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 *));
475 static void mark_func_eh_entry PROTO ((void *));
477 rtx expand_builtin_return_addr PROTO((enum built_in_function, int, rtx));
479 /* Various support routines to manipulate the various data structures
480 used by the exception handling code. */
482 extern struct obstack permanent_obstack;
484 /* Generate a SYMBOL_REF for rethrow to use */
486 create_rethrow_ref (region_num)
493 push_obstacks_nochange ();
494 end_temporary_allocation ();
496 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", region_num);
497 ptr = (char *) obstack_copy0 (&permanent_obstack, buf, strlen (buf));
498 def = gen_rtx_SYMBOL_REF (Pmode, ptr);
499 SYMBOL_REF_NEED_ADJUST (def) = 1;
505 /* Push a label entry onto the given STACK. */
508 push_label_entry (stack, rlabel, tlabel)
509 struct label_node **stack;
513 struct label_node *newnode
514 = (struct label_node *) xmalloc (sizeof (struct label_node));
517 newnode->u.rlabel = rlabel;
519 newnode->u.tlabel = tlabel;
520 newnode->chain = *stack;
524 /* Pop a label entry from the given STACK. */
527 pop_label_entry (stack)
528 struct label_node **stack;
531 struct label_node *tempnode;
537 label = tempnode->u.rlabel;
538 *stack = (*stack)->chain;
544 /* Return the top element of the given STACK. */
547 top_label_entry (stack)
548 struct label_node **stack;
553 return (*stack)->u.tlabel;
556 /* get an exception label. These must be on the permanent obstack */
559 gen_exception_label ()
562 lab = gen_label_rtx ();
566 /* Push a new eh_node entry onto STACK. */
569 push_eh_entry (stack)
570 struct eh_stack *stack;
572 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
573 struct eh_entry *entry = (struct eh_entry *) xmalloc (sizeof (struct eh_entry));
575 rtx rlab = gen_exception_label ();
576 entry->finalization = NULL_TREE;
577 entry->label_used = 0;
578 entry->exception_handler_label = rlab;
579 entry->false_label = NULL_RTX;
580 if (! flag_new_exceptions)
581 entry->outer_context = gen_label_rtx ();
583 entry->outer_context = create_rethrow_ref (CODE_LABEL_NUMBER (rlab));
584 entry->rethrow_label = entry->outer_context;
587 node->chain = stack->top;
591 /* push an existing entry onto a stack. */
593 push_entry (stack, entry)
594 struct eh_stack *stack;
595 struct eh_entry *entry;
597 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
599 node->chain = stack->top;
603 /* Pop an entry from the given STACK. */
605 static struct eh_entry *
607 struct eh_stack *stack;
609 struct eh_node *tempnode;
610 struct eh_entry *tempentry;
612 tempnode = stack->top;
613 tempentry = tempnode->entry;
614 stack->top = stack->top->chain;
620 /* Enqueue an ENTRY onto the given QUEUE. */
623 enqueue_eh_entry (queue, entry)
624 struct eh_queue *queue;
625 struct eh_entry *entry;
627 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
632 if (queue->head == NULL)
638 queue->tail->chain = node;
643 /* Dequeue an entry from the given QUEUE. */
645 static struct eh_entry *
646 dequeue_eh_entry (queue)
647 struct eh_queue *queue;
649 struct eh_node *tempnode;
650 struct eh_entry *tempentry;
652 if (queue->head == NULL)
655 tempnode = queue->head;
656 queue->head = queue->head->chain;
658 tempentry = tempnode->entry;
665 receive_exception_label (handler_label)
668 emit_label (handler_label);
670 #ifdef HAVE_exception_receiver
671 if (! exceptions_via_longjmp)
672 if (HAVE_exception_receiver)
673 emit_insn (gen_exception_receiver ());
676 #ifdef HAVE_nonlocal_goto_receiver
677 if (! exceptions_via_longjmp)
678 if (HAVE_nonlocal_goto_receiver)
679 emit_insn (gen_nonlocal_goto_receiver ());
686 int range_number; /* EH region number from EH NOTE insn's. */
687 rtx rethrow_label; /* Label for rethrow. */
688 int rethrow_ref; /* Is rethrow referenced? */
689 struct handler_info *handlers;
693 /* table of function eh regions */
694 static struct func_eh_entry *function_eh_regions = NULL;
695 static int num_func_eh_entries = 0;
696 static int current_func_eh_entry = 0;
698 #define SIZE_FUNC_EH(X) (sizeof (struct func_eh_entry) * X)
700 /* Add a new eh_entry for this function, and base it off of the information
701 in the EH_ENTRY parameter. A NULL parameter is invalid.
702 OUTER_CONTEXT is a label which is used for rethrowing. The number
703 returned is an number which uniquely identifies this exception range. */
706 new_eh_region_entry (note_eh_region, rethrow)
710 if (current_func_eh_entry == num_func_eh_entries)
712 if (num_func_eh_entries == 0)
714 function_eh_regions =
715 (struct func_eh_entry *) xmalloc (SIZE_FUNC_EH (50));
716 num_func_eh_entries = 50;
720 num_func_eh_entries = num_func_eh_entries * 3 / 2;
721 function_eh_regions = (struct func_eh_entry *)
722 xrealloc (function_eh_regions, SIZE_FUNC_EH (num_func_eh_entries));
725 function_eh_regions[current_func_eh_entry].range_number = note_eh_region;
726 if (rethrow == NULL_RTX)
727 function_eh_regions[current_func_eh_entry].rethrow_label =
728 create_rethrow_ref (note_eh_region);
730 function_eh_regions[current_func_eh_entry].rethrow_label = rethrow;
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 = last->next)
758 if (last->type_info == CATCH_ALL_TYPE)
759 pedwarn ("additional handler after ...");
760 if (last->next == NULL)
763 last->next = newhandler;
767 /* Remove a handler label. The handler label is being deleted, so all
768 regions which reference this handler should have it removed from their
769 list of possible handlers. Any region which has the final handler
770 removed can be deleted. */
772 void remove_handler (removing_label)
775 struct handler_info *handler, *last;
777 for (x = 0 ; x < current_func_eh_entry; ++x)
780 handler = function_eh_regions[x].handlers;
781 for ( ; handler; last = handler, handler = handler->next)
782 if (handler->handler_label == removing_label)
786 last->next = handler->next;
790 function_eh_regions[x].handlers = handler->next;
795 /* This function will return a malloc'd pointer to an array of
796 void pointer representing the runtime match values that
797 currently exist in all regions. */
800 find_all_handler_type_matches (array)
803 struct handler_info *handler, *last;
812 if (!doing_eh (0) || ! flag_new_exceptions)
816 ptr = (void **) xmalloc (max_ptr * sizeof (void *));
818 for (x = 0 ; x < current_func_eh_entry; x++)
821 handler = function_eh_regions[x].handlers;
822 for ( ; handler; last = handler, handler = handler->next)
824 val = handler->type_info;
825 if (val != NULL && val != CATCH_ALL_TYPE)
827 /* See if this match value has already been found. */
828 for (y = 0; y < n_ptr; y++)
832 /* If we break early, we already found this value. */
836 /* Do we need to allocate more space? */
837 if (n_ptr >= max_ptr)
839 max_ptr += max_ptr / 2;
840 ptr = (void **) xrealloc (ptr, max_ptr * sizeof (void *));
851 /* Create a new handler structure initialized with the handler label and
852 typeinfo fields passed in. */
854 struct handler_info *
855 get_new_handler (handler, typeinfo)
859 struct handler_info* ptr;
860 ptr = (struct handler_info *) xmalloc (sizeof (struct handler_info));
861 ptr->handler_label = handler;
862 ptr->handler_number = CODE_LABEL_NUMBER (handler);
863 ptr->type_info = typeinfo;
871 /* Find the index in function_eh_regions associated with a NOTE region. If
872 the region cannot be found, a -1 is returned. This should never happen! */
875 find_func_region (insn_region)
879 for (x = 0; x < current_func_eh_entry; x++)
880 if (function_eh_regions[x].range_number == insn_region)
886 /* Get a pointer to the first handler in an exception region's list. */
888 struct handler_info *
889 get_first_handler (region)
892 return function_eh_regions[find_func_region (region)].handlers;
895 /* Clean out the function_eh_region table and free all memory */
898 clear_function_eh_region ()
901 struct handler_info *ptr, *next;
902 for (x = 0; x < current_func_eh_entry; x++)
903 for (ptr = function_eh_regions[x].handlers; ptr != NULL; ptr = next)
908 free (function_eh_regions);
909 num_func_eh_entries = 0;
910 current_func_eh_entry = 0;
913 /* Make a duplicate of an exception region by copying all the handlers
914 for an exception region. Return the new handler index. The final
915 parameter is a routine which maps old labels to new ones. */
918 duplicate_eh_handlers (old_note_eh_region, new_note_eh_region, map)
919 int old_note_eh_region, new_note_eh_region;
920 rtx (*map) PARAMS ((rtx));
922 struct handler_info *ptr, *new_ptr;
923 int new_region, region;
925 region = find_func_region (old_note_eh_region);
927 fatal ("Cannot duplicate non-existant exception region.");
929 /* duplicate_eh_handlers may have been called during a symbol remap. */
930 new_region = find_func_region (new_note_eh_region);
931 if (new_region != -1)
934 new_region = new_eh_region_entry (new_note_eh_region, NULL_RTX);
936 ptr = function_eh_regions[region].handlers;
938 for ( ; ptr; ptr = ptr->next)
940 new_ptr = get_new_handler (map (ptr->handler_label), ptr->type_info);
941 add_new_handler (new_region, new_ptr);
948 /* Given a rethrow symbol, find the EH region number this is for. */
950 eh_region_from_symbol (sym)
954 if (sym == last_rethrow_symbol)
956 for (x = 0; x < current_func_eh_entry; x++)
957 if (function_eh_regions[x].rethrow_label == sym)
958 return function_eh_regions[x].range_number;
963 /* When inlining/unrolling, we have to map the symbols passed to
964 __rethrow as well. This performs the remap. If a symbol isn't foiund,
965 the original one is returned. This is not an efficient routine,
966 so don't call it on everything!! */
968 rethrow_symbol_map (sym, map)
970 rtx (*map) PARAMS ((rtx));
973 for (x = 0; x < current_func_eh_entry; x++)
974 if (function_eh_regions[x].rethrow_label == sym)
976 /* We've found the original region, now lets determine which region
978 rtx l1 = function_eh_regions[x].handlers->handler_label;
980 y = CODE_LABEL_NUMBER (l2); /* This is the new region number */
981 x = find_func_region (y); /* Get the new permanent region */
982 if (x == -1) /* Hmm, Doesn't exist yet */
984 x = duplicate_eh_handlers (CODE_LABEL_NUMBER (l1), y, map);
985 /* Since we're mapping it, it must be used. */
986 function_eh_regions[x].rethrow_ref = 1;
988 return function_eh_regions[x].rethrow_label;
994 rethrow_used (region)
997 if (flag_new_exceptions)
999 int ret = function_eh_regions[find_func_region (region)].rethrow_ref;
1006 /* Routine to see if exception handling is turned on.
1007 DO_WARN is non-zero if we want to inform the user that exception
1008 handling is turned off.
1010 This is used to ensure that -fexceptions has been specified if the
1011 compiler tries to use any exception-specific functions. */
1017 if (! flag_exceptions)
1019 static int warned = 0;
1020 if (! warned && do_warn)
1022 error ("exception handling disabled, use -fexceptions to enable");
1030 /* Given a return address in ADDR, determine the address we should use
1031 to find the corresponding EH region. */
1034 eh_outer_context (addr)
1037 /* First mask out any unwanted bits. */
1038 #ifdef MASK_RETURN_ADDR
1039 expand_and (addr, MASK_RETURN_ADDR, addr);
1042 /* Then adjust to find the real return address. */
1043 #if defined (RETURN_ADDR_OFFSET)
1044 addr = plus_constant (addr, RETURN_ADDR_OFFSET);
1050 /* Start a new exception region for a region of code that has a
1051 cleanup action and push the HANDLER for the region onto
1052 protect_list. All of the regions created with add_partial_entry
1053 will be ended when end_protect_partials is invoked. */
1056 add_partial_entry (handler)
1059 expand_eh_region_start ();
1061 /* Make sure the entry is on the correct obstack. */
1062 push_obstacks_nochange ();
1063 resume_temporary_allocation ();
1065 /* Because this is a cleanup action, we may have to protect the handler
1066 with __terminate. */
1067 handler = protect_with_terminate (handler);
1069 protect_list = tree_cons (NULL_TREE, handler, protect_list);
1073 /* Emit code to get EH context to current function. */
1076 call_get_eh_context ()
1081 if (fn == NULL_TREE)
1084 fn = get_identifier ("__get_eh_context");
1085 push_obstacks_nochange ();
1086 end_temporary_allocation ();
1087 fntype = build_pointer_type (build_pointer_type
1088 (build_pointer_type (void_type_node)));
1089 fntype = build_function_type (fntype, NULL_TREE);
1090 fn = build_decl (FUNCTION_DECL, fn, fntype);
1091 DECL_EXTERNAL (fn) = 1;
1092 TREE_PUBLIC (fn) = 1;
1093 DECL_ARTIFICIAL (fn) = 1;
1094 TREE_READONLY (fn) = 1;
1095 make_decl_rtl (fn, NULL_PTR, 1);
1096 assemble_external (fn);
1100 expr = build1 (ADDR_EXPR, build_pointer_type (TREE_TYPE (fn)), fn);
1101 expr = build (CALL_EXPR, TREE_TYPE (TREE_TYPE (fn)),
1102 expr, NULL_TREE, NULL_TREE);
1103 TREE_SIDE_EFFECTS (expr) = 1;
1105 return copy_to_reg (expand_expr (expr, NULL_RTX, VOIDmode, 0));
1108 /* Get a reference to the EH context.
1109 We will only generate a register for the current function EH context here,
1110 and emit a USE insn to mark that this is a EH context register.
1112 Later, emit_eh_context will emit needed call to __get_eh_context
1113 in libgcc2, and copy the value to the register we have generated. */
1118 if (current_function_ehc == 0)
1122 current_function_ehc = gen_reg_rtx (Pmode);
1124 insn = gen_rtx_USE (GET_MODE (current_function_ehc),
1125 current_function_ehc);
1126 insn = emit_insn_before (insn, get_first_nonparm_insn ());
1129 = gen_rtx_EXPR_LIST (REG_EH_CONTEXT, current_function_ehc,
1132 return current_function_ehc;
1135 /* Get a reference to the dynamic handler chain. It points to the
1136 pointer to the next element in the dynamic handler chain. It ends
1137 when there are no more elements in the dynamic handler chain, when
1138 the value is &top_elt from libgcc2.c. Immediately after the
1139 pointer, is an area suitable for setjmp/longjmp when
1140 DONT_USE_BUILTIN_SETJMP is defined, and an area suitable for
1141 __builtin_setjmp/__builtin_longjmp when DONT_USE_BUILTIN_SETJMP
1145 get_dynamic_handler_chain ()
1147 rtx ehc, dhc, result;
1149 ehc = get_eh_context ();
1151 /* This is the offset of dynamic_handler_chain in the eh_context struct
1152 declared in eh-common.h. If its location is change, change this offset */
1153 dhc = plus_constant (ehc, POINTER_SIZE / BITS_PER_UNIT);
1155 result = copy_to_reg (dhc);
1157 /* We don't want a copy of the dcc, but rather, the single dcc. */
1158 return gen_rtx_MEM (Pmode, result);
1161 /* Get a reference to the dynamic cleanup chain. It points to the
1162 pointer to the next element in the dynamic cleanup chain.
1163 Immediately after the pointer, are two Pmode variables, one for a
1164 pointer to a function that performs the cleanup action, and the
1165 second, the argument to pass to that function. */
1168 get_dynamic_cleanup_chain ()
1170 rtx dhc, dcc, result;
1172 dhc = get_dynamic_handler_chain ();
1173 dcc = plus_constant (dhc, POINTER_SIZE / BITS_PER_UNIT);
1175 result = copy_to_reg (dcc);
1177 /* We don't want a copy of the dcc, but rather, the single dcc. */
1178 return gen_rtx_MEM (Pmode, result);
1181 #ifdef DONT_USE_BUILTIN_SETJMP
1182 /* Generate code to evaluate X and jump to LABEL if the value is nonzero.
1183 LABEL is an rtx of code CODE_LABEL, in this function. */
1186 jumpif_rtx (x, label)
1190 jumpif (make_tree (type_for_mode (GET_MODE (x), 0), x), label);
1194 /* Start a dynamic cleanup on the EH runtime dynamic cleanup stack.
1195 We just need to create an element for the cleanup list, and push it
1198 A dynamic cleanup is a cleanup action implied by the presence of an
1199 element on the EH runtime dynamic cleanup stack that is to be
1200 performed when an exception is thrown. The cleanup action is
1201 performed by __sjthrow when an exception is thrown. Only certain
1202 actions can be optimized into dynamic cleanup actions. For the
1203 restrictions on what actions can be performed using this routine,
1204 see expand_eh_region_start_tree. */
1207 start_dynamic_cleanup (func, arg)
1212 rtx new_func, new_arg;
1216 /* We allocate enough room for a pointer to the function, and
1220 /* XXX, FIXME: The stack space allocated this way is too long lived,
1221 but there is no allocation routine that allocates at the level of
1222 the last binding contour. */
1223 buf = assign_stack_local (BLKmode,
1224 GET_MODE_SIZE (Pmode)*(size+1),
1227 buf = change_address (buf, Pmode, NULL_RTX);
1229 /* Store dcc into the first word of the newly allocated buffer. */
1231 dcc = get_dynamic_cleanup_chain ();
1232 emit_move_insn (buf, dcc);
1234 /* Store func and arg into the cleanup list element. */
1236 new_func = gen_rtx_MEM (Pmode, plus_constant (XEXP (buf, 0),
1237 GET_MODE_SIZE (Pmode)));
1238 new_arg = gen_rtx_MEM (Pmode, plus_constant (XEXP (buf, 0),
1239 GET_MODE_SIZE (Pmode)*2));
1240 x = expand_expr (func, new_func, Pmode, 0);
1242 emit_move_insn (new_func, x);
1244 x = expand_expr (arg, new_arg, Pmode, 0);
1246 emit_move_insn (new_arg, x);
1248 /* Update the cleanup chain. */
1250 x = force_operand (XEXP (buf, 0), dcc);
1252 emit_move_insn (dcc, x);
1255 /* Emit RTL to start a dynamic handler on the EH runtime dynamic
1256 handler stack. This should only be used by expand_eh_region_start
1257 or expand_eh_region_start_tree. */
1260 start_dynamic_handler ()
1266 #ifndef DONT_USE_BUILTIN_SETJMP
1267 /* The number of Pmode words for the setjmp buffer, when using the
1268 builtin setjmp/longjmp, see expand_builtin, case
1269 BUILT_IN_LONGJMP. */
1273 size = JMP_BUF_SIZE;
1275 /* Should be large enough for most systems, if it is not,
1276 JMP_BUF_SIZE should be defined with the proper value. It will
1277 also tend to be larger than necessary for most systems, a more
1278 optimal port will define JMP_BUF_SIZE. */
1279 size = FIRST_PSEUDO_REGISTER+2;
1282 /* XXX, FIXME: The stack space allocated this way is too long lived,
1283 but there is no allocation routine that allocates at the level of
1284 the last binding contour. */
1285 arg = assign_stack_local (BLKmode,
1286 GET_MODE_SIZE (Pmode)*(size+1),
1289 arg = change_address (arg, Pmode, NULL_RTX);
1291 /* Store dhc into the first word of the newly allocated buffer. */
1293 dhc = get_dynamic_handler_chain ();
1294 dcc = gen_rtx_MEM (Pmode, plus_constant (XEXP (arg, 0),
1295 GET_MODE_SIZE (Pmode)));
1296 emit_move_insn (arg, dhc);
1298 /* Zero out the start of the cleanup chain. */
1299 emit_move_insn (dcc, const0_rtx);
1301 /* The jmpbuf starts two words into the area allocated. */
1302 buf = plus_constant (XEXP (arg, 0), GET_MODE_SIZE (Pmode)*2);
1304 #ifdef DONT_USE_BUILTIN_SETJMP
1305 x = emit_library_call_value (setjmp_libfunc, NULL_RTX, 1, SImode, 1,
1307 /* If we come back here for a catch, transfer control to the handler. */
1308 jumpif_rtx (x, ehstack.top->entry->exception_handler_label);
1311 /* A label to continue execution for the no exception case. */
1312 rtx noex = gen_label_rtx();
1313 x = expand_builtin_setjmp (buf, NULL_RTX, noex,
1314 ehstack.top->entry->exception_handler_label);
1319 /* We are committed to this, so update the handler chain. */
1321 emit_move_insn (dhc, force_operand (XEXP (arg, 0), NULL_RTX));
1324 /* Start an exception handling region for the given cleanup action.
1325 All instructions emitted after this point are considered to be part
1326 of the region until expand_eh_region_end is invoked. CLEANUP is
1327 the cleanup action to perform. The return value is true if the
1328 exception region was optimized away. If that case,
1329 expand_eh_region_end does not need to be called for this cleanup,
1332 This routine notices one particular common case in C++ code
1333 generation, and optimizes it so as to not need the exception
1334 region. It works by creating a dynamic cleanup action, instead of
1335 a using an exception region. */
1338 expand_eh_region_start_tree (decl, cleanup)
1342 /* This is the old code. */
1346 /* The optimization only applies to actions protected with
1347 terminate, and only applies if we are using the setjmp/longjmp
1349 if (exceptions_via_longjmp
1350 && protect_cleanup_actions_with_terminate)
1355 /* Ignore any UNSAVE_EXPR. */
1356 if (TREE_CODE (cleanup) == UNSAVE_EXPR)
1357 cleanup = TREE_OPERAND (cleanup, 0);
1359 /* Further, it only applies if the action is a call, if there
1360 are 2 arguments, and if the second argument is 2. */
1362 if (TREE_CODE (cleanup) == CALL_EXPR
1363 && (args = TREE_OPERAND (cleanup, 1))
1364 && (func = TREE_OPERAND (cleanup, 0))
1365 && (arg = TREE_VALUE (args))
1366 && (args = TREE_CHAIN (args))
1368 /* is the second argument 2? */
1369 && TREE_CODE (TREE_VALUE (args)) == INTEGER_CST
1370 && TREE_INT_CST_LOW (TREE_VALUE (args)) == 2
1371 && TREE_INT_CST_HIGH (TREE_VALUE (args)) == 0
1373 /* Make sure there are no other arguments. */
1374 && TREE_CHAIN (args) == NULL_TREE)
1376 /* Arrange for returns and gotos to pop the entry we make on the
1377 dynamic cleanup stack. */
1378 expand_dcc_cleanup (decl);
1379 start_dynamic_cleanup (func, arg);
1384 expand_eh_region_start_for_decl (decl);
1385 ehstack.top->entry->finalization = cleanup;
1390 /* Just like expand_eh_region_start, except if a cleanup action is
1391 entered on the cleanup chain, the TREE_PURPOSE of the element put
1392 on the chain is DECL. DECL should be the associated VAR_DECL, if
1393 any, otherwise it should be NULL_TREE. */
1396 expand_eh_region_start_for_decl (decl)
1401 /* This is the old code. */
1405 /* We need a new block to record the start and end of the
1406 dynamic handler chain. We also want to prevent jumping into
1408 expand_start_bindings (0);
1410 /* But we don't need or want a new temporary level. */
1413 /* Mark this block as created by expand_eh_region_start. This
1414 is so that we can pop the block with expand_end_bindings
1416 mark_block_as_eh_region ();
1418 if (exceptions_via_longjmp)
1420 /* Arrange for returns and gotos to pop the entry we make on the
1421 dynamic handler stack. */
1422 expand_dhc_cleanup (decl);
1425 push_eh_entry (&ehstack);
1426 note = emit_note (NULL_PTR, NOTE_INSN_EH_REGION_BEG);
1427 NOTE_BLOCK_NUMBER (note)
1428 = CODE_LABEL_NUMBER (ehstack.top->entry->exception_handler_label);
1429 if (exceptions_via_longjmp)
1430 start_dynamic_handler ();
1433 /* Start an exception handling region. All instructions emitted after
1434 this point are considered to be part of the region until
1435 expand_eh_region_end is invoked. */
1438 expand_eh_region_start ()
1440 expand_eh_region_start_for_decl (NULL_TREE);
1443 /* End an exception handling region. The information about the region
1444 is found on the top of ehstack.
1446 HANDLER is either the cleanup for the exception region, or if we're
1447 marking the end of a try block, HANDLER is integer_zero_node.
1449 HANDLER will be transformed to rtl when expand_leftover_cleanups
1453 expand_eh_region_end (handler)
1456 struct eh_entry *entry;
1463 entry = pop_eh_entry (&ehstack);
1465 note = emit_note (NULL_PTR, NOTE_INSN_EH_REGION_END);
1466 ret = NOTE_BLOCK_NUMBER (note)
1467 = CODE_LABEL_NUMBER (entry->exception_handler_label);
1468 if (exceptions_via_longjmp == 0 && ! flag_new_exceptions
1469 /* We share outer_context between regions; only emit it once. */
1470 && INSN_UID (entry->outer_context) == 0)
1474 label = gen_label_rtx ();
1477 /* Emit a label marking the end of this exception region that
1478 is used for rethrowing into the outer context. */
1479 emit_label (entry->outer_context);
1480 expand_internal_throw ();
1485 entry->finalization = handler;
1487 /* create region entry in final exception table */
1488 r = new_eh_region_entry (NOTE_BLOCK_NUMBER (note), entry->rethrow_label);
1490 enqueue_eh_entry (&ehqueue, entry);
1492 /* If we have already started ending the bindings, don't recurse. */
1493 if (is_eh_region ())
1495 /* Because we don't need or want a new temporary level and
1496 because we didn't create one in expand_eh_region_start,
1497 create a fake one now to avoid removing one in
1498 expand_end_bindings. */
1501 mark_block_as_not_eh_region ();
1503 expand_end_bindings (NULL_TREE, 0, 0);
1507 /* End the EH region for a goto fixup. We only need them in the region-based
1511 expand_fixup_region_start ()
1513 if (! doing_eh (0) || exceptions_via_longjmp)
1516 expand_eh_region_start ();
1519 /* End the EH region for a goto fixup. CLEANUP is the cleanup we just
1520 expanded; to avoid running it twice if it throws, we look through the
1521 ehqueue for a matching region and rethrow from its outer_context. */
1524 expand_fixup_region_end (cleanup)
1527 struct eh_node *node;
1530 if (! doing_eh (0) || exceptions_via_longjmp)
1533 for (node = ehstack.top; node && node->entry->finalization != cleanup; )
1536 for (node = ehqueue.head; node && node->entry->finalization != cleanup; )
1541 /* If the outer context label has not been issued yet, we don't want
1542 to issue it as a part of this region, unless this is the
1543 correct region for the outer context. If we did, then the label for
1544 the outer context will be WITHIN the begin/end labels,
1545 and we could get an infinte loop when it tried to rethrow, or just
1546 generally incorrect execution following a throw. */
1548 if (flag_new_exceptions)
1551 dont_issue = ((INSN_UID (node->entry->outer_context) == 0)
1552 && (ehstack.top->entry != node->entry));
1554 ehstack.top->entry->outer_context = node->entry->outer_context;
1556 /* Since we are rethrowing to the OUTER region, we know we don't need
1557 a jump around sequence for this region, so we'll pretend the outer
1558 context label has been issued by setting INSN_UID to 1, then clearing
1559 it again afterwards. */
1562 INSN_UID (node->entry->outer_context) = 1;
1564 /* Just rethrow. size_zero_node is just a NOP. */
1565 expand_eh_region_end (size_zero_node);
1568 INSN_UID (node->entry->outer_context) = 0;
1571 /* If we are using the setjmp/longjmp EH codegen method, we emit a
1574 Otherwise, we emit a call to __throw and note that we threw
1575 something, so we know we need to generate the necessary code for
1578 Before invoking throw, the __eh_pc variable must have been set up
1579 to contain the PC being thrown from. This address is used by
1580 __throw to determine which exception region (if any) is
1581 responsible for handling the exception. */
1586 if (exceptions_via_longjmp)
1588 emit_library_call (sjthrow_libfunc, 0, VOIDmode, 0);
1592 #ifdef JUMP_TO_THROW
1593 emit_indirect_jump (throw_libfunc);
1595 emit_library_call (throw_libfunc, 0, VOIDmode, 0);
1601 /* Throw the current exception. If appropriate, this is done by jumping
1602 to the next handler. */
1605 expand_internal_throw ()
1610 /* Called from expand_exception_blocks and expand_end_catch_block to
1611 emit any pending handlers/cleanups queued from expand_eh_region_end. */
1614 expand_leftover_cleanups ()
1616 struct eh_entry *entry;
1618 while ((entry = dequeue_eh_entry (&ehqueue)) != 0)
1622 /* A leftover try block. Shouldn't be one here. */
1623 if (entry->finalization == integer_zero_node)
1626 /* Output the label for the start of the exception handler. */
1628 receive_exception_label (entry->exception_handler_label);
1630 /* register a handler for this cleanup region */
1632 find_func_region (CODE_LABEL_NUMBER (entry->exception_handler_label)),
1633 get_new_handler (entry->exception_handler_label, NULL));
1635 /* And now generate the insns for the handler. */
1636 expand_expr (entry->finalization, const0_rtx, VOIDmode, 0);
1638 prev = get_last_insn ();
1639 if (prev == NULL || GET_CODE (prev) != BARRIER)
1640 /* Emit code to throw to the outer context if we fall off
1641 the end of the handler. */
1642 expand_rethrow (entry->outer_context);
1644 do_pending_stack_adjust ();
1649 /* Called at the start of a block of try statements. */
1651 expand_start_try_stmts ()
1656 expand_eh_region_start ();
1659 /* Called to begin a catch clause. The parameter is the object which
1660 will be passed to the runtime type check routine. */
1662 start_catch_handler (rtime)
1666 int insn_region_num;
1667 int eh_region_entry;
1672 handler_label = catchstack.top->entry->exception_handler_label;
1673 insn_region_num = CODE_LABEL_NUMBER (handler_label);
1674 eh_region_entry = find_func_region (insn_region_num);
1676 /* If we've already issued this label, pick a new one */
1677 if (catchstack.top->entry->label_used)
1678 handler_label = gen_exception_label ();
1680 catchstack.top->entry->label_used = 1;
1682 receive_exception_label (handler_label);
1684 add_new_handler (eh_region_entry, get_new_handler (handler_label, rtime));
1686 if (flag_new_exceptions && ! exceptions_via_longjmp)
1689 /* Under the old mechanism, as well as setjmp/longjmp, we need to
1690 issue code to compare 'rtime' to the value in eh_info, via the
1691 matching function in eh_info. If its is false, we branch around
1692 the handler we are about to issue. */
1694 if (rtime != NULL_TREE && rtime != CATCH_ALL_TYPE)
1696 rtx call_rtx, rtime_address;
1698 if (catchstack.top->entry->false_label != NULL_RTX)
1700 error ("Never issued previous false_label");
1703 catchstack.top->entry->false_label = gen_exception_label ();
1705 rtime_address = expand_expr (rtime, NULL_RTX, Pmode, EXPAND_INITIALIZER);
1706 #ifdef POINTERS_EXTEND_UNSIGNED
1707 rtime_address = convert_memory_address (Pmode, rtime_address);
1709 rtime_address = force_reg (Pmode, rtime_address);
1711 /* Now issue the call, and branch around handler if needed */
1712 call_rtx = emit_library_call_value (eh_rtime_match_libfunc, NULL_RTX,
1713 0, SImode, 1, rtime_address, Pmode);
1715 /* Did the function return true? */
1716 emit_cmp_and_jump_insns (call_rtx, const0_rtx, EQ, NULL_RTX,
1717 GET_MODE (call_rtx), 0, 0,
1718 catchstack.top->entry->false_label);
1722 /* Called to end a catch clause. If we aren't using the new exception
1723 model tabel mechanism, we need to issue the branch-around label
1724 for the end of the catch block. */
1727 end_catch_handler ()
1732 if (flag_new_exceptions && ! exceptions_via_longjmp)
1738 /* A NULL label implies the catch clause was a catch all or cleanup */
1739 if (catchstack.top->entry->false_label == NULL_RTX)
1742 emit_label (catchstack.top->entry->false_label);
1743 catchstack.top->entry->false_label = NULL_RTX;
1746 /* Generate RTL for the start of a group of catch clauses.
1748 It is responsible for starting a new instruction sequence for the
1749 instructions in the catch block, and expanding the handlers for the
1750 internally-generated exception regions nested within the try block
1751 corresponding to this catch block. */
1754 expand_start_all_catch ()
1756 struct eh_entry *entry;
1763 outer_context = ehstack.top->entry->outer_context;
1765 /* End the try block. */
1766 expand_eh_region_end (integer_zero_node);
1768 emit_line_note (input_filename, lineno);
1769 label = build_decl (LABEL_DECL, NULL_TREE, NULL_TREE);
1771 /* The label for the exception handling block that we will save.
1772 This is Lresume in the documentation. */
1773 expand_label (label);
1775 /* Push the label that points to where normal flow is resumed onto
1776 the top of the label stack. */
1777 push_label_entry (&caught_return_label_stack, NULL_RTX, label);
1779 /* Start a new sequence for all the catch blocks. We will add this
1780 to the global sequence catch_clauses when we have completed all
1781 the handlers in this handler-seq. */
1784 entry = dequeue_eh_entry (&ehqueue);
1785 for ( ; entry->finalization != integer_zero_node;
1786 entry = dequeue_eh_entry (&ehqueue))
1790 /* Emit the label for the cleanup handler for this region, and
1791 expand the code for the handler.
1793 Note that a catch region is handled as a side-effect here;
1794 for a try block, entry->finalization will contain
1795 integer_zero_node, so no code will be generated in the
1796 expand_expr call below. But, the label for the handler will
1797 still be emitted, so any code emitted after this point will
1798 end up being the handler. */
1800 receive_exception_label (entry->exception_handler_label);
1802 /* register a handler for this cleanup region */
1804 find_func_region (CODE_LABEL_NUMBER (entry->exception_handler_label)),
1805 get_new_handler (entry->exception_handler_label, NULL));
1807 /* And now generate the insns for the cleanup handler. */
1808 expand_expr (entry->finalization, const0_rtx, VOIDmode, 0);
1810 prev = get_last_insn ();
1811 if (prev == NULL || GET_CODE (prev) != BARRIER)
1812 /* Code to throw out to outer context when we fall off end
1813 of the handler. We can't do this here for catch blocks,
1814 so it's done in expand_end_all_catch instead. */
1815 expand_rethrow (entry->outer_context);
1817 do_pending_stack_adjust ();
1821 /* At this point, all the cleanups are done, and the ehqueue now has
1822 the current exception region at its head. We dequeue it, and put it
1823 on the catch stack. */
1825 push_entry (&catchstack, entry);
1827 /* If we are not doing setjmp/longjmp EH, because we are reordered
1828 out of line, we arrange to rethrow in the outer context. We need to
1829 do this because we are not physically within the region, if any, that
1830 logically contains this catch block. */
1831 if (! exceptions_via_longjmp)
1833 expand_eh_region_start ();
1834 ehstack.top->entry->outer_context = outer_context;
1839 /* Finish up the catch block. At this point all the insns for the
1840 catch clauses have already been generated, so we only have to add
1841 them to the catch_clauses list. We also want to make sure that if
1842 we fall off the end of the catch clauses that we rethrow to the
1846 expand_end_all_catch ()
1848 rtx new_catch_clause;
1849 struct eh_entry *entry;
1854 /* Dequeue the current catch clause region. */
1855 entry = pop_eh_entry (&catchstack);
1858 if (! exceptions_via_longjmp)
1860 rtx outer_context = ehstack.top->entry->outer_context;
1862 /* Finish the rethrow region. size_zero_node is just a NOP. */
1863 expand_eh_region_end (size_zero_node);
1864 /* New exceptions handling models will never have a fall through
1865 of a catch clause */
1866 if (!flag_new_exceptions)
1867 expand_rethrow (outer_context);
1870 expand_rethrow (NULL_RTX);
1872 /* Code to throw out to outer context, if we fall off end of catch
1873 handlers. This is rethrow (Lresume, same id, same obj) in the
1874 documentation. We use Lresume because we know that it will throw
1875 to the correct context.
1877 In other words, if the catch handler doesn't exit or return, we
1878 do a "throw" (using the address of Lresume as the point being
1879 thrown from) so that the outer EH region can then try to process
1882 /* Now we have the complete catch sequence. */
1883 new_catch_clause = get_insns ();
1886 /* This level of catch blocks is done, so set up the successful
1887 catch jump label for the next layer of catch blocks. */
1888 pop_label_entry (&caught_return_label_stack);
1889 pop_label_entry (&outer_context_label_stack);
1891 /* Add the new sequence of catches to the main one for this function. */
1892 push_to_sequence (catch_clauses);
1893 emit_insns (new_catch_clause);
1894 catch_clauses = get_insns ();
1897 /* Here we fall through into the continuation code. */
1900 /* Rethrow from the outer context LABEL. */
1903 expand_rethrow (label)
1906 if (exceptions_via_longjmp)
1909 if (flag_new_exceptions)
1913 if (label == NULL_RTX)
1914 label = last_rethrow_symbol;
1915 emit_library_call (rethrow_libfunc, 0, VOIDmode, 1, label, Pmode);
1916 region = find_func_region (eh_region_from_symbol (label));
1917 function_eh_regions[region].rethrow_ref = 1;
1919 /* Search backwards for the actual call insn. */
1920 insn = get_last_insn ();
1921 while (GET_CODE (insn) != CALL_INSN)
1922 insn = PREV_INSN (insn);
1923 delete_insns_since (insn);
1925 /* Mark the label/symbol on the call. */
1926 REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_EH_RETHROW, label,
1934 /* End all the pending exception regions on protect_list. The handlers
1935 will be emitted when expand_leftover_cleanups is invoked. */
1938 end_protect_partials ()
1940 while (protect_list)
1942 expand_eh_region_end (TREE_VALUE (protect_list));
1943 protect_list = TREE_CHAIN (protect_list);
1947 /* Arrange for __terminate to be called if there is an unhandled throw
1951 protect_with_terminate (e)
1954 /* We only need to do this when using setjmp/longjmp EH and the
1955 language requires it, as otherwise we protect all of the handlers
1956 at once, if we need to. */
1957 if (exceptions_via_longjmp && protect_cleanup_actions_with_terminate)
1959 tree handler, result;
1961 /* All cleanups must be on the function_obstack. */
1962 push_obstacks_nochange ();
1963 resume_temporary_allocation ();
1965 handler = make_node (RTL_EXPR);
1966 TREE_TYPE (handler) = void_type_node;
1967 RTL_EXPR_RTL (handler) = const0_rtx;
1968 TREE_SIDE_EFFECTS (handler) = 1;
1969 start_sequence_for_rtl_expr (handler);
1971 emit_library_call (terminate_libfunc, 0, VOIDmode, 0);
1974 RTL_EXPR_SEQUENCE (handler) = get_insns ();
1977 result = build (TRY_CATCH_EXPR, TREE_TYPE (e), e, handler);
1978 TREE_SIDE_EFFECTS (result) = TREE_SIDE_EFFECTS (e);
1979 TREE_THIS_VOLATILE (result) = TREE_THIS_VOLATILE (e);
1980 TREE_READONLY (result) = TREE_READONLY (e);
1990 /* The exception table that we build that is used for looking up and
1991 dispatching exceptions, the current number of entries, and its
1992 maximum size before we have to extend it.
1994 The number in eh_table is the code label number of the exception
1995 handler for the region. This is added by add_eh_table_entry and
1996 used by output_exception_table_entry. */
1998 static int *eh_table = NULL;
1999 static int eh_table_size = 0;
2000 static int eh_table_max_size = 0;
2002 /* Note the need for an exception table entry for region N. If we
2003 don't need to output an explicit exception table, avoid all of the
2006 Called from final_scan_insn when a NOTE_INSN_EH_REGION_BEG is seen.
2007 (Or NOTE_INSN_EH_REGION_END sometimes)
2008 N is the NOTE_BLOCK_NUMBER of the note, which comes from the code
2009 label number of the exception handler for the region. */
2012 add_eh_table_entry (n)
2015 #ifndef OMIT_EH_TABLE
2016 if (eh_table_size >= eh_table_max_size)
2020 eh_table_max_size += eh_table_max_size>>1;
2022 if (eh_table_max_size < 0)
2025 eh_table = (int *) xrealloc (eh_table,
2026 eh_table_max_size * sizeof (int));
2030 eh_table_max_size = 252;
2031 eh_table = (int *) xmalloc (eh_table_max_size * sizeof (int));
2034 eh_table[eh_table_size++] = n;
2038 /* Return a non-zero value if we need to output an exception table.
2040 On some platforms, we don't have to output a table explicitly.
2041 This routine doesn't mean we don't have one. */
2044 exception_table_p ()
2052 /* Output the entry of the exception table corresponding to the
2053 exception region numbered N to file FILE.
2055 N is the code label number corresponding to the handler of the
2059 output_exception_table_entry (file, n)
2065 struct handler_info *handler = get_first_handler (n);
2066 int index = find_func_region (n);
2069 /* form and emit the rethrow label, if needed */
2070 rethrow = function_eh_regions[index].rethrow_label;
2071 if (rethrow != NULL_RTX && !flag_new_exceptions)
2073 if (rethrow != NULL_RTX && handler == NULL)
2074 if (! function_eh_regions[index].rethrow_ref)
2078 for ( ; handler != NULL || rethrow != NULL_RTX; handler = handler->next)
2080 /* rethrow label should indicate the LAST entry for a region */
2081 if (rethrow != NULL_RTX && (handler == NULL || handler->next == NULL))
2083 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", n);
2084 assemble_label(buf);
2088 ASM_GENERATE_INTERNAL_LABEL (buf, "LEHB", n);
2089 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
2090 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
2092 ASM_GENERATE_INTERNAL_LABEL (buf, "LEHE", n);
2093 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
2094 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
2096 if (handler == NULL)
2097 assemble_integer (GEN_INT (0), POINTER_SIZE / BITS_PER_UNIT, 1);
2100 ASM_GENERATE_INTERNAL_LABEL (buf, "L", handler->handler_number);
2101 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
2102 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
2105 if (flag_new_exceptions)
2107 if (handler == NULL || handler->type_info == NULL)
2108 assemble_integer (const0_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
2110 if (handler->type_info == CATCH_ALL_TYPE)
2111 assemble_integer (GEN_INT (CATCH_ALL_TYPE),
2112 POINTER_SIZE / BITS_PER_UNIT, 1);
2114 output_constant ((tree)(handler->type_info),
2115 POINTER_SIZE / BITS_PER_UNIT);
2117 putc ('\n', file); /* blank line */
2118 /* We only output the first label under the old scheme */
2119 if (! flag_new_exceptions || handler == NULL)
2124 /* Output the exception table if we have and need one. */
2126 static short language_code = 0;
2127 static short version_code = 0;
2129 /* This routine will set the language code for exceptions. */
2131 set_exception_lang_code (code)
2134 language_code = code;
2137 /* This routine will set the language version code for exceptions. */
2139 set_exception_version_code (code)
2142 version_code = code;
2147 output_exception_table ()
2151 extern FILE *asm_out_file;
2153 if (! doing_eh (0) || ! eh_table)
2156 exception_section ();
2158 /* Beginning marker for table. */
2159 assemble_align (GET_MODE_ALIGNMENT (ptr_mode));
2160 assemble_label ("__EXCEPTION_TABLE__");
2162 if (flag_new_exceptions)
2164 assemble_integer (GEN_INT (NEW_EH_RUNTIME),
2165 POINTER_SIZE / BITS_PER_UNIT, 1);
2166 assemble_integer (GEN_INT (language_code), 2 , 1);
2167 assemble_integer (GEN_INT (version_code), 2 , 1);
2169 /* Add enough padding to make sure table aligns on a pointer boundry. */
2170 i = GET_MODE_ALIGNMENT (ptr_mode) / BITS_PER_UNIT - 4;
2171 for ( ; i < 0; i = i + GET_MODE_ALIGNMENT (ptr_mode) / BITS_PER_UNIT)
2174 assemble_integer (const0_rtx, i , 1);
2176 /* Generate the label for offset calculations on rethrows */
2177 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", 0);
2178 assemble_label(buf);
2181 for (i = 0; i < eh_table_size; ++i)
2182 output_exception_table_entry (asm_out_file, eh_table[i]);
2185 clear_function_eh_region ();
2187 /* Ending marker for table. */
2188 /* Generate the label for end of table. */
2189 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", CODE_LABEL_NUMBER (final_rethrow));
2190 assemble_label(buf);
2191 assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
2193 /* for binary compatability, the old __throw checked the second
2194 position for a -1, so we should output at least 2 -1's */
2195 if (! flag_new_exceptions)
2196 assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
2198 putc ('\n', asm_out_file); /* blank line */
2201 /* Emit code to get EH context.
2203 We have to scan thru the code to find possible EH context registers.
2204 Inlined functions may use it too, and thus we'll have to be able
2207 This is done only if using exceptions_via_longjmp. */
2218 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2219 if (GET_CODE (insn) == INSN
2220 && GET_CODE (PATTERN (insn)) == USE)
2222 rtx reg = find_reg_note (insn, REG_EH_CONTEXT, 0);
2229 /* If this is the first use insn, emit the call here. This
2230 will always be at the top of our function, because if
2231 expand_inline_function notices a REG_EH_CONTEXT note, it
2232 adds a use insn to this function as well. */
2234 ehc = call_get_eh_context ();
2236 emit_move_insn (XEXP (reg, 0), ehc);
2237 insns = get_insns ();
2240 emit_insns_before (insns, insn);
2242 /* At -O0, we must make the context register stay alive so
2243 that the stupid.c register allocator doesn't get confused. */
2244 if (obey_regdecls != 0)
2246 insns = gen_rtx_USE (GET_MODE (XEXP (reg,0)), XEXP (reg,0));
2247 emit_insn_before (insns, get_last_insn ());
2253 /* Scan the current insns and build a list of handler labels. The
2254 resulting list is placed in the global variable exception_handler_labels.
2256 It is called after the last exception handling region is added to
2257 the current function (when the rtl is almost all built for the
2258 current function) and before the jump optimization pass. */
2261 find_exception_handler_labels ()
2265 exception_handler_labels = NULL_RTX;
2267 /* If we aren't doing exception handling, there isn't much to check. */
2271 /* For each start of a region, add its label to the list. */
2273 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2275 struct handler_info* ptr;
2276 if (GET_CODE (insn) == NOTE
2277 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2279 ptr = get_first_handler (NOTE_BLOCK_NUMBER (insn));
2280 for ( ; ptr; ptr = ptr->next)
2282 /* make sure label isn't in the list already */
2284 for (x = exception_handler_labels; x; x = XEXP (x, 1))
2285 if (XEXP (x, 0) == ptr->handler_label)
2288 exception_handler_labels = gen_rtx_EXPR_LIST (VOIDmode,
2289 ptr->handler_label, exception_handler_labels);
2295 /* Return a value of 1 if the parameter label number is an exception handler
2296 label. Return 0 otherwise. */
2299 is_exception_handler_label (lab)
2303 for (x = exception_handler_labels ; x ; x = XEXP (x, 1))
2304 if (lab == CODE_LABEL_NUMBER (XEXP (x, 0)))
2309 /* Perform sanity checking on the exception_handler_labels list.
2311 Can be called after find_exception_handler_labels is called to
2312 build the list of exception handlers for the current function and
2313 before we finish processing the current function. */
2316 check_exception_handler_labels ()
2320 /* If we aren't doing exception handling, there isn't much to check. */
2324 /* Make sure there is no more than 1 copy of a label */
2325 for (insn = exception_handler_labels; insn; insn = XEXP (insn, 1))
2328 for (insn2 = exception_handler_labels; insn2; insn2 = XEXP (insn2, 1))
2329 if (XEXP (insn, 0) == XEXP (insn2, 0))
2332 warning ("Counted %d copies of EH region %d in list.\n", count,
2333 CODE_LABEL_NUMBER (insn));
2338 /* Mark the children of NODE for GC. */
2342 struct eh_node *node;
2348 ggc_mark_rtx (node->entry->outer_context);
2349 ggc_mark_rtx (node->entry->exception_handler_label);
2350 ggc_mark_tree (node->entry->finalization);
2351 ggc_mark_rtx (node->entry->false_label);
2352 ggc_mark_rtx (node->entry->rethrow_label);
2354 node = node ->chain;
2358 /* Mark S for GC. */
2365 mark_eh_node (s->top);
2368 /* Mark Q for GC. */
2375 mark_eh_node (q->head);
2378 /* Mark NODE for GC. A label_node contains a union containing either
2379 a tree or an rtx. This label_node will contain a tree. */
2382 mark_tree_label_node (node)
2383 struct label_node *node;
2387 ggc_mark_tree (node->u.tlabel);
2392 /* Mark EH for GC. */
2396 struct eh_status *eh;
2398 mark_eh_stack (&eh->x_ehstack);
2399 mark_eh_stack (&eh->x_catchstack);
2400 mark_eh_queue (&eh->x_ehqueue);
2401 ggc_mark_rtx (eh->x_catch_clauses);
2403 lang_mark_false_label_stack (eh->x_false_label_stack);
2404 mark_tree_label_node (eh->x_caught_return_label_stack);
2406 ggc_mark_tree (eh->x_protect_list);
2407 ggc_mark_rtx (eh->ehc);
2408 ggc_mark_rtx (eh->x_eh_return_stub_label);
2411 /* Mark ARG (which is really a struct func_eh_entry**) for GC. */
2414 mark_func_eh_entry (arg)
2417 struct func_eh_entry *fee;
2418 struct handler_info *h;
2421 fee = *((struct func_eh_entry **) arg);
2423 for (i = 0; i < current_func_eh_entry; ++i)
2425 ggc_mark_rtx (fee->rethrow_label);
2426 for (h = fee->handlers; h; h = h->next)
2428 ggc_mark_rtx (h->handler_label);
2429 if (h->type_info != CATCH_ALL_TYPE)
2430 ggc_mark_tree ((tree) h->type_info);
2433 /* Skip to the next entry in the array. */
2438 /* This group of functions initializes the exception handling data
2439 structures at the start of the compilation, initializes the data
2440 structures at the start of a function, and saves and restores the
2441 exception handling data structures for the start/end of a nested
2444 /* Toplevel initialization for EH things. */
2449 first_rethrow_symbol = create_rethrow_ref (0);
2450 final_rethrow = gen_exception_label ();
2451 last_rethrow_symbol = create_rethrow_ref (CODE_LABEL_NUMBER (final_rethrow));
2453 ggc_add_rtx_root (&exception_handler_labels, 1);
2454 ggc_add_rtx_root (&eh_return_context, 1);
2455 ggc_add_rtx_root (&eh_return_stack_adjust, 1);
2456 ggc_add_rtx_root (&eh_return_handler, 1);
2457 ggc_add_rtx_root (&first_rethrow_symbol, 1);
2458 ggc_add_rtx_root (&final_rethrow, 1);
2459 ggc_add_rtx_root (&last_rethrow_symbol, 1);
2460 ggc_add_root (&function_eh_regions, 1, sizeof (function_eh_regions),
2461 mark_func_eh_entry);
2464 /* Initialize the per-function EH information. */
2467 init_eh_for_function ()
2469 current_function->eh = (struct eh_status *) xmalloc (sizeof (struct eh_status));
2473 ehqueue.head = ehqueue.tail = 0;
2474 catch_clauses = NULL_RTX;
2475 false_label_stack = 0;
2476 caught_return_label_stack = 0;
2477 protect_list = NULL_TREE;
2478 current_function_ehc = NULL_RTX;
2479 eh_return_context = NULL_RTX;
2480 eh_return_stack_adjust = NULL_RTX;
2481 eh_return_handler = NULL_RTX;
2482 eh_return_stub_label = NULL_RTX;
2485 /* This section is for the exception handling specific optimization
2486 pass. First are the internal routines, and then the main
2487 optimization pass. */
2489 /* Determine if the given INSN can throw an exception. */
2495 /* Calls can always potentially throw exceptions, unless they have
2496 a REG_EH_REGION note with a value of 0 or less. */
2497 if (GET_CODE (insn) == CALL_INSN)
2499 rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX);
2500 if (!note || XINT (XEXP (note, 0), 0) > 0)
2504 if (asynchronous_exceptions)
2506 /* If we wanted asynchronous exceptions, then everything but NOTEs
2507 and CODE_LABELs could throw. */
2508 if (GET_CODE (insn) != NOTE && GET_CODE (insn) != CODE_LABEL)
2515 /* Scan a exception region looking for the matching end and then
2516 remove it if possible. INSN is the start of the region, N is the
2517 region number, and DELETE_OUTER is to note if anything in this
2520 Regions are removed if they cannot possibly catch an exception.
2521 This is determined by invoking can_throw on each insn within the
2522 region; if can_throw returns true for any of the instructions, the
2523 region can catch an exception, since there is an insn within the
2524 region that is capable of throwing an exception.
2526 Returns the NOTE_INSN_EH_REGION_END corresponding to this region, or
2527 calls abort if it can't find one.
2529 Can abort if INSN is not a NOTE_INSN_EH_REGION_BEGIN, or if N doesn't
2530 correspond to the region number, or if DELETE_OUTER is NULL. */
2533 scan_region (insn, n, delete_outer)
2540 /* Assume we can delete the region. */
2543 /* Can't delete something which is rethrown to. */
2544 if (rethrow_used (n))
2547 if (insn == NULL_RTX
2548 || GET_CODE (insn) != NOTE
2549 || NOTE_LINE_NUMBER (insn) != NOTE_INSN_EH_REGION_BEG
2550 || NOTE_BLOCK_NUMBER (insn) != n
2551 || delete_outer == NULL)
2554 insn = NEXT_INSN (insn);
2556 /* Look for the matching end. */
2557 while (! (GET_CODE (insn) == NOTE
2558 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END))
2560 /* If anything can throw, we can't remove the region. */
2561 if (delete && can_throw (insn))
2566 /* Watch out for and handle nested regions. */
2567 if (GET_CODE (insn) == NOTE
2568 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2570 insn = scan_region (insn, NOTE_BLOCK_NUMBER (insn), &delete);
2573 insn = NEXT_INSN (insn);
2576 /* The _BEG/_END NOTEs must match and nest. */
2577 if (NOTE_BLOCK_NUMBER (insn) != n)
2580 /* If anything in this exception region can throw, we can throw. */
2585 /* Delete the start and end of the region. */
2586 delete_insn (start);
2589 /* We no longer removed labels here, since flow will now remove any
2590 handler which cannot be called any more. */
2593 /* Only do this part if we have built the exception handler
2595 if (exception_handler_labels)
2597 rtx x, *prev = &exception_handler_labels;
2599 /* Find it in the list of handlers. */
2600 for (x = exception_handler_labels; x; x = XEXP (x, 1))
2602 rtx label = XEXP (x, 0);
2603 if (CODE_LABEL_NUMBER (label) == n)
2605 /* If we are the last reference to the handler,
2607 if (--LABEL_NUSES (label) == 0)
2608 delete_insn (label);
2612 /* Remove it from the list of exception handler
2613 labels, if we are optimizing. If we are not, then
2614 leave it in the list, as we are not really going to
2615 remove the region. */
2616 *prev = XEXP (x, 1);
2623 prev = &XEXP (x, 1);
2631 /* Perform various interesting optimizations for exception handling
2634 We look for empty exception regions and make them go (away). The
2635 jump optimization code will remove the handler if nothing else uses
2639 exception_optimize ()
2644 /* Remove empty regions. */
2645 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2647 if (GET_CODE (insn) == NOTE
2648 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2650 /* Since scan_region will return the NOTE_INSN_EH_REGION_END
2651 insn, we will indirectly skip through all the insns
2652 inbetween. We are also guaranteed that the value of insn
2653 returned will be valid, as otherwise scan_region won't
2655 insn = scan_region (insn, NOTE_BLOCK_NUMBER (insn), &n);
2660 /* This function determines whether any of the exception regions in the
2661 current function are targets of a rethrow or not, and set the
2662 reference flag according. */
2664 update_rethrow_references ()
2668 int *saw_region, *saw_rethrow;
2670 if (!flag_new_exceptions)
2673 saw_region = (int *) alloca (current_func_eh_entry * sizeof (int));
2674 saw_rethrow = (int *) alloca (current_func_eh_entry * sizeof (int));
2675 bzero ((char *) saw_region, (current_func_eh_entry * sizeof (int)));
2676 bzero ((char *) saw_rethrow, (current_func_eh_entry * sizeof (int)));
2678 /* Determine what regions exist, and whether there are any rethrows
2679 to those regions or not. */
2680 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2681 if (GET_CODE (insn) == CALL_INSN)
2683 rtx note = find_reg_note (insn, REG_EH_RETHROW, NULL_RTX);
2686 region = eh_region_from_symbol (XEXP (note, 0));
2687 region = find_func_region (region);
2688 saw_rethrow[region] = 1;
2692 if (GET_CODE (insn) == NOTE)
2694 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2696 region = find_func_region (NOTE_BLOCK_NUMBER (insn));
2697 saw_region[region] = 1;
2701 /* For any regions we did see, set the referenced flag. */
2702 for (x = 0; x < current_func_eh_entry; x++)
2704 function_eh_regions[x].rethrow_ref = saw_rethrow[x];
2707 /* Various hooks for the DWARF 2 __throw routine. */
2709 /* Do any necessary initialization to access arbitrary stack frames.
2710 On the SPARC, this means flushing the register windows. */
2713 expand_builtin_unwind_init ()
2715 /* Set this so all the registers get saved in our frame; we need to be
2716 able to copy the saved values for any registers from frames we unwind. */
2717 current_function_has_nonlocal_label = 1;
2719 #ifdef SETUP_FRAME_ADDRESSES
2720 SETUP_FRAME_ADDRESSES ();
2724 /* Given a value extracted from the return address register or stack slot,
2725 return the actual address encoded in that value. */
2728 expand_builtin_extract_return_addr (addr_tree)
2731 rtx addr = expand_expr (addr_tree, NULL_RTX, Pmode, 0);
2732 return eh_outer_context (addr);
2735 /* Given an actual address in addr_tree, do any necessary encoding
2736 and return the value to be stored in the return address register or
2737 stack slot so the epilogue will return to that address. */
2740 expand_builtin_frob_return_addr (addr_tree)
2743 rtx addr = expand_expr (addr_tree, NULL_RTX, Pmode, 0);
2744 #ifdef RETURN_ADDR_OFFSET
2745 addr = plus_constant (addr, -RETURN_ADDR_OFFSET);
2750 /* Choose three registers for communication between the main body of
2751 __throw and the epilogue (or eh stub) and the exception handler.
2752 We must do this with hard registers because the epilogue itself
2753 will be generated after reload, at which point we may not reference
2756 The first passes the exception context to the handler. For this
2757 we use the return value register for a void*.
2759 The second holds the stack pointer value to be restored. For
2760 this we use the static chain register if it exists and is different
2761 from the previous, otherwise some arbitrary call-clobbered register.
2763 The third holds the address of the handler itself. Here we use
2764 some arbitrary call-clobbered register. */
2767 eh_regs (pcontext, psp, pra, outgoing)
2768 rtx *pcontext, *psp, *pra;
2771 rtx rcontext, rsp, rra;
2774 #ifdef FUNCTION_OUTGOING_VALUE
2776 rcontext = FUNCTION_OUTGOING_VALUE (build_pointer_type (void_type_node),
2777 current_function_decl);
2780 rcontext = FUNCTION_VALUE (build_pointer_type (void_type_node),
2781 current_function_decl);
2783 #ifdef STATIC_CHAIN_REGNUM
2785 rsp = static_chain_incoming_rtx;
2787 rsp = static_chain_rtx;
2788 if (REGNO (rsp) == REGNO (rcontext))
2789 #endif /* STATIC_CHAIN_REGNUM */
2792 if (rsp == NULL_RTX)
2794 for (i = 0; i < FIRST_PSEUDO_REGISTER; ++i)
2795 if (call_used_regs[i] && ! fixed_regs[i] && i != REGNO (rcontext))
2797 if (i == FIRST_PSEUDO_REGISTER)
2800 rsp = gen_rtx_REG (Pmode, i);
2803 for (i = 0; i < FIRST_PSEUDO_REGISTER; ++i)
2804 if (call_used_regs[i] && ! fixed_regs[i]
2805 && i != REGNO (rcontext) && i != REGNO (rsp))
2807 if (i == FIRST_PSEUDO_REGISTER)
2810 rra = gen_rtx_REG (Pmode, i);
2812 *pcontext = rcontext;
2817 /* Retrieve the register which contains the pointer to the eh_context
2818 structure set the __throw. */
2821 get_reg_for_handler ()
2824 reg1 = FUNCTION_VALUE (build_pointer_type (void_type_node),
2825 current_function_decl);
2829 /* Set up the epilogue with the magic bits we'll need to return to the
2830 exception handler. */
2833 expand_builtin_eh_return (context, stack, handler)
2834 tree context, stack, handler;
2836 if (eh_return_context)
2837 error("Duplicate call to __builtin_eh_return");
2840 = copy_to_reg (expand_expr (context, NULL_RTX, VOIDmode, 0));
2841 eh_return_stack_adjust
2842 = copy_to_reg (expand_expr (stack, NULL_RTX, VOIDmode, 0));
2844 = copy_to_reg (expand_expr (handler, NULL_RTX, VOIDmode, 0));
2850 rtx reg1, reg2, reg3;
2851 rtx stub_start, after_stub;
2854 if (!eh_return_context)
2857 current_function_cannot_inline = N_("function uses __builtin_eh_return");
2859 eh_regs (®1, ®2, ®3, 1);
2860 #ifdef POINTERS_EXTEND_UNSIGNED
2861 eh_return_context = convert_memory_address (Pmode, eh_return_context);
2862 eh_return_stack_adjust =
2863 convert_memory_address (Pmode, eh_return_stack_adjust);
2864 eh_return_handler = convert_memory_address (Pmode, eh_return_handler);
2866 emit_move_insn (reg1, eh_return_context);
2867 emit_move_insn (reg2, eh_return_stack_adjust);
2868 emit_move_insn (reg3, eh_return_handler);
2870 /* Talk directly to the target's epilogue code when possible. */
2872 #ifdef HAVE_eh_epilogue
2873 if (HAVE_eh_epilogue)
2875 emit_insn (gen_eh_epilogue (reg1, reg2, reg3));
2880 /* Otherwise, use the same stub technique we had before. */
2882 eh_return_stub_label = stub_start = gen_label_rtx ();
2883 after_stub = gen_label_rtx ();
2885 /* Set the return address to the stub label. */
2887 ra = expand_builtin_return_addr (BUILT_IN_RETURN_ADDRESS,
2888 0, hard_frame_pointer_rtx);
2889 if (GET_CODE (ra) == REG && REGNO (ra) >= FIRST_PSEUDO_REGISTER)
2892 tmp = memory_address (Pmode, gen_rtx_LABEL_REF (Pmode, stub_start));
2893 #ifdef RETURN_ADDR_OFFSET
2894 tmp = plus_constant (tmp, -RETURN_ADDR_OFFSET);
2896 tmp = force_operand (tmp, ra);
2898 emit_move_insn (ra, tmp);
2900 /* Indicate that the registers are in fact used. */
2901 emit_insn (gen_rtx_USE (VOIDmode, reg1));
2902 emit_insn (gen_rtx_USE (VOIDmode, reg2));
2903 emit_insn (gen_rtx_USE (VOIDmode, reg3));
2904 if (GET_CODE (ra) == REG)
2905 emit_insn (gen_rtx_USE (VOIDmode, ra));
2907 /* Generate the stub. */
2909 emit_jump (after_stub);
2910 emit_label (stub_start);
2912 eh_regs (®1, ®2, ®3, 0);
2913 adjust_stack (reg2);
2914 emit_indirect_jump (reg3);
2916 emit_label (after_stub);
2920 /* This contains the code required to verify whether arbitrary instructions
2921 are in the same exception region. */
2923 static int *insn_eh_region = (int *)0;
2924 static int maximum_uid;
2927 set_insn_eh_region (first, region_num)
2934 for (insn = *first; insn; insn = NEXT_INSN (insn))
2936 if ((GET_CODE (insn) == NOTE) &&
2937 (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG))
2939 rnum = NOTE_BLOCK_NUMBER (insn);
2940 insn_eh_region[INSN_UID (insn)] = rnum;
2941 insn = NEXT_INSN (insn);
2942 set_insn_eh_region (&insn, rnum);
2943 /* Upon return, insn points to the EH_REGION_END of nested region */
2946 insn_eh_region[INSN_UID (insn)] = region_num;
2947 if ((GET_CODE (insn) == NOTE) &&
2948 (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END))
2954 /* Free the insn table, an make sure it cannot be used again. */
2957 free_insn_eh_region ()
2964 free (insn_eh_region);
2965 insn_eh_region = (int *)0;
2969 /* Initialize the table. max_uid must be calculated and handed into
2970 this routine. If it is unavailable, passing a value of 0 will
2971 cause this routine to calculate it as well. */
2974 init_insn_eh_region (first, max_uid)
2984 free_insn_eh_region();
2987 for (insn = first; insn; insn = NEXT_INSN (insn))
2988 if (INSN_UID (insn) > max_uid) /* find largest UID */
2989 max_uid = INSN_UID (insn);
2991 maximum_uid = max_uid;
2992 insn_eh_region = (int *) xmalloc ((max_uid + 1) * sizeof (int));
2994 set_insn_eh_region (&insn, 0);
2998 /* Check whether 2 instructions are within the same region. */
3001 in_same_eh_region (insn1, insn2)
3004 int ret, uid1, uid2;
3006 /* If no exceptions, instructions are always in same region. */
3010 /* If the table isn't allocated, assume the worst. */
3011 if (!insn_eh_region)
3014 uid1 = INSN_UID (insn1);
3015 uid2 = INSN_UID (insn2);
3017 /* if instructions have been allocated beyond the end, either
3018 the table is out of date, or this is a late addition, or
3019 something... Assume the worst. */
3020 if (uid1 > maximum_uid || uid2 > maximum_uid)
3023 ret = (insn_eh_region[uid1] == insn_eh_region[uid2]);
3028 /* This function will initialize the handler list for a specified block.
3029 It may recursively call itself if the outer block hasn't been processed
3030 yet. At some point in the future we can trim out handlers which we
3031 know cannot be called. (ie, if a block has an INT type handler,
3032 control will never be passed to an outer INT type handler). */
3034 process_nestinfo (block, info, nested_eh_region)
3036 eh_nesting_info *info;
3037 int *nested_eh_region;
3039 handler_info *ptr, *last_ptr = NULL;
3040 int x, y, count = 0;
3042 handler_info **extra_handlers;
3043 int index = info->region_index[block];
3045 /* If we've already processed this block, simply return. */
3046 if (info->num_handlers[index] > 0)
3049 for (ptr = get_first_handler (block); ptr; last_ptr = ptr, ptr = ptr->next)
3052 /* pick up any information from the next outer region. It will already
3053 contain a summary of itself and all outer regions to it. */
3055 if (nested_eh_region [block] != 0)
3057 int nested_index = info->region_index[nested_eh_region[block]];
3058 process_nestinfo (nested_eh_region[block], info, nested_eh_region);
3059 extra = info->num_handlers[nested_index];
3060 extra_handlers = info->handlers[nested_index];
3061 info->outer_index[index] = nested_index;
3064 /* If the last handler is either a CATCH_ALL or a cleanup, then we
3065 won't use the outer ones since we know control will not go past the
3066 catch-all or cleanup. */
3068 if (last_ptr != NULL && (last_ptr->type_info == NULL
3069 || last_ptr->type_info == CATCH_ALL_TYPE))
3072 info->num_handlers[index] = count + extra;
3073 info->handlers[index] = (handler_info **) xmalloc ((count + extra)
3074 * sizeof (handler_info **));
3076 /* First put all our handlers into the list. */
3077 ptr = get_first_handler (block);
3078 for (x = 0; x < count; x++)
3080 info->handlers[index][x] = ptr;
3084 /* Now add all the outer region handlers, if they aren't they same as
3085 one of the types in the current block. We won't worry about
3086 derived types yet, we'll just look for the exact type. */
3087 for (y =0, x = 0; x < extra ; x++)
3091 /* Check to see if we have a type duplication. */
3092 for (i = 0; i < count; i++)
3093 if (info->handlers[index][i]->type_info == extra_handlers[x]->type_info)
3096 /* Record one less handler. */
3097 (info->num_handlers[index])--;
3102 info->handlers[index][y + count] = extra_handlers[x];
3108 /* This function will allocate and initialize an eh_nesting_info structure.
3109 It returns a pointer to the completed data structure. If there are
3110 no exception regions, a NULL value is returned. */
3112 init_eh_nesting_info ()
3114 int *nested_eh_region;
3115 int region_count = 0;
3116 rtx eh_note = NULL_RTX;
3117 eh_nesting_info *info;
3121 info = (eh_nesting_info *) xmalloc (sizeof (eh_nesting_info));
3122 info->region_index = (int *) xcalloc ((max_label_num () + 1), sizeof (int));
3124 nested_eh_region = (int *) alloca ((max_label_num () + 1) * sizeof (int));
3125 bzero ((char *) nested_eh_region, (max_label_num () + 1) * sizeof (int));
3127 /* Create the nested_eh_region list. If indexed with a block number, it
3128 returns the block number of the next outermost region, if any.
3129 We can count the number of regions and initialize the region_index
3130 vector at the same time. */
3131 for (insn = get_insns(); insn; insn = NEXT_INSN (insn))
3133 if (GET_CODE (insn) == NOTE)
3135 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
3137 int block = NOTE_BLOCK_NUMBER (insn);
3139 info->region_index[block] = region_count;
3141 nested_eh_region [block] =
3142 NOTE_BLOCK_NUMBER (XEXP (eh_note, 0));
3144 nested_eh_region [block] = 0;
3145 eh_note = gen_rtx_EXPR_LIST (VOIDmode, insn, eh_note);
3147 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)
3148 eh_note = XEXP (eh_note, 1);
3152 /* If there are no regions, wrap it up now. */
3153 if (region_count == 0)
3155 free (info->region_index);
3161 info->handlers = (handler_info ***) xcalloc (region_count,
3162 sizeof (handler_info ***));
3163 info->num_handlers = (int *) xcalloc (region_count, sizeof (int));
3164 info->outer_index = (int *) xcalloc (region_count, sizeof (int));
3166 /* Now initialize the handler lists for all exception blocks. */
3167 for (x = 0; x <= max_label_num (); x++)
3169 if (info->region_index[x] != 0)
3170 process_nestinfo (x, info, nested_eh_region);
3172 info->region_count = region_count;
3177 /* This function is used to retreive the vector of handlers which
3178 can be reached by a given insn in a given exception region.
3179 BLOCK is the exception block the insn is in.
3180 INFO is the eh_nesting_info structure.
3181 INSN is the (optional) insn within the block. If insn is not NULL_RTX,
3182 it may contain reg notes which modify its throwing behavior, and
3183 these will be obeyed. If NULL_RTX is passed, then we simply return the
3185 HANDLERS is the address of a pointer to a vector of handler_info pointers.
3186 Upon return, this will have the handlers which can be reached by block.
3187 This function returns the number of elements in the handlers vector. */
3189 reachable_handlers (block, info, insn, handlers)
3191 eh_nesting_info *info;
3193 handler_info ***handlers;
3201 index = info->region_index[block];
3203 if (insn && GET_CODE (insn) == CALL_INSN)
3205 /* RETHROWs specify a region number from which we are going to rethrow.
3206 This means we wont pass control to handlers in the specified
3207 region, but rather any region OUTSIDE the specified region.
3208 We accomplish this by setting block to the outer_index of the
3209 specified region. */
3210 rtx note = find_reg_note (insn, REG_EH_RETHROW, NULL_RTX);
3213 index = eh_region_from_symbol (XEXP (note, 0));
3214 index = info->region_index[index];
3216 index = info->outer_index[index];
3220 /* If there is no rethrow, we look for a REG_EH_REGION, and
3221 we'll throw from that block. A value of 0 or less
3222 indicates that this insn cannot throw. */
3223 note = find_reg_note (insn, REG_EH_REGION, NULL_RTX);
3226 int b = XINT (XEXP (note, 0), 0);
3230 index = info->region_index[b];
3234 /* If we reach this point, and index is 0, there is no throw. */
3238 *handlers = info->handlers[index];
3239 return info->num_handlers[index];
3243 /* This function will free all memory associated with the eh_nesting info. */
3246 free_eh_nesting_info (info)
3247 eh_nesting_info *info;
3252 if (info->region_index)
3253 free (info->region_index);
3254 if (info->num_handlers)
3255 free (info->num_handlers);
3256 if (info->outer_index)
3257 free (info->outer_index);
3260 for (x = 0; x < info->region_count; x++)
3261 if (info->handlers[x])
3262 free (info->handlers[x]);
3263 free (info->handlers);