1/* Language-level data type conversion for GNU C.
2   Copyright (C) 1987, 1988, 1991, 1998, 2002, 2003, 2004, 2005, 2007, 2008,
3   2009 Free Software Foundation, Inc.
4
5This file is part of GCC.
6
7GCC is free software; you can redistribute it and/or modify it under
8the terms of the GNU General Public License as published by the Free
9Software Foundation; either version 3, or (at your option) any later
10version.
11
12GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13WARRANTY; without even the implied warranty of MERCHANTABILITY or
14FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
15for more details.
16
17You should have received a copy of the GNU General Public License
18along with GCC; see the file COPYING3.  If not see
19<http://www.gnu.org/licenses/>.  */
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 "coretypes.h"
30#include "tm.h"
31#include "tree.h"
32#include "flags.h"
33#include "convert.h"
34#include "c-common.h"
35#include "c-tree.h"
36#include "langhooks.h"
37#include "toplev.h"
38#include "target.h"
39
40/* Change of width--truncation and extension of integers or reals--
41   is represented with NOP_EXPR.  Proper functioning of many things
42   assumes that no other conversions can be NOP_EXPRs.
43
44   Conversion between integer and pointer is represented with CONVERT_EXPR.
45   Converting integer to real uses FLOAT_EXPR
46   and real to integer uses FIX_TRUNC_EXPR.
47
48   Here is a list of all the functions that assume that widening and
49   narrowing is always done with a NOP_EXPR:
50     In convert.c, convert_to_integer.
51     In c-typeck.c, build_binary_op (boolean ops), and
52	c_common_truthvalue_conversion.
53     In expr.c: expand_expr, for operands of a MULT_EXPR.
54     In fold-const.c: fold.
55     In tree.c: get_narrower and get_unwidened.  */
56
57/* Subroutines of `convert'.  */
58
59
60
61/* Create an expression whose value is that of EXPR,
62   converted to type TYPE.  The TREE_TYPE of the value
63   is always TYPE.  This function implements all reasonable
64   conversions; callers should filter out those that are
65   not permitted by the language being compiled.  */
66
67tree
68convert (tree type, tree expr)
69{
70  tree e = expr;
71  enum tree_code code = TREE_CODE (type);
72  const char *invalid_conv_diag;
73  tree ret;
74  location_t loc = EXPR_LOCATION (expr);
75
76  if (type == error_mark_node
77      || expr == error_mark_node
78      || TREE_TYPE (expr) == error_mark_node)
79    return error_mark_node;
80
81  if ((invalid_conv_diag
82       = targetm.invalid_conversion (TREE_TYPE (expr), type)))
83    {
84      error (invalid_conv_diag);
85      return error_mark_node;
86    }
87
88  if (type == TREE_TYPE (expr))
89    return expr;
90  ret = targetm.convert_to_type (type, expr);
91  if (ret)
92      return ret;
93
94  STRIP_TYPE_NOPS (e);
95
96  if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
97    return fold_convert_loc (loc, type, expr);
98  if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
99    return error_mark_node;
100  if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
101    {
102      error ("void value not ignored as it ought to be");
103      return error_mark_node;
104    }
105
106  switch (code)
107    {
108    case VOID_TYPE:
109      return fold_convert_loc (loc, type, e);
110
111    case INTEGER_TYPE:
112    case ENUMERAL_TYPE:
113      ret = convert_to_integer (type, e);
114      goto maybe_fold;
115
116    case BOOLEAN_TYPE:
117      return fold_convert_loc
118	(loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
119
120    case POINTER_TYPE:
121    case REFERENCE_TYPE:
122      ret = convert_to_pointer (type, e);
123      goto maybe_fold;
124
125    case REAL_TYPE:
126      ret = convert_to_real (type, e);
127      goto maybe_fold;
128
129    case FIXED_POINT_TYPE:
130      ret = convert_to_fixed (type, e);
131      goto maybe_fold;
132
133    case COMPLEX_TYPE:
134      /* If converting from COMPLEX_TYPE to a different COMPLEX_TYPE
135	 and e is not COMPLEX_EXPR, convert_to_complex uses save_expr,
136	 but for the C FE c_save_expr needs to be called instead.  */
137      if (TREE_CODE (TREE_TYPE (e)) == COMPLEX_TYPE)
138	{
139	  tree subtype = TREE_TYPE (type);
140	  tree elt_type = TREE_TYPE (TREE_TYPE (e));
141
142	  if (TYPE_MAIN_VARIANT (elt_type) != TYPE_MAIN_VARIANT (subtype)
143	      && TREE_CODE (e) != COMPLEX_EXPR)
144	    {
145	      if (in_late_binary_op)
146		e = save_expr (e);
147	      else
148		e = c_save_expr (e);
149	      ret
150		= fold_build2 (COMPLEX_EXPR, type,
151			       convert (subtype,
152					fold_build1 (REALPART_EXPR,
153						     elt_type, e)),
154			       convert (subtype,
155					fold_build1 (IMAGPART_EXPR,
156						     elt_type, e)));
157	      goto maybe_fold;
158	    }
159	}
160      ret = convert_to_complex (type, e);
161      goto maybe_fold;
162
163    case VECTOR_TYPE:
164      ret = convert_to_vector (type, e);
165      goto maybe_fold;
166
167    case RECORD_TYPE:
168    case UNION_TYPE:
169      if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
170	return e;
171      break;
172
173    default:
174      break;
175
176    maybe_fold:
177      if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
178	ret = fold (ret);
179      return ret;
180    }
181
182  error ("conversion to non-scalar type requested");
183  return error_mark_node;
184}
185