1 /* Implements exception handling.
2 Copyright (C) 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000 Free Software Foundation, Inc.
4 Contributed by Mike Stump <mrs@cygnus.com>.
6 This file is part of GNU CC.
8 GNU CC is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2, or (at your option)
13 GNU CC is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with GNU CC; see the file COPYING. If not, write to
20 the Free Software Foundation, 59 Temple Place - Suite 330,
21 Boston, MA 02111-1307, USA. */
24 /* An exception is an event that can be signaled from within a
25 function. This event can then be "caught" or "trapped" by the
26 callers of this function. This potentially allows program flow to
27 be transferred to any arbitrary code associated with a function call
28 several levels up the stack.
30 The intended use for this mechanism is for signaling "exceptional
31 events" in an out-of-band fashion, hence its name. The C++ language
32 (and many other OO-styled or functional languages) practically
33 requires such a mechanism, as otherwise it becomes very difficult
34 or even impossible to signal failure conditions in complex
35 situations. The traditional C++ example is when an error occurs in
36 the process of constructing an object; without such a mechanism, it
37 is impossible to signal that the error occurs without adding global
38 state variables and error checks around every object construction.
40 The act of causing this event to occur is referred to as "throwing
41 an exception". (Alternate terms include "raising an exception" or
42 "signaling an exception".) The term "throw" is used because control
43 is returned to the callers of the function that is signaling the
44 exception, and thus there is the concept of "throwing" the
45 exception up the call stack.
47 There are two major codegen options for exception handling. The
48 flag -fsjlj-exceptions can be used to select the setjmp/longjmp
49 approach, which is the default. -fno-sjlj-exceptions can be used to
50 get the PC range table approach. While this is a compile time
51 flag, an entire application must be compiled with the same codegen
52 option. The first is a PC range table approach, the second is a
53 setjmp/longjmp based scheme. We will first discuss the PC range
54 table approach, after that, we will discuss the setjmp/longjmp
57 It is appropriate to speak of the "context of a throw". This
58 context refers to the address where the exception is thrown from,
59 and is used to determine which exception region will handle the
62 Regions of code within a function can be marked such that if it
63 contains the context of a throw, control will be passed to a
64 designated "exception handler". These areas are known as "exception
65 regions". Exception regions cannot overlap, but they can be nested
66 to any arbitrary depth. Also, exception regions cannot cross
69 Exception handlers can either be specified by the user (which we
70 will call a "user-defined handler") or generated by the compiler
71 (which we will designate as a "cleanup"). Cleanups are used to
72 perform tasks such as destruction of objects allocated on the
75 In the current implementation, cleanups are handled by allocating an
76 exception region for the area that the cleanup is designated for,
77 and the handler for the region performs the cleanup and then
78 rethrows the exception to the outer exception region. From the
79 standpoint of the current implementation, there is little
80 distinction made between a cleanup and a user-defined handler, and
81 the phrase "exception handler" can be used to refer to either one
82 equally well. (The section "Future Directions" below discusses how
85 Each object file that is compiled with exception handling contains
86 a static array of exception handlers named __EXCEPTION_TABLE__.
87 Each entry contains the starting and ending addresses of the
88 exception region, and the address of the handler designated for
91 If the target does not use the DWARF 2 frame unwind information, at
92 program startup each object file invokes a function named
93 __register_exceptions with the address of its local
94 __EXCEPTION_TABLE__. __register_exceptions is defined in libgcc2.c, and
95 is responsible for recording all of the exception regions into one list
96 (which is kept in a static variable named exception_table_list).
98 On targets that support crtstuff.c, the unwind information
99 is stored in a section named .eh_frame and the information for the
100 entire shared object or program is registered with a call to
101 __register_frame_info. On other targets, the information for each
102 translation unit is registered from the file generated by collect2.
103 __register_frame_info is defined in frame.c, and is responsible for
104 recording all of the unwind regions into one list (which is kept in a
105 static variable named unwind_table_list).
107 The function __throw is actually responsible for doing the
108 throw. On machines that have unwind info support, __throw is generated
109 by code in libgcc2.c, otherwise __throw is generated on a
110 per-object-file basis for each source file compiled with
111 -fexceptions by the C++ frontend. Before __throw is invoked,
112 the current context of the throw needs to be placed in the global
115 __throw attempts to find the appropriate exception handler for the
116 PC value stored in __eh_pc by calling __find_first_exception_table_match
117 (which is defined in libgcc2.c). If __find_first_exception_table_match
118 finds a relevant handler, __throw transfers control directly to it.
120 If a handler for the context being thrown from can't be found, __throw
121 walks (see Walking the stack below) the stack up the dynamic call chain to
122 continue searching for an appropriate exception handler based upon the
123 caller of the function it last sought a exception handler for. It stops
124 then either an exception handler is found, or when the top of the
125 call chain is reached.
127 If no handler is found, an external library function named
128 __terminate is called. If a handler is found, then we restart
129 our search for a handler at the end of the call chain, and repeat
130 the search process, but instead of just walking up the call chain,
131 we unwind the call chain as we walk up it.
133 Internal implementation details:
135 To associate a user-defined handler with a block of statements, the
136 function expand_start_try_stmts is used to mark the start of the
137 block of statements with which the handler is to be associated
138 (which is known as a "try block"). All statements that appear
139 afterwards will be associated with the try block.
141 A call to expand_start_all_catch marks the end of the try block,
142 and also marks the start of the "catch block" (the user-defined
143 handler) associated with the try block.
145 This user-defined handler will be invoked for *every* exception
146 thrown with the context of the try block. It is up to the handler
147 to decide whether or not it wishes to handle any given exception,
148 as there is currently no mechanism in this implementation for doing
149 this. (There are plans for conditionally processing an exception
150 based on its "type", which will provide a language-independent
153 If the handler chooses not to process the exception (perhaps by
154 looking at an "exception type" or some other additional data
155 supplied with the exception), it can fall through to the end of the
156 handler. expand_end_all_catch and expand_leftover_cleanups
157 add additional code to the end of each handler to take care of
158 rethrowing to the outer exception handler.
160 The handler also has the option to continue with "normal flow of
161 code", or in other words to resume executing at the statement
162 immediately after the end of the exception region. The variable
163 caught_return_label_stack contains a stack of labels, and jumping
164 to the topmost entry's label via expand_goto will resume normal
165 flow to the statement immediately after the end of the exception
166 region. If the handler falls through to the end, the exception will
167 be rethrown to the outer exception region.
169 The instructions for the catch block are kept as a separate
170 sequence, and will be emitted at the end of the function along with
171 the handlers specified via expand_eh_region_end. The end of the
172 catch block is marked with expand_end_all_catch.
174 Any data associated with the exception must currently be handled by
175 some external mechanism maintained in the frontend. For example,
176 the C++ exception mechanism passes an arbitrary value along with
177 the exception, and this is handled in the C++ frontend by using a
178 global variable to hold the value. (This will be changing in the
181 The mechanism in C++ for handling data associated with the
182 exception is clearly not thread-safe. For a thread-based
183 environment, another mechanism must be used (possibly using a
184 per-thread allocation mechanism if the size of the area that needs
185 to be allocated isn't known at compile time.)
187 Internally-generated exception regions (cleanups) are marked by
188 calling expand_eh_region_start to mark the start of the region,
189 and expand_eh_region_end (handler) is used to both designate the
190 end of the region and to associate a specified handler/cleanup with
191 the region. The rtl code in HANDLER will be invoked whenever an
192 exception occurs in the region between the calls to
193 expand_eh_region_start and expand_eh_region_end. After HANDLER is
194 executed, additional code is emitted to handle rethrowing the
195 exception to the outer exception handler. The code for HANDLER will
196 be emitted at the end of the function.
198 TARGET_EXPRs can also be used to designate exception regions. A
199 TARGET_EXPR gives an unwind-protect style interface commonly used
200 in functional languages such as LISP. The associated expression is
201 evaluated, and whether or not it (or any of the functions that it
202 calls) throws an exception, the protect expression is always
203 invoked. This implementation takes care of the details of
204 associating an exception table entry with the expression and
205 generating the necessary code (it actually emits the protect
206 expression twice, once for normal flow and once for the exception
207 case). As for the other handlers, the code for the exception case
208 will be emitted at the end of the function.
210 Cleanups can also be specified by using add_partial_entry (handler)
211 and end_protect_partials. add_partial_entry creates the start of
212 a new exception region; HANDLER will be invoked if an exception is
213 thrown with the context of the region between the calls to
214 add_partial_entry and end_protect_partials. end_protect_partials is
215 used to mark the end of these regions. add_partial_entry can be
216 called as many times as needed before calling end_protect_partials.
217 However, end_protect_partials should only be invoked once for each
218 group of calls to add_partial_entry as the entries are queued
219 and all of the outstanding entries are processed simultaneously
220 when end_protect_partials is invoked. Similarly to the other
221 handlers, the code for HANDLER will be emitted at the end of the
224 The generated RTL for an exception region includes
225 NOTE_INSN_EH_REGION_BEG and NOTE_INSN_EH_REGION_END notes that mark
226 the start and end of the exception region. A unique label is also
227 generated at the start of the exception region, which is available
228 by looking at the ehstack variable. The topmost entry corresponds
229 to the current region.
231 In the current implementation, an exception can only be thrown from
232 a function call (since the mechanism used to actually throw an
233 exception involves calling __throw). If an exception region is
234 created but no function calls occur within that region, the region
235 can be safely optimized away (along with its exception handlers)
236 since no exceptions can ever be caught in that region. This
237 optimization is performed unless -fasynchronous-exceptions is
238 given. If the user wishes to throw from a signal handler, or other
239 asynchronous place, -fasynchronous-exceptions should be used when
240 compiling for maximally correct code, at the cost of additional
241 exception regions. Using -fasynchronous-exceptions only produces
242 code that is reasonably safe in such situations, but a correct
243 program cannot rely upon this working. It can be used in failsafe
244 code, where trying to continue on, and proceeding with potentially
245 incorrect results is better than halting the program.
250 The stack is walked by starting with a pointer to the current
251 frame, and finding the pointer to the callers frame. The unwind info
252 tells __throw how to find it.
256 When we use the term unwinding the stack, we mean undoing the
257 effects of the function prologue in a controlled fashion so that we
258 still have the flow of control. Otherwise, we could just return
259 (jump to the normal end of function epilogue).
261 This is done in __throw in libgcc2.c when we know that a handler exists
262 in a frame higher up the call stack than its immediate caller.
264 To unwind, we find the unwind data associated with the frame, if any.
265 If we don't find any, we call the library routine __terminate. If we do
266 find it, we use the information to copy the saved register values from
267 that frame into the register save area in the frame for __throw, return
268 into a stub which updates the stack pointer, and jump to the handler.
269 The normal function epilogue for __throw handles restoring the saved
270 values into registers.
272 When unwinding, we use this method if we know it will
273 work (if DWARF2_UNWIND_INFO is defined). Otherwise, we know that
274 an inline unwinder will have been emitted for any function that
275 __unwind_function cannot unwind. The inline unwinder appears as a
276 normal exception handler for the entire function, for any function
277 that we know cannot be unwound by __unwind_function. We inform the
278 compiler of whether a function can be unwound with
279 __unwind_function by having DOESNT_NEED_UNWINDER evaluate to true
280 when the unwinder isn't needed. __unwind_function is used as an
281 action of last resort. If no other method can be used for
282 unwinding, __unwind_function is used. If it cannot unwind, it
283 should call __terminate.
285 By default, if the target-specific backend doesn't supply a definition
286 for __unwind_function and doesn't support DWARF2_UNWIND_INFO, inlined
287 unwinders will be used instead. The main tradeoff here is in text space
288 utilization. Obviously, if inline unwinders have to be generated
289 repeatedly, this uses much more space than if a single routine is used.
291 However, it is simply not possible on some platforms to write a
292 generalized routine for doing stack unwinding without having some
293 form of additional data associated with each function. The current
294 implementation can encode this data in the form of additional
295 machine instructions or as static data in tabular form. The later
296 is called the unwind data.
298 The backend macro DOESNT_NEED_UNWINDER is used to conditionalize whether
299 or not per-function unwinders are needed. If DOESNT_NEED_UNWINDER is
300 defined and has a non-zero value, a per-function unwinder is not emitted
301 for the current function. If the static unwind data is supported, then
302 a per-function unwinder is not emitted.
304 On some platforms it is possible that neither __unwind_function
305 nor inlined unwinders are available. For these platforms it is not
306 possible to throw through a function call, and abort will be
307 invoked instead of performing the throw.
309 The reason the unwind data may be needed is that on some platforms
310 the order and types of data stored on the stack can vary depending
311 on the type of function, its arguments and returned values, and the
312 compilation options used (optimization versus non-optimization,
313 -fomit-frame-pointer, processor variations, etc).
315 Unfortunately, this also means that throwing through functions that
316 aren't compiled with exception handling support will still not be
317 possible on some platforms. This problem is currently being
318 investigated, but no solutions have been found that do not imply
319 some unacceptable performance penalties.
323 Currently __throw makes no differentiation between cleanups and
324 user-defined exception regions. While this makes the implementation
325 simple, it also implies that it is impossible to determine if a
326 user-defined exception handler exists for a given exception without
327 completely unwinding the stack in the process. This is undesirable
328 from the standpoint of debugging, as ideally it would be possible
329 to trap unhandled exceptions in the debugger before the process of
330 unwinding has even started.
332 This problem can be solved by marking user-defined handlers in a
333 special way (probably by adding additional bits to exception_table_list).
334 A two-pass scheme could then be used by __throw to iterate
335 through the table. The first pass would search for a relevant
336 user-defined handler for the current context of the throw, and if
337 one is found, the second pass would then invoke all needed cleanups
338 before jumping to the user-defined handler.
340 Many languages (including C++ and Ada) make execution of a
341 user-defined handler conditional on the "type" of the exception
342 thrown. (The type of the exception is actually the type of the data
343 that is thrown with the exception.) It will thus be necessary for
344 __throw to be able to determine if a given user-defined
345 exception handler will actually be executed, given the type of
348 One scheme is to add additional information to exception_table_list
349 as to the types of exceptions accepted by each handler. __throw
350 can do the type comparisons and then determine if the handler is
351 actually going to be executed.
353 There is currently no significant level of debugging support
354 available, other than to place a breakpoint on __throw. While
355 this is sufficient in most cases, it would be helpful to be able to
356 know where a given exception was going to be thrown to before it is
357 actually thrown, and to be able to choose between stopping before
358 every exception region (including cleanups), or just user-defined
359 exception regions. This should be possible to do in the two-pass
360 scheme by adding additional labels to __throw for appropriate
361 breakpoints, and additional debugger commands could be added to
362 query various state variables to determine what actions are to be
365 Another major problem that is being worked on is the issue with stack
366 unwinding on various platforms. Currently the only platforms that have
367 support for the generation of a generic unwinder are the SPARC and MIPS.
368 All other ports require per-function unwinders, which produce large
369 amounts of code bloat.
371 For setjmp/longjmp based exception handling, some of the details
372 are as above, but there are some additional details. This section
373 discusses the details.
375 We don't use NOTE_INSN_EH_REGION_{BEG,END} pairs. We don't
376 optimize EH regions yet. We don't have to worry about machine
377 specific issues with unwinding the stack, as we rely upon longjmp
378 for all the machine specific details. There is no variable context
379 of a throw, just the one implied by the dynamic handler stack
380 pointed to by the dynamic handler chain. There is no exception
381 table, and no calls to __register_exceptions. __sjthrow is used
382 instead of __throw, and it works by using the dynamic handler
383 chain, and longjmp. -fasynchronous-exceptions has no effect, as
384 the elimination of trivial exception regions is not yet performed.
386 A frontend can set protect_cleanup_actions_with_terminate when all
387 the cleanup actions should be protected with an EH region that
388 calls terminate when an unhandled exception is throw. C++ does
389 this, Ada does not. */
393 #include "defaults.h"
394 #include "eh-common.h"
400 #include "function.h"
401 #include "insn-flags.h"
403 #include "insn-codes.h"
405 #include "hard-reg-set.h"
406 #include "insn-config.h"
415 /* One to use setjmp/longjmp method of generating code for exception
418 int exceptions_via_longjmp = 2;
420 /* One to enable asynchronous exception support. */
422 int asynchronous_exceptions = 0;
424 /* One to protect cleanup actions with a handler that calls
425 __terminate, zero otherwise. */
427 int protect_cleanup_actions_with_terminate;
429 /* A list of labels used for exception handlers. Created by
430 find_exception_handler_labels for the optimization passes. */
432 rtx exception_handler_labels;
434 /* Keeps track of the label used as the context of a throw to rethrow an
435 exception to the outer exception region. */
437 struct label_node *outer_context_label_stack = NULL;
439 /* Pseudos used to hold exception return data in the interim between
440 __builtin_eh_return and the end of the function. */
442 static rtx eh_return_context;
443 static rtx eh_return_stack_adjust;
444 static rtx eh_return_handler;
446 /* This is used for targets which can call rethrow with an offset instead
447 of an address. This is subtracted from the rethrow label we are
450 static rtx first_rethrow_symbol = NULL_RTX;
451 static rtx final_rethrow = NULL_RTX;
452 static rtx last_rethrow_symbol = NULL_RTX;
455 /* Prototypes for local functions. */
457 static void push_eh_entry PARAMS ((struct eh_stack *));
458 static struct eh_entry * pop_eh_entry PARAMS ((struct eh_stack *));
459 static void enqueue_eh_entry PARAMS ((struct eh_queue *, struct eh_entry *));
460 static struct eh_entry * dequeue_eh_entry PARAMS ((struct eh_queue *));
461 static rtx call_get_eh_context PARAMS ((void));
462 static void start_dynamic_cleanup PARAMS ((tree, tree));
463 static void start_dynamic_handler PARAMS ((void));
464 static void expand_rethrow PARAMS ((rtx));
465 static void output_exception_table_entry PARAMS ((FILE *, int));
466 static int can_throw PARAMS ((rtx));
467 static rtx scan_region PARAMS ((rtx, int, int *));
468 static void eh_regs PARAMS ((rtx *, rtx *, rtx *, int));
469 static void set_insn_eh_region PARAMS ((rtx *, int));
470 #ifdef DONT_USE_BUILTIN_SETJMP
471 static void jumpif_rtx PARAMS ((rtx, rtx));
473 static void mark_eh_node PARAMS ((struct eh_node *));
474 static void mark_eh_stack PARAMS ((struct eh_stack *));
475 static void mark_eh_queue PARAMS ((struct eh_queue *));
476 static void mark_tree_label_node PARAMS ((struct label_node *));
477 static void mark_func_eh_entry PARAMS ((void *));
478 static rtx create_rethrow_ref PARAMS ((int));
479 static void push_entry PARAMS ((struct eh_stack *, struct eh_entry*));
480 static void receive_exception_label PARAMS ((rtx));
481 static int new_eh_region_entry PARAMS ((int, rtx));
482 static int find_func_region PARAMS ((int));
483 static int find_func_region_from_symbol PARAMS ((rtx));
484 static void clear_function_eh_region PARAMS ((void));
485 static void process_nestinfo PARAMS ((int, eh_nesting_info *, int *));
487 rtx expand_builtin_return_addr PARAMS ((enum built_in_function, int, rtx));
488 static void emit_cleanup_handler PARAMS ((struct eh_entry *));
489 static int eh_region_from_symbol PARAMS ((rtx));
492 /* Various support routines to manipulate the various data structures
493 used by the exception handling code. */
495 extern struct obstack permanent_obstack;
497 /* Generate a SYMBOL_REF for rethrow to use */
499 create_rethrow_ref (region_num)
506 push_obstacks_nochange ();
507 end_temporary_allocation ();
509 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", region_num);
510 ptr = ggc_alloc_string (buf, -1);
511 def = gen_rtx_SYMBOL_REF (Pmode, ptr);
512 SYMBOL_REF_NEED_ADJUST (def) = 1;
518 /* Push a label entry onto the given STACK. */
521 push_label_entry (stack, rlabel, tlabel)
522 struct label_node **stack;
526 struct label_node *newnode
527 = (struct label_node *) xmalloc (sizeof (struct label_node));
530 newnode->u.rlabel = rlabel;
532 newnode->u.tlabel = tlabel;
533 newnode->chain = *stack;
537 /* Pop a label entry from the given STACK. */
540 pop_label_entry (stack)
541 struct label_node **stack;
544 struct label_node *tempnode;
550 label = tempnode->u.rlabel;
551 *stack = (*stack)->chain;
557 /* Return the top element of the given STACK. */
560 top_label_entry (stack)
561 struct label_node **stack;
566 return (*stack)->u.tlabel;
569 /* get an exception label. These must be on the permanent obstack */
572 gen_exception_label ()
575 lab = gen_label_rtx ();
579 /* Push a new eh_node entry onto STACK. */
582 push_eh_entry (stack)
583 struct eh_stack *stack;
585 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
586 struct eh_entry *entry = (struct eh_entry *) xmalloc (sizeof (struct eh_entry));
588 rtx rlab = gen_exception_label ();
589 entry->finalization = NULL_TREE;
590 entry->label_used = 0;
591 entry->exception_handler_label = rlab;
592 entry->false_label = NULL_RTX;
593 if (! flag_new_exceptions)
594 entry->outer_context = gen_label_rtx ();
596 entry->outer_context = create_rethrow_ref (CODE_LABEL_NUMBER (rlab));
597 entry->rethrow_label = entry->outer_context;
598 entry->goto_entry_p = 0;
601 node->chain = stack->top;
605 /* push an existing entry onto a stack. */
607 push_entry (stack, entry)
608 struct eh_stack *stack;
609 struct eh_entry *entry;
611 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
613 node->chain = stack->top;
617 /* Pop an entry from the given STACK. */
619 static struct eh_entry *
621 struct eh_stack *stack;
623 struct eh_node *tempnode;
624 struct eh_entry *tempentry;
626 tempnode = stack->top;
627 tempentry = tempnode->entry;
628 stack->top = stack->top->chain;
634 /* Enqueue an ENTRY onto the given QUEUE. */
637 enqueue_eh_entry (queue, entry)
638 struct eh_queue *queue;
639 struct eh_entry *entry;
641 struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node));
646 if (queue->head == NULL)
649 queue->tail->chain = node;
653 /* Dequeue an entry from the given QUEUE. */
655 static struct eh_entry *
656 dequeue_eh_entry (queue)
657 struct eh_queue *queue;
659 struct eh_node *tempnode;
660 struct eh_entry *tempentry;
662 if (queue->head == NULL)
665 tempnode = queue->head;
666 queue->head = queue->head->chain;
668 tempentry = tempnode->entry;
675 receive_exception_label (handler_label)
678 emit_label (handler_label);
680 #ifdef HAVE_exception_receiver
681 if (! exceptions_via_longjmp)
682 if (HAVE_exception_receiver)
683 emit_insn (gen_exception_receiver ());
686 #ifdef HAVE_nonlocal_goto_receiver
687 if (! exceptions_via_longjmp)
688 if (HAVE_nonlocal_goto_receiver)
689 emit_insn (gen_nonlocal_goto_receiver ());
696 int range_number; /* EH region number from EH NOTE insn's. */
697 rtx rethrow_label; /* Label for rethrow. */
698 int rethrow_ref; /* Is rethrow referenced? */
699 struct handler_info *handlers;
703 /* table of function eh regions */
704 static struct func_eh_entry *function_eh_regions = NULL;
705 static int num_func_eh_entries = 0;
706 static int current_func_eh_entry = 0;
708 #define SIZE_FUNC_EH(X) (sizeof (struct func_eh_entry) * X)
710 /* Add a new eh_entry for this function. The number returned is an
711 number which uniquely identifies this exception range. */
714 new_eh_region_entry (note_eh_region, rethrow)
718 if (current_func_eh_entry == num_func_eh_entries)
720 if (num_func_eh_entries == 0)
722 function_eh_regions =
723 (struct func_eh_entry *) xmalloc (SIZE_FUNC_EH (50));
724 num_func_eh_entries = 50;
728 num_func_eh_entries = num_func_eh_entries * 3 / 2;
729 function_eh_regions = (struct func_eh_entry *)
730 xrealloc (function_eh_regions, SIZE_FUNC_EH (num_func_eh_entries));
733 function_eh_regions[current_func_eh_entry].range_number = note_eh_region;
734 if (rethrow == NULL_RTX)
735 function_eh_regions[current_func_eh_entry].rethrow_label =
736 create_rethrow_ref (note_eh_region);
738 function_eh_regions[current_func_eh_entry].rethrow_label = rethrow;
739 function_eh_regions[current_func_eh_entry].handlers = NULL;
741 return current_func_eh_entry++;
744 /* Add new handler information to an exception range. The first parameter
745 specifies the range number (returned from new_eh_entry()). The second
746 parameter specifies the handler. By default the handler is inserted at
747 the end of the list. A handler list may contain only ONE NULL_TREE
748 typeinfo entry. Regardless where it is positioned, a NULL_TREE entry
749 is always output as the LAST handler in the exception table for a region. */
752 add_new_handler (region, newhandler)
754 struct handler_info *newhandler;
756 struct handler_info *last;
758 /* If find_func_region returns -1, callers might attempt to pass us
759 this region number. If that happens, something has gone wrong;
760 -1 is never a valid region. */
764 newhandler->next = NULL;
765 last = function_eh_regions[region].handlers;
767 function_eh_regions[region].handlers = newhandler;
770 for ( ; ; last = last->next)
772 if (last->type_info == CATCH_ALL_TYPE)
773 pedwarn ("additional handler after ...");
774 if (last->next == NULL)
777 last->next = newhandler;
781 /* Remove a handler label. The handler label is being deleted, so all
782 regions which reference this handler should have it removed from their
783 list of possible handlers. Any region which has the final handler
784 removed can be deleted. */
786 void remove_handler (removing_label)
789 struct handler_info *handler, *last;
791 for (x = 0 ; x < current_func_eh_entry; ++x)
794 handler = function_eh_regions[x].handlers;
795 for ( ; handler; last = handler, handler = handler->next)
796 if (handler->handler_label == removing_label)
800 last->next = handler->next;
804 function_eh_regions[x].handlers = handler->next;
809 /* This function will return a malloc'd pointer to an array of
810 void pointer representing the runtime match values that
811 currently exist in all regions. */
814 find_all_handler_type_matches (array)
817 struct handler_info *handler, *last;
826 if (!doing_eh (0) || ! flag_new_exceptions)
830 ptr = (void **) xmalloc (max_ptr * sizeof (void *));
832 for (x = 0 ; x < current_func_eh_entry; x++)
835 handler = function_eh_regions[x].handlers;
836 for ( ; handler; last = handler, handler = handler->next)
838 val = handler->type_info;
839 if (val != NULL && val != CATCH_ALL_TYPE)
841 /* See if this match value has already been found. */
842 for (y = 0; y < n_ptr; y++)
846 /* If we break early, we already found this value. */
850 /* Do we need to allocate more space? */
851 if (n_ptr >= max_ptr)
853 max_ptr += max_ptr / 2;
854 ptr = (void **) xrealloc (ptr, max_ptr * sizeof (void *));
871 /* Create a new handler structure initialized with the handler label and
872 typeinfo fields passed in. */
874 struct handler_info *
875 get_new_handler (handler, typeinfo)
879 struct handler_info* ptr;
880 ptr = (struct handler_info *) xmalloc (sizeof (struct handler_info));
881 ptr->handler_label = handler;
882 ptr->handler_number = CODE_LABEL_NUMBER (handler);
883 ptr->type_info = typeinfo;
891 /* Find the index in function_eh_regions associated with a NOTE region. If
892 the region cannot be found, a -1 is returned. */
895 find_func_region (insn_region)
899 for (x = 0; x < current_func_eh_entry; x++)
900 if (function_eh_regions[x].range_number == insn_region)
906 /* Get a pointer to the first handler in an exception region's list. */
908 struct handler_info *
909 get_first_handler (region)
912 int r = find_func_region (region);
915 return function_eh_regions[r].handlers;
918 /* Clean out the function_eh_region table and free all memory */
921 clear_function_eh_region ()
924 struct handler_info *ptr, *next;
925 for (x = 0; x < current_func_eh_entry; x++)
926 for (ptr = function_eh_regions[x].handlers; ptr != NULL; ptr = next)
931 free (function_eh_regions);
932 num_func_eh_entries = 0;
933 current_func_eh_entry = 0;
936 /* Make a duplicate of an exception region by copying all the handlers
937 for an exception region. Return the new handler index. The final
938 parameter is a routine which maps old labels to new ones. */
941 duplicate_eh_handlers (old_note_eh_region, new_note_eh_region, map)
942 int old_note_eh_region, new_note_eh_region;
943 rtx (*map) PARAMS ((rtx));
945 struct handler_info *ptr, *new_ptr;
946 int new_region, region;
948 region = find_func_region (old_note_eh_region);
950 fatal ("Cannot duplicate non-existant exception region.");
952 /* duplicate_eh_handlers may have been called during a symbol remap. */
953 new_region = find_func_region (new_note_eh_region);
954 if (new_region != -1)
957 new_region = new_eh_region_entry (new_note_eh_region, NULL_RTX);
959 ptr = function_eh_regions[region].handlers;
961 for ( ; ptr; ptr = ptr->next)
963 new_ptr = get_new_handler (map (ptr->handler_label), ptr->type_info);
964 add_new_handler (new_region, new_ptr);
971 /* Given a rethrow symbol, find the EH region number this is for. */
973 eh_region_from_symbol (sym)
977 if (sym == last_rethrow_symbol)
979 for (x = 0; x < current_func_eh_entry; x++)
980 if (function_eh_regions[x].rethrow_label == sym)
981 return function_eh_regions[x].range_number;
985 /* Like find_func_region, but using the rethrow symbol for the region
986 rather than the region number itself. */
988 find_func_region_from_symbol (sym)
991 return find_func_region (eh_region_from_symbol (sym));
994 /* When inlining/unrolling, we have to map the symbols passed to
995 __rethrow as well. This performs the remap. If a symbol isn't foiund,
996 the original one is returned. This is not an efficient routine,
997 so don't call it on everything!! */
999 rethrow_symbol_map (sym, map)
1001 rtx (*map) PARAMS ((rtx));
1004 for (x = 0; x < current_func_eh_entry; x++)
1005 if (function_eh_regions[x].rethrow_label == sym)
1007 /* We've found the original region, now lets determine which region
1008 this now maps to. */
1009 rtx l1 = function_eh_regions[x].handlers->handler_label;
1011 y = CODE_LABEL_NUMBER (l2); /* This is the new region number */
1012 x = find_func_region (y); /* Get the new permanent region */
1013 if (x == -1) /* Hmm, Doesn't exist yet */
1015 x = duplicate_eh_handlers (CODE_LABEL_NUMBER (l1), y, map);
1016 /* Since we're mapping it, it must be used. */
1017 function_eh_regions[x].rethrow_ref = 1;
1019 return function_eh_regions[x].rethrow_label;
1025 rethrow_used (region)
1028 if (flag_new_exceptions)
1030 int ret = function_eh_regions[find_func_region (region)].rethrow_ref;
1037 /* Routine to see if exception handling is turned on.
1038 DO_WARN is non-zero if we want to inform the user that exception
1039 handling is turned off.
1041 This is used to ensure that -fexceptions has been specified if the
1042 compiler tries to use any exception-specific functions. */
1048 if (! flag_exceptions)
1050 static int warned = 0;
1051 if (! warned && do_warn)
1053 error ("exception handling disabled, use -fexceptions to enable");
1061 /* Given a return address in ADDR, determine the address we should use
1062 to find the corresponding EH region. */
1065 eh_outer_context (addr)
1068 /* First mask out any unwanted bits. */
1069 #ifdef MASK_RETURN_ADDR
1070 expand_and (addr, MASK_RETURN_ADDR, addr);
1073 /* Then adjust to find the real return address. */
1074 #if defined (RETURN_ADDR_OFFSET)
1075 addr = plus_constant (addr, RETURN_ADDR_OFFSET);
1081 /* Start a new exception region for a region of code that has a
1082 cleanup action and push the HANDLER for the region onto
1083 protect_list. All of the regions created with add_partial_entry
1084 will be ended when end_protect_partials is invoked. */
1087 add_partial_entry (handler)
1090 expand_eh_region_start ();
1092 /* Make sure the entry is on the correct obstack. */
1093 push_obstacks_nochange ();
1094 resume_temporary_allocation ();
1096 /* Because this is a cleanup action, we may have to protect the handler
1097 with __terminate. */
1098 handler = protect_with_terminate (handler);
1100 /* For backwards compatibility, we allow callers to omit calls to
1101 begin_protect_partials for the outermost region. So, we must
1102 explicitly do so here. */
1104 begin_protect_partials ();
1106 /* Add this entry to the front of the list. */
1107 TREE_VALUE (protect_list)
1108 = tree_cons (NULL_TREE, handler, TREE_VALUE (protect_list));
1112 /* Emit code to get EH context to current function. */
1115 call_get_eh_context ()
1120 if (fn == NULL_TREE)
1123 fn = get_identifier ("__get_eh_context");
1124 push_obstacks_nochange ();
1125 end_temporary_allocation ();
1126 fntype = build_pointer_type (build_pointer_type
1127 (build_pointer_type (void_type_node)));
1128 fntype = build_function_type (fntype, NULL_TREE);
1129 fn = build_decl (FUNCTION_DECL, fn, fntype);
1130 DECL_EXTERNAL (fn) = 1;
1131 TREE_PUBLIC (fn) = 1;
1132 DECL_ARTIFICIAL (fn) = 1;
1133 TREE_READONLY (fn) = 1;
1134 make_decl_rtl (fn, NULL_PTR, 1);
1135 assemble_external (fn);
1138 ggc_add_tree_root (&fn, 1);
1141 expr = build1 (ADDR_EXPR, build_pointer_type (TREE_TYPE (fn)), fn);
1142 expr = build (CALL_EXPR, TREE_TYPE (TREE_TYPE (fn)),
1143 expr, NULL_TREE, NULL_TREE);
1144 TREE_SIDE_EFFECTS (expr) = 1;
1146 return copy_to_reg (expand_expr (expr, NULL_RTX, VOIDmode, 0));
1149 /* Get a reference to the EH context.
1150 We will only generate a register for the current function EH context here,
1151 and emit a USE insn to mark that this is a EH context register.
1153 Later, emit_eh_context will emit needed call to __get_eh_context
1154 in libgcc2, and copy the value to the register we have generated. */
1159 if (current_function_ehc == 0)
1163 current_function_ehc = gen_reg_rtx (Pmode);
1165 insn = gen_rtx_USE (GET_MODE (current_function_ehc),
1166 current_function_ehc);
1167 insn = emit_insn_before (insn, get_first_nonparm_insn ());
1170 = gen_rtx_EXPR_LIST (REG_EH_CONTEXT, current_function_ehc,
1173 return current_function_ehc;
1176 /* Get a reference to the dynamic handler chain. It points to the
1177 pointer to the next element in the dynamic handler chain. It ends
1178 when there are no more elements in the dynamic handler chain, when
1179 the value is &top_elt from libgcc2.c. Immediately after the
1180 pointer, is an area suitable for setjmp/longjmp when
1181 DONT_USE_BUILTIN_SETJMP is defined, and an area suitable for
1182 __builtin_setjmp/__builtin_longjmp when DONT_USE_BUILTIN_SETJMP
1186 get_dynamic_handler_chain ()
1188 rtx ehc, dhc, result;
1190 ehc = get_eh_context ();
1192 /* This is the offset of dynamic_handler_chain in the eh_context struct
1193 declared in eh-common.h. If its location is change, change this offset */
1194 dhc = plus_constant (ehc, POINTER_SIZE / BITS_PER_UNIT);
1196 result = copy_to_reg (dhc);
1198 /* We don't want a copy of the dcc, but rather, the single dcc. */
1199 return gen_rtx_MEM (Pmode, result);
1202 /* Get a reference to the dynamic cleanup chain. It points to the
1203 pointer to the next element in the dynamic cleanup chain.
1204 Immediately after the pointer, are two Pmode variables, one for a
1205 pointer to a function that performs the cleanup action, and the
1206 second, the argument to pass to that function. */
1209 get_dynamic_cleanup_chain ()
1211 rtx dhc, dcc, result;
1213 dhc = get_dynamic_handler_chain ();
1214 dcc = plus_constant (dhc, POINTER_SIZE / BITS_PER_UNIT);
1216 result = copy_to_reg (dcc);
1218 /* We don't want a copy of the dcc, but rather, the single dcc. */
1219 return gen_rtx_MEM (Pmode, result);
1222 #ifdef DONT_USE_BUILTIN_SETJMP
1223 /* Generate code to evaluate X and jump to LABEL if the value is nonzero.
1224 LABEL is an rtx of code CODE_LABEL, in this function. */
1227 jumpif_rtx (x, label)
1231 jumpif (make_tree (type_for_mode (GET_MODE (x), 0), x), label);
1235 /* Start a dynamic cleanup on the EH runtime dynamic cleanup stack.
1236 We just need to create an element for the cleanup list, and push it
1239 A dynamic cleanup is a cleanup action implied by the presence of an
1240 element on the EH runtime dynamic cleanup stack that is to be
1241 performed when an exception is thrown. The cleanup action is
1242 performed by __sjthrow when an exception is thrown. Only certain
1243 actions can be optimized into dynamic cleanup actions. For the
1244 restrictions on what actions can be performed using this routine,
1245 see expand_eh_region_start_tree. */
1248 start_dynamic_cleanup (func, arg)
1253 rtx new_func, new_arg;
1257 /* We allocate enough room for a pointer to the function, and
1261 /* XXX, FIXME: The stack space allocated this way is too long lived,
1262 but there is no allocation routine that allocates at the level of
1263 the last binding contour. */
1264 buf = assign_stack_local (BLKmode,
1265 GET_MODE_SIZE (Pmode)*(size+1),
1268 buf = change_address (buf, Pmode, NULL_RTX);
1270 /* Store dcc into the first word of the newly allocated buffer. */
1272 dcc = get_dynamic_cleanup_chain ();
1273 emit_move_insn (buf, dcc);
1275 /* Store func and arg into the cleanup list element. */
1277 new_func = gen_rtx_MEM (Pmode, plus_constant (XEXP (buf, 0),
1278 GET_MODE_SIZE (Pmode)));
1279 new_arg = gen_rtx_MEM (Pmode, plus_constant (XEXP (buf, 0),
1280 GET_MODE_SIZE (Pmode)*2));
1281 x = expand_expr (func, new_func, Pmode, 0);
1283 emit_move_insn (new_func, x);
1285 x = expand_expr (arg, new_arg, Pmode, 0);
1287 emit_move_insn (new_arg, x);
1289 /* Update the cleanup chain. */
1291 x = force_operand (XEXP (buf, 0), dcc);
1293 emit_move_insn (dcc, x);
1296 /* Emit RTL to start a dynamic handler on the EH runtime dynamic
1297 handler stack. This should only be used by expand_eh_region_start
1298 or expand_eh_region_start_tree. */
1301 start_dynamic_handler ()
1307 #ifndef DONT_USE_BUILTIN_SETJMP
1308 /* The number of Pmode words for the setjmp buffer, when using the
1309 builtin setjmp/longjmp, see expand_builtin, case BUILT_IN_LONGJMP. */
1310 /* We use 2 words here before calling expand_builtin_setjmp.
1311 expand_builtin_setjmp uses 2 words, and then calls emit_stack_save.
1312 emit_stack_save needs space of size STACK_SAVEAREA_MODE (SAVE_NONLOCAL).
1313 Subtract one, because the assign_stack_local call below adds 1. */
1314 size = (2 + 2 + (GET_MODE_SIZE (STACK_SAVEAREA_MODE (SAVE_NONLOCAL))
1315 / GET_MODE_SIZE (Pmode))
1319 size = JMP_BUF_SIZE;
1321 /* Should be large enough for most systems, if it is not,
1322 JMP_BUF_SIZE should be defined with the proper value. It will
1323 also tend to be larger than necessary for most systems, a more
1324 optimal port will define JMP_BUF_SIZE. */
1325 size = FIRST_PSEUDO_REGISTER+2;
1328 /* XXX, FIXME: The stack space allocated this way is too long lived,
1329 but there is no allocation routine that allocates at the level of
1330 the last binding contour. */
1331 arg = assign_stack_local (BLKmode,
1332 GET_MODE_SIZE (Pmode)*(size+1),
1335 arg = change_address (arg, Pmode, NULL_RTX);
1337 /* Store dhc into the first word of the newly allocated buffer. */
1339 dhc = get_dynamic_handler_chain ();
1340 dcc = gen_rtx_MEM (Pmode, plus_constant (XEXP (arg, 0),
1341 GET_MODE_SIZE (Pmode)));
1342 emit_move_insn (arg, dhc);
1344 /* Zero out the start of the cleanup chain. */
1345 emit_move_insn (dcc, const0_rtx);
1347 /* The jmpbuf starts two words into the area allocated. */
1348 buf = plus_constant (XEXP (arg, 0), GET_MODE_SIZE (Pmode)*2);
1350 #ifdef DONT_USE_BUILTIN_SETJMP
1351 x = emit_library_call_value (setjmp_libfunc, NULL_RTX, 1,
1352 TYPE_MODE (integer_type_node), 1,
1354 /* If we come back here for a catch, transfer control to the handler. */
1355 jumpif_rtx (x, ehstack.top->entry->exception_handler_label);
1358 /* A label to continue execution for the no exception case. */
1359 rtx noex = gen_label_rtx();
1360 x = expand_builtin_setjmp (buf, NULL_RTX, noex,
1361 ehstack.top->entry->exception_handler_label);
1366 /* We are committed to this, so update the handler chain. */
1368 emit_move_insn (dhc, force_operand (XEXP (arg, 0), NULL_RTX));
1371 /* Start an exception handling region for the given cleanup action.
1372 All instructions emitted after this point are considered to be part
1373 of the region until expand_eh_region_end is invoked. CLEANUP is
1374 the cleanup action to perform. The return value is true if the
1375 exception region was optimized away. If that case,
1376 expand_eh_region_end does not need to be called for this cleanup,
1379 This routine notices one particular common case in C++ code
1380 generation, and optimizes it so as to not need the exception
1381 region. It works by creating a dynamic cleanup action, instead of
1382 a using an exception region. */
1385 expand_eh_region_start_tree (decl, cleanup)
1389 /* This is the old code. */
1393 /* The optimization only applies to actions protected with
1394 terminate, and only applies if we are using the setjmp/longjmp
1396 if (exceptions_via_longjmp
1397 && protect_cleanup_actions_with_terminate)
1402 /* Ignore any UNSAVE_EXPR. */
1403 if (TREE_CODE (cleanup) == UNSAVE_EXPR)
1404 cleanup = TREE_OPERAND (cleanup, 0);
1406 /* Further, it only applies if the action is a call, if there
1407 are 2 arguments, and if the second argument is 2. */
1409 if (TREE_CODE (cleanup) == CALL_EXPR
1410 && (args = TREE_OPERAND (cleanup, 1))
1411 && (func = TREE_OPERAND (cleanup, 0))
1412 && (arg = TREE_VALUE (args))
1413 && (args = TREE_CHAIN (args))
1415 /* is the second argument 2? */
1416 && TREE_CODE (TREE_VALUE (args)) == INTEGER_CST
1417 && TREE_INT_CST_LOW (TREE_VALUE (args)) == 2
1418 && TREE_INT_CST_HIGH (TREE_VALUE (args)) == 0
1420 /* Make sure there are no other arguments. */
1421 && TREE_CHAIN (args) == NULL_TREE)
1423 /* Arrange for returns and gotos to pop the entry we make on the
1424 dynamic cleanup stack. */
1425 expand_dcc_cleanup (decl);
1426 start_dynamic_cleanup (func, arg);
1431 expand_eh_region_start_for_decl (decl);
1432 ehstack.top->entry->finalization = cleanup;
1437 /* Just like expand_eh_region_start, except if a cleanup action is
1438 entered on the cleanup chain, the TREE_PURPOSE of the element put
1439 on the chain is DECL. DECL should be the associated VAR_DECL, if
1440 any, otherwise it should be NULL_TREE. */
1443 expand_eh_region_start_for_decl (decl)
1448 /* This is the old code. */
1452 /* We need a new block to record the start and end of the
1453 dynamic handler chain. We also want to prevent jumping into
1455 expand_start_bindings (2);
1457 /* But we don't need or want a new temporary level. */
1460 /* Mark this block as created by expand_eh_region_start. This
1461 is so that we can pop the block with expand_end_bindings
1463 mark_block_as_eh_region ();
1465 if (exceptions_via_longjmp)
1467 /* Arrange for returns and gotos to pop the entry we make on the
1468 dynamic handler stack. */
1469 expand_dhc_cleanup (decl);
1472 push_eh_entry (&ehstack);
1473 note = emit_note (NULL_PTR, NOTE_INSN_EH_REGION_BEG);
1474 NOTE_EH_HANDLER (note)
1475 = CODE_LABEL_NUMBER (ehstack.top->entry->exception_handler_label);
1476 if (exceptions_via_longjmp)
1477 start_dynamic_handler ();
1480 /* Start an exception handling region. All instructions emitted after
1481 this point are considered to be part of the region until
1482 expand_eh_region_end is invoked. */
1485 expand_eh_region_start ()
1487 expand_eh_region_start_for_decl (NULL_TREE);
1490 /* End an exception handling region. The information about the region
1491 is found on the top of ehstack.
1493 HANDLER is either the cleanup for the exception region, or if we're
1494 marking the end of a try block, HANDLER is integer_zero_node.
1496 HANDLER will be transformed to rtl when expand_leftover_cleanups
1500 expand_eh_region_end (handler)
1503 struct eh_entry *entry;
1504 struct eh_node *node;
1511 entry = pop_eh_entry (&ehstack);
1513 note = emit_note (NULL_PTR, NOTE_INSN_EH_REGION_END);
1514 ret = NOTE_EH_HANDLER (note)
1515 = CODE_LABEL_NUMBER (entry->exception_handler_label);
1516 if (exceptions_via_longjmp == 0 && ! flag_new_exceptions
1517 /* We share outer_context between regions; only emit it once. */
1518 && INSN_UID (entry->outer_context) == 0)
1522 label = gen_label_rtx ();
1525 /* Emit a label marking the end of this exception region that
1526 is used for rethrowing into the outer context. */
1527 emit_label (entry->outer_context);
1528 expand_internal_throw ();
1533 entry->finalization = handler;
1535 /* create region entry in final exception table */
1536 r = new_eh_region_entry (NOTE_EH_HANDLER (note), entry->rethrow_label);
1538 enqueue_eh_entry (ehqueue, entry);
1540 /* If we have already started ending the bindings, don't recurse. */
1541 if (is_eh_region ())
1543 /* Because we don't need or want a new temporary level and
1544 because we didn't create one in expand_eh_region_start,
1545 create a fake one now to avoid removing one in
1546 expand_end_bindings. */
1549 mark_block_as_not_eh_region ();
1551 expand_end_bindings (NULL_TREE, 0, 0);
1554 /* Go through the goto handlers in the queue, emitting their
1555 handlers if we now have enough information to do so. */
1556 for (node = ehqueue->head; node; node = node->chain)
1557 if (node->entry->goto_entry_p
1558 && node->entry->outer_context == entry->rethrow_label)
1559 emit_cleanup_handler (node->entry);
1561 /* We can't emit handlers for goto entries until their scopes are
1562 complete because we don't know where they need to rethrow to,
1564 if (entry->finalization != integer_zero_node
1565 && (!entry->goto_entry_p
1566 || find_func_region_from_symbol (entry->outer_context) != -1))
1567 emit_cleanup_handler (entry);
1570 /* End the EH region for a goto fixup. We only need them in the region-based
1574 expand_fixup_region_start ()
1576 if (! doing_eh (0) || exceptions_via_longjmp)
1579 expand_eh_region_start ();
1580 /* Mark this entry as the entry for a goto. */
1581 ehstack.top->entry->goto_entry_p = 1;
1584 /* End the EH region for a goto fixup. CLEANUP is the cleanup we just
1585 expanded; to avoid running it twice if it throws, we look through the
1586 ehqueue for a matching region and rethrow from its outer_context. */
1589 expand_fixup_region_end (cleanup)
1592 struct eh_node *node;
1595 if (! doing_eh (0) || exceptions_via_longjmp)
1598 for (node = ehstack.top; node && node->entry->finalization != cleanup; )
1601 for (node = ehqueue->head; node && node->entry->finalization != cleanup; )
1606 /* If the outer context label has not been issued yet, we don't want
1607 to issue it as a part of this region, unless this is the
1608 correct region for the outer context. If we did, then the label for
1609 the outer context will be WITHIN the begin/end labels,
1610 and we could get an infinte loop when it tried to rethrow, or just
1611 generally incorrect execution following a throw. */
1613 if (flag_new_exceptions)
1616 dont_issue = ((INSN_UID (node->entry->outer_context) == 0)
1617 && (ehstack.top->entry != node->entry));
1619 ehstack.top->entry->outer_context = node->entry->outer_context;
1621 /* Since we are rethrowing to the OUTER region, we know we don't need
1622 a jump around sequence for this region, so we'll pretend the outer
1623 context label has been issued by setting INSN_UID to 1, then clearing
1624 it again afterwards. */
1627 INSN_UID (node->entry->outer_context) = 1;
1629 /* Just rethrow. size_zero_node is just a NOP. */
1630 expand_eh_region_end (size_zero_node);
1633 INSN_UID (node->entry->outer_context) = 0;
1636 /* If we are using the setjmp/longjmp EH codegen method, we emit a
1639 Otherwise, we emit a call to __throw and note that we threw
1640 something, so we know we need to generate the necessary code for
1643 Before invoking throw, the __eh_pc variable must have been set up
1644 to contain the PC being thrown from. This address is used by
1645 __throw to determine which exception region (if any) is
1646 responsible for handling the exception. */
1651 if (exceptions_via_longjmp)
1653 emit_library_call (sjthrow_libfunc, 0, VOIDmode, 0);
1657 #ifdef JUMP_TO_THROW
1658 emit_indirect_jump (throw_libfunc);
1660 emit_library_call (throw_libfunc, 0, VOIDmode, 0);
1666 /* Throw the current exception. If appropriate, this is done by jumping
1667 to the next handler. */
1670 expand_internal_throw ()
1675 /* Called from expand_exception_blocks and expand_end_catch_block to
1676 emit any pending handlers/cleanups queued from expand_eh_region_end. */
1679 expand_leftover_cleanups ()
1681 struct eh_entry *entry;
1683 for (entry = dequeue_eh_entry (ehqueue);
1685 entry = dequeue_eh_entry (ehqueue))
1687 /* A leftover try block. Shouldn't be one here. */
1688 if (entry->finalization == integer_zero_node)
1695 /* Called at the start of a block of try statements. */
1697 expand_start_try_stmts ()
1702 expand_eh_region_start ();
1705 /* Called to begin a catch clause. The parameter is the object which
1706 will be passed to the runtime type check routine. */
1708 start_catch_handler (rtime)
1712 int insn_region_num;
1713 int eh_region_entry;
1718 handler_label = catchstack.top->entry->exception_handler_label;
1719 insn_region_num = CODE_LABEL_NUMBER (handler_label);
1720 eh_region_entry = find_func_region (insn_region_num);
1722 /* If we've already issued this label, pick a new one */
1723 if (catchstack.top->entry->label_used)
1724 handler_label = gen_exception_label ();
1726 catchstack.top->entry->label_used = 1;
1728 receive_exception_label (handler_label);
1730 add_new_handler (eh_region_entry, get_new_handler (handler_label, rtime));
1732 if (flag_new_exceptions && ! exceptions_via_longjmp)
1735 /* Under the old mechanism, as well as setjmp/longjmp, we need to
1736 issue code to compare 'rtime' to the value in eh_info, via the
1737 matching function in eh_info. If its is false, we branch around
1738 the handler we are about to issue. */
1740 if (rtime != NULL_TREE && rtime != CATCH_ALL_TYPE)
1742 rtx call_rtx, rtime_address;
1744 if (catchstack.top->entry->false_label != NULL_RTX)
1746 error ("Never issued previous false_label");
1749 catchstack.top->entry->false_label = gen_exception_label ();
1751 rtime_address = expand_expr (rtime, NULL_RTX, Pmode, EXPAND_INITIALIZER);
1752 #ifdef POINTERS_EXTEND_UNSIGNED
1753 rtime_address = convert_memory_address (Pmode, rtime_address);
1755 rtime_address = force_reg (Pmode, rtime_address);
1757 /* Now issue the call, and branch around handler if needed */
1758 call_rtx = emit_library_call_value (eh_rtime_match_libfunc, NULL_RTX,
1759 0, TYPE_MODE (integer_type_node),
1760 1, rtime_address, Pmode);
1762 /* Did the function return true? */
1763 emit_cmp_and_jump_insns (call_rtx, const0_rtx, EQ, NULL_RTX,
1764 GET_MODE (call_rtx), 0, 0,
1765 catchstack.top->entry->false_label);
1769 /* Called to end a catch clause. If we aren't using the new exception
1770 model tabel mechanism, we need to issue the branch-around label
1771 for the end of the catch block. */
1774 end_catch_handler ()
1779 if (flag_new_exceptions && ! exceptions_via_longjmp)
1785 /* A NULL label implies the catch clause was a catch all or cleanup */
1786 if (catchstack.top->entry->false_label == NULL_RTX)
1789 emit_label (catchstack.top->entry->false_label);
1790 catchstack.top->entry->false_label = NULL_RTX;
1793 /* Save away the current ehqueue. */
1799 q = (struct eh_queue *) xcalloc (1, sizeof (struct eh_queue));
1804 /* Restore a previously pushed ehqueue. */
1810 expand_leftover_cleanups ();
1816 /* Emit the handler specified by ENTRY. */
1819 emit_cleanup_handler (entry)
1820 struct eh_entry *entry;
1825 /* Since the cleanup could itself contain try-catch blocks, we
1826 squirrel away the current queue and replace it when we are done
1827 with this function. */
1830 /* Put these handler instructions in a sequence. */
1831 do_pending_stack_adjust ();
1834 /* Emit the label for the cleanup handler for this region, and
1835 expand the code for the handler.
1837 Note that a catch region is handled as a side-effect here; for a
1838 try block, entry->finalization will contain integer_zero_node, so
1839 no code will be generated in the expand_expr call below. But, the
1840 label for the handler will still be emitted, so any code emitted
1841 after this point will end up being the handler. */
1843 receive_exception_label (entry->exception_handler_label);
1845 /* register a handler for this cleanup region */
1846 add_new_handler (find_func_region (CODE_LABEL_NUMBER (entry->exception_handler_label)),
1847 get_new_handler (entry->exception_handler_label, NULL));
1849 /* And now generate the insns for the cleanup handler. */
1850 expand_expr (entry->finalization, const0_rtx, VOIDmode, 0);
1852 prev = get_last_insn ();
1853 if (prev == NULL || GET_CODE (prev) != BARRIER)
1854 /* Code to throw out to outer context when we fall off end of the
1855 handler. We can't do this here for catch blocks, so it's done
1856 in expand_end_all_catch instead. */
1857 expand_rethrow (entry->outer_context);
1859 /* Finish this sequence. */
1860 do_pending_stack_adjust ();
1861 handler_insns = get_insns ();
1864 /* And add it to the CATCH_CLAUSES. */
1865 push_to_sequence (catch_clauses);
1866 emit_insns (handler_insns);
1867 catch_clauses = get_insns ();
1870 /* Now we've left the handler. */
1874 /* Generate RTL for the start of a group of catch clauses.
1876 It is responsible for starting a new instruction sequence for the
1877 instructions in the catch block, and expanding the handlers for the
1878 internally-generated exception regions nested within the try block
1879 corresponding to this catch block. */
1882 expand_start_all_catch ()
1884 struct eh_entry *entry;
1891 outer_context = ehstack.top->entry->outer_context;
1893 /* End the try block. */
1894 expand_eh_region_end (integer_zero_node);
1896 emit_line_note (input_filename, lineno);
1897 label = build_decl (LABEL_DECL, NULL_TREE, NULL_TREE);
1899 /* The label for the exception handling block that we will save.
1900 This is Lresume in the documentation. */
1901 expand_label (label);
1903 /* Push the label that points to where normal flow is resumed onto
1904 the top of the label stack. */
1905 push_label_entry (&caught_return_label_stack, NULL_RTX, label);
1907 /* Start a new sequence for all the catch blocks. We will add this
1908 to the global sequence catch_clauses when we have completed all
1909 the handlers in this handler-seq. */
1912 /* Throw away entries in the queue that we won't need anymore. We
1913 need entries for regions that have ended but to which there might
1914 still be gotos pending. */
1915 for (entry = dequeue_eh_entry (ehqueue);
1916 entry->finalization != integer_zero_node;
1917 entry = dequeue_eh_entry (ehqueue))
1920 /* At this point, all the cleanups are done, and the ehqueue now has
1921 the current exception region at its head. We dequeue it, and put it
1922 on the catch stack. */
1923 push_entry (&catchstack, entry);
1925 /* If we are not doing setjmp/longjmp EH, because we are reordered
1926 out of line, we arrange to rethrow in the outer context. We need to
1927 do this because we are not physically within the region, if any, that
1928 logically contains this catch block. */
1929 if (! exceptions_via_longjmp)
1931 expand_eh_region_start ();
1932 ehstack.top->entry->outer_context = outer_context;
1937 /* Finish up the catch block. At this point all the insns for the
1938 catch clauses have already been generated, so we only have to add
1939 them to the catch_clauses list. We also want to make sure that if
1940 we fall off the end of the catch clauses that we rethrow to the
1944 expand_end_all_catch ()
1946 rtx new_catch_clause;
1947 struct eh_entry *entry;
1952 /* Dequeue the current catch clause region. */
1953 entry = pop_eh_entry (&catchstack);
1956 if (! exceptions_via_longjmp)
1958 rtx outer_context = ehstack.top->entry->outer_context;
1960 /* Finish the rethrow region. size_zero_node is just a NOP. */
1961 expand_eh_region_end (size_zero_node);
1962 /* New exceptions handling models will never have a fall through
1963 of a catch clause */
1964 if (!flag_new_exceptions)
1965 expand_rethrow (outer_context);
1968 expand_rethrow (NULL_RTX);
1970 /* Code to throw out to outer context, if we fall off end of catch
1971 handlers. This is rethrow (Lresume, same id, same obj) in the
1972 documentation. We use Lresume because we know that it will throw
1973 to the correct context.
1975 In other words, if the catch handler doesn't exit or return, we
1976 do a "throw" (using the address of Lresume as the point being
1977 thrown from) so that the outer EH region can then try to process
1980 /* Now we have the complete catch sequence. */
1981 new_catch_clause = get_insns ();
1984 /* This level of catch blocks is done, so set up the successful
1985 catch jump label for the next layer of catch blocks. */
1986 pop_label_entry (&caught_return_label_stack);
1987 pop_label_entry (&outer_context_label_stack);
1989 /* Add the new sequence of catches to the main one for this function. */
1990 push_to_sequence (catch_clauses);
1991 emit_insns (new_catch_clause);
1992 catch_clauses = get_insns ();
1995 /* Here we fall through into the continuation code. */
1998 /* Rethrow from the outer context LABEL. */
2001 expand_rethrow (label)
2004 if (exceptions_via_longjmp)
2007 if (flag_new_exceptions)
2011 if (label == NULL_RTX)
2012 label = last_rethrow_symbol;
2013 emit_library_call (rethrow_libfunc, 0, VOIDmode, 1, label, Pmode);
2014 region = find_func_region (eh_region_from_symbol (label));
2015 /* If the region is -1, it doesn't exist yet. We should be
2016 trying to rethrow there yet. */
2019 function_eh_regions[region].rethrow_ref = 1;
2021 /* Search backwards for the actual call insn. */
2022 insn = get_last_insn ();
2023 while (GET_CODE (insn) != CALL_INSN)
2024 insn = PREV_INSN (insn);
2025 delete_insns_since (insn);
2027 /* Mark the label/symbol on the call. */
2028 REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_EH_RETHROW, label,
2036 /* Begin a region that will contain entries created with
2037 add_partial_entry. */
2040 begin_protect_partials ()
2042 /* Put the entry on the function obstack. */
2043 push_obstacks_nochange ();
2044 resume_temporary_allocation ();
2046 /* Push room for a new list. */
2047 protect_list = tree_cons (NULL_TREE, NULL_TREE, protect_list);
2049 /* We're done with the function obstack now. */
2053 /* End all the pending exception regions on protect_list. The handlers
2054 will be emitted when expand_leftover_cleanups is invoked. */
2057 end_protect_partials ()
2061 /* For backwards compatibility, we allow callers to omit the call to
2062 begin_protect_partials for the outermost region. So,
2063 PROTECT_LIST may be NULL. */
2067 /* End all the exception regions. */
2068 for (t = TREE_VALUE (protect_list); t; t = TREE_CHAIN (t))
2069 expand_eh_region_end (TREE_VALUE (t));
2071 /* Pop the topmost entry. */
2072 protect_list = TREE_CHAIN (protect_list);
2076 /* Arrange for __terminate to be called if there is an unhandled throw
2080 protect_with_terminate (e)
2083 /* We only need to do this when using setjmp/longjmp EH and the
2084 language requires it, as otherwise we protect all of the handlers
2085 at once, if we need to. */
2086 if (exceptions_via_longjmp && protect_cleanup_actions_with_terminate)
2088 tree handler, result;
2090 /* All cleanups must be on the function_obstack. */
2091 push_obstacks_nochange ();
2092 resume_temporary_allocation ();
2094 handler = make_node (RTL_EXPR);
2095 TREE_TYPE (handler) = void_type_node;
2096 RTL_EXPR_RTL (handler) = const0_rtx;
2097 TREE_SIDE_EFFECTS (handler) = 1;
2098 start_sequence_for_rtl_expr (handler);
2100 emit_library_call (terminate_libfunc, 0, VOIDmode, 0);
2103 RTL_EXPR_SEQUENCE (handler) = get_insns ();
2106 result = build (TRY_CATCH_EXPR, TREE_TYPE (e), e, handler);
2107 TREE_SIDE_EFFECTS (result) = TREE_SIDE_EFFECTS (e);
2108 TREE_THIS_VOLATILE (result) = TREE_THIS_VOLATILE (e);
2109 TREE_READONLY (result) = TREE_READONLY (e);
2119 /* The exception table that we build that is used for looking up and
2120 dispatching exceptions, the current number of entries, and its
2121 maximum size before we have to extend it.
2123 The number in eh_table is the code label number of the exception
2124 handler for the region. This is added by add_eh_table_entry and
2125 used by output_exception_table_entry. */
2127 static int *eh_table = NULL;
2128 static int eh_table_size = 0;
2129 static int eh_table_max_size = 0;
2131 /* Note the need for an exception table entry for region N. If we
2132 don't need to output an explicit exception table, avoid all of the
2135 Called from final_scan_insn when a NOTE_INSN_EH_REGION_BEG is seen.
2136 (Or NOTE_INSN_EH_REGION_END sometimes)
2137 N is the NOTE_EH_HANDLER of the note, which comes from the code
2138 label number of the exception handler for the region. */
2141 add_eh_table_entry (n)
2144 #ifndef OMIT_EH_TABLE
2145 if (eh_table_size >= eh_table_max_size)
2149 eh_table_max_size += eh_table_max_size>>1;
2151 if (eh_table_max_size < 0)
2154 eh_table = (int *) xrealloc (eh_table,
2155 eh_table_max_size * sizeof (int));
2159 eh_table_max_size = 252;
2160 eh_table = (int *) xmalloc (eh_table_max_size * sizeof (int));
2163 eh_table[eh_table_size++] = n;
2167 /* Return a non-zero value if we need to output an exception table.
2169 On some platforms, we don't have to output a table explicitly.
2170 This routine doesn't mean we don't have one. */
2173 exception_table_p ()
2181 /* Output the entry of the exception table corresponding to the
2182 exception region numbered N to file FILE.
2184 N is the code label number corresponding to the handler of the
2188 output_exception_table_entry (file, n)
2194 struct handler_info *handler = get_first_handler (n);
2195 int index = find_func_region (n);
2198 /* form and emit the rethrow label, if needed */
2199 rethrow = function_eh_regions[index].rethrow_label;
2200 if (rethrow != NULL_RTX && !flag_new_exceptions)
2202 if (rethrow != NULL_RTX && handler == NULL)
2203 if (! function_eh_regions[index].rethrow_ref)
2207 for ( ; handler != NULL || rethrow != NULL_RTX; handler = handler->next)
2209 /* rethrow label should indicate the LAST entry for a region */
2210 if (rethrow != NULL_RTX && (handler == NULL || handler->next == NULL))
2212 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", n);
2213 assemble_label(buf);
2217 ASM_GENERATE_INTERNAL_LABEL (buf, "LEHB", n);
2218 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
2219 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
2221 ASM_GENERATE_INTERNAL_LABEL (buf, "LEHE", n);
2222 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
2223 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
2225 if (handler == NULL)
2226 assemble_integer (GEN_INT (0), POINTER_SIZE / BITS_PER_UNIT, 1);
2229 ASM_GENERATE_INTERNAL_LABEL (buf, "L", handler->handler_number);
2230 sym = gen_rtx_SYMBOL_REF (Pmode, buf);
2231 assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1);
2234 if (flag_new_exceptions)
2236 if (handler == NULL || handler->type_info == NULL)
2237 assemble_integer (const0_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
2239 if (handler->type_info == CATCH_ALL_TYPE)
2240 assemble_integer (GEN_INT (CATCH_ALL_TYPE),
2241 POINTER_SIZE / BITS_PER_UNIT, 1);
2243 output_constant ((tree)(handler->type_info),
2244 POINTER_SIZE / BITS_PER_UNIT);
2246 putc ('\n', file); /* blank line */
2247 /* We only output the first label under the old scheme */
2248 if (! flag_new_exceptions || handler == NULL)
2253 /* Output the exception table if we have and need one. */
2255 static short language_code = 0;
2256 static short version_code = 0;
2258 /* This routine will set the language code for exceptions. */
2260 set_exception_lang_code (code)
2263 language_code = code;
2266 /* This routine will set the language version code for exceptions. */
2268 set_exception_version_code (code)
2271 version_code = code;
2276 output_exception_table ()
2280 extern FILE *asm_out_file;
2282 if (! doing_eh (0) || ! eh_table)
2285 exception_section ();
2287 /* Beginning marker for table. */
2288 assemble_align (GET_MODE_ALIGNMENT (ptr_mode));
2289 assemble_label ("__EXCEPTION_TABLE__");
2291 if (flag_new_exceptions)
2293 assemble_integer (GEN_INT (NEW_EH_RUNTIME),
2294 POINTER_SIZE / BITS_PER_UNIT, 1);
2295 assemble_integer (GEN_INT (language_code), 2 , 1);
2296 assemble_integer (GEN_INT (version_code), 2 , 1);
2298 /* Add enough padding to make sure table aligns on a pointer boundry. */
2299 i = GET_MODE_ALIGNMENT (ptr_mode) / BITS_PER_UNIT - 4;
2300 for ( ; i < 0; i = i + GET_MODE_ALIGNMENT (ptr_mode) / BITS_PER_UNIT)
2303 assemble_integer (const0_rtx, i , 1);
2305 /* Generate the label for offset calculations on rethrows */
2306 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", 0);
2307 assemble_label(buf);
2310 for (i = 0; i < eh_table_size; ++i)
2311 output_exception_table_entry (asm_out_file, eh_table[i]);
2314 clear_function_eh_region ();
2316 /* Ending marker for table. */
2317 /* Generate the label for end of table. */
2318 ASM_GENERATE_INTERNAL_LABEL (buf, "LRTH", CODE_LABEL_NUMBER (final_rethrow));
2319 assemble_label(buf);
2320 assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
2322 /* for binary compatability, the old __throw checked the second
2323 position for a -1, so we should output at least 2 -1's */
2324 if (! flag_new_exceptions)
2325 assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1);
2327 putc ('\n', asm_out_file); /* blank line */
2330 /* Emit code to get EH context.
2332 We have to scan thru the code to find possible EH context registers.
2333 Inlined functions may use it too, and thus we'll have to be able
2336 This is done only if using exceptions_via_longjmp. */
2347 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2348 if (GET_CODE (insn) == INSN
2349 && GET_CODE (PATTERN (insn)) == USE)
2351 rtx reg = find_reg_note (insn, REG_EH_CONTEXT, 0);
2358 /* If this is the first use insn, emit the call here. This
2359 will always be at the top of our function, because if
2360 expand_inline_function notices a REG_EH_CONTEXT note, it
2361 adds a use insn to this function as well. */
2363 ehc = call_get_eh_context ();
2365 emit_move_insn (XEXP (reg, 0), ehc);
2366 insns = get_insns ();
2369 emit_insns_before (insns, insn);
2374 /* Scan the current insns and build a list of handler labels. The
2375 resulting list is placed in the global variable exception_handler_labels.
2377 It is called after the last exception handling region is added to
2378 the current function (when the rtl is almost all built for the
2379 current function) and before the jump optimization pass. */
2382 find_exception_handler_labels ()
2386 exception_handler_labels = NULL_RTX;
2388 /* If we aren't doing exception handling, there isn't much to check. */
2392 /* For each start of a region, add its label to the list. */
2394 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2396 struct handler_info* ptr;
2397 if (GET_CODE (insn) == NOTE
2398 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2400 ptr = get_first_handler (NOTE_EH_HANDLER (insn));
2401 for ( ; ptr; ptr = ptr->next)
2403 /* make sure label isn't in the list already */
2405 for (x = exception_handler_labels; x; x = XEXP (x, 1))
2406 if (XEXP (x, 0) == ptr->handler_label)
2409 exception_handler_labels = gen_rtx_EXPR_LIST (VOIDmode,
2410 ptr->handler_label, exception_handler_labels);
2416 /* Return a value of 1 if the parameter label number is an exception handler
2417 label. Return 0 otherwise. */
2420 is_exception_handler_label (lab)
2424 for (x = exception_handler_labels ; x ; x = XEXP (x, 1))
2425 if (lab == CODE_LABEL_NUMBER (XEXP (x, 0)))
2430 /* Perform sanity checking on the exception_handler_labels list.
2432 Can be called after find_exception_handler_labels is called to
2433 build the list of exception handlers for the current function and
2434 before we finish processing the current function. */
2437 check_exception_handler_labels ()
2441 /* If we aren't doing exception handling, there isn't much to check. */
2445 /* Make sure there is no more than 1 copy of a label */
2446 for (insn = exception_handler_labels; insn; insn = XEXP (insn, 1))
2449 for (insn2 = exception_handler_labels; insn2; insn2 = XEXP (insn2, 1))
2450 if (XEXP (insn, 0) == XEXP (insn2, 0))
2453 warning ("Counted %d copies of EH region %d in list.\n", count,
2454 CODE_LABEL_NUMBER (insn));
2459 /* Mark the children of NODE for GC. */
2463 struct eh_node *node;
2469 ggc_mark_rtx (node->entry->outer_context);
2470 ggc_mark_rtx (node->entry->exception_handler_label);
2471 ggc_mark_tree (node->entry->finalization);
2472 ggc_mark_rtx (node->entry->false_label);
2473 ggc_mark_rtx (node->entry->rethrow_label);
2475 node = node ->chain;
2479 /* Mark S for GC. */
2486 mark_eh_node (s->top);
2489 /* Mark Q for GC. */
2497 mark_eh_node (q->head);
2502 /* Mark NODE for GC. A label_node contains a union containing either
2503 a tree or an rtx. This label_node will contain a tree. */
2506 mark_tree_label_node (node)
2507 struct label_node *node;
2511 ggc_mark_tree (node->u.tlabel);
2516 /* Mark EH for GC. */
2520 struct eh_status *eh;
2525 mark_eh_stack (&eh->x_ehstack);
2526 mark_eh_stack (&eh->x_catchstack);
2527 mark_eh_queue (eh->x_ehqueue);
2528 ggc_mark_rtx (eh->x_catch_clauses);
2530 lang_mark_false_label_stack (eh->x_false_label_stack);
2531 mark_tree_label_node (eh->x_caught_return_label_stack);
2533 ggc_mark_tree (eh->x_protect_list);
2534 ggc_mark_rtx (eh->ehc);
2535 ggc_mark_rtx (eh->x_eh_return_stub_label);
2538 /* Mark ARG (which is really a struct func_eh_entry**) for GC. */
2541 mark_func_eh_entry (arg)
2544 struct func_eh_entry *fee;
2545 struct handler_info *h;
2548 fee = *((struct func_eh_entry **) arg);
2550 for (i = 0; i < current_func_eh_entry; ++i)
2552 ggc_mark_rtx (fee->rethrow_label);
2553 for (h = fee->handlers; h; h = h->next)
2555 ggc_mark_rtx (h->handler_label);
2556 if (h->type_info != CATCH_ALL_TYPE)
2557 ggc_mark_tree ((tree) h->type_info);
2560 /* Skip to the next entry in the array. */
2565 /* This group of functions initializes the exception handling data
2566 structures at the start of the compilation, initializes the data
2567 structures at the start of a function, and saves and restores the
2568 exception handling data structures for the start/end of a nested
2571 /* Toplevel initialization for EH things. */
2576 first_rethrow_symbol = create_rethrow_ref (0);
2577 final_rethrow = gen_exception_label ();
2578 last_rethrow_symbol = create_rethrow_ref (CODE_LABEL_NUMBER (final_rethrow));
2580 ggc_add_rtx_root (&exception_handler_labels, 1);
2581 ggc_add_rtx_root (&eh_return_context, 1);
2582 ggc_add_rtx_root (&eh_return_stack_adjust, 1);
2583 ggc_add_rtx_root (&eh_return_handler, 1);
2584 ggc_add_rtx_root (&first_rethrow_symbol, 1);
2585 ggc_add_rtx_root (&final_rethrow, 1);
2586 ggc_add_rtx_root (&last_rethrow_symbol, 1);
2587 ggc_add_root (&function_eh_regions, 1, sizeof (function_eh_regions),
2588 mark_func_eh_entry);
2591 /* Initialize the per-function EH information. */
2594 init_eh_for_function ()
2596 cfun->eh = (struct eh_status *) xcalloc (1, sizeof (struct eh_status));
2597 ehqueue = (struct eh_queue *) xcalloc (1, sizeof (struct eh_queue));
2598 eh_return_context = NULL_RTX;
2599 eh_return_stack_adjust = NULL_RTX;
2600 eh_return_handler = NULL_RTX;
2607 free (f->eh->x_ehqueue);
2612 /* This section is for the exception handling specific optimization
2613 pass. First are the internal routines, and then the main
2614 optimization pass. */
2616 /* Determine if the given INSN can throw an exception. */
2622 /* Calls can always potentially throw exceptions, unless they have
2623 a REG_EH_REGION note with a value of 0 or less. */
2624 if (GET_CODE (insn) == CALL_INSN)
2626 rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX);
2627 if (!note || XINT (XEXP (note, 0), 0) > 0)
2631 if (asynchronous_exceptions)
2633 /* If we wanted asynchronous exceptions, then everything but NOTEs
2634 and CODE_LABELs could throw. */
2635 if (GET_CODE (insn) != NOTE && GET_CODE (insn) != CODE_LABEL)
2642 /* Scan a exception region looking for the matching end and then
2643 remove it if possible. INSN is the start of the region, N is the
2644 region number, and DELETE_OUTER is to note if anything in this
2647 Regions are removed if they cannot possibly catch an exception.
2648 This is determined by invoking can_throw on each insn within the
2649 region; if can_throw returns true for any of the instructions, the
2650 region can catch an exception, since there is an insn within the
2651 region that is capable of throwing an exception.
2653 Returns the NOTE_INSN_EH_REGION_END corresponding to this region, or
2654 calls abort if it can't find one.
2656 Can abort if INSN is not a NOTE_INSN_EH_REGION_BEGIN, or if N doesn't
2657 correspond to the region number, or if DELETE_OUTER is NULL. */
2660 scan_region (insn, n, delete_outer)
2667 /* Assume we can delete the region. */
2670 /* Can't delete something which is rethrown to. */
2671 if (rethrow_used (n))
2674 if (insn == NULL_RTX
2675 || GET_CODE (insn) != NOTE
2676 || NOTE_LINE_NUMBER (insn) != NOTE_INSN_EH_REGION_BEG
2677 || NOTE_EH_HANDLER (insn) != n
2678 || delete_outer == NULL)
2681 insn = NEXT_INSN (insn);
2683 /* Look for the matching end. */
2684 while (! (GET_CODE (insn) == NOTE
2685 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END))
2687 /* If anything can throw, we can't remove the region. */
2688 if (delete && can_throw (insn))
2693 /* Watch out for and handle nested regions. */
2694 if (GET_CODE (insn) == NOTE
2695 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2697 insn = scan_region (insn, NOTE_EH_HANDLER (insn), &delete);
2700 insn = NEXT_INSN (insn);
2703 /* The _BEG/_END NOTEs must match and nest. */
2704 if (NOTE_EH_HANDLER (insn) != n)
2707 /* If anything in this exception region can throw, we can throw. */
2712 /* Delete the start and end of the region. */
2713 delete_insn (start);
2716 /* We no longer removed labels here, since flow will now remove any
2717 handler which cannot be called any more. */
2720 /* Only do this part if we have built the exception handler
2722 if (exception_handler_labels)
2724 rtx x, *prev = &exception_handler_labels;
2726 /* Find it in the list of handlers. */
2727 for (x = exception_handler_labels; x; x = XEXP (x, 1))
2729 rtx label = XEXP (x, 0);
2730 if (CODE_LABEL_NUMBER (label) == n)
2732 /* If we are the last reference to the handler,
2734 if (--LABEL_NUSES (label) == 0)
2735 delete_insn (label);
2739 /* Remove it from the list of exception handler
2740 labels, if we are optimizing. If we are not, then
2741 leave it in the list, as we are not really going to
2742 remove the region. */
2743 *prev = XEXP (x, 1);
2750 prev = &XEXP (x, 1);
2758 /* Perform various interesting optimizations for exception handling
2761 We look for empty exception regions and make them go (away). The
2762 jump optimization code will remove the handler if nothing else uses
2766 exception_optimize ()
2771 /* Remove empty regions. */
2772 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2774 if (GET_CODE (insn) == NOTE
2775 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2777 /* Since scan_region will return the NOTE_INSN_EH_REGION_END
2778 insn, we will indirectly skip through all the insns
2779 inbetween. We are also guaranteed that the value of insn
2780 returned will be valid, as otherwise scan_region won't
2782 insn = scan_region (insn, NOTE_EH_HANDLER (insn), &n);
2787 /* This function determines whether any of the exception regions in the
2788 current function are targets of a rethrow or not, and set the
2789 reference flag according. */
2791 update_rethrow_references ()
2795 int *saw_region, *saw_rethrow;
2797 if (!flag_new_exceptions)
2800 saw_region = (int *) xcalloc (current_func_eh_entry, sizeof (int));
2801 saw_rethrow = (int *) xcalloc (current_func_eh_entry, sizeof (int));
2803 /* Determine what regions exist, and whether there are any rethrows
2804 to those regions or not. */
2805 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2806 if (GET_CODE (insn) == CALL_INSN)
2808 rtx note = find_reg_note (insn, REG_EH_RETHROW, NULL_RTX);
2811 region = eh_region_from_symbol (XEXP (note, 0));
2812 region = find_func_region (region);
2813 saw_rethrow[region] = 1;
2817 if (GET_CODE (insn) == NOTE)
2819 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
2821 region = find_func_region (NOTE_EH_HANDLER (insn));
2822 saw_region[region] = 1;
2826 /* For any regions we did see, set the referenced flag. */
2827 for (x = 0; x < current_func_eh_entry; x++)
2829 function_eh_regions[x].rethrow_ref = saw_rethrow[x];
2836 /* Various hooks for the DWARF 2 __throw routine. */
2838 /* Do any necessary initialization to access arbitrary stack frames.
2839 On the SPARC, this means flushing the register windows. */
2842 expand_builtin_unwind_init ()
2844 /* Set this so all the registers get saved in our frame; we need to be
2845 able to copy the saved values for any registers from frames we unwind. */
2846 current_function_has_nonlocal_label = 1;
2848 #ifdef SETUP_FRAME_ADDRESSES
2849 SETUP_FRAME_ADDRESSES ();
2853 /* Given a value extracted from the return address register or stack slot,
2854 return the actual address encoded in that value. */
2857 expand_builtin_extract_return_addr (addr_tree)
2860 rtx addr = expand_expr (addr_tree, NULL_RTX, Pmode, 0);
2861 return eh_outer_context (addr);
2864 /* Given an actual address in addr_tree, do any necessary encoding
2865 and return the value to be stored in the return address register or
2866 stack slot so the epilogue will return to that address. */
2869 expand_builtin_frob_return_addr (addr_tree)
2872 rtx addr = expand_expr (addr_tree, NULL_RTX, Pmode, 0);
2873 #ifdef RETURN_ADDR_OFFSET
2874 addr = plus_constant (addr, -RETURN_ADDR_OFFSET);
2879 /* Choose three registers for communication between the main body of
2880 __throw and the epilogue (or eh stub) and the exception handler.
2881 We must do this with hard registers because the epilogue itself
2882 will be generated after reload, at which point we may not reference
2885 The first passes the exception context to the handler. For this
2886 we use the return value register for a void*.
2888 The second holds the stack pointer value to be restored. For
2889 this we use the static chain register if it exists and is different
2890 from the previous, otherwise some arbitrary call-clobbered register.
2892 The third holds the address of the handler itself. Here we use
2893 some arbitrary call-clobbered register. */
2896 eh_regs (pcontext, psp, pra, outgoing)
2897 rtx *pcontext, *psp, *pra;
2898 int outgoing ATTRIBUTE_UNUSED;
2900 rtx rcontext, rsp, rra;
2903 #ifdef FUNCTION_OUTGOING_VALUE
2905 rcontext = FUNCTION_OUTGOING_VALUE (build_pointer_type (void_type_node),
2906 current_function_decl);
2909 rcontext = FUNCTION_VALUE (build_pointer_type (void_type_node),
2910 current_function_decl);
2912 #ifdef STATIC_CHAIN_REGNUM
2914 rsp = static_chain_incoming_rtx;
2916 rsp = static_chain_rtx;
2917 if (REGNO (rsp) == REGNO (rcontext))
2918 #endif /* STATIC_CHAIN_REGNUM */
2921 if (rsp == NULL_RTX)
2923 for (i = 0; i < FIRST_PSEUDO_REGISTER; ++i)
2924 if (call_used_regs[i] && ! fixed_regs[i] && i != REGNO (rcontext))
2926 if (i == FIRST_PSEUDO_REGISTER)
2929 rsp = gen_rtx_REG (Pmode, i);
2932 for (i = 0; i < FIRST_PSEUDO_REGISTER; ++i)
2933 if (call_used_regs[i] && ! fixed_regs[i]
2934 && i != REGNO (rcontext) && i != REGNO (rsp))
2936 if (i == FIRST_PSEUDO_REGISTER)
2939 rra = gen_rtx_REG (Pmode, i);
2941 *pcontext = rcontext;
2946 /* Retrieve the register which contains the pointer to the eh_context
2947 structure set the __throw. */
2951 get_reg_for_handler ()
2954 reg1 = FUNCTION_VALUE (build_pointer_type (void_type_node),
2955 current_function_decl);
2960 /* Set up the epilogue with the magic bits we'll need to return to the
2961 exception handler. */
2964 expand_builtin_eh_return (context, stack, handler)
2965 tree context, stack, handler;
2967 if (eh_return_context)
2968 error("Duplicate call to __builtin_eh_return");
2971 = copy_to_reg (expand_expr (context, NULL_RTX, VOIDmode, 0));
2972 eh_return_stack_adjust
2973 = copy_to_reg (expand_expr (stack, NULL_RTX, VOIDmode, 0));
2975 = copy_to_reg (expand_expr (handler, NULL_RTX, VOIDmode, 0));
2981 rtx reg1, reg2, reg3;
2982 rtx stub_start, after_stub;
2985 if (!eh_return_context)
2988 current_function_cannot_inline = N_("function uses __builtin_eh_return");
2990 eh_regs (®1, ®2, ®3, 1);
2991 #ifdef POINTERS_EXTEND_UNSIGNED
2992 eh_return_context = convert_memory_address (Pmode, eh_return_context);
2993 eh_return_stack_adjust =
2994 convert_memory_address (Pmode, eh_return_stack_adjust);
2995 eh_return_handler = convert_memory_address (Pmode, eh_return_handler);
2997 emit_move_insn (reg1, eh_return_context);
2998 emit_move_insn (reg2, eh_return_stack_adjust);
2999 emit_move_insn (reg3, eh_return_handler);
3001 /* Talk directly to the target's epilogue code when possible. */
3003 #ifdef HAVE_eh_epilogue
3004 if (HAVE_eh_epilogue)
3006 emit_insn (gen_eh_epilogue (reg1, reg2, reg3));
3011 /* Otherwise, use the same stub technique we had before. */
3013 eh_return_stub_label = stub_start = gen_label_rtx ();
3014 after_stub = gen_label_rtx ();
3016 /* Set the return address to the stub label. */
3018 ra = expand_builtin_return_addr (BUILT_IN_RETURN_ADDRESS,
3019 0, hard_frame_pointer_rtx);
3020 if (GET_CODE (ra) == REG && REGNO (ra) >= FIRST_PSEUDO_REGISTER)
3023 tmp = memory_address (Pmode, gen_rtx_LABEL_REF (Pmode, stub_start));
3024 #ifdef RETURN_ADDR_OFFSET
3025 tmp = plus_constant (tmp, -RETURN_ADDR_OFFSET);
3027 tmp = force_operand (tmp, ra);
3029 emit_move_insn (ra, tmp);
3031 /* Indicate that the registers are in fact used. */
3032 emit_insn (gen_rtx_USE (VOIDmode, reg1));
3033 emit_insn (gen_rtx_USE (VOIDmode, reg2));
3034 emit_insn (gen_rtx_USE (VOIDmode, reg3));
3035 if (GET_CODE (ra) == REG)
3036 emit_insn (gen_rtx_USE (VOIDmode, ra));
3038 /* Generate the stub. */
3040 emit_jump (after_stub);
3041 emit_label (stub_start);
3043 eh_regs (®1, ®2, ®3, 0);
3044 adjust_stack (reg2);
3045 emit_indirect_jump (reg3);
3047 emit_label (after_stub);
3051 /* This contains the code required to verify whether arbitrary instructions
3052 are in the same exception region. */
3054 static int *insn_eh_region = (int *)0;
3055 static int maximum_uid;
3058 set_insn_eh_region (first, region_num)
3065 for (insn = *first; insn; insn = NEXT_INSN (insn))
3067 if ((GET_CODE (insn) == NOTE)
3068 && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG))
3070 rnum = NOTE_EH_HANDLER (insn);
3071 insn_eh_region[INSN_UID (insn)] = rnum;
3072 insn = NEXT_INSN (insn);
3073 set_insn_eh_region (&insn, rnum);
3074 /* Upon return, insn points to the EH_REGION_END of nested region */
3077 insn_eh_region[INSN_UID (insn)] = region_num;
3078 if ((GET_CODE (insn) == NOTE) &&
3079 (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END))
3085 /* Free the insn table, an make sure it cannot be used again. */
3088 free_insn_eh_region ()
3095 free (insn_eh_region);
3096 insn_eh_region = (int *)0;
3100 /* Initialize the table. max_uid must be calculated and handed into
3101 this routine. If it is unavailable, passing a value of 0 will
3102 cause this routine to calculate it as well. */
3105 init_insn_eh_region (first, max_uid)
3115 free_insn_eh_region();
3118 for (insn = first; insn; insn = NEXT_INSN (insn))
3119 if (INSN_UID (insn) > max_uid) /* find largest UID */
3120 max_uid = INSN_UID (insn);
3122 maximum_uid = max_uid;
3123 insn_eh_region = (int *) xmalloc ((max_uid + 1) * sizeof (int));
3125 set_insn_eh_region (&insn, 0);
3129 /* Check whether 2 instructions are within the same region. */
3132 in_same_eh_region (insn1, insn2)
3135 int ret, uid1, uid2;
3137 /* If no exceptions, instructions are always in same region. */
3141 /* If the table isn't allocated, assume the worst. */
3142 if (!insn_eh_region)
3145 uid1 = INSN_UID (insn1);
3146 uid2 = INSN_UID (insn2);
3148 /* if instructions have been allocated beyond the end, either
3149 the table is out of date, or this is a late addition, or
3150 something... Assume the worst. */
3151 if (uid1 > maximum_uid || uid2 > maximum_uid)
3154 ret = (insn_eh_region[uid1] == insn_eh_region[uid2]);
3159 /* This function will initialize the handler list for a specified block.
3160 It may recursively call itself if the outer block hasn't been processed
3161 yet. At some point in the future we can trim out handlers which we
3162 know cannot be called. (ie, if a block has an INT type handler,
3163 control will never be passed to an outer INT type handler). */
3165 process_nestinfo (block, info, nested_eh_region)
3167 eh_nesting_info *info;
3168 int *nested_eh_region;
3170 handler_info *ptr, *last_ptr = NULL;
3171 int x, y, count = 0;
3173 handler_info **extra_handlers = 0;
3174 int index = info->region_index[block];
3176 /* If we've already processed this block, simply return. */
3177 if (info->num_handlers[index] > 0)
3180 for (ptr = get_first_handler (block); ptr; last_ptr = ptr, ptr = ptr->next)
3183 /* pick up any information from the next outer region. It will already
3184 contain a summary of itself and all outer regions to it. */
3186 if (nested_eh_region [block] != 0)
3188 int nested_index = info->region_index[nested_eh_region[block]];
3189 process_nestinfo (nested_eh_region[block], info, nested_eh_region);
3190 extra = info->num_handlers[nested_index];
3191 extra_handlers = info->handlers[nested_index];
3192 info->outer_index[index] = nested_index;
3195 /* If the last handler is either a CATCH_ALL or a cleanup, then we
3196 won't use the outer ones since we know control will not go past the
3197 catch-all or cleanup. */
3199 if (last_ptr != NULL && (last_ptr->type_info == NULL
3200 || last_ptr->type_info == CATCH_ALL_TYPE))
3203 info->num_handlers[index] = count + extra;
3204 info->handlers[index] = (handler_info **) xmalloc ((count + extra)
3205 * sizeof (handler_info **));
3207 /* First put all our handlers into the list. */
3208 ptr = get_first_handler (block);
3209 for (x = 0; x < count; x++)
3211 info->handlers[index][x] = ptr;
3215 /* Now add all the outer region handlers, if they aren't they same as
3216 one of the types in the current block. We won't worry about
3217 derived types yet, we'll just look for the exact type. */
3218 for (y =0, x = 0; x < extra ; x++)
3222 /* Check to see if we have a type duplication. */
3223 for (i = 0; i < count; i++)
3224 if (info->handlers[index][i]->type_info == extra_handlers[x]->type_info)
3227 /* Record one less handler. */
3228 (info->num_handlers[index])--;
3233 info->handlers[index][y + count] = extra_handlers[x];
3239 /* This function will allocate and initialize an eh_nesting_info structure.
3240 It returns a pointer to the completed data structure. If there are
3241 no exception regions, a NULL value is returned. */
3243 init_eh_nesting_info ()
3245 int *nested_eh_region;
3246 int region_count = 0;
3247 rtx eh_note = NULL_RTX;
3248 eh_nesting_info *info;
3252 info = (eh_nesting_info *) xmalloc (sizeof (eh_nesting_info));
3253 info->region_index = (int *) xcalloc ((max_label_num () + 1), sizeof (int));
3254 nested_eh_region = (int *) xcalloc (max_label_num () + 1, sizeof (int));
3256 /* Create the nested_eh_region list. If indexed with a block number, it
3257 returns the block number of the next outermost region, if any.
3258 We can count the number of regions and initialize the region_index
3259 vector at the same time. */
3260 for (insn = get_insns(); insn; insn = NEXT_INSN (insn))
3262 if (GET_CODE (insn) == NOTE)
3264 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
3266 int block = NOTE_EH_HANDLER (insn);
3268 info->region_index[block] = region_count;
3270 nested_eh_region [block] =
3271 NOTE_EH_HANDLER (XEXP (eh_note, 0));
3273 nested_eh_region [block] = 0;
3274 eh_note = gen_rtx_EXPR_LIST (VOIDmode, insn, eh_note);
3276 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)
3277 eh_note = XEXP (eh_note, 1);
3281 /* If there are no regions, wrap it up now. */
3282 if (region_count == 0)
3284 free (info->region_index);
3286 free (nested_eh_region);
3291 info->handlers = (handler_info ***) xcalloc (region_count,
3292 sizeof (handler_info ***));
3293 info->num_handlers = (int *) xcalloc (region_count, sizeof (int));
3294 info->outer_index = (int *) xcalloc (region_count, sizeof (int));
3296 /* Now initialize the handler lists for all exception blocks. */
3297 for (x = 0; x <= max_label_num (); x++)
3299 if (info->region_index[x] != 0)
3300 process_nestinfo (x, info, nested_eh_region);
3302 info->region_count = region_count;
3305 free (nested_eh_region);
3311 /* This function is used to retreive the vector of handlers which
3312 can be reached by a given insn in a given exception region.
3313 BLOCK is the exception block the insn is in.
3314 INFO is the eh_nesting_info structure.
3315 INSN is the (optional) insn within the block. If insn is not NULL_RTX,
3316 it may contain reg notes which modify its throwing behavior, and
3317 these will be obeyed. If NULL_RTX is passed, then we simply return the
3319 HANDLERS is the address of a pointer to a vector of handler_info pointers.
3320 Upon return, this will have the handlers which can be reached by block.
3321 This function returns the number of elements in the handlers vector. */
3323 reachable_handlers (block, info, insn, handlers)
3325 eh_nesting_info *info;
3327 handler_info ***handlers;
3335 index = info->region_index[block];
3337 if (insn && GET_CODE (insn) == CALL_INSN)
3339 /* RETHROWs specify a region number from which we are going to rethrow.
3340 This means we wont pass control to handlers in the specified
3341 region, but rather any region OUTSIDE the specified region.
3342 We accomplish this by setting block to the outer_index of the
3343 specified region. */
3344 rtx note = find_reg_note (insn, REG_EH_RETHROW, NULL_RTX);
3347 index = eh_region_from_symbol (XEXP (note, 0));
3348 index = info->region_index[index];
3350 index = info->outer_index[index];
3354 /* If there is no rethrow, we look for a REG_EH_REGION, and
3355 we'll throw from that block. A value of 0 or less
3356 indicates that this insn cannot throw. */
3357 note = find_reg_note (insn, REG_EH_REGION, NULL_RTX);
3360 int b = XINT (XEXP (note, 0), 0);
3364 index = info->region_index[b];
3368 /* If we reach this point, and index is 0, there is no throw. */
3372 *handlers = info->handlers[index];
3373 return info->num_handlers[index];
3377 /* This function will free all memory associated with the eh_nesting info. */
3380 free_eh_nesting_info (info)
3381 eh_nesting_info *info;
3386 if (info->region_index)
3387 free (info->region_index);
3388 if (info->num_handlers)
3389 free (info->num_handlers);
3390 if (info->outer_index)
3391 free (info->outer_index);
3394 for (x = 0; x < info->region_count; x++)
3395 if (info->handlers[x])
3396 free (info->handlers[x]);
3397 free (info->handlers);