see devo/configure 1.11

[binutils.git] / gas / expr.c

/* expr.c -operands, expressions-
   Copyright (C) 1987, 1990, 1991 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 1, 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. */

/* static const char rcsid[] = "$Id$"; */

/*
 * 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"

#ifdef __STDC__
static void clean_up_expression(expressionS *expressionP);
#else /* __STDC__ */
static void clean_up_expression();      /* Internal. */
#endif /* __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
/*
 * 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 char *name;  /* points to name of symbol */
  register symbolS *    symbolP; /* Points to symbol */

  extern  char hex_value[];     /* In hex_value.c */

  SKIP_WHITESPACE();            /* Leading whitespace is part of operand. */
  c = * input_line_pointer ++;  /* Input_line_pointer->past char in c. */
  if (isdigit(c))
    {
      register valueT   number; /* offset or (absolute) value */
      register short int digit; /* value of next digit in current radix */
                                /* invented for humans only, hope */
                                /* optimising compiler flushes it! */
      register short int radix; /* 2, 8, 10 or 16 */
                                /* 0 means we saw start of a floating- */
                                /* point constant. */
      register short int maxdig = 0;/* Highest permitted digit value. */
      register int too_many_digits = 0; /* If we see >= this number of */
                                /* digits, assume it is a bignum. */
      register char *   digit_2; /*->2nd digit of number. */
               int small;       /* TRUE if fits in 32 bits. */

      if (c == '0') {                   /* non-decimal radix */
              if ((c = *input_line_pointer ++)=='x' || c=='X') {
                      c = *input_line_pointer ++; /* read past "0x" or "0X" */
                      maxdig = radix = 16;
                      too_many_digits = 9;
              } else {
                      /* 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)))) {
                              maxdig = radix = 10;
                              too_many_digits = 11;
                              c = '0';
                              input_line_pointer -= 2;

                      } else if (c == 'b' || c == 'B') {
                              c = *input_line_pointer++;
                              maxdig = radix = 2;
                              too_many_digits = 33;

                      } else if (c && strchr(FLT_CHARS,c)) {
                              radix = 0;        /* Start of floating-point constant. */
                              /* input_line_pointer->1st char of number. */
                              expressionP->X_add_number =  -(isupper(c) ? tolower(c) : c);

                      } else {          /* By elimination, assume octal radix. */
                              radix = maxdig = 8;
                              too_many_digits = 11;
                      }
              } /* c == char after "0" or "0x" or "0X" or "0e" etc. */
      } else {
              maxdig = radix = 10;
              too_many_digits = 11;
      } /* if operand starts with a zero */

      if (radix) {                      /* Fixed-point integer constant. */
                                /* 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.
 */
          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=='$' && local_label_defined[number])
#endif
                      )
                    {
                      /*
                       * Backward ref to local label.
                       * Because it is backward, expect it to be DEFINED.
                       */
                      /*
                       * Construct a local label.
                       */
                      name = local_label_name ((int)number, 0);
                      if (((symbolP = symbol_find(name)) != NULL) /* seen before */
                          && (S_IS_DEFINED(symbolP))) /* symbol is defined: OK */
                        {               /* Expected path: symbol defined. */
                          /* Local labels are never absolute. Don't waste time checking absoluteness. */
                          know((S_GET_SEGMENT(symbolP) == SEG_DATA) || (S_GET_SEGMENT(symbolP) == SEG_TEXT));
                          expressionP->X_add_symbol = symbolP;
                          expressionP->X_add_number = 0;
                          expressionP->X_seg = S_GET_SEGMENT(symbolP);
                        }
                      else
                        {               /* Either not seen or not defined. */
                          as_bad("Backw. ref to unknown label \"%d:\", 0 assumed.",
                                  number);
                          expressionP->X_add_number = 0;
                          expressionP->X_seg        = SEG_ABSOLUTE;
                        }
                    }
                  else
                    {
                      if (0
#ifdef LOCAL_LABELS_FB
                          || c == 'f'
#endif
#ifdef LOCAL_LABELS_DOLLAR
                          || (c=='$' && !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. */
                          know(S_GET_SEGMENT(symbolP) == SEG_UNKNOWN
                               || S_GET_SEGMENT(symbolP) == SEG_TEXT
                               || S_GET_SEGMENT(symbolP) == SEG_DATA);
                          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) */
        }                       /* (If integer constant) */
      else
        {                       /* 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. */
          know(expressionP->X_add_number < 0); /* < 0 means "floating point". */
        }                       /* if (not floating-point constant) */
    }
  else if(c=='.' && !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;

  } else 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.
       */
      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 if (c=='(')/* 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 "(...)" */
    }
  else if (c == '~' || c == '-' || c == '+') {
          /* 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 if (c == '~') {
                      expressionP->X_add_number = ~ expressionP->X_add_number;
              } else if (c != '+') {
                      know(0);
              } /* switch on unary operator */
              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_bad("Unary operator %c ignored because bad operand follows", c);
        break;
        /* Expression undisturbed from operand(). */
      }
    }
  else if (c=='\'')
    {
/*
 * 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;
    }
  else
    {
                      /* can't imagine any other kind of operand */
      expressionP->X_seg = SEG_ABSENT;
      input_line_pointer --;
      md_operand (expressionP);
    }
/*
 * 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_TEXT:
    case SEG_DATA:
    case SEG_BSS:
    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:
      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;

  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)));
  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;
        }
    }
  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);
  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;

              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);

              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);

                      know(seg1 == SEG_TEXT || seg1 == SEG_DATA || seg1== SEG_BSS);
                      know(seg2 == SEG_TEXT || seg2 == SEG_DATA || seg2== SEG_BSS);
                      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);
}

/*
 * Local Variables:
 * comment-column: 0
 * fill-column: 131
 * End:
 */

/* end: expr.c */