[deliverable/binutils-gdb.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 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;
\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) || (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() */
\f
/* Internal. Simplify a struct expression for use by expr() */

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

static void
    clean_up_expression (expressionP)
register expressionS * expressionP;
{
    switch (expressionP->X_seg)
    {
    case SEG_ABSENT:
    case SEG_PASS1:
        expressionP->X_add_symbol       = NULL;
        expressionP->X_subtract_symbol  = NULL;
        expressionP->X_add_number       = 0;
        break;
        
    case SEG_BIG:
    case SEG_ABSOLUTE:
        expressionP->X_subtract_symbol  = NULL;
        expressionP->X_add_symbol       = NULL;
        break;
        
    case SEG_UNKNOWN:
        expressionP->X_subtract_symbol  = NULL;
        break;
        
    case SEG_DIFFERENCE:
        /*
         * It does not hurt to 'cancel' NULL==NULL
         * when comparing symbols for 'eq'ness.
         * It is faster to re-cancel them to NULL
         * than to check for this special case.
         */
        if (expressionP->X_subtract_symbol == expressionP->X_add_symbol
            || (expressionP->X_subtract_symbol
                && expressionP->X_add_symbol
                && expressionP->X_subtract_symbol->sy_frag==expressionP->X_add_symbol->sy_frag
                && S_GET_VALUE(expressionP->X_subtract_symbol) == S_GET_VALUE(expressionP->X_add_symbol))) {
            expressionP->X_subtract_symbol      = NULL;
            expressionP->X_add_symbol           = NULL;
            expressionP->X_seg                  = SEG_ABSOLUTE;
        }
        break;
        
    case SEG_REGISTER:
        expressionP->X_add_symbol       = NULL;
        expressionP->X_subtract_symbol  = NULL;
        break;
        
    default:
        if (SEG_NORMAL(expressionP->X_seg)) {
            expressionP->X_subtract_symbol      = NULL;
        }
        else {
            BAD_CASE (expressionP->X_seg);
        }
        break;
    }
} /* clean_up_expression() */
\f
/*
 *                      expr_part ()
 *
 * Internal. Made a function because this code is used in 2 places.
 * Generate error or correct X_?????_symbol of expressionS.
 */

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

static segT
    expr_part (symbol_1_PP, symbol_2_P)
symbolS **      symbol_1_PP;
symbolS *       symbol_2_P;
{
    segT                        return_value;
#ifndef MANY_SEGMENTS
    know((* symbol_1_PP) == NULL || (S_GET_SEGMENT(*symbol_1_PP) == SEG_TEXT) || (S_GET_SEGMENT(*symbol_1_PP) == SEG_DATA) || (S_GET_SEGMENT(*symbol_1_PP) == SEG_BSS) || (!S_IS_DEFINED(* symbol_1_PP)));
    know(symbol_2_P == NULL || (S_GET_SEGMENT(symbol_2_P) == SEG_TEXT) || (S_GET_SEGMENT(symbol_2_P) == SEG_DATA) || (S_GET_SEGMENT(symbol_2_P) == SEG_BSS) || (!S_IS_DEFINED(symbol_2_P)));
#endif
    if (* symbol_1_PP)
    {
        if (!S_IS_DEFINED(* symbol_1_PP))
        {
            if (symbol_2_P)
            {
                return_value = SEG_PASS1;
                * symbol_1_PP = NULL;
            }
            else
            {
                know(!S_IS_DEFINED(* symbol_1_PP));
                return_value = SEG_UNKNOWN;
            }
        }
        else
        {
            if (symbol_2_P)
            {
                if (!S_IS_DEFINED(symbol_2_P))
                {
                    * symbol_1_PP = NULL;
                    return_value = SEG_PASS1;
                }
                else
                {
                    /* {seg1} - {seg2} */
                    as_bad("Expression too complex, 2 symbols forgotten: \"%s\" \"%s\"",
                           S_GET_NAME(* symbol_1_PP), S_GET_NAME(symbol_2_P));
                    * symbol_1_PP = NULL;
                    return_value = SEG_ABSOLUTE;
                }
            }
            else
            {
                return_value = S_GET_SEGMENT(* symbol_1_PP);
            }
        }
    }
    else
    {                           /* (* symbol_1_PP) == NULL */
        if (symbol_2_P)
        {
            * symbol_1_PP = symbol_2_P;
            return_value = S_GET_SEGMENT(symbol_2_P);
        }
        else
        {
            * symbol_1_PP = NULL;
            return_value = SEG_ABSOLUTE;
        }
    }
#ifndef MANY_SEGMENTS
    know(return_value == SEG_ABSOLUTE || return_value == SEG_TEXT || return_value == SEG_DATA || return_value == SEG_BSS || return_value == SEG_UNKNOWN || return_value == SEG_PASS1);
#endif
    know((*symbol_1_PP) == NULL || (S_GET_SEGMENT(*symbol_1_PP) == return_value));
    return (return_value);
}                               /* expr_part() */
\f
/* Expression parser. */

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

typedef enum
{
    O_illegal,                  /* (0)  what we get for illegal op */
    
    O_multiply,                 /* (1)  * */
    O_divide,                   /* (2)  / */
    O_modulus,                  /* (3)  % */
    O_left_shift,                       /* (4)  < */
    O_right_shift,                      /* (5)  > */
    O_bit_inclusive_or,         /* (6)  | */
    O_bit_or_not,                       /* (7)  ! */
    O_bit_exclusive_or,         /* (8)  ^ */
    O_bit_and,                  /* (9)  & */
    O_add,                              /* (10) + */
    O_subtract                  /* (11) - */
    }
operatorT;

#define __ O_illegal

static const operatorT op_encoding [256] = {    /* maps ASCII->operators */
    
    __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
    
    __, O_bit_or_not, __, __, __, O_modulus, O_bit_and, __,
    __, __, O_multiply, O_add, __, O_subtract, __, O_divide,
    __, __, __, __, __, __, __, __,
    __, __, __, __, O_left_shift, __, O_right_shift, __,
    __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, O_bit_exclusive_or, __,
    __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __,
    __, __, __, __, O_bit_inclusive_or, __, __, __,
    
    __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
    __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __
    };


/*
 *      Rank    Examples
 *      0       operand, (expression)
 *      1       + -
 *      2       & ^ ! |
 *      3       * / % << >>
 */
static const operator_rankT
    op_rank [] = { 0, 3, 3, 3, 3, 3, 2, 2, 2, 2, 1, 1 };
\f
/* Return resultP->X_seg. */
segT expr(rank, resultP)
    register operator_rankT     rank; /* Larger # is higher rank. */
    register expressionS *resultP; /* Deliver result here. */
{
    expressionS         right;
    register operatorT  op_left;
    register char c_left;       /* 1st operator character. */
    register operatorT  op_right;
    register char c_right;
    
    know(rank >= 0);
    (void)operand (resultP);
    know(* input_line_pointer != ' '); /* Operand() gobbles spaces. */
    c_left = * input_line_pointer; /* Potential operator character. */
    op_left = op_encoding [c_left];
    while (op_left != O_illegal && op_rank [(int) op_left] > rank)
    {
        input_line_pointer ++;  /*->after 1st character of operator. */
        /* Operators "<<" and ">>" have 2 characters. */
        if (* input_line_pointer == c_left && (c_left == '<' || c_left == '>'))
        {
            input_line_pointer ++;
        }                       /*->after operator. */
        if (SEG_ABSENT == expr (op_rank[(int) op_left], &right))
        {
            as_warn("Missing operand value assumed absolute 0.");
            resultP->X_add_number       = 0;
            resultP->X_subtract_symbol  = NULL;
            resultP->X_add_symbol       = NULL;
            resultP->X_seg = SEG_ABSOLUTE;
        }
        know(* input_line_pointer != ' ');
        c_right = * input_line_pointer;
        op_right = op_encoding [c_right];
        if (* input_line_pointer == c_right && (c_right == '<' || c_right == '>'))
        {
            input_line_pointer ++;
        }                       /*->after operator. */
        know((int) op_right == 0 || op_rank [(int) op_right] <= op_rank[(int) op_left]);
        /* input_line_pointer->after right-hand quantity. */
        /* left-hand quantity in resultP */
        /* right-hand quantity in right. */
        /* operator in op_left. */
        if (resultP->X_seg == SEG_PASS1 || right . X_seg == SEG_PASS1)
        {
            resultP->X_seg = SEG_PASS1;
        }
        else
        {
            if (resultP->X_seg == SEG_BIG)
            {
                as_warn("Left operand of %c is a %s.  Integer 0 assumed.",
                        c_left, resultP->X_add_number > 0 ? "bignum" : "float");
                resultP->X_seg = SEG_ABSOLUTE;
                resultP->X_add_symbol = 0;
                resultP->X_subtract_symbol = 0;
                resultP->X_add_number = 0;
            }
            if (right . X_seg == SEG_BIG)
            {
                as_warn("Right operand of %c is a %s.  Integer 0 assumed.",
                        c_left, right . X_add_number > 0 ? "bignum" : "float");
                right . X_seg = SEG_ABSOLUTE;
                right . X_add_symbol = 0;
                right . X_subtract_symbol = 0;
                right . X_add_number = 0;
            }
            if (op_left == O_subtract)
            {
                /*
                 * Convert - into + by exchanging symbols and negating number.
                 * I know -infinity can't be negated in 2's complement:
                 * but then it can't be subtracted either. This trick
                 * does not cause any further inaccuracy.
                 */
                
                register symbolS *      symbolP;
                
                right . X_add_number      = - right . X_add_number;
                symbolP                   = right . X_add_symbol;
                right . X_add_symbol    = right . X_subtract_symbol;
                right . X_subtract_symbol = symbolP;
                if (symbolP)
                {
                    right . X_seg               = SEG_DIFFERENCE;
                }
                op_left = O_add;
            }
            \f
            if (op_left == O_add)
            {
                segT    seg1;
                segT    seg2;
#ifndef MANY_SEGMENTS
                know(resultP->X_seg == SEG_DATA || resultP->X_seg == SEG_TEXT || resultP->X_seg == SEG_BSS || resultP->X_seg == SEG_UNKNOWN || resultP->X_seg == SEG_DIFFERENCE || resultP->X_seg == SEG_ABSOLUTE || resultP->X_seg == SEG_PASS1);
                know(right.X_seg == SEG_DATA || right.X_seg == SEG_TEXT || right.X_seg == SEG_BSS || right.X_seg == SEG_UNKNOWN || right.X_seg == SEG_DIFFERENCE || right.X_seg == SEG_ABSOLUTE || right.X_seg == SEG_PASS1);
#endif
                clean_up_expression (& right);
                clean_up_expression (resultP);
                
                seg1 = expr_part (& resultP->X_add_symbol, right . X_add_symbol);
                seg2 = expr_part (& resultP->X_subtract_symbol, right . X_subtract_symbol);
                if (seg1 == SEG_PASS1 || seg2 == SEG_PASS1) {
                    need_pass_2 = 1;
                    resultP->X_seg = SEG_PASS1;
                } else if (seg2 == SEG_ABSOLUTE)
                    resultP->X_seg = seg1;
                else if (seg1 != SEG_UNKNOWN
                         && seg1 != SEG_ABSOLUTE
                         && seg2 != SEG_UNKNOWN
                         && seg1 != seg2) {
                    know(seg2 != SEG_ABSOLUTE);
                    know(resultP->X_subtract_symbol);
#ifndef MANY_SEGMENTS
                    know(seg1 == SEG_TEXT || seg1 == SEG_DATA || seg1== SEG_BSS);
                    know(seg2 == SEG_TEXT || seg2 == SEG_DATA || seg2== SEG_BSS);
#endif
                    know(resultP->X_add_symbol);
                    know(resultP->X_subtract_symbol);
                    as_bad("Expression too complex: forgetting %s - %s",
                           S_GET_NAME(resultP->X_add_symbol),
                           S_GET_NAME(resultP->X_subtract_symbol));
                    resultP->X_seg = SEG_ABSOLUTE;
                    /* Clean_up_expression() will do the rest. */
                } else
                    resultP->X_seg = SEG_DIFFERENCE;
                
                resultP->X_add_number += right . X_add_number;
                clean_up_expression (resultP);
            }
            else
            {                   /* Not +. */
                if (resultP->X_seg == SEG_UNKNOWN || right . X_seg == SEG_UNKNOWN)
                {
                    resultP->X_seg = SEG_PASS1;
                    need_pass_2 = 1;
                }
                else
                {
                    resultP->X_subtract_symbol = NULL;
                    resultP->X_add_symbol = NULL;
                    /* Will be SEG_ABSOLUTE. */
                    if (resultP->X_seg != SEG_ABSOLUTE || right . X_seg != SEG_ABSOLUTE)
                    {
                        as_bad("Relocation error. Absolute 0 assumed.");
                        resultP->X_seg        = SEG_ABSOLUTE;
                        resultP->X_add_number = 0;
                    }
                    else
                    {
                        switch (op_left)
                        {
                        case O_bit_inclusive_or:
                            resultP->X_add_number |= right . X_add_number;
                            break;
                            
                        case O_modulus:
                            if (right . X_add_number)
                            {
                                resultP->X_add_number %= right . X_add_number;
                            }
                            else
                            {
                                as_warn("Division by 0. 0 assumed.");
                                resultP->X_add_number = 0;
                            }
                            break;
                            
                        case O_bit_and:
                            resultP->X_add_number &= right . X_add_number;
                            break;
                            
                        case O_multiply:
                            resultP->X_add_number *= right . X_add_number;
                            break;
                            
                        case O_divide:
                            if (right . X_add_number)
                            {
                                resultP->X_add_number /= right . X_add_number;
                            }
                            else
                            {
                                as_warn("Division by 0. 0 assumed.");
                                resultP->X_add_number = 0;
                            }
                            break;
                            
                        case O_left_shift:
                            resultP->X_add_number <<= right . X_add_number;
                            break;
                            
                        case O_right_shift:
                            resultP->X_add_number >>= right . X_add_number;
                            break;
                            
                        case O_bit_exclusive_or:
                            resultP->X_add_number ^= right . X_add_number;
                            break;
                            
                        case O_bit_or_not:
                            resultP->X_add_number |= ~ right . X_add_number;
                            break;
                            
                        default:
                            BAD_CASE(op_left);
                            break;
                        } /* switch(operator) */
                    }
                }               /* If we have to force need_pass_2. */
            }                   /* If operator was +. */
        }                       /* If we didn't set need_pass_2. */
        op_left = op_right;
    }                           /* While next operator is >= this rank. */
    return (resultP->X_seg);
}
\f
/*
 *                      get_symbol_end()
 *
 * This lives here because it belongs equally in expr.c & read.c.
 * Expr.c is just a branch office read.c anyway, and putting it
 * here lessens the crowd at read.c.
 *
 * Assume input_line_pointer is at start of symbol name.
 * Advance input_line_pointer past symbol name.
 * Turn that character into a '\0', returning its former value.
 * This allows a string compare (RMS wants symbol names to be strings)
 * of the symbol name.
 * There will always be a char following symbol name, because all good
 * lines end in end-of-line.
 */
char
    get_symbol_end()
{
    register char c;
    
    while (is_part_of_name(c = * input_line_pointer ++))
        ;
    * -- input_line_pointer = 0;
    return (c);
}


unsigned int get_single_number()
{
    expressionS exp;
    operand(&exp);
    return exp.X_add_number;
    
}
/*
 * Local Variables:
 * comment-column: 0
 * fill-column: 131
 * End:
 */

/* end of expr.c */