* app.c: MRI compatibility - allow single quote to start a string.

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

/* expr.c -operands, expressions-
   Copyright (C) 1987, 1990, 1991, 1992 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"

#if __STDC__ == 1
static void clean_up_expression(expressionS *expressionP);
#else /* __STDC__ */
static void clean_up_expression();      /* Internal. */
#endif /* not __STDC__ */
extern const char EXP_CHARS[];  /* JF hide MD floating pt stuff all the same place */
extern const char FLT_CHARS[];

#ifdef LOCAL_LABELS_DOLLAR
extern int local_label_defined[];
#endif

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

/* LITTLENUM_TYPE       generic_buffer [6]; */  /* JF this is a hack */
/* 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 = SEG_BIG;
  /* 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  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!
     */
    if (number<10)
    {
      if (0
#ifdef local_labels_fb
          || c=='b'
#endif
#ifdef local_labels_dollar
          || (c=='$' && local_label_defined[number])
#endif
          )
      {
        /*
         * backward ref to local label.
         * because it is backward, expect it to be defined.
         */
        /*
         * construct a local label.
         */
        name = local_label_name ((int)number, 0);
        if (((symbolP = symbol_find(name)) != NULL) /* seen before */
            && (S_IS_DEFINED(symbolP))) /* symbol is defined: ok */
        { /* expected path: symbol defined. */
          /* 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_add_number = 0;
          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_add_number = 0;
          expressionP->X_seg        = SEG_ABSOLUTE;
        }
      }
      else
      {
        if (0
#ifdef local_labels_fb
            || c == 'f'
#endif
#ifdef local_labels_dollar
            || (c=='$' && !local_label_defined[number])
#endif
            )
        {
          /*
           * forward reference. expect symbol to be undefined or
           * unknown. undefined: seen it before. unknown: never seen
           * it in this pass.
           * 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 = local_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) == SEG_UNKNOWN || S_GET_SEGMENT(symbolP) == SEG_TEXT || S_GET_SEGMENT(symbolP) == SEG_DATA);
#endif
          expressionP->X_add_symbol      = symbolP;
          expressionP->X_seg             = SEG_UNKNOWN;
          expressionP->X_subtract_symbol = NULL;
          expressionP->X_add_number      = 0;
        }
        else
        { /* really a number, not a local label. */
          expressionP->X_add_number = number;
          expressionP->X_seg        = SEG_ABSOLUTE;
          input_line_pointer --; /* restore following character. */
        } /* if (c=='f') */
      } /* if (c=='b') */
    }
    else
    { /* really a number. */
      expressionP->X_add_number = number;
      expressionP->X_seg        = SEG_ABSOLUTE;
      input_line_pointer --; /* restore following character. */
    } /* if (number<10) */
  }
  else
  {
    expressionP->X_add_number = number;
    expressionP->X_seg = SEG_BIG;
    input_line_pointer --; /*->char following number. */
  } /* if (small) */
} 


/*
 * 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:
      /* The string was only zero */
      expressionP->X_add_symbol = 0;
      expressionP->X_add_number = 0;
      expressionP->X_seg = SEG_ABSOLUTE;
      break;
      
    case 'x':
    case 'X':
      input_line_pointer++;
      integer_constant(16, expressionP);
      break;
    case 'B':
    case 'b':
      input_line_pointer++;
      integer_constant(2, expressionP);
      break;

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

    case 'f':      
      /* 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' || c == 'b' || c == 'b')
          && (!*input_line_pointer ||
              (!strchr("+-.0123456789",*input_line_pointer) &&
               !strchr(EXP_CHARS,*input_line_pointer)))) 
      {
        input_line_pointer -= 2;
        integer_constant(10, expressionP);
        break;
      } 

    case 'd':
    case 'D':
    case 'F':
      
    case 'e':
    case 'E':
    case 'g':
    case 'G':
      
      input_line_pointer++;  
      floating_constant(expressionP);
      break;
    }
  
    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;


  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        = SEG_ABSOLUTE;
    break;

  case  '~':
  case  '-':
  case  '+':

  {
    /* unary operator: hope for SEG_ABSOLUTE */
    switch(operand (expressionP)) {
      case SEG_ABSOLUTE:
        /* 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;
        }
        break;

      case SEG_TEXT:
      case SEG_DATA:
      case SEG_BSS:
      case SEG_PASS1:
      case SEG_UNKNOWN:
        if(c=='-') { /* JF I hope this hack works */
            expressionP->X_subtract_symbol=expressionP->X_add_symbol;
            expressionP->X_add_symbol=0;
            expressionP->X_seg=SEG_DIFFERENCE;
            break;
          }
      default: /* unary on non-absolute is unsuported */
        as_warn("Unary operator %c ignored because bad operand follows", c);
        break;
        /* Expression undisturbed from operand(). */
      }
  }
    

  
    break;  

  case '.':
    if( !is_part_of_name(*input_line_pointer)) 
    {
      extern struct obstack frags;
      
      /*
        JF:  '.' is pseudo symbol with value of current location in current
        segment. . .
        */
      symbolP = symbol_new("L0\001",
                           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 '\n':
        /* can't imagine any other kind of operand */
        expressionP->X_seg = SEG_ABSENT;
        input_line_pointer --;
        md_operand (expressionP);
    break;    
    /* Fall through */
  default:
    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);
      switch (expressionP->X_seg)
      {
      case SEG_ABSOLUTE:
      case SEG_REGISTER:
        expressionP->X_add_number = S_GET_VALUE(symbolP);
        break;

      default:
        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 = SEG_ABSOLUTE;

    }
    
  }
  
  
  


  

  /*
   * 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;
{
  switch (expressionP->X_seg)
      {
      case SEG_ABSENT:
      case SEG_PASS1:
        expressionP->X_add_symbol       = NULL;
        expressionP->X_subtract_symbol  = NULL;
        expressionP->X_add_number       = 0;
        break;

      case SEG_BIG:
      case SEG_ABSOLUTE:
        expressionP->X_subtract_symbol  = NULL;
        expressionP->X_add_symbol       = NULL;
        break;

      case SEG_UNKNOWN:
        expressionP->X_subtract_symbol  = NULL;
        break;

      case SEG_DIFFERENCE:
        /*
         * 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                  = SEG_ABSOLUTE;
        }
        break;

      case SEG_REGISTER:
        expressionP->X_add_symbol       = NULL;
        expressionP->X_subtract_symbol  = NULL;
        break;

      default:
        if (SEG_NORMAL(expressionP->X_seg)) {
          expressionP->X_subtract_symbol        = NULL;
        }
        else {
            BAD_CASE (expressionP->X_seg);
        }
        break;
      }
} /* clean_up_expression() */
\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
    know((* symbol_1_PP) == NULL || (S_GET_SEGMENT(*symbol_1_PP) == SEG_TEXT) || (S_GET_SEGMENT(*symbol_1_PP) == SEG_DATA) || (S_GET_SEGMENT(*symbol_1_PP) == SEG_BSS) || (!S_IS_DEFINED(* symbol_1_PP)));
    know(symbol_2_P == NULL || (S_GET_SEGMENT(symbol_2_P) == SEG_TEXT) || (S_GET_SEGMENT(symbol_2_P) == SEG_DATA) || (S_GET_SEGMENT(symbol_2_P) == SEG_BSS) || (!S_IS_DEFINED(symbol_2_P)));
#endif
  if (* symbol_1_PP)
    {
      if (!S_IS_DEFINED(* symbol_1_PP))
        {
          if (symbol_2_P)
            {
                return_value = SEG_PASS1;
                * symbol_1_PP = NULL;
            }
          else
            {
                know(!S_IS_DEFINED(* symbol_1_PP));
                return_value = SEG_UNKNOWN;
            }
        }
      else
        {
          if (symbol_2_P)
            {
              if (!S_IS_DEFINED(symbol_2_P))
                {
                  * symbol_1_PP = NULL;
                  return_value = SEG_PASS1;
                }
              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 = SEG_ABSOLUTE;
                }
            }
          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 = SEG_ABSOLUTE;
        }
    }
#ifndef MANY_SEGMENTS
  know(return_value == SEG_ABSOLUTE || return_value == SEG_TEXT || return_value == SEG_DATA || return_value == SEG_BSS || return_value == SEG_UNKNOWN || return_value == SEG_PASS1);
#endif
  know((*symbol_1_PP) == NULL || (S_GET_SEGMENT(*symbol_1_PP) == return_value));
  return (return_value);
}                               /* expr_part() */
\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;

#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 (SEG_ABSENT == 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 = SEG_ABSOLUTE;
        }
      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 == SEG_PASS1 || right . X_seg == SEG_PASS1)
        {
          resultP->X_seg = SEG_PASS1;
        }
      else
        {
          if (resultP->X_seg == SEG_BIG)
            {
              as_warn("Left operand of %c is a %s.  Integer 0 assumed.",
                      c_left, resultP->X_add_number > 0 ? "bignum" : "float");
              resultP->X_seg = SEG_ABSOLUTE;
              resultP->X_add_symbol = 0;
              resultP->X_subtract_symbol = 0;
              resultP->X_add_number = 0;
            }
          if (right . X_seg == SEG_BIG)
            {
              as_warn("Right operand of %c is a %s.  Integer 0 assumed.",
                      c_left, right . X_add_number > 0 ? "bignum" : "float");
              right . X_seg = SEG_ABSOLUTE;
              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         = SEG_DIFFERENCE;
                }
              op_left = O_add;
            }
\f
          if (op_left == O_add)
            {
              segT      seg1;
              segT      seg2;
#ifndef MANY_SEGMENTS
              know(resultP->X_seg == SEG_DATA || resultP->X_seg == SEG_TEXT || resultP->X_seg == SEG_BSS || resultP->X_seg == SEG_UNKNOWN || resultP->X_seg == SEG_DIFFERENCE || resultP->X_seg == SEG_ABSOLUTE || resultP->X_seg == SEG_PASS1);
              know(right.X_seg == SEG_DATA || right.X_seg == SEG_TEXT || right.X_seg == SEG_BSS || right.X_seg == SEG_UNKNOWN || right.X_seg == SEG_DIFFERENCE || right.X_seg == SEG_ABSOLUTE || right.X_seg == SEG_PASS1);
#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 == SEG_PASS1 || seg2 == SEG_PASS1) {
                      need_pass_2 = 1;
                      resultP->X_seg = SEG_PASS1;
              } else if (seg2 == SEG_ABSOLUTE)
                  resultP->X_seg = seg1;
              else if (seg1 != SEG_UNKNOWN
                       && seg1 != SEG_ABSOLUTE
                       && seg2 != SEG_UNKNOWN
                       && seg1 != seg2) {
                      know(seg2 != SEG_ABSOLUTE);
                      know(resultP->X_subtract_symbol);
#ifndef MANY_SEGMENTS
                      know(seg1 == SEG_TEXT || seg1 == SEG_DATA || seg1== SEG_BSS);
                      know(seg2 == SEG_TEXT || seg2 == SEG_DATA || seg2== SEG_BSS);
#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 = SEG_ABSOLUTE;
                      /* Clean_up_expression() will do the rest. */
              } else
                  resultP->X_seg = SEG_DIFFERENCE;

              resultP->X_add_number += right . X_add_number;
              clean_up_expression (resultP);
      }
          else
            {                   /* Not +. */
              if (resultP->X_seg == SEG_UNKNOWN || right . X_seg == SEG_UNKNOWN)
                {
                  resultP->X_seg = SEG_PASS1;
                  need_pass_2 = 1;
                }
              else
                {
                  resultP->X_subtract_symbol = NULL;
                  resultP->X_add_symbol = NULL;
                  /* Will be SEG_ABSOLUTE. */
                  if (resultP->X_seg != SEG_ABSOLUTE || right . X_seg != SEG_ABSOLUTE)
                    {
                      as_bad("Relocation error. Absolute 0 assumed.");
                      resultP->X_seg        = SEG_ABSOLUTE;
                      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;
    
}
/*
 * Local Variables:
 * comment-column: 0
 * fill-column: 131
 * End:
 */

/* end of expr.c */