MipsISelLowering.h

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//===- MipsISelLowering.h - Mips DAG Lowering Interface ---------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the interfaces that Mips uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_LIB_TARGET_MIPS_MIPSISELLOWERING_H
#define LLVM_LIB_TARGET_MIPS_MIPSISELLOWERING_H
 
#include "MCTargetDesc/MipsABIInfo.h"
#include "MCTargetDesc/MipsBaseInfo.h"
#include "MCTargetDesc/MipsMCTargetDesc.h"
#include "Mips.h"
#include "MipsSelectionDAGInfo.h"
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/ISDOpcodes.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/CodeGenTypes/MachineValueType.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/Type.h"
#include "llvm/Target/TargetMachine.h"
#include <algorithm>
#include <deque>
#include <utility>
#include <vector>
 
namespace llvm {
 
class Argument;
class FastISel;
class FunctionLoweringInfo;
class MachineBasicBlock;
class MachineFrameInfo;
class MachineInstr;
class MipsCCState;
class MipsFunctionInfo;
class MipsSubtarget;
class MipsTargetMachine;
class TargetLibraryInfo;
class TargetRegisterClass;
 
  //===--------------------------------------------------------------------===//
  // TargetLowering Implementation
  //===--------------------------------------------------------------------===//
 
  class MipsTargetLowering : public TargetLowering  {
    bool isMicroMips;
 
  public:
    explicit MipsTargetLowering(const MipsTargetMachine &TM,
                                const MipsSubtarget &STI);
 
    static const MipsTargetLowering *create(const MipsTargetMachine &TM,
                                            const MipsSubtarget &STI);
 
    /// createFastISel - This method returns a target specific FastISel object,
    /// or null if the target does not support "fast" ISel.
    FastISel *createFastISel(FunctionLoweringInfo &funcInfo,
                             const TargetLibraryInfo *libInfo) const override;
 
    MVT getScalarShiftAmountTy(const DataLayout &, EVT) const override {
      return MVT::i32;
    }
 
    EVT getTypeForExtReturn(LLVMContext &Context, EVT VT,
                            ISD::NodeType) const override;
 
    bool isCheapToSpeculateCttz(Type *Ty) const override;
    bool isCheapToSpeculateCtlz(Type *Ty) const override;
    bool hasBitTest(SDValue X, SDValue Y) const override;
    bool shouldFoldConstantShiftPairToMask(const SDNode *N) const override;
 
    /// Return the register type for a given MVT, ensuring vectors are treated
    /// as a series of gpr sized integers.
    MVT getRegisterTypeForCallingConv(LLVMContext &Context, CallingConv::ID CC,
                                      EVT VT) const override;
 
    /// Return the number of registers for a given MVT, ensuring vectors are
    /// treated as a series of gpr sized integers.
    unsigned getNumRegistersForCallingConv(LLVMContext &Context,
                                           CallingConv::ID CC,
                                           EVT VT) const override;
 
    /// Break down vectors to the correct number of gpr sized integers.
    unsigned getVectorTypeBreakdownForCallingConv(
        LLVMContext &Context, CallingConv::ID CC, EVT VT, EVT &IntermediateVT,
        unsigned &NumIntermediates, MVT &RegisterVT) const override;
 
    /// Return the correct alignment for the current calling convention.
    Align getABIAlignmentForCallingConv(Type *ArgTy,
                                        const DataLayout &DL) const override {
      const Align ABIAlign = DL.getABITypeAlign(ArgTy);
      if (ArgTy->isVectorTy())
        return std::min(ABIAlign, Align(8));
      return ABIAlign;
    }
 
    ISD::NodeType getExtendForAtomicOps() const override {
      return ISD::SIGN_EXTEND;
    }
 
    /// LowerOperation - Provide custom lowering hooks for some operations.
    SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
 
    /// ReplaceNodeResults - Replace the results of node with an illegal result
    /// type with new values built out of custom code.
    ///
    void ReplaceNodeResults(SDNode *N, SmallVectorImpl<SDValue>&Results,
                            SelectionDAG &DAG) const override;
 
    /// getSetCCResultType - get the ISD::SETCC result ValueType
    EVT getSetCCResultType(const DataLayout &DL, LLVMContext &Context,
                           EVT VT) const override;
 
    SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;
 
    MachineBasicBlock *
    EmitInstrWithCustomInserter(MachineInstr &MI,
                                MachineBasicBlock *MBB) const override;
 
    void AdjustInstrPostInstrSelection(MachineInstr &MI,
                                       SDNode *Node) const override;
 
    void HandleByVal(CCState *, unsigned &, Align) const override;
 
    Register getRegisterByName(const char* RegName, LLT VT,
                               const MachineFunction &MF) const override;
 
    /// If a physical register, this returns the register that receives the
    /// exception address on entry to an EH pad.
    Register
    getExceptionPointerRegister(const Constant *PersonalityFn) const override {
      return ABI.IsN64() ? Mips::A0_64 : Mips::A0;
    }
 
    /// If a physical register, this returns the register that receives the
    /// exception typeid on entry to a landing pad.
    Register
    getExceptionSelectorRegister(const Constant *PersonalityFn) const override {
      return ABI.IsN64() ? Mips::A1_64 : Mips::A1;
    }
 
    bool softPromoteHalfType() const override { return true; }
 
    bool isJumpTableRelative() const override {
      return getTargetMachine().isPositionIndependent();
    }
 
   CCAssignFn *CCAssignFnForCall() const;
 
   CCAssignFn *CCAssignFnForReturn() const;
 
  protected:
    SDValue getGlobalReg(SelectionDAG &DAG, EVT Ty) const;
 
    // This method creates the following nodes, which are necessary for
    // computing a local symbol's address:
    //
    // (add (load (wrapper $gp, %got(sym)), %lo(sym))
    template <class NodeTy>
    SDValue getAddrLocal(NodeTy *N, const SDLoc &DL, EVT Ty, SelectionDAG &DAG,
                         bool IsN32OrN64) const {
      unsigned GOTFlag = IsN32OrN64 ? MipsII::MO_GOT_PAGE : MipsII::MO_GOT;
      SDValue GOT = DAG.getNode(MipsISD::Wrapper, DL, Ty, getGlobalReg(DAG, Ty),
                                getTargetNode(N, Ty, DAG, GOTFlag));
      SDValue Load =
          DAG.getLoad(Ty, DL, DAG.getEntryNode(), GOT,
                      MachinePointerInfo::getGOT(DAG.getMachineFunction()));
      unsigned LoFlag = IsN32OrN64 ? MipsII::MO_GOT_OFST : MipsII::MO_ABS_LO;
      SDValue Lo = DAG.getNode(MipsISD::Lo, DL, Ty,
                               getTargetNode(N, Ty, DAG, LoFlag));
      return DAG.getNode(ISD::ADD, DL, Ty, Load, Lo);
    }
 
    // This method creates the following nodes, which are necessary for
    // computing a global symbol's address:
    //
    // (load (wrapper $gp, %got(sym)))
    template <class NodeTy>
    SDValue getAddrGlobal(NodeTy *N, const SDLoc &DL, EVT Ty, SelectionDAG &DAG,
                          unsigned Flag, SDValue Chain,
                          const MachinePointerInfo &PtrInfo) const {
      SDValue Tgt = DAG.getNode(MipsISD::Wrapper, DL, Ty, getGlobalReg(DAG, Ty),
                                getTargetNode(N, Ty, DAG, Flag));
      return DAG.getLoad(Ty, DL, Chain, Tgt, PtrInfo);
    }
 
    // This method creates the following nodes, which are necessary for
    // computing a global symbol's address in large-GOT mode:
    //
    // (load (wrapper (add %hi(sym), $gp), %lo(sym)))
    template <class NodeTy>
    SDValue getAddrGlobalLargeGOT(NodeTy *N, const SDLoc &DL, EVT Ty,
                                  SelectionDAG &DAG, unsigned HiFlag,
                                  unsigned LoFlag, SDValue Chain,
                                  const MachinePointerInfo &PtrInfo) const {
      SDValue Hi = DAG.getNode(MipsISD::GotHi, DL, Ty,
                               getTargetNode(N, Ty, DAG, HiFlag));
      Hi = DAG.getNode(ISD::ADD, DL, Ty, Hi, getGlobalReg(DAG, Ty));
      SDValue Wrapper = DAG.getNode(MipsISD::Wrapper, DL, Ty, Hi,
                                    getTargetNode(N, Ty, DAG, LoFlag));
      return DAG.getLoad(Ty, DL, Chain, Wrapper, PtrInfo);
    }
 
    // This method creates the following nodes, which are necessary for
    // computing a symbol's address in non-PIC mode:
    //
    // (add %hi(sym), %lo(sym))
    //
    // This method covers O32, N32 and N64 in sym32 mode.
    template <class NodeTy>
    SDValue getAddrNonPIC(NodeTy *N, const SDLoc &DL, EVT Ty,
                          SelectionDAG &DAG) const {
      SDValue Hi = getTargetNode(N, Ty, DAG, MipsII::MO_ABS_HI);
      SDValue Lo = getTargetNode(N, Ty, DAG, MipsII::MO_ABS_LO);
      return DAG.getNode(ISD::ADD, DL, Ty,
                         DAG.getNode(MipsISD::Hi, DL, Ty, Hi),
                         DAG.getNode(MipsISD::Lo, DL, Ty, Lo));
   }
 
   // This method creates the following nodes, which are necessary for
   // computing a symbol's address in non-PIC mode for N64.
   //
   // (add (shl (add (shl (add %highest(sym), %higher(sim)), 16), %high(sym)),
   //            16), %lo(%sym))
   //
   // FIXME: This method is not efficent for (micro)MIPS64R6.
   template <class NodeTy>
   SDValue getAddrNonPICSym64(NodeTy *N, const SDLoc &DL, EVT Ty,
                          SelectionDAG &DAG) const {
      SDValue Hi = getTargetNode(N, Ty, DAG, MipsII::MO_ABS_HI);
      SDValue Lo = getTargetNode(N, Ty, DAG, MipsII::MO_ABS_LO);
 
      SDValue Highest =
          DAG.getNode(MipsISD::Highest, DL, Ty,
                      getTargetNode(N, Ty, DAG, MipsII::MO_HIGHEST));
      SDValue Higher = getTargetNode(N, Ty, DAG, MipsII::MO_HIGHER);
      SDValue HigherPart =
          DAG.getNode(ISD::ADD, DL, Ty, Highest,
                      DAG.getNode(MipsISD::Higher, DL, Ty, Higher));
      SDValue Cst = DAG.getConstant(16, DL, MVT::i32);
      SDValue Shift = DAG.getNode(ISD::SHL, DL, Ty, HigherPart, Cst);
      SDValue Add = DAG.getNode(ISD::ADD, DL, Ty, Shift,
                                DAG.getNode(MipsISD::Hi, DL, Ty, Hi));
      SDValue Shift2 = DAG.getNode(ISD::SHL, DL, Ty, Add, Cst);
 
      return DAG.getNode(ISD::ADD, DL, Ty, Shift2,
                         DAG.getNode(MipsISD::Lo, DL, Ty, Lo));
   }
 
    // This method creates the following nodes, which are necessary for
    // computing a symbol's address using gp-relative addressing:
    //
    // (add $gp, %gp_rel(sym))
    template <class NodeTy>
    SDValue getAddrGPRel(NodeTy *N, const SDLoc &DL, EVT Ty,
                         SelectionDAG &DAG, bool IsN64) const {
      SDValue GPRel = getTargetNode(N, Ty, DAG, MipsII::MO_GPREL);
      return DAG.getNode(
          ISD::ADD, DL, Ty,
          DAG.getRegister(IsN64 ? Mips::GP_64 : Mips::GP, Ty),
          DAG.getNode(MipsISD::GPRel, DL, DAG.getVTList(Ty), GPRel));
    }
 
    // This method creates the following nodes, which are necessary for
    // loading a dllimported symbol:
    //
    // (lw (add (shl(%high(sym), 16), %low(sym)))
    template <class NodeTy>
    SDValue getDllimportSymbol(NodeTy *N, const SDLoc &DL, EVT Ty,
                               SelectionDAG &DAG) const {
      SDValue Hi =
          getTargetNode(N, Ty, DAG, MipsII::MO_ABS_HI | MipsII::MO_DLLIMPORT);
      SDValue Lo =
          getTargetNode(N, Ty, DAG, MipsII::MO_ABS_LO | MipsII::MO_DLLIMPORT);
      return DAG.getNode(ISD::ADD, DL, Ty, DAG.getNode(MipsISD::Lo, DL, Ty, Lo),
                         DAG.getNode(MipsISD::Hi, DL, Ty, Hi));
    }
 
    // This method creates the following nodes, which are necessary for
    // loading a dllimported global variable:
    //
    // (lw (lw (add (shl(%high(sym), 16), %low(sym))))
    template <class NodeTy>
    SDValue getDllimportVariable(NodeTy *N, const SDLoc &DL, EVT Ty,
                                 SelectionDAG &DAG, SDValue Chain,
                                 const MachinePointerInfo &PtrInfo) const {
      return DAG.getLoad(Ty, DL, Chain, getDllimportSymbol(N, DL, Ty, DAG),
                         PtrInfo);
    }
 
    /// This function fills Ops, which is the list of operands that will later
    /// be used when a function call node is created. It also generates
    /// copyToReg nodes to set up argument registers.
    virtual void
    getOpndList(SmallVectorImpl<SDValue> &Ops,
                std::deque<std::pair<unsigned, SDValue>> &RegsToPass,
                bool IsPICCall, bool GlobalOrExternal, bool InternalLinkage,
                bool IsCallReloc, CallLoweringInfo &CLI, SDValue Callee,
                SDValue Chain) const;
 
  protected:
    SDValue lowerLOAD(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerSTORE(SDValue Op, SelectionDAG &DAG) const;
 
    // Subtarget Info
    const MipsSubtarget &Subtarget;
    // Cache the ABI from the TargetMachine, we use it everywhere.
    const MipsABIInfo &ABI;
 
  private:
    // Create a TargetGlobalAddress node.
    SDValue getTargetNode(GlobalAddressSDNode *N, EVT Ty, SelectionDAG &DAG,
                          unsigned Flag) const;
 
    // Create a TargetExternalSymbol node.
    SDValue getTargetNode(ExternalSymbolSDNode *N, EVT Ty, SelectionDAG &DAG,
                          unsigned Flag) const;
 
    // Create a TargetBlockAddress node.
    SDValue getTargetNode(BlockAddressSDNode *N, EVT Ty, SelectionDAG &DAG,
                          unsigned Flag) const;
 
    // Create a TargetJumpTable node.
    SDValue getTargetNode(JumpTableSDNode *N, EVT Ty, SelectionDAG &DAG,
                          unsigned Flag) const;
 
    // Create a TargetConstantPool node.
    SDValue getTargetNode(ConstantPoolSDNode *N, EVT Ty, SelectionDAG &DAG,
                          unsigned Flag) const;
 
    // Lower Operand helpers
    SDValue LowerCallResult(SDValue Chain, SDValue InGlue,
                            CallingConv::ID CallConv, bool isVarArg,
                            const SmallVectorImpl<ISD::InputArg> &Ins,
                            const SDLoc &dl, SelectionDAG &DAG,
                            SmallVectorImpl<SDValue> &InVals,
                            TargetLowering::CallLoweringInfo &CLI) const;
 
    // Lower Operand specifics
    SDValue lowerBRCOND(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerConstantPool(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerBlockAddress(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerJumpTable(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerSELECT(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerSETCC(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerFSETCC(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerVASTART(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerVAARG(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerFCOPYSIGN(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerFABS(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerFABS32(SDValue Op, SelectionDAG &DAG,
                        bool HasExtractInsert) const;
    SDValue lowerFABS64(SDValue Op, SelectionDAG &DAG,
                        bool HasExtractInsert) const;
    SDValue lowerFCANONICALIZE(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerRETURNADDR(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerEH_RETURN(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerATOMIC_FENCE(SDValue Op, SelectionDAG& DAG) const;
    SDValue lowerShiftLeftParts(SDValue Op, SelectionDAG& DAG) const;
    SDValue lowerShiftRightParts(SDValue Op, SelectionDAG& DAG,
                                 bool IsSRA) const;
    SDValue lowerEH_DWARF_CFA(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerFP_TO_SINT(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerSTRICT_FP_TO_INT(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerREADCYCLECOUNTER(SDValue Op, SelectionDAG &DAG) const;
 
    /// isEligibleForTailCallOptimization - Check whether the call is eligible
    /// for tail call optimization.
    virtual bool
    isEligibleForTailCallOptimization(const CCState &CCInfo,
                                      unsigned NextStackOffset,
                                      const MipsFunctionInfo &FI) const = 0;
 
    /// copyByValArg - Copy argument registers which were used to pass a byval
    /// argument to the stack. Create a stack frame object for the byval
    /// argument.
    void copyByValRegs(SDValue Chain, const SDLoc &DL,
                       std::vector<SDValue> &OutChains, SelectionDAG &DAG,
                       const ISD::ArgFlagsTy &Flags,
                       SmallVectorImpl<SDValue> &InVals,
                       const Argument *FuncArg, unsigned FirstReg,
                       unsigned LastReg, const CCValAssign &VA,
                       MipsCCState &State) const;
 
    /// passByValArg - Pass a byval argument in registers or on stack.
    void passByValArg(SDValue Chain, const SDLoc &DL,
                      std::deque<std::pair<unsigned, SDValue>> &RegsToPass,
                      SmallVectorImpl<SDValue> &MemOpChains, SDValue StackPtr,
                      MachineFrameInfo &MFI, SelectionDAG &DAG, SDValue Arg,
                      unsigned FirstReg, unsigned LastReg,
                      const ISD::ArgFlagsTy &Flags, bool isLittle,
                      const CCValAssign &VA) const;
 
    /// writeVarArgRegs - Write variable function arguments passed in registers
    /// to the stack. Also create a stack frame object for the first variable
    /// argument.
    void writeVarArgRegs(std::vector<SDValue> &OutChains, SDValue Chain,
                         const SDLoc &DL, SelectionDAG &DAG,
                         CCState &State) const;
 
    SDValue
    LowerFormalArguments(SDValue Chain, CallingConv::ID CallConv, bool isVarArg,
                         const SmallVectorImpl<ISD::InputArg> &Ins,
                         const SDLoc &dl, SelectionDAG &DAG,
                         SmallVectorImpl<SDValue> &InVals) const override;
 
    SDValue passArgOnStack(SDValue StackPtr, unsigned Offset, SDValue Chain,
                           SDValue Arg, const SDLoc &DL, bool IsTailCall,
                           SelectionDAG &DAG) const;
 
    SDValue LowerCall(TargetLowering::CallLoweringInfo &CLI,
                      SmallVectorImpl<SDValue> &InVals) const override;
 
    bool CanLowerReturn(CallingConv::ID CallConv, MachineFunction &MF,
                        bool isVarArg,
                        const SmallVectorImpl<ISD::OutputArg> &Outs,
                        LLVMContext &Context, const Type *RetTy) const override;
 
    SDValue LowerReturn(SDValue Chain, CallingConv::ID CallConv, bool isVarArg,
                        const SmallVectorImpl<ISD::OutputArg> &Outs,
                        const SmallVectorImpl<SDValue> &OutVals,
                        const SDLoc &dl, SelectionDAG &DAG) const override;
 
    SDValue LowerInterruptReturn(SmallVectorImpl<SDValue> &RetOps,
                                 const SDLoc &DL, SelectionDAG &DAG) const;
 
    bool shouldSignExtendTypeInLibCall(Type *Ty, bool IsSigned) const override;
 
    // Inline asm support
    ConstraintType getConstraintType(StringRef Constraint) const override;
 
    /// Examine constraint string and operand type and determine a weight value.
    /// The operand object must already have been set up with the operand type.
    ConstraintWeight getSingleConstraintMatchWeight(
      AsmOperandInfo &info, const char *constraint) const override;
 
    /// This function parses registers that appear in inline-asm constraints.
    /// It returns pair (0, 0) on failure.
    std::pair<unsigned, const TargetRegisterClass *>
    parseRegForInlineAsmConstraint(StringRef C, MVT VT) const;
 
    std::pair<unsigned, const TargetRegisterClass *>
    getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
                                 StringRef Constraint, MVT VT) const override;
 
    /// LowerAsmOperandForConstraint - Lower the specified operand into the Ops
    /// vector.  If it is invalid, don't add anything to Ops. If hasMemory is
    /// true it means one of the asm constraint of the inline asm instruction
    /// being processed is 'm'.
    void LowerAsmOperandForConstraint(SDValue Op, StringRef Constraint,
                                      std::vector<SDValue> &Ops,
                                      SelectionDAG &DAG) const override;
 
    InlineAsm::ConstraintCode
    getInlineAsmMemConstraint(StringRef ConstraintCode) const override {
      if (ConstraintCode == "o")
        return InlineAsm::ConstraintCode::o;
      if (ConstraintCode == "R")
        return InlineAsm::ConstraintCode::R;
      if (ConstraintCode == "ZC")
        return InlineAsm::ConstraintCode::ZC;
      return TargetLowering::getInlineAsmMemConstraint(ConstraintCode);
    }
 
    bool isLegalAddressingMode(const DataLayout &DL, const AddrMode &AM,
                               Type *Ty, unsigned AS,
                               Instruction *I = nullptr) const override;
 
    bool isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const override;
 
    EVT getOptimalMemOpType(LLVMContext &Context, const MemOp &Op,
                            const AttributeList &FuncAttributes) const override;
 
    /// isFPImmLegal - Returns true if the target can instruction select the
    /// specified FP immediate natively. If false, the legalizer will
    /// materialize the FP immediate as a load from a constant pool.
    bool isFPImmLegal(const APFloat &Imm, EVT VT,
                      bool ForCodeSize) const override;
 
    bool isLegalICmpImmediate(int64_t Imm) const override;
    bool isLegalAddImmediate(int64_t Imm) const override;
 
    unsigned getJumpTableEncoding() const override;
    SDValue getPICJumpTableRelocBase(SDValue Table,
                                     SelectionDAG &DAG) const override;
    bool useSoftFloat() const override;
 
    bool shouldInsertFencesForAtomic(const Instruction *I) const override {
      return true;
    }
 
    /// Emit a sign-extension using sll/sra, seb, or seh appropriately.
    MachineBasicBlock *emitSignExtendToI32InReg(MachineInstr &MI,
                                                MachineBasicBlock *BB,
                                                unsigned Size, unsigned DstReg,
                                                unsigned SrcRec) const;
 
    MachineBasicBlock *emitAtomicBinary(MachineInstr &MI,
                                        MachineBasicBlock *BB) const;
    MachineBasicBlock *emitAtomicBinaryPartword(MachineInstr &MI,
                                                MachineBasicBlock *BB,
                                                unsigned Size) const;
    MachineBasicBlock *emitAtomicCmpSwap(MachineInstr &MI,
                                         MachineBasicBlock *BB) const;
    MachineBasicBlock *emitAtomicCmpSwapPartword(MachineInstr &MI,
                                                 MachineBasicBlock *BB,
                                                 unsigned Size) const;
    MachineBasicBlock *emitSEL_D(MachineInstr &MI, MachineBasicBlock *BB) const;
    MachineBasicBlock *emitPseudoSELECT(MachineInstr &MI, MachineBasicBlock *BB,
                                        bool isFPCmp, unsigned Opc) const;
    MachineBasicBlock *emitPseudoD_SELECT(MachineInstr &MI,
                                          MachineBasicBlock *BB) const;
    MachineBasicBlock *emitLDR_W(MachineInstr &MI, MachineBasicBlock *BB) const;
    MachineBasicBlock *emitLDR_D(MachineInstr &MI, MachineBasicBlock *BB) const;
    MachineBasicBlock *emitSTR_W(MachineInstr &MI, MachineBasicBlock *BB) const;
    MachineBasicBlock *emitSTR_D(MachineInstr &MI, MachineBasicBlock *BB) const;
  };
 
  /// Create MipsTargetLowering objects.
  const MipsTargetLowering *
  createMips16TargetLowering(const MipsTargetMachine &TM,
                             const MipsSubtarget &STI);
  const MipsTargetLowering *
  createMipsSETargetLowering(const MipsTargetMachine &TM,
                             const MipsSubtarget &STI);
 
namespace Mips {
 
FastISel *createFastISel(FunctionLoweringInfo &funcInfo,
                         const TargetLibraryInfo *libInfo);
 
} // end namespace Mips
 
} // end namespace llvm
 
#endif // LLVM_LIB_TARGET_MIPS_MIPSISELLOWERING_H