binutils-gdb/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[];

/*
 * 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;

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!
     */
    
    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 = SEG_ABSOLUTE;
      }
      
      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) == 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;
      
      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 = SEG_ABSOLUTE;
      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 = SEG_BIG;
    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.
 *
 */



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 = 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 '0':
    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 'r':
    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 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        = 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 ',':    
  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() */


/* 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() */

/*
 *			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() */

/* 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 };

/* 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;
	    }

	  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
		   || resultP->X_seg == SEG_REGISTER);
	      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);
}

/*
 *			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 */