lib/Target/Alpha/AlphaISelPattern.cpp

//===- AlphaISelPattern.cpp - A pattern matching inst selector for Alpha -===//
// 
//                     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 Alpha.
//
//===----------------------------------------------------------------------===//

#include "Alpha.h"
#include "AlphaRegisterInfo.h"
#include "llvm/Constants.h"                   // FIXME: REMOVE
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineConstantPool.h" // FIXME: REMOVE
#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;

//===----------------------------------------------------------------------===//
//  AlphaTargetLowering - Alpha Implementation of the TargetLowering interface
namespace {
  class AlphaTargetLowering : public TargetLowering {
    int VarArgsFrameIndex;            // FrameIndex for start of varargs area.
    unsigned GP; //GOT vreg
  public:
    AlphaTargetLowering(TargetMachine &TM) : TargetLowering(TM) {
      // Set up the TargetLowering object.
      //I am having problems with shr n ubyte 1
      setShiftAmountType(MVT::i64); //are these needed?
      setSetCCResultType(MVT::i64); //are these needed?
      
      addRegisterClass(MVT::i64, Alpha::GPRCRegisterClass);
      addRegisterClass(MVT::f64, Alpha::FPRCRegisterClass);
      addRegisterClass(MVT::f32, Alpha::FPRCRegisterClass);

      setOperationAction(ISD::EXTLOAD          , MVT::i1   , Promote);

      setOperationAction(ISD::ZEXTLOAD         , MVT::i1   , Expand); //Should this be Promote?  Chris?
      setOperationAction(ISD::ZEXTLOAD         , MVT::i32  , Expand);

      setOperationAction(ISD::SEXTLOAD         , MVT::i1   , Expand); //Should this be Promote?  Chris?
      setOperationAction(ISD::SEXTLOAD         , MVT::i8   , Expand);
      setOperationAction(ISD::SEXTLOAD         , MVT::i16  , Expand);

      setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1, Expand); //what is the sign expansion of 1? 1 or -1?

      setOperationAction(ISD::SREM, MVT::f32, Expand);
      setOperationAction(ISD::SREM, MVT::f64, Expand);

     computeRegisterProperties();
      
     addLegalFPImmediate(+0.0); //F31
    }

    /// 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 std::pair<SDOperand, SDOperand>
    LowerCallTo(SDOperand Chain, const Type *RetTy, SDOperand Callee,
                ArgListTy &Args, SelectionDAG &DAG);

    virtual std::pair<SDOperand, SDOperand>
    LowerVAStart(SDOperand Chain, SelectionDAG &DAG);

    virtual std::pair<SDOperand,SDOperand>
    LowerVAArgNext(bool isVANext, SDOperand Chain, SDOperand VAList,
                   const Type *ArgTy, SelectionDAG &DAG);

    virtual std::pair<SDOperand, SDOperand>
    LowerFrameReturnAddress(bool isFrameAddr, SDOperand Chain, unsigned Depth,
                            SelectionDAG &DAG);

    void restoreGP(MachineBasicBlock* BB)
    {
      BuildMI(BB, Alpha::BIS, 2, Alpha::R29).addReg(GP).addReg(GP);
    }
  };
}

//http://www.cs.arizona.edu/computer.help/policy/DIGITAL_unix/AA-PY8AC-TET1_html/callCH3.html#BLOCK21

//For now, just use variable size stack frame format

//In a standard call, the first six items are passed in registers $16
//- $21 and/or registers $f16 - $f21. (See Section 4.1.2 for details
//of argument-to-register correspondence.) The remaining items are
//collected in a memory argument list that is a naturally aligned
//array of quadwords. In a standard call, this list, if present, must
//be passed at 0(SP).
//7 ... n  	  	  	0(SP) ... (n-7)*8(SP)

std::vector<SDOperand>
AlphaTargetLowering::LowerArguments(Function &F, SelectionDAG &DAG) 
{
  std::vector<SDOperand> ArgValues;
  
  // //#define FP    $15
  // //#define RA    $26
  // //#define PV    $27
  // //#define GP    $29
  // //#define SP    $30
  
  //  assert(0 && "TODO");
  MachineFunction &MF = DAG.getMachineFunction();
  MachineFrameInfo *MFI = MF.getFrameInfo();

  GP = MF.getSSARegMap()->createVirtualRegister(getRegClassFor(MVT::i64));
  MachineBasicBlock& BB = MF.front();

  //Handle the return address
  //BuildMI(&BB, Alpha::IDEF, 0, Alpha::R26);

  unsigned args_int[] = {Alpha::R16, Alpha::R17, Alpha::R18, 
			 Alpha::R19, Alpha::R20, Alpha::R21};
  unsigned args_float[] = {Alpha::F16, Alpha::F17, Alpha::F18, 
			   Alpha::F19, Alpha::F20, Alpha::F21};
  std::vector<unsigned> argVreg;
  std::vector<unsigned> argPreg;
  std::vector<unsigned> argOpc;
  int count = 0;
  for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I)
    {
      SDOperand newroot, argt;
      ++count;
      assert(count <= 6 && "More than 6 args not supported");
      switch (getValueType(I->getType())) {
      default: std::cerr << "Unknown Type " << getValueType(I->getType()) << "\n"; abort();
      case MVT::f64:
      case MVT::f32:
        BuildMI(&BB, Alpha::IDEF, 0, args_float[count - 1]);
        argVreg.push_back(MF.getSSARegMap()->createVirtualRegister(getRegClassFor(getValueType(I->getType()))));
        argPreg.push_back(args_float[count - 1]);
        argOpc.push_back(Alpha::CPYS);
        newroot = DAG.getCopyFromReg(argVreg[count], getValueType(I->getType()), DAG.getRoot());
        break;
      case MVT::i1:
      case MVT::i8:
      case MVT::i16:
      case MVT::i32:
      case MVT::i64:
        BuildMI(&BB, Alpha::IDEF, 0, args_int[count - 1]);
        argVreg.push_back(MF.getSSARegMap()->createVirtualRegister(getRegClassFor(MVT::i64)));
        argPreg.push_back(args_int[count - 1]);
        argOpc.push_back(Alpha::BIS);
        argt = newroot = DAG.getCopyFromReg(argVreg[count], MVT::i64, DAG.getRoot());
        if (getValueType(I->getType()) != MVT::i64)
          argt = DAG.getNode(ISD::TRUNCATE, getValueType(I->getType()), newroot);
        break;
      }
      DAG.setRoot(newroot.getValue(1));
      ArgValues.push_back(argt);
    }

  BuildMI(&BB, Alpha::IDEF, 0, Alpha::R29);
  BuildMI(&BB, Alpha::BIS, 2, GP).addReg(Alpha::R29).addReg(Alpha::R29);
  count = 0;
  for (int i = 0; i < count; ++i)
    BuildMI(&BB, argOpc[i], 2, argVreg[i]).addReg(argPreg[i]).addReg(argPreg[i]);
  
  return ArgValues;
}

std::pair<SDOperand, SDOperand>
AlphaTargetLowering::LowerCallTo(SDOperand Chain,
				 const Type *RetTy, SDOperand Callee,
				 ArgListTy &Args, SelectionDAG &DAG) {
  int NumBytes = 0;
  Chain = DAG.getNode(ISD::ADJCALLSTACKDOWN, MVT::Other, Chain,
		      DAG.getConstant(NumBytes, getPointerTy()));
  std::vector<SDOperand> args_to_use;
  for (unsigned i = 0, e = Args.size(); i != e; ++i)
    {
      switch (getValueType(Args[i].second)) {
      default: assert(0 && "Unexpected ValueType for argument!");
      case MVT::i1:
      case MVT::i8:
      case MVT::i16:
      case MVT::i32:
        // Promote the integer to 64 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::i64, Args[i].first);
        else
          Args[i].first = DAG.getNode(ISD::ZERO_EXTEND, MVT::i64, Args[i].first);
        break;
      case MVT::i64:
        break;
      }
      args_to_use.push_back(Args[i].first);
    }
  
  std::vector<MVT::ValueType> RetVals;
  MVT::ValueType RetTyVT = getValueType(RetTy);
  if (RetTyVT != MVT::isVoid)
    RetVals.push_back(RetTyVT);
  RetVals.push_back(MVT::Other);

  SDOperand TheCall = SDOperand(DAG.getCall(RetVals, Chain, Callee, args_to_use), 0);
  Chain = TheCall.getValue(RetTyVT != MVT::isVoid);
  Chain = DAG.getNode(ISD::ADJCALLSTACKUP, MVT::Other, Chain,
                      DAG.getConstant(NumBytes, getPointerTy()));
   return std::make_pair(TheCall, Chain);
}

std::pair<SDOperand, SDOperand>
AlphaTargetLowering::LowerVAStart(SDOperand Chain, SelectionDAG &DAG) {
  //vastart just returns the address of the VarArgsFrameIndex slot.
  return std::make_pair(DAG.getFrameIndex(VarArgsFrameIndex, MVT::i64), Chain);
}

std::pair<SDOperand,SDOperand> AlphaTargetLowering::
LowerVAArgNext(bool isVANext, SDOperand Chain, SDOperand VAList,
                const Type *ArgTy, SelectionDAG &DAG) {
  abort();
}
               

std::pair<SDOperand, SDOperand> AlphaTargetLowering::
LowerFrameReturnAddress(bool isFrameAddress, SDOperand Chain, unsigned Depth,
                        SelectionDAG &DAG) {
  abort();
}





namespace {

  //===--------------------------------------------------------------------===//
  /// ISel - Alpha specific code to select Alpha machine instructions for
  /// SelectionDAG operations.
  ///
  class ISel : public SelectionDAGISel {

    /// AlphaLowering - This object fully describes how to lower LLVM code to an
    /// Alpha-specific SelectionDAG.
    AlphaTargetLowering AlphaLowering;


    /// 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;

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

    /// InstructionSelectBasicBlock - This callback is invoked by
    /// SelectionDAGISel when it has created a SelectionDAG for us to codegen.
    virtual void InstructionSelectBasicBlock(SelectionDAG &DAG) {
      // Codegen the basic block.
      Select(DAG.getRoot());

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

    unsigned SelectExpr(SDOperand N);
    unsigned SelectExprFP(SDOperand N, unsigned Result);
    void Select(SDOperand N);
  };
}

unsigned ISel::SelectExprFP(SDOperand N, unsigned Result)
{
  unsigned Tmp1, Tmp2, Tmp3;
  unsigned Opc = 0;
  SDNode *Node = N.Val;
  MVT::ValueType DestType = N.getValueType();
  unsigned opcode = N.getOpcode();

  switch (opcode) {
  default:
    Node->dump();
    assert(0 && "Node not handled!\n");
    
  case ISD::ConstantFP:
    if (ConstantFPSDNode *CN = dyn_cast<ConstantFPSDNode>(N)) {
      if (CN->isExactlyValue(+0.0)) {
        BuildMI(BB, Alpha::CPYS, 2, Result).addReg(Alpha::F31).addReg(Alpha::F31);
      } else {
        abort();
      }
    }
    return Result;
    
  case ISD::MUL:
  case ISD::ADD:
  case ISD::SUB:
  case ISD::SDIV:
    switch( opcode ) {
    case ISD::MUL: Opc = DestType == MVT::f64 ? Alpha::MULT : Alpha::MULS; break;
    case ISD::ADD: Opc = DestType == MVT::f64 ? Alpha::ADDT : Alpha::ADDS; break;
    case ISD::SUB: Opc = DestType == MVT::f64 ? Alpha::SUBT : Alpha::SUBS; break;
    case ISD::SDIV: Opc = DestType == MVT::f64 ? Alpha::DIVT : Alpha::DIVS; break;
    };
    Tmp1 = SelectExpr(N.getOperand(0));
    Tmp2 = SelectExpr(N.getOperand(1));
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;

  case ISD::SINT_TO_FP:
    {
      assert (N.getOperand(0).getValueType() == MVT::i64 && "only quads can be loaded from");
      Tmp1 = SelectExpr(N.getOperand(0));  // Get the operand register
      Tmp2 = MakeReg(DestType);
      //so these instructions are not supported on ev56
      Opc = DestType == MVT::f64 ? Alpha::ITOFT : Alpha::ITOFS;
      BuildMI(BB,  Opc, 1, Tmp2).addReg(Tmp1);
      Opc = DestType == MVT::f64 ? Alpha::CVTQT : Alpha::CVTQS;
      BuildMI(BB, Opc, 1, Result).addReg(Tmp1);
      return Result;
    }
  }
  assert(0 && "should not get here");
  return 0;
}

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

  SDNode *Node = N.Val;
  MVT::ValueType DestType = N.getValueType();

  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 (Node->getNumValues() == 1)
      Reg = Result = 1;  // Void call, just a chain.
    else {
      Result = MakeReg(Node->getValueType(0));
      ExprMap[N.getValue(0)] = Result;
      for (unsigned i = 1, e = N.Val->getNumValues()-1; i != e; ++i)
        ExprMap[N.getValue(i)] = MakeReg(Node->getValueType(i));
      ExprMap[SDOperand(Node, Node->getNumValues()-1)] = 1;
    }
  }

  if (DestType == MVT::f64 || DestType == MVT::f32)
    return SelectExprFP(N, Result);

  switch (opcode) {
  default:
    Node->dump();
    assert(0 && "Node not handled!\n");
 
  case ISD::FrameIndex:
    Tmp1 = cast<FrameIndexSDNode>(N)->getIndex();
    BuildMI(BB, Alpha::LDA, 2, Result).addImm(Tmp1 * 8).addReg(Alpha::R30);
    return Result;
  
  case ISD::EXTLOAD:
    // 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());
    
    Select(Node->getOperand(0)); // chain
    Tmp1 = SelectExpr(Node->getOperand(1));
    
    switch(Node->getValueType(0)) {
    default: Node->dump(); assert(0 && "Unknown type to sign extend to.");
    case MVT::i64:
      switch (cast<MVTSDNode>(Node)->getExtraValueType()) {
      default:
	Node->dump();
	assert(0 && "Bad extend load!");
      case MVT::i64:
	BuildMI(BB, Alpha::LDQ, 2, Result).addImm(0).addReg(Tmp1);
	break;
      case MVT::i32:
	BuildMI(BB, Alpha::LDL, 2, Result).addImm(0).addReg(Tmp1);
        break;
      case MVT::i16:
	BuildMI(BB, Alpha::LDWU, 2, Result).addImm(0).addReg(Tmp1);
        break;
      case MVT::i1: //Treat i1 as i8 since there are problems otherwise
      case MVT::i8:
	BuildMI(BB, Alpha::LDBU, 2, Result).addImm(0).addReg(Tmp1);
        break;
      }
      break;
    }
    return Result;

  case ISD::SEXTLOAD:
    // 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());
    
    Select(Node->getOperand(0)); // chain
    Tmp1 = SelectExpr(Node->getOperand(1));
    switch(Node->getValueType(0)) {
    default: Node->dump(); assert(0 && "Unknown type to sign extend to.");
    case MVT::i64:
      switch (cast<MVTSDNode>(Node)->getExtraValueType()) {
      default:
	Node->dump();
	assert(0 && "Bad sign extend!");
      case MVT::i32:
	BuildMI(BB, Alpha::LDL, 2, Result).addImm(0).addReg(Tmp1);
        break;
      }
      break;
    }
    return Result;

  case ISD::ZEXTLOAD:
    // 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());
    
    Select(Node->getOperand(0)); // chain
    Tmp1 = SelectExpr(Node->getOperand(1));
    switch(Node->getValueType(0)) {
    default: Node->dump(); assert(0 && "Unknown type to zero extend to.");
    case MVT::i64:
      switch (cast<MVTSDNode>(Node)->getExtraValueType()) {
      default:
	Node->dump();
	assert(0 && "Bad sign extend!");
      case MVT::i16:
	BuildMI(BB, Alpha::LDWU, 2, Result).addImm(0).addReg(Tmp1);
        break;
      case MVT::i8:
	BuildMI(BB, Alpha::LDBU, 2, Result).addImm(0).addReg(Tmp1);
        break;
      }
      break;
    }
    return Result;


  case ISD::GlobalAddress:
    AlphaLowering.restoreGP(BB);
    BuildMI(BB, Alpha::LOAD_ADDR, 1, Result)
      .addGlobalAddress(cast<GlobalAddressSDNode>(N)->getGlobal());
    return Result;

  case ISD::CALL:
    {
      Select(N.getOperand(0));
      
      // The chain for this call is now lowered.
      ExprMap.insert(std::make_pair(N.getValue(Node->getNumValues()-1), 1));
      
      //grab the arguments
      std::vector<unsigned> argvregs;
      assert(Node->getNumOperands() < 8 && "Only 6 args supported");
      for(int i = 2, e = Node->getNumOperands(); i < e; ++i)
	  argvregs.push_back(SelectExpr(N.getOperand(i)));
      
      for(int i = 0, e = argvregs.size(); i < e; ++i)
	{
	  unsigned args_int[] = {Alpha::R16, Alpha::R17, Alpha::R18, 
				 Alpha::R19, Alpha::R20, Alpha::R21};
	  unsigned args_float[] = {Alpha::F16, Alpha::F17, Alpha::F18, 
				   Alpha::F19, Alpha::F20, Alpha::F21};
	  switch(N.getOperand(i+2).getValueType()) {
	  default: 
	    Node->dump(); 
	    N.getOperand(i).Val->dump();
	    std::cerr << "Type for " << i << " is: " << N.getOperand(i+2).getValueType() << "\n";
	    assert(0 && "Unknown value type for call");
	  case MVT::i1:
	  case MVT::i8:
	  case MVT::i16:
	  case MVT::i32:
	  case MVT::i64:
	    BuildMI(BB, Alpha::BIS, 2, args_int[i]).addReg(argvregs[i]).addReg(argvregs[i]);
	    break;
	  case MVT::f32:
	  case MVT::f64:
	    BuildMI(BB, Alpha::CPYS, 2, args_float[i]).addReg(argvregs[i]).addReg(argvregs[i]);
	    break;
	  }
	  
	}
      //build the right kind of call
      if (GlobalAddressSDNode *GASD =
	  dyn_cast<GlobalAddressSDNode>(N.getOperand(1))) 
	{
	  AlphaLowering.restoreGP(BB);
	  BuildMI(BB, Alpha::CALL, 1).addGlobalAddress(GASD->getGlobal(),true);
	} 
      else if (ExternalSymbolSDNode *ESSDN =
	       dyn_cast<ExternalSymbolSDNode>(N.getOperand(1))) 
	{
	  AlphaLowering.restoreGP(BB);
	  BuildMI(BB, Alpha::CALL, 0).addExternalSymbol(ESSDN->getSymbol(), true);
	} 
      else 
	{
	  Tmp1 = SelectExpr(N.getOperand(1));
	  BuildMI(BB, Alpha::CALL, 1).addReg(Tmp1);
	  AlphaLowering.restoreGP(BB);
	}
      
      //push the result into a virtual register
      //    if (Result != 1)
      //      BuildMI(BB, Alpha::BIS, 2, Result).addReg(Alpha::R0).addReg(Alpha::R0);
      
      switch (Node->getValueType(0)) {
      default: Node->dump(); assert(0 && "Unknown value type for call result!");
      case MVT::Other: return 1;
      case MVT::i1:
      case MVT::i8:
      case MVT::i16:
      case MVT::i32:
      case MVT::i64:
	BuildMI(BB, Alpha::BIS, 2, Result).addReg(Alpha::R0).addReg(Alpha::R0);
	break;
      case MVT::f32:
      case MVT::f64:
	BuildMI(BB, Alpha::CPYS, 2, Result).addReg(Alpha::F0).addReg(Alpha::F0);
	break;
      }
      return Result+N.ResNo;
    }    
    
  case ISD::SIGN_EXTEND:
    abort();
    
  case ISD::SIGN_EXTEND_INREG:
    {
      Tmp1 = SelectExpr(N.getOperand(0));
      MVTSDNode* MVN = dyn_cast<MVTSDNode>(Node);
      //std::cerr << "SrcT: " << MVN->getExtraValueType() << "\n";
      switch(MVN->getExtraValueType())
        {
        default:
          Node->dump();
          assert(0 && "Sign Extend InReg not there yet");
          break;
        case MVT::i32:
          {
            BuildMI(BB, Alpha::ADDLi, 2, Result).addReg(Tmp1).addImm(0);
            break;
          }
        case MVT::i16:
          BuildMI(BB, Alpha::SEXTW, 1, Result).addReg(Tmp1);
          break;
        case MVT::i8:
          BuildMI(BB, Alpha::SEXTB, 1, Result).addReg(Tmp1);
          break;
        }
      return Result;
    }
  case ISD::ZERO_EXTEND_INREG:
    {
      Tmp1 = SelectExpr(N.getOperand(0));
      MVTSDNode* MVN = dyn_cast<MVTSDNode>(Node);
      //std::cerr << "SrcT: " << MVN->getExtraValueType() << "\n";
      switch(MVN->getExtraValueType())
        {
        default:
          Node->dump();
          assert(0 && "Zero Extend InReg not there yet");
          break;
        case MVT::i32: Tmp2 = 0xf0; break;
        case MVT::i16: Tmp2 = 0xfc; break;
        case MVT::i8: Tmp2 = 0xfe; break;
        case MVT::i1: //handle this one special
          BuildMI(BB, Alpha::ANDi, 2, Result).addReg(Tmp1).addImm(1);
          return Result;
        }
      BuildMI(BB, Alpha::ZAPi, 2, Result).addReg(Tmp1).addImm(Tmp2);
      return Result;
    }
    
  case ISD::SETCC:
    {
      if (SetCCSDNode *SetCC = dyn_cast<SetCCSDNode>(Node)) {
        if (MVT::isInteger(SetCC->getOperand(0).getValueType())) {
          bool isConst1 = false;
          bool isConst2 = false;
          int dir;

          //Tmp1 = SelectExpr(N.getOperand(0));
          if(N.getOperand(0).getOpcode() == ISD::Constant &&
             cast<ConstantSDNode>(N.getOperand(0))->getValue() >= 0 &&
             cast<ConstantSDNode>(N.getOperand(0))->getValue() <= 255)
            isConst1 = true;
          if(N.getOperand(1).getOpcode() == ISD::Constant &&
             cast<ConstantSDNode>(N.getOperand(1))->getValue() >= 0 &&
             cast<ConstantSDNode>(N.getOperand(1))->getValue() <= 255)
            isConst2 = true;

          switch (SetCC->getCondition()) {
          default: Node->dump(); assert(0 && "Unknown integer comparison!");
          case ISD::SETEQ: Opc = Alpha::CMPEQ; dir=0; break;
          case ISD::SETLT: Opc = isConst2 ? Alpha::CMPLTi : Alpha::CMPLT; dir = 1; break;
          case ISD::SETLE: Opc = isConst2 ? Alpha::CMPLEi : Alpha::CMPLE; dir = 1; break;
          case ISD::SETGT: Opc = isConst1 ? Alpha::CMPLTi : Alpha::CMPLT; dir = 2; break;
          case ISD::SETGE: Opc = isConst1 ? Alpha::CMPLEi : Alpha::CMPLE; dir = 2; break;
          case ISD::SETULT: Opc = isConst2 ? Alpha::CMPULTi : Alpha::CMPULT; dir = 1; break;
          case ISD::SETUGT: Opc = isConst1 ? Alpha::CMPULTi : Alpha::CMPULT; dir = 2; break;
          case ISD::SETULE: Opc = isConst2 ? Alpha::CMPULEi : Alpha::CMPULE; dir = 1; break;
          case ISD::SETUGE: Opc = isConst1 ? Alpha::CMPULEi : Alpha::CMPULE; dir = 2; break;
          case ISD::SETNE: {//Handle this one special
            //std::cerr << "Alpha does not have a setne.\n";
            //abort();
            Tmp1 = SelectExpr(N.getOperand(0));
            Tmp2 = SelectExpr(N.getOperand(1));
            Tmp3 = MakeReg(MVT::i64);
            BuildMI(BB, Alpha::CMPEQ, 2, Tmp3).addReg(Tmp1).addReg(Tmp2);
            //and invert
            BuildMI(BB,Alpha::ORNOT, 2, Result).addReg(Alpha::R31).addReg(Tmp3);
            return Result;
          }
          }
          if (dir == 1) {
            Tmp1 = SelectExpr(N.getOperand(0));
            if (isConst2) {
              Tmp2 = cast<ConstantSDNode>(N.getOperand(1))->getValue();
              BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(Tmp2);
            } else {
              Tmp2 = SelectExpr(N.getOperand(1));
              BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
            }
          } else if (dir == 2) {
            Tmp1 = SelectExpr(N.getOperand(1));
            if (isConst1) {
              Tmp2 = cast<ConstantSDNode>(N.getOperand(0))->getValue();
              BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(Tmp2);
            } else {
              Tmp2 = SelectExpr(N.getOperand(0));
              BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
            }
          } else { //dir == 0
            if (isConst1) {
              Tmp1 = cast<ConstantSDNode>(N.getOperand(0))->getValue();
              Tmp2 = SelectExpr(N.getOperand(1));
              BuildMI(BB, Alpha::CMPEQi, 2, Result).addReg(Tmp2).addImm(Tmp1);
            } else if (isConst2) {
              Tmp1 = SelectExpr(N.getOperand(0));
              Tmp2 = cast<ConstantSDNode>(N.getOperand(1))->getValue();
              BuildMI(BB, Alpha::CMPEQi, 2, Result).addReg(Tmp1).addImm(Tmp2);
            } else {
              Tmp1 = SelectExpr(N.getOperand(0));
              Tmp2 = SelectExpr(N.getOperand(1));
              BuildMI(BB, Alpha::CMPEQ, 2, Result).addReg(Tmp1).addReg(Tmp2);
            }
          }
        }
        else
          {
            Node->dump();
            assert(0 && "only integer");
          }
      }
      else
        {
          Node->dump();
          assert(0 && "Not a setcc in setcc");
        }
      return Result;
    }
    
  case ISD::CopyFromReg:
    {
      // 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());
        
      SDOperand Chain   = N.getOperand(0);

      Select(Chain);
      unsigned r = dyn_cast<RegSDNode>(Node)->getReg();
      //std::cerr << "CopyFromReg " << Result << " = " << r << "\n";
      BuildMI(BB, Alpha::BIS, 2, Result).addReg(r).addReg(r);
      return Result;
    }

    //Most of the plain arithmetic and logic share the same form, and the same 
    //constant immediate test
  case ISD::AND:
  case ISD::OR:
  case ISD::XOR:
  case ISD::SHL:
  case ISD::SRL:
  case ISD::MUL:
    assert (DestType == MVT::i64 && "Only do arithmetic on i64s!");
    if(N.getOperand(1).getOpcode() == ISD::Constant &&
       cast<ConstantSDNode>(N.getOperand(1))->getValue() >= 0 &&
       cast<ConstantSDNode>(N.getOperand(1))->getValue() <= 255)
      {
        switch(opcode) {
        case ISD::AND: Opc = Alpha::ANDi; break;
        case ISD::OR:  Opc = Alpha::BISi; break;
        case ISD::XOR: Opc = Alpha::XORi; break;
        case ISD::SHL: Opc = Alpha::SLi; break;
        case ISD::SRL: Opc = Alpha::SRLi; break;
        case ISD::SRA: Opc = Alpha::SRAi; break;
        case ISD::MUL: Opc = Alpha::MULQi; break;
        };
        Tmp1 = SelectExpr(N.getOperand(0));
        Tmp2 = cast<ConstantSDNode>(N.getOperand(1))->getValue();
        BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(Tmp2);
      }
    else
      {
        switch(opcode) {
        case ISD::AND: Opc = Alpha::AND; break;
        case ISD::OR:  Opc = Alpha::BIS; break;
        case ISD::XOR: Opc = Alpha::XOR; break;
        case ISD::SHL: Opc = Alpha::SL; break;
        case ISD::SRL: Opc = Alpha::SRL; break;
        case ISD::SRA: Opc = Alpha::SRA; break;
        case ISD::MUL: Opc = Alpha::MULQ; break;
        };
        Tmp1 = SelectExpr(N.getOperand(0));
        Tmp2 = SelectExpr(N.getOperand(1));
        BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
      }
    return Result;
    
  case ISD::ADD:
  case ISD::SUB:
    {
      bool isAdd = opcode == ISD::ADD;

      //FIXME: first check for Scaled Adds and Subs!
      if(N.getOperand(1).getOpcode() == ISD::Constant &&
         cast<ConstantSDNode>(N.getOperand(1))->getValue() >= 0 &&
         cast<ConstantSDNode>(N.getOperand(1))->getValue() <= 255)
        { //Normal imm add/sub
          Opc = isAdd ? Alpha::ADDQi : Alpha::SUBQi;
          Tmp1 = SelectExpr(N.getOperand(0));
          Tmp2 = cast<ConstantSDNode>(N.getOperand(1))->getValue();
          BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addImm(Tmp2);
        }
      else if(N.getOperand(1).getOpcode() == ISD::Constant &&
              cast<ConstantSDNode>(N.getOperand(1))->getValue() >= 0 &&
              cast<ConstantSDNode>(N.getOperand(1))->getValue() <= 32767)
        { //LDA  //FIXME: expand the above condition a bit
          Tmp1 = SelectExpr(N.getOperand(0));
          Tmp2 = cast<ConstantSDNode>(N.getOperand(1))->getValue();
          if (!isAdd)
            Tmp2 = -Tmp2;
          BuildMI(BB, Alpha::LDA, 2, Result).addImm(Tmp2).addReg(Tmp1);
        }
      else
        { //Normal add/sub
          Opc = isAdd ? Alpha::ADDQ : Alpha::SUBQ;
          Tmp1 = SelectExpr(N.getOperand(0));
          Tmp2 = SelectExpr(N.getOperand(1));
          BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
        }
      return Result;
    }

  case ISD::UREM:
  case ISD::SREM:
  case ISD::SDIV:
  case ISD::UDIV:
    //FIXME: alpha really doesn't support any of these operations, 
    // the ops are expanded into special library calls with
    // special calling conventions
    switch(opcode) {
    case ISD::UREM: Opc = Alpha::REMQU; break;
    case ISD::SREM: Opc = Alpha::REMQ; break;
    case ISD::UDIV: Opc = Alpha::DIVQU; break;
    case ISD::SDIV: Opc = Alpha::DIVQ; break;
    }
    Tmp1 = SelectExpr(N.getOperand(0));
    Tmp2 = SelectExpr(N.getOperand(1));
    BuildMI(BB, Opc, 2, Result).addReg(Tmp1).addReg(Tmp2);
    return Result;
//     //  case ISD::UINT_TO_FP:

//   case ISD::FP_TO_SINT:
//     assert (N.getValueType() == MVT::f64 && "Only can convert for doubles");
//     Tmp1 = SelectExpr(N.getOperand(0));  // Get the operand register
//     Tmp2 = MakeReg(SrcTy);
//     BuildMI(BB, CVTTQ, 1, Tmp2).addReg(Tmp1);
//     BuildMI(BB, FTOIT, 1, Result).addReg(Tmp2);
//     return result;

//     //  case ISD::FP_TO_UINT: 
 
  case ISD::SELECT:
    {
      Tmp2 = SelectExpr(N.getOperand(1)); //Use if TRUE
      Tmp3 = SelectExpr(N.getOperand(2)); //Use if FALSE
      Tmp1 = SelectExpr(N.getOperand(0)); //Cond
      // Get the condition into the zero flag.
      unsigned dummy = MakeReg(MVT::i64);
      BuildMI(BB, Alpha::BIS, 2, dummy).addReg(Tmp3).addReg(Tmp3);
      BuildMI(BB, Alpha::CMOVEQ, 2, Result).addReg(Tmp2).addReg(Tmp1);
      return Result;
    }

  case ISD::Constant:
    {
      long val = cast<ConstantSDNode>(N)->getValue();
      BuildMI(BB, Alpha::LOAD_IMM, 1, Result).addImm(val);
      return Result;
    }

  case ISD::LOAD: 
    {
      // 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());
      
      SDOperand Chain   = N.getOperand(0);
      SDOperand Address = N.getOperand(1);

      if (Address.getOpcode() == ISD::GlobalAddress)
	{
	  Select(Chain);
	  AlphaLowering.restoreGP(BB);
	  BuildMI(BB, Alpha::LOAD, 1, Result).addGlobalAddress(cast<GlobalAddressSDNode>(Address)->getGlobal());
	}
      else
	{
	  Select(Chain);
	  Tmp2 = SelectExpr(Address);
	  BuildMI(BB, Alpha::LDQ, 2, Result).addImm(0).addReg(Tmp2);
	}
      return Result;
    }
  }

  return 0;
}

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

  // FIXME: Disable for our current expansion model!
  if (/*!N->hasOneUse() &&*/ !ExprMap.insert(std::make_pair(N, 1)).second)
    return;  // Already selected.

  SDNode *Node = N.Val;

  switch (N.getOpcode()) {

  default:
    Node->dump(); std::cerr << "\n";
    assert(0 && "Node not handled yet!");

  case ISD::BRCOND: {
    MachineBasicBlock *Dest =
      cast<BasicBlockSDNode>(N.getOperand(2))->getBasicBlock();

    Select(N.getOperand(0));
    Tmp1 = SelectExpr(N.getOperand(1));
    BuildMI(BB, Alpha::BNE, 2).addReg(Tmp1).addMBB(Dest);
    return;
  }

  case ISD::BR: {
    MachineBasicBlock *Dest =
      cast<BasicBlockSDNode>(N.getOperand(1))->getBasicBlock();

    Select(N.getOperand(0));
    BuildMI(BB, Alpha::BR, 1, Alpha::R31).addMBB(Dest);
    return;
  }

  case ISD::ImplicitDef:
    Select(N.getOperand(0));
    BuildMI(BB, Alpha::IDEF, 0, cast<RegSDNode>(N)->getReg());
    return;
    
  case ISD::EntryToken: return;  // Noop

  case ISD::TokenFactor:
    for (unsigned i = 0, e = Node->getNumOperands(); i != e; ++i)
      Select(Node->getOperand(i));
    
    //N.Val->dump(); std::cerr << "\n";
    //assert(0 && "Node not handled yet!");
    
    return;

  case ISD::CopyToReg:
    Select(N.getOperand(0));
    Tmp1 = SelectExpr(N.getOperand(1));
    Tmp2 = cast<RegSDNode>(N)->getReg();
    
    if (Tmp1 != Tmp2) {
      BuildMI(BB, Alpha::BIS, 2, Tmp2).addReg(Tmp1).addReg(Tmp1);
    }
    return;

   case ISD::RET:
     switch (N.getNumOperands()) {
     default:
       std::cerr << N.getNumOperands() << "\n";
       for (unsigned i = 0; i < N.getNumOperands(); ++i)
	 std::cerr << N.getOperand(i).getValueType() << "\n";
       Node->dump();
       assert(0 && "Unknown return instruction!");
     case 2:
       Select(N.getOperand(0));
       Tmp1 = SelectExpr(N.getOperand(1));
       switch (N.getOperand(1).getValueType()) {
       default: Node->dump(); assert(0 && "All other types should have been promoted!!");
       case MVT::f64:
       case MVT::f32:
	 BuildMI(BB, Alpha::CPYS, 2, Alpha::F0).addReg(Tmp1).addReg(Tmp1);
	 break;
       case MVT::i32:
       case MVT::i64:
	 BuildMI(BB, Alpha::BIS, 2, Alpha::R0).addReg(Tmp1).addReg(Tmp1);
	 break;
       }
       break;
     case 1:
       Select(N.getOperand(0));
       break;
     }
     //Tmp2 = AlphaLowering.getRetAddr();
     //BuildMI(BB, Alpha::BIS, 2, Alpha::R26).addReg(Tmp2).addReg(Tmp2);
     BuildMI(BB, Alpha::RETURN, 0); // Just emit a 'ret' instruction
     return;

  case ISD::STORE: 
    Select(N.getOperand(0));
    Tmp1 = SelectExpr(N.getOperand(1)); //value
    if (N.getOperand(2).getOpcode() == ISD::GlobalAddress)
      {
	AlphaLowering.restoreGP(BB);
	BuildMI(BB, Alpha::STORE, 2).addReg(Tmp1).addGlobalAddress(cast<GlobalAddressSDNode>(N.getOperand(2))->getGlobal());
      }
    else
      {
	Tmp2 = SelectExpr(N.getOperand(2)); //address
	BuildMI(BB, Alpha::STQ, 3).addReg(Tmp1).addImm(0).addReg(Tmp2);
      }
    return;

  case ISD::EXTLOAD:
  case ISD::SEXTLOAD:
  case ISD::ZEXTLOAD:
  case ISD::LOAD:
  case ISD::CopyFromReg:
  case ISD::CALL:
//   case ISD::DYNAMIC_STACKALLOC:
    ExprMap.erase(N);
    SelectExpr(N);
    return;


  case ISD::TRUNCSTORE: {  // truncstore chain, val, ptr :storety
    MVT::ValueType StoredTy = cast<MVTSDNode>(Node)->getExtraValueType();
    if (StoredTy == MVT::i64) {
      Node->dump();
      assert(StoredTy != MVT::i64 && "Unsupported TRUNCSTORE for this target!");
    }

    Select(N.getOperand(0));
    Tmp1 = SelectExpr(N.getOperand(1));
    Tmp2 = SelectExpr(N.getOperand(2));

    switch (StoredTy) {
    default: Node->dump(); assert(0 && "Unhandled Type"); break;
    case MVT::i1: //FIXME: DAG does not promote this load
    case MVT::i8: Opc = Alpha::STB; break;
    case MVT::i16: Opc = Alpha::STW; break;
    case MVT::i32: Opc = Alpha::STL; break;
    }

    BuildMI(BB, Opc, 2).addReg(Tmp1).addImm(0).addReg(Tmp2);
    return;
  }

  case ISD::ADJCALLSTACKDOWN:
  case ISD::ADJCALLSTACKUP:
    Select(N.getOperand(0));
    Tmp1 = cast<ConstantSDNode>(N.getOperand(1))->getValue();
    
    Opc = N.getOpcode() == ISD::ADJCALLSTACKDOWN ? Alpha::ADJUSTSTACKDOWN :
      Alpha::ADJUSTSTACKUP;
    BuildMI(BB, Opc, 1).addImm(Tmp1);
    return;
  }
  assert(0 && "Should not be reached!");
}


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