lib/Target/MBlaze/MBlazeISelLowering.cpp

//===-- MBlazeISelLowering.cpp - MBlaze 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 MBlaze uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "mblaze-lower"
#include "MBlazeISelLowering.h"
#include "MBlazeMachineFunction.h"
#include "MBlazeTargetMachine.h"
#include "MBlazeTargetObjectFile.h"
#include "MBlazeSubtarget.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"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;

const char *MBlazeTargetLowering::getTargetNodeName(unsigned Opcode) const {
  switch (Opcode) {
    case MBlazeISD::JmpLink    : return "MBlazeISD::JmpLink";
    case MBlazeISD::GPRel      : return "MBlazeISD::GPRel";
    case MBlazeISD::Wrap       : return "MBlazeISD::Wrap";
    case MBlazeISD::ICmp       : return "MBlazeISD::ICmp";
    case MBlazeISD::Ret        : return "MBlazeISD::Ret";
    case MBlazeISD::Select_CC  : return "MBlazeISD::Select_CC";
    default                    : return NULL;
  }
}

MBlazeTargetLowering::MBlazeTargetLowering(MBlazeTargetMachine &TM)
  : TargetLowering(TM, new MBlazeTargetObjectFile()) {
  Subtarget = &TM.getSubtarget<MBlazeSubtarget>();

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

  // Set up the register classes
  addRegisterClass(MVT::i32, MBlaze::CPURegsRegisterClass);
  if (Subtarget->hasFPU()) {
    addRegisterClass(MVT::f32, MBlaze::FGR32RegisterClass);
    setOperationAction(ISD::ConstantFP, MVT::f32, Legal);
  }

  // Floating point operations which are not supported
  setOperationAction(ISD::FREM,       MVT::f32, Expand);
  setOperationAction(ISD::UINT_TO_FP, MVT::i8,  Expand);
  setOperationAction(ISD::UINT_TO_FP, MVT::i16, Expand);
  setOperationAction(ISD::UINT_TO_FP, MVT::i32, Expand);
  setOperationAction(ISD::FP_TO_UINT, MVT::i32, Expand);
  setOperationAction(ISD::FP_ROUND,   MVT::f32, Expand);
  setOperationAction(ISD::FP_ROUND,   MVT::f64, Expand);
  setOperationAction(ISD::FCOPYSIGN,  MVT::f32, Expand);
  setOperationAction(ISD::FCOPYSIGN,  MVT::f64, Expand);
  setOperationAction(ISD::FSIN,       MVT::f32, Expand);
  setOperationAction(ISD::FCOS,       MVT::f32, Expand);
  setOperationAction(ISD::FPOWI,      MVT::f32, Expand);
  setOperationAction(ISD::FPOW,       MVT::f32, 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);

  // 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);

  // MBlaze has no REM or DIVREM operations.
  setOperationAction(ISD::UREM,    MVT::i32, Expand);
  setOperationAction(ISD::SREM,    MVT::i32, Expand);
  setOperationAction(ISD::SDIVREM, MVT::i32, Expand);
  setOperationAction(ISD::UDIVREM, MVT::i32, Expand);

  // If the processor doesn't support multiply then expand it
  if (!Subtarget->hasMul()) {
    setOperationAction(ISD::MUL, MVT::i32, Expand);
  }

  // If the processor doesn't support 64-bit multiply then expand
  if (!Subtarget->hasMul() || !Subtarget->hasMul64()) {
    setOperationAction(ISD::MULHS, MVT::i32, Expand);
    setOperationAction(ISD::MULHS, MVT::i64, Expand);
    setOperationAction(ISD::MULHU, MVT::i32, Expand);
    setOperationAction(ISD::MULHU, MVT::i64, Expand);
  }

  // If the processor doesn't support division then expand
  if (!Subtarget->hasDiv()) {
    setOperationAction(ISD::UDIV, MVT::i32, Expand);
    setOperationAction(ISD::SDIV, MVT::i32, Expand);
  }

  // Expand unsupported conversions
  setOperationAction(ISD::BIT_CONVERT, MVT::f32, Expand);
  setOperationAction(ISD::BIT_CONVERT, MVT::i32, Expand);

  // Expand SELECT_CC
  setOperationAction(ISD::SELECT_CC, MVT::Other, Expand);

  // MBlaze doesn't have MUL_LOHI
  setOperationAction(ISD::SMUL_LOHI, MVT::i32, Expand);
  setOperationAction(ISD::UMUL_LOHI, MVT::i32, Expand);
  setOperationAction(ISD::SMUL_LOHI, MVT::i64, Expand);
  setOperationAction(ISD::UMUL_LOHI, MVT::i64, 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);
  AddPromotedToType(ISD::SELECT, MVT::i1, MVT::i32);
  AddPromotedToType(ISD::SELECT_CC, MVT::i1, MVT::i32);

  // MBlaze Custom Operations
  setOperationAction(ISD::GlobalAddress,      MVT::i32,   Custom);
  setOperationAction(ISD::GlobalTLSAddress,   MVT::i32,   Custom);
  setOperationAction(ISD::JumpTable,          MVT::i32,   Custom);
  setOperationAction(ISD::ConstantPool,       MVT::i32,   Custom);

  // Operations not directly supported by MBlaze.
  setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i32,   Expand);
  setOperationAction(ISD::BR_JT,              MVT::Other, Expand);
  setOperationAction(ISD::BR_CC,              MVT::Other, Expand);
  setOperationAction(ISD::SIGN_EXTEND_INREG,  MVT::i1,    Expand);
  setOperationAction(ISD::ROTL,               MVT::i32,   Expand);
  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::CTLZ,               MVT::i32,   Expand);
  setOperationAction(ISD::CTTZ,               MVT::i32,   Expand);
  setOperationAction(ISD::CTPOP,              MVT::i32,   Expand);
  setOperationAction(ISD::BSWAP,              MVT::i32,   Expand);

  // We don't have line number support yet.
  setOperationAction(ISD::EH_LABEL,          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);

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

  setStackPointerRegisterToSaveRestore(MBlaze::R1);
  computeRegisterProperties();
}

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

/// getFunctionAlignment - Return the Log2 alignment of this function.
unsigned MBlazeTargetLowering::getFunctionAlignment(const Function *) const {
  return 2;
}

SDValue MBlazeTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) {
  switch (Op.getOpcode())
  {
    case ISD::ConstantPool:       return LowerConstantPool(Op, DAG);
    case ISD::GlobalAddress:      return LowerGlobalAddress(Op, DAG);
    case ISD::GlobalTLSAddress:   return LowerGlobalTLSAddress(Op, DAG);
    case ISD::JumpTable:          return LowerJumpTable(Op, DAG);
    case ISD::SELECT_CC:          return LowerSELECT_CC(Op, DAG);
  }
  return SDValue();
}

//===----------------------------------------------------------------------===//
//  Lower helper functions
//===----------------------------------------------------------------------===//
MachineBasicBlock* MBlazeTargetLowering::
EmitInstrWithCustomInserter(MachineInstr *MI, MachineBasicBlock *BB,
                            DenseMap<MachineBasicBlock*,
                            MachineBasicBlock*> *EM) const {
  const TargetInstrInfo *TII = getTargetMachine().getInstrInfo();
  DebugLoc dl = MI->getDebugLoc();

  switch (MI->getOpcode()) {
  default: assert(false && "Unexpected instr type to insert");
  case MBlaze::ShiftRL:
  case MBlaze::ShiftRA:
  case MBlaze::ShiftL: {
    // To "insert" a shift left instruction, we actually have to insert a
    // simple loop.  The incoming instruction knows the destination vreg to
    // set, the source vreg to operate over and the shift amount.
    const BasicBlock *LLVM_BB = BB->getBasicBlock();
    MachineFunction::iterator It = BB;
    ++It;

    // start:
    //   andi     samt, samt, 31
    //   beqid    samt, finish
    //   add      dst, src, r0
    // loop:
    //   addik    samt, samt, -1
    //   sra      dst, dst
    //   bneid    samt, loop
    //   nop
    // finish:
    MachineFunction *F = BB->getParent();
    MachineRegisterInfo &R = F->getRegInfo();
    MachineBasicBlock *loop = F->CreateMachineBasicBlock(LLVM_BB);
    MachineBasicBlock *finish = F->CreateMachineBasicBlock(LLVM_BB);

    unsigned IAMT = R.createVirtualRegister(MBlaze::CPURegsRegisterClass);
    BuildMI(BB, dl, TII->get(MBlaze::ANDI), IAMT)
      .addReg(MI->getOperand(2).getReg())
      .addImm(31);

    unsigned IVAL = R.createVirtualRegister(MBlaze::CPURegsRegisterClass);
    BuildMI(BB, dl, TII->get(MBlaze::ADDI), IVAL)
      .addReg(MI->getOperand(1).getReg())
      .addImm(0);

    BuildMI(BB, dl, TII->get(MBlaze::BEQID))
      .addReg(IAMT)
      .addMBB(finish);

    F->insert(It, loop);
    F->insert(It, finish);

    // Update machine-CFG edges by first adding all successors of the current
    // block to the new block which will contain the Phi node for the select.
    // Also inform sdisel of the edge changes.
    for(MachineBasicBlock::succ_iterator i = BB->succ_begin(),
          e = BB->succ_end(); i != e; ++i) {
      EM->insert(std::make_pair(*i, finish));
      finish->addSuccessor(*i);
    }

    // Next, remove all successors of the current block, and add the true
    // and fallthrough blocks as its successors.
    while(!BB->succ_empty())
      BB->removeSuccessor(BB->succ_begin());
    BB->addSuccessor(loop);
    BB->addSuccessor(finish);

    // Next, add the finish block as a successor of the loop block
    loop->addSuccessor(finish);
    loop->addSuccessor(loop);

    unsigned DST = R.createVirtualRegister(MBlaze::CPURegsRegisterClass);
    unsigned NDST = R.createVirtualRegister(MBlaze::CPURegsRegisterClass);
    BuildMI(loop, dl, TII->get(MBlaze::PHI), DST)
      .addReg(IVAL).addMBB(BB)
      .addReg(NDST).addMBB(loop);

    unsigned SAMT = R.createVirtualRegister(MBlaze::CPURegsRegisterClass);
    unsigned NAMT = R.createVirtualRegister(MBlaze::CPURegsRegisterClass);
    BuildMI(loop, dl, TII->get(MBlaze::PHI), SAMT)
      .addReg(IAMT).addMBB(BB)
      .addReg(NAMT).addMBB(loop);

    if (MI->getOpcode() == MBlaze::ShiftL)
      BuildMI(loop, dl, TII->get(MBlaze::ADD), NDST).addReg(DST).addReg(DST);
    else if (MI->getOpcode() == MBlaze::ShiftRA)
      BuildMI(loop, dl, TII->get(MBlaze::SRA), NDST).addReg(DST);
    else if (MI->getOpcode() == MBlaze::ShiftRL)
      BuildMI(loop, dl, TII->get(MBlaze::SRL), NDST).addReg(DST);
    else
        llvm_unreachable( "Cannot lower unknown shift instruction" );

    BuildMI(loop, dl, TII->get(MBlaze::ADDI), NAMT)
      .addReg(SAMT)
      .addImm(-1);

    BuildMI(loop, dl, TII->get(MBlaze::BNEID))
      .addReg(NAMT)
      .addMBB(loop);

    BuildMI(finish, dl, TII->get(MBlaze::PHI), MI->getOperand(0).getReg())
      .addReg(IVAL).addMBB(BB)
      .addReg(NDST).addMBB(loop);

    // The pseudo instruction is no longer needed so remove it
    F->DeleteMachineInstr(MI);
    return finish;
    }

  case MBlaze::Select_FCC:
  case MBlaze::Select_CC: {
    // 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
    MachineFunction *F = BB->getParent();
    MachineBasicBlock *flsBB = F->CreateMachineBasicBlock(LLVM_BB);
    MachineBasicBlock *dneBB = F->CreateMachineBasicBlock(LLVM_BB);

    unsigned Opc;
    switch (MI->getOperand(4).getImm()) {
    default: llvm_unreachable( "Unknown branch condition" );
    case MBlazeCC::EQ: Opc = MBlaze::BNEID; break;
    case MBlazeCC::NE: Opc = MBlaze::BEQID; break;
    case MBlazeCC::GT: Opc = MBlaze::BLEID; break;
    case MBlazeCC::LT: Opc = MBlaze::BGEID; break;
    case MBlazeCC::GE: Opc = MBlaze::BLTID; break;
    case MBlazeCC::LE: Opc = MBlaze::BGTID; break;
    }

    BuildMI(BB, dl, TII->get(Opc))
      .addReg(MI->getOperand(3).getReg())
      .addMBB(dneBB);

    F->insert(It, flsBB);
    F->insert(It, dneBB);

    // Update machine-CFG edges by first adding all successors of the current
    // block to the new block which will contain the Phi node for the select.
    // Also inform sdisel of the edge changes.
    for(MachineBasicBlock::succ_iterator i = BB->succ_begin(),
          e = BB->succ_end(); i != e; ++i) {
      EM->insert(std::make_pair(*i, dneBB));
      dneBB->addSuccessor(*i);
    }

    // Next, remove all successors of the current block, and add the true
    // and fallthrough blocks as its successors.
    while(!BB->succ_empty())
      BB->removeSuccessor(BB->succ_begin());
    BB->addSuccessor(flsBB);
    BB->addSuccessor(dneBB);
    flsBB->addSuccessor(dneBB);

    //  sinkMBB:
    //   %Result = phi [ %FalseValue, copy0MBB ], [ %TrueValue, thisMBB ]
    //  ...
    //BuildMI(dneBB, dl, TII->get(MBlaze::PHI), MI->getOperand(0).getReg())
    //  .addReg(MI->getOperand(1).getReg()).addMBB(flsBB)
    //  .addReg(MI->getOperand(2).getReg()).addMBB(BB);

    BuildMI(dneBB, dl, TII->get(MBlaze::PHI), MI->getOperand(0).getReg())
      .addReg(MI->getOperand(2).getReg()).addMBB(flsBB)
      .addReg(MI->getOperand(1).getReg()).addMBB(BB);

    F->DeleteMachineInstr(MI);   // The pseudo instruction is gone now.
    return dneBB;
  }
  }
}

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

SDValue MBlazeTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) {
  SDValue LHS = Op.getOperand(0);
  SDValue RHS = Op.getOperand(1);
  SDValue TrueVal = Op.getOperand(2);
  SDValue FalseVal = Op.getOperand(3);
  DebugLoc dl = Op.getDebugLoc();
  unsigned Opc;

  SDValue CompareFlag;
  if (LHS.getValueType() == MVT::i32) {
    Opc = MBlazeISD::Select_CC;
    CompareFlag = DAG.getNode(MBlazeISD::ICmp, dl, MVT::i32, LHS, RHS)
                    .getValue(1);
  } else {
    llvm_unreachable( "Cannot lower select_cc with unknown type" );
  }
 
  return DAG.getNode(Opc, dl, TrueVal.getValueType(), TrueVal, FalseVal,
                     CompareFlag);
}

SDValue MBlazeTargetLowering::
LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) {
  // FIXME there isn't actually debug info here
  DebugLoc dl = Op.getDebugLoc();
  GlobalValue *GV = cast<GlobalAddressSDNode>(Op)->getGlobal();
  SDValue GA = DAG.getTargetGlobalAddress(GV, MVT::i32);

  return DAG.getNode(MBlazeISD::Wrap, dl, MVT::i32, GA);
}

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

SDValue MBlazeTargetLowering::
LowerJumpTable(SDValue Op, SelectionDAG &DAG) {
  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 ? MBlazeII::MO_GOT : MBlazeII::MO_ABS_HILO;

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

  SDValue JTI = DAG.getTargetJumpTable(JT->getIndex(), PtrVT, OpFlag);
  return DAG.getNode(MBlazeISD::Wrap, dl, MVT::i32, JTI);
  //return JTI;
}

SDValue MBlazeTargetLowering::
LowerConstantPool(SDValue Op, SelectionDAG &DAG) {
  SDValue ResNode;
  EVT PtrVT = Op.getValueType();
  ConstantPoolSDNode *N = cast<ConstantPoolSDNode>(Op);
  Constant *C = N->getConstVal();
  SDValue Zero = DAG.getConstant(0, PtrVT);
  // FIXME there isn't actually debug info here
  DebugLoc dl = Op.getDebugLoc();

  SDValue CP = DAG.getTargetConstantPool(C, MVT::i32, N->getAlignment(),
                                         N->getOffset(), MBlazeII::MO_ABS_HILO);
  return DAG.getNode(MBlazeISD::Wrap, dl, MVT::i32, CP);
}

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

#include "MBlazeGenCallingConv.inc"

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

/// LowerCall - functions arguments are copied from virtual regs to
/// (physical regs)/(stack frame), CALLSEQ_START and CALLSEQ_END are emitted.
/// TODO: isVarArg, isTailCall.
SDValue MBlazeTargetLowering::
LowerCall(SDValue Chain, SDValue Callee, CallingConv::ID CallConv,
          bool isVarArg, bool &isTailCall,
          const SmallVectorImpl<ISD::OutputArg> &Outs,
          const SmallVectorImpl<ISD::InputArg> &Ins,
          DebugLoc dl, SelectionDAG &DAG,
          SmallVectorImpl<SDValue> &InVals) {
  MachineFunction &MF = DAG.getMachineFunction();
  MachineFrameInfo *MFI = MF.getFrameInfo();

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

  // 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));

  SmallVector<std::pair<unsigned, SDValue>, 8> RegsToPass;
  SmallVector<SDValue, 8> MemOpChains;

  // First/LastArgStackLoc contains the first/last
  // "at stack" argument location.
  int LastArgStackLoc = 0;
  unsigned FirstStackArgLoc = 4;

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

    // Promote the value if needed.
    switch (VA.getLocInfo()) {
    default: llvm_unreachable("Unknown loc info!");
    case CCValAssign::Full: break;
    case CCValAssign::SExt:
      Arg = DAG.getNode(ISD::SIGN_EXTEND, dl, RegVT, Arg);
      break;
    case CCValAssign::ZExt:
      Arg = DAG.getNode(ISD::ZERO_EXTEND, dl, RegVT, Arg);
      break;
    case CCValAssign::AExt:
      Arg = DAG.getNode(ISD::ANY_EXTEND, dl, RegVT, Arg);
      break;
    case CCValAssign::BCvt:
      Arg = DAG.getNode(ISD::BIT_CONVERT, dl, RegVT, 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));
    } else {
      // Register can't get to this point...
      assert(VA.isMemLoc());

      // Create the frame index object for this incoming parameter
      LastArgStackLoc = (FirstStackArgLoc + VA.getLocMemOffset());
      int FI = MFI->CreateFixedObject(VA.getValVT().getSizeInBits()/8,
                                      LastArgStackLoc, true, false);

      SDValue PtrOff = DAG.getFrameIndex(FI,getPointerTy());

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

  // 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 emited instructions must be
  // stuck together.
  SDValue InFlag;
  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);
  }

  // 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 = MBlazeII::MO_NO_FLAG;
  if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee))
    Callee = DAG.getTargetGlobalAddress(G->getGlobal(),
                                getPointerTy(), 0, OpFlag);
  else if (ExternalSymbolSDNode *S = dyn_cast<ExternalSymbolSDNode>(Callee))
    Callee = DAG.getTargetExternalSymbol(S->getSymbol(),
                                getPointerTy(), OpFlag);

  // MBlazeJmpLink = #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::Flag);
  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(MBlazeISD::JmpLink, dl, NodeTys, &Ops[0], Ops.size());
  InFlag = Chain.getValue(1);

  // Create the CALLSEQ_END node.
  Chain = DAG.getCALLSEQ_END(Chain, DAG.getIntPtrConstant(NumBytes, true),
                             DAG.getIntPtrConstant(0, true), InFlag);
  if (!Ins.empty())
    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 MBlazeTargetLowering::
LowerCallResult(SDValue Chain, SDValue InFlag, CallingConv::ID CallConv,
                bool isVarArg, const SmallVectorImpl<ISD::InputArg> &Ins,
                DebugLoc dl, SelectionDAG &DAG,
                SmallVectorImpl<SDValue> &InVals) {
  // 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_MBlaze);

  // 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
//===----------------------------------------------------------------------===//

/// LowerFormalArguments - transform physical registers into
/// virtual registers and generate load operations for
/// arguments places on the stack.
/// TODO: isVarArg
SDValue MBlazeTargetLowering::
LowerFormalArguments(SDValue Chain, CallingConv::ID CallConv, bool isVarArg,
                     const SmallVectorImpl<ISD::InputArg> &Ins,
                     DebugLoc dl, SelectionDAG &DAG,
                     SmallVectorImpl<SDValue> &InVals) {
  MachineFunction &MF = DAG.getMachineFunction();
  MachineFrameInfo *MFI = MF.getFrameInfo();
  MBlazeFunctionInfo *MBlazeFI = MF.getInfo<MBlazeFunctionInfo>();

  unsigned StackReg = MF.getTarget().getRegisterInfo()->getFrameRegister(MF);

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

  CCInfo.AnalyzeFormalArguments(Ins, CC_MBlaze);
  SDValue StackPtr;

  unsigned FirstStackArgLoc = 4;

  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();
      TargetRegisterClass *RC = 0;

      if (RegVT == MVT::i32)
        RC = MBlaze::CPURegsRegisterClass;
      else if (RegVT == MVT::f32)
        RC = MBlaze::FGR32RegisterClass;
      else
        llvm_unreachable("RegVT not supported by LowerFormalArguments");

      // Transform the arguments stored on
      // physical registers into virtual ones
      unsigned Reg = MF.addLiveIn(VA.getLocReg(), 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);
      }

      InVals.push_back(ArgValue);

      // To meet ABI, when VARARGS are passed on registers, the registers
      // must have their values written to the caller stack frame.
      if (isVarArg) {
        if (StackPtr.getNode() == 0)
          StackPtr = DAG.getRegister(StackReg, getPointerTy());

        // 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.
        // Arguments are always 32-bit.
        int FI = MFI->CreateFixedObject(4, 0, true, false);
        MBlazeFI->recordStoreVarArgsFI(FI, -(FirstStackArgLoc+(i*4)));
        SDValue PtrOff = DAG.getFrameIndex(FI, getPointerTy());

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

    } else { // VA.isRegLoc()

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

      // 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.
      // Arguments are always 32-bit.
      unsigned ArgSize = VA.getLocVT().getSizeInBits()/8;
      int FI = MFI->CreateFixedObject(ArgSize, 0, true, false);
      MBlazeFI->recordLoadArgsFI(FI, -(ArgSize+
        (FirstStackArgLoc + VA.getLocMemOffset())));

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

  return Chain;
}

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

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

  // 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(),
                             Outs[i].Val, Flag);

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

  // Return on MBlaze is always a "rtsd R15, 8"
  if (Flag.getNode())
    return DAG.getNode(MBlazeISD::Ret, dl, MVT::Other,
                       Chain, DAG.getRegister(MBlaze::R15, MVT::i32), Flag);
  else // Return Void
    return DAG.getNode(MBlazeISD::Ret, dl, MVT::Other,
                       Chain, DAG.getRegister(MBlaze::R15, MVT::i32));
}

//===----------------------------------------------------------------------===//
//                           MBlaze Inline Assembly Support
//===----------------------------------------------------------------------===//

/// getConstraintType - Given a constraint letter, return the type of
/// constraint it is for this target.
MBlazeTargetLowering::ConstraintType MBlazeTargetLowering::
getConstraintType(const std::string &Constraint) const
{
  // MBlaze specific constrainy
  //
  // 'd' : An address register. Equivalent to r.
  // '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);
}

/// 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*> MBlazeTargetLowering::
getRegForInlineAsmConstraint(const std::string &Constraint, EVT VT) const {
  if (Constraint.size() == 1) {
    switch (Constraint[0]) {
    case 'r':
      return std::make_pair(0U, MBlaze::CPURegsRegisterClass);
    case 'f':
      if (VT == MVT::f32)
        return std::make_pair(0U, MBlaze::FGR32RegisterClass);
    }
  }
  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> MBlazeTargetLowering::
getRegClassForInlineAsmConstraint(const std::string &Constraint, EVT VT) const {
  if (Constraint.size() != 1)
    return std::vector<unsigned>();

  switch (Constraint[0]) {
    default : break;
    case 'r':
    // GCC MBlaze Constraint Letters
    case 'd':
    case 'y':
      return make_vector<unsigned>(
        MBlaze::R3,  MBlaze::R4,  MBlaze::R5,  MBlaze::R6,
        MBlaze::R7,  MBlaze::R9,  MBlaze::R10, MBlaze::R11,
        MBlaze::R12, MBlaze::R19, MBlaze::R20, MBlaze::R21,
        MBlaze::R22, MBlaze::R23, MBlaze::R24, MBlaze::R25,
        MBlaze::R26, MBlaze::R27, MBlaze::R28, MBlaze::R29,
        MBlaze::R30, MBlaze::R31, 0);

    case 'f':
      return make_vector<unsigned>(
        MBlaze::F3,  MBlaze::F4,  MBlaze::F5,  MBlaze::F6,
        MBlaze::F7,  MBlaze::F9,  MBlaze::F10, MBlaze::F11,
        MBlaze::F12, MBlaze::F19, MBlaze::F20, MBlaze::F21,
        MBlaze::F22, MBlaze::F23, MBlaze::F24, MBlaze::F25,
        MBlaze::F26, MBlaze::F27, MBlaze::F28, MBlaze::F29,
        MBlaze::F30, MBlaze::F31, 0);
  }
  return std::vector<unsigned>();
}

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

bool MBlazeTargetLowering::isFPImmLegal(const APFloat &Imm, EVT VT) const {
  return VT != MVT::f32;
}