path: root/opcodes/aarch64-dis.c

/* aarch64-dis.c -- AArch64 disassembler.
   Copyright (C) 2009-2016 Free Software Foundation, Inc.
   Contributed by ARM Ltd.

   This file is part of the GNU opcodes library.

   This library is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3, or (at your option)
   any later version.

   It is distributed in the hope that it will be useful, but WITHOUT
   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
   License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; see the file COPYING3. If not,
   see <http://www.gnu.org/licenses/>.  */

#include "sysdep.h"
#include "bfd_stdint.h"
#include "dis-asm.h"
#include "libiberty.h"
#include "opintl.h"
#include "aarch64-dis.h"
#include "elf-bfd.h"

#define ERR_OK   0
#define ERR_UND -1
#define ERR_UNP -3
#define ERR_NYI -5

#define INSNLEN 4

/* Cached mapping symbol state.  */
enum map_type
{
  MAP_INSN,
  MAP_DATA
};

static enum map_type last_type;
static int last_mapping_sym = -1;
static bfd_vma last_mapping_addr = 0;

/* Other options */
static int no_aliases = 0;	/* If set disassemble as most general inst.  */


static void
set_default_aarch64_dis_options (struct disassemble_info *info ATTRIBUTE_UNUSED)
{
}

static void
parse_aarch64_dis_option (const char *option, unsigned int len ATTRIBUTE_UNUSED)
{
  /* Try to match options that are simple flags */
  if (CONST_STRNEQ (option, "no-aliases"))
    {
      no_aliases = 1;
      return;
    }

  if (CONST_STRNEQ (option, "aliases"))
    {
      no_aliases = 0;
      return;
    }

#ifdef DEBUG_AARCH64
  if (CONST_STRNEQ (option, "debug_dump"))
    {
      debug_dump = 1;
      return;
    }
#endif /* DEBUG_AARCH64 */

  /* Invalid option.  */
  fprintf (stderr, _("Unrecognised disassembler option: %s\n"), option);
}

static void
parse_aarch64_dis_options (const char *options)
{
  const char *option_end;

  if (options == NULL)
    return;

  while (*options != '\0')
    {
      /* Skip empty options.  */
      if (*options == ',')
	{
	  options++;
	  continue;
	}

      /* We know that *options is neither NUL or a comma.  */
      option_end = options + 1;
      while (*option_end != ',' && *option_end != '\0')
	option_end++;

      parse_aarch64_dis_option (options, option_end - options);

      /* Go on to the next one.  If option_end points to a comma, it
	 will be skipped above.  */
      options = option_end;
    }
}

/* Functions doing the instruction disassembling.  */

/* The unnamed arguments consist of the number of fields and information about
   these fields where the VALUE will be extracted from CODE and returned.
   MASK can be zero or the base mask of the opcode.

   N.B. the fields are required to be in such an order than the most signficant
   field for VALUE comes the first, e.g. the <index> in
    SQDMLAL <Va><d>, <Vb><n>, <Vm>.<Ts>[<index>]
   is encoded in H:L:M in some cases, the fields H:L:M should be passed in
   the order of H, L, M.  */

static inline aarch64_insn
extract_fields (aarch64_insn code, aarch64_insn mask, ...)
{
  uint32_t num;
  const aarch64_field *field;
  enum aarch64_field_kind kind;
  va_list va;

  va_start (va, mask);
  num = va_arg (va, uint32_t);
  assert (num <= 5);
  aarch64_insn value = 0x0;
  while (num--)
    {
      kind = va_arg (va, enum aarch64_field_kind);
      field = &fields[kind];
      value <<= field->width;
      value |= extract_field (kind, code, mask);
    }
  return value;
}

/* Sign-extend bit I of VALUE.  */
static inline int32_t
sign_extend (aarch64_insn value, unsigned i)
{
  uint32_t ret = value;

  assert (i < 32);
  if ((value >> i) & 0x1)
    {
      uint32_t val = (uint32_t)(-1) << i;
      ret = ret | val;
    }
  return (int32_t) ret;
}

/* N.B. the following inline helpfer functions create a dependency on the
   order of operand qualifier enumerators.  */

/* Given VALUE, return qualifier for a general purpose register.  */
static inline enum aarch64_opnd_qualifier
get_greg_qualifier_from_value (aarch64_insn value)
{
  enum aarch64_opnd_qualifier qualifier = AARCH64_OPND_QLF_W + value;
  assert (value <= 0x1
	  && aarch64_get_qualifier_standard_value (qualifier) == value);
  return qualifier;
}

/* Given VALUE, return qualifier for a vector register.  This does not support
   decoding instructions that accept the 2H vector type.  */

static inline enum aarch64_opnd_qualifier
get_vreg_qualifier_from_value (aarch64_insn value)
{
  enum aarch64_opnd_qualifier qualifier = AARCH64_OPND_QLF_V_8B + value;

  /* Instructions using vector type 2H should not call this function.  Skip over
     the 2H qualifier.  */
  if (qualifier >= AARCH64_OPND_QLF_V_2H)
    qualifier += 1;

  assert (value <= 0x8
	  && aarch64_get_qualifier_standard_value (qualifier) == value);
  return qualifier;
}

/* Given VALUE, return qualifier for an FP or AdvSIMD scalar register.  */
static inline enum aarch64_opnd_qualifier
get_sreg_qualifier_from_value (aarch64_insn value)
{
  enum aarch64_opnd_qualifier qualifier = AARCH64_OPND_QLF_S_B + value;

  assert (value <= 0x4
	  && aarch64_get_qualifier_standard_value (qualifier) == value);
  return qualifier;
}

/* Given the instruction in *INST which is probably half way through the
   decoding and our caller wants to know the expected qualifier for operand
   I.  Return such a qualifier if we can establish it; otherwise return
   AARCH64_OPND_QLF_NIL.  */

static aarch64_opnd_qualifier_t
get_expected_qualifier (const aarch64_inst *inst, int i)
{
  aarch64_opnd_qualifier_seq_t qualifiers;
  /* Should not be called if the qualifier is known.  */
  assert (inst->operands[i].qualifier == AARCH64_OPND_QLF_NIL);
  if (aarch64_find_best_match (inst, inst->opcode->qualifiers_list,
			       i, qualifiers))
    return qualifiers[i];
  else
    return AARCH64_OPND_QLF_NIL;
}

/* Operand extractors.  */

int
aarch64_ext_regno (const aarch64_operand *self, aarch64_opnd_info *info,
		   const aarch64_insn code,
		   const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  info->reg.regno = extract_field (self->fields[0], code, 0);
  return 1;
}

int
aarch64_ext_regno_pair (const aarch64_operand *self ATTRIBUTE_UNUSED, aarch64_opnd_info *info,
		   const aarch64_insn code ATTRIBUTE_UNUSED,
		   const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  assert (info->idx == 1
	  || info->idx ==3);
  info->reg.regno = inst->operands[info->idx - 1].reg.regno + 1;
  return 1;
}

/* e.g. IC <ic_op>{, <Xt>}.  */
int
aarch64_ext_regrt_sysins (const aarch64_operand *self, aarch64_opnd_info *info,
			  const aarch64_insn code,
			  const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  info->reg.regno = extract_field (self->fields[0], code, 0);
  assert (info->idx == 1
	  && (aarch64_get_operand_class (inst->operands[0].type)
	      == AARCH64_OPND_CLASS_SYSTEM));
  /* This will make the constraint checking happy and more importantly will
     help the disassembler determine whether this operand is optional or
     not.  */
  info->present = aarch64_sys_ins_reg_has_xt (inst->operands[0].sysins_op);

  return 1;
}

/* e.g. SQDMLAL <Va><d>, <Vb><n>, <Vm>.<Ts>[<index>].  */
int
aarch64_ext_reglane (const aarch64_operand *self, aarch64_opnd_info *info,
		     const aarch64_insn code,
		     const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  /* regno */
  info->reglane.regno = extract_field (self->fields[0], code,
				       inst->opcode->mask);

  /* Index and/or type.  */
  if (inst->opcode->iclass == asisdone
    || inst->opcode->iclass == asimdins)
    {
      if (info->type == AARCH64_OPND_En
	  && inst->opcode->operands[0] == AARCH64_OPND_Ed)
	{
	  unsigned shift;
	  /* index2 for e.g. INS <Vd>.<Ts>[<index1>], <Vn>.<Ts>[<index2>].  */
	  assert (info->idx == 1);	/* Vn */
	  aarch64_insn value = extract_field (FLD_imm4, code, 0);
	  /* Depend on AARCH64_OPND_Ed to determine the qualifier.  */
	  info->qualifier = get_expected_qualifier (inst, info->idx);
	  shift = get_logsz (aarch64_get_qualifier_esize (info->qualifier));
	  info->reglane.index = value >> shift;
	}
      else
	{
	  /* index and type for e.g. DUP <V><d>, <Vn>.<T>[<index>].
	     imm5<3:0>	<V>
	     0000	RESERVED
	     xxx1	B
	     xx10	H
	     x100	S
	     1000	D  */
	  int pos = -1;
	  aarch64_insn value = extract_field (FLD_imm5, code, 0);
	  while (++pos <= 3 && (value & 0x1) == 0)
	    value >>= 1;
	  if (pos > 3)
	    return 0;
	  info->qualifier = get_sreg_qualifier_from_value (pos);
	  info->reglane.index = (unsigned) (value >> 1);
	}
    }
  else
    {
      /* Index only for e.g. SQDMLAL <Va><d>, <Vb><n>, <Vm>.<Ts>[<index>]
         or SQDMLAL <Va><d>, <Vb><n>, <Vm>.<Ts>[<index>].  */

      /* Need information in other operand(s) to help decoding.  */
      info->qualifier = get_expected_qualifier (inst, info->idx);
      switch (info->qualifier)
	{
	case AARCH64_OPND_QLF_S_H:
	  /* h:l:m */
	  info->reglane.index = extract_fields (code, 0, 3, FLD_H, FLD_L,
						FLD_M);
	  info->reglane.regno &= 0xf;
	  break;
	case AARCH64_OPND_QLF_S_S:
	  /* h:l */
	  info->reglane.index = extract_fields (code, 0, 2, FLD_H, FLD_L);
	  break;
	case AARCH64_OPND_QLF_S_D:
	  /* H */
	  info->reglane.index = extract_field (FLD_H, code, 0);
	  break;
	default:
	  return 0;
	}
    }

  return 1;
}

int
aarch64_ext_reglist (const aarch64_operand *self, aarch64_opnd_info *info,
		     const aarch64_insn code,
		     const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  /* R */
  info->reglist.first_regno = extract_field (self->fields[0], code, 0);
  /* len */
  info->reglist.num_regs = extract_field (FLD_len, code, 0) + 1;
  return 1;
}

/* Decode Rt and opcode fields of Vt in AdvSIMD load/store instructions.  */
int
aarch64_ext_ldst_reglist (const aarch64_operand *self ATTRIBUTE_UNUSED,
			  aarch64_opnd_info *info, const aarch64_insn code,
			  const aarch64_inst *inst)
{
  aarch64_insn value;
  /* Number of elements in each structure to be loaded/stored.  */
  unsigned expected_num = get_opcode_dependent_value (inst->opcode);

  struct
    {
      unsigned is_reserved;
      unsigned num_regs;
      unsigned num_elements;
    } data [] =
  {   {0, 4, 4},
      {1, 4, 4},
      {0, 4, 1},
      {0, 4, 2},
      {0, 3, 3},
      {1, 3, 3},
      {0, 3, 1},
      {0, 1, 1},
      {0, 2, 2},
      {1, 2, 2},
      {0, 2, 1},
  };

  /* Rt */
  info->reglist.first_regno = extract_field (FLD_Rt, code, 0);
  /* opcode */
  value = extract_field (FLD_opcode, code, 0);
  if (expected_num != data[value].num_elements || data[value].is_reserved)
    return 0;
  info->reglist.num_regs = data[value].num_regs;

  return 1;
}

/* Decode Rt and S fields of Vt in AdvSIMD load single structure to all
   lanes instructions.  */
int
aarch64_ext_ldst_reglist_r (const aarch64_operand *self ATTRIBUTE_UNUSED,
			    aarch64_opnd_info *info, const aarch64_insn code,
			    const aarch64_inst *inst)
{
  aarch64_insn value;

  /* Rt */
  info->reglist.first_regno = extract_field (FLD_Rt, code, 0);
  /* S */
  value = extract_field (FLD_S, code, 0);

  /* Number of registers is equal to the number of elements in
     each structure to be loaded/stored.  */
  info->reglist.num_regs = get_opcode_dependent_value (inst->opcode);
  assert (info->reglist.num_regs >= 1 && info->reglist.num_regs <= 4);

  /* Except when it is LD1R.  */
  if (info->reglist.num_regs == 1 && value == (aarch64_insn) 1)
    info->reglist.num_regs = 2;

  return 1;
}

/* Decode Q, opcode<2:1>, S, size and Rt fields of Vt in AdvSIMD
   load/store single element instructions.  */
int
aarch64_ext_ldst_elemlist (const aarch64_operand *self ATTRIBUTE_UNUSED,
			   aarch64_opnd_info *info, const aarch64_insn code,
			   const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  aarch64_field field = {0, 0};
  aarch64_insn QSsize;		/* fields Q:S:size.  */
  aarch64_insn opcodeh2;	/* opcode<2:1> */

  /* Rt */
  info->reglist.first_regno = extract_field (FLD_Rt, code, 0);

  /* Decode the index, opcode<2:1> and size.  */
  gen_sub_field (FLD_asisdlso_opcode, 1, 2, &field);
  opcodeh2 = extract_field_2 (&field, code, 0);
  QSsize = extract_fields (code, 0, 3, FLD_Q, FLD_S, FLD_vldst_size);
  switch (opcodeh2)
    {
    case 0x0:
      info->qualifier = AARCH64_OPND_QLF_S_B;
      /* Index encoded in "Q:S:size".  */
      info->reglist.index = QSsize;
      break;
    case 0x1:
      if (QSsize & 0x1)
	/* UND.  */
	return 0;
      info->qualifier = AARCH64_OPND_QLF_S_H;
      /* Index encoded in "Q:S:size<1>".  */
      info->reglist.index = QSsize >> 1;
      break;
    case 0x2:
      if ((QSsize >> 1) & 0x1)
	/* UND.  */
	return 0;
      if ((QSsize & 0x1) == 0)
	{
	  info->qualifier = AARCH64_OPND_QLF_S_S;
	  /* Index encoded in "Q:S".  */
	  info->reglist.index = QSsize >> 2;
	}
      else
	{
	  if (extract_field (FLD_S, code, 0))
	    /* UND */
	    return 0;
	  info->qualifier = AARCH64_OPND_QLF_S_D;
	  /* Index encoded in "Q".  */
	  info->reglist.index = QSsize >> 3;
	}
      break;
    default:
      return 0;
    }

  info->reglist.has_index = 1;
  info->reglist.num_regs = 0;
  /* Number of registers is equal to the number of elements in
     each structure to be loaded/stored.  */
  info->reglist.num_regs = get_opcode_dependent_value (inst->opcode);
  assert (info->reglist.num_regs >= 1 && info->reglist.num_regs <= 4);

  return 1;
}

/* Decode fields immh:immb and/or Q for e.g.
   SSHR <Vd>.<T>, <Vn>.<T>, #<shift>
   or SSHR <V><d>, <V><n>, #<shift>.  */

int
aarch64_ext_advsimd_imm_shift (const aarch64_operand *self ATTRIBUTE_UNUSED,
			       aarch64_opnd_info *info, const aarch64_insn code,
			       const aarch64_inst *inst)
{
  int pos;
  aarch64_insn Q, imm, immh;
  enum aarch64_insn_class iclass = inst->opcode->iclass;

  immh = extract_field (FLD_immh, code, 0);
  if (immh == 0)
    return 0;
  imm = extract_fields (code, 0, 2, FLD_immh, FLD_immb);
  pos = 4;
  /* Get highest set bit in immh.  */
  while (--pos >= 0 && (immh & 0x8) == 0)
    immh <<= 1;

  assert ((iclass == asimdshf || iclass == asisdshf)
	  && (info->type == AARCH64_OPND_IMM_VLSR
	      || info->type == AARCH64_OPND_IMM_VLSL));

  if (iclass == asimdshf)
    {
      Q = extract_field (FLD_Q, code, 0);
      /* immh	Q	<T>
	 0000	x	SEE AdvSIMD modified immediate
	 0001	0	8B
	 0001	1	16B
	 001x	0	4H
	 001x	1	8H
	 01xx	0	2S
	 01xx	1	4S
	 1xxx	0	RESERVED
	 1xxx	1	2D  */
      info->qualifier =
	get_vreg_qualifier_from_value ((pos << 1) | (int) Q);
    }
  else
    info->qualifier = get_sreg_qualifier_from_value (pos);

  if (info->type == AARCH64_OPND_IMM_VLSR)
    /* immh	<shift>
       0000	SEE AdvSIMD modified immediate
       0001	(16-UInt(immh:immb))
       001x	(32-UInt(immh:immb))
       01xx	(64-UInt(immh:immb))
       1xxx	(128-UInt(immh:immb))  */
    info->imm.value = (16 << pos) - imm;
  else
    /* immh:immb
       immh	<shift>
       0000	SEE AdvSIMD modified immediate
       0001	(UInt(immh:immb)-8)
       001x	(UInt(immh:immb)-16)
       01xx	(UInt(immh:immb)-32)
       1xxx	(UInt(immh:immb)-64)  */
    info->imm.value = imm - (8 << pos);

  return 1;
}

/* Decode shift immediate for e.g. sshr (imm).  */
int
aarch64_ext_shll_imm (const aarch64_operand *self ATTRIBUTE_UNUSED,
		      aarch64_opnd_info *info, const aarch64_insn code,
		      const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  int64_t imm;
  aarch64_insn val;
  val = extract_field (FLD_size, code, 0);
  switch (val)
    {
    case 0: imm = 8; break;
    case 1: imm = 16; break;
    case 2: imm = 32; break;
    default: return 0;
    }
  info->imm.value = imm;
  return 1;
}

/* Decode imm for e.g. BFM <Wd>, <Wn>, #<immr>, #<imms>.
   value in the field(s) will be extracted as unsigned immediate value.  */
int
aarch64_ext_imm (const aarch64_operand *self, aarch64_opnd_info *info,
		 const aarch64_insn code,
		 const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  int64_t imm;
  /* Maximum of two fields to extract.  */
  assert (self->fields[2] == FLD_NIL);

  if (self->fields[1] == FLD_NIL)
    imm = extract_field (self->fields[0], code, 0);
  else
    /* e.g. TBZ b5:b40.  */
    imm = extract_fields (code, 0, 2, self->fields[0], self->fields[1]);

  if (info->type == AARCH64_OPND_FPIMM)
    info->imm.is_fp = 1;

  if (operand_need_sign_extension (self))
    imm = sign_extend (imm, get_operand_fields_width (self) - 1);

  if (operand_need_shift_by_two (self))
    imm <<= 2;

  if (info->type == AARCH64_OPND_ADDR_ADRP)
    imm <<= 12;

  info->imm.value = imm;
  return 1;
}

/* Decode imm and its shifter for e.g. MOVZ <Wd>, #<imm16>{, LSL #<shift>}.  */
int
aarch64_ext_imm_half (const aarch64_operand *self, aarch64_opnd_info *info,
		      const aarch64_insn code,
		      const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  aarch64_ext_imm (self, info, code, inst);
  info->shifter.kind = AARCH64_MOD_LSL;
  info->shifter.amount = extract_field (FLD_hw, code, 0) << 4;
  return 1;
}

/* Decode cmode and "a:b:c:d:e:f:g:h" for e.g.
     MOVI <Vd>.<T>, #<imm8> {, LSL #<amount>}.  */
int
aarch64_ext_advsimd_imm_modified (const aarch64_operand *self ATTRIBUTE_UNUSED,
				  aarch64_opnd_info *info,
				  const aarch64_insn code,
				  const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  uint64_t imm;
  enum aarch64_opnd_qualifier opnd0_qualifier = inst->operands[0].qualifier;
  aarch64_field field = {0, 0};

  assert (info->idx == 1);

  if (info->type == AARCH64_OPND_SIMD_FPIMM)
    info->imm.is_fp = 1;

  /* a:b:c:d:e:f:g:h */
  imm = extract_fields (code, 0, 2, FLD_abc, FLD_defgh);
  if (!info->imm.is_fp && aarch64_get_qualifier_esize (opnd0_qualifier) == 8)
    {
      /* Either MOVI <Dd>, #<imm>
	 or     MOVI <Vd>.2D, #<imm>.
	 <imm> is a 64-bit immediate
	 'aaaaaaaabbbbbbbbccccccccddddddddeeeeeeeeffffffffgggggggghhhhhhhh',
	 encoded in "a:b:c:d:e:f:g:h".	*/
      int i;
      unsigned abcdefgh = imm;
      for (imm = 0ull, i = 0; i < 8; i++)
	if (((abcdefgh >> i) & 0x1) != 0)
	  imm |= 0xffull << (8 * i);
    }
  info->imm.value = imm;

  /* cmode */
  info->qualifier = get_expected_qualifier (inst, info->idx);
  switch (info->qualifier)
    {
    case AARCH64_OPND_QLF_NIL:
      /* no shift */
      info->shifter.kind = AARCH64_MOD_NONE;
      return 1;
    case AARCH64_OPND_QLF_LSL:
      /* shift zeros */
      info->shifter.kind = AARCH64_MOD_LSL;
      switch (aarch64_get_qualifier_esize (opnd0_qualifier))
	{
	case 4: gen_sub_field (FLD_cmode, 1, 2, &field); break;	/* per word */
	case 2: gen_sub_field (FLD_cmode, 1, 1, &field); break;	/* per half */
	case 1: gen_sub_field (FLD_cmode, 1, 0, &field); break;	/* per byte */
	default: assert (0); return 0;
	}
      /* 00: 0; 01: 8; 10:16; 11:24.  */
      info->shifter.amount = extract_field_2 (&field, code, 0) << 3;
      break;
    case AARCH64_OPND_QLF_MSL:
      /* shift ones */
      info->shifter.kind = AARCH64_MOD_MSL;
      gen_sub_field (FLD_cmode, 0, 1, &field);		/* per word */
      info->shifter.amount = extract_field_2 (&field, code, 0) ? 16 : 8;
      break;
    default:
      assert (0);
      return 0;
    }

  return 1;
}

/* Decode scale for e.g. SCVTF <Dd>, <Wn>, #<fbits>.  */
int
aarch64_ext_fbits (const aarch64_operand *self ATTRIBUTE_UNUSED,
		   aarch64_opnd_info *info, const aarch64_insn code,
		   const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  info->imm.value = 64- extract_field (FLD_scale, code, 0);
  return 1;
}

/* Decode arithmetic immediate for e.g.
     SUBS <Wd>, <Wn|WSP>, #<imm> {, <shift>}.  */
int
aarch64_ext_aimm (const aarch64_operand *self ATTRIBUTE_UNUSED,
		  aarch64_opnd_info *info, const aarch64_insn code,
		  const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  aarch64_insn value;

  info->shifter.kind = AARCH64_MOD_LSL;
  /* shift */
  value = extract_field (FLD_shift, code, 0);
  if (value >= 2)
    return 0;
  info->shifter.amount = value ? 12 : 0;
  /* imm12 (unsigned) */
  info->imm.value = extract_field (FLD_imm12, code, 0);

  return 1;
}

/* Decode logical immediate for e.g. ORR <Wd|WSP>, <Wn>, #<imm>.  */

int
aarch64_ext_limm (const aarch64_operand *self ATTRIBUTE_UNUSED,
		  aarch64_opnd_info *info, const aarch64_insn code,
		  const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  uint64_t imm, mask;
  uint32_t sf;
  uint32_t N, R, S;
  unsigned simd_size;
  aarch64_insn value;

  value = extract_fields (code, 0, 3, FLD_N, FLD_immr, FLD_imms);
  assert (inst->operands[0].qualifier == AARCH64_OPND_QLF_W
	  || inst->operands[0].qualifier == AARCH64_OPND_QLF_X);
  sf = aarch64_get_qualifier_esize (inst->operands[0].qualifier) != 4;

  /* value is N:immr:imms.  */
  S = value & 0x3f;
  R = (value >> 6) & 0x3f;
  N = (value >> 12) & 0x1;

  if (sf == 0 && N == 1)
    return 0;

  /* The immediate value is S+1 bits to 1, left rotated by SIMDsize - R
     (in other words, right rotated by R), then replicated.  */
  if (N != 0)
    {
      simd_size = 64;
      mask = 0xffffffffffffffffull;
    }
  else
    {
      switch (S)
	{
	case 0x00 ... 0x1f: /* 0xxxxx */ simd_size = 32;           break;
	case 0x20 ... 0x2f: /* 10xxxx */ simd_size = 16; S &= 0xf; break;
	case 0x30 ... 0x37: /* 110xxx */ simd_size =  8; S &= 0x7; break;
	case 0x38 ... 0x3b: /* 1110xx */ simd_size =  4; S &= 0x3; break;
	case 0x3c ... 0x3d: /* 11110x */ simd_size =  2; S &= 0x1; break;
	default: return 0;
	}
      mask = (1ull << simd_size) - 1;
      /* Top bits are IGNORED.  */
      R &= simd_size - 1;
    }
  /* NOTE: if S = simd_size - 1 we get 0xf..f which is rejected.  */
  if (S == simd_size - 1)
    return 0;
  /* S+1 consecutive bits to 1.  */
  /* NOTE: S can't be 63 due to detection above.  */
  imm = (1ull << (S + 1)) - 1;
  /* Rotate to the left by simd_size - R.  */
  if (R != 0)
    imm = ((imm << (simd_size - R)) & mask) | (imm >> R);
  /* Replicate the value according to SIMD size.  */
  switch (simd_size)
    {
    case  2: imm = (imm <<  2) | imm;
    case  4: imm = (imm <<  4) | imm;
    case  8: imm = (imm <<  8) | imm;
    case 16: imm = (imm << 16) | imm;
    case 32: imm = (imm << 32) | imm;
    case 64: break;
    default: assert (0); return 0;
    }

  info->imm.value = sf ? imm : imm & 0xffffffff;

  return 1;
}

/* Decode Ft for e.g. STR <Qt>, [<Xn|SP>, <R><m>{, <extend> {<amount>}}]
   or LDP <Qt1>, <Qt2>, [<Xn|SP>], #<imm>.  */
int
aarch64_ext_ft (const aarch64_operand *self ATTRIBUTE_UNUSED,
		aarch64_opnd_info *info,
		const aarch64_insn code, const aarch64_inst *inst)
{
  aarch64_insn value;

  /* Rt */
  info->reg.regno = extract_field (FLD_Rt, code, 0);

  /* size */
  value = extract_field (FLD_ldst_size, code, 0);
  if (inst->opcode->iclass == ldstpair_indexed
      || inst->opcode->iclass == ldstnapair_offs
      || inst->opcode->iclass == ldstpair_off
      || inst->opcode->iclass == loadlit)
    {
      enum aarch64_opnd_qualifier qualifier;
      switch (value)
	{
	case 0: qualifier = AARCH64_OPND_QLF_S_S; break;
	case 1: qualifier = AARCH64_OPND_QLF_S_D; break;
	case 2: qualifier = AARCH64_OPND_QLF_S_Q; break;
	default: return 0;
	}
      info->qualifier = qualifier;
    }
  else
    {
      /* opc1:size */
      value = extract_fields (code, 0, 2, FLD_opc1, FLD_ldst_size);
      if (value > 0x4)
	return 0;
      info->qualifier = get_sreg_qualifier_from_value (value);
    }

  return 1;
}

/* Decode the address operand for e.g. STXRB <Ws>, <Wt>, [<Xn|SP>{,#0}].  */
int
aarch64_ext_addr_simple (const aarch64_operand *self ATTRIBUTE_UNUSED,
			 aarch64_opnd_info *info,
			 aarch64_insn code,
			 const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  /* Rn */
  info->addr.base_regno = extract_field (FLD_Rn, code, 0);
  return 1;
}

/* Decode the address operand for e.g.
     STR <Qt>, [<Xn|SP>, <R><m>{, <extend> {<amount>}}].  */
int
aarch64_ext_addr_regoff (const aarch64_operand *self ATTRIBUTE_UNUSED,
			 aarch64_opnd_info *info,
			 aarch64_insn code, const aarch64_inst *inst)
{
  aarch64_insn S, value;

  /* Rn */
  info->addr.base_regno = extract_field (FLD_Rn, code, 0);
  /* Rm */
  info->addr.offset.regno = extract_field (FLD_Rm, code, 0);
  /* option */
  value = extract_field (FLD_option, code, 0);
  info->shifter.kind =
    aarch64_get_operand_modifier_from_value (value, TRUE /* extend_p */);
  /* Fix-up the shifter kind; although the table-driven approach is
     efficient, it is slightly inflexible, thus needing this fix-up.  */
  if (info->shifter.kind == AARCH64_MOD_UXTX)
    info->shifter.kind = AARCH64_MOD_LSL;
  /* S */
  S = extract_field (FLD_S, code, 0);
  if (S == 0)
    {
      info->shifter.amount = 0;
      info->shifter.amount_present = 0;
    }
  else
    {
      int size;
      /* Need information in other operand(s) to help achieve the decoding
	 from 'S' field.  */
      info->qualifier = get_expected_qualifier (inst, info->idx);
      /* Get the size of the data element that is accessed, which may be
	 different from that of the source register size, e.g. in strb/ldrb.  */
      size = aarch64_get_qualifier_esize (info->qualifier);
      info->shifter.amount = get_logsz (size);
      info->shifter.amount_present = 1;
    }

  return 1;
}

/* Decode the address operand for e.g. LDRSW <Xt>, [<Xn|SP>], #<simm>.  */
int
aarch64_ext_addr_simm (const aarch64_operand *self, aarch64_opnd_info *info,
		       aarch64_insn code, const aarch64_inst *inst)
{
  aarch64_insn imm;
  info->qualifier = get_expected_qualifier (inst, info->idx);

  /* Rn */
  info->addr.base_regno = extract_field (FLD_Rn, code, 0);
  /* simm (imm9 or imm7)  */
  imm = extract_field (self->fields[0], code, 0);
  info->addr.offset.imm = sign_extend (imm, fields[self->fields[0]].width - 1);
  if (self->fields[0] == FLD_imm7)
    /* scaled immediate in ld/st pair instructions.  */
    info->addr.offset.imm *= aarch64_get_qualifier_esize (info->qualifier);
  /* qualifier */
  if (inst->opcode->iclass == ldst_unscaled
      || inst->opcode->iclass == ldstnapair_offs
      || inst->opcode->iclass == ldstpair_off
      || inst->opcode->iclass == ldst_unpriv)
    info->addr.writeback = 0;
  else
    {
      /* pre/post- index */
      info->addr.writeback = 1;
      if (extract_field (self->fields[1], code, 0) == 1)
	info->addr.preind = 1;
      else
	info->addr.postind = 1;
    }

  return 1;
}

/* Decode the address operand for e.g. LDRSW <Xt>, [<Xn|SP>{, #<simm>}].  */
int
aarch64_ext_addr_uimm12 (const aarch64_operand *self, aarch64_opnd_info *info,
			 aarch64_insn code,
			 const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  int shift;
  info->qualifier = get_expected_qualifier (inst, info->idx);
  shift = get_logsz (aarch64_get_qualifier_esize (info->qualifier));
  /* Rn */
  info->addr.base_regno = extract_field (self->fields[0], code, 0);
  /* uimm12 */
  info->addr.offset.imm = extract_field (self->fields[1], code, 0) << shift;
  return 1;
}

/* Decode the address operand for e.g.
     LD1 {<Vt>.<T>, <Vt2>.<T>, <Vt3>.<T>}, [<Xn|SP>], <Xm|#<amount>>.  */
int
aarch64_ext_simd_addr_post (const aarch64_operand *self ATTRIBUTE_UNUSED,
			    aarch64_opnd_info *info,
			    aarch64_insn code, const aarch64_inst *inst)
{
  /* The opcode dependent area stores the number of elements in
     each structure to be loaded/stored.  */
  int is_ld1r = get_opcode_dependent_value (inst->opcode) == 1;

  /* Rn */
  info->addr.base_regno = extract_field (FLD_Rn, code, 0);
  /* Rm | #<amount>  */
  info->addr.offset.regno = extract_field (FLD_Rm, code, 0);
  if (info->addr.offset.regno == 31)
    {
      if (inst->opcode->operands[0] == AARCH64_OPND_LVt_AL)
	/* Special handling of loading single structure to all lane.  */
	info->addr.offset.imm = (is_ld1r ? 1
				 : inst->operands[0].reglist.num_regs)
	  * aarch64_get_qualifier_esize (inst->operands[0].qualifier);
      else
	info->addr.offset.imm = inst->operands[0].reglist.num_regs
	  * aarch64_get_qualifier_esize (inst->operands[0].qualifier)
	  * aarch64_get_qualifier_nelem (inst->operands[0].qualifier);
    }
  else
    info->addr.offset.is_reg = 1;
  info->addr.writeback = 1;

  return 1;
}

/* Decode the condition operand for e.g. CSEL <Xd>, <Xn>, <Xm>, <cond>.  */
int
aarch64_ext_cond (const aarch64_operand *self ATTRIBUTE_UNUSED,
		  aarch64_opnd_info *info,
		  aarch64_insn code, const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  aarch64_insn value;
  /* cond */
  value = extract_field (FLD_cond, code, 0);
  info->cond = get_cond_from_value (value);
  return 1;
}

/* Decode the system register operand for e.g. MRS <Xt>, <systemreg>.  */
int
aarch64_ext_sysreg (const aarch64_operand *self ATTRIBUTE_UNUSED,
		    aarch64_opnd_info *info,
		    aarch64_insn code,
		    const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  /* op0:op1:CRn:CRm:op2 */
  info->sysreg = extract_fields (code, 0, 5, FLD_op0, FLD_op1, FLD_CRn,
				 FLD_CRm, FLD_op2);
  return 1;
}

/* Decode the PSTATE field operand for e.g. MSR <pstatefield>, #<imm>.  */
int
aarch64_ext_pstatefield (const aarch64_operand *self ATTRIBUTE_UNUSED,
			 aarch64_opnd_info *info, aarch64_insn code,
			 const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  int i;
  /* op1:op2 */
  info->pstatefield = extract_fields (code, 0, 2, FLD_op1, FLD_op2);
  for (i = 0; aarch64_pstatefields[i].name != NULL; ++i)
    if (aarch64_pstatefields[i].value == (aarch64_insn)info->pstatefield)
      return 1;
  /* Reserved value in <pstatefield>.  */
  return 0;
}

/* Decode the system instruction op operand for e.g. AT <at_op>, <Xt>.  */
int
aarch64_ext_sysins_op (const aarch64_operand *self ATTRIBUTE_UNUSED,
		       aarch64_opnd_info *info,
		       aarch64_insn code,
		       const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  int i;
  aarch64_insn value;
  const aarch64_sys_ins_reg *sysins_ops;
  /* op0:op1:CRn:CRm:op2 */
  value = extract_fields (code, 0, 5,
			  FLD_op0, FLD_op1, FLD_CRn,
			  FLD_CRm, FLD_op2);

  switch (info->type)
    {
    case AARCH64_OPND_SYSREG_AT: sysins_ops = aarch64_sys_regs_at; break;
    case AARCH64_OPND_SYSREG_DC: sysins_ops = aarch64_sys_regs_dc; break;
    case AARCH64_OPND_SYSREG_IC: sysins_ops = aarch64_sys_regs_ic; break;
    case AARCH64_OPND_SYSREG_TLBI: sysins_ops = aarch64_sys_regs_tlbi; break;
    default: assert (0); return 0;
    }

  for (i = 0; sysins_ops[i].name != NULL; ++i)
    if (sysins_ops[i].value == value)
      {
	info->sysins_op = sysins_ops + i;
	DEBUG_TRACE ("%s found value: %x, has_xt: %d, i: %d.",
		     info->sysins_op->name,
		     (unsigned)info->sysins_op->value,
		     aarch64_sys_ins_reg_has_xt (info->sysins_op), i);
	return 1;
      }

  return 0;
}

/* Decode the memory barrier option operand for e.g. DMB <option>|#<imm>.  */

int
aarch64_ext_barrier (const aarch64_operand *self ATTRIBUTE_UNUSED,
		     aarch64_opnd_info *info,
		     aarch64_insn code,
		     const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  /* CRm */
  info->barrier = aarch64_barrier_options + extract_field (FLD_CRm, code, 0);
  return 1;
}

/* Decode the prefetch operation option operand for e.g.
     PRFM <prfop>, [<Xn|SP>{, #<pimm>}].  */

int
aarch64_ext_prfop (const aarch64_operand *self ATTRIBUTE_UNUSED,
		   aarch64_opnd_info *info,
		   aarch64_insn code, const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  /* prfop in Rt */
  info->prfop = aarch64_prfops + extract_field (FLD_Rt, code, 0);
  return 1;
}

/* Decode the hint number for an alias taking an operand.  Set info->hint_option
   to the matching name/value pair in aarch64_hint_options.  */

int
aarch64_ext_hint (const aarch64_operand *self ATTRIBUTE_UNUSED,
		  aarch64_opnd_info *info,
		  aarch64_insn code,
		  const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  /* CRm:op2.  */
  unsigned hint_number;
  int i;

  hint_number = extract_fields (code, 0, 2, FLD_CRm, FLD_op2);

  for (i = 0; aarch64_hint_options[i].name != NULL; i++)
    {
      if (hint_number == aarch64_hint_options[i].value)
	{
	  info->hint_option = &(aarch64_hint_options[i]);
	  return 1;
	}
    }

  return 0;
}

/* Decode the extended register operand for e.g.
     STR <Qt>, [<Xn|SP>, <R><m>{, <extend> {<amount>}}].  */
int
aarch64_ext_reg_extended (const aarch64_operand *self ATTRIBUTE_UNUSED,
			  aarch64_opnd_info *info,
			  aarch64_insn code,
			  const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  aarch64_insn value;

  /* Rm */
  info->reg.regno = extract_field (FLD_Rm, code, 0);
  /* option */
  value = extract_field (FLD_option, code, 0);
  info->shifter.kind =
    aarch64_get_operand_modifier_from_value (value, TRUE /* extend_p */);
  /* imm3 */
  info->shifter.amount = extract_field (FLD_imm3, code,  0);

  /* This makes the constraint checking happy.  */
  info->shifter.operator_present = 1;

  /* Assume inst->operands[0].qualifier has been resolved.  */
  assert (inst->operands[0].qualifier != AARCH64_OPND_QLF_NIL);
  info->qualifier = AARCH64_OPND_QLF_W;
  if (inst->operands[0].qualifier == AARCH64_OPND_QLF_X
      && (info->shifter.kind == AARCH64_MOD_UXTX
	  || info->shifter.kind == AARCH64_MOD_SXTX))
    info->qualifier = AARCH64_OPND_QLF_X;

  return 1;
}

/* Decode the shifted register operand for e.g.
     SUBS <Xd>, <Xn>, <Xm> {, <shift> #<amount>}.  */
int
aarch64_ext_reg_shifted (const aarch64_operand *self ATTRIBUTE_UNUSED,
			 aarch64_opnd_info *info,
			 aarch64_insn code,
			 const aarch64_inst *inst ATTRIBUTE_UNUSED)
{
  aarch64_insn value;

  /* Rm */
  info->reg.regno = extract_field (FLD_Rm, code, 0);
  /* shift */
  value = extract_field (FLD_shift, code, 0);
  info->shifter.kind =
    aarch64_get_operand_modifier_from_value (value, FALSE /* extend_p */);
  if (info->shifter.kind == AARCH64_MOD_ROR
      && inst->opcode->iclass != log_shift)
    /* ROR is not available for the shifted register operand in arithmetic
       instructions.  */
    return 0;
  /* imm6 */
  info->shifter.amount = extract_field (FLD_imm6, code,  0);

  /* This makes the constraint checking happy.  */
  info->shifter.operator_present = 1;

  return 1;
}

/* Bitfields that are commonly used to encode certain operands' information
   may be partially used as part of the base opcode in some instructions.
   For example, the bit 1 of the field 'size' in
     FCVTXN <Vb><d>, <Va><n>
   is actually part of the base opcode, while only size<0> is available
   for encoding the register type.  Another example is the AdvSIMD
   instruction ORR (register), in which the field 'size' is also used for
   the base opcode, leaving only the field 'Q' available to encode the
   vector register arrangement specifier '8B' or '16B'.

   This function tries to deduce the qualifier from the value of partially
   constrained field(s).  Given the VALUE of such a field or fields, the
   qualifiers CANDIDATES and the MASK (indicating which bits are valid for
   operand encoding), the function returns the matching qualifier or
   AARCH64_OPND_QLF_NIL if nothing matches.

   N.B. CANDIDATES is a group of possible qualifiers that are valid for
   one operand; it has a maximum of AARCH64_MAX_QLF_SEQ_NUM qualifiers and
   may end with AARCH64_OPND_QLF_NIL.  */

static enum aarch64_opnd_qualifier
get_qualifier_from_partial_encoding (aarch64_insn value,
				     const enum aarch64_opnd_qualifier* \
				     candidates,
				     aarch64_insn mask)
{
  int i;
  DEBUG_TRACE ("enter with value: %d, mask: %d", (int)value, (int)mask);
  for (i = 0; i < AARCH64_MAX_QLF_SEQ_NUM; ++i)
    {
      aarch64_insn standard_value;
      if (candidates[i] == AARCH64_OPND_QLF_NIL)
	break;
      standard_value = aarch64_get_qualifier_standard_value (candidates[i]);
      if ((standard_value & mask) == (value & mask))
	return candidates[i];
    }
  return AARCH64_OPND_QLF_NIL;
}

/* Given a list of qualifier sequences, return all possible valid qualifiers
   for operand IDX in QUALIFIERS.
   Assume QUALIFIERS is an array whose length is large enough.  */

static void
get_operand_possible_qualifiers (int idx,
				 const aarch64_opnd_qualifier_seq_t *list,
				 enum aarch64_opnd_qualifier *qualifiers)
{
  int i;
  for (i = 0; i < AARCH64_MAX_QLF_SEQ_NUM; ++i)
    if ((qualifiers[i] = list[i][idx]) == AARCH64_OPND_QLF_NIL)
      break;
}

/* Decode the size Q field for e.g. SHADD.
   We tag one operand with the qualifer according to the code;
   whether the qualifier is valid for this opcode or not, it is the
   duty of the semantic checking.  */

static int
decode_sizeq (aarch64_inst *inst)
{
  int idx;
  enum aarch64_opnd_qualifier qualifier;
  aarch64_insn code;
  aarch64_insn value, mask;
  enum aarch64_field_kind fld_sz;
  enum aarch64_opnd_qualifier candidates[AARCH64_MAX_QLF_SEQ_NUM];

  if (inst->opcode->iclass == asisdlse
     || inst->opcode->iclass == asisdlsep
     || inst->opcode->iclass == asisdlso
     || inst->opcode->iclass == asisdlsop)
    fld_sz = FLD_vldst_size;
  else
    fld_sz = FLD_size;

  code = inst->value;
  value = extract_fields (code, inst->opcode->mask, 2, fld_sz, FLD_Q);
  /* Obtain the info that which bits of fields Q and size are actually
     available for operand encoding.  Opcodes like FMAXNM and FMLA have
     size[1] unavailable.  */
  mask = extract_fields (~inst->opcode->mask, 0, 2, fld_sz, FLD_Q);

  /* The index of the operand we are going to tag a qualifier and the qualifer
     itself are reasoned from the value of the size and Q fields and the
     possible valid qualifier lists.  */
  idx = aarch64_select_operand_for_sizeq_field_coding (inst->opcode);
  DEBUG_TRACE ("key idx: %d", idx);

  /* For most related instruciton, size:Q are fully available for operand
     encoding.  */
  if (mask == 0x7)
    {
      inst->operands[idx].qualifier = get_vreg_qualifier_from_value (value);
      return 1;
    }

  get_operand_possible_qualifiers (idx, inst->opcode->qualifiers_list,
				   candidates);
#ifdef DEBUG_AARCH64
  if (debug_dump)
    {
      int i;
      for (i = 0; candidates[i] != AARCH64_OPND_QLF_NIL
	   && i < AARCH64_MAX_QLF_SEQ_NUM; ++i)
	DEBUG_TRACE ("qualifier %d: %s", i,
		     aarch64_get_qualifier_name(candidates[i]));
      DEBUG_TRACE ("%d, %d", (int)value, (int)mask);
    }
#endif /* DEBUG_AARCH64 */

  qualifier = get_qualifier_from_partial_encoding (value, candidates, mask);

  if (qualifier == AARCH64_OPND_QLF_NIL)
    return 0;

  inst->operands[idx].qualifier = qualifier;
  return 1;
}

/* Decode size[0]:Q, i.e. bit 22 and bit 30, for
     e.g. FCVTN<Q> <Vd>.<Tb>, <Vn>.<Ta>.  */

static int
decode_asimd_fcvt (aarch64_inst *inst)
{
  aarch64_field field = {0, 0};
  aarch64_insn value;
  enum aarch64_opnd_qualifier qualifier;

  gen_sub_field (FLD_size, 0, 1, &field);
  value = extract_field_2 (&field, inst->value, 0);
  qualifier = value == 0 ? AARCH64_OPND_QLF_V_4S
    : AARCH64_OPND_QLF_V_2D;
  switch (inst->opcode->op)
    {
    case OP_FCVTN:
    case OP_FCVTN2:
      /* FCVTN<Q> <Vd>.<Tb>, <Vn>.<Ta>.  */
      inst->operands[1].qualifier = qualifier;
      break;
    case OP_FCVTL:
    case OP_FCVTL2:
      /* FCVTL<Q> <Vd>.<Ta>, <Vn>.<Tb>.  */
      inst->operands[0].qualifier = qualifier;
      break;
    default:
      assert (0);
      return 0;
    }

  return 1;
}

/* Decode size[0], i.e. bit 22, for
     e.g. FCVTXN <Vb><d>, <Va><n>.  */

static int
decode_asisd_fcvtxn (aarch64_inst *inst)
{
  aarch64_field field = {0, 0};
  gen_sub_field (FLD_size, 0, 1, &field);
  if (!extract_field_2 (&field, inst->value, 0))
    return 0;
  inst->operands[0].qualifier = AARCH64_OPND_QLF_S_S;
  return 1;
}

/* Decode the 'opc' field for e.g. FCVT <Dd>, <Sn>.  */
static int
decode_fcvt (aarch64_inst *inst)
{
  enum aarch64_opnd_qualifier qualifier;
  aarch64_insn value;
  const aarch64_field field = {15, 2};

  /* opc dstsize */
  value = extract_field_2 (&field, inst->value, 0);
  switch (value)
    {
    case 0: qualifier = AARCH64_OPND_QLF_S_S; break;
    case 1: qualifier = AARCH64_OPND_QLF_S_D; break;
    case 3: qualifier = AARCH64_OPND_QLF_S_H; break;
    default: return 0;
    }
  inst->operands[0].qualifier = qualifier;

  return 1;
}

/* Do miscellaneous decodings that are not common enough to be driven by
   flags.  */

static int
do_misc_decoding (aarch64_inst *inst)
{
  switch (inst->opcode->op)
    {
    case OP_FCVT:
      return decode_fcvt (inst);
    case OP_FCVTN:
    case OP_FCVTN2:
    case OP_FCVTL:
    case OP_FCVTL2:
      return decode_asimd_fcvt (inst);
    case OP_FCVTXN_S:
      return decode_asisd_fcvtxn (inst);
    default:
      return 0;
    }
}

/* Opcodes that have fields shared by multiple operands are usually flagged
   with flags.  In this function, we detect such flags, decode the related
   field(s) and store the information in one of the related operands.  The
   'one' operand is not any operand but one of the operands that can
   accommadate all the information that has been decoded.  */

static int
do_special_decoding (aarch64_inst *inst)
{
  int idx;
  aarch64_insn value;
  /* Condition for truly conditional executed instructions, e.g. b.cond.  */
  if (inst->opcode->flags & F_COND)
    {
      value = extract_field (FLD_cond2, inst->value, 0);
      inst->cond = get_cond_from_value (value);
    }
  /* 'sf' field.  */
  if (inst->opcode->flags & F_SF)
    {
      idx = select_operand_for_sf_field_coding (inst->opcode);
      value = extract_field (FLD_sf, inst->value, 0);
      inst->operands[idx].qualifier = get_greg_qualifier_from_value (value);
      if ((inst->opcode->flags & F_N)
	  && extract_field (FLD_N, inst->value, 0) != value)
	return 0;
    }
  /* 'sf' field.  */
  if (inst->opcode->flags & F_LSE_SZ)
    {
      idx = select_operand_for_sf_field_coding (inst->opcode);
      value = extract_field (FLD_lse_sz, inst->value, 0);
      inst->operands[idx].qualifier = get_greg_qualifier_from_value (value);
    }
  /* size:Q fields.  */
  if (inst->opcode->flags & F_SIZEQ)
    return decode_sizeq (inst);

  if (inst->opcode->flags & F_FPTYPE)
    {
      idx = select_operand_for_fptype_field_coding (inst->opcode);
      value = extract_field (FLD_type, inst->value, 0);
      switch (value)
	{
	case 0: inst->operands[idx].qualifier = AARCH64_OPND_QLF_S_S; break;
	case 1: inst->operands[idx].qualifier = AARCH64_OPND_QLF_S_D; break;
	case 3: inst->operands[idx].qualifier = AARCH64_OPND_QLF_S_H; break;
	default: return 0;
	}
    }

  if (inst->opcode->flags & F_SSIZE)
    {
      /* N.B. some opcodes like FCMGT <V><d>, <V><n>, #0 have the size[1] as part
	 of the base opcode.  */
      aarch64_insn mask;
      enum aarch64_opnd_qualifier candidates[AARCH64_MAX_QLF_SEQ_NUM];
      idx = select_operand_for_scalar_size_field_coding (inst->opcode);
      value = extract_field (FLD_size, inst->value, inst->opcode->mask);
      mask = extract_field (FLD_size, ~inst->opcode->mask, 0);
      /* For most related instruciton, the 'size' field is fully available for
	 operand encoding.  */
      if (mask == 0x3)
	inst->operands[idx].qualifier = get_sreg_qualifier_from_value (value);
      else
	{
	  get_operand_possible_qualifiers (idx, inst->opcode->qualifiers_list,
					   candidates);
	  inst->operands[idx].qualifier
	    = get_qualifier_from_partial_encoding (value, candidates, mask);
	}
    }

  if (inst->opcode->flags & F_T)
    {
      /* Num of consecutive '0's on the right side of imm5<3:0>.  */
      int num = 0;
      unsigned val, Q;
      assert (aarch64_get_operand_class (inst->opcode->operands[0])
	      == AARCH64_OPND_CLASS_SIMD_REG);
      /* imm5<3:0>	q	<t>
	 0000		x	reserved
	 xxx1		0	8b
	 xxx1		1	16b
	 xx10		0	4h
	 xx10		1	8h
	 x100		0	2s
	 x100		1	4s
	 1000		0	reserved
	 1000		1	2d  */
      val = extract_field (FLD_imm5, inst->value, 0);
      while ((val & 0x1) == 0 && ++num <= 3)
	val >>= 1;
      if (num > 3)
	return 0;
      Q = (unsigned) extract_field (FLD_Q, inst->value, inst->opcode->mask);
      inst->operands[0].qualifier =
	get_vreg_qualifier_from_value ((num << 1) | Q);
    }

  if (inst->opcode->flags & F_GPRSIZE_IN_Q)
    {
      /* Use Rt to encode in the case of e.g.
	 STXP <Ws>, <Xt1>, <Xt2>, [<Xn|SP>{,#0}].  */
      idx = aarch64_operand_index (inst->opcode->operands, AARCH64_OPND_Rt);
      if (idx == -1)
	{
	  /* Otherwise use the result operand, which has to be a integer
	     register.  */
	  assert (aarch64_get_operand_class (inst->opcode->operands[0])
		  == AARCH64_OPND_CLASS_INT_REG);
	  idx = 0;
	}
      assert (idx == 0 || idx == 1);
      value = extract_field (FLD_Q, inst->value, 0);
      inst->operands[idx].qualifier = get_greg_qualifier_from_value (value);
    }

  if (inst->opcode->flags & F_LDS_SIZE)
    {
      aarch64_field field = {0, 0};
      assert (aarch64_get_operand_class (inst->opcode->operands[0])
	      == AARCH64_OPND_CLASS_INT_REG);
      gen_sub_field (FLD_opc, 0, 1, &field);
      value = extract_field_2 (&field, inst->value, 0);
      inst->operands[0].qualifier
	= value ? AARCH64_OPND_QLF_W : AARCH64_OPND_QLF_X;
    }

  /* Miscellaneous decoding; done as the last step.  */
  if (inst->opcode->flags & F_MISC)
    return do_misc_decoding (inst);

  return 1;
}

/* Converters converting a real opcode instruction to its alias form.  */

/* ROR <Wd>, <Ws>, #<shift>
     is equivalent to:
   EXTR <Wd>, <Ws>, <Ws>, #<shift>.  */
static int
convert_extr_to_ror (aarch64_inst *inst)
{
  if (inst->operands[1].reg.regno == inst->operands[2].reg.regno)
    {
      copy_operand_info (inst, 2, 3);
      inst->operands[3].type = AARCH64_OPND_NIL;
      return 1;
    }
  return 0;
}

/* UXTL<Q> <Vd>.<Ta>, <Vn>.<Tb>
     is equivalent to:
   USHLL<Q> <Vd>.<Ta>, <Vn>.<Tb>, #0.  */
static int
convert_shll_to_xtl (aarch64_inst *inst)
{
  if (inst->operands[2].imm.value == 0)
    {
      inst->operands[2].type = AARCH64_OPND_NIL;
      return 1;
    }
  return 0;
}

/* Convert
     UBFM <Xd>, <Xn>, #<shift>, #63.
   to
     LSR <Xd>, <Xn>, #<shift>.  */
static int
convert_bfm_to_sr (aarch64_inst *inst)
{
  int64_t imms, val;

  imms = inst->operands[3].imm.value;
  val = inst->operands[2].qualifier == AARCH64_OPND_QLF_imm_0_31 ? 31 : 63;
  if (imms == val)
    {
      inst->operands[3].type = AARCH64_OPND_NIL;
      return 1;
    }

  return 0;
}

/* Convert MOV to ORR.  */
static int
convert_orr_to_mov (aarch64_inst *inst)
{
  /* MOV <Vd>.<T>, <Vn>.<T>
     is equivalent to:
     ORR <Vd>.<T>, <Vn>.<T>, <Vn>.<T>.  */
  if (inst->operands[1].reg.regno == inst->operands[2].reg.regno)
    {
      inst->operands[2].type = AARCH64_OPND_NIL;
      return 1;
    }
  return 0;
}

/* When <imms> >= <immr>, the instruction written:
     SBFX <Xd>, <Xn>, #<lsb>, #<width>
   is equivalent to:
     SBFM <Xd>, <Xn>, #<lsb>, #(<lsb>+<width>-1).  */

static int
convert_bfm_to_bfx (aarch64_inst *inst)
{
  int64_t immr, imms;

  immr = inst->operands[2].imm.value;
  imms = inst->operands[3].imm.value;
  if (imms >= immr)
    {
      int64_t lsb = immr;
      inst->operands[2].imm.value = lsb;
      inst->operands[3].imm.value = imms + 1 - lsb;
      /* The two opcodes have different qualifiers for
	 the immediate operands; reset to help the checking.  */
      reset_operand_qualifier (inst, 2);
      reset_operand_qualifier (inst, 3);
      return 1;
    }

  return 0;
}

/* When <imms> < <immr>, the instruction written:
     SBFIZ <Xd>, <Xn>, #<lsb>, #<width>
   is equivalent to:
     SBFM <Xd>, <Xn>, #((64-<lsb>)&0x3f), #(<width>-1).  */

static int
convert_bfm_to_bfi (aarch64_inst *inst)
{
  int64_t immr, imms, val;

  immr = inst->operands[2].imm.value;
  imms = inst->operands[3].imm.value;
  val = inst->operands[2].qualifier == AARCH64_OPND_QLF_imm_0_31 ? 32 : 64;
  if (imms < immr)
    {
      inst->operands[2].imm.value = (val - immr) & (val - 1);
      inst->operands[3].imm.value = imms + 1;
      /* The two opcodes have different qualifiers for
	 the immediate operands; reset to help the checking.  */
      reset_operand_qualifier (inst, 2);
      reset_operand_qualifier (inst, 3);
      return 1;
    }

  return 0;
}

/* The instruction written:
     BFC <Xd>, #<lsb>, #<width>
   is equivalent to:
     BFM <Xd>, XZR, #((64-<lsb>)&0x3f), #(<width>-1).  */

static int
convert_bfm_to_bfc (aarch64_inst *inst)
{
  int64_t immr, imms, val;

  /* Should have been assured by the base opcode value.  */
  assert (inst->operands[1].reg.regno == 0x1f);

  immr = inst->operands[2].imm.value;
  imms = inst->operands[3].imm.value;
  val = inst->operands[2].qualifier == AARCH64_OPND_QLF_imm_0_31 ? 32 : 64;
  if (imms < immr)
    {
      /* Drop XZR from the second operand.  */
      copy_operand_info (inst, 1, 2);
      copy_operand_info (inst, 2, 3);
      inst->operands[3].type = AARCH64_OPND_NIL;

      /* Recalculate the immediates.  */
      inst->operands[1].imm.value = (val - immr) & (val - 1);
      inst->operands[2].imm.value = imms + 1;

      /* The two opcodes have different qualifiers for the operands; reset to
	 help the checking.  */
      reset_operand_qualifier (inst, 1);
      reset_operand_qualifier (inst, 2);
      reset_operand_qualifier (inst, 3);

      return 1;
    }

  return 0;
}

/* The instruction written:
     LSL <Xd>, <Xn>, #<shift>
   is equivalent to:
     UBFM <Xd>, <Xn>, #((64-<shift>)&0x3f), #(63-<shift>).  */

static int
convert_ubfm_to_lsl (aarch64_inst *inst)
{
  int64_t immr = inst->operands[2].imm.value;
  int64_t imms = inst->operands[3].imm.value;
  int64_t val
    = inst->operands[2].qualifier == AARCH64_OPND_QLF_imm_0_31 ? 31 : 63;

  if ((immr == 0 && imms == val) || immr == imms + 1)
    {
      inst->operands[3].type = AARCH64_OPND_NIL;
      inst->operands[2].imm.value = val - imms;
      return 1;
    }

  return 0;
}

/* CINC <Wd>, <Wn>, <cond>
     is equivalent to:
   CSINC <Wd>, <Wn>, <Wn>, invert(<cond>)
     where <cond> is not AL or NV.  */

static int
convert_from_csel (aarch64_inst *inst)
{
  if (inst->operands[1].reg.regno == inst->operands[2].reg.regno
      && (inst->operands[3].cond->value & 0xe) != 0xe)
    {
      copy_operand_info (inst, 2, 3);
      inst->operands[2].cond = get_inverted_cond (inst->operands[3].cond);
      inst->operands[3].type = AARCH64_OPND_NIL;
      return 1;
    }
  return 0;
}

/* CSET <Wd>, <cond>
     is equivalent to:
   CSINC <Wd>, WZR, WZR, invert(<cond>)
     where <cond> is not AL or NV.  */

static int
convert_csinc_to_cset (aarch64_inst *inst)
{
  if (inst->operands[1].reg.regno == 0x1f
      && inst->operands[2].reg.regno == 0x1f
      && (inst->operands[3].cond->value & 0xe) != 0xe)
    {
      copy_operand_info (inst, 1, 3);
      inst->operands[1].cond = get_inverted_cond (inst->operands[3].cond);
      inst->operands[3].type = AARCH64_OPND_NIL;
      inst->operands[2].type = AARCH64_OPND_NIL;
      return 1;
    }
  return 0;
}

/* MOV <Wd>, #<imm>
     is equivalent to:
   MOVZ <Wd>, #<imm16>, LSL #<shift>.

   A disassembler may output ORR, MOVZ and MOVN as a MOV mnemonic, except when
   ORR has an immediate that could be generated by a MOVZ or MOVN instruction,
   or where a MOVN has an immediate that could be encoded by MOVZ, or where
   MOVZ/MOVN #0 have a shift amount other than LSL #0, in which case the
   machine-instruction mnemonic must be used.  */

static int
convert_movewide_to_mov (aarch64_inst *inst)
{
  uint64_t value = inst->operands[1].imm.value;
  /* MOVZ/MOVN #0 have a shift amount other than LSL #0.  */
  if (value == 0 && inst->operands[1].shifter.amount != 0)
    return 0;
  inst->operands[1].type = AARCH64_OPND_IMM_MOV;
  inst->operands[1].shifter.kind = AARCH64_MOD_NONE;
  value <<= inst->operands[1].shifter.amount;
  /* As an alias convertor, it has to be clear that the INST->OPCODE
     is the opcode of the real instruction.  */
  if (inst->opcode->op == OP_MOVN)
    {
      int is32 = inst->operands[0].qualifier == AARCH64_OPND_QLF_W;
      value = ~value;
      /* A MOVN has an immediate that could be encoded by MOVZ.  */
      if (aarch64_wide_constant_p (value, is32, NULL) == TRUE)
	return 0;
    }
  inst->operands[1].imm.value = value;
  inst->operands[1].shifter.amount = 0;
  return 1;
}

/* MOV <Wd>, #<imm>
     is equivalent to:
   ORR <Wd>, WZR, #<imm>.

   A disassembler may output ORR, MOVZ and MOVN as a MOV mnemonic, except when
   ORR has an immediate that could be generated by a MOVZ or MOVN instruction,
   or where a MOVN has an immediate that could be encoded by MOVZ, or where
   MOVZ/MOVN #0 have a shift amount other than LSL #0, in which case the
   machine-instruction mnemonic must be used.  */

static int
convert_movebitmask_to_mov (aarch64_inst *inst)
{
  int is32;
  uint64_t value;

  /* Should have been assured by the base opcode value.  */
  assert (inst->operands[1].reg.regno == 0x1f);
  copy_operand_info (inst, 1, 2);
  is32 = inst->operands[0].qualifier == AARCH64_OPND_QLF_W;
  inst->operands[1].type = AARCH64_OPND_IMM_MOV;
  value = inst->operands[1].imm.value;
  /* ORR has an immediate that could be generated by a MOVZ or MOVN
     instruction.  */
  if (inst->operands[0].reg.regno != 0x1f
      && (aarch64_wide_constant_p (value, is32, NULL) == TRUE
	  || aarch64_wide_constant_p (~value, is32, NULL) == TRUE))
    return 0;

  inst->operands[2].type = AARCH64_OPND_NIL;
  return 1;
}

/* Some alias opcodes are disassembled by being converted from their real-form.
   N.B. INST->OPCODE is the real opcode rather than the alias.  */

static int
convert_to_alias (aarch64_inst *inst, const aarch64_opcode *alias)
{
  switch (alias->op)
    {
    case OP_ASR_IMM:
    case OP_LSR_IMM:
      return convert_bfm_to_sr (inst);
    case OP_LSL_IMM:
      return convert_ubfm_to_lsl (inst);
    case OP_CINC:
    case OP_CINV:
    case OP_CNEG:
      return convert_from_csel (inst);
    case OP_CSET:
    case OP_CSETM:
      return convert_csinc_to_cset (inst);
    case OP_UBFX:
    case OP_BFXIL:
    case OP_SBFX:
      return convert_bfm_to_bfx (inst);
    case OP_SBFIZ:
    case OP_BFI:
    case OP_UBFIZ:
      return convert_bfm_to_bfi (inst);
    case OP_BFC:
      return convert_bfm_to_bfc (inst);
    case OP_MOV_V:
      return convert_orr_to_mov (inst);
    case OP_MOV_IMM_WIDE:
    case OP_MOV_IMM_WIDEN:
      return convert_movewide_to_mov (inst);
    case OP_MOV_IMM_LOG:
      return convert_movebitmask_to_mov (inst);
    case OP_ROR_IMM:
      return convert_extr_to_ror (inst);
    case OP_SXTL:
    case OP_SXTL2:
    case OP_UXTL:
    case OP_UXTL2:
      return convert_shll_to_xtl (inst);
    default:
      return 0;
    }
}

static int aarch64_opcode_decode (const aarch64_opcode *, const aarch64_insn,
				  aarch64_inst *, int);

/* Given the instruction information in *INST, check if the instruction has
   any alias form that can be used to represent *INST.  If the answer is yes,
   update *INST to be in the form of the determined alias.  */

/* In the opcode description table, the following flags are used in opcode
   entries to help establish the relations between the real and alias opcodes:

	F_ALIAS:	opcode is an alias
	F_HAS_ALIAS:	opcode has alias(es)
	F_P1
	F_P2
	F_P3:		Disassembly preference priority 1-3 (the larger the
			higher).  If nothing is specified, it is the priority
			0 by default, i.e. the lowest priority.

   Although the relation between the machine and the alias instructions are not
   explicitly described, it can be easily determined from the base opcode
   values, masks and the flags F_ALIAS and F_HAS_ALIAS in their opcode
   description entries:

   The mask of an alias opcode must be equal to or a super-set (i.e. more
   constrained) of that of the aliased opcode; so is the base opcode value.

   if (opcode_has_alias (real) && alias_opcode_p (opcode)
       && (opcode->mask & real->mask) == real->mask
       && (real->mask & opcode->opcode) == (real->mask & real->opcode))
   then OPCODE is an alias of, and only of, the REAL instruction

   The alias relationship is forced flat-structured to keep related algorithm
   simple; an opcode entry cannot be flagged with both F_ALIAS and F_HAS_ALIAS.

   During the disassembling, the decoding decision tree (in
   opcodes/aarch64-dis-2.c) always returns an machine instruction opcode entry;
   if the decoding of such a machine instruction succeeds (and -Mno-aliases is
   not specified), the disassembler will check whether there is any alias
   instruction exists for this real instruction.  If there is, the disassembler
   will try to disassemble the 32-bit binary again using the alias's rule, or
   try to convert the IR to the form of the alias.  In the case of the multiple
   aliases, the aliases are tried one by one from the highest priority
   (currently the flag F_P3) to the lowest priority (no priority flag), and the
   first succeeds first adopted.

   You may ask why there is a need for the conversion of IR from one form to
   another in handling certain aliases.  This is because on one hand it avoids
   adding more operand code to handle unusual encoding/decoding; on other
   hand, during the disassembling, the conversion is an effective approach to
   check the condition of an alias (as an alias may be adopted only if certain
   conditions are met).

   In order to speed up the alias opcode lookup, aarch64-gen has preprocessed
   aarch64_opcode_table and generated aarch64_find_alias_opcode and
   aarch64_find_next_alias_opcode (in opcodes/aarch64-dis-2.c) to help.  */

static void
determine_disassembling_preference (struct aarch64_inst *inst)
{
  const aarch64_opcode *opcode;
  const aarch64_opcode *alias;

  opcode = inst->opcode;

  /* This opcode does not have an alias, so use itself.  */
  if (opcode_has_alias (opcode) == FALSE)
    return;

  alias = aarch64_find_alias_opcode (opcode);
  assert (alias);

#ifdef DEBUG_AARCH64
  if (debug_dump)
    {
      const aarch64_opcode *tmp = alias;
      printf ("####   LIST    orderd: ");
      while (tmp)
	{
	  printf ("%s, ", tmp->name);
	  tmp = aarch64_find_next_alias_opcode (tmp);
	}
      printf ("\n");
    }
#endif /* DEBUG_AARCH64 */

  for (; alias; alias = aarch64_find_next_alias_opcode (alias))
    {
      DEBUG_TRACE ("try %s", alias->name);
      assert (alias_opcode_p (alias) || opcode_has_alias (opcode));

      /* An alias can be a pseudo opcode which will never be used in the
	 disassembly, e.g. BIC logical immediate is such a pseudo opcode
	 aliasing AND.  */
      if (pseudo_opcode_p (alias))
	{
	  DEBUG_TRACE ("skip pseudo %s", alias->name);
	  continue;
	}

      if ((inst->value & alias->mask) != alias->opcode)
	{
	  DEBUG_TRACE ("skip %s as base opcode not match", alias->name);
	  continue;
	}
      /* No need to do any complicated transformation on operands, if the alias
	 opcode does not have any operand.  */
      if (aarch64_num_of_operands (alias) == 0 && alias->opcode == inst->value)
	{
	  DEBUG_TRACE ("succeed with 0-operand opcode %s", alias->name);
	  aarch64_replace_opcode (inst, alias);
	  return;
	}
      if (alias->flags & F_CONV)
	{
	  aarch64_inst copy;
	  memcpy (&copy, inst, sizeof (aarch64_inst));
	  /* ALIAS is the preference as long as the instruction can be
	     successfully converted to the form of ALIAS.  */
	  if (convert_to_alias (&copy, alias) == 1)
	    {
	      aarch64_replace_opcode (&copy, alias);
	      assert (aarch64_match_operands_constraint (&copy, NULL));
	      DEBUG_TRACE ("succeed with %s via conversion", alias->name);
	      memcpy (inst, &copy, sizeof (aarch64_inst));
	      return;
	    }
	}
      else
	{
	  /* Directly decode the alias opcode.  */
	  aarch64_inst temp;
	  memset (&temp, '\0', sizeof (aarch64_inst));
	  if (aarch64_opcode_decode (alias, inst->value, &temp, 1) == 1)
	    {
	      DEBUG_TRACE ("succeed with %s via direct decoding", alias->name);
	      memcpy (inst, &temp, sizeof (aarch64_inst));
	      return;
	    }
	}
    }
}

/* Decode the CODE according to OPCODE; fill INST.  Return 0 if the decoding
   fails, which meanes that CODE is not an instruction of OPCODE; otherwise
   return 1.

   If OPCODE has alias(es) and NOALIASES_P is 0, an alias opcode may be
   determined and used to disassemble CODE; this is done just before the
   return.  */

static int
aarch64_opcode_decode (const aarch64_opcode *opcode, const aarch64_insn code,
		       aarch64_inst *inst, int noaliases_p)
{
  int i;

  DEBUG_TRACE ("enter with %s", opcode->name);

  assert (opcode && inst);

  /* Check the base opcode.  */
  if ((code & opcode->mask) != (opcode->opcode & opcode->mask))
    {
      DEBUG_TRACE ("base opcode match FAIL");
      goto decode_fail;
    }

  /* Clear inst.  */
  memset (inst, '\0', sizeof (aarch64_inst));

  inst->opcode = opcode;
  inst->value = code;

  /* Assign operand codes and indexes.  */
  for (i = 0; i < AARCH64_MAX_OPND_NUM; ++i)
    {
      if (opcode->operands[i] == AARCH64_OPND_NIL)
	break;
      inst->operands[i].type = opcode->operands[i];
      inst->operands[i].idx = i;
    }

  /* Call the opcode decoder indicated by flags.  */
  if (opcode_has_special_coder (opcode) && do_special_decoding (inst) == 0)
    {
      DEBUG_TRACE ("opcode flag-based decoder FAIL");
      goto decode_fail;
    }

  /* Call operand decoders.  */
  for (i = 0; i < AARCH64_MAX_OPND_NUM; ++i)
    {
      const aarch64_operand *opnd;
      enum aarch64_opnd type;

      type = opcode->operands[i];
      if (type == AARCH64_OPND_NIL)
	break;
      opnd = &aarch64_operands[type];
      if (operand_has_extractor (opnd)
	  && (! aarch64_extract_operand (opnd, &inst->operands[i], code, inst)))
	{
	  DEBUG_TRACE ("operand decoder FAIL at operand %d", i);
	  goto decode_fail;
	}
    }

  /* If the opcode has a verifier, then check it now.  */
  if (opcode->verifier && ! opcode->verifier (opcode, code))
    {
      DEBUG_TRACE ("operand verifier FAIL");
      goto decode_fail;
    }

  /* Match the qualifiers.  */
  if (aarch64_match_operands_constraint (inst, NULL) == 1)
    {
      /* Arriving here, the CODE has been determined as a valid instruction
	 of OPCODE and *INST has been filled with information of this OPCODE
	 instruction.  Before the return, check if the instruction has any
	 alias and should be disassembled in the form of its alias instead.
	 If the answer is yes, *INST will be updated.  */
      if (!noaliases_p)
	determine_disassembling_preference (inst);
      DEBUG_TRACE ("SUCCESS");
      return 1;
    }
  else
    {
      DEBUG_TRACE ("constraint matching FAIL");
    }

decode_fail:
  return 0;
}

/* This does some user-friendly fix-up to *INST.  It is currently focus on
   the adjustment of qualifiers to help the printed instruction
   recognized/understood more easily.  */

static void
user_friendly_fixup (aarch64_inst *inst)
{
  switch (inst->opcode->iclass)
    {
    case testbranch:
      /* TBNZ Xn|Wn, #uimm6, label
	 Test and Branch Not Zero: conditionally jumps to label if bit number
	 uimm6 in register Xn is not zero.  The bit number implies the width of
	 the register, which may be written and should be disassembled as Wn if
	 uimm is less than 32. Limited to a branch offset range of +/- 32KiB.
	 */
      if (inst->operands[1].imm.value < 32)
	inst->operands[0].qualifier = AARCH64_OPND_QLF_W;
      break;
    default: break;
    }
}

/* Decode INSN and fill in *INST the instruction information.  An alias
   opcode may be filled in *INSN if NOALIASES_P is FALSE.  Return zero on
   success.  */

int
aarch64_decode_insn (aarch64_insn insn, aarch64_inst *inst,
		     bfd_boolean noaliases_p)
{
  const aarch64_opcode *opcode = aarch64_opcode_lookup (insn);

#ifdef DEBUG_AARCH64
  if (debug_dump)
    {
      const aarch64_opcode *tmp = opcode;
      printf ("\n");
      DEBUG_TRACE ("opcode lookup:");
      while (tmp != NULL)
	{
	  aarch64_verbose ("  %s", tmp->name);
	  tmp = aarch64_find_next_opcode (tmp);
	}
    }
#endif /* DEBUG_AARCH64 */

  /* A list of opcodes may have been found, as aarch64_opcode_lookup cannot
     distinguish some opcodes, e.g. SSHR and MOVI, which almost share the same
     opcode field and value, apart from the difference that one of them has an
     extra field as part of the opcode, but such a field is used for operand
     encoding in other opcode(s) ('immh' in the case of the example).  */
  while (opcode != NULL)
    {
      /* But only one opcode can be decoded successfully for, as the
	 decoding routine will check the constraint carefully.  */
      if (aarch64_opcode_decode (opcode, insn, inst, noaliases_p) == 1)
	return ERR_OK;
      opcode = aarch64_find_next_opcode (opcode);
    }

  return ERR_UND;
}

/* Print operands.  */

static void
print_operands (bfd_vma pc, const aarch64_opcode *opcode,
		const aarch64_opnd_info *opnds, struct disassemble_info *info)
{
  int i, pcrel_p, num_printed;
  for (i = 0, num_printed = 0; i < AARCH64_MAX_OPND_NUM; ++i)
    {
      char str[128];
      /* We regard the opcode operand info more, however we also look into
	 the inst->operands to support the disassembling of the optional
	 operand.
	 The two operand code should be the same in all cases, apart from
	 when the operand can be optional.  */
      if (opcode->operands[i] == AARCH64_OPND_NIL
	  || opnds[i].type == AARCH64_OPND_NIL)
	break;

      /* Generate the operand string in STR.  */
      aarch64_print_operand (str, sizeof (str), pc, opcode, opnds, i, &pcrel_p,
			     &info->target);

      /* Print the delimiter (taking account of omitted operand(s)).  */
      if (str[0] != '\0')
	(*info->fprintf_func) (info->stream, "%s",
			       num_printed++ == 0 ? "\t" : ", ");

      /* Print the operand.  */
      if (pcrel_p)
	(*info->print_address_func) (info->target, info);
      else
	(*info->fprintf_func) (info->stream, "%s", str);
    }
}

/* Print the instruction mnemonic name.  */

static void
print_mnemonic_name (const aarch64_inst *inst, struct disassemble_info *info)
{
  if (inst->opcode->flags & F_COND)
    {
      /* For instructions that are truly conditionally executed, e.g. b.cond,
	 prepare the full mnemonic name with the corresponding condition
	 suffix.  */
      char name[8], *ptr;
      size_t len;

      ptr = strchr (inst->opcode->name, '.');
      assert (ptr && inst->cond);
      len = ptr - inst->opcode->name;
      assert (len < 8);
      strncpy (name, inst->opcode->name, len);
      name [len] = '\0';
      (*info->fprintf_func) (info->stream, "%s.%s", name, inst->cond->names[0]);
    }
  else
    (*info->fprintf_func) (info->stream, "%s", inst->opcode->name);
}

/* Print the instruction according to *INST.  */

static void
print_aarch64_insn (bfd_vma pc, const aarch64_inst *inst,
		    struct disassemble_info *info)
{
  print_mnemonic_name (inst, info);
  print_operands (pc, inst->opcode, inst->operands, info);
}

/* Entry-point of the instruction disassembler and printer.  */

static void
print_insn_aarch64_word (bfd_vma pc,
			 uint32_t word,
			 struct disassemble_info *info)
{
  static const char *err_msg[6] =
    {
      [ERR_OK]   = "_",
      [-ERR_UND] = "undefined",
      [-ERR_UNP] = "unpredictable",
      [-ERR_NYI] = "NYI"
    };

  int ret;
  aarch64_inst inst;

  info->insn_info_valid = 1;
  info->branch_delay_insns = 0;
  info->data_size = 0;
  info->target = 0;
  info->target2 = 0;

  if (info->flags & INSN_HAS_RELOC)
    /* If the instruction has a reloc associated with it, then
       the offset field in the instruction will actually be the
       addend for the reloc.  (If we are using REL type relocs).
       In such cases, we can ignore the pc when computing
       addresses, since the addend is not currently pc-relative.  */
    pc = 0;

  ret = aarch64_decode_insn (word, &inst, no_aliases);

  if (((word >> 21) & 0x3ff) == 1)
    {
      /* RESERVED for ALES.  */
      assert (ret != ERR_OK);
      ret = ERR_NYI;
    }

  switch (ret)
    {
    case ERR_UND:
    case ERR_UNP:
    case ERR_NYI:
      /* Handle undefined instructions.  */
      info->insn_type = dis_noninsn;
      (*info->fprintf_func) (info->stream,".inst\t0x%08x ; %s",
			     word, err_msg[-ret]);
      break;
    case ERR_OK:
      user_friendly_fixup (&inst);
      print_aarch64_insn (pc, &inst, info);
      break;
    default:
      abort ();
    }
}

/* Disallow mapping symbols ($x, $d etc) from
   being displayed in symbol relative addresses.  */

bfd_boolean
aarch64_symbol_is_valid (asymbol * sym,
			 struct disassemble_info * info ATTRIBUTE_UNUSED)
{
  const char * name;

  if (sym == NULL)
    return FALSE;

  name = bfd_asymbol_name (sym);

  return name
    && (name[0] != '$'
	|| (name[1] != 'x' && name[1] != 'd')
	|| (name[2] != '\0' && name[2] != '.'));
}

/* Print data bytes on INFO->STREAM.  */

static void
print_insn_data (bfd_vma pc ATTRIBUTE_UNUSED,
		 uint32_t word,
		 struct disassemble_info *info)
{
  switch (info->bytes_per_chunk)
    {
    case 1:
      info->fprintf_func (info->stream, ".byte\t0x%02x", word);
      break;
    case 2:
      info->fprintf_func (info->stream, ".short\t0x%04x", word);
      break;
    case 4:
      info->fprintf_func (info->stream, ".word\t0x%08x", word);
      break;
    default:
      abort ();
    }
}

/* Try to infer the code or data type from a symbol.
   Returns nonzero if *MAP_TYPE was set.  */

static int
get_sym_code_type (struct disassemble_info *info, int n,
		   enum map_type *map_type)
{
  elf_symbol_type *es;
  unsigned int type;
  const char *name;

  es = *(elf_symbol_type **)(info->symtab + n);
  type = ELF_ST_TYPE (es->internal_elf_sym.st_info);

  /* If the symbol has function type then use that.  */
  if (type == STT_FUNC)
    {
      *map_type = MAP_INSN;
      return TRUE;
    }

  /* Check for mapping symbols.  */
  name = bfd_asymbol_name(info->symtab[n]);
  if (name[0] == '$'
      && (name[1] == 'x' || name[1] == 'd')
      && (name[2] == '\0' || name[2] == '.'))
    {
      *map_type = (name[1] == 'x' ? MAP_INSN : MAP_DATA);
      return TRUE;
    }

  return FALSE;
}

/* Entry-point of the AArch64 disassembler.  */

int
print_insn_aarch64 (bfd_vma pc,
		    struct disassemble_info *info)
{
  bfd_byte	buffer[INSNLEN];
  int		status;
  void		(*printer) (bfd_vma, uint32_t, struct disassemble_info *);
  bfd_boolean   found = FALSE;
  unsigned int	size = 4;
  unsigned long	data;

  if (info->disassembler_options)
    {
      set_default_aarch64_dis_options (info);

      parse_aarch64_dis_options (info->disassembler_options);

      /* To avoid repeated parsing of these options, we remove them here.  */
      info->disassembler_options = NULL;
    }

  /* Aarch64 instructions are always little-endian */
  info->endian_code = BFD_ENDIAN_LITTLE;

  /* First check the full symtab for a mapping symbol, even if there
     are no usable non-mapping symbols for this address.  */
  if (info->symtab_size != 0
      && bfd_asymbol_flavour (*info->symtab) == bfd_target_elf_flavour)
    {
      enum map_type type = MAP_INSN;
      int last_sym = -1;
      bfd_vma addr;
      int n;

      if (pc <= last_mapping_addr)
	last_mapping_sym = -1;

      /* Start scanning at the start of the function, or wherever
	 we finished last time.  */
      n = info->symtab_pos + 1;
      if (n < last_mapping_sym)
	n = last_mapping_sym;

      /* Scan up to the location being disassembled.  */
      for (; n < info->symtab_size; n++)
	{
	  addr = bfd_asymbol_value (info->symtab[n]);
	  if (addr > pc)
	    break;
	  if ((info->section == NULL
	       || info->section == info->symtab[n]->section)
	      && get_sym_code_type (info, n, &type))
	    {
	      last_sym = n;
	      found = TRUE;
	    }
	}

      if (!found)
	{
	  n = info->symtab_pos;
	  if (n < last_mapping_sym)
	    n = last_mapping_sym;

	  /* No mapping symbol found at this address.  Look backwards
	     for a preceeding one.  */
	  for (; n >= 0; n--)
	    {
	      if (get_sym_code_type (info, n, &type))
		{
		  last_sym = n;
		  found = TRUE;
		  break;
		}
	    }
	}

      last_mapping_sym = last_sym;
      last_type = type;

      /* Look a little bit ahead to see if we should print out
	 less than four bytes of data.  If there's a symbol,
	 mapping or otherwise, after two bytes then don't
	 print more.  */
      if (last_type == MAP_DATA)
	{
	  size = 4 - (pc & 3);
	  for (n = last_sym + 1; n < info->symtab_size; n++)
	    {
	      addr = bfd_asymbol_value (info->symtab[n]);
	      if (addr > pc)
		{
		  if (addr - pc < size)
		    size = addr - pc;
		  break;
		}
	    }
	  /* If the next symbol is after three bytes, we need to
	     print only part of the data, so that we can use either
	     .byte or .short.  */
	  if (size == 3)
	    size = (pc & 1) ? 1 : 2;
	}
    }

  if (last_type == MAP_DATA)
    {
      /* size was set above.  */
      info->bytes_per_chunk = size;
      info->display_endian = info->endian;
      printer = print_insn_data;
    }
  else
    {
      info->bytes_per_chunk = size = INSNLEN;
      info->display_endian = info->endian_code;
      printer = print_insn_aarch64_word;
    }

  status = (*info->read_memory_func) (pc, buffer, size, info);
  if (status != 0)
    {
      (*info->memory_error_func) (status, pc, info);
      return -1;
    }

  data = bfd_get_bits (buffer, size * 8,
		       info->display_endian == BFD_ENDIAN_BIG);

  (*printer) (pc, data, info);

  return size;
}

void
print_aarch64_disassembler_options (FILE *stream)
{
  fprintf (stream, _("\n\
The following AARCH64 specific disassembler options are supported for use\n\
with the -M switch (multiple options should be separated by commas):\n"));

  fprintf (stream, _("\n\
  no-aliases         Don't print instruction aliases.\n"));

  fprintf (stream, _("\n\
  aliases            Do print instruction aliases.\n"));

#ifdef DEBUG_AARCH64
  fprintf (stream, _("\n\
  debug_dump         Temp switch for debug trace.\n"));
#endif /* DEBUG_AARCH64 */

  fprintf (stream, _("\n"));
}