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      1 /* expr.h -> header file for expr.c
      2    Copyright (C) 1987-2014 Free Software Foundation, Inc.
      3 
      4    This file is part of GAS, the GNU Assembler.
      5 
      6    GAS is free software; you can redistribute it and/or modify
      7    it under the terms of the GNU General Public License as published by
      8    the Free Software Foundation; either version 3, or (at your option)
      9    any later version.
     10 
     11    GAS is distributed in the hope that it will be useful,
     12    but WITHOUT ANY WARRANTY; without even the implied warranty of
     13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     14    GNU General Public License for more details.
     15 
     16    You should have received a copy of the GNU General Public License
     17    along with GAS; see the file COPYING.  If not, write to the Free
     18    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
     19    02110-1301, USA.  */
     20 
     21 /*
     22  * By popular demand, we define a struct to represent an expression.
     23  * This will no doubt mutate as expressions become baroque.
     24  *
     25  * Currently, we support expressions like "foo OP bar + 42".  In other
     26  * words we permit a (possibly undefined) symbol, a (possibly
     27  * undefined) symbol and the operation used to combine the symbols,
     28  * and an (absolute) augend.  RMS says this is so we can have 1-pass
     29  * assembly for any compiler emissions, and a 'case' statement might
     30  * emit 'undefined1 - undefined2'.
     31  *
     32  * The type of an expression used to be stored as a segment.  That got
     33  * confusing because it overloaded the concept of a segment.  I added
     34  * an operator field, instead.
     35  */
     36 
     37 /* This is the type of an expression.  The operator types are also
     38    used while parsing an expression.
     39 
     40    NOTE: This enumeration must match the op_rank array in expr.c.  */
     41 
     42 typedef enum {
     43   /* An illegal expression.  */
     44   O_illegal,
     45   /* A nonexistent expression.  */
     46   O_absent,
     47   /* X_add_number (a constant expression).  */
     48   O_constant,
     49   /* X_add_symbol + X_add_number.  */
     50   O_symbol,
     51   /* X_add_symbol + X_add_number - the base address of the image.  */
     52   O_symbol_rva,
     53   /* A register (X_add_number is register number).  */
     54   O_register,
     55   /* A big value.  If X_add_number is negative or 0, the value is in
     56      generic_floating_point_number.  Otherwise the value is in
     57      generic_bignum, and X_add_number is the number of LITTLENUMs in
     58      the value.  */
     59   O_big,
     60   /* (- X_add_symbol) + X_add_number.  */
     61   O_uminus,
     62   /* (~ X_add_symbol) + X_add_number.  */
     63   O_bit_not,
     64   /* (! X_add_symbol) + X_add_number.  */
     65   O_logical_not,
     66   /* (X_add_symbol * X_op_symbol) + X_add_number.  */
     67   O_multiply,
     68   /* (X_add_symbol / X_op_symbol) + X_add_number.  */
     69   O_divide,
     70   /* (X_add_symbol % X_op_symbol) + X_add_number.  */
     71   O_modulus,
     72   /* (X_add_symbol << X_op_symbol) + X_add_number.  */
     73   O_left_shift,
     74   /* (X_add_symbol >> X_op_symbol) + X_add_number.  */
     75   O_right_shift,
     76   /* (X_add_symbol | X_op_symbol) + X_add_number.  */
     77   O_bit_inclusive_or,
     78   /* (X_add_symbol |~ X_op_symbol) + X_add_number.  */
     79   O_bit_or_not,
     80   /* (X_add_symbol ^ X_op_symbol) + X_add_number.  */
     81   O_bit_exclusive_or,
     82   /* (X_add_symbol & X_op_symbol) + X_add_number.  */
     83   O_bit_and,
     84   /* (X_add_symbol + X_op_symbol) + X_add_number.  */
     85   O_add,
     86   /* (X_add_symbol - X_op_symbol) + X_add_number.  */
     87   O_subtract,
     88   /* (X_add_symbol == X_op_symbol) + X_add_number.  */
     89   O_eq,
     90   /* (X_add_symbol != X_op_symbol) + X_add_number.  */
     91   O_ne,
     92   /* (X_add_symbol < X_op_symbol) + X_add_number.  */
     93   O_lt,
     94   /* (X_add_symbol <= X_op_symbol) + X_add_number.  */
     95   O_le,
     96   /* (X_add_symbol >= X_op_symbol) + X_add_number.  */
     97   O_ge,
     98   /* (X_add_symbol > X_op_symbol) + X_add_number.  */
     99   O_gt,
    100   /* (X_add_symbol && X_op_symbol) + X_add_number.  */
    101   O_logical_and,
    102   /* (X_add_symbol || X_op_symbol) + X_add_number.  */
    103   O_logical_or,
    104   /* X_op_symbol [ X_add_symbol ] */
    105   O_index,
    106   /* machine dependent operators */
    107   O_md1,  O_md2,  O_md3,  O_md4,  O_md5,  O_md6,  O_md7,  O_md8,
    108   O_md9,  O_md10, O_md11, O_md12, O_md13, O_md14, O_md15, O_md16,
    109   O_md17, O_md18, O_md19, O_md20, O_md21, O_md22, O_md23, O_md24,
    110   O_md25, O_md26, O_md27, O_md28, O_md29, O_md30, O_md31, O_md32,
    111   /* this must be the largest value */
    112   O_max
    113 } operatorT;
    114 
    115 typedef struct expressionS {
    116   /* The main symbol.  */
    117   symbolS *X_add_symbol;
    118   /* The second symbol, if needed.  */
    119   symbolS *X_op_symbol;
    120   /* A number to add.  */
    121   offsetT X_add_number;
    122 
    123   /* The type of the expression.  We can't assume that an arbitrary
    124      compiler can handle a bitfield of enum type.  FIXME: We could
    125      check this using autoconf.  */
    126 #ifdef __GNUC__
    127   operatorT X_op : 8;
    128 #else
    129   unsigned char X_op;
    130 #endif
    131 
    132   /* Non-zero if X_add_number should be regarded as unsigned.  This is
    133      only valid for O_constant expressions.  It is only used when an
    134      O_constant must be extended into a bignum (i.e., it is not used
    135      when performing arithmetic on these values).
    136      FIXME: This field is not set very reliably.  */
    137   unsigned int X_unsigned : 1;
    138   /* This is used to implement "word size + 1 bit" arithmetic, so that e.g.
    139      expressions used with .sleb128 directives can use the full range available
    140      for an unsigned word, but can also properly represent all values of a
    141      signed word.  */
    142   unsigned int X_extrabit : 1;
    143 
    144   /* 7 additional bits can be defined if needed.  */
    145 
    146   /* Machine dependent field */
    147   unsigned short X_md;
    148 } expressionS;
    149 
    150 enum expr_mode
    151 {
    152   expr_evaluate,
    153   expr_normal,
    154   expr_defer
    155 };
    156 
    157 /* "result" should be type (expressionS *).  */
    158 #define expression(result) expr (0, result, expr_normal)
    159 #define expression_and_evaluate(result) expr (0, result, expr_evaluate)
    160 #define deferred_expression(result) expr (0, result, expr_defer)
    161 
    162 /* If an expression is O_big, look here for its value. These common
    163    data may be clobbered whenever expr() is called.  */
    164 /* Flonums returned here.  Big enough to hold most precise flonum.  */
    165 extern FLONUM_TYPE generic_floating_point_number;
    166 /* Bignums returned here.  */
    167 extern LITTLENUM_TYPE generic_bignum[];
    168 /* Number of littlenums in above.  */
    169 #define SIZE_OF_LARGE_NUMBER (20)
    170 
    171 typedef char operator_rankT;
    172 
    173 extern char get_symbol_end (void);
    174 extern void expr_begin (void);
    175 extern void expr_set_precedence (void);
    176 extern void expr_set_rank (operatorT, operator_rankT);
    177 extern void add_to_result (expressionS *, offsetT, int);
    178 extern void subtract_from_result (expressionS *, offsetT, int);
    179 extern segT expr (int, expressionS *, enum expr_mode);
    180 extern unsigned int get_single_number (void);
    181 extern symbolS *make_expr_symbol (expressionS * expressionP);
    182 extern int expr_symbol_where (symbolS *, char **, unsigned int *);
    183 extern void current_location (expressionS *);
    184 
    185 extern symbolS *expr_build_uconstant (offsetT);
    186 extern symbolS *expr_build_dot (void);
    187 
    188 int resolve_expression (expressionS *);
    189