lib/Target/PowerPC/PPCFastISel.cpp

//===-- PPCFastISel.cpp - PowerPC FastISel 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 PowerPC-specific support for the FastISel class. Some
// of the target-specific code is generated by tablegen in the file
// PPCGenFastISel.inc, which is #included here.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "ppcfastisel"
#include "PPC.h"
#include "PPCISelLowering.h"
#include "PPCSubtarget.h"
#include "PPCTargetMachine.h"
#include "MCTargetDesc/PPCPredicates.h"
#include "llvm/ADT/Optional.h"
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/FastISel.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Operator.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"

using namespace llvm;

namespace {

typedef struct Address {
  enum {
    RegBase,
    FrameIndexBase
  } BaseType;

  union {
    unsigned Reg;
    int FI;
  } Base;

  long Offset;

  // Innocuous defaults for our address.
  Address()
   : BaseType(RegBase), Offset(0) {
     Base.Reg = 0;
   }
} Address;

class PPCFastISel : public FastISel {

  const TargetMachine &TM;
  const TargetInstrInfo &TII;
  const TargetLowering &TLI;
  const PPCSubtarget &PPCSubTarget;
  LLVMContext *Context;

  public:
    explicit PPCFastISel(FunctionLoweringInfo &FuncInfo,
                         const TargetLibraryInfo *LibInfo)
    : FastISel(FuncInfo, LibInfo),
      TM(FuncInfo.MF->getTarget()),
      TII(*TM.getInstrInfo()),
      TLI(*TM.getTargetLowering()),
      PPCSubTarget(
       *((static_cast<const PPCTargetMachine *>(&TM))->getSubtargetImpl())
      ),
      Context(&FuncInfo.Fn->getContext()) { }

  // Backend specific FastISel code.
  private:
    virtual bool TargetSelectInstruction(const Instruction *I);
    virtual unsigned TargetMaterializeConstant(const Constant *C);
    virtual unsigned TargetMaterializeAlloca(const AllocaInst *AI);
    virtual bool tryToFoldLoadIntoMI(MachineInstr *MI, unsigned OpNo,
                                     const LoadInst *LI);
    virtual bool FastLowerArguments();
    virtual unsigned FastEmit_i(MVT Ty, MVT RetTy, unsigned Opc, uint64_t Imm);
    virtual unsigned FastEmitInst_ri(unsigned MachineInstOpcode,
                                     const TargetRegisterClass *RC,
                                     unsigned Op0, bool Op0IsKill,
                                     uint64_t Imm);
    virtual unsigned FastEmitInst_r(unsigned MachineInstOpcode,
                                    const TargetRegisterClass *RC,
                                    unsigned Op0, bool Op0IsKill);
    virtual unsigned FastEmitInst_rr(unsigned MachineInstOpcode,
                                     const TargetRegisterClass *RC,
                                     unsigned Op0, bool Op0IsKill,
                                     unsigned Op1, bool Op1IsKill);

  // Instruction selection routines.
  private:
    bool SelectLoad(const Instruction *I);
    bool SelectStore(const Instruction *I);
    bool SelectBranch(const Instruction *I);
    bool SelectIndirectBr(const Instruction *I);
    bool SelectBinaryIntOp(const Instruction *I, unsigned ISDOpcode);
    bool SelectRet(const Instruction *I);
    bool SelectIntExt(const Instruction *I);

  // Utility routines.
  private:
    bool isTypeLegal(Type *Ty, MVT &VT);
    bool isLoadTypeLegal(Type *Ty, MVT &VT);
    bool PPCEmitCmp(const Value *Src1Value, const Value *Src2Value,
                    bool isZExt, unsigned DestReg);
    bool PPCEmitLoad(MVT VT, unsigned &ResultReg, Address &Addr,
                     const TargetRegisterClass *RC, bool IsZExt = true,
                     unsigned FP64LoadOpc = PPC::LFD);
    bool PPCEmitStore(MVT VT, unsigned SrcReg, Address &Addr);
    bool PPCComputeAddress(const Value *Obj, Address &Addr);
    void PPCSimplifyAddress(Address &Addr, MVT VT, bool &UseOffset,
                            unsigned &IndexReg);
    bool PPCEmitIntExt(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                           unsigned DestReg, bool IsZExt);
    unsigned PPCMaterializeFP(const ConstantFP *CFP, MVT VT);
    unsigned PPCMaterializeGV(const GlobalValue *GV, MVT VT);
    unsigned PPCMaterializeInt(const Constant *C, MVT VT);
    unsigned PPCMaterialize32BitInt(int64_t Imm,
                                    const TargetRegisterClass *RC);
    unsigned PPCMaterialize64BitInt(int64_t Imm,
                                    const TargetRegisterClass *RC);

  // Call handling routines.
  private:
    CCAssignFn *usePPC32CCs(unsigned Flag);

  private:
  #include "PPCGenFastISel.inc"

};

} // end anonymous namespace

#include "PPCGenCallingConv.inc"

// Function whose sole purpose is to kill compiler warnings 
// stemming from unused functions included from PPCGenCallingConv.inc.
CCAssignFn *PPCFastISel::usePPC32CCs(unsigned Flag) {
  if (Flag == 1)
    return CC_PPC32_SVR4;
  else if (Flag == 2)
    return CC_PPC32_SVR4_ByVal;
  else if (Flag == 3)
    return CC_PPC32_SVR4_VarArg;
  else
    return RetCC_PPC;
}

static Optional<PPC::Predicate> getComparePred(CmpInst::Predicate Pred) {
  switch (Pred) {
    // These are not representable with any single compare.
    case CmpInst::FCMP_FALSE:
    case CmpInst::FCMP_UEQ:
    case CmpInst::FCMP_UGT:
    case CmpInst::FCMP_UGE:
    case CmpInst::FCMP_ULT:
    case CmpInst::FCMP_ULE:
    case CmpInst::FCMP_UNE:
    case CmpInst::FCMP_TRUE:
    default:
      return Optional<PPC::Predicate>();

    case CmpInst::FCMP_OEQ:
    case CmpInst::ICMP_EQ:
      return PPC::PRED_EQ;

    case CmpInst::FCMP_OGT:
    case CmpInst::ICMP_UGT:
    case CmpInst::ICMP_SGT:
      return PPC::PRED_GT;

    case CmpInst::FCMP_OGE:
    case CmpInst::ICMP_UGE:
    case CmpInst::ICMP_SGE:
      return PPC::PRED_GE;

    case CmpInst::FCMP_OLT:
    case CmpInst::ICMP_ULT:
    case CmpInst::ICMP_SLT:
      return PPC::PRED_LT;

    case CmpInst::FCMP_OLE:
    case CmpInst::ICMP_ULE:
    case CmpInst::ICMP_SLE:
      return PPC::PRED_LE;

    case CmpInst::FCMP_ONE:
    case CmpInst::ICMP_NE:
      return PPC::PRED_NE;

    case CmpInst::FCMP_ORD:
      return PPC::PRED_NU;

    case CmpInst::FCMP_UNO:
      return PPC::PRED_UN;
  }
}

// Determine whether the type Ty is simple enough to be handled by
// fast-isel, and return its equivalent machine type in VT.
// FIXME: Copied directly from ARM -- factor into base class?
bool PPCFastISel::isTypeLegal(Type *Ty, MVT &VT) {
  EVT Evt = TLI.getValueType(Ty, true);

  // Only handle simple types.
  if (Evt == MVT::Other || !Evt.isSimple()) return false;
  VT = Evt.getSimpleVT();

  // Handle all legal types, i.e. a register that will directly hold this
  // value.
  return TLI.isTypeLegal(VT);
}

// Determine whether the type Ty is simple enough to be handled by
// fast-isel as a load target, and return its equivalent machine type in VT.
bool PPCFastISel::isLoadTypeLegal(Type *Ty, MVT &VT) {
  if (isTypeLegal(Ty, VT)) return true;

  // If this is a type than can be sign or zero-extended to a basic operation
  // go ahead and accept it now.
  if (VT == MVT::i8 || VT == MVT::i16 || VT == MVT::i32) {
    return true;
  }

  return false;
}

// Given a value Obj, create an Address object Addr that represents its
// address.  Return false if we can't handle it.
bool PPCFastISel::PPCComputeAddress(const Value *Obj, Address &Addr) {
  const User *U = NULL;
  unsigned Opcode = Instruction::UserOp1;
  if (const Instruction *I = dyn_cast<Instruction>(Obj)) {
    // Don't walk into other basic blocks unless the object is an alloca from
    // another block, otherwise it may not have a virtual register assigned.
    if (FuncInfo.StaticAllocaMap.count(static_cast<const AllocaInst *>(Obj)) ||
        FuncInfo.MBBMap[I->getParent()] == FuncInfo.MBB) {
      Opcode = I->getOpcode();
      U = I;
    }
  } else if (const ConstantExpr *C = dyn_cast<ConstantExpr>(Obj)) {
    Opcode = C->getOpcode();
    U = C;
  }

  switch (Opcode) {
    default:
      break;
    case Instruction::BitCast:
      // Look through bitcasts.
      return PPCComputeAddress(U->getOperand(0), Addr);
    case Instruction::IntToPtr:
      // Look past no-op inttoptrs.
      if (TLI.getValueType(U->getOperand(0)->getType()) == TLI.getPointerTy())
        return PPCComputeAddress(U->getOperand(0), Addr);
      break;
    case Instruction::PtrToInt:
      // Look past no-op ptrtoints.
      if (TLI.getValueType(U->getType()) == TLI.getPointerTy())
        return PPCComputeAddress(U->getOperand(0), Addr);
      break;
    case Instruction::GetElementPtr: {
      Address SavedAddr = Addr;
      long TmpOffset = Addr.Offset;

      // Iterate through the GEP folding the constants into offsets where
      // we can.
      gep_type_iterator GTI = gep_type_begin(U);
      for (User::const_op_iterator II = U->op_begin() + 1, IE = U->op_end();
           II != IE; ++II, ++GTI) {
        const Value *Op = *II;
        if (StructType *STy = dyn_cast<StructType>(*GTI)) {
          const StructLayout *SL = TD.getStructLayout(STy);
          unsigned Idx = cast<ConstantInt>(Op)->getZExtValue();
          TmpOffset += SL->getElementOffset(Idx);
        } else {
          uint64_t S = TD.getTypeAllocSize(GTI.getIndexedType());
          for (;;) {
            if (const ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
              // Constant-offset addressing.
              TmpOffset += CI->getSExtValue() * S;
              break;
            }
            if (isa<AddOperator>(Op) &&
                (!isa<Instruction>(Op) ||
                 FuncInfo.MBBMap[cast<Instruction>(Op)->getParent()]
                 == FuncInfo.MBB) &&
                isa<ConstantInt>(cast<AddOperator>(Op)->getOperand(1))) {
              // An add (in the same block) with a constant operand. Fold the
              // constant.
              ConstantInt *CI =
              cast<ConstantInt>(cast<AddOperator>(Op)->getOperand(1));
              TmpOffset += CI->getSExtValue() * S;
              // Iterate on the other operand.
              Op = cast<AddOperator>(Op)->getOperand(0);
              continue;
            }
            // Unsupported
            goto unsupported_gep;
          }
        }
      }

      // Try to grab the base operand now.
      Addr.Offset = TmpOffset;
      if (PPCComputeAddress(U->getOperand(0), Addr)) return true;

      // We failed, restore everything and try the other options.
      Addr = SavedAddr;

      unsupported_gep:
      break;
    }
    case Instruction::Alloca: {
      const AllocaInst *AI = cast<AllocaInst>(Obj);
      DenseMap<const AllocaInst*, int>::iterator SI =
        FuncInfo.StaticAllocaMap.find(AI);
      if (SI != FuncInfo.StaticAllocaMap.end()) {
        Addr.BaseType = Address::FrameIndexBase;
        Addr.Base.FI = SI->second;
        return true;
      }
      break;
    }
  }

  // FIXME: References to parameters fall through to the behavior
  // below.  They should be able to reference a frame index since
  // they are stored to the stack, so we can get "ld rx, offset(r1)"
  // instead of "addi ry, r1, offset / ld rx, 0(ry)".  Obj will
  // just contain the parameter.  Try to handle this with a FI.

  // Try to get this in a register if nothing else has worked.
  if (Addr.Base.Reg == 0)
    Addr.Base.Reg = getRegForValue(Obj);

  // Prevent assignment of base register to X0, which is inappropriate
  // for loads and stores alike.
  if (Addr.Base.Reg != 0)
    MRI.setRegClass(Addr.Base.Reg, &PPC::G8RC_and_G8RC_NOX0RegClass);

  return Addr.Base.Reg != 0;
}

// Fix up some addresses that can't be used directly.  For example, if
// an offset won't fit in an instruction field, we may need to move it
// into an index register.
void PPCFastISel::PPCSimplifyAddress(Address &Addr, MVT VT, bool &UseOffset,
                                     unsigned &IndexReg) {

  // Check whether the offset fits in the instruction field.
  if (!isInt<16>(Addr.Offset))
    UseOffset = false;

  // If this is a stack pointer and the offset needs to be simplified then
  // put the alloca address into a register, set the base type back to
  // register and continue. This should almost never happen.
  if (!UseOffset && Addr.BaseType == Address::FrameIndexBase) {
    unsigned ResultReg = createResultReg(&PPC::G8RC_and_G8RC_NOX0RegClass);
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::ADDI8),
            ResultReg).addFrameIndex(Addr.Base.FI).addImm(0);
    Addr.Base.Reg = ResultReg;
    Addr.BaseType = Address::RegBase;
  }

  if (!UseOffset) {
    IntegerType *OffsetTy = ((VT == MVT::i32) ? Type::getInt32Ty(*Context)
                             : Type::getInt64Ty(*Context));
    const ConstantInt *Offset =
      ConstantInt::getSigned(OffsetTy, (int64_t)(Addr.Offset));
    IndexReg = PPCMaterializeInt(Offset, MVT::i64);
    assert(IndexReg && "Unexpected error in PPCMaterializeInt!");
  }
}

// Emit a load instruction if possible, returning true if we succeeded,
// otherwise false.  See commentary below for how the register class of
// the load is determined. 
bool PPCFastISel::PPCEmitLoad(MVT VT, unsigned &ResultReg, Address &Addr,
                              const TargetRegisterClass *RC,
                              bool IsZExt, unsigned FP64LoadOpc) {
  unsigned Opc;
  bool UseOffset = true;

  // If ResultReg is given, it determines the register class of the load.
  // Otherwise, RC is the register class to use.  If the result of the
  // load isn't anticipated in this block, both may be zero, in which
  // case we must make a conservative guess.  In particular, don't assign
  // R0 or X0 to the result register, as the result may be used in a load,
  // store, add-immediate, or isel that won't permit this.  (Though
  // perhaps the spill and reload of live-exit values would handle this?)
  const TargetRegisterClass *UseRC =
    (ResultReg ? MRI.getRegClass(ResultReg) :
     (RC ? RC :
      (VT == MVT::f64 ? &PPC::F8RCRegClass :
       (VT == MVT::f32 ? &PPC::F4RCRegClass :
        (VT == MVT::i64 ? &PPC::G8RC_and_G8RC_NOX0RegClass :
         &PPC::GPRC_and_GPRC_NOR0RegClass)))));

  bool Is32BitInt = UseRC->hasSuperClassEq(&PPC::GPRCRegClass);

  switch (VT.SimpleTy) {
    default: // e.g., vector types not handled
      return false;
    case MVT::i8:
      Opc = Is32BitInt ? PPC::LBZ : PPC::LBZ8;
      break;
    case MVT::i16:
      Opc = (IsZExt ?
             (Is32BitInt ? PPC::LHZ : PPC::LHZ8) : 
             (Is32BitInt ? PPC::LHA : PPC::LHA8));
      break;
    case MVT::i32:
      Opc = (IsZExt ? 
             (Is32BitInt ? PPC::LWZ : PPC::LWZ8) :
             (Is32BitInt ? PPC::LWA_32 : PPC::LWA));
      if ((Opc == PPC::LWA || Opc == PPC::LWA_32) && ((Addr.Offset & 3) != 0))
        UseOffset = false;
      break;
    case MVT::i64:
      Opc = PPC::LD;
      assert(UseRC->hasSuperClassEq(&PPC::G8RCRegClass) && 
             "64-bit load with 32-bit target??");
      UseOffset = ((Addr.Offset & 3) == 0);
      break;
    case MVT::f32:
      Opc = PPC::LFS;
      break;
    case MVT::f64:
      Opc = FP64LoadOpc;
      break;
  }

  // If necessary, materialize the offset into a register and use
  // the indexed form.  Also handle stack pointers with special needs.
  unsigned IndexReg = 0;
  PPCSimplifyAddress(Addr, VT, UseOffset, IndexReg);
  if (ResultReg == 0)
    ResultReg = createResultReg(UseRC);

  // Note: If we still have a frame index here, we know the offset is
  // in range, as otherwise PPCSimplifyAddress would have converted it
  // into a RegBase.
  if (Addr.BaseType == Address::FrameIndexBase) {

    MachineMemOperand *MMO =
      FuncInfo.MF->getMachineMemOperand(
        MachinePointerInfo::getFixedStack(Addr.Base.FI, Addr.Offset),
        MachineMemOperand::MOLoad, MFI.getObjectSize(Addr.Base.FI),
        MFI.getObjectAlignment(Addr.Base.FI));

    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc), ResultReg)
      .addImm(Addr.Offset).addFrameIndex(Addr.Base.FI).addMemOperand(MMO);

  // Base reg with offset in range.
  } else if (UseOffset) {

    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc), ResultReg)
      .addImm(Addr.Offset).addReg(Addr.Base.Reg);

  // Indexed form.
  } else {
    // Get the RR opcode corresponding to the RI one.  FIXME: It would be
    // preferable to use the ImmToIdxMap from PPCRegisterInfo.cpp, but it
    // is hard to get at.
    switch (Opc) {
      default:        llvm_unreachable("Unexpected opcode!");
      case PPC::LBZ:    Opc = PPC::LBZX;    break;
      case PPC::LBZ8:   Opc = PPC::LBZX8;   break;
      case PPC::LHZ:    Opc = PPC::LHZX;    break;
      case PPC::LHZ8:   Opc = PPC::LHZX8;   break;
      case PPC::LHA:    Opc = PPC::LHAX;    break;
      case PPC::LHA8:   Opc = PPC::LHAX8;   break;
      case PPC::LWZ:    Opc = PPC::LWZX;    break;
      case PPC::LWZ8:   Opc = PPC::LWZX8;   break;
      case PPC::LWA:    Opc = PPC::LWAX;    break;
      case PPC::LWA_32: Opc = PPC::LWAX_32; break;
      case PPC::LD:     Opc = PPC::LDX;     break;
      case PPC::LFS:    Opc = PPC::LFSX;    break;
      case PPC::LFD:    Opc = PPC::LFDX;    break;
    }
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc), ResultReg)
      .addReg(Addr.Base.Reg).addReg(IndexReg);
  }

  return true;
}

// Attempt to fast-select a load instruction.
bool PPCFastISel::SelectLoad(const Instruction *I) {
  // FIXME: No atomic loads are supported.
  if (cast<LoadInst>(I)->isAtomic())
    return false;

  // Verify we have a legal type before going any further.
  MVT VT;
  if (!isLoadTypeLegal(I->getType(), VT))
    return false;

  // See if we can handle this address.
  Address Addr;
  if (!PPCComputeAddress(I->getOperand(0), Addr))
    return false;

  // Look at the currently assigned register for this instruction
  // to determine the required register class.  This is necessary
  // to constrain RA from using R0/X0 when this is not legal.
  unsigned AssignedReg = FuncInfo.ValueMap[I];
  const TargetRegisterClass *RC =
    AssignedReg ? MRI.getRegClass(AssignedReg) : 0;

  unsigned ResultReg = 0;
  if (!PPCEmitLoad(VT, ResultReg, Addr, RC))
    return false;
  UpdateValueMap(I, ResultReg);
  return true;
}

// Emit a store instruction to store SrcReg at Addr.
bool PPCFastISel::PPCEmitStore(MVT VT, unsigned SrcReg, Address &Addr) {
  assert(SrcReg && "Nothing to store!");
  unsigned Opc;
  bool UseOffset = true;

  const TargetRegisterClass *RC = MRI.getRegClass(SrcReg);
  bool Is32BitInt = RC->hasSuperClassEq(&PPC::GPRCRegClass);

  switch (VT.SimpleTy) {
    default: // e.g., vector types not handled
      return false;
    case MVT::i8:
      Opc = Is32BitInt ? PPC::STB : PPC::STB8;
      break;
    case MVT::i16:
      Opc = Is32BitInt ? PPC::STH : PPC::STH8;
      break;
    case MVT::i32:
      assert(Is32BitInt && "Not GPRC for i32??");
      Opc = PPC::STW;
      break;
    case MVT::i64:
      Opc = PPC::STD;
      UseOffset = ((Addr.Offset & 3) == 0);
      break;
    case MVT::f32:
      Opc = PPC::STFS;
      break;
    case MVT::f64:
      Opc = PPC::STFD;
      break;
  }

  // If necessary, materialize the offset into a register and use
  // the indexed form.  Also handle stack pointers with special needs.
  unsigned IndexReg = 0;
  PPCSimplifyAddress(Addr, VT, UseOffset, IndexReg);

  // Note: If we still have a frame index here, we know the offset is
  // in range, as otherwise PPCSimplifyAddress would have converted it
  // into a RegBase.
  if (Addr.BaseType == Address::FrameIndexBase) {
    MachineMemOperand *MMO =
      FuncInfo.MF->getMachineMemOperand(
        MachinePointerInfo::getFixedStack(Addr.Base.FI, Addr.Offset),
        MachineMemOperand::MOStore, MFI.getObjectSize(Addr.Base.FI),
        MFI.getObjectAlignment(Addr.Base.FI));

    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc)).addReg(SrcReg)
      .addImm(Addr.Offset).addFrameIndex(Addr.Base.FI).addMemOperand(MMO);

  // Base reg with offset in range.
  } else if (UseOffset)
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc))
      .addReg(SrcReg).addImm(Addr.Offset).addReg(Addr.Base.Reg);

  // Indexed form.
  else {
    // Get the RR opcode corresponding to the RI one.  FIXME: It would be
    // preferable to use the ImmToIdxMap from PPCRegisterInfo.cpp, but it
    // is hard to get at.
    switch (Opc) {
      default:        llvm_unreachable("Unexpected opcode!");
      case PPC::STB:  Opc = PPC::STBX;  break;
      case PPC::STH : Opc = PPC::STHX;  break;
      case PPC::STW : Opc = PPC::STWX;  break;
      case PPC::STB8: Opc = PPC::STBX8; break;
      case PPC::STH8: Opc = PPC::STHX8; break;
      case PPC::STW8: Opc = PPC::STWX8; break;
      case PPC::STD:  Opc = PPC::STDX;  break;
      case PPC::STFS: Opc = PPC::STFSX; break;
      case PPC::STFD: Opc = PPC::STFDX; break;
    }
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc))
      .addReg(SrcReg).addReg(Addr.Base.Reg).addReg(IndexReg);
  }

  return true;
}

// Attempt to fast-select a store instruction.
bool PPCFastISel::SelectStore(const Instruction *I) {
  Value *Op0 = I->getOperand(0);
  unsigned SrcReg = 0;

  // FIXME: No atomics loads are supported.
  if (cast<StoreInst>(I)->isAtomic())
    return false;

  // Verify we have a legal type before going any further.
  MVT VT;
  if (!isLoadTypeLegal(Op0->getType(), VT))
    return false;

  // Get the value to be stored into a register.
  SrcReg = getRegForValue(Op0);
  if (SrcReg == 0)
    return false;

  // See if we can handle this address.
  Address Addr;
  if (!PPCComputeAddress(I->getOperand(1), Addr))
    return false;

  if (!PPCEmitStore(VT, SrcReg, Addr))
    return false;

  return true;
}

// Attempt to fast-select a branch instruction.
bool PPCFastISel::SelectBranch(const Instruction *I) {
  const BranchInst *BI = cast<BranchInst>(I);
  MachineBasicBlock *BrBB = FuncInfo.MBB;
  MachineBasicBlock *TBB = FuncInfo.MBBMap[BI->getSuccessor(0)];
  MachineBasicBlock *FBB = FuncInfo.MBBMap[BI->getSuccessor(1)];

  // For now, just try the simplest case where it's fed by a compare.
  if (const CmpInst *CI = dyn_cast<CmpInst>(BI->getCondition())) {
    Optional<PPC::Predicate> OptPPCPred = getComparePred(CI->getPredicate());
    if (!OptPPCPred)
      return false;

    PPC::Predicate PPCPred = OptPPCPred.getValue();

    // Take advantage of fall-through opportunities.
    if (FuncInfo.MBB->isLayoutSuccessor(TBB)) {
      std::swap(TBB, FBB);
      PPCPred = PPC::InvertPredicate(PPCPred);
    }

    unsigned CondReg = createResultReg(&PPC::CRRCRegClass);

    if (!PPCEmitCmp(CI->getOperand(0), CI->getOperand(1), CI->isUnsigned(),
                    CondReg))
      return false;

    BuildMI(*BrBB, FuncInfo.InsertPt, DL, TII.get(PPC::BCC))
      .addImm(PPCPred).addReg(CondReg).addMBB(TBB);
    FastEmitBranch(FBB, DL);
    FuncInfo.MBB->addSuccessor(TBB);
    return true;

  } else if (const ConstantInt *CI =
             dyn_cast<ConstantInt>(BI->getCondition())) {
    uint64_t Imm = CI->getZExtValue();
    MachineBasicBlock *Target = (Imm == 0) ? FBB : TBB;
    FastEmitBranch(Target, DL);
    return true;
  }

  // FIXME: ARM looks for a case where the block containing the compare
  // has been split from the block containing the branch.  If this happens,
  // there is a vreg available containing the result of the compare.  I'm
  // not sure we can do much, as we've lost the predicate information with
  // the compare instruction -- we have a 4-bit CR but don't know which bit
  // to test here.
  return false;
}

// Attempt to emit a compare of the two source values.  Signed and unsigned
// comparisons are supported.  Return false if we can't handle it.
bool PPCFastISel::PPCEmitCmp(const Value *SrcValue1, const Value *SrcValue2,
                             bool IsZExt, unsigned DestReg) {
  Type *Ty = SrcValue1->getType();
  EVT SrcEVT = TLI.getValueType(Ty, true);
  if (!SrcEVT.isSimple())
    return false;
  MVT SrcVT = SrcEVT.getSimpleVT();

  // See if operand 2 is an immediate encodeable in the compare.
  // FIXME: Operands are not in canonical order at -O0, so an immediate
  // operand in position 1 is a lost opportunity for now.  We are
  // similar to ARM in this regard.
  long Imm = 0;
  bool UseImm = false;

  // Only 16-bit integer constants can be represented in compares for 
  // PowerPC.  Others will be materialized into a register.
  if (const ConstantInt *ConstInt = dyn_cast<ConstantInt>(SrcValue2)) {
    if (SrcVT == MVT::i64 || SrcVT == MVT::i32 || SrcVT == MVT::i16 ||
        SrcVT == MVT::i8 || SrcVT == MVT::i1) {
      const APInt &CIVal = ConstInt->getValue();
      Imm = (IsZExt) ? (long)CIVal.getZExtValue() : (long)CIVal.getSExtValue();
      if ((IsZExt && isUInt<16>(Imm)) || (!IsZExt && isInt<16>(Imm)))
        UseImm = true;
    }
  }

  unsigned CmpOpc;
  bool NeedsExt = false;
  switch (SrcVT.SimpleTy) {
    default: return false;
    case MVT::f32:
      CmpOpc = PPC::FCMPUS;
      break;
    case MVT::f64:
      CmpOpc = PPC::FCMPUD;
      break;
    case MVT::i1:
    case MVT::i8:
    case MVT::i16:
      NeedsExt = true;
      // Intentional fall-through.
    case MVT::i32:
      if (!UseImm)
        CmpOpc = IsZExt ? PPC::CMPLW : PPC::CMPW;
      else
        CmpOpc = IsZExt ? PPC::CMPLWI : PPC::CMPWI;
      break;
    case MVT::i64:
      if (!UseImm)
        CmpOpc = IsZExt ? PPC::CMPLD : PPC::CMPD;
      else
        CmpOpc = IsZExt ? PPC::CMPLDI : PPC::CMPDI;
      break;
  }

  unsigned SrcReg1 = getRegForValue(SrcValue1);
  if (SrcReg1 == 0)
    return false;

  unsigned SrcReg2 = 0;
  if (!UseImm) {
    SrcReg2 = getRegForValue(SrcValue2);
    if (SrcReg2 == 0)
      return false;
  }

  if (NeedsExt) {
    unsigned ExtReg = createResultReg(&PPC::GPRCRegClass);
    if (!PPCEmitIntExt(SrcVT, SrcReg1, MVT::i32, ExtReg, IsZExt))
      return false;
    SrcReg1 = ExtReg;

    if (!UseImm) {
      unsigned ExtReg = createResultReg(&PPC::GPRCRegClass);
      if (!PPCEmitIntExt(SrcVT, SrcReg2, MVT::i32, ExtReg, IsZExt))
        return false;
      SrcReg2 = ExtReg;
    }
  }

  if (!UseImm)
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(CmpOpc), DestReg)
      .addReg(SrcReg1).addReg(SrcReg2);
  else
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(CmpOpc), DestReg)
      .addReg(SrcReg1).addImm(Imm);

  return true;
}

// Attempt to fast-select a binary integer operation that isn't already
// handled automatically.
bool PPCFastISel::SelectBinaryIntOp(const Instruction *I, unsigned ISDOpcode) {
  EVT DestVT  = TLI.getValueType(I->getType(), true);

  // We can get here in the case when we have a binary operation on a non-legal
  // type and the target independent selector doesn't know how to handle it.
  if (DestVT != MVT::i16 && DestVT != MVT::i8)
    return false;

  // Look at the currently assigned register for this instruction
  // to determine the required register class.  If there is no register,
  // make a conservative choice (don't assign R0).
  unsigned AssignedReg = FuncInfo.ValueMap[I];
  const TargetRegisterClass *RC =
    (AssignedReg ? MRI.getRegClass(AssignedReg) :
     &PPC::GPRC_and_GPRC_NOR0RegClass);
  bool IsGPRC = RC->hasSuperClassEq(&PPC::GPRCRegClass);

  unsigned Opc;
  switch (ISDOpcode) {
    default: return false;
    case ISD::ADD:
      Opc = IsGPRC ? PPC::ADD4 : PPC::ADD8;
      break;
    case ISD::OR:
      Opc = IsGPRC ? PPC::OR : PPC::OR8;
      break;
    case ISD::SUB:
      Opc = IsGPRC ? PPC::SUBF : PPC::SUBF8;
      break;
  }

  unsigned ResultReg = createResultReg(RC ? RC : &PPC::G8RCRegClass);
  unsigned SrcReg1 = getRegForValue(I->getOperand(0));
  if (SrcReg1 == 0) return false;

  // Handle case of small immediate operand.
  if (const ConstantInt *ConstInt = dyn_cast<ConstantInt>(I->getOperand(1))) {
    const APInt &CIVal = ConstInt->getValue();
    int Imm = (int)CIVal.getSExtValue();
    bool UseImm = true;
    if (isInt<16>(Imm)) {
      switch (Opc) {
        default:
          llvm_unreachable("Missing case!");
        case PPC::ADD4:
          Opc = PPC::ADDI;
          MRI.setRegClass(SrcReg1, &PPC::GPRC_and_GPRC_NOR0RegClass);
          break;
        case PPC::ADD8:
          Opc = PPC::ADDI8;
          MRI.setRegClass(SrcReg1, &PPC::G8RC_and_G8RC_NOX0RegClass);
          break;
        case PPC::OR:
          Opc = PPC::ORI;
          break;
        case PPC::OR8:
          Opc = PPC::ORI8;
          break;
        case PPC::SUBF:
          if (Imm == -32768)
            UseImm = false;
          else {
            Opc = PPC::ADDI;
            MRI.setRegClass(SrcReg1, &PPC::GPRC_and_GPRC_NOR0RegClass);
            Imm = -Imm;
          }
          break;
        case PPC::SUBF8:
          if (Imm == -32768)
            UseImm = false;
          else {
            Opc = PPC::ADDI8;
            MRI.setRegClass(SrcReg1, &PPC::G8RC_and_G8RC_NOX0RegClass);
            Imm = -Imm;
          }
          break;
      }

      if (UseImm) {
        BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc), ResultReg)
          .addReg(SrcReg1).addImm(Imm);
        UpdateValueMap(I, ResultReg);
        return true;
      }
    }
  }

  // Reg-reg case.
  unsigned SrcReg2 = getRegForValue(I->getOperand(1));
  if (SrcReg2 == 0) return false;

  // Reverse operands for subtract-from.
  if (ISDOpcode == ISD::SUB)
    std::swap(SrcReg1, SrcReg2);

  BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc), ResultReg)
    .addReg(SrcReg1).addReg(SrcReg2);
  UpdateValueMap(I, ResultReg);
  return true;
}

// Attempt to fast-select a return instruction.
bool PPCFastISel::SelectRet(const Instruction *I) {

  if (!FuncInfo.CanLowerReturn)
    return false;

  const ReturnInst *Ret = cast<ReturnInst>(I);
  const Function &F = *I->getParent()->getParent();

  // Build a list of return value registers.
  SmallVector<unsigned, 4> RetRegs;
  CallingConv::ID CC = F.getCallingConv();

  if (Ret->getNumOperands() > 0) {
    SmallVector<ISD::OutputArg, 4> Outs;
    GetReturnInfo(F.getReturnType(), F.getAttributes(), Outs, TLI);

    // Analyze operands of the call, assigning locations to each operand.
    SmallVector<CCValAssign, 16> ValLocs;
    CCState CCInfo(CC, F.isVarArg(), *FuncInfo.MF, TM, ValLocs, *Context);
    CCInfo.AnalyzeReturn(Outs, RetCC_PPC64_ELF_FIS);
    const Value *RV = Ret->getOperand(0);
    
    // FIXME: Only one output register for now.
    if (ValLocs.size() > 1)
      return false;

    // Special case for returning a constant integer of any size.
    // Materialize the constant as an i64 and copy it to the return
    // register.  This avoids an unnecessary extend or truncate.
    if (isa<ConstantInt>(*RV)) {
      const Constant *C = cast<Constant>(RV);
      unsigned SrcReg = PPCMaterializeInt(C, MVT::i64);
      unsigned RetReg = ValLocs[0].getLocReg();
      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
              RetReg).addReg(SrcReg);
      RetRegs.push_back(RetReg);

    } else {
      unsigned Reg = getRegForValue(RV);

      if (Reg == 0)
        return false;

      // Copy the result values into the output registers.
      for (unsigned i = 0; i < ValLocs.size(); ++i) {

        CCValAssign &VA = ValLocs[i];
        assert(VA.isRegLoc() && "Can only return in registers!");
        RetRegs.push_back(VA.getLocReg());
        unsigned SrcReg = Reg + VA.getValNo();

        EVT RVEVT = TLI.getValueType(RV->getType());
        if (!RVEVT.isSimple())
          return false;
        MVT RVVT = RVEVT.getSimpleVT();
        MVT DestVT = VA.getLocVT();

        if (RVVT != DestVT && RVVT != MVT::i8 &&
            RVVT != MVT::i16 && RVVT != MVT::i32)
          return false;
      
        if (RVVT != DestVT) {
          switch (VA.getLocInfo()) {
            default:
              llvm_unreachable("Unknown loc info!");
            case CCValAssign::Full:
              llvm_unreachable("Full value assign but types don't match?");
            case CCValAssign::AExt:
            case CCValAssign::ZExt: {
              const TargetRegisterClass *RC =
                (DestVT == MVT::i64) ? &PPC::G8RCRegClass : &PPC::GPRCRegClass;
              unsigned TmpReg = createResultReg(RC);
              if (!PPCEmitIntExt(RVVT, SrcReg, DestVT, TmpReg, true))
                return false;
              SrcReg = TmpReg;
              break;
            }
            case CCValAssign::SExt: {
              const TargetRegisterClass *RC =
                (DestVT == MVT::i64) ? &PPC::G8RCRegClass : &PPC::GPRCRegClass;
              unsigned TmpReg = createResultReg(RC);
              if (!PPCEmitIntExt(RVVT, SrcReg, DestVT, TmpReg, false))
                return false;
              SrcReg = TmpReg;
              break;
            }
          }
        }

        BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL,
                TII.get(TargetOpcode::COPY), RetRegs[i])
          .addReg(SrcReg);
      }
    }
  }

  MachineInstrBuilder MIB = BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL,
                                    TII.get(PPC::BLR));

  for (unsigned i = 0, e = RetRegs.size(); i != e; ++i)
    MIB.addReg(RetRegs[i], RegState::Implicit);

  return true;
}

// Attempt to emit an integer extend of SrcReg into DestReg.  Both
// signed and zero extensions are supported.  Return false if we
// can't handle it.
bool PPCFastISel::PPCEmitIntExt(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                                unsigned DestReg, bool IsZExt) {
  if (DestVT != MVT::i32 && DestVT != MVT::i64)
    return false;
  if (SrcVT != MVT::i8 && SrcVT != MVT::i16 && SrcVT != MVT::i32)
    return false;

  // Signed extensions use EXTSB, EXTSH, EXTSW.
  if (!IsZExt) {
    unsigned Opc;
    if (SrcVT == MVT::i8)
      Opc = (DestVT == MVT::i32) ? PPC::EXTSB : PPC::EXTSB8_32_64;
    else if (SrcVT == MVT::i16)
      Opc = (DestVT == MVT::i32) ? PPC::EXTSH : PPC::EXTSH8_32_64;
    else {
      assert(DestVT == MVT::i64 && "Signed extend from i32 to i32??");
      Opc = PPC::EXTSW_32_64;
    }
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc), DestReg)
      .addReg(SrcReg);

  // Unsigned 32-bit extensions use RLWINM.
  } else if (DestVT == MVT::i32) {
    unsigned MB;
    if (SrcVT == MVT::i8)
      MB = 24;
    else {
      assert(SrcVT == MVT::i16 && "Unsigned extend from i32 to i32??");
      MB = 16;
    }
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::RLWINM),
            DestReg)
      .addReg(SrcReg).addImm(/*SH=*/0).addImm(MB).addImm(/*ME=*/31);

  // Unsigned 64-bit extensions use RLDICL (with a 32-bit source).
  } else {
    unsigned MB;
    if (SrcVT == MVT::i8)
      MB = 56;
    else if (SrcVT == MVT::i16)
      MB = 48;
    else
      MB = 32;
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL,
            TII.get(PPC::RLDICL_32_64), DestReg)
      .addReg(SrcReg).addImm(/*SH=*/0).addImm(MB);
  }

  return true;
}

// Attempt to fast-select an indirect branch instruction.
bool PPCFastISel::SelectIndirectBr(const Instruction *I) {
  unsigned AddrReg = getRegForValue(I->getOperand(0));
  if (AddrReg == 0)
    return false;

  BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::MTCTR8))
    .addReg(AddrReg);
  BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::BCTR8));

  const IndirectBrInst *IB = cast<IndirectBrInst>(I);
  for (unsigned i = 0, e = IB->getNumSuccessors(); i != e; ++i)
    FuncInfo.MBB->addSuccessor(FuncInfo.MBBMap[IB->getSuccessor(i)]);

  return true;
}

// Attempt to fast-select an integer extend instruction.
bool PPCFastISel::SelectIntExt(const Instruction *I) {
  Type *DestTy = I->getType();
  Value *Src = I->getOperand(0);
  Type *SrcTy = Src->getType();

  bool IsZExt = isa<ZExtInst>(I);
  unsigned SrcReg = getRegForValue(Src);
  if (!SrcReg) return false;

  EVT SrcEVT, DestEVT;
  SrcEVT = TLI.getValueType(SrcTy, true);
  DestEVT = TLI.getValueType(DestTy, true);
  if (!SrcEVT.isSimple())
    return false;
  if (!DestEVT.isSimple())
    return false;

  MVT SrcVT = SrcEVT.getSimpleVT();
  MVT DestVT = DestEVT.getSimpleVT();

  // If we know the register class needed for the result of this
  // instruction, use it.  Otherwise pick the register class of the
  // correct size that does not contain X0/R0, since we don't know
  // whether downstream uses permit that assignment.
  unsigned AssignedReg = FuncInfo.ValueMap[I];
  const TargetRegisterClass *RC =
    (AssignedReg ? MRI.getRegClass(AssignedReg) :
     (DestVT == MVT::i64 ? &PPC::G8RC_and_G8RC_NOX0RegClass :
      &PPC::GPRC_and_GPRC_NOR0RegClass));
  unsigned ResultReg = createResultReg(RC);

  if (!PPCEmitIntExt(SrcVT, SrcReg, DestVT, ResultReg, IsZExt))
    return false;

  UpdateValueMap(I, ResultReg);
  return true;
}

// Attempt to fast-select an instruction that wasn't handled by
// the table-generated machinery.
bool PPCFastISel::TargetSelectInstruction(const Instruction *I) {

  switch (I->getOpcode()) {
    case Instruction::Load:
      return SelectLoad(I);
    case Instruction::Store:
      return SelectStore(I);
    case Instruction::Br:
      return SelectBranch(I);
    case Instruction::IndirectBr:
      return SelectIndirectBr(I);
    case Instruction::Add:
      return SelectBinaryIntOp(I, ISD::ADD);
    case Instruction::Or:
      return SelectBinaryIntOp(I, ISD::OR);
    case Instruction::Sub:
      return SelectBinaryIntOp(I, ISD::SUB);
    case Instruction::Ret:
      return SelectRet(I);
    case Instruction::ZExt:
    case Instruction::SExt:
      return SelectIntExt(I);
    // Here add other flavors of Instruction::XXX that automated
    // cases don't catch.  For example, switches are terminators
    // that aren't yet handled.
    default:
      break;
  }
  return false;
}

// Materialize a floating-point constant into a register, and return
// the register number (or zero if we failed to handle it).
unsigned PPCFastISel::PPCMaterializeFP(const ConstantFP *CFP, MVT VT) {
  // No plans to handle long double here.
  if (VT != MVT::f32 && VT != MVT::f64)
    return 0;

  // All FP constants are loaded from the constant pool.
  unsigned Align = TD.getPrefTypeAlignment(CFP->getType());
  assert(Align > 0 && "Unexpectedly missing alignment information!");
  unsigned Idx = MCP.getConstantPoolIndex(cast<Constant>(CFP), Align);
  unsigned DestReg = createResultReg(TLI.getRegClassFor(VT));
  CodeModel::Model CModel = TM.getCodeModel();

  MachineMemOperand *MMO =
    FuncInfo.MF->getMachineMemOperand(
      MachinePointerInfo::getConstantPool(), MachineMemOperand::MOLoad,
      (VT == MVT::f32) ? 4 : 8, Align);

  unsigned Opc = (VT == MVT::f32) ? PPC::LFS : PPC::LFD;
  unsigned TmpReg = createResultReg(&PPC::G8RC_and_G8RC_NOX0RegClass);

  // For small code model, generate a LF[SD](0, LDtocCPT(Idx, X2)).
  if (CModel == CodeModel::Small || CModel == CodeModel::JITDefault) {
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::LDtocCPT),
            TmpReg)
      .addConstantPoolIndex(Idx).addReg(PPC::X2);
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc), DestReg)
      .addImm(0).addReg(TmpReg).addMemOperand(MMO);
  } else {
    // Otherwise we generate LF[SD](Idx[lo], ADDIStocHA(X2, Idx)).
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::ADDIStocHA),
            TmpReg).addReg(PPC::X2).addConstantPoolIndex(Idx);
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc), DestReg)
      .addConstantPoolIndex(Idx, 0, PPCII::MO_TOC_LO)
      .addReg(TmpReg)
      .addMemOperand(MMO);
  }

  return DestReg;
}

// Materialize the address of a global value into a register, and return
// the register number (or zero if we failed to handle it).
unsigned PPCFastISel::PPCMaterializeGV(const GlobalValue *GV, MVT VT) {
  assert(VT == MVT::i64 && "Non-address!");
  const TargetRegisterClass *RC = &PPC::G8RC_and_G8RC_NOX0RegClass;
  unsigned DestReg = createResultReg(RC);

  // Global values may be plain old object addresses, TLS object
  // addresses, constant pool entries, or jump tables.  How we generate
  // code for these may depend on small, medium, or large code model.
  CodeModel::Model CModel = TM.getCodeModel();

  // FIXME: Jump tables are not yet required because fast-isel doesn't
  // handle switches; if that changes, we need them as well.  For now,
  // what follows assumes everything's a generic (or TLS) global address.
  const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
  if (!GVar) {
    // If GV is an alias, use the aliasee for determining thread-locality.
    if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
      GVar = dyn_cast_or_null<GlobalVariable>(GA->resolveAliasedGlobal(false));
    assert((GVar || isa<Function>(GV)) && "Unexpected GV subclass!");
  }

  // FIXME: We don't yet handle the complexity of TLS.
  bool IsTLS = GVar && GVar->isThreadLocal();
  if (IsTLS)
    return 0;

  // For small code model, generate a simple TOC load.
  if (CModel == CodeModel::Small || CModel == CodeModel::JITDefault)
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::LDtoc), DestReg)
      .addGlobalAddress(GV).addReg(PPC::X2);
  else {
    // If the address is an externally defined symbol, a symbol with
    // common or externally available linkage, a function address, or a
    // jump table address (not yet needed), or if we are generating code
    // for large code model, we generate:
    //       LDtocL(GV, ADDIStocHA(%X2, GV))
    // Otherwise we generate:
    //       ADDItocL(ADDIStocHA(%X2, GV), GV)
    // Either way, start with the ADDIStocHA:
    unsigned HighPartReg = createResultReg(RC);
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::ADDIStocHA),
            HighPartReg).addReg(PPC::X2).addGlobalAddress(GV);

    // !GVar implies a function address.  An external variable is one
    // without an initializer.
    // If/when switches are implemented, jump tables should be handled
    // on the "if" path here.
    if (CModel == CodeModel::Large || !GVar || !GVar->hasInitializer() ||
        GVar->hasCommonLinkage() || GVar->hasAvailableExternallyLinkage())
      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::LDtocL),
              DestReg).addGlobalAddress(GV).addReg(HighPartReg);
    else
      // Otherwise generate the ADDItocL.
      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::ADDItocL),
              DestReg).addReg(HighPartReg).addGlobalAddress(GV);
  }

  return DestReg;
}

// Materialize a 32-bit integer constant into a register, and return
// the register number (or zero if we failed to handle it).
unsigned PPCFastISel::PPCMaterialize32BitInt(int64_t Imm,
                                             const TargetRegisterClass *RC) {
  unsigned Lo = Imm & 0xFFFF;
  unsigned Hi = (Imm >> 16) & 0xFFFF;

  unsigned ResultReg = createResultReg(RC);
  bool IsGPRC = RC->hasSuperClassEq(&PPC::GPRCRegClass);

  if (isInt<16>(Imm))
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL,
            TII.get(IsGPRC ? PPC::LI : PPC::LI8), ResultReg)
      .addImm(Imm);
  else if (Lo) {
    // Both Lo and Hi have nonzero bits.
    unsigned TmpReg = createResultReg(RC);
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL,
            TII.get(IsGPRC ? PPC::LIS : PPC::LIS8), TmpReg)
      .addImm(Hi);
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL,
            TII.get(IsGPRC ? PPC::ORI : PPC::ORI8), ResultReg)
      .addReg(TmpReg).addImm(Lo);
  } else
    // Just Hi bits.
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL,
            TII.get(IsGPRC ? PPC::LIS : PPC::LIS8), ResultReg)
      .addImm(Hi);
  
  return ResultReg;
}

// Materialize a 64-bit integer constant into a register, and return
// the register number (or zero if we failed to handle it).
unsigned PPCFastISel::PPCMaterialize64BitInt(int64_t Imm,
                                             const TargetRegisterClass *RC) {
  unsigned Remainder = 0;
  unsigned Shift = 0;

  // If the value doesn't fit in 32 bits, see if we can shift it
  // so that it fits in 32 bits.
  if (!isInt<32>(Imm)) {
    Shift = countTrailingZeros<uint64_t>(Imm);
    int64_t ImmSh = static_cast<uint64_t>(Imm) >> Shift;

    if (isInt<32>(ImmSh))
      Imm = ImmSh;
    else {
      Remainder = Imm;
      Shift = 32;
      Imm >>= 32;
    }
  }

  // Handle the high-order 32 bits (if shifted) or the whole 32 bits
  // (if not shifted).
  unsigned TmpReg1 = PPCMaterialize32BitInt(Imm, RC);
  if (!Shift)
    return TmpReg1;

  // If upper 32 bits were not zero, we've built them and need to shift
  // them into place.
  unsigned TmpReg2;
  if (Imm) {
    TmpReg2 = createResultReg(RC);
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::RLDICR),
            TmpReg2).addReg(TmpReg1).addImm(Shift).addImm(63 - Shift);
  } else
    TmpReg2 = TmpReg1;

  unsigned TmpReg3, Hi, Lo;
  if ((Hi = (Remainder >> 16) & 0xFFFF)) {
    TmpReg3 = createResultReg(RC);
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::ORIS8),
            TmpReg3).addReg(TmpReg2).addImm(Hi);
  } else
    TmpReg3 = TmpReg2;

  if ((Lo = Remainder & 0xFFFF)) {
    unsigned ResultReg = createResultReg(RC);
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(PPC::ORI8),
            ResultReg).addReg(TmpReg3).addImm(Lo);
    return ResultReg;
  }

  return TmpReg3;
}


// Materialize an integer constant into a register, and return
// the register number (or zero if we failed to handle it).
unsigned PPCFastISel::PPCMaterializeInt(const Constant *C, MVT VT) {

  if (VT != MVT::i64 && VT != MVT::i32 && VT != MVT::i16 &&
      VT != MVT::i8 && VT != MVT::i1) 
    return 0;

  const TargetRegisterClass *RC = ((VT == MVT::i64) ? &PPC::G8RCRegClass :
                                   &PPC::GPRCRegClass);

  // If the constant is in range, use a load-immediate.
  const ConstantInt *CI = cast<ConstantInt>(C);
  if (isInt<16>(CI->getSExtValue())) {
    unsigned Opc = (VT == MVT::i64) ? PPC::LI8 : PPC::LI;
    unsigned ImmReg = createResultReg(RC);
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(Opc), ImmReg)
      .addImm(CI->getSExtValue());
    return ImmReg;
  }

  // Construct the constant piecewise.
  int64_t Imm = CI->getZExtValue();

  if (VT == MVT::i64)
    return PPCMaterialize64BitInt(Imm, RC);
  else if (VT == MVT::i32)
    return PPCMaterialize32BitInt(Imm, RC);

  return 0;
}

// Materialize a constant into a register, and return the register
// number (or zero if we failed to handle it).
unsigned PPCFastISel::TargetMaterializeConstant(const Constant *C) {
  EVT CEVT = TLI.getValueType(C->getType(), true);

  // Only handle simple types.
  if (!CEVT.isSimple()) return 0;
  MVT VT = CEVT.getSimpleVT();

  if (const ConstantFP *CFP = dyn_cast<ConstantFP>(C))
    return PPCMaterializeFP(CFP, VT);
  else if (const GlobalValue *GV = dyn_cast<GlobalValue>(C))
    return PPCMaterializeGV(GV, VT);
  else if (isa<ConstantInt>(C))
    return PPCMaterializeInt(C, VT);
  // TBD: Global values.

  return 0;
}

// Materialize the address created by an alloca into a register, and
// return the register number (or zero if we failed to handle it).  TBD.
unsigned PPCFastISel::TargetMaterializeAlloca(const AllocaInst *AI) {
  return AI && 0;
}

// Fold loads into extends when possible.
// FIXME: We can have multiple redundant extend/trunc instructions
// following a load.  The folding only picks up one.  Extend this
// to check subsequent instructions for the same pattern and remove
// them.  Thus ResultReg should be the def reg for the last redundant
// instruction in a chain, and all intervening instructions can be
// removed from parent.  Change test/CodeGen/PowerPC/fast-isel-fold.ll
// to add ELF64-NOT: rldicl to the appropriate tests when this works.
bool PPCFastISel::tryToFoldLoadIntoMI(MachineInstr *MI, unsigned OpNo,
                                      const LoadInst *LI) {
  // Verify we have a legal type before going any further.
  MVT VT;
  if (!isLoadTypeLegal(LI->getType(), VT))
    return false;

  // Combine load followed by zero- or sign-extend.
  bool IsZExt = false;
  switch(MI->getOpcode()) {
    default:
      return false;

    case PPC::RLDICL:
    case PPC::RLDICL_32_64: {
      IsZExt = true;
      unsigned MB = MI->getOperand(3).getImm();
      if ((VT == MVT::i8 && MB <= 56) ||
          (VT == MVT::i16 && MB <= 48) ||
          (VT == MVT::i32 && MB <= 32))
        break;
      return false;
    }

    case PPC::RLWINM:
    case PPC::RLWINM8: {
      IsZExt = true;
      unsigned MB = MI->getOperand(3).getImm();
      if ((VT == MVT::i8 && MB <= 24) ||
          (VT == MVT::i16 && MB <= 16))
        break;
      return false;
    }

    case PPC::EXTSB:
    case PPC::EXTSB8:
    case PPC::EXTSB8_32_64:
      /* There is no sign-extending load-byte instruction. */
      return false;

    case PPC::EXTSH:
    case PPC::EXTSH8:
    case PPC::EXTSH8_32_64: {
      if (VT != MVT::i16 && VT != MVT::i8)
        return false;
      break;
    }

    case PPC::EXTSW:
    case PPC::EXTSW_32_64: {
      if (VT != MVT::i32 && VT != MVT::i16 && VT != MVT::i8)
        return false;
      break;
    }
  }

  // See if we can handle this address.
  Address Addr;
  if (!PPCComputeAddress(LI->getOperand(0), Addr))
    return false;

  unsigned ResultReg = MI->getOperand(0).getReg();

  if (!PPCEmitLoad(VT, ResultReg, Addr, 0, IsZExt))
    return false;

  MI->eraseFromParent();
  return true;
}

// Attempt to lower call arguments in a faster way than done by
// the selection DAG code.
bool PPCFastISel::FastLowerArguments() {
  // Defer to normal argument lowering for now.  It's reasonably
  // efficient.  Consider doing something like ARM to handle the
  // case where all args fit in registers, no varargs, no float
  // or vector args.
  return false;
}

// Handle materializing integer constants into a register.  This is not
// automatically generated for PowerPC, so must be explicitly created here.
unsigned PPCFastISel::FastEmit_i(MVT Ty, MVT VT, unsigned Opc, uint64_t Imm) {
  
  if (Opc != ISD::Constant)
    return 0;

  if (VT != MVT::i64 && VT != MVT::i32 && VT != MVT::i16 &&
      VT != MVT::i8 && VT != MVT::i1) 
    return 0;

  const TargetRegisterClass *RC = ((VT == MVT::i64) ? &PPC::G8RCRegClass :
                                   &PPC::GPRCRegClass);
  if (VT == MVT::i64)
    return PPCMaterialize64BitInt(Imm, RC);
  else
    return PPCMaterialize32BitInt(Imm, RC);
}

// Override for ADDI and ADDI8 to set the correct register class
// on RHS operand 0.  The automatic infrastructure naively assumes
// GPRC for i32 and G8RC for i64; the concept of "no R0" is lost
// for these cases.  At the moment, none of the other automatically
// generated RI instructions require special treatment.  However, once
// SelectSelect is implemented, "isel" requires similar handling.
//
// Also be conservative about the output register class.  Avoid
// assigning R0 or X0 to the output register for GPRC and G8RC
// register classes, as any such result could be used in ADDI, etc.,
// where those regs have another meaning.
unsigned PPCFastISel::FastEmitInst_ri(unsigned MachineInstOpcode,
                                      const TargetRegisterClass *RC,
                                      unsigned Op0, bool Op0IsKill,
                                      uint64_t Imm) {
  if (MachineInstOpcode == PPC::ADDI)
    MRI.setRegClass(Op0, &PPC::GPRC_and_GPRC_NOR0RegClass);
  else if (MachineInstOpcode == PPC::ADDI8)
    MRI.setRegClass(Op0, &PPC::G8RC_and_G8RC_NOX0RegClass);

  const TargetRegisterClass *UseRC =
    (RC == &PPC::GPRCRegClass ? &PPC::GPRC_and_GPRC_NOR0RegClass :
     (RC == &PPC::G8RCRegClass ? &PPC::G8RC_and_G8RC_NOX0RegClass : RC));

  return FastISel::FastEmitInst_ri(MachineInstOpcode, UseRC,
                                   Op0, Op0IsKill, Imm);
}

// Override for instructions with one register operand to avoid use of
// R0/X0.  The automatic infrastructure isn't aware of the context so
// we must be conservative.
unsigned PPCFastISel::FastEmitInst_r(unsigned MachineInstOpcode,
                                     const TargetRegisterClass* RC,
                                     unsigned Op0, bool Op0IsKill) {
  const TargetRegisterClass *UseRC =
    (RC == &PPC::GPRCRegClass ? &PPC::GPRC_and_GPRC_NOR0RegClass :
     (RC == &PPC::G8RCRegClass ? &PPC::G8RC_and_G8RC_NOX0RegClass : RC));

  return FastISel::FastEmitInst_r(MachineInstOpcode, UseRC, Op0, Op0IsKill);
}

// Override for instructions with two register operands to avoid use
// of R0/X0.  The automatic infrastructure isn't aware of the context
// so we must be conservative.
unsigned PPCFastISel::FastEmitInst_rr(unsigned MachineInstOpcode,
                                      const TargetRegisterClass* RC,
                                      unsigned Op0, bool Op0IsKill,
                                      unsigned Op1, bool Op1IsKill) {
  const TargetRegisterClass *UseRC =
    (RC == &PPC::GPRCRegClass ? &PPC::GPRC_and_GPRC_NOR0RegClass :
     (RC == &PPC::G8RCRegClass ? &PPC::G8RC_and_G8RC_NOX0RegClass : RC));

  return FastISel::FastEmitInst_rr(MachineInstOpcode, UseRC, Op0, Op0IsKill,
                                   Op1, Op1IsKill);
}

namespace llvm {
  // Create the fast instruction selector for PowerPC64 ELF.
  FastISel *PPC::createFastISel(FunctionLoweringInfo &FuncInfo,
                                const TargetLibraryInfo *LibInfo) {
    const TargetMachine &TM = FuncInfo.MF->getTarget();

    // Only available on 64-bit ELF for now.
    const PPCSubtarget *Subtarget = &TM.getSubtarget<PPCSubtarget>();
    if (Subtarget->isPPC64() && Subtarget->isSVR4ABI())
      return new PPCFastISel(FuncInfo, LibInfo);

    return 0;
  }
}