| 1 | /* Language-level data type conversion for GNU C.
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| 2 | Copyright (C) 1987, 1988, 1991, 1998 Free Software Foundation, Inc.
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| 3 |
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| 4 | This file is part of GCC.
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| 5 |
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| 6 | GCC is free software; you can redistribute it and/or modify it under
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| 7 | the terms of the GNU General Public License as published by the Free
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| 8 | Software Foundation; either version 2, or (at your option) any later
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| 9 | version.
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| 10 |
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| 11 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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| 12 | WARRANTY; without even the implied warranty of MERCHANTABILITY or
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| 13 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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| 14 | for more details.
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| 15 |
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| 16 | You should have received a copy of the GNU General Public License
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| 17 | along with GCC; see the file COPYING. If not, write to the Free
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| 18 | Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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| 19 | 02111-1307, USA. */
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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 "tree.h"
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| 30 | #include "flags.h"
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| 31 | #include "convert.h"
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| 32 | #include "toplev.h"
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| 33 |
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| 34 | /* Change of width--truncation and extension of integers or reals--
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| 35 | is represented with NOP_EXPR. Proper functioning of many things
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| 36 | assumes that no other conversions can be NOP_EXPRs.
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| 37 |
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| 38 | Conversion between integer and pointer is represented with CONVERT_EXPR.
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| 39 | Converting integer to real uses FLOAT_EXPR
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| 40 | and real to integer uses FIX_TRUNC_EXPR.
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| 41 |
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| 42 | Here is a list of all the functions that assume that widening and
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| 43 | narrowing is always done with a NOP_EXPR:
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| 44 | In convert.c, convert_to_integer.
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| 45 | In c-typeck.c, build_binary_op (boolean ops), and truthvalue_conversion.
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| 46 | In expr.c: expand_expr, for operands of a MULT_EXPR.
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| 47 | In fold-const.c: fold.
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| 48 | In tree.c: get_narrower and get_unwidened. */
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| 49 | |
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| 50 |
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| 51 | /* Subroutines of `convert'. */
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| 52 |
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| 53 |
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| 54 | |
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| 55 |
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| 56 | /* Create an expression whose value is that of EXPR,
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| 57 | converted to type TYPE. The TREE_TYPE of the value
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| 58 | is always TYPE. This function implements all reasonable
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| 59 | conversions; callers should filter out those that are
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| 60 | not permitted by the language being compiled. */
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| 61 |
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| 62 | tree
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| 63 | convert (type, expr)
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| 64 | tree type, expr;
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| 65 | {
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| 66 | tree e = expr;
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| 67 | enum tree_code code = TREE_CODE (type);
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| 68 |
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| 69 | if (type == TREE_TYPE (expr)
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| 70 | || TREE_CODE (expr) == ERROR_MARK
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| 71 | || code == ERROR_MARK || TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
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| 72 | return expr;
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| 73 |
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| 74 | if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
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| 75 | return fold (build1 (NOP_EXPR, type, expr));
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| 76 | if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
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| 77 | return error_mark_node;
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| 78 | if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
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| 79 | {
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| 80 | error ("void value not ignored as it ought to be");
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| 81 | return error_mark_node;
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| 82 | }
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| 83 | if (code == VOID_TYPE)
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| 84 | return build1 (CONVERT_EXPR, type, e);
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| 85 | #if 0
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| 86 | /* This is incorrect. A truncation can't be stripped this way.
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| 87 | Extensions will be stripped by the use of get_unwidened. */
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| 88 | if (TREE_CODE (expr) == NOP_EXPR)
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| 89 | return convert (type, TREE_OPERAND (expr, 0));
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| 90 | #endif
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| 91 | if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
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| 92 | return fold (convert_to_integer (type, e));
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| 93 | if (code == BOOLEAN_TYPE)
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| 94 | {
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| 95 | tree t = truthvalue_conversion (expr);
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| 96 | /* If truthvalue_conversion returns a NOP_EXPR, we must fold it here
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| 97 | to avoid infinite recursion between fold () and convert (). */
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| 98 | if (TREE_CODE (t) == NOP_EXPR)
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| 99 | return fold (build1 (NOP_EXPR, type, TREE_OPERAND (t, 0)));
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| 100 | else
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| 101 | return fold (build1 (NOP_EXPR, type, t));
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| 102 | }
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| 103 | if (code == POINTER_TYPE || code == REFERENCE_TYPE)
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| 104 | return fold (convert_to_pointer (type, e));
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| 105 | if (code == REAL_TYPE)
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| 106 | return fold (convert_to_real (type, e));
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| 107 | if (code == COMPLEX_TYPE)
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| 108 | return fold (convert_to_complex (type, e));
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| 109 | if (code == VECTOR_TYPE)
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| 110 | return fold (convert_to_vector (type, e));
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| 111 |
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| 112 | error ("conversion to non-scalar type requested");
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| 113 | return error_mark_node;
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| 114 | }
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