gcc/convert.c

   1 /* Utility routines for data type conversion for GCC.
   2    Copyright (C) 1987-2013 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20
  21 /* 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 "system.h"
  26 #include "coretypes.h"
  27 #include "tm.h"
  28 #include "tree.h"
  29 #include "stor-layout.h"
  30 #include "flags.h"
  31 #include "convert.h"
  32 #include "diagnostic-core.h"
  33 #include "target.h"
  34 #include "langhooks.h"
  35
  36 /* Convert EXPR to some pointer or reference type TYPE.
  37    EXPR must be pointer, reference, integer, enumeral, or literal zero;
  38    in other cases error is called.  */
  39
  40 tree
  41 convert_to_pointer (tree type, tree expr)
  42 {
  43   location_t loc = EXPR_LOCATION (expr);
  44   if (TREE_TYPE (expr) == type)
  45     return expr;
  46
  47   switch (TREE_CODE (TREE_TYPE (expr)))
  48     {
  49     case POINTER_TYPE:
  50     case REFERENCE_TYPE:
  51       {
  52         /* If the pointers point to different address spaces, conversion needs
  53            to be done via a ADDR_SPACE_CONVERT_EXPR instead of a NOP_EXPR.  */
  54         addr_space_t to_as = TYPE_ADDR_SPACE (TREE_TYPE (type));
  55         addr_space_t from_as = TYPE_ADDR_SPACE (TREE_TYPE (TREE_TYPE (expr)));
  56
  57         if (to_as == from_as)
  58           return fold_build1_loc (loc, NOP_EXPR, type, expr);
  59         else
  60           return fold_build1_loc (loc, ADDR_SPACE_CONVERT_EXPR, type, expr);
  61       }
  62
  63     case INTEGER_TYPE:
  64     case ENUMERAL_TYPE:
  65     case BOOLEAN_TYPE:
  66       {
  67         /* If the input precision differs from the target pointer type
  68            precision, first convert the input expression to an integer type of
  69            the target precision.  Some targets, e.g. VMS, need several pointer
  70            sizes to coexist so the latter isn't necessarily POINTER_SIZE.  */
  71         unsigned int pprec = TYPE_PRECISION (type);
  72         unsigned int eprec = TYPE_PRECISION (TREE_TYPE (expr));
  73
  74         if (eprec != pprec)
  75           expr = fold_build1_loc (loc, NOP_EXPR,
  76                               lang_hooks.types.type_for_size (pprec, 0),
  77                               expr);
  78       }
  79
  80       return fold_build1_loc (loc, CONVERT_EXPR, type, expr);
  81
  82     default:
  83       error ("cannot convert to a pointer type");
  84       return convert_to_pointer (type, integer_zero_node);
  85     }
  86 }
  87
  88
  89 /* Convert EXPR to some floating-point type TYPE.
  90
  91    EXPR must be float, fixed-point, integer, or enumeral;
  92    in other cases error is called.  */
  93
  94 tree
  95 convert_to_real (tree type, tree expr)
  96 {
  97   enum built_in_function fcode = builtin_mathfn_code (expr);
  98   tree itype = TREE_TYPE (expr);
  99
 100   /* Disable until we figure out how to decide whether the functions are
 101      present in runtime.  */
 102   /* Convert (float)sqrt((double)x) where x is float into sqrtf(x) */
 103   if (optimize
 104       && (TYPE_MODE (type) == TYPE_MODE (double_type_node)
 105           || TYPE_MODE (type) == TYPE_MODE (float_type_node)))
 106     {
 107       switch (fcode)
 108         {
 109 #define CASE_MATHFN(FN) case BUILT_IN_##FN: case BUILT_IN_##FN##L:
 110           CASE_MATHFN (COSH)
 111           CASE_MATHFN (EXP)
 112           CASE_MATHFN (EXP10)
 113           CASE_MATHFN (EXP2)
 114           CASE_MATHFN (EXPM1)
 115           CASE_MATHFN (GAMMA)
 116           CASE_MATHFN (J0)
 117           CASE_MATHFN (J1)
 118           CASE_MATHFN (LGAMMA)
 119           CASE_MATHFN (POW10)
 120           CASE_MATHFN (SINH)
 121           CASE_MATHFN (TGAMMA)
 122           CASE_MATHFN (Y0)
 123           CASE_MATHFN (Y1)
 124             /* The above functions may set errno differently with float
 125                input or output so this transformation is not safe with
 126                -fmath-errno.  */
 127             if (flag_errno_math)
 128               break;
 129           CASE_MATHFN (ACOS)
 130           CASE_MATHFN (ACOSH)
 131           CASE_MATHFN (ASIN)
 132           CASE_MATHFN (ASINH)
 133           CASE_MATHFN (ATAN)
 134           CASE_MATHFN (ATANH)
 135           CASE_MATHFN (CBRT)
 136           CASE_MATHFN (COS)
 137           CASE_MATHFN (ERF)
 138           CASE_MATHFN (ERFC)
 139           CASE_MATHFN (LOG)
 140           CASE_MATHFN (LOG10)
 141           CASE_MATHFN (LOG2)
 142           CASE_MATHFN (LOG1P)
 143           CASE_MATHFN (SIN)
 144           CASE_MATHFN (TAN)
 145           CASE_MATHFN (TANH)
 146             /* The above functions are not safe to do this conversion.  */
 147             if (!flag_unsafe_math_optimizations)
 148               break;
 149           CASE_MATHFN (SQRT)
 150           CASE_MATHFN (FABS)
 151           CASE_MATHFN (LOGB)
 152 #undef CASE_MATHFN
 153             {
 154               tree arg0 = strip_float_extensions (CALL_EXPR_ARG (expr, 0));
 155               tree newtype = type;
 156
 157               /* We have (outertype)sqrt((innertype)x).  Choose the wider mode from
 158                  the both as the safe type for operation.  */
 159               if (TYPE_PRECISION (TREE_TYPE (arg0)) > TYPE_PRECISION (type))
 160                 newtype = TREE_TYPE (arg0);
 161
 162               /* We consider to convert
 163
 164                      (T1) sqrtT2 ((T2) exprT3)
 165                  to
 166                      (T1) sqrtT4 ((T4) exprT3)
 167
 168                   , where T1 is TYPE, T2 is ITYPE, T3 is TREE_TYPE (ARG0),
 169                  and T4 is NEWTYPE.  All those types are of floating point types.
 170                  T4 (NEWTYPE) should be narrower than T2 (ITYPE). This conversion
 171                  is safe only if P1 >= P2*2+2, where P1 and P2 are precisions of
 172                  T2 and T4.  See the following URL for a reference:
 173                  http://stackoverflow.com/questions/9235456/determining-
 174                  floating-point-square-root
 175                  */
 176               if ((fcode == BUILT_IN_SQRT || fcode == BUILT_IN_SQRTL)
 177                   && !flag_unsafe_math_optimizations)
 178                 {
 179                   /* The following conversion is unsafe even the precision condition
 180                      below is satisfied:
 181
 182                      (float) sqrtl ((long double) double_val) -> (float) sqrt (double_val)
 183                     */
 184                   if (TYPE_MODE (type) != TYPE_MODE (newtype))
 185                     break;
 186
 187                   int p1 = REAL_MODE_FORMAT (TYPE_MODE (itype))->p;
 188                   int p2 = REAL_MODE_FORMAT (TYPE_MODE (newtype))->p;
 189                   if (p1 < p2 * 2 + 2)
 190                     break;
 191                 }
 192
 193               /* Be careful about integer to fp conversions.
 194                  These may overflow still.  */
 195               if (FLOAT_TYPE_P (TREE_TYPE (arg0))
 196                   && TYPE_PRECISION (newtype) < TYPE_PRECISION (itype)
 197                   && (TYPE_MODE (newtype) == TYPE_MODE (double_type_node)
 198                       || TYPE_MODE (newtype) == TYPE_MODE (float_type_node)))
 199                 {
 200                   tree fn = mathfn_built_in (newtype, fcode);
 201
 202                   if (fn)
 203                   {
 204                     tree arg = fold (convert_to_real (newtype, arg0));
 205                     expr = build_call_expr (fn, 1, arg);
 206                     if (newtype == type)
 207                       return expr;
 208                   }
 209                 }
 210             }
 211         default:
 212           break;
 213         }
 214     }
 215   if (optimize
 216       && (((fcode == BUILT_IN_FLOORL
 217            || fcode == BUILT_IN_CEILL
 218            || fcode == BUILT_IN_ROUNDL
 219            || fcode == BUILT_IN_RINTL
 220            || fcode == BUILT_IN_TRUNCL
 221            || fcode == BUILT_IN_NEARBYINTL)
 222           && (TYPE_MODE (type) == TYPE_MODE (double_type_node)
 223               || TYPE_MODE (type) == TYPE_MODE (float_type_node)))
 224           || ((fcode == BUILT_IN_FLOOR
 225                || fcode == BUILT_IN_CEIL
 226                || fcode == BUILT_IN_ROUND
 227                || fcode == BUILT_IN_RINT
 228                || fcode == BUILT_IN_TRUNC
 229                || fcode == BUILT_IN_NEARBYINT)
 230               && (TYPE_MODE (type) == TYPE_MODE (float_type_node)))))
 231     {
 232       tree fn = mathfn_built_in (type, fcode);
 233
 234       if (fn)
 235         {
 236           tree arg = strip_float_extensions (CALL_EXPR_ARG (expr, 0));
 237
 238           /* Make sure (type)arg0 is an extension, otherwise we could end up
 239              changing (float)floor(double d) into floorf((float)d), which is
 240              incorrect because (float)d uses round-to-nearest and can round
 241              up to the next integer.  */
 242           if (TYPE_PRECISION (type) >= TYPE_PRECISION (TREE_TYPE (arg)))
 243             return build_call_expr (fn, 1, 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 safe for
 252            round-to-nearest rounding mode when the inner type is float.  */
 253         case ABS_EXPR:
 254         case NEGATE_EXPR:
 255           if (!flag_rounding_math
 256               && FLOAT_TYPE_P (itype)
 257               && TYPE_PRECISION (type) < TYPE_PRECISION (itype))
 258             return build1 (TREE_CODE (expr), type,
 259                            fold (convert_to_real (type,
 260                                                   TREE_OPERAND (expr, 0))));
 261           break;
 262         /* Convert (outertype)((innertype0)a+(innertype1)b)
 263            into ((newtype)a+(newtype)b) where newtype
 264            is the widest mode from all of these.  */
 265         case PLUS_EXPR:
 266         case MINUS_EXPR:
 267         case MULT_EXPR:
 268         case RDIV_EXPR:
 269            {
 270              tree arg0 = strip_float_extensions (TREE_OPERAND (expr, 0));
 271              tree arg1 = strip_float_extensions (TREE_OPERAND (expr, 1));
 272
 273              if (FLOAT_TYPE_P (TREE_TYPE (arg0))
 274                  && FLOAT_TYPE_P (TREE_TYPE (arg1))
 275                  && DECIMAL_FLOAT_TYPE_P (itype) == DECIMAL_FLOAT_TYPE_P (type))
 276                {
 277                   tree newtype = type;
 278
 279                   if (TYPE_MODE (TREE_TYPE (arg0)) == SDmode
 280                       || TYPE_MODE (TREE_TYPE (arg1)) == SDmode
 281                       || TYPE_MODE (type) == SDmode)
 282                     newtype = dfloat32_type_node;
 283                   if (TYPE_MODE (TREE_TYPE (arg0)) == DDmode
 284                       || TYPE_MODE (TREE_TYPE (arg1)) == DDmode
 285                       || TYPE_MODE (type) == DDmode)
 286                     newtype = dfloat64_type_node;
 287                   if (TYPE_MODE (TREE_TYPE (arg0)) == TDmode
 288                       || TYPE_MODE (TREE_TYPE (arg1)) == TDmode
 289                       || TYPE_MODE (type) == TDmode)
 290                     newtype = dfloat128_type_node;
 291                   if (newtype == dfloat32_type_node
 292                       || newtype == dfloat64_type_node
 293                       || newtype == dfloat128_type_node)
 294                     {
 295                       expr = build2 (TREE_CODE (expr), newtype,
 296                                      fold (convert_to_real (newtype, arg0)),
 297                                      fold (convert_to_real (newtype, arg1)));
 298                       if (newtype == type)
 299                         return expr;
 300                       break;
 301                     }
 302
 303                   if (TYPE_PRECISION (TREE_TYPE (arg0)) > TYPE_PRECISION (newtype))
 304                     newtype = TREE_TYPE (arg0);
 305                   if (TYPE_PRECISION (TREE_TYPE (arg1)) > TYPE_PRECISION (newtype))
 306                     newtype = TREE_TYPE (arg1);
 307                   /* Sometimes this transformation is safe (cannot
 308                      change results through affecting double rounding
 309                      cases) and sometimes it is not.  If NEWTYPE is
 310                      wider than TYPE, e.g. (float)((long double)double
 311                      + (long double)double) converted to
 312                      (float)(double + double), the transformation is
 313                      unsafe regardless of the details of the types
 314                      involved; double rounding can arise if the result
 315                      of NEWTYPE arithmetic is a NEWTYPE value half way
 316                      between two representable TYPE values but the
 317                      exact value is sufficiently different (in the
 318                      right direction) for this difference to be
 319                      visible in ITYPE arithmetic.  If NEWTYPE is the
 320                      same as TYPE, however, the transformation may be
 321                      safe depending on the types involved: it is safe
 322                      if the ITYPE has strictly more than twice as many
 323                      mantissa bits as TYPE, can represent infinities
 324                      and NaNs if the TYPE can, and has sufficient
 325                      exponent range for the product or ratio of two
 326                      values representable in the TYPE to be within the
 327                      range of normal values of ITYPE.  */
 328                   if (TYPE_PRECISION (newtype) < TYPE_PRECISION (itype)
 329                       && (flag_unsafe_math_optimizations
 330                           || (TYPE_PRECISION (newtype) == TYPE_PRECISION (type)
 331                               && real_can_shorten_arithmetic (TYPE_MODE (itype),
 332                                                               TYPE_MODE (type))
 333                               && !excess_precision_type (newtype))))
 334                     {
 335                       expr = build2 (TREE_CODE (expr), newtype,
 336                                      fold (convert_to_real (newtype, arg0)),
 337                                      fold (convert_to_real (newtype, arg1)));
 338                       if (newtype == type)
 339                         return expr;
 340                     }
 341                }
 342            }
 343           break;
 344         default:
 345           break;
 346       }
 347
 348   switch (TREE_CODE (TREE_TYPE (expr)))
 349     {
 350     case REAL_TYPE:
 351       /* Ignore the conversion if we don't need to store intermediate
 352          results and neither type is a decimal float.  */
 353       return build1 ((flag_float_store
 354                      || DECIMAL_FLOAT_TYPE_P (type)
 355                      || DECIMAL_FLOAT_TYPE_P (itype))
 356                      ? CONVERT_EXPR : NOP_EXPR, type, expr);
 357
 358     case INTEGER_TYPE:
 359     case ENUMERAL_TYPE:
 360     case BOOLEAN_TYPE:
 361       return build1 (FLOAT_EXPR, type, expr);
 362
 363     case FIXED_POINT_TYPE:
 364       return build1 (FIXED_CONVERT_EXPR, type, expr);
 365
 366     case COMPLEX_TYPE:
 367       return convert (type,
 368                       fold_build1 (REALPART_EXPR,
 369                                    TREE_TYPE (TREE_TYPE (expr)), expr));
 370
 371     case POINTER_TYPE:
 372     case REFERENCE_TYPE:
 373       error ("pointer value used where a floating point value was expected");
 374       return convert_to_real (type, integer_zero_node);
 375
 376     default:
 377       error ("aggregate value used where a float was expected");
 378       return convert_to_real (type, integer_zero_node);
 379     }
 380 }
 381
 382 /* Convert EXPR to some integer (or enum) type TYPE.
 383
 384    EXPR must be pointer, integer, discrete (enum, char, or bool), float,
 385    fixed-point or vector; in other cases error is called.
 386
 387    The result of this is always supposed to be a newly created tree node
 388    not in use in any existing structure.  */
 389
 390 tree
 391 convert_to_integer (tree type, tree expr)
 392 {
 393   enum tree_code ex_form = TREE_CODE (expr);
 394   tree intype = TREE_TYPE (expr);
 395   unsigned int inprec = element_precision (intype);
 396   unsigned int outprec = element_precision (type);
 397
 398   /* An INTEGER_TYPE cannot be incomplete, but an ENUMERAL_TYPE can
 399      be.  Consider `enum E = { a, b = (enum E) 3 };'.  */
 400   if (!COMPLETE_TYPE_P (type))
 401     {
 402       error ("conversion to incomplete type");
 403       return error_mark_node;
 404     }
 405
 406   /* Convert e.g. (long)round(d) -> lround(d).  */
 407   /* If we're converting to char, we may encounter differing behavior
 408      between converting from double->char vs double->long->char.
 409      We're in "undefined" territory but we prefer to be conservative,
 410      so only proceed in "unsafe" math mode.  */
 411   if (optimize
 412       && (flag_unsafe_math_optimizations
 413           || (long_integer_type_node
 414               && outprec >= TYPE_PRECISION (long_integer_type_node))))
 415     {
 416       tree s_expr = strip_float_extensions (expr);
 417       tree s_intype = TREE_TYPE (s_expr);
 418       const enum built_in_function fcode = builtin_mathfn_code (s_expr);
 419       tree fn = 0;
 420
 421       switch (fcode)
 422         {
 423         CASE_FLT_FN (BUILT_IN_CEIL):
 424           /* Only convert in ISO C99 mode.  */
 425           if (!targetm.libc_has_function (function_c99_misc))
 426             break;
 427           if (outprec < TYPE_PRECISION (integer_type_node)
 428               || (outprec == TYPE_PRECISION (integer_type_node)
 429                   && !TYPE_UNSIGNED (type)))
 430             fn = mathfn_built_in (s_intype, BUILT_IN_ICEIL);
 431           else if (outprec == TYPE_PRECISION (long_integer_type_node)
 432                    && !TYPE_UNSIGNED (type))
 433             fn = mathfn_built_in (s_intype, BUILT_IN_LCEIL);
 434           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 435                    && !TYPE_UNSIGNED (type))
 436             fn = mathfn_built_in (s_intype, BUILT_IN_LLCEIL);
 437           break;
 438
 439         CASE_FLT_FN (BUILT_IN_FLOOR):
 440           /* Only convert in ISO C99 mode.  */
 441           if (!targetm.libc_has_function (function_c99_misc))
 442             break;
 443           if (outprec < TYPE_PRECISION (integer_type_node)
 444               || (outprec == TYPE_PRECISION (integer_type_node)
 445                   && !TYPE_UNSIGNED (type)))
 446             fn = mathfn_built_in (s_intype, BUILT_IN_IFLOOR);
 447           else if (outprec == TYPE_PRECISION (long_integer_type_node)
 448                    && !TYPE_UNSIGNED (type))
 449             fn = mathfn_built_in (s_intype, BUILT_IN_LFLOOR);
 450           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 451                    && !TYPE_UNSIGNED (type))
 452             fn = mathfn_built_in (s_intype, BUILT_IN_LLFLOOR);
 453           break;
 454
 455         CASE_FLT_FN (BUILT_IN_ROUND):
 456           /* Only convert in ISO C99 mode.  */
 457           if (!targetm.libc_has_function (function_c99_misc))
 458             break;
 459           if (outprec < TYPE_PRECISION (integer_type_node)
 460               || (outprec == TYPE_PRECISION (integer_type_node)
 461                   && !TYPE_UNSIGNED (type)))
 462             fn = mathfn_built_in (s_intype, BUILT_IN_IROUND);
 463           else if (outprec == TYPE_PRECISION (long_integer_type_node)
 464                    && !TYPE_UNSIGNED (type))
 465             fn = mathfn_built_in (s_intype, BUILT_IN_LROUND);
 466           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 467                    && !TYPE_UNSIGNED (type))
 468             fn = mathfn_built_in (s_intype, BUILT_IN_LLROUND);
 469           break;
 470
 471         CASE_FLT_FN (BUILT_IN_NEARBYINT):
 472           /* Only convert nearbyint* if we can ignore math exceptions.  */
 473           if (flag_trapping_math)
 474             break;
 475           /* ... Fall through ...  */
 476         CASE_FLT_FN (BUILT_IN_RINT):
 477           /* Only convert in ISO C99 mode.  */
 478           if (!targetm.libc_has_function (function_c99_misc))
 479             break;
 480           if (outprec < TYPE_PRECISION (integer_type_node)
 481               || (outprec == TYPE_PRECISION (integer_type_node)
 482                   && !TYPE_UNSIGNED (type)))
 483             fn = mathfn_built_in (s_intype, BUILT_IN_IRINT);
 484           else if (outprec == TYPE_PRECISION (long_integer_type_node)
 485                    && !TYPE_UNSIGNED (type))
 486             fn = mathfn_built_in (s_intype, BUILT_IN_LRINT);
 487           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 488                    && !TYPE_UNSIGNED (type))
 489             fn = mathfn_built_in (s_intype, BUILT_IN_LLRINT);
 490           break;
 491
 492         CASE_FLT_FN (BUILT_IN_TRUNC):
 493           return convert_to_integer (type, CALL_EXPR_ARG (s_expr, 0));
 494
 495         default:
 496           break;
 497         }
 498
 499       if (fn)
 500         {
 501           tree newexpr = build_call_expr (fn, 1, CALL_EXPR_ARG (s_expr, 0));
 502           return convert_to_integer (type, newexpr);
 503         }
 504     }
 505
 506   /* Convert (int)logb(d) -> ilogb(d).  */
 507   if (optimize
 508       && flag_unsafe_math_optimizations
 509       && !flag_trapping_math && !flag_errno_math && flag_finite_math_only
 510       && integer_type_node
 511       && (outprec > TYPE_PRECISION (integer_type_node)
 512           || (outprec == TYPE_PRECISION (integer_type_node)
 513               && !TYPE_UNSIGNED (type))))
 514     {
 515       tree s_expr = strip_float_extensions (expr);
 516       tree s_intype = TREE_TYPE (s_expr);
 517       const enum built_in_function fcode = builtin_mathfn_code (s_expr);
 518       tree fn = 0;
 519
 520       switch (fcode)
 521         {
 522         CASE_FLT_FN (BUILT_IN_LOGB):
 523           fn = mathfn_built_in (s_intype, BUILT_IN_ILOGB);
 524           break;
 525
 526         default:
 527           break;
 528         }
 529
 530       if (fn)
 531         {
 532           tree newexpr = build_call_expr (fn, 1, CALL_EXPR_ARG (s_expr, 0));
 533           return convert_to_integer (type, newexpr);
 534         }
 535     }
 536
 537   switch (TREE_CODE (intype))
 538     {
 539     case POINTER_TYPE:
 540     case REFERENCE_TYPE:
 541       if (integer_zerop (expr))
 542         return build_int_cst (type, 0);
 543
 544       /* Convert to an unsigned integer of the correct width first, and from
 545          there widen/truncate to the required type.  Some targets support the
 546          coexistence of multiple valid pointer sizes, so fetch the one we need
 547          from the type.  */
 548       expr = fold_build1 (CONVERT_EXPR,
 549                           lang_hooks.types.type_for_size
 550                             (TYPE_PRECISION (intype), 0),
 551                           expr);
 552       return fold_convert (type, expr);
 553
 554     case INTEGER_TYPE:
 555     case ENUMERAL_TYPE:
 556     case BOOLEAN_TYPE:
 557     case OFFSET_TYPE:
 558       /* If this is a logical operation, which just returns 0 or 1, we can
 559          change the type of the expression.  */
 560
 561       if (TREE_CODE_CLASS (ex_form) == tcc_comparison)
 562         {
 563           expr = copy_node (expr);
 564           TREE_TYPE (expr) = type;
 565           return expr;
 566         }
 567
 568       /* If we are widening the type, put in an explicit conversion.
 569          Similarly if we are not changing the width.  After this, we know
 570          we are truncating EXPR.  */
 571
 572       else if (outprec >= inprec)
 573         {
 574           enum tree_code code;
 575
 576           /* If the precision of the EXPR's type is K bits and the
 577              destination mode has more bits, and the sign is changing,
 578              it is not safe to use a NOP_EXPR.  For example, suppose
 579              that EXPR's type is a 3-bit unsigned integer type, the
 580              TYPE is a 3-bit signed integer type, and the machine mode
 581              for the types is 8-bit QImode.  In that case, the
 582              conversion necessitates an explicit sign-extension.  In
 583              the signed-to-unsigned case the high-order bits have to
 584              be cleared.  */
 585           if (TYPE_UNSIGNED (type) != TYPE_UNSIGNED (TREE_TYPE (expr))
 586               && (TYPE_PRECISION (TREE_TYPE (expr))
 587                   != GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (expr)))))
 588             code = CONVERT_EXPR;
 589           else
 590             code = NOP_EXPR;
 591
 592           return fold_build1 (code, type, expr);
 593         }
 594
 595       /* If TYPE is an enumeral type or a type with a precision less
 596          than the number of bits in its mode, do the conversion to the
 597          type corresponding to its mode, then do a nop conversion
 598          to TYPE.  */
 599       else if (TREE_CODE (type) == ENUMERAL_TYPE
 600                || outprec != GET_MODE_PRECISION (TYPE_MODE (type)))
 601         return build1 (NOP_EXPR, type,
 602                        convert (lang_hooks.types.type_for_mode
 603                                 (TYPE_MODE (type), TYPE_UNSIGNED (type)),
 604                                 expr));
 605
 606       /* Here detect when we can distribute the truncation down past some
 607          arithmetic.  For example, if adding two longs and converting to an
 608          int, we can equally well convert both to ints and then add.
 609          For the operations handled here, such truncation distribution
 610          is always safe.
 611          It is desirable in these cases:
 612          1) when truncating down to full-word from a larger size
 613          2) when truncating takes no work.
 614          3) when at least one operand of the arithmetic has been extended
 615          (as by C's default conversions).  In this case we need two conversions
 616          if we do the arithmetic as already requested, so we might as well
 617          truncate both and then combine.  Perhaps that way we need only one.
 618
 619          Note that in general we cannot do the arithmetic in a type
 620          shorter than the desired result of conversion, even if the operands
 621          are both extended from a shorter type, because they might overflow
 622          if combined in that type.  The exceptions to this--the times when
 623          two narrow values can be combined in their narrow type even to
 624          make a wider result--are handled by "shorten" in build_binary_op.  */
 625
 626       switch (ex_form)
 627         {
 628         case RSHIFT_EXPR:
 629           /* We can pass truncation down through right shifting
 630              when the shift count is a nonpositive constant.  */
 631           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 632               && tree_int_cst_sgn (TREE_OPERAND (expr, 1)) <= 0)
 633             goto trunc1;
 634           break;
 635
 636         case LSHIFT_EXPR:
 637           /* We can pass truncation down through left shifting
 638              when the shift count is a nonnegative constant and
 639              the target type is unsigned.  */
 640           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 641               && tree_int_cst_sgn (TREE_OPERAND (expr, 1)) >= 0
 642               && TYPE_UNSIGNED (type)
 643               && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
 644             {
 645               /* If shift count is less than the width of the truncated type,
 646                  really shift.  */
 647               if (tree_int_cst_lt (TREE_OPERAND (expr, 1), TYPE_SIZE (type)))
 648                 /* In this case, shifting is like multiplication.  */
 649                 goto trunc1;
 650               else
 651                 {
 652                   /* If it is >= that width, result is zero.
 653                      Handling this with trunc1 would give the wrong result:
 654                      (int) ((long long) a << 32) is well defined (as 0)
 655                      but (int) a << 32 is undefined and would get a
 656                      warning.  */
 657
 658                   tree t = build_int_cst (type, 0);
 659
 660                   /* If the original expression had side-effects, we must
 661                      preserve it.  */
 662                   if (TREE_SIDE_EFFECTS (expr))
 663                     return build2 (COMPOUND_EXPR, type, expr, t);
 664                   else
 665                     return t;
 666                 }
 667             }
 668           break;
 669
 670         case TRUNC_DIV_EXPR:
 671           {
 672             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 673             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 674
 675             /* Don't distribute unless the output precision is at least as big
 676                as the actual inputs and it has the same signedness.  */
 677             if (outprec >= TYPE_PRECISION (TREE_TYPE (arg0))
 678                 && outprec >= TYPE_PRECISION (TREE_TYPE (arg1))
 679                 /* If signedness of arg0 and arg1 don't match,
 680                    we can't necessarily find a type to compare them in.  */
 681                 && (TYPE_UNSIGNED (TREE_TYPE (arg0))
 682                     == TYPE_UNSIGNED (TREE_TYPE (arg1)))
 683                 /* Do not change the sign of the division.  */
 684                 && (TYPE_UNSIGNED (TREE_TYPE (expr))
 685                     == TYPE_UNSIGNED (TREE_TYPE (arg0)))
 686                 /* Either require unsigned division or a division by
 687                    a constant that is not -1.  */
 688                 && (TYPE_UNSIGNED (TREE_TYPE (arg0))
 689                     || (TREE_CODE (arg1) == INTEGER_CST
 690                         && !integer_all_onesp (arg1))))
 691               goto trunc1;
 692             break;
 693           }
 694
 695         case MAX_EXPR:
 696         case MIN_EXPR:
 697         case MULT_EXPR:
 698           {
 699             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 700             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 701
 702             /* Don't distribute unless the output precision is at least as big
 703                as the actual inputs.  Otherwise, the comparison of the
 704                truncated values will be wrong.  */
 705             if (outprec >= TYPE_PRECISION (TREE_TYPE (arg0))
 706                 && outprec >= TYPE_PRECISION (TREE_TYPE (arg1))
 707                 /* If signedness of arg0 and arg1 don't match,
 708                    we can't necessarily find a type to compare them in.  */
 709                 && (TYPE_UNSIGNED (TREE_TYPE (arg0))
 710                     == TYPE_UNSIGNED (TREE_TYPE (arg1))))
 711               goto trunc1;
 712             break;
 713           }
 714
 715         case PLUS_EXPR:
 716         case MINUS_EXPR:
 717         case BIT_AND_EXPR:
 718         case BIT_IOR_EXPR:
 719         case BIT_XOR_EXPR:
 720         trunc1:
 721           {
 722             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 723             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 724
 725             /* Do not try to narrow operands of pointer subtraction;
 726                that will interfere with other folding.  */
 727             if (ex_form == MINUS_EXPR
 728                 && CONVERT_EXPR_P (arg0)
 729                 && CONVERT_EXPR_P (arg1)
 730                 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (arg0, 0)))
 731                 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (arg1, 0))))
 732               break;
 733
 734             if (outprec >= BITS_PER_WORD
 735                 || TRULY_NOOP_TRUNCATION (outprec, inprec)
 736                 || inprec > TYPE_PRECISION (TREE_TYPE (arg0))
 737                 || inprec > TYPE_PRECISION (TREE_TYPE (arg1)))
 738               {
 739                 /* Do the arithmetic in type TYPEX,
 740                    then convert result to TYPE.  */
 741                 tree typex = type;
 742
 743                 /* Can't do arithmetic in enumeral types
 744                    so use an integer type that will hold the values.  */
 745                 if (TREE_CODE (typex) == ENUMERAL_TYPE)
 746                   typex = lang_hooks.types.type_for_size
 747                     (TYPE_PRECISION (typex), TYPE_UNSIGNED (typex));
 748
 749                 /* But now perhaps TYPEX is as wide as INPREC.
 750                    In that case, do nothing special here.
 751                    (Otherwise would recurse infinitely in convert.  */
 752                 if (TYPE_PRECISION (typex) != inprec)
 753                   {
 754                     /* Don't do unsigned arithmetic where signed was wanted,
 755                        or vice versa.
 756                        Exception: if both of the original operands were
 757                        unsigned then we can safely do the work as unsigned.
 758                        Exception: shift operations take their type solely
 759                        from the first argument.
 760                        Exception: the LSHIFT_EXPR case above requires that
 761                        we perform this operation unsigned lest we produce
 762                        signed-overflow undefinedness.
 763                        And we may need to do it as unsigned
 764                        if we truncate to the original size.  */
 765                     if (TYPE_UNSIGNED (TREE_TYPE (expr))
 766                         || (TYPE_UNSIGNED (TREE_TYPE (arg0))
 767                             && (TYPE_UNSIGNED (TREE_TYPE (arg1))
 768                                 || ex_form == LSHIFT_EXPR
 769                                 || ex_form == RSHIFT_EXPR
 770                                 || ex_form == LROTATE_EXPR
 771                                 || ex_form == RROTATE_EXPR))
 772                         || ex_form == LSHIFT_EXPR
 773                         /* If we have !flag_wrapv, and either ARG0 or
 774                            ARG1 is of a signed type, we have to do
 775                            PLUS_EXPR, MINUS_EXPR or MULT_EXPR in an unsigned
 776                            type in case the operation in outprec precision
 777                            could overflow.  Otherwise, we would introduce
 778                            signed-overflow undefinedness.  */
 779                         || ((!TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg0))
 780                              || !TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg1)))
 781                             && ((TYPE_PRECISION (TREE_TYPE (arg0)) * 2u
 782                                  > outprec)
 783                                 || (TYPE_PRECISION (TREE_TYPE (arg1)) * 2u
 784                                     > outprec))
 785                             && (ex_form == PLUS_EXPR
 786                                 || ex_form == MINUS_EXPR
 787                                 || ex_form == MULT_EXPR)))
 788                       typex = unsigned_type_for (typex);
 789                     else
 790                       typex = signed_type_for (typex);
 791                     return convert (type,
 792                                     fold_build2 (ex_form, typex,
 793                                                  convert (typex, arg0),
 794                                                  convert (typex, arg1)));
 795                   }
 796               }
 797           }
 798           break;
 799
 800         case NEGATE_EXPR:
 801         case BIT_NOT_EXPR:
 802           /* This is not correct for ABS_EXPR,
 803              since we must test the sign before truncation.  */
 804           {
 805             tree typex = unsigned_type_for (type);
 806             return convert (type,
 807                             fold_build1 (ex_form, typex,
 808                                          convert (typex,
 809                                                   TREE_OPERAND (expr, 0))));
 810           }
 811
 812         case NOP_EXPR:
 813           /* Don't introduce a
 814              "can't convert between vector values of different size" error.  */
 815           if (TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0))) == VECTOR_TYPE
 816               && (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_OPERAND (expr, 0))))
 817                   != GET_MODE_SIZE (TYPE_MODE (type))))
 818             break;
 819           /* If truncating after truncating, might as well do all at once.
 820              If truncating after extending, we may get rid of wasted work.  */
 821           return convert (type, get_unwidened (TREE_OPERAND (expr, 0), type));
 822
 823         case COND_EXPR:
 824           /* It is sometimes worthwhile to push the narrowing down through
 825              the conditional and never loses.  A COND_EXPR may have a throw
 826              as one operand, which then has void type.  Just leave void
 827              operands as they are.  */
 828           return fold_build3 (COND_EXPR, type, TREE_OPERAND (expr, 0),
 829                               VOID_TYPE_P (TREE_TYPE (TREE_OPERAND (expr, 1)))
 830                               ? TREE_OPERAND (expr, 1)
 831                               : convert (type, TREE_OPERAND (expr, 1)),
 832                               VOID_TYPE_P (TREE_TYPE (TREE_OPERAND (expr, 2)))
 833                               ? TREE_OPERAND (expr, 2)
 834                               : convert (type, TREE_OPERAND (expr, 2)));
 835
 836         default:
 837           break;
 838         }
 839
 840       /* When parsing long initializers, we might end up with a lot of casts.
 841          Shortcut this.  */
 842       if (TREE_CODE (expr) == INTEGER_CST)
 843         return fold_convert (type, expr);
 844       return build1 (CONVERT_EXPR, type, expr);
 845
 846     case REAL_TYPE:
 847       return build1 (FIX_TRUNC_EXPR, type, expr);
 848
 849     case FIXED_POINT_TYPE:
 850       return build1 (FIXED_CONVERT_EXPR, type, expr);
 851
 852     case COMPLEX_TYPE:
 853       return convert (type,
 854                       fold_build1 (REALPART_EXPR,
 855                                    TREE_TYPE (TREE_TYPE (expr)), expr));
 856
 857     case VECTOR_TYPE:
 858       if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr))))
 859         {
 860           error ("can%'t convert between vector values of different size");
 861           return error_mark_node;
 862         }
 863       return build1 (VIEW_CONVERT_EXPR, type, expr);
 864
 865     default:
 866       error ("aggregate value used where an integer was expected");
 867       return convert (type, integer_zero_node);
 868     }
 869 }
 870
 871 /* Convert EXPR to the complex type TYPE in the usual ways.  */
 872
 873 tree
 874 convert_to_complex (tree type, tree expr)
 875 {
 876   tree subtype = TREE_TYPE (type);
 877
 878   switch (TREE_CODE (TREE_TYPE (expr)))
 879     {
 880     case REAL_TYPE:
 881     case FIXED_POINT_TYPE:
 882     case INTEGER_TYPE:
 883     case ENUMERAL_TYPE:
 884     case BOOLEAN_TYPE:
 885       return build2 (COMPLEX_EXPR, type, convert (subtype, expr),
 886                      convert (subtype, integer_zero_node));
 887
 888     case COMPLEX_TYPE:
 889       {
 890         tree elt_type = TREE_TYPE (TREE_TYPE (expr));
 891
 892         if (TYPE_MAIN_VARIANT (elt_type) == TYPE_MAIN_VARIANT (subtype))
 893           return expr;
 894         else if (TREE_CODE (expr) == COMPLEX_EXPR)
 895           return fold_build2 (COMPLEX_EXPR, type,
 896                               convert (subtype, TREE_OPERAND (expr, 0)),
 897                               convert (subtype, TREE_OPERAND (expr, 1)));
 898         else
 899           {
 900             expr = save_expr (expr);
 901             return
 902               fold_build2 (COMPLEX_EXPR, type,
 903                            convert (subtype,
 904                                     fold_build1 (REALPART_EXPR,
 905                                                  TREE_TYPE (TREE_TYPE (expr)),
 906                                                  expr)),
 907                            convert (subtype,
 908                                     fold_build1 (IMAGPART_EXPR,
 909                                                  TREE_TYPE (TREE_TYPE (expr)),
 910                                                  expr)));
 911           }
 912       }
 913
 914     case POINTER_TYPE:
 915     case REFERENCE_TYPE:
 916       error ("pointer value used where a complex was expected");
 917       return convert_to_complex (type, integer_zero_node);
 918
 919     default:
 920       error ("aggregate value used where a complex was expected");
 921       return convert_to_complex (type, integer_zero_node);
 922     }
 923 }
 924
 925 /* Convert EXPR to the vector type TYPE in the usual ways.  */
 926
 927 tree
 928 convert_to_vector (tree type, tree expr)
 929 {
 930   switch (TREE_CODE (TREE_TYPE (expr)))
 931     {
 932     case INTEGER_TYPE:
 933     case VECTOR_TYPE:
 934       if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr))))
 935         {
 936           error ("can%'t convert between vector values of different size");
 937           return error_mark_node;
 938         }
 939       return build1 (VIEW_CONVERT_EXPR, type, expr);
 940
 941     default:
 942       error ("can%'t convert value to a vector");
 943       return error_mark_node;
 944     }
 945 }
 946
 947 /* Convert EXPR to some fixed-point type TYPE.
 948
 949    EXPR must be fixed-point, float, integer, or enumeral;
 950    in other cases error is called.  */
 951
 952 tree
 953 convert_to_fixed (tree type, tree expr)
 954 {
 955   if (integer_zerop (expr))
 956     {
 957       tree fixed_zero_node = build_fixed (type, FCONST0 (TYPE_MODE (type)));
 958       return fixed_zero_node;
 959     }
 960   else if (integer_onep (expr) && ALL_SCALAR_ACCUM_MODE_P (TYPE_MODE (type)))
 961     {
 962       tree fixed_one_node = build_fixed (type, FCONST1 (TYPE_MODE (type)));
 963       return fixed_one_node;
 964     }
 965
 966   switch (TREE_CODE (TREE_TYPE (expr)))
 967     {
 968     case FIXED_POINT_TYPE:
 969     case INTEGER_TYPE:
 970     case ENUMERAL_TYPE:
 971     case BOOLEAN_TYPE:
 972     case REAL_TYPE:
 973       return build1 (FIXED_CONVERT_EXPR, type, expr);
 974
 975     case COMPLEX_TYPE:
 976       return convert (type,
 977                       fold_build1 (REALPART_EXPR,
 978                                    TREE_TYPE (TREE_TYPE (expr)), expr));
 979
 980     default:
 981       error ("aggregate value used where a fixed-point was expected");
 982       return error_mark_node;
 983     }
 984 }