1/* Exception Handling interface routines.
2   Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
3   2007, 2008, 2009  Free Software Foundation, Inc.
4   Contributed by Mike Stump <mrs@cygnus.com>.
5
6This file is part of GCC.
7
8GCC is free software; you can redistribute it and/or modify it under
9the terms of the GNU General Public License as published by the Free
10Software Foundation; either version 3, or (at your option) any later
11version.
12
13GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14WARRANTY; without even the implied warranty of MERCHANTABILITY or
15FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
16for more details.
17
18You should have received a copy of the GNU General Public License
19along with GCC; see the file COPYING3.  If not see
20<http://www.gnu.org/licenses/>.  */
21
22#include "sbitmap.h"
23#include "vecprim.h"
24
25struct function;
26struct eh_region_d;
27struct pointer_map_t;
28
29/* The type of an exception region.  */
30enum eh_region_type
31{
32  /* CLEANUP regions implement e.g. destructors run when exiting a block.
33     They can be generated from both GIMPLE_TRY_FINALLY and GIMPLE_TRY_CATCH
34     nodes.  It is expected by the runtime that cleanup regions will *not*
35     resume normal program flow, but will continue propagation of the
36     exception.  */
37  ERT_CLEANUP,
38
39  /* TRY regions implement catching an exception.  The list of types associated
40     with the attached catch handlers is examined in order by the runtime and
41     control is transfered to the appropriate handler.  Note that a NULL type
42     list is a catch-all handler, and that it will catch *all* exceptions
43     including those originating from a different language.  */
44  ERT_TRY,
45
46  /* ALLOWED_EXCEPTIONS regions implement exception filtering, e.g. the
47     throw(type-list) specification that can be added to C++ functions.
48     The runtime examines the thrown exception vs the type list, and if
49     the exception does not match, transfers control to the handler.  The
50     normal handler for C++ calls __cxa_call_unexpected.  */
51  ERT_ALLOWED_EXCEPTIONS,
52
53  /* MUST_NOT_THROW regions prevent all exceptions from propagating.  This
54     region type is used in C++ to surround destructors being run inside a
55     CLEANUP region.  This differs from an ALLOWED_EXCEPTIONS region with
56     an empty type list in that the runtime is prepared to terminate the
57     program directly.  We only generate code for MUST_NOT_THROW regions
58     along control paths that are already handling an exception within the
59     current function.  */
60  ERT_MUST_NOT_THROW
61};
62
63
64/* A landing pad for a given exception region.  Any transfer of control
65   from the EH runtime to the function happens at a landing pad.  */
66
67struct GTY(()) eh_landing_pad_d
68{
69  /* The linked list of all landing pads associated with the region.  */
70  struct eh_landing_pad_d *next_lp;
71
72  /* The region with which this landing pad is associated.  */
73  struct eh_region_d *region;
74
75  /* At the gimple level, the location to which control will be transfered
76     for this landing pad.  There can be both EH and normal edges into the
77     block containing the post-landing-pad label.  */
78  tree post_landing_pad;
79
80  /* At the rtl level, the location to which the runtime will transfer
81     control.  This differs from the post-landing-pad in that the target's
82     EXCEPTION_RECEIVER pattern will be expanded here, as well as other
83     bookkeeping specific to exceptions.  There must not be normal edges
84     into the block containing the landing-pad label.  */
85  rtx landing_pad;
86
87  /* The index of this landing pad within fun->eh->lp_array.  */
88  int index;
89};
90
91/* A catch handler associated with an ERT_TRY region.  */
92
93struct GTY(()) eh_catch_d
94{
95  /* The double-linked list of all catch handlers for the region.  */
96  struct eh_catch_d *next_catch;
97  struct eh_catch_d *prev_catch;
98
99  /* A TREE_LIST of runtime type objects that this catch handler
100     will catch, or NULL if all exceptions are caught.  */
101  tree type_list;
102
103  /* A TREE_LIST of INTEGER_CSTs that correspond to the type_list entries,
104     having been mapped by assign_filter_values.  These integers are to be
105     compared against the __builtin_eh_filter value.  */
106  tree filter_list;
107
108  /* The code that should be executed if this catch handler matches the
109     thrown exception.  This label is only maintained until
110     pass_lower_eh_dispatch, at which point it is cleared.  */
111  tree label;
112};
113
114/* Describes one exception region.  */
115
116struct GTY(()) eh_region_d
117{
118  /* The immediately surrounding region.  */
119  struct eh_region_d *outer;
120
121  /* The list of immediately contained regions.  */
122  struct eh_region_d *inner;
123  struct eh_region_d *next_peer;
124
125  /* The index of this region within fun->eh->region_array.  */
126  int index;
127
128  /* Each region does exactly one thing.  */
129  enum eh_region_type type;
130
131  /* Holds the action to perform based on the preceding type.  */
132  union eh_region_u {
133    struct eh_region_u_try {
134      /* The double-linked list of all catch handlers for this region.  */
135      struct eh_catch_d *first_catch;
136      struct eh_catch_d *last_catch;
137    } GTY ((tag ("ERT_TRY"))) eh_try;
138
139    struct eh_region_u_allowed {
140      /* A TREE_LIST of runtime type objects allowed to pass.  */
141      tree type_list;
142      /* The code that should be executed if the thrown exception does
143	 not match the type list.  This label is only maintained until
144	 pass_lower_eh_dispatch, at which point it is cleared.  */
145      tree label;
146      /* The integer that will be passed by the runtime to signal that
147	 we should execute the code at LABEL.  This integer is assigned
148	 by assign_filter_values and is to be compared against the
149	 __builtin_eh_filter value.  */
150      int filter;
151    } GTY ((tag ("ERT_ALLOWED_EXCEPTIONS"))) allowed;
152
153    struct eh_region_u_must_not_throw {
154      /* A function decl to be invoked if this region is actually reachable
155	 from within the function, rather than implementable from the runtime.
156	 The normal way for this to happen is for there to be a CLEANUP region
157	 contained within this MUST_NOT_THROW region.  Note that if the
158	 runtime handles the MUST_NOT_THROW region, we have no control over
159	 what termination function is called; it will be decided by the
160	 personality function in effect for this CIE.  */
161      tree failure_decl;
162      /* The location assigned to the call of FAILURE_DECL, if expanded.  */
163      location_t failure_loc;
164    } GTY ((tag ("ERT_MUST_NOT_THROW"))) must_not_throw;
165  } GTY ((desc ("%0.type"))) u;
166
167  /* The list of landing pads associated with this region.  */
168  struct eh_landing_pad_d *landing_pads;
169
170  /* EXC_PTR and FILTER values copied from the runtime for this region.
171     Each region gets its own psuedos so that if there are nested exceptions
172     we do not overwrite the values of the first exception.  */
173  rtx exc_ptr_reg, filter_reg;
174
175  /* True if this region should use __cxa_end_cleanup instead
176     of _Unwind_Resume.  */
177  bool use_cxa_end_cleanup;
178};
179
180typedef struct eh_landing_pad_d *eh_landing_pad;
181typedef struct eh_catch_d *eh_catch;
182typedef struct eh_region_d *eh_region;
183
184DEF_VEC_P(eh_region);
185DEF_VEC_ALLOC_P(eh_region, gc);
186DEF_VEC_ALLOC_P(eh_region, heap);
187
188DEF_VEC_P(eh_landing_pad);
189DEF_VEC_ALLOC_P(eh_landing_pad, gc);
190
191
192/* The exception status for each function.  */
193
194struct GTY(()) eh_status
195{
196  /* The tree of all regions for this function.  */
197  eh_region region_tree;
198
199  /* The same information as an indexable array.  */
200  VEC(eh_region,gc) *region_array;
201
202  /* The landing pads as an indexable array.  */
203  VEC(eh_landing_pad,gc) *lp_array;
204
205  /* At the gimple level, a mapping from gimple statement to landing pad
206     or must-not-throw region.  See record_stmt_eh_region.  */
207  htab_t GTY((param_is (struct throw_stmt_node))) throw_stmt_table;
208
209  /* All of the runtime type data used by the function.  These objects
210     are emitted to the lang-specific-data-area for the function.  */
211  VEC(tree,gc) *ttype_data;
212
213  /* The table of all action chains.  These encode the eh_region tree in
214     a compact form for use by the runtime, and is also emitted to the
215     lang-specific-data-area.  Note that the ARM EABI uses a different
216     format for the encoding than all other ports.  */
217  union eh_status_u {
218    VEC(tree,gc) * GTY((tag ("1"))) arm_eabi;
219    VEC(uchar,gc) * GTY((tag ("0"))) other;
220  } GTY ((desc ("targetm.arm_eabi_unwinder"))) ehspec_data;
221};
222
223
224/* Test: is exception handling turned on?  */
225extern int doing_eh (int);
226
227/* Invokes CALLBACK for every exception handler label.  Only used by old
228   loop hackery; should not be used by new code.  */
229extern void for_each_eh_label (void (*) (rtx));
230
231extern void init_eh (void);
232extern void init_eh_for_function (void);
233
234extern void remove_eh_landing_pad (eh_landing_pad);
235extern void remove_eh_handler (eh_region);
236
237extern bool current_function_has_exception_handlers (void);
238extern void output_function_exception_table (const char *);
239
240extern rtx expand_builtin_eh_pointer (tree);
241extern rtx expand_builtin_eh_filter (tree);
242extern rtx expand_builtin_eh_copy_values (tree);
243extern void expand_builtin_unwind_init (void);
244extern rtx expand_builtin_eh_return_data_regno (tree);
245extern rtx expand_builtin_extract_return_addr (tree);
246extern void expand_builtin_init_dwarf_reg_sizes (tree);
247extern rtx expand_builtin_frob_return_addr (tree);
248extern rtx expand_builtin_dwarf_sp_column (void);
249extern void expand_builtin_eh_return (tree, tree);
250extern void expand_eh_return (void);
251extern rtx expand_builtin_extend_pointer (tree);
252
253typedef tree (*duplicate_eh_regions_map) (tree, void *);
254extern struct pointer_map_t *duplicate_eh_regions
255  (struct function *, eh_region, int, duplicate_eh_regions_map, void *);
256
257extern void sjlj_emit_function_exit_after (rtx);
258
259extern eh_region gen_eh_region_cleanup (eh_region);
260extern eh_region gen_eh_region_try (eh_region);
261extern eh_region gen_eh_region_allowed (eh_region, tree);
262extern eh_region gen_eh_region_must_not_throw (eh_region);
263
264extern eh_catch gen_eh_region_catch (eh_region, tree);
265extern eh_landing_pad gen_eh_landing_pad (eh_region);
266
267extern eh_region get_eh_region_from_number_fn (struct function *, int);
268extern eh_region get_eh_region_from_number (int);
269extern eh_landing_pad get_eh_landing_pad_from_number_fn (struct function*,int);
270extern eh_landing_pad get_eh_landing_pad_from_number (int);
271extern eh_region get_eh_region_from_lp_number_fn (struct function *, int);
272extern eh_region get_eh_region_from_lp_number (int);
273
274extern eh_region eh_region_outermost (struct function *, eh_region, eh_region);
275
276extern void make_reg_eh_region_note (rtx insn, int ecf_flags, int lp_nr);
277extern void make_reg_eh_region_note_nothrow_nononlocal (rtx);
278
279extern void verify_eh_tree (struct function *);
280extern void dump_eh_tree (FILE *, struct function *);
281void debug_eh_tree (struct function *);
282extern void add_type_for_runtime (tree);
283extern tree lookup_type_for_runtime (tree);
284extern void assign_filter_values (void);
285
286extern eh_region get_eh_region_from_rtx (const_rtx);
287extern eh_landing_pad get_eh_landing_pad_from_rtx (const_rtx);
288
289/* If non-NULL, this is a function that returns a function decl to be
290   executed if an unhandled exception is propagated out of a cleanup
291   region.  For example, in C++, an exception thrown by a destructor
292   during stack unwinding is required to result in a call to
293   `std::terminate', so the C++ version of this function returns a
294   FUNCTION_DECL for `std::terminate'.  */
295extern tree (*lang_protect_cleanup_actions) (void);
296
297/* Return true if type A catches type B.  */
298extern int (*lang_eh_type_covers) (tree a, tree b);
299
300
301/* Just because the user configured --with-sjlj-exceptions=no doesn't
302   mean that we can use call frame exceptions.  Detect that the target
303   has appropriate support.  */
304
305#ifndef MUST_USE_SJLJ_EXCEPTIONS
306# if defined (EH_RETURN_DATA_REGNO)			\
307       && (defined (TARGET_UNWIND_INFO)			\
308	   || (DWARF2_UNWIND_INFO			\
309	       && (defined (EH_RETURN_HANDLER_RTX)	\
310		   || defined (HAVE_eh_return))))
311#  define MUST_USE_SJLJ_EXCEPTIONS	0
312# else
313#  define MUST_USE_SJLJ_EXCEPTIONS	1
314# endif
315#endif
316
317#ifdef CONFIG_SJLJ_EXCEPTIONS
318# if CONFIG_SJLJ_EXCEPTIONS == 1
319#  define USING_SJLJ_EXCEPTIONS		1
320# endif
321# if CONFIG_SJLJ_EXCEPTIONS == 0
322#  define USING_SJLJ_EXCEPTIONS		0
323#  if !defined(EH_RETURN_DATA_REGNO)
324    #error "EH_RETURN_DATA_REGNO required"
325#  endif
326#  if ! (defined(TARGET_UNWIND_INFO) || DWARF2_UNWIND_INFO)
327    #error "{DWARF2,TARGET}_UNWIND_INFO required"
328#  endif
329#  if !defined(TARGET_UNWIND_INFO) \
330	&& !(defined(EH_RETURN_HANDLER_RTX) || defined(HAVE_eh_return))
331    #error "EH_RETURN_HANDLER_RTX or eh_return required"
332#  endif
333/* Usually the above error checks will have already triggered an
334   error, but backends may set MUST_USE_SJLJ_EXCEPTIONS for their own
335   reasons.  */
336#  if MUST_USE_SJLJ_EXCEPTIONS
337    #error "Must use SJLJ exceptions but configured not to"
338#  endif
339# endif
340#else
341# define USING_SJLJ_EXCEPTIONS		MUST_USE_SJLJ_EXCEPTIONS
342#endif
343
344struct GTY(()) throw_stmt_node {
345  gimple stmt;
346  int lp_nr;
347};
348
349extern struct htab *get_eh_throw_stmt_table (struct function *);
350extern void set_eh_throw_stmt_table (struct function *, struct htab *);
351
352enum eh_personality_kind {
353  eh_personality_none,
354  eh_personality_any,
355  eh_personality_lang
356};
357
358extern enum eh_personality_kind
359function_needs_eh_personality (struct function *);
360
361/* Pre-order iteration within the eh_region tree.  */
362
363static inline eh_region
364ehr_next (eh_region r, eh_region start)
365{
366  if (r->inner)
367    r = r->inner;
368  else if (r->next_peer && r != start)
369    r = r->next_peer;
370  else
371    {
372      do
373	{
374	  r = r->outer;
375	  if (r == start)
376	    return NULL;
377	}
378      while (r->next_peer == NULL);
379      r = r->next_peer;
380    }
381  return r;
382}
383
384#define FOR_ALL_EH_REGION_AT(R, START) \
385  for ((R) = (START); (R) != NULL; (R) = ehr_next (R, START))
386
387#define FOR_ALL_EH_REGION_FN(R, FN) \
388  for ((R) = (FN)->eh->region_tree; (R) != NULL; (R) = ehr_next (R, NULL))
389
390#define FOR_ALL_EH_REGION(R) FOR_ALL_EH_REGION_FN (R, cfun)
391