gas/expr.h

   1 /* expr.h -> header file for expr.c
   2    Copyright (C) 1987, 1992, 1993 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 2, 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
  18    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 /*
  21  * By popular demand, we define a struct to represent an expression.
  22  * This will no doubt mutate as expressions become baroque.
  23  *
  24  * Currently, we support expressions like "foo OP bar + 42".  In other
  25  * words we permit a (possibly undefined) symbol, a (possibly
  26  * undefined) symbol and the operation used to combine the symbols,
  27  * and an (absolute) augend.  RMS says this is so we can have 1-pass
  28  * assembly for any compiler emissions, and a 'case' statement might
  29  * emit 'undefined1 - undefined2'.
  30  *
  31  * The type of an expression used to be stored as a segment.  That got
  32  * confusing because it overloaded the concept of a segment.  I added
  33  * an operator field, instead.
  34  */
  35
  36 /* This is the type of an expression.  The operator types are also
  37    used while parsing an expression.
  38
  39    NOTE: This enumeration must match the op_rank array in expr.c.  */
  40
  41 typedef enum
  42 {
  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   /* A register (X_add_number is register number).  */
  52   O_register,
  53   /* A big value.  If X_add_number is negative or 0, the value is in
  54      generic_floating_point_number.  Otherwise the value is in
  55      generic_bignum, and X_add_number is the number of LITTLENUMs in
  56      the value.  */
  57   O_big,
  58   /* (- X_add_symbol) + X_add_number.  */
  59   O_uminus,
  60   /* (~ X_add_symbol) + X_add_number.  */
  61   O_bit_not,
  62   /* (X_add_symbol * X_op_symbol) + X_add_number.  */
  63   O_multiply,
  64   /* (X_add_symbol / X_op_symbol) + X_add_number.  */
  65   O_divide,
  66   /* X_add_symbol % X_op_symbol) + X_add_number.  */
  67   O_modulus,
  68   /* X_add_symbol << X_op_symbol) + X_add_number.  */
  69   O_left_shift,
  70   /* X_add_symbol >> X_op_symbol) + X_add_number.  */
  71   O_right_shift,
  72   /* X_add_symbol | X_op_symbol) + X_add_number.  */
  73   O_bit_inclusive_or,
  74   /* X_add_symbol |~ X_op_symbol) + X_add_number.  */
  75   O_bit_or_not,
  76   /* X_add_symbol ^ X_op_symbol) + X_add_number.  */
  77   O_bit_exclusive_or,
  78   /* X_add_symbol & X_op_symbol) + X_add_number.  */
  79   O_bit_and,
  80   /* X_add_symbol + X_op_symbol) + X_add_number.  */
  81   O_add,
  82   /* X_add_symbol - X_op_symbol) + X_add_number.  */
  83   O_subtract
  84 } operatorT;
  85
  86 typedef struct expressionS
  87 {
  88   /* The type of the expression.  */
  89   operatorT X_op;
  90   /* The main symbol.  */
  91   struct symbol *X_add_symbol;
  92   /* The second symbol, if needed.  */
  93   struct symbol *X_op_symbol;
  94   /* A number to add.  */
  95   offsetT X_add_number;
  96   /* Non-zero if X_add_number should be regarded as unsigned.  This is
  97      only valid for O_constant expressions.  It is only used when an
  98      O_constant must be extended into a bignum (i.e., it is not used
  99      when performing arithmetic on these values).
 100      FIXME: This field is not set very reliably.
 101      If we ever need more flags here, we can make them bitfields.  */
 102   int X_unsigned;
 103 } expressionS;
 104
 105 /* "result" should be type (expressionS *). */
 106 #define expression(result) expr (0, result)
 107
 108 /* If an expression is O_big, look here for its value. These common
 109    data may be clobbered whenever expr() is called. */
 110 /* Flonums returned here.  Big enough to hold most precise flonum. */
 111 extern FLONUM_TYPE generic_floating_point_number;
 112 /* Bignums returned here. */
 113 extern LITTLENUM_TYPE generic_bignum[];
 114 /* Number of littlenums in above. */
 115 #define SIZE_OF_LARGE_NUMBER (20)
 116
 117 typedef char operator_rankT;
 118
 119 char get_symbol_end PARAMS ((void));
 120 segT expr PARAMS ((int rank, expressionS * resultP));
 121 unsigned int get_single_number PARAMS ((void));
 122 symbolS *make_expr_symbol PARAMS ((expressionS * expressionP));
 123
 124 /* end of expr.h */