//===- ARMISelLowering.h - ARM 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 ARM uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_TARGET_ARM_ARMISELLOWERING_H
#define LLVM_LIB_TARGET_ARM_ARMISELLOWERING_H

#include "MCTargetDesc/ARMBaseInfo.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/ISDOpcodes.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/MachineValueType.h"
#include <utility>

namespace llvm {

class ARMSubtarget;
class DataLayout;
class FastISel;
class FunctionLoweringInfo;
class GlobalValue;
class InstrItineraryData;
class Instruction;
class MachineBasicBlock;
class MachineInstr;
class SelectionDAG;
class TargetLibraryInfo;
class TargetMachine;
class TargetRegisterInfo;
class VectorType;

  namespace ARMISD {

    // ARM Specific DAG Nodes
    enum NodeType : unsigned {
      // Start the numbering where the builtin ops and target ops leave off.
      FIRST_NUMBER = ISD::BUILTIN_OP_END,

      Wrapper,      // Wrapper - A wrapper node for TargetConstantPool,
                    // TargetExternalSymbol, and TargetGlobalAddress.
      WrapperPIC,   // WrapperPIC - A wrapper node for TargetGlobalAddress in
                    // PIC mode.
      WrapperJT,    // WrapperJT - A wrapper node for TargetJumpTable

      // Add pseudo op to model memcpy for struct byval.
      COPY_STRUCT_BYVAL,

      CALL,         // Function call.
      CALL_PRED,    // Function call that's predicable.
      CALL_NOLINK,  // Function call with branch not branch-and-link.
      BRCOND,       // Conditional branch.
      BR_JT,        // Jumptable branch.
      BR2_JT,       // Jumptable branch (2 level - jumptable entry is a jump).
      RET_FLAG,     // Return with a flag operand.
      INTRET_FLAG,  // Interrupt return with an LR-offset and a flag operand.

      PIC_ADD,      // Add with a PC operand and a PIC label.

      CMP,          // ARM compare instructions.
      CMN,          // ARM CMN instructions.
      CMPZ,         // ARM compare that sets only Z flag.
      CMPFP,        // ARM VFP compare instruction, sets FPSCR.
      CMPFPw0,      // ARM VFP compare against zero instruction, sets FPSCR.
      FMSTAT,       // ARM fmstat instruction.

      CMOV,         // ARM conditional move instructions.
      SUBS,         // Flag-setting subtraction.

      SSAT,         // Signed saturation
      USAT,         // Unsigned saturation

      BCC_i64,

      SRL_FLAG,     // V,Flag = srl_flag X -> srl X, 1 + save carry out.
      SRA_FLAG,     // V,Flag = sra_flag X -> sra X, 1 + save carry out.
      RRX,          // V = RRX X, Flag     -> srl X, 1 + shift in carry flag.

      ADDC,         // Add with carry
      ADDE,         // Add using carry
      SUBC,         // Sub with carry
      SUBE,         // Sub using carry

      VMOVRRD,      // double to two gprs.
      VMOVDRR,      // Two gprs to double.
      VMOVSR,       // move gpr to single, used for f32 literal constructed in a gpr

      EH_SJLJ_SETJMP,         // SjLj exception handling setjmp.
      EH_SJLJ_LONGJMP,        // SjLj exception handling longjmp.
      EH_SJLJ_SETUP_DISPATCH, // SjLj exception handling setup_dispatch.

      TC_RETURN,    // Tail call return pseudo.

      THREAD_POINTER,

      DYN_ALLOC,    // Dynamic allocation on the stack.

      MEMBARRIER_MCR, // Memory barrier (MCR)

      PRELOAD,      // Preload

      WIN__CHKSTK,  // Windows' __chkstk call to do stack probing.
      WIN__DBZCHK,  // Windows' divide by zero check

      VCEQ,         // Vector compare equal.
      VCEQZ,        // Vector compare equal to zero.
      VCGE,         // Vector compare greater than or equal.
      VCGEZ,        // Vector compare greater than or equal to zero.
      VCLEZ,        // Vector compare less than or equal to zero.
      VCGEU,        // Vector compare unsigned greater than or equal.
      VCGT,         // Vector compare greater than.
      VCGTZ,        // Vector compare greater than zero.
      VCLTZ,        // Vector compare less than zero.
      VCGTU,        // Vector compare unsigned greater than.
      VTST,         // Vector test bits.

      // Vector shift by immediate:
      VSHL,         // ...left
      VSHRs,        // ...right (signed)
      VSHRu,        // ...right (unsigned)

      // Vector rounding shift by immediate:
      VRSHRs,       // ...right (signed)
      VRSHRu,       // ...right (unsigned)
      VRSHRN,       // ...right narrow

      // Vector saturating shift by immediate:
      VQSHLs,       // ...left (signed)
      VQSHLu,       // ...left (unsigned)
      VQSHLsu,      // ...left (signed to unsigned)
      VQSHRNs,      // ...right narrow (signed)
      VQSHRNu,      // ...right narrow (unsigned)
      VQSHRNsu,     // ...right narrow (signed to unsigned)

      // Vector saturating rounding shift by immediate:
      VQRSHRNs,     // ...right narrow (signed)
      VQRSHRNu,     // ...right narrow (unsigned)
      VQRSHRNsu,    // ...right narrow (signed to unsigned)

      // Vector shift and insert:
      VSLI,         // ...left
      VSRI,         // ...right

      // Vector get lane (VMOV scalar to ARM core register)
      // (These are used for 8- and 16-bit element types only.)
      VGETLANEu,    // zero-extend vector extract element
      VGETLANEs,    // sign-extend vector extract element

      // Vector move immediate and move negated immediate:
      VMOVIMM,
      VMVNIMM,

      // Vector move f32 immediate:
      VMOVFPIMM,

      // Move H <-> R, clearing top 16 bits
      VMOVrh,
      VMOVhr,

      // Vector duplicate:
      VDUP,
      VDUPLANE,

      // Vector shuffles:
      VEXT,         // extract
      VREV64,       // reverse elements within 64-bit doublewords
      VREV32,       // reverse elements within 32-bit words
      VREV16,       // reverse elements within 16-bit halfwords
      VZIP,         // zip (interleave)
      VUZP,         // unzip (deinterleave)
      VTRN,         // transpose
      VTBL1,        // 1-register shuffle with mask
      VTBL2,        // 2-register shuffle with mask

      // Vector multiply long:
      VMULLs,       // ...signed
      VMULLu,       // ...unsigned

      SMULWB,       // Signed multiply word by half word, bottom
      SMULWT,       // Signed multiply word by half word, top
      UMLAL,        // 64bit Unsigned Accumulate Multiply
      SMLAL,        // 64bit Signed Accumulate Multiply
      UMAAL,        // 64-bit Unsigned Accumulate Accumulate Multiply
      SMLALBB,      // 64-bit signed accumulate multiply bottom, bottom 16
      SMLALBT,      // 64-bit signed accumulate multiply bottom, top 16
      SMLALTB,      // 64-bit signed accumulate multiply top, bottom 16
      SMLALTT,      // 64-bit signed accumulate multiply top, top 16
      SMLALD,       // Signed multiply accumulate long dual
      SMLALDX,      // Signed multiply accumulate long dual exchange
      SMLSLD,       // Signed multiply subtract long dual
      SMLSLDX,      // Signed multiply subtract long dual exchange
      SMMLAR,       // Signed multiply long, round and add
      SMMLSR,       // Signed multiply long, subtract and round

      // Operands of the standard BUILD_VECTOR node are not legalized, which
      // is fine if BUILD_VECTORs are always lowered to shuffles or other
      // operations, but for ARM some BUILD_VECTORs are legal as-is and their
      // operands need to be legalized.  Define an ARM-specific version of
      // BUILD_VECTOR for this purpose.
      BUILD_VECTOR,

      // Bit-field insert
      BFI,

      // Vector OR with immediate
      VORRIMM,
      // Vector AND with NOT of immediate
      VBICIMM,

      // Vector bitwise select
      VBSL,

      // Pseudo-instruction representing a memory copy using ldm/stm
      // instructions.
      MEMCPY,

      // Vector load N-element structure to all lanes:
      VLD1DUP = ISD::FIRST_TARGET_MEMORY_OPCODE,
      VLD2DUP,
      VLD3DUP,
      VLD4DUP,

      // NEON loads with post-increment base updates:
      VLD1_UPD,
      VLD2_UPD,
      VLD3_UPD,
      VLD4_UPD,
      VLD2LN_UPD,
      VLD3LN_UPD,
      VLD4LN_UPD,
      VLD1DUP_UPD,
      VLD2DUP_UPD,
      VLD3DUP_UPD,
      VLD4DUP_UPD,

      // NEON stores with post-increment base updates:
      VST1_UPD,
      VST2_UPD,
      VST3_UPD,
      VST4_UPD,
      VST2LN_UPD,
      VST3LN_UPD,
      VST4LN_UPD
    };

  } // end namespace ARMISD

  /// Define some predicates that are used for node matching.
  namespace ARM {

    bool isBitFieldInvertedMask(unsigned v);

  } // end namespace ARM

  //===--------------------------------------------------------------------===//
  //  ARMTargetLowering - ARM Implementation of the TargetLowering interface

  class ARMTargetLowering : public TargetLowering {
  public:
    explicit ARMTargetLowering(const TargetMachine &TM,
                               const ARMSubtarget &STI);

    unsigned getJumpTableEncoding() const override;
    bool useSoftFloat() const override;

    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;

    const char *getTargetNodeName(unsigned Opcode) const override;

    bool isSelectSupported(SelectSupportKind Kind) const override {
      // ARM does not support scalar condition selects on vectors.
      return (Kind != ScalarCondVectorVal);
    }

    bool isReadOnly(const GlobalValue *GV) const;

    /// getSetCCResultType - Return the value type to use for ISD::SETCC.
    EVT getSetCCResultType(const DataLayout &DL, LLVMContext &Context,
                           EVT VT) const override;

    MachineBasicBlock *
    EmitInstrWithCustomInserter(MachineInstr &MI,
                                MachineBasicBlock *MBB) const override;

    void AdjustInstrPostInstrSelection(MachineInstr &MI,
                                       SDNode *Node) const override;

    SDValue PerformCMOVCombine(SDNode *N, SelectionDAG &DAG) const;
    SDValue PerformBRCONDCombine(SDNode *N, SelectionDAG &DAG) const;
    SDValue PerformCMOVToBFICombine(SDNode *N, SelectionDAG &DAG) const;
    SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;

    bool isDesirableToTransformToIntegerOp(unsigned Opc, EVT VT) const override;

    /// allowsMisalignedMemoryAccesses - Returns true if the target allows
    /// unaligned memory accesses of the specified type. Returns whether it
    /// is "fast" by reference in the second argument.
    bool allowsMisalignedMemoryAccesses(EVT VT, unsigned AddrSpace,
                                        unsigned Align,
                                        bool *Fast) const override;

    EVT getOptimalMemOpType(uint64_t Size,
                            unsigned DstAlign, unsigned SrcAlign,
                            bool IsMemset, bool ZeroMemset,
                            bool MemcpyStrSrc,
                            MachineFunction &MF) const override;

    bool isTruncateFree(Type *SrcTy, Type *DstTy) const override;
    bool isTruncateFree(EVT SrcVT, EVT DstVT) const override;
    bool isZExtFree(SDValue Val, EVT VT2) const override;
    bool isFNegFree(EVT VT) const override;

    bool isVectorLoadExtDesirable(SDValue ExtVal) const override;

    bool allowTruncateForTailCall(Type *Ty1, Type *Ty2) const override;


    /// isLegalAddressingMode - Return true if the addressing mode represented
    /// by AM is legal for this target, for a load/store of the specified type.
    bool isLegalAddressingMode(const DataLayout &DL, const AddrMode &AM,
                               Type *Ty, unsigned AS,
                               Instruction *I = nullptr) const override;

    /// getScalingFactorCost - Return the cost of the scaling used in
    /// addressing mode represented by AM.
    /// If the AM is supported, the return value must be >= 0.
    /// If the AM is not supported, the return value must be negative.
    int getScalingFactorCost(const DataLayout &DL, const AddrMode &AM, Type *Ty,
                             unsigned AS) const override;

    bool isLegalT2ScaledAddressingMode(const AddrMode &AM, EVT VT) const;

    /// Returns true if the addresing mode representing by AM is legal
    /// for the Thumb1 target, for a load/store of the specified type.
    bool isLegalT1ScaledAddressingMode(const AddrMode &AM, EVT VT) const;

    /// isLegalICmpImmediate - Return true if the specified immediate is legal
    /// icmp immediate, that is the target has icmp instructions which can
    /// compare a register against the immediate without having to materialize
    /// the immediate into a register.
    bool isLegalICmpImmediate(int64_t Imm) const override;

    /// isLegalAddImmediate - Return true if the specified immediate is legal
    /// add immediate, that is the target has add instructions which can
    /// add a register and the immediate without having to materialize
    /// the immediate into a register.
    bool isLegalAddImmediate(int64_t Imm) const override;

    /// getPreIndexedAddressParts - returns true by value, base pointer and
    /// offset pointer and addressing mode by reference if the node's address
    /// can be legally represented as pre-indexed load / store address.
    bool getPreIndexedAddressParts(SDNode *N, SDValue &Base, SDValue &Offset,
                                   ISD::MemIndexedMode &AM,
                                   SelectionDAG &DAG) const override;

    /// getPostIndexedAddressParts - returns true by value, base pointer and
    /// offset pointer and addressing mode by reference if this node can be
    /// combined with a load / store to form a post-indexed load / store.
    bool getPostIndexedAddressParts(SDNode *N, SDNode *Op, SDValue &Base,
                                    SDValue &Offset, ISD::MemIndexedMode &AM,
                                    SelectionDAG &DAG) const override;

    void computeKnownBitsForTargetNode(const SDValue Op, KnownBits &Known,
                                       const APInt &DemandedElts,
                                       const SelectionDAG &DAG,
                                       unsigned Depth) const override;

    bool targetShrinkDemandedConstant(SDValue Op, const APInt &Demanded,
                                      TargetLoweringOpt &TLO) const override;


    bool ExpandInlineAsm(CallInst *CI) const override;

    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;

    std::pair<unsigned, const TargetRegisterClass *>
    getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
                                 StringRef Constraint, MVT VT) const override;

    const char *LowerXConstraint(EVT ConstraintVT) 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, std::string &Constraint,
                                      std::vector<SDValue> &Ops,
                                      SelectionDAG &DAG) const override;

    unsigned
    getInlineAsmMemConstraint(StringRef ConstraintCode) const override {
      if (ConstraintCode == "Q")
        return InlineAsm::Constraint_Q;
      else if (ConstraintCode == "o")
        return InlineAsm::Constraint_o;
      else if (ConstraintCode.size() == 2) {
        if (ConstraintCode[0] == 'U') {
          switch(ConstraintCode[1]) {
          default:
            break;
          case 'm':
            return InlineAsm::Constraint_Um;
          case 'n':
            return InlineAsm::Constraint_Un;
          case 'q':
            return InlineAsm::Constraint_Uq;
          case 's':
            return InlineAsm::Constraint_Us;
          case 't':
            return InlineAsm::Constraint_Ut;
          case 'v':
            return InlineAsm::Constraint_Uv;
          case 'y':
            return InlineAsm::Constraint_Uy;
          }
        }
      }
      return TargetLowering::getInlineAsmMemConstraint(ConstraintCode);
    }

    const ARMSubtarget* getSubtarget() const {
      return Subtarget;
    }

    /// getRegClassFor - Return the register class that should be used for the
    /// specified value type.
    const TargetRegisterClass *getRegClassFor(MVT VT) const override;

    /// Returns true if a cast between SrcAS and DestAS is a noop.
    bool isNoopAddrSpaceCast(unsigned SrcAS, unsigned DestAS) const override {
      // Addrspacecasts are always noops.
      return true;
    }

    bool shouldAlignPointerArgs(CallInst *CI, unsigned &MinSize,
                                unsigned &PrefAlign) const override;

    /// 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;

    Sched::Preference getSchedulingPreference(SDNode *N) const override;

    bool
    isShuffleMaskLegal(ArrayRef<int> M, EVT VT) const override;
    bool isOffsetFoldingLegal(const GlobalAddressSDNode *GA) 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) const override;

    bool getTgtMemIntrinsic(IntrinsicInfo &Info,
                            const CallInst &I,
                            MachineFunction &MF,
                            unsigned Intrinsic) const override;

    /// Returns true if it is beneficial to convert a load of a constant
    /// to just the constant itself.
    bool shouldConvertConstantLoadToIntImm(const APInt &Imm,
                                           Type *Ty) const override;

    /// Return true if EXTRACT_SUBVECTOR is cheap for this result type
    /// with this index.
    bool isExtractSubvectorCheap(EVT ResVT, EVT SrcVT,
                                 unsigned Index) const override;

    /// Returns true if an argument of type Ty needs to be passed in a
    /// contiguous block of registers in calling convention CallConv.
    bool functionArgumentNeedsConsecutiveRegisters(
        Type *Ty, CallingConv::ID CallConv, bool isVarArg) const override;

    /// If a physical register, this returns the register that receives the
    /// exception address on entry to an EH pad.
    unsigned
    getExceptionPointerRegister(const Constant *PersonalityFn) const override;

    /// If a physical register, this returns the register that receives the
    /// exception typeid on entry to a landing pad.
    unsigned
    getExceptionSelectorRegister(const Constant *PersonalityFn) const override;

    Instruction *makeDMB(IRBuilder<> &Builder, ARM_MB::MemBOpt Domain) const;
    Value *emitLoadLinked(IRBuilder<> &Builder, Value *Addr,
                          AtomicOrdering Ord) const override;
    Value *emitStoreConditional(IRBuilder<> &Builder, Value *Val,
                                Value *Addr, AtomicOrdering Ord) const override;

    void emitAtomicCmpXchgNoStoreLLBalance(IRBuilder<> &Builder) const override;

    Instruction *emitLeadingFence(IRBuilder<> &Builder, Instruction *Inst,
                                  AtomicOrdering Ord) const override;
    Instruction *emitTrailingFence(IRBuilder<> &Builder, Instruction *Inst,
                                   AtomicOrdering Ord) const override;

    unsigned getMaxSupportedInterleaveFactor() const override { return 4; }

    bool lowerInterleavedLoad(LoadInst *LI,
                              ArrayRef<ShuffleVectorInst *> Shuffles,
                              ArrayRef<unsigned> Indices,
                              unsigned Factor) const override;
    bool lowerInterleavedStore(StoreInst *SI, ShuffleVectorInst *SVI,
                               unsigned Factor) const override;

    bool shouldInsertFencesForAtomic(const Instruction *I) const override;
    TargetLoweringBase::AtomicExpansionKind
    shouldExpandAtomicLoadInIR(LoadInst *LI) const override;
    bool shouldExpandAtomicStoreInIR(StoreInst *SI) const override;
    TargetLoweringBase::AtomicExpansionKind
    shouldExpandAtomicRMWInIR(AtomicRMWInst *AI) const override;
    TargetLoweringBase::AtomicExpansionKind
    shouldExpandAtomicCmpXchgInIR(AtomicCmpXchgInst *AI) const override;

    bool useLoadStackGuardNode() const override;

    bool canCombineStoreAndExtract(Type *VectorTy, Value *Idx,
                                   unsigned &Cost) const override;

    bool canMergeStoresTo(unsigned AddressSpace, EVT MemVT,
                          const SelectionDAG &DAG) const override {
      // Do not merge to larger than i32.
      return (MemVT.getSizeInBits() <= 32);
    }

    bool isCheapToSpeculateCttz() const override;
    bool isCheapToSpeculateCtlz() const override;

    bool convertSetCCLogicToBitwiseLogic(EVT VT) const override {
      return VT.isScalarInteger();
    }

    bool supportSwiftError() const override {
      return true;
    }

    bool hasStandaloneRem(EVT VT) const override {
      return HasStandaloneRem;
    }

    bool shouldExpandShift(SelectionDAG &DAG, SDNode *N) const override;

    CCAssignFn *CCAssignFnForCall(CallingConv::ID CC, bool isVarArg) const;
    CCAssignFn *CCAssignFnForReturn(CallingConv::ID CC, bool isVarArg) const;

    /// Returns true if \p VecTy is a legal interleaved access type. This
    /// function checks the vector element type and the overall width of the
    /// vector.
    bool isLegalInterleavedAccessType(VectorType *VecTy,
                                      const DataLayout &DL) const;

    bool alignLoopsWithOptSize() const override;

    /// Returns the number of interleaved accesses that will be generated when
    /// lowering accesses of the given type.
    unsigned getNumInterleavedAccesses(VectorType *VecTy,
                                       const DataLayout &DL) const;

    void finalizeLowering(MachineFunction &MF) const override;

    /// Return the correct alignment for the current calling convention.
    unsigned getABIAlignmentForCallingConv(Type *ArgTy,
                                           DataLayout DL) const override;

    bool isDesirableToCommuteWithShift(const SDNode *N,
                                       CombineLevel Level) const override;

    bool shouldFoldShiftPairToMask(const SDNode *N,
                                   CombineLevel Level) const override;
  protected:
    std::pair<const TargetRegisterClass *, uint8_t>
    findRepresentativeClass(const TargetRegisterInfo *TRI,
                            MVT VT) const override;

  private:
    /// Subtarget - Keep a pointer to the ARMSubtarget around so that we can
    /// make the right decision when generating code for different targets.
    const ARMSubtarget *Subtarget;

    const TargetRegisterInfo *RegInfo;

    const InstrItineraryData *Itins;

    /// ARMPCLabelIndex - Keep track of the number of ARM PC labels created.
    unsigned ARMPCLabelIndex;

    // TODO: remove this, and have shouldInsertFencesForAtomic do the proper
    // check.
    bool InsertFencesForAtomic;

    bool HasStandaloneRem = true;

    void addTypeForNEON(MVT VT, MVT PromotedLdStVT, MVT PromotedBitwiseVT);
    void addDRTypeForNEON(MVT VT);
    void addQRTypeForNEON(MVT VT);
    std::pair<SDValue, SDValue> getARMXALUOOp(SDValue Op, SelectionDAG &DAG, SDValue &ARMcc) const;

    using RegsToPassVector = SmallVector<std::pair<unsigned, SDValue>, 8>;

    void PassF64ArgInRegs(const SDLoc &dl, SelectionDAG &DAG, SDValue Chain,
                          SDValue &Arg, RegsToPassVector &RegsToPass,
                          CCValAssign &VA, CCValAssign &NextVA,
                          SDValue &StackPtr,
                          SmallVectorImpl<SDValue> &MemOpChains,
                          ISD::ArgFlagsTy Flags) const;
    SDValue GetF64FormalArgument(CCValAssign &VA, CCValAssign &NextVA,
                                 SDValue &Root, SelectionDAG &DAG,
                                 const SDLoc &dl) const;

    CallingConv::ID getEffectiveCallingConv(CallingConv::ID CC,
                                            bool isVarArg) const;
    CCAssignFn *CCAssignFnForNode(CallingConv::ID CC, bool Return,
                                  bool isVarArg) const;
    SDValue LowerMemOpCallTo(SDValue Chain, SDValue StackPtr, SDValue Arg,
                             const SDLoc &dl, SelectionDAG &DAG,
                             const CCValAssign &VA,
                             ISD::ArgFlagsTy Flags) const;
    SDValue LowerEH_SJLJ_SETJMP(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerEH_SJLJ_LONGJMP(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerEH_SJLJ_SETUP_DISPATCH(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerINTRINSIC_WO_CHAIN(SDValue Op, SelectionDAG &DAG,
                                    const ARMSubtarget *Subtarget) const;
    SDValue LowerBlockAddress(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerConstantPool(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerGlobalAddressDarwin(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerGlobalAddressELF(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerGlobalAddressWindows(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerToTLSGeneralDynamicModel(GlobalAddressSDNode *GA,
                                            SelectionDAG &DAG) const;
    SDValue LowerToTLSExecModels(GlobalAddressSDNode *GA,
                                 SelectionDAG &DAG,
                                 TLSModel::Model model) const;
    SDValue LowerGlobalTLSAddressDarwin(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerGlobalTLSAddressWindows(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerGLOBAL_OFFSET_TABLE(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerBR_JT(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerSignedALUO(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerUnsignedALUO(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerSELECT(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerBRCOND(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerBR_CC(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFCOPYSIGN(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerRETURNADDR(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerShiftRightParts(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerShiftLeftParts(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFLT_ROUNDS_(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerConstantFP(SDValue Op, SelectionDAG &DAG,
                            const ARMSubtarget *ST) const;
    SDValue LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG,
                              const ARMSubtarget *ST) const;
    SDValue LowerFSINCOS(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerDivRem(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerDIV_Windows(SDValue Op, SelectionDAG &DAG, bool Signed) const;
    void ExpandDIV_Windows(SDValue Op, SelectionDAG &DAG, bool Signed,
                           SmallVectorImpl<SDValue> &Results) const;
    SDValue LowerWindowsDIVLibCall(SDValue Op, SelectionDAG &DAG, bool Signed,
                                   SDValue &Chain) const;
    SDValue LowerREM(SDNode *N, SelectionDAG &DAG) const;
    SDValue LowerDYNAMIC_STACKALLOC(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFP_ROUND(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFP_EXTEND(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFP_TO_INT(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerINT_TO_FP(SDValue Op, SelectionDAG &DAG) const;

    unsigned getRegisterByName(const char* RegName, EVT VT,
                               SelectionDAG &DAG) const override;

    SDValue BuildSDIVPow2(SDNode *N, const APInt &Divisor, SelectionDAG &DAG,
                          SmallVectorImpl<SDNode *> &Created) const override;

    /// isFMAFasterThanFMulAndFAdd - Return true if an FMA operation is faster
    /// than a pair of fmul and fadd instructions. fmuladd intrinsics will be
    /// expanded to FMAs when this method returns true, otherwise fmuladd is
    /// expanded to fmul + fadd.
    ///
    /// ARM supports both fused and unfused multiply-add operations; we already
    /// lower a pair of fmul and fadd to the latter so it's not clear that there
    /// would be a gain or that the gain would be worthwhile enough to risk
    /// correctness bugs.
    bool isFMAFasterThanFMulAndFAdd(EVT VT) const override { return false; }

    SDValue ReconstructShuffle(SDValue Op, SelectionDAG &DAG) const;

    SDValue LowerCallResult(SDValue Chain, SDValue InFlag,
                            CallingConv::ID CallConv, bool isVarArg,
                            const SmallVectorImpl<ISD::InputArg> &Ins,
                            const SDLoc &dl, SelectionDAG &DAG,
                            SmallVectorImpl<SDValue> &InVals, bool isThisReturn,
                            SDValue ThisVal) const;

    bool supportSplitCSR(MachineFunction *MF) const override {
      return MF->getFunction().getCallingConv() == CallingConv::CXX_FAST_TLS &&
          MF->getFunction().hasFnAttribute(Attribute::NoUnwind);
    }

    void initializeSplitCSR(MachineBasicBlock *Entry) const override;
    void insertCopiesSplitCSR(
      MachineBasicBlock *Entry,
      const SmallVectorImpl<MachineBasicBlock *> &Exits) const override;

    SDValue
    LowerFormalArguments(SDValue Chain, CallingConv::ID CallConv, bool isVarArg,
                         const SmallVectorImpl<ISD::InputArg> &Ins,
                         const SDLoc &dl, SelectionDAG &DAG,
                         SmallVectorImpl<SDValue> &InVals) const override;

    int StoreByValRegs(CCState &CCInfo, SelectionDAG &DAG, const SDLoc &dl,
                       SDValue &Chain, const Value *OrigArg,
                       unsigned InRegsParamRecordIdx, int ArgOffset,
                       unsigned ArgSize) const;

    void VarArgStyleRegisters(CCState &CCInfo, SelectionDAG &DAG,
                              const SDLoc &dl, SDValue &Chain,
                              unsigned ArgOffset, unsigned TotalArgRegsSaveSize,
                              bool ForceMutable = false) const;

    SDValue LowerCall(TargetLowering::CallLoweringInfo &CLI,
                      SmallVectorImpl<SDValue> &InVals) const override;

    /// HandleByVal - Target-specific cleanup for ByVal support.
    void HandleByVal(CCState *, unsigned &, unsigned) const override;

    /// IsEligibleForTailCallOptimization - Check whether the call is eligible
    /// for tail call optimization. Targets which want to do tail call
    /// optimization should implement this function.
    bool IsEligibleForTailCallOptimization(SDValue Callee,
                                           CallingConv::ID CalleeCC,
                                           bool isVarArg,
                                           bool isCalleeStructRet,
                                           bool isCallerStructRet,
                                    const SmallVectorImpl<ISD::OutputArg> &Outs,
                                    const SmallVectorImpl<SDValue> &OutVals,
                                    const SmallVectorImpl<ISD::InputArg> &Ins,
                                           SelectionDAG& DAG) const;

    bool CanLowerReturn(CallingConv::ID CallConv,
                        MachineFunction &MF, bool isVarArg,
                        const SmallVectorImpl<ISD::OutputArg> &Outs,
                        LLVMContext &Context) 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;

    bool isUsedByReturnOnly(SDNode *N, SDValue &Chain) const override;

    bool mayBeEmittedAsTailCall(const CallInst *CI) const override;

    bool shouldConsiderGEPOffsetSplit() const override { return true; }

    SDValue getCMOV(const SDLoc &dl, EVT VT, SDValue FalseVal, SDValue TrueVal,
                    SDValue ARMcc, SDValue CCR, SDValue Cmp,
                    SelectionDAG &DAG) const;
    SDValue getARMCmp(SDValue LHS, SDValue RHS, ISD::CondCode CC,
                      SDValue &ARMcc, SelectionDAG &DAG, const SDLoc &dl) const;
    SDValue getVFPCmp(SDValue LHS, SDValue RHS, SelectionDAG &DAG,
                      const SDLoc &dl, bool InvalidOnQNaN) const;
    SDValue duplicateCmp(SDValue Cmp, SelectionDAG &DAG) const;

    SDValue OptimizeVFPBrcond(SDValue Op, SelectionDAG &DAG) const;

    void SetupEntryBlockForSjLj(MachineInstr &MI, MachineBasicBlock *MBB,
                                MachineBasicBlock *DispatchBB, int FI) const;

    void EmitSjLjDispatchBlock(MachineInstr &MI, MachineBasicBlock *MBB) const;

    bool RemapAddSubWithFlags(MachineInstr &MI, MachineBasicBlock *BB) const;

    MachineBasicBlock *EmitStructByval(MachineInstr &MI,
                                       MachineBasicBlock *MBB) const;

    MachineBasicBlock *EmitLowered__chkstk(MachineInstr &MI,
                                           MachineBasicBlock *MBB) const;
    MachineBasicBlock *EmitLowered__dbzchk(MachineInstr &MI,
                                           MachineBasicBlock *MBB) const;
  };

  enum NEONModImmType {
    VMOVModImm,
    VMVNModImm,
    OtherModImm
  };

  namespace ARM {

    FastISel *createFastISel(FunctionLoweringInfo &funcInfo,
                             const TargetLibraryInfo *libInfo);

  } // end namespace ARM

} // end namespace llvm

#endif // LLVM_LIB_TARGET_ARM_ARMISELLOWERING_H