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 Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 2, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING.  If not, write to the Free
  19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  20 02111-1307, USA.  */
  21
  22
  23 /* These routines are somewhat language-independent utility function
  24    intended to be called by the language-specific convert () functions.  */
  25
  26 #include "config.h"
  27 #include "system.h"
  28 #include "coretypes.h"
  29 #include "tm.h"
  30 #include "tree.h"
  31 #include "flags.h"
  32 #include "convert.h"
  33 #include "toplev.h"
  34 #include "langhooks.h"
  35 #include "real.h"
  36 /* Convert EXPR to some pointer or reference type TYPE.
  37
  38    EXPR must be pointer, reference, integer, enumeral, or literal zero;
  39    in other cases error is called.  */
  40
  41 tree
  42 convert_to_pointer (tree type, tree expr)
  43 {
  44   if (integer_zerop (expr))
  45     {
  46       expr = build_int_cst (type, 0);
  47       return expr;
  48     }
  49
  50   switch (TREE_CODE (TREE_TYPE (expr)))
  51     {
  52     case POINTER_TYPE:
  53     case REFERENCE_TYPE:
  54       return build1 (NOP_EXPR, type, expr);
  55
  56     case INTEGER_TYPE:
  57     case ENUMERAL_TYPE:
  58     case BOOLEAN_TYPE:
  59     case CHAR_TYPE:
  60       if (TYPE_PRECISION (TREE_TYPE (expr)) == POINTER_SIZE)
  61         return build1 (CONVERT_EXPR, type, expr);
  62
  63       return
  64         convert_to_pointer (type,
  65                             convert (lang_hooks.types.type_for_size
  66                                      (POINTER_SIZE, 0), expr));
  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)
  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 (TREE_CODE (exp) != NOP_EXPR
 102       && TREE_CODE (exp) != CONVERT_EXPR)
 103     return exp;
 104
 105   sub = TREE_OPERAND (exp, 0);
 106   subt = TREE_TYPE (sub);
 107   expt = TREE_TYPE (exp);
 108
 109   if (!FLOAT_TYPE_P (subt))
 110     return exp;
 111
 112   if (TYPE_PRECISION (subt) > TYPE_PRECISION (expt))
 113     return exp;
 114
 115   return strip_float_extensions (sub);
 116 }
 117
 118
 119 /* Convert EXPR to some floating-point type TYPE.
 120
 121    EXPR must be float, integer, or enumeral;
 122    in other cases error is called.  */
 123
 124 tree
 125 convert_to_real (tree type, tree expr)
 126 {
 127   enum built_in_function fcode = builtin_mathfn_code (expr);
 128   tree itype = TREE_TYPE (expr);
 129
 130   /* Disable until we figure out how to decide whether the functions are
 131      present in runtime.  */
 132   /* Convert (float)sqrt((double)x) where x is float into sqrtf(x) */
 133   if (optimize
 134       && (TYPE_MODE (type) == TYPE_MODE (double_type_node)
 135           || TYPE_MODE (type) == TYPE_MODE (float_type_node)))
 136     {
 137       switch (fcode)
 138         {
 139 #define CASE_MATHFN(FN) case BUILT_IN_##FN: case BUILT_IN_##FN##L:
 140           CASE_MATHFN (ACOS)
 141           CASE_MATHFN (ACOSH)
 142           CASE_MATHFN (ASIN)
 143           CASE_MATHFN (ASINH)
 144           CASE_MATHFN (ATAN)
 145           CASE_MATHFN (ATANH)
 146           CASE_MATHFN (CBRT)
 147           CASE_MATHFN (COS)
 148           CASE_MATHFN (COSH)
 149           CASE_MATHFN (ERF)
 150           CASE_MATHFN (ERFC)
 151           CASE_MATHFN (EXP)
 152           CASE_MATHFN (EXP10)
 153           CASE_MATHFN (EXP2)
 154           CASE_MATHFN (EXPM1)
 155           CASE_MATHFN (FABS)
 156           CASE_MATHFN (GAMMA)
 157           CASE_MATHFN (J0)
 158           CASE_MATHFN (J1)
 159           CASE_MATHFN (LGAMMA)
 160           CASE_MATHFN (LOG)
 161           CASE_MATHFN (LOG10)
 162           CASE_MATHFN (LOG1P)
 163           CASE_MATHFN (LOG2)
 164           CASE_MATHFN (LOGB)
 165           CASE_MATHFN (POW10)
 166           CASE_MATHFN (SIN)
 167           CASE_MATHFN (SINH)
 168           CASE_MATHFN (SQRT)
 169           CASE_MATHFN (TAN)
 170           CASE_MATHFN (TANH)
 171           CASE_MATHFN (TGAMMA)
 172           CASE_MATHFN (Y0)
 173           CASE_MATHFN (Y1)
 174 #undef CASE_MATHFN
 175             {
 176               tree arg0 = strip_float_extensions (TREE_VALUE (TREE_OPERAND (expr, 1)));
 177               tree newtype = type;
 178
 179               /* We have (outertype)sqrt((innertype)x).  Choose the wider mode from
 180                  the both as the safe type for operation.  */
 181               if (TYPE_PRECISION (TREE_TYPE (arg0)) > TYPE_PRECISION (type))
 182                 newtype = TREE_TYPE (arg0);
 183
 184               /* Be careful about integer to fp conversions.
 185                  These may overflow still.  */
 186               if (FLOAT_TYPE_P (TREE_TYPE (arg0))
 187                   && TYPE_PRECISION (newtype) < TYPE_PRECISION (itype)
 188                   && (TYPE_MODE (newtype) == TYPE_MODE (double_type_node)
 189                       || TYPE_MODE (newtype) == TYPE_MODE (float_type_node)))
 190                 {
 191                   tree arglist;
 192                   tree fn = mathfn_built_in (newtype, fcode);
 193
 194                   if (fn)
 195                   {
 196                     arglist = build_tree_list (NULL_TREE, fold (convert_to_real (newtype, arg0)));
 197                     expr = build_function_call_expr (fn, arglist);
 198                     if (newtype == type)
 199                       return expr;
 200                   }
 201                 }
 202             }
 203         default:
 204           break;
 205         }
 206     }
 207   if (optimize
 208       && (((fcode == BUILT_IN_FLOORL
 209            || fcode == BUILT_IN_CEILL
 210            || fcode == BUILT_IN_ROUNDL
 211            || fcode == BUILT_IN_RINTL
 212            || fcode == BUILT_IN_TRUNCL
 213            || fcode == BUILT_IN_NEARBYINTL)
 214           && (TYPE_MODE (type) == TYPE_MODE (double_type_node)
 215               || TYPE_MODE (type) == TYPE_MODE (float_type_node)))
 216           || ((fcode == BUILT_IN_FLOOR
 217                || fcode == BUILT_IN_CEIL
 218                || fcode == BUILT_IN_ROUND
 219                || fcode == BUILT_IN_RINT
 220                || fcode == BUILT_IN_TRUNC
 221                || fcode == BUILT_IN_NEARBYINT)
 222               && (TYPE_MODE (type) == TYPE_MODE (float_type_node)))))
 223     {
 224       tree fn = mathfn_built_in (type, fcode);
 225
 226       if (fn)
 227         {
 228           tree arg0 = strip_float_extensions (TREE_VALUE (TREE_OPERAND (expr,
 229                                                                         1)));
 230           tree arglist = build_tree_list (NULL_TREE,
 231                                           fold (convert_to_real (type, arg0)));
 232
 233           return build_function_call_expr (fn, arglist);
 234         }
 235     }
 236
 237   /* Propagate the cast into the operation.  */
 238   if (itype != type && FLOAT_TYPE_P (type))
 239     switch (TREE_CODE (expr))
 240       {
 241         /* Convert (float)-x into -(float)x.  This is always safe.  */
 242         case ABS_EXPR:
 243         case NEGATE_EXPR:
 244           if (TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (expr)))
 245             return build1 (TREE_CODE (expr), type,
 246                            fold (convert_to_real (type,
 247                                                   TREE_OPERAND (expr, 0))));
 248           break;
 249         /* Convert (outertype)((innertype0)a+(innertype1)b)
 250            into ((newtype)a+(newtype)b) where newtype
 251            is the widest mode from all of these.  */
 252         case PLUS_EXPR:
 253         case MINUS_EXPR:
 254         case MULT_EXPR:
 255         case RDIV_EXPR:
 256            {
 257              tree arg0 = strip_float_extensions (TREE_OPERAND (expr, 0));
 258              tree arg1 = strip_float_extensions (TREE_OPERAND (expr, 1));
 259
 260              if (FLOAT_TYPE_P (TREE_TYPE (arg0))
 261                  && FLOAT_TYPE_P (TREE_TYPE (arg1)))
 262                {
 263                   tree newtype = type;
 264                   if (TYPE_PRECISION (TREE_TYPE (arg0)) > TYPE_PRECISION (newtype))
 265                     newtype = TREE_TYPE (arg0);
 266                   if (TYPE_PRECISION (TREE_TYPE (arg1)) > TYPE_PRECISION (newtype))
 267                     newtype = TREE_TYPE (arg1);
 268                   if (TYPE_PRECISION (newtype) < TYPE_PRECISION (itype))
 269                     {
 270                       expr = build2 (TREE_CODE (expr), newtype,
 271                                      fold (convert_to_real (newtype, arg0)),
 272                                      fold (convert_to_real (newtype, arg1)));
 273                       if (newtype == type)
 274                         return expr;
 275                     }
 276                }
 277            }
 278           break;
 279         default:
 280           break;
 281       }
 282
 283   switch (TREE_CODE (TREE_TYPE (expr)))
 284     {
 285     case REAL_TYPE:
 286       return build1 (flag_float_store ? CONVERT_EXPR : NOP_EXPR,
 287                      type, expr);
 288
 289     case INTEGER_TYPE:
 290     case ENUMERAL_TYPE:
 291     case BOOLEAN_TYPE:
 292     case CHAR_TYPE:
 293       return build1 (FLOAT_EXPR, type, expr);
 294
 295     case COMPLEX_TYPE:
 296       return convert (type,
 297                       fold (build1 (REALPART_EXPR,
 298                                     TREE_TYPE (TREE_TYPE (expr)), expr)));
 299
 300     case POINTER_TYPE:
 301     case REFERENCE_TYPE:
 302       error ("pointer value used where a floating point value was expected");
 303       return convert_to_real (type, integer_zero_node);
 304
 305     default:
 306       error ("aggregate value used where a float was expected");
 307       return convert_to_real (type, integer_zero_node);
 308     }
 309 }
 310
 311 /* Convert EXPR to some integer (or enum) type TYPE.
 312
 313    EXPR must be pointer, integer, discrete (enum, char, or bool), float, or
 314    vector; in other cases error is called.
 315
 316    The result of this is always supposed to be a newly created tree node
 317    not in use in any existing structure.  */
 318
 319 tree
 320 convert_to_integer (tree type, tree expr)
 321 {
 322   enum tree_code ex_form = TREE_CODE (expr);
 323   tree intype = TREE_TYPE (expr);
 324   unsigned int inprec = TYPE_PRECISION (intype);
 325   unsigned int outprec = TYPE_PRECISION (type);
 326
 327   /* An INTEGER_TYPE cannot be incomplete, but an ENUMERAL_TYPE can
 328      be.  Consider `enum E = { a, b = (enum E) 3 };'.  */
 329   if (!COMPLETE_TYPE_P (type))
 330     {
 331       error ("conversion to incomplete type");
 332       return error_mark_node;
 333     }
 334
 335   /* Convert e.g. (long)round(d) -> lround(d).  */
 336   /* If we're converting to char, we may encounter differing behavior
 337      between converting from double->char vs double->long->char.
 338      We're in "undefined" territory but we prefer to be conservative,
 339      so only proceed in "unsafe" math mode.  */
 340   if (optimize
 341       && (flag_unsafe_math_optimizations
 342           || (long_integer_type_node
 343               && outprec >= TYPE_PRECISION (long_integer_type_node))))
 344     {
 345       tree s_expr = strip_float_extensions (expr);
 346       tree s_intype = TREE_TYPE (s_expr);
 347       const enum built_in_function fcode = builtin_mathfn_code (s_expr);
 348       tree fn = 0;
 349
 350       switch (fcode)
 351         {
 352         case BUILT_IN_CEIL: case BUILT_IN_CEILF: case BUILT_IN_CEILL:
 353           if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (long_long_integer_type_node))
 354             fn = mathfn_built_in (s_intype, BUILT_IN_LLCEIL);
 355           else
 356             fn = mathfn_built_in (s_intype, BUILT_IN_LCEIL);
 357           break;
 358
 359         case BUILT_IN_FLOOR: case BUILT_IN_FLOORF: case BUILT_IN_FLOORL:
 360           if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (long_long_integer_type_node))
 361             fn = mathfn_built_in (s_intype, BUILT_IN_LLFLOOR);
 362           else
 363             fn = mathfn_built_in (s_intype, BUILT_IN_LFLOOR);
 364           break;
 365
 366         case BUILT_IN_ROUND: case BUILT_IN_ROUNDF: case BUILT_IN_ROUNDL:
 367           if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (long_long_integer_type_node))
 368             fn = mathfn_built_in (s_intype, BUILT_IN_LLROUND);
 369           else
 370             fn = mathfn_built_in (s_intype, BUILT_IN_LROUND);
 371           break;
 372
 373         case BUILT_IN_RINT: case BUILT_IN_RINTF: case BUILT_IN_RINTL:
 374           /* Only convert rint* if we can ignore math exceptions.  */
 375           if (flag_trapping_math)
 376             break;
 377           /* ... Fall through ...  */
 378         case BUILT_IN_NEARBYINT: case BUILT_IN_NEARBYINTF: case BUILT_IN_NEARBYINTL:
 379           if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (long_long_integer_type_node))
 380             fn = mathfn_built_in (s_intype, BUILT_IN_LLRINT);
 381           else
 382             fn = mathfn_built_in (s_intype, BUILT_IN_LRINT);
 383           break;
 384         default:
 385           break;
 386         }
 387
 388       if (fn)
 389         {
 390           tree arglist = TREE_OPERAND (s_expr, 1);
 391           tree newexpr = build_function_call_expr (fn, arglist);
 392           return convert_to_integer (type, newexpr);
 393         }
 394     }
 395
 396   switch (TREE_CODE (intype))
 397     {
 398     case POINTER_TYPE:
 399     case REFERENCE_TYPE:
 400       if (integer_zerop (expr))
 401         expr = integer_zero_node;
 402       else
 403         expr = fold (build1 (CONVERT_EXPR,
 404                              lang_hooks.types.type_for_size (POINTER_SIZE, 0),
 405                              expr));
 406
 407       return convert_to_integer (type, expr);
 408
 409     case INTEGER_TYPE:
 410     case ENUMERAL_TYPE:
 411     case BOOLEAN_TYPE:
 412     case CHAR_TYPE:
 413       /* If this is a logical operation, which just returns 0 or 1, we can
 414          change the type of the expression.  */
 415
 416       if (TREE_CODE_CLASS (ex_form) == tcc_comparison)
 417         {
 418           expr = copy_node (expr);
 419           TREE_TYPE (expr) = type;
 420           return expr;
 421         }
 422
 423       /* If we are widening the type, put in an explicit conversion.
 424          Similarly if we are not changing the width.  After this, we know
 425          we are truncating EXPR.  */
 426
 427       else if (outprec >= inprec)
 428         {
 429           enum tree_code code;
 430
 431           /* If the precision of the EXPR's type is K bits and the
 432              destination mode has more bits, and the sign is changing,
 433              it is not safe to use a NOP_EXPR.  For example, suppose
 434              that EXPR's type is a 3-bit unsigned integer type, the
 435              TYPE is a 3-bit signed integer type, and the machine mode
 436              for the types is 8-bit QImode.  In that case, the
 437              conversion necessitates an explicit sign-extension.  In
 438              the signed-to-unsigned case the high-order bits have to
 439              be cleared.  */
 440           if (TYPE_UNSIGNED (type) != TYPE_UNSIGNED (TREE_TYPE (expr))
 441               && (TYPE_PRECISION (TREE_TYPE (expr))
 442                   != GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (expr)))))
 443             code = CONVERT_EXPR;
 444           else
 445             code = NOP_EXPR;
 446
 447           return build1 (code, type, expr);
 448         }
 449
 450       /* If TYPE is an enumeral type or a type with a precision less
 451          than the number of bits in its mode, do the conversion to the
 452          type corresponding to its mode, then do a nop conversion
 453          to TYPE.  */
 454       else if (TREE_CODE (type) == ENUMERAL_TYPE
 455                || outprec != GET_MODE_BITSIZE (TYPE_MODE (type)))
 456         return build1 (NOP_EXPR, type,
 457                        convert (lang_hooks.types.type_for_mode
 458                                 (TYPE_MODE (type), TYPE_UNSIGNED (type)),
 459                                 expr));
 460
 461       /* Here detect when we can distribute the truncation down past some
 462          arithmetic.  For example, if adding two longs and converting to an
 463          int, we can equally well convert both to ints and then add.
 464          For the operations handled here, such truncation distribution
 465          is always safe.
 466          It is desirable in these cases:
 467          1) when truncating down to full-word from a larger size
 468          2) when truncating takes no work.
 469          3) when at least one operand of the arithmetic has been extended
 470          (as by C's default conversions).  In this case we need two conversions
 471          if we do the arithmetic as already requested, so we might as well
 472          truncate both and then combine.  Perhaps that way we need only one.
 473
 474          Note that in general we cannot do the arithmetic in a type
 475          shorter than the desired result of conversion, even if the operands
 476          are both extended from a shorter type, because they might overflow
 477          if combined in that type.  The exceptions to this--the times when
 478          two narrow values can be combined in their narrow type even to
 479          make a wider result--are handled by "shorten" in build_binary_op.  */
 480
 481       switch (ex_form)
 482         {
 483         case RSHIFT_EXPR:
 484           /* We can pass truncation down through right shifting
 485              when the shift count is a nonpositive constant.  */
 486           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 487               && tree_int_cst_lt (TREE_OPERAND (expr, 1),
 488                                   convert (TREE_TYPE (TREE_OPERAND (expr, 1)),
 489                                            integer_one_node)))
 490             goto trunc1;
 491           break;
 492
 493         case LSHIFT_EXPR:
 494           /* We can pass truncation down through left shifting
 495              when the shift count is a nonnegative constant and
 496              the target type is unsigned.  */
 497           if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
 498               && tree_int_cst_sgn (TREE_OPERAND (expr, 1)) >= 0
 499               && TYPE_UNSIGNED (type)
 500               && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
 501             {
 502               /* If shift count is less than the width of the truncated type,
 503                  really shift.  */
 504               if (tree_int_cst_lt (TREE_OPERAND (expr, 1), TYPE_SIZE (type)))
 505                 /* In this case, shifting is like multiplication.  */
 506                 goto trunc1;
 507               else
 508                 {
 509                   /* If it is >= that width, result is zero.
 510                      Handling this with trunc1 would give the wrong result:
 511                      (int) ((long long) a << 32) is well defined (as 0)
 512                      but (int) a << 32 is undefined and would get a
 513                      warning.  */
 514
 515                   tree t = convert_to_integer (type, integer_zero_node);
 516
 517                   /* If the original expression had side-effects, we must
 518                      preserve it.  */
 519                   if (TREE_SIDE_EFFECTS (expr))
 520                     return build2 (COMPOUND_EXPR, type, expr, t);
 521                   else
 522                     return t;
 523                 }
 524             }
 525           break;
 526
 527         case MAX_EXPR:
 528         case MIN_EXPR:
 529         case MULT_EXPR:
 530           {
 531             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 532             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 533
 534             /* Don't distribute unless the output precision is at least as big
 535                as the actual inputs.  Otherwise, the comparison of the
 536                truncated values will be wrong.  */
 537             if (outprec >= TYPE_PRECISION (TREE_TYPE (arg0))
 538                 && outprec >= TYPE_PRECISION (TREE_TYPE (arg1))
 539                 /* If signedness of arg0 and arg1 don't match,
 540                    we can't necessarily find a type to compare them in.  */
 541                 && (TYPE_UNSIGNED (TREE_TYPE (arg0))
 542                     == TYPE_UNSIGNED (TREE_TYPE (arg1))))
 543               goto trunc1;
 544             break;
 545           }
 546
 547         case PLUS_EXPR:
 548         case MINUS_EXPR:
 549         case BIT_AND_EXPR:
 550         case BIT_IOR_EXPR:
 551         case BIT_XOR_EXPR:
 552         trunc1:
 553           {
 554             tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
 555             tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
 556
 557             if (outprec >= BITS_PER_WORD
 558                 || TRULY_NOOP_TRUNCATION (outprec, inprec)
 559                 || inprec > TYPE_PRECISION (TREE_TYPE (arg0))
 560                 || inprec > TYPE_PRECISION (TREE_TYPE (arg1)))
 561               {
 562                 /* Do the arithmetic in type TYPEX,
 563                    then convert result to TYPE.  */
 564                 tree typex = type;
 565
 566                 /* Can't do arithmetic in enumeral types
 567                    so use an integer type that will hold the values.  */
 568                 if (TREE_CODE (typex) == ENUMERAL_TYPE)
 569                   typex = lang_hooks.types.type_for_size
 570                     (TYPE_PRECISION (typex), TYPE_UNSIGNED (typex));
 571
 572                 /* But now perhaps TYPEX is as wide as INPREC.
 573                    In that case, do nothing special here.
 574                    (Otherwise would recurse infinitely in convert.  */
 575                 if (TYPE_PRECISION (typex) != inprec)
 576                   {
 577                     /* Don't do unsigned arithmetic where signed was wanted,
 578                        or vice versa.
 579                        Exception: if both of the original operands were
 580                        unsigned then we can safely do the work as unsigned.
 581                        Exception: shift operations take their type solely
 582                        from the first argument.
 583                        Exception: the LSHIFT_EXPR case above requires that
 584                        we perform this operation unsigned lest we produce
 585                        signed-overflow undefinedness.
 586                        And we may need to do it as unsigned
 587                        if we truncate to the original size.  */
 588                     if (TYPE_UNSIGNED (TREE_TYPE (expr))
 589                         || (TYPE_UNSIGNED (TREE_TYPE (arg0))
 590                             && (TYPE_UNSIGNED (TREE_TYPE (arg1))
 591                                 || ex_form == LSHIFT_EXPR
 592                                 || ex_form == RSHIFT_EXPR
 593                                 || ex_form == LROTATE_EXPR
 594                                 || ex_form == RROTATE_EXPR))
 595                         || ex_form == LSHIFT_EXPR)
 596                       typex = lang_hooks.types.unsigned_type (typex);
 597                     else
 598                       typex = lang_hooks.types.signed_type (typex);
 599                     return convert (type,
 600                                     fold (build2 (ex_form, typex,
 601                                                   convert (typex, arg0),
 602                                                   convert (typex, arg1))));
 603                   }
 604               }
 605           }
 606           break;
 607
 608         case NEGATE_EXPR:
 609         case BIT_NOT_EXPR:
 610           /* This is not correct for ABS_EXPR,
 611              since we must test the sign before truncation.  */
 612           {
 613             tree typex = type;
 614
 615             /* Can't do arithmetic in enumeral types
 616                so use an integer type that will hold the values.  */
 617             if (TREE_CODE (typex) == ENUMERAL_TYPE)
 618               typex = lang_hooks.types.type_for_size
 619                 (TYPE_PRECISION (typex), TYPE_UNSIGNED (typex));
 620
 621             /* But now perhaps TYPEX is as wide as INPREC.
 622                In that case, do nothing special here.
 623                (Otherwise would recurse infinitely in convert.  */
 624             if (TYPE_PRECISION (typex) != inprec)
 625               {
 626                 /* Don't do unsigned arithmetic where signed was wanted,
 627                    or vice versa.  */
 628                 if (TYPE_UNSIGNED (TREE_TYPE (expr)))
 629                   typex = lang_hooks.types.unsigned_type (typex);
 630                 else
 631                   typex = lang_hooks.types.signed_type (typex);
 632                 return convert (type,
 633                                 fold (build1 (ex_form, typex,
 634                                               convert (typex,
 635                                                        TREE_OPERAND (expr, 0)))));
 636               }
 637           }
 638
 639         case NOP_EXPR:
 640           /* Don't introduce a
 641              "can't convert between vector values of different size" error.  */
 642           if (TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0))) == VECTOR_TYPE
 643               && (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_OPERAND (expr, 0))))
 644                   != GET_MODE_SIZE (TYPE_MODE (type))))
 645             break;
 646           /* If truncating after truncating, might as well do all at once.
 647              If truncating after extending, we may get rid of wasted work.  */
 648           return convert (type, get_unwidened (TREE_OPERAND (expr, 0), type));
 649
 650         case COND_EXPR:
 651           /* It is sometimes worthwhile to push the narrowing down through
 652              the conditional and never loses.  */
 653           return fold (build3 (COND_EXPR, type, TREE_OPERAND (expr, 0),
 654                                convert (type, TREE_OPERAND (expr, 1)),
 655                                convert (type, TREE_OPERAND (expr, 2))));
 656
 657         default:
 658           break;
 659         }
 660
 661       return build1 (CONVERT_EXPR, type, expr);
 662
 663     case REAL_TYPE:
 664       return build1 (FIX_TRUNC_EXPR, type, expr);
 665
 666     case COMPLEX_TYPE:
 667       return convert (type,
 668                       fold (build1 (REALPART_EXPR,
 669                                     TREE_TYPE (TREE_TYPE (expr)), expr)));
 670
 671     case VECTOR_TYPE:
 672       if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr))))
 673         {
 674           error ("can't convert between vector values of different size");
 675           return error_mark_node;
 676         }
 677       return build1 (NOP_EXPR, type, expr);
 678
 679     default:
 680       error ("aggregate value used where an integer was expected");
 681       return convert (type, integer_zero_node);
 682     }
 683 }
 684
 685 /* Convert EXPR to the complex type TYPE in the usual ways.  */
 686
 687 tree
 688 convert_to_complex (tree type, tree expr)
 689 {
 690   tree subtype = TREE_TYPE (type);
 691
 692   switch (TREE_CODE (TREE_TYPE (expr)))
 693     {
 694     case REAL_TYPE:
 695     case INTEGER_TYPE:
 696     case ENUMERAL_TYPE:
 697     case BOOLEAN_TYPE:
 698     case CHAR_TYPE:
 699       return build2 (COMPLEX_EXPR, type, convert (subtype, expr),
 700                      convert (subtype, integer_zero_node));
 701
 702     case COMPLEX_TYPE:
 703       {
 704         tree elt_type = TREE_TYPE (TREE_TYPE (expr));
 705
 706         if (TYPE_MAIN_VARIANT (elt_type) == TYPE_MAIN_VARIANT (subtype))
 707           return expr;
 708         else if (TREE_CODE (expr) == COMPLEX_EXPR)
 709           return fold (build2 (COMPLEX_EXPR, type,
 710                                convert (subtype, TREE_OPERAND (expr, 0)),
 711                                convert (subtype, TREE_OPERAND (expr, 1))));
 712         else
 713           {
 714             expr = save_expr (expr);
 715             return
 716               fold (build2 (COMPLEX_EXPR, type,
 717                             convert (subtype,
 718                                      fold (build1 (REALPART_EXPR,
 719                                                    TREE_TYPE (TREE_TYPE (expr)),
 720                                                    expr))),
 721                             convert (subtype,
 722                                      fold (build1 (IMAGPART_EXPR,
 723                                                    TREE_TYPE (TREE_TYPE (expr)),
 724                                                    expr)))));
 725           }
 726       }
 727
 728     case POINTER_TYPE:
 729     case REFERENCE_TYPE:
 730       error ("pointer value used where a complex was expected");
 731       return convert_to_complex (type, integer_zero_node);
 732
 733     default:
 734       error ("aggregate value used where a complex was expected");
 735       return convert_to_complex (type, integer_zero_node);
 736     }
 737 }
 738
 739 /* Convert EXPR to the vector type TYPE in the usual ways.  */
 740
 741 tree
 742 convert_to_vector (tree type, tree expr)
 743 {
 744   switch (TREE_CODE (TREE_TYPE (expr)))
 745     {
 746     case INTEGER_TYPE:
 747     case VECTOR_TYPE:
 748       if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr))))
 749         {
 750           error ("can't convert between vector values of different size");
 751           return error_mark_node;
 752         }
 753       return build1 (NOP_EXPR, type, expr);
 754
 755     default:
 756       error ("can't convert value to a vector");
 757       return error_mark_node;
 758     }
 759 }