//===- AArch64Disassembler.cpp - Disassembler for AArch64 -----------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
//
//===----------------------------------------------------------------------===//

#include "AArch64Disassembler.h"
#include "AArch64ExternalSymbolizer.h"
#include "MCTargetDesc/AArch64AddressingModes.h"
#include "MCTargetDesc/AArch64MCTargetDesc.h"
#include "TargetInfo/AArch64TargetInfo.h"
#include "Utils/AArch64BaseInfo.h"
#include "llvm/MC/MCDecoderOps.h"
#include "llvm/MC/MCDisassembler/MCRelocationInfo.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include <memory>

using namespace llvm;

#define DEBUG_TYPE "aarch64-disassembler"

// Pull DecodeStatus and its enum values into the global namespace.
using DecodeStatus = MCDisassembler::DecodeStatus;

// Forward declare these because the autogenerated code will reference them.
// Definitions are further down.
template <unsigned RegClassID, unsigned FirstReg, unsigned NumRegsInClass>
static DecodeStatus DecodeSimpleRegisterClass(MCInst &Inst, unsigned RegNo,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder);
static DecodeStatus
DecodeGPR64x8ClassRegisterClass(MCInst &Inst, unsigned RegNo, uint64_t Address,
                                const MCDisassembler *Decoder);
template <unsigned Min, unsigned Max>
static DecodeStatus DecodeZPRMul2_MinMax(MCInst &Inst, unsigned RegNo,
                                         uint64_t Address,
                                         const MCDisassembler *Decoder);
static DecodeStatus DecodeZK(MCInst &Inst, unsigned RegNo, uint64_t Address,
                             const MCDisassembler *Decoder);
template <unsigned Min, unsigned Max>
static DecodeStatus DecodeZPR2Mul2RegisterClass(MCInst &Inst, unsigned RegNo,
                                                uint64_t Address,
                                                const void *Decoder);
static DecodeStatus DecodeZPR4Mul4RegisterClass(MCInst &Inst, unsigned RegNo,
                                                uint64_t Address,
                                                const void *Decoder);
template <unsigned NumBitsForTile>
static DecodeStatus DecodeMatrixTile(MCInst &Inst, unsigned RegNo,
                                     uint64_t Address,
                                     const MCDisassembler *Decoder);
static DecodeStatus
DecodeMatrixTileListRegisterClass(MCInst &Inst, unsigned RegMask,
                                  uint64_t Address,
                                  const MCDisassembler *Decoder);
static DecodeStatus DecodePPR2Mul2RegisterClass(MCInst &Inst, unsigned RegNo,
                                                uint64_t Address,
                                                const void *Decoder);

static DecodeStatus DecodeFixedPointScaleImm32(MCInst &Inst, unsigned Imm,
                                               uint64_t Address,
                                               const MCDisassembler *Decoder);
static DecodeStatus DecodeFixedPointScaleImm64(MCInst &Inst, unsigned Imm,
                                               uint64_t Address,
                                               const MCDisassembler *Decoder);
static DecodeStatus DecodePCRelLabel16(MCInst &Inst, unsigned Imm,
                                       uint64_t Address,
                                       const MCDisassembler *Decoder);
static DecodeStatus DecodePCRelLabel19(MCInst &Inst, unsigned Imm,
                                       uint64_t Address,
                                       const MCDisassembler *Decoder);
static DecodeStatus DecodePCRelLabel9(MCInst &Inst, unsigned Imm,
                                      uint64_t Address,
                                      const MCDisassembler *Decoder);
static DecodeStatus DecodeMemExtend(MCInst &Inst, unsigned Imm,
                                    uint64_t Address,
                                    const MCDisassembler *Decoder);
static DecodeStatus DecodeMRSSystemRegister(MCInst &Inst, unsigned Imm,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder);
static DecodeStatus DecodeMSRSystemRegister(MCInst &Inst, unsigned Imm,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder);
static DecodeStatus
DecodeThreeAddrSRegInstruction(MCInst &Inst, uint32_t insn, uint64_t Address,
                               const MCDisassembler *Decoder);
static DecodeStatus DecodeMoveImmInstruction(MCInst &Inst, uint32_t insn,
                                             uint64_t Address,
                                             const MCDisassembler *Decoder);
static DecodeStatus
DecodeUnsignedLdStInstruction(MCInst &Inst, uint32_t insn, uint64_t Address,
                              const MCDisassembler *Decoder);
static DecodeStatus DecodeSignedLdStInstruction(MCInst &Inst, uint32_t insn,
                                                uint64_t Address,
                                                const MCDisassembler *Decoder);
static DecodeStatus
DecodeExclusiveLdStInstruction(MCInst &Inst, uint32_t insn, uint64_t Address,
                               const MCDisassembler *Decoder);
static DecodeStatus DecodePairLdStInstruction(MCInst &Inst, uint32_t insn,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder);
static DecodeStatus DecodeAuthLoadInstruction(MCInst &Inst, uint32_t insn,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder);
static DecodeStatus DecodeAddSubERegInstruction(MCInst &Inst, uint32_t insn,
                                                uint64_t Address,
                                                const MCDisassembler *Decoder);
static DecodeStatus DecodeLogicalImmInstruction(MCInst &Inst, uint32_t insn,
                                                uint64_t Address,
                                                const MCDisassembler *Decoder);
static DecodeStatus DecodeModImmInstruction(MCInst &Inst, uint32_t insn,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder);
static DecodeStatus DecodeModImmTiedInstruction(MCInst &Inst, uint32_t insn,
                                                uint64_t Address,
                                                const MCDisassembler *Decoder);
static DecodeStatus DecodeAdrInstruction(MCInst &Inst, uint32_t insn,
                                         uint64_t Address,
                                         const MCDisassembler *Decoder);
static DecodeStatus DecodeAddSubImmShift(MCInst &Inst, uint32_t insn,
                                         uint64_t Address,
                                         const MCDisassembler *Decoder);
static DecodeStatus DecodeUnconditionalBranch(MCInst &Inst, uint32_t insn,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder);
static DecodeStatus
DecodeSystemPStateImm0_15Instruction(MCInst &Inst, uint32_t insn,
                                     uint64_t Address,
                                     const MCDisassembler *Decoder);
static DecodeStatus
DecodeSystemPStateImm0_1Instruction(MCInst &Inst, uint32_t insn,
                                    uint64_t Address,
                                    const MCDisassembler *Decoder);
static DecodeStatus DecodeTestAndBranch(MCInst &Inst, uint32_t insn,
                                        uint64_t Address,
                                        const MCDisassembler *Decoder);

static DecodeStatus DecodeFMOVLaneInstruction(MCInst &Inst, unsigned Insn,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftR64Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftR64ImmNarrow(MCInst &Inst, unsigned Imm,
                                               uint64_t Addr,
                                               const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftR32Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftR32ImmNarrow(MCInst &Inst, unsigned Imm,
                                               uint64_t Addr,
                                               const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftR16Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftR16ImmNarrow(MCInst &Inst, unsigned Imm,
                                               uint64_t Addr,
                                               const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftR8Imm(MCInst &Inst, unsigned Imm,
                                        uint64_t Addr,
                                        const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftL64Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftL32Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftL16Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder);
static DecodeStatus DecodeVecShiftL8Imm(MCInst &Inst, unsigned Imm,
                                        uint64_t Addr,
                                        const MCDisassembler *Decoder);
static DecodeStatus
DecodeWSeqPairsClassRegisterClass(MCInst &Inst, unsigned RegNo, uint64_t Addr,
                                  const MCDisassembler *Decoder);
static DecodeStatus
DecodeXSeqPairsClassRegisterClass(MCInst &Inst, unsigned RegNo, uint64_t Addr,
                                  const MCDisassembler *Decoder);
static DecodeStatus DecodeSyspXzrInstruction(MCInst &Inst, uint32_t insn,
                                             uint64_t Addr,
                                             const MCDisassembler *Decoder);
static DecodeStatus
DecodeSVELogicalImmInstruction(MCInst &Inst, uint32_t insn, uint64_t Address,
                               const MCDisassembler *Decoder);
template <int Bits>
static DecodeStatus DecodeSImm(MCInst &Inst, uint64_t Imm, uint64_t Address,
                               const MCDisassembler *Decoder);
template <int ElementWidth>
static DecodeStatus DecodeImm8OptLsl(MCInst &Inst, unsigned Imm, uint64_t Addr,
                                     const MCDisassembler *Decoder);
static DecodeStatus DecodeSVEIncDecImm(MCInst &Inst, unsigned Imm,
                                       uint64_t Addr,
                                       const MCDisassembler *Decoder);
static DecodeStatus DecodeSVCROp(MCInst &Inst, unsigned Imm, uint64_t Address,
                                 const MCDisassembler *Decoder);
static DecodeStatus DecodeCPYMemOpInstruction(MCInst &Inst, uint32_t insn,
                                              uint64_t Addr,
                                              const MCDisassembler *Decoder);
static DecodeStatus DecodeSETMemOpInstruction(MCInst &Inst, uint32_t insn,
                                              uint64_t Addr,
                                              const MCDisassembler *Decoder);
static DecodeStatus DecodePRFMRegInstruction(MCInst &Inst, uint32_t insn,
                                             uint64_t Address,
                                             const MCDisassembler *Decoder);

#include "AArch64GenDisassemblerTables.inc"
#include "AArch64GenInstrInfo.inc"

#define Success MCDisassembler::Success
#define Fail MCDisassembler::Fail
#define SoftFail MCDisassembler::SoftFail

static MCDisassembler *createAArch64Disassembler(const Target &T,
                                                 const MCSubtargetInfo &STI,
                                                 MCContext &Ctx) {

  return new AArch64Disassembler(STI, Ctx, T.createMCInstrInfo());
}

DecodeStatus AArch64Disassembler::getInstruction(MCInst &MI, uint64_t &Size,
                                                 ArrayRef<uint8_t> Bytes,
                                                 uint64_t Address,
                                                 raw_ostream &CS) const {
  CommentStream = &CS;

  Size = 0;
  // We want to read exactly 4 bytes of data.
  if (Bytes.size() < 4)
    return Fail;
  Size = 4;

  // Encoded as a small-endian 32-bit word in the stream.
  uint32_t Insn =
      (Bytes[3] << 24) | (Bytes[2] << 16) | (Bytes[1] << 8) | (Bytes[0] << 0);

  const uint8_t *Tables[] = {DecoderTable32, DecoderTableFallback32};

  for (const auto *Table : Tables) {
    DecodeStatus Result =
        decodeInstruction(Table, MI, Insn, Address, this, STI);

    const MCInstrDesc &Desc = MCII->get(MI.getOpcode());

    // For Scalable Matrix Extension (SME) instructions that have an implicit
    // operand for the accumulator (ZA) or implicit immediate zero which isn't
    // encoded, manually insert operand.
    for (unsigned i = 0; i < Desc.getNumOperands(); i++) {
      if (Desc.operands()[i].OperandType == MCOI::OPERAND_REGISTER) {
        switch (Desc.operands()[i].RegClass) {
        default:
          break;
        case AArch64::MPRRegClassID:
          MI.insert(MI.begin() + i, MCOperand::createReg(AArch64::ZA));
          break;
        case AArch64::MPR8RegClassID:
          MI.insert(MI.begin() + i, MCOperand::createReg(AArch64::ZAB0));
          break;
        case AArch64::ZTRRegClassID:
          MI.insert(MI.begin() + i, MCOperand::createReg(AArch64::ZT0));
          break;
        }
      } else if (Desc.operands()[i].OperandType ==
                 AArch64::OPERAND_IMPLICIT_IMM_0) {
        MI.insert(MI.begin() + i, MCOperand::createImm(0));
      }
    }

    if (MI.getOpcode() == AArch64::LDR_ZA ||
        MI.getOpcode() == AArch64::STR_ZA) {
      // Spill and fill instructions have a single immediate used for both
      // the vector select offset and optional memory offset. Replicate
      // the decoded immediate.
      const MCOperand &Imm4Op = MI.getOperand(2);
      assert(Imm4Op.isImm() && "Unexpected operand type!");
      MI.addOperand(Imm4Op);
    }

    if (Result != MCDisassembler::Fail)
      return Result;
  }

  return MCDisassembler::Fail;
}

uint64_t AArch64Disassembler::suggestBytesToSkip(ArrayRef<uint8_t> Bytes,
                                                 uint64_t Address) const {
  // AArch64 instructions are always 4 bytes wide, so there's no point
  // in skipping any smaller number of bytes if an instruction can't
  // be decoded.
  return 4;
}

static MCSymbolizer *
createAArch64ExternalSymbolizer(const Triple &TT, LLVMOpInfoCallback GetOpInfo,
                                LLVMSymbolLookupCallback SymbolLookUp,
                                void *DisInfo, MCContext *Ctx,
                                std::unique_ptr<MCRelocationInfo> &&RelInfo) {
  return new AArch64ExternalSymbolizer(*Ctx, std::move(RelInfo), GetOpInfo,
                                       SymbolLookUp, DisInfo);
}

extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAArch64Disassembler() {
  TargetRegistry::RegisterMCDisassembler(getTheAArch64leTarget(),
                                         createAArch64Disassembler);
  TargetRegistry::RegisterMCDisassembler(getTheAArch64beTarget(),
                                         createAArch64Disassembler);
  TargetRegistry::RegisterMCSymbolizer(getTheAArch64leTarget(),
                                       createAArch64ExternalSymbolizer);
  TargetRegistry::RegisterMCSymbolizer(getTheAArch64beTarget(),
                                       createAArch64ExternalSymbolizer);
  TargetRegistry::RegisterMCDisassembler(getTheAArch64_32Target(),
                                         createAArch64Disassembler);
  TargetRegistry::RegisterMCSymbolizer(getTheAArch64_32Target(),
                                       createAArch64ExternalSymbolizer);

  TargetRegistry::RegisterMCDisassembler(getTheARM64Target(),
                                         createAArch64Disassembler);
  TargetRegistry::RegisterMCSymbolizer(getTheARM64Target(),
                                       createAArch64ExternalSymbolizer);
  TargetRegistry::RegisterMCDisassembler(getTheARM64_32Target(),
                                         createAArch64Disassembler);
  TargetRegistry::RegisterMCSymbolizer(getTheARM64_32Target(),
                                       createAArch64ExternalSymbolizer);
}

template <unsigned RegClassID, unsigned FirstReg, unsigned NumRegsInClass>
static DecodeStatus DecodeSimpleRegisterClass(MCInst &Inst, unsigned RegNo,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder) {
  if (RegNo > NumRegsInClass - 1)
    return Fail;

  unsigned Register =
      AArch64MCRegisterClasses[RegClassID].getRegister(RegNo + FirstReg);
  Inst.addOperand(MCOperand::createReg(Register));
  return Success;
}

static DecodeStatus
DecodeGPR64x8ClassRegisterClass(MCInst &Inst, unsigned RegNo, uint64_t Address,
                                const MCDisassembler *Decoder) {
  if (RegNo > 22)
    return Fail;
  if (RegNo & 1)
    return Fail;

  unsigned Register =
      AArch64MCRegisterClasses[AArch64::GPR64x8ClassRegClassID].getRegister(
          RegNo >> 1);
  Inst.addOperand(MCOperand::createReg(Register));
  return Success;
}

template <unsigned Min, unsigned Max>
static DecodeStatus DecodeZPRMul2_MinMax(MCInst &Inst, unsigned RegNo,
                                         uint64_t Address,
                                         const MCDisassembler *Decoder) {
  unsigned Reg = (RegNo * 2) + Min;
  if (Reg < Min || Reg > Max || (Reg & 1))
    return Fail;
  unsigned Register =
      AArch64MCRegisterClasses[AArch64::ZPRRegClassID].getRegister(Reg);
  Inst.addOperand(MCOperand::createReg(Register));
  return Success;
}

template <unsigned Min, unsigned Max>
static DecodeStatus DecodeZPR2Mul2RegisterClass(MCInst &Inst, unsigned RegNo,
                                                uint64_t Address,
                                                const void *Decoder) {
  unsigned Reg = (RegNo * 2) + Min;
  if (Reg < Min || Reg > Max || (Reg & 1))
    return Fail;

  unsigned Register =
      AArch64MCRegisterClasses[AArch64::ZPR2RegClassID].getRegister(Reg);
  Inst.addOperand(MCOperand::createReg(Register));
  return Success;
}

static DecodeStatus DecodeZK(MCInst &Inst, unsigned RegNo, uint64_t Address,
                             const MCDisassembler *Decoder) {
  if (RegNo > 7)
    return Fail;

  unsigned Register =
      AArch64MCRegisterClasses[AArch64::ZPR_KRegClassID].getRegister(RegNo);
  Inst.addOperand(MCOperand::createReg(Register));
  return Success;
}

static DecodeStatus DecodeZPR4Mul4RegisterClass(MCInst &Inst, unsigned RegNo,
                                                uint64_t Address,
                                                const void *Decoder) {
  if (RegNo * 4 > 28)
    return Fail;
  unsigned Register =
      AArch64MCRegisterClasses[AArch64::ZPR4RegClassID].getRegister(RegNo * 4);
  Inst.addOperand(MCOperand::createReg(Register));
  return Success;
}

static DecodeStatus
DecodeMatrixTileListRegisterClass(MCInst &Inst, unsigned RegMask,
                                  uint64_t Address,
                                  const MCDisassembler *Decoder) {
  if (RegMask > 0xFF)
    return Fail;
  Inst.addOperand(MCOperand::createImm(RegMask));
  return Success;
}

static const MCPhysReg MatrixZATileDecoderTable[5][16] = {
    {AArch64::ZAB0},
    {AArch64::ZAH0, AArch64::ZAH1},
    {AArch64::ZAS0, AArch64::ZAS1, AArch64::ZAS2, AArch64::ZAS3},
    {AArch64::ZAD0, AArch64::ZAD1, AArch64::ZAD2, AArch64::ZAD3, AArch64::ZAD4,
     AArch64::ZAD5, AArch64::ZAD6, AArch64::ZAD7},
    {AArch64::ZAQ0, AArch64::ZAQ1, AArch64::ZAQ2, AArch64::ZAQ3, AArch64::ZAQ4,
     AArch64::ZAQ5, AArch64::ZAQ6, AArch64::ZAQ7, AArch64::ZAQ8, AArch64::ZAQ9,
     AArch64::ZAQ10, AArch64::ZAQ11, AArch64::ZAQ12, AArch64::ZAQ13,
     AArch64::ZAQ14, AArch64::ZAQ15}};

template <unsigned NumBitsForTile>
static DecodeStatus DecodeMatrixTile(MCInst &Inst, unsigned RegNo,
                                     uint64_t Address,
                                     const MCDisassembler *Decoder) {
  unsigned LastReg = (1 << NumBitsForTile) - 1;
  if (RegNo > LastReg)
    return Fail;
  Inst.addOperand(
      MCOperand::createReg(MatrixZATileDecoderTable[NumBitsForTile][RegNo]));
  return Success;
}

static DecodeStatus DecodePPR2Mul2RegisterClass(MCInst &Inst, unsigned RegNo,
                                                uint64_t Address,
                                                const void *Decoder) {
  if ((RegNo * 2) > 14)
    return Fail;
  unsigned Register =
      AArch64MCRegisterClasses[AArch64::PPR2RegClassID].getRegister(RegNo * 2);
  Inst.addOperand(MCOperand::createReg(Register));
  return Success;
}

static DecodeStatus DecodeFixedPointScaleImm32(MCInst &Inst, unsigned Imm,
                                               uint64_t Addr,
                                               const MCDisassembler *Decoder) {
  // scale{5} is asserted as 1 in tblgen.
  Imm |= 0x20;
  Inst.addOperand(MCOperand::createImm(64 - Imm));
  return Success;
}

static DecodeStatus DecodeFixedPointScaleImm64(MCInst &Inst, unsigned Imm,
                                               uint64_t Addr,
                                               const MCDisassembler *Decoder) {
  Inst.addOperand(MCOperand::createImm(64 - Imm));
  return Success;
}

static DecodeStatus DecodePCRelLabel16(MCInst &Inst, unsigned Imm,
                                       uint64_t Addr,
                                       const MCDisassembler *Decoder) {
  // Immediate is encoded as the top 16-bits of an unsigned 18-bit negative
  // PC-relative offset.
  uint64_t ImmVal = Imm;
  if (ImmVal > (1 << 16))
    return Fail;
  ImmVal = -ImmVal;
  if (!Decoder->tryAddingSymbolicOperand(Inst, (ImmVal << 2), Addr,
                                         /*IsBranch=*/false, 0, 0, 4))
    Inst.addOperand(MCOperand::createImm(ImmVal));
  return Success;
}

static DecodeStatus DecodePCRelLabel19(MCInst &Inst, unsigned Imm,
                                       uint64_t Addr,
                                       const MCDisassembler *Decoder) {
  int64_t ImmVal = Imm;

  // Sign-extend 19-bit immediate.
  if (ImmVal & (1 << (19 - 1)))
    ImmVal |= ~((1LL << 19) - 1);

  if (!Decoder->tryAddingSymbolicOperand(
          Inst, ImmVal * 4, Addr, Inst.getOpcode() != AArch64::LDRXl, 0, 0, 4))
    Inst.addOperand(MCOperand::createImm(ImmVal));
  return Success;
}

static DecodeStatus DecodePCRelLabel9(MCInst &Inst, unsigned Imm, uint64_t Addr,
                                      const MCDisassembler *Decoder) {
  int64_t ImmVal = Imm;

  // Sign-extend 9-bit immediate.
  if (ImmVal & (1 << (9 - 1)))
    ImmVal |= ~((1LL << 9) - 1);

  if (!Decoder->tryAddingSymbolicOperand(Inst, (ImmVal * 4), Addr,
                                         /*IsBranch=*/true, 0, 0, 4))
    Inst.addOperand(MCOperand::createImm(ImmVal));
  return Success;
}

static DecodeStatus DecodeMemExtend(MCInst &Inst, unsigned Imm,
                                    uint64_t Address,
                                    const MCDisassembler *Decoder) {
  Inst.addOperand(MCOperand::createImm((Imm >> 1) & 1));
  Inst.addOperand(MCOperand::createImm(Imm & 1));
  return Success;
}

static DecodeStatus DecodeMRSSystemRegister(MCInst &Inst, unsigned Imm,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  Inst.addOperand(MCOperand::createImm(Imm));

  // Every system register in the encoding space is valid with the syntax
  // S<op0>_<op1>_<Cn>_<Cm>_<op2>, so decoding system registers always succeeds.
  return Success;
}

static DecodeStatus DecodeMSRSystemRegister(MCInst &Inst, unsigned Imm,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  Inst.addOperand(MCOperand::createImm(Imm));

  return Success;
}

static DecodeStatus DecodeFMOVLaneInstruction(MCInst &Inst, unsigned Insn,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder) {
  // This decoder exists to add the dummy Lane operand to the MCInst, which must
  // be 1 in assembly but has no other real manifestation.
  unsigned Rd = fieldFromInstruction(Insn, 0, 5);
  unsigned Rn = fieldFromInstruction(Insn, 5, 5);
  unsigned IsToVec = fieldFromInstruction(Insn, 16, 1);

  if (IsToVec) {
    DecodeSimpleRegisterClass<AArch64::FPR128RegClassID, 0, 32>(
        Inst, Rd, Address, Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(
        Inst, Rn, Address, Decoder);
  } else {
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(
        Inst, Rd, Address, Decoder);
    DecodeSimpleRegisterClass<AArch64::FPR128RegClassID, 0, 32>(
        Inst, Rn, Address, Decoder);
  }

  // Add the lane
  Inst.addOperand(MCOperand::createImm(1));

  return Success;
}

static DecodeStatus DecodeVecShiftRImm(MCInst &Inst, unsigned Imm,
                                       unsigned Add) {
  Inst.addOperand(MCOperand::createImm(Add - Imm));
  return Success;
}

static DecodeStatus DecodeVecShiftLImm(MCInst &Inst, unsigned Imm,
                                       unsigned Add) {
  Inst.addOperand(MCOperand::createImm((Imm + Add) & (Add - 1)));
  return Success;
}

static DecodeStatus DecodeVecShiftR64Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder) {
  return DecodeVecShiftRImm(Inst, Imm, 64);
}

static DecodeStatus DecodeVecShiftR64ImmNarrow(MCInst &Inst, unsigned Imm,
                                               uint64_t Addr,
                                               const MCDisassembler *Decoder) {
  return DecodeVecShiftRImm(Inst, Imm | 0x20, 64);
}

static DecodeStatus DecodeVecShiftR32Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder) {
  return DecodeVecShiftRImm(Inst, Imm, 32);
}

static DecodeStatus DecodeVecShiftR32ImmNarrow(MCInst &Inst, unsigned Imm,
                                               uint64_t Addr,
                                               const MCDisassembler *Decoder) {
  return DecodeVecShiftRImm(Inst, Imm | 0x10, 32);
}

static DecodeStatus DecodeVecShiftR16Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder) {
  return DecodeVecShiftRImm(Inst, Imm, 16);
}

static DecodeStatus DecodeVecShiftR16ImmNarrow(MCInst &Inst, unsigned Imm,
                                               uint64_t Addr,
                                               const MCDisassembler *Decoder) {
  return DecodeVecShiftRImm(Inst, Imm | 0x8, 16);
}

static DecodeStatus DecodeVecShiftR8Imm(MCInst &Inst, unsigned Imm,
                                        uint64_t Addr,
                                        const MCDisassembler *Decoder) {
  return DecodeVecShiftRImm(Inst, Imm, 8);
}

static DecodeStatus DecodeVecShiftL64Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder) {
  return DecodeVecShiftLImm(Inst, Imm, 64);
}

static DecodeStatus DecodeVecShiftL32Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder) {
  return DecodeVecShiftLImm(Inst, Imm, 32);
}

static DecodeStatus DecodeVecShiftL16Imm(MCInst &Inst, unsigned Imm,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder) {
  return DecodeVecShiftLImm(Inst, Imm, 16);
}

static DecodeStatus DecodeVecShiftL8Imm(MCInst &Inst, unsigned Imm,
                                        uint64_t Addr,
                                        const MCDisassembler *Decoder) {
  return DecodeVecShiftLImm(Inst, Imm, 8);
}

static DecodeStatus
DecodeThreeAddrSRegInstruction(MCInst &Inst, uint32_t insn, uint64_t Addr,
                               const MCDisassembler *Decoder) {
  unsigned Rd = fieldFromInstruction(insn, 0, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);
  unsigned Rm = fieldFromInstruction(insn, 16, 5);
  unsigned shiftHi = fieldFromInstruction(insn, 22, 2);
  unsigned shiftLo = fieldFromInstruction(insn, 10, 6);
  unsigned shift = (shiftHi << 6) | shiftLo;
  switch (Inst.getOpcode()) {
  default:
    return Fail;
  case AArch64::ADDWrs:
  case AArch64::ADDSWrs:
  case AArch64::SUBWrs:
  case AArch64::SUBSWrs:
    // if shift == '11' then ReservedValue()
    if (shiftHi == 0x3)
      return Fail;
    [[fallthrough]];
  case AArch64::ANDWrs:
  case AArch64::ANDSWrs:
  case AArch64::BICWrs:
  case AArch64::BICSWrs:
  case AArch64::ORRWrs:
  case AArch64::ORNWrs:
  case AArch64::EORWrs:
  case AArch64::EONWrs: {
    // if sf == '0' and imm6<5> == '1' then ReservedValue()
    if (shiftLo >> 5 == 1)
      return Fail;
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rd, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rn, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rm, Addr,
                                                               Decoder);
    break;
  }
  case AArch64::ADDXrs:
  case AArch64::ADDSXrs:
  case AArch64::SUBXrs:
  case AArch64::SUBSXrs:
    // if shift == '11' then ReservedValue()
    if (shiftHi == 0x3)
      return Fail;
    [[fallthrough]];
  case AArch64::ANDXrs:
  case AArch64::ANDSXrs:
  case AArch64::BICXrs:
  case AArch64::BICSXrs:
  case AArch64::ORRXrs:
  case AArch64::ORNXrs:
  case AArch64::EORXrs:
  case AArch64::EONXrs:
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rd, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rn, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rm, Addr,
                                                               Decoder);
    break;
  }

  Inst.addOperand(MCOperand::createImm(shift));
  return Success;
}

static DecodeStatus DecodeMoveImmInstruction(MCInst &Inst, uint32_t insn,
                                             uint64_t Addr,
                                             const MCDisassembler *Decoder) {
  unsigned Rd = fieldFromInstruction(insn, 0, 5);
  unsigned imm = fieldFromInstruction(insn, 5, 16);
  unsigned shift = fieldFromInstruction(insn, 21, 2);
  shift <<= 4;
  switch (Inst.getOpcode()) {
  default:
    return Fail;
  case AArch64::MOVZWi:
  case AArch64::MOVNWi:
  case AArch64::MOVKWi:
    if (shift & (1U << 5))
      return Fail;
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rd, Addr,
                                                               Decoder);
    break;
  case AArch64::MOVZXi:
  case AArch64::MOVNXi:
  case AArch64::MOVKXi:
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rd, Addr,
                                                               Decoder);
    break;
  }

  if (Inst.getOpcode() == AArch64::MOVKWi ||
      Inst.getOpcode() == AArch64::MOVKXi)
    Inst.addOperand(Inst.getOperand(0));

  Inst.addOperand(MCOperand::createImm(imm));
  Inst.addOperand(MCOperand::createImm(shift));
  return Success;
}

static DecodeStatus
DecodeUnsignedLdStInstruction(MCInst &Inst, uint32_t insn, uint64_t Addr,
                              const MCDisassembler *Decoder) {
  unsigned Rt = fieldFromInstruction(insn, 0, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);
  unsigned offset = fieldFromInstruction(insn, 10, 12);

  switch (Inst.getOpcode()) {
  default:
    return Fail;
  case AArch64::PRFMui:
    // Rt is an immediate in prefetch.
    Inst.addOperand(MCOperand::createImm(Rt));
    break;
  case AArch64::STRBBui:
  case AArch64::LDRBBui:
  case AArch64::LDRSBWui:
  case AArch64::STRHHui:
  case AArch64::LDRHHui:
  case AArch64::LDRSHWui:
  case AArch64::STRWui:
  case AArch64::LDRWui:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::LDRSBXui:
  case AArch64::LDRSHXui:
  case AArch64::LDRSWui:
  case AArch64::STRXui:
  case AArch64::LDRXui:
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::LDRQui:
  case AArch64::STRQui:
    DecodeSimpleRegisterClass<AArch64::FPR128RegClassID, 0, 32>(Inst, Rt, Addr,
                                                                Decoder);
    break;
  case AArch64::LDRDui:
  case AArch64::STRDui:
    DecodeSimpleRegisterClass<AArch64::FPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::LDRSui:
  case AArch64::STRSui:
    DecodeSimpleRegisterClass<AArch64::FPR32RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::LDRHui:
  case AArch64::STRHui:
    DecodeSimpleRegisterClass<AArch64::FPR16RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::LDRBui:
  case AArch64::STRBui:
    DecodeSimpleRegisterClass<AArch64::FPR8RegClassID, 0, 32>(Inst, Rt, Addr,
                                                              Decoder);
    break;
  }

  DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                               Decoder);
  if (!Decoder->tryAddingSymbolicOperand(Inst, offset, Addr, Fail, 0, 0, 4))
    Inst.addOperand(MCOperand::createImm(offset));
  return Success;
}

static DecodeStatus DecodeSignedLdStInstruction(MCInst &Inst, uint32_t insn,
                                                uint64_t Addr,
                                                const MCDisassembler *Decoder) {
  unsigned Rt = fieldFromInstruction(insn, 0, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);
  int64_t offset = fieldFromInstruction(insn, 12, 9);

  // offset is a 9-bit signed immediate, so sign extend it to
  // fill the unsigned.
  if (offset & (1 << (9 - 1)))
    offset |= ~((1LL << 9) - 1);

  // First operand is always the writeback to the address register, if needed.
  switch (Inst.getOpcode()) {
  default:
    break;
  case AArch64::LDRSBWpre:
  case AArch64::LDRSHWpre:
  case AArch64::STRBBpre:
  case AArch64::LDRBBpre:
  case AArch64::STRHHpre:
  case AArch64::LDRHHpre:
  case AArch64::STRWpre:
  case AArch64::LDRWpre:
  case AArch64::LDRSBWpost:
  case AArch64::LDRSHWpost:
  case AArch64::STRBBpost:
  case AArch64::LDRBBpost:
  case AArch64::STRHHpost:
  case AArch64::LDRHHpost:
  case AArch64::STRWpost:
  case AArch64::LDRWpost:
  case AArch64::LDRSBXpre:
  case AArch64::LDRSHXpre:
  case AArch64::STRXpre:
  case AArch64::LDRSWpre:
  case AArch64::LDRXpre:
  case AArch64::LDRSBXpost:
  case AArch64::LDRSHXpost:
  case AArch64::STRXpost:
  case AArch64::LDRSWpost:
  case AArch64::LDRXpost:
  case AArch64::LDRQpre:
  case AArch64::STRQpre:
  case AArch64::LDRQpost:
  case AArch64::STRQpost:
  case AArch64::LDRDpre:
  case AArch64::STRDpre:
  case AArch64::LDRDpost:
  case AArch64::STRDpost:
  case AArch64::LDRSpre:
  case AArch64::STRSpre:
  case AArch64::LDRSpost:
  case AArch64::STRSpost:
  case AArch64::LDRHpre:
  case AArch64::STRHpre:
  case AArch64::LDRHpost:
  case AArch64::STRHpost:
  case AArch64::LDRBpre:
  case AArch64::STRBpre:
  case AArch64::LDRBpost:
  case AArch64::STRBpost:
    DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                                 Decoder);
    break;
  }

  switch (Inst.getOpcode()) {
  default:
    return Fail;
  case AArch64::PRFUMi:
    // Rt is an immediate in prefetch.
    Inst.addOperand(MCOperand::createImm(Rt));
    break;
  case AArch64::STURBBi:
  case AArch64::LDURBBi:
  case AArch64::LDURSBWi:
  case AArch64::STURHHi:
  case AArch64::LDURHHi:
  case AArch64::LDURSHWi:
  case AArch64::STURWi:
  case AArch64::LDURWi:
  case AArch64::LDTRSBWi:
  case AArch64::LDTRSHWi:
  case AArch64::STTRWi:
  case AArch64::LDTRWi:
  case AArch64::STTRHi:
  case AArch64::LDTRHi:
  case AArch64::LDTRBi:
  case AArch64::STTRBi:
  case AArch64::LDRSBWpre:
  case AArch64::LDRSHWpre:
  case AArch64::STRBBpre:
  case AArch64::LDRBBpre:
  case AArch64::STRHHpre:
  case AArch64::LDRHHpre:
  case AArch64::STRWpre:
  case AArch64::LDRWpre:
  case AArch64::LDRSBWpost:
  case AArch64::LDRSHWpost:
  case AArch64::STRBBpost:
  case AArch64::LDRBBpost:
  case AArch64::STRHHpost:
  case AArch64::LDRHHpost:
  case AArch64::STRWpost:
  case AArch64::LDRWpost:
  case AArch64::STLURBi:
  case AArch64::STLURHi:
  case AArch64::STLURWi:
  case AArch64::LDAPURBi:
  case AArch64::LDAPURSBWi:
  case AArch64::LDAPURHi:
  case AArch64::LDAPURSHWi:
  case AArch64::LDAPURi:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::LDURSBXi:
  case AArch64::LDURSHXi:
  case AArch64::LDURSWi:
  case AArch64::STURXi:
  case AArch64::LDURXi:
  case AArch64::LDTRSBXi:
  case AArch64::LDTRSHXi:
  case AArch64::LDTRSWi:
  case AArch64::STTRXi:
  case AArch64::LDTRXi:
  case AArch64::LDRSBXpre:
  case AArch64::LDRSHXpre:
  case AArch64::STRXpre:
  case AArch64::LDRSWpre:
  case AArch64::LDRXpre:
  case AArch64::LDRSBXpost:
  case AArch64::LDRSHXpost:
  case AArch64::STRXpost:
  case AArch64::LDRSWpost:
  case AArch64::LDRXpost:
  case AArch64::LDAPURSWi:
  case AArch64::LDAPURSHXi:
  case AArch64::LDAPURSBXi:
  case AArch64::STLURXi:
  case AArch64::LDAPURXi:
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::LDURQi:
  case AArch64::STURQi:
  case AArch64::LDRQpre:
  case AArch64::STRQpre:
  case AArch64::LDRQpost:
  case AArch64::STRQpost:
    DecodeSimpleRegisterClass<AArch64::FPR128RegClassID, 0, 32>(Inst, Rt, Addr,
                                                                Decoder);
    break;
  case AArch64::LDURDi:
  case AArch64::STURDi:
  case AArch64::LDRDpre:
  case AArch64::STRDpre:
  case AArch64::LDRDpost:
  case AArch64::STRDpost:
    DecodeSimpleRegisterClass<AArch64::FPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::LDURSi:
  case AArch64::STURSi:
  case AArch64::LDRSpre:
  case AArch64::STRSpre:
  case AArch64::LDRSpost:
  case AArch64::STRSpost:
    DecodeSimpleRegisterClass<AArch64::FPR32RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::LDURHi:
  case AArch64::STURHi:
  case AArch64::LDRHpre:
  case AArch64::STRHpre:
  case AArch64::LDRHpost:
  case AArch64::STRHpost:
    DecodeSimpleRegisterClass<AArch64::FPR16RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::LDURBi:
  case AArch64::STURBi:
  case AArch64::LDRBpre:
  case AArch64::STRBpre:
  case AArch64::LDRBpost:
  case AArch64::STRBpost:
    DecodeSimpleRegisterClass<AArch64::FPR8RegClassID, 0, 32>(Inst, Rt, Addr,
                                                              Decoder);
    break;
  }

  DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                               Decoder);
  Inst.addOperand(MCOperand::createImm(offset));

  bool IsLoad = fieldFromInstruction(insn, 22, 1);
  bool IsIndexed = fieldFromInstruction(insn, 10, 2) != 0;
  bool IsFP = fieldFromInstruction(insn, 26, 1);

  // Cannot write back to a transfer register (but xzr != sp).
  if (IsLoad && IsIndexed && !IsFP && Rn != 31 && Rt == Rn)
    return SoftFail;

  return Success;
}

static DecodeStatus
DecodeExclusiveLdStInstruction(MCInst &Inst, uint32_t insn, uint64_t Addr,
                               const MCDisassembler *Decoder) {
  unsigned Rt = fieldFromInstruction(insn, 0, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);
  unsigned Rt2 = fieldFromInstruction(insn, 10, 5);
  unsigned Rs = fieldFromInstruction(insn, 16, 5);

  unsigned Opcode = Inst.getOpcode();
  switch (Opcode) {
  default:
    return Fail;
  case AArch64::STLXRW:
  case AArch64::STLXRB:
  case AArch64::STLXRH:
  case AArch64::STXRW:
  case AArch64::STXRB:
  case AArch64::STXRH:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rs, Addr,
                                                               Decoder);
    [[fallthrough]];
  case AArch64::LDARW:
  case AArch64::LDARB:
  case AArch64::LDARH:
  case AArch64::LDAXRW:
  case AArch64::LDAXRB:
  case AArch64::LDAXRH:
  case AArch64::LDXRW:
  case AArch64::LDXRB:
  case AArch64::LDXRH:
  case AArch64::STLRW:
  case AArch64::STLRB:
  case AArch64::STLRH:
  case AArch64::STLLRW:
  case AArch64::STLLRB:
  case AArch64::STLLRH:
  case AArch64::LDLARW:
  case AArch64::LDLARB:
  case AArch64::LDLARH:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::STLXRX:
  case AArch64::STXRX:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rs, Addr,
                                                               Decoder);
    [[fallthrough]];
  case AArch64::LDARX:
  case AArch64::LDAXRX:
  case AArch64::LDXRX:
  case AArch64::STLRX:
  case AArch64::LDLARX:
  case AArch64::STLLRX:
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    break;
  case AArch64::STLXPW:
  case AArch64::STXPW:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rs, Addr,
                                                               Decoder);
    [[fallthrough]];
  case AArch64::LDAXPW:
  case AArch64::LDXPW:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rt2, Addr,
                                                               Decoder);
    break;
  case AArch64::STLXPX:
  case AArch64::STXPX:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rs, Addr,
                                                               Decoder);
    [[fallthrough]];
  case AArch64::LDAXPX:
  case AArch64::LDXPX:
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt2, Addr,
                                                               Decoder);
    break;
  }

  DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                               Decoder);

  // You shouldn't load to the same register twice in an instruction...
  if ((Opcode == AArch64::LDAXPW || Opcode == AArch64::LDXPW ||
       Opcode == AArch64::LDAXPX || Opcode == AArch64::LDXPX) &&
      Rt == Rt2)
    return SoftFail;

  return Success;
}

static DecodeStatus DecodePairLdStInstruction(MCInst &Inst, uint32_t insn,
                                              uint64_t Addr,
                                              const MCDisassembler *Decoder) {
  unsigned Rt = fieldFromInstruction(insn, 0, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);
  unsigned Rt2 = fieldFromInstruction(insn, 10, 5);
  int64_t offset = fieldFromInstruction(insn, 15, 7);
  bool IsLoad = fieldFromInstruction(insn, 22, 1);

  // offset is a 7-bit signed immediate, so sign extend it to
  // fill the unsigned.
  if (offset & (1 << (7 - 1)))
    offset |= ~((1LL << 7) - 1);

  unsigned Opcode = Inst.getOpcode();
  bool NeedsDisjointWritebackTransfer = false;

  // First operand is always writeback of base register.
  switch (Opcode) {
  default:
    break;
  case AArch64::LDPXpost:
  case AArch64::STPXpost:
  case AArch64::LDPSWpost:
  case AArch64::LDPXpre:
  case AArch64::STPXpre:
  case AArch64::LDPSWpre:
  case AArch64::LDPWpost:
  case AArch64::STPWpost:
  case AArch64::LDPWpre:
  case AArch64::STPWpre:
  case AArch64::LDPQpost:
  case AArch64::STPQpost:
  case AArch64::LDPQpre:
  case AArch64::STPQpre:
  case AArch64::LDPDpost:
  case AArch64::STPDpost:
  case AArch64::LDPDpre:
  case AArch64::STPDpre:
  case AArch64::LDPSpost:
  case AArch64::STPSpost:
  case AArch64::LDPSpre:
  case AArch64::STPSpre:
  case AArch64::STGPpre:
  case AArch64::STGPpost:
  case AArch64::LDTPpre:
  case AArch64::LDTPpost:
  case AArch64::LDTPQpost:
  case AArch64::LDTPQpre:
  case AArch64::STTPpost:
  case AArch64::STTPpre:
  case AArch64::STTPQpost:
  case AArch64::STTPQpre:
    DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                                 Decoder);
    break;
  }

  switch (Opcode) {
  default:
    return Fail;
  case AArch64::LDPXpost:
  case AArch64::STPXpost:
  case AArch64::LDPSWpost:
  case AArch64::LDPXpre:
  case AArch64::STPXpre:
  case AArch64::LDPSWpre:
  case AArch64::STGPpre:
  case AArch64::STGPpost:
  case AArch64::LDTPpost:
  case AArch64::LDTPpre:
  case AArch64::STTPpost:
  case AArch64::STTPpre:
    NeedsDisjointWritebackTransfer = true;
    [[fallthrough]];
  case AArch64::LDNPXi:
  case AArch64::STNPXi:
  case AArch64::LDPXi:
  case AArch64::STPXi:
  case AArch64::LDPSWi:
  case AArch64::STGPi:
  case AArch64::LDTPi:
  case AArch64::STTPi:
  case AArch64::STTNPXi:
  case AArch64::LDTNPXi:
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt2, Addr,
                                                               Decoder);
    break;
  case AArch64::LDPWpost:
  case AArch64::STPWpost:
  case AArch64::LDPWpre:
  case AArch64::STPWpre:
    NeedsDisjointWritebackTransfer = true;
    [[fallthrough]];
  case AArch64::LDNPWi:
  case AArch64::STNPWi:
  case AArch64::LDPWi:
  case AArch64::STPWi:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rt2, Addr,
                                                               Decoder);
    break;
  case AArch64::LDNPQi:
  case AArch64::STNPQi:
  case AArch64::LDPQpost:
  case AArch64::STPQpost:
  case AArch64::LDPQi:
  case AArch64::STPQi:
  case AArch64::LDPQpre:
  case AArch64::STPQpre:
  case AArch64::LDTPQi:
  case AArch64::LDTPQpost:
  case AArch64::LDTPQpre:
  case AArch64::LDTNPQi:
  case AArch64::STTPQi:
  case AArch64::STTPQpost:
  case AArch64::STTPQpre:
  case AArch64::STTNPQi:
    DecodeSimpleRegisterClass<AArch64::FPR128RegClassID, 0, 32>(Inst, Rt, Addr,
                                                                Decoder);
    DecodeSimpleRegisterClass<AArch64::FPR128RegClassID, 0, 32>(Inst, Rt2, Addr,
                                                                Decoder);
    break;
  case AArch64::LDNPDi:
  case AArch64::STNPDi:
  case AArch64::LDPDpost:
  case AArch64::STPDpost:
  case AArch64::LDPDi:
  case AArch64::STPDi:
  case AArch64::LDPDpre:
  case AArch64::STPDpre:
    DecodeSimpleRegisterClass<AArch64::FPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::FPR64RegClassID, 0, 32>(Inst, Rt2, Addr,
                                                               Decoder);
    break;
  case AArch64::LDNPSi:
  case AArch64::STNPSi:
  case AArch64::LDPSpost:
  case AArch64::STPSpost:
  case AArch64::LDPSi:
  case AArch64::STPSi:
  case AArch64::LDPSpre:
  case AArch64::STPSpre:
    DecodeSimpleRegisterClass<AArch64::FPR32RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::FPR32RegClassID, 0, 32>(Inst, Rt2, Addr,
                                                               Decoder);
    break;
  }

  DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                               Decoder);
  Inst.addOperand(MCOperand::createImm(offset));

  // You shouldn't load to the same register twice in an instruction...
  if (IsLoad && Rt == Rt2)
    return SoftFail;

  // ... or do any operation that writes-back to a transfer register. But note
  // that "stp xzr, xzr, [sp], #4" is fine because xzr and sp are different.
  if (NeedsDisjointWritebackTransfer && Rn != 31 && (Rt == Rn || Rt2 == Rn))
    return SoftFail;

  return Success;
}

static DecodeStatus DecodeAuthLoadInstruction(MCInst &Inst, uint32_t insn,
                                              uint64_t Addr,
                                              const MCDisassembler *Decoder) {
  unsigned Rt = fieldFromInstruction(insn, 0, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);
  uint64_t offset = fieldFromInstruction(insn, 22, 1) << 9 |
                    fieldFromInstruction(insn, 12, 9);
  unsigned writeback = fieldFromInstruction(insn, 11, 1);

  switch (Inst.getOpcode()) {
  default:
    return Fail;
  case AArch64::LDRAAwriteback:
  case AArch64::LDRABwriteback:
    DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(
        Inst, Rn /* writeback register */, Addr, Decoder);
    break;
  case AArch64::LDRAAindexed:
  case AArch64::LDRABindexed:
    break;
  }

  DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                             Decoder);
  DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                               Decoder);
  DecodeSImm<10>(Inst, offset, Addr, Decoder);

  if (writeback && Rt == Rn && Rn != 31) {
    return SoftFail;
  }

  return Success;
}

static DecodeStatus DecodeAddSubERegInstruction(MCInst &Inst, uint32_t insn,
                                                uint64_t Addr,
                                                const MCDisassembler *Decoder) {
  unsigned Rd = fieldFromInstruction(insn, 0, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);
  unsigned Rm = fieldFromInstruction(insn, 16, 5);
  unsigned extend = fieldFromInstruction(insn, 10, 6);

  unsigned shift = extend & 0x7;
  if (shift > 4)
    return Fail;

  switch (Inst.getOpcode()) {
  default:
    return Fail;
  case AArch64::ADDWrx:
  case AArch64::SUBWrx:
    DecodeSimpleRegisterClass<AArch64::GPR32spRegClassID, 0, 32>(Inst, Rd, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rm, Addr,
                                                               Decoder);
    break;
  case AArch64::ADDSWrx:
  case AArch64::SUBSWrx:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rd, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rm, Addr,
                                                               Decoder);
    break;
  case AArch64::ADDXrx:
  case AArch64::SUBXrx:
    DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rd, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rm, Addr,
                                                               Decoder);
    break;
  case AArch64::ADDSXrx:
  case AArch64::SUBSXrx:
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rd, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rm, Addr,
                                                               Decoder);
    break;
  case AArch64::ADDXrx64:
  case AArch64::SUBXrx64:
    DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rd, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rm, Addr,
                                                               Decoder);
    break;
  case AArch64::SUBSXrx64:
  case AArch64::ADDSXrx64:
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rd, Addr,
                                                               Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rm, Addr,
                                                               Decoder);
    break;
  }

  Inst.addOperand(MCOperand::createImm(extend));
  return Success;
}

static DecodeStatus DecodeLogicalImmInstruction(MCInst &Inst, uint32_t insn,
                                                uint64_t Addr,
                                                const MCDisassembler *Decoder) {
  unsigned Rd = fieldFromInstruction(insn, 0, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);
  unsigned Datasize = fieldFromInstruction(insn, 31, 1);
  unsigned imm;

  if (Datasize) {
    if (Inst.getOpcode() == AArch64::ANDSXri)
      DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rd, Addr,
                                                                 Decoder);
    else
      DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(
          Inst, Rd, Addr, Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rn, Addr,
                                                               Decoder);
    imm = fieldFromInstruction(insn, 10, 13);
    if (!AArch64_AM::isValidDecodeLogicalImmediate(imm, 64))
      return Fail;
  } else {
    if (Inst.getOpcode() == AArch64::ANDSWri)
      DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rd, Addr,
                                                                 Decoder);
    else
      DecodeSimpleRegisterClass<AArch64::GPR32spRegClassID, 0, 32>(
          Inst, Rd, Addr, Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rn, Addr,
                                                               Decoder);
    imm = fieldFromInstruction(insn, 10, 12);
    if (!AArch64_AM::isValidDecodeLogicalImmediate(imm, 32))
      return Fail;
  }
  Inst.addOperand(MCOperand::createImm(imm));
  return Success;
}

static DecodeStatus DecodeModImmInstruction(MCInst &Inst, uint32_t insn,
                                            uint64_t Addr,
                                            const MCDisassembler *Decoder) {
  unsigned Rd = fieldFromInstruction(insn, 0, 5);
  unsigned cmode = fieldFromInstruction(insn, 12, 4);
  unsigned imm = fieldFromInstruction(insn, 16, 3) << 5;
  imm |= fieldFromInstruction(insn, 5, 5);

  if (Inst.getOpcode() == AArch64::MOVID)
    DecodeSimpleRegisterClass<AArch64::FPR64RegClassID, 0, 32>(Inst, Rd, Addr,
                                                               Decoder);
  else
    DecodeSimpleRegisterClass<AArch64::FPR128RegClassID, 0, 32>(Inst, Rd, Addr,
                                                                Decoder);

  Inst.addOperand(MCOperand::createImm(imm));

  switch (Inst.getOpcode()) {
  default:
    break;
  case AArch64::MOVIv4i16:
  case AArch64::MOVIv8i16:
  case AArch64::MVNIv4i16:
  case AArch64::MVNIv8i16:
  case AArch64::MOVIv2i32:
  case AArch64::MOVIv4i32:
  case AArch64::MVNIv2i32:
  case AArch64::MVNIv4i32:
    Inst.addOperand(MCOperand::createImm((cmode & 6) << 2));
    break;
  case AArch64::MOVIv2s_msl:
  case AArch64::MOVIv4s_msl:
  case AArch64::MVNIv2s_msl:
  case AArch64::MVNIv4s_msl:
    Inst.addOperand(MCOperand::createImm((cmode & 1) ? 0x110 : 0x108));
    break;
  }

  return Success;
}

static DecodeStatus DecodeModImmTiedInstruction(MCInst &Inst, uint32_t insn,
                                                uint64_t Addr,
                                                const MCDisassembler *Decoder) {
  unsigned Rd = fieldFromInstruction(insn, 0, 5);
  unsigned cmode = fieldFromInstruction(insn, 12, 4);
  unsigned imm = fieldFromInstruction(insn, 16, 3) << 5;
  imm |= fieldFromInstruction(insn, 5, 5);

  // Tied operands added twice.
  DecodeSimpleRegisterClass<AArch64::FPR128RegClassID, 0, 32>(Inst, Rd, Addr,
                                                              Decoder);
  DecodeSimpleRegisterClass<AArch64::FPR128RegClassID, 0, 32>(Inst, Rd, Addr,
                                                              Decoder);

  Inst.addOperand(MCOperand::createImm(imm));
  Inst.addOperand(MCOperand::createImm((cmode & 6) << 2));

  return Success;
}

static DecodeStatus DecodeAdrInstruction(MCInst &Inst, uint32_t insn,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder) {
  unsigned Rd = fieldFromInstruction(insn, 0, 5);
  int64_t imm = fieldFromInstruction(insn, 5, 19) << 2;
  imm |= fieldFromInstruction(insn, 29, 2);

  // Sign-extend the 21-bit immediate.
  if (imm & (1 << (21 - 1)))
    imm |= ~((1LL << 21) - 1);

  DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rd, Addr,
                                                             Decoder);
  if (!Decoder->tryAddingSymbolicOperand(Inst, imm, Addr, Fail, 0, 0, 4))
    Inst.addOperand(MCOperand::createImm(imm));

  return Success;
}

static DecodeStatus DecodeAddSubImmShift(MCInst &Inst, uint32_t insn,
                                         uint64_t Addr,
                                         const MCDisassembler *Decoder) {
  unsigned Rd = fieldFromInstruction(insn, 0, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);
  unsigned Imm = fieldFromInstruction(insn, 10, 14);
  unsigned S = fieldFromInstruction(insn, 29, 1);
  unsigned Datasize = fieldFromInstruction(insn, 31, 1);

  unsigned ShifterVal = (Imm >> 12) & 3;
  unsigned ImmVal = Imm & 0xFFF;

  if (ShifterVal != 0 && ShifterVal != 1)
    return Fail;

  if (Datasize) {
    if (Rd == 31 && !S)
      DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(
          Inst, Rd, Addr, Decoder);
    else
      DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rd, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                                 Decoder);
  } else {
    if (Rd == 31 && !S)
      DecodeSimpleRegisterClass<AArch64::GPR32spRegClassID, 0, 32>(
          Inst, Rd, Addr, Decoder);
    else
      DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rd, Addr,
                                                                 Decoder);
    DecodeSimpleRegisterClass<AArch64::GPR32spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                                 Decoder);
  }

  if (!Decoder->tryAddingSymbolicOperand(Inst, Imm, Addr, Fail, 0, 0, 4))
    Inst.addOperand(MCOperand::createImm(ImmVal));
  Inst.addOperand(MCOperand::createImm(12 * ShifterVal));
  return Success;
}

static DecodeStatus DecodeUnconditionalBranch(MCInst &Inst, uint32_t insn,
                                              uint64_t Addr,
                                              const MCDisassembler *Decoder) {
  int64_t imm = fieldFromInstruction(insn, 0, 26);

  // Sign-extend the 26-bit immediate.
  if (imm & (1 << (26 - 1)))
    imm |= ~((1LL << 26) - 1);

  if (!Decoder->tryAddingSymbolicOperand(Inst, imm * 4, Addr, true, 0, 0, 4))
    Inst.addOperand(MCOperand::createImm(imm));

  return Success;
}

static bool isInvalidPState(uint64_t Op1, uint64_t Op2) {
  return Op1 == 0b000 && (Op2 == 0b000 || // CFINV
                          Op2 == 0b001 || // XAFlag
                          Op2 == 0b010);  // AXFlag
}

static DecodeStatus
DecodeSystemPStateImm0_15Instruction(MCInst &Inst, uint32_t insn, uint64_t Addr,
                                     const MCDisassembler *Decoder) {
  uint64_t op1 = fieldFromInstruction(insn, 16, 3);
  uint64_t op2 = fieldFromInstruction(insn, 5, 3);
  uint64_t imm = fieldFromInstruction(insn, 8, 4);
  uint64_t pstate_field = (op1 << 3) | op2;

  if (isInvalidPState(op1, op2))
    return Fail;

  Inst.addOperand(MCOperand::createImm(pstate_field));
  Inst.addOperand(MCOperand::createImm(imm));

  auto PState = AArch64PState::lookupPStateImm0_15ByEncoding(pstate_field);
  if (PState &&
      PState->haveFeatures(Decoder->getSubtargetInfo().getFeatureBits()))
    return Success;
  return Fail;
}

static DecodeStatus
DecodeSystemPStateImm0_1Instruction(MCInst &Inst, uint32_t insn, uint64_t Addr,
                                    const MCDisassembler *Decoder) {
  uint64_t op1 = fieldFromInstruction(insn, 16, 3);
  uint64_t op2 = fieldFromInstruction(insn, 5, 3);
  uint64_t crm_high = fieldFromInstruction(insn, 9, 3);
  uint64_t imm = fieldFromInstruction(insn, 8, 1);
  uint64_t pstate_field = (crm_high << 6) | (op1 << 3) | op2;

  if (isInvalidPState(op1, op2))
    return Fail;

  Inst.addOperand(MCOperand::createImm(pstate_field));
  Inst.addOperand(MCOperand::createImm(imm));

  auto PState = AArch64PState::lookupPStateImm0_1ByEncoding(pstate_field);
  if (PState &&
      PState->haveFeatures(Decoder->getSubtargetInfo().getFeatureBits()))
    return Success;
  return Fail;
}

static DecodeStatus DecodeTestAndBranch(MCInst &Inst, uint32_t insn,
                                        uint64_t Addr,
                                        const MCDisassembler *Decoder) {
  uint64_t Rt = fieldFromInstruction(insn, 0, 5);
  uint64_t bit = fieldFromInstruction(insn, 31, 1) << 5;
  bit |= fieldFromInstruction(insn, 19, 5);
  int64_t dst = fieldFromInstruction(insn, 5, 14);

  // Sign-extend 14-bit immediate.
  if (dst & (1 << (14 - 1)))
    dst |= ~((1LL << 14) - 1);

  if (fieldFromInstruction(insn, 31, 1) == 0)
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
  else
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                               Decoder);
  Inst.addOperand(MCOperand::createImm(bit));
  if (!Decoder->tryAddingSymbolicOperand(Inst, dst * 4, Addr, true, 0, 0, 4))
    Inst.addOperand(MCOperand::createImm(dst));

  return Success;
}

static DecodeStatus
DecodeGPRSeqPairsClassRegisterClass(MCInst &Inst, unsigned RegClassID,
                                    unsigned RegNo, uint64_t Addr,
                                    const MCDisassembler *Decoder) {
  // Register number must be even (see CASP instruction)
  if (RegNo & 0x1)
    return Fail;

  unsigned Reg = AArch64MCRegisterClasses[RegClassID].getRegister(RegNo / 2);
  Inst.addOperand(MCOperand::createReg(Reg));
  return Success;
}

static DecodeStatus
DecodeWSeqPairsClassRegisterClass(MCInst &Inst, unsigned RegNo, uint64_t Addr,
                                  const MCDisassembler *Decoder) {
  return DecodeGPRSeqPairsClassRegisterClass(
      Inst, AArch64::WSeqPairsClassRegClassID, RegNo, Addr, Decoder);
}

static DecodeStatus
DecodeXSeqPairsClassRegisterClass(MCInst &Inst, unsigned RegNo, uint64_t Addr,
                                  const MCDisassembler *Decoder) {
  return DecodeGPRSeqPairsClassRegisterClass(
      Inst, AArch64::XSeqPairsClassRegClassID, RegNo, Addr, Decoder);
}

static DecodeStatus DecodeSyspXzrInstruction(MCInst &Inst, uint32_t insn,
                                             uint64_t Addr,
                                             const MCDisassembler *Decoder) {
  unsigned op1 = fieldFromInstruction(insn, 16, 3);
  unsigned CRn = fieldFromInstruction(insn, 12, 4);
  unsigned CRm = fieldFromInstruction(insn, 8, 4);
  unsigned op2 = fieldFromInstruction(insn, 5, 3);
  unsigned Rt = fieldFromInstruction(insn, 0, 5);
  if (Rt != 0b11111)
    return Fail;

  Inst.addOperand(MCOperand::createImm(op1));
  Inst.addOperand(MCOperand::createImm(CRn));
  Inst.addOperand(MCOperand::createImm(CRm));
  Inst.addOperand(MCOperand::createImm(op2));
  DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt, Addr,
                                                             Decoder);

  return Success;
}

static DecodeStatus
DecodeSVELogicalImmInstruction(MCInst &Inst, uint32_t insn, uint64_t Addr,
                               const MCDisassembler *Decoder) {
  unsigned Zdn = fieldFromInstruction(insn, 0, 5);
  unsigned imm = fieldFromInstruction(insn, 5, 13);
  if (!AArch64_AM::isValidDecodeLogicalImmediate(imm, 64))
    return Fail;

  // The same (tied) operand is added twice to the instruction.
  DecodeSimpleRegisterClass<AArch64::ZPRRegClassID, 0, 32>(Inst, Zdn, Addr,
                                                           Decoder);
  if (Inst.getOpcode() != AArch64::DUPM_ZI)
    DecodeSimpleRegisterClass<AArch64::ZPRRegClassID, 0, 32>(Inst, Zdn, Addr,
                                                             Decoder);
  Inst.addOperand(MCOperand::createImm(imm));
  return Success;
}

template <int Bits>
static DecodeStatus DecodeSImm(MCInst &Inst, uint64_t Imm, uint64_t Address,
                               const MCDisassembler *Decoder) {
  if (Imm & ~((1LL << Bits) - 1))
    return Fail;

  // Imm is a signed immediate, so sign extend it.
  if (Imm & (1 << (Bits - 1)))
    Imm |= ~((1LL << Bits) - 1);

  Inst.addOperand(MCOperand::createImm(Imm));
  return Success;
}

// Decode 8-bit signed/unsigned immediate for a given element width.
template <int ElementWidth>
static DecodeStatus DecodeImm8OptLsl(MCInst &Inst, unsigned Imm, uint64_t Addr,
                                     const MCDisassembler *Decoder) {
  unsigned Val = (uint8_t)Imm;
  unsigned Shift = (Imm & 0x100) ? 8 : 0;
  if (ElementWidth == 8 && Shift)
    return Fail;
  Inst.addOperand(MCOperand::createImm(Val));
  Inst.addOperand(MCOperand::createImm(Shift));
  return Success;
}

// Decode uimm4 ranged from 1-16.
static DecodeStatus DecodeSVEIncDecImm(MCInst &Inst, unsigned Imm,
                                       uint64_t Addr,
                                       const MCDisassembler *Decoder) {
  Inst.addOperand(MCOperand::createImm(Imm + 1));
  return Success;
}

static DecodeStatus DecodeSVCROp(MCInst &Inst, unsigned Imm, uint64_t Address,
                                 const MCDisassembler *Decoder) {
  if (AArch64SVCR::lookupSVCRByEncoding(Imm)) {
    Inst.addOperand(MCOperand::createImm(Imm));
    return Success;
  }
  return Fail;
}

static DecodeStatus DecodeCPYMemOpInstruction(MCInst &Inst, uint32_t insn,
                                              uint64_t Addr,
                                              const MCDisassembler *Decoder) {
  unsigned Rd = fieldFromInstruction(insn, 0, 5);
  unsigned Rs = fieldFromInstruction(insn, 16, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);

  // None of the registers may alias: if they do, then the instruction is not
  // merely unpredictable but actually entirely unallocated.
  if (Rd == Rs || Rs == Rn || Rd == Rn)
    return MCDisassembler::Fail;

  // All three register operands are written back, so they all appear
  // twice in the operand list, once as outputs and once as inputs.
  if (!DecodeSimpleRegisterClass<AArch64::GPR64commonRegClassID, 0, 31>(
          Inst, Rd, Addr, Decoder) ||
      !DecodeSimpleRegisterClass<AArch64::GPR64commonRegClassID, 0, 31>(
          Inst, Rs, Addr, Decoder) ||
      !DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(
          Inst, Rn, Addr, Decoder) ||
      !DecodeSimpleRegisterClass<AArch64::GPR64commonRegClassID, 0, 31>(
          Inst, Rd, Addr, Decoder) ||
      !DecodeSimpleRegisterClass<AArch64::GPR64commonRegClassID, 0, 31>(
          Inst, Rs, Addr, Decoder) ||
      !DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(
          Inst, Rn, Addr, Decoder))
    return MCDisassembler::Fail;

  return MCDisassembler::Success;
}

static DecodeStatus DecodeSETMemOpInstruction(MCInst &Inst, uint32_t insn,
                                              uint64_t Addr,
                                              const MCDisassembler *Decoder) {
  unsigned Rd = fieldFromInstruction(insn, 0, 5);
  unsigned Rm = fieldFromInstruction(insn, 16, 5);
  unsigned Rn = fieldFromInstruction(insn, 5, 5);

  // None of the registers may alias: if they do, then the instruction is not
  // merely unpredictable but actually entirely unallocated.
  if (Rd == Rm || Rm == Rn || Rd == Rn)
    return MCDisassembler::Fail;

  // Rd and Rn (not Rm) register operands are written back, so they appear
  // twice in the operand list, once as outputs and once as inputs.
  if (!DecodeSimpleRegisterClass<AArch64::GPR64commonRegClassID, 0, 31>(
          Inst, Rd, Addr, Decoder) ||
      !DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(
          Inst, Rn, Addr, Decoder) ||
      !DecodeSimpleRegisterClass<AArch64::GPR64commonRegClassID, 0, 31>(
          Inst, Rd, Addr, Decoder) ||
      !DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(
          Inst, Rn, Addr, Decoder) ||
      !DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(
          Inst, Rm, Addr, Decoder))
    return MCDisassembler::Fail;

  return MCDisassembler::Success;
}

static DecodeStatus DecodePRFMRegInstruction(MCInst &Inst, uint32_t insn,
                                             uint64_t Addr,
                                             const MCDisassembler *Decoder) {
  // PRFM with Rt = '11xxx' should be decoded as RPRFM.
  // Fail to decode and defer to fallback decoder table to decode RPRFM.
  unsigned Mask = 0x18;
  uint64_t Rt = fieldFromInstruction(insn, 0, 5);
  if ((Rt & Mask) == Mask)
    return Fail;

  uint64_t Rn = fieldFromInstruction(insn, 5, 5);
  uint64_t Shift = fieldFromInstruction(insn, 12, 1);
  uint64_t Extend = fieldFromInstruction(insn, 15, 1);
  uint64_t Rm = fieldFromInstruction(insn, 16, 5);

  Inst.addOperand(MCOperand::createImm(Rt));
  DecodeSimpleRegisterClass<AArch64::GPR64spRegClassID, 0, 32>(Inst, Rn, Addr,
                                                               Decoder);

  switch (Inst.getOpcode()) {
  default:
    return Fail;
  case AArch64::PRFMroW:
    DecodeSimpleRegisterClass<AArch64::GPR32RegClassID, 0, 32>(Inst, Rm, Addr,
                                                               Decoder);
    break;
  case AArch64::PRFMroX:
    DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rm, Addr,
                                                               Decoder);
    break;
  }

  DecodeMemExtend(Inst, (Extend << 1) | Shift, Addr, Decoder);

  return Success;
}