llvm-6502/lib/Target/Mips/MipsFastISel.cpp

//===-- MipsastISel.cpp - Mips FastISel implementation
//---------------------===//

#include "llvm/CodeGen/FunctionLoweringInfo.h"
#include "MipsCCState.h"
#include "MipsISelLowering.h"
#include "MipsMachineFunction.h"
#include "MipsRegisterInfo.h"
#include "MipsSubtarget.h"
#include "MipsTargetMachine.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/CodeGen/FastISel.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/Target/TargetInstrInfo.h"

using namespace llvm;

namespace {

class MipsFastISel final : public FastISel {

  // All possible address modes.
  class Address {
  public:
    typedef enum { RegBase, FrameIndexBase } BaseKind;

  private:
    BaseKind Kind;
    union {
      unsigned Reg;
      int FI;
    } Base;

    int64_t Offset;

    const GlobalValue *GV;

  public:
    // Innocuous defaults for our address.
    Address() : Kind(RegBase), Offset(0), GV(0) { Base.Reg = 0; }
    void setKind(BaseKind K) { Kind = K; }
    BaseKind getKind() const { return Kind; }
    bool isRegBase() const { return Kind == RegBase; }
    void setReg(unsigned Reg) {
      assert(isRegBase() && "Invalid base register access!");
      Base.Reg = Reg;
    }
    unsigned getReg() const {
      assert(isRegBase() && "Invalid base register access!");
      return Base.Reg;
    }
    void setOffset(int64_t Offset_) { Offset = Offset_; }
    int64_t getOffset() const { return Offset; }
    void setGlobalValue(const GlobalValue *G) { GV = G; }
    const GlobalValue *getGlobalValue() { return GV; }
  };

  /// Subtarget - Keep a pointer to the MipsSubtarget around so that we can
  /// make the right decision when generating code for different targets.
  const TargetMachine &TM;
  const TargetInstrInfo &TII;
  const TargetLowering &TLI;
  const MipsSubtarget *Subtarget;
  MipsFunctionInfo *MFI;

  // Convenience variables to avoid some queries.
  LLVMContext *Context;

  bool fastLowerCall(CallLoweringInfo &CLI) override;

  bool TargetSupported;
  bool UnsupportedFPMode; // To allow fast-isel to proceed and just not handle
  // floating point but not reject doing fast-isel in other
  // situations

private:
  // Selection routines.
  bool selectLoad(const Instruction *I);
  bool selectStore(const Instruction *I);
  bool selectBranch(const Instruction *I);
  bool selectCmp(const Instruction *I);
  bool selectFPExt(const Instruction *I);
  bool selectFPTrunc(const Instruction *I);
  bool selectFPToInt(const Instruction *I, bool IsSigned);
  bool selectRet(const Instruction *I);
  bool selectTrunc(const Instruction *I);
  bool selectIntExt(const Instruction *I);

  // Utility helper routines.
  bool isTypeLegal(Type *Ty, MVT &VT);
  bool isLoadTypeLegal(Type *Ty, MVT &VT);
  bool computeAddress(const Value *Obj, Address &Addr);
  bool computeCallAddress(const Value *V, Address &Addr);

  // Emit helper routines.
  bool emitCmp(unsigned DestReg, const CmpInst *CI);
  bool emitLoad(MVT VT, unsigned &ResultReg, Address &Addr,
                unsigned Alignment = 0);
  bool emitStore(MVT VT, unsigned SrcReg, Address Addr,
                 MachineMemOperand *MMO = nullptr);
  bool emitStore(MVT VT, unsigned SrcReg, Address &Addr,
                 unsigned Alignment = 0);
  unsigned emitIntExt(MVT SrcVT, unsigned SrcReg, MVT DestVT, bool isZExt);
  bool emitIntExt(MVT SrcVT, unsigned SrcReg, MVT DestVT, unsigned DestReg,

                  bool IsZExt);
  bool emitIntZExt(MVT SrcVT, unsigned SrcReg, MVT DestVT, unsigned DestReg);

  bool emitIntSExt(MVT SrcVT, unsigned SrcReg, MVT DestVT, unsigned DestReg);
  bool emitIntSExt32r1(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                       unsigned DestReg);
  bool emitIntSExt32r2(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                       unsigned DestReg);

  unsigned getRegEnsuringSimpleIntegerWidening(const Value *, bool IsUnsigned);

  unsigned materializeFP(const ConstantFP *CFP, MVT VT);
  unsigned materializeGV(const GlobalValue *GV, MVT VT);
  unsigned materializeInt(const Constant *C, MVT VT);
  unsigned materialize32BitInt(int64_t Imm, const TargetRegisterClass *RC);

  MachineInstrBuilder emitInst(unsigned Opc) {
    return BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Opc));
  }
  MachineInstrBuilder emitInst(unsigned Opc, unsigned DstReg) {
    return BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Opc),
                   DstReg);
  }
  MachineInstrBuilder emitInstStore(unsigned Opc, unsigned SrcReg,
                                    unsigned MemReg, int64_t MemOffset) {
    return emitInst(Opc).addReg(SrcReg).addReg(MemReg).addImm(MemOffset);
  }
  MachineInstrBuilder emitInstLoad(unsigned Opc, unsigned DstReg,
                                   unsigned MemReg, int64_t MemOffset) {
    return emitInst(Opc, DstReg).addReg(MemReg).addImm(MemOffset);
  }
  // for some reason, this default is not generated by tablegen
  // so we explicitly generate it here.
  //
  unsigned fastEmitInst_riir(uint64_t inst, const TargetRegisterClass *RC,
                             unsigned Op0, bool Op0IsKill, uint64_t imm1,
                             uint64_t imm2, unsigned Op3, bool Op3IsKill) {
    return 0;
  }

  // Call handling routines.
private:
  CCAssignFn *CCAssignFnForCall(CallingConv::ID CC) const;
  bool processCallArgs(CallLoweringInfo &CLI, SmallVectorImpl<MVT> &ArgVTs,
                       unsigned &NumBytes);
  bool finishCall(CallLoweringInfo &CLI, MVT RetVT, unsigned NumBytes);

public:
  // Backend specific FastISel code.
  explicit MipsFastISel(FunctionLoweringInfo &funcInfo,
                        const TargetLibraryInfo *libInfo)
      : FastISel(funcInfo, libInfo), TM(funcInfo.MF->getTarget()),
        TII(*TM.getSubtargetImpl()->getInstrInfo()),
        TLI(*TM.getSubtargetImpl()->getTargetLowering()),
        Subtarget(&TM.getSubtarget<MipsSubtarget>()) {
    MFI = funcInfo.MF->getInfo<MipsFunctionInfo>();
    Context = &funcInfo.Fn->getContext();
    TargetSupported = ((TM.getRelocationModel() == Reloc::PIC_) &&
                       ((Subtarget->hasMips32r2() || Subtarget->hasMips32()) &&
                        (Subtarget->isABI_O32())));
    UnsupportedFPMode = Subtarget->isFP64bit();
  }

  unsigned fastMaterializeConstant(const Constant *C) override;
  bool fastSelectInstruction(const Instruction *I) override;

#include "MipsGenFastISel.inc"
};
} // end anonymous namespace.

static bool CC_Mips(unsigned ValNo, MVT ValVT, MVT LocVT,
                    CCValAssign::LocInfo LocInfo, ISD::ArgFlagsTy ArgFlags,
                    CCState &State) LLVM_ATTRIBUTE_UNUSED;

static bool CC_MipsO32_FP32(unsigned ValNo, MVT ValVT, MVT LocVT,
                            CCValAssign::LocInfo LocInfo,
                            ISD::ArgFlagsTy ArgFlags, CCState &State) {
  llvm_unreachable("should not be called");
}

bool CC_MipsO32_FP64(unsigned ValNo, MVT ValVT, MVT LocVT,
                     CCValAssign::LocInfo LocInfo, ISD::ArgFlagsTy ArgFlags,
                     CCState &State) {
  llvm_unreachable("should not be called");
}

#include "MipsGenCallingConv.inc"

CCAssignFn *MipsFastISel::CCAssignFnForCall(CallingConv::ID CC) const {
  return CC_MipsO32;
}

unsigned MipsFastISel::materializeInt(const Constant *C, MVT VT) {
  if (VT != MVT::i32 && VT != MVT::i16 && VT != MVT::i8 && VT != MVT::i1)
    return 0;
  const TargetRegisterClass *RC = &Mips::GPR32RegClass;
  const ConstantInt *CI = cast<ConstantInt>(C);
  int64_t Imm;
  if ((VT != MVT::i1) && CI->isNegative())
    Imm = CI->getSExtValue();
  else
    Imm = CI->getZExtValue();
  return materialize32BitInt(Imm, RC);
}

unsigned MipsFastISel::materialize32BitInt(int64_t Imm,
                                           const TargetRegisterClass *RC) {
  unsigned ResultReg = createResultReg(RC);

  if (isInt<16>(Imm)) {
    unsigned Opc = Mips::ADDiu;
    emitInst(Opc, ResultReg).addReg(Mips::ZERO).addImm(Imm);
    return ResultReg;
  } else if (isUInt<16>(Imm)) {
    emitInst(Mips::ORi, ResultReg).addReg(Mips::ZERO).addImm(Imm);
    return ResultReg;
  }
  unsigned Lo = Imm & 0xFFFF;
  unsigned Hi = (Imm >> 16) & 0xFFFF;
  if (Lo) {
    // Both Lo and Hi have nonzero bits.
    unsigned TmpReg = createResultReg(RC);
    emitInst(Mips::LUi, TmpReg).addImm(Hi);
    emitInst(Mips::ORi, ResultReg).addReg(TmpReg).addImm(Lo);
  } else {
    emitInst(Mips::LUi, ResultReg).addImm(Hi);
  }
  return ResultReg;
}

unsigned MipsFastISel::materializeFP(const ConstantFP *CFP, MVT VT) {
  if (UnsupportedFPMode)
    return 0;
  int64_t Imm = CFP->getValueAPF().bitcastToAPInt().getZExtValue();
  if (VT == MVT::f32) {
    const TargetRegisterClass *RC = &Mips::FGR32RegClass;
    unsigned DestReg = createResultReg(RC);
    unsigned TempReg = materialize32BitInt(Imm, &Mips::GPR32RegClass);
    emitInst(Mips::MTC1, DestReg).addReg(TempReg);
    return DestReg;
  } else if (VT == MVT::f64) {
    const TargetRegisterClass *RC = &Mips::AFGR64RegClass;
    unsigned DestReg = createResultReg(RC);
    unsigned TempReg1 = materialize32BitInt(Imm >> 32, &Mips::GPR32RegClass);
    unsigned TempReg2 =
        materialize32BitInt(Imm & 0xFFFFFFFF, &Mips::GPR32RegClass);
    emitInst(Mips::BuildPairF64, DestReg).addReg(TempReg2).addReg(TempReg1);
    return DestReg;
  }
  return 0;
}

unsigned MipsFastISel::materializeGV(const GlobalValue *GV, MVT VT) {
  // For now 32-bit only.
  if (VT != MVT::i32)
    return 0;
  const TargetRegisterClass *RC = &Mips::GPR32RegClass;
  unsigned DestReg = createResultReg(RC);
  const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
  bool IsThreadLocal = GVar && GVar->isThreadLocal();
  // TLS not supported at this time.
  if (IsThreadLocal)
    return 0;
  emitInst(Mips::LW, DestReg)
      .addReg(MFI->getGlobalBaseReg())
      .addGlobalAddress(GV, 0, MipsII::MO_GOT);
  if ((GV->hasInternalLinkage() ||
       (GV->hasLocalLinkage() && !isa<Function>(GV)))) {
    unsigned TempReg = createResultReg(RC);
    emitInst(Mips::ADDiu, TempReg)
        .addReg(DestReg)
        .addGlobalAddress(GV, 0, MipsII::MO_ABS_LO);
    DestReg = TempReg;
  }
  return DestReg;
}

// Materialize a constant into a register, and return the register
// number (or zero if we failed to handle it).
unsigned MipsFastISel::fastMaterializeConstant(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 (UnsupportedFPMode) ? 0 : materializeFP(CFP, VT);
  else if (const GlobalValue *GV = dyn_cast<GlobalValue>(C))
    return materializeGV(GV, VT);
  else if (isa<ConstantInt>(C))
    return materializeInt(C, VT);

  return 0;
}

bool MipsFastISel::computeAddress(const Value *Obj, Address &Addr) {
  // This construct looks a big awkward but it is how other ports handle this
  // and as this function is more fully completed, these cases which
  // return false will have additional code in them.
  //
  if (isa<Instruction>(Obj))
    return false;
  else if (isa<ConstantExpr>(Obj))
    return false;
  Addr.setReg(getRegForValue(Obj));
  return Addr.getReg() != 0;
}

bool MipsFastISel::computeCallAddress(const Value *V, Address &Addr) {
  const GlobalValue *GV = dyn_cast<GlobalValue>(V);
  if (GV && isa<Function>(GV) && dyn_cast<Function>(GV)->isIntrinsic())
    return false;
  if (!GV)
    return false;
  if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
    Addr.setGlobalValue(GV);
    return true;
  }
  return false;
}

bool MipsFastISel::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);
}

bool MipsFastISel::isLoadTypeLegal(Type *Ty, MVT &VT) {
  if (isTypeLegal(Ty, VT))
    return true;
  // We will extend this in a later patch:
  //   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)
    return true;
  return false;
}
// Because of how EmitCmp is called with fast-isel, you can
// end up with redundant "andi" instructions after the sequences emitted below.
// We should try and solve this issue in the future.
//
bool MipsFastISel::emitCmp(unsigned ResultReg, const CmpInst *CI) {
  const Value *Left = CI->getOperand(0), *Right = CI->getOperand(1);
  bool IsUnsigned = CI->isUnsigned();
  unsigned LeftReg = getRegEnsuringSimpleIntegerWidening(Left, IsUnsigned);
  if (LeftReg == 0)
    return false;
  unsigned RightReg = getRegEnsuringSimpleIntegerWidening(Right, IsUnsigned);
  if (RightReg == 0)
    return false;
  CmpInst::Predicate P = CI->getPredicate();

  switch (P) {
  default:
    return false;
  case CmpInst::ICMP_EQ: {
    unsigned TempReg = createResultReg(&Mips::GPR32RegClass);
    emitInst(Mips::XOR, TempReg).addReg(LeftReg).addReg(RightReg);
    emitInst(Mips::SLTiu, ResultReg).addReg(TempReg).addImm(1);
    break;
  }
  case CmpInst::ICMP_NE: {
    unsigned TempReg = createResultReg(&Mips::GPR32RegClass);
    emitInst(Mips::XOR, TempReg).addReg(LeftReg).addReg(RightReg);
    emitInst(Mips::SLTu, ResultReg).addReg(Mips::ZERO).addReg(TempReg);
    break;
  }
  case CmpInst::ICMP_UGT: {
    emitInst(Mips::SLTu, ResultReg).addReg(RightReg).addReg(LeftReg);
    break;
  }
  case CmpInst::ICMP_ULT: {
    emitInst(Mips::SLTu, ResultReg).addReg(LeftReg).addReg(RightReg);
    break;
  }
  case CmpInst::ICMP_UGE: {
    unsigned TempReg = createResultReg(&Mips::GPR32RegClass);
    emitInst(Mips::SLTu, TempReg).addReg(LeftReg).addReg(RightReg);
    emitInst(Mips::XORi, ResultReg).addReg(TempReg).addImm(1);
    break;
  }
  case CmpInst::ICMP_ULE: {
    unsigned TempReg = createResultReg(&Mips::GPR32RegClass);
    emitInst(Mips::SLTu, TempReg).addReg(RightReg).addReg(LeftReg);
    emitInst(Mips::XORi, ResultReg).addReg(TempReg).addImm(1);
    break;
  }
  case CmpInst::ICMP_SGT: {
    emitInst(Mips::SLT, ResultReg).addReg(RightReg).addReg(LeftReg);
    break;
  }
  case CmpInst::ICMP_SLT: {
    emitInst(Mips::SLT, ResultReg).addReg(LeftReg).addReg(RightReg);
    break;
  }
  case CmpInst::ICMP_SGE: {
    unsigned TempReg = createResultReg(&Mips::GPR32RegClass);
    emitInst(Mips::SLT, TempReg).addReg(LeftReg).addReg(RightReg);
    emitInst(Mips::XORi, ResultReg).addReg(TempReg).addImm(1);
    break;
  }
  case CmpInst::ICMP_SLE: {
    unsigned TempReg = createResultReg(&Mips::GPR32RegClass);
    emitInst(Mips::SLT, TempReg).addReg(RightReg).addReg(LeftReg);
    emitInst(Mips::XORi, ResultReg).addReg(TempReg).addImm(1);
    break;
  }
  case CmpInst::FCMP_OEQ:
  case CmpInst::FCMP_UNE:
  case CmpInst::FCMP_OLT:
  case CmpInst::FCMP_OLE:
  case CmpInst::FCMP_OGT:
  case CmpInst::FCMP_OGE: {
    if (UnsupportedFPMode)
      return false;
    bool IsFloat = Left->getType()->isFloatTy();
    bool IsDouble = Left->getType()->isDoubleTy();
    if (!IsFloat && !IsDouble)
      return false;
    unsigned Opc, CondMovOpc;
    switch (P) {
    case CmpInst::FCMP_OEQ:
      Opc = IsFloat ? Mips::C_EQ_S : Mips::C_EQ_D32;
      CondMovOpc = Mips::MOVT_I;
      break;
    case CmpInst::FCMP_UNE:
      Opc = IsFloat ? Mips::C_EQ_S : Mips::C_EQ_D32;
      CondMovOpc = Mips::MOVF_I;
      break;
    case CmpInst::FCMP_OLT:
      Opc = IsFloat ? Mips::C_OLT_S : Mips::C_OLT_D32;
      CondMovOpc = Mips::MOVT_I;
      break;
    case CmpInst::FCMP_OLE:
      Opc = IsFloat ? Mips::C_OLE_S : Mips::C_OLE_D32;
      CondMovOpc = Mips::MOVT_I;
      break;
    case CmpInst::FCMP_OGT:
      Opc = IsFloat ? Mips::C_ULE_S : Mips::C_ULE_D32;
      CondMovOpc = Mips::MOVF_I;
      break;
    case CmpInst::FCMP_OGE:
      Opc = IsFloat ? Mips::C_ULT_S : Mips::C_ULT_D32;
      CondMovOpc = Mips::MOVF_I;
      break;
    default:
      llvm_unreachable("Only switching of a subset of CCs.");
    }
    unsigned RegWithZero = createResultReg(&Mips::GPR32RegClass);
    unsigned RegWithOne = createResultReg(&Mips::GPR32RegClass);
    emitInst(Mips::ADDiu, RegWithZero).addReg(Mips::ZERO).addImm(0);
    emitInst(Mips::ADDiu, RegWithOne).addReg(Mips::ZERO).addImm(1);
    emitInst(Opc).addReg(LeftReg).addReg(RightReg).addReg(
        Mips::FCC0, RegState::ImplicitDefine);
    MachineInstrBuilder MI = emitInst(CondMovOpc, ResultReg)
                                 .addReg(RegWithOne)
                                 .addReg(Mips::FCC0)
                                 .addReg(RegWithZero, RegState::Implicit);
    MI->tieOperands(0, 3);
    break;
  }
  }
  return true;
}
bool MipsFastISel::emitLoad(MVT VT, unsigned &ResultReg, Address &Addr,
                            unsigned Alignment) {
  //
  // more cases will be handled here in following patches.
  //
  unsigned Opc;
  switch (VT.SimpleTy) {
  case MVT::i32: {
    ResultReg = createResultReg(&Mips::GPR32RegClass);
    Opc = Mips::LW;
    break;
  }
  case MVT::i16: {
    ResultReg = createResultReg(&Mips::GPR32RegClass);
    Opc = Mips::LHu;
    break;
  }
  case MVT::i8: {
    ResultReg = createResultReg(&Mips::GPR32RegClass);
    Opc = Mips::LBu;
    break;
  }
  case MVT::f32: {
    if (UnsupportedFPMode)
      return false;
    ResultReg = createResultReg(&Mips::FGR32RegClass);
    Opc = Mips::LWC1;
    break;
  }
  case MVT::f64: {
    if (UnsupportedFPMode)
      return false;
    ResultReg = createResultReg(&Mips::AFGR64RegClass);
    Opc = Mips::LDC1;
    break;
  }
  default:
    return false;
  }
  emitInstLoad(Opc, ResultReg, Addr.getReg(), Addr.getOffset());
  return true;
}

bool MipsFastISel::emitStore(MVT VT, unsigned SrcReg, Address &Addr,
                             unsigned Alignment) {
  //
  // more cases will be handled here in following patches.
  //
  unsigned Opc;
  switch (VT.SimpleTy) {
  case MVT::i8:
    Opc = Mips::SB;
    break;
  case MVT::i16:
    Opc = Mips::SH;
    break;
  case MVT::i32:
    Opc = Mips::SW;
    break;
  case MVT::f32:
    if (UnsupportedFPMode)
      return false;
    Opc = Mips::SWC1;
    break;
  case MVT::f64:
    if (UnsupportedFPMode)
      return false;
    Opc = Mips::SDC1;
    break;
  default:
    return false;
  }
  emitInstStore(Opc, SrcReg, Addr.getReg(), Addr.getOffset());
  return true;
}

bool MipsFastISel::selectLoad(const Instruction *I) {
  // Atomic loads need special handling.
  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 (!computeAddress(I->getOperand(0), Addr))
    return false;

  unsigned ResultReg;
  if (!emitLoad(VT, ResultReg, Addr, cast<LoadInst>(I)->getAlignment()))
    return false;
  updateValueMap(I, ResultReg);
  return true;
}

bool MipsFastISel::selectStore(const Instruction *I) {
  Value *Op0 = I->getOperand(0);
  unsigned SrcReg = 0;

  // Atomic stores need special handling.
  if (cast<StoreInst>(I)->isAtomic())
    return false;

  // Verify we have a legal type before going any further.
  MVT VT;
  if (!isLoadTypeLegal(I->getOperand(0)->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 (!computeAddress(I->getOperand(1), Addr))
    return false;

  if (!emitStore(VT, SrcReg, Addr, cast<StoreInst>(I)->getAlignment()))
    return false;
  return true;
}

//
// This can cause a redundant sltiu to be generated.
// FIXME: try and eliminate this in a future patch.
//
bool MipsFastISel::selectBranch(const Instruction *I) {
  const BranchInst *BI = cast<BranchInst>(I);
  MachineBasicBlock *BrBB = FuncInfo.MBB;
  //
  // TBB is the basic block for the case where the comparison is true.
  // FBB is the basic block for the case where the comparison is false.
  // if (cond) goto TBB
  // goto FBB
  // TBB:
  //
  MachineBasicBlock *TBB = FuncInfo.MBBMap[BI->getSuccessor(0)];
  MachineBasicBlock *FBB = FuncInfo.MBBMap[BI->getSuccessor(1)];
  BI->getCondition();
  // For now, just try the simplest case where it's fed by a compare.
  if (const CmpInst *CI = dyn_cast<CmpInst>(BI->getCondition())) {
    unsigned CondReg = createResultReg(&Mips::GPR32RegClass);
    if (!emitCmp(CondReg, CI))
      return false;
    BuildMI(*BrBB, FuncInfo.InsertPt, DbgLoc, TII.get(Mips::BGTZ))
        .addReg(CondReg)
        .addMBB(TBB);
    fastEmitBranch(FBB, DbgLoc);
    FuncInfo.MBB->addSuccessor(TBB);
    return true;
  }
  return false;
}

bool MipsFastISel::selectCmp(const Instruction *I) {
  const CmpInst *CI = cast<CmpInst>(I);
  unsigned ResultReg = createResultReg(&Mips::GPR32RegClass);
  if (!emitCmp(ResultReg, CI))
    return false;
  updateValueMap(I, ResultReg);
  return true;
}

// Attempt to fast-select a floating-point extend instruction.
bool MipsFastISel::selectFPExt(const Instruction *I) {
  if (UnsupportedFPMode)
    return false;
  Value *Src = I->getOperand(0);
  EVT SrcVT = TLI.getValueType(Src->getType(), true);
  EVT DestVT = TLI.getValueType(I->getType(), true);

  if (SrcVT != MVT::f32 || DestVT != MVT::f64)
    return false;

  unsigned SrcReg =
      getRegForValue(Src); // his must be a 32 bit floating point register class
                           // maybe we should handle this differently
  if (!SrcReg)
    return false;

  unsigned DestReg = createResultReg(&Mips::AFGR64RegClass);
  emitInst(Mips::CVT_D32_S, DestReg).addReg(SrcReg);
  updateValueMap(I, DestReg);
  return true;
}

// Attempt to fast-select a floating-point truncate instruction.
bool MipsFastISel::selectFPTrunc(const Instruction *I) {
  if (UnsupportedFPMode)
    return false;
  Value *Src = I->getOperand(0);
  EVT SrcVT = TLI.getValueType(Src->getType(), true);
  EVT DestVT = TLI.getValueType(I->getType(), true);

  if (SrcVT != MVT::f64 || DestVT != MVT::f32)
    return false;

  unsigned SrcReg = getRegForValue(Src);
  if (!SrcReg)
    return false;

  unsigned DestReg = createResultReg(&Mips::FGR32RegClass);
  if (!DestReg)
    return false;

  emitInst(Mips::CVT_S_D32, DestReg).addReg(SrcReg);
  updateValueMap(I, DestReg);
  return true;
}

// Attempt to fast-select a floating-point-to-integer conversion.
bool MipsFastISel::selectFPToInt(const Instruction *I, bool IsSigned) {
  if (UnsupportedFPMode)
    return false;
  MVT DstVT, SrcVT;
  if (!IsSigned)
    return false; // We don't handle this case yet. There is no native
                  // instruction for this but it can be synthesized.
  Type *DstTy = I->getType();
  if (!isTypeLegal(DstTy, DstVT))
    return false;

  if (DstVT != MVT::i32)
    return false;

  Value *Src = I->getOperand(0);
  Type *SrcTy = Src->getType();
  if (!isTypeLegal(SrcTy, SrcVT))
    return false;

  if (SrcVT != MVT::f32 && SrcVT != MVT::f64)
    return false;

  unsigned SrcReg = getRegForValue(Src);
  if (SrcReg == 0)
    return false;

  // Determine the opcode for the conversion, which takes place
  // entirely within FPRs.
  unsigned DestReg = createResultReg(&Mips::GPR32RegClass);
  unsigned TempReg = createResultReg(&Mips::FGR32RegClass);
  unsigned Opc;

  if (SrcVT == MVT::f32)
    Opc = Mips::TRUNC_W_S;
  else
    Opc = Mips::TRUNC_W_D32;

  // Generate the convert.
  emitInst(Opc, TempReg).addReg(SrcReg);

  emitInst(Mips::MFC1, DestReg).addReg(TempReg);

  updateValueMap(I, DestReg);
  return true;
}
//
bool MipsFastISel::processCallArgs(CallLoweringInfo &CLI,
                                   SmallVectorImpl<MVT> &OutVTs,
                                   unsigned &NumBytes) {
  CallingConv::ID CC = CLI.CallConv;
  SmallVector<CCValAssign, 16> ArgLocs;
  CCState CCInfo(CC, false, *FuncInfo.MF, ArgLocs, *Context);
  CCInfo.AnalyzeCallOperands(OutVTs, CLI.OutFlags, CCAssignFnForCall(CC));
  // Get a count of how many bytes are to be pushed on the stack.
  NumBytes = CCInfo.getNextStackOffset();
  // This is the minimum argument area used for A0-A3.
  if (NumBytes < 16)
    NumBytes = 16;

  emitInst(Mips::ADJCALLSTACKDOWN).addImm(16);
  // Process the args.
  MVT firstMVT;
  for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
    CCValAssign &VA = ArgLocs[i];
    const Value *ArgVal = CLI.OutVals[VA.getValNo()];
    MVT ArgVT = OutVTs[VA.getValNo()];

    if (i == 0) {
      firstMVT = ArgVT;
      if (ArgVT == MVT::f32) {
        VA.convertToReg(Mips::F12);
      } else if (ArgVT == MVT::f64) {
        VA.convertToReg(Mips::D6);
      }
    } else if (i == 1) {
      if ((firstMVT == MVT::f32) || (firstMVT == MVT::f64)) {
        if (ArgVT == MVT::f32) {
          VA.convertToReg(Mips::F14);
        } else if (ArgVT == MVT::f64) {
          VA.convertToReg(Mips::D7);
        }
      }
    }
    if (((ArgVT == MVT::i32) || (ArgVT == MVT::f32)) && VA.isMemLoc()) {
      switch (VA.getLocMemOffset()) {
      case 0:
        VA.convertToReg(Mips::A0);
        break;
      case 4:
        VA.convertToReg(Mips::A1);
        break;
      case 8:
        VA.convertToReg(Mips::A2);
        break;
      case 12:
        VA.convertToReg(Mips::A3);
        break;
      default:
        break;
      }
    }
    unsigned ArgReg = getRegForValue(ArgVal);
    if (!ArgReg)
      return false;

    // Handle arg promotion: SExt, ZExt, AExt.
    switch (VA.getLocInfo()) {
    case CCValAssign::Full:
      break;
    case CCValAssign::AExt:
    case CCValAssign::SExt: {
      MVT DestVT = VA.getLocVT();
      MVT SrcVT = ArgVT;
      ArgReg = emitIntExt(SrcVT, ArgReg, DestVT, /*isZExt=*/false);
      if (!ArgReg)
        return false;
      break;
    }
    case CCValAssign::ZExt: {
      MVT DestVT = VA.getLocVT();
      MVT SrcVT = ArgVT;
      ArgReg = emitIntExt(SrcVT, ArgReg, DestVT, /*isZExt=*/true);
      if (!ArgReg)
        return false;
      break;
    }
    default:
      llvm_unreachable("Unknown arg promotion!");
    }

    // Now copy/store arg to correct locations.
    if (VA.isRegLoc() && !VA.needsCustom()) {
      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
              TII.get(TargetOpcode::COPY), VA.getLocReg()).addReg(ArgReg);
      CLI.OutRegs.push_back(VA.getLocReg());
    } else if (VA.needsCustom()) {
      llvm_unreachable("Mips does not use custom args.");
      return false;
    } else {
      //
      // FIXME: This path will currently return false. It was copied
      // from the AArch64 port and should be essentially fine for Mips too.
      // The work to finish up this path will be done in a follow-on patch.
      //
      assert(VA.isMemLoc() && "Assuming store on stack.");
      // Don't emit stores for undef values.
      if (isa<UndefValue>(ArgVal))
        continue;

      // Need to store on the stack.
      // FIXME: This alignment is incorrect but this path is disabled
      // for now (will return false). We need to determine the right alignment
      // based on the normal alignment for the underlying machine type.
      //
      unsigned ArgSize = RoundUpToAlignment(ArgVT.getSizeInBits(), 4);

      unsigned BEAlign = 0;
      if (ArgSize < 8 && !Subtarget->isLittle())
        BEAlign = 8 - ArgSize;

      Address Addr;
      Addr.setKind(Address::RegBase);
      Addr.setReg(Mips::SP);
      Addr.setOffset(VA.getLocMemOffset() + BEAlign);

      unsigned Alignment = DL.getABITypeAlignment(ArgVal->getType());
      MachineMemOperand *MMO = FuncInfo.MF->getMachineMemOperand(
          MachinePointerInfo::getStack(Addr.getOffset()),
          MachineMemOperand::MOStore, ArgVT.getStoreSize(), Alignment);
      (void)(MMO);
      // if (!emitStore(ArgVT, ArgReg, Addr, MMO))
      return false; // can't store on the stack yet.
    }
  }

  return true;
}

bool MipsFastISel::finishCall(CallLoweringInfo &CLI, MVT RetVT,
                              unsigned NumBytes) {
  CallingConv::ID CC = CLI.CallConv;
  emitInst(Mips::ADJCALLSTACKUP).addImm(16);
  if (RetVT != MVT::isVoid) {
    SmallVector<CCValAssign, 16> RVLocs;
    CCState CCInfo(CC, false, *FuncInfo.MF, RVLocs, *Context);
    CCInfo.AnalyzeCallResult(RetVT, RetCC_Mips);

    // Only handle a single return value.
    if (RVLocs.size() != 1)
      return false;
    // Copy all of the result registers out of their specified physreg.
    MVT CopyVT = RVLocs[0].getValVT();
    // Special handling for extended integers.
    if (RetVT == MVT::i1 || RetVT == MVT::i8 || RetVT == MVT::i16)
      CopyVT = MVT::i32;

    unsigned ResultReg = createResultReg(TLI.getRegClassFor(CopyVT));
    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
            TII.get(TargetOpcode::COPY),
            ResultReg).addReg(RVLocs[0].getLocReg());
    CLI.InRegs.push_back(RVLocs[0].getLocReg());

    CLI.ResultReg = ResultReg;
    CLI.NumResultRegs = 1;
  }
  return true;
}

bool MipsFastISel::fastLowerCall(CallLoweringInfo &CLI) {
  CallingConv::ID CC = CLI.CallConv;
  bool IsTailCall = CLI.IsTailCall;
  bool IsVarArg = CLI.IsVarArg;
  const Value *Callee = CLI.Callee;
  // const char *SymName = CLI.SymName;

  // Allow SelectionDAG isel to handle tail calls.
  if (IsTailCall)
    return false;

  // Let SDISel handle vararg functions.
  if (IsVarArg)
    return false;

  // FIXME: Only handle *simple* calls for now.
  MVT RetVT;
  if (CLI.RetTy->isVoidTy())
    RetVT = MVT::isVoid;
  else if (!isTypeLegal(CLI.RetTy, RetVT))
    return false;

  for (auto Flag : CLI.OutFlags)
    if (Flag.isInReg() || Flag.isSRet() || Flag.isNest() || Flag.isByVal())
      return false;

  // Set up the argument vectors.
  SmallVector<MVT, 16> OutVTs;
  OutVTs.reserve(CLI.OutVals.size());

  for (auto *Val : CLI.OutVals) {
    MVT VT;
    if (!isTypeLegal(Val->getType(), VT) &&
        !(VT == MVT::i1 || VT == MVT::i8 || VT == MVT::i16))
      return false;

    // We don't handle vector parameters yet.
    if (VT.isVector() || VT.getSizeInBits() > 64)
      return false;

    OutVTs.push_back(VT);
  }

  Address Addr;
  if (!computeCallAddress(Callee, Addr))
    return false;

  // Handle the arguments now that we've gotten them.
  unsigned NumBytes;
  if (!processCallArgs(CLI, OutVTs, NumBytes))
    return false;

  // Issue the call.
  unsigned DestAddress = materializeGV(Addr.getGlobalValue(), MVT::i32);
  emitInst(TargetOpcode::COPY, Mips::T9).addReg(DestAddress);
  MachineInstrBuilder MIB =
      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Mips::JALR),
              Mips::RA).addReg(Mips::T9);

  // Add implicit physical register uses to the call.
  for (auto Reg : CLI.OutRegs)
    MIB.addReg(Reg, RegState::Implicit);

  // Add a register mask with the call-preserved registers.
  // Proper defs for return values will be added by setPhysRegsDeadExcept().
  MIB.addRegMask(TRI.getCallPreservedMask(CC));

  CLI.Call = MIB;

  // Add implicit physical register uses to the call.
  for (auto Reg : CLI.OutRegs)
    MIB.addReg(Reg, RegState::Implicit);

  // Add a register mask with the call-preserved registers.  Proper
  // defs for return values will be added by setPhysRegsDeadExcept().
  MIB.addRegMask(TRI.getCallPreservedMask(CC));

  CLI.Call = MIB;
  // Finish off the call including any return values.
  return finishCall(CLI, RetVT, NumBytes);
}

bool MipsFastISel::selectRet(const Instruction *I) {
  const ReturnInst *Ret = cast<ReturnInst>(I);

  if (!FuncInfo.CanLowerReturn)
    return false;
  if (Ret->getNumOperands() > 0) {
    return false;
  }
  emitInst(Mips::RetRA);
  return true;
}

bool MipsFastISel::selectTrunc(const Instruction *I) {
  // The high bits for a type smaller than the register size are assumed to be
  // undefined.
  Value *Op = I->getOperand(0);

  EVT SrcVT, DestVT;
  SrcVT = TLI.getValueType(Op->getType(), true);
  DestVT = TLI.getValueType(I->getType(), true);

  if (SrcVT != MVT::i32 && SrcVT != MVT::i16 && SrcVT != MVT::i8)
    return false;
  if (DestVT != MVT::i16 && DestVT != MVT::i8 && DestVT != MVT::i1)
    return false;

  unsigned SrcReg = getRegForValue(Op);
  if (!SrcReg)
    return false;

  // Because the high bits are undefined, a truncate doesn't generate
  // any code.
  updateValueMap(I, SrcReg);
  return true;
}
bool MipsFastISel::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();
  unsigned ResultReg = createResultReg(&Mips::GPR32RegClass);

  if (!emitIntExt(SrcVT, SrcReg, DestVT, ResultReg, isZExt))
    return false;
  updateValueMap(I, ResultReg);
  return true;
}
bool MipsFastISel::emitIntSExt32r1(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                                   unsigned DestReg) {
  unsigned ShiftAmt;
  switch (SrcVT.SimpleTy) {
  default:
    return false;
  case MVT::i8:
    ShiftAmt = 24;
    break;
  case MVT::i16:
    ShiftAmt = 16;
    break;
  }
  unsigned TempReg = createResultReg(&Mips::GPR32RegClass);
  emitInst(Mips::SLL, TempReg).addReg(SrcReg).addImm(ShiftAmt);
  emitInst(Mips::SRA, DestReg).addReg(TempReg).addImm(ShiftAmt);
  return true;
}

bool MipsFastISel::emitIntSExt32r2(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                                   unsigned DestReg) {
  switch (SrcVT.SimpleTy) {
  default:
    return false;
  case MVT::i8:
    emitInst(Mips::SEB, DestReg).addReg(SrcReg);
    break;
  case MVT::i16:
    emitInst(Mips::SEH, DestReg).addReg(SrcReg);
    break;
  }
  return true;
}

bool MipsFastISel::emitIntSExt(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                               unsigned DestReg) {
  if ((DestVT != MVT::i32) && (DestVT != MVT::i16))
    return false;
  if (Subtarget->hasMips32r2())
    return emitIntSExt32r2(SrcVT, SrcReg, DestVT, DestReg);
  return emitIntSExt32r1(SrcVT, SrcReg, DestVT, DestReg);
}

bool MipsFastISel::emitIntZExt(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                               unsigned DestReg) {
  switch (SrcVT.SimpleTy) {
  default:
    return false;
  case MVT::i1:
    emitInst(Mips::ANDi, DestReg).addReg(SrcReg).addImm(1);
    break;
  case MVT::i8:
    emitInst(Mips::ANDi, DestReg).addReg(SrcReg).addImm(0xff);
    break;
  case MVT::i16:
    emitInst(Mips::ANDi, DestReg).addReg(SrcReg).addImm(0xffff);
    break;
  }
  return true;
}

bool MipsFastISel::emitIntExt(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                              unsigned DestReg, bool IsZExt) {
  if (IsZExt)
    return emitIntZExt(SrcVT, SrcReg, DestVT, DestReg);
  return emitIntSExt(SrcVT, SrcReg, DestVT, DestReg);
}

unsigned MipsFastISel::emitIntExt(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                                  bool isZExt) {
  unsigned DestReg = createResultReg(&Mips::GPR32RegClass);
  return emitIntExt(SrcVT, SrcReg, DestVT, DestReg, isZExt);
}

bool MipsFastISel::fastSelectInstruction(const Instruction *I) {
  if (!TargetSupported)
    return false;
  switch (I->getOpcode()) {
  default:
    break;
  case Instruction::Load:
    return selectLoad(I);
  case Instruction::Store:
    return selectStore(I);
  case Instruction::Br:
    return selectBranch(I);
  case Instruction::Ret:
    return selectRet(I);
  case Instruction::Trunc:
    return selectTrunc(I);
  case Instruction::ZExt:
  case Instruction::SExt:
    return selectIntExt(I);
  case Instruction::FPTrunc:
    return selectFPTrunc(I);
  case Instruction::FPExt:
    return selectFPExt(I);
  case Instruction::FPToSI:
    return selectFPToInt(I, /*isSigned*/ true);
  case Instruction::FPToUI:
    return selectFPToInt(I, /*isSigned*/ false);
  case Instruction::ICmp:
  case Instruction::FCmp:
    return selectCmp(I);
  }
  return false;
}

unsigned MipsFastISel::getRegEnsuringSimpleIntegerWidening(const Value *V,
                                                           bool IsUnsigned) {
  unsigned VReg = getRegForValue(V);
  if (VReg == 0)
    return 0;
  MVT VMVT = TLI.getValueType(V->getType(), true).getSimpleVT();
  if ((VMVT == MVT::i8) || (VMVT == MVT::i16)) {
    unsigned TempReg = createResultReg(&Mips::GPR32RegClass);
    if (!emitIntExt(VMVT, VReg, MVT::i32, TempReg, IsUnsigned))
      return 0;
    VReg = TempReg;
  }
  return VReg;
}

namespace llvm {
FastISel *Mips::createFastISel(FunctionLoweringInfo &funcInfo,
                               const TargetLibraryInfo *libInfo) {
  return new MipsFastISel(funcInfo, libInfo);
}
}