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12670d88 | 1 | /* Implements exception handling. |
4956d07c MS |
2 | Copyright (C) 1989, 92-95, 1996 Free Software Foundation, Inc. |
3 | Contributed by Mike Stump <mrs@cygnus.com>. | |
4 | ||
5 | This file is part of GNU CC. | |
6 | ||
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) | |
10 | any later version. | |
11 | ||
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. | |
16 | ||
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. */ | |
21 | ||
22 | ||
12670d88 RK |
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 assocated with a function call | |
27 | several levels up the stack. | |
28 | ||
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. | |
38 | ||
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. | |
45 | ||
27a36778 MS |
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. -fnosjlj-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 | |
54 | based approach. | |
55 | ||
12670d88 RK |
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 | |
59 | exception. | |
60 | ||
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 | |
66 | function boundaries. | |
67 | ||
2ed18e63 MS |
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 | |
72 | stack. | |
73 | ||
74 | In the current implementaion, 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 | |
82 | this will change). | |
83 | ||
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 | |
88 | that region. | |
12670d88 | 89 | |
ca55abae JM |
90 | If the target does not use the DWARF 2 frame unwind information, at |
91 | program startup each object file invokes a function named | |
12670d88 | 92 | __register_exceptions with the address of its local |
ca55abae JM |
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). | |
96 | ||
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. On other targets, the information for each | |
d1485032 | 101 | translation unit is registered from the file generated by collect2. |
ca55abae JM |
102 | __register_frame 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). | |
12670d88 | 105 | |
27a36778 | 106 | The function __throw is actually responsible for doing the |
ca55abae JM |
107 | throw. On machines that have unwind info support, __throw is generated |
108 | by code in libgcc2.c, otherwise __throw is generated on a | |
12670d88 | 109 | per-object-file basis for each source file compiled with |
ca55abae JM |
110 | -fexceptions by the the C++ frontend. Before __throw is invoked, |
111 | the current context of the throw needs to be placed in the global | |
112 | variable __eh_pc. | |
12670d88 | 113 | |
27a36778 | 114 | __throw attempts to find the appropriate exception handler for the |
12670d88 | 115 | PC value stored in __eh_pc by calling __find_first_exception_table_match |
2ed18e63 | 116 | (which is defined in libgcc2.c). If __find_first_exception_table_match |
ca55abae JM |
117 | finds a relevant handler, __throw transfers control directly to it. |
118 | ||
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. | |
125 | ||
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. | |
12670d88 RK |
131 | |
132 | Internal implementation details: | |
133 | ||
12670d88 | 134 | To associate a user-defined handler with a block of statements, the |
27a36778 | 135 | function expand_start_try_stmts is used to mark the start of the |
12670d88 | 136 | block of statements with which the handler is to be associated |
2ed18e63 MS |
137 | (which is known as a "try block"). All statements that appear |
138 | afterwards will be associated with the try block. | |
139 | ||
27a36778 | 140 | A call to expand_start_all_catch marks the end of the try block, |
2ed18e63 MS |
141 | and also marks the start of the "catch block" (the user-defined |
142 | handler) associated with the try block. | |
143 | ||
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 | |
150 | mechanism). | |
151 | ||
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 | |
27a36778 | 155 | handler. expand_end_all_catch and expand_leftover_cleanups |
2ed18e63 MS |
156 | add additional code to the end of each handler to take care of |
157 | rethrowing to the outer exception handler. | |
158 | ||
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 | |
27a36778 | 163 | to the topmost entry's label via expand_goto will resume normal |
2ed18e63 MS |
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. | |
167 | ||
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 | |
27a36778 MS |
170 | the handlers specified via expand_eh_region_end. The end of the |
171 | catch block is marked with expand_end_all_catch. | |
12670d88 RK |
172 | |
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 | |
2ed18e63 MS |
177 | global variable to hold the value. (This will be changing in the |
178 | future.) | |
179 | ||
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.) | |
185 | ||
186 | Internally-generated exception regions (cleanups) are marked by | |
27a36778 | 187 | calling expand_eh_region_start to mark the start of the region, |
2ed18e63 MS |
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. | |
12670d88 RK |
196 | |
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 | |
2ed18e63 MS |
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. | |
208 | ||
209 | Cleanups can also be specified by using add_partial_entry (handler) | |
27a36778 | 210 | and end_protect_partials. add_partial_entry creates the start of |
2ed18e63 MS |
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 | |
27a36778 | 217 | group of calls to add_partial_entry as the entries are queued |
2ed18e63 MS |
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 | |
221 | function. | |
12670d88 RK |
222 | |
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 | |
2ed18e63 MS |
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. | |
12670d88 RK |
229 | |
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 | |
2ed18e63 | 234 | can be safely optimized away (along with its exception handlers) |
27a36778 MS |
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. | |
245 | ||
12670d88 | 246 | |
ca55abae | 247 | Walking the stack: |
12670d88 | 248 | |
ca55abae JM |
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. | |
12670d88 | 252 | |
ca55abae | 253 | Unwinding the stack: |
12670d88 | 254 | |
ca55abae JM |
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). | |
259 | ||
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. | |
262 | ||
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. | |
270 | ||
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 __teminate. | |
283 | ||
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. | |
2ed18e63 MS |
289 | |
290 | However, it is simply not possible on some platforms to write a | |
291 | generalized routine for doing stack unwinding without having some | |
ca55abae JM |
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. | |
12670d88 | 296 | |
ca55abae JM |
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. | |
12670d88 | 302 | |
27a36778 | 303 | On some platforms it is possible that neither __unwind_function |
12670d88 | 304 | nor inlined unwinders are available. For these platforms it is not |
27a36778 | 305 | possible to throw through a function call, and abort will be |
2ed18e63 MS |
306 | invoked instead of performing the throw. |
307 | ||
ca55abae JM |
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). | |
313 | ||
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. | |
319 | ||
2ed18e63 MS |
320 | Future directions: |
321 | ||
27a36778 | 322 | Currently __throw makes no differentiation between cleanups and |
2ed18e63 MS |
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. | |
330 | ||
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). | |
27a36778 | 333 | A two-pass scheme could then be used by __throw to iterate |
2ed18e63 MS |
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. | |
338 | ||
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 | |
27a36778 | 343 | __throw to be able to determine if a given user-defined |
2ed18e63 MS |
344 | exception handler will actually be executed, given the type of |
345 | exception. | |
346 | ||
347 | One scheme is to add additional information to exception_table_list | |
27a36778 | 348 | as to the types of exceptions accepted by each handler. __throw |
2ed18e63 MS |
349 | can do the type comparisons and then determine if the handler is |
350 | actually going to be executed. | |
351 | ||
352 | There is currently no significant level of debugging support | |
27a36778 | 353 | available, other than to place a breakpoint on __throw. While |
2ed18e63 MS |
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 | |
27a36778 | 359 | scheme by adding additional labels to __throw for appropriate |
2ed18e63 MS |
360 | breakpoints, and additional debugger commands could be added to |
361 | query various state variables to determine what actions are to be | |
362 | performed next. | |
363 | ||
ca55abae JM |
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. | |
27a36778 MS |
369 | |
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. | |
373 | ||
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_excetpions. __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. | |
384 | ||
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. */ | |
4956d07c MS |
389 | |
390 | ||
391 | #include "config.h" | |
ca55abae | 392 | #include "defaults.h" |
4956d07c MS |
393 | #include <stdio.h> |
394 | #include "rtl.h" | |
395 | #include "tree.h" | |
396 | #include "flags.h" | |
397 | #include "except.h" | |
398 | #include "function.h" | |
399 | #include "insn-flags.h" | |
400 | #include "expr.h" | |
401 | #include "insn-codes.h" | |
402 | #include "regs.h" | |
403 | #include "hard-reg-set.h" | |
404 | #include "insn-config.h" | |
405 | #include "recog.h" | |
406 | #include "output.h" | |
12670d88 | 407 | #include "assert.h" |
4956d07c | 408 | |
27a36778 MS |
409 | /* One to use setjmp/longjmp method of generating code for exception |
410 | handling. */ | |
411 | ||
d1485032 | 412 | int exceptions_via_longjmp = 2; |
27a36778 MS |
413 | |
414 | /* One to enable asynchronous exception support. */ | |
415 | ||
416 | int asynchronous_exceptions = 0; | |
417 | ||
418 | /* One to protect cleanup actions with a handler that calls | |
419 | __terminate, zero otherwise. */ | |
420 | ||
421 | int protect_cleanup_actions_with_terminate = 0; | |
422 | ||
12670d88 | 423 | /* A list of labels used for exception handlers. Created by |
4956d07c MS |
424 | find_exception_handler_labels for the optimization passes. */ |
425 | ||
426 | rtx exception_handler_labels; | |
427 | ||
12670d88 RK |
428 | /* Nonzero means that __throw was invoked. |
429 | ||
430 | This is used by the C++ frontend to know if code needs to be emitted | |
431 | for __throw or not. */ | |
4956d07c MS |
432 | |
433 | int throw_used; | |
434 | ||
27a36778 MS |
435 | /* The dynamic handler chain. Nonzero if the function has already |
436 | fetched a pointer to the dynamic handler chain for exception | |
437 | handling. */ | |
438 | ||
439 | rtx current_function_dhc; | |
440 | ||
441 | /* The dynamic cleanup chain. Nonzero if the function has already | |
442 | fetched a pointer to the dynamic cleanup chain for exception | |
443 | handling. */ | |
444 | ||
445 | rtx current_function_dcc; | |
446 | ||
4956d07c | 447 | /* A stack used for keeping track of the currectly active exception |
12670d88 | 448 | handling region. As each exception region is started, an entry |
4956d07c MS |
449 | describing the region is pushed onto this stack. The current |
450 | region can be found by looking at the top of the stack, and as we | |
12670d88 RK |
451 | exit regions, the corresponding entries are popped. |
452 | ||
27a36778 | 453 | Entries cannot overlap; they can be nested. So there is only one |
12670d88 RK |
454 | entry at most that corresponds to the current instruction, and that |
455 | is the entry on the top of the stack. */ | |
4956d07c | 456 | |
27a36778 | 457 | static struct eh_stack ehstack; |
4956d07c | 458 | |
12670d88 RK |
459 | /* A queue used for tracking which exception regions have closed but |
460 | whose handlers have not yet been expanded. Regions are emitted in | |
461 | groups in an attempt to improve paging performance. | |
462 | ||
463 | As we exit a region, we enqueue a new entry. The entries are then | |
27a36778 | 464 | dequeued during expand_leftover_cleanups and expand_start_all_catch, |
12670d88 RK |
465 | |
466 | We should redo things so that we either take RTL for the handler, | |
467 | or we expand the handler expressed as a tree immediately at region | |
468 | end time. */ | |
4956d07c | 469 | |
27a36778 | 470 | static struct eh_queue ehqueue; |
4956d07c | 471 | |
12670d88 | 472 | /* Insns for all of the exception handlers for the current function. |
abeeec2a | 473 | They are currently emitted by the frontend code. */ |
4956d07c MS |
474 | |
475 | rtx catch_clauses; | |
476 | ||
12670d88 RK |
477 | /* A TREE_CHAINed list of handlers for regions that are not yet |
478 | closed. The TREE_VALUE of each entry contains the handler for the | |
abeeec2a | 479 | corresponding entry on the ehstack. */ |
4956d07c | 480 | |
12670d88 | 481 | static tree protect_list; |
4956d07c MS |
482 | |
483 | /* Stacks to keep track of various labels. */ | |
484 | ||
12670d88 RK |
485 | /* Keeps track of the label to resume to should one want to resume |
486 | normal control flow out of a handler (instead of, say, returning to | |
487 | the caller of the current function or exiting the program). Also | |
488 | used as the context of a throw to rethrow an exception to the outer | |
abeeec2a | 489 | exception region. */ |
4956d07c MS |
490 | |
491 | struct label_node *caught_return_label_stack = NULL; | |
492 | ||
12670d88 | 493 | /* A random data area for the front end's own use. */ |
4956d07c MS |
494 | |
495 | struct label_node *false_label_stack = NULL; | |
496 | ||
843e8335 | 497 | /* The rtx and the tree for the saved PC value. */ |
4956d07c MS |
498 | |
499 | rtx eh_saved_pc_rtx; | |
843e8335 | 500 | tree eh_saved_pc; |
4956d07c MS |
501 | |
502 | rtx expand_builtin_return_addr PROTO((enum built_in_function, int, rtx)); | |
503 | \f | |
504 | /* Various support routines to manipulate the various data structures | |
505 | used by the exception handling code. */ | |
506 | ||
507 | /* Push a label entry onto the given STACK. */ | |
508 | ||
509 | void | |
510 | push_label_entry (stack, rlabel, tlabel) | |
511 | struct label_node **stack; | |
512 | rtx rlabel; | |
513 | tree tlabel; | |
514 | { | |
515 | struct label_node *newnode | |
516 | = (struct label_node *) xmalloc (sizeof (struct label_node)); | |
517 | ||
518 | if (rlabel) | |
519 | newnode->u.rlabel = rlabel; | |
520 | else | |
521 | newnode->u.tlabel = tlabel; | |
522 | newnode->chain = *stack; | |
523 | *stack = newnode; | |
524 | } | |
525 | ||
526 | /* Pop a label entry from the given STACK. */ | |
527 | ||
528 | rtx | |
529 | pop_label_entry (stack) | |
530 | struct label_node **stack; | |
531 | { | |
532 | rtx label; | |
533 | struct label_node *tempnode; | |
534 | ||
535 | if (! *stack) | |
536 | return NULL_RTX; | |
537 | ||
538 | tempnode = *stack; | |
539 | label = tempnode->u.rlabel; | |
540 | *stack = (*stack)->chain; | |
541 | free (tempnode); | |
542 | ||
543 | return label; | |
544 | } | |
545 | ||
546 | /* Return the top element of the given STACK. */ | |
547 | ||
548 | tree | |
549 | top_label_entry (stack) | |
550 | struct label_node **stack; | |
551 | { | |
552 | if (! *stack) | |
553 | return NULL_TREE; | |
554 | ||
555 | return (*stack)->u.tlabel; | |
556 | } | |
557 | ||
12670d88 | 558 | /* Make a copy of ENTRY using xmalloc to allocate the space. */ |
4956d07c MS |
559 | |
560 | static struct eh_entry * | |
561 | copy_eh_entry (entry) | |
562 | struct eh_entry *entry; | |
563 | { | |
564 | struct eh_entry *newentry; | |
565 | ||
566 | newentry = (struct eh_entry *) xmalloc (sizeof (struct eh_entry)); | |
567 | bcopy ((char *) entry, (char *) newentry, sizeof (struct eh_entry)); | |
568 | ||
569 | return newentry; | |
570 | } | |
571 | ||
478b0752 | 572 | /* Push a new eh_node entry onto STACK. */ |
4956d07c | 573 | |
478b0752 | 574 | static void |
4956d07c MS |
575 | push_eh_entry (stack) |
576 | struct eh_stack *stack; | |
577 | { | |
578 | struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node)); | |
579 | struct eh_entry *entry = (struct eh_entry *) xmalloc (sizeof (struct eh_entry)); | |
580 | ||
478b0752 | 581 | entry->outer_context = gen_label_rtx (); |
4956d07c MS |
582 | entry->exception_handler_label = gen_label_rtx (); |
583 | entry->finalization = NULL_TREE; | |
584 | ||
585 | node->entry = entry; | |
586 | node->chain = stack->top; | |
587 | stack->top = node; | |
4956d07c MS |
588 | } |
589 | ||
590 | /* Pop an entry from the given STACK. */ | |
591 | ||
592 | static struct eh_entry * | |
593 | pop_eh_entry (stack) | |
594 | struct eh_stack *stack; | |
595 | { | |
596 | struct eh_node *tempnode; | |
597 | struct eh_entry *tempentry; | |
598 | ||
599 | tempnode = stack->top; | |
600 | tempentry = tempnode->entry; | |
601 | stack->top = stack->top->chain; | |
602 | free (tempnode); | |
603 | ||
604 | return tempentry; | |
605 | } | |
606 | ||
607 | /* Enqueue an ENTRY onto the given QUEUE. */ | |
608 | ||
609 | static void | |
610 | enqueue_eh_entry (queue, entry) | |
611 | struct eh_queue *queue; | |
612 | struct eh_entry *entry; | |
613 | { | |
614 | struct eh_node *node = (struct eh_node *) xmalloc (sizeof (struct eh_node)); | |
615 | ||
616 | node->entry = entry; | |
617 | node->chain = NULL; | |
618 | ||
619 | if (queue->head == NULL) | |
620 | { | |
621 | queue->head = node; | |
622 | } | |
623 | else | |
624 | { | |
625 | queue->tail->chain = node; | |
626 | } | |
627 | queue->tail = node; | |
628 | } | |
629 | ||
630 | /* Dequeue an entry from the given QUEUE. */ | |
631 | ||
632 | static struct eh_entry * | |
633 | dequeue_eh_entry (queue) | |
634 | struct eh_queue *queue; | |
635 | { | |
636 | struct eh_node *tempnode; | |
637 | struct eh_entry *tempentry; | |
638 | ||
639 | if (queue->head == NULL) | |
640 | return NULL; | |
641 | ||
642 | tempnode = queue->head; | |
643 | queue->head = queue->head->chain; | |
644 | ||
645 | tempentry = tempnode->entry; | |
646 | free (tempnode); | |
647 | ||
648 | return tempentry; | |
649 | } | |
650 | \f | |
651 | /* Routine to see if exception exception handling is turned on. | |
652 | DO_WARN is non-zero if we want to inform the user that exception | |
12670d88 RK |
653 | handling is turned off. |
654 | ||
655 | This is used to ensure that -fexceptions has been specified if the | |
abeeec2a | 656 | compiler tries to use any exception-specific functions. */ |
4956d07c MS |
657 | |
658 | int | |
659 | doing_eh (do_warn) | |
660 | int do_warn; | |
661 | { | |
662 | if (! flag_exceptions) | |
663 | { | |
664 | static int warned = 0; | |
665 | if (! warned && do_warn) | |
666 | { | |
667 | error ("exception handling disabled, use -fexceptions to enable"); | |
668 | warned = 1; | |
669 | } | |
670 | return 0; | |
671 | } | |
672 | return 1; | |
673 | } | |
674 | ||
12670d88 | 675 | /* Given a return address in ADDR, determine the address we should use |
abeeec2a | 676 | to find the corresponding EH region. */ |
4956d07c MS |
677 | |
678 | rtx | |
679 | eh_outer_context (addr) | |
680 | rtx addr; | |
681 | { | |
682 | /* First mask out any unwanted bits. */ | |
683 | #ifdef MASK_RETURN_ADDR | |
ca55abae | 684 | expand_and (addr, MASK_RETURN_ADDR, addr); |
4956d07c MS |
685 | #endif |
686 | ||
ca55abae JM |
687 | /* Then adjust to find the real return address. */ |
688 | #if defined (RETURN_ADDR_OFFSET) | |
689 | addr = plus_constant (addr, RETURN_ADDR_OFFSET); | |
4956d07c MS |
690 | #endif |
691 | ||
692 | return addr; | |
693 | } | |
694 | ||
27a36778 MS |
695 | /* Start a new exception region for a region of code that has a |
696 | cleanup action and push the HANDLER for the region onto | |
697 | protect_list. All of the regions created with add_partial_entry | |
698 | will be ended when end_protect_partials is invoked. */ | |
12670d88 RK |
699 | |
700 | void | |
701 | add_partial_entry (handler) | |
702 | tree handler; | |
703 | { | |
704 | expand_eh_region_start (); | |
705 | ||
abeeec2a | 706 | /* Make sure the entry is on the correct obstack. */ |
12670d88 RK |
707 | push_obstacks_nochange (); |
708 | resume_temporary_allocation (); | |
27a36778 MS |
709 | |
710 | /* Because this is a cleanup action, we may have to protect the handler | |
711 | with __terminate. */ | |
712 | handler = protect_with_terminate (handler); | |
713 | ||
12670d88 RK |
714 | protect_list = tree_cons (NULL_TREE, handler, protect_list); |
715 | pop_obstacks (); | |
716 | } | |
717 | ||
27a36778 MS |
718 | /* Get a reference to the dynamic handler chain. It points to the |
719 | pointer to the next element in the dynamic handler chain. It ends | |
720 | when there are no more elements in the dynamic handler chain, when | |
721 | the value is &top_elt from libgcc2.c. Immediately after the | |
722 | pointer, is an area suitable for setjmp/longjmp when | |
6e6a07d2 MS |
723 | DONT_USE_BUILTIN_SETJMP is defined, and an area suitable for |
724 | __builtin_setjmp/__builtin_longjmp when DONT_USE_BUILTIN_SETJMP | |
725 | isn't defined. | |
27a36778 MS |
726 | |
727 | This routine is here to facilitate the porting of this code to | |
728 | systems with threads. One can either replace the routine we emit a | |
729 | call for here in libgcc2.c, or one can modify this routine to work | |
730 | with their thread system. */ | |
731 | ||
732 | rtx | |
733 | get_dynamic_handler_chain () | |
734 | { | |
735 | #if 0 | |
736 | /* Do this once we figure out how to get this to the front of the | |
737 | function, and we really only want one per real function, not one | |
738 | per inlined function. */ | |
739 | if (current_function_dhc == 0) | |
740 | { | |
741 | rtx dhc, insns; | |
742 | start_sequence (); | |
743 | ||
744 | dhc = emit_library_call_value (get_dynamic_handler_chain_libfunc, | |
745 | NULL_RTX, 1, | |
746 | Pmode, 0); | |
747 | current_function_dhc = copy_to_reg (dhc); | |
748 | insns = get_insns (); | |
749 | end_sequence (); | |
750 | emit_insns_before (insns, get_first_nonparm_insn ()); | |
751 | } | |
752 | #else | |
753 | rtx dhc; | |
754 | dhc = emit_library_call_value (get_dynamic_handler_chain_libfunc, | |
755 | NULL_RTX, 1, | |
756 | Pmode, 0); | |
757 | current_function_dhc = copy_to_reg (dhc); | |
758 | #endif | |
759 | ||
760 | /* We don't want a copy of the dhc, but rather, the single dhc. */ | |
761 | return gen_rtx (MEM, Pmode, current_function_dhc); | |
762 | } | |
763 | ||
764 | /* Get a reference to the dynamic cleanup chain. It points to the | |
765 | pointer to the next element in the dynamic cleanup chain. | |
766 | Immediately after the pointer, are two Pmode variables, one for a | |
767 | pointer to a function that performs the cleanup action, and the | |
768 | second, the argument to pass to that function. */ | |
769 | ||
770 | rtx | |
771 | get_dynamic_cleanup_chain () | |
772 | { | |
773 | rtx dhc, dcc; | |
774 | ||
775 | dhc = get_dynamic_handler_chain (); | |
776 | dcc = plus_constant (dhc, GET_MODE_SIZE (Pmode)); | |
777 | ||
778 | current_function_dcc = copy_to_reg (dcc); | |
779 | ||
780 | /* We don't want a copy of the dcc, but rather, the single dcc. */ | |
781 | return gen_rtx (MEM, Pmode, current_function_dcc); | |
782 | } | |
783 | ||
784 | /* Generate code to evaluate X and jump to LABEL if the value is nonzero. | |
785 | LABEL is an rtx of code CODE_LABEL, in this function. */ | |
786 | ||
787 | void | |
788 | jumpif_rtx (x, label) | |
789 | rtx x; | |
790 | rtx label; | |
791 | { | |
792 | jumpif (make_tree (type_for_mode (GET_MODE (x), 0), x), label); | |
793 | } | |
794 | ||
795 | /* Generate code to evaluate X and jump to LABEL if the value is zero. | |
796 | LABEL is an rtx of code CODE_LABEL, in this function. */ | |
797 | ||
798 | void | |
799 | jumpifnot_rtx (x, label) | |
800 | rtx x; | |
801 | rtx label; | |
802 | { | |
803 | jumpifnot (make_tree (type_for_mode (GET_MODE (x), 0), x), label); | |
804 | } | |
805 | ||
806 | /* Start a dynamic cleanup on the EH runtime dynamic cleanup stack. | |
807 | We just need to create an element for the cleanup list, and push it | |
808 | into the chain. | |
809 | ||
810 | A dynamic cleanup is a cleanup action implied by the presence of an | |
811 | element on the EH runtime dynamic cleanup stack that is to be | |
812 | performed when an exception is thrown. The cleanup action is | |
813 | performed by __sjthrow when an exception is thrown. Only certain | |
814 | actions can be optimized into dynamic cleanup actions. For the | |
815 | restrictions on what actions can be performed using this routine, | |
816 | see expand_eh_region_start_tree. */ | |
817 | ||
818 | static void | |
819 | start_dynamic_cleanup (func, arg) | |
820 | tree func; | |
821 | tree arg; | |
822 | { | |
823 | rtx dhc, dcc; | |
824 | rtx new_func, new_arg; | |
825 | rtx x, buf; | |
826 | int size; | |
827 | ||
828 | /* We allocate enough room for a pointer to the function, and | |
829 | one argument. */ | |
830 | size = 2; | |
831 | ||
832 | /* XXX, FIXME: The stack space allocated this way is too long lived, | |
833 | but there is no allocation routine that allocates at the level of | |
834 | the last binding contour. */ | |
835 | buf = assign_stack_local (BLKmode, | |
836 | GET_MODE_SIZE (Pmode)*(size+1), | |
837 | 0); | |
838 | ||
839 | buf = change_address (buf, Pmode, NULL_RTX); | |
840 | ||
841 | /* Store dcc into the first word of the newly allocated buffer. */ | |
842 | ||
843 | dcc = get_dynamic_cleanup_chain (); | |
844 | emit_move_insn (buf, dcc); | |
845 | ||
846 | /* Store func and arg into the cleanup list element. */ | |
847 | ||
848 | new_func = gen_rtx (MEM, Pmode, plus_constant (XEXP (buf, 0), | |
849 | GET_MODE_SIZE (Pmode))); | |
850 | new_arg = gen_rtx (MEM, Pmode, plus_constant (XEXP (buf, 0), | |
851 | GET_MODE_SIZE (Pmode)*2)); | |
852 | x = expand_expr (func, new_func, Pmode, 0); | |
853 | if (x != new_func) | |
854 | emit_move_insn (new_func, x); | |
855 | ||
856 | x = expand_expr (arg, new_arg, Pmode, 0); | |
857 | if (x != new_arg) | |
858 | emit_move_insn (new_arg, x); | |
859 | ||
860 | /* Update the cleanup chain. */ | |
861 | ||
862 | emit_move_insn (dcc, XEXP (buf, 0)); | |
863 | } | |
864 | ||
865 | /* Emit RTL to start a dynamic handler on the EH runtime dynamic | |
866 | handler stack. This should only be used by expand_eh_region_start | |
867 | or expand_eh_region_start_tree. */ | |
868 | ||
869 | static void | |
870 | start_dynamic_handler () | |
871 | { | |
872 | rtx dhc, dcc; | |
6e6a07d2 | 873 | rtx x, arg, buf; |
27a36778 MS |
874 | int size; |
875 | ||
6e6a07d2 | 876 | #ifndef DONT_USE_BUILTIN_SETJMP |
27a36778 MS |
877 | /* The number of Pmode words for the setjmp buffer, when using the |
878 | builtin setjmp/longjmp, see expand_builtin, case | |
879 | BUILT_IN_LONGJMP. */ | |
880 | size = 5; | |
881 | #else | |
882 | #ifdef JMP_BUF_SIZE | |
883 | size = JMP_BUF_SIZE; | |
884 | #else | |
885 | /* Should be large enough for most systems, if it is not, | |
886 | JMP_BUF_SIZE should be defined with the proper value. It will | |
887 | also tend to be larger than necessary for most systems, a more | |
888 | optimal port will define JMP_BUF_SIZE. */ | |
889 | size = FIRST_PSEUDO_REGISTER+2; | |
890 | #endif | |
891 | #endif | |
892 | /* XXX, FIXME: The stack space allocated this way is too long lived, | |
893 | but there is no allocation routine that allocates at the level of | |
894 | the last binding contour. */ | |
895 | arg = assign_stack_local (BLKmode, | |
896 | GET_MODE_SIZE (Pmode)*(size+1), | |
897 | 0); | |
898 | ||
899 | arg = change_address (arg, Pmode, NULL_RTX); | |
900 | ||
901 | /* Store dhc into the first word of the newly allocated buffer. */ | |
902 | ||
903 | dhc = get_dynamic_handler_chain (); | |
904 | dcc = gen_rtx (MEM, Pmode, plus_constant (XEXP (arg, 0), | |
905 | GET_MODE_SIZE (Pmode))); | |
906 | emit_move_insn (arg, dhc); | |
907 | ||
908 | /* Zero out the start of the cleanup chain. */ | |
909 | emit_move_insn (dcc, const0_rtx); | |
910 | ||
911 | /* The jmpbuf starts two words into the area allocated. */ | |
6e6a07d2 | 912 | buf = plus_constant (XEXP (arg, 0), GET_MODE_SIZE (Pmode)*2); |
27a36778 | 913 | |
6e6a07d2 | 914 | #ifdef DONT_USE_BUILTIN_SETJMP |
27a36778 | 915 | x = emit_library_call_value (setjmp_libfunc, NULL_RTX, 1, SImode, 1, |
6e6a07d2 MS |
916 | buf, Pmode); |
917 | #else | |
918 | x = expand_builtin_setjmp (buf, NULL_RTX); | |
919 | #endif | |
27a36778 MS |
920 | |
921 | /* If we come back here for a catch, transfer control to the | |
922 | handler. */ | |
923 | ||
924 | jumpif_rtx (x, ehstack.top->entry->exception_handler_label); | |
925 | ||
926 | /* We are committed to this, so update the handler chain. */ | |
927 | ||
928 | emit_move_insn (dhc, XEXP (arg, 0)); | |
929 | } | |
930 | ||
931 | /* Start an exception handling region for the given cleanup action. | |
12670d88 | 932 | All instructions emitted after this point are considered to be part |
27a36778 MS |
933 | of the region until expand_eh_region_end is invoked. CLEANUP is |
934 | the cleanup action to perform. The return value is true if the | |
935 | exception region was optimized away. If that case, | |
936 | expand_eh_region_end does not need to be called for this cleanup, | |
937 | nor should it be. | |
938 | ||
939 | This routine notices one particular common case in C++ code | |
940 | generation, and optimizes it so as to not need the exception | |
941 | region. It works by creating a dynamic cleanup action, instead of | |
942 | of a using an exception region. */ | |
943 | ||
944 | int | |
4c581243 MS |
945 | expand_eh_region_start_tree (decl, cleanup) |
946 | tree decl; | |
27a36778 MS |
947 | tree cleanup; |
948 | { | |
949 | rtx note; | |
950 | ||
951 | /* This is the old code. */ | |
952 | if (! doing_eh (0)) | |
953 | return 0; | |
954 | ||
955 | /* The optimization only applies to actions protected with | |
956 | terminate, and only applies if we are using the setjmp/longjmp | |
957 | codegen method. */ | |
958 | if (exceptions_via_longjmp | |
959 | && protect_cleanup_actions_with_terminate) | |
960 | { | |
961 | tree func, arg; | |
962 | tree args; | |
963 | ||
964 | /* Ignore any UNSAVE_EXPR. */ | |
965 | if (TREE_CODE (cleanup) == UNSAVE_EXPR) | |
966 | cleanup = TREE_OPERAND (cleanup, 0); | |
967 | ||
968 | /* Further, it only applies if the action is a call, if there | |
969 | are 2 arguments, and if the second argument is 2. */ | |
970 | ||
971 | if (TREE_CODE (cleanup) == CALL_EXPR | |
972 | && (args = TREE_OPERAND (cleanup, 1)) | |
973 | && (func = TREE_OPERAND (cleanup, 0)) | |
974 | && (arg = TREE_VALUE (args)) | |
975 | && (args = TREE_CHAIN (args)) | |
976 | ||
977 | /* is the second argument 2? */ | |
978 | && TREE_CODE (TREE_VALUE (args)) == INTEGER_CST | |
979 | && TREE_INT_CST_LOW (TREE_VALUE (args)) == 2 | |
980 | && TREE_INT_CST_HIGH (TREE_VALUE (args)) == 0 | |
981 | ||
982 | /* Make sure there are no other arguments. */ | |
983 | && TREE_CHAIN (args) == NULL_TREE) | |
984 | { | |
985 | /* Arrange for returns and gotos to pop the entry we make on the | |
986 | dynamic cleanup stack. */ | |
4c581243 | 987 | expand_dcc_cleanup (decl); |
27a36778 MS |
988 | start_dynamic_cleanup (func, arg); |
989 | return 1; | |
990 | } | |
991 | } | |
992 | ||
4c581243 | 993 | expand_eh_region_start_for_decl (decl); |
27a36778 MS |
994 | |
995 | return 0; | |
996 | } | |
997 | ||
4c581243 MS |
998 | /* Just like expand_eh_region_start, except if a cleanup action is |
999 | entered on the cleanup chain, the TREE_PURPOSE of the element put | |
1000 | on the chain is DECL. DECL should be the associated VAR_DECL, if | |
1001 | any, otherwise it should be NULL_TREE. */ | |
4956d07c MS |
1002 | |
1003 | void | |
4c581243 MS |
1004 | expand_eh_region_start_for_decl (decl) |
1005 | tree decl; | |
4956d07c MS |
1006 | { |
1007 | rtx note; | |
1008 | ||
1009 | /* This is the old code. */ | |
1010 | if (! doing_eh (0)) | |
1011 | return; | |
1012 | ||
27a36778 MS |
1013 | if (exceptions_via_longjmp) |
1014 | { | |
1015 | /* We need a new block to record the start and end of the | |
1016 | dynamic handler chain. We could always do this, but we | |
1017 | really want to permit jumping into such a block, and we want | |
1018 | to avoid any errors or performance impact in the SJ EH code | |
1019 | for now. */ | |
1020 | expand_start_bindings (0); | |
1021 | ||
1022 | /* But we don't need or want a new temporary level. */ | |
1023 | pop_temp_slots (); | |
1024 | ||
1025 | /* Mark this block as created by expand_eh_region_start. This | |
1026 | is so that we can pop the block with expand_end_bindings | |
1027 | automatically. */ | |
1028 | mark_block_as_eh_region (); | |
1029 | ||
1030 | /* Arrange for returns and gotos to pop the entry we make on the | |
1031 | dynamic handler stack. */ | |
4c581243 | 1032 | expand_dhc_cleanup (decl); |
27a36778 | 1033 | } |
4956d07c | 1034 | |
27a36778 MS |
1035 | if (exceptions_via_longjmp == 0) |
1036 | note = emit_note (NULL_PTR, NOTE_INSN_EH_REGION_BEG); | |
478b0752 | 1037 | push_eh_entry (&ehstack); |
27a36778 MS |
1038 | if (exceptions_via_longjmp == 0) |
1039 | NOTE_BLOCK_NUMBER (note) | |
1040 | = CODE_LABEL_NUMBER (ehstack.top->entry->exception_handler_label); | |
1041 | if (exceptions_via_longjmp) | |
1042 | start_dynamic_handler (); | |
4956d07c MS |
1043 | } |
1044 | ||
4c581243 MS |
1045 | /* Start an exception handling region. All instructions emitted after |
1046 | this point are considered to be part of the region until | |
1047 | expand_eh_region_end is invoked. */ | |
1048 | ||
1049 | void | |
1050 | expand_eh_region_start () | |
1051 | { | |
1052 | expand_eh_region_start_for_decl (NULL_TREE); | |
1053 | } | |
1054 | ||
27a36778 MS |
1055 | /* End an exception handling region. The information about the region |
1056 | is found on the top of ehstack. | |
12670d88 RK |
1057 | |
1058 | HANDLER is either the cleanup for the exception region, or if we're | |
1059 | marking the end of a try block, HANDLER is integer_zero_node. | |
1060 | ||
27a36778 | 1061 | HANDLER will be transformed to rtl when expand_leftover_cleanups |
abeeec2a | 1062 | is invoked. */ |
4956d07c MS |
1063 | |
1064 | void | |
1065 | expand_eh_region_end (handler) | |
1066 | tree handler; | |
1067 | { | |
4956d07c MS |
1068 | struct eh_entry *entry; |
1069 | ||
1070 | if (! doing_eh (0)) | |
1071 | return; | |
1072 | ||
1073 | entry = pop_eh_entry (&ehstack); | |
1074 | ||
27a36778 MS |
1075 | if (exceptions_via_longjmp == 0) |
1076 | { | |
478b0752 | 1077 | rtx label; |
27a36778 MS |
1078 | rtx note = emit_note (NULL_PTR, NOTE_INSN_EH_REGION_END); |
1079 | NOTE_BLOCK_NUMBER (note) = CODE_LABEL_NUMBER (entry->exception_handler_label); | |
4956d07c | 1080 | |
478b0752 MS |
1081 | label = gen_label_rtx (); |
1082 | emit_jump (label); | |
1083 | ||
1084 | /* Emit a label marking the end of this exception region that | |
1085 | is used for rethrowing into the outer context. */ | |
1086 | emit_label (entry->outer_context); | |
4956d07c | 1087 | |
27a36778 MS |
1088 | /* Put in something that takes up space, as otherwise the end |
1089 | address for this EH region could have the exact same address as | |
1090 | its outer region. This would cause us to miss the fact that | |
1091 | resuming exception handling with this PC value would be inside | |
1092 | the outer region. */ | |
1093 | emit_insn (gen_nop ()); | |
478b0752 MS |
1094 | emit_barrier (); |
1095 | emit_label (label); | |
27a36778 | 1096 | } |
4956d07c MS |
1097 | |
1098 | entry->finalization = handler; | |
1099 | ||
1100 | enqueue_eh_entry (&ehqueue, entry); | |
1101 | ||
27a36778 MS |
1102 | /* If we have already started ending the bindings, don't recurse. |
1103 | This only happens when exceptions_via_longjmp is true. */ | |
1104 | if (is_eh_region ()) | |
1105 | { | |
1106 | /* Because we don't need or want a new temporary level and | |
1107 | because we didn't create one in expand_eh_region_start, | |
1108 | create a fake one now to avoid removing one in | |
1109 | expand_end_bindings. */ | |
1110 | push_temp_slots (); | |
1111 | ||
1112 | mark_block_as_not_eh_region (); | |
1113 | ||
1114 | /* Maybe do this to prevent jumping in and so on... */ | |
1115 | expand_end_bindings (NULL_TREE, 0, 0); | |
1116 | } | |
4956d07c MS |
1117 | } |
1118 | ||
27a36778 MS |
1119 | /* If we are using the setjmp/longjmp EH codegen method, we emit a |
1120 | call to __sjthrow. | |
1121 | ||
1122 | Otherwise, we emit a call to __throw and note that we threw | |
1123 | something, so we know we need to generate the necessary code for | |
1124 | __throw. | |
12670d88 RK |
1125 | |
1126 | Before invoking throw, the __eh_pc variable must have been set up | |
1127 | to contain the PC being thrown from. This address is used by | |
27a36778 | 1128 | __throw to determine which exception region (if any) is |
abeeec2a | 1129 | responsible for handling the exception. */ |
4956d07c | 1130 | |
27a36778 | 1131 | void |
4956d07c MS |
1132 | emit_throw () |
1133 | { | |
27a36778 MS |
1134 | if (exceptions_via_longjmp) |
1135 | { | |
1136 | emit_library_call (sjthrow_libfunc, 0, VOIDmode, 0); | |
1137 | } | |
1138 | else | |
1139 | { | |
4956d07c | 1140 | #ifdef JUMP_TO_THROW |
27a36778 | 1141 | emit_indirect_jump (throw_libfunc); |
4956d07c | 1142 | #else |
ca55abae JM |
1143 | #ifndef DWARF2_UNWIND_INFO |
1144 | /* Prevent assemble_external from doing anything with this symbol. */ | |
27a36778 | 1145 | SYMBOL_REF_USED (throw_libfunc) = 1; |
ca55abae | 1146 | #endif |
27a36778 | 1147 | emit_library_call (throw_libfunc, 0, VOIDmode, 0); |
4956d07c | 1148 | #endif |
27a36778 MS |
1149 | throw_used = 1; |
1150 | } | |
4956d07c MS |
1151 | emit_barrier (); |
1152 | } | |
1153 | ||
12670d88 | 1154 | /* An internal throw with an indirect CONTEXT we want to throw from. |
abeeec2a | 1155 | CONTEXT evaluates to the context of the throw. */ |
4956d07c | 1156 | |
12670d88 | 1157 | static void |
4956d07c MS |
1158 | expand_internal_throw_indirect (context) |
1159 | rtx context; | |
1160 | { | |
843e8335 | 1161 | assemble_external (eh_saved_pc); |
4956d07c MS |
1162 | emit_move_insn (eh_saved_pc_rtx, context); |
1163 | emit_throw (); | |
1164 | } | |
1165 | ||
12670d88 RK |
1166 | /* An internal throw with a direct CONTEXT we want to throw from. |
1167 | CONTEXT must be a label; its address will be used as the context of | |
abeeec2a | 1168 | the throw. */ |
4956d07c MS |
1169 | |
1170 | void | |
1171 | expand_internal_throw (context) | |
1172 | rtx context; | |
1173 | { | |
1174 | expand_internal_throw_indirect (gen_rtx (LABEL_REF, Pmode, context)); | |
1175 | } | |
1176 | ||
1177 | /* Called from expand_exception_blocks and expand_end_catch_block to | |
27a36778 | 1178 | emit any pending handlers/cleanups queued from expand_eh_region_end. */ |
4956d07c MS |
1179 | |
1180 | void | |
1181 | expand_leftover_cleanups () | |
1182 | { | |
1183 | struct eh_entry *entry; | |
1184 | ||
1185 | while ((entry = dequeue_eh_entry (&ehqueue)) != 0) | |
1186 | { | |
1187 | rtx prev; | |
1188 | ||
12670d88 RK |
1189 | /* A leftover try block. Shouldn't be one here. */ |
1190 | if (entry->finalization == integer_zero_node) | |
1191 | abort (); | |
1192 | ||
abeeec2a | 1193 | /* Output the label for the start of the exception handler. */ |
4956d07c MS |
1194 | emit_label (entry->exception_handler_label); |
1195 | ||
f51430ed MS |
1196 | #ifdef HAVE_exception_receiver |
1197 | if (! exceptions_via_longjmp) | |
1198 | if (HAVE_exception_receiver) | |
1199 | emit_insn (gen_exception_receiver ()); | |
1200 | #endif | |
1201 | ||
05f5b2cd MS |
1202 | #ifdef HAVE_nonlocal_goto_receiver |
1203 | if (! exceptions_via_longjmp) | |
1204 | if (HAVE_nonlocal_goto_receiver) | |
1205 | emit_insn (gen_nonlocal_goto_receiver ()); | |
1206 | #endif | |
1207 | ||
abeeec2a | 1208 | /* And now generate the insns for the handler. */ |
4956d07c MS |
1209 | expand_expr (entry->finalization, const0_rtx, VOIDmode, 0); |
1210 | ||
1211 | prev = get_last_insn (); | |
27a36778 | 1212 | if (prev == NULL || GET_CODE (prev) != BARRIER) |
4956d07c | 1213 | { |
27a36778 MS |
1214 | if (exceptions_via_longjmp) |
1215 | emit_throw (); | |
1216 | else | |
1217 | { | |
478b0752 MS |
1218 | /* The below can be optimized away, and we could just |
1219 | fall into the next EH handler, if we are certain they | |
1220 | are nested. */ | |
27a36778 MS |
1221 | /* Emit code to throw to the outer context if we fall off |
1222 | the end of the handler. */ | |
478b0752 | 1223 | expand_internal_throw (entry->outer_context); |
27a36778 | 1224 | } |
4956d07c MS |
1225 | } |
1226 | ||
4956d07c MS |
1227 | free (entry); |
1228 | } | |
1229 | } | |
1230 | ||
abeeec2a | 1231 | /* Called at the start of a block of try statements. */ |
12670d88 RK |
1232 | void |
1233 | expand_start_try_stmts () | |
1234 | { | |
1235 | if (! doing_eh (1)) | |
1236 | return; | |
1237 | ||
1238 | expand_eh_region_start (); | |
1239 | } | |
1240 | ||
1241 | /* Generate RTL for the start of a group of catch clauses. | |
1242 | ||
1243 | It is responsible for starting a new instruction sequence for the | |
1244 | instructions in the catch block, and expanding the handlers for the | |
1245 | internally-generated exception regions nested within the try block | |
abeeec2a | 1246 | corresponding to this catch block. */ |
4956d07c MS |
1247 | |
1248 | void | |
1249 | expand_start_all_catch () | |
1250 | { | |
1251 | struct eh_entry *entry; | |
1252 | tree label; | |
1253 | ||
1254 | if (! doing_eh (1)) | |
1255 | return; | |
1256 | ||
abeeec2a | 1257 | /* End the try block. */ |
12670d88 RK |
1258 | expand_eh_region_end (integer_zero_node); |
1259 | ||
4956d07c MS |
1260 | emit_line_note (input_filename, lineno); |
1261 | label = build_decl (LABEL_DECL, NULL_TREE, NULL_TREE); | |
1262 | ||
12670d88 RK |
1263 | /* The label for the exception handling block that we will save. |
1264 | This is Lresume in the documention. */ | |
4956d07c MS |
1265 | expand_label (label); |
1266 | ||
27a36778 MS |
1267 | if (exceptions_via_longjmp == 0) |
1268 | { | |
1269 | /* Put in something that takes up space, as otherwise the end | |
1270 | address for the EH region could have the exact same address as | |
1271 | the outer region, causing us to miss the fact that resuming | |
1272 | exception handling with this PC value would be inside the outer | |
1273 | region. */ | |
1274 | emit_insn (gen_nop ()); | |
1275 | } | |
4956d07c | 1276 | |
12670d88 | 1277 | /* Push the label that points to where normal flow is resumed onto |
abeeec2a | 1278 | the top of the label stack. */ |
4956d07c MS |
1279 | push_label_entry (&caught_return_label_stack, NULL_RTX, label); |
1280 | ||
1281 | /* Start a new sequence for all the catch blocks. We will add this | |
12670d88 | 1282 | to the global sequence catch_clauses when we have completed all |
4956d07c MS |
1283 | the handlers in this handler-seq. */ |
1284 | start_sequence (); | |
1285 | ||
1286 | while (1) | |
1287 | { | |
1288 | rtx prev; | |
1289 | ||
1290 | entry = dequeue_eh_entry (&ehqueue); | |
12670d88 RK |
1291 | /* Emit the label for the exception handler for this region, and |
1292 | expand the code for the handler. | |
1293 | ||
1294 | Note that a catch region is handled as a side-effect here; | |
1295 | for a try block, entry->finalization will contain | |
1296 | integer_zero_node, so no code will be generated in the | |
1297 | expand_expr call below. But, the label for the handler will | |
1298 | still be emitted, so any code emitted after this point will | |
abeeec2a | 1299 | end up being the handler. */ |
4956d07c | 1300 | emit_label (entry->exception_handler_label); |
4956d07c | 1301 | |
f51430ed MS |
1302 | #ifdef HAVE_exception_receiver |
1303 | if (! exceptions_via_longjmp) | |
1304 | if (HAVE_exception_receiver) | |
1305 | emit_insn (gen_exception_receiver ()); | |
1306 | #endif | |
1307 | ||
05f5b2cd MS |
1308 | #ifdef HAVE_nonlocal_goto_receiver |
1309 | if (! exceptions_via_longjmp) | |
1310 | if (HAVE_nonlocal_goto_receiver) | |
1311 | emit_insn (gen_nonlocal_goto_receiver ()); | |
1312 | #endif | |
1313 | ||
12670d88 | 1314 | /* When we get down to the matching entry for this try block, stop. */ |
4956d07c | 1315 | if (entry->finalization == integer_zero_node) |
12670d88 | 1316 | { |
abeeec2a | 1317 | /* Don't forget to free this entry. */ |
12670d88 RK |
1318 | free (entry); |
1319 | break; | |
1320 | } | |
4956d07c | 1321 | |
27a36778 MS |
1322 | /* And now generate the insns for the handler. */ |
1323 | expand_expr (entry->finalization, const0_rtx, VOIDmode, 0); | |
1324 | ||
4956d07c | 1325 | prev = get_last_insn (); |
12670d88 | 1326 | if (prev == NULL || GET_CODE (prev) != BARRIER) |
4956d07c | 1327 | { |
27a36778 MS |
1328 | if (exceptions_via_longjmp) |
1329 | emit_throw (); | |
1330 | else | |
1331 | { | |
1332 | /* Code to throw out to outer context when we fall off end | |
1333 | of the handler. We can't do this here for catch blocks, | |
1334 | so it's done in expand_end_all_catch instead. | |
12670d88 | 1335 | |
27a36778 MS |
1336 | The below can be optimized away (and we could just fall |
1337 | into the next EH handler) if we are certain they are | |
1338 | nested. */ | |
12670d88 | 1339 | |
478b0752 | 1340 | expand_internal_throw (entry->outer_context); |
27a36778 | 1341 | } |
4956d07c | 1342 | } |
4956d07c MS |
1343 | free (entry); |
1344 | } | |
1345 | } | |
1346 | ||
12670d88 RK |
1347 | /* Finish up the catch block. At this point all the insns for the |
1348 | catch clauses have already been generated, so we only have to add | |
1349 | them to the catch_clauses list. We also want to make sure that if | |
1350 | we fall off the end of the catch clauses that we rethrow to the | |
abeeec2a | 1351 | outer EH region. */ |
4956d07c MS |
1352 | |
1353 | void | |
1354 | expand_end_all_catch () | |
1355 | { | |
1356 | rtx new_catch_clause; | |
1357 | ||
1358 | if (! doing_eh (1)) | |
1359 | return; | |
1360 | ||
27a36778 MS |
1361 | if (exceptions_via_longjmp) |
1362 | emit_throw (); | |
1363 | else | |
1364 | { | |
1365 | /* Code to throw out to outer context, if we fall off end of catch | |
1366 | handlers. This is rethrow (Lresume, same id, same obj) in the | |
1367 | documentation. We use Lresume because we know that it will throw | |
1368 | to the correct context. | |
12670d88 | 1369 | |
27a36778 MS |
1370 | In other words, if the catch handler doesn't exit or return, we |
1371 | do a "throw" (using the address of Lresume as the point being | |
1372 | thrown from) so that the outer EH region can then try to process | |
1373 | the exception. */ | |
12670d88 | 1374 | |
27a36778 MS |
1375 | expand_internal_throw (DECL_RTL (top_label_entry (&caught_return_label_stack))); |
1376 | } | |
4956d07c MS |
1377 | |
1378 | /* Now we have the complete catch sequence. */ | |
1379 | new_catch_clause = get_insns (); | |
1380 | end_sequence (); | |
1381 | ||
1382 | /* This level of catch blocks is done, so set up the successful | |
1383 | catch jump label for the next layer of catch blocks. */ | |
1384 | pop_label_entry (&caught_return_label_stack); | |
1385 | ||
1386 | /* Add the new sequence of catches to the main one for this function. */ | |
1387 | push_to_sequence (catch_clauses); | |
1388 | emit_insns (new_catch_clause); | |
1389 | catch_clauses = get_insns (); | |
1390 | end_sequence (); | |
1391 | ||
1392 | /* Here we fall through into the continuation code. */ | |
1393 | } | |
1394 | ||
12670d88 | 1395 | /* End all the pending exception regions on protect_list. The handlers |
27a36778 | 1396 | will be emitted when expand_leftover_cleanups is invoked. */ |
4956d07c MS |
1397 | |
1398 | void | |
1399 | end_protect_partials () | |
1400 | { | |
1401 | while (protect_list) | |
1402 | { | |
1403 | expand_eh_region_end (TREE_VALUE (protect_list)); | |
1404 | protect_list = TREE_CHAIN (protect_list); | |
1405 | } | |
1406 | } | |
27a36778 MS |
1407 | |
1408 | /* Arrange for __terminate to be called if there is an unhandled throw | |
1409 | from within E. */ | |
1410 | ||
1411 | tree | |
1412 | protect_with_terminate (e) | |
1413 | tree e; | |
1414 | { | |
1415 | /* We only need to do this when using setjmp/longjmp EH and the | |
1416 | language requires it, as otherwise we protect all of the handlers | |
1417 | at once, if we need to. */ | |
1418 | if (exceptions_via_longjmp && protect_cleanup_actions_with_terminate) | |
1419 | { | |
1420 | tree handler, result; | |
1421 | ||
1422 | /* All cleanups must be on the function_obstack. */ | |
1423 | push_obstacks_nochange (); | |
1424 | resume_temporary_allocation (); | |
1425 | ||
1426 | handler = make_node (RTL_EXPR); | |
1427 | TREE_TYPE (handler) = void_type_node; | |
1428 | RTL_EXPR_RTL (handler) = const0_rtx; | |
1429 | TREE_SIDE_EFFECTS (handler) = 1; | |
1430 | start_sequence_for_rtl_expr (handler); | |
1431 | ||
1432 | emit_library_call (terminate_libfunc, 0, VOIDmode, 0); | |
1433 | emit_barrier (); | |
1434 | ||
1435 | RTL_EXPR_SEQUENCE (handler) = get_insns (); | |
1436 | end_sequence (); | |
1437 | ||
1438 | result = build (TRY_CATCH_EXPR, TREE_TYPE (e), e, handler); | |
1439 | TREE_SIDE_EFFECTS (result) = TREE_SIDE_EFFECTS (e); | |
1440 | TREE_THIS_VOLATILE (result) = TREE_THIS_VOLATILE (e); | |
1441 | TREE_READONLY (result) = TREE_READONLY (e); | |
1442 | ||
1443 | pop_obstacks (); | |
1444 | ||
1445 | e = result; | |
1446 | } | |
1447 | ||
1448 | return e; | |
1449 | } | |
4956d07c MS |
1450 | \f |
1451 | /* The exception table that we build that is used for looking up and | |
12670d88 RK |
1452 | dispatching exceptions, the current number of entries, and its |
1453 | maximum size before we have to extend it. | |
1454 | ||
1455 | The number in eh_table is the code label number of the exception | |
27a36778 MS |
1456 | handler for the region. This is added by add_eh_table_entry and |
1457 | used by output_exception_table_entry. */ | |
12670d88 | 1458 | |
4956d07c MS |
1459 | static int *eh_table; |
1460 | static int eh_table_size; | |
1461 | static int eh_table_max_size; | |
1462 | ||
1463 | /* Note the need for an exception table entry for region N. If we | |
12670d88 RK |
1464 | don't need to output an explicit exception table, avoid all of the |
1465 | extra work. | |
1466 | ||
1467 | Called from final_scan_insn when a NOTE_INSN_EH_REGION_BEG is seen. | |
1468 | N is the NOTE_BLOCK_NUMBER of the note, which comes from the code | |
abeeec2a | 1469 | label number of the exception handler for the region. */ |
4956d07c MS |
1470 | |
1471 | void | |
1472 | add_eh_table_entry (n) | |
1473 | int n; | |
1474 | { | |
1475 | #ifndef OMIT_EH_TABLE | |
1476 | if (eh_table_size >= eh_table_max_size) | |
1477 | { | |
1478 | if (eh_table) | |
1479 | { | |
1480 | eh_table_max_size += eh_table_max_size>>1; | |
1481 | ||
1482 | if (eh_table_max_size < 0) | |
1483 | abort (); | |
1484 | ||
ca55abae JM |
1485 | eh_table = (int *) xrealloc (eh_table, |
1486 | eh_table_max_size * sizeof (int)); | |
4956d07c MS |
1487 | } |
1488 | else | |
1489 | { | |
1490 | eh_table_max_size = 252; | |
1491 | eh_table = (int *) xmalloc (eh_table_max_size * sizeof (int)); | |
1492 | } | |
1493 | } | |
1494 | eh_table[eh_table_size++] = n; | |
1495 | #endif | |
1496 | } | |
1497 | ||
12670d88 RK |
1498 | /* Return a non-zero value if we need to output an exception table. |
1499 | ||
1500 | On some platforms, we don't have to output a table explicitly. | |
1501 | This routine doesn't mean we don't have one. */ | |
4956d07c MS |
1502 | |
1503 | int | |
1504 | exception_table_p () | |
1505 | { | |
1506 | if (eh_table) | |
1507 | return 1; | |
1508 | ||
1509 | return 0; | |
1510 | } | |
1511 | ||
ca55abae JM |
1512 | /* 1 if we need a static constructor to register EH table info. */ |
1513 | ||
1514 | int | |
1515 | register_exception_table_p () | |
1516 | { | |
1517 | #if defined (DWARF2_UNWIND_INFO) | |
1518 | return 0; | |
1519 | #endif | |
1520 | ||
1521 | return exception_table_p (); | |
1522 | } | |
1523 | ||
12670d88 RK |
1524 | /* Output the entry of the exception table corresponding to to the |
1525 | exception region numbered N to file FILE. | |
1526 | ||
1527 | N is the code label number corresponding to the handler of the | |
abeeec2a | 1528 | region. */ |
4956d07c MS |
1529 | |
1530 | static void | |
1531 | output_exception_table_entry (file, n) | |
1532 | FILE *file; | |
1533 | int n; | |
1534 | { | |
1535 | char buf[256]; | |
1536 | rtx sym; | |
1537 | ||
1538 | ASM_GENERATE_INTERNAL_LABEL (buf, "LEHB", n); | |
1539 | sym = gen_rtx (SYMBOL_REF, Pmode, buf); | |
1540 | assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1); | |
1541 | ||
1542 | ASM_GENERATE_INTERNAL_LABEL (buf, "LEHE", n); | |
1543 | sym = gen_rtx (SYMBOL_REF, Pmode, buf); | |
1544 | assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1); | |
1545 | ||
1546 | ASM_GENERATE_INTERNAL_LABEL (buf, "L", n); | |
1547 | sym = gen_rtx (SYMBOL_REF, Pmode, buf); | |
1548 | assemble_integer (sym, POINTER_SIZE / BITS_PER_UNIT, 1); | |
1549 | ||
1550 | putc ('\n', file); /* blank line */ | |
1551 | } | |
1552 | ||
abeeec2a | 1553 | /* Output the exception table if we have and need one. */ |
4956d07c MS |
1554 | |
1555 | void | |
1556 | output_exception_table () | |
1557 | { | |
1558 | int i; | |
1559 | extern FILE *asm_out_file; | |
1560 | ||
ca55abae | 1561 | if (! doing_eh (0) || ! eh_table) |
4956d07c MS |
1562 | return; |
1563 | ||
1564 | exception_section (); | |
1565 | ||
1566 | /* Beginning marker for table. */ | |
1567 | assemble_align (GET_MODE_ALIGNMENT (ptr_mode)); | |
1568 | assemble_label ("__EXCEPTION_TABLE__"); | |
1569 | ||
4956d07c MS |
1570 | for (i = 0; i < eh_table_size; ++i) |
1571 | output_exception_table_entry (asm_out_file, eh_table[i]); | |
1572 | ||
1573 | free (eh_table); | |
1574 | ||
1575 | /* Ending marker for table. */ | |
1576 | assemble_label ("__EXCEPTION_END__"); | |
1577 | assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1); | |
1578 | assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1); | |
1579 | assemble_integer (constm1_rtx, POINTER_SIZE / BITS_PER_UNIT, 1); | |
1580 | putc ('\n', asm_out_file); /* blank line */ | |
1581 | } | |
1582 | ||
1583 | /* Generate code to initialize the exception table at program startup | |
1584 | time. */ | |
1585 | ||
1586 | void | |
1587 | register_exception_table () | |
1588 | { | |
1589 | emit_library_call (gen_rtx (SYMBOL_REF, Pmode, "__register_exceptions"), 0, | |
1590 | VOIDmode, 1, | |
1591 | gen_rtx (SYMBOL_REF, Pmode, "__EXCEPTION_TABLE__"), | |
1592 | Pmode); | |
1593 | } | |
1594 | \f | |
12670d88 | 1595 | /* Emit the RTL for the start of the per-function unwinder for the |
27a36778 | 1596 | current function. See emit_unwinder for further information. |
12670d88 RK |
1597 | |
1598 | DOESNT_NEED_UNWINDER is a target-specific macro that determines if | |
1599 | the current function actually needs a per-function unwinder or not. | |
abeeec2a | 1600 | By default, all functions need one. */ |
4956d07c MS |
1601 | |
1602 | void | |
1603 | start_eh_unwinder () | |
1604 | { | |
1605 | #ifdef DOESNT_NEED_UNWINDER | |
1606 | if (DOESNT_NEED_UNWINDER) | |
1607 | return; | |
1608 | #endif | |
1609 | ||
27a36778 MS |
1610 | /* If we are using the setjmp/longjmp implementation, we don't need a |
1611 | per function unwinder. */ | |
1612 | ||
1613 | if (exceptions_via_longjmp) | |
1614 | return; | |
1615 | ||
ca55abae JM |
1616 | #ifdef DWARF2_UNWIND_INFO |
1617 | return; | |
1618 | #endif | |
1619 | ||
4956d07c MS |
1620 | expand_eh_region_start (); |
1621 | } | |
1622 | ||
12670d88 | 1623 | /* Emit insns for the end of the per-function unwinder for the |
4956d07c MS |
1624 | current function. */ |
1625 | ||
1626 | void | |
1627 | end_eh_unwinder () | |
1628 | { | |
1629 | tree expr; | |
1630 | rtx return_val_rtx, ret_val, label, end, insns; | |
1631 | ||
1632 | if (! doing_eh (0)) | |
1633 | return; | |
1634 | ||
1635 | #ifdef DOESNT_NEED_UNWINDER | |
1636 | if (DOESNT_NEED_UNWINDER) | |
1637 | return; | |
1638 | #endif | |
1639 | ||
27a36778 MS |
1640 | /* If we are using the setjmp/longjmp implementation, we don't need a |
1641 | per function unwinder. */ | |
1642 | ||
1643 | if (exceptions_via_longjmp) | |
1644 | return; | |
1645 | ||
ca55abae JM |
1646 | #ifdef DWARF2_UNWIND_INFO |
1647 | return; | |
1648 | #else /* DWARF2_UNWIND_INFO */ | |
1649 | ||
843e8335 MS |
1650 | assemble_external (eh_saved_pc); |
1651 | ||
4956d07c MS |
1652 | expr = make_node (RTL_EXPR); |
1653 | TREE_TYPE (expr) = void_type_node; | |
1654 | RTL_EXPR_RTL (expr) = const0_rtx; | |
1655 | TREE_SIDE_EFFECTS (expr) = 1; | |
1656 | start_sequence_for_rtl_expr (expr); | |
1657 | ||
12670d88 | 1658 | /* ret_val will contain the address of the code where the call |
abeeec2a | 1659 | to the current function occurred. */ |
4956d07c MS |
1660 | ret_val = expand_builtin_return_addr (BUILT_IN_RETURN_ADDRESS, |
1661 | 0, hard_frame_pointer_rtx); | |
1662 | return_val_rtx = copy_to_reg (ret_val); | |
1663 | ||
12670d88 | 1664 | /* Get the address we need to use to determine what exception |
abeeec2a | 1665 | handler should be invoked, and store it in __eh_pc. */ |
4956d07c | 1666 | return_val_rtx = eh_outer_context (return_val_rtx); |
6020d360 JM |
1667 | return_val_rtx = expand_binop (Pmode, sub_optab, return_val_rtx, GEN_INT (1), |
1668 | NULL_RTX, 0, OPTAB_LIB_WIDEN); | |
4956d07c MS |
1669 | emit_move_insn (eh_saved_pc_rtx, return_val_rtx); |
1670 | ||
12670d88 | 1671 | /* Either set things up so we do a return directly to __throw, or |
abeeec2a | 1672 | we return here instead. */ |
4956d07c MS |
1673 | #ifdef JUMP_TO_THROW |
1674 | emit_move_insn (ret_val, throw_libfunc); | |
1675 | #else | |
1676 | label = gen_label_rtx (); | |
1677 | emit_move_insn (ret_val, gen_rtx (LABEL_REF, Pmode, label)); | |
1678 | #endif | |
1679 | ||
1680 | #ifdef RETURN_ADDR_OFFSET | |
1681 | return_val_rtx = plus_constant (ret_val, -RETURN_ADDR_OFFSET); | |
1682 | if (return_val_rtx != ret_val) | |
1683 | emit_move_insn (ret_val, return_val_rtx); | |
1684 | #endif | |
1685 | ||
1686 | end = gen_label_rtx (); | |
1687 | emit_jump (end); | |
1688 | ||
1689 | RTL_EXPR_SEQUENCE (expr) = get_insns (); | |
1690 | end_sequence (); | |
27a36778 | 1691 | |
4956d07c MS |
1692 | expand_eh_region_end (expr); |
1693 | ||
1694 | emit_jump (end); | |
1695 | ||
1696 | #ifndef JUMP_TO_THROW | |
1697 | emit_label (label); | |
1698 | emit_throw (); | |
1699 | #endif | |
1700 | ||
1701 | expand_leftover_cleanups (); | |
1702 | ||
1703 | emit_label (end); | |
16c81040 MS |
1704 | |
1705 | #ifdef HAVE_return | |
1706 | if (HAVE_return) | |
1707 | { | |
1708 | emit_jump_insn (gen_return ()); | |
1709 | emit_barrier (); | |
1710 | } | |
1711 | #endif | |
ca55abae | 1712 | #endif /* DWARF2_UNWIND_INFO */ |
4956d07c MS |
1713 | } |
1714 | ||
12670d88 RK |
1715 | /* If necessary, emit insns for the per function unwinder for the |
1716 | current function. Called after all the code that needs unwind | |
1717 | protection is output. | |
1718 | ||
1719 | The unwinder takes care of catching any exceptions that have not | |
1720 | been previously caught within the function, unwinding the stack to | |
1721 | the next frame, and rethrowing using the address of the current | |
1722 | function's caller as the context of the throw. | |
1723 | ||
1724 | On some platforms __throw can do this by itself (or with the help | |
1725 | of __unwind_function) so the per-function unwinder is | |
1726 | unnecessary. | |
1727 | ||
1728 | We cannot place the unwinder into the function until after we know | |
1729 | we are done inlining, as we don't want to have more than one | |
1730 | unwinder per non-inlined function. */ | |
4956d07c MS |
1731 | |
1732 | void | |
1733 | emit_unwinder () | |
1734 | { | |
12670d88 | 1735 | rtx insns, insn; |
4956d07c MS |
1736 | |
1737 | start_sequence (); | |
1738 | start_eh_unwinder (); | |
1739 | insns = get_insns (); | |
1740 | end_sequence (); | |
1741 | ||
12670d88 RK |
1742 | /* We place the start of the exception region associated with the |
1743 | per function unwinder at the top of the function. */ | |
4956d07c MS |
1744 | if (insns) |
1745 | emit_insns_after (insns, get_insns ()); | |
1746 | ||
12670d88 | 1747 | start_sequence (); |
4956d07c | 1748 | end_eh_unwinder (); |
12670d88 RK |
1749 | insns = get_insns (); |
1750 | end_sequence (); | |
1751 | ||
1752 | /* And we place the end of the exception region before the USE and | |
1753 | CLOBBER insns that may come at the end of the function. */ | |
1754 | if (insns == 0) | |
1755 | return; | |
1756 | ||
1757 | insn = get_last_insn (); | |
1758 | while (GET_CODE (insn) == NOTE | |
1759 | || (GET_CODE (insn) == INSN | |
1760 | && (GET_CODE (PATTERN (insn)) == USE | |
1761 | || GET_CODE (PATTERN (insn)) == CLOBBER))) | |
1762 | insn = PREV_INSN (insn); | |
1763 | ||
1764 | if (GET_CODE (insn) == CODE_LABEL | |
1765 | && GET_CODE (PREV_INSN (insn)) == BARRIER) | |
1766 | { | |
1767 | insn = PREV_INSN (insn); | |
1768 | } | |
1769 | else | |
1770 | { | |
1771 | rtx label = gen_label_rtx (); | |
1772 | emit_label_after (label, insn); | |
1773 | insn = emit_jump_insn_after (gen_jump (label), insn); | |
1774 | insn = emit_barrier_after (insn); | |
1775 | } | |
1776 | ||
1777 | emit_insns_after (insns, insn); | |
4956d07c MS |
1778 | } |
1779 | ||
12670d88 RK |
1780 | /* Scan the current insns and build a list of handler labels. The |
1781 | resulting list is placed in the global variable exception_handler_labels. | |
1782 | ||
1783 | It is called after the last exception handling region is added to | |
1784 | the current function (when the rtl is almost all built for the | |
1785 | current function) and before the jump optimization pass. */ | |
4956d07c MS |
1786 | |
1787 | void | |
1788 | find_exception_handler_labels () | |
1789 | { | |
1790 | rtx insn; | |
1791 | int max_labelno = max_label_num (); | |
1792 | int min_labelno = get_first_label_num (); | |
1793 | rtx *labels; | |
1794 | ||
1795 | exception_handler_labels = NULL_RTX; | |
1796 | ||
1797 | /* If we aren't doing exception handling, there isn't much to check. */ | |
1798 | if (! doing_eh (0)) | |
1799 | return; | |
1800 | ||
12670d88 | 1801 | /* Generate a handy reference to each label. */ |
4956d07c | 1802 | |
1d77fa53 BK |
1803 | /* We call xmalloc here instead of alloca; we did the latter in the past, |
1804 | but found that it can sometimes end up being asked to allocate space | |
1805 | for more than 1 million labels. */ | |
1806 | labels = (rtx *) xmalloc ((max_labelno - min_labelno) * sizeof (rtx)); | |
abeeec2a | 1807 | bzero ((char *) labels, (max_labelno - min_labelno) * sizeof (rtx)); |
12670d88 | 1808 | |
abeeec2a | 1809 | /* Arrange for labels to be indexed directly by CODE_LABEL_NUMBER. */ |
4956d07c MS |
1810 | labels -= min_labelno; |
1811 | ||
1812 | for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) | |
1813 | { | |
1814 | if (GET_CODE (insn) == CODE_LABEL) | |
1815 | if (CODE_LABEL_NUMBER (insn) >= min_labelno | |
1816 | && CODE_LABEL_NUMBER (insn) < max_labelno) | |
1817 | labels[CODE_LABEL_NUMBER (insn)] = insn; | |
1818 | } | |
1819 | ||
12670d88 RK |
1820 | /* For each start of a region, add its label to the list. */ |
1821 | ||
4956d07c MS |
1822 | for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) |
1823 | { | |
1824 | if (GET_CODE (insn) == NOTE | |
1825 | && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG) | |
1826 | { | |
1827 | rtx label = NULL_RTX; | |
1828 | ||
1829 | if (NOTE_BLOCK_NUMBER (insn) >= min_labelno | |
1830 | && NOTE_BLOCK_NUMBER (insn) < max_labelno) | |
1831 | { | |
1832 | label = labels[NOTE_BLOCK_NUMBER (insn)]; | |
1833 | ||
1834 | if (label) | |
1835 | exception_handler_labels | |
1836 | = gen_rtx (EXPR_LIST, VOIDmode, | |
1837 | label, exception_handler_labels); | |
1838 | else | |
1839 | warning ("didn't find handler for EH region %d", | |
1840 | NOTE_BLOCK_NUMBER (insn)); | |
1841 | } | |
1842 | else | |
1843 | warning ("mismatched EH region %d", NOTE_BLOCK_NUMBER (insn)); | |
1844 | } | |
1845 | } | |
988cea7d | 1846 | |
3f34faec | 1847 | free (labels + min_labelno); |
4956d07c MS |
1848 | } |
1849 | ||
12670d88 RK |
1850 | /* Perform sanity checking on the exception_handler_labels list. |
1851 | ||
1852 | Can be called after find_exception_handler_labels is called to | |
1853 | build the list of exception handlers for the current function and | |
1854 | before we finish processing the current function. */ | |
4956d07c MS |
1855 | |
1856 | void | |
1857 | check_exception_handler_labels () | |
1858 | { | |
1859 | rtx insn, handler; | |
1860 | ||
1861 | /* If we aren't doing exception handling, there isn't much to check. */ | |
1862 | if (! doing_eh (0)) | |
1863 | return; | |
1864 | ||
12670d88 RK |
1865 | /* Ensure that the CODE_LABEL_NUMBER for the CODE_LABEL entry point |
1866 | in each handler corresponds to the CODE_LABEL_NUMBER of the | |
abeeec2a | 1867 | handler. */ |
12670d88 | 1868 | |
4956d07c MS |
1869 | for (handler = exception_handler_labels; |
1870 | handler; | |
1871 | handler = XEXP (handler, 1)) | |
1872 | { | |
1873 | for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) | |
1874 | { | |
1875 | if (GET_CODE (insn) == CODE_LABEL) | |
1876 | { | |
1877 | if (CODE_LABEL_NUMBER (insn) | |
1878 | == CODE_LABEL_NUMBER (XEXP (handler, 0))) | |
1879 | { | |
1880 | if (insn != XEXP (handler, 0)) | |
1881 | warning ("mismatched handler %d", | |
1882 | CODE_LABEL_NUMBER (insn)); | |
1883 | break; | |
1884 | } | |
1885 | } | |
1886 | } | |
1887 | if (insn == NULL_RTX) | |
1888 | warning ("handler not found %d", | |
1889 | CODE_LABEL_NUMBER (XEXP (handler, 0))); | |
1890 | } | |
1891 | ||
12670d88 RK |
1892 | /* Now go through and make sure that for each region there is a |
1893 | corresponding label. */ | |
4956d07c MS |
1894 | for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) |
1895 | { | |
1896 | if (GET_CODE (insn) == NOTE | |
27a36778 MS |
1897 | && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG |
1898 | || NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)) | |
4956d07c MS |
1899 | { |
1900 | for (handler = exception_handler_labels; | |
1901 | handler; | |
1902 | handler = XEXP (handler, 1)) | |
1903 | { | |
1904 | if (CODE_LABEL_NUMBER (XEXP (handler, 0)) | |
1905 | == NOTE_BLOCK_NUMBER (insn)) | |
1906 | break; | |
1907 | } | |
1908 | if (handler == NULL_RTX) | |
1909 | warning ("region exists, no handler %d", | |
1910 | NOTE_BLOCK_NUMBER (insn)); | |
1911 | } | |
1912 | } | |
1913 | } | |
1914 | \f | |
1915 | /* This group of functions initializes the exception handling data | |
1916 | structures at the start of the compilation, initializes the data | |
12670d88 | 1917 | structures at the start of a function, and saves and restores the |
4956d07c MS |
1918 | exception handling data structures for the start/end of a nested |
1919 | function. */ | |
1920 | ||
1921 | /* Toplevel initialization for EH things. */ | |
1922 | ||
1923 | void | |
1924 | init_eh () | |
1925 | { | |
12670d88 | 1926 | /* Generate rtl to reference the variable in which the PC of the |
abeeec2a | 1927 | current context is saved. */ |
843e8335 MS |
1928 | tree type = build_pointer_type (make_node (VOID_TYPE)); |
1929 | ||
1930 | eh_saved_pc = build_decl (VAR_DECL, get_identifier ("__eh_pc"), type); | |
1931 | DECL_EXTERNAL (eh_saved_pc) = 1; | |
1932 | TREE_PUBLIC (eh_saved_pc) = 1; | |
1933 | make_decl_rtl (eh_saved_pc, NULL_PTR, 1); | |
1934 | eh_saved_pc_rtx = DECL_RTL (eh_saved_pc); | |
4956d07c MS |
1935 | } |
1936 | ||
abeeec2a | 1937 | /* Initialize the per-function EH information. */ |
4956d07c MS |
1938 | |
1939 | void | |
1940 | init_eh_for_function () | |
1941 | { | |
1942 | ehstack.top = 0; | |
1943 | ehqueue.head = ehqueue.tail = 0; | |
1944 | catch_clauses = NULL_RTX; | |
1945 | false_label_stack = 0; | |
1946 | caught_return_label_stack = 0; | |
1947 | protect_list = NULL_TREE; | |
27a36778 MS |
1948 | current_function_dhc = NULL_RTX; |
1949 | current_function_dcc = NULL_RTX; | |
4956d07c MS |
1950 | } |
1951 | ||
12670d88 RK |
1952 | /* Save some of the per-function EH info into the save area denoted by |
1953 | P. | |
1954 | ||
27a36778 | 1955 | This is currently called from save_stmt_status. */ |
4956d07c MS |
1956 | |
1957 | void | |
1958 | save_eh_status (p) | |
1959 | struct function *p; | |
1960 | { | |
12670d88 RK |
1961 | assert (p != NULL); |
1962 | ||
4956d07c MS |
1963 | p->ehstack = ehstack; |
1964 | p->ehqueue = ehqueue; | |
1965 | p->catch_clauses = catch_clauses; | |
1966 | p->false_label_stack = false_label_stack; | |
1967 | p->caught_return_label_stack = caught_return_label_stack; | |
1968 | p->protect_list = protect_list; | |
27a36778 MS |
1969 | p->dhc = current_function_dhc; |
1970 | p->dcc = current_function_dcc; | |
4956d07c MS |
1971 | |
1972 | init_eh (); | |
1973 | } | |
1974 | ||
12670d88 RK |
1975 | /* Restore the per-function EH info saved into the area denoted by P. |
1976 | ||
abeeec2a | 1977 | This is currently called from restore_stmt_status. */ |
4956d07c MS |
1978 | |
1979 | void | |
1980 | restore_eh_status (p) | |
1981 | struct function *p; | |
1982 | { | |
12670d88 RK |
1983 | assert (p != NULL); |
1984 | ||
4956d07c MS |
1985 | protect_list = p->protect_list; |
1986 | caught_return_label_stack = p->caught_return_label_stack; | |
1987 | false_label_stack = p->false_label_stack; | |
1988 | catch_clauses = p->catch_clauses; | |
1989 | ehqueue = p->ehqueue; | |
1990 | ehstack = p->ehstack; | |
27a36778 MS |
1991 | current_function_dhc = p->dhc; |
1992 | current_function_dcc = p->dcc; | |
4956d07c MS |
1993 | } |
1994 | \f | |
1995 | /* This section is for the exception handling specific optimization | |
1996 | pass. First are the internal routines, and then the main | |
1997 | optimization pass. */ | |
1998 | ||
1999 | /* Determine if the given INSN can throw an exception. */ | |
2000 | ||
2001 | static int | |
2002 | can_throw (insn) | |
2003 | rtx insn; | |
2004 | { | |
abeeec2a | 2005 | /* Calls can always potentially throw exceptions. */ |
4956d07c MS |
2006 | if (GET_CODE (insn) == CALL_INSN) |
2007 | return 1; | |
2008 | ||
27a36778 MS |
2009 | if (asynchronous_exceptions) |
2010 | { | |
2011 | /* If we wanted asynchronous exceptions, then everything but NOTEs | |
2012 | and CODE_LABELs could throw. */ | |
2013 | if (GET_CODE (insn) != NOTE && GET_CODE (insn) != CODE_LABEL) | |
2014 | return 1; | |
2015 | } | |
4956d07c MS |
2016 | |
2017 | return 0; | |
2018 | } | |
2019 | ||
12670d88 RK |
2020 | /* Scan a exception region looking for the matching end and then |
2021 | remove it if possible. INSN is the start of the region, N is the | |
2022 | region number, and DELETE_OUTER is to note if anything in this | |
2023 | region can throw. | |
2024 | ||
2025 | Regions are removed if they cannot possibly catch an exception. | |
27a36778 | 2026 | This is determined by invoking can_throw on each insn within the |
12670d88 RK |
2027 | region; if can_throw returns true for any of the instructions, the |
2028 | region can catch an exception, since there is an insn within the | |
2029 | region that is capable of throwing an exception. | |
2030 | ||
2031 | Returns the NOTE_INSN_EH_REGION_END corresponding to this region, or | |
27a36778 | 2032 | calls abort if it can't find one. |
12670d88 RK |
2033 | |
2034 | Can abort if INSN is not a NOTE_INSN_EH_REGION_BEGIN, or if N doesn't | |
abeeec2a | 2035 | correspond to the region number, or if DELETE_OUTER is NULL. */ |
4956d07c MS |
2036 | |
2037 | static rtx | |
2038 | scan_region (insn, n, delete_outer) | |
2039 | rtx insn; | |
2040 | int n; | |
2041 | int *delete_outer; | |
2042 | { | |
2043 | rtx start = insn; | |
2044 | ||
2045 | /* Assume we can delete the region. */ | |
2046 | int delete = 1; | |
2047 | ||
12670d88 RK |
2048 | assert (insn != NULL_RTX |
2049 | && GET_CODE (insn) == NOTE | |
2050 | && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG | |
2051 | && NOTE_BLOCK_NUMBER (insn) == n | |
2052 | && delete_outer != NULL); | |
2053 | ||
4956d07c MS |
2054 | insn = NEXT_INSN (insn); |
2055 | ||
2056 | /* Look for the matching end. */ | |
2057 | while (! (GET_CODE (insn) == NOTE | |
2058 | && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)) | |
2059 | { | |
2060 | /* If anything can throw, we can't remove the region. */ | |
2061 | if (delete && can_throw (insn)) | |
2062 | { | |
2063 | delete = 0; | |
2064 | } | |
2065 | ||
2066 | /* Watch out for and handle nested regions. */ | |
2067 | if (GET_CODE (insn) == NOTE | |
2068 | && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG) | |
2069 | { | |
2070 | insn = scan_region (insn, NOTE_BLOCK_NUMBER (insn), &delete); | |
2071 | } | |
2072 | ||
2073 | insn = NEXT_INSN (insn); | |
2074 | } | |
2075 | ||
2076 | /* The _BEG/_END NOTEs must match and nest. */ | |
2077 | if (NOTE_BLOCK_NUMBER (insn) != n) | |
2078 | abort (); | |
2079 | ||
12670d88 | 2080 | /* If anything in this exception region can throw, we can throw. */ |
4956d07c MS |
2081 | if (! delete) |
2082 | *delete_outer = 0; | |
2083 | else | |
2084 | { | |
2085 | /* Delete the start and end of the region. */ | |
2086 | delete_insn (start); | |
2087 | delete_insn (insn); | |
2088 | ||
2089 | /* Only do this part if we have built the exception handler | |
2090 | labels. */ | |
2091 | if (exception_handler_labels) | |
2092 | { | |
2093 | rtx x, *prev = &exception_handler_labels; | |
2094 | ||
2095 | /* Find it in the list of handlers. */ | |
2096 | for (x = exception_handler_labels; x; x = XEXP (x, 1)) | |
2097 | { | |
2098 | rtx label = XEXP (x, 0); | |
2099 | if (CODE_LABEL_NUMBER (label) == n) | |
2100 | { | |
2101 | /* If we are the last reference to the handler, | |
2102 | delete it. */ | |
2103 | if (--LABEL_NUSES (label) == 0) | |
2104 | delete_insn (label); | |
2105 | ||
2106 | if (optimize) | |
2107 | { | |
2108 | /* Remove it from the list of exception handler | |
2109 | labels, if we are optimizing. If we are not, then | |
2110 | leave it in the list, as we are not really going to | |
2111 | remove the region. */ | |
2112 | *prev = XEXP (x, 1); | |
2113 | XEXP (x, 1) = 0; | |
2114 | XEXP (x, 0) = 0; | |
2115 | } | |
2116 | ||
2117 | break; | |
2118 | } | |
2119 | prev = &XEXP (x, 1); | |
2120 | } | |
2121 | } | |
2122 | } | |
2123 | return insn; | |
2124 | } | |
2125 | ||
2126 | /* Perform various interesting optimizations for exception handling | |
2127 | code. | |
2128 | ||
12670d88 RK |
2129 | We look for empty exception regions and make them go (away). The |
2130 | jump optimization code will remove the handler if nothing else uses | |
abeeec2a | 2131 | it. */ |
4956d07c MS |
2132 | |
2133 | void | |
2134 | exception_optimize () | |
2135 | { | |
2136 | rtx insn, regions = NULL_RTX; | |
2137 | int n; | |
2138 | ||
27a36778 MS |
2139 | /* The below doesn't apply to setjmp/longjmp EH. */ |
2140 | if (exceptions_via_longjmp) | |
2141 | return; | |
2142 | ||
12670d88 | 2143 | /* Remove empty regions. */ |
4956d07c MS |
2144 | for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) |
2145 | { | |
2146 | if (GET_CODE (insn) == NOTE | |
2147 | && NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG) | |
2148 | { | |
27a36778 | 2149 | /* Since scan_region will return the NOTE_INSN_EH_REGION_END |
12670d88 RK |
2150 | insn, we will indirectly skip through all the insns |
2151 | inbetween. We are also guaranteed that the value of insn | |
27a36778 | 2152 | returned will be valid, as otherwise scan_region won't |
abeeec2a | 2153 | return. */ |
4956d07c MS |
2154 | insn = scan_region (insn, NOTE_BLOCK_NUMBER (insn), &n); |
2155 | } | |
2156 | } | |
2157 | } | |
ca55abae JM |
2158 | \f |
2159 | /* Various hooks for the DWARF 2 __throw routine. */ | |
2160 | ||
2161 | /* Do any necessary initialization to access arbitrary stack frames. | |
2162 | On the SPARC, this means flushing the register windows. */ | |
2163 | ||
2164 | void | |
2165 | expand_builtin_unwind_init () | |
2166 | { | |
2167 | /* Set this so all the registers get saved in our frame; we need to be | |
2168 | able to copy the saved values for any registers from frames we unwind. */ | |
2169 | current_function_has_nonlocal_label = 1; | |
2170 | ||
2171 | #ifdef SETUP_FRAME_ADDRESSES | |
2172 | SETUP_FRAME_ADDRESSES (); | |
2173 | #endif | |
2174 | } | |
2175 | ||
2176 | /* Given a value extracted from the return address register or stack slot, | |
2177 | return the actual address encoded in that value. */ | |
2178 | ||
2179 | rtx | |
2180 | expand_builtin_extract_return_addr (addr_tree) | |
2181 | tree addr_tree; | |
2182 | { | |
2183 | rtx addr = expand_expr (addr_tree, NULL_RTX, Pmode, 0); | |
2184 | return eh_outer_context (addr); | |
2185 | } | |
2186 | ||
2187 | /* Given an actual address in addr_tree, do any necessary encoding | |
2188 | and return the value to be stored in the return address register or | |
2189 | stack slot so the epilogue will return to that address. */ | |
2190 | ||
2191 | rtx | |
2192 | expand_builtin_frob_return_addr (addr_tree) | |
2193 | tree addr_tree; | |
2194 | { | |
2195 | rtx addr = expand_expr (addr_tree, NULL_RTX, Pmode, 0); | |
2196 | #ifdef RETURN_ADDR_OFFSET | |
2197 | addr = plus_constant (addr, -RETURN_ADDR_OFFSET); | |
2198 | #endif | |
2199 | return addr; | |
2200 | } | |
2201 | ||
2202 | /* Given an actual address in addr_tree, set the return address register up | |
2203 | so the epilogue will return to that address. If the return address is | |
2204 | not in a register, do nothing. */ | |
2205 | ||
2206 | void | |
2207 | expand_builtin_set_return_addr_reg (addr_tree) | |
2208 | tree addr_tree; | |
2209 | { | |
4f870c04 | 2210 | rtx tmp; |
ca55abae JM |
2211 | rtx ra = expand_builtin_return_addr (BUILT_IN_RETURN_ADDRESS, |
2212 | 0, hard_frame_pointer_rtx); | |
2213 | ||
2214 | if (GET_CODE (ra) != REG || REGNO (ra) >= FIRST_PSEUDO_REGISTER) | |
2215 | return; | |
2216 | ||
4f870c04 JM |
2217 | tmp = force_operand (expand_builtin_frob_return_addr (addr_tree), ra); |
2218 | if (tmp != ra) | |
2219 | emit_move_insn (ra, tmp); | |
ca55abae JM |
2220 | } |
2221 | ||
2222 | /* Choose two registers for communication between the main body of | |
2223 | __throw and the stub for adjusting the stack pointer. The first register | |
2224 | is used to pass the address of the exception handler; the second register | |
2225 | is used to pass the stack pointer offset. | |
2226 | ||
2227 | For register 1 we use the return value register for a void *. | |
2228 | For register 2 we use the static chain register if it exists and is | |
2229 | different from register 1, otherwise some arbitrary call-clobbered | |
2230 | register. */ | |
2231 | ||
2232 | static void | |
2233 | eh_regs (r1, r2, outgoing) | |
2234 | rtx *r1, *r2; | |
2235 | int outgoing; | |
2236 | { | |
2237 | rtx reg1, reg2; | |
2238 | ||
2239 | #ifdef FUNCTION_OUTGOING_VALUE | |
2240 | if (outgoing) | |
2241 | reg1 = FUNCTION_OUTGOING_VALUE (build_pointer_type (void_type_node), | |
2242 | current_function_decl); | |
2243 | else | |
2244 | #endif | |
2245 | reg1 = FUNCTION_VALUE (build_pointer_type (void_type_node), | |
2246 | current_function_decl); | |
2247 | ||
2248 | #ifdef STATIC_CHAIN_REGNUM | |
2249 | if (outgoing) | |
2250 | reg2 = static_chain_incoming_rtx; | |
2251 | else | |
2252 | reg2 = static_chain_rtx; | |
2253 | if (REGNO (reg2) == REGNO (reg1)) | |
2254 | #endif /* STATIC_CHAIN_REGNUM */ | |
2255 | reg2 = NULL_RTX; | |
2256 | ||
2257 | if (reg2 == NULL_RTX) | |
2258 | { | |
2259 | int i; | |
2260 | for (i = 0; i < FIRST_PSEUDO_REGISTER; ++i) | |
2261 | if (call_used_regs[i] && ! fixed_regs[i] && i != REGNO (reg1)) | |
2262 | { | |
2263 | reg2 = gen_rtx (REG, Pmode, i); | |
2264 | break; | |
2265 | } | |
2266 | ||
2267 | if (reg2 == NULL_RTX) | |
2268 | abort (); | |
2269 | } | |
2270 | ||
2271 | *r1 = reg1; | |
2272 | *r2 = reg2; | |
2273 | } | |
2274 | ||
2275 | /* Emit inside of __throw a stub which adjusts the stack pointer and jumps | |
2276 | to the exception handler. __throw will set up the necessary values | |
2277 | and then return to the stub. */ | |
2278 | ||
2279 | rtx | |
2280 | expand_builtin_eh_stub () | |
2281 | { | |
2282 | rtx stub_start = gen_label_rtx (); | |
2283 | rtx after_stub = gen_label_rtx (); | |
2284 | rtx handler, offset, temp; | |
2285 | ||
2286 | emit_jump (after_stub); | |
2287 | emit_label (stub_start); | |
2288 | ||
2289 | eh_regs (&handler, &offset, 0); | |
2290 | ||
2291 | adjust_stack (offset); | |
2292 | emit_indirect_jump (handler); | |
2293 | ||
2294 | emit_label (after_stub); | |
2295 | return gen_rtx (LABEL_REF, Pmode, stub_start); | |
2296 | } | |
2297 | ||
2298 | /* Set up the registers for passing the handler address and stack offset | |
2299 | to the stub above. */ | |
2300 | ||
2301 | void | |
2302 | expand_builtin_set_eh_regs (handler, offset) | |
2303 | tree handler, offset; | |
2304 | { | |
2305 | rtx reg1, reg2; | |
2306 | ||
2307 | eh_regs (®1, ®2, 1); | |
2308 | ||
2309 | store_expr (offset, reg2, 0); | |
2310 | store_expr (handler, reg1, 0); | |
2311 | ||
2312 | /* These will be used by the stub. */ | |
2313 | emit_insn (gen_rtx (USE, VOIDmode, reg1)); | |
2314 | emit_insn (gen_rtx (USE, VOIDmode, reg2)); | |
2315 | } |