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1 /* Language-level data type conversion for GNU C.
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2 Copyright (C) 1987, 1988, 1991, 1998, 2002, 2003, 2004, 2005, 2007, 2008
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3 Free Software Foundation, Inc.
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4
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5 This file is part of GCC.
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6
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7 GCC is free software; you can redistribute it and/or modify it under
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8 the terms of the GNU General Public License as published by the Free
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9 Software Foundation; either version 3, or (at your option) any later
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10 version.
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11
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12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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15 for more details.
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16
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17 You should have received a copy of the GNU General Public License
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18 along with GCC; see the file COPYING3. If not see
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19 <http://www.gnu.org/licenses/>. */
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20
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21
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22 /* This file contains the functions for converting C expressions
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23 to different data types. The only entry point is `convert'.
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24 Every language front end must have a `convert' function
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25 but what kind of conversions it does will depend on the language. */
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26
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27 #include "config.h"
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28 #include "system.h"
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29 #include "coretypes.h"
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30 #include "tm.h"
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31 #include "tree.h"
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32 #include "flags.h"
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33 #include "convert.h"
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34 #include "c-common.h"
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35 #include "c-tree.h"
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36 #include "langhooks.h"
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37 #include "toplev.h"
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38 #include "target.h"
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39
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40 /* Change of width--truncation and extension of integers or reals--
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41 is represented with NOP_EXPR. Proper functioning of many things
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42 assumes that no other conversions can be NOP_EXPRs.
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43
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44 Conversion between integer and pointer is represented with CONVERT_EXPR.
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45 Converting integer to real uses FLOAT_EXPR
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46 and real to integer uses FIX_TRUNC_EXPR.
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47
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48 Here is a list of all the functions that assume that widening and
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49 narrowing is always done with a NOP_EXPR:
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50 In convert.c, convert_to_integer.
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51 In c-typeck.c, build_binary_op (boolean ops), and
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52 c_common_truthvalue_conversion.
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53 In expr.c: expand_expr, for operands of a MULT_EXPR.
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54 In fold-const.c: fold.
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55 In tree.c: get_narrower and get_unwidened. */
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56
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57 /* Subroutines of `convert'. */
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58
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59
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60
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61 /* Create an expression whose value is that of EXPR,
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62 converted to type TYPE. The TREE_TYPE of the value
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63 is always TYPE. This function implements all reasonable
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64 conversions; callers should filter out those that are
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65 not permitted by the language being compiled. */
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66
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67 tree
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68 convert (tree type, tree expr)
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69 {
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70 tree e = expr;
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71 enum tree_code code = TREE_CODE (type);
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72 const char *invalid_conv_diag;
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73
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74 if (type == error_mark_node
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75 || expr == error_mark_node
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76 || TREE_TYPE (expr) == error_mark_node)
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77 return error_mark_node;
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78
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79 if ((invalid_conv_diag
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80 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
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81 {
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82 error (invalid_conv_diag);
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83 return error_mark_node;
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84 }
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85
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86 if (type == TREE_TYPE (expr))
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87 return expr;
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88
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89 if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
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90 return fold_convert (type, expr);
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91 if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
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92 return error_mark_node;
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93 if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
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94 {
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95 error ("void value not ignored as it ought to be");
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96 return error_mark_node;
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97 }
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98 if (code == VOID_TYPE)
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99 return fold_convert (type, e);
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100 if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
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101 return fold (convert_to_integer (type, e));
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102 if (code == BOOLEAN_TYPE)
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103 return fold_convert
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104 (type, c_objc_common_truthvalue_conversion (input_location, expr));
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105 if (code == POINTER_TYPE || code == REFERENCE_TYPE)
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106 return fold (convert_to_pointer (type, e));
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107 if (code == REAL_TYPE)
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108 return fold (convert_to_real (type, e));
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109 if (code == FIXED_POINT_TYPE)
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110 return fold (convert_to_fixed (type, e));
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111 if (code == COMPLEX_TYPE)
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112 return fold (convert_to_complex (type, e));
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113 if (code == VECTOR_TYPE)
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114 return fold (convert_to_vector (type, e));
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115 if ((code == RECORD_TYPE || code == UNION_TYPE)
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116 && lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
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117 return e;
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118
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119 error ("conversion to non-scalar type requested");
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120 return error_mark_node;
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121 }
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