1 /* Control flow graph analysis code for GNU compiler.
2 Copyright (C) 1987-2018 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
9 version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
19
20 /* This file contains various simple utilities to analyze the CFG. */
21
22 #include "config.h"
23 #include "system.h"
24 #include "coretypes.h"
25 #include "backend.h"
26 #include "cfghooks.h"
27 #include "timevar.h"
28 #include "cfganal.h"
29 #include "cfgloop.h"
30
31 namespace {
32 /* Store the data structures necessary for depth-first search. */
33 class depth_first_search
34 {
35 public:
36 depth_first_search ();
37
38 basic_block execute (basic_block);
39 void add_bb (basic_block);
40
41 private:
42 /* stack for backtracking during the algorithm */
43 auto_vec<basic_block, 20> m_stack;
44
45 /* record of basic blocks already seen by depth-first search */
46 auto_sbitmap m_visited_blocks;
47 };
48 }
49
50 /* Mark the back edges in DFS traversal.
51 Return nonzero if a loop (natural or otherwise) is present.
52 Inspired by Depth_First_Search_PP described in:
53
54 Advanced Compiler Design and Implementation
55 Steven Muchnick
56 Morgan Kaufmann, 1997
57
58 and heavily borrowed from pre_and_rev_post_order_compute. */
59
60 bool
mark_dfs_back_edges(void)61 mark_dfs_back_edges (void)
62 {
63 int *pre;
64 int *post;
65 int prenum = 1;
66 int postnum = 1;
67 bool found = false;
68
69 /* Allocate the preorder and postorder number arrays. */
70 pre = XCNEWVEC (int, last_basic_block_for_fn (cfun));
71 post = XCNEWVEC (int, last_basic_block_for_fn (cfun));
72
73 /* Allocate stack for back-tracking up CFG. */
74 auto_vec<edge_iterator, 20> stack (n_basic_blocks_for_fn (cfun) + 1);
75
76 /* Allocate bitmap to track nodes that have been visited. */
77 auto_sbitmap visited (last_basic_block_for_fn (cfun));
78
79 /* None of the nodes in the CFG have been visited yet. */
80 bitmap_clear (visited);
81
82 /* Push the first edge on to the stack. */
83 stack.quick_push (ei_start (ENTRY_BLOCK_PTR_FOR_FN (cfun)->succs));
84
85 while (!stack.is_empty ())
86 {
87 basic_block src;
88 basic_block dest;
89
90 /* Look at the edge on the top of the stack. */
91 edge_iterator ei = stack.last ();
92 src = ei_edge (ei)->src;
93 dest = ei_edge (ei)->dest;
94 ei_edge (ei)->flags &= ~EDGE_DFS_BACK;
95
96 /* Check if the edge destination has been visited yet. */
97 if (dest != EXIT_BLOCK_PTR_FOR_FN (cfun) && ! bitmap_bit_p (visited,
98 dest->index))
99 {
100 /* Mark that we have visited the destination. */
101 bitmap_set_bit (visited, dest->index);
102
103 pre[dest->index] = prenum++;
104 if (EDGE_COUNT (dest->succs) > 0)
105 {
106 /* Since the DEST node has been visited for the first
107 time, check its successors. */
108 stack.quick_push (ei_start (dest->succs));
109 }
110 else
111 post[dest->index] = postnum++;
112 }
113 else
114 {
115 if (dest != EXIT_BLOCK_PTR_FOR_FN (cfun)
116 && src != ENTRY_BLOCK_PTR_FOR_FN (cfun)
117 && pre[src->index] >= pre[dest->index]
118 && post[dest->index] == 0)
119 ei_edge (ei)->flags |= EDGE_DFS_BACK, found = true;
120
121 if (ei_one_before_end_p (ei)
122 && src != ENTRY_BLOCK_PTR_FOR_FN (cfun))
123 post[src->index] = postnum++;
124
125 if (!ei_one_before_end_p (ei))
126 ei_next (&stack.last ());
127 else
128 stack.pop ();
129 }
130 }
131
132 free (pre);
133 free (post);
134
135 return found;
136 }
137
138 /* Find unreachable blocks. An unreachable block will have 0 in
139 the reachable bit in block->flags. A nonzero value indicates the
140 block is reachable. */
141
142 void
find_unreachable_blocks(void)143 find_unreachable_blocks (void)
144 {
145 edge e;
146 edge_iterator ei;
147 basic_block *tos, *worklist, bb;
148
149 tos = worklist = XNEWVEC (basic_block, n_basic_blocks_for_fn (cfun));
150
151 /* Clear all the reachability flags. */
152
153 FOR_EACH_BB_FN (bb, cfun)
154 bb->flags &= ~BB_REACHABLE;
155
156 /* Add our starting points to the worklist. Almost always there will
157 be only one. It isn't inconceivable that we might one day directly
158 support Fortran alternate entry points. */
159
160 FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR_FOR_FN (cfun)->succs)
161 {
162 *tos++ = e->dest;
163
164 /* Mark the block reachable. */
165 e->dest->flags |= BB_REACHABLE;
166 }
167
168 /* Iterate: find everything reachable from what we've already seen. */
169
170 while (tos != worklist)
171 {
172 basic_block b = *--tos;
173
174 FOR_EACH_EDGE (e, ei, b->succs)
175 {
176 basic_block dest = e->dest;
177
178 if (!(dest->flags & BB_REACHABLE))
179 {
180 *tos++ = dest;
181 dest->flags |= BB_REACHABLE;
182 }
183 }
184 }
185
186 free (worklist);
187 }
188
189 /* Verify that there are no unreachable blocks in the current function. */
190
191 void
verify_no_unreachable_blocks(void)192 verify_no_unreachable_blocks (void)
193 {
194 find_unreachable_blocks ();
195
196 basic_block bb;
197 FOR_EACH_BB_FN (bb, cfun)
198 gcc_assert ((bb->flags & BB_REACHABLE) != 0);
199 }
200
201
202 /* Functions to access an edge list with a vector representation.
203 Enough data is kept such that given an index number, the
204 pred and succ that edge represents can be determined, or
205 given a pred and a succ, its index number can be returned.
206 This allows algorithms which consume a lot of memory to
207 represent the normally full matrix of edge (pred,succ) with a
208 single indexed vector, edge (EDGE_INDEX (pred, succ)), with no
209 wasted space in the client code due to sparse flow graphs. */
210
211 /* This functions initializes the edge list. Basically the entire
212 flowgraph is processed, and all edges are assigned a number,
213 and the data structure is filled in. */
214
215 struct edge_list *
create_edge_list(void)216 create_edge_list (void)
217 {
218 struct edge_list *elist;
219 edge e;
220 int num_edges;
221 basic_block bb;
222 edge_iterator ei;
223
224 /* Determine the number of edges in the flow graph by counting successor
225 edges on each basic block. */
226 num_edges = 0;
227 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun),
228 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb)
229 {
230 num_edges += EDGE_COUNT (bb->succs);
231 }
232
233 elist = XNEW (struct edge_list);
234 elist->num_edges = num_edges;
235 elist->index_to_edge = XNEWVEC (edge, num_edges);
236
237 num_edges = 0;
238
239 /* Follow successors of blocks, and register these edges. */
240 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun),
241 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb)
242 FOR_EACH_EDGE (e, ei, bb->succs)
243 elist->index_to_edge[num_edges++] = e;
244
245 return elist;
246 }
247
248 /* This function free's memory associated with an edge list. */
249
250 void
free_edge_list(struct edge_list * elist)251 free_edge_list (struct edge_list *elist)
252 {
253 if (elist)
254 {
255 free (elist->index_to_edge);
256 free (elist);
257 }
258 }
259
260 /* This function provides debug output showing an edge list. */
261
262 DEBUG_FUNCTION void
print_edge_list(FILE * f,struct edge_list * elist)263 print_edge_list (FILE *f, struct edge_list *elist)
264 {
265 int x;
266
267 fprintf (f, "Compressed edge list, %d BBs + entry & exit, and %d edges\n",
268 n_basic_blocks_for_fn (cfun), elist->num_edges);
269
270 for (x = 0; x < elist->num_edges; x++)
271 {
272 fprintf (f, " %-4d - edge(", x);
273 if (INDEX_EDGE_PRED_BB (elist, x) == ENTRY_BLOCK_PTR_FOR_FN (cfun))
274 fprintf (f, "entry,");
275 else
276 fprintf (f, "%d,", INDEX_EDGE_PRED_BB (elist, x)->index);
277
278 if (INDEX_EDGE_SUCC_BB (elist, x) == EXIT_BLOCK_PTR_FOR_FN (cfun))
279 fprintf (f, "exit)\n");
280 else
281 fprintf (f, "%d)\n", INDEX_EDGE_SUCC_BB (elist, x)->index);
282 }
283 }
284
285 /* This function provides an internal consistency check of an edge list,
286 verifying that all edges are present, and that there are no
287 extra edges. */
288
289 DEBUG_FUNCTION void
verify_edge_list(FILE * f,struct edge_list * elist)290 verify_edge_list (FILE *f, struct edge_list *elist)
291 {
292 int pred, succ, index;
293 edge e;
294 basic_block bb, p, s;
295 edge_iterator ei;
296
297 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun),
298 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb)
299 {
300 FOR_EACH_EDGE (e, ei, bb->succs)
301 {
302 pred = e->src->index;
303 succ = e->dest->index;
304 index = EDGE_INDEX (elist, e->src, e->dest);
305 if (index == EDGE_INDEX_NO_EDGE)
306 {
307 fprintf (f, "*p* No index for edge from %d to %d\n", pred, succ);
308 continue;
309 }
310
311 if (INDEX_EDGE_PRED_BB (elist, index)->index != pred)
312 fprintf (f, "*p* Pred for index %d should be %d not %d\n",
313 index, pred, INDEX_EDGE_PRED_BB (elist, index)->index);
314 if (INDEX_EDGE_SUCC_BB (elist, index)->index != succ)
315 fprintf (f, "*p* Succ for index %d should be %d not %d\n",
316 index, succ, INDEX_EDGE_SUCC_BB (elist, index)->index);
317 }
318 }
319
320 /* We've verified that all the edges are in the list, now lets make sure
321 there are no spurious edges in the list. This is an expensive check! */
322
323 FOR_BB_BETWEEN (p, ENTRY_BLOCK_PTR_FOR_FN (cfun),
324 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb)
325 FOR_BB_BETWEEN (s, ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb, NULL, next_bb)
326 {
327 int found_edge = 0;
328
329 FOR_EACH_EDGE (e, ei, p->succs)
330 if (e->dest == s)
331 {
332 found_edge = 1;
333 break;
334 }
335
336 FOR_EACH_EDGE (e, ei, s->preds)
337 if (e->src == p)
338 {
339 found_edge = 1;
340 break;
341 }
342
343 if (EDGE_INDEX (elist, p, s)
344 == EDGE_INDEX_NO_EDGE && found_edge != 0)
345 fprintf (f, "*** Edge (%d, %d) appears to not have an index\n",
346 p->index, s->index);
347 if (EDGE_INDEX (elist, p, s)
348 != EDGE_INDEX_NO_EDGE && found_edge == 0)
349 fprintf (f, "*** Edge (%d, %d) has index %d, but there is no edge\n",
350 p->index, s->index, EDGE_INDEX (elist, p, s));
351 }
352 }
353
354
355 /* Functions to compute control dependences. */
356
357 /* Indicate block BB is control dependent on an edge with index EDGE_INDEX. */
358 void
set_control_dependence_map_bit(basic_block bb,int edge_index)359 control_dependences::set_control_dependence_map_bit (basic_block bb,
360 int edge_index)
361 {
362 if (bb == ENTRY_BLOCK_PTR_FOR_FN (cfun))
363 return;
364 gcc_assert (bb != EXIT_BLOCK_PTR_FOR_FN (cfun));
365 bitmap_set_bit (control_dependence_map[bb->index], edge_index);
366 }
367
368 /* Clear all control dependences for block BB. */
369 void
clear_control_dependence_bitmap(basic_block bb)370 control_dependences::clear_control_dependence_bitmap (basic_block bb)
371 {
372 bitmap_clear (control_dependence_map[bb->index]);
373 }
374
375 /* Find the immediate postdominator PDOM of the specified basic block BLOCK.
376 This function is necessary because some blocks have negative numbers. */
377
378 static inline basic_block
find_pdom(basic_block block)379 find_pdom (basic_block block)
380 {
381 gcc_assert (block != ENTRY_BLOCK_PTR_FOR_FN (cfun));
382
383 if (block == EXIT_BLOCK_PTR_FOR_FN (cfun))
384 return EXIT_BLOCK_PTR_FOR_FN (cfun);
385 else
386 {
387 basic_block bb = get_immediate_dominator (CDI_POST_DOMINATORS, block);
388 if (! bb)
389 return EXIT_BLOCK_PTR_FOR_FN (cfun);
390 return bb;
391 }
392 }
393
394 /* Determine all blocks' control dependences on the given edge with edge_list
395 EL index EDGE_INDEX, ala Morgan, Section 3.6. */
396
397 void
find_control_dependence(int edge_index)398 control_dependences::find_control_dependence (int edge_index)
399 {
400 basic_block current_block;
401 basic_block ending_block;
402
403 gcc_assert (get_edge_src (edge_index) != EXIT_BLOCK_PTR_FOR_FN (cfun));
404
405 /* For abnormal edges, we don't make current_block control
406 dependent because instructions that throw are always necessary
407 anyway. */
408 edge e = find_edge (get_edge_src (edge_index), get_edge_dest (edge_index));
409 if (e->flags & EDGE_ABNORMAL)
410 return;
411
412 if (get_edge_src (edge_index) == ENTRY_BLOCK_PTR_FOR_FN (cfun))
413 ending_block = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun));
414 else
415 ending_block = find_pdom (get_edge_src (edge_index));
416
417 for (current_block = get_edge_dest (edge_index);
418 current_block != ending_block
419 && current_block != EXIT_BLOCK_PTR_FOR_FN (cfun);
420 current_block = find_pdom (current_block))
421 set_control_dependence_map_bit (current_block, edge_index);
422 }
423
424 /* Record all blocks' control dependences on all edges in the edge
425 list EL, ala Morgan, Section 3.6. */
426
control_dependences()427 control_dependences::control_dependences ()
428 {
429 timevar_push (TV_CONTROL_DEPENDENCES);
430
431 /* Initialize the edge list. */
432 int num_edges = 0;
433 basic_block bb;
434 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun),
435 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb)
436 num_edges += EDGE_COUNT (bb->succs);
437 m_el.create (num_edges);
438 edge e;
439 edge_iterator ei;
440 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun),
441 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb)
442 FOR_EACH_EDGE (e, ei, bb->succs)
443 m_el.quick_push (std::make_pair (e->src->index, e->dest->index));
444
445 control_dependence_map.create (last_basic_block_for_fn (cfun));
446 for (int i = 0; i < last_basic_block_for_fn (cfun); ++i)
447 control_dependence_map.quick_push (BITMAP_ALLOC (NULL));
448 for (int i = 0; i < num_edges; ++i)
449 find_control_dependence (i);
450
451 timevar_pop (TV_CONTROL_DEPENDENCES);
452 }
453
454 /* Free control dependences and the associated edge list. */
455
~control_dependences()456 control_dependences::~control_dependences ()
457 {
458 for (unsigned i = 0; i < control_dependence_map.length (); ++i)
459 BITMAP_FREE (control_dependence_map[i]);
460 control_dependence_map.release ();
461 m_el.release ();
462 }
463
464 /* Returns the bitmap of edges the basic-block I is dependent on. */
465
466 bitmap
get_edges_dependent_on(int i)467 control_dependences::get_edges_dependent_on (int i)
468 {
469 return control_dependence_map[i];
470 }
471
472 /* Returns the edge source with index I from the edge list. */
473
474 basic_block
get_edge_src(int i)475 control_dependences::get_edge_src (int i)
476 {
477 return BASIC_BLOCK_FOR_FN (cfun, m_el[i].first);
478 }
479
480 /* Returns the edge destination with index I from the edge list. */
481
482 basic_block
get_edge_dest(int i)483 control_dependences::get_edge_dest (int i)
484 {
485 return BASIC_BLOCK_FOR_FN (cfun, m_el[i].second);
486 }
487
488
489 /* Given PRED and SUCC blocks, return the edge which connects the blocks.
490 If no such edge exists, return NULL. */
491
492 edge
find_edge(basic_block pred,basic_block succ)493 find_edge (basic_block pred, basic_block succ)
494 {
495 edge e;
496 edge_iterator ei;
497
498 if (EDGE_COUNT (pred->succs) <= EDGE_COUNT (succ->preds))
499 {
500 FOR_EACH_EDGE (e, ei, pred->succs)
501 if (e->dest == succ)
502 return e;
503 }
504 else
505 {
506 FOR_EACH_EDGE (e, ei, succ->preds)
507 if (e->src == pred)
508 return e;
509 }
510
511 return NULL;
512 }
513
514 /* This routine will determine what, if any, edge there is between
515 a specified predecessor and successor. */
516
517 int
find_edge_index(struct edge_list * edge_list,basic_block pred,basic_block succ)518 find_edge_index (struct edge_list *edge_list, basic_block pred, basic_block succ)
519 {
520 int x;
521
522 for (x = 0; x < NUM_EDGES (edge_list); x++)
523 if (INDEX_EDGE_PRED_BB (edge_list, x) == pred
524 && INDEX_EDGE_SUCC_BB (edge_list, x) == succ)
525 return x;
526
527 return (EDGE_INDEX_NO_EDGE);
528 }
529
530 /* This routine will remove any fake predecessor edges for a basic block.
531 When the edge is removed, it is also removed from whatever successor
532 list it is in. */
533
534 static void
remove_fake_predecessors(basic_block bb)535 remove_fake_predecessors (basic_block bb)
536 {
537 edge e;
538 edge_iterator ei;
539
540 for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); )
541 {
542 if ((e->flags & EDGE_FAKE) == EDGE_FAKE)
543 remove_edge (e);
544 else
545 ei_next (&ei);
546 }
547 }
548
549 /* This routine will remove all fake edges from the flow graph. If
550 we remove all fake successors, it will automatically remove all
551 fake predecessors. */
552
553 void
remove_fake_edges(void)554 remove_fake_edges (void)
555 {
556 basic_block bb;
557
558 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb, NULL, next_bb)
559 remove_fake_predecessors (bb);
560 }
561
562 /* This routine will remove all fake edges to the EXIT_BLOCK. */
563
564 void
remove_fake_exit_edges(void)565 remove_fake_exit_edges (void)
566 {
567 remove_fake_predecessors (EXIT_BLOCK_PTR_FOR_FN (cfun));
568 }
569
570
571 /* This function will add a fake edge between any block which has no
572 successors, and the exit block. Some data flow equations require these
573 edges to exist. */
574
575 void
add_noreturn_fake_exit_edges(void)576 add_noreturn_fake_exit_edges (void)
577 {
578 basic_block bb;
579
580 FOR_EACH_BB_FN (bb, cfun)
581 if (EDGE_COUNT (bb->succs) == 0)
582 make_single_succ_edge (bb, EXIT_BLOCK_PTR_FOR_FN (cfun), EDGE_FAKE);
583 }
584
585 /* This function adds a fake edge between any infinite loops to the
586 exit block. Some optimizations require a path from each node to
587 the exit node.
588
589 See also Morgan, Figure 3.10, pp. 82-83.
590
591 The current implementation is ugly, not attempting to minimize the
592 number of inserted fake edges. To reduce the number of fake edges
593 to insert, add fake edges from _innermost_ loops containing only
594 nodes not reachable from the exit block. */
595
596 void
connect_infinite_loops_to_exit(void)597 connect_infinite_loops_to_exit (void)
598 {
599 /* Perform depth-first search in the reverse graph to find nodes
600 reachable from the exit block. */
601 depth_first_search dfs;
602 dfs.add_bb (EXIT_BLOCK_PTR_FOR_FN (cfun));
603
604 /* Repeatedly add fake edges, updating the unreachable nodes. */
605 basic_block unvisited_block = EXIT_BLOCK_PTR_FOR_FN (cfun);
606 while (1)
607 {
608 unvisited_block = dfs.execute (unvisited_block);
609 if (!unvisited_block)
610 break;
611
612 basic_block deadend_block = dfs_find_deadend (unvisited_block);
613 edge e = make_edge (deadend_block, EXIT_BLOCK_PTR_FOR_FN (cfun),
614 EDGE_FAKE);
615 e->probability = profile_probability::never ();
616 dfs.add_bb (deadend_block);
617 }
618 }
619
620 /* Compute reverse top sort order. This is computing a post order
621 numbering of the graph. If INCLUDE_ENTRY_EXIT is true, then
622 ENTRY_BLOCK and EXIT_BLOCK are included. If DELETE_UNREACHABLE is
623 true, unreachable blocks are deleted. */
624
625 int
post_order_compute(int * post_order,bool include_entry_exit,bool delete_unreachable)626 post_order_compute (int *post_order, bool include_entry_exit,
627 bool delete_unreachable)
628 {
629 int post_order_num = 0;
630 int count;
631
632 if (include_entry_exit)
633 post_order[post_order_num++] = EXIT_BLOCK;
634
635 /* Allocate stack for back-tracking up CFG. */
636 auto_vec<edge_iterator, 20> stack (n_basic_blocks_for_fn (cfun) + 1);
637
638 /* Allocate bitmap to track nodes that have been visited. */
639 auto_sbitmap visited (last_basic_block_for_fn (cfun));
640
641 /* None of the nodes in the CFG have been visited yet. */
642 bitmap_clear (visited);
643
644 /* Push the first edge on to the stack. */
645 stack.quick_push (ei_start (ENTRY_BLOCK_PTR_FOR_FN (cfun)->succs));
646
647 while (!stack.is_empty ())
648 {
649 basic_block src;
650 basic_block dest;
651
652 /* Look at the edge on the top of the stack. */
653 edge_iterator ei = stack.last ();
654 src = ei_edge (ei)->src;
655 dest = ei_edge (ei)->dest;
656
657 /* Check if the edge destination has been visited yet. */
658 if (dest != EXIT_BLOCK_PTR_FOR_FN (cfun)
659 && ! bitmap_bit_p (visited, dest->index))
660 {
661 /* Mark that we have visited the destination. */
662 bitmap_set_bit (visited, dest->index);
663
664 if (EDGE_COUNT (dest->succs) > 0)
665 /* Since the DEST node has been visited for the first
666 time, check its successors. */
667 stack.quick_push (ei_start (dest->succs));
668 else
669 post_order[post_order_num++] = dest->index;
670 }
671 else
672 {
673 if (ei_one_before_end_p (ei)
674 && src != ENTRY_BLOCK_PTR_FOR_FN (cfun))
675 post_order[post_order_num++] = src->index;
676
677 if (!ei_one_before_end_p (ei))
678 ei_next (&stack.last ());
679 else
680 stack.pop ();
681 }
682 }
683
684 if (include_entry_exit)
685 {
686 post_order[post_order_num++] = ENTRY_BLOCK;
687 count = post_order_num;
688 }
689 else
690 count = post_order_num + 2;
691
692 /* Delete the unreachable blocks if some were found and we are
693 supposed to do it. */
694 if (delete_unreachable && (count != n_basic_blocks_for_fn (cfun)))
695 {
696 basic_block b;
697 basic_block next_bb;
698 for (b = ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb; b
699 != EXIT_BLOCK_PTR_FOR_FN (cfun); b = next_bb)
700 {
701 next_bb = b->next_bb;
702
703 if (!(bitmap_bit_p (visited, b->index)))
704 delete_basic_block (b);
705 }
706
707 tidy_fallthru_edges ();
708 }
709
710 return post_order_num;
711 }
712
713
714 /* Helper routine for inverted_post_order_compute
715 flow_dfs_compute_reverse_execute, and the reverse-CFG
716 deapth first search in dominance.c.
717 BB has to belong to a region of CFG
718 unreachable by inverted traversal from the exit.
719 i.e. there's no control flow path from ENTRY to EXIT
720 that contains this BB.
721 This can happen in two cases - if there's an infinite loop
722 or if there's a block that has no successor
723 (call to a function with no return).
724 Some RTL passes deal with this condition by
725 calling connect_infinite_loops_to_exit () and/or
726 add_noreturn_fake_exit_edges ().
727 However, those methods involve modifying the CFG itself
728 which may not be desirable.
729 Hence, we deal with the infinite loop/no return cases
730 by identifying a unique basic block that can reach all blocks
731 in such a region by inverted traversal.
732 This function returns a basic block that guarantees
733 that all blocks in the region are reachable
734 by starting an inverted traversal from the returned block. */
735
736 basic_block
dfs_find_deadend(basic_block bb)737 dfs_find_deadend (basic_block bb)
738 {
739 auto_bitmap visited;
740 basic_block next = bb;
741
742 for (;;)
743 {
744 if (EDGE_COUNT (next->succs) == 0)
745 return next;
746
747 if (! bitmap_set_bit (visited, next->index))
748 return bb;
749
750 bb = next;
751 /* If we are in an analyzed cycle make sure to try exiting it.
752 Note this is a heuristic only and expected to work when loop
753 fixup is needed as well. */
754 if (! bb->loop_father
755 || ! loop_outer (bb->loop_father))
756 next = EDGE_SUCC (bb, 0)->dest;
757 else
758 {
759 edge_iterator ei;
760 edge e;
761 FOR_EACH_EDGE (e, ei, bb->succs)
762 if (loop_exit_edge_p (bb->loop_father, e))
763 break;
764 next = e ? e->dest : EDGE_SUCC (bb, 0)->dest;
765 }
766 }
767
768 gcc_unreachable ();
769 }
770
771
772 /* Compute the reverse top sort order of the inverted CFG
773 i.e. starting from the exit block and following the edges backward
774 (from successors to predecessors).
775 This ordering can be used for forward dataflow problems among others.
776
777 Optionally if START_POINTS is specified, start from exit block and all
778 basic blocks in START_POINTS. This is used by CD-DCE.
779
780 This function assumes that all blocks in the CFG are reachable
781 from the ENTRY (but not necessarily from EXIT).
782
783 If there's an infinite loop,
784 a simple inverted traversal starting from the blocks
785 with no successors can't visit all blocks.
786 To solve this problem, we first do inverted traversal
787 starting from the blocks with no successor.
788 And if there's any block left that's not visited by the regular
789 inverted traversal from EXIT,
790 those blocks are in such problematic region.
791 Among those, we find one block that has
792 any visited predecessor (which is an entry into such a region),
793 and start looking for a "dead end" from that block
794 and do another inverted traversal from that block. */
795
796 void
inverted_post_order_compute(vec<int> * post_order,sbitmap * start_points)797 inverted_post_order_compute (vec<int> *post_order,
798 sbitmap *start_points)
799 {
800 basic_block bb;
801 post_order->reserve_exact (n_basic_blocks_for_fn (cfun));
802
803 if (flag_checking)
804 verify_no_unreachable_blocks ();
805
806 /* Allocate stack for back-tracking up CFG. */
807 auto_vec<edge_iterator, 20> stack (n_basic_blocks_for_fn (cfun) + 1);
808
809 /* Allocate bitmap to track nodes that have been visited. */
810 auto_sbitmap visited (last_basic_block_for_fn (cfun));
811
812 /* None of the nodes in the CFG have been visited yet. */
813 bitmap_clear (visited);
814
815 if (start_points)
816 {
817 FOR_ALL_BB_FN (bb, cfun)
818 if (bitmap_bit_p (*start_points, bb->index)
819 && EDGE_COUNT (bb->preds) > 0)
820 {
821 stack.quick_push (ei_start (bb->preds));
822 bitmap_set_bit (visited, bb->index);
823 }
824 if (EDGE_COUNT (EXIT_BLOCK_PTR_FOR_FN (cfun)->preds))
825 {
826 stack.quick_push (ei_start (EXIT_BLOCK_PTR_FOR_FN (cfun)->preds));
827 bitmap_set_bit (visited, EXIT_BLOCK_PTR_FOR_FN (cfun)->index);
828 }
829 }
830 else
831 /* Put all blocks that have no successor into the initial work list. */
832 FOR_ALL_BB_FN (bb, cfun)
833 if (EDGE_COUNT (bb->succs) == 0)
834 {
835 /* Push the initial edge on to the stack. */
836 if (EDGE_COUNT (bb->preds) > 0)
837 {
838 stack.quick_push (ei_start (bb->preds));
839 bitmap_set_bit (visited, bb->index);
840 }
841 }
842
843 do
844 {
845 bool has_unvisited_bb = false;
846
847 /* The inverted traversal loop. */
848 while (!stack.is_empty ())
849 {
850 edge_iterator ei;
851 basic_block pred;
852
853 /* Look at the edge on the top of the stack. */
854 ei = stack.last ();
855 bb = ei_edge (ei)->dest;
856 pred = ei_edge (ei)->src;
857
858 /* Check if the predecessor has been visited yet. */
859 if (! bitmap_bit_p (visited, pred->index))
860 {
861 /* Mark that we have visited the destination. */
862 bitmap_set_bit (visited, pred->index);
863
864 if (EDGE_COUNT (pred->preds) > 0)
865 /* Since the predecessor node has been visited for the first
866 time, check its predecessors. */
867 stack.quick_push (ei_start (pred->preds));
868 else
869 post_order->quick_push (pred->index);
870 }
871 else
872 {
873 if (bb != EXIT_BLOCK_PTR_FOR_FN (cfun)
874 && ei_one_before_end_p (ei))
875 post_order->quick_push (bb->index);
876
877 if (!ei_one_before_end_p (ei))
878 ei_next (&stack.last ());
879 else
880 stack.pop ();
881 }
882 }
883
884 /* Detect any infinite loop and activate the kludge.
885 Note that this doesn't check EXIT_BLOCK itself
886 since EXIT_BLOCK is always added after the outer do-while loop. */
887 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun),
888 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb)
889 if (!bitmap_bit_p (visited, bb->index))
890 {
891 has_unvisited_bb = true;
892
893 if (EDGE_COUNT (bb->preds) > 0)
894 {
895 edge_iterator ei;
896 edge e;
897 basic_block visited_pred = NULL;
898
899 /* Find an already visited predecessor. */
900 FOR_EACH_EDGE (e, ei, bb->preds)
901 {
902 if (bitmap_bit_p (visited, e->src->index))
903 visited_pred = e->src;
904 }
905
906 if (visited_pred)
907 {
908 basic_block be = dfs_find_deadend (bb);
909 gcc_assert (be != NULL);
910 bitmap_set_bit (visited, be->index);
911 stack.quick_push (ei_start (be->preds));
912 break;
913 }
914 }
915 }
916
917 if (has_unvisited_bb && stack.is_empty ())
918 {
919 /* No blocks are reachable from EXIT at all.
920 Find a dead-end from the ENTRY, and restart the iteration. */
921 basic_block be = dfs_find_deadend (ENTRY_BLOCK_PTR_FOR_FN (cfun));
922 gcc_assert (be != NULL);
923 bitmap_set_bit (visited, be->index);
924 stack.quick_push (ei_start (be->preds));
925 }
926
927 /* The only case the below while fires is
928 when there's an infinite loop. */
929 }
930 while (!stack.is_empty ());
931
932 /* EXIT_BLOCK is always included. */
933 post_order->quick_push (EXIT_BLOCK);
934 }
935
936 /* Compute the depth first search order of FN and store in the array
937 PRE_ORDER if nonzero. If REV_POST_ORDER is nonzero, return the
938 reverse completion number for each node. Returns the number of nodes
939 visited. A depth first search tries to get as far away from the starting
940 point as quickly as possible.
941
942 In case the function has unreachable blocks the number of nodes
943 visited does not include them.
944
945 pre_order is a really a preorder numbering of the graph.
946 rev_post_order is really a reverse postorder numbering of the graph. */
947
948 int
pre_and_rev_post_order_compute_fn(struct function * fn,int * pre_order,int * rev_post_order,bool include_entry_exit)949 pre_and_rev_post_order_compute_fn (struct function *fn,
950 int *pre_order, int *rev_post_order,
951 bool include_entry_exit)
952 {
953 int pre_order_num = 0;
954 int rev_post_order_num = n_basic_blocks_for_fn (cfun) - 1;
955
956 /* Allocate stack for back-tracking up CFG. */
957 auto_vec<edge_iterator, 20> stack (n_basic_blocks_for_fn (cfun) + 1);
958
959 if (include_entry_exit)
960 {
961 if (pre_order)
962 pre_order[pre_order_num] = ENTRY_BLOCK;
963 pre_order_num++;
964 if (rev_post_order)
965 rev_post_order[rev_post_order_num--] = EXIT_BLOCK;
966 }
967 else
968 rev_post_order_num -= NUM_FIXED_BLOCKS;
969
970 /* Allocate bitmap to track nodes that have been visited. */
971 auto_sbitmap visited (last_basic_block_for_fn (cfun));
972
973 /* None of the nodes in the CFG have been visited yet. */
974 bitmap_clear (visited);
975
976 /* Push the first edge on to the stack. */
977 stack.quick_push (ei_start (ENTRY_BLOCK_PTR_FOR_FN (fn)->succs));
978
979 while (!stack.is_empty ())
980 {
981 basic_block src;
982 basic_block dest;
983
984 /* Look at the edge on the top of the stack. */
985 edge_iterator ei = stack.last ();
986 src = ei_edge (ei)->src;
987 dest = ei_edge (ei)->dest;
988
989 /* Check if the edge destination has been visited yet. */
990 if (dest != EXIT_BLOCK_PTR_FOR_FN (fn)
991 && ! bitmap_bit_p (visited, dest->index))
992 {
993 /* Mark that we have visited the destination. */
994 bitmap_set_bit (visited, dest->index);
995
996 if (pre_order)
997 pre_order[pre_order_num] = dest->index;
998
999 pre_order_num++;
1000
1001 if (EDGE_COUNT (dest->succs) > 0)
1002 /* Since the DEST node has been visited for the first
1003 time, check its successors. */
1004 stack.quick_push (ei_start (dest->succs));
1005 else if (rev_post_order)
1006 /* There are no successors for the DEST node so assign
1007 its reverse completion number. */
1008 rev_post_order[rev_post_order_num--] = dest->index;
1009 }
1010 else
1011 {
1012 if (ei_one_before_end_p (ei)
1013 && src != ENTRY_BLOCK_PTR_FOR_FN (fn)
1014 && rev_post_order)
1015 /* There are no more successors for the SRC node
1016 so assign its reverse completion number. */
1017 rev_post_order[rev_post_order_num--] = src->index;
1018
1019 if (!ei_one_before_end_p (ei))
1020 ei_next (&stack.last ());
1021 else
1022 stack.pop ();
1023 }
1024 }
1025
1026 if (include_entry_exit)
1027 {
1028 if (pre_order)
1029 pre_order[pre_order_num] = EXIT_BLOCK;
1030 pre_order_num++;
1031 if (rev_post_order)
1032 rev_post_order[rev_post_order_num--] = ENTRY_BLOCK;
1033 }
1034
1035 return pre_order_num;
1036 }
1037
1038 /* Like pre_and_rev_post_order_compute_fn but operating on the
1039 current function and asserting that all nodes were visited. */
1040
1041 int
pre_and_rev_post_order_compute(int * pre_order,int * rev_post_order,bool include_entry_exit)1042 pre_and_rev_post_order_compute (int *pre_order, int *rev_post_order,
1043 bool include_entry_exit)
1044 {
1045 int pre_order_num
1046 = pre_and_rev_post_order_compute_fn (cfun, pre_order, rev_post_order,
1047 include_entry_exit);
1048 if (include_entry_exit)
1049 /* The number of nodes visited should be the number of blocks. */
1050 gcc_assert (pre_order_num == n_basic_blocks_for_fn (cfun));
1051 else
1052 /* The number of nodes visited should be the number of blocks minus
1053 the entry and exit blocks which are not visited here. */
1054 gcc_assert (pre_order_num
1055 == (n_basic_blocks_for_fn (cfun) - NUM_FIXED_BLOCKS));
1056
1057 return pre_order_num;
1058 }
1059
1060 /* Compute the depth first search order on the _reverse_ graph and
1061 store in the array DFS_ORDER, marking the nodes visited in VISITED.
1062 Returns the number of nodes visited.
1063
1064 The computation is split into three pieces:
1065
1066 flow_dfs_compute_reverse_init () creates the necessary data
1067 structures.
1068
1069 flow_dfs_compute_reverse_add_bb () adds a basic block to the data
1070 structures. The block will start the search.
1071
1072 flow_dfs_compute_reverse_execute () continues (or starts) the
1073 search using the block on the top of the stack, stopping when the
1074 stack is empty.
1075
1076 flow_dfs_compute_reverse_finish () destroys the necessary data
1077 structures.
1078
1079 Thus, the user will probably call ..._init(), call ..._add_bb() to
1080 add a beginning basic block to the stack, call ..._execute(),
1081 possibly add another bb to the stack and again call ..._execute(),
1082 ..., and finally call _finish(). */
1083
1084 /* Initialize the data structures used for depth-first search on the
1085 reverse graph. If INITIALIZE_STACK is nonzero, the exit block is
1086 added to the basic block stack. DATA is the current depth-first
1087 search context. If INITIALIZE_STACK is nonzero, there is an
1088 element on the stack. */
1089
depth_first_search()1090 depth_first_search::depth_first_search () :
1091 m_stack (n_basic_blocks_for_fn (cfun)),
1092 m_visited_blocks (last_basic_block_for_fn (cfun))
1093 {
1094 bitmap_clear (m_visited_blocks);
1095 }
1096
1097 /* Add the specified basic block to the top of the dfs data
1098 structures. When the search continues, it will start at the
1099 block. */
1100
1101 void
add_bb(basic_block bb)1102 depth_first_search::add_bb (basic_block bb)
1103 {
1104 m_stack.quick_push (bb);
1105 bitmap_set_bit (m_visited_blocks, bb->index);
1106 }
1107
1108 /* Continue the depth-first search through the reverse graph starting with the
1109 block at the stack's top and ending when the stack is empty. Visited nodes
1110 are marked. Returns an unvisited basic block, or NULL if there is none
1111 available. */
1112
1113 basic_block
execute(basic_block last_unvisited)1114 depth_first_search::execute (basic_block last_unvisited)
1115 {
1116 basic_block bb;
1117 edge e;
1118 edge_iterator ei;
1119
1120 while (!m_stack.is_empty ())
1121 {
1122 bb = m_stack.pop ();
1123
1124 /* Perform depth-first search on adjacent vertices. */
1125 FOR_EACH_EDGE (e, ei, bb->preds)
1126 if (!bitmap_bit_p (m_visited_blocks, e->src->index))
1127 add_bb (e->src);
1128 }
1129
1130 /* Determine if there are unvisited basic blocks. */
1131 FOR_BB_BETWEEN (bb, last_unvisited, NULL, prev_bb)
1132 if (!bitmap_bit_p (m_visited_blocks, bb->index))
1133 return bb;
1134
1135 return NULL;
1136 }
1137
1138 /* Performs dfs search from BB over vertices satisfying PREDICATE;
1139 if REVERSE, go against direction of edges. Returns number of blocks
1140 found and their list in RSLT. RSLT can contain at most RSLT_MAX items. */
1141 int
dfs_enumerate_from(basic_block bb,int reverse,bool (* predicate)(const_basic_block,const void *),basic_block * rslt,int rslt_max,const void * data)1142 dfs_enumerate_from (basic_block bb, int reverse,
1143 bool (*predicate) (const_basic_block, const void *),
1144 basic_block *rslt, int rslt_max, const void *data)
1145 {
1146 basic_block *st, lbb;
1147 int sp = 0, tv = 0;
1148 unsigned size;
1149
1150 /* A bitmap to keep track of visited blocks. Allocating it each time
1151 this function is called is not possible, since dfs_enumerate_from
1152 is often used on small (almost) disjoint parts of cfg (bodies of
1153 loops), and allocating a large sbitmap would lead to quadratic
1154 behavior. */
1155 static sbitmap visited;
1156 static unsigned v_size;
1157
1158 #define MARK_VISITED(BB) (bitmap_set_bit (visited, (BB)->index))
1159 #define UNMARK_VISITED(BB) (bitmap_clear_bit (visited, (BB)->index))
1160 #define VISITED_P(BB) (bitmap_bit_p (visited, (BB)->index))
1161
1162 /* Resize the VISITED sbitmap if necessary. */
1163 size = last_basic_block_for_fn (cfun);
1164 if (size < 10)
1165 size = 10;
1166
1167 if (!visited)
1168 {
1169
1170 visited = sbitmap_alloc (size);
1171 bitmap_clear (visited);
1172 v_size = size;
1173 }
1174 else if (v_size < size)
1175 {
1176 /* Ensure that we increase the size of the sbitmap exponentially. */
1177 if (2 * v_size > size)
1178 size = 2 * v_size;
1179
1180 visited = sbitmap_resize (visited, size, 0);
1181 v_size = size;
1182 }
1183
1184 st = XNEWVEC (basic_block, rslt_max);
1185 rslt[tv++] = st[sp++] = bb;
1186 MARK_VISITED (bb);
1187 while (sp)
1188 {
1189 edge e;
1190 edge_iterator ei;
1191 lbb = st[--sp];
1192 if (reverse)
1193 {
1194 FOR_EACH_EDGE (e, ei, lbb->preds)
1195 if (!VISITED_P (e->src) && predicate (e->src, data))
1196 {
1197 gcc_assert (tv != rslt_max);
1198 rslt[tv++] = st[sp++] = e->src;
1199 MARK_VISITED (e->src);
1200 }
1201 }
1202 else
1203 {
1204 FOR_EACH_EDGE (e, ei, lbb->succs)
1205 if (!VISITED_P (e->dest) && predicate (e->dest, data))
1206 {
1207 gcc_assert (tv != rslt_max);
1208 rslt[tv++] = st[sp++] = e->dest;
1209 MARK_VISITED (e->dest);
1210 }
1211 }
1212 }
1213 free (st);
1214 for (sp = 0; sp < tv; sp++)
1215 UNMARK_VISITED (rslt[sp]);
1216 return tv;
1217 #undef MARK_VISITED
1218 #undef UNMARK_VISITED
1219 #undef VISITED_P
1220 }
1221
1222
1223 /* Compute dominance frontiers, ala Harvey, Ferrante, et al.
1224
1225 This algorithm can be found in Timothy Harvey's PhD thesis, at
1226 http://www.cs.rice.edu/~harv/dissertation.pdf in the section on iterative
1227 dominance algorithms.
1228
1229 First, we identify each join point, j (any node with more than one
1230 incoming edge is a join point).
1231
1232 We then examine each predecessor, p, of j and walk up the dominator tree
1233 starting at p.
1234
1235 We stop the walk when we reach j's immediate dominator - j is in the
1236 dominance frontier of each of the nodes in the walk, except for j's
1237 immediate dominator. Intuitively, all of the rest of j's dominators are
1238 shared by j's predecessors as well.
1239 Since they dominate j, they will not have j in their dominance frontiers.
1240
1241 The number of nodes touched by this algorithm is equal to the size
1242 of the dominance frontiers, no more, no less.
1243 */
1244
1245
1246 static void
compute_dominance_frontiers_1(bitmap_head * frontiers)1247 compute_dominance_frontiers_1 (bitmap_head *frontiers)
1248 {
1249 edge p;
1250 edge_iterator ei;
1251 basic_block b;
1252 FOR_EACH_BB_FN (b, cfun)
1253 {
1254 if (EDGE_COUNT (b->preds) >= 2)
1255 {
1256 FOR_EACH_EDGE (p, ei, b->preds)
1257 {
1258 basic_block runner = p->src;
1259 basic_block domsb;
1260 if (runner == ENTRY_BLOCK_PTR_FOR_FN (cfun))
1261 continue;
1262
1263 domsb = get_immediate_dominator (CDI_DOMINATORS, b);
1264 while (runner != domsb)
1265 {
1266 if (!bitmap_set_bit (&frontiers[runner->index],
1267 b->index))
1268 break;
1269 runner = get_immediate_dominator (CDI_DOMINATORS,
1270 runner);
1271 }
1272 }
1273 }
1274 }
1275 }
1276
1277
1278 void
compute_dominance_frontiers(bitmap_head * frontiers)1279 compute_dominance_frontiers (bitmap_head *frontiers)
1280 {
1281 timevar_push (TV_DOM_FRONTIERS);
1282
1283 compute_dominance_frontiers_1 (frontiers);
1284
1285 timevar_pop (TV_DOM_FRONTIERS);
1286 }
1287
1288 /* Given a set of blocks with variable definitions (DEF_BLOCKS),
1289 return a bitmap with all the blocks in the iterated dominance
1290 frontier of the blocks in DEF_BLOCKS. DFS contains dominance
1291 frontier information as returned by compute_dominance_frontiers.
1292
1293 The resulting set of blocks are the potential sites where PHI nodes
1294 are needed. The caller is responsible for freeing the memory
1295 allocated for the return value. */
1296
1297 bitmap
compute_idf(bitmap def_blocks,bitmap_head * dfs)1298 compute_idf (bitmap def_blocks, bitmap_head *dfs)
1299 {
1300 bitmap_iterator bi;
1301 unsigned bb_index, i;
1302 bitmap phi_insertion_points;
1303
1304 /* Each block can appear at most twice on the work-stack. */
1305 auto_vec<int> work_stack (2 * n_basic_blocks_for_fn (cfun));
1306 phi_insertion_points = BITMAP_ALLOC (NULL);
1307
1308 /* Seed the work list with all the blocks in DEF_BLOCKS. We use
1309 vec::quick_push here for speed. This is safe because we know that
1310 the number of definition blocks is no greater than the number of
1311 basic blocks, which is the initial capacity of WORK_STACK. */
1312 EXECUTE_IF_SET_IN_BITMAP (def_blocks, 0, bb_index, bi)
1313 work_stack.quick_push (bb_index);
1314
1315 /* Pop a block off the worklist, add every block that appears in
1316 the original block's DF that we have not already processed to
1317 the worklist. Iterate until the worklist is empty. Blocks
1318 which are added to the worklist are potential sites for
1319 PHI nodes. */
1320 while (work_stack.length () > 0)
1321 {
1322 bb_index = work_stack.pop ();
1323
1324 /* Since the registration of NEW -> OLD name mappings is done
1325 separately from the call to update_ssa, when updating the SSA
1326 form, the basic blocks where new and/or old names are defined
1327 may have disappeared by CFG cleanup calls. In this case,
1328 we may pull a non-existing block from the work stack. */
1329 gcc_checking_assert (bb_index
1330 < (unsigned) last_basic_block_for_fn (cfun));
1331
1332 EXECUTE_IF_AND_COMPL_IN_BITMAP (&dfs[bb_index], phi_insertion_points,
1333 0, i, bi)
1334 {
1335 work_stack.quick_push (i);
1336 bitmap_set_bit (phi_insertion_points, i);
1337 }
1338 }
1339
1340 return phi_insertion_points;
1341 }
1342
1343 /* Intersection and union of preds/succs for sbitmap based data flow
1344 solvers. All four functions defined below take the same arguments:
1345 B is the basic block to perform the operation for. DST is the
1346 target sbitmap, i.e. the result. SRC is an sbitmap vector of size
1347 last_basic_block so that it can be indexed with basic block indices.
1348 DST may be (but does not have to be) SRC[B->index]. */
1349
1350 /* Set the bitmap DST to the intersection of SRC of successors of
1351 basic block B. */
1352
1353 void
bitmap_intersection_of_succs(sbitmap dst,sbitmap * src,basic_block b)1354 bitmap_intersection_of_succs (sbitmap dst, sbitmap *src, basic_block b)
1355 {
1356 unsigned int set_size = dst->size;
1357 edge e;
1358 unsigned ix;
1359
1360 for (e = NULL, ix = 0; ix < EDGE_COUNT (b->succs); ix++)
1361 {
1362 e = EDGE_SUCC (b, ix);
1363 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
1364 continue;
1365
1366 bitmap_copy (dst, src[e->dest->index]);
1367 break;
1368 }
1369
1370 if (e == 0)
1371 bitmap_ones (dst);
1372 else
1373 for (++ix; ix < EDGE_COUNT (b->succs); ix++)
1374 {
1375 unsigned int i;
1376 SBITMAP_ELT_TYPE *p, *r;
1377
1378 e = EDGE_SUCC (b, ix);
1379 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
1380 continue;
1381
1382 p = src[e->dest->index]->elms;
1383 r = dst->elms;
1384 for (i = 0; i < set_size; i++)
1385 *r++ &= *p++;
1386 }
1387 }
1388
1389 /* Set the bitmap DST to the intersection of SRC of predecessors of
1390 basic block B. */
1391
1392 void
bitmap_intersection_of_preds(sbitmap dst,sbitmap * src,basic_block b)1393 bitmap_intersection_of_preds (sbitmap dst, sbitmap *src, basic_block b)
1394 {
1395 unsigned int set_size = dst->size;
1396 edge e;
1397 unsigned ix;
1398
1399 for (e = NULL, ix = 0; ix < EDGE_COUNT (b->preds); ix++)
1400 {
1401 e = EDGE_PRED (b, ix);
1402 if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun))
1403 continue;
1404
1405 bitmap_copy (dst, src[e->src->index]);
1406 break;
1407 }
1408
1409 if (e == 0)
1410 bitmap_ones (dst);
1411 else
1412 for (++ix; ix < EDGE_COUNT (b->preds); ix++)
1413 {
1414 unsigned int i;
1415 SBITMAP_ELT_TYPE *p, *r;
1416
1417 e = EDGE_PRED (b, ix);
1418 if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun))
1419 continue;
1420
1421 p = src[e->src->index]->elms;
1422 r = dst->elms;
1423 for (i = 0; i < set_size; i++)
1424 *r++ &= *p++;
1425 }
1426 }
1427
1428 /* Set the bitmap DST to the union of SRC of successors of
1429 basic block B. */
1430
1431 void
bitmap_union_of_succs(sbitmap dst,sbitmap * src,basic_block b)1432 bitmap_union_of_succs (sbitmap dst, sbitmap *src, basic_block b)
1433 {
1434 unsigned int set_size = dst->size;
1435 edge e;
1436 unsigned ix;
1437
1438 for (ix = 0; ix < EDGE_COUNT (b->succs); ix++)
1439 {
1440 e = EDGE_SUCC (b, ix);
1441 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
1442 continue;
1443
1444 bitmap_copy (dst, src[e->dest->index]);
1445 break;
1446 }
1447
1448 if (ix == EDGE_COUNT (b->succs))
1449 bitmap_clear (dst);
1450 else
1451 for (ix++; ix < EDGE_COUNT (b->succs); ix++)
1452 {
1453 unsigned int i;
1454 SBITMAP_ELT_TYPE *p, *r;
1455
1456 e = EDGE_SUCC (b, ix);
1457 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
1458 continue;
1459
1460 p = src[e->dest->index]->elms;
1461 r = dst->elms;
1462 for (i = 0; i < set_size; i++)
1463 *r++ |= *p++;
1464 }
1465 }
1466
1467 /* Set the bitmap DST to the union of SRC of predecessors of
1468 basic block B. */
1469
1470 void
bitmap_union_of_preds(sbitmap dst,sbitmap * src,basic_block b)1471 bitmap_union_of_preds (sbitmap dst, sbitmap *src, basic_block b)
1472 {
1473 unsigned int set_size = dst->size;
1474 edge e;
1475 unsigned ix;
1476
1477 for (ix = 0; ix < EDGE_COUNT (b->preds); ix++)
1478 {
1479 e = EDGE_PRED (b, ix);
1480 if (e->src== ENTRY_BLOCK_PTR_FOR_FN (cfun))
1481 continue;
1482
1483 bitmap_copy (dst, src[e->src->index]);
1484 break;
1485 }
1486
1487 if (ix == EDGE_COUNT (b->preds))
1488 bitmap_clear (dst);
1489 else
1490 for (ix++; ix < EDGE_COUNT (b->preds); ix++)
1491 {
1492 unsigned int i;
1493 SBITMAP_ELT_TYPE *p, *r;
1494
1495 e = EDGE_PRED (b, ix);
1496 if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun))
1497 continue;
1498
1499 p = src[e->src->index]->elms;
1500 r = dst->elms;
1501 for (i = 0; i < set_size; i++)
1502 *r++ |= *p++;
1503 }
1504 }
1505
1506 /* Returns the list of basic blocks in the function in an order that guarantees
1507 that if a block X has just a single predecessor Y, then Y is after X in the
1508 ordering. */
1509
1510 basic_block *
single_pred_before_succ_order(void)1511 single_pred_before_succ_order (void)
1512 {
1513 basic_block x, y;
1514 basic_block *order = XNEWVEC (basic_block, n_basic_blocks_for_fn (cfun));
1515 unsigned n = n_basic_blocks_for_fn (cfun) - NUM_FIXED_BLOCKS;
1516 unsigned np, i;
1517 auto_sbitmap visited (last_basic_block_for_fn (cfun));
1518
1519 #define MARK_VISITED(BB) (bitmap_set_bit (visited, (BB)->index))
1520 #define VISITED_P(BB) (bitmap_bit_p (visited, (BB)->index))
1521
1522 bitmap_clear (visited);
1523
1524 MARK_VISITED (ENTRY_BLOCK_PTR_FOR_FN (cfun));
1525 FOR_EACH_BB_FN (x, cfun)
1526 {
1527 if (VISITED_P (x))
1528 continue;
1529
1530 /* Walk the predecessors of x as long as they have precisely one
1531 predecessor and add them to the list, so that they get stored
1532 after x. */
1533 for (y = x, np = 1;
1534 single_pred_p (y) && !VISITED_P (single_pred (y));
1535 y = single_pred (y))
1536 np++;
1537 for (y = x, i = n - np;
1538 single_pred_p (y) && !VISITED_P (single_pred (y));
1539 y = single_pred (y), i++)
1540 {
1541 order[i] = y;
1542 MARK_VISITED (y);
1543 }
1544 order[i] = y;
1545 MARK_VISITED (y);
1546
1547 gcc_assert (i == n - 1);
1548 n -= np;
1549 }
1550
1551 gcc_assert (n == 0);
1552 return order;
1553
1554 #undef MARK_VISITED
1555 #undef VISITED_P
1556 }
1557
1558 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1559 return that edge. Otherwise return NULL.
1560
1561 When IGNORE_NOT_EXECUTABLE is true, also ignore edges that are not marked
1562 as executable. */
1563
1564 edge
single_pred_edge_ignoring_loop_edges(basic_block bb,bool ignore_not_executable)1565 single_pred_edge_ignoring_loop_edges (basic_block bb,
1566 bool ignore_not_executable)
1567 {
1568 edge retval = NULL;
1569 edge e;
1570 edge_iterator ei;
1571
1572 FOR_EACH_EDGE (e, ei, bb->preds)
1573 {
1574 /* A loop back edge can be identified by the destination of
1575 the edge dominating the source of the edge. */
1576 if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
1577 continue;
1578
1579 /* We can safely ignore edges that are not executable. */
1580 if (ignore_not_executable
1581 && (e->flags & EDGE_EXECUTABLE) == 0)
1582 continue;
1583
1584 /* If we have already seen a non-loop edge, then we must have
1585 multiple incoming non-loop edges and thus we return NULL. */
1586 if (retval)
1587 return NULL;
1588
1589 /* This is the first non-loop incoming edge we have found. Record
1590 it. */
1591 retval = e;
1592 }
1593
1594 return retval;
1595 }
1596