path: root/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 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"

#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;

/*
 * 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 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) || (c == 'H' && input_line_pointer[0] == '\''))
    {
	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 == 'H' || c == '0') {			/* non-decimal radix */
	    if ((c = *input_line_pointer ++)=='x' || c=='X' || c=='\'') {
		c = *input_line_pointer ++; /* read past "0x" or "0X" or H' */
		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(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) */
	}			/* (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;
	    
	default:		/* unary on non-absolute is unsuported */
	    if (!SEG_NORMAL(operand(expressionP))) 
	    {
		as_bad("Unary operator %c ignored because bad operand follows", c);
		break;
	    }
	    /* Fall through for normal segments ****/
	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;
	    }
	    /* 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() */

/* 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);
		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: expr.c */