gcc/convert.c

   1 /* Utility routines for data type conversion for GCC.
   2    Copyright (C) 1987, 1988, 1991, 1992, 1993, 1994, 1995, 1997, 1998,
   3    2000, 2001, 2002, 2003, 2004, 2005, 2006 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 2, 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 COPYING.  If not, write to the Free
  19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  20 02110-1301, USA.  */
  21
  22
  23 /* These routines are somewhat language-independent utility function
  24    intended to be called by the language-specific convert () functions.  */
  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 "toplev.h"
  34 #include "langhooks.h"
  35 #include "real.h"
  36
  37 /* Convert EXPR to some pointer or reference type TYPE.
  38    EXPR must be pointer, reference, integer, enumeral, or literal zero;
  39    in other cases error is called.  */
  40
  41 tree
  42 convert_to_pointer (tree type, tree expr)
  43 {
  44   if (TREE_TYPE (expr) == type)
  45     return expr;
  46
  47   if (integer_zerop (expr))
  48     {
  49       tree t = build_int_cst (type, 0);
  50       if (TREE_OVERFLOW (expr) || TREE_CONSTANT_OVERFLOW (expr))
  51         t = force_fit_type (t, 0, TREE_OVERFLOW (expr),
  52                             TREE_CONSTANT_OVERFLOW (expr));
  53       return t;
  54     }
  55
  56   switch (TREE_CODE (TREE_TYPE (expr)))
  57     {
  58     case POINTER_TYPE:
  59     case REFERENCE_TYPE:
  60       return fold_build1 (NOP_EXPR, type, expr);
  61
  62     case INTEGER_TYPE:
  63     case ENUMERAL_TYPE:
  64     case BOOLEAN_TYPE:
  65       if (TYPE_PRECISION (TREE_TYPE (expr)) != POINTER_SIZE)
  66         expr = fold_build1 (NOP_EXPR,
  67                             lang_hooks.types.type_for_size (POINTER_SIZE, 0),
  68                             expr);
  69       return fold_build1 (CONVERT_EXPR, type, expr);
  70
  71
  72     default:
  73       error ("cannot convert to a pointer type");
  74       return convert_to_pointer (type, integer_zero_node);
  75     }
  76 }
  77
  78 /* Avoid any floating point extensions from EXP.  */
  79 tree
  80 strip_float_extensions (tree exp)
  81 {
  82   tree sub, expt, subt;
  83
  84   /*  For floating point constant look up the narrowest type that can hold
  85       it properly and handle it like (type)(narrowest_type)constant.
  86       This way we can optimize for instance a=a*2.0 where "a" is float
  87       but 2.0 is double constant.  */
  88   if (TREE_CODE (exp) == REAL_CST)
  89     {
  90       REAL_VALUE_TYPE orig;
  91       tree type = NULL;
  92
  93       orig = TREE_REAL_CST (exp);
  94       if (TYPE_PRECISION (TREE_TYPE (exp)) > TYPE_PRECISION (float_type_node)
  95           && exact_real_truncate (TYPE_MODE (float_type_node), &orig))
  96         type = float_type_node;
  97       else if (TYPE_PRECISION (TREE_TYPE (exp))
  98                > TYPE_PRECISION (double_type_node)
  99                && exact_real_truncate (TYPE_MODE (double_type_node), &orig))
 100         type = double_type_node;
 101       if (type)
 102         return build_real (type, real_value_truncate (TYPE_MODE (type), orig));
 103     }
 104
 105   if (TREE_CODE (exp) != NOP_EXPR
 106       && TREE_CODE (exp) != CONVERT_EXPR)
 107     return exp;
 108
 109   sub = TREE_OPERAND (exp, 0);
 110   subt = TREE_TYPE (sub);
 111   expt = TREE_TYPE (exp);
 112
 113   if (!FLOAT_TYPE_P (subt))
 114     return exp;
 115
 116   if (TYPE_PRECISION (subt) > TYPE_PRECISION (expt))
 117     return exp;
 118
 119   return strip_float_extensions (sub);
 120 }
 121
 122
 123 /* Convert EXPR to some floating-point type TYPE.
 124
 125    EXPR must be float, integer, or enumeral;
 126    in other cases error is called.  */
 127
 128 tree
 129 convert_to_real (tree type, tree expr)
 130 {
 131   enum built_in_function fcode = builtin_mathfn_code (expr);
 132   tree itype = TREE_TYPE (expr);
 133
 134   /* Disable until we figure out how to decide whether the functions are
 135      present in runtime.  */
 136   /* Convert (float)sqrt((double)x) where x is float into sqrtf(x) */
 137   if (optimize
 138       && (TYPE_MODE (type) == TYPE_MODE (double_type_node)
 139           || TYPE_MODE (type) == TYPE_MODE (float_type_node)))
 140     {
 141       switch (fcode)
 142         {
 143 #define CASE_MATHFN(FN) case BUILT_IN_##FN: case BUILT_IN_##FN##L:
 144           CASE_MATHFN (ACOS)
 145           CASE_MATHFN (ACOSH)
 146           CASE_MATHFN (ASIN)
 147           CASE_MATHFN (ASINH)
 148           CASE_MATHFN (ATAN)
 149           CASE_MATHFN (ATANH)
 150           CASE_MATHFN (CBRT)
 151           CASE_MATHFN (COS)
 152           CASE_MATHFN (COSH)
 153           CASE_MATHFN (ERF)
 154           CASE_MATHFN (ERFC)
 155           CASE_MATHFN (EXP)
 156           CASE_MATHFN (EXP10)
 157           CASE_MATHFN (EXP2)
 158           CASE_MATHFN (EXPM1)
 159           CASE_MATHFN (FABS)
 160           CASE_MATHFN (GAMMA)
 161           CASE_MATHFN (J0)
 162           CASE_MATHFN (J1)
 163           CASE_MATHFN (LGAMMA)
 164           CASE_MATHFN (LOG)
 165           CASE_MATHFN (LOG10)
 166           CASE_MATHFN (LOG1P)
 167           CASE_MATHFN (LOG2)
 168           CASE_MATHFN (LOGB)
 169           CASE_MATHFN (POW10)
 170           CASE_MATHFN (SIN)
 171           CASE_MATHFN (SINH)
 172           CASE_MATHFN (SQRT)
 173           CASE_MATHFN (TAN)
 174           CASE_MATHFN (TANH)
 175           CASE_MATHFN (TGAMMA)
 176           CASE_MATHFN (Y0)
 177           CASE_MATHFN (Y1)
 178 #undef CASE_MATHFN
 179             {
 180               tree arg0 = strip_float_extensions (TREE_VALUE (TREE_OPERAND (expr, 1)));
 181               tree newtype = type;
 182
 183               /* We have (outertype)sqrt((innertype)x).  Choose the wider mode from
 184                  the both as the safe type for operation.  */
 185               if (TYPE_PRECISION (TREE_TYPE (arg0)) > TYPE_PRECISION (type))
 186                 newtype = TREE_TYPE (arg0);
 187
 188               /* Be careful about integer to fp conversions.
 189                  These may overflow still.  */
 190               if (FLOAT_TYPE_P (TREE_TYPE (arg0))
 191                   && TYPE_PRECISION (newtype) < TYPE_PRECISION (itype)
 192                   && (TYPE_MODE (newtype) == TYPE_MODE (double_type_node)
 193                       || TYPE_MODE (newtype) == TYPE_MODE (float_type_node)))
 194                 {
 195                   tree arglist;
 196                   tree fn = mathfn_built_in (newtype, fcode);
 197
 198                   if (fn)
 199                   {
 200                     arglist = build_tree_list (NULL_TREE, fold (convert_to_real (newtype, arg0)));
 201                     expr = build_function_call_expr (fn, arglist);
 202                     if (newtype == type)
 203                       return expr;
 204                   }
 205                 }
 206             }
 207         default:
 208           break;
 209         }
 210     }
 211   if (optimize
 212       && (((fcode == BUILT_IN_FLOORL
 213            || fcode == BUILT_IN_CEILL
 214            || fcode == BUILT_IN_ROUNDL
 215            || fcode == BUILT_IN_RINTL
 216            || fcode == BUILT_IN_TRUNCL
 217            || fcode == BUILT_IN_NEARBYINTL)
 218           && (TYPE_MODE (type) == TYPE_MODE (double_type_node)
 219               || TYPE_MODE (type) == TYPE_MODE (float_type_node)))
 220           || ((fcode == BUILT_IN_FLOOR
 221                || fcode == BUILT_IN_CEIL
 222                || fcode == BUILT_IN_ROUND
 223                || fcode == BUILT_IN_RINT
 224                || fcode == BUILT_IN_TRUNC
 225                || fcode == BUILT_IN_NEARBYINT)
 226               && (TYPE_MODE (type) == TYPE_MODE (float_type_node)))))
 227     {
 228       tree fn = mathfn_built_in (type, fcode);
 229
 230       if (fn)
 231         {
 232           tree arg
 233             = strip_float_extensions (TREE_VALUE (TREE_OPERAND (expr, 1)));
 234
 235           /* Make sure (type)arg0 is an extension, otherwise we could end up
 236              changing (float)floor(double d) into floorf((float)d), which is
 237              incorrect because (float)d uses round-to-nearest and can round
 238              up to the next integer.  */
 239           if (TYPE_PRECISION (type) >= TYPE_PRECISION (TREE_TYPE (arg)))
 240             return
 241               build_function_call_expr (fn,
 242                                         build_tree_list (NULL_TREE,
 243                                           fold (convert_to_real (type, arg))));
 244         }
 245     }
 246
 247   /* Propagate the cast into the operation.  */
 248   if (itype != type && FLOAT_TYPE_P (type))
 249     switch (TREE_CODE (expr))
 250       {
 251         /* Convert (float)-x into -(float)x.  This is always safe.  */
 252         case ABS_EXPR:
 253         case NEGATE_EXPR:
 254           if (TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (expr)))
 255             return build1 (TREE_CODE (expr), type,
 256                            fold (convert_to_real (type,
 257                                                   TREE_OPERAND (expr, 0))));
 258           break;
 259         /* Convert (outertype)((innertype0)a+(innertype1)b)
 260            into ((newtype)a+(newtype)b) where newtype
 261            is the widest mode from all of these.  */
 262         case PLUS_EXPR:
 263         case MINUS_EXPR:
 264         case MULT_EXPR:
 265         case RDIV_EXPR:
 266            {
 267              tree arg0 = strip_float_extensions (TREE_OPERAND (expr, 0));
 268              tree arg1 = strip_float_extensions (TREE_OPERAND (expr, 1));
 269
 270              if (FLOAT_TYPE_P (TREE_TYPE (arg0))
 271                  && FLOAT_TYPE_P (TREE_TYPE (arg1)))
 272                {
 273                   tree newtype = type;
 274
 275                   if (TYPE_MODE (TREE_TYPE (arg0)) == SDmode
 276                       || TYPE_MODE (TREE_TYPE (arg1)) == SDmode)
 277                     newtype = dfloat32_type_node;
 278                   if (TYPE_MODE (TREE_TYPE (arg0)) == DDmode
 279                       || TYPE_MODE (TREE_TYPE (arg1)) == DDmode)
 280                     newtype = dfloat64_type_node;
 281                   if (TYPE_MODE (TREE_TYPE (arg0)) == TDmode
 282                       || TYPE_MODE (TREE_TYPE (arg1)) == TDmode)
 283                     newtype = dfloat128_type_node;
 284                   if (newtype == dfloat32_type_node
 285                       || newtype == dfloat64_type_node
 286                       || newtype == dfloat128_type_node)
 287                     {
 288                       expr = build2 (TREE_CODE (expr), newtype,
 289                                      fold (convert_to_real (newtype, arg0)),
 290                                      fold (convert_to_real (newtype, arg1)));
 291                       if (newtype == type)
 292                         return expr;
 293                       break;
 294                     }
 295
 296                   if (TYPE_PRECISION (TREE_TYPE (arg0)) > TYPE_PRECISION (newtype))
 297                     newtype = TREE_TYPE (arg0);
 298                   if (TYPE_PRECISION (TREE_TYPE (arg1)) > TYPE_PRECISION (newtype))
 299                     newtype = TREE_TYPE (arg1);
 300                   if (TYPE_PRECISION (newtype) < TYPE_PRECISION (itype))
 301                     {
 302                       expr = build2 (TREE_CODE (expr), newtype,
 303                                      fold (convert_to_real (newtype, arg0)),
 304                                      fold (convert_to_real (newtype, arg1)));
 305                       if (newtype == type)
 306                         return expr;
 307                     }
 308                }
 309            }
 310           break;
 311         default:
 312           break;
 313       }
 314
 315   switch (TREE_CODE (TREE_TYPE (expr)))
 316     {
 317     case REAL_TYPE:
 318       /* Ignore the conversion if we don't need to store intermediate
 319          results and neither type is a decimal float.  */
 320       return build1 ((flag_float_store
 321                      || DECIMAL_FLOAT_TYPE_P (type)
 322                      || DECIMAL_FLOAT_TYPE_P (itype))
 323                      ? CONVERT_EXPR : NOP_EXPR, type, expr);
 324
 325     case INTEGER_TYPE:
 326     case ENUMERAL_TYPE:
 327     case BOOLEAN_TYPE:
 328       return build1 (FLOAT_EXPR, type, expr);
 329
 330     case COMPLEX_TYPE:
 331       return convert (type,
 332                       fold_build1 (REALPART_EXPR,
 333                                    TREE_TYPE (TREE_TYPE (expr)), expr));
 334
 335     case POINTER_TYPE:
 336     case REFERENCE_TYPE:
 337       error ("pointer value used where a floating point value was expected");
 338       return convert_to_real (type, integer_zero_node);
 339
 340     default:
 341       error ("aggregate value used where a float was expected");
 342       return convert_to_real (type, integer_zero_node);
 343     }
 344 }
 345
 346 /* Convert EXPR to some integer (or enum) type TYPE.
 347
 348    EXPR must be pointer, integer, discrete (enum, char, or bool), float, or
 349    vector; in other cases error is called.
 350
 351    The result of this is always supposed to be a newly created tree node
 352    not in use in any existing structure.  */
 353
 354 tree
 355 convert_to_integer (tree type, tree expr)
 356 {
 357   enum tree_code ex_form = TREE_CODE (expr);
 358   tree intype = TREE_TYPE (expr);
 359   unsigned int inprec = TYPE_PRECISION (intype);
 360   unsigned int outprec = TYPE_PRECISION (type);
 361
 362   /* An INTEGER_TYPE cannot be incomplete, but an ENUMERAL_TYPE can
 363      be.  Consider `enum E = { a, b = (enum E) 3 };'.  */
 364   if (!COMPLETE_TYPE_P (type))
 365     {
 366       error ("conversion to incomplete type");
 367       return error_mark_node;
 368     }
 369
 370   /* Convert e.g. (long)round(d) -> lround(d).  */
 371   /* If we're converting to char, we may encounter differing behavior
 372      between converting from double->char vs double->long->char.
 373      We're in "undefined" territory but we prefer to be conservative,
 374      so only proceed in "unsafe" math mode.  */
 375   if (optimize
 376       && (flag_unsafe_math_optimizations
 377           || (long_integer_type_node
 378               && outprec >= TYPE_PRECISION (long_integer_type_node))))
 379     {
 380       tree s_expr = strip_float_extensions (expr);
 381       tree s_intype = TREE_TYPE (s_expr);
 382       const enum built_in_function fcode = builtin_mathfn_code (s_expr);
 383       tree fn = 0;
 384
 385       switch (fcode)
 386         {
 387         CASE_FLT_FN (BUILT_IN_CEIL):
 388           /* Only convert in ISO C99 mode.  */
 389           if (!TARGET_C99_FUNCTIONS)
 390             break;
 391           if (outprec < TYPE_PRECISION (long_integer_type_node)
 392               || (outprec == TYPE_PRECISION (long_integer_type_node)
 393                   && !TYPE_UNSIGNED (type)))
 394             fn = mathfn_built_in (s_intype, BUILT_IN_LCEIL);
 395           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 396                    && !TYPE_UNSIGNED (type))
 397             fn = mathfn_built_in (s_intype, BUILT_IN_LLCEIL);
 398           break;
 399
 400         CASE_FLT_FN (BUILT_IN_FLOOR):
 401           /* Only convert in ISO C99 mode.  */
 402           if (!TARGET_C99_FUNCTIONS)
 403             break;
 404           if (outprec < TYPE_PRECISION (long_integer_type_node)
 405               || (outprec == TYPE_PRECISION (long_integer_type_node)
 406                   && !TYPE_UNSIGNED (type)))
 407             fn = mathfn_built_in (s_intype, BUILT_IN_LFLOOR);
 408           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 409                    && !TYPE_UNSIGNED (type))
 410             fn = mathfn_built_in (s_intype, BUILT_IN_LLFLOOR);
 411           break;
 412
 413         CASE_FLT_FN (BUILT_IN_ROUND):
 414           if (outprec < TYPE_PRECISION (long_integer_type_node)
 415               || (outprec == TYPE_PRECISION (long_integer_type_node)
 416                   && !TYPE_UNSIGNED (type)))
 417             fn = mathfn_built_in (s_intype, BUILT_IN_LROUND);
 418           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 419                    && !TYPE_UNSIGNED (type))
 420             fn = mathfn_built_in (s_intype, BUILT_IN_LLROUND);
 421           break;
 422
 423         CASE_FLT_FN (BUILT_IN_RINT):
 424           /* Only convert rint* if we can ignore math exceptions.  */
 425           if (flag_trapping_math)
 426             break;
 427           /* ... Fall through ...  */
 428         CASE_FLT_FN (BUILT_IN_NEARBYINT):
 429           if (outprec < TYPE_PRECISION (long_integer_type_node)
 430               || (outprec == TYPE_PRECISION (long_integer_type_node)
 431                   && !TYPE_UNSIGNED (type)))
 432             fn = mathfn_built_in (s_intype, BUILT_IN_LRINT);
 433           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 434                    && !TYPE_UNSIGNED (type))
 435             fn = mathfn_built_in (s_intype, BUILT_IN_LLRINT);
 436           break;
 437
 438         CASE_FLT_FN (BUILT_IN_TRUNC):
 439           {
 440             tree arglist = TREE_OPERAND (s_expr, 1);
 441             return convert_to_integer (type, TREE_VALUE (arglist));
 442           }
 443
 444         default:
 445           break;
 446         }
 447
 448       if (fn)
 449         {
 450           tree arglist = TREE_OPERAND (s_expr, 1);
 451           tree newexpr = build_function_call_expr (fn, arglist);
 452           return convert_to_integer (type, newexpr);
 453         }
 454     }
 455
 456   switch (TREE_CODE (intype))
 457     {
 458     case POINTER_TYPE:
 459     case REFERENCE_TYPE:
 460       if (integer_zerop (expr))
 461         return build_int_cst (type, 0);
 462
 463       /* Convert to an unsigned integer of the correct width first,
 464          and from there widen/truncate to the required type.  */
 465       expr = fold_build1 (CONVERT_EXPR,
 466                           lang_hooks.types.type_for_size (POINTER_SIZE, 0),
 467                           expr);
 468       return fold_convert (type, expr);
 469
 470     case INTEGER_TYPE:
 471     case ENUMERAL_TYPE:
 472     case BOOLEAN_TYPE:
 473       /* If this is a logical operation, which just returns 0 or 1, we can
 474          change the type of the expression.  */
 475
 476       if (TREE_CODE_CLASS (ex_form) == tcc_comparison)
 477         {
 478           expr = copy_node (expr);
 479           TREE_TYPE (expr) = type;
 480           return expr;
 481         }
 482
 483       /* If we are widening the type, put in an explicit conversion.
 484          Similarly if we are not changing the width.  After this, we know
 485          we are truncating EXPR.  */
 486
 487       else if (outprec >= inprec)
 488         {
 489           enum tree_code code;
 490
 491           /* If the precision of the EXPR's type is K bits and the
 492              destination mode has more bits, and the sign is changing,
 493              it is not safe to use a NOP_EXPR.  For example, suppose
 494              that EXPR's type is a 3-bit unsigned integer type, the
 495              TYPE is a 3-bit signed integer type, and the machine mode
 496              for the types is 8-bit QImode.  In that case, the
 497              conversion necessitates an explicit sign-extension.  In
 498              the signed-to-unsigned case the high-order bits have to
 499              be cleared.  */
 500           if (TYPE_UNSIGNED (type) != TYPE_UNSIGNED (TREE_TYPE (expr))
 501               && (TYPE_PRECISION (TREE_TYPE (expr))
 502                   != GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (expr)))))
 503             code = CONVERT_EXPR;
 504           else
 505             code = NOP_EXPR;
 506
 507           return fold_build1 (code, type, expr);
 508         }
 509
 510       /* If TYPE is an enumeral type or a type with a precision less
 511          than the number of bits in its mode, do the conversion to the
 512          type corresponding to its mode, then do a nop conversion
 513          to TYPE.  */
 514       else if (TREE_CODE (type) == ENUMERAL_TYPE
 515                || outprec != GET_MODE_BITSIZE (TYPE_MODE (type)))
 516         return build1 (NOP_EXPR, type,
 517                        convert (lang_hooks.types.type_for_mode
 518                                 (TYPE_MODE (type), TYPE_UNSIGNED (type)),
 519                                 expr));
 520
 521       /* Here detect when we can distribute the truncation down past some
 522          arithmetic.  For example, if adding two longs and converting to an
 523          int, we can equally well convert both to ints and then add.
 524          For the operations handled here, such truncation distribution
 525          is always safe.
 526          It is desirable in these cases:
 527          1) when truncating down to full-word from a larger size
 528          2) when truncating takes no work.
 529          3) when at least one operand of the arithmetic has been extended
 530          (as by C's default conversions).  In this case we need two conversions
 531          if we do the arithmetic as already requested, so we might as well
 532          truncate both and then combine.  Perhaps that way we need only one.
 533
 534          Note that in general we cannot do the arithmetic in a type
 535          shorter than the desired result of conversion, even if the operands
 536          are both extended from a shorter type, because they might overflow
 537          if combined in that type.  The exceptions to this--the times when
 538          two narrow values can be combined in their narrow type even to
 539          make a wider result--are handled by "shorten" in build_binary_op.  */
 540
 541       switch (ex_form)
 542         {
 543         case RSHIFT_EXPR:
 544           /* We can pass truncation down through right shifting
 545              when the shift count is a nonpositive constant.  */
 546           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 547               && tree_int_cst_sgn (TREE_OPERAND (expr, 1)) <= 0)
 548             goto trunc1;
 549           break;
 550
 551         case LSHIFT_EXPR:
 552           /* We can pass truncation down through left shifting
 553              when the shift count is a nonnegative constant and
 554              the target type is unsigned.  */
 555           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 556               && tree_int_cst_sgn (TREE_OPERAND (expr, 1)) >= 0
 557               && TYPE_UNSIGNED (type)
 558               && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
 559             {
 560               /* If shift count is less than the width of the truncated type,
 561                  really shift.  */
 562               if (tree_int_cst_lt (TREE_OPERAND (expr, 1), TYPE_SIZE (type)))
 563                 /* In this case, shifting is like multiplication.  */
 564                 goto trunc1;
 565               else
 566                 {
 567                   /* If it is >= that width, result is zero.
 568                      Handling this with trunc1 would give the wrong result:
 569                      (int) ((long long) a << 32) is well defined (as 0)
 570                      but (int) a << 32 is undefined and would get a
 571                      warning.  */
 572
 573                   tree t = build_int_cst (type, 0);
 574
 575                   /* If the original expression had side-effects, we must
 576                      preserve it.  */
 577                   if (TREE_SIDE_EFFECTS (expr))
 578                     return build2 (COMPOUND_EXPR, type, expr, t);
 579                   else
 580                     return t;
 581                 }
 582             }
 583           break;
 584
 585         case MAX_EXPR:
 586         case MIN_EXPR:
 587         case MULT_EXPR:
 588           {
 589             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 590             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 591
 592             /* Don't distribute unless the output precision is at least as big
 593                as the actual inputs.  Otherwise, the comparison of the
 594                truncated values will be wrong.  */
 595             if (outprec >= TYPE_PRECISION (TREE_TYPE (arg0))
 596                 && outprec >= TYPE_PRECISION (TREE_TYPE (arg1))
 597                 /* If signedness of arg0 and arg1 don't match,
 598                    we can't necessarily find a type to compare them in.  */
 599                 && (TYPE_UNSIGNED (TREE_TYPE (arg0))
 600                     == TYPE_UNSIGNED (TREE_TYPE (arg1))))
 601               goto trunc1;
 602             break;
 603           }
 604
 605         case PLUS_EXPR:
 606         case MINUS_EXPR:
 607         case BIT_AND_EXPR:
 608         case BIT_IOR_EXPR:
 609         case BIT_XOR_EXPR:
 610         trunc1:
 611           {
 612             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 613             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 614
 615             if (outprec >= BITS_PER_WORD
 616                 || TRULY_NOOP_TRUNCATION (outprec, inprec)
 617                 || inprec > TYPE_PRECISION (TREE_TYPE (arg0))
 618                 || inprec > TYPE_PRECISION (TREE_TYPE (arg1)))
 619               {
 620                 /* Do the arithmetic in type TYPEX,
 621                    then convert result to TYPE.  */
 622                 tree typex = type;
 623
 624                 /* Can't do arithmetic in enumeral types
 625                    so use an integer type that will hold the values.  */
 626                 if (TREE_CODE (typex) == ENUMERAL_TYPE)
 627                   typex = lang_hooks.types.type_for_size
 628                     (TYPE_PRECISION (typex), TYPE_UNSIGNED (typex));
 629
 630                 /* But now perhaps TYPEX is as wide as INPREC.
 631                    In that case, do nothing special here.
 632                    (Otherwise would recurse infinitely in convert.  */
 633                 if (TYPE_PRECISION (typex) != inprec)
 634                   {
 635                     /* Don't do unsigned arithmetic where signed was wanted,
 636                        or vice versa.
 637                        Exception: if both of the original operands were
 638                        unsigned then we can safely do the work as unsigned.
 639                        Exception: shift operations take their type solely
 640                        from the first argument.
 641                        Exception: the LSHIFT_EXPR case above requires that
 642                        we perform this operation unsigned lest we produce
 643                        signed-overflow undefinedness.
 644                        And we may need to do it as unsigned
 645                        if we truncate to the original size.  */
 646                     if (TYPE_UNSIGNED (TREE_TYPE (expr))
 647                         || (TYPE_UNSIGNED (TREE_TYPE (arg0))
 648                             && (TYPE_UNSIGNED (TREE_TYPE (arg1))
 649                                 || ex_form == LSHIFT_EXPR
 650                                 || ex_form == RSHIFT_EXPR
 651                                 || ex_form == LROTATE_EXPR
 652                                 || ex_form == RROTATE_EXPR))
 653                         || ex_form == LSHIFT_EXPR
 654                         /* If we have !flag_wrapv, and either ARG0 or
 655                            ARG1 is of a signed type, we have to do
 656                            PLUS_EXPR or MINUS_EXPR in an unsigned
 657                            type.  Otherwise, we would introduce
 658                            signed-overflow undefinedness.  */
 659                         || (!flag_wrapv
 660                             && (ex_form == PLUS_EXPR
 661                                 || ex_form == MINUS_EXPR)
 662                             && (!TYPE_UNSIGNED (TREE_TYPE (arg0))
 663                                 || !TYPE_UNSIGNED (TREE_TYPE (arg1)))))
 664                       typex = lang_hooks.types.unsigned_type (typex);
 665                     else
 666                       typex = lang_hooks.types.signed_type (typex);
 667                     return convert (type,
 668                                     fold_build2 (ex_form, typex,
 669                                                  convert (typex, arg0),
 670                                                  convert (typex, arg1)));
 671                   }
 672               }
 673           }
 674           break;
 675
 676         case NEGATE_EXPR:
 677         case BIT_NOT_EXPR:
 678           /* This is not correct for ABS_EXPR,
 679              since we must test the sign before truncation.  */
 680           {
 681             tree typex;
 682
 683             /* Don't do unsigned arithmetic where signed was wanted,
 684                or vice versa.  */
 685             if (TYPE_UNSIGNED (TREE_TYPE (expr)))
 686               typex = lang_hooks.types.unsigned_type (type);
 687             else
 688               typex = lang_hooks.types.signed_type (type);
 689             return convert (type,
 690                             fold_build1 (ex_form, typex,
 691                                          convert (typex,
 692                                                   TREE_OPERAND (expr, 0))));
 693           }
 694
 695         case NOP_EXPR:
 696           /* Don't introduce a
 697              "can't convert between vector values of different size" error.  */
 698           if (TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0))) == VECTOR_TYPE
 699               && (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_OPERAND (expr, 0))))
 700                   != GET_MODE_SIZE (TYPE_MODE (type))))
 701             break;
 702           /* If truncating after truncating, might as well do all at once.
 703              If truncating after extending, we may get rid of wasted work.  */
 704           return convert (type, get_unwidened (TREE_OPERAND (expr, 0), type));
 705
 706         case COND_EXPR:
 707           /* It is sometimes worthwhile to push the narrowing down through
 708              the conditional and never loses.  */
 709           return fold_build3 (COND_EXPR, type, TREE_OPERAND (expr, 0),
 710                               convert (type, TREE_OPERAND (expr, 1)),
 711                               convert (type, TREE_OPERAND (expr, 2)));
 712
 713         default:
 714           break;
 715         }
 716
 717       return build1 (CONVERT_EXPR, type, expr);
 718
 719     case REAL_TYPE:
 720       return build1 (FIX_TRUNC_EXPR, type, expr);
 721
 722     case COMPLEX_TYPE:
 723       return convert (type,
 724                       fold_build1 (REALPART_EXPR,
 725                                    TREE_TYPE (TREE_TYPE (expr)), expr));
 726
 727     case VECTOR_TYPE:
 728       if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr))))
 729         {
 730           error ("can't convert between vector values of different size");
 731           return error_mark_node;
 732         }
 733       return build1 (VIEW_CONVERT_EXPR, type, expr);
 734
 735     default:
 736       error ("aggregate value used where an integer was expected");
 737       return convert (type, integer_zero_node);
 738     }
 739 }
 740
 741 /* Convert EXPR to the complex type TYPE in the usual ways.  */
 742
 743 tree
 744 convert_to_complex (tree type, tree expr)
 745 {
 746   tree subtype = TREE_TYPE (type);
 747
 748   switch (TREE_CODE (TREE_TYPE (expr)))
 749     {
 750     case REAL_TYPE:
 751     case INTEGER_TYPE:
 752     case ENUMERAL_TYPE:
 753     case BOOLEAN_TYPE:
 754       return build2 (COMPLEX_EXPR, type, convert (subtype, expr),
 755                      convert (subtype, integer_zero_node));
 756
 757     case COMPLEX_TYPE:
 758       {
 759         tree elt_type = TREE_TYPE (TREE_TYPE (expr));
 760
 761         if (TYPE_MAIN_VARIANT (elt_type) == TYPE_MAIN_VARIANT (subtype))
 762           return expr;
 763         else if (TREE_CODE (expr) == COMPLEX_EXPR)
 764           return fold_build2 (COMPLEX_EXPR, type,
 765                               convert (subtype, TREE_OPERAND (expr, 0)),
 766                               convert (subtype, TREE_OPERAND (expr, 1)));
 767         else
 768           {
 769             expr = save_expr (expr);
 770             return
 771               fold_build2 (COMPLEX_EXPR, type,
 772                            convert (subtype,
 773                                     fold_build1 (REALPART_EXPR,
 774                                                  TREE_TYPE (TREE_TYPE (expr)),
 775                                                  expr)),
 776                            convert (subtype,
 777                                     fold_build1 (IMAGPART_EXPR,
 778                                                  TREE_TYPE (TREE_TYPE (expr)),
 779                                                  expr)));
 780           }
 781       }
 782
 783     case POINTER_TYPE:
 784     case REFERENCE_TYPE:
 785       error ("pointer value used where a complex was expected");
 786       return convert_to_complex (type, integer_zero_node);
 787
 788     default:
 789       error ("aggregate value used where a complex was expected");
 790       return convert_to_complex (type, integer_zero_node);
 791     }
 792 }
 793
 794 /* Convert EXPR to the vector type TYPE in the usual ways.  */
 795
 796 tree
 797 convert_to_vector (tree type, tree expr)
 798 {
 799   switch (TREE_CODE (TREE_TYPE (expr)))
 800     {
 801     case INTEGER_TYPE:
 802     case VECTOR_TYPE:
 803       if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr))))
 804         {
 805           error ("can't convert between vector values of different size");
 806           return error_mark_node;
 807         }
 808       return build1 (VIEW_CONVERT_EXPR, type, expr);
 809
 810     default:
 811       error ("can't convert value to a vector");
 812       return error_mark_node;
 813     }
 814 }