gcc/c/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987-2014 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20
  21 /* This file contains the functions for converting C expressions
  22    to different data types.  The only entry point is `convert'.
  23    Every language front end must have a `convert' function
  24    but what kind of conversions it does will depend on the language.  */
  25
  26 #include "config.h"
  27 #include "system.h"
  28 #include "coretypes.h"
  29 #include "tm.h"
  30 #include "tree.h"
  31 #include "flags.h"
  32 #include "convert.h"
  33 #include "c-family/c-common.h"
  34 #include "c-tree.h"
  35 #include "langhooks.h"
  36 #include "target.h"
  37
  38 /* Change of width--truncation and extension of integers or reals--
  39    is represented with NOP_EXPR.  Proper functioning of many things
  40    assumes that no other conversions can be NOP_EXPRs.
  41
  42    Conversion between integer and pointer is represented with CONVERT_EXPR.
  43    Converting integer to real uses FLOAT_EXPR
  44    and real to integer uses FIX_TRUNC_EXPR.
  45
  46    Here is a list of all the functions that assume that widening and
  47    narrowing is always done with a NOP_EXPR:
  48      In convert.c, convert_to_integer.
  49      In c-typeck.c, build_binary_op (boolean ops), and
  50         c_common_truthvalue_conversion.
  51      In expr.c: expand_expr, for operands of a MULT_EXPR.
  52      In fold-const.c: fold.
  53      In tree.c: get_narrower and get_unwidened.  */
  54 \f
  55 /* Subroutines of `convert'.  */
  56
  57
  58 \f
  59 /* Create an expression whose value is that of EXPR,
  60    converted to type TYPE.  The TREE_TYPE of the value
  61    is always TYPE.  This function implements all reasonable
  62    conversions; callers should filter out those that are
  63    not permitted by the language being compiled.  */
  64
  65 tree
  66 convert (tree type, tree expr)
  67 {
  68   tree e = expr;
  69   enum tree_code code = TREE_CODE (type);
  70   const char *invalid_conv_diag;
  71   tree ret;
  72   location_t loc = EXPR_LOCATION (expr);
  73
  74   if (type == error_mark_node
  75       || expr == error_mark_node
  76       || TREE_TYPE (expr) == error_mark_node)
  77     return error_mark_node;
  78
  79   if ((invalid_conv_diag
  80        = targetm.invalid_conversion (TREE_TYPE (expr), type)))
  81     {
  82       error (invalid_conv_diag);
  83       return error_mark_node;
  84     }
  85
  86   if (type == TREE_TYPE (expr))
  87     return expr;
  88   ret = targetm.convert_to_type (type, expr);
  89   if (ret)
  90       return ret;
  91
  92   STRIP_TYPE_NOPS (e);
  93
  94   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
  95       && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
  96           || TREE_CODE (e) == COMPLEX_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           if (TREE_CODE (e) != COMPLEX_EXPR)
 140             {
 141               tree subtype = TREE_TYPE (type);
 142               tree elt_type = TREE_TYPE (TREE_TYPE (e));
 143
 144               if (in_late_binary_op)
 145                 e = save_expr (e);
 146               else
 147                 e = c_save_expr (e);
 148               ret
 149                 = fold_build2_loc (loc, COMPLEX_EXPR, type,
 150                                    convert (subtype,
 151                                             fold_build1 (REALPART_EXPR,
 152                                                          elt_type, e)),
 153                                    convert (subtype,
 154                                             fold_build1 (IMAGPART_EXPR,
 155                                                          elt_type, e)));
 156               goto maybe_fold;
 157             }
 158         }
 159       ret = convert_to_complex (type, e);
 160       goto maybe_fold;
 161
 162     case VECTOR_TYPE:
 163       ret = convert_to_vector (type, e);
 164       goto maybe_fold;
 165
 166     case RECORD_TYPE:
 167     case UNION_TYPE:
 168       if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
 169         return e;
 170       break;
 171
 172     default:
 173       break;
 174
 175     maybe_fold:
 176       if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
 177         ret = fold (ret);
 178       return ret;
 179     }
 180
 181   error ("conversion to non-scalar type requested");
 182   return error_mark_node;
 183 }