//===-- RISCVDisassembler.cpp - Disassembler for RISC-V -------------------===//
//
// 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 implements the RISCVDisassembler class.
//
//===----------------------------------------------------------------------===//

#include "MCTargetDesc/RISCVBaseInfo.h"
#include "MCTargetDesc/RISCVMCTargetDesc.h"
#include "TargetInfo/RISCVTargetInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDecoderOps.h"
#include "llvm/MC/MCDisassembler/MCDisassembler.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Support/Endian.h"

using namespace llvm;

#define DEBUG_TYPE "riscv-disassembler"

typedef MCDisassembler::DecodeStatus DecodeStatus;

namespace {
class RISCVDisassembler : public MCDisassembler {
  std::unique_ptr<MCInstrInfo const> const MCII;

public:
  RISCVDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx,
                    MCInstrInfo const *MCII)
      : MCDisassembler(STI, Ctx), MCII(MCII) {}

  DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
                              ArrayRef<uint8_t> Bytes, uint64_t Address,
                              raw_ostream &CStream) const override;

private:
  void addSPOperands(MCInst &MI) const;
};
} // end anonymous namespace

static MCDisassembler *createRISCVDisassembler(const Target &T,
                                               const MCSubtargetInfo &STI,
                                               MCContext &Ctx) {
  return new RISCVDisassembler(STI, Ctx, T.createMCInstrInfo());
}

extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeRISCVDisassembler() {
  // Register the disassembler for each target.
  TargetRegistry::RegisterMCDisassembler(getTheRISCV32Target(),
                                         createRISCVDisassembler);
  TargetRegistry::RegisterMCDisassembler(getTheRISCV64Target(),
                                         createRISCVDisassembler);
}

static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, uint32_t RegNo,
                                           uint64_t Address,
                                           const MCDisassembler *Decoder) {
  bool IsRVE = Decoder->getSubtargetInfo().hasFeature(RISCV::FeatureRVE);

  if (RegNo >= 32 || (IsRVE && RegNo >= 16))
    return MCDisassembler::Fail;

  MCRegister Reg = RISCV::X0 + RegNo;
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeFPR16RegisterClass(MCInst &Inst, uint32_t RegNo,
                                             uint64_t Address,
                                             const MCDisassembler *Decoder) {
  if (RegNo >= 32)
    return MCDisassembler::Fail;

  MCRegister Reg = RISCV::F0_H + RegNo;
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeFPR32RegisterClass(MCInst &Inst, uint32_t RegNo,
                                             uint64_t Address,
                                             const MCDisassembler *Decoder) {
  if (RegNo >= 32)
    return MCDisassembler::Fail;

  MCRegister Reg = RISCV::F0_F + RegNo;
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeFPR32CRegisterClass(MCInst &Inst, uint32_t RegNo,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder) {
  if (RegNo >= 8) {
    return MCDisassembler::Fail;
  }
  MCRegister Reg = RISCV::F8_F + RegNo;
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeFPR64RegisterClass(MCInst &Inst, uint32_t RegNo,
                                             uint64_t Address,
                                             const MCDisassembler *Decoder) {
  if (RegNo >= 32)
    return MCDisassembler::Fail;

  MCRegister Reg = RISCV::F0_D + RegNo;
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeFPR64CRegisterClass(MCInst &Inst, uint32_t RegNo,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder) {
  if (RegNo >= 8) {
    return MCDisassembler::Fail;
  }
  MCRegister Reg = RISCV::F8_D + RegNo;
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeGPRNoX0RegisterClass(MCInst &Inst, uint32_t RegNo,
                                               uint64_t Address,
                                               const MCDisassembler *Decoder) {
  if (RegNo == 0) {
    return MCDisassembler::Fail;
  }

  return DecodeGPRRegisterClass(Inst, RegNo, Address, Decoder);
}

static DecodeStatus
DecodeGPRNoX0X2RegisterClass(MCInst &Inst, uint64_t RegNo, uint32_t Address,
                             const MCDisassembler *Decoder) {
  if (RegNo == 2) {
    return MCDisassembler::Fail;
  }

  return DecodeGPRNoX0RegisterClass(Inst, RegNo, Address, Decoder);
}

static DecodeStatus DecodeGPRCRegisterClass(MCInst &Inst, uint32_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  if (RegNo >= 8)
    return MCDisassembler::Fail;

  MCRegister Reg = RISCV::X8 + RegNo;
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeGPRPF64RegisterClass(MCInst &Inst, uint32_t RegNo,
                                               uint64_t Address,
                                               const MCDisassembler *Decoder) {
  if (RegNo >= 32 || RegNo & 1)
    return MCDisassembler::Fail;

  MCRegister Reg = RISCV::X0 + RegNo;
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeSR07RegisterClass(MCInst &Inst, uint64_t RegNo,
                                            uint64_t Address,
                                            const void *Decoder) {
  if (RegNo >= 8)
    return MCDisassembler::Fail;

  MCRegister Reg = (RegNo < 2) ? (RegNo + RISCV::X8) : (RegNo - 2 + RISCV::X18);
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeVRRegisterClass(MCInst &Inst, uint32_t RegNo,
                                          uint64_t Address,
                                          const MCDisassembler *Decoder) {
  if (RegNo >= 32)
    return MCDisassembler::Fail;

  MCRegister Reg = RISCV::V0 + RegNo;
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeVRM2RegisterClass(MCInst &Inst, uint32_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  if (RegNo >= 32)
    return MCDisassembler::Fail;

  if (RegNo % 2)
    return MCDisassembler::Fail;

  const RISCVDisassembler *Dis =
      static_cast<const RISCVDisassembler *>(Decoder);
  const MCRegisterInfo *RI = Dis->getContext().getRegisterInfo();
  MCRegister Reg =
      RI->getMatchingSuperReg(RISCV::V0 + RegNo, RISCV::sub_vrm1_0,
                              &RISCVMCRegisterClasses[RISCV::VRM2RegClassID]);

  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeVRM4RegisterClass(MCInst &Inst, uint32_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  if (RegNo >= 32)
    return MCDisassembler::Fail;

  if (RegNo % 4)
    return MCDisassembler::Fail;

  const RISCVDisassembler *Dis =
      static_cast<const RISCVDisassembler *>(Decoder);
  const MCRegisterInfo *RI = Dis->getContext().getRegisterInfo();
  MCRegister Reg =
      RI->getMatchingSuperReg(RISCV::V0 + RegNo, RISCV::sub_vrm1_0,
                              &RISCVMCRegisterClasses[RISCV::VRM4RegClassID]);

  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus DecodeVRM8RegisterClass(MCInst &Inst, uint32_t RegNo,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  if (RegNo >= 32)
    return MCDisassembler::Fail;

  if (RegNo % 8)
    return MCDisassembler::Fail;

  const RISCVDisassembler *Dis =
      static_cast<const RISCVDisassembler *>(Decoder);
  const MCRegisterInfo *RI = Dis->getContext().getRegisterInfo();
  MCRegister Reg =
      RI->getMatchingSuperReg(RISCV::V0 + RegNo, RISCV::sub_vrm1_0,
                              &RISCVMCRegisterClasses[RISCV::VRM8RegClassID]);

  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

static DecodeStatus decodeVMaskReg(MCInst &Inst, uint64_t RegNo,
                                   uint64_t Address,
                                   const MCDisassembler *Decoder) {
  MCRegister Reg = RISCV::NoRegister;
  switch (RegNo) {
  default:
    return MCDisassembler::Fail;
  case 0:
    Reg = RISCV::V0;
    break;
  case 1:
    break;
  }
  Inst.addOperand(MCOperand::createReg(Reg));
  return MCDisassembler::Success;
}

template <unsigned N>
static DecodeStatus decodeUImmOperand(MCInst &Inst, uint32_t Imm,
                                      int64_t Address,
                                      const MCDisassembler *Decoder) {
  assert(isUInt<N>(Imm) && "Invalid immediate");
  Inst.addOperand(MCOperand::createImm(Imm));
  return MCDisassembler::Success;
}

template <unsigned N>
static DecodeStatus decodeUImmNonZeroOperand(MCInst &Inst, uint32_t Imm,
                                             int64_t Address,
                                             const MCDisassembler *Decoder) {
  if (Imm == 0)
    return MCDisassembler::Fail;
  return decodeUImmOperand<N>(Inst, Imm, Address, Decoder);
}

template <unsigned N>
static DecodeStatus decodeSImmOperand(MCInst &Inst, uint32_t Imm,
                                      int64_t Address,
                                      const MCDisassembler *Decoder) {
  assert(isUInt<N>(Imm) && "Invalid immediate");
  // Sign-extend the number in the bottom N bits of Imm
  Inst.addOperand(MCOperand::createImm(SignExtend64<N>(Imm)));
  return MCDisassembler::Success;
}

template <unsigned N>
static DecodeStatus decodeSImmNonZeroOperand(MCInst &Inst, uint32_t Imm,
                                             int64_t Address,
                                             const MCDisassembler *Decoder) {
  if (Imm == 0)
    return MCDisassembler::Fail;
  return decodeSImmOperand<N>(Inst, Imm, Address, Decoder);
}

template <unsigned N>
static DecodeStatus decodeSImmOperandAndLsl1(MCInst &Inst, uint32_t Imm,
                                             int64_t Address,
                                             const MCDisassembler *Decoder) {
  assert(isUInt<N>(Imm) && "Invalid immediate");
  // Sign-extend the number in the bottom N bits of Imm after accounting for
  // the fact that the N bit immediate is stored in N-1 bits (the LSB is
  // always zero)
  Inst.addOperand(MCOperand::createImm(SignExtend64<N>(Imm << 1)));
  return MCDisassembler::Success;
}

static DecodeStatus decodeCLUIImmOperand(MCInst &Inst, uint32_t Imm,
                                         int64_t Address,
                                         const MCDisassembler *Decoder) {
  assert(isUInt<6>(Imm) && "Invalid immediate");
  if (Imm > 31) {
    Imm = (SignExtend64<6>(Imm) & 0xfffff);
  }
  Inst.addOperand(MCOperand::createImm(Imm));
  return MCDisassembler::Success;
}

static DecodeStatus decodeFRMArg(MCInst &Inst, uint32_t Imm, int64_t Address,
                                 const MCDisassembler *Decoder) {
  assert(isUInt<3>(Imm) && "Invalid immediate");
  if (!llvm::RISCVFPRndMode::isValidRoundingMode(Imm))
    return MCDisassembler::Fail;

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

static DecodeStatus decodeRVCInstrRdRs1ImmZero(MCInst &Inst, uint32_t Insn,
                                               uint64_t Address,
                                               const MCDisassembler *Decoder);

static DecodeStatus decodeRVCInstrRdSImm(MCInst &Inst, uint32_t Insn,
                                         uint64_t Address,
                                         const MCDisassembler *Decoder);

static DecodeStatus decodeRVCInstrRdRs1UImm(MCInst &Inst, uint32_t Insn,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder);

static DecodeStatus decodeRVCInstrRdRs2(MCInst &Inst, uint32_t Insn,
                                        uint64_t Address,
                                        const MCDisassembler *Decoder);

static DecodeStatus decodeRVCInstrRdRs1Rs2(MCInst &Inst, uint32_t Insn,
                                           uint64_t Address,
                                           const MCDisassembler *Decoder);

static DecodeStatus decodeXTHeadMemPair(MCInst &Inst, uint32_t Insn,
                                        uint64_t Address,
                                        const MCDisassembler *Decoder);

static DecodeStatus decodeZcmpRlist(MCInst &Inst, unsigned Imm,
                                    uint64_t Address, const void *Decoder);

static DecodeStatus decodeZcmpSpimm(MCInst &Inst, unsigned Imm,
                                    uint64_t Address, const void *Decoder);

#include "RISCVGenDisassemblerTables.inc"

static DecodeStatus decodeRVCInstrRdRs1ImmZero(MCInst &Inst, uint32_t Insn,
                                               uint64_t Address,
                                               const MCDisassembler *Decoder) {
  uint32_t Rd = fieldFromInstruction(Insn, 7, 5);
  DecodeStatus Result = DecodeGPRNoX0RegisterClass(Inst, Rd, Address, Decoder);
  (void)Result;
  assert(Result == MCDisassembler::Success && "Invalid register");
  Inst.addOperand(Inst.getOperand(0));
  Inst.addOperand(MCOperand::createImm(0));
  return MCDisassembler::Success;
}

static DecodeStatus decodeRVCInstrRdSImm(MCInst &Inst, uint32_t Insn,
                                         uint64_t Address,
                                         const MCDisassembler *Decoder) {
  Inst.addOperand(MCOperand::createReg(RISCV::X0));
  uint32_t SImm6 =
      fieldFromInstruction(Insn, 12, 1) << 5 | fieldFromInstruction(Insn, 2, 5);
  DecodeStatus Result = decodeSImmOperand<6>(Inst, SImm6, Address, Decoder);
  (void)Result;
  assert(Result == MCDisassembler::Success && "Invalid immediate");
  return MCDisassembler::Success;
}

static DecodeStatus decodeRVCInstrRdRs1UImm(MCInst &Inst, uint32_t Insn,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
  Inst.addOperand(MCOperand::createReg(RISCV::X0));
  Inst.addOperand(Inst.getOperand(0));
  uint32_t UImm6 =
      fieldFromInstruction(Insn, 12, 1) << 5 | fieldFromInstruction(Insn, 2, 5);
  DecodeStatus Result = decodeUImmOperand<6>(Inst, UImm6, Address, Decoder);
  (void)Result;
  assert(Result == MCDisassembler::Success && "Invalid immediate");
  return MCDisassembler::Success;
}

static DecodeStatus decodeRVCInstrRdRs2(MCInst &Inst, uint32_t Insn,
                                        uint64_t Address,
                                        const MCDisassembler *Decoder) {
  uint32_t Rd = fieldFromInstruction(Insn, 7, 5);
  uint32_t Rs2 = fieldFromInstruction(Insn, 2, 5);
  DecodeGPRRegisterClass(Inst, Rd, Address, Decoder);
  DecodeGPRRegisterClass(Inst, Rs2, Address, Decoder);
  return MCDisassembler::Success;
}

static DecodeStatus decodeRVCInstrRdRs1Rs2(MCInst &Inst, uint32_t Insn,
                                           uint64_t Address,
                                           const MCDisassembler *Decoder) {
  uint32_t Rd = fieldFromInstruction(Insn, 7, 5);
  uint32_t Rs2 = fieldFromInstruction(Insn, 2, 5);
  DecodeGPRRegisterClass(Inst, Rd, Address, Decoder);
  Inst.addOperand(Inst.getOperand(0));
  DecodeGPRRegisterClass(Inst, Rs2, Address, Decoder);
  return MCDisassembler::Success;
}

static DecodeStatus decodeXTHeadMemPair(MCInst &Inst, uint32_t Insn,
                                        uint64_t Address,
                                        const MCDisassembler *Decoder) {
  uint32_t Rd1 = fieldFromInstruction(Insn, 7, 5);
  uint32_t Rs1 = fieldFromInstruction(Insn, 15, 5);
  uint32_t Rd2 = fieldFromInstruction(Insn, 20, 5);
  uint32_t UImm2 = fieldFromInstruction(Insn, 25, 2);
  DecodeGPRRegisterClass(Inst, Rd1, Address, Decoder);
  DecodeGPRRegisterClass(Inst, Rd2, Address, Decoder);
  DecodeGPRRegisterClass(Inst, Rs1, Address, Decoder);
  DecodeStatus Result = decodeUImmOperand<2>(Inst, UImm2, Address, Decoder);
  (void)Result;
  assert(Result == MCDisassembler::Success && "Invalid immediate");

  // Disassemble the final operand which is implicit.
  unsigned Opcode = Inst.getOpcode();
  bool IsWordOp = (Opcode == RISCV::TH_LWD || Opcode == RISCV::TH_LWUD ||
                   Opcode == RISCV::TH_SWD);
  if (IsWordOp)
    Inst.addOperand(MCOperand::createImm(3));
  else
    Inst.addOperand(MCOperand::createImm(4));

  return MCDisassembler::Success;
}

static DecodeStatus decodeZcmpRlist(MCInst &Inst, unsigned Imm,
                                    uint64_t Address, const void *Decoder) {
  if (Imm <= 3)
    return MCDisassembler::Fail;
  Inst.addOperand(MCOperand::createImm(Imm));
  return MCDisassembler::Success;
}

// spimm is based on rlist now.
static DecodeStatus decodeZcmpSpimm(MCInst &Inst, unsigned Imm,
                                    uint64_t Address, const void *Decoder) {
  // TODO: check if spimm matches rlist
  Inst.addOperand(MCOperand::createImm(Imm));
  return MCDisassembler::Success;
}

// Add implied SP operand for C.*SP compressed instructions. The SP operand
// isn't explicitly encoded in the instruction.
void RISCVDisassembler::addSPOperands(MCInst &MI) const {
  const MCInstrDesc &MCID = MCII->get(MI.getOpcode());
  for (unsigned i = 0; i < MCID.getNumOperands(); i++)
    if (MCID.operands()[i].RegClass == RISCV::SPRegClassID)
      MI.insert(MI.begin() + i, MCOperand::createReg(RISCV::X2));
}

DecodeStatus RISCVDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
                                               ArrayRef<uint8_t> Bytes,
                                               uint64_t Address,
                                               raw_ostream &CS) const {
  // TODO: This will need modification when supporting instruction set
  // extensions with instructions > 32-bits (up to 176 bits wide).
  uint32_t Insn;
  DecodeStatus Result;

#define TRY_TO_DECODE_WITH_ADDITIONAL_OPERATION(FEATURE_CHECKS, DECODER_TABLE, \
                                                DESC, ADDITIONAL_OPERATION)    \
  do {                                                                         \
    if (FEATURE_CHECKS) {                                                      \
      LLVM_DEBUG(dbgs() << "Trying " DESC ":\n");                              \
      Result = decodeInstruction(DECODER_TABLE, MI, Insn, Address, this, STI); \
      if (Result != MCDisassembler::Fail) {                                    \
        ADDITIONAL_OPERATION;                                                  \
        return Result;                                                         \
      }                                                                        \
    }                                                                          \
  } while (false)
#define TRY_TO_DECODE_AND_ADD_SP(FEATURE_CHECKS, DECODER_TABLE, DESC)          \
  TRY_TO_DECODE_WITH_ADDITIONAL_OPERATION(FEATURE_CHECKS, DECODER_TABLE, DESC, \
                                          addSPOperands(MI))
#define TRY_TO_DECODE(FEATURE_CHECKS, DECODER_TABLE, DESC)                     \
  TRY_TO_DECODE_WITH_ADDITIONAL_OPERATION(FEATURE_CHECKS, DECODER_TABLE, DESC, \
                                          (void)nullptr)
#define TRY_TO_DECODE_FEATURE(FEATURE, DECODER_TABLE, DESC)                    \
  TRY_TO_DECODE(STI.hasFeature(FEATURE), DECODER_TABLE, DESC)

  // It's a 32 bit instruction if bit 0 and 1 are 1.
  if ((Bytes[0] & 0x3) == 0x3) {
    if (Bytes.size() < 4) {
      Size = 0;
      return MCDisassembler::Fail;
    }
    Size = 4;

    Insn = support::endian::read32le(Bytes.data());

    TRY_TO_DECODE(STI.hasFeature(RISCV::FeatureStdExtZdinx) &&
                      !STI.hasFeature(RISCV::Feature64Bit),
                  DecoderTableRV32Zdinx32,
                  "RV32Zdinx table (Double in Integer and rv32)");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureStdExtZfinx, DecoderTableRVZfinx32,
                          "RVZfinx table (Float in Integer)");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXVentanaCondOps,
                          DecoderTableVentana32, "Ventana custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadBa, DecoderTableTHeadBa32,
                          "XTHeadBa custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadBb, DecoderTableTHeadBb32,
                          "XTHeadBb custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadBs, DecoderTableTHeadBs32,
                          "XTHeadBs custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadCondMov,
                          DecoderTableTHeadCondMov32,
                          "XTHeadCondMov custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadCmo, DecoderTableTHeadCmo32,
                          "XTHeadCmo custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadFMemIdx,
                          DecoderTableTHeadFMemIdx32,
                          "XTHeadFMemIdx custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadMac, DecoderTableTHeadMac32,
                          "XTHeadMac custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadMemIdx,
                          DecoderTableTHeadMemIdx32,
                          "XTHeadMemIdx custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadMemPair,
                          DecoderTableTHeadMemPair32,
                          "XTHeadMemPair custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadSync,
                          DecoderTableTHeadSync32,
                          "XTHeadSync custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXTHeadVdot, DecoderTableTHeadV32,
                          "XTHeadVdot custom opcode table");
    TRY_TO_DECODE_FEATURE(RISCV::FeatureVendorXSfvcp, DecoderTableXSfvcp32,
                          "SiFive VCIX custom opcode table");
    TRY_TO_DECODE(true, DecoderTable32, "RISCV32 table");

    return MCDisassembler::Fail;
  }

  if (Bytes.size() < 2) {
    Size = 0;
    return MCDisassembler::Fail;
  }
  Size = 2;

  Insn = support::endian::read16le(Bytes.data());
  TRY_TO_DECODE_AND_ADD_SP(!STI.hasFeature(RISCV::Feature64Bit),
                           DecoderTableRISCV32Only_16,
                           "RISCV32Only_16 table (16-bit Instruction)");
  TRY_TO_DECODE_FEATURE(RISCV::FeatureStdExtZcmt, DecoderTableRVZcmt16,
                        "Zcmt table (16-bit Table Jump Instructions)");
  TRY_TO_DECODE_FEATURE(
      RISCV::FeatureStdExtZcmp, DecoderTableRVZcmp16,
      "Zcmp table (16-bit Push/Pop & Double Move Instructions)");
  TRY_TO_DECODE_AND_ADD_SP(true, DecoderTable16,
                           "RISCV_C table (16-bit Instruction)");

  return MCDisassembler::Fail;
}