gas/expr.h

   1 /* expr.h -> header file for expr.c
   2    Copyright (C) 1987, 1992 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  * Abbreviations (mnemonics).
  22  *
  23  *      O       operator
  24  *      Q       quantity,  operand
  25  *      X       eXpression
  26  */
  27
  28 /*
  29  * By popular demand, we define a struct to represent an expression.
  30  * This will no doubt mutate as expressions become baroque.
  31  *
  32  * Currently, we support expressions like "foo-bar+42".
  33  * In other words we permit a (possibly undefined) minuend, a
  34  * (possibly undefined) subtrahend and an (absolute) augend.
  35  * RMS says this is so we can have 1-pass assembly for any compiler
  36  * emmissions, and a 'case' statement might emit 'undefined1 - undefined2'.
  37  *
  38  * To simplify table-driven dispatch, we also have a "segment" for the
  39  * entire expression. That way we don't require complex reasoning about
  40  * whether particular components are defined; and we can change component
  41  * semantics without re-working all the dispatch tables in the assembler.
  42  * In other words the "type" of an expression is its segment.
  43  */
  44
  45 typedef struct
  46 {
  47   symbolS *X_add_symbol;        /* foo */
  48   symbolS *X_subtract_symbol;   /* bar */
  49   long X_add_number;            /* 42.    Must be signed. */
  50   segT X_seg;                   /* What segment (expr type)? */
  51 }
  52
  53 expressionS;
  54
  55 /* result should be type (expressionS *). */
  56 #define expression(result) expr(0,result)
  57
  58 /* If an expression is SEG_BIG, look here */
  59 /* for its value. These common data may */
  60 /* be clobbered whenever expr() is called. */
  61 extern FLONUM_TYPE generic_floating_point_number;       /* Flonums returned here. */
  62 /* Enough to hold most precise flonum. */
  63 extern LITTLENUM_TYPE generic_bignum[]; /* Bignums returned here. */
  64 #define SIZE_OF_LARGE_NUMBER (20)       /* Number of littlenums in above. */
  65
  66 typedef char operator_rankT;
  67
  68 #if __STDC__ == 1
  69
  70 char get_symbol_end (void);
  71 segT expr (int rank, expressionS * resultP);
  72 unsigned int get_single_number (void);
  73
  74 #else /* not __STDC__ */
  75
  76 char get_symbol_end ();
  77 segT expr ();
  78 unsigned int get_single_number ();
  79
  80 #endif /* not __STDC__ */
  81
  82 /* end of expr.h */