1 /* Implements exception handling.
2 Copyright (C) 1989, 1992-1999 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"
413 /* One to use setjmp/longjmp method of generating code for exception
416 int exceptions_via_longjmp = 2;
418 /* One to enable asynchronous exception support. */
420 int asynchronous_exceptions = 0;
422 /* One to protect cleanup actions with a handler that calls
423 __terminate, zero otherwise. */
425 int protect_cleanup_actions_with_terminate;
427 /* A list of labels used for exception handlers. Created by
428 find_exception_handler_labels for the optimization passes. */
430 rtx exception_handler_labels;
432 /* Keeps track of the label used as the context of a throw to rethrow an
433 exception to the outer exception region. */
435 struct label_node *outer_context_label_stack = NULL;
437 /* Pseudos used to hold exception return data in the interim between
438 __builtin_eh_return and the end of the function. */
440 static rtx eh_return_context;
441 static rtx eh_return_stack_adjust;
442 static rtx eh_return_handler;
444 /* This is used for targets which can call rethrow with an offset instead
445 of an address. This is subtracted from the rethrow label we are
448 static rtx first_rethrow_symbol = NULL_RTX;
449 static rtx final_rethrow = NULL_RTX;
450 static rtx last_rethrow_symbol = NULL_RTX;
453 /* Prototypes for local functions. */
455 static void push_eh_entry PROTO((struct eh_stack *));
456 static struct eh_entry * pop_eh_entry PROTO((struct eh_stack *));
457 static void enqueue_eh_entry PROTO((struct eh_queue *, struct eh_entry *));
458 static struct eh_entry * dequeue_eh_entry PROTO((struct eh_queue *));
459 static rtx call_get_eh_context PROTO((void));
460 static void start_dynamic_cleanup PROTO((tree, tree));
461 static void start_dynamic_handler PROTO((void));
462 static void expand_rethrow PROTO((rtx));
463 static void output_exception_table_entry PROTO((FILE *, int));
464 static int can_throw PROTO((rtx));
465 static rtx scan_region PROTO((rtx, int, int *));
466 static void eh_regs PROTO((rtx *, rtx *, rtx *, int));
467 static void set_insn_eh_region PROTO((rtx *, int));
468 #ifdef DONT_USE_BUILTIN_SETJMP
469 static void jumpif_rtx PROTO((rtx, rtx));
471 static void mark_eh_node PROTO((struct eh_node *));
472 static void mark_eh_stack PROTO((struct eh_stack *));
473 static void mark_eh_queue PROTO((struct eh_queue *));
474 static void mark_tree_label_node PROTO ((struct label_node *));
476 rtx expand_builtin_return_addr PROTO((enum built_in_function, int, rtx));
478 /* Various support routines to manipulate the various data structures
479 used by the exception handling code. */
481 extern struct obstack permanent_obstack;
483 /* Generate a SYMBOL_REF for rethrow to use */
485 create_rethrow_ref (region_num)
492 push_obstacks_nochange ();
493 end_temporary_allocation ();
495 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", region_num);
496 ptr = (char *) obstack_copy0 (&permanent_obstack, buf, strlen (buf));
497 def = gen_rtx_SYMBOL_REF (Pmode, ptr);
498 SYMBOL_REF_NEED_ADJUST (def) = 1;
504 /* Push a label entry onto the given STACK. */
507 push_label_entry (stack, rlabel, tlabel)
508 struct label_node **stack;
512 struct label_node *newnode
513 = (struct label_node *) xmalloc (sizeof (struct label_node));
516 newnode->u.rlabel = rlabel;
518 newnode->u.tlabel = tlabel;
519 newnode->chain = *stack;
523 /* Pop a label entry from the given STACK. */
526 pop_label_entry (stack)
527 struct label_node **stack;
530 struct label_node *tempnode;
536 label = tempnode->u.rlabel;
537 *stack = (*stack)->chain;
543 /* Return the top element of the given STACK. */
546 top_label_entry (stack)
547 struct label_node **stack;
552 return (*stack)->u.tlabel;
555 /* get an exception label. These must be on the permanent obstack */
558 gen_exception_label ()
561 lab = gen_label_rtx ();
565 /* Push a new eh_node entry onto STACK. */
568 push_eh_entry (stack)
569 struct eh_stack *stack;
571 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
572 struct eh_entry *entry = (struct eh_entry *) xmalloc (sizeof (struct eh_entry));
574 rtx rlab = gen_exception_label ();
575 entry->finalization = NULL_TREE;
576 entry->label_used = 0;
577 entry->exception_handler_label = rlab;
578 entry->false_label = NULL_RTX;
579 if (! flag_new_exceptions)
580 entry->outer_context = gen_label_rtx ();
582 entry->outer_context = create_rethrow_ref (CODE_LABEL_NUMBER (rlab));
583 entry->rethrow_label = entry->outer_context;
586 node->chain = stack->top;
590 /* push an existing entry onto a stack. */
592 push_entry (stack, entry)
593 struct eh_stack *stack;
594 struct eh_entry *entry;
596 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
598 node->chain = stack->top;
602 /* Pop an entry from the given STACK. */
604 static struct eh_entry *
606 struct eh_stack *stack;
608 struct eh_node *tempnode;
609 struct eh_entry *tempentry;
611 tempnode = stack->top;
612 tempentry = tempnode->entry;
613 stack->top = stack->top->chain;
619 /* Enqueue an ENTRY onto the given QUEUE. */
622 enqueue_eh_entry (queue, entry)
623 struct eh_queue *queue;
624 struct eh_entry *entry;
626 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
631 if (queue->head == NULL)
637 queue->tail->chain = node;
642 /* Dequeue an entry from the given QUEUE. */
644 static struct eh_entry *
645 dequeue_eh_entry (queue)
646 struct eh_queue *queue;
648 struct eh_node *tempnode;
649 struct eh_entry *tempentry;
651 if (queue->head == NULL)
654 tempnode = queue->head;
655 queue->head = queue->head->chain;
657 tempentry = tempnode->entry;
664 receive_exception_label (handler_label)
667 emit_label (handler_label);
669 #ifdef HAVE_exception_receiver
670 if (! exceptions_via_longjmp)
671 if (HAVE_exception_receiver)
672 emit_insn (gen_exception_receiver ());
675 #ifdef HAVE_nonlocal_goto_receiver
676 if (! exceptions_via_longjmp)
677 if (HAVE_nonlocal_goto_receiver)
678 emit_insn (gen_nonlocal_goto_receiver ());
685 int range_number; /* EH region number from EH NOTE insn's. */
686 rtx rethrow_label; /* Label for rethrow. */
687 int rethrow_ref; /* Is rethrow referenced? */
688 struct handler_info *handlers;
692 /* table of function eh regions */
693 static struct func_eh_entry *function_eh_regions = NULL;
694 static int num_func_eh_entries = 0;
695 static int current_func_eh_entry = 0;
697 #define SIZE_FUNC_EH(X) (sizeof (struct func_eh_entry) * X)
699 /* Add a new eh_entry for this function, and base it off of the information
700 in the EH_ENTRY parameter. A NULL parameter is invalid.
701 OUTER_CONTEXT is a label which is used for rethrowing. The number
702 returned is an number which uniquely identifies this exception range. */
705 new_eh_region_entry (note_eh_region, rethrow)
709 if (current_func_eh_entry == num_func_eh_entries)
711 if (num_func_eh_entries == 0)
713 function_eh_regions =
714 (struct func_eh_entry *) malloc (SIZE_FUNC_EH (50));
715 num_func_eh_entries = 50;
719 num_func_eh_entries = num_func_eh_entries * 3 / 2;
720 function_eh_regions = (struct func_eh_entry *)
721 realloc (function_eh_regions, SIZE_FUNC_EH (num_func_eh_entries));
724 function_eh_regions[current_func_eh_entry].range_number = note_eh_region;
725 if (rethrow == NULL_RTX)
726 function_eh_regions[current_func_eh_entry].rethrow_label =
727 create_rethrow_ref (note_eh_region);
729 function_eh_regions[current_func_eh_entry].rethrow_label = rethrow;
730 function_eh_regions[current_func_eh_entry].handlers = NULL;
732 return current_func_eh_entry++;
735 /* Add new handler information to an exception range. The first parameter
736 specifies the range number (returned from new_eh_entry()). The second
737 parameter specifies the handler. By default the handler is inserted at
738 the end of the list. A handler list may contain only ONE NULL_TREE
739 typeinfo entry. Regardless where it is positioned, a NULL_TREE entry
740 is always output as the LAST handler in the exception table for a region. */
743 add_new_handler (region, newhandler)
745 struct handler_info *newhandler;
747 struct handler_info *last;
749 newhandler->next = NULL;
750 last = function_eh_regions[region].handlers;
752 function_eh_regions[region].handlers = newhandler;
755 for ( ; ; last = last->next)
757 if (last->type_info == CATCH_ALL_TYPE)
758 pedwarn ("additional handler after ...");
759 if (last->next == NULL)
762 last->next = newhandler;
766 /* Remove a handler label. The handler label is being deleted, so all
767 regions which reference this handler should have it removed from their
768 list of possible handlers. Any region which has the final handler
769 removed can be deleted. */
771 void remove_handler (removing_label)
774 struct handler_info *handler, *last;
776 for (x = 0 ; x < current_func_eh_entry; ++x)
779 handler = function_eh_regions[x].handlers;
780 for ( ; handler; last = handler, handler = handler->next)
781 if (handler->handler_label == removing_label)
785 last->next = handler->next;
789 function_eh_regions[x].handlers = handler->next;
794 /* This function will return a malloc'd pointer to an array of
795 void pointer representing the runtime match values that
796 currently exist in all regions. */
799 find_all_handler_type_matches (array)
802 struct handler_info *handler, *last;
811 if (!doing_eh (0) || ! flag_new_exceptions)
815 ptr = (void **)malloc (max_ptr * sizeof (void *));
820 for (x = 0 ; x < current_func_eh_entry; x++)
823 handler = function_eh_regions[x].handlers;
824 for ( ; handler; last = handler, handler = handler->next)
826 val = handler->type_info;
827 if (val != NULL && val != CATCH_ALL_TYPE)
829 /* See if this match value has already been found. */
830 for (y = 0; y < n_ptr; y++)
834 /* If we break early, we already found this value. */
838 /* Do we need to allocate more space? */
839 if (n_ptr >= max_ptr)
841 max_ptr += max_ptr / 2;
842 ptr = (void **)realloc (ptr, max_ptr * sizeof (void *));
855 /* Create a new handler structure initialized with the handler label and
856 typeinfo fields passed in. */
858 struct handler_info *
859 get_new_handler (handler, typeinfo)
863 struct handler_info* ptr;
864 ptr = (struct handler_info *) malloc (sizeof (struct handler_info));
865 ptr->handler_label = handler;
866 ptr->handler_number = CODE_LABEL_NUMBER (handler);
867 ptr->type_info = typeinfo;
875 /* Find the index in function_eh_regions associated with a NOTE region. If
876 the region cannot be found, a -1 is returned. This should never happen! */
879 find_func_region (insn_region)
883 for (x = 0; x < current_func_eh_entry; x++)
884 if (function_eh_regions[x].range_number == insn_region)
890 /* Get a pointer to the first handler in an exception region's list. */
892 struct handler_info *
893 get_first_handler (region)
896 return function_eh_regions[find_func_region (region)].handlers;
899 /* Clean out the function_eh_region table and free all memory */
902 clear_function_eh_region ()
905 struct handler_info *ptr, *next;
906 for (x = 0; x < current_func_eh_entry; x++)
907 for (ptr = function_eh_regions[x].handlers; ptr != NULL; ptr = next)
912 free (function_eh_regions);
913 num_func_eh_entries = 0;
914 current_func_eh_entry = 0;
917 /* Make a duplicate of an exception region by copying all the handlers
918 for an exception region. Return the new handler index. The final
919 parameter is a routine which maps old labels to new ones. */
922 duplicate_eh_handlers (old_note_eh_region, new_note_eh_region, map)
923 int old_note_eh_region, new_note_eh_region;
924 rtx (*map) PARAMS ((rtx));
926 struct handler_info *ptr, *new_ptr;
927 int new_region, region;
929 region = find_func_region (old_note_eh_region);
931 fatal ("Cannot duplicate non-existant exception region.");
933 /* duplicate_eh_handlers may have been called during a symbol remap. */
934 new_region = find_func_region (new_note_eh_region);
935 if (new_region != -1)
938 new_region = new_eh_region_entry (new_note_eh_region, NULL_RTX);
940 ptr = function_eh_regions[region].handlers;
942 for ( ; ptr; ptr = ptr->next)
944 new_ptr = get_new_handler (map (ptr->handler_label), ptr->type_info);
945 add_new_handler (new_region, new_ptr);
952 /* Given a rethrow symbol, find the EH region number this is for. */
954 eh_region_from_symbol (sym)
958 if (sym == last_rethrow_symbol)
960 for (x = 0; x < current_func_eh_entry; x++)
961 if (function_eh_regions[x].rethrow_label == sym)
962 return function_eh_regions[x].range_number;
967 /* When inlining/unrolling, we have to map the symbols passed to
968 __rethrow as well. This performs the remap. If a symbol isn't foiund,
969 the original one is returned. This is not an efficient routine,
970 so don't call it on everything!! */
972 rethrow_symbol_map (sym, map)
974 rtx (*map) PARAMS ((rtx));
977 for (x = 0; x < current_func_eh_entry; x++)
978 if (function_eh_regions[x].rethrow_label == sym)
980 /* We've found the original region, now lets determine which region
982 rtx l1 = function_eh_regions[x].handlers->handler_label;
984 y = CODE_LABEL_NUMBER (l2); /* This is the new region number */
985 x = find_func_region (y); /* Get the new permanent region */
986 if (x == -1) /* Hmm, Doesn't exist yet */
988 x = duplicate_eh_handlers (CODE_LABEL_NUMBER (l1), y, map);
989 /* Since we're mapping it, it must be used. */
990 function_eh_regions[x].rethrow_ref = 1;
992 return function_eh_regions[x].rethrow_label;
998 rethrow_used (region)
1001 if (flag_new_exceptions)
1003 int ret = function_eh_regions[find_func_region (region)].rethrow_ref;
1010 /* Routine to see if exception handling is turned on.
1011 DO_WARN is non-zero if we want to inform the user that exception
1012 handling is turned off.
1014 This is used to ensure that -fexceptions has been specified if the
1015 compiler tries to use any exception-specific functions. */
1021 if (! flag_exceptions)
1023 static int warned = 0;
1024 if (! warned && do_warn)
1026 error ("exception handling disabled, use -fexceptions to enable");
1034 /* Given a return address in ADDR, determine the address we should use
1035 to find the corresponding EH region. */
1038 eh_outer_context (addr)
1041 /* First mask out any unwanted bits. */
1042 #ifdef MASK_RETURN_ADDR
1043 expand_and (addr, MASK_RETURN_ADDR, addr);
1046 /* Then adjust to find the real return address. */
1047 #if defined (RETURN_ADDR_OFFSET)
1048 addr = plus_constant (addr, RETURN_ADDR_OFFSET);
1054 /* Start a new exception region for a region of code that has a
1055 cleanup action and push the HANDLER for the region onto
1056 protect_list. All of the regions created with add_partial_entry
1057 will be ended when end_protect_partials is invoked. */
1060 add_partial_entry (handler)
1063 expand_eh_region_start ();
1065 /* Make sure the entry is on the correct obstack. */
1066 push_obstacks_nochange ();
1067 resume_temporary_allocation ();
1069 /* Because this is a cleanup action, we may have to protect the handler
1070 with __terminate. */
1071 handler = protect_with_terminate (handler);
1073 protect_list = tree_cons (NULL_TREE, handler, protect_list);
1077 /* Emit code to get EH context to current function. */
1080 call_get_eh_context ()
1085 if (fn == NULL_TREE)
1088 fn = get_identifier ("__get_eh_context");
1089 push_obstacks_nochange ();
1090 end_temporary_allocation ();
1091 fntype = build_pointer_type (build_pointer_type
1092 (build_pointer_type (void_type_node)));
1093 fntype = build_function_type (fntype, NULL_TREE);
1094 fn = build_decl (FUNCTION_DECL, fn, fntype);
1095 DECL_EXTERNAL (fn) = 1;
1096 TREE_PUBLIC (fn) = 1;
1097 DECL_ARTIFICIAL (fn) = 1;
1098 TREE_READONLY (fn) = 1;
1099 make_decl_rtl (fn, NULL_PTR, 1);
1100 assemble_external (fn);
1104 expr = build1 (ADDR_EXPR, build_pointer_type (TREE_TYPE (fn)), fn);
1105 expr = build (CALL_EXPR, TREE_TYPE (TREE_TYPE (fn)),
1106 expr, NULL_TREE, NULL_TREE);
1107 TREE_SIDE_EFFECTS (expr) = 1;
1109 return copy_to_reg (expand_expr (expr, NULL_RTX, VOIDmode, 0));
1112 /* Get a reference to the EH context.
1113 We will only generate a register for the current function EH context here,
1114 and emit a USE insn to mark that this is a EH context register.
1116 Later, emit_eh_context will emit needed call to __get_eh_context
1117 in libgcc2, and copy the value to the register we have generated. */
1122 if (current_function_ehc == 0)
1126 current_function_ehc = gen_reg_rtx (Pmode);
1128 insn = gen_rtx_USE (GET_MODE (current_function_ehc),
1129 current_function_ehc);
1130 insn = emit_insn_before (insn, get_first_nonparm_insn ());
1133 = gen_rtx_EXPR_LIST (REG_EH_CONTEXT, current_function_ehc,
1136 return current_function_ehc;
1139 /* Get a reference to the dynamic handler chain. It points to the
1140 pointer to the next element in the dynamic handler chain. It ends
1141 when there are no more elements in the dynamic handler chain, when
1142 the value is &top_elt from libgcc2.c. Immediately after the
1143 pointer, is an area suitable for setjmp/longjmp when
1144 DONT_USE_BUILTIN_SETJMP is defined, and an area suitable for
1145 __builtin_setjmp/__builtin_longjmp when DONT_USE_BUILTIN_SETJMP
1149 get_dynamic_handler_chain ()
1151 rtx ehc, dhc, result;
1153 ehc = get_eh_context ();
1155 /* This is the offset of dynamic_handler_chain in the eh_context struct
1156 declared in eh-common.h. If its location is change, change this offset */
1157 dhc = plus_constant (ehc, POINTER_SIZE / BITS_PER_UNIT);
1159 result = copy_to_reg (dhc);
1161 /* We don't want a copy of the dcc, but rather, the single dcc. */
1162 return gen_rtx_MEM (Pmode, result);
1165 /* Get a reference to the dynamic cleanup chain. It points to the
1166 pointer to the next element in the dynamic cleanup chain.
1167 Immediately after the pointer, are two Pmode variables, one for a
1168 pointer to a function that performs the cleanup action, and the
1169 second, the argument to pass to that function. */
1172 get_dynamic_cleanup_chain ()
1174 rtx dhc, dcc, result;
1176 dhc = get_dynamic_handler_chain ();
1177 dcc = plus_constant (dhc, POINTER_SIZE / BITS_PER_UNIT);
1179 result = copy_to_reg (dcc);
1181 /* We don't want a copy of the dcc, but rather, the single dcc. */
1182 return gen_rtx_MEM (Pmode, result);
1185 #ifdef DONT_USE_BUILTIN_SETJMP
1186 /* Generate code to evaluate X and jump to LABEL if the value is nonzero.
1187 LABEL is an rtx of code CODE_LABEL, in this function. */
1190 jumpif_rtx (x, label)
1194 jumpif (make_tree (type_for_mode (GET_MODE (x), 0), x), label);
1198 /* Start a dynamic cleanup on the EH runtime dynamic cleanup stack.
1199 We just need to create an element for the cleanup list, and push it
1202 A dynamic cleanup is a cleanup action implied by the presence of an
1203 element on the EH runtime dynamic cleanup stack that is to be
1204 performed when an exception is thrown. The cleanup action is
1205 performed by __sjthrow when an exception is thrown. Only certain
1206 actions can be optimized into dynamic cleanup actions. For the
1207 restrictions on what actions can be performed using this routine,
1208 see expand_eh_region_start_tree. */
1211 start_dynamic_cleanup (func, arg)
1216 rtx new_func, new_arg;
1220 /* We allocate enough room for a pointer to the function, and
1224 /* XXX, FIXME: The stack space allocated this way is too long lived,
1225 but there is no allocation routine that allocates at the level of
1226 the last binding contour. */
1227 buf = assign_stack_local (BLKmode,
1228 GET_MODE_SIZE (Pmode)*(size+1),
1231 buf = change_address (buf, Pmode, NULL_RTX);
1233 /* Store dcc into the first word of the newly allocated buffer. */
1235 dcc = get_dynamic_cleanup_chain ();
1236 emit_move_insn (buf, dcc);
1238 /* Store func and arg into the cleanup list element. */
1240 new_func = gen_rtx_MEM (Pmode, plus_constant (XEXP (buf, 0),
1241 GET_MODE_SIZE (Pmode)));
1242 new_arg = gen_rtx_MEM (Pmode, plus_constant (XEXP (buf, 0),
1243 GET_MODE_SIZE (Pmode)*2));
1244 x = expand_expr (func, new_func, Pmode, 0);
1246 emit_move_insn (new_func, x);
1248 x = expand_expr (arg, new_arg, Pmode, 0);
1250 emit_move_insn (new_arg, x);
1252 /* Update the cleanup chain. */
1254 x = force_operand (XEXP (buf, 0), dcc);
1256 emit_move_insn (dcc, x);
1259 /* Emit RTL to start a dynamic handler on the EH runtime dynamic
1260 handler stack. This should only be used by expand_eh_region_start
1261 or expand_eh_region_start_tree. */
1264 start_dynamic_handler ()
1270 #ifndef DONT_USE_BUILTIN_SETJMP
1271 /* The number of Pmode words for the setjmp buffer, when using the
1272 builtin setjmp/longjmp, see expand_builtin, case
1273 BUILT_IN_LONGJMP. */
1277 size = JMP_BUF_SIZE;
1279 /* Should be large enough for most systems, if it is not,
1280 JMP_BUF_SIZE should be defined with the proper value. It will
1281 also tend to be larger than necessary for most systems, a more
1282 optimal port will define JMP_BUF_SIZE. */
1283 size = FIRST_PSEUDO_REGISTER+2;
1286 /* XXX, FIXME: The stack space allocated this way is too long lived,
1287 but there is no allocation routine that allocates at the level of
1288 the last binding contour. */
1289 arg = assign_stack_local (BLKmode,
1290 GET_MODE_SIZE (Pmode)*(size+1),
1293 arg = change_address (arg, Pmode, NULL_RTX);
1295 /* Store dhc into the first word of the newly allocated buffer. */
1297 dhc = get_dynamic_handler_chain ();
1298 dcc = gen_rtx_MEM (Pmode, plus_constant (XEXP (arg, 0),
1299 GET_MODE_SIZE (Pmode)));
1300 emit_move_insn (arg, dhc);
1302 /* Zero out the start of the cleanup chain. */
1303 emit_move_insn (dcc, const0_rtx);
1305 /* The jmpbuf starts two words into the area allocated. */
1306 buf = plus_constant (XEXP (arg, 0), GET_MODE_SIZE (Pmode)*2);
1308 #ifdef DONT_USE_BUILTIN_SETJMP
1309 x = emit_library_call_value (setjmp_libfunc, NULL_RTX, 1, SImode, 1,
1311 /* If we come back here for a catch, transfer control to the handler. */
1312 jumpif_rtx (x, ehstack.top->entry->exception_handler_label);
1315 /* A label to continue execution for the no exception case. */
1316 rtx noex = gen_label_rtx();
1317 x = expand_builtin_setjmp (buf, NULL_RTX, noex,
1318 ehstack.top->entry->exception_handler_label);
1323 /* We are committed to this, so update the handler chain. */
1325 emit_move_insn (dhc, force_operand (XEXP (arg, 0), NULL_RTX));
1328 /* Start an exception handling region for the given cleanup action.
1329 All instructions emitted after this point are considered to be part
1330 of the region until expand_eh_region_end is invoked. CLEANUP is
1331 the cleanup action to perform. The return value is true if the
1332 exception region was optimized away. If that case,
1333 expand_eh_region_end does not need to be called for this cleanup,
1336 This routine notices one particular common case in C++ code
1337 generation, and optimizes it so as to not need the exception
1338 region. It works by creating a dynamic cleanup action, instead of
1339 a using an exception region. */
1342 expand_eh_region_start_tree (decl, cleanup)
1346 /* This is the old code. */
1350 /* The optimization only applies to actions protected with
1351 terminate, and only applies if we are using the setjmp/longjmp
1353 if (exceptions_via_longjmp
1354 && protect_cleanup_actions_with_terminate)
1359 /* Ignore any UNSAVE_EXPR. */
1360 if (TREE_CODE (cleanup) == UNSAVE_EXPR)
1361 cleanup = TREE_OPERAND (cleanup, 0);
1363 /* Further, it only applies if the action is a call, if there
1364 are 2 arguments, and if the second argument is 2. */
1366 if (TREE_CODE (cleanup) == CALL_EXPR
1367 && (args = TREE_OPERAND (cleanup, 1))
1368 && (func = TREE_OPERAND (cleanup, 0))
1369 && (arg = TREE_VALUE (args))
1370 && (args = TREE_CHAIN (args))
1372 /* is the second argument 2? */
1373 && TREE_CODE (TREE_VALUE (args)) == INTEGER_CST
1374 && TREE_INT_CST_LOW (TREE_VALUE (args)) == 2
1375 && TREE_INT_CST_HIGH (TREE_VALUE (args)) == 0
1377 /* Make sure there are no other arguments. */
1378 && TREE_CHAIN (args) == NULL_TREE)
1380 /* Arrange for returns and gotos to pop the entry we make on the
1381 dynamic cleanup stack. */
1382 expand_dcc_cleanup (decl);
1383 start_dynamic_cleanup (func, arg);
1388 expand_eh_region_start_for_decl (decl);
1389 ehstack.top->entry->finalization = cleanup;
1394 /* Just like expand_eh_region_start, except if a cleanup action is
1395 entered on the cleanup chain, the TREE_PURPOSE of the element put
1396 on the chain is DECL. DECL should be the associated VAR_DECL, if
1397 any, otherwise it should be NULL_TREE. */
1400 expand_eh_region_start_for_decl (decl)
1405 /* This is the old code. */
1409 /* We need a new block to record the start and end of the
1410 dynamic handler chain. We also want to prevent jumping into
1412 expand_start_bindings (0);
1414 /* But we don't need or want a new temporary level. */
1417 /* Mark this block as created by expand_eh_region_start. This
1418 is so that we can pop the block with expand_end_bindings
1420 mark_block_as_eh_region ();
1422 if (exceptions_via_longjmp)
1424 /* Arrange for returns and gotos to pop the entry we make on the
1425 dynamic handler stack. */
1426 expand_dhc_cleanup (decl);
1429 push_eh_entry (&ehstack);
1430 note = emit_note (NULL_PTR, NOTE_INSN_EH_REGION_BEG);
1431 NOTE_BLOCK_NUMBER (note)
1432 = CODE_LABEL_NUMBER (ehstack.top->entry->exception_handler_label);
1433 if (exceptions_via_longjmp)
1434 start_dynamic_handler ();
1437 /* Start an exception handling region. All instructions emitted after
1438 this point are considered to be part of the region until
1439 expand_eh_region_end is invoked. */
1442 expand_eh_region_start ()
1444 expand_eh_region_start_for_decl (NULL_TREE);
1447 /* End an exception handling region. The information about the region
1448 is found on the top of ehstack.
1450 HANDLER is either the cleanup for the exception region, or if we're
1451 marking the end of a try block, HANDLER is integer_zero_node.
1453 HANDLER will be transformed to rtl when expand_leftover_cleanups
1457 expand_eh_region_end (handler)
1460 struct eh_entry *entry;
1467 entry = pop_eh_entry (&ehstack);
1469 note = emit_note (NULL_PTR, NOTE_INSN_EH_REGION_END);
1470 ret = NOTE_BLOCK_NUMBER (note)
1471 = CODE_LABEL_NUMBER (entry->exception_handler_label);
1472 if (exceptions_via_longjmp == 0 && ! flag_new_exceptions
1473 /* We share outer_context between regions; only emit it once. */
1474 && INSN_UID (entry->outer_context) == 0)
1478 label = gen_label_rtx ();
1481 /* Emit a label marking the end of this exception region that
1482 is used for rethrowing into the outer context. */
1483 emit_label (entry->outer_context);
1484 expand_internal_throw ();
1489 entry->finalization = handler;
1491 /* create region entry in final exception table */
1492 r = new_eh_region_entry (NOTE_BLOCK_NUMBER (note), entry->rethrow_label);
1494 enqueue_eh_entry (&ehqueue, entry);
1496 /* If we have already started ending the bindings, don't recurse. */
1497 if (is_eh_region ())
1499 /* Because we don't need or want a new temporary level and
1500 because we didn't create one in expand_eh_region_start,
1501 create a fake one now to avoid removing one in
1502 expand_end_bindings. */
1505 mark_block_as_not_eh_region ();
1507 expand_end_bindings (NULL_TREE, 0, 0);
1511 /* End the EH region for a goto fixup. We only need them in the region-based
1515 expand_fixup_region_start ()
1517 if (! doing_eh (0) || exceptions_via_longjmp)
1520 expand_eh_region_start ();
1523 /* End the EH region for a goto fixup. CLEANUP is the cleanup we just
1524 expanded; to avoid running it twice if it throws, we look through the
1525 ehqueue for a matching region and rethrow from its outer_context. */
1528 expand_fixup_region_end (cleanup)
1531 struct eh_node *node;
1534 if (! doing_eh (0) || exceptions_via_longjmp)
1537 for (node = ehstack.top; node && node->entry->finalization != cleanup; )
1540 for (node = ehqueue.head; node && node->entry->finalization != cleanup; )
1545 /* If the outer context label has not been issued yet, we don't want
1546 to issue it as a part of this region, unless this is the
1547 correct region for the outer context. If we did, then the label for
1548 the outer context will be WITHIN the begin/end labels,
1549 and we could get an infinte loop when it tried to rethrow, or just
1550 generally incorrect execution following a throw. */
1552 if (flag_new_exceptions)
1555 dont_issue = ((INSN_UID (node->entry->outer_context) == 0)
1556 && (ehstack.top->entry != node->entry));
1558 ehstack.top->entry->outer_context = node->entry->outer_context;
1560 /* Since we are rethrowing to the OUTER region, we know we don't need
1561 a jump around sequence for this region, so we'll pretend the outer
1562 context label has been issued by setting INSN_UID to 1, then clearing
1563 it again afterwards. */
1566 INSN_UID (node->entry->outer_context) = 1;
1568 /* Just rethrow. size_zero_node is just a NOP. */
1569 expand_eh_region_end (size_zero_node);
1572 INSN_UID (node->entry->outer_context) = 0;
1575 /* If we are using the setjmp/longjmp EH codegen method, we emit a
1578 Otherwise, we emit a call to __throw and note that we threw
1579 something, so we know we need to generate the necessary code for
1582 Before invoking throw, the __eh_pc variable must have been set up
1583 to contain the PC being thrown from. This address is used by
1584 __throw to determine which exception region (if any) is
1585 responsible for handling the exception. */
1590 if (exceptions_via_longjmp)
1592 emit_library_call (sjthrow_libfunc, 0, VOIDmode, 0);
1596 #ifdef JUMP_TO_THROW
1597 emit_indirect_jump (throw_libfunc);
1599 emit_library_call (throw_libfunc, 0, VOIDmode, 0);
1605 /* Throw the current exception. If appropriate, this is done by jumping
1606 to the next handler. */
1609 expand_internal_throw ()
1614 /* Called from expand_exception_blocks and expand_end_catch_block to
1615 emit any pending handlers/cleanups queued from expand_eh_region_end. */
1618 expand_leftover_cleanups ()
1620 struct eh_entry *entry;
1622 while ((entry = dequeue_eh_entry (&ehqueue)) != 0)
1626 /* A leftover try block. Shouldn't be one here. */
1627 if (entry->finalization == integer_zero_node)
1630 /* Output the label for the start of the exception handler. */
1632 receive_exception_label (entry->exception_handler_label);
1634 /* register a handler for this cleanup region */
1636 find_func_region (CODE_LABEL_NUMBER (entry->exception_handler_label)),
1637 get_new_handler (entry->exception_handler_label, NULL));
1639 /* And now generate the insns for the handler. */
1640 expand_expr (entry->finalization, const0_rtx, VOIDmode, 0);
1642 prev = get_last_insn ();
1643 if (prev == NULL || GET_CODE (prev) != BARRIER)
1644 /* Emit code to throw to the outer context if we fall off
1645 the end of the handler. */
1646 expand_rethrow (entry->outer_context);
1648 do_pending_stack_adjust ();
1653 /* Called at the start of a block of try statements. */
1655 expand_start_try_stmts ()
1660 expand_eh_region_start ();
1663 /* Called to begin a catch clause. The parameter is the object which
1664 will be passed to the runtime type check routine. */
1666 start_catch_handler (rtime)
1670 int insn_region_num;
1671 int eh_region_entry;
1676 handler_label = catchstack.top->entry->exception_handler_label;
1677 insn_region_num = CODE_LABEL_NUMBER (handler_label);
1678 eh_region_entry = find_func_region (insn_region_num);
1680 /* If we've already issued this label, pick a new one */
1681 if (catchstack.top->entry->label_used)
1682 handler_label = gen_exception_label ();
1684 catchstack.top->entry->label_used = 1;
1686 receive_exception_label (handler_label);
1688 add_new_handler (eh_region_entry, get_new_handler (handler_label, rtime));
1690 if (flag_new_exceptions && ! exceptions_via_longjmp)
1693 /* Under the old mechanism, as well as setjmp/longjmp, we need to
1694 issue code to compare 'rtime' to the value in eh_info, via the
1695 matching function in eh_info. If its is false, we branch around
1696 the handler we are about to issue. */
1698 if (rtime != NULL_TREE && rtime != CATCH_ALL_TYPE)
1700 rtx call_rtx, rtime_address;
1702 if (catchstack.top->entry->false_label != NULL_RTX)
1704 error ("Never issued previous false_label");
1707 catchstack.top->entry->false_label = gen_exception_label ();
1709 rtime_address = expand_expr (rtime, NULL_RTX, Pmode, EXPAND_INITIALIZER);
1710 #ifdef POINTERS_EXTEND_UNSIGNED
1711 rtime_address = convert_memory_address (Pmode, rtime_address);
1713 rtime_address = force_reg (Pmode, rtime_address);
1715 /* Now issue the call, and branch around handler if needed */
1716 call_rtx = emit_library_call_value (eh_rtime_match_libfunc, NULL_RTX,
1717 0, SImode, 1, rtime_address, Pmode);
1719 /* Did the function return true? */
1720 emit_cmp_and_jump_insns (call_rtx, const0_rtx, EQ, NULL_RTX,
1721 GET_MODE (call_rtx), 0, 0,
1722 catchstack.top->entry->false_label);
1726 /* Called to end a catch clause. If we aren't using the new exception
1727 model tabel mechanism, we need to issue the branch-around label
1728 for the end of the catch block. */
1731 end_catch_handler ()
1736 if (flag_new_exceptions && ! exceptions_via_longjmp)
1742 /* A NULL label implies the catch clause was a catch all or cleanup */
1743 if (catchstack.top->entry->false_label == NULL_RTX)
1746 emit_label (catchstack.top->entry->false_label);
1747 catchstack.top->entry->false_label = NULL_RTX;
1750 /* Generate RTL for the start of a group of catch clauses.
1752 It is responsible for starting a new instruction sequence for the
1753 instructions in the catch block, and expanding the handlers for the
1754 internally-generated exception regions nested within the try block
1755 corresponding to this catch block. */
1758 expand_start_all_catch ()
1760 struct eh_entry *entry;
1767 outer_context = ehstack.top->entry->outer_context;
1769 /* End the try block. */
1770 expand_eh_region_end (integer_zero_node);
1772 emit_line_note (input_filename, lineno);
1773 label = build_decl (LABEL_DECL, NULL_TREE, NULL_TREE);
1775 /* The label for the exception handling block that we will save.
1776 This is Lresume in the documentation. */
1777 expand_label (label);
1779 /* Push the label that points to where normal flow is resumed onto
1780 the top of the label stack. */
1781 push_label_entry (&caught_return_label_stack, NULL_RTX, label);
1783 /* Start a new sequence for all the catch blocks. We will add this
1784 to the global sequence catch_clauses when we have completed all
1785 the handlers in this handler-seq. */
1788 entry = dequeue_eh_entry (&ehqueue);
1789 for ( ; entry->finalization != integer_zero_node;
1790 entry = dequeue_eh_entry (&ehqueue))
1794 /* Emit the label for the cleanup handler for this region, and
1795 expand the code for the handler.
1797 Note that a catch region is handled as a side-effect here;
1798 for a try block, entry->finalization will contain
1799 integer_zero_node, so no code will be generated in the
1800 expand_expr call below. But, the label for the handler will
1801 still be emitted, so any code emitted after this point will
1802 end up being the handler. */
1804 receive_exception_label (entry->exception_handler_label);
1806 /* register a handler for this cleanup region */
1808 find_func_region (CODE_LABEL_NUMBER (entry->exception_handler_label)),
1809 get_new_handler (entry->exception_handler_label, NULL));
1811 /* And now generate the insns for the cleanup handler. */
1812 expand_expr (entry->finalization, const0_rtx, VOIDmode, 0);
1814 prev = get_last_insn ();
1815 if (prev == NULL || GET_CODE (prev) != BARRIER)
1816 /* Code to throw out to outer context when we fall off end
1817 of the handler. We can't do this here for catch blocks,
1818 so it's done in expand_end_all_catch instead. */
1819 expand_rethrow (entry->outer_context);
1821 do_pending_stack_adjust ();
1825 /* At this point, all the cleanups are done, and the ehqueue now has
1826 the current exception region at its head. We dequeue it, and put it
1827 on the catch stack. */
1829 push_entry (&catchstack, entry);
1831 /* If we are not doing setjmp/longjmp EH, because we are reordered
1832 out of line, we arrange to rethrow in the outer context. We need to
1833 do this because we are not physically within the region, if any, that
1834 logically contains this catch block. */
1835 if (! exceptions_via_longjmp)
1837 expand_eh_region_start ();
1838 ehstack.top->entry->outer_context = outer_context;
1843 /* Finish up the catch block. At this point all the insns for the
1844 catch clauses have already been generated, so we only have to add
1845 them to the catch_clauses list. We also want to make sure that if
1846 we fall off the end of the catch clauses that we rethrow to the
1850 expand_end_all_catch ()
1852 rtx new_catch_clause;
1853 struct eh_entry *entry;
1858 /* Dequeue the current catch clause region. */
1859 entry = pop_eh_entry (&catchstack);
1862 if (! exceptions_via_longjmp)
1864 rtx outer_context = ehstack.top->entry->outer_context;
1866 /* Finish the rethrow region. size_zero_node is just a NOP. */
1867 expand_eh_region_end (size_zero_node);
1868 /* New exceptions handling models will never have a fall through
1869 of a catch clause */
1870 if (!flag_new_exceptions)
1871 expand_rethrow (outer_context);
1874 expand_rethrow (NULL_RTX);
1876 /* Code to throw out to outer context, if we fall off end of catch
1877 handlers. This is rethrow (Lresume, same id, same obj) in the
1878 documentation. We use Lresume because we know that it will throw
1879 to the correct context.
1881 In other words, if the catch handler doesn't exit or return, we
1882 do a "throw" (using the address of Lresume as the point being
1883 thrown from) so that the outer EH region can then try to process
1886 /* Now we have the complete catch sequence. */
1887 new_catch_clause = get_insns ();
1890 /* This level of catch blocks is done, so set up the successful
1891 catch jump label for the next layer of catch blocks. */
1892 pop_label_entry (&caught_return_label_stack);
1893 pop_label_entry (&outer_context_label_stack);
1895 /* Add the new sequence of catches to the main one for this function. */
1896 push_to_sequence (catch_clauses);
1897 emit_insns (new_catch_clause);
1898 catch_clauses = get_insns ();
1901 /* Here we fall through into the continuation code. */
1904 /* Rethrow from the outer context LABEL. */
1907 expand_rethrow (label)
1910 if (exceptions_via_longjmp)
1913 if (flag_new_exceptions)
1917 if (label == NULL_RTX)
1918 label = last_rethrow_symbol;
1919 emit_library_call (rethrow_libfunc, 0, VOIDmode, 1, label, Pmode);
1920 region = find_func_region (eh_region_from_symbol (label));
1921 function_eh_regions[region].rethrow_ref = 1;
1923 /* Search backwards for the actual call insn. */
1924 insn = get_last_insn ();
1925 while (GET_CODE (insn) != CALL_INSN)
1926 insn = PREV_INSN (insn);
1927 delete_insns_since (insn);
1929 /* Mark the label/symbol on the call. */
1930 REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_EH_RETHROW, label,
1938 /* End all the pending exception regions on protect_list. The handlers
1939 will be emitted when expand_leftover_cleanups is invoked. */
1942 end_protect_partials ()
1944 while (protect_list)
1946 expand_eh_region_end (TREE_VALUE (protect_list));
1947 protect_list = TREE_CHAIN (protect_list);
1951 /* Arrange for __terminate to be called if there is an unhandled throw
1955 protect_with_terminate (e)
1958 /* We only need to do this when using setjmp/longjmp EH and the
1959 language requires it, as otherwise we protect all of the handlers
1960 at once, if we need to. */
1961 if (exceptions_via_longjmp && protect_cleanup_actions_with_terminate)
1963 tree handler, result;
1965 /* All cleanups must be on the function_obstack. */
1966 push_obstacks_nochange ();
1967 resume_temporary_allocation ();
1969 handler = make_node (RTL_EXPR);
1970 TREE_TYPE (handler) = void_type_node;
1971 RTL_EXPR_RTL (handler) = const0_rtx;
1972 TREE_SIDE_EFFECTS (handler) = 1;
1973 start_sequence_for_rtl_expr (handler);
1975 emit_library_call (terminate_libfunc, 0, VOIDmode, 0);
1978 RTL_EXPR_SEQUENCE (handler) = get_insns ();
1981 result = build (TRY_CATCH_EXPR, TREE_TYPE (e), e, handler);
1982 TREE_SIDE_EFFECTS (result) = TREE_SIDE_EFFECTS (e);
1983 TREE_THIS_VOLATILE (result) = TREE_THIS_VOLATILE (e);
1984 TREE_READONLY (result) = TREE_READONLY (e);
1994 /* The exception table that we build that is used for looking up and
1995 dispatching exceptions, the current number of entries, and its
1996 maximum size before we have to extend it.
1998 The number in eh_table is the code label number of the exception
1999 handler for the region. This is added by add_eh_table_entry and
2000 used by output_exception_table_entry. */
2002 static int *eh_table = NULL;
2003 static int eh_table_size = 0;
2004 static int eh_table_max_size = 0;
2006 /* Note the need for an exception table entry for region N. If we
2007 don't need to output an explicit exception table, avoid all of the
2010 Called from final_scan_insn when a NOTE_INSN_EH_REGION_BEG is seen.
2011 (Or NOTE_INSN_EH_REGION_END sometimes)
2012 N is the NOTE_BLOCK_NUMBER of the note, which comes from the code
2013 label number of the exception handler for the region. */
2016 add_eh_table_entry (n)
2019 #ifndef OMIT_EH_TABLE
2020 if (eh_table_size >= eh_table_max_size)
2024 eh_table_max_size += eh_table_max_size>>1;
2026 if (eh_table_max_size < 0)
2029 eh_table = (int *) xrealloc (eh_table,
2030 eh_table_max_size * sizeof (int));
2034 eh_table_max_size = 252;
2035 eh_table = (int *) xmalloc (eh_table_max_size * sizeof (int));
2038 eh_table[eh_table_size++] = n;
2042 /* Return a non-zero value if we need to output an exception table.
2044 On some platforms, we don't have to output a table explicitly.
2045 This routine doesn't mean we don't have one. */
2048 exception_table_p ()
2056 /* Output the entry of the exception table corresponding to the
2057 exception region numbered N to file FILE.
2059 N is the code label number corresponding to the handler of the
2063 output_exception_table_entry (file, n)
2069 struct handler_info *handler = get_first_handler (n);
2070 int index = find_func_region (n);
2073 /* form and emit the rethrow label, if needed */
2074 rethrow = function_eh_regions[index].rethrow_label;
2075 if (rethrow != NULL_RTX && !flag_new_exceptions)
2077 if (rethrow != NULL_RTX && handler == NULL)
2078 if (! function_eh_regions[index].rethrow_ref)
2082 for ( ; handler != NULL || rethrow != NULL_RTX; handler = handler->next)
2084 /* rethrow label should indicate the LAST entry for a region */
2085 if (rethrow != NULL_RTX && (handler == NULL || handler->next == NULL))
2087 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", n);
2088 assemble_label(buf);
2092 ASM_GENERATE_INTERNAL_LABEL (buf, "LEHB", n);
2093 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
2094 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
2096 ASM_GENERATE_INTERNAL_LABEL (buf, "LEHE", n);
2097 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
2098 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
2100 if (handler == NULL)
2101 assemble_integer (GEN_INT (0), POINTER_SIZE / BITS_PER_UNIT, 1);
2104 ASM_GENERATE_INTERNAL_LABEL (buf, "L", handler->handler_number);
2105 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
2106 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
2109 if (flag_new_exceptions)
2111 if (handler == NULL || handler->type_info == NULL)
2112 assemble_integer (const0_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
2114 if (handler->type_info == CATCH_ALL_TYPE)
2115 assemble_integer (GEN_INT (CATCH_ALL_TYPE),
2116 POINTER_SIZE / BITS_PER_UNIT, 1);
2118 output_constant ((tree)(handler->type_info),
2119 POINTER_SIZE / BITS_PER_UNIT);
2121 putc ('\n', file); /* blank line */
2122 /* We only output the first label under the old scheme */
2123 if (! flag_new_exceptions || handler == NULL)
2128 /* Output the exception table if we have and need one. */
2130 static short language_code = 0;
2131 static short version_code = 0;
2133 /* This routine will set the language code for exceptions. */
2135 set_exception_lang_code (code)
2138 language_code = code;
2141 /* This routine will set the language version code for exceptions. */
2143 set_exception_version_code (code)
2146 version_code = code;
2151 output_exception_table ()
2155 extern FILE *asm_out_file;
2157 if (! doing_eh (0) || ! eh_table)
2160 exception_section ();
2162 /* Beginning marker for table. */
2163 assemble_align (GET_MODE_ALIGNMENT (ptr_mode));
2164 assemble_label ("__EXCEPTION_TABLE__");
2166 if (flag_new_exceptions)
2168 assemble_integer (GEN_INT (NEW_EH_RUNTIME),
2169 POINTER_SIZE / BITS_PER_UNIT, 1);
2170 assemble_integer (GEN_INT (language_code), 2 , 1);
2171 assemble_integer (GEN_INT (version_code), 2 , 1);
2173 /* Add enough padding to make sure table aligns on a pointer boundry. */
2174 i = GET_MODE_ALIGNMENT (ptr_mode) / BITS_PER_UNIT - 4;
2175 for ( ; i < 0; i = i + GET_MODE_ALIGNMENT (ptr_mode) / BITS_PER_UNIT)
2178 assemble_integer (const0_rtx, i , 1);
2180 /* Generate the label for offset calculations on rethrows */
2181 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", 0);
2182 assemble_label(buf);
2185 for (i = 0; i < eh_table_size; ++i)
2186 output_exception_table_entry (asm_out_file, eh_table[i]);
2189 clear_function_eh_region ();
2191 /* Ending marker for table. */
2192 /* Generate the label for end of table. */
2193 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", CODE_LABEL_NUMBER (final_rethrow));
2194 assemble_label(buf);
2195 assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
2197 /* for binary compatability, the old __throw checked the second
2198 position for a -1, so we should output at least 2 -1's */
2199 if (! flag_new_exceptions)
2200 assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
2202 putc ('\n', asm_out_file); /* blank line */
2205 /* Emit code to get EH context.
2207 We have to scan thru the code to find possible EH context registers.
2208 Inlined functions may use it too, and thus we'll have to be able
2211 This is done only if using exceptions_via_longjmp. */
2222 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2223 if (GET_CODE (insn) == INSN
2224 && GET_CODE (PATTERN (insn)) == USE)
2226 rtx reg = find_reg_note (insn, REG_EH_CONTEXT, 0);
2233 /* If this is the first use insn, emit the call here. This
2234 will always be at the top of our function, because if
2235 expand_inline_function notices a REG_EH_CONTEXT note, it
2236 adds a use insn to this function as well. */
2238 ehc = call_get_eh_context ();
2240 emit_move_insn (XEXP (reg, 0), ehc);
2241 insns = get_insns ();
2244 emit_insns_before (insns, insn);
2246 /* At -O0, we must make the context register stay alive so
2247 that the stupid.c register allocator doesn't get confused. */
2248 if (obey_regdecls != 0)
2250 insns = gen_rtx_USE (GET_MODE (XEXP (reg,0)), XEXP (reg,0));
2251 emit_insn_before (insns, get_last_insn ());
2257 /* Scan the current insns and build a list of handler labels. The
2258 resulting list is placed in the global variable exception_handler_labels.
2260 It is called after the last exception handling region is added to
2261 the current function (when the rtl is almost all built for the
2262 current function) and before the jump optimization pass. */
2265 find_exception_handler_labels ()
2269 exception_handler_labels = NULL_RTX;
2271 /* If we aren't doing exception handling, there isn't much to check. */
2275 /* For each start of a region, add its label to the list. */
2277 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2279 struct handler_info* ptr;
2280 if (GET_CODE (insn) == NOTE
2281 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2283 ptr = get_first_handler (NOTE_BLOCK_NUMBER (insn));
2284 for ( ; ptr; ptr = ptr->next)
2286 /* make sure label isn't in the list already */
2288 for (x = exception_handler_labels; x; x = XEXP (x, 1))
2289 if (XEXP (x, 0) == ptr->handler_label)
2292 exception_handler_labels = gen_rtx_EXPR_LIST (VOIDmode,
2293 ptr->handler_label, exception_handler_labels);
2299 /* Return a value of 1 if the parameter label number is an exception handler
2300 label. Return 0 otherwise. */
2303 is_exception_handler_label (lab)
2307 for (x = exception_handler_labels ; x ; x = XEXP (x, 1))
2308 if (lab == CODE_LABEL_NUMBER (XEXP (x, 0)))
2313 /* Perform sanity checking on the exception_handler_labels list.
2315 Can be called after find_exception_handler_labels is called to
2316 build the list of exception handlers for the current function and
2317 before we finish processing the current function. */
2320 check_exception_handler_labels ()
2324 /* If we aren't doing exception handling, there isn't much to check. */
2328 /* Make sure there is no more than 1 copy of a label */
2329 for (insn = exception_handler_labels; insn; insn = XEXP (insn, 1))
2332 for (insn2 = exception_handler_labels; insn2; insn2 = XEXP (insn2, 1))
2333 if (XEXP (insn, 0) == XEXP (insn2, 0))
2336 warning ("Counted %d copies of EH region %d in list.\n", count,
2337 CODE_LABEL_NUMBER (insn));
2342 /* Mark the children of NODE for GC. */
2346 struct eh_node *node;
2352 ggc_mark_rtx (node->entry->outer_context);
2353 ggc_mark_rtx (node->entry->exception_handler_label);
2354 ggc_mark_tree (node->entry->finalization);
2356 node = node ->chain;
2360 /* Mark S for GC. */
2367 mark_eh_node (s->top);
2370 /* Mark Q for GC. */
2377 mark_eh_node (q->head);
2380 /* Mark NODE for GC. A label_node contains a union containing either
2381 a tree or an rtx. This label_node will contain a tree. */
2384 mark_tree_label_node (node)
2385 struct label_node *node;
2389 ggc_mark_tree (node->u.tlabel);
2394 /* Mark EH for GC. */
2398 struct eh_status *eh;
2400 mark_eh_stack (&eh->x_ehstack);
2401 mark_eh_queue (&eh->x_ehqueue);
2402 ggc_mark_rtx (eh->x_catch_clauses);
2404 lang_mark_false_label_stack (eh->x_false_label_stack);
2405 mark_tree_label_node (eh->x_caught_return_label_stack);
2407 ggc_mark_tree (eh->x_protect_list);
2408 ggc_mark_rtx (eh->ehc);
2411 /* This group of functions initializes the exception handling data
2412 structures at the start of the compilation, initializes the data
2413 structures at the start of a function, and saves and restores the
2414 exception handling data structures for the start/end of a nested
2417 /* Toplevel initialization for EH things. */
2422 first_rethrow_symbol = create_rethrow_ref (0);
2423 final_rethrow = gen_exception_label ();
2424 last_rethrow_symbol = create_rethrow_ref (CODE_LABEL_NUMBER (final_rethrow));
2427 /* Initialize the per-function EH information. */
2430 init_eh_for_function ()
2432 current_function->eh = (struct eh_status *) xmalloc (sizeof (struct eh_status));
2436 ehqueue.head = ehqueue.tail = 0;
2437 catch_clauses = NULL_RTX;
2438 false_label_stack = 0;
2439 caught_return_label_stack = 0;
2440 protect_list = NULL_TREE;
2441 current_function_ehc = NULL_RTX;
2442 eh_return_context = NULL_RTX;
2443 eh_return_stack_adjust = NULL_RTX;
2444 eh_return_handler = NULL_RTX;
2445 eh_return_stub_label = NULL_RTX;
2448 /* This section is for the exception handling specific optimization
2449 pass. First are the internal routines, and then the main
2450 optimization pass. */
2452 /* Determine if the given INSN can throw an exception. */
2458 /* Calls can always potentially throw exceptions, unless they have
2459 a REG_EH_REGION note with a value of 0 or less. */
2460 if (GET_CODE (insn) == CALL_INSN)
2462 rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX);
2463 if (!note || XINT (XEXP (note, 0), 0) > 0)
2467 if (asynchronous_exceptions)
2469 /* If we wanted asynchronous exceptions, then everything but NOTEs
2470 and CODE_LABELs could throw. */
2471 if (GET_CODE (insn) != NOTE && GET_CODE (insn) != CODE_LABEL)
2478 /* Scan a exception region looking for the matching end and then
2479 remove it if possible. INSN is the start of the region, N is the
2480 region number, and DELETE_OUTER is to note if anything in this
2483 Regions are removed if they cannot possibly catch an exception.
2484 This is determined by invoking can_throw on each insn within the
2485 region; if can_throw returns true for any of the instructions, the
2486 region can catch an exception, since there is an insn within the
2487 region that is capable of throwing an exception.
2489 Returns the NOTE_INSN_EH_REGION_END corresponding to this region, or
2490 calls abort if it can't find one.
2492 Can abort if INSN is not a NOTE_INSN_EH_REGION_BEGIN, or if N doesn't
2493 correspond to the region number, or if DELETE_OUTER is NULL. */
2496 scan_region (insn, n, delete_outer)
2503 /* Assume we can delete the region. */
2506 /* Can't delete something which is rethrown to. */
2507 if (rethrow_used (n))
2510 if (insn == NULL_RTX
2511 || GET_CODE (insn) != NOTE
2512 || NOTE_LINE_NUMBER (insn) != NOTE_INSN_EH_REGION_BEG
2513 || NOTE_BLOCK_NUMBER (insn) != n
2514 || delete_outer == NULL)
2517 insn = NEXT_INSN (insn);
2519 /* Look for the matching end. */
2520 while (! (GET_CODE (insn) == NOTE
2521 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END))
2523 /* If anything can throw, we can't remove the region. */
2524 if (delete && can_throw (insn))
2529 /* Watch out for and handle nested regions. */
2530 if (GET_CODE (insn) == NOTE
2531 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2533 insn = scan_region (insn, NOTE_BLOCK_NUMBER (insn), &delete);
2536 insn = NEXT_INSN (insn);
2539 /* The _BEG/_END NOTEs must match and nest. */
2540 if (NOTE_BLOCK_NUMBER (insn) != n)
2543 /* If anything in this exception region can throw, we can throw. */
2548 /* Delete the start and end of the region. */
2549 delete_insn (start);
2552 /* We no longer removed labels here, since flow will now remove any
2553 handler which cannot be called any more. */
2556 /* Only do this part if we have built the exception handler
2558 if (exception_handler_labels)
2560 rtx x, *prev = &exception_handler_labels;
2562 /* Find it in the list of handlers. */
2563 for (x = exception_handler_labels; x; x = XEXP (x, 1))
2565 rtx label = XEXP (x, 0);
2566 if (CODE_LABEL_NUMBER (label) == n)
2568 /* If we are the last reference to the handler,
2570 if (--LABEL_NUSES (label) == 0)
2571 delete_insn (label);
2575 /* Remove it from the list of exception handler
2576 labels, if we are optimizing. If we are not, then
2577 leave it in the list, as we are not really going to
2578 remove the region. */
2579 *prev = XEXP (x, 1);
2586 prev = &XEXP (x, 1);
2594 /* Perform various interesting optimizations for exception handling
2597 We look for empty exception regions and make them go (away). The
2598 jump optimization code will remove the handler if nothing else uses
2602 exception_optimize ()
2607 /* Remove empty regions. */
2608 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2610 if (GET_CODE (insn) == NOTE
2611 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2613 /* Since scan_region will return the NOTE_INSN_EH_REGION_END
2614 insn, we will indirectly skip through all the insns
2615 inbetween. We are also guaranteed that the value of insn
2616 returned will be valid, as otherwise scan_region won't
2618 insn = scan_region (insn, NOTE_BLOCK_NUMBER (insn), &n);
2623 /* This function determines whether any of the exception regions in the
2624 current function are targets of a rethrow or not, and set the
2625 reference flag according. */
2627 update_rethrow_references ()
2631 int *saw_region, *saw_rethrow;
2633 if (!flag_new_exceptions)
2636 saw_region = (int *) alloca (current_func_eh_entry * sizeof (int));
2637 saw_rethrow = (int *) alloca (current_func_eh_entry * sizeof (int));
2638 bzero ((char *) saw_region, (current_func_eh_entry * sizeof (int)));
2639 bzero ((char *) saw_rethrow, (current_func_eh_entry * sizeof (int)));
2641 /* Determine what regions exist, and whether there are any rethrows
2642 to those regions or not. */
2643 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2644 if (GET_CODE (insn) == CALL_INSN)
2646 rtx note = find_reg_note (insn, REG_EH_RETHROW, NULL_RTX);
2649 region = eh_region_from_symbol (XEXP (note, 0));
2650 region = find_func_region (region);
2651 saw_rethrow[region] = 1;
2655 if (GET_CODE (insn) == NOTE)
2657 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2659 region = find_func_region (NOTE_BLOCK_NUMBER (insn));
2660 saw_region[region] = 1;
2664 /* For any regions we did see, set the referenced flag. */
2665 for (x = 0; x < current_func_eh_entry; x++)
2667 function_eh_regions[x].rethrow_ref = saw_rethrow[x];
2670 /* Various hooks for the DWARF 2 __throw routine. */
2672 /* Do any necessary initialization to access arbitrary stack frames.
2673 On the SPARC, this means flushing the register windows. */
2676 expand_builtin_unwind_init ()
2678 /* Set this so all the registers get saved in our frame; we need to be
2679 able to copy the saved values for any registers from frames we unwind. */
2680 current_function_has_nonlocal_label = 1;
2682 #ifdef SETUP_FRAME_ADDRESSES
2683 SETUP_FRAME_ADDRESSES ();
2687 /* Given a value extracted from the return address register or stack slot,
2688 return the actual address encoded in that value. */
2691 expand_builtin_extract_return_addr (addr_tree)
2694 rtx addr = expand_expr (addr_tree, NULL_RTX, Pmode, 0);
2695 return eh_outer_context (addr);
2698 /* Given an actual address in addr_tree, do any necessary encoding
2699 and return the value to be stored in the return address register or
2700 stack slot so the epilogue will return to that address. */
2703 expand_builtin_frob_return_addr (addr_tree)
2706 rtx addr = expand_expr (addr_tree, NULL_RTX, Pmode, 0);
2707 #ifdef RETURN_ADDR_OFFSET
2708 addr = plus_constant (addr, -RETURN_ADDR_OFFSET);
2713 /* Choose three registers for communication between the main body of
2714 __throw and the epilogue (or eh stub) and the exception handler.
2715 We must do this with hard registers because the epilogue itself
2716 will be generated after reload, at which point we may not reference
2719 The first passes the exception context to the handler. For this
2720 we use the return value register for a void*.
2722 The second holds the stack pointer value to be restored. For
2723 this we use the static chain register if it exists and is different
2724 from the previous, otherwise some arbitrary call-clobbered register.
2726 The third holds the address of the handler itself. Here we use
2727 some arbitrary call-clobbered register. */
2730 eh_regs (pcontext, psp, pra, outgoing)
2731 rtx *pcontext, *psp, *pra;
2734 rtx rcontext, rsp, rra;
2737 #ifdef FUNCTION_OUTGOING_VALUE
2739 rcontext = FUNCTION_OUTGOING_VALUE (build_pointer_type (void_type_node),
2740 current_function_decl);
2743 rcontext = FUNCTION_VALUE (build_pointer_type (void_type_node),
2744 current_function_decl);
2746 #ifdef STATIC_CHAIN_REGNUM
2748 rsp = static_chain_incoming_rtx;
2750 rsp = static_chain_rtx;
2751 if (REGNO (rsp) == REGNO (rcontext))
2752 #endif /* STATIC_CHAIN_REGNUM */
2755 if (rsp == NULL_RTX)
2757 for (i = 0; i < FIRST_PSEUDO_REGISTER; ++i)
2758 if (call_used_regs[i] && ! fixed_regs[i] && i != REGNO (rcontext))
2760 if (i == FIRST_PSEUDO_REGISTER)
2763 rsp = gen_rtx_REG (Pmode, i);
2766 for (i = 0; i < FIRST_PSEUDO_REGISTER; ++i)
2767 if (call_used_regs[i] && ! fixed_regs[i]
2768 && i != REGNO (rcontext) && i != REGNO (rsp))
2770 if (i == FIRST_PSEUDO_REGISTER)
2773 rra = gen_rtx_REG (Pmode, i);
2775 *pcontext = rcontext;
2780 /* Retrieve the register which contains the pointer to the eh_context
2781 structure set the __throw. */
2784 get_reg_for_handler ()
2787 reg1 = FUNCTION_VALUE (build_pointer_type (void_type_node),
2788 current_function_decl);
2792 /* Set up the epilogue with the magic bits we'll need to return to the
2793 exception handler. */
2796 expand_builtin_eh_return (context, stack, handler)
2797 tree context, stack, handler;
2799 if (eh_return_context)
2800 error("Duplicate call to __builtin_eh_return");
2803 = copy_to_reg (expand_expr (context, NULL_RTX, VOIDmode, 0));
2804 eh_return_stack_adjust
2805 = copy_to_reg (expand_expr (stack, NULL_RTX, VOIDmode, 0));
2807 = copy_to_reg (expand_expr (handler, NULL_RTX, VOIDmode, 0));
2813 rtx reg1, reg2, reg3;
2814 rtx stub_start, after_stub;
2817 if (!eh_return_context)
2820 current_function_cannot_inline = N_("function uses __builtin_eh_return");
2822 eh_regs (®1, ®2, ®3, 1);
2823 #ifdef POINTERS_EXTEND_UNSIGNED
2824 eh_return_context = convert_memory_address (Pmode, eh_return_context);
2825 eh_return_stack_adjust =
2826 convert_memory_address (Pmode, eh_return_stack_adjust);
2827 eh_return_handler = convert_memory_address (Pmode, eh_return_handler);
2829 emit_move_insn (reg1, eh_return_context);
2830 emit_move_insn (reg2, eh_return_stack_adjust);
2831 emit_move_insn (reg3, eh_return_handler);
2833 /* Talk directly to the target's epilogue code when possible. */
2835 #ifdef HAVE_eh_epilogue
2836 if (HAVE_eh_epilogue)
2838 emit_insn (gen_eh_epilogue (reg1, reg2, reg3));
2843 /* Otherwise, use the same stub technique we had before. */
2845 eh_return_stub_label = stub_start = gen_label_rtx ();
2846 after_stub = gen_label_rtx ();
2848 /* Set the return address to the stub label. */
2850 ra = expand_builtin_return_addr (BUILT_IN_RETURN_ADDRESS,
2851 0, hard_frame_pointer_rtx);
2852 if (GET_CODE (ra) == REG && REGNO (ra) >= FIRST_PSEUDO_REGISTER)
2855 tmp = memory_address (Pmode, gen_rtx_LABEL_REF (Pmode, stub_start));
2856 #ifdef RETURN_ADDR_OFFSET
2857 tmp = plus_constant (tmp, -RETURN_ADDR_OFFSET);
2859 tmp = force_operand (tmp, ra);
2861 emit_move_insn (ra, tmp);
2863 /* Indicate that the registers are in fact used. */
2864 emit_insn (gen_rtx_USE (VOIDmode, reg1));
2865 emit_insn (gen_rtx_USE (VOIDmode, reg2));
2866 emit_insn (gen_rtx_USE (VOIDmode, reg3));
2867 if (GET_CODE (ra) == REG)
2868 emit_insn (gen_rtx_USE (VOIDmode, ra));
2870 /* Generate the stub. */
2872 emit_jump (after_stub);
2873 emit_label (stub_start);
2875 eh_regs (®1, ®2, ®3, 0);
2876 adjust_stack (reg2);
2877 emit_indirect_jump (reg3);
2879 emit_label (after_stub);
2883 /* This contains the code required to verify whether arbitrary instructions
2884 are in the same exception region. */
2886 static int *insn_eh_region = (int *)0;
2887 static int maximum_uid;
2890 set_insn_eh_region (first, region_num)
2897 for (insn = *first; insn; insn = NEXT_INSN (insn))
2899 if ((GET_CODE (insn) == NOTE) &&
2900 (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG))
2902 rnum = NOTE_BLOCK_NUMBER (insn);
2903 insn_eh_region[INSN_UID (insn)] = rnum;
2904 insn = NEXT_INSN (insn);
2905 set_insn_eh_region (&insn, rnum);
2906 /* Upon return, insn points to the EH_REGION_END of nested region */
2909 insn_eh_region[INSN_UID (insn)] = region_num;
2910 if ((GET_CODE (insn) == NOTE) &&
2911 (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END))
2917 /* Free the insn table, an make sure it cannot be used again. */
2920 free_insn_eh_region ()
2927 free (insn_eh_region);
2928 insn_eh_region = (int *)0;
2932 /* Initialize the table. max_uid must be calculated and handed into
2933 this routine. If it is unavailable, passing a value of 0 will
2934 cause this routine to calculate it as well. */
2937 init_insn_eh_region (first, max_uid)
2947 free_insn_eh_region();
2950 for (insn = first; insn; insn = NEXT_INSN (insn))
2951 if (INSN_UID (insn) > max_uid) /* find largest UID */
2952 max_uid = INSN_UID (insn);
2954 maximum_uid = max_uid;
2955 insn_eh_region = (int *) malloc ((max_uid + 1) * sizeof (int));
2957 set_insn_eh_region (&insn, 0);
2961 /* Check whether 2 instructions are within the same region. */
2964 in_same_eh_region (insn1, insn2)
2967 int ret, uid1, uid2;
2969 /* If no exceptions, instructions are always in same region. */
2973 /* If the table isn't allocated, assume the worst. */
2974 if (!insn_eh_region)
2977 uid1 = INSN_UID (insn1);
2978 uid2 = INSN_UID (insn2);
2980 /* if instructions have been allocated beyond the end, either
2981 the table is out of date, or this is a late addition, or
2982 something... Assume the worst. */
2983 if (uid1 > maximum_uid || uid2 > maximum_uid)
2986 ret = (insn_eh_region[uid1] == insn_eh_region[uid2]);
2991 /* This function will initialize the handler list for a specified block.
2992 It may recursively call itself if the outer block hasn't been processed
2993 yet. At some point in the future we can trim out handlers which we
2994 know cannot be called. (ie, if a block has an INT type handler,
2995 control will never be passed to an outer INT type handler). */
2997 process_nestinfo (block, info, nested_eh_region)
2999 eh_nesting_info *info;
3000 int *nested_eh_region;
3002 handler_info *ptr, *last_ptr = NULL;
3003 int x, y, count = 0;
3005 handler_info **extra_handlers;
3006 int index = info->region_index[block];
3008 /* If we've already processed this block, simply return. */
3009 if (info->num_handlers[index] > 0)
3012 for (ptr = get_first_handler (block); ptr; last_ptr = ptr, ptr = ptr->next)
3015 /* pick up any information from the next outer region. It will already
3016 contain a summary of itself and all outer regions to it. */
3018 if (nested_eh_region [block] != 0)
3020 int nested_index = info->region_index[nested_eh_region[block]];
3021 process_nestinfo (nested_eh_region[block], info, nested_eh_region);
3022 extra = info->num_handlers[nested_index];
3023 extra_handlers = info->handlers[nested_index];
3024 info->outer_index[index] = nested_index;
3027 /* If the last handler is either a CATCH_ALL or a cleanup, then we
3028 won't use the outer ones since we know control will not go past the
3029 catch-all or cleanup. */
3031 if (last_ptr != NULL && (last_ptr->type_info == NULL
3032 || last_ptr->type_info == CATCH_ALL_TYPE))
3035 info->num_handlers[index] = count + extra;
3036 info->handlers[index] = (handler_info **) malloc ((count + extra)
3037 * sizeof (handler_info **));
3039 /* First put all our handlers into the list. */
3040 ptr = get_first_handler (block);
3041 for (x = 0; x < count; x++)
3043 info->handlers[index][x] = ptr;
3047 /* Now add all the outer region handlers, if they aren't they same as
3048 one of the types in the current block. We won't worry about
3049 derived types yet, we'll just look for the exact type. */
3050 for (y =0, x = 0; x < extra ; x++)
3054 /* Check to see if we have a type duplication. */
3055 for (i = 0; i < count; i++)
3056 if (info->handlers[index][i]->type_info == extra_handlers[x]->type_info)
3059 /* Record one less handler. */
3060 (info->num_handlers[index])--;
3065 info->handlers[index][y + count] = extra_handlers[x];
3071 /* This function will allocate and initialize an eh_nesting_info structure.
3072 It returns a pointer to the completed data structure. If there are
3073 no exception regions, a NULL value is returned. */
3075 init_eh_nesting_info ()
3077 int *nested_eh_region;
3078 int region_count = 0;
3079 rtx eh_note = NULL_RTX;
3080 eh_nesting_info *info;
3084 info = (eh_nesting_info *) malloc (sizeof (eh_nesting_info));
3085 info->region_index = (int *) malloc ((max_label_num () + 1) * sizeof (int));
3086 bzero ((char *) info->region_index, (max_label_num () + 1) * sizeof (int));
3088 nested_eh_region = (int *) alloca ((max_label_num () + 1) * sizeof (int));
3089 bzero ((char *) nested_eh_region, (max_label_num () + 1) * sizeof (int));
3091 /* Create the nested_eh_region list. If indexed with a block number, it
3092 returns the block number of the next outermost region, if any.
3093 We can count the number of regions and initialize the region_index
3094 vector at the same time. */
3095 for (insn = get_insns(); insn; insn = NEXT_INSN (insn))
3097 if (GET_CODE (insn) == NOTE)
3099 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
3101 int block = NOTE_BLOCK_NUMBER (insn);
3103 info->region_index[block] = region_count;
3105 nested_eh_region [block] =
3106 NOTE_BLOCK_NUMBER (XEXP (eh_note, 0));
3108 nested_eh_region [block] = 0;
3109 eh_note = gen_rtx_EXPR_LIST (VOIDmode, insn, eh_note);
3111 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)
3112 eh_note = XEXP (eh_note, 1);
3116 /* If there are no regions, wrap it up now. */
3117 if (region_count == 0)
3119 free (info->region_index);
3125 info->handlers = (handler_info ***) malloc (region_count
3126 * sizeof (handler_info ***));
3127 info->num_handlers = (int *) malloc (region_count * sizeof (int));
3128 info->outer_index = (int *) malloc (region_count * sizeof (int));
3130 bzero ((char *) info->handlers, region_count * sizeof (rtx *));
3131 bzero ((char *) info->num_handlers, region_count * sizeof (int));
3132 bzero ((char *) info->outer_index, region_count * sizeof (int));
3134 /* Now initialize the handler lists for all exception blocks. */
3135 for (x = 0; x <= max_label_num (); x++)
3137 if (info->region_index[x] != 0)
3138 process_nestinfo (x, info, nested_eh_region);
3140 info->region_count = region_count;
3145 /* This function is used to retreive the vector of handlers which
3146 can be reached by a given insn in a given exception region.
3147 BLOCK is the exception block the insn is in.
3148 INFO is the eh_nesting_info structure.
3149 INSN is the (optional) insn within the block. If insn is not NULL_RTX,
3150 it may contain reg notes which modify its throwing behavior, and
3151 these will be obeyed. If NULL_RTX is passed, then we simply return the
3153 HANDLERS is the address of a pointer to a vector of handler_info pointers.
3154 Upon return, this will have the handlers which can be reached by block.
3155 This function returns the number of elements in the handlers vector. */
3157 reachable_handlers (block, info, insn, handlers)
3159 eh_nesting_info *info;
3161 handler_info ***handlers;
3169 index = info->region_index[block];
3171 if (insn && GET_CODE (insn) == CALL_INSN)
3173 /* RETHROWs specify a region number from which we are going to rethrow.
3174 This means we wont pass control to handlers in the specified
3175 region, but rather any region OUTSIDE the specified region.
3176 We accomplish this by setting block to the outer_index of the
3177 specified region. */
3178 rtx note = find_reg_note (insn, REG_EH_RETHROW, NULL_RTX);
3181 index = eh_region_from_symbol (XEXP (note, 0));
3182 index = info->region_index[index];
3184 index = info->outer_index[index];
3188 /* If there is no rethrow, we look for a REG_EH_REGION, and
3189 we'll throw from that block. A value of 0 or less
3190 indicates that this insn cannot throw. */
3191 note = find_reg_note (insn, REG_EH_REGION, NULL_RTX);
3194 int b = XINT (XEXP (note, 0), 0);
3198 index = info->region_index[b];
3202 /* If we reach this point, and index is 0, there is no throw. */
3206 *handlers = info->handlers[index];
3207 return info->num_handlers[index];
3211 /* This function will free all memory associated with the eh_nesting info. */
3214 free_eh_nesting_info (info)
3215 eh_nesting_info *info;
3220 if (info->region_index)
3221 free (info->region_index);
3222 if (info->num_handlers)
3223 free (info->num_handlers);
3224 if (info->outer_index)
3225 free (info->outer_index);
3228 for (x = 0; x < info->region_count; x++)
3229 if (info->handlers[x])
3230 free (info->handlers[x]);
3231 free (info->handlers);