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, 2007
   4    Free Software Foundation, Inc.
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 3, or (at your option) any later
  11 version.
  12
  13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  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 #include "fixed-value.h"
  37
  38 /* Convert EXPR to some pointer or reference type TYPE.
  39    EXPR must be pointer, reference, integer, enumeral, or literal zero;
  40    in other cases error is called.  */
  41
  42 tree
  43 convert_to_pointer (tree type, tree expr)
  44 {
  45   if (TREE_TYPE (expr) == type)
  46     return expr;
  47
  48   /* Propagate overflow to the NULL pointer.  */
  49   if (integer_zerop (expr))
  50     return force_fit_type_double (type, 0, 0, 0, TREE_OVERFLOW (expr));
  51
  52   switch (TREE_CODE (TREE_TYPE (expr)))
  53     {
  54     case POINTER_TYPE:
  55     case REFERENCE_TYPE:
  56       return fold_build1 (NOP_EXPR, type, expr);
  57
  58     case INTEGER_TYPE:
  59     case ENUMERAL_TYPE:
  60     case BOOLEAN_TYPE:
  61       if (TYPE_PRECISION (TREE_TYPE (expr)) != POINTER_SIZE)
  62         expr = fold_build1 (NOP_EXPR,
  63                             lang_hooks.types.type_for_size (POINTER_SIZE, 0),
  64                             expr);
  65       return fold_build1 (CONVERT_EXPR, type, expr);
  66
  67
  68     default:
  69       error ("cannot convert to a pointer type");
  70       return convert_to_pointer (type, integer_zero_node);
  71     }
  72 }
  73
  74 /* Avoid any floating point extensions from EXP.  */
  75 tree
  76 strip_float_extensions (tree exp)
  77 {
  78   tree sub, expt, subt;
  79
  80   /*  For floating point constant look up the narrowest type that can hold
  81       it properly and handle it like (type)(narrowest_type)constant.
  82       This way we can optimize for instance a=a*2.0 where "a" is float
  83       but 2.0 is double constant.  */
  84   if (TREE_CODE (exp) == REAL_CST && !DECIMAL_FLOAT_TYPE_P (TREE_TYPE (exp)))
  85     {
  86       REAL_VALUE_TYPE orig;
  87       tree type = NULL;
  88
  89       orig = TREE_REAL_CST (exp);
  90       if (TYPE_PRECISION (TREE_TYPE (exp)) > TYPE_PRECISION (float_type_node)
  91           && exact_real_truncate (TYPE_MODE (float_type_node), &orig))
  92         type = float_type_node;
  93       else if (TYPE_PRECISION (TREE_TYPE (exp))
  94                > TYPE_PRECISION (double_type_node)
  95                && exact_real_truncate (TYPE_MODE (double_type_node), &orig))
  96         type = double_type_node;
  97       if (type)
  98         return build_real (type, real_value_truncate (TYPE_MODE (type), orig));
  99     }
 100
 101   if (!CONVERT_EXPR_P (exp))
 102     return exp;
 103
 104   sub = TREE_OPERAND (exp, 0);
 105   subt = TREE_TYPE (sub);
 106   expt = TREE_TYPE (exp);
 107
 108   if (!FLOAT_TYPE_P (subt))
 109     return exp;
 110
 111   if (DECIMAL_FLOAT_TYPE_P (expt) != DECIMAL_FLOAT_TYPE_P (subt))
 112     return exp;
 113
 114   if (TYPE_PRECISION (subt) > TYPE_PRECISION (expt))
 115     return exp;
 116
 117   return strip_float_extensions (sub);
 118 }
 119
 120
 121 /* Convert EXPR to some floating-point type TYPE.
 122
 123    EXPR must be float, fixed-point, integer, or enumeral;
 124    in other cases error is called.  */
 125
 126 tree
 127 convert_to_real (tree type, tree expr)
 128 {
 129   enum built_in_function fcode = builtin_mathfn_code (expr);
 130   tree itype = TREE_TYPE (expr);
 131
 132   /* Disable until we figure out how to decide whether the functions are
 133      present in runtime.  */
 134   /* Convert (float)sqrt((double)x) where x is float into sqrtf(x) */
 135   if (optimize
 136       && (TYPE_MODE (type) == TYPE_MODE (double_type_node)
 137           || TYPE_MODE (type) == TYPE_MODE (float_type_node)))
 138     {
 139       switch (fcode)
 140         {
 141 #define CASE_MATHFN(FN) case BUILT_IN_##FN: case BUILT_IN_##FN##L:
 142           CASE_MATHFN (ACOS)
 143           CASE_MATHFN (ACOSH)
 144           CASE_MATHFN (ASIN)
 145           CASE_MATHFN (ASINH)
 146           CASE_MATHFN (ATAN)
 147           CASE_MATHFN (ATANH)
 148           CASE_MATHFN (CBRT)
 149           CASE_MATHFN (COS)
 150           CASE_MATHFN (COSH)
 151           CASE_MATHFN (ERF)
 152           CASE_MATHFN (ERFC)
 153           CASE_MATHFN (EXP)
 154           CASE_MATHFN (EXP10)
 155           CASE_MATHFN (EXP2)
 156           CASE_MATHFN (EXPM1)
 157           CASE_MATHFN (FABS)
 158           CASE_MATHFN (GAMMA)
 159           CASE_MATHFN (J0)
 160           CASE_MATHFN (J1)
 161           CASE_MATHFN (LGAMMA)
 162           CASE_MATHFN (LOG)
 163           CASE_MATHFN (LOG10)
 164           CASE_MATHFN (LOG1P)
 165           CASE_MATHFN (LOG2)
 166           CASE_MATHFN (LOGB)
 167           CASE_MATHFN (POW10)
 168           CASE_MATHFN (SIN)
 169           CASE_MATHFN (SINH)
 170           CASE_MATHFN (SQRT)
 171           CASE_MATHFN (TAN)
 172           CASE_MATHFN (TANH)
 173           CASE_MATHFN (TGAMMA)
 174           CASE_MATHFN (Y0)
 175           CASE_MATHFN (Y1)
 176 #undef CASE_MATHFN
 177             {
 178               tree arg0 = strip_float_extensions (CALL_EXPR_ARG (expr, 0));
 179               tree newtype = type;
 180
 181               /* We have (outertype)sqrt((innertype)x).  Choose the wider mode from
 182                  the both as the safe type for operation.  */
 183               if (TYPE_PRECISION (TREE_TYPE (arg0)) > TYPE_PRECISION (type))
 184                 newtype = TREE_TYPE (arg0);
 185
 186               /* Be careful about integer to fp conversions.
 187                  These may overflow still.  */
 188               if (FLOAT_TYPE_P (TREE_TYPE (arg0))
 189                   && TYPE_PRECISION (newtype) < TYPE_PRECISION (itype)
 190                   && (TYPE_MODE (newtype) == TYPE_MODE (double_type_node)
 191                       || TYPE_MODE (newtype) == TYPE_MODE (float_type_node)))
 192                 {
 193                   tree fn = mathfn_built_in (newtype, fcode);
 194
 195                   if (fn)
 196                   {
 197                     tree arg = fold (convert_to_real (newtype, arg0));
 198                     expr = build_call_expr (fn, 1, arg);
 199                     if (newtype == type)
 200                       return expr;
 201                   }
 202                 }
 203             }
 204         default:
 205           break;
 206         }
 207     }
 208   if (optimize
 209       && (((fcode == BUILT_IN_FLOORL
 210            || fcode == BUILT_IN_CEILL
 211            || fcode == BUILT_IN_ROUNDL
 212            || fcode == BUILT_IN_RINTL
 213            || fcode == BUILT_IN_TRUNCL
 214            || fcode == BUILT_IN_NEARBYINTL)
 215           && (TYPE_MODE (type) == TYPE_MODE (double_type_node)
 216               || TYPE_MODE (type) == TYPE_MODE (float_type_node)))
 217           || ((fcode == BUILT_IN_FLOOR
 218                || fcode == BUILT_IN_CEIL
 219                || fcode == BUILT_IN_ROUND
 220                || fcode == BUILT_IN_RINT
 221                || fcode == BUILT_IN_TRUNC
 222                || fcode == BUILT_IN_NEARBYINT)
 223               && (TYPE_MODE (type) == TYPE_MODE (float_type_node)))))
 224     {
 225       tree fn = mathfn_built_in (type, fcode);
 226
 227       if (fn)
 228         {
 229           tree arg = strip_float_extensions (CALL_EXPR_ARG (expr, 0));
 230
 231           /* Make sure (type)arg0 is an extension, otherwise we could end up
 232              changing (float)floor(double d) into floorf((float)d), which is
 233              incorrect because (float)d uses round-to-nearest and can round
 234              up to the next integer.  */
 235           if (TYPE_PRECISION (type) >= TYPE_PRECISION (TREE_TYPE (arg)))
 236             return build_call_expr (fn, 1, fold (convert_to_real (type, arg)));
 237         }
 238     }
 239
 240   /* Propagate the cast into the operation.  */
 241   if (itype != type && FLOAT_TYPE_P (type))
 242     switch (TREE_CODE (expr))
 243       {
 244         /* Convert (float)-x into -(float)x.  This is safe for
 245            round-to-nearest rounding mode.  */
 246         case ABS_EXPR:
 247         case NEGATE_EXPR:
 248           if (!flag_rounding_math
 249               && TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (expr)))
 250             return build1 (TREE_CODE (expr), type,
 251                            fold (convert_to_real (type,
 252                                                   TREE_OPERAND (expr, 0))));
 253           break;
 254         /* Convert (outertype)((innertype0)a+(innertype1)b)
 255            into ((newtype)a+(newtype)b) where newtype
 256            is the widest mode from all of these.  */
 257         case PLUS_EXPR:
 258         case MINUS_EXPR:
 259         case MULT_EXPR:
 260         case RDIV_EXPR:
 261            {
 262              tree arg0 = strip_float_extensions (TREE_OPERAND (expr, 0));
 263              tree arg1 = strip_float_extensions (TREE_OPERAND (expr, 1));
 264
 265              if (FLOAT_TYPE_P (TREE_TYPE (arg0))
 266                  && FLOAT_TYPE_P (TREE_TYPE (arg1))
 267                  && DECIMAL_FLOAT_TYPE_P (itype) == DECIMAL_FLOAT_TYPE_P (type))
 268                {
 269                   tree newtype = type;
 270
 271                   if (TYPE_MODE (TREE_TYPE (arg0)) == SDmode
 272                       || TYPE_MODE (TREE_TYPE (arg1)) == SDmode
 273                       || TYPE_MODE (type) == SDmode)
 274                     newtype = dfloat32_type_node;
 275                   if (TYPE_MODE (TREE_TYPE (arg0)) == DDmode
 276                       || TYPE_MODE (TREE_TYPE (arg1)) == DDmode
 277                       || TYPE_MODE (type) == DDmode)
 278                     newtype = dfloat64_type_node;
 279                   if (TYPE_MODE (TREE_TYPE (arg0)) == TDmode
 280                       || TYPE_MODE (TREE_TYPE (arg1)) == TDmode
 281                       || TYPE_MODE (type) == TDmode)
 282                     newtype = dfloat128_type_node;
 283                   if (newtype == dfloat32_type_node
 284                       || newtype == dfloat64_type_node
 285                       || newtype == dfloat128_type_node)
 286                     {
 287                       expr = build2 (TREE_CODE (expr), newtype,
 288                                      fold (convert_to_real (newtype, arg0)),
 289                                      fold (convert_to_real (newtype, arg1)));
 290                       if (newtype == type)
 291                         return expr;
 292                       break;
 293                     }
 294
 295                   if (TYPE_PRECISION (TREE_TYPE (arg0)) > TYPE_PRECISION (newtype))
 296                     newtype = TREE_TYPE (arg0);
 297                   if (TYPE_PRECISION (TREE_TYPE (arg1)) > TYPE_PRECISION (newtype))
 298                     newtype = TREE_TYPE (arg1);
 299                   /* Sometimes this transformation is safe (cannot
 300                      change results through affecting double rounding
 301                      cases) and sometimes it is not.  If NEWTYPE is
 302                      wider than TYPE, e.g. (float)((long double)double
 303                      + (long double)double) converted to
 304                      (float)(double + double), the transformation is
 305                      unsafe regardless of the details of the types
 306                      involved; double rounding can arise if the result
 307                      of NEWTYPE arithmetic is a NEWTYPE value half way
 308                      between two representable TYPE values but the
 309                      exact value is sufficiently different (in the
 310                      right direction) for this difference to be
 311                      visible in ITYPE arithmetic.  If NEWTYPE is the
 312                      same as TYPE, however, the transformation may be
 313                      safe depending on the types involved: it is safe
 314                      if the ITYPE has strictly more than twice as many
 315                      mantissa bits as TYPE, can represent infinities
 316                      and NaNs if the TYPE can, and has sufficient
 317                      exponent range for the product or ratio of two
 318                      values representable in the TYPE to be within the
 319                      range of normal values of ITYPE.  */
 320                   if (TYPE_PRECISION (newtype) < TYPE_PRECISION (itype)
 321                       && (flag_unsafe_math_optimizations
 322                           || (TYPE_PRECISION (newtype) == TYPE_PRECISION (type)
 323                               && real_can_shorten_arithmetic (TYPE_MODE (itype),
 324                                                               TYPE_MODE (type)))))
 325                     {
 326                       expr = build2 (TREE_CODE (expr), newtype,
 327                                      fold (convert_to_real (newtype, arg0)),
 328                                      fold (convert_to_real (newtype, arg1)));
 329                       if (newtype == type)
 330                         return expr;
 331                     }
 332                }
 333            }
 334           break;
 335         default:
 336           break;
 337       }
 338
 339   switch (TREE_CODE (TREE_TYPE (expr)))
 340     {
 341     case REAL_TYPE:
 342       /* Ignore the conversion if we don't need to store intermediate
 343          results and neither type is a decimal float.  */
 344       return build1 ((flag_float_store
 345                      || DECIMAL_FLOAT_TYPE_P (type)
 346                      || DECIMAL_FLOAT_TYPE_P (itype))
 347                      ? CONVERT_EXPR : NOP_EXPR, type, expr);
 348
 349     case INTEGER_TYPE:
 350     case ENUMERAL_TYPE:
 351     case BOOLEAN_TYPE:
 352       return build1 (FLOAT_EXPR, type, expr);
 353
 354     case FIXED_POINT_TYPE:
 355       return build1 (FIXED_CONVERT_EXPR, type, expr);
 356
 357     case COMPLEX_TYPE:
 358       return convert (type,
 359                       fold_build1 (REALPART_EXPR,
 360                                    TREE_TYPE (TREE_TYPE (expr)), expr));
 361
 362     case POINTER_TYPE:
 363     case REFERENCE_TYPE:
 364       error ("pointer value used where a floating point value was expected");
 365       return convert_to_real (type, integer_zero_node);
 366
 367     default:
 368       error ("aggregate value used where a float was expected");
 369       return convert_to_real (type, integer_zero_node);
 370     }
 371 }
 372
 373 /* Convert EXPR to some integer (or enum) type TYPE.
 374
 375    EXPR must be pointer, integer, discrete (enum, char, or bool), float,
 376    fixed-point or vector; in other cases error is called.
 377
 378    The result of this is always supposed to be a newly created tree node
 379    not in use in any existing structure.  */
 380
 381 tree
 382 convert_to_integer (tree type, tree expr)
 383 {
 384   enum tree_code ex_form = TREE_CODE (expr);
 385   tree intype = TREE_TYPE (expr);
 386   unsigned int inprec = TYPE_PRECISION (intype);
 387   unsigned int outprec = TYPE_PRECISION (type);
 388
 389   /* An INTEGER_TYPE cannot be incomplete, but an ENUMERAL_TYPE can
 390      be.  Consider `enum E = { a, b = (enum E) 3 };'.  */
 391   if (!COMPLETE_TYPE_P (type))
 392     {
 393       error ("conversion to incomplete type");
 394       return error_mark_node;
 395     }
 396
 397   /* Convert e.g. (long)round(d) -> lround(d).  */
 398   /* If we're converting to char, we may encounter differing behavior
 399      between converting from double->char vs double->long->char.
 400      We're in "undefined" territory but we prefer to be conservative,
 401      so only proceed in "unsafe" math mode.  */
 402   if (optimize
 403       && (flag_unsafe_math_optimizations
 404           || (long_integer_type_node
 405               && outprec >= TYPE_PRECISION (long_integer_type_node))))
 406     {
 407       tree s_expr = strip_float_extensions (expr);
 408       tree s_intype = TREE_TYPE (s_expr);
 409       const enum built_in_function fcode = builtin_mathfn_code (s_expr);
 410       tree fn = 0;
 411
 412       switch (fcode)
 413         {
 414         CASE_FLT_FN (BUILT_IN_CEIL):
 415           /* Only convert in ISO C99 mode.  */
 416           if (!TARGET_C99_FUNCTIONS)
 417             break;
 418           if (outprec < TYPE_PRECISION (long_integer_type_node)
 419               || (outprec == TYPE_PRECISION (long_integer_type_node)
 420                   && !TYPE_UNSIGNED (type)))
 421             fn = mathfn_built_in (s_intype, BUILT_IN_LCEIL);
 422           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 423                    && !TYPE_UNSIGNED (type))
 424             fn = mathfn_built_in (s_intype, BUILT_IN_LLCEIL);
 425           break;
 426
 427         CASE_FLT_FN (BUILT_IN_FLOOR):
 428           /* Only convert in ISO C99 mode.  */
 429           if (!TARGET_C99_FUNCTIONS)
 430             break;
 431           if (outprec < TYPE_PRECISION (long_integer_type_node)
 432               || (outprec == TYPE_PRECISION (long_integer_type_node)
 433                   && !TYPE_UNSIGNED (type)))
 434             fn = mathfn_built_in (s_intype, BUILT_IN_LFLOOR);
 435           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 436                    && !TYPE_UNSIGNED (type))
 437             fn = mathfn_built_in (s_intype, BUILT_IN_LLFLOOR);
 438           break;
 439
 440         CASE_FLT_FN (BUILT_IN_ROUND):
 441           if (outprec < TYPE_PRECISION (long_integer_type_node)
 442               || (outprec == TYPE_PRECISION (long_integer_type_node)
 443                   && !TYPE_UNSIGNED (type)))
 444             fn = mathfn_built_in (s_intype, BUILT_IN_LROUND);
 445           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 446                    && !TYPE_UNSIGNED (type))
 447             fn = mathfn_built_in (s_intype, BUILT_IN_LLROUND);
 448           break;
 449
 450         CASE_FLT_FN (BUILT_IN_NEARBYINT):
 451           /* Only convert nearbyint* if we can ignore math exceptions.  */
 452           if (flag_trapping_math)
 453             break;
 454           /* ... Fall through ...  */
 455         CASE_FLT_FN (BUILT_IN_RINT):
 456           if (outprec < TYPE_PRECISION (long_integer_type_node)
 457               || (outprec == TYPE_PRECISION (long_integer_type_node)
 458                   && !TYPE_UNSIGNED (type)))
 459             fn = mathfn_built_in (s_intype, BUILT_IN_LRINT);
 460           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 461                    && !TYPE_UNSIGNED (type))
 462             fn = mathfn_built_in (s_intype, BUILT_IN_LLRINT);
 463           break;
 464
 465         CASE_FLT_FN (BUILT_IN_TRUNC):
 466           return convert_to_integer (type, CALL_EXPR_ARG (s_expr, 0));
 467
 468         default:
 469           break;
 470         }
 471
 472       if (fn)
 473         {
 474           tree newexpr = build_call_expr (fn, 1, CALL_EXPR_ARG (s_expr, 0));
 475           return convert_to_integer (type, newexpr);
 476         }
 477     }
 478
 479   switch (TREE_CODE (intype))
 480     {
 481     case POINTER_TYPE:
 482     case REFERENCE_TYPE:
 483       if (integer_zerop (expr))
 484         return build_int_cst (type, 0);
 485
 486       /* Convert to an unsigned integer of the correct width first,
 487          and from there widen/truncate to the required type.  */
 488       expr = fold_build1 (CONVERT_EXPR,
 489                           lang_hooks.types.type_for_size (POINTER_SIZE, 0),
 490                           expr);
 491       return fold_convert (type, expr);
 492
 493     case INTEGER_TYPE:
 494     case ENUMERAL_TYPE:
 495     case BOOLEAN_TYPE:
 496       /* If this is a logical operation, which just returns 0 or 1, we can
 497          change the type of the expression.  */
 498
 499       if (TREE_CODE_CLASS (ex_form) == tcc_comparison)
 500         {
 501           expr = copy_node (expr);
 502           TREE_TYPE (expr) = type;
 503           return expr;
 504         }
 505
 506       /* If we are widening the type, put in an explicit conversion.
 507          Similarly if we are not changing the width.  After this, we know
 508          we are truncating EXPR.  */
 509
 510       else if (outprec >= inprec)
 511         {
 512           enum tree_code code;
 513           tree tem;
 514
 515           /* If the precision of the EXPR's type is K bits and the
 516              destination mode has more bits, and the sign is changing,
 517              it is not safe to use a NOP_EXPR.  For example, suppose
 518              that EXPR's type is a 3-bit unsigned integer type, the
 519              TYPE is a 3-bit signed integer type, and the machine mode
 520              for the types is 8-bit QImode.  In that case, the
 521              conversion necessitates an explicit sign-extension.  In
 522              the signed-to-unsigned case the high-order bits have to
 523              be cleared.  */
 524           if (TYPE_UNSIGNED (type) != TYPE_UNSIGNED (TREE_TYPE (expr))
 525               && (TYPE_PRECISION (TREE_TYPE (expr))
 526                   != GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (expr)))))
 527             code = CONVERT_EXPR;
 528           else
 529             code = NOP_EXPR;
 530
 531           tem = fold_unary (code, type, expr);
 532           if (tem)
 533             return tem;
 534
 535           tem = build1 (code, type, expr);
 536           TREE_NO_WARNING (tem) = 1;
 537           return tem;
 538         }
 539
 540       /* If TYPE is an enumeral type or a type with a precision less
 541          than the number of bits in its mode, do the conversion to the
 542          type corresponding to its mode, then do a nop conversion
 543          to TYPE.  */
 544       else if (TREE_CODE (type) == ENUMERAL_TYPE
 545                || outprec != GET_MODE_BITSIZE (TYPE_MODE (type)))
 546         return build1 (NOP_EXPR, type,
 547                        convert (lang_hooks.types.type_for_mode
 548                                 (TYPE_MODE (type), TYPE_UNSIGNED (type)),
 549                                 expr));
 550
 551       /* Here detect when we can distribute the truncation down past some
 552          arithmetic.  For example, if adding two longs and converting to an
 553          int, we can equally well convert both to ints and then add.
 554          For the operations handled here, such truncation distribution
 555          is always safe.
 556          It is desirable in these cases:
 557          1) when truncating down to full-word from a larger size
 558          2) when truncating takes no work.
 559          3) when at least one operand of the arithmetic has been extended
 560          (as by C's default conversions).  In this case we need two conversions
 561          if we do the arithmetic as already requested, so we might as well
 562          truncate both and then combine.  Perhaps that way we need only one.
 563
 564          Note that in general we cannot do the arithmetic in a type
 565          shorter than the desired result of conversion, even if the operands
 566          are both extended from a shorter type, because they might overflow
 567          if combined in that type.  The exceptions to this--the times when
 568          two narrow values can be combined in their narrow type even to
 569          make a wider result--are handled by "shorten" in build_binary_op.  */
 570
 571       switch (ex_form)
 572         {
 573         case RSHIFT_EXPR:
 574           /* We can pass truncation down through right shifting
 575              when the shift count is a nonpositive constant.  */
 576           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 577               && tree_int_cst_sgn (TREE_OPERAND (expr, 1)) <= 0)
 578             goto trunc1;
 579           break;
 580
 581         case LSHIFT_EXPR:
 582           /* We can pass truncation down through left shifting
 583              when the shift count is a nonnegative constant and
 584              the target type is unsigned.  */
 585           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 586               && tree_int_cst_sgn (TREE_OPERAND (expr, 1)) >= 0
 587               && TYPE_UNSIGNED (type)
 588               && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
 589             {
 590               /* If shift count is less than the width of the truncated type,
 591                  really shift.  */
 592               if (tree_int_cst_lt (TREE_OPERAND (expr, 1), TYPE_SIZE (type)))
 593                 /* In this case, shifting is like multiplication.  */
 594                 goto trunc1;
 595               else
 596                 {
 597                   /* If it is >= that width, result is zero.
 598                      Handling this with trunc1 would give the wrong result:
 599                      (int) ((long long) a << 32) is well defined (as 0)
 600                      but (int) a << 32 is undefined and would get a
 601                      warning.  */
 602
 603                   tree t = build_int_cst (type, 0);
 604
 605                   /* If the original expression had side-effects, we must
 606                      preserve it.  */
 607                   if (TREE_SIDE_EFFECTS (expr))
 608                     return build2 (COMPOUND_EXPR, type, expr, t);
 609                   else
 610                     return t;
 611                 }
 612             }
 613           break;
 614
 615         case MAX_EXPR:
 616         case MIN_EXPR:
 617         case MULT_EXPR:
 618           {
 619             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 620             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 621
 622             /* Don't distribute unless the output precision is at least as big
 623                as the actual inputs.  Otherwise, the comparison of the
 624                truncated values will be wrong.  */
 625             if (outprec >= TYPE_PRECISION (TREE_TYPE (arg0))
 626                 && outprec >= TYPE_PRECISION (TREE_TYPE (arg1))
 627                 /* If signedness of arg0 and arg1 don't match,
 628                    we can't necessarily find a type to compare them in.  */
 629                 && (TYPE_UNSIGNED (TREE_TYPE (arg0))
 630                     == TYPE_UNSIGNED (TREE_TYPE (arg1))))
 631               goto trunc1;
 632             break;
 633           }
 634
 635         case PLUS_EXPR:
 636         case MINUS_EXPR:
 637         case BIT_AND_EXPR:
 638         case BIT_IOR_EXPR:
 639         case BIT_XOR_EXPR:
 640         trunc1:
 641           {
 642             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 643             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 644
 645             if (outprec >= BITS_PER_WORD
 646                 || TRULY_NOOP_TRUNCATION (outprec, inprec)
 647                 || inprec > TYPE_PRECISION (TREE_TYPE (arg0))
 648                 || inprec > TYPE_PRECISION (TREE_TYPE (arg1)))
 649               {
 650                 /* Do the arithmetic in type TYPEX,
 651                    then convert result to TYPE.  */
 652                 tree typex = type;
 653
 654                 /* Can't do arithmetic in enumeral types
 655                    so use an integer type that will hold the values.  */
 656                 if (TREE_CODE (typex) == ENUMERAL_TYPE)
 657                   typex = lang_hooks.types.type_for_size
 658                     (TYPE_PRECISION (typex), TYPE_UNSIGNED (typex));
 659
 660                 /* But now perhaps TYPEX is as wide as INPREC.
 661                    In that case, do nothing special here.
 662                    (Otherwise would recurse infinitely in convert.  */
 663                 if (TYPE_PRECISION (typex) != inprec)
 664                   {
 665                     /* Don't do unsigned arithmetic where signed was wanted,
 666                        or vice versa.
 667                        Exception: if both of the original operands were
 668                        unsigned then we can safely do the work as unsigned.
 669                        Exception: shift operations take their type solely
 670                        from the first argument.
 671                        Exception: the LSHIFT_EXPR case above requires that
 672                        we perform this operation unsigned lest we produce
 673                        signed-overflow undefinedness.
 674                        And we may need to do it as unsigned
 675                        if we truncate to the original size.  */
 676                     if (TYPE_UNSIGNED (TREE_TYPE (expr))
 677                         || (TYPE_UNSIGNED (TREE_TYPE (arg0))
 678                             && (TYPE_UNSIGNED (TREE_TYPE (arg1))
 679                                 || ex_form == LSHIFT_EXPR
 680                                 || ex_form == RSHIFT_EXPR
 681                                 || ex_form == LROTATE_EXPR
 682                                 || ex_form == RROTATE_EXPR))
 683                         || ex_form == LSHIFT_EXPR
 684                         /* If we have !flag_wrapv, and either ARG0 or
 685                            ARG1 is of a signed type, we have to do
 686                            PLUS_EXPR or MINUS_EXPR in an unsigned
 687                            type.  Otherwise, we would introduce
 688                            signed-overflow undefinedness.  */
 689                         || ((!TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg0))
 690                              || !TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg1)))
 691                             && (ex_form == PLUS_EXPR
 692                                 || ex_form == MINUS_EXPR)))
 693                       typex = unsigned_type_for (typex);
 694                     else
 695                       typex = signed_type_for (typex);
 696                     return convert (type,
 697                                     fold_build2 (ex_form, typex,
 698                                                  convert (typex, arg0),
 699                                                  convert (typex, arg1)));
 700                   }
 701               }
 702           }
 703           break;
 704
 705         case NEGATE_EXPR:
 706         case BIT_NOT_EXPR:
 707           /* This is not correct for ABS_EXPR,
 708              since we must test the sign before truncation.  */
 709           {
 710             tree typex;
 711
 712             /* Don't do unsigned arithmetic where signed was wanted,
 713                or vice versa.  */
 714             if (TYPE_UNSIGNED (TREE_TYPE (expr)))
 715               typex = unsigned_type_for (type);
 716             else
 717               typex = signed_type_for (type);
 718             return convert (type,
 719                             fold_build1 (ex_form, typex,
 720                                          convert (typex,
 721                                                   TREE_OPERAND (expr, 0))));
 722           }
 723
 724         case NOP_EXPR:
 725           /* Don't introduce a
 726              "can't convert between vector values of different size" error.  */
 727           if (TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0))) == VECTOR_TYPE
 728               && (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_OPERAND (expr, 0))))
 729                   != GET_MODE_SIZE (TYPE_MODE (type))))
 730             break;
 731           /* If truncating after truncating, might as well do all at once.
 732              If truncating after extending, we may get rid of wasted work.  */
 733           return convert (type, get_unwidened (TREE_OPERAND (expr, 0), type));
 734
 735         case COND_EXPR:
 736           /* It is sometimes worthwhile to push the narrowing down through
 737              the conditional and never loses.  */
 738           return fold_build3 (COND_EXPR, type, TREE_OPERAND (expr, 0),
 739                               convert (type, TREE_OPERAND (expr, 1)),
 740                               convert (type, TREE_OPERAND (expr, 2)));
 741
 742         default:
 743           break;
 744         }
 745
 746       return build1 (CONVERT_EXPR, type, expr);
 747
 748     case REAL_TYPE:
 749       return build1 (FIX_TRUNC_EXPR, type, expr);
 750
 751     case FIXED_POINT_TYPE:
 752       return build1 (FIXED_CONVERT_EXPR, type, expr);
 753
 754     case COMPLEX_TYPE:
 755       return convert (type,
 756                       fold_build1 (REALPART_EXPR,
 757                                    TREE_TYPE (TREE_TYPE (expr)), expr));
 758
 759     case VECTOR_TYPE:
 760       if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr))))
 761         {
 762           error ("can't convert between vector values of different size");
 763           return error_mark_node;
 764         }
 765       return build1 (VIEW_CONVERT_EXPR, type, expr);
 766
 767     default:
 768       error ("aggregate value used where an integer was expected");
 769       return convert (type, integer_zero_node);
 770     }
 771 }
 772
 773 /* Convert EXPR to the complex type TYPE in the usual ways.  */
 774
 775 tree
 776 convert_to_complex (tree type, tree expr)
 777 {
 778   tree subtype = TREE_TYPE (type);
 779
 780   switch (TREE_CODE (TREE_TYPE (expr)))
 781     {
 782     case REAL_TYPE:
 783     case FIXED_POINT_TYPE:
 784     case INTEGER_TYPE:
 785     case ENUMERAL_TYPE:
 786     case BOOLEAN_TYPE:
 787       return build2 (COMPLEX_EXPR, type, convert (subtype, expr),
 788                      convert (subtype, integer_zero_node));
 789
 790     case COMPLEX_TYPE:
 791       {
 792         tree elt_type = TREE_TYPE (TREE_TYPE (expr));
 793
 794         if (TYPE_MAIN_VARIANT (elt_type) == TYPE_MAIN_VARIANT (subtype))
 795           return expr;
 796         else if (TREE_CODE (expr) == COMPLEX_EXPR)
 797           return fold_build2 (COMPLEX_EXPR, type,
 798                               convert (subtype, TREE_OPERAND (expr, 0)),
 799                               convert (subtype, TREE_OPERAND (expr, 1)));
 800         else
 801           {
 802             expr = save_expr (expr);
 803             return
 804               fold_build2 (COMPLEX_EXPR, type,
 805                            convert (subtype,
 806                                     fold_build1 (REALPART_EXPR,
 807                                                  TREE_TYPE (TREE_TYPE (expr)),
 808                                                  expr)),
 809                            convert (subtype,
 810                                     fold_build1 (IMAGPART_EXPR,
 811                                                  TREE_TYPE (TREE_TYPE (expr)),
 812                                                  expr)));
 813           }
 814       }
 815
 816     case POINTER_TYPE:
 817     case REFERENCE_TYPE:
 818       error ("pointer value used where a complex was expected");
 819       return convert_to_complex (type, integer_zero_node);
 820
 821     default:
 822       error ("aggregate value used where a complex was expected");
 823       return convert_to_complex (type, integer_zero_node);
 824     }
 825 }
 826
 827 /* Convert EXPR to the vector type TYPE in the usual ways.  */
 828
 829 tree
 830 convert_to_vector (tree type, tree expr)
 831 {
 832   switch (TREE_CODE (TREE_TYPE (expr)))
 833     {
 834     case INTEGER_TYPE:
 835     case VECTOR_TYPE:
 836       if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr))))
 837         {
 838           error ("can't convert between vector values of different size");
 839           return error_mark_node;
 840         }
 841       return build1 (VIEW_CONVERT_EXPR, type, expr);
 842
 843     default:
 844       error ("can't convert value to a vector");
 845       return error_mark_node;
 846     }
 847 }
 848
 849 /* Convert EXPR to some fixed-point type TYPE.
 850
 851    EXPR must be fixed-point, float, integer, or enumeral;
 852    in other cases error is called.  */
 853
 854 tree
 855 convert_to_fixed (tree type, tree expr)
 856 {
 857   if (integer_zerop (expr))
 858     {
 859       tree fixed_zero_node = build_fixed (type, FCONST0 (TYPE_MODE (type)));
 860       return fixed_zero_node;
 861     }
 862   else if (integer_onep (expr) && ALL_SCALAR_ACCUM_MODE_P (TYPE_MODE (type)))
 863     {
 864       tree fixed_one_node = build_fixed (type, FCONST1 (TYPE_MODE (type)));
 865       return fixed_one_node;
 866     }
 867
 868   switch (TREE_CODE (TREE_TYPE (expr)))
 869     {
 870     case FIXED_POINT_TYPE:
 871     case INTEGER_TYPE:
 872     case ENUMERAL_TYPE:
 873     case BOOLEAN_TYPE:
 874     case REAL_TYPE:
 875       return build1 (FIXED_CONVERT_EXPR, type, expr);
 876
 877     case COMPLEX_TYPE:
 878       return convert (type,
 879                       fold_build1 (REALPART_EXPR,
 880                                    TREE_TYPE (TREE_TYPE (expr)), expr));
 881
 882     default:
 883       error ("aggregate value used where a fixed-point was expected");
 884       return error_mark_node;
 885     }
 886 }