[deliverable/binutils-gdb.git] / gas / expr.c

/* expr.c -operands, expressions-
   Copyright (C) 1987, 1990, 1991, 1992, 1993 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 2, 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, 675 Mass Ave, Cambridge, MA 02139, USA. */

/*
 * This is really a branch office of as-read.c. I split it out to clearly
 * distinguish the world of expressions from the world of statements.
 * (It also gives smaller files to re-compile.)
 * Here, "operand"s are of expressions, not instructions.
 */

#include <ctype.h>
#include <string.h>

#include "as.h"

#include "obstack.h"

static void clean_up_expression PARAMS ((expressionS * expressionP));
extern const char EXP_CHARS[], FLT_CHARS[];

/*
 * Build any floating-point literal here.
 * Also build any bignum literal here.
 */

/* Seems atof_machine can backscan through generic_bignum and hit whatever
   happens to be loaded before it in memory.  And its way too complicated
   for me to fix right.  Thus a hack.  JF:  Just make generic_bignum bigger,
   and never write into the early words, thus they'll always be zero.
   I hate Dean's floating-point code.  Bleh.  */
LITTLENUM_TYPE generic_bignum[SIZE_OF_LARGE_NUMBER + 6];
FLONUM_TYPE generic_floating_point_number =
{
  &generic_bignum[6],           /* low (JF: Was 0) */
  &generic_bignum[SIZE_OF_LARGE_NUMBER + 6 - 1],        /* high JF: (added +6) */
  0,                            /* leader */
  0,                            /* exponent */
  0                             /* sign */
};
/* If nonzero, we've been asked to assemble nan, +inf or -inf */
int generic_floating_point_magic;
\f
floating_constant (expressionP)
     expressionS *expressionP;
{
  /* input_line_pointer->*/
  /* floating-point constant. */
  int error_code;

  error_code = atof_generic
    (&input_line_pointer, ".", EXP_CHARS,
     &generic_floating_point_number);

  if (error_code)
    {
      if (error_code == ERROR_EXPONENT_OVERFLOW)
        {
          as_bad ("bad floating-point constant: exponent overflow, probably assembling junk");
        }
      else
        {
          as_bad ("bad floating-point constant: unknown error code=%d.", error_code);
        }
    }
  expressionP->X_seg = big_section;
  /* input_line_pointer->just after constant, */
  /* which may point to whitespace. */
  expressionP->X_add_number = -1;
}



integer_constant (radix, expressionP)
     int radix;
     expressionS *expressionP;
{
  register char *digit_2;       /*->2nd digit of number. */
  char c;

  register valueT number;       /* offset or (absolute) value */
  register short int digit;     /* value of next digit in current radix */
  register short int maxdig = 0;/* highest permitted digit value. */
  register int too_many_digits = 0;     /* if we see >= this number of */
  register char *name;          /* points to name of symbol */
  register symbolS *symbolP;    /* points to symbol */

  int small;                    /* true if fits in 32 bits. */
  extern const char hex_value[]; /* in hex_value.c */

  /* may be bignum, or may fit in 32 bits. */
  /*
   * most numbers fit into 32 bits, and we want this case to be fast.
   * so we pretend it will fit into 32 bits. if, after making up a 32
   * bit number, we realise that we have scanned more digits than
   * comfortably fit into 32 bits, we re-scan the digits coding
   * them into a bignum. for decimal and octal numbers we are conservative: some
   * numbers may be assumed bignums when in fact they do fit into 32 bits.
   * numbers of any radix can have excess leading zeros: we strive
   * to recognise this and cast them back into 32 bits.
   * we must check that the bignum really is more than 32
   * bits, and change it back to a 32-bit number if it fits.
   * the number we are looking for is expected to be positive, but
   * if it fits into 32 bits as an unsigned number, we let it be a 32-bit
   * number. the cavalier approach is for speed in ordinary cases.
   */

  switch (radix)
    {

    case 2:
      maxdig = 2;
      too_many_digits = 33;
      break;
    case 8:
      maxdig = radix = 8;
      too_many_digits = 11;
      break;
    case 16:


      maxdig = radix = 16;
      too_many_digits = 9;
      break;
    case 10:
      maxdig = radix = 10;
      too_many_digits = 11;
    }
  c = *input_line_pointer;
  input_line_pointer++;
  digit_2 = input_line_pointer;
  for (number = 0; (digit = hex_value[c]) < maxdig; c = *input_line_pointer++)
    {
      number = number * radix + digit;
    }
  /* c contains character after number. */
  /* input_line_pointer->char after c. */
  small = input_line_pointer - digit_2 < too_many_digits;
  if (!small)
    {
      /*
       * we saw a lot of digits. manufacture a bignum the hard way.
       */
      LITTLENUM_TYPE *leader;   /*->high order littlenum of the bignum. */
      LITTLENUM_TYPE *pointer;  /*->littlenum we are frobbing now. */
      long carry;

      leader = generic_bignum;
      generic_bignum[0] = 0;
      generic_bignum[1] = 0;
      /* we could just use digit_2, but lets be mnemonic. */
      input_line_pointer = --digit_2;   /*->1st digit. */
      c = *input_line_pointer++;
      for (; (carry = hex_value[c]) < maxdig; c = *input_line_pointer++)
        {
          for (pointer = generic_bignum;
               pointer <= leader;
               pointer++)
            {
              long work;

              work = carry + radix * *pointer;
              *pointer = work & LITTLENUM_MASK;
              carry = work >> LITTLENUM_NUMBER_OF_BITS;
            }
          if (carry)
            {
              if (leader < generic_bignum + SIZE_OF_LARGE_NUMBER - 1)
                {               /* room to grow a longer bignum. */
                  *++leader = carry;
                }
            }
        }
      /* again, c is char after number, */
      /* input_line_pointer->after c. */
      know (sizeof (int) * 8 == 32);
      know (LITTLENUM_NUMBER_OF_BITS == 16);
      /* hence the constant "2" in the next line. */
      if (leader < generic_bignum + 2)
        {                       /* will fit into 32 bits. */
          number =
            ((generic_bignum[1] & LITTLENUM_MASK) << LITTLENUM_NUMBER_OF_BITS)
            | (generic_bignum[0] & LITTLENUM_MASK);
          small = 1;
        }
      else
        {
          number = leader - generic_bignum + 1; /* number of littlenums in the bignum. */
        }
    }
  if (small)
    {
      /*
       * here with number, in correct radix. c is the next char.
       * note that unlike un*x, we allow "011f" "0x9f" to
       * both mean the same as the (conventional) "9f". this is simply easier
       * than checking for strict canonical form. syntax sux!
       */

      switch (c)
        {

#ifdef LOCAL_LABELS_FB
        case 'b':
          {
            /*
             * backward ref to local label.
             * because it is backward, expect it to be defined.
             */
            /* Construct a local label.  */
            name = fb_label_name ((int) number, 0);

            /* seen before, or symbol is defined: ok */
            symbolP = symbol_find (name);
            if ((symbolP != NULL) && (S_IS_DEFINED (symbolP)))
              {

                /* local labels are never absolute. don't waste time
                   checking absoluteness. */
                know (SEG_NORMAL (S_GET_SEGMENT (symbolP)));

                expressionP->X_add_symbol = symbolP;
                expressionP->X_seg = S_GET_SEGMENT (symbolP);

              }
            else
              {                 /* either not seen or not defined. */
                as_bad ("backw. ref to unknown label \"%d:\", 0 assumed.", number);
                expressionP->X_seg = absolute_section;
              }

            expressionP->X_add_number = 0;
            break;
          }                     /* case 'b' */

        case 'f':
          {
            /*
             * forward reference. expect symbol to be undefined or
             * unknown. undefined: seen it before. unknown: never seen
             * it before.
             * construct a local label name, then an undefined symbol.
             * don't create a xseg frag for it: caller may do that.
             * just return it as never seen before.
             */
            name = fb_label_name ((int) number, 1);
            symbolP = symbol_find_or_make (name);
            /* we have no need to check symbol properties. */
#ifndef many_segments
            /* since "know" puts its arg into a "string", we
               can't have newlines in the argument.  */
            know (S_GET_SEGMENT (symbolP) == undefined_section || S_GET_SEGMENT (symbolP) == text_section || S_GET_SEGMENT (symbolP) == data_section);
#endif
            expressionP->X_add_symbol = symbolP;
            expressionP->X_seg = undefined_section;
            expressionP->X_subtract_symbol = NULL;
            expressionP->X_add_number = 0;

            break;
          }                     /* case 'f' */

#endif /* LOCAL_LABELS_FB */

#ifdef LOCAL_LABELS_DOLLAR

        case '$':
          {

            /* If the dollar label is *currently* defined, then this is just
               another reference to it.  If it is not *currently* defined,
               then this is a fresh instantiation of that number, so create
               it.  */

            if (dollar_label_defined (number))
              {
                name = dollar_label_name (number, 0);
                symbolP = symbol_find (name);
                know (symbolP != NULL);
              }
            else
              {
                name = dollar_label_name (number, 1);
                symbolP = symbol_find_or_make (name);
              }

            expressionP->X_add_symbol = symbolP;
            expressionP->X_add_number = 0;
            expressionP->X_seg = S_GET_SEGMENT (symbolP);

            break;
          }                     /* case '$' */

#endif /* LOCAL_LABELS_DOLLAR */

        default:
          {
            expressionP->X_add_number = number;
            expressionP->X_seg = absolute_section;
            input_line_pointer--;       /* restore following character. */
            break;
          }                     /* really just a number */

        }                       /* switch on char following the number */


    }
  else
    {                           /* not a small number */
      expressionP->X_add_number = number;
      expressionP->X_seg = big_section;
      input_line_pointer--;     /*->char following number. */
    }                           /* if (small) */
}                               /* integer_constant() */


/*
 * Summary of operand().
 *
 * in:  Input_line_pointer points to 1st char of operand, which may
 *      be a space.
 *
 * out: A expressionS. X_seg determines how to understand the rest of the
 *      expressionS.
 *      The operand may have been empty: in this case X_seg == SEG_ABSENT.
 *      Input_line_pointer->(next non-blank) char after operand.
 *
 */
\f


static segT
operand (expressionP)
     register expressionS *expressionP;
{
  register char c;
  register symbolS *symbolP;    /* points to symbol */
  register char *name;          /* points to name of symbol */
  /* invented for humans only, hope */
  /* optimising compiler flushes it! */
  register short int radix;     /* 2, 8, 10 or 16, 0 when floating */
  /* 0 means we saw start of a floating- */
  /* point constant. */

  /* digits, assume it is a bignum. */

  SKIP_WHITESPACE ();           /* leading whitespace is part of operand. */
  c = *input_line_pointer++;    /* input_line_pointer->past char in c. */

  switch (c)
    {
#ifdef MRI
    case '%':
      integer_constant (2, expressionP);
      break;
    case '@':
      integer_constant (8, expressionP);
      break;
    case '$':
      integer_constant (16, expressionP);
      break;
#endif
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
      input_line_pointer--;

      integer_constant (10, expressionP);
      break;

    case '0':
      /* non-decimal radix */


      c = *input_line_pointer;
      switch (c)
        {

        default:
          if (c && strchr (FLT_CHARS, c))
            {
              input_line_pointer++;
              floating_constant (expressionP);
            }
          else
            {
              /* The string was only zero */
              expressionP->X_add_symbol = 0;
              expressionP->X_add_number = 0;
              expressionP->X_seg = absolute_section;
            }

          break;

        case 'x':
        case 'X':
          input_line_pointer++;
          integer_constant (16, expressionP);
          break;

        case 'b':
#ifdef LOCAL_LABELS_FB
          if (!*input_line_pointer
              || (!strchr ("+-.0123456789", *input_line_pointer)
                  && !strchr (EXP_CHARS, *input_line_pointer)))
            {
              input_line_pointer--;
              integer_constant (10, expressionP);
              break;
            }
#endif
        case 'B':
          input_line_pointer++;
          integer_constant (2, expressionP);
          break;

        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
          integer_constant (8, expressionP);
          break;

        case 'f':
#ifdef LOCAL_LABELS_FB
          /* if it says '0f' and the line ends or it doesn't look like
             a floating point #, its a local label ref.  dtrt */
          /* likewise for the b's.  xoxorich. */
          if (c == 'f'
              && (!*input_line_pointer ||
                  (!strchr ("+-.0123456789", *input_line_pointer) &&
                   !strchr (EXP_CHARS, *input_line_pointer))))
            {
              input_line_pointer -= 1;
              integer_constant (10, expressionP);
              break;
            }
#endif

        case 'd':
        case 'D':
        case 'F':
        case 'r':
        case 'e':
        case 'E':
        case 'g':
        case 'G':

          input_line_pointer++;
          floating_constant (expressionP);
          expressionP->X_add_number = -(isupper (c) ? tolower (c) : c);
          break;

#ifdef LOCAL_LABELS_DOLLAR
        case '$':
          integer_constant (10, expressionP);
          break;
#endif
        }

      break;
    case '(':
      /* didn't begin with digit & not a name */
      {
        (void) expression (expressionP);
        /* Expression() will pass trailing whitespace */
        if (*input_line_pointer++ != ')')
          {
            as_bad ("Missing ')' assumed");
            input_line_pointer--;
          }
        /* here with input_line_pointer->char after "(...)" */
      }
      return expressionP->X_seg;


    case '\'':
      /* Warning: to conform to other people's assemblers NO ESCAPEMENT is
         permitted for a single quote. The next character, parity errors and
         all, is taken as the value of the operand. VERY KINKY.  */
      expressionP->X_add_number = *input_line_pointer++;
      expressionP->X_seg = absolute_section;
      break;

    case '+':
      operand (expressionP);
      break;

    case '~':
    case '-':
      {
        /* unary operator: hope for SEG_ABSOLUTE */
        segT opseg = operand (expressionP);
        if (opseg == absolute_section)
          {
            /* input_line_pointer -> char after operand */
            if (c == '-')
              {
                expressionP->X_add_number = -expressionP->X_add_number;
                /* Notice: '-' may overflow: no warning is given. This is
                   compatible with other people's assemblers. Sigh.  */
              }
            else
              {
                expressionP->X_add_number = ~expressionP->X_add_number;
              }
          }
        else if (opseg == text_section
                 || opseg == data_section
                 || opseg == bss_section
                 || opseg == pass1_section
                 || opseg == undefined_section)
          {
            if (c == '-')
              {
                expressionP->X_subtract_symbol = expressionP->X_add_symbol;
                expressionP->X_add_symbol = 0;
                expressionP->X_seg = diff_section;
              }
            else
              as_warn ("Unary operator %c ignored because bad operand follows",
                       c);
          }
        else
          as_warn ("Unary operator %c ignored because bad operand follows", c);
      }
      break;

    case '.':
      if (!is_part_of_name (*input_line_pointer))
        {
          char *fake;
          extern struct obstack frags;

          /* JF: '.' is pseudo symbol with value of current location
             in current segment.  */
#ifdef DOT_LABEL_PREFIX
          fake = ".L0\001";
#else
          fake = "L0\001";
#endif
          symbolP = symbol_new (fake,
                                now_seg,
               (valueT) (obstack_next_free (&frags) - frag_now->fr_literal),
                                frag_now);

          expressionP->X_add_number = 0;
          expressionP->X_add_symbol = symbolP;
          expressionP->X_seg = now_seg;
          break;

        }
      else
        {
          goto isname;


        }
    case ',':
    case '\n':
    case '\0':
    eol:
      /* can't imagine any other kind of operand */
      expressionP->X_seg = absent_section;
      input_line_pointer--;
      md_operand (expressionP);
      break;

    default:
      if (is_end_of_line[c])
        goto eol;
      if (is_name_beginner (c)) /* here if did not begin with a digit */
        {
          /*
           * Identifier begins here.
           * This is kludged for speed, so code is repeated.
           */
        isname:
          name = --input_line_pointer;
          c = get_symbol_end ();
          symbolP = symbol_find_or_make (name);
          /* If we have an absolute symbol or a reg, then we know its value
             now.  */
          expressionP->X_seg = S_GET_SEGMENT (symbolP);
          if (expressionP->X_seg == absolute_section
              || expressionP->X_seg == reg_section)
            expressionP->X_add_number = S_GET_VALUE (symbolP);
          else
            {
              expressionP->X_add_number = 0;
              expressionP->X_add_symbol = symbolP;
            }
          *input_line_pointer = c;
          expressionP->X_subtract_symbol = NULL;
        }
      else
        {
          as_bad ("Bad expression");
          expressionP->X_add_number = 0;
          expressionP->X_seg = absolute_section;
        }
    }

  /*
   * It is more 'efficient' to clean up the expressionS when they are created.
   * Doing it here saves lines of code.
   */
  clean_up_expression (expressionP);
  SKIP_WHITESPACE ();           /*->1st char after operand. */
  know (*input_line_pointer != ' ');
  return (expressionP->X_seg);
}                               /* operand() */
\f

/* Internal. Simplify a struct expression for use by expr() */

/*
 * In:  address of a expressionS.
 *      The X_seg field of the expressionS may only take certain values.
 *      Now, we permit SEG_PASS1 to make code smaller & faster.
 *      Elsewise we waste time special-case testing. Sigh. Ditto SEG_ABSENT.
 * Out: expressionS may have been modified:
 *      'foo-foo' symbol references cancelled to 0,
 *              which changes X_seg from SEG_DIFFERENCE to SEG_ABSOLUTE;
 *      Unused fields zeroed to help expr().
 */

static void
clean_up_expression (expressionP)
     register expressionS *expressionP;
{
  segT s = expressionP->X_seg;
  if (s == absent_section
      || s == pass1_section)
    {
      expressionP->X_add_symbol = NULL;
      expressionP->X_subtract_symbol = NULL;
      expressionP->X_add_number = 0;
    }
  else if (s == big_section
           || s == absolute_section)
    {
      expressionP->X_subtract_symbol = NULL;
      expressionP->X_add_symbol = NULL;
    }
  else if (s == undefined_section)
    expressionP->X_subtract_symbol = NULL;
  else if (s == diff_section)
    {
      /*
       * It does not hurt to 'cancel' NULL==NULL
       * when comparing symbols for 'eq'ness.
       * It is faster to re-cancel them to NULL
       * than to check for this special case.
       */
      if (expressionP->X_subtract_symbol == expressionP->X_add_symbol
          || (expressionP->X_subtract_symbol
              && expressionP->X_add_symbol
              && (expressionP->X_subtract_symbol->sy_frag
                  == expressionP->X_add_symbol->sy_frag)
              && (S_GET_VALUE (expressionP->X_subtract_symbol)
                  == S_GET_VALUE (expressionP->X_add_symbol))))
        {
          expressionP->X_subtract_symbol = NULL;
          expressionP->X_add_symbol = NULL;
          expressionP->X_seg = absolute_section;
        }
    }
  else if (s == reg_section)
    {
      expressionP->X_add_symbol = NULL;
      expressionP->X_subtract_symbol = NULL;
    }
  else
    {
      if (SEG_NORMAL (expressionP->X_seg))
        {
          expressionP->X_subtract_symbol = NULL;
        }
      else
        {
          BAD_CASE (expressionP->X_seg);
        }
    }
}
\f
/*
 *                      expr_part ()
 *
 * Internal. Made a function because this code is used in 2 places.
 * Generate error or correct X_?????_symbol of expressionS.
 */

/*
 * symbol_1 += symbol_2 ... well ... sort of.
 */

static segT
expr_part (symbol_1_PP, symbol_2_P)
     symbolS **symbol_1_PP;
     symbolS *symbol_2_P;
{
  segT return_value;
#ifndef MANY_SEGMENTS
#ifndef OBJ_ECOFF
  int test = ((*symbol_1_PP) == NULL
              || (S_GET_SEGMENT (*symbol_1_PP) == text_section)
              || (S_GET_SEGMENT (*symbol_1_PP) == data_section)
              || (S_GET_SEGMENT (*symbol_1_PP) == bss_section)
              || (!S_IS_DEFINED (*symbol_1_PP)));
  assert (test);
  test = (symbol_2_P == NULL
          || (S_GET_SEGMENT (symbol_2_P) == text_section)
          || (S_GET_SEGMENT (symbol_2_P) == data_section)
          || (S_GET_SEGMENT (symbol_2_P) == bss_section)
          || (!S_IS_DEFINED (symbol_2_P)));
  assert (test);
#endif
#endif
  if (*symbol_1_PP)
    {
      if (!S_IS_DEFINED (*symbol_1_PP))
        {
          if (symbol_2_P)
            {
              return_value = pass1_section;
              *symbol_1_PP = NULL;
            }
          else
            {
              know (!S_IS_DEFINED (*symbol_1_PP));
              return_value = undefined_section;
            }
        }
      else
        {
          if (symbol_2_P)
            {
              if (!S_IS_DEFINED (symbol_2_P))
                {
                  *symbol_1_PP = NULL;
                  return_value = pass1_section;
                }
              else
                {
                  /* {seg1} - {seg2} */
                  as_bad ("Expression too complex, 2 symbolS forgotten: \"%s\" \"%s\"",
                        S_GET_NAME (*symbol_1_PP), S_GET_NAME (symbol_2_P));
                  *symbol_1_PP = NULL;
                  return_value = absolute_section;
                }
            }
          else
            {
              return_value = S_GET_SEGMENT (*symbol_1_PP);
            }
        }
    }
  else
    {                           /* (* symbol_1_PP) == NULL */
      if (symbol_2_P)
        {
          *symbol_1_PP = symbol_2_P;
          return_value = S_GET_SEGMENT (symbol_2_P);
        }
      else
        {
          *symbol_1_PP = NULL;
          return_value = absolute_section;
        }
    }
#ifndef MANY_SEGMENTS
#ifndef OBJ_ECOFF
  test = (return_value == absolute_section
          || return_value == text_section
          || return_value == data_section
          || return_value == bss_section
          || return_value == undefined_section
          || return_value == pass1_section);
  assert (test);
#endif
#endif
  know ((*symbol_1_PP) == NULL
        || (S_GET_SEGMENT (*symbol_1_PP) == return_value));
  return (return_value);
}
\f
/* Expression parser. */

/*
 * We allow an empty expression, and just assume (absolute,0) silently.
 * Unary operators and parenthetical expressions are treated as operands.
 * As usual, Q==quantity==operand, O==operator, X==expression mnemonics.
 *
 * We used to do a aho/ullman shift-reduce parser, but the logic got so
 * warped that I flushed it and wrote a recursive-descent parser instead.
 * Now things are stable, would anybody like to write a fast parser?
 * Most expressions are either register (which does not even reach here)
 * or 1 symbol. Then "symbol+constant" and "symbol-symbol" are common.
 * So I guess it doesn't really matter how inefficient more complex expressions
 * are parsed.
 *
 * After expr(RANK,resultP) input_line_pointer->operator of rank <= RANK.
 * Also, we have consumed any leading or trailing spaces (operand does that)
 * and done all intervening operators.
 */

typedef enum
{
  O_illegal,                    /* (0)  what we get for illegal op */

  O_multiply,                   /* (1)  * */
  O_divide,                     /* (2)  / */
  O_modulus,                    /* (3)  % */
  O_left_shift,                 /* (4)  < */
  O_right_shift,                /* (5)  > */
  O_bit_inclusive_or,           /* (6)  | */
  O_bit_or_not,                 /* (7)  ! */
  O_bit_exclusive_or,           /* (8)  ^ */
  O_bit_and,                    /* (9)  & */
  O_add,                        /* (10) + */
  O_subtract                    /* (11) - */
}

operatorT;

#undef __
#define __ O_illegal

static const operatorT op_encoding[256] =
{                               /* maps ASCII->operators */

  __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,

  __, O_bit_or_not, __, __, __, O_modulus, O_bit_and, __,
  __, __, O_multiply, O_add, __, O_subtract, __, O_divide,
  __, __, __, __, __, __, __, __,
  __, __, __, __, O_left_shift, __, O_right_shift, __,
  __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, O_bit_exclusive_or, __,
  __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __,
  __, __, __, __, O_bit_inclusive_or, __, __, __,

  __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
  __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __
};


/*
 *      Rank    Examples
 *      0       operand, (expression)
 *      1       + -
 *      2       & ^ ! |
 *      3       * / % << >>
 */
static const operator_rankT
  op_rank[] =
{0, 3, 3, 3, 3, 3, 2, 2, 2, 2, 1, 1};
\f
/* Return resultP->X_seg. */
segT 
expr (rank, resultP)
     register operator_rankT rank;      /* Larger # is higher rank. */
     register expressionS *resultP;     /* Deliver result here. */
{
  expressionS right;
  register operatorT op_left;
  register char c_left;         /* 1st operator character. */
  register operatorT op_right;
  register char c_right;

  know (rank >= 0);
  (void) operand (resultP);
  know (*input_line_pointer != ' ');    /* Operand() gobbles spaces. */
  c_left = *input_line_pointer; /* Potential operator character. */
  op_left = op_encoding[c_left];
  while (op_left != O_illegal && op_rank[(int) op_left] > rank)
    {
      input_line_pointer++;     /*->after 1st character of operator. */
      /* Operators "<<" and ">>" have 2 characters. */
      if (*input_line_pointer == c_left && (c_left == '<' || c_left == '>'))
        {
          input_line_pointer++;
        }                       /*->after operator. */
      if (absent_section == expr (op_rank[(int) op_left], &right))
        {
          as_warn ("Missing operand value assumed absolute 0.");
          resultP->X_add_number = 0;
          resultP->X_subtract_symbol = NULL;
          resultP->X_add_symbol = NULL;
          resultP->X_seg = absolute_section;
        }
      know (*input_line_pointer != ' ');
      c_right = *input_line_pointer;
      op_right = op_encoding[c_right];
      if (*input_line_pointer == c_right && (c_right == '<' || c_right == '>'))
        {
          input_line_pointer++;
        }                       /*->after operator. */
      know ((int) op_right == 0 || op_rank[(int) op_right] <= op_rank[(int) op_left]);
      /* input_line_pointer->after right-hand quantity. */
      /* left-hand quantity in resultP */
      /* right-hand quantity in right. */
      /* operator in op_left. */
      if (resultP->X_seg == pass1_section || right.X_seg == pass1_section)
        {
          resultP->X_seg = pass1_section;
        }
      else
        {
          if (resultP->X_seg == big_section)
            {
              as_warn ("Left operand of %c is a %s.  Integer 0 assumed.",
                    c_left, resultP->X_add_number > 0 ? "bignum" : "float");
              resultP->X_seg = absolute_section;
              resultP->X_add_symbol = 0;
              resultP->X_subtract_symbol = 0;
              resultP->X_add_number = 0;
            }
          if (right.X_seg == big_section)
            {
              as_warn ("Right operand of %c is a %s.  Integer 0 assumed.",
                       c_left, right.X_add_number > 0 ? "bignum" : "float");
              right.X_seg = absolute_section;
              right.X_add_symbol = 0;
              right.X_subtract_symbol = 0;
              right.X_add_number = 0;
            }
          if (op_left == O_subtract)
            {
              /*
               * Convert - into + by exchanging symbolS and negating number.
               * I know -infinity can't be negated in 2's complement:
               * but then it can't be subtracted either. This trick
               * does not cause any further inaccuracy.
               */

              register symbolS *symbolP;

              right.X_add_number = -right.X_add_number;
              symbolP = right.X_add_symbol;
              right.X_add_symbol = right.X_subtract_symbol;
              right.X_subtract_symbol = symbolP;
              if (symbolP)
                {
                  right.X_seg = diff_section;
                }
              op_left = O_add;
            }
\f
          if (op_left == O_add)
            {
              segT seg1;
              segT seg2;
#ifndef MANY_SEGMENTS
#ifndef OBJ_ECOFF
              know (resultP->X_seg == data_section || resultP->X_seg == text_section || resultP->X_seg == bss_section || resultP->X_seg == undefined_section || resultP->X_seg == diff_section || resultP->X_seg == absolute_section || resultP->X_seg == pass1_section || resultP->X_seg == reg_section);

              know (right.X_seg == data_section || right.X_seg == text_section || right.X_seg == bss_section || right.X_seg == undefined_section || right.X_seg == diff_section || right.X_seg == absolute_section || right.X_seg == pass1_section);
#endif
#endif
              clean_up_expression (&right);
              clean_up_expression (resultP);

              seg1 = expr_part (&resultP->X_add_symbol, right.X_add_symbol);
              seg2 = expr_part (&resultP->X_subtract_symbol, right.X_subtract_symbol);
              if (seg1 == pass1_section || seg2 == pass1_section)
                {
                  need_pass_2 = 1;
                  resultP->X_seg = pass1_section;
                }
              else if (seg2 == absolute_section)
                resultP->X_seg = seg1;
              else if (seg1 != undefined_section
                       && seg1 != absolute_section
                       && seg2 != undefined_section
                       && seg1 != seg2)
                {
                  know (seg2 != absolute_section);
                  know (resultP->X_subtract_symbol);
#ifndef MANY_SEGMENTS
#ifndef OBJ_ECOFF
                  know (seg1 == text_section || seg1 == data_section || seg1 == bss_section);
                  know (seg2 == text_section || seg2 == data_section || seg2 == bss_section);
#endif
#endif
                  know (resultP->X_add_symbol);
                  know (resultP->X_subtract_symbol);
                  as_bad ("Expression too complex: forgetting %s - %s",
                          S_GET_NAME (resultP->X_add_symbol),
                          S_GET_NAME (resultP->X_subtract_symbol));
                  resultP->X_seg = absolute_section;
                  /* Clean_up_expression() will do the rest. */
                }
              else
                resultP->X_seg = diff_section;

              resultP->X_add_number += right.X_add_number;
              clean_up_expression (resultP);
            }
          else
            {                   /* Not +. */
              if (resultP->X_seg == undefined_section || right.X_seg == undefined_section)
                {
                  resultP->X_seg = pass1_section;
                  need_pass_2 = 1;
                }
              else
                {
                  resultP->X_subtract_symbol = NULL;
                  resultP->X_add_symbol = NULL;
                  /* Will be absolute_section. */
                  if (resultP->X_seg != absolute_section || right.X_seg != absolute_section)
                    {
                      as_bad ("Relocation error. Absolute 0 assumed.");
                      resultP->X_seg = absolute_section;
                      resultP->X_add_number = 0;
                    }
                  else
                    {
                      switch (op_left)
                        {
                        case O_bit_inclusive_or:
                          resultP->X_add_number |= right.X_add_number;
                          break;

                        case O_modulus:
                          if (right.X_add_number)
                            {
                              resultP->X_add_number %= right.X_add_number;
                            }
                          else
                            {
                              as_warn ("Division by 0. 0 assumed.");
                              resultP->X_add_number = 0;
                            }
                          break;

                        case O_bit_and:
                          resultP->X_add_number &= right.X_add_number;
                          break;

                        case O_multiply:
                          resultP->X_add_number *= right.X_add_number;
                          break;

                        case O_divide:
                          if (right.X_add_number)
                            {
                              resultP->X_add_number /= right.X_add_number;
                            }
                          else
                            {
                              as_warn ("Division by 0. 0 assumed.");
                              resultP->X_add_number = 0;
                            }
                          break;

                        case O_left_shift:
                          resultP->X_add_number <<= right.X_add_number;
                          break;

                        case O_right_shift:
                          resultP->X_add_number >>= right.X_add_number;
                          break;

                        case O_bit_exclusive_or:
                          resultP->X_add_number ^= right.X_add_number;
                          break;

                        case O_bit_or_not:
                          resultP->X_add_number |= ~right.X_add_number;
                          break;

                        default:
                          BAD_CASE (op_left);
                          break;
                        }       /* switch(operator) */
                    }
                }               /* If we have to force need_pass_2. */
            }                   /* If operator was +. */
        }                       /* If we didn't set need_pass_2. */
      op_left = op_right;
    }                           /* While next operator is >= this rank. */
  return (resultP->X_seg);
}
\f
/*
 *                      get_symbol_end()
 *
 * This lives here because it belongs equally in expr.c & read.c.
 * Expr.c is just a branch office read.c anyway, and putting it
 * here lessens the crowd at read.c.
 *
 * Assume input_line_pointer is at start of symbol name.
 * Advance input_line_pointer past symbol name.
 * Turn that character into a '\0', returning its former value.
 * This allows a string compare (RMS wants symbol names to be strings)
 * of the symbol name.
 * There will always be a char following symbol name, because all good
 * lines end in end-of-line.
 */
char
get_symbol_end ()
{
  register char c;

  while (is_part_of_name (c = *input_line_pointer++))
    ;
  *--input_line_pointer = 0;
  return (c);
}


unsigned int 
get_single_number ()
{
  expressionS exp;
  operand (&exp);
  return exp.X_add_number;

}

/* end of expr.c */