gcc/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987, 1988, 1991, 1998, 2002, 2003, 2004, 2005, 2007, 2008,
   3    2009, 2010, 2011, 2012 Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along 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-family/c-common.h"
  35 #include "c-tree.h"
  36 #include "langhooks.h"
  37 #include "target.h"
  38
  39 /* Change of width--truncation and extension of integers or reals--
  40    is represented with NOP_EXPR.  Proper functioning of many things
  41    assumes that no other conversions can be NOP_EXPRs.
  42
  43    Conversion between integer and pointer is represented with CONVERT_EXPR.
  44    Converting integer to real uses FLOAT_EXPR
  45    and real to integer uses FIX_TRUNC_EXPR.
  46
  47    Here is a list of all the functions that assume that widening and
  48    narrowing is always done with a NOP_EXPR:
  49      In convert.c, convert_to_integer.
  50      In c-typeck.c, build_binary_op (boolean ops), and
  51         c_common_truthvalue_conversion.
  52      In expr.c: expand_expr, for operands of a MULT_EXPR.
  53      In fold-const.c: fold.
  54      In tree.c: get_narrower and get_unwidened.  */
  55 \f
  56 /* Subroutines of `convert'.  */
  57
  58
  59 \f
  60 /* Create an expression whose value is that of EXPR,
  61    converted to type TYPE.  The TREE_TYPE of the value
  62    is always TYPE.  This function implements all reasonable
  63    conversions; callers should filter out those that are
  64    not permitted by the language being compiled.  */
  65
  66 tree
  67 convert (tree type, tree expr)
  68 {
  69   tree e = expr;
  70   enum tree_code code = TREE_CODE (type);
  71   const char *invalid_conv_diag;
  72   tree ret;
  73   location_t loc = EXPR_LOCATION (expr);
  74
  75   if (type == error_mark_node
  76       || expr == error_mark_node
  77       || TREE_TYPE (expr) == error_mark_node)
  78     return error_mark_node;
  79
  80   if ((invalid_conv_diag
  81        = targetm.invalid_conversion (TREE_TYPE (expr), type)))
  82     {
  83       error (invalid_conv_diag);
  84       return error_mark_node;
  85     }
  86
  87   if (type == TREE_TYPE (expr))
  88     return expr;
  89   ret = targetm.convert_to_type (type, expr);
  90   if (ret)
  91       return ret;
  92
  93   STRIP_TYPE_NOPS (e);
  94
  95   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
  96       && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
  97           || TREE_CODE (e) == COMPLEX_EXPR))
  98     return fold_convert_loc (loc, type, expr);
  99   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
 100     return error_mark_node;
 101   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
 102     {
 103       error ("void value not ignored as it ought to be");
 104       return error_mark_node;
 105     }
 106
 107   switch (code)
 108     {
 109     case VOID_TYPE:
 110       return fold_convert_loc (loc, type, e);
 111
 112     case INTEGER_TYPE:
 113     case ENUMERAL_TYPE:
 114       ret = convert_to_integer (type, e);
 115       goto maybe_fold;
 116
 117     case BOOLEAN_TYPE:
 118       return fold_convert_loc
 119         (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
 120
 121     case POINTER_TYPE:
 122     case REFERENCE_TYPE:
 123       ret = convert_to_pointer (type, e);
 124       goto maybe_fold;
 125
 126     case REAL_TYPE:
 127       ret = convert_to_real (type, e);
 128       goto maybe_fold;
 129
 130     case FIXED_POINT_TYPE:
 131       ret = convert_to_fixed (type, e);
 132       goto maybe_fold;
 133
 134     case COMPLEX_TYPE:
 135       /* If converting from COMPLEX_TYPE to a different COMPLEX_TYPE
 136          and e is not COMPLEX_EXPR, convert_to_complex uses save_expr,
 137          but for the C FE c_save_expr needs to be called instead.  */
 138       if (TREE_CODE (TREE_TYPE (e)) == COMPLEX_TYPE)
 139         {
 140           if (TREE_CODE (e) != COMPLEX_EXPR)
 141             {
 142               tree subtype = TREE_TYPE (type);
 143               tree elt_type = TREE_TYPE (TREE_TYPE (e));
 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_loc (loc, 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 }