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f8032688 MM |
1 | /* Calculate (post)dominators in slightly super-linear time. |
2 | Copyright (C) 2000 Free Software Foundation, Inc. | |
3 | Contributed by Michael Matz (matz@ifh.de). | |
4 | ||
1322177d | 5 | This file is part of GCC. |
f8032688 | 6 | |
1322177d LB |
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 | |
f8032688 MM |
9 | the Free Software Foundation; either version 2, or (at your option) |
10 | any later version. | |
11 | ||
1322177d LB |
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. | |
f8032688 MM |
16 | |
17 | You should have received a copy of the GNU General Public License | |
1322177d LB |
18 | along with GCC; see the file COPYING. If not, write to the Free |
19 | Software Foundation, 59 Temple Place - Suite 330, Boston, MA | |
20 | 02111-1307, USA. */ | |
f8032688 MM |
21 | |
22 | /* This file implements the well known algorithm from Lengauer and Tarjan | |
23 | to compute the dominators in a control flow graph. A basic block D is said | |
24 | to dominate another block X, when all paths from the entry node of the CFG | |
25 | to X go also over D. The dominance relation is a transitive reflexive | |
26 | relation and its minimal transitive reduction is a tree, called the | |
27 | dominator tree. So for each block X besides the entry block exists a | |
28 | block I(X), called the immediate dominator of X, which is the parent of X | |
29 | in the dominator tree. | |
30 | ||
31 | The algorithm computes this dominator tree implicitely by computing for | |
32 | each block its immediate dominator. We use tree balancing and path | |
33 | compression, so its the O(e*a(e,v)) variant, where a(e,v) is the very | |
34 | slowly growing functional inverse of the Ackerman function. */ | |
35 | ||
36 | #include "config.h" | |
37 | #include "system.h" | |
38 | #include "rtl.h" | |
39 | #include "hard-reg-set.h" | |
40 | #include "basic-block.h" | |
41 | ||
42 | ||
43 | /* We name our nodes with integers, beginning with 1. Zero is reserved for | |
44 | 'undefined' or 'end of list'. The name of each node is given by the dfs | |
45 | number of the corresponding basic block. Please note, that we include the | |
46 | artificial ENTRY_BLOCK (or EXIT_BLOCK in the post-dom case) in our lists to | |
47 | support multiple entry points. As it has no real basic block index we use | |
48 | 'n_basic_blocks' for that. Its dfs number is of course 1. */ | |
49 | ||
50 | /* Type of Basic Block aka. TBB */ | |
51 | typedef unsigned int TBB; | |
52 | ||
53 | /* We work in a poor-mans object oriented fashion, and carry an instance of | |
54 | this structure through all our 'methods'. It holds various arrays | |
55 | reflecting the (sub)structure of the flowgraph. Most of them are of type | |
56 | TBB and are also indexed by TBB. */ | |
57 | ||
58 | struct dom_info | |
59 | { | |
60 | /* The parent of a node in the DFS tree. */ | |
61 | TBB *dfs_parent; | |
62 | /* For a node x key[x] is roughly the node nearest to the root from which | |
63 | exists a way to x only over nodes behind x. Such a node is also called | |
64 | semidominator. */ | |
65 | TBB *key; | |
66 | /* The value in path_min[x] is the node y on the path from x to the root of | |
67 | the tree x is in with the smallest key[y]. */ | |
68 | TBB *path_min; | |
69 | /* bucket[x] points to the first node of the set of nodes having x as key. */ | |
70 | TBB *bucket; | |
71 | /* And next_bucket[x] points to the next node. */ | |
72 | TBB *next_bucket; | |
73 | /* After the algorithm is done, dom[x] contains the immediate dominator | |
74 | of x. */ | |
75 | TBB *dom; | |
76 | ||
77 | /* The following few fields implement the structures needed for disjoint | |
78 | sets. */ | |
79 | /* set_chain[x] is the next node on the path from x to the representant | |
80 | of the set containing x. If set_chain[x]==0 then x is a root. */ | |
81 | TBB *set_chain; | |
82 | /* set_size[x] is the number of elements in the set named by x. */ | |
83 | unsigned int *set_size; | |
84 | /* set_child[x] is used for balancing the tree representing a set. It can | |
85 | be understood as the next sibling of x. */ | |
86 | TBB *set_child; | |
87 | ||
88 | /* If b is the number of a basic block (BB->index), dfs_order[b] is the | |
89 | number of that node in DFS order counted from 1. This is an index | |
90 | into most of the other arrays in this structure. */ | |
91 | TBB *dfs_order; | |
92 | /* If x is the DFS-index of a node which correspondends with an basic block, | |
93 | dfs_to_bb[x] is that basic block. Note, that in our structure there are | |
94 | more nodes that basic blocks, so only dfs_to_bb[dfs_order[bb->index]]==bb | |
95 | is true for every basic block bb, but not the opposite. */ | |
96 | basic_block *dfs_to_bb; | |
97 | ||
30f7a378 | 98 | /* This is the next free DFS number when creating the DFS tree or forest. */ |
f8032688 MM |
99 | unsigned int dfsnum; |
100 | /* The number of nodes in the DFS tree (==dfsnum-1). */ | |
101 | unsigned int nodes; | |
102 | }; | |
103 | ||
104 | static void init_dom_info PARAMS ((struct dom_info *)); | |
105 | static void free_dom_info PARAMS ((struct dom_info *)); | |
106 | static void calc_dfs_tree_nonrec PARAMS ((struct dom_info *, | |
107 | basic_block, | |
108 | enum cdi_direction)); | |
109 | static void calc_dfs_tree PARAMS ((struct dom_info *, | |
110 | enum cdi_direction)); | |
111 | static void compress PARAMS ((struct dom_info *, TBB)); | |
112 | static TBB eval PARAMS ((struct dom_info *, TBB)); | |
113 | static void link_roots PARAMS ((struct dom_info *, TBB, TBB)); | |
114 | static void calc_idoms PARAMS ((struct dom_info *, | |
115 | enum cdi_direction)); | |
116 | static void idoms_to_doms PARAMS ((struct dom_info *, | |
117 | sbitmap *)); | |
118 | ||
119 | /* Helper macro for allocating and initializing an array, | |
120 | for aesthetic reasons. */ | |
121 | #define init_ar(var, type, num, content) \ | |
122 | do { \ | |
123 | unsigned int i = 1; /* Catch content == i. */ \ | |
124 | if (! (content)) \ | |
125 | (var) = (type *) xcalloc ((num), sizeof (type)); \ | |
126 | else \ | |
127 | { \ | |
128 | (var) = (type *) xmalloc ((num) * sizeof (type)); \ | |
129 | for (i = 0; i < num; i++) \ | |
130 | (var)[i] = (content); \ | |
131 | } \ | |
132 | } while (0) | |
133 | ||
134 | /* Allocate all needed memory in a pessimistic fashion (so we round up). | |
135 | This initialises the contents of DI, which already must be allocated. */ | |
136 | ||
137 | static void | |
138 | init_dom_info (di) | |
139 | struct dom_info *di; | |
140 | { | |
141 | /* We need memory for n_basic_blocks nodes and the ENTRY_BLOCK or | |
142 | EXIT_BLOCK. */ | |
143 | unsigned int num = n_basic_blocks + 1 + 1; | |
144 | init_ar (di->dfs_parent, TBB, num, 0); | |
145 | init_ar (di->path_min, TBB, num, i); | |
146 | init_ar (di->key, TBB, num, i); | |
147 | init_ar (di->dom, TBB, num, 0); | |
148 | ||
149 | init_ar (di->bucket, TBB, num, 0); | |
150 | init_ar (di->next_bucket, TBB, num, 0); | |
151 | ||
152 | init_ar (di->set_chain, TBB, num, 0); | |
153 | init_ar (di->set_size, unsigned int, num, 1); | |
154 | init_ar (di->set_child, TBB, num, 0); | |
155 | ||
156 | init_ar (di->dfs_order, TBB, (unsigned int) n_basic_blocks + 1, 0); | |
157 | init_ar (di->dfs_to_bb, basic_block, num, 0); | |
158 | ||
159 | di->dfsnum = 1; | |
160 | di->nodes = 0; | |
161 | } | |
162 | ||
163 | #undef init_ar | |
164 | ||
165 | /* Free all allocated memory in DI, but not DI itself. */ | |
166 | ||
167 | static void | |
168 | free_dom_info (di) | |
169 | struct dom_info *di; | |
170 | { | |
171 | free (di->dfs_parent); | |
172 | free (di->path_min); | |
173 | free (di->key); | |
174 | free (di->dom); | |
175 | free (di->bucket); | |
176 | free (di->next_bucket); | |
177 | free (di->set_chain); | |
178 | free (di->set_size); | |
179 | free (di->set_child); | |
180 | free (di->dfs_order); | |
181 | free (di->dfs_to_bb); | |
182 | } | |
183 | ||
184 | /* The nonrecursive variant of creating a DFS tree. DI is our working | |
185 | structure, BB the starting basic block for this tree and REVERSE | |
186 | is true, if predecessors should be visited instead of successors of a | |
187 | node. After this is done all nodes reachable from BB were visited, have | |
188 | assigned their dfs number and are linked together to form a tree. */ | |
189 | ||
190 | static void | |
191 | calc_dfs_tree_nonrec (di, bb, reverse) | |
192 | struct dom_info *di; | |
193 | basic_block bb; | |
194 | enum cdi_direction reverse; | |
195 | { | |
30f7a378 | 196 | /* We never call this with bb==EXIT_BLOCK_PTR (ENTRY_BLOCK_PTR if REVERSE). */ |
f8032688 MM |
197 | /* We call this _only_ if bb is not already visited. */ |
198 | edge e; | |
199 | TBB child_i, my_i = 0; | |
200 | edge *stack; | |
201 | int sp; | |
202 | /* Start block (ENTRY_BLOCK_PTR for forward problem, EXIT_BLOCK for backward | |
203 | problem). */ | |
204 | basic_block en_block; | |
205 | /* Ending block. */ | |
206 | basic_block ex_block; | |
207 | ||
208 | stack = (edge *) xmalloc ((n_basic_blocks + 3) * sizeof (edge)); | |
209 | sp = 0; | |
210 | ||
211 | /* Initialize our border blocks, and the first edge. */ | |
212 | if (reverse) | |
213 | { | |
214 | e = bb->pred; | |
215 | en_block = EXIT_BLOCK_PTR; | |
216 | ex_block = ENTRY_BLOCK_PTR; | |
217 | } | |
218 | else | |
219 | { | |
220 | e = bb->succ; | |
221 | en_block = ENTRY_BLOCK_PTR; | |
222 | ex_block = EXIT_BLOCK_PTR; | |
223 | } | |
224 | ||
225 | /* When the stack is empty we break out of this loop. */ | |
226 | while (1) | |
227 | { | |
228 | basic_block bn; | |
229 | ||
230 | /* This loop traverses edges e in depth first manner, and fills the | |
231 | stack. */ | |
232 | while (e) | |
233 | { | |
234 | edge e_next; | |
235 | ||
236 | /* Deduce from E the current and the next block (BB and BN), and the | |
237 | next edge. */ | |
238 | if (reverse) | |
239 | { | |
240 | bn = e->src; | |
241 | ||
242 | /* If the next node BN is either already visited or a border | |
243 | block the current edge is useless, and simply overwritten | |
244 | with the next edge out of the current node. */ | |
94fc7dea | 245 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 MM |
246 | { |
247 | e = e->pred_next; | |
248 | continue; | |
249 | } | |
250 | bb = e->dest; | |
251 | e_next = bn->pred; | |
252 | } | |
253 | else | |
254 | { | |
255 | bn = e->dest; | |
94fc7dea | 256 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 MM |
257 | { |
258 | e = e->succ_next; | |
259 | continue; | |
260 | } | |
261 | bb = e->src; | |
262 | e_next = bn->succ; | |
263 | } | |
264 | ||
265 | if (bn == en_block) | |
266 | abort (); | |
267 | ||
268 | /* Fill the DFS tree info calculatable _before_ recursing. */ | |
269 | if (bb != en_block) | |
270 | my_i = di->dfs_order[bb->index]; | |
271 | else | |
272 | my_i = di->dfs_order[n_basic_blocks]; | |
273 | child_i = di->dfs_order[bn->index] = di->dfsnum++; | |
274 | di->dfs_to_bb[child_i] = bn; | |
275 | di->dfs_parent[child_i] = my_i; | |
276 | ||
277 | /* Save the current point in the CFG on the stack, and recurse. */ | |
278 | stack[sp++] = e; | |
279 | e = e_next; | |
280 | } | |
281 | ||
282 | if (!sp) | |
283 | break; | |
284 | e = stack[--sp]; | |
285 | ||
286 | /* OK. The edge-list was exhausted, meaning normally we would | |
287 | end the recursion. After returning from the recursive call, | |
288 | there were (may be) other statements which were run after a | |
289 | child node was completely considered by DFS. Here is the | |
290 | point to do it in the non-recursive variant. | |
291 | E.g. The block just completed is in e->dest for forward DFS, | |
292 | the block not yet completed (the parent of the one above) | |
293 | in e->src. This could be used e.g. for computing the number of | |
294 | descendants or the tree depth. */ | |
295 | if (reverse) | |
296 | e = e->pred_next; | |
297 | else | |
298 | e = e->succ_next; | |
299 | } | |
300 | free (stack); | |
301 | } | |
302 | ||
303 | /* The main entry for calculating the DFS tree or forest. DI is our working | |
304 | structure and REVERSE is true, if we are interested in the reverse flow | |
305 | graph. In that case the result is not necessarily a tree but a forest, | |
306 | because there may be nodes from which the EXIT_BLOCK is unreachable. */ | |
307 | ||
308 | static void | |
309 | calc_dfs_tree (di, reverse) | |
310 | struct dom_info *di; | |
311 | enum cdi_direction reverse; | |
312 | { | |
313 | /* The first block is the ENTRY_BLOCK (or EXIT_BLOCK if REVERSE). */ | |
314 | basic_block begin = reverse ? EXIT_BLOCK_PTR : ENTRY_BLOCK_PTR; | |
315 | di->dfs_order[n_basic_blocks] = di->dfsnum; | |
316 | di->dfs_to_bb[di->dfsnum] = begin; | |
317 | di->dfsnum++; | |
318 | ||
319 | calc_dfs_tree_nonrec (di, begin, reverse); | |
320 | ||
321 | if (reverse) | |
322 | { | |
323 | /* In the post-dom case we may have nodes without a path to EXIT_BLOCK. | |
324 | They are reverse-unreachable. In the dom-case we disallow such | |
325 | nodes, but in post-dom we have to deal with them, so we simply | |
326 | include them in the DFS tree which actually becomes a forest. */ | |
327 | int i; | |
328 | for (i = n_basic_blocks - 1; i >= 0; i--) | |
329 | { | |
330 | basic_block b = BASIC_BLOCK (i); | |
331 | if (di->dfs_order[b->index]) | |
332 | continue; | |
333 | di->dfs_order[b->index] = di->dfsnum; | |
334 | di->dfs_to_bb[di->dfsnum] = b; | |
335 | di->dfsnum++; | |
336 | calc_dfs_tree_nonrec (di, b, reverse); | |
337 | } | |
338 | } | |
339 | ||
340 | di->nodes = di->dfsnum - 1; | |
341 | ||
342 | /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. */ | |
343 | if (di->nodes != (unsigned int) n_basic_blocks + 1) | |
344 | abort (); | |
345 | } | |
346 | ||
347 | /* Compress the path from V to the root of its set and update path_min at the | |
348 | same time. After compress(di, V) set_chain[V] is the root of the set V is | |
349 | in and path_min[V] is the node with the smallest key[] value on the path | |
350 | from V to that root. */ | |
351 | ||
352 | static void | |
353 | compress (di, v) | |
354 | struct dom_info *di; | |
355 | TBB v; | |
356 | { | |
357 | /* Btw. It's not worth to unrecurse compress() as the depth is usually not | |
358 | greater than 5 even for huge graphs (I've not seen call depth > 4). | |
359 | Also performance wise compress() ranges _far_ behind eval(). */ | |
360 | TBB parent = di->set_chain[v]; | |
361 | if (di->set_chain[parent]) | |
362 | { | |
363 | compress (di, parent); | |
364 | if (di->key[di->path_min[parent]] < di->key[di->path_min[v]]) | |
365 | di->path_min[v] = di->path_min[parent]; | |
366 | di->set_chain[v] = di->set_chain[parent]; | |
367 | } | |
368 | } | |
369 | ||
370 | /* Compress the path from V to the set root of V if needed (when the root has | |
371 | changed since the last call). Returns the node with the smallest key[] | |
372 | value on the path from V to the root. */ | |
373 | ||
374 | static inline TBB | |
375 | eval (di, v) | |
376 | struct dom_info *di; | |
377 | TBB v; | |
378 | { | |
379 | /* The representant of the set V is in, also called root (as the set | |
380 | representation is a tree). */ | |
381 | TBB rep = di->set_chain[v]; | |
382 | ||
383 | /* V itself is the root. */ | |
384 | if (!rep) | |
385 | return di->path_min[v]; | |
386 | ||
387 | /* Compress only if necessary. */ | |
388 | if (di->set_chain[rep]) | |
389 | { | |
390 | compress (di, v); | |
391 | rep = di->set_chain[v]; | |
392 | } | |
393 | ||
394 | if (di->key[di->path_min[rep]] >= di->key[di->path_min[v]]) | |
395 | return di->path_min[v]; | |
396 | else | |
397 | return di->path_min[rep]; | |
398 | } | |
399 | ||
400 | /* This essentially merges the two sets of V and W, giving a single set with | |
401 | the new root V. The internal representation of these disjoint sets is a | |
402 | balanced tree. Currently link(V,W) is only used with V being the parent | |
403 | of W. */ | |
404 | ||
405 | static void | |
406 | link_roots (di, v, w) | |
407 | struct dom_info *di; | |
408 | TBB v, w; | |
409 | { | |
410 | TBB s = w; | |
411 | ||
412 | /* Rebalance the tree. */ | |
413 | while (di->key[di->path_min[w]] < di->key[di->path_min[di->set_child[s]]]) | |
414 | { | |
415 | if (di->set_size[s] + di->set_size[di->set_child[di->set_child[s]]] | |
416 | >= 2 * di->set_size[di->set_child[s]]) | |
417 | { | |
418 | di->set_chain[di->set_child[s]] = s; | |
419 | di->set_child[s] = di->set_child[di->set_child[s]]; | |
420 | } | |
421 | else | |
422 | { | |
423 | di->set_size[di->set_child[s]] = di->set_size[s]; | |
424 | s = di->set_chain[s] = di->set_child[s]; | |
425 | } | |
426 | } | |
427 | ||
428 | di->path_min[s] = di->path_min[w]; | |
429 | di->set_size[v] += di->set_size[w]; | |
430 | if (di->set_size[v] < 2 * di->set_size[w]) | |
431 | { | |
432 | TBB tmp = s; | |
433 | s = di->set_child[v]; | |
434 | di->set_child[v] = tmp; | |
435 | } | |
436 | ||
437 | /* Merge all subtrees. */ | |
438 | while (s) | |
439 | { | |
440 | di->set_chain[s] = v; | |
441 | s = di->set_child[s]; | |
442 | } | |
443 | } | |
444 | ||
445 | /* This calculates the immediate dominators (or post-dominators if REVERSE is | |
446 | true). DI is our working structure and should hold the DFS forest. | |
447 | On return the immediate dominator to node V is in di->dom[V]. */ | |
448 | ||
449 | static void | |
450 | calc_idoms (di, reverse) | |
451 | struct dom_info *di; | |
452 | enum cdi_direction reverse; | |
453 | { | |
454 | TBB v, w, k, par; | |
455 | basic_block en_block; | |
456 | if (reverse) | |
457 | en_block = EXIT_BLOCK_PTR; | |
458 | else | |
459 | en_block = ENTRY_BLOCK_PTR; | |
460 | ||
461 | /* Go backwards in DFS order, to first look at the leafs. */ | |
462 | v = di->nodes; | |
463 | while (v > 1) | |
464 | { | |
465 | basic_block bb = di->dfs_to_bb[v]; | |
466 | edge e, e_next; | |
467 | ||
468 | par = di->dfs_parent[v]; | |
469 | k = v; | |
470 | if (reverse) | |
471 | e = bb->succ; | |
472 | else | |
473 | e = bb->pred; | |
474 | ||
475 | /* Search all direct predecessors for the smallest node with a path | |
476 | to them. That way we have the smallest node with also a path to | |
477 | us only over nodes behind us. In effect we search for our | |
478 | semidominator. */ | |
479 | for (; e; e = e_next) | |
480 | { | |
481 | TBB k1; | |
482 | basic_block b; | |
483 | ||
484 | if (reverse) | |
485 | { | |
486 | b = e->dest; | |
487 | e_next = e->succ_next; | |
488 | } | |
489 | else | |
490 | { | |
491 | b = e->src; | |
492 | e_next = e->pred_next; | |
493 | } | |
494 | if (b == en_block) | |
495 | k1 = di->dfs_order[n_basic_blocks]; | |
496 | else | |
497 | k1 = di->dfs_order[b->index]; | |
498 | ||
499 | /* Call eval() only if really needed. If k1 is above V in DFS tree, | |
500 | then we know, that eval(k1) == k1 and key[k1] == k1. */ | |
501 | if (k1 > v) | |
502 | k1 = di->key[eval (di, k1)]; | |
503 | if (k1 < k) | |
504 | k = k1; | |
505 | } | |
506 | ||
507 | di->key[v] = k; | |
508 | link_roots (di, par, v); | |
509 | di->next_bucket[v] = di->bucket[k]; | |
510 | di->bucket[k] = v; | |
511 | ||
512 | /* Transform semidominators into dominators. */ | |
513 | for (w = di->bucket[par]; w; w = di->next_bucket[w]) | |
514 | { | |
515 | k = eval (di, w); | |
516 | if (di->key[k] < di->key[w]) | |
517 | di->dom[w] = k; | |
518 | else | |
519 | di->dom[w] = par; | |
520 | } | |
521 | /* We don't need to cleanup next_bucket[]. */ | |
522 | di->bucket[par] = 0; | |
523 | v--; | |
524 | } | |
525 | ||
526 | /* Explicitely define the dominators. */ | |
527 | di->dom[1] = 0; | |
528 | for (v = 2; v <= di->nodes; v++) | |
529 | if (di->dom[v] != di->key[v]) | |
530 | di->dom[v] = di->dom[di->dom[v]]; | |
531 | } | |
532 | ||
533 | /* Convert the information about immediate dominators (in DI) to sets of all | |
534 | dominators (in DOMINATORS). */ | |
535 | ||
536 | static void | |
537 | idoms_to_doms (di, dominators) | |
538 | struct dom_info *di; | |
539 | sbitmap *dominators; | |
540 | { | |
541 | TBB i, e_index; | |
542 | int bb, bb_idom; | |
543 | sbitmap_vector_zero (dominators, n_basic_blocks); | |
544 | /* We have to be careful, to not include the ENTRY_BLOCK or EXIT_BLOCK | |
545 | in the list of (post)-doms, so remember that in e_index. */ | |
546 | e_index = di->dfs_order[n_basic_blocks]; | |
547 | ||
548 | for (i = 1; i <= di->nodes; i++) | |
549 | { | |
550 | if (i == e_index) | |
551 | continue; | |
552 | bb = di->dfs_to_bb[i]->index; | |
553 | ||
554 | if (di->dom[i] && (di->dom[i] != e_index)) | |
555 | { | |
556 | bb_idom = di->dfs_to_bb[di->dom[i]]->index; | |
557 | sbitmap_copy (dominators[bb], dominators[bb_idom]); | |
558 | } | |
559 | else | |
560 | { | |
561 | /* It has no immediate dom or only ENTRY_BLOCK or EXIT_BLOCK. | |
562 | If it is a child of ENTRY_BLOCK that's OK, and it's only | |
563 | dominated by itself; if it's _not_ a child of ENTRY_BLOCK, it | |
564 | means, it is unreachable. That case has been disallowed in the | |
565 | building of the DFS tree, so we are save here. For the reverse | |
566 | flow graph it means, it has no children, so, to be compatible | |
567 | with the old code, we set the post_dominators to all one. */ | |
568 | if (!di->dom[i]) | |
569 | { | |
570 | sbitmap_ones (dominators[bb]); | |
571 | } | |
572 | } | |
573 | SET_BIT (dominators[bb], bb); | |
574 | } | |
575 | } | |
576 | ||
577 | /* The main entry point into this module. IDOM is an integer array with room | |
578 | for n_basic_blocks integers, DOMS is a preallocated sbitmap array having | |
579 | room for n_basic_blocks^2 bits, and POST is true if the caller wants to | |
580 | know post-dominators. | |
581 | ||
582 | On return IDOM[i] will be the BB->index of the immediate (post) dominator | |
583 | of basic block i, and DOMS[i] will have set bit j if basic block j is a | |
584 | (post)dominator for block i. | |
585 | ||
586 | Either IDOM or DOMS may be NULL (meaning the caller is not interested in | |
587 | immediate resp. all dominators). */ | |
588 | ||
589 | void | |
590 | calculate_dominance_info (idom, doms, reverse) | |
591 | int *idom; | |
592 | sbitmap *doms; | |
593 | enum cdi_direction reverse; | |
594 | { | |
595 | struct dom_info di; | |
596 | ||
597 | if (!doms && !idom) | |
598 | return; | |
599 | init_dom_info (&di); | |
600 | calc_dfs_tree (&di, reverse); | |
601 | calc_idoms (&di, reverse); | |
602 | ||
603 | if (idom) | |
604 | { | |
605 | int i; | |
606 | for (i = 0; i < n_basic_blocks; i++) | |
607 | { | |
608 | basic_block b = BASIC_BLOCK (i); | |
609 | TBB d = di.dom[di.dfs_order[b->index]]; | |
610 | ||
611 | /* The old code didn't modify array elements of nodes having only | |
612 | itself as dominator (d==0) or only ENTRY_BLOCK (resp. EXIT_BLOCK) | |
613 | (d==1). */ | |
614 | if (d > 1) | |
615 | idom[i] = di.dfs_to_bb[d]->index; | |
616 | } | |
617 | } | |
618 | if (doms) | |
619 | idoms_to_doms (&di, doms); | |
620 | ||
621 | free_dom_info (&di); | |
622 | } |