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Commit | Line | Data |
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402209ff | 1 | /* Natural loop discovery code for GNU compiler. |
6fb5fa3c DB |
2 | Copyright (C) 2000, 2001, 2003, 2004, 2005, 2006, 2007 |
3 | Free Software Foundation, Inc. | |
402209ff JH |
4 | |
5 | This file is part of GCC. | |
6 | ||
7 | GCC is free software; you can redistribute it and/or modify it under | |
8 | the terms of the GNU General Public License as published by the Free | |
9dcd6f09 | 9 | Software Foundation; either version 3, or (at your option) any later |
402209ff JH |
10 | version. |
11 | ||
12 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
13 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
14 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
15 | for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
9dcd6f09 NC |
18 | along with GCC; see the file COPYING3. If not see |
19 | <http://www.gnu.org/licenses/>. */ | |
402209ff JH |
20 | |
21 | #include "config.h" | |
22 | #include "system.h" | |
4977bab6 ZW |
23 | #include "coretypes.h" |
24 | #include "tm.h" | |
402209ff JH |
25 | #include "rtl.h" |
26 | #include "hard-reg-set.h" | |
7932a3db | 27 | #include "obstack.h" |
a310245f | 28 | #include "function.h" |
402209ff | 29 | #include "basic-block.h" |
2ecfd709 | 30 | #include "toplev.h" |
3d436d2a ZD |
31 | #include "cfgloop.h" |
32 | #include "flags.h" | |
6de9cd9a DN |
33 | #include "tree.h" |
34 | #include "tree-flow.h" | |
89f8f30f ZD |
35 | #include "pointer-set.h" |
36 | #include "output.h" | |
9e2f83a5 | 37 | #include "ggc.h" |
f470c378 | 38 | |
d73be268 | 39 | static void flow_loops_cfg_dump (FILE *); |
402209ff JH |
40 | \f |
41 | /* Dump loop related CFG information. */ | |
42 | ||
43 | static void | |
d73be268 | 44 | flow_loops_cfg_dump (FILE *file) |
402209ff | 45 | { |
e0082a72 | 46 | basic_block bb; |
402209ff | 47 | |
d73be268 | 48 | if (!file) |
402209ff JH |
49 | return; |
50 | ||
e0082a72 | 51 | FOR_EACH_BB (bb) |
402209ff JH |
52 | { |
53 | edge succ; | |
628f6a4e | 54 | edge_iterator ei; |
402209ff | 55 | |
e0082a72 | 56 | fprintf (file, ";; %d succs { ", bb->index); |
628f6a4e | 57 | FOR_EACH_EDGE (succ, ei, bb->succs) |
0b17ab2f | 58 | fprintf (file, "%d ", succ->dest->index); |
2ecfd709 | 59 | fprintf (file, "}\n"); |
402209ff | 60 | } |
402209ff JH |
61 | } |
62 | ||
da7d8304 | 63 | /* Return nonzero if the nodes of LOOP are a subset of OUTER. */ |
402209ff | 64 | |
2ecfd709 | 65 | bool |
d329e058 | 66 | flow_loop_nested_p (const struct loop *outer, const struct loop *loop) |
402209ff | 67 | { |
9ba025a2 ZD |
68 | unsigned odepth = loop_depth (outer); |
69 | ||
70 | return (loop_depth (loop) > odepth | |
71 | && VEC_index (loop_p, loop->superloops, odepth) == outer); | |
402209ff JH |
72 | } |
73 | ||
1ad03593 SP |
74 | /* Returns the loop such that LOOP is nested DEPTH (indexed from zero) |
75 | loops within LOOP. */ | |
a7e5372d ZD |
76 | |
77 | struct loop * | |
78 | superloop_at_depth (struct loop *loop, unsigned depth) | |
79 | { | |
9ba025a2 ZD |
80 | unsigned ldepth = loop_depth (loop); |
81 | ||
82 | gcc_assert (depth <= ldepth); | |
a7e5372d | 83 | |
9ba025a2 | 84 | if (depth == ldepth) |
a7e5372d ZD |
85 | return loop; |
86 | ||
9ba025a2 | 87 | return VEC_index (loop_p, loop->superloops, depth); |
a7e5372d ZD |
88 | } |
89 | ||
89f8f30f ZD |
90 | /* Returns the list of the latch edges of LOOP. */ |
91 | ||
92 | static VEC (edge, heap) * | |
93 | get_loop_latch_edges (const struct loop *loop) | |
94 | { | |
95 | edge_iterator ei; | |
96 | edge e; | |
97 | VEC (edge, heap) *ret = NULL; | |
98 | ||
99 | FOR_EACH_EDGE (e, ei, loop->header->preds) | |
100 | { | |
101 | if (dominated_by_p (CDI_DOMINATORS, e->src, loop->header)) | |
102 | VEC_safe_push (edge, heap, ret, e); | |
103 | } | |
104 | ||
105 | return ret; | |
106 | } | |
107 | ||
402209ff JH |
108 | /* Dump the loop information specified by LOOP to the stream FILE |
109 | using auxiliary dump callback function LOOP_DUMP_AUX if non null. */ | |
110 | ||
111 | void | |
d329e058 AJ |
112 | flow_loop_dump (const struct loop *loop, FILE *file, |
113 | void (*loop_dump_aux) (const struct loop *, FILE *, int), | |
114 | int verbose) | |
402209ff | 115 | { |
2ecfd709 | 116 | basic_block *bbs; |
3d436d2a | 117 | unsigned i; |
89f8f30f ZD |
118 | VEC (edge, heap) *latches; |
119 | edge e; | |
2ecfd709 | 120 | |
402209ff JH |
121 | if (! loop || ! loop->header) |
122 | return; | |
123 | ||
7490e6c4 | 124 | fprintf (file, ";;\n;; Loop %d\n", loop->num); |
402209ff | 125 | |
89f8f30f ZD |
126 | fprintf (file, ";; header %d, ", loop->header->index); |
127 | if (loop->latch) | |
128 | fprintf (file, "latch %d\n", loop->latch->index); | |
129 | else | |
130 | { | |
131 | fprintf (file, "multiple latches:"); | |
132 | latches = get_loop_latch_edges (loop); | |
133 | for (i = 0; VEC_iterate (edge, latches, i, e); i++) | |
134 | fprintf (file, " %d", e->src->index); | |
135 | VEC_free (edge, heap, latches); | |
136 | fprintf (file, "\n"); | |
137 | } | |
138 | ||
99f8a411 | 139 | fprintf (file, ";; depth %d, outer %ld\n", |
9ba025a2 ZD |
140 | loop_depth (loop), (long) (loop_outer (loop) |
141 | ? loop_outer (loop)->num : -1)); | |
402209ff | 142 | |
2ecfd709 ZD |
143 | fprintf (file, ";; nodes:"); |
144 | bbs = get_loop_body (loop); | |
145 | for (i = 0; i < loop->num_nodes; i++) | |
146 | fprintf (file, " %d", bbs[i]->index); | |
147 | free (bbs); | |
148 | fprintf (file, "\n"); | |
5f0d2358 | 149 | |
402209ff JH |
150 | if (loop_dump_aux) |
151 | loop_dump_aux (loop, file, verbose); | |
152 | } | |
153 | ||
d73be268 | 154 | /* Dump the loop information about loops to the stream FILE, |
402209ff JH |
155 | using auxiliary dump callback function LOOP_DUMP_AUX if non null. */ |
156 | ||
157 | void | |
d73be268 | 158 | flow_loops_dump (FILE *file, void (*loop_dump_aux) (const struct loop *, FILE *, int), int verbose) |
402209ff | 159 | { |
42fd6772 ZD |
160 | loop_iterator li; |
161 | struct loop *loop; | |
402209ff | 162 | |
d73be268 | 163 | if (!current_loops || ! file) |
402209ff JH |
164 | return; |
165 | ||
42fd6772 | 166 | fprintf (file, ";; %d loops found\n", number_of_loops ()); |
2ecfd709 | 167 | |
42fd6772 | 168 | FOR_EACH_LOOP (li, loop, LI_INCLUDE_ROOT) |
402209ff | 169 | { |
2ecfd709 | 170 | flow_loop_dump (loop, file, loop_dump_aux, verbose); |
402209ff JH |
171 | } |
172 | ||
173 | if (verbose) | |
d73be268 | 174 | flow_loops_cfg_dump (file); |
402209ff JH |
175 | } |
176 | ||
2ecfd709 | 177 | /* Free data allocated for LOOP. */ |
9e2f83a5 | 178 | |
35b07080 | 179 | void |
d329e058 | 180 | flow_loop_free (struct loop *loop) |
2ecfd709 | 181 | { |
6270df4c ZD |
182 | struct loop_exit *exit, *next; |
183 | ||
9e2f83a5 | 184 | VEC_free (loop_p, gc, loop->superloops); |
6270df4c ZD |
185 | |
186 | /* Break the list of the loop exit records. They will be freed when the | |
187 | corresponding edge is rescanned or removed, and this avoids | |
188 | accessing the (already released) head of the list stored in the | |
189 | loop structure. */ | |
9e2f83a5 | 190 | for (exit = loop->exits->next; exit != loop->exits; exit = next) |
6270df4c ZD |
191 | { |
192 | next = exit->next; | |
193 | exit->next = exit; | |
194 | exit->prev = exit; | |
195 | } | |
9e2f83a5 ZD |
196 | |
197 | ggc_free (loop->exits); | |
198 | ggc_free (loop); | |
2ecfd709 ZD |
199 | } |
200 | ||
402209ff JH |
201 | /* Free all the memory allocated for LOOPS. */ |
202 | ||
203 | void | |
d329e058 | 204 | flow_loops_free (struct loops *loops) |
402209ff | 205 | { |
42fd6772 | 206 | if (loops->larray) |
402209ff | 207 | { |
3d436d2a | 208 | unsigned i; |
42fd6772 | 209 | loop_p loop; |
402209ff JH |
210 | |
211 | /* Free the loop descriptors. */ | |
42fd6772 | 212 | for (i = 0; VEC_iterate (loop_p, loops->larray, i, loop); i++) |
402209ff | 213 | { |
2ecfd709 ZD |
214 | if (!loop) |
215 | continue; | |
216 | ||
217 | flow_loop_free (loop); | |
402209ff | 218 | } |
5f0d2358 | 219 | |
9e2f83a5 | 220 | VEC_free (loop_p, gc, loops->larray); |
402209ff JH |
221 | } |
222 | } | |
223 | ||
2ecfd709 ZD |
224 | /* Find the nodes contained within the LOOP with header HEADER. |
225 | Return the number of nodes within the loop. */ | |
402209ff | 226 | |
2b271002 | 227 | int |
d329e058 | 228 | flow_loop_nodes_find (basic_block header, struct loop *loop) |
402209ff | 229 | { |
89f8f30f | 230 | VEC (basic_block, heap) *stack = NULL; |
2ecfd709 | 231 | int num_nodes = 1; |
89f8f30f ZD |
232 | edge latch; |
233 | edge_iterator latch_ei; | |
9ba025a2 | 234 | unsigned depth = loop_depth (loop); |
402209ff | 235 | |
2ecfd709 | 236 | header->loop_father = loop; |
9ba025a2 | 237 | header->loop_depth = depth; |
402209ff | 238 | |
89f8f30f | 239 | FOR_EACH_EDGE (latch, latch_ei, loop->header->preds) |
402209ff | 240 | { |
89f8f30f ZD |
241 | if (latch->src->loop_father == loop |
242 | || !dominated_by_p (CDI_DOMINATORS, latch->src, loop->header)) | |
243 | continue; | |
244 | ||
402209ff | 245 | num_nodes++; |
89f8f30f ZD |
246 | VEC_safe_push (basic_block, heap, stack, latch->src); |
247 | latch->src->loop_father = loop; | |
9ba025a2 | 248 | latch->src->loop_depth = depth; |
d329e058 | 249 | |
89f8f30f | 250 | while (!VEC_empty (basic_block, stack)) |
402209ff | 251 | { |
2ecfd709 ZD |
252 | basic_block node; |
253 | edge e; | |
628f6a4e | 254 | edge_iterator ei; |
402209ff | 255 | |
89f8f30f | 256 | node = VEC_pop (basic_block, stack); |
d329e058 | 257 | |
628f6a4e | 258 | FOR_EACH_EDGE (e, ei, node->preds) |
402209ff | 259 | { |
2ecfd709 ZD |
260 | basic_block ancestor = e->src; |
261 | ||
89f8f30f | 262 | if (ancestor->loop_father != loop) |
2ecfd709 ZD |
263 | { |
264 | ancestor->loop_father = loop; | |
9ba025a2 | 265 | ancestor->loop_depth = depth; |
2ecfd709 | 266 | num_nodes++; |
89f8f30f | 267 | VEC_safe_push (basic_block, heap, stack, ancestor); |
2ecfd709 | 268 | } |
402209ff JH |
269 | } |
270 | } | |
271 | } | |
89f8f30f ZD |
272 | VEC_free (basic_block, heap, stack); |
273 | ||
402209ff JH |
274 | return num_nodes; |
275 | } | |
276 | ||
9ba025a2 ZD |
277 | /* Records the vector of superloops of the loop LOOP, whose immediate |
278 | superloop is FATHER. */ | |
279 | ||
35b07080 | 280 | static void |
9ba025a2 | 281 | establish_preds (struct loop *loop, struct loop *father) |
35b07080 | 282 | { |
9ba025a2 ZD |
283 | loop_p ploop; |
284 | unsigned depth = loop_depth (father) + 1; | |
285 | unsigned i; | |
a310245f | 286 | |
9ba025a2 | 287 | VEC_truncate (loop_p, loop->superloops, 0); |
9e2f83a5 | 288 | VEC_reserve (loop_p, gc, loop->superloops, depth); |
9ba025a2 ZD |
289 | for (i = 0; VEC_iterate (loop_p, father->superloops, i, ploop); i++) |
290 | VEC_quick_push (loop_p, loop->superloops, ploop); | |
291 | VEC_quick_push (loop_p, loop->superloops, father); | |
35b07080 ZD |
292 | |
293 | for (ploop = loop->inner; ploop; ploop = ploop->next) | |
9ba025a2 | 294 | establish_preds (ploop, loop); |
35b07080 ZD |
295 | } |
296 | ||
2ecfd709 | 297 | /* Add LOOP to the loop hierarchy tree where FATHER is father of the |
35b07080 ZD |
298 | added loop. If LOOP has some children, take care of that their |
299 | pred field will be initialized correctly. */ | |
402209ff | 300 | |
2ecfd709 | 301 | void |
d329e058 | 302 | flow_loop_tree_node_add (struct loop *father, struct loop *loop) |
402209ff | 303 | { |
2ecfd709 ZD |
304 | loop->next = father->inner; |
305 | father->inner = loop; | |
2ecfd709 | 306 | |
9ba025a2 | 307 | establish_preds (loop, father); |
402209ff JH |
308 | } |
309 | ||
2ecfd709 | 310 | /* Remove LOOP from the loop hierarchy tree. */ |
402209ff | 311 | |
2ecfd709 | 312 | void |
d329e058 | 313 | flow_loop_tree_node_remove (struct loop *loop) |
402209ff | 314 | { |
2ecfd709 | 315 | struct loop *prev, *father; |
402209ff | 316 | |
9ba025a2 | 317 | father = loop_outer (loop); |
402209ff | 318 | |
2ecfd709 ZD |
319 | /* Remove loop from the list of sons. */ |
320 | if (father->inner == loop) | |
321 | father->inner = loop->next; | |
322 | else | |
323 | { | |
9ba025a2 ZD |
324 | for (prev = father->inner; prev->next != loop; prev = prev->next) |
325 | continue; | |
2ecfd709 ZD |
326 | prev->next = loop->next; |
327 | } | |
402209ff | 328 | |
9ba025a2 | 329 | VEC_truncate (loop_p, loop->superloops, 0); |
402209ff JH |
330 | } |
331 | ||
6270df4c ZD |
332 | /* Allocates and returns new loop structure. */ |
333 | ||
334 | struct loop * | |
335 | alloc_loop (void) | |
336 | { | |
9e2f83a5 ZD |
337 | struct loop *loop = GGC_CNEW (struct loop); |
338 | ||
339 | loop->exits = GGC_CNEW (struct loop_exit); | |
340 | loop->exits->next = loop->exits->prev = loop->exits; | |
6270df4c | 341 | |
6270df4c ZD |
342 | return loop; |
343 | } | |
344 | ||
4ed88ee3 ZD |
345 | /* Initializes loops structure LOOPS, reserving place for NUM_LOOPS loops |
346 | (including the root of the loop tree). */ | |
347 | ||
348 | static void | |
349 | init_loops_structure (struct loops *loops, unsigned num_loops) | |
350 | { | |
351 | struct loop *root; | |
352 | ||
353 | memset (loops, 0, sizeof *loops); | |
354 | loops->larray = VEC_alloc (loop_p, gc, num_loops); | |
355 | ||
356 | /* Dummy loop containing whole function. */ | |
357 | root = alloc_loop (); | |
358 | root->num_nodes = n_basic_blocks; | |
359 | root->latch = EXIT_BLOCK_PTR; | |
360 | root->header = ENTRY_BLOCK_PTR; | |
361 | ENTRY_BLOCK_PTR->loop_father = root; | |
362 | EXIT_BLOCK_PTR->loop_father = root; | |
363 | ||
364 | VEC_quick_push (loop_p, loops->larray, root); | |
365 | loops->tree_root = root; | |
366 | } | |
367 | ||
5f0d2358 | 368 | /* Find all the natural loops in the function and save in LOOPS structure and |
70388d94 ZD |
369 | recalculate loop_depth information in basic block structures. |
370 | Return the number of natural loops found. */ | |
402209ff JH |
371 | |
372 | int | |
70388d94 | 373 | flow_loops_find (struct loops *loops) |
402209ff | 374 | { |
0b17ab2f | 375 | int b; |
402209ff JH |
376 | int num_loops; |
377 | edge e; | |
378 | sbitmap headers; | |
402209ff JH |
379 | int *dfs_order; |
380 | int *rc_order; | |
355be0dc JH |
381 | basic_block header; |
382 | basic_block bb; | |
402209ff | 383 | |
4ed88ee3 ZD |
384 | /* Ensure that the dominators are computed. */ |
385 | calculate_dominance_info (CDI_DOMINATORS); | |
402209ff JH |
386 | |
387 | /* Taking care of this degenerate case makes the rest of | |
388 | this code simpler. */ | |
24bd1a0b | 389 | if (n_basic_blocks == NUM_FIXED_BLOCKS) |
4ed88ee3 ZD |
390 | { |
391 | init_loops_structure (loops, 1); | |
392 | return 1; | |
393 | } | |
402209ff JH |
394 | |
395 | dfs_order = NULL; | |
396 | rc_order = NULL; | |
397 | ||
2ecfd709 | 398 | /* Count the number of loop headers. This should be the |
402209ff | 399 | same as the number of natural loops. */ |
2ecfd709 ZD |
400 | headers = sbitmap_alloc (last_basic_block); |
401 | sbitmap_zero (headers); | |
402 | ||
402209ff | 403 | num_loops = 0; |
e0082a72 | 404 | FOR_EACH_BB (header) |
402209ff | 405 | { |
628f6a4e | 406 | edge_iterator ei; |
d329e058 | 407 | |
402209ff JH |
408 | header->loop_depth = 0; |
409 | ||
16f2b86a ZD |
410 | /* If we have an abnormal predecessor, do not consider the |
411 | loop (not worth the problems). */ | |
628f6a4e | 412 | FOR_EACH_EDGE (e, ei, header->preds) |
16f2b86a ZD |
413 | if (e->flags & EDGE_ABNORMAL) |
414 | break; | |
415 | if (e) | |
416 | continue; | |
417 | ||
628f6a4e | 418 | FOR_EACH_EDGE (e, ei, header->preds) |
402209ff JH |
419 | { |
420 | basic_block latch = e->src; | |
421 | ||
341c100f | 422 | gcc_assert (!(e->flags & EDGE_ABNORMAL)); |
2ecfd709 | 423 | |
402209ff JH |
424 | /* Look for back edges where a predecessor is dominated |
425 | by this block. A natural loop has a single entry | |
426 | node (header) that dominates all the nodes in the | |
427 | loop. It also has single back edge to the header | |
2ecfd709 | 428 | from a latch node. */ |
d47cc544 SB |
429 | if (latch != ENTRY_BLOCK_PTR |
430 | && dominated_by_p (CDI_DOMINATORS, latch, header)) | |
2ecfd709 ZD |
431 | { |
432 | /* Shared headers should be eliminated by now. */ | |
2ecfd709 ZD |
433 | SET_BIT (headers, header->index); |
434 | num_loops++; | |
435 | } | |
402209ff JH |
436 | } |
437 | } | |
438 | ||
2ecfd709 | 439 | /* Allocate loop structures. */ |
4ed88ee3 | 440 | init_loops_structure (loops, num_loops + 1); |
2ecfd709 ZD |
441 | |
442 | /* Find and record information about all the natural loops | |
443 | in the CFG. */ | |
2ecfd709 ZD |
444 | FOR_EACH_BB (bb) |
445 | bb->loop_father = loops->tree_root; | |
446 | ||
402209ff JH |
447 | if (num_loops) |
448 | { | |
449 | /* Compute depth first search order of the CFG so that outer | |
450 | natural loops will be found before inner natural loops. */ | |
5ed6ace5 MD |
451 | dfs_order = XNEWVEC (int, n_basic_blocks); |
452 | rc_order = XNEWVEC (int, n_basic_blocks); | |
f91a0beb | 453 | pre_and_rev_post_order_compute (dfs_order, rc_order, false); |
402209ff | 454 | |
2ecfd709 | 455 | num_loops = 1; |
402209ff | 456 | |
24bd1a0b | 457 | for (b = 0; b < n_basic_blocks - NUM_FIXED_BLOCKS; b++) |
402209ff | 458 | { |
2ecfd709 | 459 | struct loop *loop; |
628f6a4e | 460 | edge_iterator ei; |
402209ff JH |
461 | |
462 | /* Search the nodes of the CFG in reverse completion order | |
463 | so that we can find outer loops first. */ | |
2ecfd709 ZD |
464 | if (!TEST_BIT (headers, rc_order[b])) |
465 | continue; | |
466 | ||
467 | header = BASIC_BLOCK (rc_order[b]); | |
d329e058 | 468 | |
6270df4c | 469 | loop = alloc_loop (); |
42fd6772 | 470 | VEC_quick_push (loop_p, loops->larray, loop); |
402209ff | 471 | |
2ecfd709 ZD |
472 | loop->header = header; |
473 | loop->num = num_loops; | |
474 | num_loops++; | |
475 | ||
89f8f30f ZD |
476 | flow_loop_tree_node_add (header->loop_father, loop); |
477 | loop->num_nodes = flow_loop_nodes_find (loop->header, loop); | |
478 | ||
479 | /* Look for the latch for this header block, if it has just a | |
480 | single one. */ | |
628f6a4e | 481 | FOR_EACH_EDGE (e, ei, header->preds) |
402209ff | 482 | { |
2ecfd709 ZD |
483 | basic_block latch = e->src; |
484 | ||
89f8f30f | 485 | if (flow_bb_inside_loop_p (loop, latch)) |
402209ff | 486 | { |
89f8f30f ZD |
487 | if (loop->latch != NULL) |
488 | { | |
489 | /* More than one latch edge. */ | |
490 | loop->latch = NULL; | |
491 | break; | |
492 | } | |
402209ff | 493 | loop->latch = latch; |
402209ff JH |
494 | } |
495 | } | |
402209ff JH |
496 | } |
497 | ||
598ec7bd ZD |
498 | free (dfs_order); |
499 | free (rc_order); | |
2ecfd709 | 500 | } |
3d436d2a | 501 | |
36579663 AP |
502 | sbitmap_free (headers); |
503 | ||
6270df4c | 504 | loops->exits = NULL; |
3d436d2a | 505 | loops->state = 0; |
42fd6772 | 506 | return VEC_length (loop_p, loops->larray); |
402209ff JH |
507 | } |
508 | ||
89f8f30f ZD |
509 | /* Ratio of frequencies of edges so that one of more latch edges is |
510 | considered to belong to inner loop with same header. */ | |
511 | #define HEAVY_EDGE_RATIO 8 | |
512 | ||
513 | /* Minimum number of samples for that we apply | |
514 | find_subloop_latch_edge_by_profile heuristics. */ | |
515 | #define HEAVY_EDGE_MIN_SAMPLES 10 | |
516 | ||
517 | /* If the profile info is available, finds an edge in LATCHES that much more | |
518 | frequent than the remaining edges. Returns such an edge, or NULL if we do | |
519 | not find one. | |
520 | ||
521 | We do not use guessed profile here, only the measured one. The guessed | |
522 | profile is usually too flat and unreliable for this (and it is mostly based | |
523 | on the loop structure of the program, so it does not make much sense to | |
524 | derive the loop structure from it). */ | |
525 | ||
526 | static edge | |
527 | find_subloop_latch_edge_by_profile (VEC (edge, heap) *latches) | |
528 | { | |
529 | unsigned i; | |
530 | edge e, me = NULL; | |
531 | gcov_type mcount = 0, tcount = 0; | |
532 | ||
533 | for (i = 0; VEC_iterate (edge, latches, i, e); i++) | |
534 | { | |
535 | if (e->count > mcount) | |
536 | { | |
537 | me = e; | |
538 | mcount = e->count; | |
539 | } | |
540 | tcount += e->count; | |
541 | } | |
542 | ||
543 | if (tcount < HEAVY_EDGE_MIN_SAMPLES | |
544 | || (tcount - mcount) * HEAVY_EDGE_RATIO > tcount) | |
545 | return NULL; | |
546 | ||
547 | if (dump_file) | |
548 | fprintf (dump_file, | |
549 | "Found latch edge %d -> %d using profile information.\n", | |
550 | me->src->index, me->dest->index); | |
551 | return me; | |
552 | } | |
553 | ||
554 | /* Among LATCHES, guesses a latch edge of LOOP corresponding to subloop, based | |
555 | on the structure of induction variables. Returns this edge, or NULL if we | |
556 | do not find any. | |
557 | ||
558 | We are quite conservative, and look just for an obvious simple innermost | |
559 | loop (which is the case where we would lose the most performance by not | |
560 | disambiguating the loop). More precisely, we look for the following | |
561 | situation: The source of the chosen latch edge dominates sources of all | |
562 | the other latch edges. Additionally, the header does not contain a phi node | |
563 | such that the argument from the chosen edge is equal to the argument from | |
564 | another edge. */ | |
565 | ||
566 | static edge | |
567 | find_subloop_latch_edge_by_ivs (struct loop *loop, VEC (edge, heap) *latches) | |
568 | { | |
569 | edge e, latch = VEC_index (edge, latches, 0); | |
570 | unsigned i; | |
571 | tree phi, lop; | |
572 | basic_block bb; | |
573 | ||
574 | /* Find the candidate for the latch edge. */ | |
575 | for (i = 1; VEC_iterate (edge, latches, i, e); i++) | |
576 | if (dominated_by_p (CDI_DOMINATORS, latch->src, e->src)) | |
577 | latch = e; | |
578 | ||
579 | /* Verify that it dominates all the latch edges. */ | |
580 | for (i = 0; VEC_iterate (edge, latches, i, e); i++) | |
581 | if (!dominated_by_p (CDI_DOMINATORS, e->src, latch->src)) | |
582 | return NULL; | |
583 | ||
584 | /* Check for a phi node that would deny that this is a latch edge of | |
585 | a subloop. */ | |
586 | for (phi = phi_nodes (loop->header); phi; phi = PHI_CHAIN (phi)) | |
587 | { | |
588 | lop = PHI_ARG_DEF_FROM_EDGE (phi, latch); | |
589 | ||
590 | /* Ignore the values that are not changed inside the subloop. */ | |
591 | if (TREE_CODE (lop) != SSA_NAME | |
592 | || SSA_NAME_DEF_STMT (lop) == phi) | |
593 | continue; | |
594 | bb = bb_for_stmt (SSA_NAME_DEF_STMT (lop)); | |
595 | if (!bb || !flow_bb_inside_loop_p (loop, bb)) | |
596 | continue; | |
597 | ||
598 | for (i = 0; VEC_iterate (edge, latches, i, e); i++) | |
599 | if (e != latch | |
600 | && PHI_ARG_DEF_FROM_EDGE (phi, e) == lop) | |
601 | return NULL; | |
602 | } | |
603 | ||
604 | if (dump_file) | |
605 | fprintf (dump_file, | |
606 | "Found latch edge %d -> %d using iv structure.\n", | |
607 | latch->src->index, latch->dest->index); | |
608 | return latch; | |
609 | } | |
610 | ||
611 | /* If we can determine that one of the several latch edges of LOOP behaves | |
612 | as a latch edge of a separate subloop, returns this edge. Otherwise | |
613 | returns NULL. */ | |
614 | ||
615 | static edge | |
616 | find_subloop_latch_edge (struct loop *loop) | |
617 | { | |
618 | VEC (edge, heap) *latches = get_loop_latch_edges (loop); | |
619 | edge latch = NULL; | |
620 | ||
621 | if (VEC_length (edge, latches) > 1) | |
622 | { | |
623 | latch = find_subloop_latch_edge_by_profile (latches); | |
624 | ||
625 | if (!latch | |
626 | /* We consider ivs to guess the latch edge only in SSA. Perhaps we | |
627 | should use cfghook for this, but it is hard to imagine it would | |
628 | be useful elsewhere. */ | |
629 | && current_ir_type () == IR_GIMPLE) | |
630 | latch = find_subloop_latch_edge_by_ivs (loop, latches); | |
631 | } | |
632 | ||
633 | VEC_free (edge, heap, latches); | |
634 | return latch; | |
635 | } | |
636 | ||
637 | /* Callback for make_forwarder_block. Returns true if the edge E is marked | |
638 | in the set MFB_REIS_SET. */ | |
639 | ||
640 | static struct pointer_set_t *mfb_reis_set; | |
641 | static bool | |
642 | mfb_redirect_edges_in_set (edge e) | |
643 | { | |
644 | return pointer_set_contains (mfb_reis_set, e); | |
645 | } | |
646 | ||
647 | /* Creates a subloop of LOOP with latch edge LATCH. */ | |
648 | ||
649 | static void | |
650 | form_subloop (struct loop *loop, edge latch) | |
651 | { | |
652 | edge_iterator ei; | |
653 | edge e, new_entry; | |
654 | struct loop *new_loop; | |
655 | ||
656 | mfb_reis_set = pointer_set_create (); | |
657 | FOR_EACH_EDGE (e, ei, loop->header->preds) | |
658 | { | |
659 | if (e != latch) | |
660 | pointer_set_insert (mfb_reis_set, e); | |
661 | } | |
662 | new_entry = make_forwarder_block (loop->header, mfb_redirect_edges_in_set, | |
663 | NULL); | |
664 | pointer_set_destroy (mfb_reis_set); | |
665 | ||
666 | loop->header = new_entry->src; | |
667 | ||
668 | /* Find the blocks and subloops that belong to the new loop, and add it to | |
669 | the appropriate place in the loop tree. */ | |
670 | new_loop = alloc_loop (); | |
671 | new_loop->header = new_entry->dest; | |
672 | new_loop->latch = latch->src; | |
673 | add_loop (new_loop, loop); | |
674 | } | |
675 | ||
676 | /* Make all the latch edges of LOOP to go to a single forwarder block -- | |
677 | a new latch of LOOP. */ | |
678 | ||
679 | static void | |
680 | merge_latch_edges (struct loop *loop) | |
681 | { | |
682 | VEC (edge, heap) *latches = get_loop_latch_edges (loop); | |
683 | edge latch, e; | |
684 | unsigned i; | |
685 | ||
686 | gcc_assert (VEC_length (edge, latches) > 0); | |
687 | ||
688 | if (VEC_length (edge, latches) == 1) | |
689 | loop->latch = VEC_index (edge, latches, 0)->src; | |
690 | else | |
691 | { | |
692 | if (dump_file) | |
693 | fprintf (dump_file, "Merged latch edges of loop %d\n", loop->num); | |
694 | ||
695 | mfb_reis_set = pointer_set_create (); | |
696 | for (i = 0; VEC_iterate (edge, latches, i, e); i++) | |
697 | pointer_set_insert (mfb_reis_set, e); | |
698 | latch = make_forwarder_block (loop->header, mfb_redirect_edges_in_set, | |
699 | NULL); | |
700 | pointer_set_destroy (mfb_reis_set); | |
701 | ||
702 | loop->header = latch->dest; | |
703 | loop->latch = latch->src; | |
704 | } | |
705 | ||
706 | VEC_free (edge, heap, latches); | |
707 | } | |
708 | ||
709 | /* LOOP may have several latch edges. Transform it into (possibly several) | |
710 | loops with single latch edge. */ | |
711 | ||
712 | static void | |
713 | disambiguate_multiple_latches (struct loop *loop) | |
714 | { | |
715 | edge e; | |
716 | ||
ea2c620c | 717 | /* We eliminate the multiple latches by splitting the header to the forwarder |
89f8f30f ZD |
718 | block F and the rest R, and redirecting the edges. There are two cases: |
719 | ||
720 | 1) If there is a latch edge E that corresponds to a subloop (we guess | |
721 | that based on profile -- if it is taken much more often than the | |
722 | remaining edges; and on trees, using the information about induction | |
723 | variables of the loops), we redirect E to R, all the remaining edges to | |
724 | F, then rescan the loops and try again for the outer loop. | |
725 | 2) If there is no such edge, we redirect all latch edges to F, and the | |
726 | entry edges to R, thus making F the single latch of the loop. */ | |
727 | ||
728 | if (dump_file) | |
729 | fprintf (dump_file, "Disambiguating loop %d with multiple latches\n", | |
730 | loop->num); | |
731 | ||
732 | /* During latch merging, we may need to redirect the entry edges to a new | |
733 | block. This would cause problems if the entry edge was the one from the | |
734 | entry block. To avoid having to handle this case specially, split | |
735 | such entry edge. */ | |
736 | e = find_edge (ENTRY_BLOCK_PTR, loop->header); | |
737 | if (e) | |
738 | split_edge (e); | |
739 | ||
740 | while (1) | |
741 | { | |
742 | e = find_subloop_latch_edge (loop); | |
743 | if (!e) | |
744 | break; | |
745 | ||
746 | form_subloop (loop, e); | |
747 | } | |
748 | ||
749 | merge_latch_edges (loop); | |
750 | } | |
751 | ||
752 | /* Split loops with multiple latch edges. */ | |
753 | ||
754 | void | |
755 | disambiguate_loops_with_multiple_latches (void) | |
756 | { | |
757 | loop_iterator li; | |
758 | struct loop *loop; | |
759 | ||
760 | FOR_EACH_LOOP (li, loop, 0) | |
761 | { | |
762 | if (!loop->latch) | |
763 | disambiguate_multiple_latches (loop); | |
764 | } | |
765 | } | |
766 | ||
da7d8304 | 767 | /* Return nonzero if basic block BB belongs to LOOP. */ |
2ecfd709 | 768 | bool |
d329e058 | 769 | flow_bb_inside_loop_p (const struct loop *loop, const basic_block bb) |
2ecfd709 ZD |
770 | { |
771 | struct loop *source_loop; | |
772 | ||
773 | if (bb == ENTRY_BLOCK_PTR || bb == EXIT_BLOCK_PTR) | |
774 | return 0; | |
775 | ||
776 | source_loop = bb->loop_father; | |
777 | return loop == source_loop || flow_loop_nested_p (loop, source_loop); | |
778 | } | |
779 | ||
89f8f30f | 780 | /* Enumeration predicate for get_loop_body_with_size. */ |
2ecfd709 | 781 | static bool |
89f8f30f | 782 | glb_enum_p (basic_block bb, void *glb_loop) |
2ecfd709 | 783 | { |
ae50c0cb | 784 | struct loop *loop = (struct loop *) glb_loop; |
89f8f30f ZD |
785 | return (bb != loop->header |
786 | && dominated_by_p (CDI_DOMINATORS, bb, loop->header)); | |
787 | } | |
788 | ||
789 | /* Gets basic blocks of a LOOP. Header is the 0-th block, rest is in dfs | |
790 | order against direction of edges from latch. Specially, if | |
791 | header != latch, latch is the 1-st block. LOOP cannot be the fake | |
792 | loop tree root, and its size must be at most MAX_SIZE. The blocks | |
793 | in the LOOP body are stored to BODY, and the size of the LOOP is | |
794 | returned. */ | |
795 | ||
796 | unsigned | |
797 | get_loop_body_with_size (const struct loop *loop, basic_block *body, | |
798 | unsigned max_size) | |
799 | { | |
800 | return dfs_enumerate_from (loop->header, 1, glb_enum_p, | |
801 | body, max_size, (void *) loop); | |
2ecfd709 ZD |
802 | } |
803 | ||
8d28e87d ZD |
804 | /* Gets basic blocks of a LOOP. Header is the 0-th block, rest is in dfs |
805 | order against direction of edges from latch. Specially, if | |
806 | header != latch, latch is the 1-st block. */ | |
89f8f30f | 807 | |
2ecfd709 | 808 | basic_block * |
d329e058 | 809 | get_loop_body (const struct loop *loop) |
2ecfd709 | 810 | { |
89f8f30f | 811 | basic_block *body, bb; |
3d436d2a | 812 | unsigned tv = 0; |
2ecfd709 | 813 | |
341c100f | 814 | gcc_assert (loop->num_nodes); |
2ecfd709 | 815 | |
89f8f30f | 816 | body = XCNEWVEC (basic_block, loop->num_nodes); |
2ecfd709 ZD |
817 | |
818 | if (loop->latch == EXIT_BLOCK_PTR) | |
819 | { | |
89f8f30f ZD |
820 | /* There may be blocks unreachable from EXIT_BLOCK, hence we need to |
821 | special-case the fake loop that contains the whole function. */ | |
24bd1a0b | 822 | gcc_assert (loop->num_nodes == (unsigned) n_basic_blocks); |
89f8f30f ZD |
823 | body[tv++] = loop->header; |
824 | body[tv++] = EXIT_BLOCK_PTR; | |
2ecfd709 | 825 | FOR_EACH_BB (bb) |
89f8f30f | 826 | body[tv++] = bb; |
2ecfd709 | 827 | } |
89f8f30f ZD |
828 | else |
829 | tv = get_loop_body_with_size (loop, body, loop->num_nodes); | |
2ecfd709 | 830 | |
341c100f | 831 | gcc_assert (tv == loop->num_nodes); |
89f8f30f | 832 | return body; |
2ecfd709 ZD |
833 | } |
834 | ||
50654f6c ZD |
835 | /* Fills dominance descendants inside LOOP of the basic block BB into |
836 | array TOVISIT from index *TV. */ | |
837 | ||
838 | static void | |
839 | fill_sons_in_loop (const struct loop *loop, basic_block bb, | |
840 | basic_block *tovisit, int *tv) | |
841 | { | |
842 | basic_block son, postpone = NULL; | |
843 | ||
844 | tovisit[(*tv)++] = bb; | |
845 | for (son = first_dom_son (CDI_DOMINATORS, bb); | |
846 | son; | |
847 | son = next_dom_son (CDI_DOMINATORS, son)) | |
848 | { | |
849 | if (!flow_bb_inside_loop_p (loop, son)) | |
850 | continue; | |
851 | ||
852 | if (dominated_by_p (CDI_DOMINATORS, loop->latch, son)) | |
853 | { | |
854 | postpone = son; | |
855 | continue; | |
856 | } | |
857 | fill_sons_in_loop (loop, son, tovisit, tv); | |
858 | } | |
859 | ||
860 | if (postpone) | |
861 | fill_sons_in_loop (loop, postpone, tovisit, tv); | |
862 | } | |
863 | ||
864 | /* Gets body of a LOOP (that must be different from the outermost loop) | |
865 | sorted by dominance relation. Additionally, if a basic block s dominates | |
866 | the latch, then only blocks dominated by s are be after it. */ | |
867 | ||
868 | basic_block * | |
869 | get_loop_body_in_dom_order (const struct loop *loop) | |
870 | { | |
871 | basic_block *tovisit; | |
872 | int tv; | |
873 | ||
341c100f | 874 | gcc_assert (loop->num_nodes); |
50654f6c | 875 | |
5ed6ace5 | 876 | tovisit = XCNEWVEC (basic_block, loop->num_nodes); |
50654f6c | 877 | |
341c100f | 878 | gcc_assert (loop->latch != EXIT_BLOCK_PTR); |
50654f6c ZD |
879 | |
880 | tv = 0; | |
881 | fill_sons_in_loop (loop, loop->header, tovisit, &tv); | |
882 | ||
341c100f | 883 | gcc_assert (tv == (int) loop->num_nodes); |
50654f6c ZD |
884 | |
885 | return tovisit; | |
886 | } | |
887 | ||
40923b20 DP |
888 | /* Get body of a LOOP in breadth first sort order. */ |
889 | ||
890 | basic_block * | |
891 | get_loop_body_in_bfs_order (const struct loop *loop) | |
892 | { | |
893 | basic_block *blocks; | |
894 | basic_block bb; | |
895 | bitmap visited; | |
896 | unsigned int i = 0; | |
897 | unsigned int vc = 1; | |
898 | ||
341c100f NS |
899 | gcc_assert (loop->num_nodes); |
900 | gcc_assert (loop->latch != EXIT_BLOCK_PTR); | |
40923b20 | 901 | |
5ed6ace5 | 902 | blocks = XCNEWVEC (basic_block, loop->num_nodes); |
8bdbfff5 | 903 | visited = BITMAP_ALLOC (NULL); |
40923b20 DP |
904 | |
905 | bb = loop->header; | |
906 | while (i < loop->num_nodes) | |
907 | { | |
908 | edge e; | |
628f6a4e | 909 | edge_iterator ei; |
c22cacf3 | 910 | |
40923b20 | 911 | if (!bitmap_bit_p (visited, bb->index)) |
c22cacf3 MS |
912 | { |
913 | /* This basic block is now visited */ | |
914 | bitmap_set_bit (visited, bb->index); | |
915 | blocks[i++] = bb; | |
916 | } | |
917 | ||
628f6a4e | 918 | FOR_EACH_EDGE (e, ei, bb->succs) |
c22cacf3 MS |
919 | { |
920 | if (flow_bb_inside_loop_p (loop, e->dest)) | |
921 | { | |
922 | if (!bitmap_bit_p (visited, e->dest->index)) | |
923 | { | |
924 | bitmap_set_bit (visited, e->dest->index); | |
925 | blocks[i++] = e->dest; | |
926 | } | |
927 | } | |
928 | } | |
929 | ||
341c100f | 930 | gcc_assert (i >= vc); |
c22cacf3 | 931 | |
40923b20 DP |
932 | bb = blocks[vc++]; |
933 | } | |
c22cacf3 | 934 | |
8bdbfff5 | 935 | BITMAP_FREE (visited); |
40923b20 DP |
936 | return blocks; |
937 | } | |
938 | ||
6270df4c ZD |
939 | /* Hash function for struct loop_exit. */ |
940 | ||
941 | static hashval_t | |
942 | loop_exit_hash (const void *ex) | |
943 | { | |
5f754896 | 944 | const struct loop_exit *const exit = (const struct loop_exit *) ex; |
6270df4c ZD |
945 | |
946 | return htab_hash_pointer (exit->e); | |
947 | } | |
948 | ||
949 | /* Equality function for struct loop_exit. Compares with edge. */ | |
950 | ||
951 | static int | |
952 | loop_exit_eq (const void *ex, const void *e) | |
953 | { | |
5f754896 | 954 | const struct loop_exit *const exit = (const struct loop_exit *) ex; |
6270df4c ZD |
955 | |
956 | return exit->e == e; | |
957 | } | |
958 | ||
959 | /* Frees the list of loop exit descriptions EX. */ | |
960 | ||
961 | static void | |
962 | loop_exit_free (void *ex) | |
963 | { | |
964 | struct loop_exit *exit = (struct loop_exit *) ex, *next; | |
965 | ||
966 | for (; exit; exit = next) | |
967 | { | |
968 | next = exit->next_e; | |
969 | ||
970 | exit->next->prev = exit->prev; | |
971 | exit->prev->next = exit->next; | |
972 | ||
9e2f83a5 | 973 | ggc_free (exit); |
6270df4c ZD |
974 | } |
975 | } | |
976 | ||
977 | /* Returns the list of records for E as an exit of a loop. */ | |
978 | ||
979 | static struct loop_exit * | |
980 | get_exit_descriptions (edge e) | |
981 | { | |
ae50c0cb TN |
982 | return (struct loop_exit *) htab_find_with_hash (current_loops->exits, e, |
983 | htab_hash_pointer (e)); | |
6270df4c ZD |
984 | } |
985 | ||
986 | /* Updates the lists of loop exits in that E appears. | |
987 | If REMOVED is true, E is being removed, and we | |
988 | just remove it from the lists of exits. | |
989 | If NEW_EDGE is true and E is not a loop exit, we | |
990 | do not try to remove it from loop exit lists. */ | |
991 | ||
992 | void | |
993 | rescan_loop_exit (edge e, bool new_edge, bool removed) | |
994 | { | |
995 | void **slot; | |
996 | struct loop_exit *exits = NULL, *exit; | |
997 | struct loop *aloop, *cloop; | |
998 | ||
999 | if ((current_loops->state & LOOPS_HAVE_RECORDED_EXITS) == 0) | |
1000 | return; | |
1001 | ||
1002 | if (!removed | |
1003 | && e->src->loop_father != NULL | |
1004 | && e->dest->loop_father != NULL | |
1005 | && !flow_bb_inside_loop_p (e->src->loop_father, e->dest)) | |
1006 | { | |
1007 | cloop = find_common_loop (e->src->loop_father, e->dest->loop_father); | |
1008 | for (aloop = e->src->loop_father; | |
1009 | aloop != cloop; | |
9ba025a2 | 1010 | aloop = loop_outer (aloop)) |
6270df4c | 1011 | { |
9e2f83a5 | 1012 | exit = GGC_NEW (struct loop_exit); |
6270df4c ZD |
1013 | exit->e = e; |
1014 | ||
9e2f83a5 ZD |
1015 | exit->next = aloop->exits->next; |
1016 | exit->prev = aloop->exits; | |
6270df4c ZD |
1017 | exit->next->prev = exit; |
1018 | exit->prev->next = exit; | |
1019 | ||
1020 | exit->next_e = exits; | |
1021 | exits = exit; | |
1022 | } | |
1023 | } | |
1024 | ||
1025 | if (!exits && new_edge) | |
1026 | return; | |
1027 | ||
1028 | slot = htab_find_slot_with_hash (current_loops->exits, e, | |
1029 | htab_hash_pointer (e), | |
1030 | exits ? INSERT : NO_INSERT); | |
1031 | if (!slot) | |
1032 | return; | |
1033 | ||
1034 | if (exits) | |
1035 | { | |
1036 | if (*slot) | |
1037 | loop_exit_free (*slot); | |
1038 | *slot = exits; | |
1039 | } | |
1040 | else | |
1041 | htab_clear_slot (current_loops->exits, slot); | |
1042 | } | |
1043 | ||
1044 | /* For each loop, record list of exit edges, and start maintaining these | |
1045 | lists. */ | |
1046 | ||
1047 | void | |
1048 | record_loop_exits (void) | |
1049 | { | |
1050 | basic_block bb; | |
1051 | edge_iterator ei; | |
1052 | edge e; | |
1053 | ||
4839cb59 ZD |
1054 | if (!current_loops) |
1055 | return; | |
1056 | ||
6270df4c ZD |
1057 | if (current_loops->state & LOOPS_HAVE_RECORDED_EXITS) |
1058 | return; | |
1059 | current_loops->state |= LOOPS_HAVE_RECORDED_EXITS; | |
1060 | ||
1061 | gcc_assert (current_loops->exits == NULL); | |
9e2f83a5 ZD |
1062 | current_loops->exits = htab_create_alloc (2 * number_of_loops (), |
1063 | loop_exit_hash, | |
1064 | loop_exit_eq, | |
1065 | loop_exit_free, | |
1066 | ggc_calloc, ggc_free); | |
6270df4c ZD |
1067 | |
1068 | FOR_EACH_BB (bb) | |
1069 | { | |
1070 | FOR_EACH_EDGE (e, ei, bb->succs) | |
1071 | { | |
1072 | rescan_loop_exit (e, true, false); | |
1073 | } | |
1074 | } | |
1075 | } | |
1076 | ||
1077 | /* Dumps information about the exit in *SLOT to FILE. | |
1078 | Callback for htab_traverse. */ | |
1079 | ||
1080 | static int | |
1081 | dump_recorded_exit (void **slot, void *file) | |
1082 | { | |
ae50c0cb | 1083 | struct loop_exit *exit = (struct loop_exit *) *slot; |
6270df4c ZD |
1084 | unsigned n = 0; |
1085 | edge e = exit->e; | |
1086 | ||
1087 | for (; exit != NULL; exit = exit->next_e) | |
1088 | n++; | |
1089 | ||
ae50c0cb | 1090 | fprintf ((FILE*) file, "Edge %d->%d exits %u loops\n", |
6270df4c ZD |
1091 | e->src->index, e->dest->index, n); |
1092 | ||
1093 | return 1; | |
1094 | } | |
1095 | ||
1096 | /* Dumps the recorded exits of loops to FILE. */ | |
1097 | ||
1098 | extern void dump_recorded_exits (FILE *); | |
1099 | void | |
1100 | dump_recorded_exits (FILE *file) | |
1101 | { | |
1102 | if (!current_loops->exits) | |
1103 | return; | |
1104 | htab_traverse (current_loops->exits, dump_recorded_exit, file); | |
1105 | } | |
1106 | ||
1107 | /* Releases lists of loop exits. */ | |
1108 | ||
1109 | void | |
1110 | release_recorded_exits (void) | |
1111 | { | |
1112 | gcc_assert (current_loops->state & LOOPS_HAVE_RECORDED_EXITS); | |
1113 | htab_delete (current_loops->exits); | |
1114 | current_loops->exits = NULL; | |
1115 | current_loops->state &= ~LOOPS_HAVE_RECORDED_EXITS; | |
1116 | } | |
1117 | ||
ca83d385 ZD |
1118 | /* Returns the list of the exit edges of a LOOP. */ |
1119 | ||
1120 | VEC (edge, heap) * | |
1121 | get_loop_exit_edges (const struct loop *loop) | |
35b07080 | 1122 | { |
ca83d385 ZD |
1123 | VEC (edge, heap) *edges = NULL; |
1124 | edge e; | |
1125 | unsigned i; | |
1126 | basic_block *body; | |
628f6a4e | 1127 | edge_iterator ei; |
6270df4c | 1128 | struct loop_exit *exit; |
35b07080 | 1129 | |
341c100f | 1130 | gcc_assert (loop->latch != EXIT_BLOCK_PTR); |
35b07080 | 1131 | |
6270df4c ZD |
1132 | /* If we maintain the lists of exits, use them. Otherwise we must |
1133 | scan the body of the loop. */ | |
1134 | if (current_loops->state & LOOPS_HAVE_RECORDED_EXITS) | |
1135 | { | |
9e2f83a5 | 1136 | for (exit = loop->exits->next; exit->e; exit = exit->next) |
6270df4c ZD |
1137 | VEC_safe_push (edge, heap, edges, exit->e); |
1138 | } | |
1139 | else | |
1140 | { | |
1141 | body = get_loop_body (loop); | |
1142 | for (i = 0; i < loop->num_nodes; i++) | |
1143 | FOR_EACH_EDGE (e, ei, body[i]->succs) | |
1144 | { | |
1145 | if (!flow_bb_inside_loop_p (loop, e->dest)) | |
1146 | VEC_safe_push (edge, heap, edges, e); | |
1147 | } | |
1148 | free (body); | |
1149 | } | |
35b07080 ZD |
1150 | |
1151 | return edges; | |
1152 | } | |
1153 | ||
50654f6c ZD |
1154 | /* Counts the number of conditional branches inside LOOP. */ |
1155 | ||
1156 | unsigned | |
1157 | num_loop_branches (const struct loop *loop) | |
1158 | { | |
1159 | unsigned i, n; | |
1160 | basic_block * body; | |
1161 | ||
341c100f | 1162 | gcc_assert (loop->latch != EXIT_BLOCK_PTR); |
50654f6c ZD |
1163 | |
1164 | body = get_loop_body (loop); | |
1165 | n = 0; | |
1166 | for (i = 0; i < loop->num_nodes; i++) | |
628f6a4e | 1167 | if (EDGE_COUNT (body[i]->succs) >= 2) |
50654f6c ZD |
1168 | n++; |
1169 | free (body); | |
1170 | ||
1171 | return n; | |
1172 | } | |
1173 | ||
2ecfd709 ZD |
1174 | /* Adds basic block BB to LOOP. */ |
1175 | void | |
d329e058 AJ |
1176 | add_bb_to_loop (basic_block bb, struct loop *loop) |
1177 | { | |
9ba025a2 ZD |
1178 | unsigned i; |
1179 | loop_p ploop; | |
6270df4c ZD |
1180 | edge_iterator ei; |
1181 | edge e; | |
1182 | ||
1183 | gcc_assert (bb->loop_father == NULL); | |
1184 | bb->loop_father = loop; | |
9ba025a2 | 1185 | bb->loop_depth = loop_depth (loop); |
6270df4c | 1186 | loop->num_nodes++; |
9ba025a2 ZD |
1187 | for (i = 0; VEC_iterate (loop_p, loop->superloops, i, ploop); i++) |
1188 | ploop->num_nodes++; | |
6270df4c ZD |
1189 | |
1190 | FOR_EACH_EDGE (e, ei, bb->succs) | |
1191 | { | |
1192 | rescan_loop_exit (e, true, false); | |
1193 | } | |
1194 | FOR_EACH_EDGE (e, ei, bb->preds) | |
1195 | { | |
1196 | rescan_loop_exit (e, true, false); | |
1197 | } | |
598ec7bd | 1198 | } |
2ecfd709 ZD |
1199 | |
1200 | /* Remove basic block BB from loops. */ | |
1201 | void | |
d329e058 AJ |
1202 | remove_bb_from_loops (basic_block bb) |
1203 | { | |
6270df4c ZD |
1204 | int i; |
1205 | struct loop *loop = bb->loop_father; | |
9ba025a2 | 1206 | loop_p ploop; |
6270df4c ZD |
1207 | edge_iterator ei; |
1208 | edge e; | |
1209 | ||
1210 | gcc_assert (loop != NULL); | |
1211 | loop->num_nodes--; | |
9ba025a2 ZD |
1212 | for (i = 0; VEC_iterate (loop_p, loop->superloops, i, ploop); i++) |
1213 | ploop->num_nodes--; | |
6270df4c ZD |
1214 | bb->loop_father = NULL; |
1215 | bb->loop_depth = 0; | |
1216 | ||
1217 | FOR_EACH_EDGE (e, ei, bb->succs) | |
1218 | { | |
1219 | rescan_loop_exit (e, false, true); | |
1220 | } | |
1221 | FOR_EACH_EDGE (e, ei, bb->preds) | |
1222 | { | |
1223 | rescan_loop_exit (e, false, true); | |
1224 | } | |
a310245f | 1225 | } |
2ecfd709 ZD |
1226 | |
1227 | /* Finds nearest common ancestor in loop tree for given loops. */ | |
1228 | struct loop * | |
d329e058 | 1229 | find_common_loop (struct loop *loop_s, struct loop *loop_d) |
2ecfd709 | 1230 | { |
9ba025a2 ZD |
1231 | unsigned sdepth, ddepth; |
1232 | ||
2ecfd709 ZD |
1233 | if (!loop_s) return loop_d; |
1234 | if (!loop_d) return loop_s; | |
d329e058 | 1235 | |
9ba025a2 ZD |
1236 | sdepth = loop_depth (loop_s); |
1237 | ddepth = loop_depth (loop_d); | |
1238 | ||
1239 | if (sdepth < ddepth) | |
1240 | loop_d = VEC_index (loop_p, loop_d->superloops, sdepth); | |
1241 | else if (sdepth > ddepth) | |
1242 | loop_s = VEC_index (loop_p, loop_s->superloops, ddepth); | |
2ecfd709 ZD |
1243 | |
1244 | while (loop_s != loop_d) | |
1245 | { | |
9ba025a2 ZD |
1246 | loop_s = loop_outer (loop_s); |
1247 | loop_d = loop_outer (loop_d); | |
2ecfd709 ZD |
1248 | } |
1249 | return loop_s; | |
1250 | } | |
1251 | ||
42fd6772 ZD |
1252 | /* Removes LOOP from structures and frees its data. */ |
1253 | ||
1254 | void | |
1255 | delete_loop (struct loop *loop) | |
1256 | { | |
1257 | /* Remove the loop from structure. */ | |
1258 | flow_loop_tree_node_remove (loop); | |
1259 | ||
1260 | /* Remove loop from loops array. */ | |
1261 | VEC_replace (loop_p, current_loops->larray, loop->num, NULL); | |
1262 | ||
1263 | /* Free loop data. */ | |
1264 | flow_loop_free (loop); | |
1265 | } | |
1266 | ||
3d436d2a | 1267 | /* Cancels the LOOP; it must be innermost one. */ |
b00bf166 KH |
1268 | |
1269 | static void | |
d73be268 | 1270 | cancel_loop (struct loop *loop) |
3d436d2a ZD |
1271 | { |
1272 | basic_block *bbs; | |
1273 | unsigned i; | |
9ba025a2 | 1274 | struct loop *outer = loop_outer (loop); |
3d436d2a | 1275 | |
341c100f | 1276 | gcc_assert (!loop->inner); |
3d436d2a ZD |
1277 | |
1278 | /* Move blocks up one level (they should be removed as soon as possible). */ | |
1279 | bbs = get_loop_body (loop); | |
1280 | for (i = 0; i < loop->num_nodes; i++) | |
9ba025a2 | 1281 | bbs[i]->loop_father = outer; |
3d436d2a | 1282 | |
42fd6772 | 1283 | delete_loop (loop); |
3d436d2a ZD |
1284 | } |
1285 | ||
1286 | /* Cancels LOOP and all its subloops. */ | |
1287 | void | |
d73be268 | 1288 | cancel_loop_tree (struct loop *loop) |
3d436d2a ZD |
1289 | { |
1290 | while (loop->inner) | |
d73be268 ZD |
1291 | cancel_loop_tree (loop->inner); |
1292 | cancel_loop (loop); | |
3d436d2a ZD |
1293 | } |
1294 | ||
d73be268 | 1295 | /* Checks that information about loops is correct |
e0bb17a8 | 1296 | -- sizes of loops are all right |
2ecfd709 ZD |
1297 | -- results of get_loop_body really belong to the loop |
1298 | -- loop header have just single entry edge and single latch edge | |
1299 | -- loop latches have only single successor that is header of their loop | |
3d436d2a | 1300 | -- irreducible loops are correctly marked |
2ecfd709 ZD |
1301 | */ |
1302 | void | |
d73be268 | 1303 | verify_loop_structure (void) |
2ecfd709 | 1304 | { |
3d436d2a ZD |
1305 | unsigned *sizes, i, j; |
1306 | sbitmap irreds; | |
2ecfd709 ZD |
1307 | basic_block *bbs, bb; |
1308 | struct loop *loop; | |
1309 | int err = 0; | |
35b07080 | 1310 | edge e; |
42fd6772 ZD |
1311 | unsigned num = number_of_loops (); |
1312 | loop_iterator li; | |
6270df4c | 1313 | struct loop_exit *exit, *mexit; |
2ecfd709 ZD |
1314 | |
1315 | /* Check sizes. */ | |
42fd6772 | 1316 | sizes = XCNEWVEC (unsigned, num); |
2ecfd709 ZD |
1317 | sizes[0] = 2; |
1318 | ||
1319 | FOR_EACH_BB (bb) | |
9ba025a2 | 1320 | for (loop = bb->loop_father; loop; loop = loop_outer (loop)) |
2ecfd709 ZD |
1321 | sizes[loop->num]++; |
1322 | ||
42fd6772 | 1323 | FOR_EACH_LOOP (li, loop, LI_INCLUDE_ROOT) |
2ecfd709 | 1324 | { |
42fd6772 | 1325 | i = loop->num; |
2ecfd709 | 1326 | |
42fd6772 | 1327 | if (loop->num_nodes != sizes[i]) |
2ecfd709 | 1328 | { |
ab532386 | 1329 | error ("size of loop %d should be %d, not %d", |
42fd6772 | 1330 | i, sizes[i], loop->num_nodes); |
2ecfd709 ZD |
1331 | err = 1; |
1332 | } | |
1333 | } | |
1334 | ||
2ecfd709 | 1335 | /* Check get_loop_body. */ |
42fd6772 | 1336 | FOR_EACH_LOOP (li, loop, 0) |
2ecfd709 | 1337 | { |
2ecfd709 ZD |
1338 | bbs = get_loop_body (loop); |
1339 | ||
1340 | for (j = 0; j < loop->num_nodes; j++) | |
1341 | if (!flow_bb_inside_loop_p (loop, bbs[j])) | |
1342 | { | |
ab532386 | 1343 | error ("bb %d do not belong to loop %d", |
42fd6772 | 1344 | bbs[j]->index, loop->num); |
2ecfd709 ZD |
1345 | err = 1; |
1346 | } | |
1347 | free (bbs); | |
1348 | } | |
1349 | ||
1350 | /* Check headers and latches. */ | |
42fd6772 | 1351 | FOR_EACH_LOOP (li, loop, 0) |
2ecfd709 | 1352 | { |
42fd6772 | 1353 | i = loop->num; |
2ecfd709 | 1354 | |
d73be268 | 1355 | if ((current_loops->state & LOOPS_HAVE_PREHEADERS) |
628f6a4e | 1356 | && EDGE_COUNT (loop->header->preds) != 2) |
2ecfd709 | 1357 | { |
ab532386 | 1358 | error ("loop %d's header does not have exactly 2 entries", i); |
2ecfd709 ZD |
1359 | err = 1; |
1360 | } | |
d73be268 | 1361 | if (current_loops->state & LOOPS_HAVE_SIMPLE_LATCHES) |
2ecfd709 | 1362 | { |
c5cbcccf | 1363 | if (!single_succ_p (loop->latch)) |
2ecfd709 | 1364 | { |
ab532386 | 1365 | error ("loop %d's latch does not have exactly 1 successor", i); |
2ecfd709 ZD |
1366 | err = 1; |
1367 | } | |
c5cbcccf | 1368 | if (single_succ (loop->latch) != loop->header) |
2ecfd709 | 1369 | { |
ab532386 | 1370 | error ("loop %d's latch does not have header as successor", i); |
2ecfd709 ZD |
1371 | err = 1; |
1372 | } | |
1373 | if (loop->latch->loop_father != loop) | |
1374 | { | |
ab532386 | 1375 | error ("loop %d's latch does not belong directly to it", i); |
2ecfd709 ZD |
1376 | err = 1; |
1377 | } | |
1378 | } | |
1379 | if (loop->header->loop_father != loop) | |
1380 | { | |
ab532386 | 1381 | error ("loop %d's header does not belong directly to it", i); |
2ecfd709 ZD |
1382 | err = 1; |
1383 | } | |
d73be268 | 1384 | if ((current_loops->state & LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS) |
35b07080 ZD |
1385 | && (loop_latch_edge (loop)->flags & EDGE_IRREDUCIBLE_LOOP)) |
1386 | { | |
ab532386 | 1387 | error ("loop %d's latch is marked as part of irreducible region", i); |
35b07080 ZD |
1388 | err = 1; |
1389 | } | |
2ecfd709 ZD |
1390 | } |
1391 | ||
3d436d2a | 1392 | /* Check irreducible loops. */ |
d73be268 | 1393 | if (current_loops->state & LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS) |
3d436d2a ZD |
1394 | { |
1395 | /* Record old info. */ | |
1396 | irreds = sbitmap_alloc (last_basic_block); | |
1397 | FOR_EACH_BB (bb) | |
35b07080 | 1398 | { |
628f6a4e | 1399 | edge_iterator ei; |
35b07080 ZD |
1400 | if (bb->flags & BB_IRREDUCIBLE_LOOP) |
1401 | SET_BIT (irreds, bb->index); | |
1402 | else | |
1403 | RESET_BIT (irreds, bb->index); | |
628f6a4e | 1404 | FOR_EACH_EDGE (e, ei, bb->succs) |
35b07080 | 1405 | if (e->flags & EDGE_IRREDUCIBLE_LOOP) |
d329e058 | 1406 | e->flags |= EDGE_ALL_FLAGS + 1; |
35b07080 | 1407 | } |
3d436d2a ZD |
1408 | |
1409 | /* Recount it. */ | |
d73be268 | 1410 | mark_irreducible_loops (); |
3d436d2a ZD |
1411 | |
1412 | /* Compare. */ | |
1413 | FOR_EACH_BB (bb) | |
1414 | { | |
628f6a4e BE |
1415 | edge_iterator ei; |
1416 | ||
3d436d2a ZD |
1417 | if ((bb->flags & BB_IRREDUCIBLE_LOOP) |
1418 | && !TEST_BIT (irreds, bb->index)) | |
1419 | { | |
ab532386 | 1420 | error ("basic block %d should be marked irreducible", bb->index); |
3d436d2a ZD |
1421 | err = 1; |
1422 | } | |
1423 | else if (!(bb->flags & BB_IRREDUCIBLE_LOOP) | |
1424 | && TEST_BIT (irreds, bb->index)) | |
1425 | { | |
ab532386 | 1426 | error ("basic block %d should not be marked irreducible", bb->index); |
3d436d2a ZD |
1427 | err = 1; |
1428 | } | |
628f6a4e | 1429 | FOR_EACH_EDGE (e, ei, bb->succs) |
35b07080 ZD |
1430 | { |
1431 | if ((e->flags & EDGE_IRREDUCIBLE_LOOP) | |
1432 | && !(e->flags & (EDGE_ALL_FLAGS + 1))) | |
1433 | { | |
ab532386 | 1434 | error ("edge from %d to %d should be marked irreducible", |
35b07080 ZD |
1435 | e->src->index, e->dest->index); |
1436 | err = 1; | |
1437 | } | |
1438 | else if (!(e->flags & EDGE_IRREDUCIBLE_LOOP) | |
1439 | && (e->flags & (EDGE_ALL_FLAGS + 1))) | |
1440 | { | |
ab532386 | 1441 | error ("edge from %d to %d should not be marked irreducible", |
35b07080 ZD |
1442 | e->src->index, e->dest->index); |
1443 | err = 1; | |
1444 | } | |
1445 | e->flags &= ~(EDGE_ALL_FLAGS + 1); | |
1446 | } | |
3d436d2a ZD |
1447 | } |
1448 | free (irreds); | |
1449 | } | |
1450 | ||
6270df4c ZD |
1451 | /* Check the recorded loop exits. */ |
1452 | FOR_EACH_LOOP (li, loop, 0) | |
82b85a85 | 1453 | { |
9e2f83a5 | 1454 | if (!loop->exits || loop->exits->e != NULL) |
6270df4c ZD |
1455 | { |
1456 | error ("corrupted head of the exits list of loop %d", | |
1457 | loop->num); | |
1458 | err = 1; | |
1459 | } | |
1460 | else | |
1461 | { | |
1462 | /* Check that the list forms a cycle, and all elements except | |
1463 | for the head are nonnull. */ | |
9e2f83a5 | 1464 | for (mexit = loop->exits, exit = mexit->next, i = 0; |
6270df4c ZD |
1465 | exit->e && exit != mexit; |
1466 | exit = exit->next) | |
1467 | { | |
1468 | if (i++ & 1) | |
1469 | mexit = mexit->next; | |
1470 | } | |
1471 | ||
9e2f83a5 | 1472 | if (exit != loop->exits) |
6270df4c ZD |
1473 | { |
1474 | error ("corrupted exits list of loop %d", loop->num); | |
1475 | err = 1; | |
1476 | } | |
1477 | } | |
1478 | ||
1479 | if ((current_loops->state & LOOPS_HAVE_RECORDED_EXITS) == 0) | |
1480 | { | |
9e2f83a5 | 1481 | if (loop->exits->next != loop->exits) |
6270df4c ZD |
1482 | { |
1483 | error ("nonempty exits list of loop %d, but exits are not recorded", | |
1484 | loop->num); | |
1485 | err = 1; | |
1486 | } | |
1487 | } | |
1488 | } | |
1489 | ||
1490 | if (current_loops->state & LOOPS_HAVE_RECORDED_EXITS) | |
1491 | { | |
1492 | unsigned n_exits = 0, eloops; | |
1493 | ||
42fd6772 | 1494 | memset (sizes, 0, sizeof (unsigned) * num); |
82b85a85 ZD |
1495 | FOR_EACH_BB (bb) |
1496 | { | |
628f6a4e | 1497 | edge_iterator ei; |
d73be268 | 1498 | if (bb->loop_father == current_loops->tree_root) |
82b85a85 | 1499 | continue; |
628f6a4e | 1500 | FOR_EACH_EDGE (e, ei, bb->succs) |
82b85a85 | 1501 | { |
82b85a85 ZD |
1502 | if (flow_bb_inside_loop_p (bb->loop_father, e->dest)) |
1503 | continue; | |
1504 | ||
6270df4c ZD |
1505 | n_exits++; |
1506 | exit = get_exit_descriptions (e); | |
1507 | if (!exit) | |
1508 | { | |
1509 | error ("Exit %d->%d not recorded", | |
1510 | e->src->index, e->dest->index); | |
1511 | err = 1; | |
1512 | } | |
1513 | eloops = 0; | |
1514 | for (; exit; exit = exit->next_e) | |
1515 | eloops++; | |
1516 | ||
82b85a85 ZD |
1517 | for (loop = bb->loop_father; |
1518 | loop != e->dest->loop_father; | |
9ba025a2 | 1519 | loop = loop_outer (loop)) |
82b85a85 | 1520 | { |
6270df4c | 1521 | eloops--; |
82b85a85 | 1522 | sizes[loop->num]++; |
6270df4c ZD |
1523 | } |
1524 | ||
1525 | if (eloops != 0) | |
1526 | { | |
1527 | error ("Wrong list of exited loops for edge %d->%d", | |
1528 | e->src->index, e->dest->index); | |
1529 | err = 1; | |
82b85a85 ZD |
1530 | } |
1531 | } | |
1532 | } | |
1533 | ||
6270df4c | 1534 | if (n_exits != htab_elements (current_loops->exits)) |
82b85a85 | 1535 | { |
6270df4c ZD |
1536 | error ("Too many loop exits recorded"); |
1537 | err = 1; | |
1538 | } | |
82b85a85 | 1539 | |
6270df4c ZD |
1540 | FOR_EACH_LOOP (li, loop, 0) |
1541 | { | |
1542 | eloops = 0; | |
9e2f83a5 | 1543 | for (exit = loop->exits->next; exit->e; exit = exit->next) |
6270df4c ZD |
1544 | eloops++; |
1545 | if (eloops != sizes[loop->num]) | |
82b85a85 | 1546 | { |
6270df4c ZD |
1547 | error ("%d exits recorded for loop %d (having %d exits)", |
1548 | eloops, loop->num, sizes[loop->num]); | |
82b85a85 ZD |
1549 | err = 1; |
1550 | } | |
1551 | } | |
1552 | } | |
1553 | ||
341c100f | 1554 | gcc_assert (!err); |
82b85a85 ZD |
1555 | |
1556 | free (sizes); | |
2ecfd709 ZD |
1557 | } |
1558 | ||
1559 | /* Returns latch edge of LOOP. */ | |
1560 | edge | |
d329e058 | 1561 | loop_latch_edge (const struct loop *loop) |
2ecfd709 | 1562 | { |
9ff3d2de | 1563 | return find_edge (loop->latch, loop->header); |
402209ff | 1564 | } |
2ecfd709 ZD |
1565 | |
1566 | /* Returns preheader edge of LOOP. */ | |
1567 | edge | |
d329e058 | 1568 | loop_preheader_edge (const struct loop *loop) |
2ecfd709 ZD |
1569 | { |
1570 | edge e; | |
628f6a4e | 1571 | edge_iterator ei; |
2ecfd709 | 1572 | |
c7b852c8 ZD |
1573 | gcc_assert ((current_loops->state & LOOPS_HAVE_PREHEADERS) != 0); |
1574 | ||
628f6a4e BE |
1575 | FOR_EACH_EDGE (e, ei, loop->header->preds) |
1576 | if (e->src != loop->latch) | |
1577 | break; | |
2ecfd709 ZD |
1578 | |
1579 | return e; | |
1580 | } | |
70388d94 ZD |
1581 | |
1582 | /* Returns true if E is an exit of LOOP. */ | |
1583 | ||
1584 | bool | |
1585 | loop_exit_edge_p (const struct loop *loop, edge e) | |
1586 | { | |
1587 | return (flow_bb_inside_loop_p (loop, e->src) | |
1588 | && !flow_bb_inside_loop_p (loop, e->dest)); | |
1589 | } | |
ac8f6c69 ZD |
1590 | |
1591 | /* Returns the single exit edge of LOOP, or NULL if LOOP has either no exit | |
6270df4c ZD |
1592 | or more than one exit. If loops do not have the exits recorded, NULL |
1593 | is returned always. */ | |
ac8f6c69 ZD |
1594 | |
1595 | edge | |
1596 | single_exit (const struct loop *loop) | |
1597 | { | |
9e2f83a5 | 1598 | struct loop_exit *exit = loop->exits->next; |
ac8f6c69 | 1599 | |
6270df4c ZD |
1600 | if ((current_loops->state & LOOPS_HAVE_RECORDED_EXITS) == 0) |
1601 | return NULL; | |
ac8f6c69 | 1602 | |
9e2f83a5 | 1603 | if (exit->e && exit->next == loop->exits) |
6270df4c ZD |
1604 | return exit->e; |
1605 | else | |
1606 | return NULL; | |
ac8f6c69 | 1607 | } |