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