lib/Target/Mips/MipsISelLowering.cpp

//===-- MipsISelLowering.cpp - Mips DAG Lowering Implementation -----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the interfaces that Mips uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "mips-lower"
//#include <algorithm>
#include "MipsISelLowering.h"
#include "MipsMachineFunction.h"
#include "MipsTargetMachine.h"
#include "MipsTargetObjectFile.h"
#include "MipsSubtarget.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Intrinsics.h"
#include "llvm/CallingConv.h"
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
using namespace llvm;

const char *MipsTargetLowering::getTargetNodeName(unsigned Opcode) const {
  switch (Opcode) {
  case MipsISD::JmpLink:           return "MipsISD::JmpLink";
  case MipsISD::Hi:                return "MipsISD::Hi";
  case MipsISD::Lo:                return "MipsISD::Lo";
  case MipsISD::GPRel:             return "MipsISD::GPRel";
  case MipsISD::Ret:               return "MipsISD::Ret";
  case MipsISD::FPBrcond:          return "MipsISD::FPBrcond";
  case MipsISD::FPCmp:             return "MipsISD::FPCmp";
  case MipsISD::CMovFP_T:          return "MipsISD::CMovFP_T";
  case MipsISD::CMovFP_F:          return "MipsISD::CMovFP_F";
  case MipsISD::FPRound:           return "MipsISD::FPRound";
  case MipsISD::MAdd:              return "MipsISD::MAdd";
  case MipsISD::MAddu:             return "MipsISD::MAddu";
  case MipsISD::MSub:              return "MipsISD::MSub";
  case MipsISD::MSubu:             return "MipsISD::MSubu";
  case MipsISD::DivRem:            return "MipsISD::DivRem";
  case MipsISD::DivRemU:           return "MipsISD::DivRemU";
  case MipsISD::BuildPairF64:      return "MipsISD::BuildPairF64";
  case MipsISD::ExtractElementF64: return "MipsISD::ExtractElementF64";
  default: return NULL;
  }
}

MipsTargetLowering::
MipsTargetLowering(MipsTargetMachine &TM)
  : TargetLowering(TM, new MipsTargetObjectFile()) {
  Subtarget = &TM.getSubtarget<MipsSubtarget>();

  // Mips does not have i1 type, so use i32 for
  // setcc operations results (slt, sgt, ...).
  setBooleanContents(ZeroOrOneBooleanContent);

  // Set up the register classes
  addRegisterClass(MVT::i32, Mips::CPURegsRegisterClass);
  addRegisterClass(MVT::f32, Mips::FGR32RegisterClass);

  // When dealing with single precision only, use libcalls
  if (!Subtarget->isSingleFloat())
    if (!Subtarget->isFP64bit())
      addRegisterClass(MVT::f64, Mips::AFGR64RegisterClass);

  // Load extented operations for i1 types must be promoted
  setLoadExtAction(ISD::EXTLOAD,  MVT::i1,  Promote);
  setLoadExtAction(ISD::ZEXTLOAD, MVT::i1,  Promote);
  setLoadExtAction(ISD::SEXTLOAD, MVT::i1,  Promote);

  // MIPS doesn't have extending float->double load/store
  setLoadExtAction(ISD::EXTLOAD, MVT::f32, Expand);
  setTruncStoreAction(MVT::f64, MVT::f32, Expand);

  // Used by legalize types to correctly generate the setcc result.
  // Without this, every float setcc comes with a AND/OR with the result,
  // we don't want this, since the fpcmp result goes to a flag register,
  // which is used implicitly by brcond and select operations.
  AddPromotedToType(ISD::SETCC, MVT::i1, MVT::i32);

  // Mips Custom Operations
  setOperationAction(ISD::GlobalAddress,      MVT::i32,   Custom);
  setOperationAction(ISD::BlockAddress,       MVT::i32,   Custom);
  setOperationAction(ISD::GlobalTLSAddress,   MVT::i32,   Custom);
  setOperationAction(ISD::JumpTable,          MVT::i32,   Custom);
  setOperationAction(ISD::ConstantPool,       MVT::i32,   Custom);
  setOperationAction(ISD::SELECT,             MVT::f32,   Custom);
  setOperationAction(ISD::SELECT,             MVT::f64,   Custom);
  setOperationAction(ISD::SELECT,             MVT::i32,   Custom);
  setOperationAction(ISD::BRCOND,             MVT::Other, Custom);
  setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i32,   Custom);
  setOperationAction(ISD::FP_TO_SINT,         MVT::i32,   Custom);
  setOperationAction(ISD::VASTART,            MVT::Other, Custom);

  setOperationAction(ISD::SDIV, MVT::i32, Expand);
  setOperationAction(ISD::SREM, MVT::i32, Expand);
  setOperationAction(ISD::UDIV, MVT::i32, Expand);
  setOperationAction(ISD::UREM, MVT::i32, Expand);

  // Operations not directly supported by Mips.
  setOperationAction(ISD::BR_JT,             MVT::Other, Expand);
  setOperationAction(ISD::BR_CC,             MVT::Other, Expand);
  setOperationAction(ISD::SELECT_CC,         MVT::Other, Expand);
  setOperationAction(ISD::UINT_TO_FP,        MVT::i32,   Expand);
  setOperationAction(ISD::FP_TO_UINT,        MVT::i32,   Expand);
  setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1,    Expand);
  setOperationAction(ISD::CTPOP,             MVT::i32,   Expand);
  setOperationAction(ISD::CTTZ,              MVT::i32,   Expand);
  setOperationAction(ISD::ROTL,              MVT::i32,   Expand);

  if (!Subtarget->isMips32r2())
    setOperationAction(ISD::ROTR, MVT::i32,   Expand);

  setOperationAction(ISD::SHL_PARTS,         MVT::i32,   Expand);
  setOperationAction(ISD::SRA_PARTS,         MVT::i32,   Expand);
  setOperationAction(ISD::SRL_PARTS,         MVT::i32,   Expand);
  setOperationAction(ISD::FCOPYSIGN,         MVT::f32,   Expand);
  setOperationAction(ISD::FCOPYSIGN,         MVT::f64,   Expand);
  setOperationAction(ISD::FSIN,              MVT::f32,   Expand);
  setOperationAction(ISD::FSIN,              MVT::f64,   Expand);
  setOperationAction(ISD::FCOS,              MVT::f32,   Expand);
  setOperationAction(ISD::FCOS,              MVT::f64,   Expand);
  setOperationAction(ISD::FPOWI,             MVT::f32,   Expand);
  setOperationAction(ISD::FPOW,              MVT::f32,   Expand);
  setOperationAction(ISD::FPOW,              MVT::f64,   Expand);
  setOperationAction(ISD::FLOG,              MVT::f32,   Expand);
  setOperationAction(ISD::FLOG2,             MVT::f32,   Expand);
  setOperationAction(ISD::FLOG10,            MVT::f32,   Expand);
  setOperationAction(ISD::FEXP,              MVT::f32,   Expand);

  setOperationAction(ISD::EH_LABEL,          MVT::Other, Expand);

  setOperationAction(ISD::VAARG,             MVT::Other, Expand);
  setOperationAction(ISD::VACOPY,            MVT::Other, Expand);
  setOperationAction(ISD::VAEND,             MVT::Other, Expand);

  // Use the default for now
  setOperationAction(ISD::STACKSAVE,         MVT::Other, Expand);
  setOperationAction(ISD::STACKRESTORE,      MVT::Other, Expand);
  setOperationAction(ISD::MEMBARRIER,        MVT::Other, Expand);

  if (Subtarget->isSingleFloat())
    setOperationAction(ISD::SELECT_CC, MVT::f64, Expand);

  if (!Subtarget->hasSEInReg()) {
    setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i8,  Expand);
    setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i16, Expand);
  }

  if (!Subtarget->hasBitCount())
    setOperationAction(ISD::CTLZ, MVT::i32, Expand);

  if (!Subtarget->hasSwap())
    setOperationAction(ISD::BSWAP, MVT::i32, Expand);

  setTargetDAGCombine(ISD::ADDE);
  setTargetDAGCombine(ISD::SUBE);
  setTargetDAGCombine(ISD::SDIVREM);
  setTargetDAGCombine(ISD::UDIVREM);
  setTargetDAGCombine(ISD::SETCC);

  setMinFunctionAlignment(2);

  setStackPointerRegisterToSaveRestore(Mips::SP);
  computeRegisterProperties();
}

MVT::SimpleValueType MipsTargetLowering::getSetCCResultType(EVT VT) const {
  return MVT::i32;
}

// SelectMadd -
// Transforms a subgraph in CurDAG if the following pattern is found:
//  (addc multLo, Lo0), (adde multHi, Hi0),
// where,
//  multHi/Lo: product of multiplication
//  Lo0: initial value of Lo register
//  Hi0: initial value of Hi register
// Return true if pattern matching was successful.
static bool SelectMadd(SDNode* ADDENode, SelectionDAG* CurDAG) {
  // ADDENode's second operand must be a flag output of an ADDC node in order
  // for the matching to be successful.
  SDNode* ADDCNode = ADDENode->getOperand(2).getNode();

  if (ADDCNode->getOpcode() != ISD::ADDC)
    return false;

  SDValue MultHi = ADDENode->getOperand(0);
  SDValue MultLo = ADDCNode->getOperand(0);
  SDNode* MultNode = MultHi.getNode();
  unsigned MultOpc = MultHi.getOpcode();

  // MultHi and MultLo must be generated by the same node,
  if (MultLo.getNode() != MultNode)
    return false;

  // and it must be a multiplication.
  if (MultOpc != ISD::SMUL_LOHI && MultOpc != ISD::UMUL_LOHI)
    return false;

  // MultLo amd MultHi must be the first and second output of MultNode
  // respectively.
  if (MultHi.getResNo() != 1 || MultLo.getResNo() != 0)
    return false;

  // Transform this to a MADD only if ADDENode and ADDCNode are the only users
  // of the values of MultNode, in which case MultNode will be removed in later
  // phases.
  // If there exist users other than ADDENode or ADDCNode, this function returns
  // here, which will result in MultNode being mapped to a single MULT
  // instruction node rather than a pair of MULT and MADD instructions being
  // produced.
  if (!MultHi.hasOneUse() || !MultLo.hasOneUse())
    return false;

  SDValue Chain = CurDAG->getEntryNode();
  DebugLoc dl = ADDENode->getDebugLoc();

  // create MipsMAdd(u) node
  MultOpc = MultOpc == ISD::UMUL_LOHI ? MipsISD::MAddu : MipsISD::MAdd;

  SDValue MAdd = CurDAG->getNode(MultOpc, dl,
                                 MVT::Glue,
                                 MultNode->getOperand(0),// Factor 0
                                 MultNode->getOperand(1),// Factor 1
                                 ADDCNode->getOperand(1),// Lo0
                                 ADDENode->getOperand(1));// Hi0

  // create CopyFromReg nodes
  SDValue CopyFromLo = CurDAG->getCopyFromReg(Chain, dl, Mips::LO, MVT::i32,
                                              MAdd);
  SDValue CopyFromHi = CurDAG->getCopyFromReg(CopyFromLo.getValue(1), dl,
                                              Mips::HI, MVT::i32,
                                              CopyFromLo.getValue(2));

  // replace uses of adde and addc here
  if (!SDValue(ADDCNode, 0).use_empty())
    CurDAG->ReplaceAllUsesOfValueWith(SDValue(ADDCNode, 0), CopyFromLo);

  if (!SDValue(ADDENode, 0).use_empty())
    CurDAG->ReplaceAllUsesOfValueWith(SDValue(ADDENode, 0), CopyFromHi);

  return true;
}

// SelectMsub -
// Transforms a subgraph in CurDAG if the following pattern is found:
//  (addc Lo0, multLo), (sube Hi0, multHi),
// where,
//  multHi/Lo: product of multiplication
//  Lo0: initial value of Lo register
//  Hi0: initial value of Hi register
// Return true if pattern matching was successful.
static bool SelectMsub(SDNode* SUBENode, SelectionDAG* CurDAG) {
  // SUBENode's second operand must be a flag output of an SUBC node in order
  // for the matching to be successful.
  SDNode* SUBCNode = SUBENode->getOperand(2).getNode();

  if (SUBCNode->getOpcode() != ISD::SUBC)
    return false;

  SDValue MultHi = SUBENode->getOperand(1);
  SDValue MultLo = SUBCNode->getOperand(1);
  SDNode* MultNode = MultHi.getNode();
  unsigned MultOpc = MultHi.getOpcode();

  // MultHi and MultLo must be generated by the same node,
  if (MultLo.getNode() != MultNode)
    return false;

  // and it must be a multiplication.
  if (MultOpc != ISD::SMUL_LOHI && MultOpc != ISD::UMUL_LOHI)
    return false;

  // MultLo amd MultHi must be the first and second output of MultNode
  // respectively.
  if (MultHi.getResNo() != 1 || MultLo.getResNo() != 0)
    return false;

  // Transform this to a MSUB only if SUBENode and SUBCNode are the only users
  // of the values of MultNode, in which case MultNode will be removed in later
  // phases.
  // If there exist users other than SUBENode or SUBCNode, this function returns
  // here, which will result in MultNode being mapped to a single MULT
  // instruction node rather than a pair of MULT and MSUB instructions being
  // produced.
  if (!MultHi.hasOneUse() || !MultLo.hasOneUse())
    return false;

  SDValue Chain = CurDAG->getEntryNode();
  DebugLoc dl = SUBENode->getDebugLoc();

  // create MipsSub(u) node
  MultOpc = MultOpc == ISD::UMUL_LOHI ? MipsISD::MSubu : MipsISD::MSub;

  SDValue MSub = CurDAG->getNode(MultOpc, dl,
                                 MVT::Glue,
                                 MultNode->getOperand(0),// Factor 0
                                 MultNode->getOperand(1),// Factor 1
                                 SUBCNode->getOperand(0),// Lo0
                                 SUBENode->getOperand(0));// Hi0

  // create CopyFromReg nodes
  SDValue CopyFromLo = CurDAG->getCopyFromReg(Chain, dl, Mips::LO, MVT::i32,
                                              MSub);
  SDValue CopyFromHi = CurDAG->getCopyFromReg(CopyFromLo.getValue(1), dl,
                                              Mips::HI, MVT::i32,
                                              CopyFromLo.getValue(2));

  // replace uses of sube and subc here
  if (!SDValue(SUBCNode, 0).use_empty())
    CurDAG->ReplaceAllUsesOfValueWith(SDValue(SUBCNode, 0), CopyFromLo);

  if (!SDValue(SUBENode, 0).use_empty())
    CurDAG->ReplaceAllUsesOfValueWith(SDValue(SUBENode, 0), CopyFromHi);

  return true;
}

static SDValue PerformADDECombine(SDNode *N, SelectionDAG& DAG,
                                  TargetLowering::DAGCombinerInfo &DCI,
                                  const MipsSubtarget* Subtarget) {
  if (DCI.isBeforeLegalize())
    return SDValue();

  if (Subtarget->isMips32() && SelectMadd(N, &DAG))
    return SDValue(N, 0);

  return SDValue();
}

static SDValue PerformSUBECombine(SDNode *N, SelectionDAG& DAG,
                                  TargetLowering::DAGCombinerInfo &DCI,
                                  const MipsSubtarget* Subtarget) {
  if (DCI.isBeforeLegalize())
    return SDValue();

  if (Subtarget->isMips32() && SelectMsub(N, &DAG))
    return SDValue(N, 0);

  return SDValue();
}

static SDValue PerformDivRemCombine(SDNode *N, SelectionDAG& DAG,
                                    TargetLowering::DAGCombinerInfo &DCI,
                                    const MipsSubtarget* Subtarget) {
  if (DCI.isBeforeLegalizeOps())
    return SDValue();

  unsigned opc = N->getOpcode() == ISD::SDIVREM ? MipsISD::DivRem :
                                                  MipsISD::DivRemU;
  DebugLoc dl = N->getDebugLoc();

  SDValue DivRem = DAG.getNode(opc, dl, MVT::Glue,
                               N->getOperand(0), N->getOperand(1));
  SDValue InChain = DAG.getEntryNode();
  SDValue InGlue = DivRem;

  // insert MFLO
  if (N->hasAnyUseOfValue(0)) {
    SDValue CopyFromLo = DAG.getCopyFromReg(InChain, dl, Mips::LO, MVT::i32,
                                            InGlue);
    DAG.ReplaceAllUsesOfValueWith(SDValue(N, 0), CopyFromLo);
    InChain = CopyFromLo.getValue(1);
    InGlue = CopyFromLo.getValue(2);
  }

  // insert MFHI
  if (N->hasAnyUseOfValue(1)) {
    SDValue CopyFromHi = DAG.getCopyFromReg(InChain, dl,
                                            Mips::HI, MVT::i32, InGlue);
    DAG.ReplaceAllUsesOfValueWith(SDValue(N, 1), CopyFromHi);
  }

  return SDValue();
}

static Mips::CondCode FPCondCCodeToFCC(ISD::CondCode CC) {
  switch (CC) {
  default: llvm_unreachable("Unknown fp condition code!");
  case ISD::SETEQ:
  case ISD::SETOEQ: return Mips::FCOND_OEQ;
  case ISD::SETUNE: return Mips::FCOND_UNE;
  case ISD::SETLT:
  case ISD::SETOLT: return Mips::FCOND_OLT;
  case ISD::SETGT:
  case ISD::SETOGT: return Mips::FCOND_OGT;
  case ISD::SETLE:
  case ISD::SETOLE: return Mips::FCOND_OLE;
  case ISD::SETGE:
  case ISD::SETOGE: return Mips::FCOND_OGE;
  case ISD::SETULT: return Mips::FCOND_ULT;
  case ISD::SETULE: return Mips::FCOND_ULE;
  case ISD::SETUGT: return Mips::FCOND_UGT;
  case ISD::SETUGE: return Mips::FCOND_UGE;
  case ISD::SETUO:  return Mips::FCOND_UN;
  case ISD::SETO:   return Mips::FCOND_OR;
  case ISD::SETNE:
  case ISD::SETONE: return Mips::FCOND_ONE;
  case ISD::SETUEQ: return Mips::FCOND_UEQ;
  }
}


// Returns true if condition code has to be inverted.
static bool InvertFPCondCode(Mips::CondCode CC) {
  if (CC >= Mips::FCOND_F && CC <= Mips::FCOND_NGT)
    return false;

  if (CC >= Mips::FCOND_T && CC <= Mips::FCOND_GT)
    return true;

  assert(false && "Illegal Condition Code");
  return false;
}

// Creates and returns an FPCmp node from a setcc node.
// Returns Op if setcc is not a floating point comparison.
static SDValue CreateFPCmp(SelectionDAG& DAG, const SDValue& Op) {
  // must be a SETCC node
  if (Op.getOpcode() != ISD::SETCC)
    return Op;

  SDValue LHS = Op.getOperand(0);

  if (!LHS.getValueType().isFloatingPoint())
    return Op;

  SDValue RHS = Op.getOperand(1);
  DebugLoc dl = Op.getDebugLoc();

  // Assume the 3rd operand is a CondCodeSDNode. Add code to check the type of
  // node if necessary.
  ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(2))->get();

  return DAG.getNode(MipsISD::FPCmp, dl, MVT::Glue, LHS, RHS,
                     DAG.getConstant(FPCondCCodeToFCC(CC), MVT::i32));
}

// Creates and returns a CMovFPT/F node.
static SDValue CreateCMovFP(SelectionDAG& DAG, SDValue Cond, SDValue True,
                            SDValue False, DebugLoc DL) {
  bool invert = InvertFPCondCode((Mips::CondCode)
                                 cast<ConstantSDNode>(Cond.getOperand(2))
                                 ->getSExtValue());

  return DAG.getNode((invert ? MipsISD::CMovFP_F : MipsISD::CMovFP_T), DL,
                     True.getValueType(), True, False, Cond);
}

static SDValue PerformSETCCCombine(SDNode *N, SelectionDAG& DAG,
                                   TargetLowering::DAGCombinerInfo &DCI,
                                   const MipsSubtarget* Subtarget) {
  if (DCI.isBeforeLegalizeOps())
    return SDValue();

  SDValue Cond = CreateFPCmp(DAG, SDValue(N, 0));

  if (Cond.getOpcode() != MipsISD::FPCmp)
    return SDValue();

  SDValue True  = DAG.getConstant(1, MVT::i32);
  SDValue False = DAG.getConstant(0, MVT::i32);

  return CreateCMovFP(DAG, Cond, True, False, N->getDebugLoc());
}

SDValue  MipsTargetLowering::PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI)
  const {
  SelectionDAG &DAG = DCI.DAG;
  unsigned opc = N->getOpcode();

  switch (opc) {
  default: break;
  case ISD::ADDE:
    return PerformADDECombine(N, DAG, DCI, Subtarget);
  case ISD::SUBE:
    return PerformSUBECombine(N, DAG, DCI, Subtarget);
  case ISD::SDIVREM:
  case ISD::UDIVREM:
    return PerformDivRemCombine(N, DAG, DCI, Subtarget);
  case ISD::SETCC:
    return PerformSETCCCombine(N, DAG, DCI, Subtarget);
  }

  return SDValue();
}

SDValue MipsTargetLowering::
LowerOperation(SDValue Op, SelectionDAG &DAG) const
{
  switch (Op.getOpcode())
  {
    case ISD::BRCOND:             return LowerBRCOND(Op, DAG);
    case ISD::ConstantPool:       return LowerConstantPool(Op, DAG);
    case ISD::DYNAMIC_STACKALLOC: return LowerDYNAMIC_STACKALLOC(Op, DAG);
    case ISD::FP_TO_SINT:         return LowerFP_TO_SINT(Op, DAG);
    case ISD::GlobalAddress:      return LowerGlobalAddress(Op, DAG);
    case ISD::BlockAddress:       return LowerBlockAddress(Op, DAG);
    case ISD::GlobalTLSAddress:   return LowerGlobalTLSAddress(Op, DAG);
    case ISD::JumpTable:          return LowerJumpTable(Op, DAG);
    case ISD::SELECT:             return LowerSELECT(Op, DAG);
    case ISD::VASTART:            return LowerVASTART(Op, DAG);
  }
  return SDValue();
}

//===----------------------------------------------------------------------===//
//  Lower helper functions
//===----------------------------------------------------------------------===//

// AddLiveIn - This helper function adds the specified physical register to the
// MachineFunction as a live in value.  It also creates a corresponding
// virtual register for it.
static unsigned
AddLiveIn(MachineFunction &MF, unsigned PReg, TargetRegisterClass *RC)
{
  assert(RC->contains(PReg) && "Not the correct regclass!");
  unsigned VReg = MF.getRegInfo().createVirtualRegister(RC);
  MF.getRegInfo().addLiveIn(PReg, VReg);
  return VReg;
}

// Get fp branch code (not opcode) from condition code.
static Mips::FPBranchCode GetFPBranchCodeFromCond(Mips::CondCode CC) {
  if (CC >= Mips::FCOND_F && CC <= Mips::FCOND_NGT)
    return Mips::BRANCH_T;

  if (CC >= Mips::FCOND_T && CC <= Mips::FCOND_GT)
    return Mips::BRANCH_F;

  return Mips::BRANCH_INVALID;
}

MachineBasicBlock *
MipsTargetLowering::EmitInstrWithCustomInserter(MachineInstr *MI,
                                                MachineBasicBlock *BB) const {
  // There is no need to expand CMov instructions if target has
  // conditional moves.
  if (Subtarget->hasCondMov())
    return BB;

  const TargetInstrInfo *TII = getTargetMachine().getInstrInfo();
  bool isFPCmp = false;
  DebugLoc dl = MI->getDebugLoc();
  unsigned Opc;

  switch (MI->getOpcode()) {
  default: assert(false && "Unexpected instr type to insert");
  case Mips::MOVT:
  case Mips::MOVT_S:
  case Mips::MOVT_D:
    isFPCmp = true;
    Opc = Mips::BC1F;
    break;
  case Mips::MOVF:
  case Mips::MOVF_S:
  case Mips::MOVF_D:
    isFPCmp = true;
    Opc = Mips::BC1T;
    break;
  case Mips::MOVZ_I:
  case Mips::MOVZ_S:
  case Mips::MOVZ_D:
    Opc = Mips::BNE;
    break;
  case Mips::MOVN_I:
  case Mips::MOVN_S:
  case Mips::MOVN_D:
    Opc = Mips::BEQ;
    break;
  }

  // To "insert" a SELECT_CC instruction, we actually have to insert the
  // diamond control-flow pattern.  The incoming instruction knows the
  // destination vreg to set, the condition code register to branch on, the
  // true/false values to select between, and a branch opcode to use.
  const BasicBlock *LLVM_BB = BB->getBasicBlock();
  MachineFunction::iterator It = BB;
  ++It;

  //  thisMBB:
  //  ...
  //   TrueVal = ...
  //   setcc r1, r2, r3
  //   bNE   r1, r0, copy1MBB
  //   fallthrough --> copy0MBB
  MachineBasicBlock *thisMBB  = BB;
  MachineFunction *F = BB->getParent();
  MachineBasicBlock *copy0MBB = F->CreateMachineBasicBlock(LLVM_BB);
  MachineBasicBlock *sinkMBB  = F->CreateMachineBasicBlock(LLVM_BB);
  F->insert(It, copy0MBB);
  F->insert(It, sinkMBB);

  // Transfer the remainder of BB and its successor edges to sinkMBB.
  sinkMBB->splice(sinkMBB->begin(), BB,
                  llvm::next(MachineBasicBlock::iterator(MI)),
                  BB->end());
  sinkMBB->transferSuccessorsAndUpdatePHIs(BB);

  // Next, add the true and fallthrough blocks as its successors.
  BB->addSuccessor(copy0MBB);
  BB->addSuccessor(sinkMBB);

  // Emit the right instruction according to the type of the operands compared
  if (isFPCmp)
    BuildMI(BB, dl, TII->get(Opc)).addMBB(sinkMBB);
  else
    BuildMI(BB, dl, TII->get(Opc)).addReg(MI->getOperand(2).getReg())
      .addReg(Mips::ZERO).addMBB(sinkMBB);


  //  copy0MBB:
  //   %FalseValue = ...
  //   # fallthrough to sinkMBB
  BB = copy0MBB;

  // Update machine-CFG edges
  BB->addSuccessor(sinkMBB);

  //  sinkMBB:
  //   %Result = phi [ %TrueValue, thisMBB ], [ %FalseValue, copy0MBB ]
  //  ...
  BB = sinkMBB;

  if (isFPCmp)
    BuildMI(*BB, BB->begin(), dl,
            TII->get(Mips::PHI), MI->getOperand(0).getReg())
      .addReg(MI->getOperand(2).getReg()).addMBB(thisMBB)
      .addReg(MI->getOperand(1).getReg()).addMBB(copy0MBB);
  else
    BuildMI(*BB, BB->begin(), dl,
            TII->get(Mips::PHI), MI->getOperand(0).getReg())
      .addReg(MI->getOperand(3).getReg()).addMBB(thisMBB)
      .addReg(MI->getOperand(1).getReg()).addMBB(copy0MBB);

  MI->eraseFromParent();   // The pseudo instruction is gone now.
  return BB;
}

//===----------------------------------------------------------------------===//
//  Misc Lower Operation implementation
//===----------------------------------------------------------------------===//

SDValue MipsTargetLowering::
LowerFP_TO_SINT(SDValue Op, SelectionDAG &DAG) const
{
  if (!Subtarget->isMips1())
    return Op;

  MachineFunction &MF = DAG.getMachineFunction();
  unsigned CCReg = AddLiveIn(MF, Mips::FCR31, Mips::CCRRegisterClass);

  SDValue Chain = DAG.getEntryNode();
  DebugLoc dl = Op.getDebugLoc();
  SDValue Src = Op.getOperand(0);

  // Set the condition register
  SDValue CondReg = DAG.getCopyFromReg(Chain, dl, CCReg, MVT::i32);
  CondReg = DAG.getCopyToReg(Chain, dl, Mips::AT, CondReg);
  CondReg = DAG.getCopyFromReg(CondReg, dl, Mips::AT, MVT::i32);

  SDValue Cst = DAG.getConstant(3, MVT::i32);
  SDValue Or = DAG.getNode(ISD::OR, dl, MVT::i32, CondReg, Cst);
  Cst = DAG.getConstant(2, MVT::i32);
  SDValue Xor = DAG.getNode(ISD::XOR, dl, MVT::i32, Or, Cst);

  SDValue InFlag(0, 0);
  CondReg = DAG.getCopyToReg(Chain, dl, Mips::FCR31, Xor, InFlag);

  // Emit the round instruction and bit convert to integer
  SDValue Trunc = DAG.getNode(MipsISD::FPRound, dl, MVT::f32,
                              Src, CondReg.getValue(1));
  SDValue BitCvt = DAG.getNode(ISD::BITCAST, dl, MVT::i32, Trunc);
  return BitCvt;
}

SDValue MipsTargetLowering::
LowerDYNAMIC_STACKALLOC(SDValue Op, SelectionDAG &DAG) const
{
  unsigned StackAlignment =
    getTargetMachine().getFrameLowering()->getStackAlignment();
  assert(StackAlignment >=
         cast<ConstantSDNode>(Op.getOperand(2).getNode())->getZExtValue() &&
         "Cannot lower if the alignment of the allocated space is larger than \
          that of the stack.");

  SDValue Chain = Op.getOperand(0);
  SDValue Size = Op.getOperand(1);
  DebugLoc dl = Op.getDebugLoc();

  // Get a reference from Mips stack pointer
  SDValue StackPointer = DAG.getCopyFromReg(Chain, dl, Mips::SP, MVT::i32);

  // Subtract the dynamic size from the actual stack size to
  // obtain the new stack size.
  SDValue Sub = DAG.getNode(ISD::SUB, dl, MVT::i32, StackPointer, Size);

  // The Sub result contains the new stack start address, so it
  // must be placed in the stack pointer register.
  Chain = DAG.getCopyToReg(StackPointer.getValue(1), dl, Mips::SP, Sub,
                           SDValue());
  SDValue NewSP = DAG.getCopyFromReg(Chain, dl, Mips::SP, MVT::i32,
                                     Chain.getValue(1));
  
  // Align the allocated space.
  MachineFunction &MF = DAG.getMachineFunction();
  MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
  unsigned SPOffset = (MipsFI->getMaxCallFrameSize() + StackAlignment - 1) /
                      StackAlignment * StackAlignment;
  SDValue AllocPtr = DAG.getNode(ISD::ADD, dl, MVT::i32, NewSP,
                                 DAG.getConstant(SPOffset, MVT::i32));

  // This node always has two return values: a new stack pointer
  // value and a chain
  SDValue Ops[2] = { AllocPtr, NewSP.getValue(1) };
  return DAG.getMergeValues(Ops, 2, dl);
}

SDValue MipsTargetLowering::
LowerBRCOND(SDValue Op, SelectionDAG &DAG) const
{
  // The first operand is the chain, the second is the condition, the third is
  // the block to branch to if the condition is true.
  SDValue Chain = Op.getOperand(0);
  SDValue Dest = Op.getOperand(2);
  DebugLoc dl = Op.getDebugLoc();

  SDValue CondRes = CreateFPCmp(DAG, Op.getOperand(1));

  // Return if flag is not set by a floating point comparison.
  if (CondRes.getOpcode() != MipsISD::FPCmp)
    return Op;

  SDValue CCNode  = CondRes.getOperand(2);
  Mips::CondCode CC =
    (Mips::CondCode)cast<ConstantSDNode>(CCNode)->getZExtValue();
  SDValue BrCode = DAG.getConstant(GetFPBranchCodeFromCond(CC), MVT::i32);

  return DAG.getNode(MipsISD::FPBrcond, dl, Op.getValueType(), Chain, BrCode,
                     Dest, CondRes);
}

SDValue MipsTargetLowering::
LowerSELECT(SDValue Op, SelectionDAG &DAG) const
{
  SDValue Cond = CreateFPCmp(DAG, Op.getOperand(0));

  // Return if flag is not set by a floating point comparison.
  if (Cond.getOpcode() != MipsISD::FPCmp)
    return Op;

  return CreateCMovFP(DAG, Cond, Op.getOperand(1), Op.getOperand(2),
                      Op.getDebugLoc());
}

SDValue MipsTargetLowering::LowerGlobalAddress(SDValue Op,
                                               SelectionDAG &DAG) const {
  // FIXME there isn't actually debug info here
  DebugLoc dl = Op.getDebugLoc();
  const GlobalValue *GV = cast<GlobalAddressSDNode>(Op)->getGlobal();

  if (getTargetMachine().getRelocationModel() != Reloc::PIC_) {
    SDVTList VTs = DAG.getVTList(MVT::i32);

    MipsTargetObjectFile &TLOF = (MipsTargetObjectFile&)getObjFileLowering();

    // %gp_rel relocation
    if (TLOF.IsGlobalInSmallSection(GV, getTargetMachine())) {
      SDValue GA = DAG.getTargetGlobalAddress(GV, dl, MVT::i32, 0,
                                              MipsII::MO_GPREL);
      SDValue GPRelNode = DAG.getNode(MipsISD::GPRel, dl, VTs, &GA, 1);
      SDValue GOT = DAG.getGLOBAL_OFFSET_TABLE(MVT::i32);
      return DAG.getNode(ISD::ADD, dl, MVT::i32, GOT, GPRelNode);
    }
    // %hi/%lo relocation
    SDValue GAHi = DAG.getTargetGlobalAddress(GV, dl, MVT::i32, 0,
                                              MipsII::MO_ABS_HI);
    SDValue GALo = DAG.getTargetGlobalAddress(GV, dl, MVT::i32, 0,
                                              MipsII::MO_ABS_LO);
    SDValue HiPart = DAG.getNode(MipsISD::Hi, dl, VTs, &GAHi, 1);
    SDValue Lo = DAG.getNode(MipsISD::Lo, dl, MVT::i32, GALo);
    return DAG.getNode(ISD::ADD, dl, MVT::i32, HiPart, Lo);
  } else {
    SDValue GA = DAG.getTargetGlobalAddress(GV, dl, MVT::i32, 0,
                                            MipsII::MO_GOT);
    SDValue ResNode = DAG.getLoad(MVT::i32, dl,
                                  DAG.getEntryNode(), GA, MachinePointerInfo(),
                                  false, false, 0);
    // On functions and global targets not internal linked only
    // a load from got/GP is necessary for PIC to work.
    if (!GV->hasInternalLinkage() &&
        (!GV->hasLocalLinkage() || isa<Function>(GV)))
      return ResNode;
    SDValue GALo = DAG.getTargetGlobalAddress(GV, dl, MVT::i32, 0,
                                              MipsII::MO_ABS_LO);
    SDValue Lo = DAG.getNode(MipsISD::Lo, dl, MVT::i32, GALo);
    return DAG.getNode(ISD::ADD, dl, MVT::i32, ResNode, Lo);
  }

  llvm_unreachable("Dont know how to handle GlobalAddress");
  return SDValue(0,0);
}

SDValue MipsTargetLowering::LowerBlockAddress(SDValue Op,
                                              SelectionDAG &DAG) const {
  const BlockAddress *BA = cast<BlockAddressSDNode>(Op)->getBlockAddress();
  // FIXME there isn't actually debug info here
  DebugLoc dl = Op.getDebugLoc();

  if (getTargetMachine().getRelocationModel() != Reloc::PIC_) {
    // %hi/%lo relocation
    SDValue BAHi = DAG.getBlockAddress(BA, MVT::i32, true,
                                       MipsII::MO_ABS_HI);
    SDValue BALo = DAG.getBlockAddress(BA, MVT::i32, true,
                                       MipsII::MO_ABS_LO);
    SDValue Hi = DAG.getNode(MipsISD::Hi, dl, MVT::i32, BAHi);
    SDValue Lo = DAG.getNode(MipsISD::Lo, dl, MVT::i32, BALo);
    return DAG.getNode(ISD::ADD, dl, MVT::i32, Hi, Lo);
  }

  SDValue BAGOTOffset = DAG.getBlockAddress(BA, MVT::i32, true,
                                            MipsII::MO_GOT);
  SDValue BALOOffset = DAG.getBlockAddress(BA, MVT::i32, true,
                                           MipsII::MO_ABS_LO);
  SDValue Load = DAG.getLoad(MVT::i32, dl,
                             DAG.getEntryNode(), BAGOTOffset,
                             MachinePointerInfo(), false, false, 0);
  SDValue Lo = DAG.getNode(MipsISD::Lo, dl, MVT::i32, BALOOffset);
  return DAG.getNode(ISD::ADD, dl, MVT::i32, Load, Lo);
}

SDValue MipsTargetLowering::
LowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const
{
  llvm_unreachable("TLS not implemented for MIPS.");
  return SDValue(); // Not reached
}

SDValue MipsTargetLowering::
LowerJumpTable(SDValue Op, SelectionDAG &DAG) const
{
  SDValue ResNode;
  SDValue HiPart;
  // FIXME there isn't actually debug info here
  DebugLoc dl = Op.getDebugLoc();
  bool IsPIC = getTargetMachine().getRelocationModel() == Reloc::PIC_;
  unsigned char OpFlag = IsPIC ? MipsII::MO_GOT : MipsII::MO_ABS_HI;

  EVT PtrVT = Op.getValueType();
  JumpTableSDNode *JT  = cast<JumpTableSDNode>(Op);

  SDValue JTI = DAG.getTargetJumpTable(JT->getIndex(), PtrVT, OpFlag);

  if (!IsPIC) {
    SDValue Ops[] = { JTI };
    HiPart = DAG.getNode(MipsISD::Hi, dl, DAG.getVTList(MVT::i32), Ops, 1);
  } else // Emit Load from Global Pointer
    HiPart = DAG.getLoad(MVT::i32, dl, DAG.getEntryNode(), JTI,
                         MachinePointerInfo(),
                         false, false, 0);

  SDValue JTILo = DAG.getTargetJumpTable(JT->getIndex(), PtrVT,
                                         MipsII::MO_ABS_LO);
  SDValue Lo = DAG.getNode(MipsISD::Lo, dl, MVT::i32, JTILo);
  ResNode = DAG.getNode(ISD::ADD, dl, MVT::i32, HiPart, Lo);

  return ResNode;
}

SDValue MipsTargetLowering::
LowerConstantPool(SDValue Op, SelectionDAG &DAG) const
{
  SDValue ResNode;
  ConstantPoolSDNode *N = cast<ConstantPoolSDNode>(Op);
  const Constant *C = N->getConstVal();
  // FIXME there isn't actually debug info here
  DebugLoc dl = Op.getDebugLoc();

  // gp_rel relocation
  // FIXME: we should reference the constant pool using small data sections,
  // but the asm printer currently doesn't support this feature without
  // hacking it. This feature should come soon so we can uncomment the
  // stuff below.
  //if (IsInSmallSection(C->getType())) {
  //  SDValue GPRelNode = DAG.getNode(MipsISD::GPRel, MVT::i32, CP);
  //  SDValue GOT = DAG.getGLOBAL_OFFSET_TABLE(MVT::i32);
  //  ResNode = DAG.getNode(ISD::ADD, MVT::i32, GOT, GPRelNode);

  if (getTargetMachine().getRelocationModel() != Reloc::PIC_) {
    SDValue CPHi = DAG.getTargetConstantPool(C, MVT::i32, N->getAlignment(),
                                             N->getOffset(), MipsII::MO_ABS_HI);
    SDValue CPLo = DAG.getTargetConstantPool(C, MVT::i32, N->getAlignment(),
                                             N->getOffset(), MipsII::MO_ABS_LO);
    SDValue HiPart = DAG.getNode(MipsISD::Hi, dl, MVT::i32, CPHi);
    SDValue Lo = DAG.getNode(MipsISD::Lo, dl, MVT::i32, CPLo);
    ResNode = DAG.getNode(ISD::ADD, dl, MVT::i32, HiPart, Lo);
  } else {
    SDValue CP = DAG.getTargetConstantPool(C, MVT::i32, N->getAlignment(),
                                           N->getOffset(), MipsII::MO_GOT);
    SDValue Load = DAG.getLoad(MVT::i32, dl, DAG.getEntryNode(),
                               CP, MachinePointerInfo::getConstantPool(),
                               false, false, 0);
    SDValue CPLo = DAG.getTargetConstantPool(C, MVT::i32, N->getAlignment(),
                                             N->getOffset(), MipsII::MO_ABS_LO);
    SDValue Lo = DAG.getNode(MipsISD::Lo, dl, MVT::i32, CPLo);
    ResNode = DAG.getNode(ISD::ADD, dl, MVT::i32, Load, Lo);
  }

  return ResNode;
}

SDValue MipsTargetLowering::LowerVASTART(SDValue Op, SelectionDAG &DAG) const {
  MachineFunction &MF = DAG.getMachineFunction();
  MipsFunctionInfo *FuncInfo = MF.getInfo<MipsFunctionInfo>();

  DebugLoc dl = Op.getDebugLoc();
  SDValue FI = DAG.getFrameIndex(FuncInfo->getVarArgsFrameIndex(),
                                 getPointerTy());

  // vastart just stores the address of the VarArgsFrameIndex slot into the
  // memory location argument.
  const Value *SV = cast<SrcValueSDNode>(Op.getOperand(2))->getValue();
  return DAG.getStore(Op.getOperand(0), dl, FI, Op.getOperand(1),
                      MachinePointerInfo(SV),
                      false, false, 0);
}

//===----------------------------------------------------------------------===//
//                      Calling Convention Implementation
//===----------------------------------------------------------------------===//

#include "MipsGenCallingConv.inc"

//===----------------------------------------------------------------------===//
// TODO: Implement a generic logic using tblgen that can support this.
// Mips O32 ABI rules:
// ---
// i32 - Passed in A0, A1, A2, A3 and stack
// f32 - Only passed in f32 registers if no int reg has been used yet to hold
//       an argument. Otherwise, passed in A1, A2, A3 and stack.
// f64 - Only passed in two aliased f32 registers if no int reg has been used
//       yet to hold an argument. Otherwise, use A2, A3 and stack. If A1 is
//       not used, it must be shadowed. If only A3 is avaiable, shadow it and
//       go to stack.
//
//  For vararg functions, all arguments are passed in A0, A1, A2, A3 and stack.
//===----------------------------------------------------------------------===//

static bool CC_MipsO32(unsigned ValNo, MVT ValVT,
                       MVT LocVT, CCValAssign::LocInfo LocInfo,
                       ISD::ArgFlagsTy ArgFlags, CCState &State) {

  static const unsigned IntRegsSize=4, FloatRegsSize=2;

  static const unsigned IntRegs[] = {
      Mips::A0, Mips::A1, Mips::A2, Mips::A3
  };
  static const unsigned F32Regs[] = {
      Mips::F12, Mips::F14
  };
  static const unsigned F64Regs[] = {
      Mips::D6, Mips::D7
  };

  // ByVal Args
  if (ArgFlags.isByVal()) {
    State.HandleByVal(ValNo, ValVT, LocVT, LocInfo,
                      1 /*MinSize*/, 4 /*MinAlign*/, ArgFlags);
    unsigned NextReg = (State.getNextStackOffset() + 3) / 4;
    for (unsigned r = State.getFirstUnallocated(IntRegs, IntRegsSize);
         r < std::min(IntRegsSize, NextReg); ++r)
      State.AllocateReg(IntRegs[r]);
    return false;
  }

  // Promote i8 and i16
  if (LocVT == MVT::i8 || LocVT == MVT::i16) {
    LocVT = MVT::i32;
    if (ArgFlags.isSExt())
      LocInfo = CCValAssign::SExt;
    else if (ArgFlags.isZExt())
      LocInfo = CCValAssign::ZExt;
    else
      LocInfo = CCValAssign::AExt;
  }

  unsigned Reg;

  // f32 and f64 are allocated in A0, A1, A2, A3 when either of the following
  // is true: function is vararg, argument is 3rd or higher, there is previous
  // argument which is not f32 or f64.
  bool AllocateFloatsInIntReg = State.isVarArg() || ValNo > 1
      || State.getFirstUnallocated(F32Regs, FloatRegsSize) != ValNo;
  unsigned OrigAlign = ArgFlags.getOrigAlign();
  bool isI64 = (ValVT == MVT::i32 && OrigAlign == 8);

  if (ValVT == MVT::i32 || (ValVT == MVT::f32 && AllocateFloatsInIntReg)) {
    Reg = State.AllocateReg(IntRegs, IntRegsSize);
    // If this is the first part of an i64 arg,
    // the allocated register must be either A0 or A2.
    if (isI64 && (Reg == Mips::A1 || Reg == Mips::A3))
      Reg = State.AllocateReg(IntRegs, IntRegsSize);
    LocVT = MVT::i32;
  } else if (ValVT == MVT::f64 && AllocateFloatsInIntReg) {
    // Allocate int register and shadow next int register. If first
    // available register is Mips::A1 or Mips::A3, shadow it too.
    Reg = State.AllocateReg(IntRegs, IntRegsSize);
    if (Reg == Mips::A1 || Reg == Mips::A3)
      Reg = State.AllocateReg(IntRegs, IntRegsSize);
    State.AllocateReg(IntRegs, IntRegsSize);
    LocVT = MVT::i32;
  } else if (ValVT.isFloatingPoint() && !AllocateFloatsInIntReg) {
    // we are guaranteed to find an available float register
    if (ValVT == MVT::f32) {
      Reg = State.AllocateReg(F32Regs, FloatRegsSize);
      // Shadow int register
      State.AllocateReg(IntRegs, IntRegsSize);
    } else {
      Reg = State.AllocateReg(F64Regs, FloatRegsSize);
      // Shadow int registers
      unsigned Reg2 = State.AllocateReg(IntRegs, IntRegsSize);
      if (Reg2 == Mips::A1 || Reg2 == Mips::A3)
        State.AllocateReg(IntRegs, IntRegsSize);
      State.AllocateReg(IntRegs, IntRegsSize);
    }
  } else
    llvm_unreachable("Cannot handle this ValVT.");

  unsigned SizeInBytes = ValVT.getSizeInBits() >> 3;
  unsigned Offset = State.AllocateStack(SizeInBytes, OrigAlign);

  if (!Reg)
    State.addLoc(CCValAssign::getMem(ValNo, ValVT, Offset, LocVT, LocInfo));
  else
    State.addLoc(CCValAssign::getReg(ValNo, ValVT, Reg, LocVT, LocInfo));

  return false; // CC must always match
}

//===----------------------------------------------------------------------===//
//                  Call Calling Convention Implementation
//===----------------------------------------------------------------------===//

static const unsigned O32IntRegsSize = 4;

static const unsigned O32IntRegs[] = {
  Mips::A0, Mips::A1, Mips::A2, Mips::A3
};

// Write ByVal Arg to arg registers and stack.
static void
WriteByValArg(SDValue& Chain, DebugLoc dl,
              SmallVector<std::pair<unsigned, SDValue>, 16>& RegsToPass,
              SmallVector<SDValue, 8>& MemOpChains, int& LastFI,
              MachineFrameInfo *MFI, SelectionDAG &DAG, SDValue Arg,
              const CCValAssign &VA, const ISD::ArgFlagsTy& Flags, MVT PtrType) {
  unsigned FirstWord = VA.getLocMemOffset() / 4;
  unsigned NumWords = (Flags.getByValSize() + 3) / 4;
  unsigned LastWord = FirstWord + NumWords;
  unsigned CurWord;

  // copy the first 4 words of byval arg to registers A0 - A3
  for (CurWord = FirstWord; CurWord < std::min(LastWord, O32IntRegsSize);
       ++CurWord) {
    SDValue LoadPtr = DAG.getNode(ISD::ADD, dl, MVT::i32, Arg,
                                  DAG.getConstant((CurWord - FirstWord) * 4,
                                                  MVT::i32));
    SDValue LoadVal = DAG.getLoad(MVT::i32, dl, Chain, LoadPtr,
                                  MachinePointerInfo(),
                                  false, false, 0);
    MemOpChains.push_back(LoadVal.getValue(1));
    unsigned DstReg = O32IntRegs[CurWord];
    RegsToPass.push_back(std::make_pair(DstReg, LoadVal));
  }

  // copy remaining part of byval arg to stack.
  if (CurWord < LastWord) {
    unsigned SizeInBytes = (LastWord - CurWord) * 4; 
    SDValue Src = DAG.getNode(ISD::ADD, dl, MVT::i32, Arg,
                              DAG.getConstant((CurWord - FirstWord) * 4,
                                              MVT::i32));
    LastFI = MFI->CreateFixedObject(SizeInBytes, CurWord * 4, true);
    SDValue Dst = DAG.getFrameIndex(LastFI, PtrType);
    Chain = DAG.getMemcpy(Chain, dl, Dst, Src,
                          DAG.getConstant(SizeInBytes, MVT::i32),
                          /*Align*/4,
                          /*isVolatile=*/false, /*AlwaysInline=*/false,
                          MachinePointerInfo(0), MachinePointerInfo(0));
    MemOpChains.push_back(Chain);
  }
}

/// LowerCall - functions arguments are copied from virtual regs to
/// (physical regs)/(stack frame), CALLSEQ_START and CALLSEQ_END are emitted.
/// TODO: isTailCall.
SDValue
MipsTargetLowering::LowerCall(SDValue Chain, SDValue Callee,
                              CallingConv::ID CallConv, bool isVarArg,
                              bool &isTailCall,
                              const SmallVectorImpl<ISD::OutputArg> &Outs,
                              const SmallVectorImpl<SDValue> &OutVals,
                              const SmallVectorImpl<ISD::InputArg> &Ins,
                              DebugLoc dl, SelectionDAG &DAG,
                              SmallVectorImpl<SDValue> &InVals) const {
  // MIPs target does not yet support tail call optimization.
  isTailCall = false;

  MachineFunction &MF = DAG.getMachineFunction();
  MachineFrameInfo *MFI = MF.getFrameInfo();
  const TargetFrameLowering *TFL = MF.getTarget().getFrameLowering();
  bool IsPIC = getTargetMachine().getRelocationModel() == Reloc::PIC_;
  MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();

  // Analyze operands of the call, assigning locations to each operand.
  SmallVector<CCValAssign, 16> ArgLocs;
  CCState CCInfo(CallConv, isVarArg, getTargetMachine(), ArgLocs,
                 *DAG.getContext());

  if (Subtarget->isABI_O32())
    CCInfo.AnalyzeCallOperands(Outs, CC_MipsO32);
  else
    CCInfo.AnalyzeCallOperands(Outs, CC_Mips);

  // Get a count of how many bytes are to be pushed on the stack.
  unsigned NumBytes = CCInfo.getNextStackOffset();
  Chain = DAG.getCALLSEQ_START(Chain, DAG.getIntPtrConstant(NumBytes, true));

  // With EABI is it possible to have 16 args on registers.
  SmallVector<std::pair<unsigned, SDValue>, 16> RegsToPass;
  SmallVector<SDValue, 8> MemOpChains;

  MipsFI->setHasCall();

  // Create GP frame object if this is the first call. 
  // SPOffset will be updated after call frame size is known.
  if (IsPIC && !MipsFI->getGPFI())
    MipsFI->setGPFI(MFI->CreateFixedObject(4, 0, true));

  int FirstFI = -MFI->getNumFixedObjects() - 1, LastFI = 0; 

  // Walk the register/memloc assignments, inserting copies/loads.
  for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
    SDValue Arg = OutVals[i];
    CCValAssign &VA = ArgLocs[i];

    // Promote the value if needed.
    switch (VA.getLocInfo()) {
    default: llvm_unreachable("Unknown loc info!");
    case CCValAssign::Full:
      if (Subtarget->isABI_O32() && VA.isRegLoc()) {
        if (VA.getValVT() == MVT::f32 && VA.getLocVT() == MVT::i32)
          Arg = DAG.getNode(ISD::BITCAST, dl, MVT::i32, Arg);
        if (VA.getValVT() == MVT::f64 && VA.getLocVT() == MVT::i32) {
          SDValue Lo = DAG.getNode(MipsISD::ExtractElementF64, dl, MVT::i32,
                                   Arg, DAG.getConstant(0, MVT::i32));
          SDValue Hi = DAG.getNode(MipsISD::ExtractElementF64, dl, MVT::i32,
                                   Arg, DAG.getConstant(1, MVT::i32));
          if (!Subtarget->isLittle())
            std::swap(Lo, Hi);
          RegsToPass.push_back(std::make_pair(VA.getLocReg(), Lo));
          RegsToPass.push_back(std::make_pair(VA.getLocReg()+1, Hi));
          continue;
        }
      }
      break;
    case CCValAssign::SExt:
      Arg = DAG.getNode(ISD::SIGN_EXTEND, dl, VA.getLocVT(), Arg);
      break;
    case CCValAssign::ZExt:
      Arg = DAG.getNode(ISD::ZERO_EXTEND, dl, VA.getLocVT(), Arg);
      break;
    case CCValAssign::AExt:
      Arg = DAG.getNode(ISD::ANY_EXTEND, dl, VA.getLocVT(), Arg);
      break;
    }

    // Arguments that can be passed on register must be kept at
    // RegsToPass vector
    if (VA.isRegLoc()) {
      RegsToPass.push_back(std::make_pair(VA.getLocReg(), Arg));
      continue;
    }

    // Register can't get to this point...
    assert(VA.isMemLoc());

    // ByVal Arg. 
    ISD::ArgFlagsTy Flags = Outs[i].Flags;
    if (Flags.isByVal()) {
      assert(Subtarget->isABI_O32() &&
             "No support for ByVal args by ABIs other than O32 yet.");
      assert(Flags.getByValSize() &&
             "ByVal args of size 0 should have been ignored by front-end.");
      WriteByValArg(Chain, dl, RegsToPass, MemOpChains, LastFI, MFI, DAG, Arg,
                    VA, Flags, getPointerTy());
      continue;
    }

    // Create the frame index object for this incoming parameter
    // This guarantees that when allocating Local Area the firsts
    // 16 bytes which are alwayes reserved won't be overwritten
    // if O32 ABI is used. For EABI the first address is zero.
    LastFI = MFI->CreateFixedObject(VA.getValVT().getSizeInBits()/8, 
                                    VA.getLocMemOffset(), true);
    SDValue PtrOff = DAG.getFrameIndex(LastFI, getPointerTy());

    // emit ISD::STORE whichs stores the
    // parameter value to a stack Location
    MemOpChains.push_back(DAG.getStore(Chain, dl, Arg, PtrOff,
                                       MachinePointerInfo(),
                                       false, false, 0));
  }

  // Transform all store nodes into one single node because all store
  // nodes are independent of each other.
  if (!MemOpChains.empty())
    Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
                        &MemOpChains[0], MemOpChains.size());

  // If the callee is a GlobalAddress/ExternalSymbol node (quite common, every
  // direct call is) turn it into a TargetGlobalAddress/TargetExternalSymbol
  // node so that legalize doesn't hack it.
  unsigned char OpFlag = IsPIC ? MipsII::MO_GOT_CALL : MipsII::MO_NO_FLAG;
  bool LoadSymAddr = false;
  SDValue CalleeLo;

  if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
    if (IsPIC && G->getGlobal()->hasInternalLinkage()) {
      Callee = DAG.getTargetGlobalAddress(G->getGlobal(), dl,
                                          getPointerTy(), 0,MipsII:: MO_GOT);
      CalleeLo = DAG.getTargetGlobalAddress(G->getGlobal(), dl, getPointerTy(),
                                            0, MipsII::MO_ABS_LO);
    } else {
      Callee = DAG.getTargetGlobalAddress(G->getGlobal(), dl,
                                          getPointerTy(), 0, OpFlag);
    }

    LoadSymAddr = true;
  }
  else if (ExternalSymbolSDNode *S = dyn_cast<ExternalSymbolSDNode>(Callee)) {
    Callee = DAG.getTargetExternalSymbol(S->getSymbol(),
                                getPointerTy(), OpFlag);
    LoadSymAddr = true;
  }

  SDValue InFlag;

  // Create nodes that load address of callee and copy it to T9
  if (IsPIC) {
    if (LoadSymAddr) {
      // Load callee address
      SDValue LoadValue = DAG.getLoad(MVT::i32, dl, Chain, Callee,
                                      MachinePointerInfo::getGOT(),
                                      false, false, 0);

      // Use GOT+LO if callee has internal linkage.
      if (CalleeLo.getNode()) {
        SDValue Lo = DAG.getNode(MipsISD::Lo, dl, MVT::i32, CalleeLo);
        Callee = DAG.getNode(ISD::ADD, dl, MVT::i32, LoadValue, Lo);
      } else
        Callee = LoadValue;

      // Use chain output from LoadValue 
      Chain = LoadValue.getValue(1);
    }

    // copy to T9
    Chain = DAG.getCopyToReg(Chain, dl, Mips::T9, Callee, SDValue(0, 0));
    InFlag = Chain.getValue(1);
    Callee = DAG.getRegister(Mips::T9, MVT::i32);
  }

  // Build a sequence of copy-to-reg nodes chained together with token
  // chain and flag operands which copy the outgoing args into registers.
  // The InFlag in necessary since all emitted instructions must be
  // stuck together.
  for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i) {
    Chain = DAG.getCopyToReg(Chain, dl, RegsToPass[i].first,
                             RegsToPass[i].second, InFlag);
    InFlag = Chain.getValue(1);
  }

  // MipsJmpLink = #chain, #target_address, #opt_in_flags...
  //             = Chain, Callee, Reg#1, Reg#2, ...
  //
  // Returns a chain & a flag for retval copy to use.
  SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
  SmallVector<SDValue, 8> Ops;
  Ops.push_back(Chain);
  Ops.push_back(Callee);

  // Add argument registers to the end of the list so that they are
  // known live into the call.
  for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i)
    Ops.push_back(DAG.getRegister(RegsToPass[i].first,
                                  RegsToPass[i].second.getValueType()));

  if (InFlag.getNode())
    Ops.push_back(InFlag);

  Chain  = DAG.getNode(MipsISD::JmpLink, dl, NodeTys, &Ops[0], Ops.size());
  InFlag = Chain.getValue(1);

  // Create a stack location to hold GP when PIC is used. This stack
  // location is used on function prologue to save GP and also after all
  // emitted CALL's to restore GP.
  if (IsPIC) {
    // Function can have an arbitrary number of calls, so
    // hold the LastArgStackLoc with the biggest offset.
    int MaxCallFrameSize = MipsFI->getMaxCallFrameSize();
    unsigned NextStackOffset = CCInfo.getNextStackOffset();

    // For O32, a minimum of four words (16 bytes) of argument space is
    // allocated.
    if (Subtarget->isABI_O32())
      NextStackOffset = std::max(NextStackOffset, (unsigned)16);

    if (MaxCallFrameSize < (int)NextStackOffset) {
      MipsFI->setMaxCallFrameSize(NextStackOffset);

      // $gp restore slot must be aligned.
      unsigned StackAlignment = TFL->getStackAlignment();
      NextStackOffset = (NextStackOffset + StackAlignment - 1) / 
                        StackAlignment * StackAlignment;
      int GPFI = MipsFI->getGPFI();
      MFI->setObjectOffset(GPFI, NextStackOffset);
    }
  }

  // Extend range of indices of frame objects for outgoing arguments that were
  // created during this function call. Skip this step if no such objects were
  // created.
  if (LastFI)
    MipsFI->extendOutArgFIRange(FirstFI, LastFI);

  // Create the CALLSEQ_END node.
  Chain = DAG.getCALLSEQ_END(Chain, DAG.getIntPtrConstant(NumBytes, true),
                             DAG.getIntPtrConstant(0, true), InFlag);
  InFlag = Chain.getValue(1);

  // Handle result values, copying them out of physregs into vregs that we
  // return.
  return LowerCallResult(Chain, InFlag, CallConv, isVarArg,
                         Ins, dl, DAG, InVals);
}

/// LowerCallResult - Lower the result values of a call into the
/// appropriate copies out of appropriate physical registers.
SDValue
MipsTargetLowering::LowerCallResult(SDValue Chain, SDValue InFlag,
                                    CallingConv::ID CallConv, bool isVarArg,
                                    const SmallVectorImpl<ISD::InputArg> &Ins,
                                    DebugLoc dl, SelectionDAG &DAG,
                                    SmallVectorImpl<SDValue> &InVals) const {

  // Assign locations to each value returned by this call.
  SmallVector<CCValAssign, 16> RVLocs;
  CCState CCInfo(CallConv, isVarArg, getTargetMachine(),
                 RVLocs, *DAG.getContext());

  CCInfo.AnalyzeCallResult(Ins, RetCC_Mips);

  // Copy all of the result registers out of their specified physreg.
  for (unsigned i = 0; i != RVLocs.size(); ++i) {
    Chain = DAG.getCopyFromReg(Chain, dl, RVLocs[i].getLocReg(),
                               RVLocs[i].getValVT(), InFlag).getValue(1);
    InFlag = Chain.getValue(2);
    InVals.push_back(Chain.getValue(0));
  }

  return Chain;
}

//===----------------------------------------------------------------------===//
//             Formal Arguments Calling Convention Implementation
//===----------------------------------------------------------------------===//
static void ReadByValArg(MachineFunction &MF, SDValue Chain, DebugLoc dl,
                         std::vector<SDValue>& OutChains,
                         SelectionDAG &DAG, unsigned NumWords, SDValue FIN,
                         const CCValAssign &VA, const ISD::ArgFlagsTy& Flags) {
  unsigned LocMem = VA.getLocMemOffset();
  unsigned FirstWord = LocMem / 4;

  // copy register A0 - A3 to frame object
  for (unsigned i = 0; i < NumWords; ++i) {
    unsigned CurWord = FirstWord + i;
    if (CurWord >= O32IntRegsSize)
      break;

    unsigned SrcReg = O32IntRegs[CurWord];
    unsigned Reg = AddLiveIn(MF, SrcReg, Mips::CPURegsRegisterClass);
    SDValue StorePtr = DAG.getNode(ISD::ADD, dl, MVT::i32, FIN,
                                   DAG.getConstant(i * 4, MVT::i32));
    SDValue Store = DAG.getStore(Chain, dl, DAG.getRegister(Reg, MVT::i32),
                                 StorePtr, MachinePointerInfo(), false,
                                 false, 0);
    OutChains.push_back(Store);
  }
}

/// LowerFormalArguments - transform physical registers into virtual registers
/// and generate load operations for arguments places on the stack.
SDValue
MipsTargetLowering::LowerFormalArguments(SDValue Chain,
                                         CallingConv::ID CallConv,
                                         bool isVarArg,
                                         const SmallVectorImpl<ISD::InputArg>
                                         &Ins,
                                         DebugLoc dl, SelectionDAG &DAG,
                                         SmallVectorImpl<SDValue> &InVals)
                                          const {

  MachineFunction &MF = DAG.getMachineFunction();
  MachineFrameInfo *MFI = MF.getFrameInfo();
  MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();

  MipsFI->setVarArgsFrameIndex(0);

  // Used with vargs to acumulate store chains.
  std::vector<SDValue> OutChains;

  // Assign locations to all of the incoming arguments.
  SmallVector<CCValAssign, 16> ArgLocs;
  CCState CCInfo(CallConv, isVarArg, getTargetMachine(),
                 ArgLocs, *DAG.getContext());

  if (Subtarget->isABI_O32())
    CCInfo.AnalyzeFormalArguments(Ins, CC_MipsO32);
  else
    CCInfo.AnalyzeFormalArguments(Ins, CC_Mips);

  int LastFI = 0;// MipsFI->LastInArgFI is 0 at the entry of this function.

  for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
    CCValAssign &VA = ArgLocs[i];

    // Arguments stored on registers
    if (VA.isRegLoc()) {
      EVT RegVT = VA.getLocVT();
      unsigned ArgReg = VA.getLocReg();
      TargetRegisterClass *RC = 0;

      if (RegVT == MVT::i32)
        RC = Mips::CPURegsRegisterClass;
      else if (RegVT == MVT::f32)
        RC = Mips::FGR32RegisterClass;
      else if (RegVT == MVT::f64) {
        if (!Subtarget->isSingleFloat())
          RC = Mips::AFGR64RegisterClass;
      } else
        llvm_unreachable("RegVT not supported by FormalArguments Lowering");

      // Transform the arguments stored on
      // physical registers into virtual ones
      unsigned Reg = AddLiveIn(DAG.getMachineFunction(), ArgReg, RC);
      SDValue ArgValue = DAG.getCopyFromReg(Chain, dl, Reg, RegVT);

      // If this is an 8 or 16-bit value, it has been passed promoted
      // to 32 bits.  Insert an assert[sz]ext to capture this, then
      // truncate to the right size.
      if (VA.getLocInfo() != CCValAssign::Full) {
        unsigned Opcode = 0;
        if (VA.getLocInfo() == CCValAssign::SExt)
          Opcode = ISD::AssertSext;
        else if (VA.getLocInfo() == CCValAssign::ZExt)
          Opcode = ISD::AssertZext;
        if (Opcode)
          ArgValue = DAG.getNode(Opcode, dl, RegVT, ArgValue,
                                 DAG.getValueType(VA.getValVT()));
        ArgValue = DAG.getNode(ISD::TRUNCATE, dl, VA.getValVT(), ArgValue);
      }

      // Handle O32 ABI cases: i32->f32 and (i32,i32)->f64
      if (Subtarget->isABI_O32()) {
        if (RegVT == MVT::i32 && VA.getValVT() == MVT::f32)
          ArgValue = DAG.getNode(ISD::BITCAST, dl, MVT::f32, ArgValue);
        if (RegVT == MVT::i32 && VA.getValVT() == MVT::f64) {
          unsigned Reg2 = AddLiveIn(DAG.getMachineFunction(),
                                    VA.getLocReg()+1, RC);
          SDValue ArgValue2 = DAG.getCopyFromReg(Chain, dl, Reg2, RegVT);
          if (!Subtarget->isLittle())
            std::swap(ArgValue, ArgValue2);
          ArgValue = DAG.getNode(MipsISD::BuildPairF64, dl, MVT::f64,
                                 ArgValue, ArgValue2);
        }
      }

      InVals.push_back(ArgValue);
    } else { // VA.isRegLoc()

      // sanity check
      assert(VA.isMemLoc());

      ISD::ArgFlagsTy Flags = Ins[i].Flags;

      if (Flags.isByVal()) {
        assert(Subtarget->isABI_O32() &&
               "No support for ByVal args by ABIs other than O32 yet.");
        assert(Flags.getByValSize() &&
               "ByVal args of size 0 should have been ignored by front-end.");
        unsigned NumWords = (Flags.getByValSize() + 3) / 4;
        LastFI = MFI->CreateFixedObject(NumWords * 4, VA.getLocMemOffset(),
                                        true);
        SDValue FIN = DAG.getFrameIndex(LastFI, getPointerTy());
        InVals.push_back(FIN);
        ReadByValArg(MF, Chain, dl, OutChains, DAG, NumWords, FIN, VA, Flags);

        continue;
      }

      // The stack pointer offset is relative to the caller stack frame.
      // Since the real stack size is unknown here, a negative SPOffset
      // is used so there's a way to adjust these offsets when the stack
      // size get known (on EliminateFrameIndex). A dummy SPOffset is
      // used instead of a direct negative address (which is recorded to
      // be used on emitPrologue) to avoid mis-calc of the first stack
      // offset on PEI::calculateFrameObjectOffsets.
      LastFI = MFI->CreateFixedObject(VA.getValVT().getSizeInBits()/8,
                                      VA.getLocMemOffset(), true);

      // Create load nodes to retrieve arguments from the stack
      SDValue FIN = DAG.getFrameIndex(LastFI, getPointerTy());
      InVals.push_back(DAG.getLoad(VA.getValVT(), dl, Chain, FIN,
                                   MachinePointerInfo::getFixedStack(LastFI),
                                   false, false, 0));
    }
  }

  // The mips ABIs for returning structs by value requires that we copy
  // the sret argument into $v0 for the return. Save the argument into
  // a virtual register so that we can access it from the return points.
  if (DAG.getMachineFunction().getFunction()->hasStructRetAttr()) {
    unsigned Reg = MipsFI->getSRetReturnReg();
    if (!Reg) {
      Reg = MF.getRegInfo().createVirtualRegister(getRegClassFor(MVT::i32));
      MipsFI->setSRetReturnReg(Reg);
    }
    SDValue Copy = DAG.getCopyToReg(DAG.getEntryNode(), dl, Reg, InVals[0]);
    Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Copy, Chain);
  }

  // To meet ABI, when VARARGS are passed on registers, the registers
  // must have their values written to the caller stack frame. If the last
  // argument was placed in the stack, there's no need to save any register.
  if (isVarArg && Subtarget->isABI_O32()) {
    // Record the frame index of the first variable argument
    // which is a value necessary to VASTART.    
    unsigned NextStackOffset = CCInfo.getNextStackOffset();
    assert(NextStackOffset % 4 == 0 &&
           "NextStackOffset must be aligned to 4-byte boundaries.");
    LastFI = MFI->CreateFixedObject(4, NextStackOffset, true);
    MipsFI->setVarArgsFrameIndex(LastFI);
    
   // Copy variable arguments passed in registers to stack.
    for (; NextStackOffset < 16; NextStackOffset += 4) {
      TargetRegisterClass *RC = Mips::CPURegsRegisterClass;
      unsigned Idx = NextStackOffset / 4;
      unsigned Reg = AddLiveIn(DAG.getMachineFunction(), O32IntRegs[Idx], RC);
      SDValue ArgValue = DAG.getCopyFromReg(Chain, dl, Reg, MVT::i32);
      LastFI = MFI->CreateFixedObject(4, NextStackOffset, true);
      SDValue PtrOff = DAG.getFrameIndex(LastFI, getPointerTy());
      OutChains.push_back(DAG.getStore(Chain, dl, ArgValue, PtrOff,
                                       MachinePointerInfo(),
                                       false, false, 0));
    }
  }

  MipsFI->setLastInArgFI(LastFI);

  // All stores are grouped in one node to allow the matching between
  // the size of Ins and InVals. This only happens when on varg functions
  if (!OutChains.empty()) {
    OutChains.push_back(Chain);
    Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
                        &OutChains[0], OutChains.size());
  }

  return Chain;
}

//===----------------------------------------------------------------------===//
//               Return Value Calling Convention Implementation
//===----------------------------------------------------------------------===//

SDValue
MipsTargetLowering::LowerReturn(SDValue Chain,
                                CallingConv::ID CallConv, bool isVarArg,
                                const SmallVectorImpl<ISD::OutputArg> &Outs,
                                const SmallVectorImpl<SDValue> &OutVals,
                                DebugLoc dl, SelectionDAG &DAG) const {

  // CCValAssign - represent the assignment of
  // the return value to a location
  SmallVector<CCValAssign, 16> RVLocs;

  // CCState - Info about the registers and stack slot.
  CCState CCInfo(CallConv, isVarArg, getTargetMachine(),
                 RVLocs, *DAG.getContext());

  // Analize return values.
  CCInfo.AnalyzeReturn(Outs, RetCC_Mips);

  // If this is the first return lowered for this function, add
  // the regs to the liveout set for the function.
  if (DAG.getMachineFunction().getRegInfo().liveout_empty()) {
    for (unsigned i = 0; i != RVLocs.size(); ++i)
      if (RVLocs[i].isRegLoc())
        DAG.getMachineFunction().getRegInfo().addLiveOut(RVLocs[i].getLocReg());
  }

  SDValue Flag;

  // Copy the result values into the output registers.
  for (unsigned i = 0; i != RVLocs.size(); ++i) {
    CCValAssign &VA = RVLocs[i];
    assert(VA.isRegLoc() && "Can only return in registers!");

    Chain = DAG.getCopyToReg(Chain, dl, VA.getLocReg(),
                             OutVals[i], Flag);

    // guarantee that all emitted copies are
    // stuck together, avoiding something bad
    Flag = Chain.getValue(1);
  }

  // The mips ABIs for returning structs by value requires that we copy
  // the sret argument into $v0 for the return. We saved the argument into
  // a virtual register in the entry block, so now we copy the value out
  // and into $v0.
  if (DAG.getMachineFunction().getFunction()->hasStructRetAttr()) {
    MachineFunction &MF      = DAG.getMachineFunction();
    MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
    unsigned Reg = MipsFI->getSRetReturnReg();

    if (!Reg)
      llvm_unreachable("sret virtual register not created in the entry block");
    SDValue Val = DAG.getCopyFromReg(Chain, dl, Reg, getPointerTy());

    Chain = DAG.getCopyToReg(Chain, dl, Mips::V0, Val, Flag);
    Flag = Chain.getValue(1);
  }

  // Return on Mips is always a "jr $ra"
  if (Flag.getNode())
    return DAG.getNode(MipsISD::Ret, dl, MVT::Other,
                       Chain, DAG.getRegister(Mips::RA, MVT::i32), Flag);
  else // Return Void
    return DAG.getNode(MipsISD::Ret, dl, MVT::Other,
                       Chain, DAG.getRegister(Mips::RA, MVT::i32));
}

//===----------------------------------------------------------------------===//
//                           Mips Inline Assembly Support
//===----------------------------------------------------------------------===//

/// getConstraintType - Given a constraint letter, return the type of
/// constraint it is for this target.
MipsTargetLowering::ConstraintType MipsTargetLowering::
getConstraintType(const std::string &Constraint) const
{
  // Mips specific constrainy
  // GCC config/mips/constraints.md
  //
  // 'd' : An address register. Equivalent to r
  //       unless generating MIPS16 code.
  // 'y' : Equivalent to r; retained for
  //       backwards compatibility.
  // 'f' : Floating Point registers.
  if (Constraint.size() == 1) {
    switch (Constraint[0]) {
      default : break;
      case 'd':
      case 'y':
      case 'f':
        return C_RegisterClass;
        break;
    }
  }
  return TargetLowering::getConstraintType(Constraint);
}

/// Examine constraint type and operand type and determine a weight value.
/// This object must already have been set up with the operand type
/// and the current alternative constraint selected.
TargetLowering::ConstraintWeight
MipsTargetLowering::getSingleConstraintMatchWeight(
    AsmOperandInfo &info, const char *constraint) const {
  ConstraintWeight weight = CW_Invalid;
  Value *CallOperandVal = info.CallOperandVal;
    // If we don't have a value, we can't do a match,
    // but allow it at the lowest weight.
  if (CallOperandVal == NULL)
    return CW_Default;
  const Type *type = CallOperandVal->getType();
  // Look at the constraint type.
  switch (*constraint) {
  default:
    weight = TargetLowering::getSingleConstraintMatchWeight(info, constraint);
    break;
  case 'd':
  case 'y':
    if (type->isIntegerTy())
      weight = CW_Register;
    break;
  case 'f':
    if (type->isFloatTy())
      weight = CW_Register;
    break;
  }
  return weight;
}

/// getRegClassForInlineAsmConstraint - Given a constraint letter (e.g. "r"),
/// return a list of registers that can be used to satisfy the constraint.
/// This should only be used for C_RegisterClass constraints.
std::pair<unsigned, const TargetRegisterClass*> MipsTargetLowering::
getRegForInlineAsmConstraint(const std::string &Constraint, EVT VT) const
{
  if (Constraint.size() == 1) {
    switch (Constraint[0]) {
    case 'r':
      return std::make_pair(0U, Mips::CPURegsRegisterClass);
    case 'f':
      if (VT == MVT::f32)
        return std::make_pair(0U, Mips::FGR32RegisterClass);
      if (VT == MVT::f64)
        if ((!Subtarget->isSingleFloat()) && (!Subtarget->isFP64bit()))
          return std::make_pair(0U, Mips::AFGR64RegisterClass);
    }
  }
  return TargetLowering::getRegForInlineAsmConstraint(Constraint, VT);
}

/// Given a register class constraint, like 'r', if this corresponds directly
/// to an LLVM register class, return a register of 0 and the register class
/// pointer.
std::vector<unsigned> MipsTargetLowering::
getRegClassForInlineAsmConstraint(const std::string &Constraint,
                                  EVT VT) const
{
  if (Constraint.size() != 1)
    return std::vector<unsigned>();

  switch (Constraint[0]) {
    default : break;
    case 'r':
    // GCC Mips Constraint Letters
    case 'd':
    case 'y':
      return make_vector<unsigned>(Mips::T0, Mips::T1, Mips::T2, Mips::T3,
             Mips::T4, Mips::T5, Mips::T6, Mips::T7, Mips::S0, Mips::S1,
             Mips::S2, Mips::S3, Mips::S4, Mips::S5, Mips::S6, Mips::S7,
             Mips::T8, 0);

    case 'f':
      if (VT == MVT::f32) {
        if (Subtarget->isSingleFloat())
          return make_vector<unsigned>(Mips::F2, Mips::F3, Mips::F4, Mips::F5,
                 Mips::F6, Mips::F7, Mips::F8, Mips::F9, Mips::F10, Mips::F11,
                 Mips::F20, Mips::F21, Mips::F22, Mips::F23, Mips::F24,
                 Mips::F25, Mips::F26, Mips::F27, Mips::F28, Mips::F29,
                 Mips::F30, Mips::F31, 0);
        else
          return make_vector<unsigned>(Mips::F2, Mips::F4, Mips::F6, Mips::F8,
                 Mips::F10, Mips::F20, Mips::F22, Mips::F24, Mips::F26,
                 Mips::F28, Mips::F30, 0);
      }

      if (VT == MVT::f64)
        if ((!Subtarget->isSingleFloat()) && (!Subtarget->isFP64bit()))
          return make_vector<unsigned>(Mips::D1, Mips::D2, Mips::D3, Mips::D4,
                 Mips::D5, Mips::D10, Mips::D11, Mips::D12, Mips::D13,
                 Mips::D14, Mips::D15, 0);
  }
  return std::vector<unsigned>();
}

bool
MipsTargetLowering::isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const {
  // The Mips target isn't yet aware of offsets.
  return false;
}

bool MipsTargetLowering::isFPImmLegal(const APFloat &Imm, EVT VT) const {
  if (VT != MVT::f32 && VT != MVT::f64)
    return false;
  if (Imm.isNegZero())
    return false;
  return Imm.isZero();
}