gcc/convert.c

   1 /* Utility routines for data type conversion for GCC.
   2    Copyright (C) 1987-2015 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 "target.h"
  28 #include "tree.h"
  29 #include "diagnostic-core.h"
  30 #include "alias.h"
  31 #include "fold-const.h"
  32 #include "stor-layout.h"
  33 #include "flags.h"
  34 #include "convert.h"
  35 #include "langhooks.h"
  36 #include "builtins.h"
  37 #include "ubsan.h"
  38
  39 /* Convert EXPR to some pointer or reference type TYPE.
  40    EXPR must be pointer, reference, integer, enumeral, or literal zero;
  41    in other cases error is called.  */
  42
  43 tree
  44 convert_to_pointer (tree type, tree expr)
  45 {
  46   location_t loc = EXPR_LOCATION (expr);
  47   if (TREE_TYPE (expr) == type)
  48     return expr;
  49
  50   switch (TREE_CODE (TREE_TYPE (expr)))
  51     {
  52     case POINTER_TYPE:
  53     case REFERENCE_TYPE:
  54       {
  55         /* If the pointers point to different address spaces, conversion needs
  56            to be done via a ADDR_SPACE_CONVERT_EXPR instead of a NOP_EXPR.  */
  57         addr_space_t to_as = TYPE_ADDR_SPACE (TREE_TYPE (type));
  58         addr_space_t from_as = TYPE_ADDR_SPACE (TREE_TYPE (TREE_TYPE (expr)));
  59
  60         if (to_as == from_as)
  61           return fold_build1_loc (loc, NOP_EXPR, type, expr);
  62         else
  63           return fold_build1_loc (loc, ADDR_SPACE_CONVERT_EXPR, type, expr);
  64       }
  65
  66     case INTEGER_TYPE:
  67     case ENUMERAL_TYPE:
  68     case BOOLEAN_TYPE:
  69       {
  70         /* If the input precision differs from the target pointer type
  71            precision, first convert the input expression to an integer type of
  72            the target precision.  Some targets, e.g. VMS, need several pointer
  73            sizes to coexist so the latter isn't necessarily POINTER_SIZE.  */
  74         unsigned int pprec = TYPE_PRECISION (type);
  75         unsigned int eprec = TYPE_PRECISION (TREE_TYPE (expr));
  76
  77         if (eprec != pprec)
  78           expr = fold_build1_loc (loc, NOP_EXPR,
  79                               lang_hooks.types.type_for_size (pprec, 0),
  80                               expr);
  81       }
  82
  83       return fold_build1_loc (loc, CONVERT_EXPR, type, expr);
  84
  85     default:
  86       error ("cannot convert to a pointer type");
  87       return convert_to_pointer (type, integer_zero_node);
  88     }
  89 }
  90
  91
  92 /* Convert EXPR to some floating-point type TYPE.
  93
  94    EXPR must be float, fixed-point, integer, or enumeral;
  95    in other cases error is called.  */
  96
  97 tree
  98 convert_to_real (tree type, tree expr)
  99 {
 100   enum built_in_function fcode = builtin_mathfn_code (expr);
 101   tree itype = TREE_TYPE (expr);
 102
 103   if (TREE_CODE (expr) == COMPOUND_EXPR)
 104     {
 105       tree t = convert_to_real (type, TREE_OPERAND (expr, 1));
 106       if (t == TREE_OPERAND (expr, 1))
 107         return expr;
 108       return build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (t),
 109                          TREE_OPERAND (expr, 0), t);
 110     }
 111
 112   /* Disable until we figure out how to decide whether the functions are
 113      present in runtime.  */
 114   /* Convert (float)sqrt((double)x) where x is float into sqrtf(x) */
 115   if (optimize
 116       && (TYPE_MODE (type) == TYPE_MODE (double_type_node)
 117           || TYPE_MODE (type) == TYPE_MODE (float_type_node)))
 118     {
 119       switch (fcode)
 120         {
 121 #define CASE_MATHFN(FN) case BUILT_IN_##FN: case BUILT_IN_##FN##L:
 122           CASE_MATHFN (COSH)
 123           CASE_MATHFN (EXP)
 124           CASE_MATHFN (EXP10)
 125           CASE_MATHFN (EXP2)
 126           CASE_MATHFN (EXPM1)
 127           CASE_MATHFN (GAMMA)
 128           CASE_MATHFN (J0)
 129           CASE_MATHFN (J1)
 130           CASE_MATHFN (LGAMMA)
 131           CASE_MATHFN (POW10)
 132           CASE_MATHFN (SINH)
 133           CASE_MATHFN (TGAMMA)
 134           CASE_MATHFN (Y0)
 135           CASE_MATHFN (Y1)
 136             /* The above functions may set errno differently with float
 137                input or output so this transformation is not safe with
 138                -fmath-errno.  */
 139             if (flag_errno_math)
 140               break;
 141           CASE_MATHFN (ACOS)
 142           CASE_MATHFN (ACOSH)
 143           CASE_MATHFN (ASIN)
 144           CASE_MATHFN (ASINH)
 145           CASE_MATHFN (ATAN)
 146           CASE_MATHFN (ATANH)
 147           CASE_MATHFN (CBRT)
 148           CASE_MATHFN (COS)
 149           CASE_MATHFN (ERF)
 150           CASE_MATHFN (ERFC)
 151           CASE_MATHFN (LOG)
 152           CASE_MATHFN (LOG10)
 153           CASE_MATHFN (LOG2)
 154           CASE_MATHFN (LOG1P)
 155           CASE_MATHFN (SIN)
 156           CASE_MATHFN (TAN)
 157           CASE_MATHFN (TANH)
 158             /* The above functions are not safe to do this conversion.  */
 159             if (!flag_unsafe_math_optimizations)
 160               break;
 161           CASE_MATHFN (SQRT)
 162           CASE_MATHFN (FABS)
 163           CASE_MATHFN (LOGB)
 164 #undef CASE_MATHFN
 165             {
 166               tree arg0 = strip_float_extensions (CALL_EXPR_ARG (expr, 0));
 167               tree newtype = type;
 168
 169               /* We have (outertype)sqrt((innertype)x).  Choose the wider mode from
 170                  the both as the safe type for operation.  */
 171               if (TYPE_PRECISION (TREE_TYPE (arg0)) > TYPE_PRECISION (type))
 172                 newtype = TREE_TYPE (arg0);
 173
 174               /* We consider to convert
 175
 176                      (T1) sqrtT2 ((T2) exprT3)
 177                  to
 178                      (T1) sqrtT4 ((T4) exprT3)
 179
 180                   , where T1 is TYPE, T2 is ITYPE, T3 is TREE_TYPE (ARG0),
 181                  and T4 is NEWTYPE.  All those types are of floating point types.
 182                  T4 (NEWTYPE) should be narrower than T2 (ITYPE). This conversion
 183                  is safe only if P1 >= P2*2+2, where P1 and P2 are precisions of
 184                  T2 and T4.  See the following URL for a reference:
 185                  http://stackoverflow.com/questions/9235456/determining-
 186                  floating-point-square-root
 187                  */
 188               if ((fcode == BUILT_IN_SQRT || fcode == BUILT_IN_SQRTL)
 189                   && !flag_unsafe_math_optimizations)
 190                 {
 191                   /* The following conversion is unsafe even the precision condition
 192                      below is satisfied:
 193
 194                      (float) sqrtl ((long double) double_val) -> (float) sqrt (double_val)
 195                     */
 196                   if (TYPE_MODE (type) != TYPE_MODE (newtype))
 197                     break;
 198
 199                   int p1 = REAL_MODE_FORMAT (TYPE_MODE (itype))->p;
 200                   int p2 = REAL_MODE_FORMAT (TYPE_MODE (newtype))->p;
 201                   if (p1 < p2 * 2 + 2)
 202                     break;
 203                 }
 204
 205               /* Be careful about integer to fp conversions.
 206                  These may overflow still.  */
 207               if (FLOAT_TYPE_P (TREE_TYPE (arg0))
 208                   && TYPE_PRECISION (newtype) < TYPE_PRECISION (itype)
 209                   && (TYPE_MODE (newtype) == TYPE_MODE (double_type_node)
 210                       || TYPE_MODE (newtype) == TYPE_MODE (float_type_node)))
 211                 {
 212                   tree fn = mathfn_built_in (newtype, fcode);
 213
 214                   if (fn)
 215                   {
 216                     tree arg = fold (convert_to_real (newtype, arg0));
 217                     expr = build_call_expr (fn, 1, arg);
 218                     if (newtype == type)
 219                       return expr;
 220                   }
 221                 }
 222             }
 223         default:
 224           break;
 225         }
 226     }
 227
 228   /* Propagate the cast into the operation.  */
 229   if (itype != type && FLOAT_TYPE_P (type))
 230     switch (TREE_CODE (expr))
 231       {
 232         /* Convert (float)-x into -(float)x.  This is safe for
 233            round-to-nearest rounding mode when the inner type is float.  */
 234         case ABS_EXPR:
 235         case NEGATE_EXPR:
 236           if (!flag_rounding_math
 237               && FLOAT_TYPE_P (itype)
 238               && TYPE_PRECISION (type) < TYPE_PRECISION (itype))
 239             return build1 (TREE_CODE (expr), type,
 240                            fold (convert_to_real (type,
 241                                                   TREE_OPERAND (expr, 0))));
 242           break;
 243         /* Convert (outertype)((innertype0)a+(innertype1)b)
 244            into ((newtype)a+(newtype)b) where newtype
 245            is the widest mode from all of these.  */
 246         case PLUS_EXPR:
 247         case MINUS_EXPR:
 248         case MULT_EXPR:
 249         case RDIV_EXPR:
 250            {
 251              tree arg0 = strip_float_extensions (TREE_OPERAND (expr, 0));
 252              tree arg1 = strip_float_extensions (TREE_OPERAND (expr, 1));
 253
 254              if (FLOAT_TYPE_P (TREE_TYPE (arg0))
 255                  && FLOAT_TYPE_P (TREE_TYPE (arg1))
 256                  && DECIMAL_FLOAT_TYPE_P (itype) == DECIMAL_FLOAT_TYPE_P (type))
 257                {
 258                   tree newtype = type;
 259
 260                   if (TYPE_MODE (TREE_TYPE (arg0)) == SDmode
 261                       || TYPE_MODE (TREE_TYPE (arg1)) == SDmode
 262                       || TYPE_MODE (type) == SDmode)
 263                     newtype = dfloat32_type_node;
 264                   if (TYPE_MODE (TREE_TYPE (arg0)) == DDmode
 265                       || TYPE_MODE (TREE_TYPE (arg1)) == DDmode
 266                       || TYPE_MODE (type) == DDmode)
 267                     newtype = dfloat64_type_node;
 268                   if (TYPE_MODE (TREE_TYPE (arg0)) == TDmode
 269                       || TYPE_MODE (TREE_TYPE (arg1)) == TDmode
 270                       || TYPE_MODE (type) == TDmode)
 271                     newtype = dfloat128_type_node;
 272                   if (newtype == dfloat32_type_node
 273                       || newtype == dfloat64_type_node
 274                       || newtype == dfloat128_type_node)
 275                     {
 276                       expr = build2 (TREE_CODE (expr), newtype,
 277                                      fold (convert_to_real (newtype, arg0)),
 278                                      fold (convert_to_real (newtype, arg1)));
 279                       if (newtype == type)
 280                         return expr;
 281                       break;
 282                     }
 283
 284                   if (TYPE_PRECISION (TREE_TYPE (arg0)) > TYPE_PRECISION (newtype))
 285                     newtype = TREE_TYPE (arg0);
 286                   if (TYPE_PRECISION (TREE_TYPE (arg1)) > TYPE_PRECISION (newtype))
 287                     newtype = TREE_TYPE (arg1);
 288                   /* Sometimes this transformation is safe (cannot
 289                      change results through affecting double rounding
 290                      cases) and sometimes it is not.  If NEWTYPE is
 291                      wider than TYPE, e.g. (float)((long double)double
 292                      + (long double)double) converted to
 293                      (float)(double + double), the transformation is
 294                      unsafe regardless of the details of the types
 295                      involved; double rounding can arise if the result
 296                      of NEWTYPE arithmetic is a NEWTYPE value half way
 297                      between two representable TYPE values but the
 298                      exact value is sufficiently different (in the
 299                      right direction) for this difference to be
 300                      visible in ITYPE arithmetic.  If NEWTYPE is the
 301                      same as TYPE, however, the transformation may be
 302                      safe depending on the types involved: it is safe
 303                      if the ITYPE has strictly more than twice as many
 304                      mantissa bits as TYPE, can represent infinities
 305                      and NaNs if the TYPE can, and has sufficient
 306                      exponent range for the product or ratio of two
 307                      values representable in the TYPE to be within the
 308                      range of normal values of ITYPE.  */
 309                   if (TYPE_PRECISION (newtype) < TYPE_PRECISION (itype)
 310                       && (flag_unsafe_math_optimizations
 311                           || (TYPE_PRECISION (newtype) == TYPE_PRECISION (type)
 312                               && real_can_shorten_arithmetic (TYPE_MODE (itype),
 313                                                               TYPE_MODE (type))
 314                               && !excess_precision_type (newtype))))
 315                     {
 316                       expr = build2 (TREE_CODE (expr), newtype,
 317                                      fold (convert_to_real (newtype, arg0)),
 318                                      fold (convert_to_real (newtype, arg1)));
 319                       if (newtype == type)
 320                         return expr;
 321                     }
 322                }
 323            }
 324           break;
 325         default:
 326           break;
 327       }
 328
 329   switch (TREE_CODE (TREE_TYPE (expr)))
 330     {
 331     case REAL_TYPE:
 332       /* Ignore the conversion if we don't need to store intermediate
 333          results and neither type is a decimal float.  */
 334       return build1 ((flag_float_store
 335                      || DECIMAL_FLOAT_TYPE_P (type)
 336                      || DECIMAL_FLOAT_TYPE_P (itype))
 337                      ? CONVERT_EXPR : NOP_EXPR, type, expr);
 338
 339     case INTEGER_TYPE:
 340     case ENUMERAL_TYPE:
 341     case BOOLEAN_TYPE:
 342       return build1 (FLOAT_EXPR, type, expr);
 343
 344     case FIXED_POINT_TYPE:
 345       return build1 (FIXED_CONVERT_EXPR, type, expr);
 346
 347     case COMPLEX_TYPE:
 348       return convert (type,
 349                       fold_build1 (REALPART_EXPR,
 350                                    TREE_TYPE (TREE_TYPE (expr)), expr));
 351
 352     case POINTER_TYPE:
 353     case REFERENCE_TYPE:
 354       error ("pointer value used where a floating point value was expected");
 355       return convert_to_real (type, integer_zero_node);
 356
 357     default:
 358       error ("aggregate value used where a float was expected");
 359       return convert_to_real (type, integer_zero_node);
 360     }
 361 }
 362
 363 /* Convert EXPR to some integer (or enum) type TYPE.
 364
 365    EXPR must be pointer, integer, discrete (enum, char, or bool), float,
 366    fixed-point or vector; in other cases error is called.
 367
 368    The result of this is always supposed to be a newly created tree node
 369    not in use in any existing structure.  */
 370
 371 tree
 372 convert_to_integer (tree type, tree expr)
 373 {
 374   enum tree_code ex_form = TREE_CODE (expr);
 375   tree intype = TREE_TYPE (expr);
 376   unsigned int inprec = element_precision (intype);
 377   unsigned int outprec = element_precision (type);
 378   location_t loc = EXPR_LOCATION (expr);
 379
 380   /* An INTEGER_TYPE cannot be incomplete, but an ENUMERAL_TYPE can
 381      be.  Consider `enum E = { a, b = (enum E) 3 };'.  */
 382   if (!COMPLETE_TYPE_P (type))
 383     {
 384       error ("conversion to incomplete type");
 385       return error_mark_node;
 386     }
 387
 388   if (ex_form == COMPOUND_EXPR)
 389     {
 390       tree t = convert_to_integer (type, TREE_OPERAND (expr, 1));
 391       if (t == TREE_OPERAND (expr, 1))
 392         return expr;
 393       return build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (t),
 394                          TREE_OPERAND (expr, 0), t);
 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 (!targetm.libc_has_function (function_c99_misc))
 417             break;
 418           if (outprec < TYPE_PRECISION (integer_type_node)
 419               || (outprec == TYPE_PRECISION (integer_type_node)
 420                   && !TYPE_UNSIGNED (type)))
 421             fn = mathfn_built_in (s_intype, BUILT_IN_ICEIL);
 422           else if (outprec == TYPE_PRECISION (long_integer_type_node)
 423                    && !TYPE_UNSIGNED (type))
 424             fn = mathfn_built_in (s_intype, BUILT_IN_LCEIL);
 425           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 426                    && !TYPE_UNSIGNED (type))
 427             fn = mathfn_built_in (s_intype, BUILT_IN_LLCEIL);
 428           break;
 429
 430         CASE_FLT_FN (BUILT_IN_FLOOR):
 431           /* Only convert in ISO C99 mode.  */
 432           if (!targetm.libc_has_function (function_c99_misc))
 433             break;
 434           if (outprec < TYPE_PRECISION (integer_type_node)
 435               || (outprec == TYPE_PRECISION (integer_type_node)
 436                   && !TYPE_UNSIGNED (type)))
 437             fn = mathfn_built_in (s_intype, BUILT_IN_IFLOOR);
 438           else if (outprec == TYPE_PRECISION (long_integer_type_node)
 439                    && !TYPE_UNSIGNED (type))
 440             fn = mathfn_built_in (s_intype, BUILT_IN_LFLOOR);
 441           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 442                    && !TYPE_UNSIGNED (type))
 443             fn = mathfn_built_in (s_intype, BUILT_IN_LLFLOOR);
 444           break;
 445
 446         CASE_FLT_FN (BUILT_IN_ROUND):
 447           /* Only convert in ISO C99 mode and with -fno-math-errno.  */
 448           if (!targetm.libc_has_function (function_c99_misc) || flag_errno_math)
 449             break;
 450           if (outprec < TYPE_PRECISION (integer_type_node)
 451               || (outprec == TYPE_PRECISION (integer_type_node)
 452                   && !TYPE_UNSIGNED (type)))
 453             fn = mathfn_built_in (s_intype, BUILT_IN_IROUND);
 454           else if (outprec == TYPE_PRECISION (long_integer_type_node)
 455                    && !TYPE_UNSIGNED (type))
 456             fn = mathfn_built_in (s_intype, BUILT_IN_LROUND);
 457           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 458                    && !TYPE_UNSIGNED (type))
 459             fn = mathfn_built_in (s_intype, BUILT_IN_LLROUND);
 460           break;
 461
 462         CASE_FLT_FN (BUILT_IN_NEARBYINT):
 463           /* Only convert nearbyint* if we can ignore math exceptions.  */
 464           if (flag_trapping_math)
 465             break;
 466           /* ... Fall through ...  */
 467         CASE_FLT_FN (BUILT_IN_RINT):
 468           /* Only convert in ISO C99 mode and with -fno-math-errno.  */
 469           if (!targetm.libc_has_function (function_c99_misc) || flag_errno_math)
 470             break;
 471           if (outprec < TYPE_PRECISION (integer_type_node)
 472               || (outprec == TYPE_PRECISION (integer_type_node)
 473                   && !TYPE_UNSIGNED (type)))
 474             fn = mathfn_built_in (s_intype, BUILT_IN_IRINT);
 475           else if (outprec == TYPE_PRECISION (long_integer_type_node)
 476                    && !TYPE_UNSIGNED (type))
 477             fn = mathfn_built_in (s_intype, BUILT_IN_LRINT);
 478           else if (outprec == TYPE_PRECISION (long_long_integer_type_node)
 479                    && !TYPE_UNSIGNED (type))
 480             fn = mathfn_built_in (s_intype, BUILT_IN_LLRINT);
 481           break;
 482
 483         CASE_FLT_FN (BUILT_IN_TRUNC):
 484           return convert_to_integer (type, CALL_EXPR_ARG (s_expr, 0));
 485
 486         default:
 487           break;
 488         }
 489
 490       if (fn)
 491         {
 492           tree newexpr = build_call_expr (fn, 1, CALL_EXPR_ARG (s_expr, 0));
 493           return convert_to_integer (type, newexpr);
 494         }
 495     }
 496
 497   /* Convert (int)logb(d) -> ilogb(d).  */
 498   if (optimize
 499       && flag_unsafe_math_optimizations
 500       && !flag_trapping_math && !flag_errno_math && flag_finite_math_only
 501       && integer_type_node
 502       && (outprec > TYPE_PRECISION (integer_type_node)
 503           || (outprec == TYPE_PRECISION (integer_type_node)
 504               && !TYPE_UNSIGNED (type))))
 505     {
 506       tree s_expr = strip_float_extensions (expr);
 507       tree s_intype = TREE_TYPE (s_expr);
 508       const enum built_in_function fcode = builtin_mathfn_code (s_expr);
 509       tree fn = 0;
 510
 511       switch (fcode)
 512         {
 513         CASE_FLT_FN (BUILT_IN_LOGB):
 514           fn = mathfn_built_in (s_intype, BUILT_IN_ILOGB);
 515           break;
 516
 517         default:
 518           break;
 519         }
 520
 521       if (fn)
 522         {
 523           tree newexpr = build_call_expr (fn, 1, CALL_EXPR_ARG (s_expr, 0));
 524           return convert_to_integer (type, newexpr);
 525         }
 526     }
 527
 528   switch (TREE_CODE (intype))
 529     {
 530     case POINTER_TYPE:
 531     case REFERENCE_TYPE:
 532       if (integer_zerop (expr))
 533         return build_int_cst (type, 0);
 534
 535       /* Convert to an unsigned integer of the correct width first, and from
 536          there widen/truncate to the required type.  Some targets support the
 537          coexistence of multiple valid pointer sizes, so fetch the one we need
 538          from the type.  */
 539       expr = fold_build1 (CONVERT_EXPR,
 540                           lang_hooks.types.type_for_size
 541                             (TYPE_PRECISION (intype), 0),
 542                           expr);
 543       return fold_convert (type, expr);
 544
 545     case INTEGER_TYPE:
 546     case ENUMERAL_TYPE:
 547     case BOOLEAN_TYPE:
 548     case OFFSET_TYPE:
 549       /* If this is a logical operation, which just returns 0 or 1, we can
 550          change the type of the expression.  */
 551
 552       if (TREE_CODE_CLASS (ex_form) == tcc_comparison)
 553         {
 554           expr = copy_node (expr);
 555           TREE_TYPE (expr) = type;
 556           return expr;
 557         }
 558
 559       /* If we are widening the type, put in an explicit conversion.
 560          Similarly if we are not changing the width.  After this, we know
 561          we are truncating EXPR.  */
 562
 563       else if (outprec >= inprec)
 564         {
 565           enum tree_code code;
 566
 567           /* If the precision of the EXPR's type is K bits and the
 568              destination mode has more bits, and the sign is changing,
 569              it is not safe to use a NOP_EXPR.  For example, suppose
 570              that EXPR's type is a 3-bit unsigned integer type, the
 571              TYPE is a 3-bit signed integer type, and the machine mode
 572              for the types is 8-bit QImode.  In that case, the
 573              conversion necessitates an explicit sign-extension.  In
 574              the signed-to-unsigned case the high-order bits have to
 575              be cleared.  */
 576           if (TYPE_UNSIGNED (type) != TYPE_UNSIGNED (TREE_TYPE (expr))
 577               && (TYPE_PRECISION (TREE_TYPE (expr))
 578                   != GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (expr)))))
 579             code = CONVERT_EXPR;
 580           else
 581             code = NOP_EXPR;
 582
 583           return fold_build1 (code, type, expr);
 584         }
 585
 586       /* If TYPE is an enumeral type or a type with a precision less
 587          than the number of bits in its mode, do the conversion to the
 588          type corresponding to its mode, then do a nop conversion
 589          to TYPE.  */
 590       else if (TREE_CODE (type) == ENUMERAL_TYPE
 591                || outprec != GET_MODE_PRECISION (TYPE_MODE (type)))
 592         return build1 (NOP_EXPR, type,
 593                        convert (lang_hooks.types.type_for_mode
 594                                 (TYPE_MODE (type), TYPE_UNSIGNED (type)),
 595                                 expr));
 596
 597       /* Here detect when we can distribute the truncation down past some
 598          arithmetic.  For example, if adding two longs and converting to an
 599          int, we can equally well convert both to ints and then add.
 600          For the operations handled here, such truncation distribution
 601          is always safe.
 602          It is desirable in these cases:
 603          1) when truncating down to full-word from a larger size
 604          2) when truncating takes no work.
 605          3) when at least one operand of the arithmetic has been extended
 606          (as by C's default conversions).  In this case we need two conversions
 607          if we do the arithmetic as already requested, so we might as well
 608          truncate both and then combine.  Perhaps that way we need only one.
 609
 610          Note that in general we cannot do the arithmetic in a type
 611          shorter than the desired result of conversion, even if the operands
 612          are both extended from a shorter type, because they might overflow
 613          if combined in that type.  The exceptions to this--the times when
 614          two narrow values can be combined in their narrow type even to
 615          make a wider result--are handled by "shorten" in build_binary_op.  */
 616
 617       switch (ex_form)
 618         {
 619         case RSHIFT_EXPR:
 620           /* We can pass truncation down through right shifting
 621              when the shift count is a nonpositive constant.  */
 622           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 623               && tree_int_cst_sgn (TREE_OPERAND (expr, 1)) <= 0)
 624             goto trunc1;
 625           break;
 626
 627         case LSHIFT_EXPR:
 628           /* We can pass truncation down through left shifting
 629              when the shift count is a nonnegative constant and
 630              the target type is unsigned.  */
 631           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 632               && tree_int_cst_sgn (TREE_OPERAND (expr, 1)) >= 0
 633               && TYPE_UNSIGNED (type)
 634               && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
 635             {
 636               /* If shift count is less than the width of the truncated type,
 637                  really shift.  */
 638               if (tree_int_cst_lt (TREE_OPERAND (expr, 1), TYPE_SIZE (type)))
 639                 /* In this case, shifting is like multiplication.  */
 640                 goto trunc1;
 641               else
 642                 {
 643                   /* If it is >= that width, result is zero.
 644                      Handling this with trunc1 would give the wrong result:
 645                      (int) ((long long) a << 32) is well defined (as 0)
 646                      but (int) a << 32 is undefined and would get a
 647                      warning.  */
 648
 649                   tree t = build_int_cst (type, 0);
 650
 651                   /* If the original expression had side-effects, we must
 652                      preserve it.  */
 653                   if (TREE_SIDE_EFFECTS (expr))
 654                     return build2 (COMPOUND_EXPR, type, expr, t);
 655                   else
 656                     return t;
 657                 }
 658             }
 659           break;
 660
 661         case TRUNC_DIV_EXPR:
 662           {
 663             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 664             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 665
 666             /* Don't distribute unless the output precision is at least as big
 667                as the actual inputs and it has the same signedness.  */
 668             if (outprec >= TYPE_PRECISION (TREE_TYPE (arg0))
 669                 && outprec >= TYPE_PRECISION (TREE_TYPE (arg1))
 670                 /* If signedness of arg0 and arg1 don't match,
 671                    we can't necessarily find a type to compare them in.  */
 672                 && (TYPE_UNSIGNED (TREE_TYPE (arg0))
 673                     == TYPE_UNSIGNED (TREE_TYPE (arg1)))
 674                 /* Do not change the sign of the division.  */
 675                 && (TYPE_UNSIGNED (TREE_TYPE (expr))
 676                     == TYPE_UNSIGNED (TREE_TYPE (arg0)))
 677                 /* Either require unsigned division or a division by
 678                    a constant that is not -1.  */
 679                 && (TYPE_UNSIGNED (TREE_TYPE (arg0))
 680                     || (TREE_CODE (arg1) == INTEGER_CST
 681                         && !integer_all_onesp (arg1))))
 682               goto trunc1;
 683             break;
 684           }
 685
 686         case MAX_EXPR:
 687         case MIN_EXPR:
 688         case MULT_EXPR:
 689           {
 690             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 691             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 692
 693             /* Don't distribute unless the output precision is at least as big
 694                as the actual inputs.  Otherwise, the comparison of the
 695                truncated values will be wrong.  */
 696             if (outprec >= TYPE_PRECISION (TREE_TYPE (arg0))
 697                 && outprec >= TYPE_PRECISION (TREE_TYPE (arg1))
 698                 /* If signedness of arg0 and arg1 don't match,
 699                    we can't necessarily find a type to compare them in.  */
 700                 && (TYPE_UNSIGNED (TREE_TYPE (arg0))
 701                     == TYPE_UNSIGNED (TREE_TYPE (arg1))))
 702               goto trunc1;
 703             break;
 704           }
 705
 706         case PLUS_EXPR:
 707         case MINUS_EXPR:
 708         case BIT_AND_EXPR:
 709         case BIT_IOR_EXPR:
 710         case BIT_XOR_EXPR:
 711         trunc1:
 712           {
 713             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 714             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 715
 716             /* Do not try to narrow operands of pointer subtraction;
 717                that will interfere with other folding.  */
 718             if (ex_form == MINUS_EXPR
 719                 && CONVERT_EXPR_P (arg0)
 720                 && CONVERT_EXPR_P (arg1)
 721                 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (arg0, 0)))
 722                 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (arg1, 0))))
 723               break;
 724
 725             if (outprec >= BITS_PER_WORD
 726                 || TRULY_NOOP_TRUNCATION (outprec, inprec)
 727                 || inprec > TYPE_PRECISION (TREE_TYPE (arg0))
 728                 || inprec > TYPE_PRECISION (TREE_TYPE (arg1)))
 729               {
 730                 /* Do the arithmetic in type TYPEX,
 731                    then convert result to TYPE.  */
 732                 tree typex = type;
 733
 734                 /* Can't do arithmetic in enumeral types
 735                    so use an integer type that will hold the values.  */
 736                 if (TREE_CODE (typex) == ENUMERAL_TYPE)
 737                   typex
 738                     = lang_hooks.types.type_for_size (TYPE_PRECISION (typex),
 739                                                       TYPE_UNSIGNED (typex));
 740
 741                 /* But now perhaps TYPEX is as wide as INPREC.
 742                    In that case, do nothing special here.
 743                    (Otherwise would recurse infinitely in convert.  */
 744                 if (TYPE_PRECISION (typex) != inprec)
 745                   {
 746                     /* Don't do unsigned arithmetic where signed was wanted,
 747                        or vice versa.
 748                        Exception: if both of the original operands were
 749                        unsigned then we can safely do the work as unsigned.
 750                        Exception: shift operations take their type solely
 751                        from the first argument.
 752                        Exception: the LSHIFT_EXPR case above requires that
 753                        we perform this operation unsigned lest we produce
 754                        signed-overflow undefinedness.
 755                        And we may need to do it as unsigned
 756                        if we truncate to the original size.  */
 757                     if (TYPE_UNSIGNED (TREE_TYPE (expr))
 758                         || (TYPE_UNSIGNED (TREE_TYPE (arg0))
 759                             && (TYPE_UNSIGNED (TREE_TYPE (arg1))
 760                                 || ex_form == LSHIFT_EXPR
 761                                 || ex_form == RSHIFT_EXPR
 762                                 || ex_form == LROTATE_EXPR
 763                                 || ex_form == RROTATE_EXPR))
 764                         || ex_form == LSHIFT_EXPR
 765                         /* If we have !flag_wrapv, and either ARG0 or
 766                            ARG1 is of a signed type, we have to do
 767                            PLUS_EXPR, MINUS_EXPR or MULT_EXPR in an unsigned
 768                            type in case the operation in outprec precision
 769                            could overflow.  Otherwise, we would introduce
 770                            signed-overflow undefinedness.  */
 771                         || ((!TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg0))
 772                              || !TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg1)))
 773                             && ((TYPE_PRECISION (TREE_TYPE (arg0)) * 2u
 774                                  > outprec)
 775                                 || (TYPE_PRECISION (TREE_TYPE (arg1)) * 2u
 776                                     > outprec))
 777                             && (ex_form == PLUS_EXPR
 778                                 || ex_form == MINUS_EXPR
 779                                 || ex_form == MULT_EXPR)))
 780                       {
 781                         if (!TYPE_UNSIGNED (typex))
 782                           typex = unsigned_type_for (typex);
 783                       }
 784                     else
 785                       {
 786                         if (TYPE_UNSIGNED (typex))
 787                           typex = signed_type_for (typex);
 788                       }
 789                     return convert (type,
 790                                     fold_build2 (ex_form, typex,
 791                                                  convert (typex, arg0),
 792                                                  convert (typex, arg1)));
 793                   }
 794               }
 795           }
 796           break;
 797
 798         case NEGATE_EXPR:
 799         case BIT_NOT_EXPR:
 800           /* This is not correct for ABS_EXPR,
 801              since we must test the sign before truncation.  */
 802           {
 803             /* Do the arithmetic in type TYPEX,
 804                then convert result to TYPE.  */
 805             tree typex = type;
 806
 807             /* Can't do arithmetic in enumeral types
 808                so use an integer type that will hold the values.  */
 809             if (TREE_CODE (typex) == ENUMERAL_TYPE)
 810               typex
 811                 = lang_hooks.types.type_for_size (TYPE_PRECISION (typex),
 812                                                   TYPE_UNSIGNED (typex));
 813
 814             if (!TYPE_UNSIGNED (typex))
 815               typex = unsigned_type_for (typex);
 816             return convert (type,
 817                             fold_build1 (ex_form, typex,
 818                                          convert (typex,
 819                                                   TREE_OPERAND (expr, 0))));
 820           }
 821
 822         CASE_CONVERT:
 823           /* Don't introduce a
 824              "can't convert between vector values of different size" error.  */
 825           if (TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0))) == VECTOR_TYPE
 826               && (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_OPERAND (expr, 0))))
 827                   != GET_MODE_SIZE (TYPE_MODE (type))))
 828             break;
 829           /* If truncating after truncating, might as well do all at once.
 830              If truncating after extending, we may get rid of wasted work.  */
 831           return convert (type, get_unwidened (TREE_OPERAND (expr, 0), type));
 832
 833         case COND_EXPR:
 834           /* It is sometimes worthwhile to push the narrowing down through
 835              the conditional and never loses.  A COND_EXPR may have a throw
 836              as one operand, which then has void type.  Just leave void
 837              operands as they are.  */
 838           return fold_build3 (COND_EXPR, type, TREE_OPERAND (expr, 0),
 839                               VOID_TYPE_P (TREE_TYPE (TREE_OPERAND (expr, 1)))
 840                               ? TREE_OPERAND (expr, 1)
 841                               : convert (type, TREE_OPERAND (expr, 1)),
 842                               VOID_TYPE_P (TREE_TYPE (TREE_OPERAND (expr, 2)))
 843                               ? TREE_OPERAND (expr, 2)
 844                               : convert (type, TREE_OPERAND (expr, 2)));
 845
 846         default:
 847           break;
 848         }
 849
 850       /* When parsing long initializers, we might end up with a lot of casts.
 851          Shortcut this.  */
 852       if (TREE_CODE (expr) == INTEGER_CST)
 853         return fold_convert (type, expr);
 854       return build1 (CONVERT_EXPR, type, expr);
 855
 856     case REAL_TYPE:
 857       if (flag_sanitize & SANITIZE_FLOAT_CAST
 858           && do_ubsan_in_current_function ())
 859         {
 860           expr = save_expr (expr);
 861           tree check = ubsan_instrument_float_cast (loc, type, expr, expr);
 862           expr = build1 (FIX_TRUNC_EXPR, type, expr);
 863           if (check == NULL)
 864             return expr;
 865           return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
 866         }
 867       else
 868         return build1 (FIX_TRUNC_EXPR, type, expr);
 869
 870     case FIXED_POINT_TYPE:
 871       return build1 (FIXED_CONVERT_EXPR, type, expr);
 872
 873     case COMPLEX_TYPE:
 874       return convert (type,
 875                       fold_build1 (REALPART_EXPR,
 876                                    TREE_TYPE (TREE_TYPE (expr)), expr));
 877
 878     case VECTOR_TYPE:
 879       if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr))))
 880         {
 881           error ("can%'t convert a vector of type %qT"
 882                  " to type %qT which has different size",
 883                  TREE_TYPE (expr), type);
 884           return error_mark_node;
 885         }
 886       return build1 (VIEW_CONVERT_EXPR, type, expr);
 887
 888     default:
 889       error ("aggregate value used where an integer was expected");
 890       return convert (type, integer_zero_node);
 891     }
 892 }
 893
 894 /* Convert EXPR to the complex type TYPE in the usual ways.  */
 895
 896 tree
 897 convert_to_complex (tree type, tree expr)
 898 {
 899   tree subtype = TREE_TYPE (type);
 900
 901   switch (TREE_CODE (TREE_TYPE (expr)))
 902     {
 903     case REAL_TYPE:
 904     case FIXED_POINT_TYPE:
 905     case INTEGER_TYPE:
 906     case ENUMERAL_TYPE:
 907     case BOOLEAN_TYPE:
 908       return build2 (COMPLEX_EXPR, type, convert (subtype, expr),
 909                      convert (subtype, integer_zero_node));
 910
 911     case COMPLEX_TYPE:
 912       {
 913         tree elt_type = TREE_TYPE (TREE_TYPE (expr));
 914
 915         if (TYPE_MAIN_VARIANT (elt_type) == TYPE_MAIN_VARIANT (subtype))
 916           return expr;
 917         else if (TREE_CODE (expr) == COMPOUND_EXPR)
 918           {
 919             tree t = convert_to_complex (type, TREE_OPERAND (expr, 1));
 920             if (t == TREE_OPERAND (expr, 1))
 921               return expr;
 922             return build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR,
 923                                TREE_TYPE (t), TREE_OPERAND (expr, 0), t);
 924           }
 925         else if (TREE_CODE (expr) == COMPLEX_EXPR)
 926           return fold_build2 (COMPLEX_EXPR, type,
 927                               convert (subtype, TREE_OPERAND (expr, 0)),
 928                               convert (subtype, TREE_OPERAND (expr, 1)));
 929         else
 930           {
 931             expr = save_expr (expr);
 932             return
 933               fold_build2 (COMPLEX_EXPR, type,
 934                            convert (subtype,
 935                                     fold_build1 (REALPART_EXPR,
 936                                                  TREE_TYPE (TREE_TYPE (expr)),
 937                                                  expr)),
 938                            convert (subtype,
 939                                     fold_build1 (IMAGPART_EXPR,
 940                                                  TREE_TYPE (TREE_TYPE (expr)),
 941                                                  expr)));
 942           }
 943       }
 944
 945     case POINTER_TYPE:
 946     case REFERENCE_TYPE:
 947       error ("pointer value used where a complex was expected");
 948       return convert_to_complex (type, integer_zero_node);
 949
 950     default:
 951       error ("aggregate value used where a complex was expected");
 952       return convert_to_complex (type, integer_zero_node);
 953     }
 954 }
 955
 956 /* Convert EXPR to the vector type TYPE in the usual ways.  */
 957
 958 tree
 959 convert_to_vector (tree type, tree expr)
 960 {
 961   switch (TREE_CODE (TREE_TYPE (expr)))
 962     {
 963     case INTEGER_TYPE:
 964     case VECTOR_TYPE:
 965       if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr))))
 966         {
 967           error ("can%'t convert a value of type %qT"
 968                  " to vector type %qT which has different size",
 969                  TREE_TYPE (expr), type);
 970           return error_mark_node;
 971         }
 972       return build1 (VIEW_CONVERT_EXPR, type, expr);
 973
 974     default:
 975       error ("can%'t convert value to a vector");
 976       return error_mark_node;
 977     }
 978 }
 979
 980 /* Convert EXPR to some fixed-point type TYPE.
 981
 982    EXPR must be fixed-point, float, integer, or enumeral;
 983    in other cases error is called.  */
 984
 985 tree
 986 convert_to_fixed (tree type, tree expr)
 987 {
 988   if (integer_zerop (expr))
 989     {
 990       tree fixed_zero_node = build_fixed (type, FCONST0 (TYPE_MODE (type)));
 991       return fixed_zero_node;
 992     }
 993   else if (integer_onep (expr) && ALL_SCALAR_ACCUM_MODE_P (TYPE_MODE (type)))
 994     {
 995       tree fixed_one_node = build_fixed (type, FCONST1 (TYPE_MODE (type)));
 996       return fixed_one_node;
 997     }
 998
 999   switch (TREE_CODE (TREE_TYPE (expr)))
1000     {
1001     case FIXED_POINT_TYPE:
1002     case INTEGER_TYPE:
1003     case ENUMERAL_TYPE:
1004     case BOOLEAN_TYPE:
1005     case REAL_TYPE:
1006       return build1 (FIXED_CONVERT_EXPR, type, expr);
1007
1008     case COMPLEX_TYPE:
1009       return convert (type,
1010                       fold_build1 (REALPART_EXPR,
1011                                    TREE_TYPE (TREE_TYPE (expr)), expr));
1012
1013     default:
1014       error ("aggregate value used where a fixed-point was expected");
1015       return error_mark_node;
1016     }
1017 }