1 /* Implements exception handling.
2 Copyright (C) 1989, 92-97, 1998 Free Software Foundation, Inc.
3 Contributed by Mike Stump <mrs@cygnus.com>.
5 This file is part of GNU CC.
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)
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.
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. */
23 /* An exception is an event that can be signaled from within a
24 function. This event can then be "caught" or "trapped" by the
25 callers of this function. This potentially allows program flow to
26 be transferred to any arbitrary code associated with a function call
27 several levels up the stack.
29 The intended use for this mechanism is for signaling "exceptional
30 events" in an out-of-band fashion, hence its name. The C++ language
31 (and many other OO-styled or functional languages) practically
32 requires such a mechanism, as otherwise it becomes very difficult
33 or even impossible to signal failure conditions in complex
34 situations. The traditional C++ example is when an error occurs in
35 the process of constructing an object; without such a mechanism, it
36 is impossible to signal that the error occurs without adding global
37 state variables and error checks around every object construction.
39 The act of causing this event to occur is referred to as "throwing
40 an exception". (Alternate terms include "raising an exception" or
41 "signaling an exception".) The term "throw" is used because control
42 is returned to the callers of the function that is signaling the
43 exception, and thus there is the concept of "throwing" the
44 exception up the call stack.
46 There are two major codegen options for exception handling. The
47 flag -fsjlj-exceptions can be used to select the setjmp/longjmp
48 approach, which is the default. -fno-sjlj-exceptions can be used to
49 get the PC range table approach. While this is a compile time
50 flag, an entire application must be compiled with the same codegen
51 option. The first is a PC range table approach, the second is a
52 setjmp/longjmp based scheme. We will first discuss the PC range
53 table approach, after that, we will discuss the setjmp/longjmp
56 It is appropriate to speak of the "context of a throw". This
57 context refers to the address where the exception is thrown from,
58 and is used to determine which exception region will handle the
61 Regions of code within a function can be marked such that if it
62 contains the context of a throw, control will be passed to a
63 designated "exception handler". These areas are known as "exception
64 regions". Exception regions cannot overlap, but they can be nested
65 to any arbitrary depth. Also, exception regions cannot cross
68 Exception handlers can either be specified by the user (which we
69 will call a "user-defined handler") or generated by the compiler
70 (which we will designate as a "cleanup"). Cleanups are used to
71 perform tasks such as destruction of objects allocated on the
74 In the current implementation, cleanups are handled by allocating an
75 exception region for the area that the cleanup is designated for,
76 and the handler for the region performs the cleanup and then
77 rethrows the exception to the outer exception region. From the
78 standpoint of the current implementation, there is little
79 distinction made between a cleanup and a user-defined handler, and
80 the phrase "exception handler" can be used to refer to either one
81 equally well. (The section "Future Directions" below discusses how
84 Each object file that is compiled with exception handling contains
85 a static array of exception handlers named __EXCEPTION_TABLE__.
86 Each entry contains the starting and ending addresses of the
87 exception region, and the address of the handler designated for
90 If the target does not use the DWARF 2 frame unwind information, at
91 program startup each object file invokes a function named
92 __register_exceptions with the address of its local
93 __EXCEPTION_TABLE__. __register_exceptions is defined in libgcc2.c, and
94 is responsible for recording all of the exception regions into one list
95 (which is kept in a static variable named exception_table_list).
97 On targets that support crtstuff.c, the unwind information
98 is stored in a section named .eh_frame and the information for the
99 entire shared object or program is registered with a call to
100 __register_frame_info. On other targets, the information for each
101 translation unit is registered from the file generated by collect2.
102 __register_frame_info is defined in frame.c, and is responsible for
103 recording all of the unwind regions into one list (which is kept in a
104 static variable named unwind_table_list).
106 The function __throw is actually responsible for doing the
107 throw. On machines that have unwind info support, __throw is generated
108 by code in libgcc2.c, otherwise __throw is generated on a
109 per-object-file basis for each source file compiled with
110 -fexceptions by the C++ frontend. Before __throw is invoked,
111 the current context of the throw needs to be placed in the global
114 __throw attempts to find the appropriate exception handler for the
115 PC value stored in __eh_pc by calling __find_first_exception_table_match
116 (which is defined in libgcc2.c). If __find_first_exception_table_match
117 finds a relevant handler, __throw transfers control directly to it.
119 If a handler for the context being thrown from can't be found, __throw
120 walks (see Walking the stack below) the stack up the dynamic call chain to
121 continue searching for an appropriate exception handler based upon the
122 caller of the function it last sought a exception handler for. It stops
123 then either an exception handler is found, or when the top of the
124 call chain is reached.
126 If no handler is found, an external library function named
127 __terminate is called. If a handler is found, then we restart
128 our search for a handler at the end of the call chain, and repeat
129 the search process, but instead of just walking up the call chain,
130 we unwind the call chain as we walk up it.
132 Internal implementation details:
134 To associate a user-defined handler with a block of statements, the
135 function expand_start_try_stmts is used to mark the start of the
136 block of statements with which the handler is to be associated
137 (which is known as a "try block"). All statements that appear
138 afterwards will be associated with the try block.
140 A call to expand_start_all_catch marks the end of the try block,
141 and also marks the start of the "catch block" (the user-defined
142 handler) associated with the try block.
144 This user-defined handler will be invoked for *every* exception
145 thrown with the context of the try block. It is up to the handler
146 to decide whether or not it wishes to handle any given exception,
147 as there is currently no mechanism in this implementation for doing
148 this. (There are plans for conditionally processing an exception
149 based on its "type", which will provide a language-independent
152 If the handler chooses not to process the exception (perhaps by
153 looking at an "exception type" or some other additional data
154 supplied with the exception), it can fall through to the end of the
155 handler. expand_end_all_catch and expand_leftover_cleanups
156 add additional code to the end of each handler to take care of
157 rethrowing to the outer exception handler.
159 The handler also has the option to continue with "normal flow of
160 code", or in other words to resume executing at the statement
161 immediately after the end of the exception region. The variable
162 caught_return_label_stack contains a stack of labels, and jumping
163 to the topmost entry's label via expand_goto will resume normal
164 flow to the statement immediately after the end of the exception
165 region. If the handler falls through to the end, the exception will
166 be rethrown to the outer exception region.
168 The instructions for the catch block are kept as a separate
169 sequence, and will be emitted at the end of the function along with
170 the handlers specified via expand_eh_region_end. The end of the
171 catch block is marked with expand_end_all_catch.
173 Any data associated with the exception must currently be handled by
174 some external mechanism maintained in the frontend. For example,
175 the C++ exception mechanism passes an arbitrary value along with
176 the exception, and this is handled in the C++ frontend by using a
177 global variable to hold the value. (This will be changing in the
180 The mechanism in C++ for handling data associated with the
181 exception is clearly not thread-safe. For a thread-based
182 environment, another mechanism must be used (possibly using a
183 per-thread allocation mechanism if the size of the area that needs
184 to be allocated isn't known at compile time.)
186 Internally-generated exception regions (cleanups) are marked by
187 calling expand_eh_region_start to mark the start of the region,
188 and expand_eh_region_end (handler) is used to both designate the
189 end of the region and to associate a specified handler/cleanup with
190 the region. The rtl code in HANDLER will be invoked whenever an
191 exception occurs in the region between the calls to
192 expand_eh_region_start and expand_eh_region_end. After HANDLER is
193 executed, additional code is emitted to handle rethrowing the
194 exception to the outer exception handler. The code for HANDLER will
195 be emitted at the end of the function.
197 TARGET_EXPRs can also be used to designate exception regions. A
198 TARGET_EXPR gives an unwind-protect style interface commonly used
199 in functional languages such as LISP. The associated expression is
200 evaluated, and whether or not it (or any of the functions that it
201 calls) throws an exception, the protect expression is always
202 invoked. This implementation takes care of the details of
203 associating an exception table entry with the expression and
204 generating the necessary code (it actually emits the protect
205 expression twice, once for normal flow and once for the exception
206 case). As for the other handlers, the code for the exception case
207 will be emitted at the end of the function.
209 Cleanups can also be specified by using add_partial_entry (handler)
210 and end_protect_partials. add_partial_entry creates the start of
211 a new exception region; HANDLER will be invoked if an exception is
212 thrown with the context of the region between the calls to
213 add_partial_entry and end_protect_partials. end_protect_partials is
214 used to mark the end of these regions. add_partial_entry can be
215 called as many times as needed before calling end_protect_partials.
216 However, end_protect_partials should only be invoked once for each
217 group of calls to add_partial_entry as the entries are queued
218 and all of the outstanding entries are processed simultaneously
219 when end_protect_partials is invoked. Similarly to the other
220 handlers, the code for HANDLER will be emitted at the end of the
223 The generated RTL for an exception region includes
224 NOTE_INSN_EH_REGION_BEG and NOTE_INSN_EH_REGION_END notes that mark
225 the start and end of the exception region. A unique label is also
226 generated at the start of the exception region, which is available
227 by looking at the ehstack variable. The topmost entry corresponds
228 to the current region.
230 In the current implementation, an exception can only be thrown from
231 a function call (since the mechanism used to actually throw an
232 exception involves calling __throw). If an exception region is
233 created but no function calls occur within that region, the region
234 can be safely optimized away (along with its exception handlers)
235 since no exceptions can ever be caught in that region. This
236 optimization is performed unless -fasynchronous-exceptions is
237 given. If the user wishes to throw from a signal handler, or other
238 asynchronous place, -fasynchronous-exceptions should be used when
239 compiling for maximally correct code, at the cost of additional
240 exception regions. Using -fasynchronous-exceptions only produces
241 code that is reasonably safe in such situations, but a correct
242 program cannot rely upon this working. It can be used in failsafe
243 code, where trying to continue on, and proceeding with potentially
244 incorrect results is better than halting the program.
249 The stack is walked by starting with a pointer to the current
250 frame, and finding the pointer to the callers frame. The unwind info
251 tells __throw how to find it.
255 When we use the term unwinding the stack, we mean undoing the
256 effects of the function prologue in a controlled fashion so that we
257 still have the flow of control. Otherwise, we could just return
258 (jump to the normal end of function epilogue).
260 This is done in __throw in libgcc2.c when we know that a handler exists
261 in a frame higher up the call stack than its immediate caller.
263 To unwind, we find the unwind data associated with the frame, if any.
264 If we don't find any, we call the library routine __terminate. If we do
265 find it, we use the information to copy the saved register values from
266 that frame into the register save area in the frame for __throw, return
267 into a stub which updates the stack pointer, and jump to the handler.
268 The normal function epilogue for __throw handles restoring the saved
269 values into registers.
271 When unwinding, we use this method if we know it will
272 work (if DWARF2_UNWIND_INFO is defined). Otherwise, we know that
273 an inline unwinder will have been emitted for any function that
274 __unwind_function cannot unwind. The inline unwinder appears as a
275 normal exception handler for the entire function, for any function
276 that we know cannot be unwound by __unwind_function. We inform the
277 compiler of whether a function can be unwound with
278 __unwind_function by having DOESNT_NEED_UNWINDER evaluate to true
279 when the unwinder isn't needed. __unwind_function is used as an
280 action of last resort. If no other method can be used for
281 unwinding, __unwind_function is used. If it cannot unwind, it
282 should call __terminate.
284 By default, if the target-specific backend doesn't supply a definition
285 for __unwind_function and doesn't support DWARF2_UNWIND_INFO, inlined
286 unwinders will be used instead. The main tradeoff here is in text space
287 utilization. Obviously, if inline unwinders have to be generated
288 repeatedly, this uses much more space than if a single routine is used.
290 However, it is simply not possible on some platforms to write a
291 generalized routine for doing stack unwinding without having some
292 form of additional data associated with each function. The current
293 implementation can encode this data in the form of additional
294 machine instructions or as static data in tabular form. The later
295 is called the unwind data.
297 The backend macro DOESNT_NEED_UNWINDER is used to conditionalize whether
298 or not per-function unwinders are needed. If DOESNT_NEED_UNWINDER is
299 defined and has a non-zero value, a per-function unwinder is not emitted
300 for the current function. If the static unwind data is supported, then
301 a per-function unwinder is not emitted.
303 On some platforms it is possible that neither __unwind_function
304 nor inlined unwinders are available. For these platforms it is not
305 possible to throw through a function call, and abort will be
306 invoked instead of performing the throw.
308 The reason the unwind data may be needed is that on some platforms
309 the order and types of data stored on the stack can vary depending
310 on the type of function, its arguments and returned values, and the
311 compilation options used (optimization versus non-optimization,
312 -fomit-frame-pointer, processor variations, etc).
314 Unfortunately, this also means that throwing through functions that
315 aren't compiled with exception handling support will still not be
316 possible on some platforms. This problem is currently being
317 investigated, but no solutions have been found that do not imply
318 some unacceptable performance penalties.
322 Currently __throw makes no differentiation between cleanups and
323 user-defined exception regions. While this makes the implementation
324 simple, it also implies that it is impossible to determine if a
325 user-defined exception handler exists for a given exception without
326 completely unwinding the stack in the process. This is undesirable
327 from the standpoint of debugging, as ideally it would be possible
328 to trap unhandled exceptions in the debugger before the process of
329 unwinding has even started.
331 This problem can be solved by marking user-defined handlers in a
332 special way (probably by adding additional bits to exception_table_list).
333 A two-pass scheme could then be used by __throw to iterate
334 through the table. The first pass would search for a relevant
335 user-defined handler for the current context of the throw, and if
336 one is found, the second pass would then invoke all needed cleanups
337 before jumping to the user-defined handler.
339 Many languages (including C++ and Ada) make execution of a
340 user-defined handler conditional on the "type" of the exception
341 thrown. (The type of the exception is actually the type of the data
342 that is thrown with the exception.) It will thus be necessary for
343 __throw to be able to determine if a given user-defined
344 exception handler will actually be executed, given the type of
347 One scheme is to add additional information to exception_table_list
348 as to the types of exceptions accepted by each handler. __throw
349 can do the type comparisons and then determine if the handler is
350 actually going to be executed.
352 There is currently no significant level of debugging support
353 available, other than to place a breakpoint on __throw. While
354 this is sufficient in most cases, it would be helpful to be able to
355 know where a given exception was going to be thrown to before it is
356 actually thrown, and to be able to choose between stopping before
357 every exception region (including cleanups), or just user-defined
358 exception regions. This should be possible to do in the two-pass
359 scheme by adding additional labels to __throw for appropriate
360 breakpoints, and additional debugger commands could be added to
361 query various state variables to determine what actions are to be
364 Another major problem that is being worked on is the issue with stack
365 unwinding on various platforms. Currently the only platforms that have
366 support for the generation of a generic unwinder are the SPARC and MIPS.
367 All other ports require per-function unwinders, which produce large
368 amounts of code bloat.
370 For setjmp/longjmp based exception handling, some of the details
371 are as above, but there are some additional details. This section
372 discusses the details.
374 We don't use NOTE_INSN_EH_REGION_{BEG,END} pairs. We don't
375 optimize EH regions yet. We don't have to worry about machine
376 specific issues with unwinding the stack, as we rely upon longjmp
377 for all the machine specific details. There is no variable context
378 of a throw, just the one implied by the dynamic handler stack
379 pointed to by the dynamic handler chain. There is no exception
380 table, and no calls to __register_exceptions. __sjthrow is used
381 instead of __throw, and it works by using the dynamic handler
382 chain, and longjmp. -fasynchronous-exceptions has no effect, as
383 the elimination of trivial exception regions is not yet performed.
385 A frontend can set protect_cleanup_actions_with_terminate when all
386 the cleanup actions should be protected with an EH region that
387 calls terminate when an unhandled exception is throw. C++ does
388 this, Ada does not. */
392 #include "defaults.h"
393 #include "eh-common.h"
399 #include "function.h"
400 #include "insn-flags.h"
402 #include "insn-codes.h"
404 #include "hard-reg-set.h"
405 #include "insn-config.h"
410 /* One to use setjmp/longjmp method of generating code for exception
413 int exceptions_via_longjmp = 2;
415 /* One to enable asynchronous exception support. */
417 int asynchronous_exceptions = 0;
419 /* One to protect cleanup actions with a handler that calls
420 __terminate, zero otherwise. */
422 int protect_cleanup_actions_with_terminate;
424 /* A list of labels used for exception handlers. Created by
425 find_exception_handler_labels for the optimization passes. */
427 rtx exception_handler_labels;
429 /* The EH context. Nonzero if the function has already
430 fetched a pointer to the EH context for exception handling. */
432 rtx current_function_ehc;
434 /* A stack used for keeping track of the currently active exception
435 handling region. As each exception region is started, an entry
436 describing the region is pushed onto this stack. The current
437 region can be found by looking at the top of the stack, and as we
438 exit regions, the corresponding entries are popped.
440 Entries cannot overlap; they can be nested. So there is only one
441 entry at most that corresponds to the current instruction, and that
442 is the entry on the top of the stack. */
444 static struct eh_stack ehstack;
447 /* This stack is used to represent what the current eh region is
448 for the catch blocks beings processed */
450 static struct eh_stack catchstack;
452 /* A queue used for tracking which exception regions have closed but
453 whose handlers have not yet been expanded. Regions are emitted in
454 groups in an attempt to improve paging performance.
456 As we exit a region, we enqueue a new entry. The entries are then
457 dequeued during expand_leftover_cleanups and expand_start_all_catch,
459 We should redo things so that we either take RTL for the handler,
460 or we expand the handler expressed as a tree immediately at region
463 static struct eh_queue ehqueue;
465 /* Insns for all of the exception handlers for the current function.
466 They are currently emitted by the frontend code. */
470 /* A TREE_CHAINed list of handlers for regions that are not yet
471 closed. The TREE_VALUE of each entry contains the handler for the
472 corresponding entry on the ehstack. */
474 static tree protect_list;
476 /* Stacks to keep track of various labels. */
478 /* Keeps track of the label to resume to should one want to resume
479 normal control flow out of a handler (instead of, say, returning to
480 the caller of the current function or exiting the program). */
482 struct label_node *caught_return_label_stack = NULL;
484 /* Keeps track of the label used as the context of a throw to rethrow an
485 exception to the outer exception region. */
487 struct label_node *outer_context_label_stack = NULL;
489 /* A random data area for the front end's own use. */
491 struct label_node *false_label_stack = NULL;
493 static void push_eh_entry PROTO((struct eh_stack *));
494 static struct eh_entry * pop_eh_entry PROTO((struct eh_stack *));
495 static void enqueue_eh_entry PROTO((struct eh_queue *, struct eh_entry *));
496 static struct eh_entry * dequeue_eh_entry PROTO((struct eh_queue *));
497 static rtx call_get_eh_context PROTO((void));
498 static void start_dynamic_cleanup PROTO((tree, tree));
499 static void start_dynamic_handler PROTO((void));
500 static void expand_rethrow PROTO((rtx));
501 static void output_exception_table_entry PROTO((FILE *, int));
502 static int can_throw PROTO((rtx));
503 static rtx scan_region PROTO((rtx, int, int *));
504 static void eh_regs PROTO((rtx *, rtx *, int));
505 static void set_insn_eh_region PROTO((rtx *, int));
506 #ifdef DONT_USE_BUILTIN_SETJMP
507 static void jumpif_rtx PROTO((rtx, rtx));
511 rtx expand_builtin_return_addr PROTO((enum built_in_function, int, rtx));
513 /* Various support routines to manipulate the various data structures
514 used by the exception handling code. */
516 /* Push a label entry onto the given STACK. */
519 push_label_entry (stack, rlabel, tlabel)
520 struct label_node **stack;
524 struct label_node *newnode
525 = (struct label_node *) xmalloc (sizeof (struct label_node));
528 newnode->u.rlabel = rlabel;
530 newnode->u.tlabel = tlabel;
531 newnode->chain = *stack;
535 /* Pop a label entry from the given STACK. */
538 pop_label_entry (stack)
539 struct label_node **stack;
542 struct label_node *tempnode;
548 label = tempnode->u.rlabel;
549 *stack = (*stack)->chain;
555 /* Return the top element of the given STACK. */
558 top_label_entry (stack)
559 struct label_node **stack;
564 return (*stack)->u.tlabel;
567 /* get an exception label. These must be on the permanent obstack */
570 gen_exception_label ()
574 push_obstacks_nochange ();
575 end_temporary_allocation ();
576 lab = gen_label_rtx ();
581 /* Push a new eh_node entry onto STACK. */
584 push_eh_entry (stack)
585 struct eh_stack *stack;
587 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
588 struct eh_entry *entry = (struct eh_entry *) xmalloc (sizeof (struct eh_entry));
590 entry->outer_context = gen_label_rtx ();
591 entry->finalization = NULL_TREE;
592 entry->label_used = 0;
593 entry->exception_handler_label = gen_exception_label ();
596 node->chain = stack->top;
600 /* push an existing entry onto a stack. */
602 push_entry (stack, entry)
603 struct eh_stack *stack;
604 struct eh_entry *entry;
606 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
608 node->chain = stack->top;
612 /* Pop an entry from the given STACK. */
614 static struct eh_entry *
616 struct eh_stack *stack;
618 struct eh_node *tempnode;
619 struct eh_entry *tempentry;
621 tempnode = stack->top;
622 tempentry = tempnode->entry;
623 stack->top = stack->top->chain;
629 /* Enqueue an ENTRY onto the given QUEUE. */
632 enqueue_eh_entry (queue, entry)
633 struct eh_queue *queue;
634 struct eh_entry *entry;
636 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
641 if (queue->head == NULL)
647 queue->tail->chain = node;
652 /* Dequeue an entry from the given QUEUE. */
654 static struct eh_entry *
655 dequeue_eh_entry (queue)
656 struct eh_queue *queue;
658 struct eh_node *tempnode;
659 struct eh_entry *tempentry;
661 if (queue->head == NULL)
664 tempnode = queue->head;
665 queue->head = queue->head->chain;
667 tempentry = tempnode->entry;
674 receive_exception_label (handler_label)
677 emit_label (handler_label);
679 #ifdef HAVE_exception_receiver
680 if (! exceptions_via_longjmp)
681 if (HAVE_exception_receiver)
682 emit_insn (gen_exception_receiver ());
685 #ifdef HAVE_nonlocal_goto_receiver
686 if (! exceptions_via_longjmp)
687 if (HAVE_nonlocal_goto_receiver)
688 emit_insn (gen_nonlocal_goto_receiver ());
695 int range_number; /* EH region number from EH NOTE insn's */
696 struct handler_info *handlers;
700 /* table of function eh regions */
701 static struct func_eh_entry *function_eh_regions = NULL;
702 static int num_func_eh_entries = 0;
703 static int current_func_eh_entry = 0;
705 #define SIZE_FUNC_EH(X) (sizeof (struct func_eh_entry) * X)
707 /* Add a new eh_entry for this function, and base it off of the information
708 in the EH_ENTRY parameter. A NULL parameter is invalid. The number
709 returned is an number which uniquely identifies this exception range. */
712 new_eh_region_entry (note_eh_region)
715 if (current_func_eh_entry == num_func_eh_entries)
717 if (num_func_eh_entries == 0)
719 function_eh_regions =
720 (struct func_eh_entry *) malloc (SIZE_FUNC_EH (50));
721 num_func_eh_entries = 50;
725 num_func_eh_entries = num_func_eh_entries * 3 / 2;
726 function_eh_regions = (struct func_eh_entry *)
727 realloc (function_eh_regions, SIZE_FUNC_EH (num_func_eh_entries));
730 function_eh_regions[current_func_eh_entry].range_number = note_eh_region;
731 function_eh_regions[current_func_eh_entry].handlers = NULL;
733 return current_func_eh_entry++;
736 /* Add new handler information to an exception range. The first parameter
737 specifies the range number (returned from new_eh_entry()). The second
738 parameter specifies the handler. By default the handler is inserted at
739 the end of the list. A handler list may contain only ONE NULL_TREE
740 typeinfo entry. Regardless where it is positioned, a NULL_TREE entry
741 is always output as the LAST handler in the exception table for a region. */
744 add_new_handler (region, newhandler)
746 struct handler_info *newhandler;
748 struct handler_info *last;
750 newhandler->next = NULL;
751 last = function_eh_regions[region].handlers;
753 function_eh_regions[region].handlers = newhandler;
756 for ( ; last->next != NULL; last = last->next)
758 last->next = newhandler;
762 /* Remove a handler label. The handler label is being deleted, so all
763 regions which reference this handler should have it removed from their
764 list of possible handlers. Any region which has the final handler
765 removed can be deleted. */
767 void remove_handler (removing_label)
770 struct handler_info *handler, *last;
772 for (x = 0 ; x < current_func_eh_entry; ++x)
775 handler = function_eh_regions[x].handlers;
776 for ( ; handler; last = handler, handler = handler->next)
777 if (handler->handler_label == removing_label)
781 last->next = handler->next;
785 function_eh_regions[x].handlers = handler->next;
790 /* Create a new handler structure initialized with the handler label and
791 typeinfo fields passed in. */
793 struct handler_info *
794 get_new_handler (handler, typeinfo)
798 struct handler_info* ptr;
799 ptr = (struct handler_info *) malloc (sizeof (struct handler_info));
800 ptr->handler_label = handler;
801 ptr->type_info = typeinfo;
809 /* Find the index in function_eh_regions associated with a NOTE region. If
810 the region cannot be found, a -1 is returned. This should never happen! */
813 find_func_region (insn_region)
817 for (x = 0; x < current_func_eh_entry; x++)
818 if (function_eh_regions[x].range_number == insn_region)
824 /* Get a pointer to the first handler in an exception region's list. */
826 struct handler_info *
827 get_first_handler (region)
830 return function_eh_regions[find_func_region (region)].handlers;
833 /* Clean out the function_eh_region table and free all memory */
836 clear_function_eh_region ()
839 struct handler_info *ptr, *next;
840 for (x = 0; x < current_func_eh_entry; x++)
841 for (ptr = function_eh_regions[x].handlers; ptr != NULL; ptr = next)
846 free (function_eh_regions);
847 num_func_eh_entries = 0;
848 current_func_eh_entry = 0;
851 /* Make a duplicate of an exception region by copying all the handlers
852 for an exception region. Return the new handler index. */
855 duplicate_handlers (old_note_eh_region, new_note_eh_region)
856 int old_note_eh_region, new_note_eh_region;
858 struct handler_info *ptr, *new_ptr;
859 int new_region, region;
861 region = find_func_region (old_note_eh_region);
863 error ("Cannot duplicate non-existant exception region.");
865 if (find_func_region (new_note_eh_region) != -1)
866 error ("Cannot duplicate EH region because new note region already exists");
868 new_region = new_eh_region_entry (new_note_eh_region);
869 ptr = function_eh_regions[region].handlers;
871 for ( ; ptr; ptr = ptr->next)
873 new_ptr = get_new_handler (ptr->handler_label, ptr->type_info);
874 add_new_handler (new_region, new_ptr);
881 /* Routine to see if exception handling is turned on.
882 DO_WARN is non-zero if we want to inform the user that exception
883 handling is turned off.
885 This is used to ensure that -fexceptions has been specified if the
886 compiler tries to use any exception-specific functions. */
892 if (! flag_exceptions)
894 static int warned = 0;
895 if (! warned && do_warn)
897 error ("exception handling disabled, use -fexceptions to enable");
905 /* Given a return address in ADDR, determine the address we should use
906 to find the corresponding EH region. */
909 eh_outer_context (addr)
912 /* First mask out any unwanted bits. */
913 #ifdef MASK_RETURN_ADDR
914 expand_and (addr, MASK_RETURN_ADDR, addr);
917 /* Then adjust to find the real return address. */
918 #if defined (RETURN_ADDR_OFFSET)
919 addr = plus_constant (addr, RETURN_ADDR_OFFSET);
925 /* Start a new exception region for a region of code that has a
926 cleanup action and push the HANDLER for the region onto
927 protect_list. All of the regions created with add_partial_entry
928 will be ended when end_protect_partials is invoked. */
931 add_partial_entry (handler)
934 expand_eh_region_start ();
936 /* Make sure the entry is on the correct obstack. */
937 push_obstacks_nochange ();
938 resume_temporary_allocation ();
940 /* Because this is a cleanup action, we may have to protect the handler
942 handler = protect_with_terminate (handler);
944 protect_list = tree_cons (NULL_TREE, handler, protect_list);
948 /* Emit code to get EH context to current function. */
951 call_get_eh_context ()
959 fn = get_identifier ("__get_eh_context");
960 push_obstacks_nochange ();
961 end_temporary_allocation ();
962 fntype = build_pointer_type (build_pointer_type
963 (build_pointer_type (void_type_node)));
964 fntype = build_function_type (fntype, NULL_TREE);
965 fn = build_decl (FUNCTION_DECL, fn, fntype);
966 DECL_EXTERNAL (fn) = 1;
967 TREE_PUBLIC (fn) = 1;
968 DECL_ARTIFICIAL (fn) = 1;
969 TREE_READONLY (fn) = 1;
970 make_decl_rtl (fn, NULL_PTR, 1);
971 assemble_external (fn);
975 expr = build1 (ADDR_EXPR, build_pointer_type (TREE_TYPE (fn)), fn);
976 expr = build (CALL_EXPR, TREE_TYPE (TREE_TYPE (fn)),
977 expr, NULL_TREE, NULL_TREE);
978 TREE_SIDE_EFFECTS (expr) = 1;
980 return copy_to_reg (expand_expr (expr, NULL_RTX, VOIDmode, 0));
983 /* Get a reference to the EH context.
984 We will only generate a register for the current function EH context here,
985 and emit a USE insn to mark that this is a EH context register.
987 Later, emit_eh_context will emit needed call to __get_eh_context
988 in libgcc2, and copy the value to the register we have generated. */
993 if (current_function_ehc == 0)
997 current_function_ehc = gen_reg_rtx (Pmode);
999 insn = gen_rtx_USE (GET_MODE (current_function_ehc),
1000 current_function_ehc);
1001 insn = emit_insn_before (insn, get_first_nonparm_insn ());
1004 = gen_rtx_EXPR_LIST (REG_EH_CONTEXT, current_function_ehc,
1007 return current_function_ehc;
1010 /* Get a reference to the dynamic handler chain. It points to the
1011 pointer to the next element in the dynamic handler chain. It ends
1012 when there are no more elements in the dynamic handler chain, when
1013 the value is &top_elt from libgcc2.c. Immediately after the
1014 pointer, is an area suitable for setjmp/longjmp when
1015 DONT_USE_BUILTIN_SETJMP is defined, and an area suitable for
1016 __builtin_setjmp/__builtin_longjmp when DONT_USE_BUILTIN_SETJMP
1020 get_dynamic_handler_chain ()
1022 rtx ehc, dhc, result;
1024 ehc = get_eh_context ();
1026 /* This is the offset of dynamic_handler_chain in the eh_context struct
1027 declared in eh-common.h. If its location is change, change this offset */
1028 dhc = plus_constant (ehc, POINTER_SIZE / BITS_PER_UNIT);
1030 result = copy_to_reg (dhc);
1032 /* We don't want a copy of the dcc, but rather, the single dcc. */
1033 return gen_rtx_MEM (Pmode, result);
1036 /* Get a reference to the dynamic cleanup chain. It points to the
1037 pointer to the next element in the dynamic cleanup chain.
1038 Immediately after the pointer, are two Pmode variables, one for a
1039 pointer to a function that performs the cleanup action, and the
1040 second, the argument to pass to that function. */
1043 get_dynamic_cleanup_chain ()
1045 rtx dhc, dcc, result;
1047 dhc = get_dynamic_handler_chain ();
1048 dcc = plus_constant (dhc, POINTER_SIZE / BITS_PER_UNIT);
1050 result = copy_to_reg (dcc);
1052 /* We don't want a copy of the dcc, but rather, the single dcc. */
1053 return gen_rtx_MEM (Pmode, result);
1056 #ifdef DONT_USE_BUILTIN_SETJMP
1057 /* Generate code to evaluate X and jump to LABEL if the value is nonzero.
1058 LABEL is an rtx of code CODE_LABEL, in this function. */
1061 jumpif_rtx (x, label)
1065 jumpif (make_tree (type_for_mode (GET_MODE (x), 0), x), label);
1069 /* Start a dynamic cleanup on the EH runtime dynamic cleanup stack.
1070 We just need to create an element for the cleanup list, and push it
1073 A dynamic cleanup is a cleanup action implied by the presence of an
1074 element on the EH runtime dynamic cleanup stack that is to be
1075 performed when an exception is thrown. The cleanup action is
1076 performed by __sjthrow when an exception is thrown. Only certain
1077 actions can be optimized into dynamic cleanup actions. For the
1078 restrictions on what actions can be performed using this routine,
1079 see expand_eh_region_start_tree. */
1082 start_dynamic_cleanup (func, arg)
1087 rtx new_func, new_arg;
1091 /* We allocate enough room for a pointer to the function, and
1095 /* XXX, FIXME: The stack space allocated this way is too long lived,
1096 but there is no allocation routine that allocates at the level of
1097 the last binding contour. */
1098 buf = assign_stack_local (BLKmode,
1099 GET_MODE_SIZE (Pmode)*(size+1),
1102 buf = change_address (buf, Pmode, NULL_RTX);
1104 /* Store dcc into the first word of the newly allocated buffer. */
1106 dcc = get_dynamic_cleanup_chain ();
1107 emit_move_insn (buf, dcc);
1109 /* Store func and arg into the cleanup list element. */
1111 new_func = gen_rtx_MEM (Pmode, plus_constant (XEXP (buf, 0),
1112 GET_MODE_SIZE (Pmode)));
1113 new_arg = gen_rtx_MEM (Pmode, plus_constant (XEXP (buf, 0),
1114 GET_MODE_SIZE (Pmode)*2));
1115 x = expand_expr (func, new_func, Pmode, 0);
1117 emit_move_insn (new_func, x);
1119 x = expand_expr (arg, new_arg, Pmode, 0);
1121 emit_move_insn (new_arg, x);
1123 /* Update the cleanup chain. */
1125 emit_move_insn (dcc, XEXP (buf, 0));
1128 /* Emit RTL to start a dynamic handler on the EH runtime dynamic
1129 handler stack. This should only be used by expand_eh_region_start
1130 or expand_eh_region_start_tree. */
1133 start_dynamic_handler ()
1139 #ifndef DONT_USE_BUILTIN_SETJMP
1140 /* The number of Pmode words for the setjmp buffer, when using the
1141 builtin setjmp/longjmp, see expand_builtin, case
1142 BUILT_IN_LONGJMP. */
1146 size = JMP_BUF_SIZE;
1148 /* Should be large enough for most systems, if it is not,
1149 JMP_BUF_SIZE should be defined with the proper value. It will
1150 also tend to be larger than necessary for most systems, a more
1151 optimal port will define JMP_BUF_SIZE. */
1152 size = FIRST_PSEUDO_REGISTER+2;
1155 /* XXX, FIXME: The stack space allocated this way is too long lived,
1156 but there is no allocation routine that allocates at the level of
1157 the last binding contour. */
1158 arg = assign_stack_local (BLKmode,
1159 GET_MODE_SIZE (Pmode)*(size+1),
1162 arg = change_address (arg, Pmode, NULL_RTX);
1164 /* Store dhc into the first word of the newly allocated buffer. */
1166 dhc = get_dynamic_handler_chain ();
1167 dcc = gen_rtx_MEM (Pmode, plus_constant (XEXP (arg, 0),
1168 GET_MODE_SIZE (Pmode)));
1169 emit_move_insn (arg, dhc);
1171 /* Zero out the start of the cleanup chain. */
1172 emit_move_insn (dcc, const0_rtx);
1174 /* The jmpbuf starts two words into the area allocated. */
1175 buf = plus_constant (XEXP (arg, 0), GET_MODE_SIZE (Pmode)*2);
1177 #ifdef DONT_USE_BUILTIN_SETJMP
1178 x = emit_library_call_value (setjmp_libfunc, NULL_RTX, 1, SImode, 1,
1180 /* If we come back here for a catch, transfer control to the handler. */
1181 jumpif_rtx (x, ehstack.top->entry->exception_handler_label);
1184 /* A label to continue execution for the no exception case. */
1185 rtx noex = gen_label_rtx();
1186 x = expand_builtin_setjmp (buf, NULL_RTX, noex,
1187 ehstack.top->entry->exception_handler_label);
1192 /* We are committed to this, so update the handler chain. */
1194 emit_move_insn (dhc, XEXP (arg, 0));
1197 /* Start an exception handling region for the given cleanup action.
1198 All instructions emitted after this point are considered to be part
1199 of the region until expand_eh_region_end is invoked. CLEANUP is
1200 the cleanup action to perform. The return value is true if the
1201 exception region was optimized away. If that case,
1202 expand_eh_region_end does not need to be called for this cleanup,
1205 This routine notices one particular common case in C++ code
1206 generation, and optimizes it so as to not need the exception
1207 region. It works by creating a dynamic cleanup action, instead of
1208 a using an exception region. */
1211 expand_eh_region_start_tree (decl, cleanup)
1215 /* This is the old code. */
1219 /* The optimization only applies to actions protected with
1220 terminate, and only applies if we are using the setjmp/longjmp
1222 if (exceptions_via_longjmp
1223 && protect_cleanup_actions_with_terminate)
1228 /* Ignore any UNSAVE_EXPR. */
1229 if (TREE_CODE (cleanup) == UNSAVE_EXPR)
1230 cleanup = TREE_OPERAND (cleanup, 0);
1232 /* Further, it only applies if the action is a call, if there
1233 are 2 arguments, and if the second argument is 2. */
1235 if (TREE_CODE (cleanup) == CALL_EXPR
1236 && (args = TREE_OPERAND (cleanup, 1))
1237 && (func = TREE_OPERAND (cleanup, 0))
1238 && (arg = TREE_VALUE (args))
1239 && (args = TREE_CHAIN (args))
1241 /* is the second argument 2? */
1242 && TREE_CODE (TREE_VALUE (args)) == INTEGER_CST
1243 && TREE_INT_CST_LOW (TREE_VALUE (args)) == 2
1244 && TREE_INT_CST_HIGH (TREE_VALUE (args)) == 0
1246 /* Make sure there are no other arguments. */
1247 && TREE_CHAIN (args) == NULL_TREE)
1249 /* Arrange for returns and gotos to pop the entry we make on the
1250 dynamic cleanup stack. */
1251 expand_dcc_cleanup (decl);
1252 start_dynamic_cleanup (func, arg);
1257 expand_eh_region_start_for_decl (decl);
1258 ehstack.top->entry->finalization = cleanup;
1263 /* Just like expand_eh_region_start, except if a cleanup action is
1264 entered on the cleanup chain, the TREE_PURPOSE of the element put
1265 on the chain is DECL. DECL should be the associated VAR_DECL, if
1266 any, otherwise it should be NULL_TREE. */
1269 expand_eh_region_start_for_decl (decl)
1274 /* This is the old code. */
1278 if (exceptions_via_longjmp)
1280 /* We need a new block to record the start and end of the
1281 dynamic handler chain. We could always do this, but we
1282 really want to permit jumping into such a block, and we want
1283 to avoid any errors or performance impact in the SJ EH code
1285 expand_start_bindings (0);
1287 /* But we don't need or want a new temporary level. */
1290 /* Mark this block as created by expand_eh_region_start. This
1291 is so that we can pop the block with expand_end_bindings
1293 mark_block_as_eh_region ();
1295 /* Arrange for returns and gotos to pop the entry we make on the
1296 dynamic handler stack. */
1297 expand_dhc_cleanup (decl);
1300 push_eh_entry (&ehstack);
1301 note = emit_note (NULL_PTR, NOTE_INSN_EH_REGION_BEG);
1302 NOTE_BLOCK_NUMBER (note)
1303 = CODE_LABEL_NUMBER (ehstack.top->entry->exception_handler_label);
1304 if (exceptions_via_longjmp)
1305 start_dynamic_handler ();
1308 /* Start an exception handling region. All instructions emitted after
1309 this point are considered to be part of the region until
1310 expand_eh_region_end is invoked. */
1313 expand_eh_region_start ()
1315 expand_eh_region_start_for_decl (NULL_TREE);
1318 /* End an exception handling region. The information about the region
1319 is found on the top of ehstack.
1321 HANDLER is either the cleanup for the exception region, or if we're
1322 marking the end of a try block, HANDLER is integer_zero_node.
1324 HANDLER will be transformed to rtl when expand_leftover_cleanups
1328 expand_eh_region_end (handler)
1331 struct eh_entry *entry;
1337 entry = pop_eh_entry (&ehstack);
1339 note = emit_note (NULL_PTR, NOTE_INSN_EH_REGION_END);
1340 NOTE_BLOCK_NUMBER (note)
1341 = CODE_LABEL_NUMBER (entry->exception_handler_label);
1342 if (exceptions_via_longjmp == 0
1343 /* We share outer_context between regions; only emit it once. */
1344 && INSN_UID (entry->outer_context) == 0)
1348 label = gen_label_rtx ();
1351 /* Emit a label marking the end of this exception region that
1352 is used for rethrowing into the outer context. */
1353 emit_label (entry->outer_context);
1354 expand_internal_throw ();
1359 entry->finalization = handler;
1361 /* create region entry in final exception table */
1362 new_eh_region_entry (NOTE_BLOCK_NUMBER (note));
1364 enqueue_eh_entry (&ehqueue, entry);
1366 /* If we have already started ending the bindings, don't recurse.
1367 This only happens when exceptions_via_longjmp is true. */
1368 if (is_eh_region ())
1370 /* Because we don't need or want a new temporary level and
1371 because we didn't create one in expand_eh_region_start,
1372 create a fake one now to avoid removing one in
1373 expand_end_bindings. */
1376 mark_block_as_not_eh_region ();
1378 /* Maybe do this to prevent jumping in and so on... */
1379 expand_end_bindings (NULL_TREE, 0, 0);
1383 /* End the EH region for a goto fixup. We only need them in the region-based
1387 expand_fixup_region_start ()
1389 if (! doing_eh (0) || exceptions_via_longjmp)
1392 expand_eh_region_start ();
1395 /* End the EH region for a goto fixup. CLEANUP is the cleanup we just
1396 expanded; to avoid running it twice if it throws, we look through the
1397 ehqueue for a matching region and rethrow from its outer_context. */
1400 expand_fixup_region_end (cleanup)
1403 struct eh_node *node;
1405 if (! doing_eh (0) || exceptions_via_longjmp)
1408 for (node = ehstack.top; node && node->entry->finalization != cleanup; )
1411 for (node = ehqueue.head; node && node->entry->finalization != cleanup; )
1416 ehstack.top->entry->outer_context = node->entry->outer_context;
1418 /* Just rethrow. size_zero_node is just a NOP. */
1419 expand_eh_region_end (size_zero_node);
1422 /* If we are using the setjmp/longjmp EH codegen method, we emit a
1425 Otherwise, we emit a call to __throw and note that we threw
1426 something, so we know we need to generate the necessary code for
1429 Before invoking throw, the __eh_pc variable must have been set up
1430 to contain the PC being thrown from. This address is used by
1431 __throw to determine which exception region (if any) is
1432 responsible for handling the exception. */
1437 if (exceptions_via_longjmp)
1439 emit_library_call (sjthrow_libfunc, 0, VOIDmode, 0);
1443 #ifdef JUMP_TO_THROW
1444 emit_indirect_jump (throw_libfunc);
1446 emit_library_call (throw_libfunc, 0, VOIDmode, 0);
1452 /* Throw the current exception. If appropriate, this is done by jumping
1453 to the next handler. */
1456 expand_internal_throw ()
1461 /* Called from expand_exception_blocks and expand_end_catch_block to
1462 emit any pending handlers/cleanups queued from expand_eh_region_end. */
1465 expand_leftover_cleanups ()
1467 struct eh_entry *entry;
1469 while ((entry = dequeue_eh_entry (&ehqueue)) != 0)
1473 /* A leftover try block. Shouldn't be one here. */
1474 if (entry->finalization == integer_zero_node)
1477 /* Output the label for the start of the exception handler. */
1479 receive_exception_label (entry->exception_handler_label);
1481 /* register a handler for this cleanup region */
1483 find_func_region (CODE_LABEL_NUMBER (entry->exception_handler_label)),
1484 get_new_handler (entry->exception_handler_label, NULL));
1486 /* And now generate the insns for the handler. */
1487 expand_expr (entry->finalization, const0_rtx, VOIDmode, 0);
1489 prev = get_last_insn ();
1490 if (prev == NULL || GET_CODE (prev) != BARRIER)
1491 /* Emit code to throw to the outer context if we fall off
1492 the end of the handler. */
1493 expand_rethrow (entry->outer_context);
1495 do_pending_stack_adjust ();
1500 /* Called at the start of a block of try statements. */
1502 expand_start_try_stmts ()
1507 expand_eh_region_start ();
1510 /* Called to begin a catch clause. The parameter is the object which
1511 will be passed to the runtime type check routine. */
1513 start_catch_handler (rtime)
1516 rtx handler_label = catchstack.top->entry->exception_handler_label;
1517 int insn_region_num = CODE_LABEL_NUMBER (handler_label);
1518 int eh_region_entry = find_func_region (insn_region_num);
1520 /* If we've already issued this label, pick a new one */
1521 if (catchstack.top->entry->label_used)
1522 handler_label = gen_exception_label ();
1524 catchstack.top->entry->label_used = 1;
1526 receive_exception_label (handler_label);
1528 add_new_handler (eh_region_entry, get_new_handler (handler_label, rtime));
1531 /* Generate RTL for the start of a group of catch clauses.
1533 It is responsible for starting a new instruction sequence for the
1534 instructions in the catch block, and expanding the handlers for the
1535 internally-generated exception regions nested within the try block
1536 corresponding to this catch block. */
1539 expand_start_all_catch ()
1541 struct eh_entry *entry;
1548 outer_context = ehstack.top->entry->outer_context;
1550 /* End the try block. */
1551 expand_eh_region_end (integer_zero_node);
1553 emit_line_note (input_filename, lineno);
1554 label = build_decl (LABEL_DECL, NULL_TREE, NULL_TREE);
1556 /* The label for the exception handling block that we will save.
1557 This is Lresume in the documentation. */
1558 expand_label (label);
1560 /* Push the label that points to where normal flow is resumed onto
1561 the top of the label stack. */
1562 push_label_entry (&caught_return_label_stack, NULL_RTX, label);
1564 /* Start a new sequence for all the catch blocks. We will add this
1565 to the global sequence catch_clauses when we have completed all
1566 the handlers in this handler-seq. */
1569 entry = dequeue_eh_entry (&ehqueue);
1570 for ( ; entry->finalization != integer_zero_node;
1571 entry = dequeue_eh_entry (&ehqueue))
1575 /* Emit the label for the cleanup handler for this region, and
1576 expand the code for the handler.
1578 Note that a catch region is handled as a side-effect here;
1579 for a try block, entry->finalization will contain
1580 integer_zero_node, so no code will be generated in the
1581 expand_expr call below. But, the label for the handler will
1582 still be emitted, so any code emitted after this point will
1583 end up being the handler. */
1585 receive_exception_label (entry->exception_handler_label);
1587 /* register a handler for this cleanup region */
1589 find_func_region (CODE_LABEL_NUMBER (entry->exception_handler_label)),
1590 get_new_handler (entry->exception_handler_label, NULL));
1592 /* And now generate the insns for the cleanup handler. */
1593 expand_expr (entry->finalization, const0_rtx, VOIDmode, 0);
1595 prev = get_last_insn ();
1596 if (prev == NULL || GET_CODE (prev) != BARRIER)
1597 /* Code to throw out to outer context when we fall off end
1598 of the handler. We can't do this here for catch blocks,
1599 so it's done in expand_end_all_catch instead. */
1600 expand_rethrow (entry->outer_context);
1602 do_pending_stack_adjust ();
1606 /* At this point, all the cleanups are done, and the ehqueue now has
1607 the current exception region at its head. We dequeue it, and put it
1608 on the catch stack. */
1610 push_entry (&catchstack, entry);
1612 /* If we are not doing setjmp/longjmp EH, because we are reordered
1613 out of line, we arrange to rethrow in the outer context. We need to
1614 do this because we are not physically within the region, if any, that
1615 logically contains this catch block. */
1616 if (! exceptions_via_longjmp)
1618 expand_eh_region_start ();
1619 ehstack.top->entry->outer_context = outer_context;
1622 /* We also have to start the handler if we aren't using the new model. */
1623 if (! flag_new_exceptions)
1624 start_catch_handler (NULL);
1627 /* Finish up the catch block. At this point all the insns for the
1628 catch clauses have already been generated, so we only have to add
1629 them to the catch_clauses list. We also want to make sure that if
1630 we fall off the end of the catch clauses that we rethrow to the
1634 expand_end_all_catch ()
1636 rtx new_catch_clause, outer_context = NULL_RTX;
1637 struct eh_entry *entry;
1642 /* Dequeue the current catch clause region. */
1643 entry = pop_eh_entry (&catchstack);
1646 if (! exceptions_via_longjmp)
1648 outer_context = ehstack.top->entry->outer_context;
1650 /* Finish the rethrow region. size_zero_node is just a NOP. */
1651 expand_eh_region_end (size_zero_node);
1654 /* Code to throw out to outer context, if we fall off end of catch
1655 handlers. This is rethrow (Lresume, same id, same obj) in the
1656 documentation. We use Lresume because we know that it will throw
1657 to the correct context.
1659 In other words, if the catch handler doesn't exit or return, we
1660 do a "throw" (using the address of Lresume as the point being
1661 thrown from) so that the outer EH region can then try to process
1663 expand_rethrow (outer_context);
1665 /* Now we have the complete catch sequence. */
1666 new_catch_clause = get_insns ();
1669 /* This level of catch blocks is done, so set up the successful
1670 catch jump label for the next layer of catch blocks. */
1671 pop_label_entry (&caught_return_label_stack);
1672 pop_label_entry (&outer_context_label_stack);
1674 /* Add the new sequence of catches to the main one for this function. */
1675 push_to_sequence (catch_clauses);
1676 emit_insns (new_catch_clause);
1677 catch_clauses = get_insns ();
1680 /* Here we fall through into the continuation code. */
1683 /* Rethrow from the outer context LABEL. */
1686 expand_rethrow (label)
1689 if (exceptions_via_longjmp)
1695 /* End all the pending exception regions on protect_list. The handlers
1696 will be emitted when expand_leftover_cleanups is invoked. */
1699 end_protect_partials ()
1701 while (protect_list)
1703 expand_eh_region_end (TREE_VALUE (protect_list));
1704 protect_list = TREE_CHAIN (protect_list);
1708 /* Arrange for __terminate to be called if there is an unhandled throw
1712 protect_with_terminate (e)
1715 /* We only need to do this when using setjmp/longjmp EH and the
1716 language requires it, as otherwise we protect all of the handlers
1717 at once, if we need to. */
1718 if (exceptions_via_longjmp && protect_cleanup_actions_with_terminate)
1720 tree handler, result;
1722 /* All cleanups must be on the function_obstack. */
1723 push_obstacks_nochange ();
1724 resume_temporary_allocation ();
1726 handler = make_node (RTL_EXPR);
1727 TREE_TYPE (handler) = void_type_node;
1728 RTL_EXPR_RTL (handler) = const0_rtx;
1729 TREE_SIDE_EFFECTS (handler) = 1;
1730 start_sequence_for_rtl_expr (handler);
1732 emit_library_call (terminate_libfunc, 0, VOIDmode, 0);
1735 RTL_EXPR_SEQUENCE (handler) = get_insns ();
1738 result = build (TRY_CATCH_EXPR, TREE_TYPE (e), e, handler);
1739 TREE_SIDE_EFFECTS (result) = TREE_SIDE_EFFECTS (e);
1740 TREE_THIS_VOLATILE (result) = TREE_THIS_VOLATILE (e);
1741 TREE_READONLY (result) = TREE_READONLY (e);
1751 /* The exception table that we build that is used for looking up and
1752 dispatching exceptions, the current number of entries, and its
1753 maximum size before we have to extend it.
1755 The number in eh_table is the code label number of the exception
1756 handler for the region. This is added by add_eh_table_entry and
1757 used by output_exception_table_entry. */
1759 static int *eh_table = NULL;
1760 static int eh_table_size = 0;
1761 static int eh_table_max_size = 0;
1763 /* Note the need for an exception table entry for region N. If we
1764 don't need to output an explicit exception table, avoid all of the
1767 Called from final_scan_insn when a NOTE_INSN_EH_REGION_BEG is seen.
1768 (Or NOTE_INSN_EH_REGION_END sometimes)
1769 N is the NOTE_BLOCK_NUMBER of the note, which comes from the code
1770 label number of the exception handler for the region. */
1773 add_eh_table_entry (n)
1776 #ifndef OMIT_EH_TABLE
1777 if (eh_table_size >= eh_table_max_size)
1781 eh_table_max_size += eh_table_max_size>>1;
1783 if (eh_table_max_size < 0)
1786 eh_table = (int *) xrealloc (eh_table,
1787 eh_table_max_size * sizeof (int));
1791 eh_table_max_size = 252;
1792 eh_table = (int *) xmalloc (eh_table_max_size * sizeof (int));
1795 eh_table[eh_table_size++] = n;
1799 /* Return a non-zero value if we need to output an exception table.
1801 On some platforms, we don't have to output a table explicitly.
1802 This routine doesn't mean we don't have one. */
1805 exception_table_p ()
1813 /* Output the entry of the exception table corresponding to the
1814 exception region numbered N to file FILE.
1816 N is the code label number corresponding to the handler of the
1820 output_exception_table_entry (file, n)
1826 struct handler_info *handler;
1828 handler = get_first_handler (n);
1830 for ( ; handler != NULL; handler = handler->next)
1832 ASM_GENERATE_INTERNAL_LABEL (buf, "LEHB", n);
1833 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
1834 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
1836 ASM_GENERATE_INTERNAL_LABEL (buf, "LEHE", n);
1837 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
1838 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
1840 assemble_integer (handler->handler_label,
1841 POINTER_SIZE / BITS_PER_UNIT, 1);
1843 if (flag_new_exceptions)
1845 if (handler->type_info == NULL)
1846 assemble_integer (const0_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
1848 output_constant ((tree)(handler->type_info),
1849 POINTER_SIZE / BITS_PER_UNIT);
1851 putc ('\n', file); /* blank line */
1855 /* Output the exception table if we have and need one. */
1857 static short language_code = 0;
1858 static short version_code = 0;
1860 /* This routine will set the language code for exceptions. */
1861 void set_exception_lang_code (code)
1864 language_code = code;
1867 /* This routine will set the language version code for exceptions. */
1868 void set_exception_version_code (code)
1871 version_code = code;
1876 output_exception_table ()
1879 extern FILE *asm_out_file;
1881 if (! doing_eh (0) || ! eh_table)
1884 exception_section ();
1886 /* Beginning marker for table. */
1887 assemble_align (GET_MODE_ALIGNMENT (ptr_mode));
1888 assemble_label ("__EXCEPTION_TABLE__");
1890 if (flag_new_exceptions)
1892 assemble_integer (GEN_INT (NEW_EH_RUNTIME),
1893 POINTER_SIZE / BITS_PER_UNIT, 1);
1894 assemble_integer (GEN_INT (language_code), 2 , 1);
1895 assemble_integer (GEN_INT (version_code), 2 , 1);
1897 /* Add enough padding to make sure table aligns on a pointer boundry. */
1898 i = GET_MODE_ALIGNMENT (ptr_mode) / BITS_PER_UNIT - 4;
1899 for ( ; i < 0; i = i + GET_MODE_ALIGNMENT (ptr_mode) / BITS_PER_UNIT)
1902 assemble_integer (const0_rtx, i , 1);
1905 for (i = 0; i < eh_table_size; ++i)
1906 output_exception_table_entry (asm_out_file, eh_table[i]);
1909 clear_function_eh_region ();
1911 /* Ending marker for table. */
1912 assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
1914 /* for binary compatability, the old __throw checked the second
1915 position for a -1, so we should output at least 2 -1's */
1916 if (! flag_new_exceptions)
1917 assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
1919 putc ('\n', asm_out_file); /* blank line */
1922 /* Emit code to get EH context.
1924 We have to scan thru the code to find possible EH context registers.
1925 Inlined functions may use it too, and thus we'll have to be able
1928 This is done only if using exceptions_via_longjmp. */
1939 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
1940 if (GET_CODE (insn) == INSN
1941 && GET_CODE (PATTERN (insn)) == USE)
1943 rtx reg = find_reg_note (insn, REG_EH_CONTEXT, 0);
1950 /* If this is the first use insn, emit the call here. This
1951 will always be at the top of our function, because if
1952 expand_inline_function notices a REG_EH_CONTEXT note, it
1953 adds a use insn to this function as well. */
1955 ehc = call_get_eh_context ();
1957 emit_move_insn (XEXP (reg, 0), ehc);
1958 insns = get_insns ();
1961 emit_insns_before (insns, insn);
1966 /* Scan the current insns and build a list of handler labels. The
1967 resulting list is placed in the global variable exception_handler_labels.
1969 It is called after the last exception handling region is added to
1970 the current function (when the rtl is almost all built for the
1971 current function) and before the jump optimization pass. */
1974 find_exception_handler_labels ()
1978 exception_handler_labels = NULL_RTX;
1980 /* If we aren't doing exception handling, there isn't much to check. */
1984 /* For each start of a region, add its label to the list. */
1986 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
1988 struct handler_info* ptr;
1989 if (GET_CODE (insn) == NOTE
1990 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
1992 ptr = get_first_handler (NOTE_BLOCK_NUMBER (insn));
1993 for ( ; ptr; ptr = ptr->next)
1995 /* make sure label isn't in the list already */
1997 for (x = exception_handler_labels; x; x = XEXP (x, 1))
1998 if (XEXP (x, 0) == ptr->handler_label)
2001 exception_handler_labels = gen_rtx_EXPR_LIST (VOIDmode,
2002 ptr->handler_label, exception_handler_labels);
2008 /* Return a value of 1 if the parameter label number is an exception handler
2009 label. Return 0 otherwise. */
2012 is_exception_handler_label (lab)
2016 for (x = exception_handler_labels ; x ; x = XEXP (x, 1))
2017 if (lab == CODE_LABEL_NUMBER (XEXP (x, 0)))
2022 /* Perform sanity checking on the exception_handler_labels list.
2024 Can be called after find_exception_handler_labels is called to
2025 build the list of exception handlers for the current function and
2026 before we finish processing the current function. */
2029 check_exception_handler_labels ()
2033 /* If we aren't doing exception handling, there isn't much to check. */
2037 /* Make sure there is no more than 1 copy of a label */
2038 for (insn = exception_handler_labels; insn; insn = XEXP (insn, 1))
2041 for (insn2 = exception_handler_labels; insn2; insn2 = XEXP (insn2, 1))
2042 if (XEXP (insn, 0) == XEXP (insn2, 0))
2045 warning ("Counted %d copies of EH region %d in list.\n", count,
2046 CODE_LABEL_NUMBER (insn));
2051 /* This group of functions initializes the exception handling data
2052 structures at the start of the compilation, initializes the data
2053 structures at the start of a function, and saves and restores the
2054 exception handling data structures for the start/end of a nested
2057 /* Toplevel initialization for EH things. */
2064 /* Initialize the per-function EH information. */
2067 init_eh_for_function ()
2071 ehqueue.head = ehqueue.tail = 0;
2072 catch_clauses = NULL_RTX;
2073 false_label_stack = 0;
2074 caught_return_label_stack = 0;
2075 protect_list = NULL_TREE;
2076 current_function_ehc = NULL_RTX;
2079 /* Save some of the per-function EH info into the save area denoted by
2082 This is currently called from save_stmt_status. */
2091 p->ehstack = ehstack;
2092 p->catchstack = catchstack;
2093 p->ehqueue = ehqueue;
2094 p->catch_clauses = catch_clauses;
2095 p->false_label_stack = false_label_stack;
2096 p->caught_return_label_stack = caught_return_label_stack;
2097 p->protect_list = protect_list;
2098 p->ehc = current_function_ehc;
2100 init_eh_for_function ();
2103 /* Restore the per-function EH info saved into the area denoted by P.
2105 This is currently called from restore_stmt_status. */
2108 restore_eh_status (p)
2114 protect_list = p->protect_list;
2115 caught_return_label_stack = p->caught_return_label_stack;
2116 false_label_stack = p->false_label_stack;
2117 catch_clauses = p->catch_clauses;
2118 ehqueue = p->ehqueue;
2119 ehstack = p->ehstack;
2120 catchstack = p->catchstack;
2121 current_function_ehc = p->ehc;
2124 /* This section is for the exception handling specific optimization
2125 pass. First are the internal routines, and then the main
2126 optimization pass. */
2128 /* Determine if the given INSN can throw an exception. */
2134 /* Calls can always potentially throw exceptions. */
2135 if (GET_CODE (insn) == CALL_INSN)
2138 if (asynchronous_exceptions)
2140 /* If we wanted asynchronous exceptions, then everything but NOTEs
2141 and CODE_LABELs could throw. */
2142 if (GET_CODE (insn) != NOTE && GET_CODE (insn) != CODE_LABEL)
2149 /* Scan a exception region looking for the matching end and then
2150 remove it if possible. INSN is the start of the region, N is the
2151 region number, and DELETE_OUTER is to note if anything in this
2154 Regions are removed if they cannot possibly catch an exception.
2155 This is determined by invoking can_throw on each insn within the
2156 region; if can_throw returns true for any of the instructions, the
2157 region can catch an exception, since there is an insn within the
2158 region that is capable of throwing an exception.
2160 Returns the NOTE_INSN_EH_REGION_END corresponding to this region, or
2161 calls abort if it can't find one.
2163 Can abort if INSN is not a NOTE_INSN_EH_REGION_BEGIN, or if N doesn't
2164 correspond to the region number, or if DELETE_OUTER is NULL. */
2167 scan_region (insn, n, delete_outer)
2174 /* Assume we can delete the region. */
2177 if (insn == NULL_RTX
2178 || GET_CODE (insn) != NOTE
2179 || NOTE_LINE_NUMBER (insn) != NOTE_INSN_EH_REGION_BEG
2180 || NOTE_BLOCK_NUMBER (insn) != n
2181 || delete_outer == NULL)
2184 insn = NEXT_INSN (insn);
2186 /* Look for the matching end. */
2187 while (! (GET_CODE (insn) == NOTE
2188 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END))
2190 /* If anything can throw, we can't remove the region. */
2191 if (delete && can_throw (insn))
2196 /* Watch out for and handle nested regions. */
2197 if (GET_CODE (insn) == NOTE
2198 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2200 insn = scan_region (insn, NOTE_BLOCK_NUMBER (insn), &delete);
2203 insn = NEXT_INSN (insn);
2206 /* The _BEG/_END NOTEs must match and nest. */
2207 if (NOTE_BLOCK_NUMBER (insn) != n)
2210 /* If anything in this exception region can throw, we can throw. */
2215 /* Delete the start and end of the region. */
2216 delete_insn (start);
2219 /* We no longer removed labels here, since flow will now remove any
2220 handler which cannot be called any more. */
2223 /* Only do this part if we have built the exception handler
2225 if (exception_handler_labels)
2227 rtx x, *prev = &exception_handler_labels;
2229 /* Find it in the list of handlers. */
2230 for (x = exception_handler_labels; x; x = XEXP (x, 1))
2232 rtx label = XEXP (x, 0);
2233 if (CODE_LABEL_NUMBER (label) == n)
2235 /* If we are the last reference to the handler,
2237 if (--LABEL_NUSES (label) == 0)
2238 delete_insn (label);
2242 /* Remove it from the list of exception handler
2243 labels, if we are optimizing. If we are not, then
2244 leave it in the list, as we are not really going to
2245 remove the region. */
2246 *prev = XEXP (x, 1);
2253 prev = &XEXP (x, 1);
2261 /* Perform various interesting optimizations for exception handling
2264 We look for empty exception regions and make them go (away). The
2265 jump optimization code will remove the handler if nothing else uses
2269 exception_optimize ()
2274 /* Remove empty regions. */
2275 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2277 if (GET_CODE (insn) == NOTE
2278 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2280 /* Since scan_region will return the NOTE_INSN_EH_REGION_END
2281 insn, we will indirectly skip through all the insns
2282 inbetween. We are also guaranteed that the value of insn
2283 returned will be valid, as otherwise scan_region won't
2285 insn = scan_region (insn, NOTE_BLOCK_NUMBER (insn), &n);
2290 /* Various hooks for the DWARF 2 __throw routine. */
2292 /* Do any necessary initialization to access arbitrary stack frames.
2293 On the SPARC, this means flushing the register windows. */
2296 expand_builtin_unwind_init ()
2298 /* Set this so all the registers get saved in our frame; we need to be
2299 able to copy the saved values for any registers from frames we unwind. */
2300 current_function_has_nonlocal_label = 1;
2302 #ifdef SETUP_FRAME_ADDRESSES
2303 SETUP_FRAME_ADDRESSES ();
2307 /* Given a value extracted from the return address register or stack slot,
2308 return the actual address encoded in that value. */
2311 expand_builtin_extract_return_addr (addr_tree)
2314 rtx addr = expand_expr (addr_tree, NULL_RTX, Pmode, 0);
2315 return eh_outer_context (addr);
2318 /* Given an actual address in addr_tree, do any necessary encoding
2319 and return the value to be stored in the return address register or
2320 stack slot so the epilogue will return to that address. */
2323 expand_builtin_frob_return_addr (addr_tree)
2326 rtx addr = expand_expr (addr_tree, NULL_RTX, Pmode, 0);
2327 #ifdef RETURN_ADDR_OFFSET
2328 addr = plus_constant (addr, -RETURN_ADDR_OFFSET);
2333 /* Given an actual address in addr_tree, set the return address register up
2334 so the epilogue will return to that address. If the return address is
2335 not in a register, do nothing. */
2338 expand_builtin_set_return_addr_reg (addr_tree)
2342 rtx ra = expand_builtin_return_addr (BUILT_IN_RETURN_ADDRESS,
2343 0, hard_frame_pointer_rtx);
2345 if (GET_CODE (ra) != REG || REGNO (ra) >= FIRST_PSEUDO_REGISTER)
2348 tmp = force_operand (expand_builtin_frob_return_addr (addr_tree), ra);
2350 emit_move_insn (ra, tmp);
2353 /* Choose two registers for communication between the main body of
2354 __throw and the stub for adjusting the stack pointer. The first register
2355 is used to pass the address of the exception handler; the second register
2356 is used to pass the stack pointer offset.
2358 For register 1 we use the return value register for a void *.
2359 For register 2 we use the static chain register if it exists and is
2360 different from register 1, otherwise some arbitrary call-clobbered
2364 eh_regs (r1, r2, outgoing)
2370 #ifdef FUNCTION_OUTGOING_VALUE
2372 reg1 = FUNCTION_OUTGOING_VALUE (build_pointer_type (void_type_node),
2373 current_function_decl);
2376 reg1 = FUNCTION_VALUE (build_pointer_type (void_type_node),
2377 current_function_decl);
2379 #ifdef STATIC_CHAIN_REGNUM
2381 reg2 = static_chain_incoming_rtx;
2383 reg2 = static_chain_rtx;
2384 if (REGNO (reg2) == REGNO (reg1))
2385 #endif /* STATIC_CHAIN_REGNUM */
2388 if (reg2 == NULL_RTX)
2391 for (i = 0; i < FIRST_PSEUDO_REGISTER; ++i)
2392 if (call_used_regs[i] && ! fixed_regs[i] && i != REGNO (reg1))
2394 reg2 = gen_rtx_REG (Pmode, i);
2398 if (reg2 == NULL_RTX)
2407 /* Retrieve the register which contains the pointer to the eh_context
2408 structure set the __throw. */
2411 get_reg_for_handler ()
2414 reg1 = FUNCTION_VALUE (build_pointer_type (void_type_node),
2415 current_function_decl);
2420 /* Emit inside of __throw a stub which adjusts the stack pointer and jumps
2421 to the exception handler. __throw will set up the necessary values
2422 and then return to the stub. */
2425 expand_builtin_eh_stub_old ()
2427 rtx stub_start = gen_label_rtx ();
2428 rtx after_stub = gen_label_rtx ();
2429 rtx handler, offset;
2431 emit_jump (after_stub);
2432 emit_label (stub_start);
2434 eh_regs (&handler, &offset, 0);
2436 adjust_stack (offset);
2437 emit_indirect_jump (handler);
2438 emit_label (after_stub);
2439 return gen_rtx_LABEL_REF (Pmode, stub_start);
2443 expand_builtin_eh_stub ()
2445 rtx stub_start = gen_label_rtx ();
2446 rtx after_stub = gen_label_rtx ();
2447 rtx handler, offset;
2450 emit_jump (after_stub);
2451 emit_label (stub_start);
2453 eh_regs (&handler, &offset, 0);
2455 adjust_stack (offset);
2457 /* Handler is in fact a pointer to the _eh_context structure, we need
2458 to pick out the handler field (first element), and jump to there,
2459 leaving the pointer to _eh_conext in the same hardware register. */
2461 temp = gen_rtx_MEM (Pmode, handler);
2462 MEM_IN_STRUCT_P (temp) = 1;
2463 RTX_UNCHANGING_P (temp) = 1;
2464 emit_move_insn (offset, temp);
2465 emit_insn (gen_rtx_USE (Pmode, handler));
2467 emit_indirect_jump (offset);
2469 emit_label (after_stub);
2470 return gen_rtx_LABEL_REF (Pmode, stub_start);
2473 /* Set up the registers for passing the handler address and stack offset
2474 to the stub above. */
2477 expand_builtin_set_eh_regs (handler, offset)
2478 tree handler, offset;
2482 eh_regs (®1, ®2, 1);
2484 store_expr (offset, reg2, 0);
2485 store_expr (handler, reg1, 0);
2487 /* These will be used by the stub. */
2488 emit_insn (gen_rtx_USE (VOIDmode, reg1));
2489 emit_insn (gen_rtx_USE (VOIDmode, reg2));
2494 /* This contains the code required to verify whether arbitrary instructions
2495 are in the same exception region. */
2497 static int *insn_eh_region = (int *)0;
2498 static int maximum_uid;
2501 set_insn_eh_region (first, region_num)
2508 for (insn = *first; insn; insn = NEXT_INSN (insn))
2510 if ((GET_CODE (insn) == NOTE) &&
2511 (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG))
2513 rnum = NOTE_BLOCK_NUMBER (insn);
2514 insn_eh_region[INSN_UID (insn)] = rnum;
2515 insn = NEXT_INSN (insn);
2516 set_insn_eh_region (&insn, rnum);
2517 /* Upon return, insn points to the EH_REGION_END of nested region */
2520 insn_eh_region[INSN_UID (insn)] = region_num;
2521 if ((GET_CODE (insn) == NOTE) &&
2522 (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END))
2528 /* Free the insn table, an make sure it cannot be used again. */
2531 free_insn_eh_region ()
2538 free (insn_eh_region);
2539 insn_eh_region = (int *)0;
2543 /* Initialize the table. max_uid must be calculated and handed into
2544 this routine. If it is unavailable, passing a value of 0 will
2545 cause this routine to calculate it as well. */
2548 init_insn_eh_region (first, max_uid)
2558 free_insn_eh_region();
2561 for (insn = first; insn; insn = NEXT_INSN (insn))
2562 if (INSN_UID (insn) > max_uid) /* find largest UID */
2563 max_uid = INSN_UID (insn);
2565 maximum_uid = max_uid;
2566 insn_eh_region = (int *) malloc ((max_uid + 1) * sizeof (int));
2568 set_insn_eh_region (&insn, 0);
2572 /* Check whether 2 instructions are within the same region. */
2575 in_same_eh_region (insn1, insn2)
2578 int ret, uid1, uid2;
2580 /* If no exceptions, instructions are always in same region. */
2584 /* If the table isn't allocated, assume the worst. */
2585 if (!insn_eh_region)
2588 uid1 = INSN_UID (insn1);
2589 uid2 = INSN_UID (insn2);
2591 /* if instructions have been allocated beyond the end, either
2592 the table is out of date, or this is a late addition, or
2593 something... Assume the worst. */
2594 if (uid1 > maximum_uid || uid2 > maximum_uid)
2597 ret = (insn_eh_region[uid1] == insn_eh_region[uid2]);