Line data Source code
1 : /* Calculate (post)dominators in slightly super-linear time.
2 : Copyright (C) 2000-2026 Free Software Foundation, Inc.
3 : Contributed by Michael Matz (matz@ifh.de).
4 :
5 : This file is part of GCC.
6 :
7 : GCC is free software; you can redistribute it and/or modify it
8 : under the terms of the GNU General Public License as published by
9 : the Free Software Foundation; either version 3, or (at your option)
10 : any later version.
11 :
12 : GCC is distributed in the hope that it will be useful, but WITHOUT
13 : ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14 : or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
15 : License for more details.
16 :
17 : You should have received a copy of the GNU General Public License
18 : along with GCC; see the file COPYING3. If not see
19 : <http://www.gnu.org/licenses/>. */
20 :
21 : /* This file implements the well known algorithm from Lengauer and Tarjan
22 : to compute the dominators in a control flow graph. A basic block D is said
23 : to dominate another block X, when all paths from the entry node of the CFG
24 : to X go also over D. The dominance relation is a transitive reflexive
25 : relation and its minimal transitive reduction is a tree, called the
26 : dominator tree. So for each block X besides the entry block exists a
27 : block I(X), called the immediate dominator of X, which is the parent of X
28 : in the dominator tree.
29 :
30 : The algorithm computes this dominator tree implicitly by computing for
31 : each block its immediate dominator. We use tree balancing and path
32 : compression, so it's the O(e*a(e,v)) variant, where a(e,v) is the very
33 : slowly growing functional inverse of the Ackerman function. */
34 :
35 : #include "config.h"
36 : #include "system.h"
37 : #include "coretypes.h"
38 : #include "backend.h"
39 : #include "timevar.h"
40 : #include "diagnostic-core.h"
41 : #include "cfganal.h"
42 : #include "et-forest.h"
43 : #include "graphds.h"
44 :
45 : /* We name our nodes with integers, beginning with 1. Zero is reserved for
46 : 'undefined' or 'end of list'. The name of each node is given by the dfs
47 : number of the corresponding basic block. Please note, that we include the
48 : artificial ENTRY_BLOCK (or EXIT_BLOCK in the post-dom case) in our lists to
49 : support multiple entry points. Its dfs number is of course 1. */
50 :
51 : /* Type of Basic Block aka. TBB */
52 : typedef unsigned int TBB;
53 :
54 : namespace {
55 :
56 : /* This class holds various arrays reflecting the (sub)structure of the
57 : flowgraph. Most of them are of type TBB and are also indexed by TBB. */
58 :
59 : class dom_info
60 : {
61 : public:
62 : dom_info (function *, cdi_direction);
63 : dom_info (vec <basic_block>, cdi_direction);
64 : ~dom_info ();
65 : void calc_dfs_tree ();
66 : void calc_idoms ();
67 :
68 : inline basic_block get_idom (basic_block);
69 : private:
70 : void calc_dfs_tree_nonrec (basic_block);
71 : void compress (TBB);
72 : void dom_init (void);
73 : TBB eval (TBB);
74 : void link_roots (TBB, TBB);
75 :
76 : /* The parent of a node in the DFS tree. */
77 : TBB *m_dfs_parent;
78 : /* For a node x m_key[x] is roughly the node nearest to the root from which
79 : exists a way to x only over nodes behind x. Such a node is also called
80 : semidominator. */
81 : TBB *m_key;
82 : /* The value in m_path_min[x] is the node y on the path from x to the root of
83 : the tree x is in with the smallest m_key[y]. */
84 : TBB *m_path_min;
85 : /* m_bucket[x] points to the first node of the set of nodes having x as
86 : key. */
87 : TBB *m_bucket;
88 : /* And m_next_bucket[x] points to the next node. */
89 : TBB *m_next_bucket;
90 : /* After the algorithm is done, m_dom[x] contains the immediate dominator
91 : of x. */
92 : TBB *m_dom;
93 :
94 : /* The following few fields implement the structures needed for disjoint
95 : sets. */
96 : /* m_set_chain[x] is the next node on the path from x to the representative
97 : of the set containing x. If m_set_chain[x]==0 then x is a root. */
98 : TBB *m_set_chain;
99 : /* m_set_size[x] is the number of elements in the set named by x. */
100 : unsigned int *m_set_size;
101 : /* m_set_child[x] is used for balancing the tree representing a set. It can
102 : be understood as the next sibling of x. */
103 : TBB *m_set_child;
104 :
105 : /* If b is the number of a basic block (BB->index), m_dfs_order[b] is the
106 : number of that node in DFS order counted from 1. This is an index
107 : into most of the other arrays in this structure. */
108 : TBB *m_dfs_order;
109 : /* Points to last element in m_dfs_order array. */
110 : TBB *m_dfs_last;
111 : /* If x is the DFS-index of a node which corresponds with a basic block,
112 : m_dfs_to_bb[x] is that basic block. Note, that in our structure there are
113 : more nodes that basic blocks, so only
114 : m_dfs_to_bb[m_dfs_order[bb->index]]==bb is true for every basic block bb,
115 : but not the opposite. */
116 : basic_block *m_dfs_to_bb;
117 :
118 : /* This is the next free DFS number when creating the DFS tree. */
119 : unsigned int m_dfsnum;
120 : /* The number of nodes in the DFS tree (==m_dfsnum-1). */
121 : unsigned int m_nodes;
122 :
123 : /* Blocks with bits set here have a fake edge to EXIT. These are used
124 : to turn a DFS forest into a proper tree. */
125 : bitmap m_fake_exit_edge;
126 :
127 : /* Number of basic blocks in the function being compiled. */
128 : unsigned m_n_basic_blocks;
129 :
130 : /* True, if we are computing postdominators (rather than dominators). */
131 : bool m_reverse;
132 :
133 : /* Start block (the entry block for forward problem, exit block for backward
134 : problem). */
135 : basic_block m_start_block;
136 : /* Ending block. */
137 : basic_block m_end_block;
138 : };
139 :
140 : } // anonymous namespace
141 :
142 : void debug_dominance_info (cdi_direction);
143 : void debug_dominance_tree (cdi_direction, basic_block);
144 :
145 : /* Allocate and zero-initialize NUM elements of type T (T must be a
146 : POD-type). Note: after transition to C++11 or later,
147 : `x = new_zero_array <T> (num);' can be replaced with
148 : `x = new T[num] {};'. */
149 :
150 : template<typename T>
151 8066505616 : inline T *new_zero_array (unsigned num)
152 : {
153 8066505616 : T *result = new T[num];
154 8066505616 : memset (result, 0, sizeof (T) * num);
155 8066505616 : return result;
156 : }
157 :
158 : /* Helper function for constructors to initialize a part of class members. */
159 :
160 : void
161 1008313202 : dom_info::dom_init (void)
162 : {
163 1008313202 : unsigned num = m_n_basic_blocks;
164 :
165 1008313202 : m_dfs_parent = new_zero_array <TBB> (num);
166 1008313202 : m_dom = new_zero_array <TBB> (num);
167 :
168 1008313202 : m_path_min = new TBB[num];
169 1008313202 : m_key = new TBB[num];
170 1008313202 : m_set_size = new unsigned int[num];
171 12406338291 : for (unsigned i = 0; i < num; i++)
172 : {
173 11398025089 : m_path_min[i] = m_key[i] = i;
174 11398025089 : m_set_size[i] = 1;
175 : }
176 :
177 1008313202 : m_bucket = new_zero_array <TBB> (num);
178 1008313202 : m_next_bucket = new_zero_array <TBB> (num);
179 :
180 1008313202 : m_set_chain = new_zero_array <TBB> (num);
181 1008313202 : m_set_child = new_zero_array <TBB> (num);
182 :
183 1008313202 : m_dfs_to_bb = new_zero_array <basic_block> (num);
184 :
185 1008313202 : m_dfsnum = 1;
186 1008313202 : m_nodes = 0;
187 1008313202 : }
188 :
189 : /* Allocate all needed memory in a pessimistic fashion (so we round up). */
190 :
191 1008272450 : dom_info::dom_info (function *fn, cdi_direction dir)
192 : {
193 1008272450 : m_n_basic_blocks = n_basic_blocks_for_fn (fn);
194 :
195 1008272450 : dom_init ();
196 :
197 1008272450 : unsigned last_bb_index = last_basic_block_for_fn (fn);
198 1008272450 : m_dfs_order = new_zero_array <TBB> (last_bb_index + 1);
199 1008272450 : m_dfs_last = &m_dfs_order[last_bb_index];
200 :
201 1008272450 : switch (dir)
202 : {
203 982241840 : case CDI_DOMINATORS:
204 982241840 : m_reverse = false;
205 982241840 : m_fake_exit_edge = NULL;
206 982241840 : m_start_block = ENTRY_BLOCK_PTR_FOR_FN (fn);
207 982241840 : m_end_block = EXIT_BLOCK_PTR_FOR_FN (fn);
208 982241840 : break;
209 26030610 : case CDI_POST_DOMINATORS:
210 26030610 : m_reverse = true;
211 26030610 : m_fake_exit_edge = BITMAP_ALLOC (NULL);
212 26030610 : m_start_block = EXIT_BLOCK_PTR_FOR_FN (fn);
213 26030610 : m_end_block = ENTRY_BLOCK_PTR_FOR_FN (fn);
214 26030610 : break;
215 0 : default:
216 0 : gcc_unreachable ();
217 : }
218 1008272450 : }
219 :
220 : /* Constructor for reducible region REGION. */
221 :
222 40752 : dom_info::dom_info (vec<basic_block> region, cdi_direction dir)
223 : {
224 40752 : m_n_basic_blocks = region.length ();
225 40752 : unsigned nm1 = m_n_basic_blocks - 1;
226 :
227 40752 : dom_init ();
228 :
229 : /* Determine max basic block index in region. */
230 40752 : int max_index = region[0]->index;
231 302372 : for (unsigned i = 1; i <= nm1; i++)
232 261620 : if (region[i]->index > max_index)
233 : max_index = region[i]->index;
234 40752 : max_index += 1; /* set index on the first bb out of region. */
235 :
236 40752 : m_dfs_order = new_zero_array <TBB> (max_index + 1);
237 40752 : m_dfs_last = &m_dfs_order[max_index];
238 :
239 40752 : m_fake_exit_edge = NULL; /* Assume that region is reducible. */
240 :
241 40752 : switch (dir)
242 : {
243 0 : case CDI_DOMINATORS:
244 0 : m_reverse = false;
245 0 : m_start_block = region[0];
246 0 : m_end_block = region[nm1];
247 0 : break;
248 40752 : case CDI_POST_DOMINATORS:
249 40752 : m_reverse = true;
250 40752 : m_start_block = region[nm1];
251 40752 : m_end_block = region[0];
252 40752 : break;
253 0 : default:
254 0 : gcc_unreachable ();
255 : }
256 40752 : }
257 :
258 : inline basic_block
259 9381480189 : dom_info::get_idom (basic_block bb)
260 : {
261 9381480189 : TBB d = m_dom[m_dfs_order[bb->index]];
262 9381480189 : return m_dfs_to_bb[d];
263 : }
264 :
265 : /* Map dominance calculation type to array index used for various
266 : dominance information arrays. This version is simple -- it will need
267 : to be modified, obviously, if additional values are added to
268 : cdi_direction. */
269 :
270 : static inline unsigned int
271 32696375874 : dom_convert_dir_to_idx (cdi_direction dir)
272 : {
273 32696375874 : gcc_checking_assert (dir == CDI_DOMINATORS || dir == CDI_POST_DOMINATORS);
274 32696375874 : return dir - 1;
275 : }
276 :
277 : /* Free all allocated memory in dom_info. */
278 :
279 1008313202 : dom_info::~dom_info ()
280 : {
281 1008313202 : delete[] m_dfs_parent;
282 1008313202 : delete[] m_path_min;
283 1008313202 : delete[] m_key;
284 1008313202 : delete[] m_dom;
285 1008313202 : delete[] m_bucket;
286 1008313202 : delete[] m_next_bucket;
287 1008313202 : delete[] m_set_chain;
288 1008313202 : delete[] m_set_size;
289 1008313202 : delete[] m_set_child;
290 1008313202 : delete[] m_dfs_order;
291 1008313202 : delete[] m_dfs_to_bb;
292 1008313202 : BITMAP_FREE (m_fake_exit_edge);
293 1008313202 : }
294 :
295 : /* The nonrecursive variant of creating a DFS tree. BB is the starting basic
296 : block for this tree and m_reverse is true, if predecessors should be visited
297 : instead of successors of a node. After this is done all nodes reachable
298 : from BB were visited, have assigned their dfs number and are linked together
299 : to form a tree. */
300 :
301 : void
302 1020137082 : dom_info::calc_dfs_tree_nonrec (basic_block bb)
303 : {
304 1020137082 : edge_iterator *stack = new edge_iterator[m_n_basic_blocks + 1];
305 1020137082 : int sp = 0;
306 2002378922 : unsigned d_i = dom_convert_dir_to_idx (m_reverse ? CDI_POST_DOMINATORS
307 : : CDI_DOMINATORS);
308 :
309 : /* Initialize the first edge. */
310 1020137082 : edge_iterator ei = m_reverse ? ei_start (bb->preds)
311 982241840 : : ei_start (bb->succs);
312 :
313 : /* When the stack is empty we break out of this loop. */
314 9369574805 : while (1)
315 : {
316 : basic_block bn;
317 : edge_iterator einext;
318 :
319 : /* This loop traverses edges e in depth first manner, and fills the
320 : stack. */
321 24572106682 : while (!ei_end_p (ei))
322 : {
323 14182394795 : edge e = ei_edge (ei);
324 :
325 : /* Deduce from E the current and the next block (BB and BN), and the
326 : next edge. */
327 14182394795 : if (m_reverse)
328 : {
329 327360905 : bn = e->src;
330 :
331 : /* If the next node BN is either already visited or a border
332 : block or out of region the current edge is useless, and simply
333 : overwritten with the next edge out of the current node. */
334 327360905 : if (bn == m_end_block || bn->dom[d_i] == NULL
335 301274715 : || m_dfs_order[bn->index])
336 : {
337 123065147 : ei_next (&ei);
338 123065147 : continue;
339 : }
340 204295758 : bb = e->dest;
341 204295758 : einext = ei_start (bn->preds);
342 : }
343 : else
344 : {
345 13855033890 : bn = e->dest;
346 13855033890 : if (bn == m_end_block || bn->dom[d_i] == NULL
347 12884676368 : || m_dfs_order[bn->index])
348 : {
349 4689754843 : ei_next (&ei);
350 4689754843 : continue;
351 : }
352 9165279047 : bb = e->src;
353 9165279047 : einext = ei_start (bn->succs);
354 : }
355 :
356 9369574805 : gcc_assert (bn != m_start_block);
357 :
358 : /* Fill the DFS tree info calculatable _before_ recursing. */
359 9369574805 : TBB my_i;
360 9369574805 : if (bb != m_start_block)
361 8359752475 : my_i = m_dfs_order[bb->index];
362 : else
363 1009822330 : my_i = *m_dfs_last;
364 9369574805 : TBB child_i = m_dfs_order[bn->index] = m_dfsnum++;
365 9369574805 : m_dfs_to_bb[child_i] = bn;
366 9369574805 : m_dfs_parent[child_i] = my_i;
367 :
368 : /* Save the current point in the CFG on the stack, and recurse. */
369 9369574805 : stack[sp++] = ei;
370 9369574805 : ei = einext;
371 : }
372 :
373 10389711887 : if (!sp)
374 : break;
375 9369574805 : ei = stack[--sp];
376 :
377 : /* OK. The edge-list was exhausted, meaning normally we would
378 : end the recursion. After returning from the recursive call,
379 : there were (may be) other statements which were run after a
380 : child node was completely considered by DFS. Here is the
381 : point to do it in the non-recursive variant.
382 : E.g. The block just completed is in e->dest for forward DFS,
383 : the block not yet completed (the parent of the one above)
384 : in e->src. This could be used e.g. for computing the number of
385 : descendants or the tree depth. */
386 9369574805 : ei_next (&ei);
387 9369574805 : }
388 1020137082 : delete[] stack;
389 1020137082 : }
390 :
391 : /* The main entry for calculating the DFS tree or forest. m_reverse is true,
392 : if we are interested in the reverse flow graph. In that case the result is
393 : not necessarily a tree but a forest, because there may be nodes from which
394 : the EXIT_BLOCK is unreachable. */
395 :
396 : void
397 1008313202 : dom_info::calc_dfs_tree ()
398 : {
399 1008313202 : *m_dfs_last = m_dfsnum;
400 1008313202 : m_dfs_to_bb[m_dfsnum] = m_start_block;
401 1008313202 : m_dfsnum++;
402 :
403 1008313202 : calc_dfs_tree_nonrec (m_start_block);
404 :
405 1008313202 : if (m_fake_exit_edge)
406 : {
407 : /* In the post-dom case we may have nodes without a path to EXIT_BLOCK.
408 : They are reverse-unreachable. In the dom-case we disallow such
409 : nodes, but in post-dom we have to deal with them.
410 :
411 : There are two situations in which this occurs. First, noreturn
412 : functions. Second, infinite loops. In the first case we need to
413 : pretend that there is an edge to the exit block. In the second
414 : case, we wind up with a forest. We need to process all noreturn
415 : blocks before we know if we've got any infinite loops. */
416 :
417 26030610 : basic_block b;
418 26030610 : bool saw_unconnected = false;
419 :
420 241929380 : FOR_BB_BETWEEN (b, m_start_block->prev_bb, m_end_block, prev_bb)
421 : {
422 215898770 : if (EDGE_COUNT (b->succs) > 0)
423 : {
424 204169526 : if (m_dfs_order[b->index] == 0)
425 1148045 : saw_unconnected = true;
426 204169526 : continue;
427 : }
428 11729244 : bitmap_set_bit (m_fake_exit_edge, b->index);
429 11729244 : m_dfs_order[b->index] = m_dfsnum;
430 11729244 : m_dfs_to_bb[m_dfsnum] = b;
431 11729244 : m_dfs_parent[m_dfsnum] = *m_dfs_last;
432 11729244 : m_dfsnum++;
433 11729244 : calc_dfs_tree_nonrec (b);
434 : }
435 :
436 26030610 : if (saw_unconnected)
437 : {
438 9535676 : FOR_BB_BETWEEN (b, m_start_block->prev_bb, m_end_block, prev_bb)
439 : {
440 9326506 : if (m_dfs_order[b->index])
441 9231870 : continue;
442 94636 : basic_block b2 = dfs_find_deadend (b);
443 94636 : gcc_checking_assert (m_dfs_order[b2->index] == 0);
444 94636 : bitmap_set_bit (m_fake_exit_edge, b2->index);
445 94636 : m_dfs_order[b2->index] = m_dfsnum;
446 94636 : m_dfs_to_bb[m_dfsnum] = b2;
447 94636 : m_dfs_parent[m_dfsnum] = *m_dfs_last;
448 94636 : m_dfsnum++;
449 94636 : calc_dfs_tree_nonrec (b2);
450 94636 : gcc_checking_assert (m_dfs_order[b->index]);
451 : }
452 : }
453 : }
454 :
455 1008313202 : m_nodes = m_dfsnum - 1;
456 :
457 : /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. */
458 1008313202 : gcc_assert (m_nodes == (unsigned int) m_n_basic_blocks - 1);
459 1008313202 : }
460 :
461 : /* Compress the path from V to the root of its set and update path_min at the
462 : same time. After compress(di, V) set_chain[V] is the root of the set V is
463 : in and path_min[V] is the node with the smallest key[] value on the path
464 : from V to that root. */
465 :
466 : void
467 3619788553 : dom_info::compress (TBB v)
468 : {
469 : /* Btw. It's not worth to unrecurse compress() as the depth is usually not
470 : greater than 5 even for huge graphs (I've not seen call depth > 4).
471 : Also performance wise compress() ranges _far_ behind eval(). */
472 3619788553 : TBB parent = m_set_chain[v];
473 3619788553 : if (m_set_chain[parent])
474 : {
475 2015329391 : compress (parent);
476 2015329391 : if (m_key[m_path_min[parent]] < m_key[m_path_min[v]])
477 1354844104 : m_path_min[v] = m_path_min[parent];
478 2015329391 : m_set_chain[v] = m_set_chain[parent];
479 : }
480 3619788553 : }
481 :
482 : /* Compress the path from V to the set root of V if needed (when the root has
483 : changed since the last call). Returns the node with the smallest key[]
484 : value on the path from V to the root. */
485 :
486 : inline TBB
487 12360987859 : dom_info::eval (TBB v)
488 : {
489 : /* The representative of the set V is in, also called root (as the set
490 : representation is a tree). */
491 12360987859 : TBB rep = m_set_chain[v];
492 :
493 : /* V itself is the root. */
494 12360987859 : if (!rep)
495 2729183099 : return m_path_min[v];
496 :
497 : /* Compress only if necessary. */
498 9631804760 : if (m_set_chain[rep])
499 : {
500 1604459162 : compress (v);
501 1604459162 : rep = m_set_chain[v];
502 : }
503 :
504 9631804760 : if (m_key[m_path_min[rep]] >= m_key[m_path_min[v]])
505 : return m_path_min[v];
506 : else
507 1684504053 : return m_path_min[rep];
508 : }
509 :
510 : /* This essentially merges the two sets of V and W, giving a single set with
511 : the new root V. The internal representation of these disjoint sets is a
512 : balanced tree. Currently link(V,W) is only used with V being the parent
513 : of W. */
514 :
515 : void
516 9381398685 : dom_info::link_roots (TBB v, TBB w)
517 : {
518 9381398685 : TBB s = w;
519 :
520 : /* Rebalance the tree. */
521 13908724501 : while (m_key[m_path_min[w]] < m_key[m_path_min[m_set_child[s]]])
522 : {
523 4527325816 : if (m_set_size[s] + m_set_size[m_set_child[m_set_child[s]]]
524 4527325816 : >= 2 * m_set_size[m_set_child[s]])
525 : {
526 1532081627 : m_set_chain[m_set_child[s]] = s;
527 1532081627 : m_set_child[s] = m_set_child[m_set_child[s]];
528 : }
529 : else
530 : {
531 2995244189 : m_set_size[m_set_child[s]] = m_set_size[s];
532 2995244189 : s = m_set_chain[s] = m_set_child[s];
533 : }
534 : }
535 :
536 9381398685 : m_path_min[s] = m_path_min[w];
537 9381398685 : m_set_size[v] += m_set_size[w];
538 9381398685 : if (m_set_size[v] < 2 * m_set_size[w])
539 5425851033 : std::swap (m_set_child[v], s);
540 :
541 : /* Merge all subtrees. */
542 13711954627 : while (s)
543 : {
544 4330555942 : m_set_chain[s] = v;
545 4330555942 : s = m_set_child[s];
546 : }
547 9381398685 : }
548 :
549 : /* This calculates the immediate dominators (or post-dominators). THIS is our
550 : working structure and should hold the DFS forest.
551 : On return the immediate dominator to node V is in m_dom[V]. */
552 :
553 : void
554 1008313202 : dom_info::calc_idoms ()
555 : {
556 : /* Go backwards in DFS order, to first look at the leafs. */
557 10389711887 : for (TBB v = m_nodes; v > 1; v--)
558 : {
559 9381398685 : basic_block bb = m_dfs_to_bb[v];
560 9381398685 : edge e;
561 :
562 9381398685 : TBB par = m_dfs_parent[v];
563 9381398685 : TBB k = v;
564 :
565 9381398685 : edge_iterator ei = m_reverse ? ei_start (bb->succs)
566 9165279047 : : ei_start (bb->preds);
567 9381398685 : edge_iterator einext;
568 :
569 9381398685 : if (m_fake_exit_edge)
570 : {
571 : /* If this block has a fake edge to exit, process that first. */
572 215898770 : if (bitmap_bit_p (m_fake_exit_edge, bb->index))
573 : {
574 11823880 : einext = ei;
575 11823880 : einext.index = 0;
576 11823880 : goto do_fake_exit_edge;
577 : }
578 : }
579 :
580 : /* Search all direct predecessors for the smallest node with a path
581 : to them. That way we have the smallest node with also a path to
582 : us only over nodes behind us. In effect we search for our
583 : semidominator. */
584 22567349768 : while (!ei_end_p (ei))
585 : {
586 13185951083 : basic_block b;
587 13185951083 : TBB k1;
588 :
589 13185951083 : e = ei_edge (ei);
590 13185951083 : b = m_reverse ? e->dest : e->src;
591 13185951083 : einext = ei;
592 13185951083 : ei_next (&einext);
593 :
594 13185951083 : if (b == m_start_block)
595 : {
596 1009822354 : do_fake_exit_edge:
597 1021646234 : k1 = *m_dfs_last;
598 : }
599 : else
600 12176128729 : k1 = m_dfs_order[b->index];
601 :
602 : /* Call eval() only if really needed. If k1 is above V in DFS tree,
603 : then we know, that eval(k1) == k1 and key[k1] == k1. */
604 13197774963 : if (k1 > v)
605 2979589174 : k1 = m_key[eval (k1)];
606 13197774963 : if (k1 < k)
607 : k = k1;
608 :
609 13197774963 : ei = einext;
610 : }
611 :
612 9381398685 : m_key[v] = k;
613 9381398685 : link_roots (par, v);
614 9381398685 : m_next_bucket[v] = m_bucket[k];
615 9381398685 : m_bucket[k] = v;
616 :
617 : /* Transform semidominators into dominators. */
618 18762797370 : for (TBB w = m_bucket[par]; w; w = m_next_bucket[w])
619 : {
620 9381398685 : k = eval (w);
621 9381398685 : if (m_key[k] < m_key[w])
622 42292048 : m_dom[w] = k;
623 : else
624 9339106637 : m_dom[w] = par;
625 : }
626 : /* We don't need to cleanup next_bucket[]. */
627 9381398685 : m_bucket[par] = 0;
628 : }
629 :
630 : /* Explicitly define the dominators. */
631 1008313202 : m_dom[1] = 0;
632 10389711887 : for (TBB v = 2; v <= m_nodes; v++)
633 9381398685 : if (m_dom[v] != m_key[v])
634 42292048 : m_dom[v] = m_dom[m_dom[v]];
635 1008313202 : }
636 :
637 : /* Assign dfs numbers starting from NUM to NODE and its sons. */
638 :
639 : static void
640 518121279 : assign_dfs_numbers (struct et_node *node, int *num)
641 : {
642 518121279 : et_node *n = node;
643 2792408765 : while (1)
644 : {
645 2792408765 : n->dfs_num_in = (*num)++;
646 2792408765 : if (n->son)
647 : n = n->son;
648 : else
649 : {
650 2792408765 : while (!n->right || n->right == n->father->son)
651 : {
652 1876334961 : n->dfs_num_out = (*num)++;
653 1876334961 : if (n == node)
654 518121279 : return;
655 1358213682 : n = n->father;
656 : }
657 916073804 : n->dfs_num_out = (*num)++;
658 916073804 : n = n->right;
659 : }
660 : }
661 : }
662 :
663 : /* Compute the data necessary for fast resolving of dominator queries in a
664 : static dominator tree. */
665 :
666 : static void
667 259060930 : compute_dom_fast_query (enum cdi_direction dir)
668 : {
669 259060930 : int num = 0;
670 259060930 : basic_block bb;
671 259060930 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
672 :
673 259060930 : gcc_checking_assert (dom_info_available_p (dir));
674 :
675 259060930 : if (dom_computed[dir_index] == DOM_OK)
676 0 : return;
677 :
678 3051469695 : FOR_ALL_BB_FN (bb, cfun)
679 : {
680 2792408765 : if (!bb->dom[dir_index]->father)
681 518121279 : assign_dfs_numbers (bb->dom[dir_index], &num);
682 : }
683 :
684 259060930 : dom_computed[dir_index] = DOM_OK;
685 : }
686 :
687 : /* Analogous to the previous function but compute the data for reducible
688 : region REGION. */
689 :
690 : static void
691 40752 : compute_dom_fast_query_in_region (enum cdi_direction dir,
692 : vec<basic_block> region)
693 : {
694 40752 : int num = 0;
695 40752 : basic_block bb;
696 40752 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
697 :
698 40752 : gcc_checking_assert (dom_info_available_p (dir));
699 :
700 40752 : if (dom_computed[dir_index] == DOM_OK)
701 0 : return;
702 :
703 : /* Assign dfs numbers for region nodes except for entry and exit nodes. */
704 523240 : for (unsigned int i = 1; i < region.length () - 1; i++)
705 : {
706 220868 : bb = region[i];
707 220868 : if (!bb->dom[dir_index]->father)
708 0 : assign_dfs_numbers (bb->dom[dir_index], &num);
709 : }
710 :
711 40752 : dom_computed[dir_index] = DOM_OK;
712 : }
713 :
714 : /* The main entry point into this module. DIR is set depending on whether
715 : we want to compute dominators or postdominators. If COMPUTE_FAST_QUERY
716 : is false then the DFS numbers allowing for a O(1) dominance query
717 : are not computed. */
718 :
719 : void
720 535076197 : calculate_dominance_info (cdi_direction dir, bool compute_fast_query)
721 : {
722 535076197 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
723 :
724 535076197 : if (dom_computed[dir_index] == DOM_OK)
725 : {
726 267514351 : checking_verify_dominators (dir);
727 267514351 : return;
728 : }
729 :
730 267561846 : timevar_push (TV_DOMINANCE);
731 267561846 : if (!dom_info_available_p (dir))
732 : {
733 246499582 : gcc_assert (!n_bbs_in_dom_tree[dir_index]);
734 :
735 246499582 : basic_block b;
736 2688025390 : FOR_ALL_BB_FN (b, cfun)
737 : {
738 2441525808 : b->dom[dir_index] = et_new_tree (b);
739 : }
740 246499582 : n_bbs_in_dom_tree[dir_index] = n_basic_blocks_for_fn (cfun);
741 :
742 246499582 : dom_info di (cfun, dir);
743 246499582 : di.calc_dfs_tree ();
744 246499582 : di.calc_idoms ();
745 :
746 2195026226 : FOR_EACH_BB_FN (b, cfun)
747 : {
748 1948526644 : if (basic_block d = di.get_idom (b))
749 1948526644 : et_set_father (b->dom[dir_index], d->dom[dir_index]);
750 : }
751 :
752 246499582 : dom_computed[dir_index] = DOM_NO_FAST_QUERY;
753 246499582 : }
754 : else
755 21062264 : checking_verify_dominators (dir);
756 :
757 267561846 : if (compute_fast_query)
758 259060930 : compute_dom_fast_query (dir);
759 :
760 267561846 : timevar_pop (TV_DOMINANCE);
761 : }
762 :
763 : /* Analogous to the previous function but compute dominance info for regions
764 : which are single entry, multiple exit regions for CDI_DOMINATORs and
765 : multiple entry, single exit regions for CDI_POST_DOMINATORs. */
766 :
767 : void
768 40752 : calculate_dominance_info_for_region (cdi_direction dir,
769 : vec<basic_block> region)
770 : {
771 40752 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
772 40752 : basic_block bb;
773 40752 : unsigned int i;
774 :
775 40752 : if (dom_computed[dir_index] == DOM_OK)
776 0 : return;
777 :
778 40752 : timevar_push (TV_DOMINANCE);
779 : /* Assume that dom info is not partially computed. */
780 40752 : gcc_assert (!dom_info_available_p (dir));
781 :
782 343124 : FOR_EACH_VEC_ELT (region, i, bb)
783 : {
784 302372 : bb->dom[dir_index] = et_new_tree (bb);
785 : }
786 40752 : dom_info di (region, dir);
787 40752 : di.calc_dfs_tree ();
788 40752 : di.calc_idoms ();
789 :
790 343124 : FOR_EACH_VEC_ELT (region, i, bb)
791 302372 : if (basic_block d = di.get_idom (bb))
792 220868 : et_set_father (bb->dom[dir_index], d->dom[dir_index]);
793 :
794 40752 : dom_computed[dir_index] = DOM_NO_FAST_QUERY;
795 40752 : compute_dom_fast_query_in_region (dir, region);
796 :
797 40752 : timevar_pop (TV_DOMINANCE);
798 40752 : }
799 :
800 : /* Free dominance information for direction DIR. */
801 : void
802 443033929 : free_dominance_info (function *fn, enum cdi_direction dir)
803 : {
804 443033929 : basic_block bb;
805 443033929 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
806 :
807 443033929 : if (!dom_info_available_p (fn, dir))
808 : return;
809 :
810 2671306928 : FOR_ALL_BB_FN (bb, fn)
811 : {
812 2424862722 : et_free_tree_force (bb->dom[dir_index]);
813 2424862722 : bb->dom[dir_index] = NULL;
814 : }
815 246444206 : et_free_pools ();
816 :
817 246444206 : fn->cfg->x_n_bbs_in_dom_tree[dir_index] = 0;
818 :
819 246444206 : fn->cfg->x_dom_computed[dir_index] = DOM_NONE;
820 : }
821 :
822 : void
823 285940986 : free_dominance_info (enum cdi_direction dir)
824 : {
825 285940986 : free_dominance_info (cfun, dir);
826 285940986 : }
827 :
828 : /* Free dominance information for direction DIR in region REGION. */
829 :
830 : void
831 40752 : free_dominance_info_for_region (function *fn,
832 : enum cdi_direction dir,
833 : vec<basic_block> region)
834 : {
835 40752 : basic_block bb;
836 40752 : unsigned int i;
837 40752 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
838 :
839 40752 : if (!dom_info_available_p (dir))
840 40752 : return;
841 :
842 343124 : FOR_EACH_VEC_ELT (region, i, bb)
843 : {
844 302372 : et_free_tree_force (bb->dom[dir_index]);
845 302372 : bb->dom[dir_index] = NULL;
846 : }
847 40752 : et_free_pools ();
848 :
849 40752 : fn->cfg->x_dom_computed[dir_index] = DOM_NONE;
850 :
851 40752 : fn->cfg->x_n_bbs_in_dom_tree[dir_index] = 0;
852 : }
853 :
854 : /* Return the immediate dominator of basic block BB. */
855 : basic_block
856 9639183909 : get_immediate_dominator (enum cdi_direction dir, basic_block bb)
857 : {
858 9639183909 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
859 9639183909 : struct et_node *node = bb->dom[dir_index];
860 :
861 9639183909 : gcc_checking_assert (dom_computed[dir_index]);
862 :
863 9639183909 : if (!node->father)
864 : return NULL;
865 :
866 9603343350 : return (basic_block) node->father->data;
867 : }
868 :
869 : /* Set the immediate dominator of the block possibly removing
870 : existing edge. NULL can be used to remove any edge. */
871 : void
872 67850199 : set_immediate_dominator (enum cdi_direction dir, basic_block bb,
873 : basic_block dominated_by)
874 : {
875 67850199 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
876 67850199 : struct et_node *node = bb->dom[dir_index];
877 :
878 67850199 : gcc_checking_assert (dom_computed[dir_index]);
879 :
880 67850199 : if (node->father)
881 : {
882 36553299 : if (node->father->data == dominated_by)
883 : return;
884 14322361 : et_split (node);
885 : }
886 :
887 45619261 : if (dominated_by)
888 43608324 : et_set_father (node, dominated_by->dom[dir_index]);
889 :
890 45619261 : if (dom_computed[dir_index] == DOM_OK)
891 899663 : dom_computed[dir_index] = DOM_NO_FAST_QUERY;
892 : }
893 :
894 : /* Returns the list of basic blocks immediately dominated by BB, in the
895 : direction DIR. */
896 : auto_vec<basic_block>
897 820305 : get_dominated_by (enum cdi_direction dir, basic_block bb)
898 : {
899 820305 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
900 820305 : struct et_node *node = bb->dom[dir_index], *son = node->son, *ason;
901 820305 : auto_vec<basic_block> bbs;
902 :
903 820305 : gcc_checking_assert (dom_computed[dir_index]);
904 :
905 820305 : if (!son)
906 : return bbs;
907 :
908 491818 : bbs.safe_push ((basic_block) son->data);
909 815210 : for (ason = son->right; ason != son; ason = ason->right)
910 323392 : bbs.safe_push ((basic_block) ason->data);
911 :
912 : return bbs;
913 : }
914 :
915 : /* Returns the list of basic blocks that are immediately dominated (in
916 : direction DIR) by some block between N_REGION ones stored in REGION,
917 : except for blocks in the REGION itself. */
918 :
919 : auto_vec<basic_block>
920 612872 : get_dominated_by_region (enum cdi_direction dir, basic_block *region,
921 : unsigned n_region)
922 : {
923 612872 : unsigned i;
924 612872 : basic_block dom;
925 612872 : auto_vec<basic_block> doms;
926 :
927 1830799 : for (i = 0; i < n_region; i++)
928 1217927 : region[i]->flags |= BB_DUPLICATED;
929 1830799 : for (i = 0; i < n_region; i++)
930 1217927 : for (dom = first_dom_son (dir, region[i]);
931 2945697 : dom;
932 1727770 : dom = next_dom_son (dir, dom))
933 1727770 : if (!(dom->flags & BB_DUPLICATED))
934 1122715 : doms.safe_push (dom);
935 1830799 : for (i = 0; i < n_region; i++)
936 1217927 : region[i]->flags &= ~BB_DUPLICATED;
937 :
938 612872 : return doms;
939 : }
940 :
941 : /* Returns the list of basic blocks including BB dominated by BB, in the
942 : direction DIR up to DEPTH in the dominator tree. The DEPTH of zero will
943 : produce a vector containing all dominated blocks. The vector will be sorted
944 : in preorder. */
945 :
946 : auto_vec<basic_block>
947 11883471 : get_dominated_to_depth (enum cdi_direction dir, basic_block bb, int depth)
948 : {
949 11883471 : auto_vec<basic_block> bbs;
950 11883471 : unsigned i;
951 11883471 : unsigned next_level_start;
952 :
953 11883471 : i = 0;
954 11883471 : bbs.safe_push (bb);
955 11883471 : next_level_start = 1; /* = bbs.length (); */
956 :
957 111417014 : do
958 : {
959 111417014 : basic_block son;
960 :
961 111417014 : bb = bbs[i++];
962 111417014 : for (son = first_dom_son (dir, bb);
963 211039513 : son;
964 99622499 : son = next_dom_son (dir, son))
965 99622499 : bbs.safe_push (son);
966 :
967 111417014 : if (i == next_level_start && --depth)
968 48012673 : next_level_start = bbs.length ();
969 : }
970 111417014 : while (i < next_level_start);
971 :
972 11883471 : return bbs;
973 : }
974 :
975 : /* Returns the list of basic blocks including BB dominated by BB, in the
976 : direction DIR. The vector will be sorted in preorder. */
977 :
978 : auto_vec<basic_block>
979 11558020 : get_all_dominated_blocks (enum cdi_direction dir, basic_block bb)
980 : {
981 11558020 : return get_dominated_to_depth (dir, bb, 0);
982 : }
983 :
984 : /* Redirect all edges pointing to BB to TO. */
985 : void
986 17356102 : redirect_immediate_dominators (enum cdi_direction dir, basic_block bb,
987 : basic_block to)
988 : {
989 17356102 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
990 17356102 : struct et_node *bb_node, *to_node, *son;
991 :
992 17356102 : bb_node = bb->dom[dir_index];
993 17356102 : to_node = to->dom[dir_index];
994 :
995 17356102 : gcc_checking_assert (dom_computed[dir_index]);
996 :
997 17356102 : if (!bb_node->son)
998 : return;
999 :
1000 30824507 : while (bb_node->son)
1001 : {
1002 17835290 : son = bb_node->son;
1003 :
1004 17835290 : et_split (son);
1005 17835290 : et_set_father (son, to_node);
1006 : }
1007 :
1008 12989217 : if (dom_computed[dir_index] == DOM_OK)
1009 1344589 : dom_computed[dir_index] = DOM_NO_FAST_QUERY;
1010 : }
1011 :
1012 : /* Find first basic block in the tree dominating both BB1 and BB2. */
1013 : basic_block
1014 113860497 : nearest_common_dominator (enum cdi_direction dir, basic_block bb1, basic_block bb2)
1015 : {
1016 113860497 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1017 :
1018 113860497 : gcc_checking_assert (dom_computed[dir_index]);
1019 :
1020 113860497 : if (!bb1)
1021 : return bb2;
1022 111618437 : if (!bb2)
1023 : return bb1;
1024 :
1025 111618437 : return (basic_block) et_nca (bb1->dom[dir_index], bb2->dom[dir_index])->data;
1026 : }
1027 :
1028 :
1029 : /* Find the nearest common dominator for the basic blocks in BLOCKS,
1030 : using dominance direction DIR. */
1031 :
1032 : basic_block
1033 11398572 : nearest_common_dominator_for_set (enum cdi_direction dir, bitmap blocks)
1034 : {
1035 11398572 : unsigned i, first;
1036 11398572 : bitmap_iterator bi;
1037 11398572 : basic_block dom;
1038 :
1039 11398572 : first = bitmap_first_set_bit (blocks);
1040 11398572 : dom = BASIC_BLOCK_FOR_FN (cfun, first);
1041 67676387 : EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi)
1042 56277815 : if (dom != BASIC_BLOCK_FOR_FN (cfun, i))
1043 44558028 : dom = nearest_common_dominator (dir, dom, BASIC_BLOCK_FOR_FN (cfun, i));
1044 :
1045 11398572 : return dom;
1046 : }
1047 :
1048 : /* Given a dominator tree, we can determine whether one thing
1049 : dominates another in constant time by using two DFS numbers:
1050 :
1051 : 1. The number for when we visit a node on the way down the tree
1052 : 2. The number for when we visit a node on the way back up the tree
1053 :
1054 : You can view these as bounds for the range of dfs numbers the
1055 : nodes in the subtree of the dominator tree rooted at that node
1056 : will contain.
1057 :
1058 : The dominator tree is always a simple acyclic tree, so there are
1059 : only three possible relations two nodes in the dominator tree have
1060 : to each other:
1061 :
1062 : 1. Node A is above Node B (and thus, Node A dominates node B)
1063 :
1064 : A
1065 : |
1066 : C
1067 : / \
1068 : B D
1069 :
1070 :
1071 : In the above case, DFS_Number_In of A will be <= DFS_Number_In of
1072 : B, and DFS_Number_Out of A will be >= DFS_Number_Out of B. This is
1073 : because we must hit A in the dominator tree *before* B on the walk
1074 : down, and we will hit A *after* B on the walk back up
1075 :
1076 : 2. Node A is below node B (and thus, node B dominates node A)
1077 :
1078 :
1079 : B
1080 : |
1081 : A
1082 : / \
1083 : C D
1084 :
1085 : In the above case, DFS_Number_In of A will be >= DFS_Number_In of
1086 : B, and DFS_Number_Out of A will be <= DFS_Number_Out of B.
1087 :
1088 : This is because we must hit A in the dominator tree *after* B on
1089 : the walk down, and we will hit A *before* B on the walk back up
1090 :
1091 : 3. Node A and B are siblings (and thus, neither dominates the other)
1092 :
1093 : C
1094 : |
1095 : D
1096 : / \
1097 : A B
1098 :
1099 : In the above case, DFS_Number_In of A will *always* be <=
1100 : DFS_Number_In of B, and DFS_Number_Out of A will *always* be <=
1101 : DFS_Number_Out of B. This is because we will always finish the dfs
1102 : walk of one of the subtrees before the other, and thus, the dfs
1103 : numbers for one subtree can't intersect with the range of dfs
1104 : numbers for the other subtree. If you swap A and B's position in
1105 : the dominator tree, the comparison changes direction, but the point
1106 : is that both comparisons will always go the same way if there is no
1107 : dominance relationship.
1108 :
1109 : Thus, it is sufficient to write
1110 :
1111 : A_Dominates_B (node A, node B)
1112 : {
1113 : return DFS_Number_In(A) <= DFS_Number_In(B)
1114 : && DFS_Number_Out (A) >= DFS_Number_Out(B);
1115 : }
1116 :
1117 : A_Dominated_by_B (node A, node B)
1118 : {
1119 : return DFS_Number_In(A) >= DFS_Number_In(B)
1120 : && DFS_Number_Out (A) <= DFS_Number_Out(B);
1121 : } */
1122 :
1123 : /* Return TRUE in case BB1 is dominated by BB2. */
1124 : bool
1125 12470365916 : dominated_by_p (enum cdi_direction dir, const_basic_block bb1, const_basic_block bb2)
1126 : {
1127 12470365916 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1128 12470365916 : struct et_node *n1 = bb1->dom[dir_index], *n2 = bb2->dom[dir_index];
1129 :
1130 12470365916 : gcc_checking_assert (dom_computed[dir_index]);
1131 :
1132 12470365916 : if (dom_computed[dir_index] == DOM_OK)
1133 11773243201 : return (n1->dfs_num_in >= n2->dfs_num_in
1134 18681235966 : && n1->dfs_num_out <= n2->dfs_num_out);
1135 :
1136 697122715 : return et_below (n1, n2);
1137 : }
1138 :
1139 : /* Returns the entry dfs number for basic block BB, in the direction DIR. */
1140 :
1141 : unsigned
1142 83150540 : bb_dom_dfs_in (enum cdi_direction dir, basic_block bb)
1143 : {
1144 83150540 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1145 83150540 : struct et_node *n = bb->dom[dir_index];
1146 :
1147 83150540 : gcc_checking_assert (dom_computed[dir_index] == DOM_OK);
1148 83150540 : return n->dfs_num_in;
1149 : }
1150 :
1151 : /* Returns the exit dfs number for basic block BB, in the direction DIR. */
1152 :
1153 : unsigned
1154 47428231 : bb_dom_dfs_out (enum cdi_direction dir, basic_block bb)
1155 : {
1156 47428231 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1157 47428231 : struct et_node *n = bb->dom[dir_index];
1158 :
1159 47428231 : gcc_checking_assert (dom_computed[dir_index] == DOM_OK);
1160 47428231 : return n->dfs_num_out;
1161 : }
1162 :
1163 : /* Verify invariants of dominator structure. */
1164 : DEBUG_FUNCTION void
1165 761772868 : verify_dominators (cdi_direction dir)
1166 : {
1167 761772868 : gcc_assert (dom_info_available_p (dir));
1168 :
1169 761772868 : dom_info di (cfun, dir);
1170 761772868 : di.calc_dfs_tree ();
1171 761772868 : di.calc_idoms ();
1172 :
1173 761772868 : bool err = false;
1174 761772868 : basic_block bb;
1175 8194424041 : FOR_EACH_BB_FN (bb, cfun)
1176 : {
1177 7432651173 : basic_block imm_bb = get_immediate_dominator (dir, bb);
1178 7432651173 : if (!imm_bb)
1179 : {
1180 0 : error ("dominator of %d status unknown", bb->index);
1181 0 : err = true;
1182 0 : continue;
1183 : }
1184 :
1185 7432651173 : basic_block imm_bb_correct = di.get_idom (bb);
1186 7432651173 : if (imm_bb != imm_bb_correct)
1187 : {
1188 0 : error ("dominator of %d should be %d, not %d",
1189 : bb->index, imm_bb_correct->index, imm_bb->index);
1190 0 : err = true;
1191 : }
1192 : }
1193 :
1194 761772868 : gcc_assert (!err);
1195 761772868 : }
1196 :
1197 : /* Determine immediate dominator (or postdominator, according to DIR) of BB,
1198 : assuming that dominators of other blocks are correct. We also use it to
1199 : recompute the dominators in a restricted area, by iterating it until it
1200 : reaches a fixed point. */
1201 :
1202 : basic_block
1203 441529 : recompute_dominator (enum cdi_direction dir, basic_block bb)
1204 : {
1205 441529 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1206 441529 : basic_block dom_bb = NULL;
1207 441529 : edge e;
1208 441529 : edge_iterator ei;
1209 :
1210 441529 : gcc_checking_assert (dom_computed[dir_index]);
1211 :
1212 441529 : if (dir == CDI_DOMINATORS)
1213 : {
1214 2753358 : FOR_EACH_EDGE (e, ei, bb->preds)
1215 : {
1216 2311829 : if (!dominated_by_p (dir, e->src, bb))
1217 2137107 : dom_bb = nearest_common_dominator (dir, dom_bb, e->src);
1218 : }
1219 : }
1220 : else
1221 : {
1222 0 : FOR_EACH_EDGE (e, ei, bb->succs)
1223 : {
1224 0 : if (!dominated_by_p (dir, e->dest, bb))
1225 0 : dom_bb = nearest_common_dominator (dir, dom_bb, e->dest);
1226 : }
1227 : }
1228 :
1229 441529 : return dom_bb;
1230 : }
1231 :
1232 : /* Use simple heuristics (see iterate_fix_dominators) to determine dominators
1233 : of BBS. We assume that all the immediate dominators except for those of the
1234 : blocks in BBS are correct. If CONSERVATIVE is true, we also assume that the
1235 : currently recorded immediate dominators of blocks in BBS really dominate the
1236 : blocks. The basic blocks for that we determine the dominator are removed
1237 : from BBS. */
1238 :
1239 : static void
1240 1353474 : prune_bbs_to_update_dominators (vec<basic_block> &bbs,
1241 : bool conservative)
1242 : {
1243 1353474 : unsigned i;
1244 1353474 : bool single;
1245 1353474 : basic_block bb, dom = NULL;
1246 1353474 : edge_iterator ei;
1247 1353474 : edge e;
1248 :
1249 4599969 : for (i = 0; bbs.iterate (i, &bb);)
1250 : {
1251 3246495 : if (bb == ENTRY_BLOCK_PTR_FOR_FN (cfun))
1252 0 : goto succeed;
1253 :
1254 3246495 : if (single_pred_p (bb))
1255 : {
1256 1306873 : set_immediate_dominator (CDI_DOMINATORS, bb, single_pred (bb));
1257 1306873 : goto succeed;
1258 : }
1259 :
1260 1939622 : if (!conservative)
1261 1288405 : goto fail;
1262 :
1263 651217 : single = true;
1264 651217 : dom = NULL;
1265 12566470 : FOR_EACH_EDGE (e, ei, bb->preds)
1266 : {
1267 11915253 : if (dominated_by_p (CDI_DOMINATORS, e->src, bb))
1268 12391 : continue;
1269 :
1270 11902862 : if (!dom)
1271 651217 : dom = e->src;
1272 : else
1273 : {
1274 11251645 : single = false;
1275 11251645 : dom = nearest_common_dominator (CDI_DOMINATORS, dom, e->src);
1276 : }
1277 : }
1278 :
1279 651217 : gcc_assert (dom != NULL);
1280 651217 : if (single
1281 651217 : || find_edge (dom, bb))
1282 : {
1283 435836 : set_immediate_dominator (CDI_DOMINATORS, bb, dom);
1284 435836 : goto succeed;
1285 : }
1286 :
1287 1503786 : fail:
1288 1503786 : i++;
1289 1503786 : continue;
1290 :
1291 1742709 : succeed:
1292 1742709 : bbs.unordered_remove (i);
1293 : }
1294 1503786 : }
1295 :
1296 : /* Returns root of the dominance tree in the direction DIR that contains
1297 : BB. */
1298 :
1299 : static basic_block
1300 7572971 : root_of_dom_tree (enum cdi_direction dir, basic_block bb)
1301 : {
1302 7572971 : return (basic_block) et_root (bb->dom[dom_convert_dir_to_idx (dir)])->data;
1303 : }
1304 :
1305 : /* See the comment in iterate_fix_dominators. Finds the immediate dominators
1306 : for the sons of Y, found using the SON and BROTHER arrays representing
1307 : the dominance tree of graph G. BBS maps the vertices of G to the basic
1308 : blocks. */
1309 :
1310 : static void
1311 1855729 : determine_dominators_for_sons (struct graph *g, vec<basic_block> bbs,
1312 : int y, int *son, int *brother)
1313 : {
1314 1855729 : bitmap gprime;
1315 1855729 : int i, a, nc;
1316 1855729 : vec<int> *sccs;
1317 1855729 : basic_block bb, dom, ybb;
1318 1855729 : unsigned si;
1319 1855729 : edge e;
1320 1855729 : edge_iterator ei;
1321 :
1322 1855729 : if (son[y] == -1)
1323 1308883 : return;
1324 1335520 : if (y == (int) bbs.length ())
1325 586589 : ybb = ENTRY_BLOCK_PTR_FOR_FN (cfun);
1326 : else
1327 81171 : ybb = bbs[y];
1328 :
1329 667760 : if (brother[son[y]] == -1)
1330 : {
1331 : /* Handle the common case Y has just one son specially. */
1332 120914 : bb = bbs[son[y]];
1333 120914 : set_immediate_dominator (CDI_DOMINATORS, bb,
1334 : recompute_dominator (CDI_DOMINATORS, bb));
1335 120914 : identify_vertices (g, y, son[y]);
1336 120914 : return;
1337 : }
1338 :
1339 546846 : gprime = BITMAP_ALLOC (NULL);
1340 1695072 : for (a = son[y]; a != -1; a = brother[a])
1341 1148226 : bitmap_set_bit (gprime, a);
1342 :
1343 546846 : nc = graphds_scc (g, gprime);
1344 546846 : BITMAP_FREE (gprime);
1345 :
1346 : /* ??? Needed to work around the pre-processor confusion with
1347 : using a multi-argument template type as macro argument. */
1348 546846 : typedef vec<int> vec_int_heap;
1349 546846 : sccs = XCNEWVEC (vec_int_heap, nc);
1350 1695072 : for (a = son[y]; a != -1; a = brother[a])
1351 1148226 : sccs[g->vertices[a].component].safe_push (a);
1352 :
1353 1694238 : for (i = nc - 1; i >= 0; i--)
1354 : {
1355 : dom = NULL;
1356 2295618 : FOR_EACH_VEC_ELT (sccs[i], si, a)
1357 : {
1358 1148226 : bb = bbs[a];
1359 4802751 : FOR_EACH_EDGE (e, ei, bb->preds)
1360 : {
1361 3654525 : if (root_of_dom_tree (CDI_DOMINATORS, e->src) != ybb)
1362 507680 : continue;
1363 :
1364 3146845 : dom = nearest_common_dominator (CDI_DOMINATORS, dom, e->src);
1365 : }
1366 : }
1367 :
1368 1147392 : gcc_assert (dom != NULL);
1369 3443010 : FOR_EACH_VEC_ELT (sccs[i], si, a)
1370 : {
1371 1148226 : bb = bbs[a];
1372 1148226 : set_immediate_dominator (CDI_DOMINATORS, bb, dom);
1373 : }
1374 : }
1375 :
1376 1694238 : for (i = 0; i < nc; i++)
1377 1147392 : sccs[i].release ();
1378 546846 : free (sccs);
1379 :
1380 1695072 : for (a = son[y]; a != -1; a = brother[a])
1381 1148226 : identify_vertices (g, y, a);
1382 : }
1383 :
1384 : /* Recompute dominance information for basic blocks in the set BBS. The
1385 : function assumes that the immediate dominators of all the other blocks
1386 : in CFG are correct, and that there are no unreachable blocks.
1387 :
1388 : If CONSERVATIVE is true, we additionally assume that all the ancestors of
1389 : a block of BBS in the current dominance tree dominate it. */
1390 :
1391 : void
1392 1353474 : iterate_fix_dominators (enum cdi_direction dir, vec<basic_block> &bbs,
1393 : bool conservative)
1394 : {
1395 1353474 : unsigned i;
1396 1353474 : basic_block bb, dom;
1397 1353474 : struct graph *g;
1398 1353474 : int n, y;
1399 1353474 : size_t dom_i;
1400 1353474 : edge e;
1401 1353474 : edge_iterator ei;
1402 1353474 : int *parent, *son, *brother;
1403 1353474 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1404 :
1405 : /* We only support updating dominators. There are some problems with
1406 : updating postdominators (need to add fake edges from infinite loops
1407 : and noreturn functions), and since we do not currently use
1408 : iterate_fix_dominators for postdominators, any attempt to handle these
1409 : problems would be unused, untested, and almost surely buggy. We keep
1410 : the DIR argument for consistency with the rest of the dominator analysis
1411 : interface. */
1412 1353474 : gcc_checking_assert (dir == CDI_DOMINATORS && dom_computed[dir_index]);
1413 :
1414 : /* The algorithm we use takes inspiration from the following papers, although
1415 : the details are quite different from any of them:
1416 :
1417 : [1] G. Ramalingam, T. Reps, An Incremental Algorithm for Maintaining the
1418 : Dominator Tree of a Reducible Flowgraph
1419 : [2] V. C. Sreedhar, G. R. Gao, Y.-F. Lee: Incremental computation of
1420 : dominator trees
1421 : [3] K. D. Cooper, T. J. Harvey and K. Kennedy: A Simple, Fast Dominance
1422 : Algorithm
1423 :
1424 : First, we use the following heuristics to decrease the size of the BBS
1425 : set:
1426 : a) if BB has a single predecessor, then its immediate dominator is this
1427 : predecessor
1428 : additionally, if CONSERVATIVE is true:
1429 : b) if all the predecessors of BB except for one (X) are dominated by BB,
1430 : then X is the immediate dominator of BB
1431 : c) if the nearest common ancestor of the predecessors of BB is X and
1432 : X -> BB is an edge in CFG, then X is the immediate dominator of BB
1433 :
1434 : Then, we need to establish the dominance relation among the basic blocks
1435 : in BBS. We split the dominance tree by removing the immediate dominator
1436 : edges from BBS, creating a forest F. We form a graph G whose vertices
1437 : are BBS and ENTRY and X -> Y is an edge of G if there exists an edge
1438 : X' -> Y in CFG such that X' belongs to the tree of the dominance forest
1439 : whose root is X. We then determine dominance tree of G. Note that
1440 : for X, Y in BBS, X dominates Y in CFG if and only if X dominates Y in G.
1441 : In this step, we can use arbitrary algorithm to determine dominators.
1442 : We decided to prefer the algorithm [3] to the algorithm of
1443 : Lengauer and Tarjan, since the set BBS is usually small (rarely exceeding
1444 : 10 during gcc bootstrap), and [3] should perform better in this case.
1445 :
1446 : Finally, we need to determine the immediate dominators for the basic
1447 : blocks of BBS. If the immediate dominator of X in G is Y, then
1448 : the immediate dominator of X in CFG belongs to the tree of F rooted in
1449 : Y. We process the dominator tree T of G recursively, starting from leaves.
1450 : Suppose that X_1, X_2, ..., X_k are the sons of Y in T, and that the
1451 : subtrees of the dominance tree of CFG rooted in X_i are already correct.
1452 : Let G' be the subgraph of G induced by {X_1, X_2, ..., X_k}. We make
1453 : the following observations:
1454 : (i) the immediate dominator of all blocks in a strongly connected
1455 : component of G' is the same
1456 : (ii) if X has no predecessors in G', then the immediate dominator of X
1457 : is the nearest common ancestor of the predecessors of X in the
1458 : subtree of F rooted in Y
1459 : Therefore, it suffices to find the topological ordering of G', and
1460 : process the nodes X_i in this order using the rules (i) and (ii).
1461 : Then, we contract all the nodes X_i with Y in G, so that the further
1462 : steps work correctly. */
1463 :
1464 1353474 : if (!conservative)
1465 : {
1466 : /* Split the tree now. If the idoms of blocks in BBS are not
1467 : conservatively correct, setting the dominators using the
1468 : heuristics in prune_bbs_to_update_dominators could
1469 : create cycles in the dominance "tree", and cause ICE. */
1470 2629857 : FOR_EACH_VEC_ELT (bbs, i, bb)
1471 1910884 : set_immediate_dominator (CDI_DOMINATORS, bb, NULL);
1472 : }
1473 :
1474 1353474 : prune_bbs_to_update_dominators (bbs, conservative);
1475 1353474 : n = bbs.length ();
1476 :
1477 1353474 : if (n == 0)
1478 766885 : return;
1479 :
1480 821235 : if (n == 1)
1481 : {
1482 234646 : bb = bbs[0];
1483 234646 : set_immediate_dominator (CDI_DOMINATORS, bb,
1484 : recompute_dominator (CDI_DOMINATORS, bb));
1485 234646 : return;
1486 : }
1487 :
1488 586589 : timevar_push (TV_DOMINANCE);
1489 :
1490 : /* Construct the graph G. */
1491 586589 : hash_map<basic_block, int> map (251);
1492 2442318 : FOR_EACH_VEC_ELT (bbs, i, bb)
1493 : {
1494 : /* If the dominance tree is conservatively correct, split it now. */
1495 1269140 : if (conservative)
1496 100053 : set_immediate_dominator (CDI_DOMINATORS, bb, NULL);
1497 1269140 : map.put (bb, i);
1498 : }
1499 586589 : map.put (ENTRY_BLOCK_PTR_FOR_FN (cfun), n);
1500 :
1501 586589 : g = new_graph (n + 1);
1502 3028907 : for (y = 0; y < g->n_vertices; y++)
1503 1855729 : g->vertices[y].data = BITMAP_ALLOC (NULL);
1504 1855729 : FOR_EACH_VEC_ELT (bbs, i, bb)
1505 : {
1506 5187586 : FOR_EACH_EDGE (e, ei, bb->preds)
1507 : {
1508 3918446 : dom = root_of_dom_tree (CDI_DOMINATORS, e->src);
1509 3918446 : if (dom == bb)
1510 555230 : continue;
1511 :
1512 3363216 : dom_i = *map.get (dom);
1513 :
1514 : /* Do not include parallel edges to G. */
1515 3363216 : if (!bitmap_set_bit ((bitmap) g->vertices[dom_i].data, i))
1516 1464276 : continue;
1517 :
1518 1898940 : add_edge (g, dom_i, i);
1519 : }
1520 : }
1521 2442318 : for (y = 0; y < g->n_vertices; y++)
1522 1855729 : BITMAP_FREE (g->vertices[y].data);
1523 :
1524 : /* Find the dominator tree of G. */
1525 586589 : son = XNEWVEC (int, n + 1);
1526 586589 : brother = XNEWVEC (int, n + 1);
1527 586589 : parent = XNEWVEC (int, n + 1);
1528 586589 : graphds_domtree (g, n, parent, son, brother);
1529 :
1530 : /* Finally, traverse the tree and find the immediate dominators. */
1531 1814444 : for (y = n; son[y] != -1; y = son[y])
1532 641266 : continue;
1533 2442318 : while (y != -1)
1534 : {
1535 1855729 : determine_dominators_for_sons (g, bbs, y, son, brother);
1536 :
1537 1855729 : if (brother[y] != -1)
1538 : {
1539 : y = brother[y];
1540 627874 : while (son[y] != -1)
1541 : y = son[y];
1542 : }
1543 : else
1544 1254349 : y = parent[y];
1545 : }
1546 :
1547 586589 : free (son);
1548 586589 : free (brother);
1549 586589 : free (parent);
1550 :
1551 586589 : free_graph (g);
1552 :
1553 586589 : timevar_pop (TV_DOMINANCE);
1554 586589 : }
1555 :
1556 : void
1557 31715739 : add_to_dominance_info (enum cdi_direction dir, basic_block bb)
1558 : {
1559 31715739 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1560 :
1561 31715739 : gcc_checking_assert (dom_computed[dir_index] && !bb->dom[dir_index]);
1562 :
1563 31715739 : n_bbs_in_dom_tree[dir_index]++;
1564 :
1565 31715739 : bb->dom[dir_index] = et_new_tree (bb);
1566 :
1567 31715739 : if (dom_computed[dir_index] == DOM_OK)
1568 4482955 : dom_computed[dir_index] = DOM_NO_FAST_QUERY;
1569 31715739 : }
1570 :
1571 : void
1572 48020304 : delete_from_dominance_info (enum cdi_direction dir, basic_block bb)
1573 : {
1574 48020304 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1575 :
1576 48020304 : gcc_checking_assert (dom_computed[dir_index]);
1577 :
1578 48020304 : et_free_tree (bb->dom[dir_index]);
1579 48020304 : bb->dom[dir_index] = NULL;
1580 48020304 : n_bbs_in_dom_tree[dir_index]--;
1581 :
1582 48020304 : if (dom_computed[dir_index] == DOM_OK)
1583 2154559 : dom_computed[dir_index] = DOM_NO_FAST_QUERY;
1584 48020304 : }
1585 :
1586 : /* Returns the first son of BB in the dominator or postdominator tree
1587 : as determined by DIR. */
1588 :
1589 : basic_block
1590 762171160 : first_dom_son (enum cdi_direction dir, basic_block bb)
1591 : {
1592 762171160 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1593 762171160 : struct et_node *son = bb->dom[dir_index]->son;
1594 :
1595 762171160 : return (basic_block) (son ? son->data : NULL);
1596 : }
1597 :
1598 : /* Returns the next dominance son after BB in the dominator or postdominator
1599 : tree as determined by DIR, or NULL if it was the last one. */
1600 :
1601 : basic_block
1602 670272670 : next_dom_son (enum cdi_direction dir, basic_block bb)
1603 : {
1604 670272670 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1605 670272670 : struct et_node *next = bb->dom[dir_index]->right;
1606 :
1607 670272670 : return (basic_block) (next->father->son == next ? NULL : next->data);
1608 : }
1609 :
1610 : /* Return dominance availability for dominance info DIR. */
1611 :
1612 : enum dom_state
1613 6444846046 : dom_info_state (function *fn, enum cdi_direction dir)
1614 : {
1615 6444846046 : if (!fn->cfg)
1616 : return DOM_NONE;
1617 :
1618 6278108629 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1619 6278108629 : return fn->cfg->x_dom_computed[dir_index];
1620 : }
1621 :
1622 : enum dom_state
1623 541585548 : dom_info_state (enum cdi_direction dir)
1624 : {
1625 541585548 : return dom_info_state (cfun, dir);
1626 : }
1627 :
1628 : /* Set the dominance availability for dominance info DIR to NEW_STATE. */
1629 :
1630 : void
1631 199273305 : set_dom_info_availability (enum cdi_direction dir, enum dom_state new_state)
1632 : {
1633 199273305 : unsigned int dir_index = dom_convert_dir_to_idx (dir);
1634 :
1635 199273305 : dom_computed[dir_index] = new_state;
1636 199273305 : }
1637 :
1638 : /* Returns true if dominance information for direction DIR is available. */
1639 :
1640 : bool
1641 2689488976 : dom_info_available_p (function *fn, enum cdi_direction dir)
1642 : {
1643 2689488976 : return dom_info_state (fn, dir) != DOM_NONE;
1644 : }
1645 :
1646 : bool
1647 2243103629 : dom_info_available_p (enum cdi_direction dir)
1648 : {
1649 2243103629 : return dom_info_available_p (cfun, dir);
1650 : }
1651 :
1652 : DEBUG_FUNCTION void
1653 0 : debug_dominance_info (enum cdi_direction dir)
1654 : {
1655 0 : basic_block bb, bb2;
1656 0 : FOR_EACH_BB_FN (bb, cfun)
1657 0 : if ((bb2 = get_immediate_dominator (dir, bb)))
1658 0 : fprintf (stderr, "%i %i\n", bb->index, bb2->index);
1659 0 : }
1660 :
1661 : /* Dump the dominance tree in direction DIR to the file F in dot form.
1662 : This allows easily visualizing the tree using graphviz. */
1663 :
1664 : DEBUG_FUNCTION void
1665 0 : dot_dominance_tree (FILE *f, enum cdi_direction dir)
1666 : {
1667 0 : fprintf (f, "digraph {\n");
1668 0 : basic_block bb, idom;
1669 0 : FOR_EACH_BB_FN (bb, cfun)
1670 0 : if ((idom = get_immediate_dominator (dir, bb)))
1671 0 : fprintf (f, "%i -> %i;\n", idom->index, bb->index);
1672 0 : fprintf (f, "}\n");
1673 0 : }
1674 :
1675 : /* Convenience wrapper around the above that dumps the dominance tree in
1676 : direction DIR to the file at path FNAME in dot form. */
1677 :
1678 : DEBUG_FUNCTION void
1679 0 : dot_dominance_tree (const char *fname, enum cdi_direction dir)
1680 : {
1681 0 : FILE *f = fopen (fname, "w");
1682 0 : if (f)
1683 : {
1684 0 : dot_dominance_tree (f, dir);
1685 0 : fclose (f);
1686 : }
1687 : else
1688 0 : fprintf (stderr, "failed to open %s: %s\n", fname, xstrerror (errno));
1689 0 : }
1690 :
1691 : /* Prints to stderr representation of the dominance tree (for direction DIR)
1692 : rooted in ROOT, indented by INDENT tabulators. If INDENT_FIRST is false,
1693 : the first line of the output is not indented. */
1694 :
1695 : static void
1696 0 : debug_dominance_tree_1 (enum cdi_direction dir, basic_block root,
1697 : unsigned indent, bool indent_first)
1698 : {
1699 0 : basic_block son;
1700 0 : unsigned i;
1701 0 : bool first = true;
1702 :
1703 0 : if (indent_first)
1704 0 : for (i = 0; i < indent; i++)
1705 0 : fprintf (stderr, "\t");
1706 0 : fprintf (stderr, "%d\t", root->index);
1707 :
1708 0 : for (son = first_dom_son (dir, root);
1709 0 : son;
1710 0 : son = next_dom_son (dir, son))
1711 : {
1712 0 : debug_dominance_tree_1 (dir, son, indent + 1, !first);
1713 0 : first = false;
1714 : }
1715 :
1716 0 : if (first)
1717 0 : fprintf (stderr, "\n");
1718 0 : }
1719 :
1720 : /* Prints to stderr representation of the dominance tree (for direction DIR)
1721 : rooted in ROOT. */
1722 :
1723 : DEBUG_FUNCTION void
1724 0 : debug_dominance_tree (enum cdi_direction dir, basic_block root)
1725 : {
1726 0 : debug_dominance_tree_1 (dir, root, 0, false);
1727 0 : }
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