gcc/cp/expr.c

   1 /* Convert language-specific tree expression to rtl instructions,
   2    for GNU compiler.
   3    Copyright (C) 1988, 92-97, 1998 Free Software Foundation, Inc.
   4
   5 This file is part of GNU CC.
   6
   7 GNU CC is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2, or (at your option)
  10 any later version.
  11
  12 GNU CC is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU CC; see the file COPYING.  If not, write to
  19 the Free Software Foundation, 59 Temple Place - Suite 330,
  20 Boston, MA 02111-1307, USA.  */
  21
  22
  23 #include "config.h"
  24 #include "system.h"
  25 #include "rtl.h"
  26 #include "tree.h"
  27 #include "flags.h"
  28 #include "expr.h"
  29 #include "cp-tree.h"
  30 #include "toplev.h"
  31 #include "except.h"
  32 #include "tm_p.h"
  33
  34 #if 0
  35 static tree extract_aggr_init PROTO((tree, tree));
  36 static tree extract_scalar_init PROTO((tree, tree));
  37 #endif
  38 static rtx cplus_expand_expr PROTO((tree, rtx, enum machine_mode,
  39                                     enum expand_modifier));
  40
  41 /* Hook used by output_constant to expand language-specific
  42    constants.  */
  43
  44 tree
  45 cplus_expand_constant (cst)
  46      tree cst;
  47 {
  48   switch (TREE_CODE (cst))
  49     {
  50     case PTRMEM_CST:
  51       {
  52         tree type = TREE_TYPE (cst);
  53         tree member;
  54         tree offset;
  55
  56         /* Find the member.  */
  57         member = PTRMEM_CST_MEMBER (cst);
  58
  59         if (TREE_CODE (member) == FIELD_DECL)
  60           {
  61             /* Find the offset for the field.  */
  62             offset = convert (sizetype,
  63                               size_binop (EASY_DIV_EXPR,
  64                                           DECL_FIELD_BITPOS (member),
  65                                           size_int (BITS_PER_UNIT)));
  66
  67             /* We offset all pointer to data members by 1 so that we
  68                can distinguish between a null pointer to data member
  69                and the first data member of a structure.  */
  70             offset = size_binop (PLUS_EXPR, offset, size_int (1));
  71
  72             cst = cp_convert (type, offset);
  73           }
  74         else
  75           {
  76             tree delta;
  77             tree idx;
  78             tree pfn;
  79             tree delta2;
  80
  81             expand_ptrmemfunc_cst (cst, &delta, &idx, &pfn, &delta2);
  82
  83             cst = build_ptrmemfunc1 (type, delta, idx,
  84                                      pfn, delta2);
  85           }
  86       }
  87       break;
  88
  89     default:
  90       /* There's nothing to do.  */
  91       break;
  92     }
  93
  94   return cst;
  95 }
  96
  97 /* Hook used by expand_expr to expand language-specific tree codes.  */
  98
  99 static rtx
 100 cplus_expand_expr (exp, target, tmode, modifier)
 101      tree exp;
 102      rtx target;
 103      enum machine_mode tmode;
 104      enum expand_modifier modifier;
 105 {
 106   tree type = TREE_TYPE (exp);
 107   register enum machine_mode mode = TYPE_MODE (type);
 108   register enum tree_code code = TREE_CODE (exp);
 109   int ignore = target == const0_rtx;
 110
 111   if (ignore)
 112     target = 0;
 113
 114   /* No sense saving up arithmetic to be done
 115      if it's all in the wrong mode to form part of an address.
 116      And force_operand won't know whether to sign-extend or zero-extend.  */
 117
 118   if (mode != Pmode && modifier == EXPAND_SUM)
 119     modifier = EXPAND_NORMAL;
 120
 121   switch (code)
 122     {
 123     case AGGR_INIT_EXPR:
 124       {
 125         /* Something needs to be initialized, but we didn't know
 126            where that thing was when building the tree.  For example,
 127            it could be the return value of a function, or a parameter
 128            to a function which lays down in the stack, or a temporary
 129            variable which must be passed by reference.
 130
 131            Cleanups are handled in a language-specific way: they
 132            might be run by the called function (true in GNU C++
 133            for parameters with cleanups), or they might be
 134            run by the caller, after the call (true in GNU C++
 135            for other cleanup needs).  */
 136
 137         tree func = TREE_OPERAND (exp, 0);
 138         tree args = TREE_OPERAND (exp, 1);
 139         tree type = TREE_TYPE (exp), slot;
 140         tree call_exp;
 141         rtx call_target, return_target;
 142         int pcc_struct_return = 0;
 143
 144         /* The expression `init' wants to initialize what
 145            `target' represents.  SLOT holds the slot for TARGET.  */
 146         slot = TREE_OPERAND (exp, 2);
 147
 148         /* Should always be called with a target.  */
 149         my_friendly_assert (target != NULL_RTX, 205);
 150
 151         /* The target the initializer will initialize (CALL_TARGET)
 152            must now be directed to initialize the target we are
 153            supposed to initialize (TARGET).  The semantics for
 154            choosing what CALL_TARGET is is language-specific,
 155            as is building the call which will perform the
 156            initialization.  It is left here to show the choices that
 157            exist for C++.  */
 158
 159         if (AGGR_INIT_VIA_CTOR_P (exp))
 160           {
 161             type = build_pointer_type (type);
 162             mark_addressable (slot);
 163             args = tree_cons (NULL_TREE,
 164                               build1 (ADDR_EXPR, type, slot),
 165                               TREE_CHAIN (args));
 166             call_target = 0;
 167           }
 168         else
 169           {
 170             call_target = target;
 171 #ifdef PCC_STATIC_STRUCT_RETURN
 172             if (aggregate_value_p (type))
 173               {
 174                 pcc_struct_return = 1;
 175                 call_target = 0;
 176               }
 177 #endif
 178           }
 179
 180         call_exp = build (CALL_EXPR, type, func, args, NULL_TREE);
 181         TREE_SIDE_EFFECTS (call_exp) = 1;
 182         return_target = expand_call (call_exp, call_target, ignore);
 183
 184         if (call_target)
 185           /* Trust that the right thing has been done; it's too hard to
 186              verify.  */
 187           return return_target;
 188
 189         /* If we're suffering under the ancient PCC_STATIC_STRUCT_RETURN
 190            calling convention, we need to copy the return value out of
 191            the static return buffer into slot.  */
 192         if (pcc_struct_return)
 193           {
 194             extern int flag_access_control;
 195             int old_ac = flag_access_control;
 196
 197             tree init = build_decl (VAR_DECL, NULL_TREE,
 198                                     build_reference_type (type));
 199             DECL_RTL (init) = XEXP (return_target, 0);
 200             init = convert_from_reference (init);
 201
 202             flag_access_control = 0;
 203             expand_expr (build_aggr_init (slot, init,
 204                                           LOOKUP_ONLYCONVERTING),
 205                          target, tmode, EXPAND_NORMAL);
 206             flag_access_control = old_ac;
 207
 208             if (TYPE_NEEDS_DESTRUCTOR (type))
 209               {
 210                 init = maybe_build_cleanup (init);
 211                 if (init != NULL_TREE)
 212                   expand_expr (init, const0_rtx, VOIDmode, 0);
 213               }
 214           }
 215
 216         return DECL_RTL (slot);
 217       }
 218
 219     case PTRMEM_CST:
 220       return expand_expr (cplus_expand_constant (exp),
 221                           target, tmode, modifier);
 222
 223     case OFFSET_REF:
 224       {
 225         return expand_expr (default_conversion (resolve_offset_ref (exp)),
 226                             target, tmode, EXPAND_NORMAL);
 227       }
 228
 229     case THUNK_DECL:
 230       return DECL_RTL (exp);
 231
 232     case THROW_EXPR:
 233       expand_expr (TREE_OPERAND (exp, 0), const0_rtx, VOIDmode, 0);
 234       expand_internal_throw ();
 235       return NULL;
 236
 237     case EMPTY_CLASS_EXPR:
 238       /* We don't need to generate any code for an empty class.  */
 239       return const0_rtx;
 240
 241     case STMT_EXPR:
 242       {
 243         tree rtl_expr = begin_stmt_expr ();
 244         expand_stmt (STMT_EXPR_STMT (exp));
 245         finish_stmt_expr (rtl_expr);
 246         return expand_expr (rtl_expr, target, tmode, modifier);
 247       }
 248       break;
 249
 250     default:
 251       break;
 252     }
 253   my_friendly_abort (40);
 254   /* NOTREACHED */
 255   return NULL;
 256 }
 257
 258 void
 259 init_cplus_expand ()
 260 {
 261   lang_expand_expr = cplus_expand_expr;
 262   lang_expand_constant = cplus_expand_constant;
 263 }
 264
 265 /* If DECL had its rtl moved from where callers expect it
 266    to be, fix it up.  RESULT is the nominal rtl for the RESULT_DECL,
 267    which may be a pseudo instead of a hard register.  */
 268
 269 void
 270 fixup_result_decl (decl, result)
 271      tree decl;
 272      rtx result;
 273 {
 274   if (REG_P (result))
 275     {
 276       if (REGNO (result) >= FIRST_PSEUDO_REGISTER)
 277         {
 278           rtx real_decl_result;
 279
 280 #ifdef FUNCTION_OUTGOING_VALUE
 281           real_decl_result
 282             = FUNCTION_OUTGOING_VALUE (TREE_TYPE (decl), current_function_decl);
 283 #else
 284           real_decl_result
 285             = FUNCTION_VALUE (TREE_TYPE (decl), current_function_decl);
 286 #endif
 287           REG_FUNCTION_VALUE_P (real_decl_result) = 1;
 288           result = real_decl_result;
 289         }
 290       store_expr (decl, result, 0);
 291       emit_insn (gen_rtx (USE, VOIDmode, result));
 292     }
 293 }
 294
 295 #if 0
 296 /* Expand this initialization inline and see if it's simple enough that
 297    it can be done at compile-time.  */
 298
 299 static tree
 300 extract_aggr_init (decl, init)
 301      tree decl, init;
 302 {
 303   return 0;
 304 }
 305
 306 static tree
 307 extract_scalar_init (decl, init)
 308      tree decl, init;
 309 {
 310   rtx value, insns, insn;
 311   extern struct obstack temporary_obstack;
 312   tree t = NULL_TREE;
 313
 314   push_obstacks (&temporary_obstack, &temporary_obstack);
 315   start_sequence ();
 316   value = expand_expr (init, NULL_RTX, VOIDmode, 0);
 317   insns = get_insns ();
 318   end_sequence ();
 319   reg_scan (insns, max_reg_num (), 0);
 320   jump_optimize (insns, 0, 0, 1);
 321   pop_obstacks ();
 322
 323   for (insn = insns; insn; insn = NEXT_INSN (insn))
 324     {
 325       rtx r, to;
 326
 327       if (GET_CODE (insn) == NOTE)
 328         continue;
 329       else if (GET_CODE (insn) != INSN)
 330         return 0;
 331
 332       r = PATTERN (insn);
 333       if (GET_CODE (r) != SET)
 334         return 0;
 335
 336       to = XEXP (r, 0);
 337
 338       if (! (to == value
 339              || (GET_CODE (to) == SUBREG && XEXP (to, 0) == value)))
 340         return 0;
 341
 342       r = XEXP (r, 1);
 343
 344       switch (GET_CODE (r))
 345         {
 346         case CONST_INT:
 347           t = build_int_2 (XEXP (r, 0), 0);
 348           break;
 349         default:
 350           return 0;
 351         }
 352     }
 353
 354   return t;
 355 }
 356 #endif
 357
 358 int
 359 extract_init (decl, init)
 360      tree decl ATTRIBUTE_UNUSED, init ATTRIBUTE_UNUSED;
 361 {
 362   return 0;
 363
 364 #if 0
 365   if (IS_AGGR_TYPE (TREE_TYPE (decl))
 366       || TREE_CODE (TREE_TYPE (decl)) == ARRAY_TYPE)
 367     init = extract_aggr_init (decl, init);
 368   else
 369     init = extract_scalar_init (decl, init);
 370
 371   if (init == NULL_TREE)
 372     return 0;
 373
 374   DECL_INITIAL (decl) = init;
 375   return 1;
 376 #endif
 377 }
 378
 379 void
 380 do_case (start, end)
 381      tree start, end;
 382 {
 383   tree value1 = NULL_TREE, value2 = NULL_TREE, label;
 384
 385   if (start != NULL_TREE && TREE_TYPE (start) != NULL_TREE
 386       && POINTER_TYPE_P (TREE_TYPE (start)))
 387     error ("pointers are not permitted as case values");
 388
 389   if (end && pedantic)
 390     pedwarn ("ANSI C++ forbids range expressions in switch statement");
 391
 392   if (start)
 393     value1 = check_cp_case_value (start);
 394   if (end)
 395     value2 = check_cp_case_value (end);
 396
 397   label = build_decl (LABEL_DECL, NULL_TREE, NULL_TREE);
 398
 399   if (value1 != error_mark_node
 400       && value2 != error_mark_node)
 401     {
 402       tree duplicate;
 403       int success;
 404
 405       if (end)
 406         success = pushcase_range (value1, value2, convert_and_check,
 407                                   label, &duplicate);
 408       else if (start)
 409         success = pushcase (value1, convert_and_check, label, &duplicate);
 410       else
 411         success = pushcase (NULL_TREE, 0, label, &duplicate);
 412
 413       if (success == 1)
 414         {
 415           if (end)
 416             error ("case label not within a switch statement");
 417           else if (start)
 418             cp_error ("case label `%E' not within a switch statement", start);
 419           else
 420             error ("default label not within a switch statement");
 421         }
 422       else if (success == 2)
 423         {
 424           if (end)
 425             {
 426               error ("duplicate (or overlapping) case value");
 427               cp_error_at ("this is the first entry overlapping that value",
 428                            duplicate);
 429             }
 430           else if (start)
 431             {
 432               cp_error ("duplicate case value `%E'", start);
 433               cp_error_at ("previously used here", duplicate);
 434             }
 435           else
 436             {
 437               error ("multiple default labels in one switch");
 438               cp_error_at ("this is the first default label", duplicate);
 439             }
 440         }
 441       else if (success == 3)
 442         warning ("case value out of range");
 443       else if (success == 4)
 444         warning ("empty range specified");
 445       else if (success == 5)
 446         {
 447           if (end)
 448             error ("case label within scope of cleanup or variable array");
 449           else if (! start)
 450             error ("`default' label within scope of cleanup or variable array");
 451           else
 452             cp_error ("case label `%E' within scope of cleanup or variable array", start);
 453         }
 454     }
 455
 456   current_function_return_value = NULL_TREE;
 457 }