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f8032688 | 1 | /* Calculate (post)dominators in slightly super-linear time. |
c8d3e15a | 2 | Copyright (C) 2000, 2003, 2004, 2005 Free Software Foundation, Inc. |
f8032688 | 3 | Contributed by Michael Matz (matz@ifh.de). |
3a538a66 | 4 | |
1322177d | 5 | This file is part of GCC. |
3a538a66 | 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 | 18 | along with GCC; see the file COPYING. If not, write to the Free |
366ccddb KC |
19 | Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA |
20 | 02110-1301, 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 | ||
a1f300c0 | 31 | The algorithm computes this dominator tree implicitly by computing for |
f8032688 | 32 | each block its immediate dominator. We use tree balancing and path |
f3b569ca | 33 | compression, so it's the O(e*a(e,v)) variant, where a(e,v) is the very |
f8032688 MM |
34 | slowly growing functional inverse of the Ackerman function. */ |
35 | ||
36 | #include "config.h" | |
37 | #include "system.h" | |
4977bab6 ZW |
38 | #include "coretypes.h" |
39 | #include "tm.h" | |
f8032688 MM |
40 | #include "rtl.h" |
41 | #include "hard-reg-set.h" | |
7932a3db | 42 | #include "obstack.h" |
f8032688 | 43 | #include "basic-block.h" |
4c714dd4 | 44 | #include "toplev.h" |
355be0dc | 45 | #include "et-forest.h" |
f8032688 | 46 | |
d47cc544 SB |
47 | /* Whether the dominators and the postdominators are available. */ |
48 | enum dom_state dom_computed[2]; | |
f8032688 MM |
49 | |
50 | /* We name our nodes with integers, beginning with 1. Zero is reserved for | |
51 | 'undefined' or 'end of list'. The name of each node is given by the dfs | |
52 | number of the corresponding basic block. Please note, that we include the | |
53 | artificial ENTRY_BLOCK (or EXIT_BLOCK in the post-dom case) in our lists to | |
24bd1a0b | 54 | support multiple entry points. Its dfs number is of course 1. */ |
f8032688 MM |
55 | |
56 | /* Type of Basic Block aka. TBB */ | |
57 | typedef unsigned int TBB; | |
58 | ||
59 | /* We work in a poor-mans object oriented fashion, and carry an instance of | |
60 | this structure through all our 'methods'. It holds various arrays | |
61 | reflecting the (sub)structure of the flowgraph. Most of them are of type | |
62 | TBB and are also indexed by TBB. */ | |
63 | ||
64 | struct dom_info | |
65 | { | |
66 | /* The parent of a node in the DFS tree. */ | |
67 | TBB *dfs_parent; | |
68 | /* For a node x key[x] is roughly the node nearest to the root from which | |
69 | exists a way to x only over nodes behind x. Such a node is also called | |
70 | semidominator. */ | |
71 | TBB *key; | |
72 | /* The value in path_min[x] is the node y on the path from x to the root of | |
73 | the tree x is in with the smallest key[y]. */ | |
74 | TBB *path_min; | |
75 | /* bucket[x] points to the first node of the set of nodes having x as key. */ | |
76 | TBB *bucket; | |
77 | /* And next_bucket[x] points to the next node. */ | |
78 | TBB *next_bucket; | |
79 | /* After the algorithm is done, dom[x] contains the immediate dominator | |
80 | of x. */ | |
81 | TBB *dom; | |
82 | ||
83 | /* The following few fields implement the structures needed for disjoint | |
84 | sets. */ | |
85 | /* set_chain[x] is the next node on the path from x to the representant | |
86 | of the set containing x. If set_chain[x]==0 then x is a root. */ | |
87 | TBB *set_chain; | |
88 | /* set_size[x] is the number of elements in the set named by x. */ | |
89 | unsigned int *set_size; | |
90 | /* set_child[x] is used for balancing the tree representing a set. It can | |
91 | be understood as the next sibling of x. */ | |
92 | TBB *set_child; | |
93 | ||
94 | /* If b is the number of a basic block (BB->index), dfs_order[b] is the | |
95 | number of that node in DFS order counted from 1. This is an index | |
96 | into most of the other arrays in this structure. */ | |
97 | TBB *dfs_order; | |
09da1532 | 98 | /* If x is the DFS-index of a node which corresponds with a basic block, |
f8032688 MM |
99 | dfs_to_bb[x] is that basic block. Note, that in our structure there are |
100 | more nodes that basic blocks, so only dfs_to_bb[dfs_order[bb->index]]==bb | |
101 | is true for every basic block bb, but not the opposite. */ | |
102 | basic_block *dfs_to_bb; | |
103 | ||
26e0e410 | 104 | /* This is the next free DFS number when creating the DFS tree. */ |
f8032688 MM |
105 | unsigned int dfsnum; |
106 | /* The number of nodes in the DFS tree (==dfsnum-1). */ | |
107 | unsigned int nodes; | |
26e0e410 RH |
108 | |
109 | /* Blocks with bits set here have a fake edge to EXIT. These are used | |
110 | to turn a DFS forest into a proper tree. */ | |
111 | bitmap fake_exit_edge; | |
f8032688 MM |
112 | }; |
113 | ||
26e0e410 | 114 | static void init_dom_info (struct dom_info *, enum cdi_direction); |
7080f735 AJ |
115 | static void free_dom_info (struct dom_info *); |
116 | static void calc_dfs_tree_nonrec (struct dom_info *, basic_block, | |
117 | enum cdi_direction); | |
118 | static void calc_dfs_tree (struct dom_info *, enum cdi_direction); | |
119 | static void compress (struct dom_info *, TBB); | |
120 | static TBB eval (struct dom_info *, TBB); | |
121 | static void link_roots (struct dom_info *, TBB, TBB); | |
122 | static void calc_idoms (struct dom_info *, enum cdi_direction); | |
d47cc544 | 123 | void debug_dominance_info (enum cdi_direction); |
f8032688 | 124 | |
6de9cd9a DN |
125 | /* Keeps track of the*/ |
126 | static unsigned n_bbs_in_dom_tree[2]; | |
127 | ||
f8032688 MM |
128 | /* Helper macro for allocating and initializing an array, |
129 | for aesthetic reasons. */ | |
130 | #define init_ar(var, type, num, content) \ | |
3a538a66 KH |
131 | do \ |
132 | { \ | |
133 | unsigned int i = 1; /* Catch content == i. */ \ | |
134 | if (! (content)) \ | |
703ad42b | 135 | (var) = xcalloc ((num), sizeof (type)); \ |
3a538a66 KH |
136 | else \ |
137 | { \ | |
703ad42b | 138 | (var) = xmalloc ((num) * sizeof (type)); \ |
3a538a66 KH |
139 | for (i = 0; i < num; i++) \ |
140 | (var)[i] = (content); \ | |
141 | } \ | |
142 | } \ | |
143 | while (0) | |
f8032688 MM |
144 | |
145 | /* Allocate all needed memory in a pessimistic fashion (so we round up). | |
4912a07c | 146 | This initializes the contents of DI, which already must be allocated. */ |
f8032688 MM |
147 | |
148 | static void | |
26e0e410 | 149 | init_dom_info (struct dom_info *di, enum cdi_direction dir) |
f8032688 | 150 | { |
24bd1a0b | 151 | unsigned int num = n_basic_blocks; |
f8032688 MM |
152 | init_ar (di->dfs_parent, TBB, num, 0); |
153 | init_ar (di->path_min, TBB, num, i); | |
154 | init_ar (di->key, TBB, num, i); | |
155 | init_ar (di->dom, TBB, num, 0); | |
156 | ||
157 | init_ar (di->bucket, TBB, num, 0); | |
158 | init_ar (di->next_bucket, TBB, num, 0); | |
159 | ||
160 | init_ar (di->set_chain, TBB, num, 0); | |
161 | init_ar (di->set_size, unsigned int, num, 1); | |
162 | init_ar (di->set_child, TBB, num, 0); | |
163 | ||
d55bc081 | 164 | init_ar (di->dfs_order, TBB, (unsigned int) last_basic_block + 1, 0); |
f8032688 MM |
165 | init_ar (di->dfs_to_bb, basic_block, num, 0); |
166 | ||
167 | di->dfsnum = 1; | |
168 | di->nodes = 0; | |
26e0e410 | 169 | |
8bdbfff5 | 170 | di->fake_exit_edge = dir ? BITMAP_ALLOC (NULL) : NULL; |
f8032688 MM |
171 | } |
172 | ||
173 | #undef init_ar | |
174 | ||
175 | /* Free all allocated memory in DI, but not DI itself. */ | |
176 | ||
177 | static void | |
7080f735 | 178 | free_dom_info (struct dom_info *di) |
f8032688 MM |
179 | { |
180 | free (di->dfs_parent); | |
181 | free (di->path_min); | |
182 | free (di->key); | |
183 | free (di->dom); | |
184 | free (di->bucket); | |
185 | free (di->next_bucket); | |
186 | free (di->set_chain); | |
187 | free (di->set_size); | |
188 | free (di->set_child); | |
189 | free (di->dfs_order); | |
190 | free (di->dfs_to_bb); | |
8bdbfff5 | 191 | BITMAP_FREE (di->fake_exit_edge); |
f8032688 MM |
192 | } |
193 | ||
194 | /* The nonrecursive variant of creating a DFS tree. DI is our working | |
195 | structure, BB the starting basic block for this tree and REVERSE | |
196 | is true, if predecessors should be visited instead of successors of a | |
197 | node. After this is done all nodes reachable from BB were visited, have | |
198 | assigned their dfs number and are linked together to form a tree. */ | |
199 | ||
200 | static void | |
26e0e410 RH |
201 | calc_dfs_tree_nonrec (struct dom_info *di, basic_block bb, |
202 | enum cdi_direction reverse) | |
f8032688 | 203 | { |
f8032688 MM |
204 | /* We call this _only_ if bb is not already visited. */ |
205 | edge e; | |
206 | TBB child_i, my_i = 0; | |
628f6a4e BE |
207 | edge_iterator *stack; |
208 | edge_iterator ei, einext; | |
f8032688 MM |
209 | int sp; |
210 | /* Start block (ENTRY_BLOCK_PTR for forward problem, EXIT_BLOCK for backward | |
211 | problem). */ | |
212 | basic_block en_block; | |
213 | /* Ending block. */ | |
214 | basic_block ex_block; | |
215 | ||
24bd1a0b | 216 | stack = xmalloc ((n_basic_blocks + 1) * sizeof (edge_iterator)); |
f8032688 MM |
217 | sp = 0; |
218 | ||
219 | /* Initialize our border blocks, and the first edge. */ | |
220 | if (reverse) | |
221 | { | |
628f6a4e | 222 | ei = ei_start (bb->preds); |
f8032688 MM |
223 | en_block = EXIT_BLOCK_PTR; |
224 | ex_block = ENTRY_BLOCK_PTR; | |
225 | } | |
226 | else | |
227 | { | |
628f6a4e | 228 | ei = ei_start (bb->succs); |
f8032688 MM |
229 | en_block = ENTRY_BLOCK_PTR; |
230 | ex_block = EXIT_BLOCK_PTR; | |
231 | } | |
232 | ||
233 | /* When the stack is empty we break out of this loop. */ | |
234 | while (1) | |
235 | { | |
236 | basic_block bn; | |
237 | ||
238 | /* This loop traverses edges e in depth first manner, and fills the | |
239 | stack. */ | |
628f6a4e | 240 | while (!ei_end_p (ei)) |
f8032688 | 241 | { |
628f6a4e | 242 | e = ei_edge (ei); |
f8032688 MM |
243 | |
244 | /* Deduce from E the current and the next block (BB and BN), and the | |
245 | next edge. */ | |
246 | if (reverse) | |
247 | { | |
248 | bn = e->src; | |
249 | ||
250 | /* If the next node BN is either already visited or a border | |
251 | block the current edge is useless, and simply overwritten | |
252 | with the next edge out of the current node. */ | |
0b17ab2f | 253 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 | 254 | { |
628f6a4e | 255 | ei_next (&ei); |
f8032688 MM |
256 | continue; |
257 | } | |
258 | bb = e->dest; | |
628f6a4e | 259 | einext = ei_start (bn->preds); |
f8032688 MM |
260 | } |
261 | else | |
262 | { | |
263 | bn = e->dest; | |
0b17ab2f | 264 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 | 265 | { |
628f6a4e | 266 | ei_next (&ei); |
f8032688 MM |
267 | continue; |
268 | } | |
269 | bb = e->src; | |
628f6a4e | 270 | einext = ei_start (bn->succs); |
f8032688 MM |
271 | } |
272 | ||
ced3f397 | 273 | gcc_assert (bn != en_block); |
f8032688 MM |
274 | |
275 | /* Fill the DFS tree info calculatable _before_ recursing. */ | |
276 | if (bb != en_block) | |
0b17ab2f | 277 | my_i = di->dfs_order[bb->index]; |
f8032688 | 278 | else |
d55bc081 | 279 | my_i = di->dfs_order[last_basic_block]; |
0b17ab2f | 280 | child_i = di->dfs_order[bn->index] = di->dfsnum++; |
f8032688 MM |
281 | di->dfs_to_bb[child_i] = bn; |
282 | di->dfs_parent[child_i] = my_i; | |
283 | ||
284 | /* Save the current point in the CFG on the stack, and recurse. */ | |
628f6a4e BE |
285 | stack[sp++] = ei; |
286 | ei = einext; | |
f8032688 MM |
287 | } |
288 | ||
289 | if (!sp) | |
290 | break; | |
628f6a4e | 291 | ei = stack[--sp]; |
f8032688 MM |
292 | |
293 | /* OK. The edge-list was exhausted, meaning normally we would | |
294 | end the recursion. After returning from the recursive call, | |
295 | there were (may be) other statements which were run after a | |
296 | child node was completely considered by DFS. Here is the | |
297 | point to do it in the non-recursive variant. | |
298 | E.g. The block just completed is in e->dest for forward DFS, | |
299 | the block not yet completed (the parent of the one above) | |
300 | in e->src. This could be used e.g. for computing the number of | |
301 | descendants or the tree depth. */ | |
628f6a4e | 302 | ei_next (&ei); |
f8032688 MM |
303 | } |
304 | free (stack); | |
305 | } | |
306 | ||
307 | /* The main entry for calculating the DFS tree or forest. DI is our working | |
308 | structure and REVERSE is true, if we are interested in the reverse flow | |
309 | graph. In that case the result is not necessarily a tree but a forest, | |
310 | because there may be nodes from which the EXIT_BLOCK is unreachable. */ | |
311 | ||
312 | static void | |
7080f735 | 313 | calc_dfs_tree (struct dom_info *di, enum cdi_direction reverse) |
f8032688 MM |
314 | { |
315 | /* The first block is the ENTRY_BLOCK (or EXIT_BLOCK if REVERSE). */ | |
316 | basic_block begin = reverse ? EXIT_BLOCK_PTR : ENTRY_BLOCK_PTR; | |
d55bc081 | 317 | di->dfs_order[last_basic_block] = di->dfsnum; |
f8032688 MM |
318 | di->dfs_to_bb[di->dfsnum] = begin; |
319 | di->dfsnum++; | |
320 | ||
321 | calc_dfs_tree_nonrec (di, begin, reverse); | |
322 | ||
323 | if (reverse) | |
324 | { | |
325 | /* In the post-dom case we may have nodes without a path to EXIT_BLOCK. | |
326 | They are reverse-unreachable. In the dom-case we disallow such | |
26e0e410 RH |
327 | nodes, but in post-dom we have to deal with them. |
328 | ||
329 | There are two situations in which this occurs. First, noreturn | |
330 | functions. Second, infinite loops. In the first case we need to | |
331 | pretend that there is an edge to the exit block. In the second | |
332 | case, we wind up with a forest. We need to process all noreturn | |
333 | blocks before we know if we've got any infinite loops. */ | |
334 | ||
e0082a72 | 335 | basic_block b; |
26e0e410 RH |
336 | bool saw_unconnected = false; |
337 | ||
e0082a72 | 338 | FOR_EACH_BB_REVERSE (b) |
f8032688 | 339 | { |
628f6a4e | 340 | if (EDGE_COUNT (b->succs) > 0) |
26e0e410 RH |
341 | { |
342 | if (di->dfs_order[b->index] == 0) | |
343 | saw_unconnected = true; | |
344 | continue; | |
345 | } | |
346 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
0b17ab2f | 347 | di->dfs_order[b->index] = di->dfsnum; |
f8032688 | 348 | di->dfs_to_bb[di->dfsnum] = b; |
26e0e410 | 349 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; |
f8032688 MM |
350 | di->dfsnum++; |
351 | calc_dfs_tree_nonrec (di, b, reverse); | |
352 | } | |
26e0e410 RH |
353 | |
354 | if (saw_unconnected) | |
355 | { | |
356 | FOR_EACH_BB_REVERSE (b) | |
357 | { | |
358 | if (di->dfs_order[b->index]) | |
359 | continue; | |
360 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
361 | di->dfs_order[b->index] = di->dfsnum; | |
362 | di->dfs_to_bb[di->dfsnum] = b; | |
363 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; | |
364 | di->dfsnum++; | |
365 | calc_dfs_tree_nonrec (di, b, reverse); | |
366 | } | |
367 | } | |
f8032688 MM |
368 | } |
369 | ||
370 | di->nodes = di->dfsnum - 1; | |
371 | ||
24bd1a0b DB |
372 | /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. */ |
373 | gcc_assert (di->nodes == (unsigned int) n_basic_blocks - 1); | |
f8032688 MM |
374 | } |
375 | ||
376 | /* Compress the path from V to the root of its set and update path_min at the | |
377 | same time. After compress(di, V) set_chain[V] is the root of the set V is | |
378 | in and path_min[V] is the node with the smallest key[] value on the path | |
379 | from V to that root. */ | |
380 | ||
381 | static void | |
7080f735 | 382 | compress (struct dom_info *di, TBB v) |
f8032688 MM |
383 | { |
384 | /* Btw. It's not worth to unrecurse compress() as the depth is usually not | |
385 | greater than 5 even for huge graphs (I've not seen call depth > 4). | |
386 | Also performance wise compress() ranges _far_ behind eval(). */ | |
387 | TBB parent = di->set_chain[v]; | |
388 | if (di->set_chain[parent]) | |
389 | { | |
390 | compress (di, parent); | |
391 | if (di->key[di->path_min[parent]] < di->key[di->path_min[v]]) | |
392 | di->path_min[v] = di->path_min[parent]; | |
393 | di->set_chain[v] = di->set_chain[parent]; | |
394 | } | |
395 | } | |
396 | ||
397 | /* Compress the path from V to the set root of V if needed (when the root has | |
398 | changed since the last call). Returns the node with the smallest key[] | |
399 | value on the path from V to the root. */ | |
400 | ||
401 | static inline TBB | |
7080f735 | 402 | eval (struct dom_info *di, TBB v) |
f8032688 MM |
403 | { |
404 | /* The representant of the set V is in, also called root (as the set | |
405 | representation is a tree). */ | |
406 | TBB rep = di->set_chain[v]; | |
407 | ||
408 | /* V itself is the root. */ | |
409 | if (!rep) | |
410 | return di->path_min[v]; | |
411 | ||
412 | /* Compress only if necessary. */ | |
413 | if (di->set_chain[rep]) | |
414 | { | |
415 | compress (di, v); | |
416 | rep = di->set_chain[v]; | |
417 | } | |
418 | ||
419 | if (di->key[di->path_min[rep]] >= di->key[di->path_min[v]]) | |
420 | return di->path_min[v]; | |
421 | else | |
422 | return di->path_min[rep]; | |
423 | } | |
424 | ||
425 | /* This essentially merges the two sets of V and W, giving a single set with | |
426 | the new root V. The internal representation of these disjoint sets is a | |
427 | balanced tree. Currently link(V,W) is only used with V being the parent | |
428 | of W. */ | |
429 | ||
430 | static void | |
7080f735 | 431 | link_roots (struct dom_info *di, TBB v, TBB w) |
f8032688 MM |
432 | { |
433 | TBB s = w; | |
434 | ||
435 | /* Rebalance the tree. */ | |
436 | while (di->key[di->path_min[w]] < di->key[di->path_min[di->set_child[s]]]) | |
437 | { | |
438 | if (di->set_size[s] + di->set_size[di->set_child[di->set_child[s]]] | |
439 | >= 2 * di->set_size[di->set_child[s]]) | |
440 | { | |
441 | di->set_chain[di->set_child[s]] = s; | |
442 | di->set_child[s] = di->set_child[di->set_child[s]]; | |
443 | } | |
444 | else | |
445 | { | |
446 | di->set_size[di->set_child[s]] = di->set_size[s]; | |
447 | s = di->set_chain[s] = di->set_child[s]; | |
448 | } | |
449 | } | |
450 | ||
451 | di->path_min[s] = di->path_min[w]; | |
452 | di->set_size[v] += di->set_size[w]; | |
453 | if (di->set_size[v] < 2 * di->set_size[w]) | |
454 | { | |
455 | TBB tmp = s; | |
456 | s = di->set_child[v]; | |
457 | di->set_child[v] = tmp; | |
458 | } | |
459 | ||
460 | /* Merge all subtrees. */ | |
461 | while (s) | |
462 | { | |
463 | di->set_chain[s] = v; | |
464 | s = di->set_child[s]; | |
465 | } | |
466 | } | |
467 | ||
468 | /* This calculates the immediate dominators (or post-dominators if REVERSE is | |
469 | true). DI is our working structure and should hold the DFS forest. | |
470 | On return the immediate dominator to node V is in di->dom[V]. */ | |
471 | ||
472 | static void | |
7080f735 | 473 | calc_idoms (struct dom_info *di, enum cdi_direction reverse) |
f8032688 MM |
474 | { |
475 | TBB v, w, k, par; | |
476 | basic_block en_block; | |
628f6a4e BE |
477 | edge_iterator ei, einext; |
478 | ||
f8032688 MM |
479 | if (reverse) |
480 | en_block = EXIT_BLOCK_PTR; | |
481 | else | |
482 | en_block = ENTRY_BLOCK_PTR; | |
483 | ||
484 | /* Go backwards in DFS order, to first look at the leafs. */ | |
485 | v = di->nodes; | |
486 | while (v > 1) | |
487 | { | |
488 | basic_block bb = di->dfs_to_bb[v]; | |
628f6a4e | 489 | edge e; |
f8032688 MM |
490 | |
491 | par = di->dfs_parent[v]; | |
492 | k = v; | |
628f6a4e BE |
493 | |
494 | ei = (reverse) ? ei_start (bb->succs) : ei_start (bb->preds); | |
495 | ||
f8032688 | 496 | if (reverse) |
26e0e410 | 497 | { |
26e0e410 RH |
498 | /* If this block has a fake edge to exit, process that first. */ |
499 | if (bitmap_bit_p (di->fake_exit_edge, bb->index)) | |
500 | { | |
628f6a4e BE |
501 | einext = ei; |
502 | einext.index = 0; | |
26e0e410 RH |
503 | goto do_fake_exit_edge; |
504 | } | |
505 | } | |
f8032688 MM |
506 | |
507 | /* Search all direct predecessors for the smallest node with a path | |
508 | to them. That way we have the smallest node with also a path to | |
509 | us only over nodes behind us. In effect we search for our | |
510 | semidominator. */ | |
628f6a4e | 511 | while (!ei_end_p (ei)) |
f8032688 MM |
512 | { |
513 | TBB k1; | |
514 | basic_block b; | |
515 | ||
628f6a4e BE |
516 | e = ei_edge (ei); |
517 | b = (reverse) ? e->dest : e->src; | |
518 | einext = ei; | |
519 | ei_next (&einext); | |
520 | ||
f8032688 | 521 | if (b == en_block) |
26e0e410 RH |
522 | { |
523 | do_fake_exit_edge: | |
524 | k1 = di->dfs_order[last_basic_block]; | |
525 | } | |
f8032688 | 526 | else |
0b17ab2f | 527 | k1 = di->dfs_order[b->index]; |
f8032688 MM |
528 | |
529 | /* Call eval() only if really needed. If k1 is above V in DFS tree, | |
530 | then we know, that eval(k1) == k1 and key[k1] == k1. */ | |
531 | if (k1 > v) | |
532 | k1 = di->key[eval (di, k1)]; | |
533 | if (k1 < k) | |
534 | k = k1; | |
628f6a4e BE |
535 | |
536 | ei = einext; | |
f8032688 MM |
537 | } |
538 | ||
539 | di->key[v] = k; | |
540 | link_roots (di, par, v); | |
541 | di->next_bucket[v] = di->bucket[k]; | |
542 | di->bucket[k] = v; | |
543 | ||
544 | /* Transform semidominators into dominators. */ | |
545 | for (w = di->bucket[par]; w; w = di->next_bucket[w]) | |
546 | { | |
547 | k = eval (di, w); | |
548 | if (di->key[k] < di->key[w]) | |
549 | di->dom[w] = k; | |
550 | else | |
551 | di->dom[w] = par; | |
552 | } | |
553 | /* We don't need to cleanup next_bucket[]. */ | |
554 | di->bucket[par] = 0; | |
555 | v--; | |
556 | } | |
557 | ||
a1f300c0 | 558 | /* Explicitly define the dominators. */ |
f8032688 MM |
559 | di->dom[1] = 0; |
560 | for (v = 2; v <= di->nodes; v++) | |
561 | if (di->dom[v] != di->key[v]) | |
562 | di->dom[v] = di->dom[di->dom[v]]; | |
563 | } | |
564 | ||
d47cc544 SB |
565 | /* Assign dfs numbers starting from NUM to NODE and its sons. */ |
566 | ||
567 | static void | |
568 | assign_dfs_numbers (struct et_node *node, int *num) | |
569 | { | |
570 | struct et_node *son; | |
571 | ||
572 | node->dfs_num_in = (*num)++; | |
573 | ||
574 | if (node->son) | |
575 | { | |
576 | assign_dfs_numbers (node->son, num); | |
577 | for (son = node->son->right; son != node->son; son = son->right) | |
6de9cd9a | 578 | assign_dfs_numbers (son, num); |
d47cc544 | 579 | } |
f8032688 | 580 | |
d47cc544 SB |
581 | node->dfs_num_out = (*num)++; |
582 | } | |
f8032688 | 583 | |
5d3cc252 | 584 | /* Compute the data necessary for fast resolving of dominator queries in a |
d47cc544 | 585 | static dominator tree. */ |
f8032688 | 586 | |
d47cc544 SB |
587 | static void |
588 | compute_dom_fast_query (enum cdi_direction dir) | |
589 | { | |
590 | int num = 0; | |
591 | basic_block bb; | |
592 | ||
fce22de5 | 593 | gcc_assert (dom_info_available_p (dir)); |
d47cc544 SB |
594 | |
595 | if (dom_computed[dir] == DOM_OK) | |
596 | return; | |
597 | ||
598 | FOR_ALL_BB (bb) | |
599 | { | |
600 | if (!bb->dom[dir]->father) | |
6de9cd9a | 601 | assign_dfs_numbers (bb->dom[dir], &num); |
d47cc544 SB |
602 | } |
603 | ||
604 | dom_computed[dir] = DOM_OK; | |
605 | } | |
606 | ||
607 | /* The main entry point into this module. DIR is set depending on whether | |
608 | we want to compute dominators or postdominators. */ | |
609 | ||
610 | void | |
611 | calculate_dominance_info (enum cdi_direction dir) | |
f8032688 MM |
612 | { |
613 | struct dom_info di; | |
355be0dc JH |
614 | basic_block b; |
615 | ||
d47cc544 SB |
616 | if (dom_computed[dir] == DOM_OK) |
617 | return; | |
355be0dc | 618 | |
fce22de5 | 619 | if (!dom_info_available_p (dir)) |
d47cc544 | 620 | { |
ced3f397 | 621 | gcc_assert (!n_bbs_in_dom_tree[dir]); |
f8032688 | 622 | |
d47cc544 SB |
623 | FOR_ALL_BB (b) |
624 | { | |
625 | b->dom[dir] = et_new_tree (b); | |
626 | } | |
24bd1a0b | 627 | n_bbs_in_dom_tree[dir] = n_basic_blocks; |
f8032688 | 628 | |
26e0e410 | 629 | init_dom_info (&di, dir); |
d47cc544 SB |
630 | calc_dfs_tree (&di, dir); |
631 | calc_idoms (&di, dir); | |
355be0dc | 632 | |
d47cc544 SB |
633 | FOR_EACH_BB (b) |
634 | { | |
635 | TBB d = di.dom[di.dfs_order[b->index]]; | |
636 | ||
637 | if (di.dfs_to_bb[d]) | |
638 | et_set_father (b->dom[dir], di.dfs_to_bb[d]->dom[dir]); | |
639 | } | |
e0082a72 | 640 | |
d47cc544 SB |
641 | free_dom_info (&di); |
642 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
643 | } |
644 | ||
d47cc544 | 645 | compute_dom_fast_query (dir); |
355be0dc JH |
646 | } |
647 | ||
d47cc544 | 648 | /* Free dominance information for direction DIR. */ |
355be0dc | 649 | void |
d47cc544 | 650 | free_dominance_info (enum cdi_direction dir) |
355be0dc JH |
651 | { |
652 | basic_block bb; | |
653 | ||
fce22de5 | 654 | if (!dom_info_available_p (dir)) |
d47cc544 SB |
655 | return; |
656 | ||
657 | FOR_ALL_BB (bb) | |
658 | { | |
bef87a34 KH |
659 | et_free_tree_force (bb->dom[dir]); |
660 | bb->dom[dir] = NULL; | |
d47cc544 SB |
661 | } |
662 | ||
bef87a34 | 663 | n_bbs_in_dom_tree[dir] = 0; |
6de9cd9a | 664 | |
d47cc544 | 665 | dom_computed[dir] = DOM_NONE; |
355be0dc JH |
666 | } |
667 | ||
668 | /* Return the immediate dominator of basic block BB. */ | |
669 | basic_block | |
d47cc544 | 670 | get_immediate_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 671 | { |
d47cc544 SB |
672 | struct et_node *node = bb->dom[dir]; |
673 | ||
ced3f397 | 674 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
675 | |
676 | if (!node->father) | |
677 | return NULL; | |
678 | ||
6de9cd9a | 679 | return node->father->data; |
355be0dc JH |
680 | } |
681 | ||
682 | /* Set the immediate dominator of the block possibly removing | |
683 | existing edge. NULL can be used to remove any edge. */ | |
684 | inline void | |
d47cc544 SB |
685 | set_immediate_dominator (enum cdi_direction dir, basic_block bb, |
686 | basic_block dominated_by) | |
355be0dc | 687 | { |
d47cc544 SB |
688 | struct et_node *node = bb->dom[dir]; |
689 | ||
ced3f397 | 690 | gcc_assert (dom_computed[dir]); |
355be0dc | 691 | |
d47cc544 | 692 | if (node->father) |
355be0dc | 693 | { |
d47cc544 | 694 | if (node->father->data == dominated_by) |
6de9cd9a | 695 | return; |
d47cc544 | 696 | et_split (node); |
355be0dc | 697 | } |
d47cc544 SB |
698 | |
699 | if (dominated_by) | |
700 | et_set_father (node, dominated_by->dom[dir]); | |
701 | ||
702 | if (dom_computed[dir] == DOM_OK) | |
703 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
704 | } |
705 | ||
5d3cc252 | 706 | /* Store all basic blocks immediately dominated by BB into BBS and return |
d47cc544 | 707 | their number. */ |
355be0dc | 708 | int |
d47cc544 | 709 | get_dominated_by (enum cdi_direction dir, basic_block bb, basic_block **bbs) |
355be0dc | 710 | { |
d47cc544 SB |
711 | int n; |
712 | struct et_node *node = bb->dom[dir], *son = node->son, *ason; | |
713 | ||
ced3f397 | 714 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
715 | |
716 | if (!son) | |
717 | { | |
718 | *bbs = NULL; | |
719 | return 0; | |
720 | } | |
721 | ||
722 | for (ason = son->right, n = 1; ason != son; ason = ason->right) | |
723 | n++; | |
724 | ||
725 | *bbs = xmalloc (n * sizeof (basic_block)); | |
726 | (*bbs)[0] = son->data; | |
727 | for (ason = son->right, n = 1; ason != son; ason = ason->right) | |
728 | (*bbs)[n++] = ason->data; | |
355be0dc | 729 | |
355be0dc JH |
730 | return n; |
731 | } | |
732 | ||
42759f1e ZD |
733 | /* Find all basic blocks that are immediately dominated (in direction DIR) |
734 | by some block between N_REGION ones stored in REGION, except for blocks | |
735 | in the REGION itself. The found blocks are stored to DOMS and their number | |
736 | is returned. */ | |
737 | ||
738 | unsigned | |
739 | get_dominated_by_region (enum cdi_direction dir, basic_block *region, | |
740 | unsigned n_region, basic_block *doms) | |
741 | { | |
742 | unsigned n_doms = 0, i; | |
743 | basic_block dom; | |
744 | ||
745 | for (i = 0; i < n_region; i++) | |
6580ee77 | 746 | region[i]->flags |= BB_DUPLICATED; |
42759f1e ZD |
747 | for (i = 0; i < n_region; i++) |
748 | for (dom = first_dom_son (dir, region[i]); | |
749 | dom; | |
750 | dom = next_dom_son (dir, dom)) | |
6580ee77 | 751 | if (!(dom->flags & BB_DUPLICATED)) |
42759f1e ZD |
752 | doms[n_doms++] = dom; |
753 | for (i = 0; i < n_region; i++) | |
6580ee77 | 754 | region[i]->flags &= ~BB_DUPLICATED; |
42759f1e ZD |
755 | |
756 | return n_doms; | |
757 | } | |
758 | ||
355be0dc JH |
759 | /* Redirect all edges pointing to BB to TO. */ |
760 | void | |
d47cc544 SB |
761 | redirect_immediate_dominators (enum cdi_direction dir, basic_block bb, |
762 | basic_block to) | |
355be0dc | 763 | { |
d47cc544 SB |
764 | struct et_node *bb_node = bb->dom[dir], *to_node = to->dom[dir], *son; |
765 | ||
ced3f397 | 766 | gcc_assert (dom_computed[dir]); |
355be0dc | 767 | |
d47cc544 SB |
768 | if (!bb_node->son) |
769 | return; | |
770 | ||
771 | while (bb_node->son) | |
355be0dc | 772 | { |
d47cc544 SB |
773 | son = bb_node->son; |
774 | ||
775 | et_split (son); | |
776 | et_set_father (son, to_node); | |
355be0dc | 777 | } |
d47cc544 SB |
778 | |
779 | if (dom_computed[dir] == DOM_OK) | |
780 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
781 | } |
782 | ||
783 | /* Find first basic block in the tree dominating both BB1 and BB2. */ | |
784 | basic_block | |
d47cc544 | 785 | nearest_common_dominator (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
355be0dc | 786 | { |
ced3f397 | 787 | gcc_assert (dom_computed[dir]); |
d47cc544 | 788 | |
355be0dc JH |
789 | if (!bb1) |
790 | return bb2; | |
791 | if (!bb2) | |
792 | return bb1; | |
d47cc544 SB |
793 | |
794 | return et_nca (bb1->dom[dir], bb2->dom[dir])->data; | |
355be0dc JH |
795 | } |
796 | ||
0bca51f0 DN |
797 | |
798 | /* Find the nearest common dominator for the basic blocks in BLOCKS, | |
799 | using dominance direction DIR. */ | |
800 | ||
801 | basic_block | |
802 | nearest_common_dominator_for_set (enum cdi_direction dir, bitmap blocks) | |
803 | { | |
804 | unsigned i, first; | |
805 | bitmap_iterator bi; | |
806 | basic_block dom; | |
807 | ||
808 | first = bitmap_first_set_bit (blocks); | |
809 | dom = BASIC_BLOCK (first); | |
810 | EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi) | |
811 | if (dom != BASIC_BLOCK (i)) | |
812 | dom = nearest_common_dominator (dir, dom, BASIC_BLOCK (i)); | |
813 | ||
814 | return dom; | |
815 | } | |
816 | ||
817 | ||
355be0dc JH |
818 | /* Return TRUE in case BB1 is dominated by BB2. */ |
819 | bool | |
d47cc544 | 820 | dominated_by_p (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
6de9cd9a | 821 | { |
d47cc544 SB |
822 | struct et_node *n1 = bb1->dom[dir], *n2 = bb2->dom[dir]; |
823 | ||
ced3f397 | 824 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
825 | |
826 | if (dom_computed[dir] == DOM_OK) | |
827 | return (n1->dfs_num_in >= n2->dfs_num_in | |
6de9cd9a | 828 | && n1->dfs_num_out <= n2->dfs_num_out); |
d47cc544 SB |
829 | |
830 | return et_below (n1, n2); | |
355be0dc JH |
831 | } |
832 | ||
833 | /* Verify invariants of dominator structure. */ | |
834 | void | |
d47cc544 | 835 | verify_dominators (enum cdi_direction dir) |
355be0dc JH |
836 | { |
837 | int err = 0; | |
838 | basic_block bb; | |
839 | ||
fce22de5 | 840 | gcc_assert (dom_info_available_p (dir)); |
d47cc544 | 841 | |
355be0dc JH |
842 | FOR_EACH_BB (bb) |
843 | { | |
844 | basic_block dom_bb; | |
df485d80 | 845 | basic_block imm_bb; |
355be0dc | 846 | |
d47cc544 | 847 | dom_bb = recount_dominator (dir, bb); |
df485d80 FCE |
848 | imm_bb = get_immediate_dominator (dir, bb); |
849 | if (dom_bb != imm_bb) | |
f8032688 | 850 | { |
df485d80 FCE |
851 | if ((dom_bb == NULL) || (imm_bb == NULL)) |
852 | error ("dominator of %d status unknown", bb->index); | |
08fb229e FCE |
853 | else |
854 | error ("dominator of %d should be %d, not %d", | |
df485d80 | 855 | bb->index, dom_bb->index, imm_bb->index); |
355be0dc JH |
856 | err = 1; |
857 | } | |
858 | } | |
e7bd94cc | 859 | |
fce22de5 | 860 | if (dir == CDI_DOMINATORS) |
e7bd94cc ZD |
861 | { |
862 | FOR_EACH_BB (bb) | |
863 | { | |
864 | if (!dominated_by_p (dir, bb, ENTRY_BLOCK_PTR)) | |
865 | { | |
866 | error ("ENTRY does not dominate bb %d", bb->index); | |
867 | err = 1; | |
868 | } | |
869 | } | |
870 | } | |
871 | ||
ced3f397 | 872 | gcc_assert (!err); |
355be0dc JH |
873 | } |
874 | ||
738ed977 ZD |
875 | /* Determine immediate dominator (or postdominator, according to DIR) of BB, |
876 | assuming that dominators of other blocks are correct. We also use it to | |
877 | recompute the dominators in a restricted area, by iterating it until it | |
71cc389b | 878 | reaches a fixed point. */ |
738ed977 | 879 | |
355be0dc | 880 | basic_block |
d47cc544 | 881 | recount_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 882 | { |
738ed977 ZD |
883 | basic_block dom_bb = NULL; |
884 | edge e; | |
628f6a4e | 885 | edge_iterator ei; |
355be0dc | 886 | |
ced3f397 | 887 | gcc_assert (dom_computed[dir]); |
d47cc544 | 888 | |
738ed977 ZD |
889 | if (dir == CDI_DOMINATORS) |
890 | { | |
628f6a4e | 891 | FOR_EACH_EDGE (e, ei, bb->preds) |
738ed977 | 892 | { |
e7bd94cc ZD |
893 | /* Ignore the predecessors that either are not reachable from |
894 | the entry block, or whose dominator was not determined yet. */ | |
895 | if (!dominated_by_p (dir, e->src, ENTRY_BLOCK_PTR)) | |
896 | continue; | |
897 | ||
738ed977 ZD |
898 | if (!dominated_by_p (dir, e->src, bb)) |
899 | dom_bb = nearest_common_dominator (dir, dom_bb, e->src); | |
900 | } | |
901 | } | |
902 | else | |
903 | { | |
628f6a4e | 904 | FOR_EACH_EDGE (e, ei, bb->succs) |
738ed977 ZD |
905 | { |
906 | if (!dominated_by_p (dir, e->dest, bb)) | |
907 | dom_bb = nearest_common_dominator (dir, dom_bb, e->dest); | |
908 | } | |
909 | } | |
f8032688 | 910 | |
738ed977 | 911 | return dom_bb; |
355be0dc JH |
912 | } |
913 | ||
914 | /* Iteratively recount dominators of BBS. The change is supposed to be local | |
915 | and not to grow further. */ | |
916 | void | |
d47cc544 | 917 | iterate_fix_dominators (enum cdi_direction dir, basic_block *bbs, int n) |
355be0dc JH |
918 | { |
919 | int i, changed = 1; | |
920 | basic_block old_dom, new_dom; | |
921 | ||
ced3f397 | 922 | gcc_assert (dom_computed[dir]); |
d47cc544 | 923 | |
e7bd94cc ZD |
924 | for (i = 0; i < n; i++) |
925 | set_immediate_dominator (dir, bbs[i], NULL); | |
926 | ||
355be0dc JH |
927 | while (changed) |
928 | { | |
929 | changed = 0; | |
930 | for (i = 0; i < n; i++) | |
931 | { | |
d47cc544 SB |
932 | old_dom = get_immediate_dominator (dir, bbs[i]); |
933 | new_dom = recount_dominator (dir, bbs[i]); | |
355be0dc JH |
934 | if (old_dom != new_dom) |
935 | { | |
936 | changed = 1; | |
d47cc544 | 937 | set_immediate_dominator (dir, bbs[i], new_dom); |
355be0dc | 938 | } |
f8032688 MM |
939 | } |
940 | } | |
e7bd94cc ZD |
941 | |
942 | for (i = 0; i < n; i++) | |
ced3f397 | 943 | gcc_assert (get_immediate_dominator (dir, bbs[i])); |
355be0dc | 944 | } |
f8032688 | 945 | |
355be0dc | 946 | void |
d47cc544 | 947 | add_to_dominance_info (enum cdi_direction dir, basic_block bb) |
355be0dc | 948 | { |
ced3f397 NS |
949 | gcc_assert (dom_computed[dir]); |
950 | gcc_assert (!bb->dom[dir]); | |
d47cc544 | 951 | |
6de9cd9a DN |
952 | n_bbs_in_dom_tree[dir]++; |
953 | ||
d47cc544 SB |
954 | bb->dom[dir] = et_new_tree (bb); |
955 | ||
956 | if (dom_computed[dir] == DOM_OK) | |
957 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
958 | } |
959 | ||
960 | void | |
d47cc544 SB |
961 | delete_from_dominance_info (enum cdi_direction dir, basic_block bb) |
962 | { | |
ced3f397 | 963 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
964 | |
965 | et_free_tree (bb->dom[dir]); | |
966 | bb->dom[dir] = NULL; | |
6de9cd9a | 967 | n_bbs_in_dom_tree[dir]--; |
d47cc544 SB |
968 | |
969 | if (dom_computed[dir] == DOM_OK) | |
970 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
971 | } | |
972 | ||
973 | /* Returns the first son of BB in the dominator or postdominator tree | |
974 | as determined by DIR. */ | |
975 | ||
976 | basic_block | |
977 | first_dom_son (enum cdi_direction dir, basic_block bb) | |
355be0dc | 978 | { |
d47cc544 SB |
979 | struct et_node *son = bb->dom[dir]->son; |
980 | ||
981 | return son ? son->data : NULL; | |
982 | } | |
983 | ||
984 | /* Returns the next dominance son after BB in the dominator or postdominator | |
985 | tree as determined by DIR, or NULL if it was the last one. */ | |
986 | ||
987 | basic_block | |
988 | next_dom_son (enum cdi_direction dir, basic_block bb) | |
989 | { | |
990 | struct et_node *next = bb->dom[dir]->right; | |
991 | ||
992 | return next->father->son == next ? NULL : next->data; | |
355be0dc JH |
993 | } |
994 | ||
fce22de5 ZD |
995 | /* Returns true if dominance information for direction DIR is available. */ |
996 | ||
997 | bool | |
998 | dom_info_available_p (enum cdi_direction dir) | |
999 | { | |
1000 | return dom_computed[dir] != DOM_NONE; | |
1001 | } | |
1002 | ||
355be0dc | 1003 | void |
d47cc544 | 1004 | debug_dominance_info (enum cdi_direction dir) |
355be0dc JH |
1005 | { |
1006 | basic_block bb, bb2; | |
1007 | FOR_EACH_BB (bb) | |
d47cc544 | 1008 | if ((bb2 = get_immediate_dominator (dir, bb))) |
355be0dc | 1009 | fprintf (stderr, "%i %i\n", bb->index, bb2->index); |
f8032688 | 1010 | } |