PR ld/11384

[binutils/dougsmingw.git] / gas / config / tc-i386-intel.c

/* tc-i386.c -- Assemble Intel syntax code for ix86/x86-64
   Copyright 2009
   Free Software Foundation, Inc.

   This file is part of GAS, the GNU Assembler.

   GAS 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.

   GAS 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 GAS; see the file COPYING.  If not, write to the Free
   Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
   02110-1301, USA.  */

static struct
  {
    operatorT op_modifier;      /* Operand modifier.  */
    int is_mem;                 /* 1 if operand is memory reference.  */
    int has_offset;             /* 1 if operand has offset.  */
    unsigned int in_offset;     /* >=1 if processing operand of offset.  */
    unsigned int in_bracket;    /* >=1 if processing operand in brackets.  */
    unsigned int in_scale;      /* >=1 if processing multipication operand
                                 * in brackets.  */
    i386_operand_type reloc_types;      /* Value obtained from lex_got().  */
    const reg_entry *base;      /* Base register (if any).  */
    const reg_entry *index;     /* Index register (if any).  */
    offsetT scale_factor;       /* Accumulated scale factor.  */
    symbolS *seg;
  }
intel_state;

/* offset X_add_symbol */
#define O_offset O_md32
/* offset X_add_symbol */
#define O_short O_md31
/* near ptr X_add_symbol */
#define O_near_ptr O_md30
/* far ptr X_add_symbol */
#define O_far_ptr O_md29
/* byte ptr X_add_symbol */
#define O_byte_ptr O_md28
/* word ptr X_add_symbol */
#define O_word_ptr O_md27
/* dword ptr X_add_symbol */
#define O_dword_ptr O_md26
/* qword ptr X_add_symbol */
#define O_qword_ptr O_md25
/* oword ptr X_add_symbol */
#define O_oword_ptr O_md24
/* fword ptr X_add_symbol */
#define O_fword_ptr O_md23
/* tbyte ptr X_add_symbol */
#define O_tbyte_ptr O_md22
/* xmmword ptr X_add_symbol */
#define O_xmmword_ptr O_md21
/* ymmword ptr X_add_symbol */
#define O_ymmword_ptr O_md20

static struct
  {
    const char *name;
    operatorT op;
    unsigned int operands;
  }
const i386_operators[] =
  {
    { "and", O_bit_and, 2 },
    { "eq", O_eq, 2 },
    { "ge", O_ge, 2 },
    { "gt", O_gt, 2 },
    { "le", O_le, 2 },
    { "lt", O_lt, 2 },
    { "mod", O_modulus, 2 },
    { "ne", O_ne, 2 },
    { "not", O_bit_not, 1 },
    { "offset", O_offset, 1 },
    { "or", O_bit_inclusive_or, 2 },
    { "shl", O_left_shift, 2 },
    { "short", O_short, 1 },
    { "shr", O_right_shift, 2 },
    { "xor", O_bit_exclusive_or, 2 },
    { NULL, O_illegal, 0 }
  };

static struct
  {
    const char *name;
    operatorT op;
    unsigned short sz[3];
  }
const i386_types[] =
  {
#define I386_TYPE(t, n) { #t, O_##t##_ptr, { n, n, n } }
    I386_TYPE(byte, 1),
    I386_TYPE(word, 2),
    I386_TYPE(dword, 4),
    I386_TYPE(fword, 6),
    I386_TYPE(qword, 8),
    I386_TYPE(tbyte, 10),
    I386_TYPE(oword, 16),
    I386_TYPE(xmmword, 16),
    I386_TYPE(ymmword, 32),
#undef I386_TYPE
    { "near", O_near_ptr, { 0xff04, 0xff02, 0xff08 } },
    { "far", O_far_ptr, { 0xff06, 0xff05, 0xff06 } },
    { NULL, O_illegal, { 0, 0, 0 } }
  };

operatorT i386_operator (const char *name, unsigned int operands, char *pc)
{
  unsigned int j;

  if (!intel_syntax)
    return O_absent;

  if (!name)
    {
      if (operands != 2)
        return O_illegal;
      switch (*input_line_pointer)
        {
        case ':':
          ++input_line_pointer;
          return O_full_ptr;
        case '[':
          ++input_line_pointer;
          return O_index;
        case '@':
          if (this_operand >= 0 && i.reloc[this_operand] == NO_RELOC)
            {
              int adjust = 0;
              char *gotfree_input_line = lex_got (&i.reloc[this_operand],
                                                  &adjust,
                                                  &intel_state.reloc_types);

              if (!gotfree_input_line)
                break;
              free (gotfree_input_line);
              *input_line_pointer++ = '+';
              memset (input_line_pointer, '0', adjust - 1);
              input_line_pointer[adjust - 1] = ' ';
              return O_add;
            }
          break;
        }
      return O_illegal;
    }

  for (j = 0; i386_operators[j].name; ++j)
    if (strcasecmp (i386_operators[j].name, name) == 0)
      {
        if (i386_operators[j].operands
            && i386_operators[j].operands != operands)
          return O_illegal;
        return i386_operators[j].op;
      }

  for (j = 0; i386_types[j].name; ++j)
    if (strcasecmp (i386_types[j].name, name) == 0)
      break;
  if (i386_types[j].name && *pc == ' ')
    {
      char *pname = ++input_line_pointer;
      char c = get_symbol_end ();

      if (strcasecmp (pname, "ptr") == 0)
        {
          pname[-1] = *pc;
          *pc = c;
          if (intel_syntax > 0 || operands != 1)
            return O_illegal;
          return i386_types[j].op;
        }

      *input_line_pointer = c;
      input_line_pointer = pname - 1;
    }

  return O_absent;
}

static int i386_intel_parse_name (const char *name, expressionS *e)
{
  unsigned int j;

  for (j = 0; i386_types[j].name; ++j)
    if (strcasecmp(i386_types[j].name, name) == 0)
      {
        e->X_op = O_constant;
        e->X_add_number = i386_types[j].sz[flag_code];
        e->X_add_symbol = NULL;
        e->X_op_symbol = NULL;
        return 1;
      }

  return 0;
}

static INLINE int i386_intel_check (const reg_entry *rreg,
                                    const reg_entry *base,
                                    const reg_entry *iindex)
{
  if ((this_operand >= 0 && rreg != i.op[this_operand].regs)
      || base != intel_state.base || iindex != intel_state.index)
    {
      as_bad (_("invalid use of register"));
      return 0;
    }
  return 1;
}

static INLINE void i386_intel_fold (expressionS *e, symbolS *sym)
{
  if (S_GET_SEGMENT (sym) == absolute_section)
    {
      offsetT val = e->X_add_number;

      *e = *symbol_get_value_expression (sym);
      e->X_add_number += val;
    }
  else
    {
      e->X_add_symbol = sym;
      e->X_op_symbol = NULL;
      e->X_op = O_symbol;
    }
}

static int i386_intel_simplify (expressionS *);

static INLINE int i386_intel_simplify_symbol(symbolS *sym)
{
  int ret = i386_intel_simplify (symbol_get_value_expression (sym));

  if (ret == 2)
  {
    S_SET_SEGMENT(sym, absolute_section);
    ret = 1;
  }
  return ret;
}

static int i386_intel_simplify (expressionS *e)
{
  const reg_entry *the_reg = this_operand >= 0 ? i.op[this_operand].regs : NULL;
  const reg_entry *base = intel_state.base;
  const reg_entry *state_index = intel_state.index;
  int ret;

  if (!intel_syntax)
    return 1;

  switch (e->X_op)
    {
    case O_index:
      if (e->X_add_symbol)
        {
          if (!i386_intel_simplify_symbol (e->X_add_symbol)
              || !i386_intel_check(the_reg, intel_state.base, intel_state.index))
            return 0;;
        }
      if (!intel_state.in_offset)
        ++intel_state.in_bracket;
      ret = i386_intel_simplify_symbol (e->X_op_symbol);
      if (!intel_state.in_offset)
        --intel_state.in_bracket;
      if (!ret)
        return 0;
      if (e->X_add_symbol)
        e->X_op = O_add;
      else
        i386_intel_fold (e, e->X_op_symbol);
      break;

    case O_offset:
      intel_state.has_offset = 1;
      ++intel_state.in_offset;
      ret = i386_intel_simplify_symbol (e->X_add_symbol);
      --intel_state.in_offset;
      if (!ret || !i386_intel_check(the_reg, base, state_index))
        return 0;
      i386_intel_fold (e, e->X_add_symbol);
      return ret;

    case O_byte_ptr:
    case O_word_ptr:
    case O_dword_ptr:
    case O_fword_ptr:
    case O_qword_ptr:
    case O_tbyte_ptr:
    case O_oword_ptr:
    case O_xmmword_ptr:
    case O_ymmword_ptr:
    case O_near_ptr:
    case O_far_ptr:
      if (intel_state.op_modifier == O_absent)
        intel_state.op_modifier = e->X_op;
      /* FALLTHROUGH */
    case O_short:
      if (symbol_get_value_expression (e->X_add_symbol)->X_op == O_register)
        {
          as_bad (_("invalid use of register"));
          return 0;
        }
      if (!i386_intel_simplify_symbol (e->X_add_symbol))
        return 0;
      i386_intel_fold (e, e->X_add_symbol);
      break;

    case O_full_ptr:
      if (symbol_get_value_expression (e->X_op_symbol)->X_op == O_register)
        {
          as_bad (_("invalid use of register"));
          return 0;
        }
      if (!i386_intel_simplify_symbol (e->X_op_symbol)
          || !i386_intel_check(the_reg, intel_state.base, intel_state.index))
        return 0;
      if (!intel_state.in_offset)
        intel_state.seg = e->X_add_symbol;
      i386_intel_fold (e, e->X_op_symbol);
      break;

    case O_register:
      if (this_operand < 0 || intel_state.in_offset)
        {
          as_bad (_("invalid use of register"));
          return 0;
        }
      if (!intel_state.in_bracket)
        {
          if (i.op[this_operand].regs)
            {
              as_bad (_("invalid use of register"));
              return 0;
            }
          if (i386_regtab[e->X_add_number].reg_type.bitfield.sreg3
              && i386_regtab[e->X_add_number].reg_num == RegFlat)
            {
              as_bad (_("invalid use of pseudo-register"));
              return 0;
            }
          i.op[this_operand].regs = i386_regtab + e->X_add_number;
        }
      else if (!intel_state.base && !intel_state.in_scale)
        intel_state.base = i386_regtab + e->X_add_number;
      else if (!intel_state.index)
        intel_state.index = i386_regtab + e->X_add_number;
      else
        {
          /* esp is invalid as index */
          intel_state.index = i386_regtab + REGNAM_EAX + 4;
        }
      e->X_op = O_constant;
      e->X_add_number = 0;
      return 2;

    case O_multiply:
      if (this_operand >= 0 && intel_state.in_bracket)
        {
          expressionS *scale = NULL;

          if (intel_state.index)
            --scale;

          if (!intel_state.in_scale++)
            intel_state.scale_factor = 1;

          ret = i386_intel_simplify_symbol (e->X_add_symbol);
          if (ret && !scale && intel_state.index)
            scale = symbol_get_value_expression (e->X_op_symbol);

          if (ret)
            ret = i386_intel_simplify_symbol (e->X_op_symbol);
          if (ret && !scale && intel_state.index)
            scale = symbol_get_value_expression (e->X_add_symbol);

          if (ret && scale && (scale + 1))
            {
              resolve_expression (scale);
              if (scale->X_op != O_constant
                  || intel_state.index->reg_type.bitfield.reg16)
                scale->X_add_number = 0;
              intel_state.scale_factor *= scale->X_add_number;
            }

          --intel_state.in_scale;
          if (!ret)
            return 0;

          if (!intel_state.in_scale)
            switch (intel_state.scale_factor)
              {
              case 1:
                i.log2_scale_factor = 0;
                break;
              case 2:
                i.log2_scale_factor = 1;
                break;
              case 4:
                i.log2_scale_factor = 2;
                break;
              case 8:
                i.log2_scale_factor = 3;
                break;
              default:
                /* esp is invalid as index */
                intel_state.index = i386_regtab + REGNAM_EAX + 4;
                break;
              }

          break;
        }
      /* FALLTHROUGH */
    default:
      if (e->X_add_symbol && !i386_intel_simplify_symbol (e->X_add_symbol))
        return 0;
      if (e->X_op == O_add || e->X_op == O_subtract)
        {
          base = intel_state.base;
          state_index = intel_state.index;
        }
      if (!i386_intel_check (the_reg, base, state_index)
          || (e->X_op_symbol && !i386_intel_simplify_symbol (e->X_op_symbol))
          || !i386_intel_check (the_reg,
                                e->X_op != O_add ? base : intel_state.base,
                                e->X_op != O_add ? state_index : intel_state.index))
        return 0;
      break;
    }

  if (this_operand >= 0 && e->X_op == O_symbol && !intel_state.in_offset)
    {
      segT seg = S_GET_SEGMENT (e->X_add_symbol);

      if (seg != absolute_section
          && seg != reg_section
          && seg != expr_section)
        intel_state.is_mem |= 2 - !intel_state.in_bracket;
    }

  return 1;
}

int i386_need_index_operator (void)
{
  return intel_syntax < 0;
}

static int
i386_intel_operand (char *operand_string, int got_a_float)
{
  char *saved_input_line_pointer, *buf;
  segT exp_seg;
  expressionS exp, *expP;
  char suffix = 0;
  int ret;

  /* Initialize state structure.  */
  intel_state.op_modifier = O_absent;
  intel_state.is_mem = 0;
  intel_state.has_offset = 0;
  intel_state.base = NULL;
  intel_state.index = NULL;
  intel_state.seg = NULL;
  operand_type_set (&intel_state.reloc_types, ~0);
  gas_assert (!intel_state.in_offset);
  gas_assert (!intel_state.in_bracket);
  gas_assert (!intel_state.in_scale);

  saved_input_line_pointer = input_line_pointer;
  input_line_pointer = buf = xstrdup (operand_string);

  /* A '$' followed by an identifier char is an identifier.  Otherwise,
     it's operator '.' followed by an expression.  */
  if (*buf == '$' && !is_identifier_char (buf[1]))
    *buf = '.';

  intel_syntax = -1;
  memset (&exp, 0, sizeof(exp));
  exp_seg = expression (&exp);
  ret = i386_intel_simplify (&exp);
  intel_syntax = 1;

  SKIP_WHITESPACE ();
  if (!is_end_of_line[(unsigned char) *input_line_pointer])
    {
      as_bad (_("junk `%s' after expression"), input_line_pointer);
      ret = 0;
    }
  else if (exp.X_op == O_illegal || exp.X_op == O_absent)
    {
      as_bad (_("invalid expression"));
      ret = 0;
    }
  else if (!intel_state.has_offset
           && input_line_pointer > buf
           && *(input_line_pointer - 1) == ']')
    intel_state.is_mem |= 1;

  input_line_pointer = saved_input_line_pointer;
  free (buf);

  gas_assert (!intel_state.in_offset);
  gas_assert (!intel_state.in_bracket);
  gas_assert (!intel_state.in_scale);

  if (!ret)
    return 0;

  if (intel_state.op_modifier != O_absent
      && current_templates->start->base_opcode != 0x8d /* lea */)
    {
      i.types[this_operand].bitfield.unspecified = 0;

      switch (intel_state.op_modifier)
        {
        case O_byte_ptr:
          i.types[this_operand].bitfield.byte = 1;
          suffix = BYTE_MNEM_SUFFIX;
          break;

        case O_word_ptr:
          i.types[this_operand].bitfield.word = 1;
          if ((current_templates->start->name[0] == 'l'
               && current_templates->start->name[2] == 's'
               && current_templates->start->name[3] == 0)
              || current_templates->start->base_opcode == 0x62 /* bound */)
            suffix = BYTE_MNEM_SUFFIX; /* so it will cause an error */
          else if (got_a_float == 2)    /* "fi..." */
            suffix = SHORT_MNEM_SUFFIX;
          else
            suffix = WORD_MNEM_SUFFIX;
          break;

        case O_dword_ptr:
          i.types[this_operand].bitfield.dword = 1;
          if ((current_templates->start->name[0] == 'l'
               && current_templates->start->name[2] == 's'
               && current_templates->start->name[3] == 0)
              || current_templates->start->base_opcode == 0x62 /* bound */)
            suffix = WORD_MNEM_SUFFIX;
          else if (flag_code == CODE_16BIT
                   && (current_templates->start->opcode_modifier.jump
                       || current_templates->start->opcode_modifier.jumpdword))
            suffix = LONG_DOUBLE_MNEM_SUFFIX;
          else if (got_a_float == 1)    /* "f..." */
            suffix = SHORT_MNEM_SUFFIX;
          else
            suffix = LONG_MNEM_SUFFIX;
          break;

        case O_fword_ptr:
          i.types[this_operand].bitfield.fword = 1;
          if (current_templates->start->name[0] == 'l'
              && current_templates->start->name[2] == 's'
              && current_templates->start->name[3] == 0)
            suffix = LONG_MNEM_SUFFIX;
          else if (!got_a_float)
            {
              if (flag_code == CODE_16BIT)
                add_prefix (DATA_PREFIX_OPCODE);
              suffix = LONG_DOUBLE_MNEM_SUFFIX;
            }
          else
            suffix = BYTE_MNEM_SUFFIX; /* so it will cause an error */
          break;

        case O_qword_ptr:
          i.types[this_operand].bitfield.qword = 1;
          if (current_templates->start->base_opcode == 0x62 /* bound */
              || got_a_float == 1)      /* "f..." */
            suffix = LONG_MNEM_SUFFIX;
          else
            suffix = QWORD_MNEM_SUFFIX;
          break;

        case O_tbyte_ptr:
          i.types[this_operand].bitfield.tbyte = 1;
          if (got_a_float == 1)
            suffix = LONG_DOUBLE_MNEM_SUFFIX;
          else
            suffix = BYTE_MNEM_SUFFIX; /* so it will cause an error */
          break;

        case O_oword_ptr:
        case O_xmmword_ptr:
          i.types[this_operand].bitfield.xmmword = 1;
          suffix = XMMWORD_MNEM_SUFFIX;
          break;

        case O_ymmword_ptr:
          i.types[this_operand].bitfield.ymmword = 1;
          suffix = YMMWORD_MNEM_SUFFIX;
          break;

        case O_far_ptr:
          suffix = LONG_DOUBLE_MNEM_SUFFIX;
          /* FALLTHROUGH */
        case O_near_ptr:
          if (!current_templates->start->opcode_modifier.jump
              && !current_templates->start->opcode_modifier.jumpdword)
            suffix = got_a_float /* so it will cause an error */
                     ? BYTE_MNEM_SUFFIX
                     : LONG_DOUBLE_MNEM_SUFFIX;
          break;

        default:
          BAD_CASE (intel_state.op_modifier);
          break;
        }

      if (!i.suffix)
        i.suffix = suffix;
      else if (i.suffix != suffix)
        {
          as_bad (_("conflicting operand size modifiers"));
          return 0;
        }
    }

  /* Operands for jump/call need special consideration.  */
  if (current_templates->start->opcode_modifier.jump
      || current_templates->start->opcode_modifier.jumpdword
      || current_templates->start->opcode_modifier.jumpintersegment)
    {
      if (i.op[this_operand].regs || intel_state.base || intel_state.index
          || intel_state.is_mem > 1)
        i.types[this_operand].bitfield.jumpabsolute = 1;
      else
        switch (intel_state.op_modifier)
          {
          case O_near_ptr:
            if (intel_state.seg)
              i.types[this_operand].bitfield.jumpabsolute = 1;
            else
              intel_state.is_mem = 1;
            break;
          case O_far_ptr:
          case O_absent:
            if (!intel_state.seg)
              {
                intel_state.is_mem = 1;
                if (intel_state.op_modifier == O_absent)
                  break;
                as_bad (_("cannot infer the segment part of the operand"));
                return 0;
              }
            else if (S_GET_SEGMENT (intel_state.seg) == reg_section)
              i.types[this_operand].bitfield.jumpabsolute = 1;
            else
              {
                i386_operand_type types;

                if (i.imm_operands >= MAX_IMMEDIATE_OPERANDS)
                  {
                    as_bad (_("at most %d immediate operands are allowed"),
                            MAX_IMMEDIATE_OPERANDS);
                    return 0;
                  }
                expP = &im_expressions[i.imm_operands++];
                memset (expP, 0, sizeof(*expP));
                expP->X_op = O_symbol;
                expP->X_add_symbol = intel_state.seg;
                i.op[this_operand].imms = expP;

                resolve_expression (expP);
                operand_type_set (&types, ~0);
                if (!i386_finalize_immediate (S_GET_SEGMENT (intel_state.seg),
                                              expP, types, operand_string))
                  return 0;
                if (i.operands < MAX_OPERANDS)
                  {
                    this_operand = i.operands++;
                    i.types[this_operand].bitfield.unspecified = 1;
                  }
                if (suffix == LONG_DOUBLE_MNEM_SUFFIX)
                  i.suffix = 0;
                intel_state.seg = NULL;
                intel_state.is_mem = 0;
              }
            break;
          default:
            i.types[this_operand].bitfield.jumpabsolute = 1;
            break;
          }
      if (i.types[this_operand].bitfield.jumpabsolute)
        intel_state.is_mem |= 1;
    }
  else if (intel_state.seg)
    intel_state.is_mem |= 1;

  if (i.op[this_operand].regs)
    {
      i386_operand_type temp;

      /* Register operand.  */
      if (intel_state.base || intel_state.index || intel_state.seg)
        {
          as_bad (_("invalid operand"));
          return 0;
        }

      temp = i.op[this_operand].regs->reg_type;
      temp.bitfield.baseindex = 0;
      i.types[this_operand] = operand_type_or (i.types[this_operand], temp);
      i.types[this_operand].bitfield.unspecified = 0;
      ++i.reg_operands;
    }
  else if (intel_state.base || intel_state.index || intel_state.seg
           || intel_state.is_mem)
    {
      /* Memory operand.  */
      if (i.mem_operands
          >= 2 - !current_templates->start->opcode_modifier.isstring)
        {
          /* Handle

             call       0x9090,0x90909090
             lcall      0x9090,0x90909090
             jmp        0x9090,0x90909090
             ljmp       0x9090,0x90909090
           */

          if ((current_templates->start->opcode_modifier.jumpintersegment
               || current_templates->start->opcode_modifier.jumpdword
               || current_templates->start->opcode_modifier.jump)
              && this_operand == 1
              && intel_state.seg == NULL
              && i.mem_operands == 1
              && i.disp_operands == 1
              && intel_state.op_modifier == O_absent)
            {
              /* Try to process the first operand as immediate,  */
              this_operand = 0;
              if (i386_finalize_immediate (exp_seg, i.op[0].imms,
                                           intel_state.reloc_types,
                                           NULL))
                {
                  this_operand = 1;
                  expP = &im_expressions[0];
                  i.op[this_operand].imms = expP;
                  *expP = exp;

                  /* Try to process the second operand as immediate,  */
                  if (i386_finalize_immediate (exp_seg, expP,
                                               intel_state.reloc_types,
                                               NULL))
                    {
                      i.mem_operands = 0;
                      i.disp_operands = 0;
                      i.imm_operands = 2;
                      i.types[0].bitfield.mem = 0;
                      i.types[0].bitfield.disp16 = 0;
                      i.types[0].bitfield.disp32 = 0;
                      i.types[0].bitfield.disp32s = 0;
                      return 1;
                    }
                }
            }

          as_bad (_("too many memory references for `%s'"),
                  current_templates->start->name);
          return 0;
        }

      expP = &disp_expressions[i.disp_operands];
      memcpy (expP, &exp, sizeof(exp));
      resolve_expression (expP);

      if (expP->X_op != O_constant || expP->X_add_number
          || (!intel_state.base && !intel_state.index))
        {
          i.op[this_operand].disps = expP;
          i.disp_operands++;

          if (flag_code == CODE_64BIT)
            {
              i.types[this_operand].bitfield.disp32 = 1;
              if (!i.prefix[ADDR_PREFIX])
                {
                  i.types[this_operand].bitfield.disp64 = 1;
                  i.types[this_operand].bitfield.disp32s = 1;
                }
            }
          else if (!i.prefix[ADDR_PREFIX] ^ (flag_code == CODE_16BIT))
            i.types[this_operand].bitfield.disp32 = 1;
          else
            i.types[this_operand].bitfield.disp16 = 1;

#if defined (OBJ_AOUT) || defined (OBJ_MAYBE_AOUT)
          /*
           * exp_seg is used only for verification in
           * i386_finalize_displacement, and we can end up seeing reg_section
           * here - but we know we removed all registers from the expression
           * (or error-ed on any remaining ones) in i386_intel_simplify.  I
           * consider the check in i386_finalize_displacement bogus anyway, in
           * particular because it doesn't allow for expr_section, so I'd
           * rather see that check (and the similar one in
           * i386_finalize_immediate) use SEG_NORMAL(), but not being an a.out
           * expert I can't really say whether that would have other bad side
           * effects.
           */
          if (OUTPUT_FLAVOR == bfd_target_aout_flavour
              && exp_seg == reg_section)
            exp_seg = expP->X_op != O_constant ? undefined_section
                                               : absolute_section;
#endif

          if (!i386_finalize_displacement (exp_seg, expP,
                                           intel_state.reloc_types,
                                           operand_string))
            return 0;
        }

      if (intel_state.base || intel_state.index)
        i.types[this_operand].bitfield.baseindex = 1;

      if (intel_state.seg)
        {
          for (;;)
            {
              expP = symbol_get_value_expression (intel_state.seg);
              if (expP->X_op != O_full_ptr)
                break;
              intel_state.seg = expP->X_add_symbol;
            }
          if (expP->X_op != O_register)
            {
              as_bad (_("segment register name expected"));
              return 0;
            }
          if (!i386_regtab[expP->X_add_number].reg_type.bitfield.sreg2
              && !i386_regtab[expP->X_add_number].reg_type.bitfield.sreg3)
            {
              as_bad (_("invalid use of register"));
              return 0;
            }
          switch (i386_regtab[expP->X_add_number].reg_num)
            {
            case 0: i.seg[i.mem_operands] = &es; break;
            case 1: i.seg[i.mem_operands] = &cs; break;
            case 2: i.seg[i.mem_operands] = &ss; break;
            case 3: i.seg[i.mem_operands] = &ds; break;
            case 4: i.seg[i.mem_operands] = &fs; break;
            case 5: i.seg[i.mem_operands] = &gs; break;
            case RegFlat: i.seg[i.mem_operands] = NULL; break;
            }
        }

      /* Swap base and index in 16-bit memory operands like
         [si+bx]. Since i386_index_check is also used in AT&T
         mode we have to do that here.  */
      if (intel_state.base
          && intel_state.index
          && intel_state.base->reg_type.bitfield.reg16
          && intel_state.index->reg_type.bitfield.reg16
          && intel_state.base->reg_num >= 6
          && intel_state.index->reg_num < 6)
        {
          i.base_reg = intel_state.index;
          i.index_reg = intel_state.base;
        }
      else
        {
          i.base_reg = intel_state.base;
          i.index_reg = intel_state.index;
        }

      if (!i386_index_check (operand_string))
        return 0;

      i.types[this_operand].bitfield.mem = 1;
      ++i.mem_operands;
    }
  else
    {
      /* Immediate.  */
      if (i.imm_operands >= MAX_IMMEDIATE_OPERANDS)
        {
          as_bad (_("at most %d immediate operands are allowed"),
                  MAX_IMMEDIATE_OPERANDS);
          return 0;
        }

      expP = &im_expressions[i.imm_operands++];
      i.op[this_operand].imms = expP;
      *expP = exp;

      return i386_finalize_immediate (exp_seg, expP, intel_state.reloc_types,
                                      operand_string);
    }

  return 1;
}