gcc/except.h

   1 /* Exception Handling interface routines.
   2    Copyright (C) 1996, 1997, 1998 Free Software Foundation, Inc.
   3    Contributed by Mike Stump <mrs@cygnus.com>.
   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 #if !defined(NULL_RTX) && !defined(rtx)
  23 typedef struct rtx_def *_except_rtx;
  24 #define rtx _except_rtx
  25 #endif
  26
  27 #ifdef TREE_CODE
  28
  29 /* A stack of labels. CHAIN points to the next entry in the stack.  */
  30
  31 struct label_node {
  32   union {
  33     rtx rlabel;
  34     tree tlabel;
  35   } u;
  36   struct label_node *chain;
  37 };
  38
  39 /* An eh_entry is used to describe one exception handling region.
  40
  41    OUTER_CONTEXT is the label used for rethrowing into the outer context.
  42
  43    EXCEPTION_HANDLER_LABEL is the label corresponding to the handler
  44    for this region.
  45
  46    LABEL_USED indicates whether a CATCH block has already used this
  47    label or not. New ones are needed for additional catch blocks if
  48    it has.
  49
  50    FALSE_LABEL is used when either setjmp/longjmp exceptions are in
  51    use, or old style table exceptions. It contains the label for
  52    branching to the next runtime type check as handlers are processed.
  53
  54    FINALIZATION is the tree codes for the handler, or is NULL_TREE if
  55    one hasn't been generated yet, or is integer_zero_node to mark the
  56    end of a group of try blocks.  */
  57
  58 struct eh_entry {
  59   rtx outer_context;
  60   rtx exception_handler_label;
  61   tree finalization;
  62   int label_used;
  63   rtx false_label;
  64   rtx rethrow_label;
  65 };
  66 #else
  67 struct label_node;
  68 struct eh_entry;
  69 #endif
  70
  71 /* A list of EH_ENTRYs. ENTRY is the entry; CHAIN points to the next
  72    entry in the list, or is NULL if this is the last entry.  */
  73
  74 struct eh_node {
  75   struct eh_entry *entry;
  76   struct eh_node *chain;
  77 };
  78
  79 /* A stack of EH_ENTRYs. TOP is the topmost entry on the stack. TOP is
  80    NULL if the stack is empty.  */
  81
  82 struct eh_stack {
  83   struct eh_node *top;
  84 };
  85
  86 /* A queue of EH_ENTRYs. HEAD is the front of the queue; TAIL is the
  87    end (the latest entry). HEAD and TAIL are NULL if the queue is
  88    empty.  */
  89
  90 struct eh_queue {
  91   struct eh_node *head;
  92   struct eh_node *tail;
  93 };
  94
  95 /* Used to save exception handling status for each function.  */
  96 struct eh_status
  97 {
  98   /* A stack used for keeping track of the currently active exception
  99      handling region.  As each exception region is started, an entry
 100      describing the region is pushed onto this stack.  The current
 101      region can be found by looking at the top of the stack, and as we
 102      exit regions, the corresponding entries are popped.
 103
 104      Entries cannot overlap; they can be nested. So there is only one
 105      entry at most that corresponds to the current instruction, and that
 106      is the entry on the top of the stack.  */
 107   struct eh_stack x_ehstack;
 108   /* This stack is used to represent what the current eh region is
 109      for the catch blocks beings processed */
 110   struct eh_stack x_catchstack;
 111   /* A queue used for tracking which exception regions have closed but
 112      whose handlers have not yet been expanded. Regions are emitted in
 113      groups in an attempt to improve paging performance.
 114
 115      As we exit a region, we enqueue a new entry. The entries are then
 116      dequeued during expand_leftover_cleanups and expand_start_all_catch,
 117
 118      We should redo things so that we either take RTL for the handler,
 119      or we expand the handler expressed as a tree immediately at region
 120      end time.  */
 121   struct eh_queue x_ehqueue;
 122   /* Insns for all of the exception handlers for the current function.
 123      They are currently emitted by the frontend code.  */
 124   rtx x_catch_clauses;
 125   /* A random data area for the front end's own use.  */
 126   struct label_node *x_false_label_stack;
 127   /* Keeps track of the label to resume to should one want to resume
 128      normal control flow out of a handler (instead of, say, returning to
 129      the caller of the current function or exiting the program).  */
 130   struct label_node *x_caught_return_label_stack;
 131   /* A TREE_CHAINed list of handlers for regions that are not yet
 132      closed. The TREE_VALUE of each entry contains the handler for the
 133      corresponding entry on the ehstack.  */
 134   union tree_node *x_protect_list;
 135   /* The EH context.  Nonzero if the function has already
 136      fetched a pointer to the EH context  for exception handling.  */
 137   rtx ehc;
 138   /* The label generated by expand_builtin_eh_return.  */
 139   rtx x_eh_return_stub_label;
 140 };
 141
 142 #define ehstack (current_function->eh->x_ehstack)
 143 #define catchstack (current_function->eh->x_catchstack)
 144 #define ehqueue (current_function->eh->x_ehqueue)
 145 #define catch_clauses (current_function->eh->x_catch_clauses)
 146 #define false_label_stack (current_function->eh->x_false_label_stack)
 147 #define caught_return_label_stack (current_function->eh->x_caught_return_label_stack)
 148 #define protect_list (current_function->eh->x_protect_list)
 149 #define current_function_ehc (current_function->eh->ehc)
 150 #define eh_return_stub_label (current_function->eh->x_eh_return_stub_label)
 151
 152 #ifdef TREE_CODE
 153 /* Start an exception handling region.  All instructions emitted after
 154    this point are considered to be part of the region until
 155    expand_eh_region_end () is invoked.  */
 156
 157 extern void expand_eh_region_start              PROTO((void));
 158
 159 /* Just like expand_eh_region_start, except if a cleanup action is
 160    entered on the cleanup chain, the TREE_PURPOSE of the element put
 161    on the chain is DECL.  DECL should be the associated VAR_DECL, if
 162    any, otherwise it should be NULL_TREE.  */
 163
 164 extern void expand_eh_region_start_for_decl     PROTO((tree));
 165
 166 /* Start an exception handling region for the given cleanup action.
 167    All instructions emitted after this point are considered to be part
 168    of the region until expand_eh_region_end () is invoked.  CLEANUP is
 169    the cleanup action to perform.  The return value is true if the
 170    exception region was optimized away.  If that case,
 171    expand_eh_region_end does not need to be called for this cleanup,
 172    nor should it be.
 173
 174    This routine notices one particular common case in C++ code
 175    generation, and optimizes it so as to not need the exception
 176    region.  */
 177
 178 extern int expand_eh_region_start_tree          PROTO((tree, tree));
 179
 180 /* End an exception handling region.  The information about the region
 181    is found on the top of ehstack.
 182
 183    HANDLER is either the cleanup for the exception region, or if we're
 184    marking the end of a try block, HANDLER is integer_zero_node.
 185
 186    HANDLER will be transformed to rtl when expand_leftover_cleanups ()
 187    is invoked.  */
 188
 189 extern void expand_eh_region_end                PROTO((tree));
 190
 191 /* Push RLABEL or TLABEL onto LABELSTACK. Only one of RLABEL or TLABEL
 192    should be set; the other must be NULL.  */
 193
 194 extern void push_label_entry                    PROTO((struct label_node **labelstack, rtx rlabel, tree tlabel));
 195
 196 /* Pop the topmost entry from LABELSTACK and return its value as an
 197    rtx node. If LABELSTACK is empty, return NULL.  */
 198
 199 extern rtx pop_label_entry                      PROTO((struct label_node **labelstack));
 200
 201 /* Return the topmost entry of LABELSTACK as a tree node, or return
 202    NULL_TREE if LABELSTACK is empty.  */
 203
 204 extern tree top_label_entry                     PROTO((struct label_node **labelstack));
 205
 206 #endif
 207
 208 /* Test: is exception handling turned on? */
 209
 210 extern int doing_eh                                    PROTO ((int));
 211
 212 /* Toplevel initialization for EH.  */
 213
 214 void set_exception_lang_code                    PROTO((int));
 215 void set_exception_version_code                 PROTO((int));
 216
 217 /* A list of handlers asocciated with an exception region. HANDLER_LABEL
 218    is the the label that control should be transfered to if the data
 219    in TYPE_INFO matches an exception. a value of NULL_TREE for TYPE_INFO
 220    means This is a cleanup, and must always be called. A value of
 221    CATCH_ALL_TYPE works like a cleanup, but a call to the runtime matcher
 222    is still performed to avoid being caught by a different language
 223    exception. NEXT is a pointer to the next handler for this region.
 224    NULL means there are no more. */
 225
 226 typedef struct handler_info
 227 {
 228   rtx handler_label;
 229   int handler_number;
 230   void *type_info;
 231   struct handler_info *next;
 232 } handler_info;
 233
 234
 235 /* Add new handler information to an exception range. The  first parameter
 236    specifies the range number (returned from new_eh_entry()). The second
 237    parameter specifies the handler.  By default the handler is inserted at
 238    the end of the list. A handler list may contain only ONE NULL_TREE
 239    typeinfo entry. Regardless where it is positioned, a NULL_TREE entry
 240    is always output as the LAST handler in the exception table for a region. */
 241
 242 void add_new_handler                       PROTO((int, struct handler_info *));
 243
 244 /* Remove a handler label. The handler label is being deleted, so all
 245    regions which reference this handler should have it removed from their
 246    list of possible handlers. Any region which has the final handler
 247    removed can be deleted. */
 248
 249 void remove_handler                        PROTO((rtx));
 250
 251 /* Create a new handler structure initialized with the handler label and
 252    typeinfo fields passed in. */
 253
 254 struct handler_info *get_new_handler            PROTO((rtx, void *));
 255
 256 /* Make a duplicate of an exception region by copying all the handlers
 257    for an exception region. Return the new handler index. */
 258
 259 int duplicate_eh_handlers                       PROTO((int, int, rtx (*)(rtx)));
 260
 261 /* map symbol refs for rethrow */
 262
 263 rtx rethrow_symbol_map                          PROTO((rtx, rtx (*)(rtx)));
 264
 265 /* Is the rethrow label for a region used? */
 266
 267 int rethrow_used                                PROTO((int));
 268
 269 /* Update the rethrow references to reflect rethrows which have been
 270    optimized away.  */
 271
 272 void update_rethrow_references                  PROTO((void));
 273
 274 /* Return the region number a this is the rethrow label for. */
 275
 276 int eh_region_from_symbol                       PROTO((rtx));
 277
 278 /* Get a pointer to the first handler in an exception region's list. */
 279
 280 struct handler_info *get_first_handler          PROTO((int));
 281
 282 /* Find all the runtime handlers type matches currently referenced */
 283
 284 int find_all_handler_type_matches               PROTO((void ***));
 285
 286 /* The eh_nesting_info structure is used to find a list of valid handlers
 287    for any arbitrary exception region.  When init_eh_nesting_info is called,
 288    the information is all pre-calculated and entered in this structure.
 289    REGION_INDEX is a vector over all possible region numbers.  Since the
 290    number of regions is typically much smaller than the range of block
 291    numbers, this is a sparse vector and the other data structures are
 292    represented as dense vectors.  Indexed with an exception region number, this
 293    returns the index to use in the other data structures to retreive the
 294    correct information.
 295    HANDLERS is an array of vectors which point to handler_info structures.
 296    when indexed, it gives the list of all possible handlers which can
 297    be reached by a throw from this exception region.
 298    NUM_HANDLERS is the equivilent array indicating how many handler
 299    pointers there are in the HANDLERS vector.
 300    OUTER_INDEX indicates which index represents the information for the
 301    outer block.  0 indicates there is no outer context.
 302    REGION_COUNT is the number of regions.  */
 303
 304 typedef struct eh_nesting
 305 {
 306   int *region_index;
 307   handler_info ***handlers;
 308   int *num_handlers;
 309   int *outer_index;
 310   int region_count;
 311 } eh_nesting_info;
 312
 313 /* Initialize the eh_nesting_info structure.  */
 314
 315 eh_nesting_info *init_eh_nesting_info           PROTO((void));
 316
 317 /* Get a list of handlers reachable from a an exception region/insn.  */
 318
 319 int reachable_handlers                  PROTO((int, eh_nesting_info *, rtx,
 320                                                handler_info ***handlers));
 321
 322 /* Free the eh_nesting_info structure.  */
 323
 324 void free_eh_nesting_info                       PROTO((eh_nesting_info *));
 325
 326 extern void init_eh                             PROTO((void));
 327
 328 /* Initialization for the per-function EH data.  */
 329
 330 extern void init_eh_for_function                PROTO((void));
 331
 332 /* Generate an exception label. Use instead of gen_label_rtx */
 333
 334 extern rtx gen_exception_label                  PROTO((void));
 335
 336 /* Adds an EH table entry for EH entry number N. Called from
 337    final_scan_insn for NOTE_INSN_EH_REGION_BEG.  */
 338
 339 extern void add_eh_table_entry                  PROTO((int n));
 340
 341 /* Start a catch clause, triggered by runtime value paramter. */
 342
 343 #ifdef TREE_CODE
 344 extern void start_catch_handler                 PROTO((tree));
 345 #endif
 346
 347 /* End an individual catch clause. */
 348
 349 extern void end_catch_handler                   PROTO((void));
 350
 351 /* Returns a non-zero value if we need to output an exception table.  */
 352
 353 extern int exception_table_p                    PROTO((void));
 354
 355 /* Outputs the exception table if we have one.  */
 356
 357 extern void output_exception_table              PROTO((void));
 358
 359 /* Given a return address in ADDR, determine the address we should use
 360    to find the corresponding EH region.  */
 361
 362 extern rtx eh_outer_context                     PROTO((rtx addr));
 363
 364 /* Called at the start of a block of try statements for which there is
 365    a supplied catch handler.  */
 366
 367 extern void expand_start_try_stmts              PROTO((void));
 368
 369 /* Called at the start of a block of catch statements. It terminates the
 370    previous set of try statements.  */
 371
 372 extern void expand_start_all_catch              PROTO((void));
 373
 374 /* Called at the end of a block of catch statements.  */
 375
 376 extern void expand_end_all_catch                PROTO((void));
 377
 378 #ifdef TREE_CODE
 379 /* Create a new exception region and add the handler for the region
 380    onto a list. These regions will be ended (and their handlers
 381    emitted) when end_protect_partials is invoked.  */
 382
 383 extern void add_partial_entry                   PROTO((tree handler));
 384 #endif
 385
 386 /* End all of the pending exception regions that have handlers added with
 387    push_protect_entry ().  */
 388
 389 extern void end_protect_partials                PROTO((void));
 390
 391 /* An internal throw.  */
 392
 393 extern void expand_internal_throw               PROTO((void));
 394
 395 /* Called from expand_exception_blocks and expand_end_catch_block to
 396    expand and pending handlers.  */
 397
 398 extern void expand_leftover_cleanups            PROTO((void));
 399
 400 /* If necessary, emit insns to get EH context for the current
 401    function. */
 402
 403 extern void emit_eh_context                     PROTO((void));
 404
 405 /* Builds a list of handler labels and puts them in the global
 406    variable exception_handler_labels.  */
 407
 408 extern void find_exception_handler_labels       PROTO((void));
 409
 410 /* Determine if an arbitrary label is an exception label */
 411
 412 extern int is_exception_handler_label           PROTO((int));
 413
 414 /* Performs sanity checking on the check_exception_handler_labels
 415    list.  */
 416
 417 extern void check_exception_handler_labels      PROTO((void));
 418
 419 /* Keeps track of the label used as the context of a throw to rethrow an
 420    exception to the outer exception region.  */
 421
 422 extern struct label_node *outer_context_label_stack;
 423
 424 /* A list of labels used for exception handlers. It is created by
 425    find_exception_handler_labels for the optimization passes.  */
 426
 427 extern rtx exception_handler_labels;
 428
 429 /* Performs optimizations for exception handling, such as removing
 430    unnecessary exception regions. Invoked from jump_optimize ().  */
 431
 432 extern void exception_optimize                  PROTO((void));
 433
 434 /* Return EH context (and set it up once per fn).  */
 435 extern rtx get_eh_context                       PROTO((void));
 436
 437 /* Get the dynamic handler chain.  */
 438 extern rtx get_dynamic_handler_chain            PROTO((void));
 439
 440 /* Get the dynamic cleanup chain.  */
 441 extern rtx get_dynamic_cleanup_chain            PROTO((void));
 442
 443 /* Throw an exception.  */
 444
 445 extern void emit_throw                          PROTO((void));
 446
 447 /* One to use setjmp/longjmp method of generating code.  */
 448
 449 extern int exceptions_via_longjmp;
 450
 451 /* One to enable asynchronous exception support.  */
 452
 453 extern int asynchronous_exceptions;
 454
 455 /* One to protect cleanup actions with a handler that calls
 456    __terminate, zero otherwise.  */
 457
 458 extern int protect_cleanup_actions_with_terminate;
 459
 460 #ifdef TREE_CODE
 461 extern tree protect_with_terminate              PROTO((tree));
 462 #endif
 463
 464 extern void expand_fixup_region_start   PROTO((void));
 465 #ifdef TREE_CODE
 466 extern void expand_fixup_region_end     PROTO((tree));
 467 #endif
 468
 469 /* Various hooks for the DWARF 2 __throw routine.  */
 470
 471 void expand_builtin_unwind_init         PROTO((void));
 472 rtx expand_builtin_dwarf_fp_regnum      PROTO((void));
 473 #ifdef TREE_CODE
 474 rtx expand_builtin_frob_return_addr     PROTO((tree));
 475 rtx expand_builtin_extract_return_addr  PROTO((tree));
 476 void expand_builtin_init_dwarf_reg_sizes        PROTO((tree));
 477 void expand_builtin_eh_return           PROTO((tree, tree, tree));
 478 #endif
 479 void expand_eh_return                   PROTO((void));
 480
 481
 482 /* Checking whether 2 instructions are within the same exception region. */
 483
 484 int in_same_eh_region                   PROTO((rtx, rtx));
 485 void free_insn_eh_region                PROTO((void));
 486 void init_insn_eh_region                PROTO((rtx, int));
 487
 488 #ifdef rtx
 489 #undef rtx
 490 #endif