gcc/c-semantics.c

   1 /* This file contains the definitions and documentation for the common
   2    tree codes used in the GNU C and C++ compilers (see c-common.def
   3    for the standard codes).
   4    Copyright (C) 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
   5    Written by Benjamin Chelf (chelf@codesourcery.com).
   6
   7 This file is part of GCC.
   8
   9 GCC is free software; you can redistribute it and/or modify it under
  10 the terms of the GNU General Public License as published by the Free
  11 Software Foundation; either version 2, or (at your option) any later
  12 version.
  13
  14 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  15 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  16 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  17 for more details.
  18
  19 You should have received a copy of the GNU General Public License
  20 along with GCC; see the file COPYING.  If not, write to the Free
  21 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  22 02111-1307, USA.  */
  23
  24 #include "config.h"
  25 #include "system.h"
  26 #include "coretypes.h"
  27 #include "tm.h"
  28 #include "tree.h"
  29 #include "function.h"
  30 #include "splay-tree.h"
  31 #include "varray.h"
  32 #include "c-common.h"
  33 #include "except.h"
  34 #include "toplev.h"
  35 #include "flags.h"
  36 #include "ggc.h"
  37 #include "rtl.h"
  38 #include "expr.h"
  39 #include "output.h"
  40 #include "timevar.h"
  41 #include "predict.h"
  42 #include "tree-inline.h"
  43
  44 /* If non-NULL, the address of a language-specific function for
  45    expanding statements.  */
  46 void (*lang_expand_stmt) PARAMS ((tree));
  47
  48 /* If non-NULL, the address of a language-specific function for
  49    expanding a DECL_STMT.  After the language-independent cases are
  50    handled, this function will be called.  If this function is not
  51    defined, it is assumed that declarations other than those for
  52    variables and labels do not require any RTL generation.  */
  53 void (*lang_expand_decl_stmt) PARAMS ((tree));
  54
  55 static tree find_reachable_label_1      PARAMS ((tree *, int *, void *));
  56 static tree find_reachable_label        PARAMS ((tree));
  57 static bool expand_unreachable_if_stmt  PARAMS ((tree));
  58 static bool expand_unreachable_stmt     PARAMS ((tree, int));
  59
  60 /* Create an empty statement tree rooted at T.  */
  61
  62 void
  63 begin_stmt_tree (t)
  64      tree *t;
  65 {
  66   /* We create a trivial EXPR_STMT so that last_tree is never NULL in
  67      what follows.  We remove the extraneous statement in
  68      finish_stmt_tree.  */
  69   *t = build_nt (EXPR_STMT, void_zero_node);
  70   last_tree = *t;
  71   last_expr_type = NULL_TREE;
  72   last_expr_filename = input_filename;
  73 }
  74
  75 /* T is a statement.  Add it to the statement-tree.  */
  76
  77 tree
  78 add_stmt (t)
  79      tree t;
  80 {
  81   if (input_filename != last_expr_filename)
  82     {
  83       /* If the filename has changed, also add in a FILE_STMT.  Do a string
  84          compare first, though, as it might be an equivalent string.  */
  85       int add = (strcmp (input_filename, last_expr_filename) != 0);
  86       last_expr_filename = input_filename;
  87       if (add)
  88         {
  89           tree pos = build_nt (FILE_STMT, get_identifier (input_filename));
  90           add_stmt (pos);
  91         }
  92     }
  93
  94   /* Add T to the statement-tree.  */
  95   TREE_CHAIN (last_tree) = t;
  96   last_tree = t;
  97
  98   /* When we expand a statement-tree, we must know whether or not the
  99      statements are full-expressions.  We record that fact here.  */
 100   STMT_IS_FULL_EXPR_P (last_tree) = stmts_are_full_exprs_p ();
 101
 102   /* Keep track of the number of statements in this function.  */
 103   if (current_function_decl)
 104     ++DECL_NUM_STMTS (current_function_decl);
 105
 106   return t;
 107 }
 108
 109 /* Create a declaration statement for the declaration given by the
 110    DECL.  */
 111
 112 void
 113 add_decl_stmt (decl)
 114      tree decl;
 115 {
 116   tree decl_stmt;
 117
 118   /* We need the type to last until instantiation time.  */
 119   decl_stmt = build_stmt (DECL_STMT, decl);
 120   add_stmt (decl_stmt);
 121 }
 122
 123 /* Add a scope-statement to the statement-tree.  BEGIN_P indicates
 124    whether this statements opens or closes a scope.  PARTIAL_P is true
 125    for a partial scope, i.e, the scope that begins after a label when
 126    an object that needs a cleanup is created.  If BEGIN_P is nonzero,
 127    returns a new TREE_LIST representing the top of the SCOPE_STMT
 128    stack.  The TREE_PURPOSE is the new SCOPE_STMT.  If BEGIN_P is
 129    zero, returns a TREE_LIST whose TREE_VALUE is the new SCOPE_STMT,
 130    and whose TREE_PURPOSE is the matching SCOPE_STMT with
 131    SCOPE_BEGIN_P set.  */
 132
 133 tree
 134 add_scope_stmt (begin_p, partial_p)
 135      int begin_p;
 136      int partial_p;
 137 {
 138   tree *stack_ptr = current_scope_stmt_stack ();
 139   tree ss;
 140   tree top = *stack_ptr;
 141
 142   /* Build the statement.  */
 143   ss = build_stmt (SCOPE_STMT, NULL_TREE);
 144   SCOPE_BEGIN_P (ss) = begin_p;
 145   SCOPE_PARTIAL_P (ss) = partial_p;
 146
 147   /* Keep the scope stack up to date.  */
 148   if (begin_p)
 149     {
 150       top = tree_cons (ss, NULL_TREE, top);
 151       *stack_ptr = top;
 152     }
 153   else
 154     {
 155       if (partial_p != SCOPE_PARTIAL_P (TREE_PURPOSE (top)))
 156         abort ();
 157       TREE_VALUE (top) = ss;
 158       *stack_ptr = TREE_CHAIN (top);
 159     }
 160
 161   /* Add the new statement to the statement-tree.  */
 162   add_stmt (ss);
 163
 164   return top;
 165 }
 166
 167 /* Finish the statement tree rooted at T.  */
 168
 169 void
 170 finish_stmt_tree (t)
 171      tree *t;
 172 {
 173   tree stmt;
 174
 175   /* Remove the fake extra statement added in begin_stmt_tree.  */
 176   stmt = TREE_CHAIN (*t);
 177   *t = stmt;
 178   last_tree = NULL_TREE;
 179
 180   if (cfun && stmt)
 181     {
 182       /* The line-number recorded in the outermost statement in a function
 183          is the line number of the end of the function.  */
 184       STMT_LINENO (stmt) = lineno;
 185       STMT_LINENO_FOR_FN_P (stmt) = 1;
 186     }
 187 }
 188
 189 /* Build a generic statement based on the given type of node and
 190    arguments. Similar to `build_nt', except that we set
 191    STMT_LINENO to be the current line number.  */
 192 /* ??? This should be obsolete with the lineno_stmt productions
 193    in the grammar.  */
 194
 195 tree
 196 build_stmt VPARAMS ((enum tree_code code, ...))
 197 {
 198   tree t;
 199   int length;
 200   int i;
 201
 202   VA_OPEN (p, code);
 203   VA_FIXEDARG (p, enum tree_code, code);
 204
 205   t = make_node (code);
 206   length = TREE_CODE_LENGTH (code);
 207   STMT_LINENO (t) = lineno;
 208
 209   for (i = 0; i < length; i++)
 210     TREE_OPERAND (t, i) = va_arg (p, tree);
 211
 212   VA_CLOSE (p);
 213   return t;
 214 }
 215
 216 /* Some statements, like for-statements or if-statements, require a
 217    condition.  This condition can be a declaration.  If T is such a
 218    declaration it is processed, and an expression appropriate to use
 219    as the condition is returned.  Otherwise, T itself is returned.  */
 220
 221 tree
 222 expand_cond (t)
 223      tree t;
 224 {
 225   if (t && TREE_CODE (t) == TREE_LIST)
 226     {
 227       expand_stmt (TREE_PURPOSE (t));
 228       return TREE_VALUE (t);
 229     }
 230   else
 231     return t;
 232 }
 233
 234 /* Create RTL for the local static variable DECL.  */
 235
 236 void
 237 make_rtl_for_local_static (decl)
 238      tree decl;
 239 {
 240   const char *asmspec = NULL;
 241
 242   /* If we inlined this variable, we could see it's declaration
 243      again.  */
 244   if (TREE_ASM_WRITTEN (decl))
 245     return;
 246
 247   /* If the DECL_ASSEMBLER_NAME is not the same as the DECL_NAME, then
 248      either we already created RTL for this DECL (and since it was a
 249      local variable, its DECL_ASSEMBLER_NAME got hacked up to prevent
 250      clashes with other local statics with the same name by a previous
 251      call to make_decl_rtl), or the user explicitly requested a
 252      particular assembly name for this variable, using the GNU
 253      extension for this purpose:
 254
 255        int i asm ("j");
 256
 257      There's no way to know which case we're in, here.  But, it turns
 258      out we're safe.  If there's already RTL, then
 259      rest_of_decl_compilation ignores the ASMSPEC parameter, so we
 260      may as well not pass it in.  If there isn't RTL, then we didn't
 261      already create RTL, which means that the modification to
 262      DECL_ASSEMBLER_NAME came only via the explicit extension.  */
 263   if (DECL_ASSEMBLER_NAME (decl) != DECL_NAME (decl)
 264       && !DECL_RTL_SET_P (decl))
 265     asmspec = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl));
 266
 267   rest_of_decl_compilation (decl, asmspec, /*top_level=*/0, /*at_end=*/0);
 268 }
 269
 270 /* Let the back-end know about DECL.  */
 271
 272 void
 273 emit_local_var (decl)
 274      tree decl;
 275 {
 276   /* Create RTL for this variable.  */
 277   if (!DECL_RTL_SET_P (decl))
 278     {
 279       if (DECL_C_HARD_REGISTER (decl))
 280         /* The user specified an assembler name for this variable.
 281            Set that up now.  */
 282         rest_of_decl_compilation
 283           (decl, IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl)),
 284            /*top_level=*/0, /*at_end=*/0);
 285       else
 286         expand_decl (decl);
 287     }
 288
 289   /* Actually do the initialization.  */
 290   if (stmts_are_full_exprs_p ())
 291     expand_start_target_temps ();
 292
 293   expand_decl_init (decl);
 294
 295   if (stmts_are_full_exprs_p ())
 296     expand_end_target_temps ();
 297 }
 298
 299 /* Helper for generating the RTL at the beginning of a scope.  */
 300
 301 void
 302 genrtl_do_pushlevel ()
 303 {
 304   emit_line_note (input_filename, lineno);
 305   clear_last_expr ();
 306 }
 307
 308 /* Generate the RTL for DESTINATION, which is a GOTO_STMT.  */
 309
 310 void
 311 genrtl_goto_stmt (destination)
 312      tree destination;
 313 {
 314   if (TREE_CODE (destination) == IDENTIFIER_NODE)
 315     abort ();
 316
 317   /* We warn about unused labels with -Wunused.  That means we have to
 318      mark the used labels as used.  */
 319   if (TREE_CODE (destination) == LABEL_DECL)
 320     TREE_USED (destination) = 1;
 321
 322   emit_line_note (input_filename, lineno);
 323
 324   if (TREE_CODE (destination) == LABEL_DECL)
 325     {
 326       label_rtx (destination);
 327       expand_goto (destination);
 328     }
 329   else
 330     expand_computed_goto (destination);
 331 }
 332
 333 /* Generate the RTL for EXPR, which is an EXPR_STMT.  Provided just
 334    for backward compatibility.  genrtl_expr_stmt_value() should be
 335    used for new code.  */
 336
 337 void
 338 genrtl_expr_stmt (expr)
 339      tree expr;
 340 {
 341   genrtl_expr_stmt_value (expr, -1, 1);
 342 }
 343
 344 /* Generate the RTL for EXPR, which is an EXPR_STMT.  WANT_VALUE tells
 345    whether to (1) save the value of the expression, (0) discard it or
 346    (-1) use expr_stmts_for_value to tell.  The use of -1 is
 347    deprecated, and retained only for backward compatibility.
 348    MAYBE_LAST is nonzero if this EXPR_STMT might be the last statement
 349    in expression statement.  */
 350
 351 void
 352 genrtl_expr_stmt_value (expr, want_value, maybe_last)
 353      tree expr;
 354      int want_value, maybe_last;
 355 {
 356   if (expr != NULL_TREE)
 357     {
 358       emit_line_note (input_filename, lineno);
 359
 360       if (stmts_are_full_exprs_p ())
 361         expand_start_target_temps ();
 362
 363       if (expr != error_mark_node)
 364         expand_expr_stmt_value (expr, want_value, maybe_last);
 365
 366       if (stmts_are_full_exprs_p ())
 367         expand_end_target_temps ();
 368     }
 369 }
 370
 371 /* Generate the RTL for T, which is a DECL_STMT.  */
 372
 373 void
 374 genrtl_decl_stmt (t)
 375      tree t;
 376 {
 377   tree decl;
 378   emit_line_note (input_filename, lineno);
 379   decl = DECL_STMT_DECL (t);
 380   /* If this is a declaration for an automatic local
 381      variable, initialize it.  Note that we might also see a
 382      declaration for a namespace-scope object (declared with
 383      `extern').  We don't have to handle the initialization
 384      of those objects here; they can only be declarations,
 385      rather than definitions.  */
 386   if (TREE_CODE (decl) == VAR_DECL
 387       && !TREE_STATIC (decl)
 388       && !DECL_EXTERNAL (decl))
 389     {
 390       /* Let the back-end know about this variable.  */
 391       if (!anon_aggr_type_p (TREE_TYPE (decl)))
 392         emit_local_var (decl);
 393       else
 394         expand_anon_union_decl (decl, NULL_TREE,
 395                                 DECL_ANON_UNION_ELEMS (decl));
 396     }
 397   else if (TREE_CODE (decl) == VAR_DECL && TREE_STATIC (decl))
 398     make_rtl_for_local_static (decl);
 399   else if (TREE_CODE (decl) == LABEL_DECL
 400            && C_DECLARED_LABEL_FLAG (decl))
 401     declare_nonlocal_label (decl);
 402   else if (lang_expand_decl_stmt)
 403     (*lang_expand_decl_stmt) (t);
 404 }
 405
 406 /* Generate the RTL for T, which is an IF_STMT.  */
 407
 408 void
 409 genrtl_if_stmt (t)
 410      tree t;
 411 {
 412   tree cond;
 413   genrtl_do_pushlevel ();
 414   cond = expand_cond (IF_COND (t));
 415   emit_line_note (input_filename, lineno);
 416   expand_start_cond (cond, 0);
 417   if (THEN_CLAUSE (t))
 418     {
 419       if (cond && integer_zerop (cond))
 420         expand_unreachable_stmt (THEN_CLAUSE (t), warn_notreached);
 421       else
 422         expand_stmt (THEN_CLAUSE (t));
 423     }
 424
 425   if (ELSE_CLAUSE (t))
 426     {
 427       expand_start_else ();
 428       if (cond && integer_nonzerop (cond))
 429         expand_unreachable_stmt (ELSE_CLAUSE (t), warn_notreached);
 430       else
 431         expand_stmt (ELSE_CLAUSE (t));
 432     }
 433   expand_end_cond ();
 434 }
 435
 436 /* Generate the RTL for T, which is a WHILE_STMT.  */
 437
 438 void
 439 genrtl_while_stmt (t)
 440      tree t;
 441 {
 442   tree cond = WHILE_COND (t);
 443
 444   emit_nop ();
 445   emit_line_note (input_filename, lineno);
 446   expand_start_loop (1);
 447   genrtl_do_pushlevel ();
 448
 449   if (cond && !integer_nonzerop (cond))
 450     {
 451       cond = expand_cond (cond);
 452       emit_line_note (input_filename, lineno);
 453       expand_exit_loop_top_cond (0, cond);
 454       genrtl_do_pushlevel ();
 455     }
 456
 457   expand_stmt (WHILE_BODY (t));
 458
 459   expand_end_loop ();
 460 }
 461
 462 /* Generate the RTL for T, which is a DO_STMT.  */
 463
 464 void
 465 genrtl_do_stmt (t)
 466      tree t;
 467 {
 468   tree cond = DO_COND (t);
 469
 470   /* Recognize the common special-case of do { ... } while (0) and do
 471      not emit the loop widgetry in this case.  In particular this
 472      avoids cluttering the rtl with dummy loop notes, which can affect
 473      alignment of adjacent labels.  COND can be NULL due to parse
 474      errors.  */
 475   if (!cond || integer_zerop (cond))
 476     {
 477       expand_start_null_loop ();
 478       expand_stmt (DO_BODY (t));
 479       expand_end_null_loop ();
 480     }
 481   else if (integer_nonzerop (cond))
 482     {
 483       emit_nop ();
 484       emit_line_note (input_filename, lineno);
 485       expand_start_loop (1);
 486
 487       expand_stmt (DO_BODY (t));
 488
 489       emit_line_note (input_filename, lineno);
 490       expand_end_loop ();
 491     }
 492   else
 493     {
 494       emit_nop ();
 495       emit_line_note (input_filename, lineno);
 496       expand_start_loop_continue_elsewhere (1);
 497
 498       expand_stmt (DO_BODY (t));
 499
 500       expand_loop_continue_here ();
 501       cond = expand_cond (cond);
 502       emit_line_note (input_filename, lineno);
 503       expand_exit_loop_if_false (0, cond);
 504       expand_end_loop ();
 505     }
 506 }
 507
 508 /* Build the node for a return statement and return it.  */
 509
 510 tree
 511 build_return_stmt (expr)
 512      tree expr;
 513 {
 514   return (build_stmt (RETURN_STMT, expr));
 515 }
 516
 517 /* Generate the RTL for STMT, which is a RETURN_STMT.  */
 518
 519 void
 520 genrtl_return_stmt (stmt)
 521      tree stmt;
 522 {
 523   tree expr;
 524
 525   expr = RETURN_STMT_EXPR (stmt);
 526
 527   emit_line_note (input_filename, lineno);
 528   if (!expr)
 529     expand_null_return ();
 530   else
 531     {
 532       expand_start_target_temps ();
 533       expand_return (expr);
 534       expand_end_target_temps ();
 535     }
 536 }
 537
 538 /* Generate the RTL for T, which is a FOR_STMT.  */
 539
 540 void
 541 genrtl_for_stmt (t)
 542      tree t;
 543 {
 544   tree cond = FOR_COND (t);
 545   const char *saved_filename;
 546   int saved_lineno;
 547
 548   if (NEW_FOR_SCOPE_P (t))
 549     genrtl_do_pushlevel ();
 550
 551   expand_stmt (FOR_INIT_STMT (t));
 552
 553   /* Expand the initialization.  */
 554   emit_nop ();
 555   emit_line_note (input_filename, lineno);
 556   if (FOR_EXPR (t))
 557     expand_start_loop_continue_elsewhere (1);
 558   else
 559     expand_start_loop (1);
 560   genrtl_do_pushlevel ();
 561
 562   /* Save the filename and line number so that we expand the FOR_EXPR
 563      we can reset them back to the saved values.  */
 564   saved_filename = input_filename;
 565   saved_lineno = lineno;
 566
 567   /* Expand the condition.  */
 568   if (cond && !integer_nonzerop (cond))
 569     {
 570       cond = expand_cond (cond);
 571       emit_line_note (input_filename, lineno);
 572       expand_exit_loop_top_cond (0, cond);
 573       genrtl_do_pushlevel ();
 574     }
 575
 576   /* Expand the body.  */
 577   expand_stmt (FOR_BODY (t));
 578
 579   /* Expand the increment expression.  */
 580   input_filename = saved_filename;
 581   lineno = saved_lineno;
 582   emit_line_note (input_filename, lineno);
 583   if (FOR_EXPR (t))
 584     {
 585       expand_loop_continue_here ();
 586       genrtl_expr_stmt (FOR_EXPR (t));
 587     }
 588   expand_end_loop ();
 589 }
 590
 591 /* Build a break statement node and return it.  */
 592
 593 tree
 594 build_break_stmt ()
 595 {
 596   return (build_stmt (BREAK_STMT));
 597 }
 598
 599 /* Generate the RTL for a BREAK_STMT.  */
 600
 601 void
 602 genrtl_break_stmt ()
 603 {
 604   emit_line_note (input_filename, lineno);
 605   if ( ! expand_exit_something ())
 606     error ("break statement not within loop or switch");
 607 }
 608
 609 /* Build a continue statement node and return it.  */
 610
 611 tree
 612 build_continue_stmt ()
 613 {
 614   return (build_stmt (CONTINUE_STMT));
 615 }
 616
 617 /* Generate the RTL for a CONTINUE_STMT.  */
 618
 619 void
 620 genrtl_continue_stmt ()
 621 {
 622   emit_line_note (input_filename, lineno);
 623   if (! expand_continue_loop (0))
 624     error ("continue statement not within a loop");
 625 }
 626
 627 /* Generate the RTL for T, which is a SCOPE_STMT.  */
 628
 629 void
 630 genrtl_scope_stmt (t)
 631      tree t;
 632 {
 633   tree block = SCOPE_STMT_BLOCK (t);
 634
 635   if (!SCOPE_NO_CLEANUPS_P (t))
 636     {
 637       if (SCOPE_BEGIN_P (t))
 638         expand_start_bindings_and_block (2 * SCOPE_NULLIFIED_P (t), block);
 639       else if (SCOPE_END_P (t))
 640         expand_end_bindings (NULL_TREE, !SCOPE_NULLIFIED_P (t), 0);
 641     }
 642   else if (!SCOPE_NULLIFIED_P (t))
 643     {
 644       rtx note = emit_note (NULL,
 645                             (SCOPE_BEGIN_P (t)
 646                              ? NOTE_INSN_BLOCK_BEG
 647                              : NOTE_INSN_BLOCK_END));
 648       NOTE_BLOCK (note) = block;
 649     }
 650
 651   /* If we're at the end of a scope that contains inlined nested
 652      functions, we have to decide whether or not to write them out.  */
 653   if (block && SCOPE_END_P (t))
 654     {
 655       tree fn;
 656
 657       for (fn = BLOCK_VARS (block); fn; fn = TREE_CHAIN (fn))
 658         {
 659           if (TREE_CODE (fn) == FUNCTION_DECL
 660               && DECL_CONTEXT (fn) == current_function_decl
 661               && DECL_SAVED_INSNS (fn)
 662               && !TREE_ASM_WRITTEN (fn)
 663               && TREE_ADDRESSABLE (fn))
 664             {
 665               push_function_context ();
 666               output_inline_function (fn);
 667               pop_function_context ();
 668             }
 669         }
 670     }
 671 }
 672
 673 /* Generate the RTL for T, which is a SWITCH_STMT.  */
 674
 675 void
 676 genrtl_switch_stmt (t)
 677      tree t;
 678 {
 679   tree cond;
 680   genrtl_do_pushlevel ();
 681
 682   cond = expand_cond (SWITCH_COND (t));
 683   if (cond == error_mark_node)
 684     /* The code is in error, but we don't want expand_end_case to
 685        crash.  */
 686     cond = boolean_false_node;
 687
 688   emit_line_note (input_filename, lineno);
 689   expand_start_case (1, cond, TREE_TYPE (cond), "switch statement");
 690   expand_unreachable_stmt (SWITCH_BODY (t), warn_notreached);
 691   expand_end_case_type (cond, SWITCH_TYPE (t));
 692 }
 693
 694 /* Create a CASE_LABEL tree node and return it.  */
 695
 696 tree
 697 build_case_label (low_value, high_value, label_decl)
 698      tree low_value;
 699      tree high_value;
 700      tree label_decl;
 701 {
 702   return build_stmt (CASE_LABEL, low_value, high_value, label_decl);
 703 }
 704
 705
 706 /* Generate the RTL for a CASE_LABEL.  */
 707
 708 void
 709 genrtl_case_label (case_label)
 710      tree case_label;
 711 {
 712   tree duplicate;
 713   tree cleanup;
 714
 715   cleanup = last_cleanup_this_contour ();
 716   if (cleanup)
 717     {
 718       static int explained = 0;
 719       warning ("destructor needed for `%#D'", (TREE_PURPOSE (cleanup)));
 720       warning ("where case label appears here");
 721       if (!explained)
 722         {
 723           warning ("(enclose actions of previous case statements requiring destructors in their own scope.)");
 724           explained = 1;
 725         }
 726     }
 727
 728   add_case_node (CASE_LOW (case_label), CASE_HIGH (case_label),
 729                  CASE_LABEL_DECL (case_label), &duplicate);
 730 }
 731
 732 /* Generate the RTL for T, which is a COMPOUND_STMT.  */
 733
 734 void
 735 genrtl_compound_stmt (t)
 736     tree t;
 737 {
 738 #ifdef ENABLE_CHECKING
 739   struct nesting *n = current_nesting_level ();
 740 #endif
 741
 742   expand_stmt (COMPOUND_BODY (t));
 743
 744 #ifdef ENABLE_CHECKING
 745   /* Make sure that we've pushed and popped the same number of levels.  */
 746   if (!COMPOUND_STMT_NO_SCOPE (t) && n != current_nesting_level ())
 747     abort ();
 748 #endif
 749 }
 750
 751 /* Generate the RTL for an ASM_STMT.  */
 752
 753 void
 754 genrtl_asm_stmt (cv_qualifier, string, output_operands,
 755                  input_operands, clobbers, asm_input_p)
 756      tree cv_qualifier;
 757      tree string;
 758      tree output_operands;
 759      tree input_operands;
 760      tree clobbers;
 761      int asm_input_p;
 762 {
 763   if (cv_qualifier != NULL_TREE
 764       && cv_qualifier != ridpointers[(int) RID_VOLATILE])
 765     {
 766       warning ("%s qualifier ignored on asm",
 767                IDENTIFIER_POINTER (cv_qualifier));
 768       cv_qualifier = NULL_TREE;
 769     }
 770
 771   emit_line_note (input_filename, lineno);
 772   if (asm_input_p)
 773     expand_asm (string, cv_qualifier != NULL_TREE);
 774   else
 775     c_expand_asm_operands (string, output_operands, input_operands,
 776                            clobbers, cv_qualifier != NULL_TREE,
 777                            input_filename, lineno);
 778 }
 779
 780 /* Generate the RTL for a DECL_CLEANUP.  */
 781
 782 void
 783 genrtl_decl_cleanup (t)
 784      tree t;
 785 {
 786   tree decl = CLEANUP_DECL (t);
 787   if (!decl || (DECL_SIZE (decl) && TREE_TYPE (decl) != error_mark_node))
 788     expand_decl_cleanup_eh (decl, CLEANUP_EXPR (t), CLEANUP_EH_ONLY (t));
 789 }
 790
 791 /* We're about to expand T, a statement.  Set up appropriate context
 792    for the substitution.  */
 793
 794 void
 795 prep_stmt (t)
 796      tree t;
 797 {
 798   if (!STMT_LINENO_FOR_FN_P (t))
 799     lineno = STMT_LINENO (t);
 800   current_stmt_tree ()->stmts_are_full_exprs_p = STMT_IS_FULL_EXPR_P (t);
 801 }
 802
 803 /* Generate the RTL for the statement T, its substatements, and any
 804    other statements at its nesting level.  */
 805
 806 void
 807 expand_stmt (t)
 808      tree t;
 809 {
 810   while (t && t != error_mark_node)
 811     {
 812       int saved_stmts_are_full_exprs_p;
 813
 814       /* Set up context appropriately for handling this statement.  */
 815       saved_stmts_are_full_exprs_p = stmts_are_full_exprs_p ();
 816       prep_stmt (t);
 817
 818       switch (TREE_CODE (t))
 819         {
 820         case FILE_STMT:
 821           input_filename = FILE_STMT_FILENAME (t);
 822           break;
 823
 824         case RETURN_STMT:
 825           genrtl_return_stmt (t);
 826           expand_unreachable_stmt (TREE_CHAIN (t), warn_notreached);
 827           return;
 828
 829         case EXPR_STMT:
 830           genrtl_expr_stmt_value (EXPR_STMT_EXPR (t), TREE_ADDRESSABLE (t),
 831                                   TREE_CHAIN (t) == NULL
 832                                   || (TREE_CODE (TREE_CHAIN (t)) == SCOPE_STMT
 833                                       && TREE_CHAIN (TREE_CHAIN (t)) == NULL));
 834           break;
 835
 836         case DECL_STMT:
 837           genrtl_decl_stmt (t);
 838           break;
 839
 840         case FOR_STMT:
 841           genrtl_for_stmt (t);
 842           break;
 843
 844         case WHILE_STMT:
 845           genrtl_while_stmt (t);
 846           break;
 847
 848         case DO_STMT:
 849           genrtl_do_stmt (t);
 850           break;
 851
 852         case IF_STMT:
 853           genrtl_if_stmt (t);
 854           break;
 855
 856         case COMPOUND_STMT:
 857           genrtl_compound_stmt (t);
 858           break;
 859
 860         case BREAK_STMT:
 861           genrtl_break_stmt ();
 862           expand_unreachable_stmt (TREE_CHAIN (t), warn_notreached);
 863           return;
 864
 865         case CONTINUE_STMT:
 866           genrtl_continue_stmt ();
 867           expand_unreachable_stmt (TREE_CHAIN (t), warn_notreached);
 868           return;
 869
 870         case SWITCH_STMT:
 871           genrtl_switch_stmt (t);
 872           break;
 873
 874         case CASE_LABEL:
 875           genrtl_case_label (t);
 876           break;
 877
 878         case LABEL_STMT:
 879           expand_label (LABEL_STMT_LABEL (t));
 880           break;
 881
 882         case GOTO_STMT:
 883           /* Emit information for branch prediction.  */
 884           if (!GOTO_FAKE_P (t)
 885               && TREE_CODE (GOTO_DESTINATION (t)) == LABEL_DECL
 886               && flag_guess_branch_prob)
 887             {
 888               rtx note = emit_note (NULL, NOTE_INSN_PREDICTION);
 889
 890               NOTE_PREDICTION (note) = NOTE_PREDICT (PRED_GOTO, NOT_TAKEN);
 891             }
 892           genrtl_goto_stmt (GOTO_DESTINATION (t));
 893           expand_unreachable_stmt (TREE_CHAIN (t), warn_notreached);
 894           return;
 895
 896         case ASM_STMT:
 897           genrtl_asm_stmt (ASM_CV_QUAL (t), ASM_STRING (t),
 898                            ASM_OUTPUTS (t), ASM_INPUTS (t),
 899                            ASM_CLOBBERS (t), ASM_INPUT_P (t));
 900           break;
 901
 902         case SCOPE_STMT:
 903           genrtl_scope_stmt (t);
 904           break;
 905
 906         case CLEANUP_STMT:
 907           genrtl_decl_cleanup (t);
 908           break;
 909
 910         default:
 911           if (lang_expand_stmt)
 912             (*lang_expand_stmt) (t);
 913           else
 914             abort ();
 915           break;
 916         }
 917
 918       /* Restore saved state.  */
 919       current_stmt_tree ()->stmts_are_full_exprs_p
 920         = saved_stmts_are_full_exprs_p;
 921
 922       /* Go on to the next statement in this scope.  */
 923       t = TREE_CHAIN (t);
 924     }
 925 }
 926 \f
 927 /* If *TP is a potentially reachable label, return nonzero.  */
 928
 929 static tree
 930 find_reachable_label_1 (tp, walk_subtrees, data)
 931      tree *tp;
 932      int *walk_subtrees ATTRIBUTE_UNUSED;
 933      void *data ATTRIBUTE_UNUSED;
 934 {
 935   switch (TREE_CODE (*tp))
 936     {
 937     case LABEL_STMT:
 938     case CASE_LABEL:
 939       return *tp;
 940
 941     default:
 942       break;
 943     }
 944   return NULL_TREE;
 945 }
 946
 947 /* Determine whether expression EXP contains a potentially
 948    reachable label.  */
 949 static tree
 950 find_reachable_label (exp)
 951      tree exp;
 952 {
 953   int line = lineno;
 954   const char *file = input_filename;
 955   tree ret = walk_tree (&exp, find_reachable_label_1, NULL, NULL);
 956   input_filename = file;
 957   lineno = line;
 958   return ret;
 959 }
 960
 961 /* Expand an unreachable if statement, T.  This function returns
 962    true if the IF_STMT contains a potentially reachable code_label.  */
 963 static bool
 964 expand_unreachable_if_stmt (t)
 965      tree t;
 966 {
 967   if (find_reachable_label (IF_COND (t)) != NULL_TREE)
 968     {
 969       genrtl_if_stmt (t);
 970       return true;
 971     }
 972
 973   if (THEN_CLAUSE (t) && ELSE_CLAUSE (t))
 974     {
 975       if (expand_unreachable_stmt (THEN_CLAUSE (t), 0))
 976         {
 977           rtx label;
 978           label = gen_label_rtx ();
 979           emit_jump (label);
 980           expand_unreachable_stmt (ELSE_CLAUSE (t), 0);
 981           emit_label (label);
 982           return true;
 983         }
 984       else
 985         return expand_unreachable_stmt (ELSE_CLAUSE (t), 0);
 986     }
 987   else if (THEN_CLAUSE (t))
 988     return expand_unreachable_stmt (THEN_CLAUSE (t), 0);
 989   else if (ELSE_CLAUSE (t))
 990     return expand_unreachable_stmt (ELSE_CLAUSE (t), 0);
 991
 992   return false;
 993 }
 994
 995 /* Expand an unreachable statement list.  This function skips all
 996    statements preceding the first potentially reachable label and
 997    then expands the statements normally with expand_stmt.  This
 998    function returns true if such a reachable label was found.  */
 999 static bool
1000 expand_unreachable_stmt (t, warn)
1001      tree t;
1002      int warn;
1003 {
1004   int saved;
1005
1006   while (t && t != error_mark_node)
1007     {
1008       if (warn)
1009         switch (TREE_CODE (t))
1010           {
1011           case BREAK_STMT:
1012           case CONTINUE_STMT:
1013           case EXPR_STMT:
1014           case GOTO_STMT:
1015           case IF_STMT:
1016           case RETURN_STMT:
1017             if (!STMT_LINENO_FOR_FN_P (t))
1018               lineno = STMT_LINENO (t);
1019             warning("will never be executed");
1020             warn = false;
1021             break;
1022
1023           default:
1024             break;
1025           }
1026
1027       switch (TREE_CODE (t))
1028         {
1029         case GOTO_STMT:
1030         case CONTINUE_STMT:
1031         case BREAK_STMT:
1032           break;
1033
1034         case FILE_STMT:
1035           input_filename = FILE_STMT_FILENAME (t);
1036           break;
1037
1038         case RETURN_STMT:
1039           if (find_reachable_label (RETURN_STMT_EXPR (t)) != NULL_TREE)
1040             {
1041               expand_stmt (t);
1042               return true;
1043             }
1044           break;
1045
1046         case EXPR_STMT:
1047           if (find_reachable_label (EXPR_STMT_EXPR (t)) != NULL_TREE)
1048             {
1049               expand_stmt (t);
1050               return true;
1051             }
1052           break;
1053
1054         case IF_STMT:
1055           if (expand_unreachable_if_stmt (t))
1056             {
1057               expand_stmt (TREE_CHAIN (t));
1058               return true;
1059             }
1060           break;
1061
1062         case COMPOUND_STMT:
1063           if (expand_unreachable_stmt (COMPOUND_BODY (t), warn))
1064             {
1065               expand_stmt (TREE_CHAIN (t));
1066               return true;
1067             }
1068           warn = false;
1069           break;
1070
1071         case SCOPE_STMT:
1072           saved = stmts_are_full_exprs_p ();
1073           prep_stmt (t);
1074           genrtl_scope_stmt (t);
1075           current_stmt_tree ()->stmts_are_full_exprs_p = saved;
1076           break;
1077
1078         default:
1079           expand_stmt (t);
1080           return true;
1081         }
1082       t = TREE_CHAIN (t);
1083     }
1084   return false;
1085 }
1086