1/* Language-level data type conversion for GNU C.
2   Copyright (C) 1987, 1988, 1991, 1998, 2002 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 2, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along with GCC; see the file COPYING.  If not, write to the Free
18Software Foundation, 59 Temple Place - Suite 330, Boston, MA
1902111-1307, USA.  */
20
21
22/* This file contains the functions for converting C expressions
23   to different data types.  The only entry point is `convert'.
24   Every language front end must have a `convert' function
25   but what kind of conversions it does will depend on the language.  */
26
27#include "config.h"
28#include "system.h"
29#include "tree.h"
30#include "flags.h"
31#include "convert.h"
32#include "c-common.h"
33#include "toplev.h"
34
35/* Change of width--truncation and extension of integers or reals--
36   is represented with NOP_EXPR.  Proper functioning of many things
37   assumes that no other conversions can be NOP_EXPRs.
38
39   Conversion between integer and pointer is represented with CONVERT_EXPR.
40   Converting integer to real uses FLOAT_EXPR
41   and real to integer uses FIX_TRUNC_EXPR.
42
43   Here is a list of all the functions that assume that widening and
44   narrowing is always done with a NOP_EXPR:
45     In convert.c, convert_to_integer.
46     In c-typeck.c, build_binary_op (boolean ops), and
47	c_common_truthvalue_conversion.
48     In expr.c: expand_expr, for operands of a MULT_EXPR.
49     In fold-const.c: fold.
50     In tree.c: get_narrower and get_unwidened.  */
51
52/* Subroutines of `convert'.  */
53
54
55
56/* Create an expression whose value is that of EXPR,
57   converted to type TYPE.  The TREE_TYPE of the value
58   is always TYPE.  This function implements all reasonable
59   conversions; callers should filter out those that are
60   not permitted by the language being compiled.  */
61
62tree
63convert (type, expr)
64     tree type, expr;
65{
66  tree e = expr;
67  enum tree_code code = TREE_CODE (type);
68
69  if (type == TREE_TYPE (expr)
70      || TREE_CODE (expr) == ERROR_MARK
71      || code == ERROR_MARK || TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
72    return expr;
73
74  if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
75    return fold (build1 (NOP_EXPR, type, expr));
76  if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
77    return error_mark_node;
78  if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
79    {
80      error ("void value not ignored as it ought to be");
81      return error_mark_node;
82    }
83  if (code == VOID_TYPE)
84    return build1 (CONVERT_EXPR, type, e);
85#if 0
86  /* This is incorrect.  A truncation can't be stripped this way.
87     Extensions will be stripped by the use of get_unwidened.  */
88  if (TREE_CODE (expr) == NOP_EXPR)
89    return convert (type, TREE_OPERAND (expr, 0));
90#endif
91  if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
92    return fold (convert_to_integer (type, e));
93  if (code == BOOLEAN_TYPE)
94    {
95      tree t = c_common_truthvalue_conversion (expr);
96      /* If it returns a NOP_EXPR, we must fold it here to avoid
97	 infinite recursion between fold () and convert ().  */
98      if (TREE_CODE (t) == NOP_EXPR)
99	return fold (build1 (NOP_EXPR, type, TREE_OPERAND (t, 0)));
100      else
101	return fold (build1 (NOP_EXPR, type, t));
102    }
103  if (code == POINTER_TYPE || code == REFERENCE_TYPE)
104    return fold (convert_to_pointer (type, e));
105  if (code == REAL_TYPE)
106    return fold (convert_to_real (type, e));
107  if (code == COMPLEX_TYPE)
108    return fold (convert_to_complex (type, e));
109  if (code == VECTOR_TYPE)
110    return fold (convert_to_vector (type, e));
111
112  error ("conversion to non-scalar type requested");
113  return error_mark_node;
114}
115