1 /* Implements exception handling.
2 Copyright (C) 1989, 92-97, 1998 Free Software Foundation, Inc.
3 Contributed by Mike Stump <mrs@cygnus.com>.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
23 /* An exception is an event that can be signaled from within a
24 function. This event can then be "caught" or "trapped" by the
25 callers of this function. This potentially allows program flow to
26 be transferred to any arbitrary code associated with a function call
27 several levels up the stack.
29 The intended use for this mechanism is for signaling "exceptional
30 events" in an out-of-band fashion, hence its name. The C++ language
31 (and many other OO-styled or functional languages) practically
32 requires such a mechanism, as otherwise it becomes very difficult
33 or even impossible to signal failure conditions in complex
34 situations. The traditional C++ example is when an error occurs in
35 the process of constructing an object; without such a mechanism, it
36 is impossible to signal that the error occurs without adding global
37 state variables and error checks around every object construction.
39 The act of causing this event to occur is referred to as "throwing
40 an exception". (Alternate terms include "raising an exception" or
41 "signaling an exception".) The term "throw" is used because control
42 is returned to the callers of the function that is signaling the
43 exception, and thus there is the concept of "throwing" the
44 exception up the call stack.
46 There are two major codegen options for exception handling. The
47 flag -fsjlj-exceptions can be used to select the setjmp/longjmp
48 approach, which is the default. -fno-sjlj-exceptions can be used to
49 get the PC range table approach. While this is a compile time
50 flag, an entire application must be compiled with the same codegen
51 option. The first is a PC range table approach, the second is a
52 setjmp/longjmp based scheme. We will first discuss the PC range
53 table approach, after that, we will discuss the setjmp/longjmp
56 It is appropriate to speak of the "context of a throw". This
57 context refers to the address where the exception is thrown from,
58 and is used to determine which exception region will handle the
61 Regions of code within a function can be marked such that if it
62 contains the context of a throw, control will be passed to a
63 designated "exception handler". These areas are known as "exception
64 regions". Exception regions cannot overlap, but they can be nested
65 to any arbitrary depth. Also, exception regions cannot cross
68 Exception handlers can either be specified by the user (which we
69 will call a "user-defined handler") or generated by the compiler
70 (which we will designate as a "cleanup"). Cleanups are used to
71 perform tasks such as destruction of objects allocated on the
74 In the current implementation, cleanups are handled by allocating an
75 exception region for the area that the cleanup is designated for,
76 and the handler for the region performs the cleanup and then
77 rethrows the exception to the outer exception region. From the
78 standpoint of the current implementation, there is little
79 distinction made between a cleanup and a user-defined handler, and
80 the phrase "exception handler" can be used to refer to either one
81 equally well. (The section "Future Directions" below discusses how
84 Each object file that is compiled with exception handling contains
85 a static array of exception handlers named __EXCEPTION_TABLE__.
86 Each entry contains the starting and ending addresses of the
87 exception region, and the address of the handler designated for
90 If the target does not use the DWARF 2 frame unwind information, at
91 program startup each object file invokes a function named
92 __register_exceptions with the address of its local
93 __EXCEPTION_TABLE__. __register_exceptions is defined in libgcc2.c, and
94 is responsible for recording all of the exception regions into one list
95 (which is kept in a static variable named exception_table_list).
97 On targets that support crtstuff.c, the unwind information
98 is stored in a section named .eh_frame and the information for the
99 entire shared object or program is registered with a call to
100 __register_frame_info. On other targets, the information for each
101 translation unit is registered from the file generated by collect2.
102 __register_frame_info is defined in frame.c, and is responsible for
103 recording all of the unwind regions into one list (which is kept in a
104 static variable named unwind_table_list).
106 The function __throw is actually responsible for doing the
107 throw. On machines that have unwind info support, __throw is generated
108 by code in libgcc2.c, otherwise __throw is generated on a
109 per-object-file basis for each source file compiled with
110 -fexceptions by the C++ frontend. Before __throw is invoked,
111 the current context of the throw needs to be placed in the global
114 __throw attempts to find the appropriate exception handler for the
115 PC value stored in __eh_pc by calling __find_first_exception_table_match
116 (which is defined in libgcc2.c). If __find_first_exception_table_match
117 finds a relevant handler, __throw transfers control directly to it.
119 If a handler for the context being thrown from can't be found, __throw
120 walks (see Walking the stack below) the stack up the dynamic call chain to
121 continue searching for an appropriate exception handler based upon the
122 caller of the function it last sought a exception handler for. It stops
123 then either an exception handler is found, or when the top of the
124 call chain is reached.
126 If no handler is found, an external library function named
127 __terminate is called. If a handler is found, then we restart
128 our search for a handler at the end of the call chain, and repeat
129 the search process, but instead of just walking up the call chain,
130 we unwind the call chain as we walk up it.
132 Internal implementation details:
134 To associate a user-defined handler with a block of statements, the
135 function expand_start_try_stmts is used to mark the start of the
136 block of statements with which the handler is to be associated
137 (which is known as a "try block"). All statements that appear
138 afterwards will be associated with the try block.
140 A call to expand_start_all_catch marks the end of the try block,
141 and also marks the start of the "catch block" (the user-defined
142 handler) associated with the try block.
144 This user-defined handler will be invoked for *every* exception
145 thrown with the context of the try block. It is up to the handler
146 to decide whether or not it wishes to handle any given exception,
147 as there is currently no mechanism in this implementation for doing
148 this. (There are plans for conditionally processing an exception
149 based on its "type", which will provide a language-independent
152 If the handler chooses not to process the exception (perhaps by
153 looking at an "exception type" or some other additional data
154 supplied with the exception), it can fall through to the end of the
155 handler. expand_end_all_catch and expand_leftover_cleanups
156 add additional code to the end of each handler to take care of
157 rethrowing to the outer exception handler.
159 The handler also has the option to continue with "normal flow of
160 code", or in other words to resume executing at the statement
161 immediately after the end of the exception region. The variable
162 caught_return_label_stack contains a stack of labels, and jumping
163 to the topmost entry's label via expand_goto will resume normal
164 flow to the statement immediately after the end of the exception
165 region. If the handler falls through to the end, the exception will
166 be rethrown to the outer exception region.
168 The instructions for the catch block are kept as a separate
169 sequence, and will be emitted at the end of the function along with
170 the handlers specified via expand_eh_region_end. The end of the
171 catch block is marked with expand_end_all_catch.
173 Any data associated with the exception must currently be handled by
174 some external mechanism maintained in the frontend. For example,
175 the C++ exception mechanism passes an arbitrary value along with
176 the exception, and this is handled in the C++ frontend by using a
177 global variable to hold the value. (This will be changing in the
180 The mechanism in C++ for handling data associated with the
181 exception is clearly not thread-safe. For a thread-based
182 environment, another mechanism must be used (possibly using a
183 per-thread allocation mechanism if the size of the area that needs
184 to be allocated isn't known at compile time.)
186 Internally-generated exception regions (cleanups) are marked by
187 calling expand_eh_region_start to mark the start of the region,
188 and expand_eh_region_end (handler) is used to both designate the
189 end of the region and to associate a specified handler/cleanup with
190 the region. The rtl code in HANDLER will be invoked whenever an
191 exception occurs in the region between the calls to
192 expand_eh_region_start and expand_eh_region_end. After HANDLER is
193 executed, additional code is emitted to handle rethrowing the
194 exception to the outer exception handler. The code for HANDLER will
195 be emitted at the end of the function.
197 TARGET_EXPRs can also be used to designate exception regions. A
198 TARGET_EXPR gives an unwind-protect style interface commonly used
199 in functional languages such as LISP. The associated expression is
200 evaluated, and whether or not it (or any of the functions that it
201 calls) throws an exception, the protect expression is always
202 invoked. This implementation takes care of the details of
203 associating an exception table entry with the expression and
204 generating the necessary code (it actually emits the protect
205 expression twice, once for normal flow and once for the exception
206 case). As for the other handlers, the code for the exception case
207 will be emitted at the end of the function.
209 Cleanups can also be specified by using add_partial_entry (handler)
210 and end_protect_partials. add_partial_entry creates the start of
211 a new exception region; HANDLER will be invoked if an exception is
212 thrown with the context of the region between the calls to
213 add_partial_entry and end_protect_partials. end_protect_partials is
214 used to mark the end of these regions. add_partial_entry can be
215 called as many times as needed before calling end_protect_partials.
216 However, end_protect_partials should only be invoked once for each
217 group of calls to add_partial_entry as the entries are queued
218 and all of the outstanding entries are processed simultaneously
219 when end_protect_partials is invoked. Similarly to the other
220 handlers, the code for HANDLER will be emitted at the end of the
223 The generated RTL for an exception region includes
224 NOTE_INSN_EH_REGION_BEG and NOTE_INSN_EH_REGION_END notes that mark
225 the start and end of the exception region. A unique label is also
226 generated at the start of the exception region, which is available
227 by looking at the ehstack variable. The topmost entry corresponds
228 to the current region.
230 In the current implementation, an exception can only be thrown from
231 a function call (since the mechanism used to actually throw an
232 exception involves calling __throw). If an exception region is
233 created but no function calls occur within that region, the region
234 can be safely optimized away (along with its exception handlers)
235 since no exceptions can ever be caught in that region. This
236 optimization is performed unless -fasynchronous-exceptions is
237 given. If the user wishes to throw from a signal handler, or other
238 asynchronous place, -fasynchronous-exceptions should be used when
239 compiling for maximally correct code, at the cost of additional
240 exception regions. Using -fasynchronous-exceptions only produces
241 code that is reasonably safe in such situations, but a correct
242 program cannot rely upon this working. It can be used in failsafe
243 code, where trying to continue on, and proceeding with potentially
244 incorrect results is better than halting the program.
249 The stack is walked by starting with a pointer to the current
250 frame, and finding the pointer to the callers frame. The unwind info
251 tells __throw how to find it.
255 When we use the term unwinding the stack, we mean undoing the
256 effects of the function prologue in a controlled fashion so that we
257 still have the flow of control. Otherwise, we could just return
258 (jump to the normal end of function epilogue).
260 This is done in __throw in libgcc2.c when we know that a handler exists
261 in a frame higher up the call stack than its immediate caller.
263 To unwind, we find the unwind data associated with the frame, if any.
264 If we don't find any, we call the library routine __terminate. If we do
265 find it, we use the information to copy the saved register values from
266 that frame into the register save area in the frame for __throw, return
267 into a stub which updates the stack pointer, and jump to the handler.
268 The normal function epilogue for __throw handles restoring the saved
269 values into registers.
271 When unwinding, we use this method if we know it will
272 work (if DWARF2_UNWIND_INFO is defined). Otherwise, we know that
273 an inline unwinder will have been emitted for any function that
274 __unwind_function cannot unwind. The inline unwinder appears as a
275 normal exception handler for the entire function, for any function
276 that we know cannot be unwound by __unwind_function. We inform the
277 compiler of whether a function can be unwound with
278 __unwind_function by having DOESNT_NEED_UNWINDER evaluate to true
279 when the unwinder isn't needed. __unwind_function is used as an
280 action of last resort. If no other method can be used for
281 unwinding, __unwind_function is used. If it cannot unwind, it
282 should call __terminate.
284 By default, if the target-specific backend doesn't supply a definition
285 for __unwind_function and doesn't support DWARF2_UNWIND_INFO, inlined
286 unwinders will be used instead. The main tradeoff here is in text space
287 utilization. Obviously, if inline unwinders have to be generated
288 repeatedly, this uses much more space than if a single routine is used.
290 However, it is simply not possible on some platforms to write a
291 generalized routine for doing stack unwinding without having some
292 form of additional data associated with each function. The current
293 implementation can encode this data in the form of additional
294 machine instructions or as static data in tabular form. The later
295 is called the unwind data.
297 The backend macro DOESNT_NEED_UNWINDER is used to conditionalize whether
298 or not per-function unwinders are needed. If DOESNT_NEED_UNWINDER is
299 defined and has a non-zero value, a per-function unwinder is not emitted
300 for the current function. If the static unwind data is supported, then
301 a per-function unwinder is not emitted.
303 On some platforms it is possible that neither __unwind_function
304 nor inlined unwinders are available. For these platforms it is not
305 possible to throw through a function call, and abort will be
306 invoked instead of performing the throw.
308 The reason the unwind data may be needed is that on some platforms
309 the order and types of data stored on the stack can vary depending
310 on the type of function, its arguments and returned values, and the
311 compilation options used (optimization versus non-optimization,
312 -fomit-frame-pointer, processor variations, etc).
314 Unfortunately, this also means that throwing through functions that
315 aren't compiled with exception handling support will still not be
316 possible on some platforms. This problem is currently being
317 investigated, but no solutions have been found that do not imply
318 some unacceptable performance penalties.
322 Currently __throw makes no differentiation between cleanups and
323 user-defined exception regions. While this makes the implementation
324 simple, it also implies that it is impossible to determine if a
325 user-defined exception handler exists for a given exception without
326 completely unwinding the stack in the process. This is undesirable
327 from the standpoint of debugging, as ideally it would be possible
328 to trap unhandled exceptions in the debugger before the process of
329 unwinding has even started.
331 This problem can be solved by marking user-defined handlers in a
332 special way (probably by adding additional bits to exception_table_list).
333 A two-pass scheme could then be used by __throw to iterate
334 through the table. The first pass would search for a relevant
335 user-defined handler for the current context of the throw, and if
336 one is found, the second pass would then invoke all needed cleanups
337 before jumping to the user-defined handler.
339 Many languages (including C++ and Ada) make execution of a
340 user-defined handler conditional on the "type" of the exception
341 thrown. (The type of the exception is actually the type of the data
342 that is thrown with the exception.) It will thus be necessary for
343 __throw to be able to determine if a given user-defined
344 exception handler will actually be executed, given the type of
347 One scheme is to add additional information to exception_table_list
348 as to the types of exceptions accepted by each handler. __throw
349 can do the type comparisons and then determine if the handler is
350 actually going to be executed.
352 There is currently no significant level of debugging support
353 available, other than to place a breakpoint on __throw. While
354 this is sufficient in most cases, it would be helpful to be able to
355 know where a given exception was going to be thrown to before it is
356 actually thrown, and to be able to choose between stopping before
357 every exception region (including cleanups), or just user-defined
358 exception regions. This should be possible to do in the two-pass
359 scheme by adding additional labels to __throw for appropriate
360 breakpoints, and additional debugger commands could be added to
361 query various state variables to determine what actions are to be
364 Another major problem that is being worked on is the issue with stack
365 unwinding on various platforms. Currently the only platforms that have
366 support for the generation of a generic unwinder are the SPARC and MIPS.
367 All other ports require per-function unwinders, which produce large
368 amounts of code bloat.
370 For setjmp/longjmp based exception handling, some of the details
371 are as above, but there are some additional details. This section
372 discusses the details.
374 We don't use NOTE_INSN_EH_REGION_{BEG,END} pairs. We don't
375 optimize EH regions yet. We don't have to worry about machine
376 specific issues with unwinding the stack, as we rely upon longjmp
377 for all the machine specific details. There is no variable context
378 of a throw, just the one implied by the dynamic handler stack
379 pointed to by the dynamic handler chain. There is no exception
380 table, and no calls to __register_exceptions. __sjthrow is used
381 instead of __throw, and it works by using the dynamic handler
382 chain, and longjmp. -fasynchronous-exceptions has no effect, as
383 the elimination of trivial exception regions is not yet performed.
385 A frontend can set protect_cleanup_actions_with_terminate when all
386 the cleanup actions should be protected with an EH region that
387 calls terminate when an unhandled exception is throw. C++ does
388 this, Ada does not. */
392 #include "defaults.h"
398 #include "function.h"
399 #include "insn-flags.h"
401 #include "insn-codes.h"
403 #include "hard-reg-set.h"
404 #include "insn-config.h"
409 /* One to use setjmp/longjmp method of generating code for exception
412 int exceptions_via_longjmp
= 2;
414 /* One to enable asynchronous exception support. */
416 int asynchronous_exceptions
= 0;
418 /* One to protect cleanup actions with a handler that calls
419 __terminate, zero otherwise. */
421 int protect_cleanup_actions_with_terminate
;
423 /* A list of labels used for exception handlers. Created by
424 find_exception_handler_labels for the optimization passes. */
426 rtx exception_handler_labels
;
428 /* The EH context. Nonzero if the function has already
429 fetched a pointer to the EH context for exception handling. */
431 rtx current_function_ehc
;
433 /* A stack used for keeping track of the currently active exception
434 handling region. As each exception region is started, an entry
435 describing the region is pushed onto this stack. The current
436 region can be found by looking at the top of the stack, and as we
437 exit regions, the corresponding entries are popped.
439 Entries cannot overlap; they can be nested. So there is only one
440 entry at most that corresponds to the current instruction, and that
441 is the entry on the top of the stack. */
443 static struct eh_stack ehstack
;
445 /* A queue used for tracking which exception regions have closed but
446 whose handlers have not yet been expanded. Regions are emitted in
447 groups in an attempt to improve paging performance.
449 As we exit a region, we enqueue a new entry. The entries are then
450 dequeued during expand_leftover_cleanups and expand_start_all_catch,
452 We should redo things so that we either take RTL for the handler,
453 or we expand the handler expressed as a tree immediately at region
456 static struct eh_queue ehqueue
;
458 /* Insns for all of the exception handlers for the current function.
459 They are currently emitted by the frontend code. */
463 /* A TREE_CHAINed list of handlers for regions that are not yet
464 closed. The TREE_VALUE of each entry contains the handler for the
465 corresponding entry on the ehstack. */
467 static tree protect_list
;
469 /* Stacks to keep track of various labels. */
471 /* Keeps track of the label to resume to should one want to resume
472 normal control flow out of a handler (instead of, say, returning to
473 the caller of the current function or exiting the program). */
475 struct label_node
*caught_return_label_stack
= NULL
;
477 /* Keeps track of the label used as the context of a throw to rethrow an
478 exception to the outer exception region. */
480 struct label_node
*outer_context_label_stack
= NULL
;
482 /* A random data area for the front end's own use. */
484 struct label_node
*false_label_stack
= NULL
;
486 static void push_eh_entry
PROTO((struct eh_stack
*));
487 static struct eh_entry
* pop_eh_entry
PROTO((struct eh_stack
*));
488 static void enqueue_eh_entry
PROTO((struct eh_queue
*, struct eh_entry
*));
489 static struct eh_entry
* dequeue_eh_entry
PROTO((struct eh_queue
*));
490 static rtx call_get_eh_context
PROTO((void));
491 static void start_dynamic_cleanup
PROTO((tree
, tree
));
492 static void start_dynamic_handler
PROTO((void));
493 static void expand_rethrow
PROTO((rtx
));
494 static void output_exception_table_entry
PROTO((FILE *, int));
495 static int can_throw
PROTO((rtx
));
496 static rtx scan_region
PROTO((rtx
, int, int *));
497 static void eh_regs
PROTO((rtx
*, rtx
*, int));
498 static void set_insn_eh_region
PROTO((rtx
*, int));
500 rtx expand_builtin_return_addr
PROTO((enum built_in_function
, int, rtx
));
502 /* Various support routines to manipulate the various data structures
503 used by the exception handling code. */
505 /* Push a label entry onto the given STACK. */
508 push_label_entry (stack
, rlabel
, tlabel
)
509 struct label_node
**stack
;
513 struct label_node
*newnode
514 = (struct label_node
*) xmalloc (sizeof (struct label_node
));
517 newnode
->u
.rlabel
= rlabel
;
519 newnode
->u
.tlabel
= tlabel
;
520 newnode
->chain
= *stack
;
524 /* Pop a label entry from the given STACK. */
527 pop_label_entry (stack
)
528 struct label_node
**stack
;
531 struct label_node
*tempnode
;
537 label
= tempnode
->u
.rlabel
;
538 *stack
= (*stack
)->chain
;
544 /* Return the top element of the given STACK. */
547 top_label_entry (stack
)
548 struct label_node
**stack
;
553 return (*stack
)->u
.tlabel
;
556 /* Push a new eh_node entry onto STACK. */
559 push_eh_entry (stack
)
560 struct eh_stack
*stack
;
562 struct eh_node
*node
= (struct eh_node
*) xmalloc (sizeof (struct eh_node
));
563 struct eh_entry
*entry
= (struct eh_entry
*) xmalloc (sizeof (struct eh_entry
));
565 entry
->outer_context
= gen_label_rtx ();
566 entry
->exception_handler_label
= gen_label_rtx ();
567 entry
->finalization
= NULL_TREE
;
570 node
->chain
= stack
->top
;
574 /* Pop an entry from the given STACK. */
576 static struct eh_entry
*
578 struct eh_stack
*stack
;
580 struct eh_node
*tempnode
;
581 struct eh_entry
*tempentry
;
583 tempnode
= stack
->top
;
584 tempentry
= tempnode
->entry
;
585 stack
->top
= stack
->top
->chain
;
591 /* Enqueue an ENTRY onto the given QUEUE. */
594 enqueue_eh_entry (queue
, entry
)
595 struct eh_queue
*queue
;
596 struct eh_entry
*entry
;
598 struct eh_node
*node
= (struct eh_node
*) xmalloc (sizeof (struct eh_node
));
603 if (queue
->head
== NULL
)
609 queue
->tail
->chain
= node
;
614 /* Dequeue an entry from the given QUEUE. */
616 static struct eh_entry
*
617 dequeue_eh_entry (queue
)
618 struct eh_queue
*queue
;
620 struct eh_node
*tempnode
;
621 struct eh_entry
*tempentry
;
623 if (queue
->head
== NULL
)
626 tempnode
= queue
->head
;
627 queue
->head
= queue
->head
->chain
;
629 tempentry
= tempnode
->entry
;
635 /* Routine to see if exception handling is turned on.
636 DO_WARN is non-zero if we want to inform the user that exception
637 handling is turned off.
639 This is used to ensure that -fexceptions has been specified if the
640 compiler tries to use any exception-specific functions. */
646 if (! flag_exceptions
)
648 static int warned
= 0;
649 if (! warned
&& do_warn
)
651 error ("exception handling disabled, use -fexceptions to enable");
659 /* Given a return address in ADDR, determine the address we should use
660 to find the corresponding EH region. */
663 eh_outer_context (addr
)
666 /* First mask out any unwanted bits. */
667 #ifdef MASK_RETURN_ADDR
668 expand_and (addr
, MASK_RETURN_ADDR
, addr
);
671 /* Then adjust to find the real return address. */
672 #if defined (RETURN_ADDR_OFFSET)
673 addr
= plus_constant (addr
, RETURN_ADDR_OFFSET
);
679 /* Start a new exception region for a region of code that has a
680 cleanup action and push the HANDLER for the region onto
681 protect_list. All of the regions created with add_partial_entry
682 will be ended when end_protect_partials is invoked. */
685 add_partial_entry (handler
)
688 expand_eh_region_start ();
690 /* Make sure the entry is on the correct obstack. */
691 push_obstacks_nochange ();
692 resume_temporary_allocation ();
694 /* Because this is a cleanup action, we may have to protect the handler
696 handler
= protect_with_terminate (handler
);
698 protect_list
= tree_cons (NULL_TREE
, handler
, protect_list
);
702 /* Emit code to get EH context to current function. */
705 call_get_eh_context ()
713 fn
= get_identifier ("__get_eh_context");
714 push_obstacks_nochange ();
715 end_temporary_allocation ();
716 fntype
= build_pointer_type (build_pointer_type
717 (build_pointer_type (void_type_node
)));
718 fntype
= build_function_type (fntype
, NULL_TREE
);
719 fn
= build_decl (FUNCTION_DECL
, fn
, fntype
);
720 DECL_EXTERNAL (fn
) = 1;
721 TREE_PUBLIC (fn
) = 1;
722 DECL_ARTIFICIAL (fn
) = 1;
723 TREE_READONLY (fn
) = 1;
724 make_decl_rtl (fn
, NULL_PTR
, 1);
725 assemble_external (fn
);
729 expr
= build1 (ADDR_EXPR
, build_pointer_type (TREE_TYPE (fn
)), fn
);
730 expr
= build (CALL_EXPR
, TREE_TYPE (TREE_TYPE (fn
)),
731 expr
, NULL_TREE
, NULL_TREE
);
732 TREE_SIDE_EFFECTS (expr
) = 1;
734 return copy_to_reg (expand_expr (expr
, NULL_RTX
, VOIDmode
, 0));
737 /* Get a reference to the EH context.
738 We will only generate a register for the current function EH context here,
739 and emit a USE insn to mark that this is a EH context register.
741 Later, emit_eh_context will emit needed call to __get_eh_context
742 in libgcc2, and copy the value to the register we have generated. */
747 if (current_function_ehc
== 0)
751 current_function_ehc
= gen_reg_rtx (Pmode
);
753 insn
= gen_rtx_USE (GET_MODE (current_function_ehc
),
754 current_function_ehc
);
755 insn
= emit_insn_before (insn
, get_first_nonparm_insn ());
758 = gen_rtx_EXPR_LIST (REG_EH_CONTEXT
, current_function_ehc
,
761 return current_function_ehc
;
764 /* Get a reference to the dynamic handler chain. It points to the
765 pointer to the next element in the dynamic handler chain. It ends
766 when there are no more elements in the dynamic handler chain, when
767 the value is &top_elt from libgcc2.c. Immediately after the
768 pointer, is an area suitable for setjmp/longjmp when
769 DONT_USE_BUILTIN_SETJMP is defined, and an area suitable for
770 __builtin_setjmp/__builtin_longjmp when DONT_USE_BUILTIN_SETJMP
774 get_dynamic_handler_chain ()
776 rtx ehc
, dhc
, result
;
778 ehc
= get_eh_context ();
781 result
= copy_to_reg (dhc
);
783 /* We don't want a copy of the dcc, but rather, the single dcc. */
784 return gen_rtx_MEM (Pmode
, result
);
787 /* Get a reference to the dynamic cleanup chain. It points to the
788 pointer to the next element in the dynamic cleanup chain.
789 Immediately after the pointer, are two Pmode variables, one for a
790 pointer to a function that performs the cleanup action, and the
791 second, the argument to pass to that function. */
794 get_dynamic_cleanup_chain ()
796 rtx dhc
, dcc
, result
;
798 dhc
= get_dynamic_handler_chain ();
799 dcc
= plus_constant (dhc
, GET_MODE_SIZE (Pmode
));
801 result
= copy_to_reg (dcc
);
803 /* We don't want a copy of the dcc, but rather, the single dcc. */
804 return gen_rtx_MEM (Pmode
, result
);
807 /* Generate code to evaluate X and jump to LABEL if the value is nonzero.
808 LABEL is an rtx of code CODE_LABEL, in this function. */
811 jumpif_rtx (x
, label
)
815 jumpif (make_tree (type_for_mode (GET_MODE (x
), 0), x
), label
);
818 /* Generate code to evaluate X and jump to LABEL if the value is zero.
819 LABEL is an rtx of code CODE_LABEL, in this function. */
822 jumpifnot_rtx (x
, label
)
826 jumpifnot (make_tree (type_for_mode (GET_MODE (x
), 0), x
), label
);
829 /* Start a dynamic cleanup on the EH runtime dynamic cleanup stack.
830 We just need to create an element for the cleanup list, and push it
833 A dynamic cleanup is a cleanup action implied by the presence of an
834 element on the EH runtime dynamic cleanup stack that is to be
835 performed when an exception is thrown. The cleanup action is
836 performed by __sjthrow when an exception is thrown. Only certain
837 actions can be optimized into dynamic cleanup actions. For the
838 restrictions on what actions can be performed using this routine,
839 see expand_eh_region_start_tree. */
842 start_dynamic_cleanup (func
, arg
)
847 rtx new_func
, new_arg
;
851 /* We allocate enough room for a pointer to the function, and
855 /* XXX, FIXME: The stack space allocated this way is too long lived,
856 but there is no allocation routine that allocates at the level of
857 the last binding contour. */
858 buf
= assign_stack_local (BLKmode
,
859 GET_MODE_SIZE (Pmode
)*(size
+1),
862 buf
= change_address (buf
, Pmode
, NULL_RTX
);
864 /* Store dcc into the first word of the newly allocated buffer. */
866 dcc
= get_dynamic_cleanup_chain ();
867 emit_move_insn (buf
, dcc
);
869 /* Store func and arg into the cleanup list element. */
871 new_func
= gen_rtx_MEM (Pmode
, plus_constant (XEXP (buf
, 0),
872 GET_MODE_SIZE (Pmode
)));
873 new_arg
= gen_rtx_MEM (Pmode
, plus_constant (XEXP (buf
, 0),
874 GET_MODE_SIZE (Pmode
)*2));
875 x
= expand_expr (func
, new_func
, Pmode
, 0);
877 emit_move_insn (new_func
, x
);
879 x
= expand_expr (arg
, new_arg
, Pmode
, 0);
881 emit_move_insn (new_arg
, x
);
883 /* Update the cleanup chain. */
885 emit_move_insn (dcc
, XEXP (buf
, 0));
888 /* Emit RTL to start a dynamic handler on the EH runtime dynamic
889 handler stack. This should only be used by expand_eh_region_start
890 or expand_eh_region_start_tree. */
893 start_dynamic_handler ()
899 #ifndef DONT_USE_BUILTIN_SETJMP
900 /* The number of Pmode words for the setjmp buffer, when using the
901 builtin setjmp/longjmp, see expand_builtin, case
908 /* Should be large enough for most systems, if it is not,
909 JMP_BUF_SIZE should be defined with the proper value. It will
910 also tend to be larger than necessary for most systems, a more
911 optimal port will define JMP_BUF_SIZE. */
912 size
= FIRST_PSEUDO_REGISTER
+2;
915 /* XXX, FIXME: The stack space allocated this way is too long lived,
916 but there is no allocation routine that allocates at the level of
917 the last binding contour. */
918 arg
= assign_stack_local (BLKmode
,
919 GET_MODE_SIZE (Pmode
)*(size
+1),
922 arg
= change_address (arg
, Pmode
, NULL_RTX
);
924 /* Store dhc into the first word of the newly allocated buffer. */
926 dhc
= get_dynamic_handler_chain ();
927 dcc
= gen_rtx_MEM (Pmode
, plus_constant (XEXP (arg
, 0),
928 GET_MODE_SIZE (Pmode
)));
929 emit_move_insn (arg
, dhc
);
931 /* Zero out the start of the cleanup chain. */
932 emit_move_insn (dcc
, const0_rtx
);
934 /* The jmpbuf starts two words into the area allocated. */
935 buf
= plus_constant (XEXP (arg
, 0), GET_MODE_SIZE (Pmode
)*2);
937 #ifdef DONT_USE_BUILTIN_SETJMP
938 x
= emit_library_call_value (setjmp_libfunc
, NULL_RTX
, 1, SImode
, 1,
940 /* If we come back here for a catch, transfer control to the handler. */
941 jumpif_rtx (x
, ehstack
.top
->entry
->exception_handler_label
);
944 /* A label to continue execution for the no exception case. */
945 rtx noex
= gen_label_rtx();
946 x
= expand_builtin_setjmp (buf
, NULL_RTX
, noex
,
947 ehstack
.top
->entry
->exception_handler_label
);
952 /* We are committed to this, so update the handler chain. */
954 emit_move_insn (dhc
, XEXP (arg
, 0));
957 /* Start an exception handling region for the given cleanup action.
958 All instructions emitted after this point are considered to be part
959 of the region until expand_eh_region_end is invoked. CLEANUP is
960 the cleanup action to perform. The return value is true if the
961 exception region was optimized away. If that case,
962 expand_eh_region_end does not need to be called for this cleanup,
965 This routine notices one particular common case in C++ code
966 generation, and optimizes it so as to not need the exception
967 region. It works by creating a dynamic cleanup action, instead of
968 a using an exception region. */
971 expand_eh_region_start_tree (decl
, cleanup
)
975 /* This is the old code. */
979 /* The optimization only applies to actions protected with
980 terminate, and only applies if we are using the setjmp/longjmp
982 if (exceptions_via_longjmp
983 && protect_cleanup_actions_with_terminate
)
988 /* Ignore any UNSAVE_EXPR. */
989 if (TREE_CODE (cleanup
) == UNSAVE_EXPR
)
990 cleanup
= TREE_OPERAND (cleanup
, 0);
992 /* Further, it only applies if the action is a call, if there
993 are 2 arguments, and if the second argument is 2. */
995 if (TREE_CODE (cleanup
) == CALL_EXPR
996 && (args
= TREE_OPERAND (cleanup
, 1))
997 && (func
= TREE_OPERAND (cleanup
, 0))
998 && (arg
= TREE_VALUE (args
))
999 && (args
= TREE_CHAIN (args
))
1001 /* is the second argument 2? */
1002 && TREE_CODE (TREE_VALUE (args
)) == INTEGER_CST
1003 && TREE_INT_CST_LOW (TREE_VALUE (args
)) == 2
1004 && TREE_INT_CST_HIGH (TREE_VALUE (args
)) == 0
1006 /* Make sure there are no other arguments. */
1007 && TREE_CHAIN (args
) == NULL_TREE
)
1009 /* Arrange for returns and gotos to pop the entry we make on the
1010 dynamic cleanup stack. */
1011 expand_dcc_cleanup (decl
);
1012 start_dynamic_cleanup (func
, arg
);
1017 expand_eh_region_start_for_decl (decl
);
1018 ehstack
.top
->entry
->finalization
= cleanup
;
1023 /* Just like expand_eh_region_start, except if a cleanup action is
1024 entered on the cleanup chain, the TREE_PURPOSE of the element put
1025 on the chain is DECL. DECL should be the associated VAR_DECL, if
1026 any, otherwise it should be NULL_TREE. */
1029 expand_eh_region_start_for_decl (decl
)
1034 /* This is the old code. */
1038 if (exceptions_via_longjmp
)
1040 /* We need a new block to record the start and end of the
1041 dynamic handler chain. We could always do this, but we
1042 really want to permit jumping into such a block, and we want
1043 to avoid any errors or performance impact in the SJ EH code
1045 expand_start_bindings (0);
1047 /* But we don't need or want a new temporary level. */
1050 /* Mark this block as created by expand_eh_region_start. This
1051 is so that we can pop the block with expand_end_bindings
1053 mark_block_as_eh_region ();
1055 /* Arrange for returns and gotos to pop the entry we make on the
1056 dynamic handler stack. */
1057 expand_dhc_cleanup (decl
);
1060 push_eh_entry (&ehstack
);
1061 note
= emit_note (NULL_PTR
, NOTE_INSN_EH_REGION_BEG
);
1062 NOTE_BLOCK_NUMBER (note
)
1063 = CODE_LABEL_NUMBER (ehstack
.top
->entry
->exception_handler_label
);
1064 if (exceptions_via_longjmp
)
1065 start_dynamic_handler ();
1068 /* Start an exception handling region. All instructions emitted after
1069 this point are considered to be part of the region until
1070 expand_eh_region_end is invoked. */
1073 expand_eh_region_start ()
1075 expand_eh_region_start_for_decl (NULL_TREE
);
1078 /* End an exception handling region. The information about the region
1079 is found on the top of ehstack.
1081 HANDLER is either the cleanup for the exception region, or if we're
1082 marking the end of a try block, HANDLER is integer_zero_node.
1084 HANDLER will be transformed to rtl when expand_leftover_cleanups
1088 expand_eh_region_end (handler
)
1091 struct eh_entry
*entry
;
1097 entry
= pop_eh_entry (&ehstack
);
1099 note
= emit_note (NULL_PTR
, NOTE_INSN_EH_REGION_END
);
1100 NOTE_BLOCK_NUMBER (note
)
1101 = CODE_LABEL_NUMBER (entry
->exception_handler_label
);
1102 if (exceptions_via_longjmp
== 0
1103 /* We share outer_context between regions; only emit it once. */
1104 && INSN_UID (entry
->outer_context
) == 0)
1108 label
= gen_label_rtx ();
1111 /* Emit a label marking the end of this exception region that
1112 is used for rethrowing into the outer context. */
1113 emit_label (entry
->outer_context
);
1114 expand_internal_throw ();
1119 entry
->finalization
= handler
;
1121 enqueue_eh_entry (&ehqueue
, entry
);
1123 /* If we have already started ending the bindings, don't recurse.
1124 This only happens when exceptions_via_longjmp is true. */
1125 if (is_eh_region ())
1127 /* Because we don't need or want a new temporary level and
1128 because we didn't create one in expand_eh_region_start,
1129 create a fake one now to avoid removing one in
1130 expand_end_bindings. */
1133 mark_block_as_not_eh_region ();
1135 /* Maybe do this to prevent jumping in and so on... */
1136 expand_end_bindings (NULL_TREE
, 0, 0);
1140 /* End the EH region for a goto fixup. We only need them in the region-based
1144 expand_fixup_region_start ()
1146 if (! doing_eh (0) || exceptions_via_longjmp
)
1149 expand_eh_region_start ();
1152 /* End the EH region for a goto fixup. CLEANUP is the cleanup we just
1153 expanded; to avoid running it twice if it throws, we look through the
1154 ehqueue for a matching region and rethrow from its outer_context. */
1157 expand_fixup_region_end (cleanup
)
1160 struct eh_node
*node
;
1162 if (! doing_eh (0) || exceptions_via_longjmp
)
1165 for (node
= ehstack
.top
; node
&& node
->entry
->finalization
!= cleanup
; )
1168 for (node
= ehqueue
.head
; node
&& node
->entry
->finalization
!= cleanup
; )
1173 ehstack
.top
->entry
->outer_context
= node
->entry
->outer_context
;
1175 /* Just rethrow. size_zero_node is just a NOP. */
1176 expand_eh_region_end (size_zero_node
);
1179 /* If we are using the setjmp/longjmp EH codegen method, we emit a
1182 Otherwise, we emit a call to __throw and note that we threw
1183 something, so we know we need to generate the necessary code for
1186 Before invoking throw, the __eh_pc variable must have been set up
1187 to contain the PC being thrown from. This address is used by
1188 __throw to determine which exception region (if any) is
1189 responsible for handling the exception. */
1194 if (exceptions_via_longjmp
)
1196 emit_library_call (sjthrow_libfunc
, 0, VOIDmode
, 0);
1200 #ifdef JUMP_TO_THROW
1201 emit_indirect_jump (throw_libfunc
);
1203 emit_library_call (throw_libfunc
, 0, VOIDmode
, 0);
1209 /* Throw the current exception. If appropriate, this is done by jumping
1210 to the next handler. */
1213 expand_internal_throw ()
1218 /* Called from expand_exception_blocks and expand_end_catch_block to
1219 emit any pending handlers/cleanups queued from expand_eh_region_end. */
1222 expand_leftover_cleanups ()
1224 struct eh_entry
*entry
;
1226 while ((entry
= dequeue_eh_entry (&ehqueue
)) != 0)
1230 /* A leftover try block. Shouldn't be one here. */
1231 if (entry
->finalization
== integer_zero_node
)
1234 /* Output the label for the start of the exception handler. */
1235 emit_label (entry
->exception_handler_label
);
1237 #ifdef HAVE_exception_receiver
1238 if (! exceptions_via_longjmp
)
1239 if (HAVE_exception_receiver
)
1240 emit_insn (gen_exception_receiver ());
1243 #ifdef HAVE_nonlocal_goto_receiver
1244 if (! exceptions_via_longjmp
)
1245 if (HAVE_nonlocal_goto_receiver
)
1246 emit_insn (gen_nonlocal_goto_receiver ());
1249 /* And now generate the insns for the handler. */
1250 expand_expr (entry
->finalization
, const0_rtx
, VOIDmode
, 0);
1252 prev
= get_last_insn ();
1253 if (prev
== NULL
|| GET_CODE (prev
) != BARRIER
)
1254 /* Emit code to throw to the outer context if we fall off
1255 the end of the handler. */
1256 expand_rethrow (entry
->outer_context
);
1258 do_pending_stack_adjust ();
1263 /* Called at the start of a block of try statements. */
1265 expand_start_try_stmts ()
1270 expand_eh_region_start ();
1273 /* Generate RTL for the start of a group of catch clauses.
1275 It is responsible for starting a new instruction sequence for the
1276 instructions in the catch block, and expanding the handlers for the
1277 internally-generated exception regions nested within the try block
1278 corresponding to this catch block. */
1281 expand_start_all_catch ()
1283 struct eh_entry
*entry
;
1290 outer_context
= ehstack
.top
->entry
->outer_context
;
1292 /* End the try block. */
1293 expand_eh_region_end (integer_zero_node
);
1295 emit_line_note (input_filename
, lineno
);
1296 label
= build_decl (LABEL_DECL
, NULL_TREE
, NULL_TREE
);
1298 /* The label for the exception handling block that we will save.
1299 This is Lresume in the documentation. */
1300 expand_label (label
);
1302 /* Push the label that points to where normal flow is resumed onto
1303 the top of the label stack. */
1304 push_label_entry (&caught_return_label_stack
, NULL_RTX
, label
);
1306 /* Start a new sequence for all the catch blocks. We will add this
1307 to the global sequence catch_clauses when we have completed all
1308 the handlers in this handler-seq. */
1315 entry
= dequeue_eh_entry (&ehqueue
);
1316 /* Emit the label for the exception handler for this region, and
1317 expand the code for the handler.
1319 Note that a catch region is handled as a side-effect here;
1320 for a try block, entry->finalization will contain
1321 integer_zero_node, so no code will be generated in the
1322 expand_expr call below. But, the label for the handler will
1323 still be emitted, so any code emitted after this point will
1324 end up being the handler. */
1325 emit_label (entry
->exception_handler_label
);
1327 #ifdef HAVE_exception_receiver
1328 if (! exceptions_via_longjmp
)
1329 if (HAVE_exception_receiver
)
1330 emit_insn (gen_exception_receiver ());
1333 #ifdef HAVE_nonlocal_goto_receiver
1334 if (! exceptions_via_longjmp
)
1335 if (HAVE_nonlocal_goto_receiver
)
1336 emit_insn (gen_nonlocal_goto_receiver ());
1339 /* When we get down to the matching entry for this try block, stop. */
1340 if (entry
->finalization
== integer_zero_node
)
1342 /* Don't forget to free this entry. */
1347 /* And now generate the insns for the handler. */
1348 expand_expr (entry
->finalization
, const0_rtx
, VOIDmode
, 0);
1350 prev
= get_last_insn ();
1351 if (prev
== NULL
|| GET_CODE (prev
) != BARRIER
)
1352 /* Code to throw out to outer context when we fall off end
1353 of the handler. We can't do this here for catch blocks,
1354 so it's done in expand_end_all_catch instead. */
1355 expand_rethrow (entry
->outer_context
);
1357 do_pending_stack_adjust ();
1361 /* If we are not doing setjmp/longjmp EH, because we are reordered
1362 out of line, we arrange to rethrow in the outer context. We need to
1363 do this because we are not physically within the region, if any, that
1364 logically contains this catch block. */
1365 if (! exceptions_via_longjmp
)
1367 expand_eh_region_start ();
1368 ehstack
.top
->entry
->outer_context
= outer_context
;
1372 /* Finish up the catch block. At this point all the insns for the
1373 catch clauses have already been generated, so we only have to add
1374 them to the catch_clauses list. We also want to make sure that if
1375 we fall off the end of the catch clauses that we rethrow to the
1379 expand_end_all_catch ()
1381 rtx new_catch_clause
, outer_context
= NULL_RTX
;
1386 if (! exceptions_via_longjmp
)
1388 outer_context
= ehstack
.top
->entry
->outer_context
;
1390 /* Finish the rethrow region. size_zero_node is just a NOP. */
1391 expand_eh_region_end (size_zero_node
);
1394 /* Code to throw out to outer context, if we fall off end of catch
1395 handlers. This is rethrow (Lresume, same id, same obj) in the
1396 documentation. We use Lresume because we know that it will throw
1397 to the correct context.
1399 In other words, if the catch handler doesn't exit or return, we
1400 do a "throw" (using the address of Lresume as the point being
1401 thrown from) so that the outer EH region can then try to process
1403 expand_rethrow (outer_context
);
1405 /* Now we have the complete catch sequence. */
1406 new_catch_clause
= get_insns ();
1409 /* This level of catch blocks is done, so set up the successful
1410 catch jump label for the next layer of catch blocks. */
1411 pop_label_entry (&caught_return_label_stack
);
1412 pop_label_entry (&outer_context_label_stack
);
1414 /* Add the new sequence of catches to the main one for this function. */
1415 push_to_sequence (catch_clauses
);
1416 emit_insns (new_catch_clause
);
1417 catch_clauses
= get_insns ();
1420 /* Here we fall through into the continuation code. */
1423 /* Rethrow from the outer context LABEL. */
1426 expand_rethrow (label
)
1429 if (exceptions_via_longjmp
)
1435 /* End all the pending exception regions on protect_list. The handlers
1436 will be emitted when expand_leftover_cleanups is invoked. */
1439 end_protect_partials ()
1441 while (protect_list
)
1443 expand_eh_region_end (TREE_VALUE (protect_list
));
1444 protect_list
= TREE_CHAIN (protect_list
);
1448 /* Arrange for __terminate to be called if there is an unhandled throw
1452 protect_with_terminate (e
)
1455 /* We only need to do this when using setjmp/longjmp EH and the
1456 language requires it, as otherwise we protect all of the handlers
1457 at once, if we need to. */
1458 if (exceptions_via_longjmp
&& protect_cleanup_actions_with_terminate
)
1460 tree handler
, result
;
1462 /* All cleanups must be on the function_obstack. */
1463 push_obstacks_nochange ();
1464 resume_temporary_allocation ();
1466 handler
= make_node (RTL_EXPR
);
1467 TREE_TYPE (handler
) = void_type_node
;
1468 RTL_EXPR_RTL (handler
) = const0_rtx
;
1469 TREE_SIDE_EFFECTS (handler
) = 1;
1470 start_sequence_for_rtl_expr (handler
);
1472 emit_library_call (terminate_libfunc
, 0, VOIDmode
, 0);
1475 RTL_EXPR_SEQUENCE (handler
) = get_insns ();
1478 result
= build (TRY_CATCH_EXPR
, TREE_TYPE (e
), e
, handler
);
1479 TREE_SIDE_EFFECTS (result
) = TREE_SIDE_EFFECTS (e
);
1480 TREE_THIS_VOLATILE (result
) = TREE_THIS_VOLATILE (e
);
1481 TREE_READONLY (result
) = TREE_READONLY (e
);
1491 /* The exception table that we build that is used for looking up and
1492 dispatching exceptions, the current number of entries, and its
1493 maximum size before we have to extend it.
1495 The number in eh_table is the code label number of the exception
1496 handler for the region. This is added by add_eh_table_entry and
1497 used by output_exception_table_entry. */
1499 static int *eh_table
;
1500 static int eh_table_size
;
1501 static int eh_table_max_size
;
1503 /* Note the need for an exception table entry for region N. If we
1504 don't need to output an explicit exception table, avoid all of the
1507 Called from final_scan_insn when a NOTE_INSN_EH_REGION_BEG is seen.
1508 N is the NOTE_BLOCK_NUMBER of the note, which comes from the code
1509 label number of the exception handler for the region. */
1512 add_eh_table_entry (n
)
1515 #ifndef OMIT_EH_TABLE
1516 if (eh_table_size
>= eh_table_max_size
)
1520 eh_table_max_size
+= eh_table_max_size
>>1;
1522 if (eh_table_max_size
< 0)
1525 eh_table
= (int *) xrealloc (eh_table
,
1526 eh_table_max_size
* sizeof (int));
1530 eh_table_max_size
= 252;
1531 eh_table
= (int *) xmalloc (eh_table_max_size
* sizeof (int));
1534 eh_table
[eh_table_size
++] = n
;
1538 /* Return a non-zero value if we need to output an exception table.
1540 On some platforms, we don't have to output a table explicitly.
1541 This routine doesn't mean we don't have one. */
1544 exception_table_p ()
1552 /* Output the entry of the exception table corresponding to the
1553 exception region numbered N to file FILE.
1555 N is the code label number corresponding to the handler of the
1559 output_exception_table_entry (file
, n
)
1566 ASM_GENERATE_INTERNAL_LABEL (buf
, "LEHB", n
);
1567 sym
= gen_rtx_SYMBOL_REF (Pmode
, buf
);
1568 assemble_integer (sym
, POINTER_SIZE
/ BITS_PER_UNIT
, 1);
1570 ASM_GENERATE_INTERNAL_LABEL (buf
, "LEHE", n
);
1571 sym
= gen_rtx_SYMBOL_REF (Pmode
, buf
);
1572 assemble_integer (sym
, POINTER_SIZE
/ BITS_PER_UNIT
, 1);
1574 ASM_GENERATE_INTERNAL_LABEL (buf
, "L", n
);
1575 sym
= gen_rtx_SYMBOL_REF (Pmode
, buf
);
1576 assemble_integer (sym
, POINTER_SIZE
/ BITS_PER_UNIT
, 1);
1578 putc ('\n', file
); /* blank line */
1581 /* Output the exception table if we have and need one. */
1584 output_exception_table ()
1587 extern FILE *asm_out_file
;
1589 if (! doing_eh (0) || ! eh_table
)
1592 exception_section ();
1594 /* Beginning marker for table. */
1595 assemble_align (GET_MODE_ALIGNMENT (ptr_mode
));
1596 assemble_label ("__EXCEPTION_TABLE__");
1598 for (i
= 0; i
< eh_table_size
; ++i
)
1599 output_exception_table_entry (asm_out_file
, eh_table
[i
]);
1603 /* Ending marker for table. */
1604 assemble_integer (constm1_rtx
, POINTER_SIZE
/ BITS_PER_UNIT
, 1);
1605 assemble_integer (constm1_rtx
, POINTER_SIZE
/ BITS_PER_UNIT
, 1);
1606 assemble_integer (constm1_rtx
, POINTER_SIZE
/ BITS_PER_UNIT
, 1);
1607 putc ('\n', asm_out_file
); /* blank line */
1610 /* Emit code to get EH context.
1612 We have to scan thru the code to find possible EH context registers.
1613 Inlined functions may use it too, and thus we'll have to be able
1616 This is done only if using exceptions_via_longjmp. */
1627 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
1628 if (GET_CODE (insn
) == INSN
1629 && GET_CODE (PATTERN (insn
)) == USE
)
1631 rtx reg
= find_reg_note (insn
, REG_EH_CONTEXT
, 0);
1638 /* If this is the first use insn, emit the call here. This
1639 will always be at the top of our function, because if
1640 expand_inline_function notices a REG_EH_CONTEXT note, it
1641 adds a use insn to this function as well. */
1643 ehc
= call_get_eh_context ();
1645 emit_move_insn (XEXP (reg
, 0), ehc
);
1646 insns
= get_insns ();
1649 emit_insns_before (insns
, insn
);
1654 /* Scan the current insns and build a list of handler labels. The
1655 resulting list is placed in the global variable exception_handler_labels.
1657 It is called after the last exception handling region is added to
1658 the current function (when the rtl is almost all built for the
1659 current function) and before the jump optimization pass. */
1662 find_exception_handler_labels ()
1665 int max_labelno
= max_label_num ();
1666 int min_labelno
= get_first_label_num ();
1669 exception_handler_labels
= NULL_RTX
;
1671 /* If we aren't doing exception handling, there isn't much to check. */
1675 /* Generate a handy reference to each label. */
1677 /* We call xmalloc here instead of alloca; we did the latter in the past,
1678 but found that it can sometimes end up being asked to allocate space
1679 for more than 1 million labels. */
1680 labels
= (rtx
*) xmalloc ((max_labelno
- min_labelno
) * sizeof (rtx
));
1681 bzero ((char *) labels
, (max_labelno
- min_labelno
) * sizeof (rtx
));
1683 /* Arrange for labels to be indexed directly by CODE_LABEL_NUMBER. */
1684 labels
-= min_labelno
;
1686 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
1688 if (GET_CODE (insn
) == CODE_LABEL
)
1689 if (CODE_LABEL_NUMBER (insn
) >= min_labelno
1690 && CODE_LABEL_NUMBER (insn
) < max_labelno
)
1691 labels
[CODE_LABEL_NUMBER (insn
)] = insn
;
1694 /* For each start of a region, add its label to the list. */
1696 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
1698 if (GET_CODE (insn
) == NOTE
1699 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_EH_REGION_BEG
)
1701 rtx label
= NULL_RTX
;
1703 if (NOTE_BLOCK_NUMBER (insn
) >= min_labelno
1704 && NOTE_BLOCK_NUMBER (insn
) < max_labelno
)
1706 label
= labels
[NOTE_BLOCK_NUMBER (insn
)];
1709 exception_handler_labels
1710 = gen_rtx_EXPR_LIST (VOIDmode
,
1711 label
, exception_handler_labels
);
1713 warning ("didn't find handler for EH region %d",
1714 NOTE_BLOCK_NUMBER (insn
));
1717 warning ("mismatched EH region %d", NOTE_BLOCK_NUMBER (insn
));
1721 free (labels
+ min_labelno
);
1724 /* Perform sanity checking on the exception_handler_labels list.
1726 Can be called after find_exception_handler_labels is called to
1727 build the list of exception handlers for the current function and
1728 before we finish processing the current function. */
1731 check_exception_handler_labels ()
1735 /* If we aren't doing exception handling, there isn't much to check. */
1739 /* Ensure that the CODE_LABEL_NUMBER for the CODE_LABEL entry point
1740 in each handler corresponds to the CODE_LABEL_NUMBER of the
1743 for (handler
= exception_handler_labels
;
1745 handler
= XEXP (handler
, 1))
1747 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
1749 if (GET_CODE (insn
) == CODE_LABEL
)
1751 if (CODE_LABEL_NUMBER (insn
)
1752 == CODE_LABEL_NUMBER (XEXP (handler
, 0)))
1754 if (insn
!= XEXP (handler
, 0))
1755 warning ("mismatched handler %d",
1756 CODE_LABEL_NUMBER (insn
));
1761 if (insn
== NULL_RTX
)
1762 warning ("handler not found %d",
1763 CODE_LABEL_NUMBER (XEXP (handler
, 0)));
1766 /* Now go through and make sure that for each region there is a
1767 corresponding label. */
1768 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
1770 if (GET_CODE (insn
) == NOTE
1771 && (NOTE_LINE_NUMBER (insn
) == NOTE_INSN_EH_REGION_BEG
1772 || NOTE_LINE_NUMBER (insn
) == NOTE_INSN_EH_REGION_END
))
1774 for (handler
= exception_handler_labels
;
1776 handler
= XEXP (handler
, 1))
1778 if (CODE_LABEL_NUMBER (XEXP (handler
, 0))
1779 == NOTE_BLOCK_NUMBER (insn
))
1782 if (handler
== NULL_RTX
&& !flag_syntax_only
)
1783 warning ("region exists, no handler %d",
1784 NOTE_BLOCK_NUMBER (insn
));
1789 /* This group of functions initializes the exception handling data
1790 structures at the start of the compilation, initializes the data
1791 structures at the start of a function, and saves and restores the
1792 exception handling data structures for the start/end of a nested
1795 /* Toplevel initialization for EH things. */
1802 /* Initialize the per-function EH information. */
1805 init_eh_for_function ()
1808 ehqueue
.head
= ehqueue
.tail
= 0;
1809 catch_clauses
= NULL_RTX
;
1810 false_label_stack
= 0;
1811 caught_return_label_stack
= 0;
1812 protect_list
= NULL_TREE
;
1813 current_function_ehc
= NULL_RTX
;
1816 /* Save some of the per-function EH info into the save area denoted by
1819 This is currently called from save_stmt_status. */
1828 p
->ehstack
= ehstack
;
1829 p
->ehqueue
= ehqueue
;
1830 p
->catch_clauses
= catch_clauses
;
1831 p
->false_label_stack
= false_label_stack
;
1832 p
->caught_return_label_stack
= caught_return_label_stack
;
1833 p
->protect_list
= protect_list
;
1834 p
->ehc
= current_function_ehc
;
1836 init_eh_for_function ();
1839 /* Restore the per-function EH info saved into the area denoted by P.
1841 This is currently called from restore_stmt_status. */
1844 restore_eh_status (p
)
1850 protect_list
= p
->protect_list
;
1851 caught_return_label_stack
= p
->caught_return_label_stack
;
1852 false_label_stack
= p
->false_label_stack
;
1853 catch_clauses
= p
->catch_clauses
;
1854 ehqueue
= p
->ehqueue
;
1855 ehstack
= p
->ehstack
;
1856 current_function_ehc
= p
->ehc
;
1859 /* This section is for the exception handling specific optimization
1860 pass. First are the internal routines, and then the main
1861 optimization pass. */
1863 /* Determine if the given INSN can throw an exception. */
1869 /* Calls can always potentially throw exceptions. */
1870 if (GET_CODE (insn
) == CALL_INSN
)
1873 if (asynchronous_exceptions
)
1875 /* If we wanted asynchronous exceptions, then everything but NOTEs
1876 and CODE_LABELs could throw. */
1877 if (GET_CODE (insn
) != NOTE
&& GET_CODE (insn
) != CODE_LABEL
)
1884 /* Scan a exception region looking for the matching end and then
1885 remove it if possible. INSN is the start of the region, N is the
1886 region number, and DELETE_OUTER is to note if anything in this
1889 Regions are removed if they cannot possibly catch an exception.
1890 This is determined by invoking can_throw on each insn within the
1891 region; if can_throw returns true for any of the instructions, the
1892 region can catch an exception, since there is an insn within the
1893 region that is capable of throwing an exception.
1895 Returns the NOTE_INSN_EH_REGION_END corresponding to this region, or
1896 calls abort if it can't find one.
1898 Can abort if INSN is not a NOTE_INSN_EH_REGION_BEGIN, or if N doesn't
1899 correspond to the region number, or if DELETE_OUTER is NULL. */
1902 scan_region (insn
, n
, delete_outer
)
1909 /* Assume we can delete the region. */
1912 if (insn
== NULL_RTX
1913 || GET_CODE (insn
) != NOTE
1914 || NOTE_LINE_NUMBER (insn
) != NOTE_INSN_EH_REGION_BEG
1915 || NOTE_BLOCK_NUMBER (insn
) != n
1916 || delete_outer
== NULL
)
1919 insn
= NEXT_INSN (insn
);
1921 /* Look for the matching end. */
1922 while (! (GET_CODE (insn
) == NOTE
1923 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_EH_REGION_END
))
1925 /* If anything can throw, we can't remove the region. */
1926 if (delete && can_throw (insn
))
1931 /* Watch out for and handle nested regions. */
1932 if (GET_CODE (insn
) == NOTE
1933 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_EH_REGION_BEG
)
1935 insn
= scan_region (insn
, NOTE_BLOCK_NUMBER (insn
), &delete);
1938 insn
= NEXT_INSN (insn
);
1941 /* The _BEG/_END NOTEs must match and nest. */
1942 if (NOTE_BLOCK_NUMBER (insn
) != n
)
1945 /* If anything in this exception region can throw, we can throw. */
1950 /* Delete the start and end of the region. */
1951 delete_insn (start
);
1954 /* Only do this part if we have built the exception handler
1956 if (exception_handler_labels
)
1958 rtx x
, *prev
= &exception_handler_labels
;
1960 /* Find it in the list of handlers. */
1961 for (x
= exception_handler_labels
; x
; x
= XEXP (x
, 1))
1963 rtx label
= XEXP (x
, 0);
1964 if (CODE_LABEL_NUMBER (label
) == n
)
1966 /* If we are the last reference to the handler,
1968 if (--LABEL_NUSES (label
) == 0)
1969 delete_insn (label
);
1973 /* Remove it from the list of exception handler
1974 labels, if we are optimizing. If we are not, then
1975 leave it in the list, as we are not really going to
1976 remove the region. */
1977 *prev
= XEXP (x
, 1);
1984 prev
= &XEXP (x
, 1);
1991 /* Perform various interesting optimizations for exception handling
1994 We look for empty exception regions and make them go (away). The
1995 jump optimization code will remove the handler if nothing else uses
1999 exception_optimize ()
2004 /* Remove empty regions. */
2005 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2007 if (GET_CODE (insn
) == NOTE
2008 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_EH_REGION_BEG
)
2010 /* Since scan_region will return the NOTE_INSN_EH_REGION_END
2011 insn, we will indirectly skip through all the insns
2012 inbetween. We are also guaranteed that the value of insn
2013 returned will be valid, as otherwise scan_region won't
2015 insn
= scan_region (insn
, NOTE_BLOCK_NUMBER (insn
), &n
);
2020 /* Various hooks for the DWARF 2 __throw routine. */
2022 /* Do any necessary initialization to access arbitrary stack frames.
2023 On the SPARC, this means flushing the register windows. */
2026 expand_builtin_unwind_init ()
2028 /* Set this so all the registers get saved in our frame; we need to be
2029 able to copy the saved values for any registers from frames we unwind. */
2030 current_function_has_nonlocal_label
= 1;
2032 #ifdef SETUP_FRAME_ADDRESSES
2033 SETUP_FRAME_ADDRESSES ();
2037 /* Given a value extracted from the return address register or stack slot,
2038 return the actual address encoded in that value. */
2041 expand_builtin_extract_return_addr (addr_tree
)
2044 rtx addr
= expand_expr (addr_tree
, NULL_RTX
, Pmode
, 0);
2045 return eh_outer_context (addr
);
2048 /* Given an actual address in addr_tree, do any necessary encoding
2049 and return the value to be stored in the return address register or
2050 stack slot so the epilogue will return to that address. */
2053 expand_builtin_frob_return_addr (addr_tree
)
2056 rtx addr
= expand_expr (addr_tree
, NULL_RTX
, Pmode
, 0);
2057 #ifdef RETURN_ADDR_OFFSET
2058 addr
= plus_constant (addr
, -RETURN_ADDR_OFFSET
);
2063 /* Given an actual address in addr_tree, set the return address register up
2064 so the epilogue will return to that address. If the return address is
2065 not in a register, do nothing. */
2068 expand_builtin_set_return_addr_reg (addr_tree
)
2072 rtx ra
= expand_builtin_return_addr (BUILT_IN_RETURN_ADDRESS
,
2073 0, hard_frame_pointer_rtx
);
2075 if (GET_CODE (ra
) != REG
|| REGNO (ra
) >= FIRST_PSEUDO_REGISTER
)
2078 tmp
= force_operand (expand_builtin_frob_return_addr (addr_tree
), ra
);
2080 emit_move_insn (ra
, tmp
);
2083 /* Choose two registers for communication between the main body of
2084 __throw and the stub for adjusting the stack pointer. The first register
2085 is used to pass the address of the exception handler; the second register
2086 is used to pass the stack pointer offset.
2088 For register 1 we use the return value register for a void *.
2089 For register 2 we use the static chain register if it exists and is
2090 different from register 1, otherwise some arbitrary call-clobbered
2094 eh_regs (r1
, r2
, outgoing
)
2100 #ifdef FUNCTION_OUTGOING_VALUE
2102 reg1
= FUNCTION_OUTGOING_VALUE (build_pointer_type (void_type_node
),
2103 current_function_decl
);
2106 reg1
= FUNCTION_VALUE (build_pointer_type (void_type_node
),
2107 current_function_decl
);
2109 #ifdef STATIC_CHAIN_REGNUM
2111 reg2
= static_chain_incoming_rtx
;
2113 reg2
= static_chain_rtx
;
2114 if (REGNO (reg2
) == REGNO (reg1
))
2115 #endif /* STATIC_CHAIN_REGNUM */
2118 if (reg2
== NULL_RTX
)
2121 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; ++i
)
2122 if (call_used_regs
[i
] && ! fixed_regs
[i
] && i
!= REGNO (reg1
))
2124 reg2
= gen_rtx_REG (Pmode
, i
);
2128 if (reg2
== NULL_RTX
)
2136 /* Emit inside of __throw a stub which adjusts the stack pointer and jumps
2137 to the exception handler. __throw will set up the necessary values
2138 and then return to the stub. */
2141 expand_builtin_eh_stub ()
2143 rtx stub_start
= gen_label_rtx ();
2144 rtx after_stub
= gen_label_rtx ();
2145 rtx handler
, offset
;
2147 emit_jump (after_stub
);
2148 emit_label (stub_start
);
2150 eh_regs (&handler
, &offset
, 0);
2152 adjust_stack (offset
);
2153 emit_indirect_jump (handler
);
2155 emit_label (after_stub
);
2156 return gen_rtx_LABEL_REF (Pmode
, stub_start
);
2159 /* Set up the registers for passing the handler address and stack offset
2160 to the stub above. */
2163 expand_builtin_set_eh_regs (handler
, offset
)
2164 tree handler
, offset
;
2168 eh_regs (®1
, ®2
, 1);
2170 store_expr (offset
, reg2
, 0);
2171 store_expr (handler
, reg1
, 0);
2173 /* These will be used by the stub. */
2174 emit_insn (gen_rtx_USE (VOIDmode
, reg1
));
2175 emit_insn (gen_rtx_USE (VOIDmode
, reg2
));
2180 /* This contains the code required to verify whether arbitrary instructions
2181 are in the same exception region. */
2183 static int *insn_eh_region
= (int *)0;
2184 static int maximum_uid
;
2187 set_insn_eh_region (first
, region_num
)
2194 for (insn
= *first
; insn
; insn
= NEXT_INSN (insn
))
2196 if ((GET_CODE (insn
) == NOTE
) &&
2197 (NOTE_LINE_NUMBER (insn
) == NOTE_INSN_EH_REGION_BEG
))
2199 rnum
= NOTE_BLOCK_NUMBER (insn
);
2200 insn_eh_region
[INSN_UID (insn
)] = rnum
;
2201 insn
= NEXT_INSN (insn
);
2202 set_insn_eh_region (&insn
, rnum
);
2203 /* Upon return, insn points to the EH_REGION_END of nested region */
2206 insn_eh_region
[INSN_UID (insn
)] = region_num
;
2207 if ((GET_CODE (insn
) == NOTE
) &&
2208 (NOTE_LINE_NUMBER (insn
) == NOTE_INSN_EH_REGION_END
))
2214 /* Free the insn table, an make sure it cannot be used again. */
2216 void free_insn_eh_region ()
2223 free (insn_eh_region
);
2224 insn_eh_region
= (int *)0;
2228 /* Initialize the table. max_uid must be calculated and handed into
2229 this routine. If it is unavailable, passing a value of 0 will
2230 cause this routine to calculate it as well. */
2232 void init_insn_eh_region (first
, max_uid
)
2242 free_insn_eh_region();
2245 for (insn
= first
; insn
; insn
= NEXT_INSN (insn
))
2246 if (INSN_UID (insn
) > max_uid
) /* find largest UID */
2247 max_uid
= INSN_UID (insn
);
2249 maximum_uid
= max_uid
;
2250 insn_eh_region
= (int *) malloc ((max_uid
+ 1) * sizeof (int));
2252 set_insn_eh_region (&insn
, 0);
2256 /* Check whether 2 instructions are within the same region. */
2258 int in_same_eh_region(insn1
, insn2
)
2261 int ret
, uid1
, uid2
;
2263 /* If no exceptions, instructions are always in same region. */
2267 /* If the table isn't allocated, assume the worst. */
2268 if (!insn_eh_region
)
2271 uid1
= INSN_UID (insn1
);
2272 uid2
= INSN_UID (insn2
);
2274 /* if instructions have been allocated beyond the end, either
2275 the table is out of date, or this is a late addition, or
2276 something... Assume the worst. */
2277 if (uid1
> maximum_uid
|| uid2
> maximum_uid
)
2280 ret
= (insn_eh_region
[uid1
] == insn_eh_region
[uid2
]);