gcc/convert.c

   1 /* Utility routines for data type conversion for GNU C.
   2    Copyright (C) 1987, 1988, 1991, 1992 Free Software Foundation, Inc.
   3
   4 This file is part of GNU C.
   5
   6 GNU CC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU CC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU CC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20
  21 /* These routines are somewhat language-independent utility function
  22    intended to be called by the language-specific convert () functions. */
  23
  24 #include "config.h"
  25 #include "tree.h"
  26 #include "flags.h"
  27 #include "convert.h"
  28
  29 /* Convert EXPR to some pointer type TYPE.
  30
  31    EXPR must be pointer, integer, enumeral, or literal zero;
  32    in other cases error is called. */
  33
  34 tree
  35 convert_to_pointer (type, expr)
  36      tree type, expr;
  37 {
  38   register tree intype = TREE_TYPE (expr);
  39   register enum tree_code form = TREE_CODE (intype);
  40
  41   if (integer_zerop (expr))
  42     {
  43       if (type == TREE_TYPE (null_pointer_node))
  44         return null_pointer_node;
  45       expr = build_int_2 (0, 0);
  46       TREE_TYPE (expr) = type;
  47       return expr;
  48     }
  49
  50   if (form == POINTER_TYPE)
  51     return build1 (NOP_EXPR, type, expr);
  52
  53
  54   if (form == INTEGER_TYPE || form == ENUMERAL_TYPE)
  55     {
  56       if (type_precision (intype) == POINTER_SIZE)
  57         return build1 (CONVERT_EXPR, type, expr);
  58       expr = convert (type_for_size (POINTER_SIZE, 0), expr);
  59       /* Modes may be different but sizes should be the same.  */
  60       if (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
  61           != GET_MODE_SIZE (TYPE_MODE (type)))
  62         /* There is supposed to be some integral type
  63            that is the same width as a pointer.  */
  64         abort ();
  65       return convert_to_pointer (type, expr);
  66     }
  67
  68   error ("cannot convert to a pointer type");
  69
  70   return null_pointer_node;
  71 }
  72
  73 /* Convert EXPR to some floating-point type TYPE.
  74
  75    EXPR must be float, integer, or enumeral;
  76    in other cases error is called. */
  77
  78 tree
  79 convert_to_real (type, expr)
  80      tree type, expr;
  81 {
  82   register enum tree_code form = TREE_CODE (TREE_TYPE (expr));
  83
  84   if (form == REAL_TYPE)
  85     return build1 (flag_float_store ? CONVERT_EXPR : NOP_EXPR,
  86                    type, expr);
  87
  88   if (form == INTEGER_TYPE || form == ENUMERAL_TYPE)
  89     return build1 (FLOAT_EXPR, type, expr);
  90
  91   if (form == COMPLEX_TYPE)
  92     return convert (type, fold (build1 (REALPART_EXPR,
  93                                         TREE_TYPE (TREE_TYPE (expr)), expr)));
  94
  95   if (form == POINTER_TYPE)
  96     error ("pointer value used where a floating point value was expected");
  97   else
  98     error ("aggregate value used where a float was expected");
  99
 100   {
 101     register tree tem = make_node (REAL_CST);
 102     TREE_TYPE (tem) = type;
 103     TREE_REAL_CST (tem) = REAL_VALUE_ATOF ("0.0", TYPE_MODE (type));
 104     return tem;
 105   }
 106 }
 107
 108 /* Convert EXPR to some integer (or enum) type TYPE.
 109
 110    EXPR must be pointer, integer, discrete (enum, char, or bool), or float;
 111    in other cases error is called.
 112
 113    The result of this is always supposed to be a newly created tree node
 114    not in use in any existing structure.  */
 115
 116 tree
 117 convert_to_integer (type, expr)
 118      tree type, expr;
 119 {
 120   register tree intype = TREE_TYPE (expr);
 121   register enum tree_code form = TREE_CODE (intype);
 122
 123   if (form == POINTER_TYPE)
 124     {
 125       if (integer_zerop (expr))
 126         expr = integer_zero_node;
 127       else
 128         expr = fold (build1 (CONVERT_EXPR,
 129                              type_for_size (POINTER_SIZE, 0), expr));
 130       intype = TREE_TYPE (expr);
 131       form = TREE_CODE (intype);
 132       if (intype == type)
 133         return expr;
 134     }
 135
 136   if (form == INTEGER_TYPE || form == ENUMERAL_TYPE
 137       || form == BOOLEAN_TYPE || form == CHAR_TYPE)
 138     {
 139       register unsigned outprec = TYPE_PRECISION (type);
 140       register unsigned inprec = TYPE_PRECISION (intype);
 141       register enum tree_code ex_form = TREE_CODE (expr);
 142
 143       /* If we are widening the type, put in an explicit conversion.
 144          Similarly if we are not changing the width.  However, if this is
 145          a logical operation that just returns 0 or 1, we can change the
 146          type of the expression (see below).  */
 147
 148       if (TREE_CODE_CLASS (ex_form) == '<'
 149           || ex_form == TRUTH_AND_EXPR || ex_form == TRUTH_ANDIF_EXPR
 150           || ex_form == TRUTH_OR_EXPR || ex_form == TRUTH_ORIF_EXPR
 151           || ex_form == TRUTH_XOR_EXPR || ex_form == TRUTH_NOT_EXPR)
 152         {
 153           TREE_TYPE (expr) = type;
 154           return expr;
 155         }
 156       else if (outprec >= inprec)
 157         return build1 (NOP_EXPR, type, expr);
 158
 159 /* Here detect when we can distribute the truncation down past some arithmetic.
 160    For example, if adding two longs and converting to an int,
 161    we can equally well convert both to ints and then add.
 162    For the operations handled here, such truncation distribution
 163    is always safe.
 164    It is desirable in these cases:
 165    1) when truncating down to full-word from a larger size
 166    2) when truncating takes no work.
 167    3) when at least one operand of the arithmetic has been extended
 168    (as by C's default conversions).  In this case we need two conversions
 169    if we do the arithmetic as already requested, so we might as well
 170    truncate both and then combine.  Perhaps that way we need only one.
 171
 172    Note that in general we cannot do the arithmetic in a type
 173    shorter than the desired result of conversion, even if the operands
 174    are both extended from a shorter type, because they might overflow
 175    if combined in that type.  The exceptions to this--the times when
 176    two narrow values can be combined in their narrow type even to
 177    make a wider result--are handled by "shorten" in build_binary_op.  */
 178
 179       switch (ex_form)
 180         {
 181         case RSHIFT_EXPR:
 182           /* We can pass truncation down through right shifting
 183              when the shift count is a nonpositive constant.  */
 184           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 185               && tree_int_cst_lt (TREE_OPERAND (expr, 1), integer_one_node))
 186             goto trunc1;
 187           break;
 188
 189         case LSHIFT_EXPR:
 190           /* We can pass truncation down through left shifting
 191              when the shift count is a nonnegative constant.  */
 192           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 193               && ! tree_int_cst_lt (TREE_OPERAND (expr, 1), integer_zero_node)
 194               && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
 195             {
 196               /* If shift count is less than the width of the truncated type,
 197                  really shift.  */
 198               if (tree_int_cst_lt (TREE_OPERAND (expr, 1), TYPE_SIZE (type)))
 199                 /* In this case, shifting is like multiplication.  */
 200                 goto trunc1;
 201               else
 202                 /* If it is >= that width, result is zero.
 203                    Handling this with trunc1 would give the wrong result:
 204                    (int) ((long long) a << 32) is well defined (as 0)
 205                    but (int) a << 32 is undefined and would get a warning.  */
 206                 return convert_to_integer (type, integer_zero_node);
 207             }
 208           break;
 209
 210         case MAX_EXPR:
 211         case MIN_EXPR:
 212         case MULT_EXPR:
 213           {
 214             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 215             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 216
 217             /* Don't distribute unless the output precision is at least as big
 218                as the actual inputs.  Otherwise, the comparison of the
 219                truncated values will be wrong.  */
 220             if (outprec >= TYPE_PRECISION (TREE_TYPE (arg0))
 221                 && outprec >= TYPE_PRECISION (TREE_TYPE (arg1))
 222                 /* If signedness of arg0 and arg1 don't match,
 223                    we can't necessarily find a type to compare them in.  */
 224                 && (TREE_UNSIGNED (TREE_TYPE (arg0))
 225                     == TREE_UNSIGNED (TREE_TYPE (arg1))))
 226               goto trunc1;
 227             break;
 228           }
 229
 230         case PLUS_EXPR:
 231         case MINUS_EXPR:
 232         case BIT_AND_EXPR:
 233         case BIT_IOR_EXPR:
 234         case BIT_XOR_EXPR:
 235         case BIT_ANDTC_EXPR:
 236         trunc1:
 237           {
 238             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 239             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 240
 241             if (outprec >= BITS_PER_WORD
 242                 || TRULY_NOOP_TRUNCATION (outprec, inprec)
 243                 || inprec > TYPE_PRECISION (TREE_TYPE (arg0))
 244                 || inprec > TYPE_PRECISION (TREE_TYPE (arg1)))
 245               {
 246                 /* Do the arithmetic in type TYPEX,
 247                    then convert result to TYPE.  */
 248                 register tree typex = type;
 249
 250                 /* Can't do arithmetic in enumeral types
 251                    so use an integer type that will hold the values.  */
 252                 if (TREE_CODE (typex) == ENUMERAL_TYPE)
 253                   typex = type_for_size (TYPE_PRECISION (typex),
 254                                          TREE_UNSIGNED (typex));
 255
 256                 /* But now perhaps TYPEX is as wide as INPREC.
 257                    In that case, do nothing special here.
 258                    (Otherwise would recurse infinitely in convert.  */
 259                 if (TYPE_PRECISION (typex) != inprec)
 260                   {
 261                     /* Don't do unsigned arithmetic where signed was wanted,
 262                        or vice versa.
 263                        Exception: if either of the original operands were
 264                        unsigned then can safely do the work as unsigned.
 265                        And we may need to do it as unsigned
 266                        if we truncate to the original size.  */
 267                     typex = ((TREE_UNSIGNED (TREE_TYPE (expr))
 268                               || TREE_UNSIGNED (TREE_TYPE (arg0))
 269                               || TREE_UNSIGNED (TREE_TYPE (arg1)))
 270                              ? unsigned_type (typex) : signed_type (typex));
 271                     return convert (type,
 272                                     build_binary_op (ex_form,
 273                                                      convert (typex, arg0),
 274                                                      convert (typex, arg1),
 275                                                      0));
 276                   }
 277               }
 278           }
 279           break;
 280
 281         case NEGATE_EXPR:
 282         case BIT_NOT_EXPR:
 283         case ABS_EXPR:
 284           {
 285             register tree typex = type;
 286
 287             /* Can't do arithmetic in enumeral types
 288                so use an integer type that will hold the values.  */
 289             if (TREE_CODE (typex) == ENUMERAL_TYPE)
 290               typex = type_for_size (TYPE_PRECISION (typex),
 291                                      TREE_UNSIGNED (typex));
 292
 293             /* But now perhaps TYPEX is as wide as INPREC.
 294                In that case, do nothing special here.
 295                (Otherwise would recurse infinitely in convert.  */
 296             if (TYPE_PRECISION (typex) != inprec)
 297               {
 298                 /* Don't do unsigned arithmetic where signed was wanted,
 299                    or vice versa.  */
 300                 typex = (TREE_UNSIGNED (TREE_TYPE (expr))
 301                          ? unsigned_type (typex) : signed_type (typex));
 302                 return convert (type,
 303                                 build_unary_op (ex_form,
 304                                                 convert (typex, TREE_OPERAND (expr, 0)),
 305                                                 1));
 306               }
 307           }
 308
 309         case NOP_EXPR:
 310           /* If truncating after truncating, might as well do all at once.
 311              If truncating after extending, we may get rid of wasted work.  */
 312           return convert (type, get_unwidened (TREE_OPERAND (expr, 0), type));
 313
 314         case COND_EXPR:
 315           /* Can treat the two alternative values like the operands
 316              of an arithmetic expression.  */
 317           {
 318             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 319             tree arg2 = get_unwidened (TREE_OPERAND (expr, 2), type);
 320
 321             if (outprec >= BITS_PER_WORD
 322                 || TRULY_NOOP_TRUNCATION (outprec, inprec)
 323                 || inprec > TYPE_PRECISION (TREE_TYPE (arg1))
 324                 || inprec > TYPE_PRECISION (TREE_TYPE (arg2)))
 325               {
 326                 /* Do the arithmetic in type TYPEX,
 327                    then convert result to TYPE.  */
 328                 register tree typex = type;
 329
 330                 /* Can't do arithmetic in enumeral types
 331                    so use an integer type that will hold the values.  */
 332                 if (TREE_CODE (typex) == ENUMERAL_TYPE)
 333                   typex = type_for_size (TYPE_PRECISION (typex),
 334                                          TREE_UNSIGNED (typex));
 335
 336                 /* But now perhaps TYPEX is as wide as INPREC.
 337                    In that case, do nothing special here.
 338                    (Otherwise would recurse infinitely in convert.  */
 339                 if (TYPE_PRECISION (typex) != inprec)
 340                   {
 341                     /* Don't do unsigned arithmetic where signed was wanted,
 342                        or vice versa.  */
 343                     typex = (TREE_UNSIGNED (TREE_TYPE (expr))
 344                              ? unsigned_type (typex) : signed_type (typex));
 345                     return convert (type,
 346                                     fold (build (COND_EXPR, typex,
 347                                                  TREE_OPERAND (expr, 0),
 348                                                  convert (typex, arg1),
 349                                                  convert (typex, arg2))));
 350                   }
 351                 else
 352                   /* It is sometimes worthwhile
 353                      to push the narrowing down through the conditional.  */
 354                   return fold (build (COND_EXPR, type,
 355                                       TREE_OPERAND (expr, 0),
 356                                       convert (type, TREE_OPERAND (expr, 1)),
 357                                       convert (type, TREE_OPERAND (expr, 2))));
 358               }
 359           }
 360
 361         }
 362
 363       return build1 (NOP_EXPR, type, expr);
 364     }
 365
 366   if (form == REAL_TYPE)
 367     return build1 (FIX_TRUNC_EXPR, type, expr);
 368
 369   if (form == COMPLEX_TYPE)
 370     return convert (type, fold (build1 (REALPART_EXPR,
 371                                         TREE_TYPE (TREE_TYPE (expr)), expr)));
 372
 373   error ("aggregate value used where an integer was expected");
 374
 375   {
 376     register tree tem = build_int_2 (0, 0);
 377     TREE_TYPE (tem) = type;
 378     return tem;
 379   }
 380 }
 381
 382 /* Convert EXPR to the complex type TYPE in the usual ways.  */
 383
 384 tree
 385 convert_to_complex (type, expr)
 386      tree type, expr;
 387 {
 388   register enum tree_code form = TREE_CODE (TREE_TYPE (expr));
 389   tree subtype = TREE_TYPE (type);
 390
 391   if (form == REAL_TYPE || form == INTEGER_TYPE || form == ENUMERAL_TYPE)
 392     {
 393       expr = convert (subtype, expr);
 394       return build (COMPLEX_EXPR, type, expr,
 395                     convert (subtype, integer_zero_node));
 396     }
 397
 398   if (form == COMPLEX_TYPE)
 399     {
 400       tree elt_type = TREE_TYPE (TREE_TYPE (expr));
 401       if (TYPE_MAIN_VARIANT (elt_type) == TYPE_MAIN_VARIANT (subtype))
 402         return expr;
 403       else if (TREE_CODE (expr) == COMPLEX_EXPR)
 404         return fold (build (COMPLEX_EXPR,
 405                             type,
 406                             convert (subtype, TREE_OPERAND (expr, 0)),
 407                             convert (subtype, TREE_OPERAND (expr, 1))));
 408       else
 409         {
 410           expr = save_expr (expr);
 411           return fold (build (COMPLEX_EXPR,
 412                               type,
 413                               convert (subtype,
 414                                        build_unary_op (REALPART_EXPR, expr, 1)),
 415                               convert (subtype,
 416                                        build_unary_op (IMAGPART_EXPR, expr, 1))));
 417         }
 418     }
 419
 420   if (form == POINTER_TYPE)
 421     error ("pointer value used where a complex was expected");
 422   else
 423     error ("aggregate value used where a complex was expected");
 424
 425   return build (COMPLEX_EXPR, type,
 426                 convert (subtype, integer_zero_node),
 427                 convert (subtype, integer_zero_node));
 428 }