch (N.getValueType()) {
          default: assert("Unknown type to signed divide!");
          case MVT::i8:
            SAROpc = X86::SAR8ri;
            SHROpc = X86::SHR8ri;
            ADDOpc = X86::ADD8rr;
            NEGOpc = X86::NEG8r;
            break;
          case MVT::i16:
            SAROpc = X86::SAR16ri;
            SHROpc = X86::SHR16ri;
            ADDOpc = X86::ADD16rr;
            NEGOpc = X86::NEG16r;
            break;
          case MVT::i32:
            SAROpc = X86::SAR32ri;
            SHROpc = X86::SHR32ri;
            ADDOpc = X86::ADD32rr;
            NEGOpc = X86::NEG32r;
            break;
          }
          BuildMI(BB, SAROpc, 2, TmpReg).addReg(Tmp1).addImm(Log-1);
          unsigned TmpReg2 = MakeReg(N.getValueType());
          BuildMI(BB, SHROpc, 2, TmpReg2).addReg(TmpReg).addImm(32-Log);
          unsigned TmpReg3 = MakeReg(N.getValueType());
          BuildMI(BB, ADDOpc, 2, TmpReg3).addReg(Tmp1).addReg(TmpReg2);
          
          unsigned TmpReg4 = isNeg ? MakeReg(N.getValueType()) : Result;
          BuildMI(BB, SAROpc, 2, TmpReg4).addReg(TmpReg3).addImm(Log);
          if (isNeg)
            BuildMI(BB, NEGOpc, 1, Result).addReg(TmpReg4);
          return Result;
        }
      }

    Tmp2 = SelectExpr(N.getOperand(1));

    bool isSigned = N.getOpcode() == ISD::SDIV || N.getOpcode() == ISD::SREM;
    bool isDiv    = N.getOpcode() == ISD::SDIV || N.getOpcode() == ISD::UDIV;
    unsigned LoReg, HiReg, DivOpcode, MovOpcode, ClrOpcode, SExtOpcode;
    switch (N.getValueType()) {
    default: assert(0 && "Cannot sdiv this type!");
    case MVT::i8:
      DivOpcode = isSigned ? X86::IDIV8r : X86::DIV8r;
      LoReg = X86::AL;
      HiReg = X86::AH;
      MovOpcode = X86::MOV8rr;
      ClrOpcode = X86::MOV8ri;
      SExtOpcode = X86::CBW;
      break;
    case MVT::i16:
      DivOpcode = isSigned ? X86::IDIV16r : X86::DIV16r;
      LoReg = X86::AX;
      HiReg = X86::DX;
      MovOpcode = X86::MOV16rr;
      ClrOpcode = X86::MOV16ri;
      SExtOpcode = X86::CWD;
      break;
    case MVT::i32:
      DivOpcode = isSigned ? X86::IDIV32r : X86::DIV32r;
      LoReg =X86::EAX;
      HiReg = X86::EDX;
      MovOpcode = X86::MOV32rr;
      ClrOpcode = X86::MOV32ri;
      SExtOpcode = X86::CDQ;
      break;
    case MVT::i64: assert(0 && "FIXME: implement i64 DIV/REM libcalls!");
    case MVT::f32: 
    case MVT::f64:
      ContainsFPCode = true;
      if (N.getOpcode() == ISD::SDIV)
        BuildMI(BB, X86::FpDIV, 2, Result).addReg(Tmp1).addReg(Tmp2);
      else
        assert(0 && "FIXME: Emit frem libcall to fmod!");
      return Result;
    }

    // Set up the low part.
    BuildMI(BB, MovOpcode, 1, LoReg).addReg(Tmp1);

    if (isSigned) {
      // Sign extend the low part into the high part.
      BuildMI(BB, SExtOpcode, 0);
    } else {
      // Zero out the high part, effectively zero extending the input.
      BuildMI(BB, ClrOpcode, 1, HiReg).addImm(0);
    }

    // Emit the DIV/IDIV instruction.
    BuildMI(BB, DivOpcode, 1).addReg(Tmp2);    

    // Get the result of the divide or rem.
    BuildMI(BB, MovOpcode, 1, Result).addReg(isDiv ? LoReg : HiReg);
    return Result;
  }

  case ISD::SHL:
    Tmp1 = SelectExpr(N.getOperand(0));
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      switch (N.getValueType()) {
      default: assert(0 && "Cannot shift this type!");
      case MVT::i8:  Opc = X86::SHL8ri; break;
      case MVT::i16: Opc = X86::SHL16ri; break;
      case MVT::i32: Opc = X86::SHL32ri; break;
      }
      BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(CN->getValue());
      return Result;
    }
    Tmp2 = SelectExpr(N.getOperand(1));
    switch (N.getValueType()) {
    default: assert(0 && "Cannot shift this type!");
    case MVT::i8 : Opc = X86::SHL8rCL; break;
    case MVT::i16: Opc = X86::SHL16rCL; break;
    case MVT::i32: Opc = X86::SHL32rCL; break;
    }
    BuildMI(BB, X86::MOV8rr, 1, X86::CL).addReg(Tmp2);
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;
  case ISD::SRL:
    Tmp1 = SelectExpr(N.getOperand(0));
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      switch (N.getValueType()) {
      default: assert(0 && "Cannot shift this type!");
      case MVT::i8:  Opc = X86::SHR8ri; break;
      case MVT::i16: Opc = X86::SHR16ri; break;
      case MVT::i32: Opc = X86::SHR32ri; break;
      }
      BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(CN->getValue());
      return Result;
    }
    Tmp2 = SelectExpr(N.getOperand(1));
    switch (N.getValueType()) {
    default: assert(0 && "Cannot shift this type!");
    case MVT::i8 : Opc = X86::SHR8rCL; break;
    case MVT::i16: Opc = X86::SHR16rCL; break;
    case MVT::i32: Opc = X86::SHR32rCL; break;
    }
    BuildMI(BB, X86::MOV8rr, 1, X86::CL).addReg(Tmp2);
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;
  case ISD::SRA:
    Tmp1 = SelectExpr(N.getOperand(0));
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      switch (N.getValueType()) {
      default: assert(0 && "Cannot shift this type!");
      case MVT::i8:  Opc = X86::SAR8ri; break;
      case MVT::i16: Opc = X86::SAR16ri; break;
      case MVT::i32: Opc = X86::SAR32ri; break;
      }
      BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(CN->getValue());
      return Result;
    }
    Tmp2 = SelectExpr(N.getOperand(1));
    switch (N.getValueType()) {
    default: assert(0 && "Cannot shift this type!");
    case MVT::i8 : Opc = X86::SAR8rCL; break;
    case MVT::i16: Opc = X86::SAR16rCL; break;
    case MVT::i32: Opc = X86::SAR32rCL; break;
    }
    BuildMI(BB, X86::MOV8rr, 1, X86::CL).addReg(Tmp2);
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;

  case ISD::SETCC:
    if (MVT::isFloatingPoint(N.getOperand(0).getValueType()))
      ContainsFPCode = true;
    EmitCMP(N.getOperand(0), N.getOperand(1));
    EmitSetCC(BB, Result, cast<SetCCSDNode>(N)->getCondition(),
              MVT::isFloatingPoint(N.getOperand(1).getValueType()));
    return Result;
  case ISD::LOAD: {
    Select(N.getOperand(0));

    // Make sure we generate both values.
    if (Result != 1)
      ExprMap[N.getValue(1)] = 1;   // Generate the token
    else
      Result = ExprMap[N.getValue(0)] = MakeReg(N.getValue(0).getValueType());

    switch (N.Val->getValueType(0)) {
    default: assert(0 && "Cannot load this type!");
    case MVT::i1:
    case MVT::i8:  Opc = X86::MOV8rm; break;
    case MVT::i16: Opc = X86::MOV16rm; break;
    case MVT::i32: Opc = X86::MOV32rm; break;
    case MVT::f32: Opc = X86::FLD32m; ContainsFPCode = true; break;
    case MVT::f64: Opc = X86::FLD64m; ContainsFPCode = true; break;
    }
    if (ConstantPoolSDNode *CP = dyn_cast<ConstantPoolSDNode>(N.getOperand(1))){
      addConstantPoolReference(BuildMI(BB, Opc, 4, Result), CP->getIndex());
    } else {
      X86AddressMode AM;
      SelectAddress(N.getOperand(1), AM);
      addFullAddress(BuildMI(BB, Opc, 4, Result), AM);
    }
    return Result;
  }
  case ISD::DYNAMIC_STACKALLOC:
    Select(N.getOperand(0));

    // Generate both result values.
    if (Result != 1)
      ExprMap[N.getValue(1)] = 1;   // Generate the token
    else
      Result = ExprMap[N.getValue(0)] = MakeReg(N.getValue(0).getValueType());

    // FIXME: We are currently ignoring the requested alignment for handling
    // greater than the stack alignment.  This will need to be revisited at some
    // point.  Align = N.getOperand(2);

    if (!isa<ConstantSDNode>(N.getOperand(2)) ||
        cast<ConstantSDNode>(N.getOperand(2))->getValue() != 0) {
      std::cerr << "Cannot allocate stack object with greater alignment than"
                << " the stack alignment yet!";
      abort();
    }
  
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      BuildMI(BB, X86::SUB32ri, 2, X86::ESP).addReg(X86::ESP)
        .addImm(CN->getValue());
    } else {
      Tmp1 = SelectExpr(N.getOperand(1));

      // Subtract size from stack pointer, thereby allocating some space.
      BuildMI(BB, X86::SUB32rr, 2, X86::ESP).addReg(X86::ESP).addReg(Tmp1);
    }

    // Put a pointer to the space into the result register, by copying the stack
    // pointer.
    BuildMI(BB, X86::MOV32rr, 1, Result).addReg(X86::ESP);
    return Result;

  case ISD::CALL:
    Select(N.getOperand(0));
    if (GlobalAddressSDNode *GASD =
               dyn_cast<GlobalAddressSDNode>(N.getOperand(1))) {
      BuildMI(BB, X86::CALLpcrel32, 1).addGlobalAddress(GASD->getGlobal(),true);
    } else if (ExternalSymbolSDNode *ESSDN =
               dyn_cast<ExternalSymbolSDNode>(N.getOperand(1))) {
      BuildMI(BB, X86::CALLpcrel32,
              1).addExternalSymbol(ESSDN->getSymbol(), true);
    } else {
      Tmp1 = SelectExpr(N.getOperand(1));
      BuildMI(BB, X86::CALL32r, 1).addReg(Tmp1);
    }
    switch (N.Val->getValueType(0)) {
    default: assert(0 && "Unknown value type for call result!");
    case MVT::Other: return 1;
    case MVT::i1:
    case MVT::i8:
      BuildMI(BB, X86::MOV8rr, 1, Result).addReg(X86::AL);
      break;
    case MVT::i16:
      BuildMI(BB, X86::MOV16rr, 1, Result).addReg(X86::AX);
      break;
    case MVT::i32:
      BuildMI(BB, X86::MOV32rr, 1, Result).addReg(X86::EAX);
      if (N.Val->getValueType(1) == MVT::i32)
        BuildMI(BB, X86::MOV32rr, 1, Result+1).addReg(X86::EDX);
      break;
    case MVT::f32:
    case MVT::f64:     // Floating-point return values live in %ST(0)
      ContainsFPCode = true;
      BuildMI(BB, X86::FpGETRESULT, 1, Result);
      break;
    }
    return Result+N.ResNo;
  }

  return 0;
}

void ISel::Select(SDOperand N) {
  unsigned Tmp1, Tmp2, Opc;

  // FIXME: Disable for our current expansion model!
  if (/*!N->hasOneUse() &&*/ !LoweredTokens.insert(N).second)
    return;  // Already selected.

  switch (N.getOpcode()) {
  default:
    N.Val->dump(); std::cerr << "\n";
    assert(0 && "Node not handled yet!");
  case ISD::EntryToken: return;  // Noop
  case ISD::CopyToReg:
    Select(N.getOperand(0));
    Tmp1 = SelectExpr(N.getOperand(1));
    Tmp2 = cast<CopyRegSDNode>(N)->getReg();
    
    if (Tmp1 != Tmp2) {
      switch (N.getOperand(1).getValueType()) {
      default: assert(0 && "Invalid type for operation!");
      case MVT::i1:
      case MVT::i8:  Opc = X86::MOV8rr; break;
      case MVT::i16: Opc = X86::MOV16rr; break;
      case MVT::i32: Opc = X86::MOV32rr; break;
      case MVT::f32:
      case MVT::f64: Opc = X86::FpMOV; break;
      }
      BuildMI(BB, Opc, 1, Tmp2).addReg(Tmp1);
    }
    return;
  case ISD::RET:
    Select(N.getOperand(0));
    switch (N.getNumOperands()) {
    default:
      assert(0 && "Unknown return instruction!");
    case 3:
      Tmp1 = SelectExpr(N.getOperand(1));
      Tmp2 = SelectExpr(N.getOperand(2));
      assert(N.getOperand(1).getValueType() == MVT::i32 &&
	     N.getOperand(2).getValueType() == MVT::i32 &&
	     "Unknown two-register value!");
      BuildMI(BB, X86::MOV32rr, 1, X86::EAX).addReg(Tmp1);
      BuildMI(BB, X86::MOV32rr, 1, X86::EDX).addReg(Tmp2);
      // Declare that EAX & EDX are live on exit.
      BuildMI(BB, X86::IMPLICIT_USE, 3).addReg(X86::EAX).addReg(X86::EDX)
	.addReg(X86::ESP);
      break;
    case 2:
      Tmp1 = SelectExpr(N.getOperand(1));
      switch (N.getOperand(1).getValueType()) {
      default: assert(0 && "All other types should have been promoted!!");
      case MVT::f64:
	BuildMI(BB, X86::FpSETRESULT, 1).addReg(Tmp1);
	// Declare that top-of-stack is live on exit
	BuildMI(BB, X86::IMPLICIT_USE, 2).addReg(X86::ST0).addReg(X86::ESP);
	break;
      case MVT::i32:
	BuildMI(BB, X86::MOV32rr, 1, X86::EAX).addReg(Tmp1);
	BuildMI(BB, X86::IMPLICIT_USE, 2).addReg(X86::EAX).addReg(X86::ESP);
	break;
      }
      break;
    case 1:
      break;
    }
    BuildMI(BB, X86::RET, 0); // Just emit a 'ret' instruction
    return;
  case ISD::BR: {
    Select(N.getOperand(0));
    MachineBasicBlock *Dest =
      cast<BasicBlockSDNode>(N.getOperand(1))->getBasicBlock();
    BuildMI(BB, X86::JMP, 1).addMBB(Dest);
    return;
  }

  case ISD::BRCOND: {
    Select(N.getOperand(0));
    MachineBasicBlock *Dest =
      cast<BasicBlockSDNode>(N.getOperand(2))->getBasicBlock();
    // Try to fold a setcc into the branch.  If this fails, emit a test/jne
    // pair.
    if (EmitBranchCC(Dest, N.getOperand(1))) {
      Tmp1 = SelectExpr(N.getOperand(1));
      BuildMI(BB, X86::TEST8rr, 2).addReg(Tmp1).addReg(Tmp1);
      BuildMI(BB, X86::JNE, 1).addMBB(Dest);
    }
    return;
  }
  case ISD::LOAD:
  case ISD::CALL:
  case ISD::DYNAMIC_STACKALLOC:
    SelectExpr(N);
    return;
  case ISD::STORE: {
    Select(N.getOperand(0));
    // Select the address.
    X86AddressMode AM;
    SelectAddress(N.getOperand(2), AM);

    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
      Opc = 0;
      switch (CN->getValueType(0)) {
      default: assert(0 && "Invalid type for operation!");
      case MVT::i1:
      case MVT::i8:  Opc = X86::MOV8mi; break;
      case MVT::i16: Opc = X86::MOV16mi; break;
      case MVT::i32: Opc = X86::MOV32mi; break;
      case MVT::f32:
      case MVT::f64: break;
      }
      if (Opc) {
        addFullAddress(BuildMI(BB, Opc, 4+1), AM).addImm(CN->getValue());
        return;
      }
    }
    Tmp1 = SelectExpr(N.getOperand(1));

    switch (N.getOperand(1).getValueType()) {
    default: assert(0 && "Cannot store this type!");
    case MVT::i1:
    case MVT::i8:  Opc = X86::MOV8mr; break;
    case MVT::i16: Opc = X86::MOV16mr; break;
    case MVT::i32: Opc = X86::MOV32mr; break;
    case MVT::f32: Opc = X86::FST32m; ContainsFPCode = true; break;
    case MVT::f64: Opc = X86::FST64m; ContainsFPCode = true; break;
    }
    addFullAddress(BuildMI(BB, Opc, 4+1), AM).addReg(Tmp1);
    return;
  }
  case ISD::ADJCALLSTACKDOWN:
  case ISD::ADJCALLSTACKUP:
    Select(N.getOperand(0));
    Tmp1 = cast<ConstantSDNode>(N.getOperand(1))->getValue();
    
    Opc = N.getOpcode() == ISD::ADJCALLSTACKDOWN ? X86::ADJCALLSTACKDOWN :
                                                   X86::ADJCALLSTACKUP;
    BuildMI(BB, Opc, 1).addImm(Tmp1);
    return;
  }
  assert(0 && "Should not be reached!");
}


/// createX86PatternInstructionSelector - This pass converts an LLVM function
/// into a machine code representation using pattern matching and a machine
/// description file.
///
FunctionPass *llvm::createX86PatternInstructionSelector(TargetMachine &TM) {
  return new ISel(TM);  
}