// Copyright 2013 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <assert.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>

#if V8_TARGET_ARCH_ARM64

#include "src/arm64/decoder-arm64-inl.h"
#include "src/arm64/disasm-arm64.h"
#include "src/arm64/utils-arm64.h"
#include "src/base/platform/platform.h"
#include "src/disasm.h"
#include "src/macro-assembler.h"

namespace v8 {
namespace internal {


DisassemblingDecoder::DisassemblingDecoder() {
  buffer_size_ = 256;
  buffer_ = reinterpret_cast<char*>(malloc(buffer_size_));
  buffer_pos_ = 0;
  own_buffer_ = true;
}


DisassemblingDecoder::DisassemblingDecoder(char* text_buffer, int buffer_size) {
  buffer_size_ = buffer_size;
  buffer_ = text_buffer;
  buffer_pos_ = 0;
  own_buffer_ = false;
}


DisassemblingDecoder::~DisassemblingDecoder() {
  if (own_buffer_) {
    free(buffer_);
  }
}


char* DisassemblingDecoder::GetOutput() { return buffer_; }


void DisassemblingDecoder::VisitAddSubImmediate(Instruction* instr) {
  bool rd_is_zr = RdIsZROrSP(instr);
  bool stack_op = (rd_is_zr || RnIsZROrSP(instr)) &&
                  (instr->ImmAddSub() == 0) ? true : false;
  const char *mnemonic = "";
  const char *form = "'Rds, 'Rns, 'IAddSub";
  const char *form_cmp = "'Rns, 'IAddSub";
  const char *form_mov = "'Rds, 'Rns";

  switch (instr->Mask(AddSubImmediateMask)) {
    case ADD_w_imm:
    case ADD_x_imm: {
      mnemonic = "add";
      if (stack_op) {
        mnemonic = "mov";
        form = form_mov;
      }
      break;
    }
    case ADDS_w_imm:
    case ADDS_x_imm: {
      mnemonic = "adds";
      if (rd_is_zr) {
        mnemonic = "cmn";
        form = form_cmp;
      }
      break;
    }
    case SUB_w_imm:
    case SUB_x_imm: mnemonic = "sub"; break;
    case SUBS_w_imm:
    case SUBS_x_imm: {
      mnemonic = "subs";
      if (rd_is_zr) {
        mnemonic = "cmp";
        form = form_cmp;
      }
      break;
    }
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitAddSubShifted(Instruction* instr) {
  bool rd_is_zr = RdIsZROrSP(instr);
  bool rn_is_zr = RnIsZROrSP(instr);
  const char *mnemonic = "";
  const char* form = "'Rd, 'Rn, 'Rm'NDP";
  const char* form_cmp = "'Rn, 'Rm'NDP";
  const char* form_neg = "'Rd, 'Rm'NDP";

  switch (instr->Mask(AddSubShiftedMask)) {
    case ADD_w_shift:
    case ADD_x_shift: mnemonic = "add"; break;
    case ADDS_w_shift:
    case ADDS_x_shift: {
      mnemonic = "adds";
      if (rd_is_zr) {
        mnemonic = "cmn";
        form = form_cmp;
      }
      break;
    }
    case SUB_w_shift:
    case SUB_x_shift: {
      mnemonic = "sub";
      if (rn_is_zr) {
        mnemonic = "neg";
        form = form_neg;
      }
      break;
    }
    case SUBS_w_shift:
    case SUBS_x_shift: {
      mnemonic = "subs";
      if (rd_is_zr) {
        mnemonic = "cmp";
        form = form_cmp;
      } else if (rn_is_zr) {
        mnemonic = "negs";
        form = form_neg;
      }
      break;
    }
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitAddSubExtended(Instruction* instr) {
  bool rd_is_zr = RdIsZROrSP(instr);
  const char *mnemonic = "";
  Extend mode = static_cast<Extend>(instr->ExtendMode());
  const char *form = ((mode == UXTX) || (mode == SXTX)) ?
                     "'Rds, 'Rns, 'Xm'Ext" : "'Rds, 'Rns, 'Wm'Ext";
  const char *form_cmp = ((mode == UXTX) || (mode == SXTX)) ?
                         "'Rns, 'Xm'Ext" : "'Rns, 'Wm'Ext";

  switch (instr->Mask(AddSubExtendedMask)) {
    case ADD_w_ext:
    case ADD_x_ext: mnemonic = "add"; break;
    case ADDS_w_ext:
    case ADDS_x_ext: {
      mnemonic = "adds";
      if (rd_is_zr) {
        mnemonic = "cmn";
        form = form_cmp;
      }
      break;
    }
    case SUB_w_ext:
    case SUB_x_ext: mnemonic = "sub"; break;
    case SUBS_w_ext:
    case SUBS_x_ext: {
      mnemonic = "subs";
      if (rd_is_zr) {
        mnemonic = "cmp";
        form = form_cmp;
      }
      break;
    }
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitAddSubWithCarry(Instruction* instr) {
  bool rn_is_zr = RnIsZROrSP(instr);
  const char *mnemonic = "";
  const char *form = "'Rd, 'Rn, 'Rm";
  const char *form_neg = "'Rd, 'Rm";

  switch (instr->Mask(AddSubWithCarryMask)) {
    case ADC_w:
    case ADC_x: mnemonic = "adc"; break;
    case ADCS_w:
    case ADCS_x: mnemonic = "adcs"; break;
    case SBC_w:
    case SBC_x: {
      mnemonic = "sbc";
      if (rn_is_zr) {
        mnemonic = "ngc";
        form = form_neg;
      }
      break;
    }
    case SBCS_w:
    case SBCS_x: {
      mnemonic = "sbcs";
      if (rn_is_zr) {
        mnemonic = "ngcs";
        form = form_neg;
      }
      break;
    }
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitLogicalImmediate(Instruction* instr) {
  bool rd_is_zr = RdIsZROrSP(instr);
  bool rn_is_zr = RnIsZROrSP(instr);
  const char *mnemonic = "";
  const char *form = "'Rds, 'Rn, 'ITri";

  if (instr->ImmLogical() == 0) {
    // The immediate encoded in the instruction is not in the expected format.
    Format(instr, "unallocated", "(LogicalImmediate)");
    return;
  }

  switch (instr->Mask(LogicalImmediateMask)) {
    case AND_w_imm:
    case AND_x_imm: mnemonic = "and"; break;
    case ORR_w_imm:
    case ORR_x_imm: {
      mnemonic = "orr";
      unsigned reg_size = (instr->SixtyFourBits() == 1) ? kXRegSizeInBits
                                                        : kWRegSizeInBits;
      if (rn_is_zr && !IsMovzMovnImm(reg_size, instr->ImmLogical())) {
        mnemonic = "mov";
        form = "'Rds, 'ITri";
      }
      break;
    }
    case EOR_w_imm:
    case EOR_x_imm: mnemonic = "eor"; break;
    case ANDS_w_imm:
    case ANDS_x_imm: {
      mnemonic = "ands";
      if (rd_is_zr) {
        mnemonic = "tst";
        form = "'Rn, 'ITri";
      }
      break;
    }
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


bool DisassemblingDecoder::IsMovzMovnImm(unsigned reg_size, uint64_t value) {
  DCHECK((reg_size == kXRegSizeInBits) ||
         ((reg_size == kWRegSizeInBits) && (value <= 0xFFFFFFFF)));

  // Test for movz: 16-bits set at positions 0, 16, 32 or 48.
  if (((value & 0xFFFFFFFFFFFF0000UL) == 0UL) ||
      ((value & 0xFFFFFFFF0000FFFFUL) == 0UL) ||
      ((value & 0xFFFF0000FFFFFFFFUL) == 0UL) ||
      ((value & 0x0000FFFFFFFFFFFFUL) == 0UL)) {
    return true;
  }

  // Test for movn: NOT(16-bits set at positions 0, 16, 32 or 48).
  if ((reg_size == kXRegSizeInBits) &&
      (((value & 0xFFFFFFFFFFFF0000UL) == 0xFFFFFFFFFFFF0000UL) ||
       ((value & 0xFFFFFFFF0000FFFFUL) == 0xFFFFFFFF0000FFFFUL) ||
       ((value & 0xFFFF0000FFFFFFFFUL) == 0xFFFF0000FFFFFFFFUL) ||
       ((value & 0x0000FFFFFFFFFFFFUL) == 0x0000FFFFFFFFFFFFUL))) {
    return true;
  }
  if ((reg_size == kWRegSizeInBits) && (((value & 0xFFFF0000) == 0xFFFF0000) ||
                                        ((value & 0x0000FFFF) == 0x0000FFFF))) {
    return true;
  }
  return false;
}


void DisassemblingDecoder::VisitLogicalShifted(Instruction* instr) {
  bool rd_is_zr = RdIsZROrSP(instr);
  bool rn_is_zr = RnIsZROrSP(instr);
  const char *mnemonic = "";
  const char* form = "'Rd, 'Rn, 'Rm'NLo";

  switch (instr->Mask(LogicalShiftedMask)) {
    case AND_w:
    case AND_x: mnemonic = "and"; break;
    case BIC_w:
    case BIC_x: mnemonic = "bic"; break;
    case EOR_w:
    case EOR_x: mnemonic = "eor"; break;
    case EON_w:
    case EON_x: mnemonic = "eon"; break;
    case BICS_w:
    case BICS_x: mnemonic = "bics"; break;
    case ANDS_w:
    case ANDS_x: {
      mnemonic = "ands";
      if (rd_is_zr) {
        mnemonic = "tst";
        form = "'Rn, 'Rm'NLo";
      }
      break;
    }
    case ORR_w:
    case ORR_x: {
      mnemonic = "orr";
      if (rn_is_zr && (instr->ImmDPShift() == 0) && (instr->ShiftDP() == LSL)) {
        mnemonic = "mov";
        form = "'Rd, 'Rm";
      }
      break;
    }
    case ORN_w:
    case ORN_x: {
      mnemonic = "orn";
      if (rn_is_zr) {
        mnemonic = "mvn";
        form = "'Rd, 'Rm'NLo";
      }
      break;
    }
    default: UNREACHABLE();
  }

  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitConditionalCompareRegister(Instruction* instr) {
  const char *mnemonic = "";
  const char *form = "'Rn, 'Rm, 'INzcv, 'Cond";

  switch (instr->Mask(ConditionalCompareRegisterMask)) {
    case CCMN_w:
    case CCMN_x: mnemonic = "ccmn"; break;
    case CCMP_w:
    case CCMP_x: mnemonic = "ccmp"; break;
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitConditionalCompareImmediate(
    Instruction* instr) {
  const char *mnemonic = "";
  const char *form = "'Rn, 'IP, 'INzcv, 'Cond";

  switch (instr->Mask(ConditionalCompareImmediateMask)) {
    case CCMN_w_imm:
    case CCMN_x_imm: mnemonic = "ccmn"; break;
    case CCMP_w_imm:
    case CCMP_x_imm: mnemonic = "ccmp"; break;
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitConditionalSelect(Instruction* instr) {
  bool rnm_is_zr = (RnIsZROrSP(instr) && RmIsZROrSP(instr));
  bool rn_is_rm = (instr->Rn() == instr->Rm());
  const char *mnemonic = "";
  const char *form = "'Rd, 'Rn, 'Rm, 'Cond";
  const char *form_test = "'Rd, 'CInv";
  const char *form_update = "'Rd, 'Rn, 'CInv";

  Condition cond = static_cast<Condition>(instr->Condition());
  bool invertible_cond = (cond != al) && (cond != nv);

  switch (instr->Mask(ConditionalSelectMask)) {
    case CSEL_w:
    case CSEL_x: mnemonic = "csel"; break;
    case CSINC_w:
    case CSINC_x: {
      mnemonic = "csinc";
      if (rnm_is_zr && invertible_cond) {
        mnemonic = "cset";
        form = form_test;
      } else if (rn_is_rm && invertible_cond) {
        mnemonic = "cinc";
        form = form_update;
      }
      break;
    }
    case CSINV_w:
    case CSINV_x: {
      mnemonic = "csinv";
      if (rnm_is_zr && invertible_cond) {
        mnemonic = "csetm";
        form = form_test;
      } else if (rn_is_rm && invertible_cond) {
        mnemonic = "cinv";
        form = form_update;
      }
      break;
    }
    case CSNEG_w:
    case CSNEG_x: {
      mnemonic = "csneg";
      if (rn_is_rm && invertible_cond) {
        mnemonic = "cneg";
        form = form_update;
      }
      break;
    }
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitBitfield(Instruction* instr) {
  unsigned s = instr->ImmS();
  unsigned r = instr->ImmR();
  unsigned rd_size_minus_1 =
    ((instr->SixtyFourBits() == 1) ? kXRegSizeInBits : kWRegSizeInBits) - 1;
  const char *mnemonic = "";
  const char *form = "";
  const char *form_shift_right = "'Rd, 'Rn, 'IBr";
  const char *form_extend = "'Rd, 'Wn";
  const char *form_bfiz = "'Rd, 'Rn, 'IBZ-r, 'IBs+1";
  const char *form_bfx = "'Rd, 'Rn, 'IBr, 'IBs-r+1";
  const char *form_lsl = "'Rd, 'Rn, 'IBZ-r";

  switch (instr->Mask(BitfieldMask)) {
    case SBFM_w:
    case SBFM_x: {
      mnemonic = "sbfx";
      form = form_bfx;
      if (r == 0) {
        form = form_extend;
        if (s == 7) {
          mnemonic = "sxtb";
        } else if (s == 15) {
          mnemonic = "sxth";
        } else if ((s == 31) && (instr->SixtyFourBits() == 1)) {
          mnemonic = "sxtw";
        } else {
          form = form_bfx;
        }
      } else if (s == rd_size_minus_1) {
        mnemonic = "asr";
        form = form_shift_right;
      } else if (s < r) {
        mnemonic = "sbfiz";
        form = form_bfiz;
      }
      break;
    }
    case UBFM_w:
    case UBFM_x: {
      mnemonic = "ubfx";
      form = form_bfx;
      if (r == 0) {
        form = form_extend;
        if (s == 7) {
          mnemonic = "uxtb";
        } else if (s == 15) {
          mnemonic = "uxth";
        } else {
          form = form_bfx;
        }
      }
      if (s == rd_size_minus_1) {
        mnemonic = "lsr";
        form = form_shift_right;
      } else if (r == s + 1) {
        mnemonic = "lsl";
        form = form_lsl;
      } else if (s < r) {
        mnemonic = "ubfiz";
        form = form_bfiz;
      }
      break;
    }
    case BFM_w:
    case BFM_x: {
      mnemonic = "bfxil";
      form = form_bfx;
      if (s < r) {
        mnemonic = "bfi";
        form = form_bfiz;
      }
    }
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitExtract(Instruction* instr) {
  const char *mnemonic = "";
  const char *form = "'Rd, 'Rn, 'Rm, 'IExtract";

  switch (instr->Mask(ExtractMask)) {
    case EXTR_w:
    case EXTR_x: {
      if (instr->Rn() == instr->Rm()) {
        mnemonic = "ror";
        form = "'Rd, 'Rn, 'IExtract";
      } else {
        mnemonic = "extr";
      }
      break;
    }
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitPCRelAddressing(Instruction* instr) {
  switch (instr->Mask(PCRelAddressingMask)) {
    case ADR: Format(instr, "adr", "'Xd, 'AddrPCRelByte"); break;
    // ADRP is not implemented.
    default: Format(instr, "unimplemented", "(PCRelAddressing)");
  }
}


void DisassemblingDecoder::VisitConditionalBranch(Instruction* instr) {
  switch (instr->Mask(ConditionalBranchMask)) {
    case B_cond:
      Format(instr, "b.'CBrn", "'TImmCond");
      break;
    default: UNREACHABLE();
  }
}


void DisassemblingDecoder::VisitUnconditionalBranchToRegister(
    Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "'Xn";

  switch (instr->Mask(UnconditionalBranchToRegisterMask)) {
    case BR: mnemonic = "br"; break;
    case BLR: mnemonic = "blr"; break;
    case RET: {
      mnemonic = "ret";
      if (instr->Rn() == kLinkRegCode) {
        form = nullptr;
      }
      break;
    }
    default: form = "(UnconditionalBranchToRegister)";
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitUnconditionalBranch(Instruction* instr) {
  const char *mnemonic = "";
  const char* form = "'TImmUncn";

  switch (instr->Mask(UnconditionalBranchMask)) {
    case B: mnemonic = "b"; break;
    case BL: mnemonic = "bl"; break;
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitDataProcessing1Source(Instruction* instr) {
  const char *mnemonic = "";
  const char *form = "'Rd, 'Rn";

  switch (instr->Mask(DataProcessing1SourceMask)) {
    #define FORMAT(A, B)  \
    case A##_w:           \
    case A##_x: mnemonic = B; break;
    FORMAT(RBIT, "rbit");
    FORMAT(REV16, "rev16");
    FORMAT(REV, "rev");
    FORMAT(CLZ, "clz");
    FORMAT(CLS, "cls");
    #undef FORMAT
    case REV32_x: mnemonic = "rev32"; break;
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitDataProcessing2Source(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "'Rd, 'Rn, 'Rm";

  switch (instr->Mask(DataProcessing2SourceMask)) {
    #define FORMAT(A, B)  \
    case A##_w:           \
    case A##_x: mnemonic = B; break;
    FORMAT(UDIV, "udiv");
    FORMAT(SDIV, "sdiv");
    FORMAT(LSLV, "lsl");
    FORMAT(LSRV, "lsr");
    FORMAT(ASRV, "asr");
    FORMAT(RORV, "ror");
    #undef FORMAT
    default: form = "(DataProcessing2Source)";
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitDataProcessing3Source(Instruction* instr) {
  bool ra_is_zr = RaIsZROrSP(instr);
  const char *mnemonic = "";
  const char *form = "'Xd, 'Wn, 'Wm, 'Xa";
  const char *form_rrr = "'Rd, 'Rn, 'Rm";
  const char *form_rrrr = "'Rd, 'Rn, 'Rm, 'Ra";
  const char *form_xww = "'Xd, 'Wn, 'Wm";
  const char *form_xxx = "'Xd, 'Xn, 'Xm";

  switch (instr->Mask(DataProcessing3SourceMask)) {
    case MADD_w:
    case MADD_x: {
      mnemonic = "madd";
      form = form_rrrr;
      if (ra_is_zr) {
        mnemonic = "mul";
        form = form_rrr;
      }
      break;
    }
    case MSUB_w:
    case MSUB_x: {
      mnemonic = "msub";
      form = form_rrrr;
      if (ra_is_zr) {
        mnemonic = "mneg";
        form = form_rrr;
      }
      break;
    }
    case SMADDL_x: {
      mnemonic = "smaddl";
      if (ra_is_zr) {
        mnemonic = "smull";
        form = form_xww;
      }
      break;
    }
    case SMSUBL_x: {
      mnemonic = "smsubl";
      if (ra_is_zr) {
        mnemonic = "smnegl";
        form = form_xww;
      }
      break;
    }
    case UMADDL_x: {
      mnemonic = "umaddl";
      if (ra_is_zr) {
        mnemonic = "umull";
        form = form_xww;
      }
      break;
    }
    case UMSUBL_x: {
      mnemonic = "umsubl";
      if (ra_is_zr) {
        mnemonic = "umnegl";
        form = form_xww;
      }
      break;
    }
    case SMULH_x: {
      mnemonic = "smulh";
      form = form_xxx;
      break;
    }
    case UMULH_x: {
      mnemonic = "umulh";
      form = form_xxx;
      break;
    }
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitCompareBranch(Instruction* instr) {
  const char *mnemonic = "";
  const char* form = "'Rt, 'TImmCmpa";

  switch (instr->Mask(CompareBranchMask)) {
    case CBZ_w:
    case CBZ_x: mnemonic = "cbz"; break;
    case CBNZ_w:
    case CBNZ_x: mnemonic = "cbnz"; break;
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitTestBranch(Instruction* instr) {
  const char *mnemonic = "";
  // If the top bit of the immediate is clear, the tested register is
  // disassembled as Wt, otherwise Xt. As the top bit of the immediate is
  // encoded in bit 31 of the instruction, we can reuse the Rt form, which
  // uses bit 31 (normally "sf") to choose the register size.
  const char* form = "'Rt, 'IS, 'TImmTest";

  switch (instr->Mask(TestBranchMask)) {
    case TBZ: mnemonic = "tbz"; break;
    case TBNZ: mnemonic = "tbnz"; break;
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitMoveWideImmediate(Instruction* instr) {
  const char *mnemonic = "";
  const char *form = "'Rd, 'IMoveImm";

  // Print the shift separately for movk, to make it clear which half word will
  // be overwritten. Movn and movz print the computed immediate, which includes
  // shift calculation.
  switch (instr->Mask(MoveWideImmediateMask)) {
    case MOVN_w:
    case MOVN_x: mnemonic = "movn"; break;
    case MOVZ_w:
    case MOVZ_x: mnemonic = "movz"; break;
    case MOVK_w:
    case MOVK_x: mnemonic = "movk"; form = "'Rd, 'IMoveLSL"; break;
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}

#define LOAD_STORE_LIST(V)   \
  V(STRB_w, "strb", "'Wt")   \
  V(STRH_w, "strh", "'Wt")   \
  V(STR_w, "str", "'Wt")     \
  V(STR_x, "str", "'Xt")     \
  V(LDRB_w, "ldrb", "'Wt")   \
  V(LDRH_w, "ldrh", "'Wt")   \
  V(LDR_w, "ldr", "'Wt")     \
  V(LDR_x, "ldr", "'Xt")     \
  V(LDRSB_x, "ldrsb", "'Xt") \
  V(LDRSH_x, "ldrsh", "'Xt") \
  V(LDRSW_x, "ldrsw", "'Xt") \
  V(LDRSB_w, "ldrsb", "'Wt") \
  V(LDRSH_w, "ldrsh", "'Wt") \
  V(STR_b, "str", "'Bt")     \
  V(STR_h, "str", "'Ht")     \
  V(STR_s, "str", "'St")     \
  V(STR_d, "str", "'Dt")     \
  V(LDR_b, "ldr", "'Bt")     \
  V(LDR_h, "ldr", "'Ht")     \
  V(LDR_s, "ldr", "'St")     \
  V(LDR_d, "ldr", "'Dt")     \
  V(STR_q, "str", "'Qt")     \
  V(LDR_q, "ldr", "'Qt")

void DisassemblingDecoder::VisitLoadStorePreIndex(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "(LoadStorePreIndex)";

  switch (instr->Mask(LoadStorePreIndexMask)) {
    #define LS_PREINDEX(A, B, C) \
    case A##_pre: mnemonic = B; form = C ", ['Xns'ILS]!"; break;
    LOAD_STORE_LIST(LS_PREINDEX)
    #undef LS_PREINDEX
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitLoadStorePostIndex(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "(LoadStorePostIndex)";

  switch (instr->Mask(LoadStorePostIndexMask)) {
    #define LS_POSTINDEX(A, B, C) \
    case A##_post: mnemonic = B; form = C ", ['Xns]'ILS"; break;
    LOAD_STORE_LIST(LS_POSTINDEX)
    #undef LS_POSTINDEX
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitLoadStoreUnsignedOffset(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "(LoadStoreUnsignedOffset)";

  switch (instr->Mask(LoadStoreUnsignedOffsetMask)) {
    #define LS_UNSIGNEDOFFSET(A, B, C) \
    case A##_unsigned: mnemonic = B; form = C ", ['Xns'ILU]"; break;
    LOAD_STORE_LIST(LS_UNSIGNEDOFFSET)
    #undef LS_UNSIGNEDOFFSET
    case PRFM_unsigned: mnemonic = "prfm"; form = "'PrefOp, ['Xn'ILU]";
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitLoadStoreRegisterOffset(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "(LoadStoreRegisterOffset)";

  switch (instr->Mask(LoadStoreRegisterOffsetMask)) {
    #define LS_REGISTEROFFSET(A, B, C) \
    case A##_reg: mnemonic = B; form = C ", ['Xns, 'Offsetreg]"; break;
    LOAD_STORE_LIST(LS_REGISTEROFFSET)
    #undef LS_REGISTEROFFSET
    case PRFM_reg: mnemonic = "prfm"; form = "'PrefOp, ['Xns, 'Offsetreg]";
  }
  Format(instr, mnemonic, form);
}

#define LOAD_STORE_UNSCALED_LIST(V) \
  V(STURB_w, "sturb", "'Wt")        \
  V(STURH_w, "sturh", "'Wt")        \
  V(STUR_w, "stur", "'Wt")          \
  V(STUR_x, "stur", "'Xt")          \
  V(LDURB_w, "ldurb", "'Wt")        \
  V(LDURH_w, "ldurh", "'Wt")        \
  V(LDUR_w, "ldur", "'Wt")          \
  V(LDUR_x, "ldur", "'Xt")          \
  V(LDURSB_x, "ldursb", "'Xt")      \
  V(LDURSH_x, "ldursh", "'Xt")      \
  V(LDURSW_x, "ldursw", "'Xt")      \
  V(LDURSB_w, "ldursb", "'Wt")      \
  V(LDURSH_w, "ldursh", "'Wt")      \
  V(STUR_b, "stur", "'Bt")          \
  V(STUR_h, "stur", "'Ht")          \
  V(STUR_s, "stur", "'St")          \
  V(STUR_d, "stur", "'Dt")          \
  V(LDUR_b, "ldur", "'Bt")          \
  V(LDUR_h, "ldur", "'Ht")          \
  V(LDUR_s, "ldur", "'St")          \
  V(LDUR_d, "ldur", "'Dt")          \
  V(STUR_q, "stur", "'Qt")          \
  V(LDUR_q, "ldur", "'Qt")

void DisassemblingDecoder::VisitLoadStoreUnscaledOffset(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "(LoadStoreUnscaledOffset)";

  switch (instr->Mask(LoadStoreUnscaledOffsetMask)) {
#define LS_UNSCALEDOFFSET(A, B, C) \
  case A:                          \
    mnemonic = B;                  \
    form = C ", ['Xns'ILS]";       \
    break;
    LOAD_STORE_UNSCALED_LIST(LS_UNSCALEDOFFSET)
#undef LS_UNSCALEDOFFSET
  }
  Format(instr, mnemonic, form);
}

void DisassemblingDecoder::VisitLoadLiteral(Instruction* instr) {
  const char *mnemonic = "ldr";
  const char *form = "(LoadLiteral)";

  switch (instr->Mask(LoadLiteralMask)) {
    case LDR_w_lit: form = "'Wt, 'ILLiteral 'LValue"; break;
    case LDR_x_lit: form = "'Xt, 'ILLiteral 'LValue"; break;
    case LDR_s_lit: form = "'St, 'ILLiteral 'LValue"; break;
    case LDR_d_lit: form = "'Dt, 'ILLiteral 'LValue"; break;
    default: mnemonic = "unimplemented";
  }
  Format(instr, mnemonic, form);
}

#define LOAD_STORE_PAIR_LIST(V)         \
  V(STP_w, "stp", "'Wt, 'Wt2", "2")     \
  V(LDP_w, "ldp", "'Wt, 'Wt2", "2")     \
  V(LDPSW_x, "ldpsw", "'Xt, 'Xt2", "2") \
  V(STP_x, "stp", "'Xt, 'Xt2", "3")     \
  V(LDP_x, "ldp", "'Xt, 'Xt2", "3")     \
  V(STP_s, "stp", "'St, 'St2", "2")     \
  V(LDP_s, "ldp", "'St, 'St2", "2")     \
  V(STP_d, "stp", "'Dt, 'Dt2", "3")     \
  V(LDP_d, "ldp", "'Dt, 'Dt2", "3")     \
  V(LDP_q, "ldp", "'Qt, 'Qt2", "4")     \
  V(STP_q, "stp", "'Qt, 'Qt2", "4")

void DisassemblingDecoder::VisitLoadStorePairPostIndex(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "(LoadStorePairPostIndex)";

  switch (instr->Mask(LoadStorePairPostIndexMask)) {
    #define LSP_POSTINDEX(A, B, C, D) \
    case A##_post: mnemonic = B; form = C ", ['Xns]'ILP" D; break;
    LOAD_STORE_PAIR_LIST(LSP_POSTINDEX)
    #undef LSP_POSTINDEX
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitLoadStorePairPreIndex(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "(LoadStorePairPreIndex)";

  switch (instr->Mask(LoadStorePairPreIndexMask)) {
    #define LSP_PREINDEX(A, B, C, D) \
    case A##_pre: mnemonic = B; form = C ", ['Xns'ILP" D "]!"; break;
    LOAD_STORE_PAIR_LIST(LSP_PREINDEX)
    #undef LSP_PREINDEX
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitLoadStorePairOffset(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "(LoadStorePairOffset)";

  switch (instr->Mask(LoadStorePairOffsetMask)) {
    #define LSP_OFFSET(A, B, C, D) \
    case A##_off: mnemonic = B; form = C ", ['Xns'ILP" D "]"; break;
    LOAD_STORE_PAIR_LIST(LSP_OFFSET)
    #undef LSP_OFFSET
  }
  Format(instr, mnemonic, form);
}

void DisassemblingDecoder::VisitLoadStoreAcquireRelease(Instruction *instr) {
  const char *mnemonic = "unimplemented";
  const char* form = "'Wt, ['Xns]";
  const char* form_x = "'Xt, ['Xns]";
  const char* form_stlx = "'Ws, 'Wt, ['Xns]";
  const char* form_stlx_x = "'Ws, 'Xt, ['Xns]";

  switch (instr->Mask(LoadStoreAcquireReleaseMask)) {
    case LDAXR_b: mnemonic = "ldaxrb"; break;
    case STLR_b:  mnemonic = "stlrb"; break;
    case LDAR_b:  mnemonic = "ldarb"; break;
    case LDAXR_h: mnemonic = "ldaxrh"; break;
    case STLR_h:  mnemonic = "stlrh"; break;
    case LDAR_h:  mnemonic = "ldarh"; break;
    case LDAXR_w: mnemonic = "ldaxr"; break;
    case STLR_w:  mnemonic = "stlr"; break;
    case LDAR_w:  mnemonic = "ldar"; break;
    case LDAXR_x: mnemonic = "ldaxr"; form = form_x; break;
    case STLR_x:  mnemonic = "stlr"; form = form_x; break;
    case LDAR_x:  mnemonic = "ldar"; form = form_x; break;
    case STLXR_h: mnemonic = "stlxrh"; form = form_stlx; break;
    case STLXR_b: mnemonic = "stlxrb"; form = form_stlx; break;
    case STLXR_w: mnemonic = "stlxr"; form = form_stlx; break;
    case STLXR_x: mnemonic = "stlxr"; form = form_stlx_x; break;
    default:
      form = "(LoadStoreAcquireRelease)";
  }
  Format(instr, mnemonic, form);
}

void DisassemblingDecoder::VisitFPCompare(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "'Fn, 'Fm";
  const char *form_zero = "'Fn, #0.0";

  switch (instr->Mask(FPCompareMask)) {
    case FCMP_s_zero:
    case FCMP_d_zero: form = form_zero;  // Fall through.
    case FCMP_s:
    case FCMP_d: mnemonic = "fcmp"; break;
    default: form = "(FPCompare)";
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitFPConditionalCompare(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "'Fn, 'Fm, 'INzcv, 'Cond";

  switch (instr->Mask(FPConditionalCompareMask)) {
    case FCCMP_s:
    case FCCMP_d: mnemonic = "fccmp"; break;
    case FCCMPE_s:
    case FCCMPE_d: mnemonic = "fccmpe"; break;
    default: form = "(FPConditionalCompare)";
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitFPConditionalSelect(Instruction* instr) {
  const char *mnemonic = "";
  const char *form = "'Fd, 'Fn, 'Fm, 'Cond";

  switch (instr->Mask(FPConditionalSelectMask)) {
    case FCSEL_s:
    case FCSEL_d: mnemonic = "fcsel"; break;
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitFPDataProcessing1Source(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "'Fd, 'Fn";

  switch (instr->Mask(FPDataProcessing1SourceMask)) {
    #define FORMAT(A, B)  \
    case A##_s:           \
    case A##_d: mnemonic = B; break;
    FORMAT(FMOV, "fmov");
    FORMAT(FABS, "fabs");
    FORMAT(FNEG, "fneg");
    FORMAT(FSQRT, "fsqrt");
    FORMAT(FRINTN, "frintn");
    FORMAT(FRINTP, "frintp");
    FORMAT(FRINTM, "frintm");
    FORMAT(FRINTZ, "frintz");
    FORMAT(FRINTA, "frinta");
    FORMAT(FRINTX, "frintx");
    FORMAT(FRINTI, "frinti");
    #undef FORMAT
    case FCVT_ds: mnemonic = "fcvt"; form = "'Dd, 'Sn"; break;
    case FCVT_sd: mnemonic = "fcvt"; form = "'Sd, 'Dn"; break;
    case FCVT_hs:
      mnemonic = "fcvt";
      form = "'Hd, 'Sn";
      break;
    case FCVT_sh:
      mnemonic = "fcvt";
      form = "'Sd, 'Hn";
      break;
    case FCVT_dh:
      mnemonic = "fcvt";
      form = "'Dd, 'Hn";
      break;
    case FCVT_hd:
      mnemonic = "fcvt";
      form = "'Hd, 'Dn";
      break;
    default: form = "(FPDataProcessing1Source)";
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitFPDataProcessing2Source(Instruction* instr) {
  const char *mnemonic = "";
  const char *form = "'Fd, 'Fn, 'Fm";

  switch (instr->Mask(FPDataProcessing2SourceMask)) {
    #define FORMAT(A, B)  \
    case A##_s:           \
    case A##_d: mnemonic = B; break;
    FORMAT(FMUL, "fmul");
    FORMAT(FDIV, "fdiv");
    FORMAT(FADD, "fadd");
    FORMAT(FSUB, "fsub");
    FORMAT(FMAX, "fmax");
    FORMAT(FMIN, "fmin");
    FORMAT(FMAXNM, "fmaxnm");
    FORMAT(FMINNM, "fminnm");
    FORMAT(FNMUL, "fnmul");
    #undef FORMAT
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitFPDataProcessing3Source(Instruction* instr) {
  const char *mnemonic = "";
  const char *form = "'Fd, 'Fn, 'Fm, 'Fa";

  switch (instr->Mask(FPDataProcessing3SourceMask)) {
    #define FORMAT(A, B)  \
    case A##_s:           \
    case A##_d: mnemonic = B; break;
    FORMAT(FMADD, "fmadd");
    FORMAT(FMSUB, "fmsub");
    FORMAT(FNMADD, "fnmadd");
    FORMAT(FNMSUB, "fnmsub");
    #undef FORMAT
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitFPImmediate(Instruction* instr) {
  const char *mnemonic = "";
  const char *form = "(FPImmediate)";

  switch (instr->Mask(FPImmediateMask)) {
    case FMOV_s_imm: mnemonic = "fmov"; form = "'Sd, 'IFPSingle"; break;
    case FMOV_d_imm: mnemonic = "fmov"; form = "'Dd, 'IFPDouble"; break;
    default: UNREACHABLE();
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitFPIntegerConvert(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "(FPIntegerConvert)";
  const char *form_rf = "'Rd, 'Fn";
  const char *form_fr = "'Fd, 'Rn";

  switch (instr->Mask(FPIntegerConvertMask)) {
    case FMOV_ws:
    case FMOV_xd: mnemonic = "fmov"; form = form_rf; break;
    case FMOV_sw:
    case FMOV_dx: mnemonic = "fmov"; form = form_fr; break;
    case FMOV_d1_x:
      mnemonic = "fmov";
      form = "'Vd.D[1], 'Rn";
      break;
    case FMOV_x_d1:
      mnemonic = "fmov";
      form = "'Rd, 'Vn.D[1]";
      break;
    case FCVTAS_ws:
    case FCVTAS_xs:
    case FCVTAS_wd:
    case FCVTAS_xd: mnemonic = "fcvtas"; form = form_rf; break;
    case FCVTAU_ws:
    case FCVTAU_xs:
    case FCVTAU_wd:
    case FCVTAU_xd: mnemonic = "fcvtau"; form = form_rf; break;
    case FCVTMS_ws:
    case FCVTMS_xs:
    case FCVTMS_wd:
    case FCVTMS_xd: mnemonic = "fcvtms"; form = form_rf; break;
    case FCVTMU_ws:
    case FCVTMU_xs:
    case FCVTMU_wd:
    case FCVTMU_xd: mnemonic = "fcvtmu"; form = form_rf; break;
    case FCVTNS_ws:
    case FCVTNS_xs:
    case FCVTNS_wd:
    case FCVTNS_xd: mnemonic = "fcvtns"; form = form_rf; break;
    case FCVTNU_ws:
    case FCVTNU_xs:
    case FCVTNU_wd:
    case FCVTNU_xd: mnemonic = "fcvtnu"; form = form_rf; break;
    case FCVTZU_xd:
    case FCVTZU_ws:
    case FCVTZU_wd:
    case FCVTZU_xs: mnemonic = "fcvtzu"; form = form_rf; break;
    case FCVTZS_xd:
    case FCVTZS_wd:
    case FCVTZS_xs:
    case FCVTZS_ws: mnemonic = "fcvtzs"; form = form_rf; break;
    case FCVTPU_xd:
    case FCVTPU_ws:
    case FCVTPU_wd:
    case FCVTPU_xs:
      mnemonic = "fcvtpu";
      form = form_rf;
      break;
    case FCVTPS_xd:
    case FCVTPS_wd:
    case FCVTPS_xs:
    case FCVTPS_ws:
      mnemonic = "fcvtps";
      form = form_rf;
      break;
    case SCVTF_sw:
    case SCVTF_sx:
    case SCVTF_dw:
    case SCVTF_dx: mnemonic = "scvtf"; form = form_fr; break;
    case UCVTF_sw:
    case UCVTF_sx:
    case UCVTF_dw:
    case UCVTF_dx: mnemonic = "ucvtf"; form = form_fr; break;
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitFPFixedPointConvert(Instruction* instr) {
  const char *mnemonic = "";
  const char *form = "'Rd, 'Fn, 'IFPFBits";
  const char *form_fr = "'Fd, 'Rn, 'IFPFBits";

  switch (instr->Mask(FPFixedPointConvertMask)) {
    case FCVTZS_ws_fixed:
    case FCVTZS_xs_fixed:
    case FCVTZS_wd_fixed:
    case FCVTZS_xd_fixed: mnemonic = "fcvtzs"; break;
    case FCVTZU_ws_fixed:
    case FCVTZU_xs_fixed:
    case FCVTZU_wd_fixed:
    case FCVTZU_xd_fixed: mnemonic = "fcvtzu"; break;
    case SCVTF_sw_fixed:
    case SCVTF_sx_fixed:
    case SCVTF_dw_fixed:
    case SCVTF_dx_fixed: mnemonic = "scvtf"; form = form_fr; break;
    case UCVTF_sw_fixed:
    case UCVTF_sx_fixed:
    case UCVTF_dw_fixed:
    case UCVTF_dx_fixed: mnemonic = "ucvtf"; form = form_fr; break;
  }
  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitSystem(Instruction* instr) {
  // Some system instructions hijack their Op and Cp fields to represent a
  // range of immediates instead of indicating a different instruction. This
  // makes the decoding tricky.
  const char *mnemonic = "unimplemented";
  const char *form = "(System)";

  if (instr->Mask(SystemSysRegFMask) == SystemSysRegFixed) {
    switch (instr->Mask(SystemSysRegMask)) {
      case MRS: {
        mnemonic = "mrs";
        switch (instr->ImmSystemRegister()) {
          case NZCV: form = "'Xt, nzcv"; break;
          case FPCR: form = "'Xt, fpcr"; break;
          default: form = "'Xt, (unknown)"; break;
        }
        break;
      }
      case MSR: {
        mnemonic = "msr";
        switch (instr->ImmSystemRegister()) {
          case NZCV: form = "nzcv, 'Xt"; break;
          case FPCR: form = "fpcr, 'Xt"; break;
          default: form = "(unknown), 'Xt"; break;
        }
        break;
      }
    }
  } else if (instr->Mask(SystemHintFMask) == SystemHintFixed) {
    DCHECK(instr->Mask(SystemHintMask) == HINT);
    switch (instr->ImmHint()) {
      case NOP: {
        mnemonic = "nop";
        form = nullptr;
        break;
      }
    }
  } else if (instr->Mask(MemBarrierFMask) == MemBarrierFixed) {
    switch (instr->Mask(MemBarrierMask)) {
      case DMB: {
        mnemonic = "dmb";
        form = "'M";
        break;
      }
      case DSB: {
        mnemonic = "dsb";
        form = "'M";
        break;
      }
      case ISB: {
        mnemonic = "isb";
        form = nullptr;
        break;
      }
    }
  }

  Format(instr, mnemonic, form);
}


void DisassemblingDecoder::VisitException(Instruction* instr) {
  const char *mnemonic = "unimplemented";
  const char *form = "'IDebug";

  switch (instr->Mask(ExceptionMask)) {
    case HLT: mnemonic = "hlt"; break;
    case BRK: mnemonic = "brk"; break;
    case SVC: mnemonic = "svc"; break;
    case HVC: mnemonic = "hvc"; break;
    case SMC: mnemonic = "smc"; break;
    case DCPS1: mnemonic = "dcps1"; form = "{'IDebug}"; break;
    case DCPS2: mnemonic = "dcps2"; form = "{'IDebug}"; break;
    case DCPS3: mnemonic = "dcps3"; form = "{'IDebug}"; break;
    default: form = "(Exception)";
  }
  Format(instr, mnemonic, form);
}

void DisassemblingDecoder::VisitNEON3Same(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "'Vd.%s, 'Vn.%s, 'Vm.%s";
  NEONFormatDecoder nfd(instr);

  if (instr->Mask(NEON3SameLogicalFMask) == NEON3SameLogicalFixed) {
    switch (instr->Mask(NEON3SameLogicalMask)) {
      case NEON_AND:
        mnemonic = "and";
        break;
      case NEON_ORR:
        mnemonic = "orr";
        if (instr->Rm() == instr->Rn()) {
          mnemonic = "mov";
          form = "'Vd.%s, 'Vn.%s";
        }
        break;
      case NEON_ORN:
        mnemonic = "orn";
        break;
      case NEON_EOR:
        mnemonic = "eor";
        break;
      case NEON_BIC:
        mnemonic = "bic";
        break;
      case NEON_BIF:
        mnemonic = "bif";
        break;
      case NEON_BIT:
        mnemonic = "bit";
        break;
      case NEON_BSL:
        mnemonic = "bsl";
        break;
      default:
        form = "(NEON3Same)";
    }
    nfd.SetFormatMaps(nfd.LogicalFormatMap());
  } else {
    static const char* mnemonics[] = {
        "shadd",       "uhadd",       "shadd",       "uhadd",
        "sqadd",       "uqadd",       "sqadd",       "uqadd",
        "srhadd",      "urhadd",      "srhadd",      "urhadd",
        nullptr,       nullptr,       nullptr,
        nullptr,  // Handled by logical cases above.
        "shsub",       "uhsub",       "shsub",       "uhsub",
        "sqsub",       "uqsub",       "sqsub",       "uqsub",
        "cmgt",        "cmhi",        "cmgt",        "cmhi",
        "cmge",        "cmhs",        "cmge",        "cmhs",
        "sshl",        "ushl",        "sshl",        "ushl",
        "sqshl",       "uqshl",       "sqshl",       "uqshl",
        "srshl",       "urshl",       "srshl",       "urshl",
        "sqrshl",      "uqrshl",      "sqrshl",      "uqrshl",
        "smax",        "umax",        "smax",        "umax",
        "smin",        "umin",        "smin",        "umin",
        "sabd",        "uabd",        "sabd",        "uabd",
        "saba",        "uaba",        "saba",        "uaba",
        "add",         "sub",         "add",         "sub",
        "cmtst",       "cmeq",        "cmtst",       "cmeq",
        "mla",         "mls",         "mla",         "mls",
        "mul",         "pmul",        "mul",         "pmul",
        "smaxp",       "umaxp",       "smaxp",       "umaxp",
        "sminp",       "uminp",       "sminp",       "uminp",
        "sqdmulh",     "sqrdmulh",    "sqdmulh",     "sqrdmulh",
        "addp",        "unallocated", "addp",        "unallocated",
        "fmaxnm",      "fmaxnmp",     "fminnm",      "fminnmp",
        "fmla",        "unallocated", "fmls",        "unallocated",
        "fadd",        "faddp",       "fsub",        "fabd",
        "fmulx",       "fmul",        "unallocated", "unallocated",
        "fcmeq",       "fcmge",       "unallocated", "fcmgt",
        "unallocated", "facge",       "unallocated", "facgt",
        "fmax",        "fmaxp",       "fmin",        "fminp",
        "frecps",      "fdiv",        "frsqrts",     "unallocated"};

    // Operation is determined by the opcode bits (15-11), the top bit of
    // size (23) and the U bit (29).
    unsigned index =
        (instr->Bits(15, 11) << 2) | (instr->Bit(23) << 1) | instr->Bit(29);
    DCHECK_LT(index, arraysize(mnemonics));
    mnemonic = mnemonics[index];
    // Assert that index is not one of the previously handled logical
    // instructions.
    DCHECK_NOT_NULL(mnemonic);

    if (instr->Mask(NEON3SameFPFMask) == NEON3SameFPFixed) {
      nfd.SetFormatMaps(nfd.FPFormatMap());
    }
  }
  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEON2RegMisc(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "'Vd.%s, 'Vn.%s";
  const char* form_cmp_zero = "'Vd.%s, 'Vn.%s, #0";
  const char* form_fcmp_zero = "'Vd.%s, 'Vn.%s, #0.0";
  NEONFormatDecoder nfd(instr);

  static const NEONFormatMap map_lp_ta = {
      {23, 22, 30}, {NF_4H, NF_8H, NF_2S, NF_4S, NF_1D, NF_2D}};

  static const NEONFormatMap map_cvt_ta = {{22}, {NF_4S, NF_2D}};

  static const NEONFormatMap map_cvt_tb = {{22, 30},
                                           {NF_4H, NF_8H, NF_2S, NF_4S}};

  if (instr->Mask(NEON2RegMiscOpcode) <= NEON_NEG_opcode) {
    // These instructions all use a two bit size field, except NOT and RBIT,
    // which use the field to encode the operation.
    switch (instr->Mask(NEON2RegMiscMask)) {
      case NEON_REV64:
        mnemonic = "rev64";
        break;
      case NEON_REV32:
        mnemonic = "rev32";
        break;
      case NEON_REV16:
        mnemonic = "rev16";
        break;
      case NEON_SADDLP:
        mnemonic = "saddlp";
        nfd.SetFormatMap(0, &map_lp_ta);
        break;
      case NEON_UADDLP:
        mnemonic = "uaddlp";
        nfd.SetFormatMap(0, &map_lp_ta);
        break;
      case NEON_SUQADD:
        mnemonic = "suqadd";
        break;
      case NEON_USQADD:
        mnemonic = "usqadd";
        break;
      case NEON_CLS:
        mnemonic = "cls";
        break;
      case NEON_CLZ:
        mnemonic = "clz";
        break;
      case NEON_CNT:
        mnemonic = "cnt";
        break;
      case NEON_SADALP:
        mnemonic = "sadalp";
        nfd.SetFormatMap(0, &map_lp_ta);
        break;
      case NEON_UADALP:
        mnemonic = "uadalp";
        nfd.SetFormatMap(0, &map_lp_ta);
        break;
      case NEON_SQABS:
        mnemonic = "sqabs";
        break;
      case NEON_SQNEG:
        mnemonic = "sqneg";
        break;
      case NEON_CMGT_zero:
        mnemonic = "cmgt";
        form = form_cmp_zero;
        break;
      case NEON_CMGE_zero:
        mnemonic = "cmge";
        form = form_cmp_zero;
        break;
      case NEON_CMEQ_zero:
        mnemonic = "cmeq";
        form = form_cmp_zero;
        break;
      case NEON_CMLE_zero:
        mnemonic = "cmle";
        form = form_cmp_zero;
        break;
      case NEON_CMLT_zero:
        mnemonic = "cmlt";
        form = form_cmp_zero;
        break;
      case NEON_ABS:
        mnemonic = "abs";
        break;
      case NEON_NEG:
        mnemonic = "neg";
        break;
      case NEON_RBIT_NOT:
        switch (instr->FPType()) {
          case 0:
            mnemonic = "mvn";
            break;
          case 1:
            mnemonic = "rbit";
            break;
          default:
            form = "(NEON2RegMisc)";
        }
        nfd.SetFormatMaps(nfd.LogicalFormatMap());
        break;
    }
  } else {
    // These instructions all use a one bit size field, except XTN, SQXTUN,
    // SHLL, SQXTN and UQXTN, which use a two bit size field.
    nfd.SetFormatMaps(nfd.FPFormatMap());
    switch (instr->Mask(NEON2RegMiscFPMask)) {
      case NEON_FABS:
        mnemonic = "fabs";
        break;
      case NEON_FNEG:
        mnemonic = "fneg";
        break;
      case NEON_FCVTN:
        mnemonic = instr->Mask(NEON_Q) ? "fcvtn2" : "fcvtn";
        nfd.SetFormatMap(0, &map_cvt_tb);
        nfd.SetFormatMap(1, &map_cvt_ta);
        break;
      case NEON_FCVTXN:
        mnemonic = instr->Mask(NEON_Q) ? "fcvtxn2" : "fcvtxn";
        nfd.SetFormatMap(0, &map_cvt_tb);
        nfd.SetFormatMap(1, &map_cvt_ta);
        break;
      case NEON_FCVTL:
        mnemonic = instr->Mask(NEON_Q) ? "fcvtl2" : "fcvtl";
        nfd.SetFormatMap(0, &map_cvt_ta);
        nfd.SetFormatMap(1, &map_cvt_tb);
        break;
      case NEON_FRINTN:
        mnemonic = "frintn";
        break;
      case NEON_FRINTA:
        mnemonic = "frinta";
        break;
      case NEON_FRINTP:
        mnemonic = "frintp";
        break;
      case NEON_FRINTM:
        mnemonic = "frintm";
        break;
      case NEON_FRINTX:
        mnemonic = "frintx";
        break;
      case NEON_FRINTZ:
        mnemonic = "frintz";
        break;
      case NEON_FRINTI:
        mnemonic = "frinti";
        break;
      case NEON_FCVTNS:
        mnemonic = "fcvtns";
        break;
      case NEON_FCVTNU:
        mnemonic = "fcvtnu";
        break;
      case NEON_FCVTPS:
        mnemonic = "fcvtps";
        break;
      case NEON_FCVTPU:
        mnemonic = "fcvtpu";
        break;
      case NEON_FCVTMS:
        mnemonic = "fcvtms";
        break;
      case NEON_FCVTMU:
        mnemonic = "fcvtmu";
        break;
      case NEON_FCVTZS:
        mnemonic = "fcvtzs";
        break;
      case NEON_FCVTZU:
        mnemonic = "fcvtzu";
        break;
      case NEON_FCVTAS:
        mnemonic = "fcvtas";
        break;
      case NEON_FCVTAU:
        mnemonic = "fcvtau";
        break;
      case NEON_FSQRT:
        mnemonic = "fsqrt";
        break;
      case NEON_SCVTF:
        mnemonic = "scvtf";
        break;
      case NEON_UCVTF:
        mnemonic = "ucvtf";
        break;
      case NEON_URSQRTE:
        mnemonic = "ursqrte";
        break;
      case NEON_URECPE:
        mnemonic = "urecpe";
        break;
      case NEON_FRSQRTE:
        mnemonic = "frsqrte";
        break;
      case NEON_FRECPE:
        mnemonic = "frecpe";
        break;
      case NEON_FCMGT_zero:
        mnemonic = "fcmgt";
        form = form_fcmp_zero;
        break;
      case NEON_FCMGE_zero:
        mnemonic = "fcmge";
        form = form_fcmp_zero;
        break;
      case NEON_FCMEQ_zero:
        mnemonic = "fcmeq";
        form = form_fcmp_zero;
        break;
      case NEON_FCMLE_zero:
        mnemonic = "fcmle";
        form = form_fcmp_zero;
        break;
      case NEON_FCMLT_zero:
        mnemonic = "fcmlt";
        form = form_fcmp_zero;
        break;
      default:
        if ((NEON_XTN_opcode <= instr->Mask(NEON2RegMiscOpcode)) &&
            (instr->Mask(NEON2RegMiscOpcode) <= NEON_UQXTN_opcode)) {
          nfd.SetFormatMap(0, nfd.IntegerFormatMap());
          nfd.SetFormatMap(1, nfd.LongIntegerFormatMap());

          switch (instr->Mask(NEON2RegMiscMask)) {
            case NEON_XTN:
              mnemonic = "xtn";
              break;
            case NEON_SQXTN:
              mnemonic = "sqxtn";
              break;
            case NEON_UQXTN:
              mnemonic = "uqxtn";
              break;
            case NEON_SQXTUN:
              mnemonic = "sqxtun";
              break;
            case NEON_SHLL:
              mnemonic = "shll";
              nfd.SetFormatMap(0, nfd.LongIntegerFormatMap());
              nfd.SetFormatMap(1, nfd.IntegerFormatMap());
              switch (instr->NEONSize()) {
                case 0:
                  form = "'Vd.%s, 'Vn.%s, #8";
                  break;
                case 1:
                  form = "'Vd.%s, 'Vn.%s, #16";
                  break;
                case 2:
                  form = "'Vd.%s, 'Vn.%s, #32";
                  break;
                default:
                  Format(instr, "unallocated", "(NEON2RegMisc)");
                  return;
              }
          }
          Format(instr, nfd.Mnemonic(mnemonic), nfd.Substitute(form));
          return;
        } else {
          form = "(NEON2RegMisc)";
        }
    }
  }
  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEON3Different(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "'Vd.%s, 'Vn.%s, 'Vm.%s";

  NEONFormatDecoder nfd(instr);
  nfd.SetFormatMap(0, nfd.LongIntegerFormatMap());

  // Ignore the Q bit. Appending a "2" suffix is handled later.
  switch (instr->Mask(NEON3DifferentMask) & ~NEON_Q) {
    case NEON_PMULL:
      mnemonic = "pmull";
      break;
    case NEON_SABAL:
      mnemonic = "sabal";
      break;
    case NEON_SABDL:
      mnemonic = "sabdl";
      break;
    case NEON_SADDL:
      mnemonic = "saddl";
      break;
    case NEON_SMLAL:
      mnemonic = "smlal";
      break;
    case NEON_SMLSL:
      mnemonic = "smlsl";
      break;
    case NEON_SMULL:
      mnemonic = "smull";
      break;
    case NEON_SSUBL:
      mnemonic = "ssubl";
      break;
    case NEON_SQDMLAL:
      mnemonic = "sqdmlal";
      break;
    case NEON_SQDMLSL:
      mnemonic = "sqdmlsl";
      break;
    case NEON_SQDMULL:
      mnemonic = "sqdmull";
      break;
    case NEON_UABAL:
      mnemonic = "uabal";
      break;
    case NEON_UABDL:
      mnemonic = "uabdl";
      break;
    case NEON_UADDL:
      mnemonic = "uaddl";
      break;
    case NEON_UMLAL:
      mnemonic = "umlal";
      break;
    case NEON_UMLSL:
      mnemonic = "umlsl";
      break;
    case NEON_UMULL:
      mnemonic = "umull";
      break;
    case NEON_USUBL:
      mnemonic = "usubl";
      break;
    case NEON_SADDW:
      mnemonic = "saddw";
      nfd.SetFormatMap(1, nfd.LongIntegerFormatMap());
      break;
    case NEON_SSUBW:
      mnemonic = "ssubw";
      nfd.SetFormatMap(1, nfd.LongIntegerFormatMap());
      break;
    case NEON_UADDW:
      mnemonic = "uaddw";
      nfd.SetFormatMap(1, nfd.LongIntegerFormatMap());
      break;
    case NEON_USUBW:
      mnemonic = "usubw";
      nfd.SetFormatMap(1, nfd.LongIntegerFormatMap());
      break;
    case NEON_ADDHN:
      mnemonic = "addhn";
      nfd.SetFormatMaps(nfd.LongIntegerFormatMap());
      nfd.SetFormatMap(0, nfd.IntegerFormatMap());
      break;
    case NEON_RADDHN:
      mnemonic = "raddhn";
      nfd.SetFormatMaps(nfd.LongIntegerFormatMap());
      nfd.SetFormatMap(0, nfd.IntegerFormatMap());
      break;
    case NEON_RSUBHN:
      mnemonic = "rsubhn";
      nfd.SetFormatMaps(nfd.LongIntegerFormatMap());
      nfd.SetFormatMap(0, nfd.IntegerFormatMap());
      break;
    case NEON_SUBHN:
      mnemonic = "subhn";
      nfd.SetFormatMaps(nfd.LongIntegerFormatMap());
      nfd.SetFormatMap(0, nfd.IntegerFormatMap());
      break;
    default:
      form = "(NEON3Different)";
  }
  Format(instr, nfd.Mnemonic(mnemonic), nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEONAcrossLanes(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "%sd, 'Vn.%s";

  NEONFormatDecoder nfd(instr, NEONFormatDecoder::ScalarFormatMap(),
                        NEONFormatDecoder::IntegerFormatMap());

  if (instr->Mask(NEONAcrossLanesFPFMask) == NEONAcrossLanesFPFixed) {
    nfd.SetFormatMap(0, nfd.FPScalarFormatMap());
    nfd.SetFormatMap(1, nfd.FPFormatMap());
    switch (instr->Mask(NEONAcrossLanesFPMask)) {
      case NEON_FMAXV:
        mnemonic = "fmaxv";
        break;
      case NEON_FMINV:
        mnemonic = "fminv";
        break;
      case NEON_FMAXNMV:
        mnemonic = "fmaxnmv";
        break;
      case NEON_FMINNMV:
        mnemonic = "fminnmv";
        break;
      default:
        form = "(NEONAcrossLanes)";
        break;
    }
  } else if (instr->Mask(NEONAcrossLanesFMask) == NEONAcrossLanesFixed) {
    switch (instr->Mask(NEONAcrossLanesMask)) {
      case NEON_ADDV:
        mnemonic = "addv";
        break;
      case NEON_SMAXV:
        mnemonic = "smaxv";
        break;
      case NEON_SMINV:
        mnemonic = "sminv";
        break;
      case NEON_UMAXV:
        mnemonic = "umaxv";
        break;
      case NEON_UMINV:
        mnemonic = "uminv";
        break;
      case NEON_SADDLV:
        mnemonic = "saddlv";
        nfd.SetFormatMap(0, nfd.LongScalarFormatMap());
        break;
      case NEON_UADDLV:
        mnemonic = "uaddlv";
        nfd.SetFormatMap(0, nfd.LongScalarFormatMap());
        break;
      default:
        form = "(NEONAcrossLanes)";
        break;
    }
  }
  Format(instr, mnemonic,
         nfd.Substitute(form, NEONFormatDecoder::kPlaceholder,
                        NEONFormatDecoder::kFormat));
}

void DisassemblingDecoder::VisitNEONByIndexedElement(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  bool l_instr = false;
  bool fp_instr = false;

  const char* form = "'Vd.%s, 'Vn.%s, 'Ve.%s['IVByElemIndex]";

  static const NEONFormatMap map_ta = {{23, 22}, {NF_UNDEF, NF_4S, NF_2D}};
  NEONFormatDecoder nfd(instr, &map_ta, NEONFormatDecoder::IntegerFormatMap(),
                        NEONFormatDecoder::ScalarFormatMap());

  switch (instr->Mask(NEONByIndexedElementMask)) {
    case NEON_SMULL_byelement:
      mnemonic = "smull";
      l_instr = true;
      break;
    case NEON_UMULL_byelement:
      mnemonic = "umull";
      l_instr = true;
      break;
    case NEON_SMLAL_byelement:
      mnemonic = "smlal";
      l_instr = true;
      break;
    case NEON_UMLAL_byelement:
      mnemonic = "umlal";
      l_instr = true;
      break;
    case NEON_SMLSL_byelement:
      mnemonic = "smlsl";
      l_instr = true;
      break;
    case NEON_UMLSL_byelement:
      mnemonic = "umlsl";
      l_instr = true;
      break;
    case NEON_SQDMULL_byelement:
      mnemonic = "sqdmull";
      l_instr = true;
      break;
    case NEON_SQDMLAL_byelement:
      mnemonic = "sqdmlal";
      l_instr = true;
      break;
    case NEON_SQDMLSL_byelement:
      mnemonic = "sqdmlsl";
      l_instr = true;
      break;
    case NEON_MUL_byelement:
      mnemonic = "mul";
      break;
    case NEON_MLA_byelement:
      mnemonic = "mla";
      break;
    case NEON_MLS_byelement:
      mnemonic = "mls";
      break;
    case NEON_SQDMULH_byelement:
      mnemonic = "sqdmulh";
      break;
    case NEON_SQRDMULH_byelement:
      mnemonic = "sqrdmulh";
      break;
    default:
      switch (instr->Mask(NEONByIndexedElementFPMask)) {
        case NEON_FMUL_byelement:
          mnemonic = "fmul";
          fp_instr = true;
          break;
        case NEON_FMLA_byelement:
          mnemonic = "fmla";
          fp_instr = true;
          break;
        case NEON_FMLS_byelement:
          mnemonic = "fmls";
          fp_instr = true;
          break;
        case NEON_FMULX_byelement:
          mnemonic = "fmulx";
          fp_instr = true;
          break;
      }
  }

  if (l_instr) {
    Format(instr, nfd.Mnemonic(mnemonic), nfd.Substitute(form));
  } else if (fp_instr) {
    nfd.SetFormatMap(0, nfd.FPFormatMap());
    Format(instr, mnemonic, nfd.Substitute(form));
  } else {
    nfd.SetFormatMap(0, nfd.IntegerFormatMap());
    Format(instr, mnemonic, nfd.Substitute(form));
  }
}

void DisassemblingDecoder::VisitNEONCopy(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "(NEONCopy)";

  NEONFormatDecoder nfd(instr, NEONFormatDecoder::TriangularFormatMap(),
                        NEONFormatDecoder::TriangularScalarFormatMap());

  if (instr->Mask(NEONCopyInsElementMask) == NEON_INS_ELEMENT) {
    mnemonic = "mov";
    nfd.SetFormatMap(0, nfd.TriangularScalarFormatMap());
    form = "'Vd.%s['IVInsIndex1], 'Vn.%s['IVInsIndex2]";
  } else if (instr->Mask(NEONCopyInsGeneralMask) == NEON_INS_GENERAL) {
    mnemonic = "mov";
    nfd.SetFormatMap(0, nfd.TriangularScalarFormatMap());
    if (nfd.GetVectorFormat() == kFormatD) {
      form = "'Vd.%s['IVInsIndex1], 'Xn";
    } else {
      form = "'Vd.%s['IVInsIndex1], 'Wn";
    }
  } else if (instr->Mask(NEONCopyUmovMask) == NEON_UMOV) {
    if (instr->Mask(NEON_Q) || ((instr->ImmNEON5() & 7) == 4)) {
      mnemonic = "mov";
    } else {
      mnemonic = "umov";
    }
    nfd.SetFormatMap(0, nfd.TriangularScalarFormatMap());
    if (nfd.GetVectorFormat() == kFormatD) {
      form = "'Xd, 'Vn.%s['IVInsIndex1]";
    } else {
      form = "'Wd, 'Vn.%s['IVInsIndex1]";
    }
  } else if (instr->Mask(NEONCopySmovMask) == NEON_SMOV) {
    mnemonic = "smov";
    nfd.SetFormatMap(0, nfd.TriangularScalarFormatMap());
    form = "'Rdq, 'Vn.%s['IVInsIndex1]";
  } else if (instr->Mask(NEONCopyDupElementMask) == NEON_DUP_ELEMENT) {
    mnemonic = "dup";
    form = "'Vd.%s, 'Vn.%s['IVInsIndex1]";
  } else if (instr->Mask(NEONCopyDupGeneralMask) == NEON_DUP_GENERAL) {
    mnemonic = "dup";
    if (nfd.GetVectorFormat() == kFormat2D) {
      form = "'Vd.%s, 'Xn";
    } else {
      form = "'Vd.%s, 'Wn";
    }
  }
  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEONExtract(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "(NEONExtract)";
  NEONFormatDecoder nfd(instr, NEONFormatDecoder::LogicalFormatMap());
  if (instr->Mask(NEONExtractMask) == NEON_EXT) {
    mnemonic = "ext";
    form = "'Vd.%s, 'Vn.%s, 'Vm.%s, 'IVExtract";
  }
  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEONLoadStoreMultiStruct(Instruction* instr) {
  const char* mnemonic = nullptr;
  const char* form = nullptr;
  const char* form_1v = "{'Vt.%1$s}, ['Xns]";
  const char* form_2v = "{'Vt.%1$s, 'Vt2.%1$s}, ['Xns]";
  const char* form_3v = "{'Vt.%1$s, 'Vt2.%1$s, 'Vt3.%1$s}, ['Xns]";
  const char* form_4v = "{'Vt.%1$s, 'Vt2.%1$s, 'Vt3.%1$s, 'Vt4.%1$s}, ['Xns]";
  NEONFormatDecoder nfd(instr, NEONFormatDecoder::LoadStoreFormatMap());

  switch (instr->Mask(NEONLoadStoreMultiStructMask)) {
    case NEON_LD1_1v:
      mnemonic = "ld1";
      form = form_1v;
      break;
    case NEON_LD1_2v:
      mnemonic = "ld1";
      form = form_2v;
      break;
    case NEON_LD1_3v:
      mnemonic = "ld1";
      form = form_3v;
      break;
    case NEON_LD1_4v:
      mnemonic = "ld1";
      form = form_4v;
      break;
    case NEON_LD2:
      mnemonic = "ld2";
      form = form_2v;
      break;
    case NEON_LD3:
      mnemonic = "ld3";
      form = form_3v;
      break;
    case NEON_LD4:
      mnemonic = "ld4";
      form = form_4v;
      break;
    case NEON_ST1_1v:
      mnemonic = "st1";
      form = form_1v;
      break;
    case NEON_ST1_2v:
      mnemonic = "st1";
      form = form_2v;
      break;
    case NEON_ST1_3v:
      mnemonic = "st1";
      form = form_3v;
      break;
    case NEON_ST1_4v:
      mnemonic = "st1";
      form = form_4v;
      break;
    case NEON_ST2:
      mnemonic = "st2";
      form = form_2v;
      break;
    case NEON_ST3:
      mnemonic = "st3";
      form = form_3v;
      break;
    case NEON_ST4:
      mnemonic = "st4";
      form = form_4v;
      break;
    default:
      break;
  }

  // Work out unallocated encodings.
  bool allocated = (mnemonic != nullptr);
  switch (instr->Mask(NEONLoadStoreMultiStructMask)) {
    case NEON_LD2:
    case NEON_LD3:
    case NEON_LD4:
    case NEON_ST2:
    case NEON_ST3:
    case NEON_ST4:
      // LD[2-4] and ST[2-4] cannot use .1d format.
      allocated = (instr->NEONQ() != 0) || (instr->NEONLSSize() != 3);
      break;
    default:
      break;
  }
  if (allocated) {
    DCHECK_NOT_NULL(mnemonic);
    DCHECK_NOT_NULL(form);
  } else {
    mnemonic = "unallocated";
    form = "(NEONLoadStoreMultiStruct)";
  }

  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEONLoadStoreMultiStructPostIndex(
    Instruction* instr) {
  const char* mnemonic = nullptr;
  const char* form = nullptr;
  const char* form_1v = "{'Vt.%1$s}, ['Xns], 'Xmr1";
  const char* form_2v = "{'Vt.%1$s, 'Vt2.%1$s}, ['Xns], 'Xmr2";
  const char* form_3v = "{'Vt.%1$s, 'Vt2.%1$s, 'Vt3.%1$s}, ['Xns], 'Xmr3";
  const char* form_4v =
      "{'Vt.%1$s, 'Vt2.%1$s, 'Vt3.%1$s, 'Vt4.%1$s}, ['Xns], 'Xmr4";
  NEONFormatDecoder nfd(instr, NEONFormatDecoder::LoadStoreFormatMap());

  switch (instr->Mask(NEONLoadStoreMultiStructPostIndexMask)) {
    case NEON_LD1_1v_post:
      mnemonic = "ld1";
      form = form_1v;
      break;
    case NEON_LD1_2v_post:
      mnemonic = "ld1";
      form = form_2v;
      break;
    case NEON_LD1_3v_post:
      mnemonic = "ld1";
      form = form_3v;
      break;
    case NEON_LD1_4v_post:
      mnemonic = "ld1";
      form = form_4v;
      break;
    case NEON_LD2_post:
      mnemonic = "ld2";
      form = form_2v;
      break;
    case NEON_LD3_post:
      mnemonic = "ld3";
      form = form_3v;
      break;
    case NEON_LD4_post:
      mnemonic = "ld4";
      form = form_4v;
      break;
    case NEON_ST1_1v_post:
      mnemonic = "st1";
      form = form_1v;
      break;
    case NEON_ST1_2v_post:
      mnemonic = "st1";
      form = form_2v;
      break;
    case NEON_ST1_3v_post:
      mnemonic = "st1";
      form = form_3v;
      break;
    case NEON_ST1_4v_post:
      mnemonic = "st1";
      form = form_4v;
      break;
    case NEON_ST2_post:
      mnemonic = "st2";
      form = form_2v;
      break;
    case NEON_ST3_post:
      mnemonic = "st3";
      form = form_3v;
      break;
    case NEON_ST4_post:
      mnemonic = "st4";
      form = form_4v;
      break;
    default:
      break;
  }

  // Work out unallocated encodings.
  bool allocated = (mnemonic != nullptr);
  switch (instr->Mask(NEONLoadStoreMultiStructPostIndexMask)) {
    case NEON_LD2_post:
    case NEON_LD3_post:
    case NEON_LD4_post:
    case NEON_ST2_post:
    case NEON_ST3_post:
    case NEON_ST4_post:
      // LD[2-4] and ST[2-4] cannot use .1d format.
      allocated = (instr->NEONQ() != 0) || (instr->NEONLSSize() != 3);
      break;
    default:
      break;
  }
  if (allocated) {
    DCHECK_NOT_NULL(mnemonic);
    DCHECK_NOT_NULL(form);
  } else {
    mnemonic = "unallocated";
    form = "(NEONLoadStoreMultiStructPostIndex)";
  }

  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEONLoadStoreSingleStruct(Instruction* instr) {
  const char* mnemonic = nullptr;
  const char* form = nullptr;

  const char* form_1b = "{'Vt.b}['IVLSLane0], ['Xns]";
  const char* form_1h = "{'Vt.h}['IVLSLane1], ['Xns]";
  const char* form_1s = "{'Vt.s}['IVLSLane2], ['Xns]";
  const char* form_1d = "{'Vt.d}['IVLSLane3], ['Xns]";
  NEONFormatDecoder nfd(instr, NEONFormatDecoder::LoadStoreFormatMap());

  switch (instr->Mask(NEONLoadStoreSingleStructMask)) {
    case NEON_LD1_b:
      mnemonic = "ld1";
      form = form_1b;
      break;
    case NEON_LD1_h:
      mnemonic = "ld1";
      form = form_1h;
      break;
    case NEON_LD1_s:
      mnemonic = "ld1";
      static_assert((NEON_LD1_s | (1 << NEONLSSize_offset)) == NEON_LD1_d,
                    "LSB of size distinguishes S and D registers.");
      form = ((instr->NEONLSSize() & 1) == 0) ? form_1s : form_1d;
      break;
    case NEON_ST1_b:
      mnemonic = "st1";
      form = form_1b;
      break;
    case NEON_ST1_h:
      mnemonic = "st1";
      form = form_1h;
      break;
    case NEON_ST1_s:
      mnemonic = "st1";
      static_assert((NEON_ST1_s | (1 << NEONLSSize_offset)) == NEON_ST1_d,
                    "LSB of size distinguishes S and D registers.");
      form = ((instr->NEONLSSize() & 1) == 0) ? form_1s : form_1d;
      break;
    case NEON_LD1R:
      mnemonic = "ld1r";
      form = "{'Vt.%s}, ['Xns]";
      break;
    case NEON_LD2_b:
    case NEON_ST2_b:
      mnemonic = (instr->NEONLoad() == 1) ? "ld2" : "st2";
      form = "{'Vt.b, 'Vt2.b}['IVLSLane0], ['Xns]";
      break;
    case NEON_LD2_h:
    case NEON_ST2_h:
      mnemonic = (instr->NEONLoad() == 1) ? "ld2" : "st2";
      form = "{'Vt.h, 'Vt2.h}['IVLSLane1], ['Xns]";
      break;
    case NEON_LD2_s:
    case NEON_ST2_s:
      static_assert((NEON_ST2_s | (1 << NEONLSSize_offset)) == NEON_ST2_d,
                    "LSB of size distinguishes S and D registers.");
      static_assert((NEON_LD2_s | (1 << NEONLSSize_offset)) == NEON_LD2_d,
                    "LSB of size distinguishes S and D registers.");
      mnemonic = (instr->NEONLoad() == 1) ? "ld2" : "st2";
      if ((instr->NEONLSSize() & 1) == 0) {
        form = "{'Vt.s, 'Vt2.s}['IVLSLane2], ['Xns]";
      } else {
        form = "{'Vt.d, 'Vt2.d}['IVLSLane3], ['Xns]";
      }
      break;
    case NEON_LD2R:
      mnemonic = "ld2r";
      form = "{'Vt.%s, 'Vt2.%s}, ['Xns]";
      break;
    case NEON_LD3_b:
    case NEON_ST3_b:
      mnemonic = (instr->NEONLoad() == 1) ? "ld3" : "st3";
      form = "{'Vt.b, 'Vt2.b, 'Vt3.b}['IVLSLane0], ['Xns]";
      break;
    case NEON_LD3_h:
    case NEON_ST3_h:
      mnemonic = (instr->NEONLoad() == 1) ? "ld3" : "st3";
      form = "{'Vt.h, 'Vt2.h, 'Vt3.h}['IVLSLane1], ['Xns]";
      break;
    case NEON_LD3_s:
    case NEON_ST3_s:
      mnemonic = (instr->NEONLoad() == 1) ? "ld3" : "st3";
      if ((instr->NEONLSSize() & 1) == 0) {
        form = "{'Vt.s, 'Vt2.s, 'Vt3.s}['IVLSLane2], ['Xns]";
      } else {
        form = "{'Vt.d, 'Vt2.d, 'Vt3.d}['IVLSLane3], ['Xns]";
      }
      break;
    case NEON_LD3R:
      mnemonic = "ld3r";
      form = "{'Vt.%s, 'Vt2.%s, 'Vt3.%s}, ['Xns]";
      break;
    case NEON_LD4_b:
    case NEON_ST4_b:
      mnemonic = (instr->NEONLoad() == 1) ? "ld4" : "st4";
      form = "{'Vt.b, 'Vt2.b, 'Vt3.b, 'Vt4.b}['IVLSLane0], ['Xns]";
      break;
    case NEON_LD4_h:
    case NEON_ST4_h:
      mnemonic = (instr->NEONLoad() == 1) ? "ld4" : "st4";
      form = "{'Vt.h, 'Vt2.h, 'Vt3.h, 'Vt4.h}['IVLSLane1], ['Xns]";
      break;
    case NEON_LD4_s:
    case NEON_ST4_s:
      static_assert((NEON_LD4_s | (1 << NEONLSSize_offset)) == NEON_LD4_d,
                    "LSB of size distinguishes S and D registers.");
      static_assert((NEON_ST4_s | (1 << NEONLSSize_offset)) == NEON_ST4_d,
                    "LSB of size distinguishes S and D registers.");
      mnemonic = (instr->NEONLoad() == 1) ? "ld4" : "st4";
      if ((instr->NEONLSSize() & 1) == 0) {
        form = "{'Vt.s, 'Vt2.s, 'Vt3.s, 'Vt4.s}['IVLSLane2], ['Xns]";
      } else {
        form = "{'Vt.d, 'Vt2.d, 'Vt3.d, 'Vt4.d}['IVLSLane3], ['Xns]";
      }
      break;
    case NEON_LD4R:
      mnemonic = "ld4r";
      form = "{'Vt.%1$s, 'Vt2.%1$s, 'Vt3.%1$s, 'Vt4.%1$s}, ['Xns]";
      break;
    default:
      break;
  }

  // Work out unallocated encodings.
  bool allocated = (mnemonic != nullptr);
  switch (instr->Mask(NEONLoadStoreSingleStructMask)) {
    case NEON_LD1_h:
    case NEON_LD2_h:
    case NEON_LD3_h:
    case NEON_LD4_h:
    case NEON_ST1_h:
    case NEON_ST2_h:
    case NEON_ST3_h:
    case NEON_ST4_h:
      DCHECK(allocated);
      allocated = ((instr->NEONLSSize() & 1) == 0);
      break;
    case NEON_LD1_s:
    case NEON_LD2_s:
    case NEON_LD3_s:
    case NEON_LD4_s:
    case NEON_ST1_s:
    case NEON_ST2_s:
    case NEON_ST3_s:
    case NEON_ST4_s:
      DCHECK(allocated);
      allocated = (instr->NEONLSSize() <= 1) &&
                  ((instr->NEONLSSize() == 0) || (instr->NEONS() == 0));
      break;
    case NEON_LD1R:
    case NEON_LD2R:
    case NEON_LD3R:
    case NEON_LD4R:
      DCHECK(allocated);
      allocated = (instr->NEONS() == 0);
      break;
    default:
      break;
  }
  if (allocated) {
    DCHECK_NOT_NULL(mnemonic);
    DCHECK_NOT_NULL(form);
  } else {
    mnemonic = "unallocated";
    form = "(NEONLoadStoreSingleStruct)";
  }

  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEONLoadStoreSingleStructPostIndex(
    Instruction* instr) {
  const char* mnemonic = nullptr;
  const char* form = nullptr;

  const char* form_1b = "{'Vt.b}['IVLSLane0], ['Xns], 'Xmb1";
  const char* form_1h = "{'Vt.h}['IVLSLane1], ['Xns], 'Xmb2";
  const char* form_1s = "{'Vt.s}['IVLSLane2], ['Xns], 'Xmb4";
  const char* form_1d = "{'Vt.d}['IVLSLane3], ['Xns], 'Xmb8";
  NEONFormatDecoder nfd(instr, NEONFormatDecoder::LoadStoreFormatMap());

  switch (instr->Mask(NEONLoadStoreSingleStructPostIndexMask)) {
    case NEON_LD1_b_post:
      mnemonic = "ld1";
      form = form_1b;
      break;
    case NEON_LD1_h_post:
      mnemonic = "ld1";
      form = form_1h;
      break;
    case NEON_LD1_s_post:
      mnemonic = "ld1";
      static_assert((NEON_LD1_s | (1 << NEONLSSize_offset)) == NEON_LD1_d,
                    "LSB of size distinguishes S and D registers.");
      form = ((instr->NEONLSSize() & 1) == 0) ? form_1s : form_1d;
      break;
    case NEON_ST1_b_post:
      mnemonic = "st1";
      form = form_1b;
      break;
    case NEON_ST1_h_post:
      mnemonic = "st1";
      form = form_1h;
      break;
    case NEON_ST1_s_post:
      mnemonic = "st1";
      static_assert((NEON_ST1_s | (1 << NEONLSSize_offset)) == NEON_ST1_d,
                    "LSB of size distinguishes S and D registers.");
      form = ((instr->NEONLSSize() & 1) == 0) ? form_1s : form_1d;
      break;
    case NEON_LD1R_post:
      mnemonic = "ld1r";
      form = "{'Vt.%s}, ['Xns], 'Xmz1";
      break;
    case NEON_LD2_b_post:
    case NEON_ST2_b_post:
      mnemonic = (instr->NEONLoad() == 1) ? "ld2" : "st2";
      form = "{'Vt.b, 'Vt2.b}['IVLSLane0], ['Xns], 'Xmb2";
      break;
    case NEON_ST2_h_post:
    case NEON_LD2_h_post:
      mnemonic = (instr->NEONLoad() == 1) ? "ld2" : "st2";
      form = "{'Vt.h, 'Vt2.h}['IVLSLane1], ['Xns], 'Xmb4";
      break;
    case NEON_LD2_s_post:
    case NEON_ST2_s_post:
      mnemonic = (instr->NEONLoad() == 1) ? "ld2" : "st2";
      if ((instr->NEONLSSize() & 1) == 0)
        form = "{'Vt.s, 'Vt2.s}['IVLSLane2], ['Xns], 'Xmb8";
      else
        form = "{'Vt.d, 'Vt2.d}['IVLSLane3], ['Xns], 'Xmb16";
      break;
    case NEON_LD2R_post:
      mnemonic = "ld2r";
      form = "{'Vt.%s, 'Vt2.%s}, ['Xns], 'Xmz2";
      break;
    case NEON_LD3_b_post:
    case NEON_ST3_b_post:
      mnemonic = (instr->NEONLoad() == 1) ? "ld3" : "st3";
      form = "{'Vt.b, 'Vt2.b, 'Vt3.b}['IVLSLane0], ['Xns], 'Xmb3";
      break;
    case NEON_LD3_h_post:
    case NEON_ST3_h_post:
      mnemonic = (instr->NEONLoad() == 1) ? "ld3" : "st3";
      form = "{'Vt.h, 'Vt2.h, 'Vt3.h}['IVLSLane1], ['Xns], 'Xmb6";
      break;
    case NEON_LD3_s_post:
    case NEON_ST3_s_post:
      mnemonic = (instr->NEONLoad() == 1) ? "ld3" : "st3";
      if ((instr->NEONLSSize() & 1) == 0)
        form = "{'Vt.s, 'Vt2.s, 'Vt3.s}['IVLSLane2], ['Xns], 'Xmb12";
      else
        form = "{'Vt.d, 'Vt2.d, 'Vt3.d}['IVLSLane3], ['Xns], 'Xmb24";
      break;
    case NEON_LD3R_post:
      mnemonic = "ld3r";
      form = "{'Vt.%s, 'Vt2.%s, 'Vt3.%s}, ['Xns], 'Xmz3";
      break;
    case NEON_LD4_b_post:
    case NEON_ST4_b_post:
      mnemonic = (instr->NEONLoad() == 1) ? "ld4" : "st4";
      form = "{'Vt.b, 'Vt2.b, 'Vt3.b, 'Vt4.b}['IVLSLane0], ['Xns], 'Xmb4";
      break;
    case NEON_LD4_h_post:
    case NEON_ST4_h_post:
      mnemonic = (instr->NEONLoad()) == 1 ? "ld4" : "st4";
      form = "{'Vt.h, 'Vt2.h, 'Vt3.h, 'Vt4.h}['IVLSLane1], ['Xns], 'Xmb8";
      break;
    case NEON_LD4_s_post:
    case NEON_ST4_s_post:
      mnemonic = (instr->NEONLoad() == 1) ? "ld4" : "st4";
      if ((instr->NEONLSSize() & 1) == 0)
        form = "{'Vt.s, 'Vt2.s, 'Vt3.s, 'Vt4.s}['IVLSLane2], ['Xns], 'Xmb16";
      else
        form = "{'Vt.d, 'Vt2.d, 'Vt3.d, 'Vt4.d}['IVLSLane3], ['Xns], 'Xmb32";
      break;
    case NEON_LD4R_post:
      mnemonic = "ld4r";
      form = "{'Vt.%1$s, 'Vt2.%1$s, 'Vt3.%1$s, 'Vt4.%1$s}, ['Xns], 'Xmz4";
      break;
    default:
      break;
  }

  // Work out unallocated encodings.
  bool allocated = (mnemonic != nullptr);
  switch (instr->Mask(NEONLoadStoreSingleStructPostIndexMask)) {
    case NEON_LD1_h_post:
    case NEON_LD2_h_post:
    case NEON_LD3_h_post:
    case NEON_LD4_h_post:
    case NEON_ST1_h_post:
    case NEON_ST2_h_post:
    case NEON_ST3_h_post:
    case NEON_ST4_h_post:
      DCHECK(allocated);
      allocated = ((instr->NEONLSSize() & 1) == 0);
      break;
    case NEON_LD1_s_post:
    case NEON_LD2_s_post:
    case NEON_LD3_s_post:
    case NEON_LD4_s_post:
    case NEON_ST1_s_post:
    case NEON_ST2_s_post:
    case NEON_ST3_s_post:
    case NEON_ST4_s_post:
      DCHECK(allocated);
      allocated = (instr->NEONLSSize() <= 1) &&
                  ((instr->NEONLSSize() == 0) || (instr->NEONS() == 0));
      break;
    case NEON_LD1R_post:
    case NEON_LD2R_post:
    case NEON_LD3R_post:
    case NEON_LD4R_post:
      DCHECK(allocated);
      allocated = (instr->NEONS() == 0);
      break;
    default:
      break;
  }
  if (allocated) {
    DCHECK_NOT_NULL(mnemonic);
    DCHECK_NOT_NULL(form);
  } else {
    mnemonic = "unallocated";
    form = "(NEONLoadStoreSingleStructPostIndex)";
  }

  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEONModifiedImmediate(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "'Vt.%s, 'IVMIImm8, lsl 'IVMIShiftAmt1";

  int cmode = instr->NEONCmode();
  int cmode_3 = (cmode >> 3) & 1;
  int cmode_2 = (cmode >> 2) & 1;
  int cmode_1 = (cmode >> 1) & 1;
  int cmode_0 = cmode & 1;
  int q = instr->NEONQ();
  int op = instr->NEONModImmOp();

  static const NEONFormatMap map_b = {{30}, {NF_8B, NF_16B}};
  static const NEONFormatMap map_h = {{30}, {NF_4H, NF_8H}};
  static const NEONFormatMap map_s = {{30}, {NF_2S, NF_4S}};
  NEONFormatDecoder nfd(instr, &map_b);

  if (cmode_3 == 0) {
    if (cmode_0 == 0) {
      mnemonic = (op == 1) ? "mvni" : "movi";
    } else {  // cmode<0> == '1'.
      mnemonic = (op == 1) ? "bic" : "orr";
    }
    nfd.SetFormatMap(0, &map_s);
  } else {  // cmode<3> == '1'.
    if (cmode_2 == 0) {
      if (cmode_0 == 0) {
        mnemonic = (op == 1) ? "mvni" : "movi";
      } else {  // cmode<0> == '1'.
        mnemonic = (op == 1) ? "bic" : "orr";
      }
      nfd.SetFormatMap(0, &map_h);
    } else {  // cmode<2> == '1'.
      if (cmode_1 == 0) {
        mnemonic = (op == 1) ? "mvni" : "movi";
        form = "'Vt.%s, 'IVMIImm8, msl 'IVMIShiftAmt2";
        nfd.SetFormatMap(0, &map_s);
      } else {  // cmode<1> == '1'.
        if (cmode_0 == 0) {
          mnemonic = "movi";
          if (op == 0) {
            form = "'Vt.%s, 'IVMIImm8";
          } else {
            form = (q == 0) ? "'Dd, 'IVMIImm" : "'Vt.2d, 'IVMIImm";
          }
        } else {  // cmode<0> == '1'
          mnemonic = "fmov";
          if (op == 0) {
            form = "'Vt.%s, 'IVMIImmFPSingle";
            nfd.SetFormatMap(0, &map_s);
          } else {
            if (q == 1) {
              form = "'Vt.2d, 'IVMIImmFPDouble";
            } else {
              mnemonic = "unallocated";
              form = "(NEONModifiedImmediate)";
            }
          }
        }
      }
    }
  }
  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEONPerm(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "'Vd.%s, 'Vn.%s, 'Vm.%s";
  NEONFormatDecoder nfd(instr);

  switch (instr->Mask(NEONPermMask)) {
    case NEON_TRN1:
      mnemonic = "trn1";
      break;
    case NEON_TRN2:
      mnemonic = "trn2";
      break;
    case NEON_UZP1:
      mnemonic = "uzp1";
      break;
    case NEON_UZP2:
      mnemonic = "uzp2";
      break;
    case NEON_ZIP1:
      mnemonic = "zip1";
      break;
    case NEON_ZIP2:
      mnemonic = "zip2";
      break;
    default:
      form = "(NEONPerm)";
  }
  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEONScalar2RegMisc(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "%sd, %sn";
  const char* form_0 = "%sd, %sn, #0";
  const char* form_fp0 = "%sd, %sn, #0.0";

  NEONFormatDecoder nfd(instr, NEONFormatDecoder::ScalarFormatMap());

  if (instr->Mask(NEON2RegMiscOpcode) <= NEON_NEG_scalar_opcode) {
    // These instructions all use a two bit size field, except NOT and RBIT,
    // which use the field to encode the operation.
    switch (instr->Mask(NEONScalar2RegMiscMask)) {
      case NEON_CMGT_zero_scalar:
        mnemonic = "cmgt";
        form = form_0;
        break;
      case NEON_CMGE_zero_scalar:
        mnemonic = "cmge";
        form = form_0;
        break;
      case NEON_CMLE_zero_scalar:
        mnemonic = "cmle";
        form = form_0;
        break;
      case NEON_CMLT_zero_scalar:
        mnemonic = "cmlt";
        form = form_0;
        break;
      case NEON_CMEQ_zero_scalar:
        mnemonic = "cmeq";
        form = form_0;
        break;
      case NEON_NEG_scalar:
        mnemonic = "neg";
        break;
      case NEON_SQNEG_scalar:
        mnemonic = "sqneg";
        break;
      case NEON_ABS_scalar:
        mnemonic = "abs";
        break;
      case NEON_SQABS_scalar:
        mnemonic = "sqabs";
        break;
      case NEON_SUQADD_scalar:
        mnemonic = "suqadd";
        break;
      case NEON_USQADD_scalar:
        mnemonic = "usqadd";
        break;
      default:
        form = "(NEONScalar2RegMisc)";
    }
  } else {
    // These instructions all use a one bit size field, except SQXTUN, SQXTN
    // and UQXTN, which use a two bit size field.
    nfd.SetFormatMaps(nfd.FPScalarFormatMap());
    switch (instr->Mask(NEONScalar2RegMiscFPMask)) {
      case NEON_FRSQRTE_scalar:
        mnemonic = "frsqrte";
        break;
      case NEON_FRECPE_scalar:
        mnemonic = "frecpe";
        break;
      case NEON_SCVTF_scalar:
        mnemonic = "scvtf";
        break;
      case NEON_UCVTF_scalar:
        mnemonic = "ucvtf";
        break;
      case NEON_FCMGT_zero_scalar:
        mnemonic = "fcmgt";
        form = form_fp0;
        break;
      case NEON_FCMGE_zero_scalar:
        mnemonic = "fcmge";
        form = form_fp0;
        break;
      case NEON_FCMLE_zero_scalar:
        mnemonic = "fcmle";
        form = form_fp0;
        break;
      case NEON_FCMLT_zero_scalar:
        mnemonic = "fcmlt";
        form = form_fp0;
        break;
      case NEON_FCMEQ_zero_scalar:
        mnemonic = "fcmeq";
        form = form_fp0;
        break;
      case NEON_FRECPX_scalar:
        mnemonic = "frecpx";
        break;
      case NEON_FCVTNS_scalar:
        mnemonic = "fcvtns";
        break;
      case NEON_FCVTNU_scalar:
        mnemonic = "fcvtnu";
        break;
      case NEON_FCVTPS_scalar:
        mnemonic = "fcvtps";
        break;
      case NEON_FCVTPU_scalar:
        mnemonic = "fcvtpu";
        break;
      case NEON_FCVTMS_scalar:
        mnemonic = "fcvtms";
        break;
      case NEON_FCVTMU_scalar:
        mnemonic = "fcvtmu";
        break;
      case NEON_FCVTZS_scalar:
        mnemonic = "fcvtzs";
        break;
      case NEON_FCVTZU_scalar:
        mnemonic = "fcvtzu";
        break;
      case NEON_FCVTAS_scalar:
        mnemonic = "fcvtas";
        break;
      case NEON_FCVTAU_scalar:
        mnemonic = "fcvtau";
        break;
      case NEON_FCVTXN_scalar:
        nfd.SetFormatMap(0, nfd.LongScalarFormatMap());
        mnemonic = "fcvtxn";
        break;
      default:
        nfd.SetFormatMap(0, nfd.ScalarFormatMap());
        nfd.SetFormatMap(1, nfd.LongScalarFormatMap());
        switch (instr->Mask(NEONScalar2RegMiscMask)) {
          case NEON_SQXTN_scalar:
            mnemonic = "sqxtn";
            break;
          case NEON_UQXTN_scalar:
            mnemonic = "uqxtn";
            break;
          case NEON_SQXTUN_scalar:
            mnemonic = "sqxtun";
            break;
          default:
            form = "(NEONScalar2RegMisc)";
        }
    }
  }
  Format(instr, mnemonic, nfd.SubstitutePlaceholders(form));
}

void DisassemblingDecoder::VisitNEONScalar3Diff(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "%sd, %sn, %sm";
  NEONFormatDecoder nfd(instr, NEONFormatDecoder::LongScalarFormatMap(),
                        NEONFormatDecoder::ScalarFormatMap());

  switch (instr->Mask(NEONScalar3DiffMask)) {
    case NEON_SQDMLAL_scalar:
      mnemonic = "sqdmlal";
      break;
    case NEON_SQDMLSL_scalar:
      mnemonic = "sqdmlsl";
      break;
    case NEON_SQDMULL_scalar:
      mnemonic = "sqdmull";
      break;
    default:
      form = "(NEONScalar3Diff)";
  }
  Format(instr, mnemonic, nfd.SubstitutePlaceholders(form));
}

void DisassemblingDecoder::VisitNEONScalar3Same(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "%sd, %sn, %sm";
  NEONFormatDecoder nfd(instr, NEONFormatDecoder::ScalarFormatMap());

  if (instr->Mask(NEONScalar3SameFPFMask) == NEONScalar3SameFPFixed) {
    nfd.SetFormatMaps(nfd.FPScalarFormatMap());
    switch (instr->Mask(NEONScalar3SameFPMask)) {
      case NEON_FACGE_scalar:
        mnemonic = "facge";
        break;
      case NEON_FACGT_scalar:
        mnemonic = "facgt";
        break;
      case NEON_FCMEQ_scalar:
        mnemonic = "fcmeq";
        break;
      case NEON_FCMGE_scalar:
        mnemonic = "fcmge";
        break;
      case NEON_FCMGT_scalar:
        mnemonic = "fcmgt";
        break;
      case NEON_FMULX_scalar:
        mnemonic = "fmulx";
        break;
      case NEON_FRECPS_scalar:
        mnemonic = "frecps";
        break;
      case NEON_FRSQRTS_scalar:
        mnemonic = "frsqrts";
        break;
      case NEON_FABD_scalar:
        mnemonic = "fabd";
        break;
      default:
        form = "(NEONScalar3Same)";
    }
  } else {
    switch (instr->Mask(NEONScalar3SameMask)) {
      case NEON_ADD_scalar:
        mnemonic = "add";
        break;
      case NEON_SUB_scalar:
        mnemonic = "sub";
        break;
      case NEON_CMEQ_scalar:
        mnemonic = "cmeq";
        break;
      case NEON_CMGE_scalar:
        mnemonic = "cmge";
        break;
      case NEON_CMGT_scalar:
        mnemonic = "cmgt";
        break;
      case NEON_CMHI_scalar:
        mnemonic = "cmhi";
        break;
      case NEON_CMHS_scalar:
        mnemonic = "cmhs";
        break;
      case NEON_CMTST_scalar:
        mnemonic = "cmtst";
        break;
      case NEON_UQADD_scalar:
        mnemonic = "uqadd";
        break;
      case NEON_SQADD_scalar:
        mnemonic = "sqadd";
        break;
      case NEON_UQSUB_scalar:
        mnemonic = "uqsub";
        break;
      case NEON_SQSUB_scalar:
        mnemonic = "sqsub";
        break;
      case NEON_USHL_scalar:
        mnemonic = "ushl";
        break;
      case NEON_SSHL_scalar:
        mnemonic = "sshl";
        break;
      case NEON_UQSHL_scalar:
        mnemonic = "uqshl";
        break;
      case NEON_SQSHL_scalar:
        mnemonic = "sqshl";
        break;
      case NEON_URSHL_scalar:
        mnemonic = "urshl";
        break;
      case NEON_SRSHL_scalar:
        mnemonic = "srshl";
        break;
      case NEON_UQRSHL_scalar:
        mnemonic = "uqrshl";
        break;
      case NEON_SQRSHL_scalar:
        mnemonic = "sqrshl";
        break;
      case NEON_SQDMULH_scalar:
        mnemonic = "sqdmulh";
        break;
      case NEON_SQRDMULH_scalar:
        mnemonic = "sqrdmulh";
        break;
      default:
        form = "(NEONScalar3Same)";
    }
  }
  Format(instr, mnemonic, nfd.SubstitutePlaceholders(form));
}

void DisassemblingDecoder::VisitNEONScalarByIndexedElement(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "%sd, %sn, 'Ve.%s['IVByElemIndex]";
  NEONFormatDecoder nfd(instr, NEONFormatDecoder::ScalarFormatMap());
  bool long_instr = false;

  switch (instr->Mask(NEONScalarByIndexedElementMask)) {
    case NEON_SQDMULL_byelement_scalar:
      mnemonic = "sqdmull";
      long_instr = true;
      break;
    case NEON_SQDMLAL_byelement_scalar:
      mnemonic = "sqdmlal";
      long_instr = true;
      break;
    case NEON_SQDMLSL_byelement_scalar:
      mnemonic = "sqdmlsl";
      long_instr = true;
      break;
    case NEON_SQDMULH_byelement_scalar:
      mnemonic = "sqdmulh";
      break;
    case NEON_SQRDMULH_byelement_scalar:
      mnemonic = "sqrdmulh";
      break;
    default:
      nfd.SetFormatMap(0, nfd.FPScalarFormatMap());
      switch (instr->Mask(NEONScalarByIndexedElementFPMask)) {
        case NEON_FMUL_byelement_scalar:
          mnemonic = "fmul";
          break;
        case NEON_FMLA_byelement_scalar:
          mnemonic = "fmla";
          break;
        case NEON_FMLS_byelement_scalar:
          mnemonic = "fmls";
          break;
        case NEON_FMULX_byelement_scalar:
          mnemonic = "fmulx";
          break;
        default:
          form = "(NEONScalarByIndexedElement)";
      }
  }

  if (long_instr) {
    nfd.SetFormatMap(0, nfd.LongScalarFormatMap());
  }

  Format(instr, mnemonic,
         nfd.Substitute(form, nfd.kPlaceholder, nfd.kPlaceholder, nfd.kFormat));
}

void DisassemblingDecoder::VisitNEONScalarCopy(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "(NEONScalarCopy)";

  NEONFormatDecoder nfd(instr, NEONFormatDecoder::TriangularScalarFormatMap());

  if (instr->Mask(NEONScalarCopyMask) == NEON_DUP_ELEMENT_scalar) {
    mnemonic = "mov";
    form = "%sd, 'Vn.%s['IVInsIndex1]";
  }

  Format(instr, mnemonic, nfd.Substitute(form, nfd.kPlaceholder, nfd.kFormat));
}

void DisassemblingDecoder::VisitNEONScalarPairwise(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "%sd, 'Vn.%s";
  NEONFormatMap map = {{22}, {NF_2S, NF_2D}};
  NEONFormatDecoder nfd(instr, NEONFormatDecoder::FPScalarFormatMap(), &map);

  switch (instr->Mask(NEONScalarPairwiseMask)) {
    case NEON_ADDP_scalar:
      mnemonic = "addp";
      break;
    case NEON_FADDP_scalar:
      mnemonic = "faddp";
      break;
    case NEON_FMAXP_scalar:
      mnemonic = "fmaxp";
      break;
    case NEON_FMAXNMP_scalar:
      mnemonic = "fmaxnmp";
      break;
    case NEON_FMINP_scalar:
      mnemonic = "fminp";
      break;
    case NEON_FMINNMP_scalar:
      mnemonic = "fminnmp";
      break;
    default:
      form = "(NEONScalarPairwise)";
  }
  Format(instr, mnemonic,
         nfd.Substitute(form, NEONFormatDecoder::kPlaceholder,
                        NEONFormatDecoder::kFormat));
}

void DisassemblingDecoder::VisitNEONScalarShiftImmediate(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "%sd, %sn, 'Is1";
  const char* form_2 = "%sd, %sn, 'Is2";

  static const NEONFormatMap map_shift = {
      {22, 21, 20, 19},
      {NF_UNDEF, NF_B, NF_H, NF_H, NF_S, NF_S, NF_S, NF_S, NF_D, NF_D, NF_D,
       NF_D, NF_D, NF_D, NF_D, NF_D}};
  static const NEONFormatMap map_shift_narrow = {
      {21, 20, 19}, {NF_UNDEF, NF_H, NF_S, NF_S, NF_D, NF_D, NF_D, NF_D}};
  NEONFormatDecoder nfd(instr, &map_shift);

  if (instr->ImmNEONImmh()) {  // immh has to be non-zero.
    switch (instr->Mask(NEONScalarShiftImmediateMask)) {
      case NEON_FCVTZU_imm_scalar:
        mnemonic = "fcvtzu";
        break;
      case NEON_FCVTZS_imm_scalar:
        mnemonic = "fcvtzs";
        break;
      case NEON_SCVTF_imm_scalar:
        mnemonic = "scvtf";
        break;
      case NEON_UCVTF_imm_scalar:
        mnemonic = "ucvtf";
        break;
      case NEON_SRI_scalar:
        mnemonic = "sri";
        break;
      case NEON_SSHR_scalar:
        mnemonic = "sshr";
        break;
      case NEON_USHR_scalar:
        mnemonic = "ushr";
        break;
      case NEON_SRSHR_scalar:
        mnemonic = "srshr";
        break;
      case NEON_URSHR_scalar:
        mnemonic = "urshr";
        break;
      case NEON_SSRA_scalar:
        mnemonic = "ssra";
        break;
      case NEON_USRA_scalar:
        mnemonic = "usra";
        break;
      case NEON_SRSRA_scalar:
        mnemonic = "srsra";
        break;
      case NEON_URSRA_scalar:
        mnemonic = "ursra";
        break;
      case NEON_SHL_scalar:
        mnemonic = "shl";
        form = form_2;
        break;
      case NEON_SLI_scalar:
        mnemonic = "sli";
        form = form_2;
        break;
      case NEON_SQSHLU_scalar:
        mnemonic = "sqshlu";
        form = form_2;
        break;
      case NEON_SQSHL_imm_scalar:
        mnemonic = "sqshl";
        form = form_2;
        break;
      case NEON_UQSHL_imm_scalar:
        mnemonic = "uqshl";
        form = form_2;
        break;
      case NEON_UQSHRN_scalar:
        mnemonic = "uqshrn";
        nfd.SetFormatMap(1, &map_shift_narrow);
        break;
      case NEON_UQRSHRN_scalar:
        mnemonic = "uqrshrn";
        nfd.SetFormatMap(1, &map_shift_narrow);
        break;
      case NEON_SQSHRN_scalar:
        mnemonic = "sqshrn";
        nfd.SetFormatMap(1, &map_shift_narrow);
        break;
      case NEON_SQRSHRN_scalar:
        mnemonic = "sqrshrn";
        nfd.SetFormatMap(1, &map_shift_narrow);
        break;
      case NEON_SQSHRUN_scalar:
        mnemonic = "sqshrun";
        nfd.SetFormatMap(1, &map_shift_narrow);
        break;
      case NEON_SQRSHRUN_scalar:
        mnemonic = "sqrshrun";
        nfd.SetFormatMap(1, &map_shift_narrow);
        break;
      default:
        form = "(NEONScalarShiftImmediate)";
    }
  } else {
    form = "(NEONScalarShiftImmediate)";
  }
  Format(instr, mnemonic, nfd.SubstitutePlaceholders(form));
}

void DisassemblingDecoder::VisitNEONShiftImmediate(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "'Vd.%s, 'Vn.%s, 'Is1";
  const char* form_shift_2 = "'Vd.%s, 'Vn.%s, 'Is2";
  const char* form_xtl = "'Vd.%s, 'Vn.%s";

  // 0001->8H, 001x->4S, 01xx->2D, all others undefined.
  static const NEONFormatMap map_shift_ta = {
      {22, 21, 20, 19},
      {NF_UNDEF, NF_8H, NF_4S, NF_4S, NF_2D, NF_2D, NF_2D, NF_2D}};

  // 00010->8B, 00011->16B, 001x0->4H, 001x1->8H,
  // 01xx0->2S, 01xx1->4S, 1xxx1->2D, all others undefined.
  static const NEONFormatMap map_shift_tb = {
      {22, 21, 20, 19, 30},
      {NF_UNDEF, NF_UNDEF, NF_8B,    NF_16B, NF_4H,    NF_8H, NF_4H,    NF_8H,
       NF_2S,    NF_4S,    NF_2S,    NF_4S,  NF_2S,    NF_4S, NF_2S,    NF_4S,
       NF_UNDEF, NF_2D,    NF_UNDEF, NF_2D,  NF_UNDEF, NF_2D, NF_UNDEF, NF_2D,
       NF_UNDEF, NF_2D,    NF_UNDEF, NF_2D,  NF_UNDEF, NF_2D, NF_UNDEF, NF_2D}};

  NEONFormatDecoder nfd(instr, &map_shift_tb);

  if (instr->ImmNEONImmh()) {  // immh has to be non-zero.
    switch (instr->Mask(NEONShiftImmediateMask)) {
      case NEON_SQSHLU:
        mnemonic = "sqshlu";
        form = form_shift_2;
        break;
      case NEON_SQSHL_imm:
        mnemonic = "sqshl";
        form = form_shift_2;
        break;
      case NEON_UQSHL_imm:
        mnemonic = "uqshl";
        form = form_shift_2;
        break;
      case NEON_SHL:
        mnemonic = "shl";
        form = form_shift_2;
        break;
      case NEON_SLI:
        mnemonic = "sli";
        form = form_shift_2;
        break;
      case NEON_SCVTF_imm:
        mnemonic = "scvtf";
        break;
      case NEON_UCVTF_imm:
        mnemonic = "ucvtf";
        break;
      case NEON_FCVTZU_imm:
        mnemonic = "fcvtzu";
        break;
      case NEON_FCVTZS_imm:
        mnemonic = "fcvtzs";
        break;
      case NEON_SRI:
        mnemonic = "sri";
        break;
      case NEON_SSHR:
        mnemonic = "sshr";
        break;
      case NEON_USHR:
        mnemonic = "ushr";
        break;
      case NEON_SRSHR:
        mnemonic = "srshr";
        break;
      case NEON_URSHR:
        mnemonic = "urshr";
        break;
      case NEON_SSRA:
        mnemonic = "ssra";
        break;
      case NEON_USRA:
        mnemonic = "usra";
        break;
      case NEON_SRSRA:
        mnemonic = "srsra";
        break;
      case NEON_URSRA:
        mnemonic = "ursra";
        break;
      case NEON_SHRN:
        mnemonic = instr->Mask(NEON_Q) ? "shrn2" : "shrn";
        nfd.SetFormatMap(1, &map_shift_ta);
        break;
      case NEON_RSHRN:
        mnemonic = instr->Mask(NEON_Q) ? "rshrn2" : "rshrn";
        nfd.SetFormatMap(1, &map_shift_ta);
        break;
      case NEON_UQSHRN:
        mnemonic = instr->Mask(NEON_Q) ? "uqshrn2" : "uqshrn";
        nfd.SetFormatMap(1, &map_shift_ta);
        break;
      case NEON_UQRSHRN:
        mnemonic = instr->Mask(NEON_Q) ? "uqrshrn2" : "uqrshrn";
        nfd.SetFormatMap(1, &map_shift_ta);
        break;
      case NEON_SQSHRN:
        mnemonic = instr->Mask(NEON_Q) ? "sqshrn2" : "sqshrn";
        nfd.SetFormatMap(1, &map_shift_ta);
        break;
      case NEON_SQRSHRN:
        mnemonic = instr->Mask(NEON_Q) ? "sqrshrn2" : "sqrshrn";
        nfd.SetFormatMap(1, &map_shift_ta);
        break;
      case NEON_SQSHRUN:
        mnemonic = instr->Mask(NEON_Q) ? "sqshrun2" : "sqshrun";
        nfd.SetFormatMap(1, &map_shift_ta);
        break;
      case NEON_SQRSHRUN:
        mnemonic = instr->Mask(NEON_Q) ? "sqrshrun2" : "sqrshrun";
        nfd.SetFormatMap(1, &map_shift_ta);
        break;
      case NEON_SSHLL:
        nfd.SetFormatMap(0, &map_shift_ta);
        if (instr->ImmNEONImmb() == 0 &&
            CountSetBits(instr->ImmNEONImmh(), 32) == 1) {  // sxtl variant.
          form = form_xtl;
          mnemonic = instr->Mask(NEON_Q) ? "sxtl2" : "sxtl";
        } else {  // sshll variant.
          form = form_shift_2;
          mnemonic = instr->Mask(NEON_Q) ? "sshll2" : "sshll";
        }
        break;
      case NEON_USHLL:
        nfd.SetFormatMap(0, &map_shift_ta);
        if (instr->ImmNEONImmb() == 0 &&
            CountSetBits(instr->ImmNEONImmh(), 32) == 1) {  // uxtl variant.
          form = form_xtl;
          mnemonic = instr->Mask(NEON_Q) ? "uxtl2" : "uxtl";
        } else {  // ushll variant.
          form = form_shift_2;
          mnemonic = instr->Mask(NEON_Q) ? "ushll2" : "ushll";
        }
        break;
      default:
        form = "(NEONShiftImmediate)";
    }
  } else {
    form = "(NEONShiftImmediate)";
  }
  Format(instr, mnemonic, nfd.Substitute(form));
}

void DisassemblingDecoder::VisitNEONTable(Instruction* instr) {
  const char* mnemonic = "unimplemented";
  const char* form = "(NEONTable)";
  const char form_1v[] = "'Vd.%%s, {'Vn.16b}, 'Vm.%%s";
  const char form_2v[] = "'Vd.%%s, {'Vn.16b, v%d.16b}, 'Vm.%%s";
  const char form_3v[] = "'Vd.%%s, {'Vn.16b, v%d.16b, v%d.16b}, 'Vm.%%s";
  const char form_4v[] =
      "'Vd.%%s, {'Vn.16b, v%d.16b, v%d.16b, v%d.16b}, 'Vm.%%s";
  static const NEONFormatMap map_b = {{30}, {NF_8B, NF_16B}};
  NEONFormatDecoder nfd(instr, &map_b);

  switch (instr->Mask(NEONTableMask)) {
    case NEON_TBL_1v:
      mnemonic = "tbl";
      form = form_1v;
      break;
    case NEON_TBL_2v:
      mnemonic = "tbl";
      form = form_2v;
      break;
    case NEON_TBL_3v:
      mnemonic = "tbl";
      form = form_3v;
      break;
    case NEON_TBL_4v:
      mnemonic = "tbl";
      form = form_4v;
      break;
    case NEON_TBX_1v:
      mnemonic = "tbx";
      form = form_1v;
      break;
    case NEON_TBX_2v:
      mnemonic = "tbx";
      form = form_2v;
      break;
    case NEON_TBX_3v:
      mnemonic = "tbx";
      form = form_3v;
      break;
    case NEON_TBX_4v:
      mnemonic = "tbx";
      form = form_4v;
      break;
    default:
      break;
  }

  char re_form[sizeof(form_4v)];
  int reg_num = instr->Rn();
  snprintf(re_form, sizeof(re_form), form, (reg_num + 1) % kNumberOfVRegisters,
           (reg_num + 2) % kNumberOfVRegisters,
           (reg_num + 3) % kNumberOfVRegisters);

  Format(instr, mnemonic, nfd.Substitute(re_form));
}

void DisassemblingDecoder::VisitUnimplemented(Instruction* instr) {
  Format(instr, "unimplemented", "(Unimplemented)");
}

void DisassemblingDecoder::VisitUnallocated(Instruction* instr) {
  Format(instr, "unallocated", "(Unallocated)");
}

void DisassemblingDecoder::ProcessOutput(Instruction* /*instr*/) {
  // The base disasm does nothing more than disassembling into a buffer.
}

void DisassemblingDecoder::AppendRegisterNameToOutput(const CPURegister& reg) {
  DCHECK(reg.IsValid());
  char reg_char;

  if (reg.IsRegister()) {
    reg_char = reg.Is64Bits() ? 'x' : 'w';
  } else {
    DCHECK(reg.IsVRegister());
    switch (reg.SizeInBits()) {
      case kBRegSizeInBits:
        reg_char = 'b';
        break;
      case kHRegSizeInBits:
        reg_char = 'h';
        break;
      case kSRegSizeInBits:
        reg_char = 's';
        break;
      case kDRegSizeInBits:
        reg_char = 'd';
        break;
      default:
        DCHECK(reg.Is128Bits());
        reg_char = 'q';
    }
  }

  if (reg.IsVRegister() || !(reg.Aliases(csp) || reg.Aliases(xzr))) {
    // Filter special registers
    if (reg.IsX() && (reg.code() == 27)) {
      AppendToOutput("cp");
    } else if (reg.IsX() && (reg.code() == 29)) {
      AppendToOutput("fp");
    } else if (reg.IsX() && (reg.code() == 30)) {
      AppendToOutput("lr");
    } else {
      // A core or scalar/vector register: [wx]0 - 30, [bhsdq]0 - 31.
      AppendToOutput("%c%d", reg_char, reg.code());
    }
  } else if (reg.Aliases(csp)) {
    // Disassemble w31/x31 as stack pointer wcsp/csp.
    AppendToOutput("%s", reg.Is64Bits() ? "csp" : "wcsp");
  } else {
    // Disassemble w31/x31 as zero register wzr/xzr.
    AppendToOutput("%czr", reg_char);
  }
}

void DisassemblingDecoder::Format(Instruction* instr, const char* mnemonic,
                                  const char* format) {
  // TODO(mcapewel) don't think I can use the instr address here - there needs
  //                to be a base address too
  DCHECK_NOT_NULL(mnemonic);
  ResetOutput();
  Substitute(instr, mnemonic);
  if (format != nullptr) {
    buffer_[buffer_pos_++] = ' ';
    Substitute(instr, format);
  }
  buffer_[buffer_pos_] = 0;
  ProcessOutput(instr);
}

void DisassemblingDecoder::Substitute(Instruction* instr, const char* string) {
  char chr = *string++;
  while (chr != '\0') {
    if (chr == '\'') {
      string += SubstituteField(instr, string);
    } else {
      buffer_[buffer_pos_++] = chr;
    }
    chr = *string++;
  }
}

int DisassemblingDecoder::SubstituteField(Instruction* instr,
                                          const char* format) {
  switch (format[0]) {
    // NB. The remaining substitution prefix characters are: GJKUZ.
    case 'R':  // Register. X or W, selected by sf bit.
    case 'F':  // FP register. S or D, selected by type field.
    case 'V':  // Vector register, V, vector format.
    case 'W':
    case 'X':
    case 'B':
    case 'H':
    case 'S':
    case 'D':
    case 'Q':
      return SubstituteRegisterField(instr, format);
    case 'I':
      return SubstituteImmediateField(instr, format);
    case 'L':
      return SubstituteLiteralField(instr, format);
    case 'N':
      return SubstituteShiftField(instr, format);
    case 'P':
      return SubstitutePrefetchField(instr, format);
    case 'C':
      return SubstituteConditionField(instr, format);
    case 'E':
      return SubstituteExtendField(instr, format);
    case 'A':
      return SubstitutePCRelAddressField(instr, format);
    case 'T':
      return SubstituteBranchTargetField(instr, format);
    case 'O':
      return SubstituteLSRegOffsetField(instr, format);
    case 'M':
      return SubstituteBarrierField(instr, format);
    default:
      UNREACHABLE();
  }
}

int DisassemblingDecoder::SubstituteRegisterField(Instruction* instr,
                                                  const char* format) {
  char reg_prefix = format[0];
  unsigned reg_num = 0;
  unsigned field_len = 2;

  switch (format[1]) {
    case 'd':
      reg_num = instr->Rd();
      if (format[2] == 'q') {
        reg_prefix = instr->NEONQ() ? 'X' : 'W';
        field_len = 3;
      }
      break;
    case 'n':
      reg_num = instr->Rn();
      break;
    case 'm':
      reg_num = instr->Rm();
      switch (format[2]) {
        // Handle registers tagged with b (bytes), z (instruction), or
        // r (registers), used for address updates in
        // NEON load/store instructions.
        case 'r':
        case 'b':
        case 'z': {
          field_len = 3;
          char* eimm;
          int imm = static_cast<int>(strtol(&format[3], &eimm, 10));
          field_len += eimm - &format[3];
          if (reg_num == 31) {
            switch (format[2]) {
              case 'z':
                imm *= (1 << instr->NEONLSSize());
                break;
              case 'r':
                imm *= (instr->NEONQ() == 0) ? kDRegSize : kQRegSize;
                break;
              case 'b':
                break;
            }
            AppendToOutput("#%d", imm);
            return field_len;
          }
          break;
        }
      }
      break;
    case 'e':
      // This is register Rm, but using a 4-bit specifier. Used in NEON
      // by-element instructions.
      reg_num = (instr->Rm() & 0xF);
      break;
    case 'a':
      reg_num = instr->Ra();
      break;
    case 't':
      reg_num = instr->Rt();
      if (format[0] == 'V') {
        if ((format[2] >= '2') && (format[2] <= '4')) {
          // Handle consecutive vector register specifiers Vt2, Vt3 and Vt4.
          reg_num = (reg_num + format[2] - '1') % 32;
          field_len = 3;
        }
      } else {
        if (format[2] == '2') {
          // Handle register specifier Rt2.
          reg_num = instr->Rt2();
          field_len = 3;
        }
      }
      break;
    case 's':
      reg_num = instr->Rs();
      break;
    default:
      UNREACHABLE();
  }

  // Increase field length for registers tagged as stack.
  if (format[2] == 's') {
    field_len = 3;
  }

  CPURegister::RegisterType reg_type;
  unsigned reg_size;

  if (reg_prefix == 'R') {
    reg_prefix = instr->SixtyFourBits() ? 'X' : 'W';
  } else if (reg_prefix == 'F') {
    reg_prefix = ((instr->FPType() & 1) == 0) ? 'S' : 'D';
  }

  switch (reg_prefix) {
    case 'W':
      reg_type = CPURegister::kRegister;
      reg_size = kWRegSizeInBits;
      break;
    case 'X':
      reg_type = CPURegister::kRegister;
      reg_size = kXRegSizeInBits;
      break;
    case 'B':
      reg_type = CPURegister::kVRegister;
      reg_size = kBRegSizeInBits;
      break;
    case 'H':
      reg_type = CPURegister::kVRegister;
      reg_size = kHRegSizeInBits;
      break;
    case 'S':
      reg_type = CPURegister::kVRegister;
      reg_size = kSRegSizeInBits;
      break;
    case 'D':
      reg_type = CPURegister::kVRegister;
      reg_size = kDRegSizeInBits;
      break;
    case 'Q':
      reg_type = CPURegister::kVRegister;
      reg_size = kQRegSizeInBits;
      break;
    case 'V':
      AppendToOutput("v%d", reg_num);
      return field_len;
    default:
      UNREACHABLE();
  }

  if ((reg_type == CPURegister::kRegister) && (reg_num == kZeroRegCode) &&
      (format[2] == 's')) {
    reg_num = kSPRegInternalCode;
  }

  AppendRegisterNameToOutput(CPURegister::Create(reg_num, reg_size, reg_type));

  return field_len;
}

int DisassemblingDecoder::SubstituteImmediateField(Instruction* instr,
                                                   const char* format) {
  DCHECK_EQ(format[0], 'I');

  switch (format[1]) {
    case 'M': {  // IMoveImm or IMoveLSL.
      if (format[5] == 'I' || format[5] == 'N') {
        uint64_t imm = static_cast<uint64_t>(instr->ImmMoveWide())
                       << (16 * instr->ShiftMoveWide());
        if (format[5] == 'N') imm = ~imm;
        if (!instr->SixtyFourBits()) imm &= UINT64_C(0xFFFFFFFF);
        AppendToOutput("#0x%" PRIx64, imm);
      } else {
        DCHECK_EQ(format[5], 'L');
        AppendToOutput("#0x%" PRIx64, instr->ImmMoveWide());
        if (instr->ShiftMoveWide() > 0) {
          AppendToOutput(", lsl #%d", 16 * instr->ShiftMoveWide());
        }
      }
      return 8;
    }
    case 'L': {
      switch (format[2]) {
        case 'L': {  // ILLiteral - Immediate Load Literal.
          AppendToOutput("pc%+" PRId32, instr->ImmLLiteral()
                                            << kLoadLiteralScaleLog2);
          return 9;
        }
        case 'S': {  // ILS - Immediate Load/Store.
          if (instr->ImmLS() != 0) {
            AppendToOutput(", #%" PRId32, instr->ImmLS());
          }
          return 3;
        }
        case 'P': {  // ILPx - Immediate Load/Store Pair, x = access size.
          if (instr->ImmLSPair() != 0) {
            // format[3] is the scale value. Convert to a number.
            int scale = 1 << (format[3] - '0');
            AppendToOutput(", #%" PRId32, instr->ImmLSPair() * scale);
          }
          return 4;
        }
        case 'U': {  // ILU - Immediate Load/Store Unsigned.
          if (instr->ImmLSUnsigned() != 0) {
            int shift = instr->SizeLS();
            AppendToOutput(", #%" PRId32, instr->ImmLSUnsigned() << shift);
          }
          return 3;
        }
      }
    }
    case 'C': {  // ICondB - Immediate Conditional Branch.
      int64_t offset = instr->ImmCondBranch() << 2;
      char sign = (offset >= 0) ? '+' : '-';
      AppendToOutput("#%c0x%" PRIx64, sign, offset);
      return 6;
    }
    case 'A': {  // IAddSub.
      DCHECK_LE(instr->ShiftAddSub(), 1);
      int64_t imm = instr->ImmAddSub() << (12 * instr->ShiftAddSub());
      AppendToOutput("#0x%" PRIx64 " (%" PRId64 ")", imm, imm);
      return 7;
    }
    case 'F': {  // IFPSingle, IFPDouble or IFPFBits.
      if (format[3] == 'F') {  // IFPFBits.
        AppendToOutput("#%d", 64 - instr->FPScale());
        return 8;
      } else {
        AppendToOutput("#0x%" PRIx32 " (%.4f)", instr->ImmFP(),
                       format[3] == 'S' ? instr->ImmFP32() : instr->ImmFP64());
        return 9;
      }
    }
    case 'T': {  // ITri - Immediate Triangular Encoded.
      AppendToOutput("#0x%" PRIx64, instr->ImmLogical());
      return 4;
    }
    case 'N': {  // INzcv.
      int nzcv = (instr->Nzcv() << Flags_offset);
      AppendToOutput("#%c%c%c%c", ((nzcv & NFlag) == 0) ? 'n' : 'N',
                                  ((nzcv & ZFlag) == 0) ? 'z' : 'Z',
                                  ((nzcv & CFlag) == 0) ? 'c' : 'C',
                                  ((nzcv & VFlag) == 0) ? 'v' : 'V');
      return 5;
    }
    case 'P': {  // IP - Conditional compare.
      AppendToOutput("#%d", instr->ImmCondCmp());
      return 2;
    }
    case 'B': {  // Bitfields.
      return SubstituteBitfieldImmediateField(instr, format);
    }
    case 'E': {  // IExtract.
      AppendToOutput("#%d", instr->ImmS());
      return 8;
    }
    case 'S': {  // IS - Test and branch bit.
      AppendToOutput("#%d", (instr->ImmTestBranchBit5() << 5) |
                            instr->ImmTestBranchBit40());
      return 2;
    }
    case 's': {  // Is - Shift (immediate).
      switch (format[2]) {
        case '1': {  // Is1 - SSHR.
          int shift = 16 << HighestSetBitPosition(instr->ImmNEONImmh());
          shift -= instr->ImmNEONImmhImmb();
          AppendToOutput("#%d", shift);
          return 3;
        }
        case '2': {  // Is2 - SLI.
          int shift = instr->ImmNEONImmhImmb();
          shift -= 8 << HighestSetBitPosition(instr->ImmNEONImmh());
          AppendToOutput("#%d", shift);
          return 3;
        }
        default: {
          UNIMPLEMENTED();
          return 0;
        }
      }
    }
    case 'D': {  // IDebug - HLT and BRK instructions.
      AppendToOutput("#0x%x", instr->ImmException());
      return 6;
    }
    case 'V': {  // Immediate Vector.
      switch (format[2]) {
        case 'E': {  // IVExtract.
          AppendToOutput("#%" PRId64, instr->ImmNEONExt());
          return 9;
        }
        case 'B': {  // IVByElemIndex.
          int vm_index = (instr->NEONH() << 1) | instr->NEONL();
          if (instr->NEONSize() == 1) {
            vm_index = (vm_index << 1) | instr->NEONM();
          }
          AppendToOutput("%d", vm_index);
          return static_cast<int>(strlen("IVByElemIndex"));
        }
        case 'I': {  // INS element.
          if (strncmp(format, "IVInsIndex", strlen("IVInsIndex")) == 0) {
            unsigned rd_index, rn_index;
            unsigned imm5 = instr->ImmNEON5();
            unsigned imm4 = instr->ImmNEON4();
            int tz = CountTrailingZeros(imm5, 32);
            if (tz <= 3) {  // Defined for 0 <= tz <= 3 only.
              rd_index = imm5 >> (tz + 1);
              rn_index = imm4 >> tz;
              if (strncmp(format, "IVInsIndex1", strlen("IVInsIndex1")) == 0) {
                AppendToOutput("%d", rd_index);
                return static_cast<int>(strlen("IVInsIndex1"));
              } else if (strncmp(format, "IVInsIndex2",
                                 strlen("IVInsIndex2")) == 0) {
                AppendToOutput("%d", rn_index);
                return static_cast<int>(strlen("IVInsIndex2"));
              }
            }
            return 0;
          }
        }
        case 'L': {  // IVLSLane[0123] - suffix indicates access size shift.
          AppendToOutput("%d", instr->NEONLSIndex(format[8] - '0'));
          return 9;
        }
        case 'M': {  // Modified Immediate cases.
          if (strncmp(format, "IVMIImmFPSingle", strlen("IVMIImmFPSingle")) ==
              0) {
            AppendToOutput("#0x%" PRIx32 " (%.4f)", instr->ImmNEONabcdefgh(),
                           instr->ImmNEONFP32());
            return static_cast<int>(strlen("IVMIImmFPSingle"));
          } else if (strncmp(format, "IVMIImmFPDouble",
                             strlen("IVMIImmFPDouble")) == 0) {
            AppendToOutput("#0x%" PRIx32 " (%.4f)", instr->ImmNEONabcdefgh(),
                           instr->ImmNEONFP64());
            return static_cast<int>(strlen("IVMIImmFPDouble"));
          } else if (strncmp(format, "IVMIImm8", strlen("IVMIImm8")) == 0) {
            uint64_t imm8 = instr->ImmNEONabcdefgh();
            AppendToOutput("#0x%" PRIx64, imm8);
            return static_cast<int>(strlen("IVMIImm8"));
          } else if (strncmp(format, "IVMIImm", strlen("IVMIImm")) == 0) {
            uint64_t imm8 = instr->ImmNEONabcdefgh();
            uint64_t imm = 0;
            for (int i = 0; i < 8; ++i) {
              if (imm8 & (1 << i)) {
                imm |= (UINT64_C(0xFF) << (8 * i));
              }
            }
            AppendToOutput("#0x%" PRIx64, imm);
            return static_cast<int>(strlen("IVMIImm"));
          } else if (strncmp(format, "IVMIShiftAmt1",
                             strlen("IVMIShiftAmt1")) == 0) {
            int cmode = instr->NEONCmode();
            int shift_amount = 8 * ((cmode >> 1) & 3);
            AppendToOutput("#%d", shift_amount);
            return static_cast<int>(strlen("IVMIShiftAmt1"));
          } else if (strncmp(format, "IVMIShiftAmt2",
                             strlen("IVMIShiftAmt2")) == 0) {
            int cmode = instr->NEONCmode();
            int shift_amount = 8 << (cmode & 1);
            AppendToOutput("#%d", shift_amount);
            return static_cast<int>(strlen("IVMIShiftAmt2"));
          } else {
            UNIMPLEMENTED();
            return 0;
          }
        }
        default: {
          UNIMPLEMENTED();
          return 0;
        }
      }
    }
    default: {
      printf("%s", format);
      UNREACHABLE();
    }
  }
}


int DisassemblingDecoder::SubstituteBitfieldImmediateField(Instruction* instr,
                                                           const char* format) {
  DCHECK((format[0] == 'I') && (format[1] == 'B'));
  unsigned r = instr->ImmR();
  unsigned s = instr->ImmS();

  switch (format[2]) {
    case 'r': {  // IBr.
      AppendToOutput("#%d", r);
      return 3;
    }
    case 's': {  // IBs+1 or IBs-r+1.
      if (format[3] == '+') {
        AppendToOutput("#%d", s + 1);
        return 5;
      } else {
        DCHECK_EQ(format[3], '-');
        AppendToOutput("#%d", s - r + 1);
        return 7;
      }
    }
    case 'Z': {  // IBZ-r.
      DCHECK((format[3] == '-') && (format[4] == 'r'));
      unsigned reg_size = (instr->SixtyFourBits() == 1) ? kXRegSizeInBits
                                                        : kWRegSizeInBits;
      AppendToOutput("#%d", reg_size - r);
      return 5;
    }
    default: {
      UNREACHABLE();
    }
  }
}


int DisassemblingDecoder::SubstituteLiteralField(Instruction* instr,
                                                 const char* format) {
  DCHECK_EQ(strncmp(format, "LValue", 6), 0);
  USE(format);

  switch (instr->Mask(LoadLiteralMask)) {
    case LDR_w_lit:
    case LDR_x_lit:
    case LDR_s_lit:
    case LDR_d_lit:
      AppendToOutput("(addr 0x%016" PRIxPTR ")", instr->LiteralAddress());
      break;
    default: UNREACHABLE();
  }

  return 6;
}


int DisassemblingDecoder::SubstituteShiftField(Instruction* instr,
                                               const char* format) {
  DCHECK_EQ(format[0], 'N');
  DCHECK_LE(instr->ShiftDP(), 0x3);

  switch (format[1]) {
    case 'D': {  // NDP.
      DCHECK(instr->ShiftDP() != ROR);
    }  // Fall through.
    case 'L': {  // NLo.
      if (instr->ImmDPShift() != 0) {
        const char* shift_type[] = {"lsl", "lsr", "asr", "ror"};
        AppendToOutput(", %s #%" PRId32, shift_type[instr->ShiftDP()],
                       instr->ImmDPShift());
      }
      return 3;
    }
    default:
      UNREACHABLE();
  }
}


int DisassemblingDecoder::SubstituteConditionField(Instruction* instr,
                                                   const char* format) {
  DCHECK_EQ(format[0], 'C');
  const char* condition_code[] = { "eq", "ne", "hs", "lo",
                                   "mi", "pl", "vs", "vc",
                                   "hi", "ls", "ge", "lt",
                                   "gt", "le", "al", "nv" };
  int cond;
  switch (format[1]) {
    case 'B': cond = instr->ConditionBranch(); break;
    case 'I': {
      cond = NegateCondition(static_cast<Condition>(instr->Condition()));
      break;
    }
    default: cond = instr->Condition();
  }
  AppendToOutput("%s", condition_code[cond]);
  return 4;
}


int DisassemblingDecoder::SubstitutePCRelAddressField(Instruction* instr,
                                                      const char* format) {
  USE(format);
  DCHECK_EQ(strncmp(format, "AddrPCRel", 9), 0);

  int offset = instr->ImmPCRel();

  // Only ADR (AddrPCRelByte) is supported.
  DCHECK_EQ(strcmp(format, "AddrPCRelByte"), 0);

  char sign = '+';
  if (offset < 0) {
    offset = -offset;
    sign = '-';
  }
  AppendToOutput("#%c0x%x (addr %p)", sign, offset,
                 instr->InstructionAtOffset(offset, Instruction::NO_CHECK));
  return 13;
}


int DisassemblingDecoder::SubstituteBranchTargetField(Instruction* instr,
                                                      const char* format) {
  DCHECK_EQ(strncmp(format, "TImm", 4), 0);

  int64_t offset = 0;
  switch (format[5]) {
    // TImmUncn - unconditional branch immediate.
    case 'n': offset = instr->ImmUncondBranch(); break;
    // TImmCond - conditional branch immediate.
    case 'o': offset = instr->ImmCondBranch(); break;
    // TImmCmpa - compare and branch immediate.
    case 'm': offset = instr->ImmCmpBranch(); break;
    // TImmTest - test and branch immediate.
    case 'e': offset = instr->ImmTestBranch(); break;
    default: UNREACHABLE();
  }
  offset <<= kInstructionSizeLog2;
  char sign = '+';
  if (offset < 0) {
    sign = '-';
  }
  AppendToOutput("#%c0x%" PRIx64 " (addr %p)", sign, Abs(offset),
                 instr->InstructionAtOffset(offset), Instruction::NO_CHECK);
  return 8;
}


int DisassemblingDecoder::SubstituteExtendField(Instruction* instr,
                                                const char* format) {
  DCHECK_EQ(strncmp(format, "Ext", 3), 0);
  DCHECK_LE(instr->ExtendMode(), 7);
  USE(format);

  const char* extend_mode[] = { "uxtb", "uxth", "uxtw", "uxtx",
                                "sxtb", "sxth", "sxtw", "sxtx" };

  // If rd or rn is SP, uxtw on 32-bit registers and uxtx on 64-bit
  // registers becomes lsl.
  if (((instr->Rd() == kZeroRegCode) || (instr->Rn() == kZeroRegCode)) &&
      (((instr->ExtendMode() == UXTW) && (instr->SixtyFourBits() == 0)) ||
       (instr->ExtendMode() == UXTX))) {
    if (instr->ImmExtendShift() > 0) {
      AppendToOutput(", lsl #%d", instr->ImmExtendShift());
    }
  } else {
    AppendToOutput(", %s", extend_mode[instr->ExtendMode()]);
    if (instr->ImmExtendShift() > 0) {
      AppendToOutput(" #%d", instr->ImmExtendShift());
    }
  }
  return 3;
}


int DisassemblingDecoder::SubstituteLSRegOffsetField(Instruction* instr,
                                                     const char* format) {
  DCHECK_EQ(strncmp(format, "Offsetreg", 9), 0);
  const char* extend_mode[] = { "undefined", "undefined", "uxtw", "lsl",
                                "undefined", "undefined", "sxtw", "sxtx" };
  USE(format);

  unsigned shift = instr->ImmShiftLS();
  Extend ext = static_cast<Extend>(instr->ExtendMode());
  char reg_type = ((ext == UXTW) || (ext == SXTW)) ? 'w' : 'x';

  unsigned rm = instr->Rm();
  if (rm == kZeroRegCode) {
    AppendToOutput("%czr", reg_type);
  } else {
    AppendToOutput("%c%d", reg_type, rm);
  }

  // Extend mode UXTX is an alias for shift mode LSL here.
  if (!((ext == UXTX) && (shift == 0))) {
    AppendToOutput(", %s", extend_mode[ext]);
    if (shift != 0) {
      AppendToOutput(" #%d", instr->SizeLS());
    }
  }
  return 9;
}


int DisassemblingDecoder::SubstitutePrefetchField(Instruction* instr,
                                                  const char* format) {
  DCHECK_EQ(format[0], 'P');
  USE(format);

  int prefetch_mode = instr->PrefetchMode();

  const char* ls = (prefetch_mode & 0x10) ? "st" : "ld";
  int level = (prefetch_mode >> 1) + 1;
  const char* ks = (prefetch_mode & 1) ? "strm" : "keep";

  AppendToOutput("p%sl%d%s", ls, level, ks);
  return 6;
}

int DisassemblingDecoder::SubstituteBarrierField(Instruction* instr,
                                                 const char* format) {
  DCHECK_EQ(format[0], 'M');
  USE(format);

  static const char* const options[4][4] = {
    { "sy (0b0000)", "oshld", "oshst", "osh" },
    { "sy (0b0100)", "nshld", "nshst", "nsh" },
    { "sy (0b1000)", "ishld", "ishst", "ish" },
    { "sy (0b1100)", "ld", "st", "sy" }
  };
  int domain = instr->ImmBarrierDomain();
  int type = instr->ImmBarrierType();

  AppendToOutput("%s", options[domain][type]);
  return 1;
}


void DisassemblingDecoder::ResetOutput() {
  buffer_pos_ = 0;
  buffer_[buffer_pos_] = 0;
}


void DisassemblingDecoder::AppendToOutput(const char* format, ...) {
  va_list args;
  va_start(args, format);
  buffer_pos_ += vsnprintf(&buffer_[buffer_pos_], buffer_size_, format, args);
  va_end(args);
}


void PrintDisassembler::ProcessOutput(Instruction* instr) {
  fprintf(stream_, "0x%016" PRIx64 "  %08" PRIx32 "\t\t%s\n",
          reinterpret_cast<uint64_t>(instr), instr->InstructionBits(),
          GetOutput());
}

}  // namespace internal
}  // namespace v8


namespace disasm {


const char* NameConverter::NameOfAddress(byte* addr) const {
  v8::internal::SNPrintF(tmp_buffer_, "%p", static_cast<void *>(addr));
  return tmp_buffer_.start();
}


const char* NameConverter::NameOfConstant(byte* addr) const {
  return NameOfAddress(addr);
}


const char* NameConverter::NameOfCPURegister(int reg) const {
  unsigned ureg = reg;  // Avoid warnings about signed/unsigned comparisons.
  if (ureg >= v8::internal::kNumberOfRegisters) {
    return "noreg";
  }
  if (ureg == v8::internal::kZeroRegCode) {
    return "xzr";
  }
  v8::internal::SNPrintF(tmp_buffer_, "x%u", ureg);
  return tmp_buffer_.start();
}


const char* NameConverter::NameOfByteCPURegister(int reg) const {
  UNREACHABLE();  // ARM64 does not have the concept of a byte register
  return "nobytereg";
}


const char* NameConverter::NameOfXMMRegister(int reg) const {
  UNREACHABLE();  // ARM64 does not have any XMM registers
  return "noxmmreg";
}


const char* NameConverter::NameInCode(byte* addr) const {
  // The default name converter is called for unknown code, so we will not try
  // to access any memory.
  return "";
}


//------------------------------------------------------------------------------

class BufferDisassembler : public v8::internal::DisassemblingDecoder {
 public:
  explicit BufferDisassembler(v8::internal::Vector<char> out_buffer)
      : out_buffer_(out_buffer) { }

  ~BufferDisassembler() { }

  virtual void ProcessOutput(v8::internal::Instruction* instr) {
    v8::internal::SNPrintF(out_buffer_, "%08" PRIx32 "       %s",
                           instr->InstructionBits(), GetOutput());
  }

 private:
  v8::internal::Vector<char> out_buffer_;
};

Disassembler::Disassembler(const NameConverter& converter)
    : converter_(converter) {}


Disassembler::~Disassembler() { USE(converter_); }


int Disassembler::InstructionDecode(v8::internal::Vector<char> buffer,
                                    byte* instr) {
  v8::internal::Decoder<v8::internal::DispatchingDecoderVisitor> decoder;
  BufferDisassembler disasm(buffer);
  decoder.AppendVisitor(&disasm);

  decoder.Decode(reinterpret_cast<v8::internal::Instruction*>(instr));
  return v8::internal::kInstructionSize;
}


int Disassembler::ConstantPoolSizeAt(byte* instr) {
  return v8::internal::Assembler::ConstantPoolSizeAt(
      reinterpret_cast<v8::internal::Instruction*>(instr));
}


void Disassembler::Disassemble(FILE* file, byte* start, byte* end) {
  v8::internal::Decoder<v8::internal::DispatchingDecoderVisitor> decoder;
  v8::internal::PrintDisassembler disasm(file);
  decoder.AppendVisitor(&disasm);

  for (byte* pc = start; pc < end; pc += v8::internal::kInstructionSize) {
    decoder.Decode(reinterpret_cast<v8::internal::Instruction*>(pc));
  }
}

}  // namespace disasm

#endif  // V8_TARGET_ARCH_ARM64