as/expr.h

   1 #ifndef _EXPR_H_
   2 #define _EXPR_H_
   3 /* expr.h -> header file for expr.c
   4    Copyright (C) 1987 Free Software Foundation, Inc.
   5
   6 This file is part of GAS, the GNU Assembler.
   7
   8 GAS is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 1, or (at your option)
  11 any later version.
  12
  13 GAS is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GAS; see the file COPYING.  If not, write to
  20 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  21
  22 #include "as.h"
  23 #import "struc-symbol.h"
  24 #import "bignum.h"
  25 #import "flonum.h"
  26
  27 enum {
  28   /* FROM expr.h line 46 */
  29   /* A nonexistent expression.  */
  30   O_absent = SEG_NONE, /* HACK, this isn't going to work, absent ones come up
  31                           illegal currently.  */
  32   /* X_add_symbol + X_add_number.  */
  33   O_symbol = SEG_SECT,
  34   /* X_add_number (a constant expression).  */
  35   O_constant = SEG_ABSOLUTE,
  36   /* A big value.  If X_add_number is negative or 0, the value is in
  37      generic_floating_point_number.  Otherwise the value is in
  38      generic_bignum, and X_add_number is the number of LITTLENUMs in
  39      the value.  */
  40   O_big = SEG_BIG,
  41 };
  42
  43 extern char *seg_name[];
  44 extern segT N_TYPE_seg[];
  45
  46 /*
  47  * When an expression is SEG_BIG, it is in these globals (see comments above
  48  * about SEG_BIG).  This data may be clobbered whenever expr() is called.
  49  */
  50 extern FLONUM_TYPE    generic_floating_point_number;
  51 extern LITTLENUM_TYPE generic_bignum[];
  52 #define SIZE_OF_LARGE_NUMBER (20)       /* Number of littlenums in above */
  53                                         /* generic_bignum which is enough to */
  54                                         /* hold most precise flonum. */
  55
  56 /*
  57  * Abbreviations (mnemonics).
  58  *
  59  *      O       operator
  60  *      Q       quantity,  operand
  61  *      X       eXpression
  62  */
  63
  64 /*
  65  * By popular demand, we define a struct to represent an expression.
  66  * This will no doubt mutate as expressions become baroque.
  67  *
  68  * Currently, we support expressions like "foo-bar+42".
  69  * In other words we permit a (possibly undefined) minuend, a
  70  * (possibly undefined) subtrahend and an (absolute) augend.
  71  * RMS says this is so we can have 1-pass assembly for any compiler
  72  * emmissions, and a 'case' statement might emit 'undefined1 - undefined2'.
  73  *
  74  * To simplify table-driven dispatch, we also have a "segment" for the
  75  * entire expression. That way we don't require complex reasoning about
  76  * whether particular components are defined; and we can change component
  77  * semantics without re-working all the dispatch tables in the assembler.
  78  * In other words the "type" of an expression is its segment.
  79  */
  80
  81 // This isn't really up to date with GNU as, but it helps for source
  82 // compatibility.
  83 #define X_op X_seg
  84 #define X_op_symbol X_add_symbol
  85
  86 /*
  87  * To allow 32-bit architectures to use things like .quad we need to make
  88  * all expressions be 64-bit regardless of the target architecture's address
  89  * size.
  90  */
  91 #include <stdint.h>
  92 typedef int64_t signed_expr_t;
  93
  94 typedef struct {
  95     symbolS *X_add_symbol;      /* foo */
  96     symbolS *X_subtract_symbol; /* bar */
  97     signed_expr_t
  98     X_add_number;       /* 42 (must be signed) */
  99     segT     X_seg;             /* What segment (expr type) */
 100
 101         /* Non-zero if X_add_number should be regarded as unsigned.  This is
 102      only valid for O_constant expressions.  It is only used when an
 103      O_constant must be extended into a bignum (i.e., it is not used
 104      when performing arithmetic on these values).
 105      FIXME: This field is not set very reliably.  */
 106         unsigned int X_unsigned : 1,
 107
 108         /* Non-zero if we have the special assembly time constant expression
 109      of the difference of two symbols defined in the same section then divided
 110      by exactly 2. */
 111                      X_sectdiff_divide_by_two : 1;
 112 } expressionS;
 113
 114 extern segT expression(
 115     expressionS *resultP);
 116 extern char get_symbol_end(
 117     void);
 118 extern segT try_to_make_absolute(
 119     expressionS *expressionP);
 120 /* FROM line 165 */
 121 extern symbolS *make_expr_symbol (expressionS * expressionP);
 122
 123 extern symbolS *expr_build_uconstant (offsetT);
 124 #endif /* _EXPR_H_ */