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f8032688 | 1 | /* Calculate (post)dominators in slightly super-linear time. |
d9221e01 | 2 | Copyright (C) 2000, 2003, 2004 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 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 | ||
a1f300c0 | 31 | The algorithm computes this dominator tree implicitly by computing for |
f8032688 MM |
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" | |
4977bab6 ZW |
38 | #include "coretypes.h" |
39 | #include "tm.h" | |
f8032688 MM |
40 | #include "rtl.h" |
41 | #include "hard-reg-set.h" | |
42 | #include "basic-block.h" | |
8a67e083 | 43 | #include "errors.h" |
355be0dc | 44 | #include "et-forest.h" |
f8032688 | 45 | |
d47cc544 SB |
46 | /* Whether the dominators and the postdominators are available. */ |
47 | enum dom_state dom_computed[2]; | |
f8032688 MM |
48 | |
49 | /* We name our nodes with integers, beginning with 1. Zero is reserved for | |
50 | 'undefined' or 'end of list'. The name of each node is given by the dfs | |
51 | number of the corresponding basic block. Please note, that we include the | |
52 | artificial ENTRY_BLOCK (or EXIT_BLOCK in the post-dom case) in our lists to | |
53 | support multiple entry points. As it has no real basic block index we use | |
d55bc081 | 54 | 'last_basic_block' for that. 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 | { |
0b17ab2f | 151 | /* We need memory for n_basic_blocks nodes and the ENTRY_BLOCK or |
f8032688 | 152 | EXIT_BLOCK. */ |
0b17ab2f | 153 | unsigned int num = n_basic_blocks + 1 + 1; |
f8032688 MM |
154 | init_ar (di->dfs_parent, TBB, num, 0); |
155 | init_ar (di->path_min, TBB, num, i); | |
156 | init_ar (di->key, TBB, num, i); | |
157 | init_ar (di->dom, TBB, num, 0); | |
158 | ||
159 | init_ar (di->bucket, TBB, num, 0); | |
160 | init_ar (di->next_bucket, TBB, num, 0); | |
161 | ||
162 | init_ar (di->set_chain, TBB, num, 0); | |
163 | init_ar (di->set_size, unsigned int, num, 1); | |
164 | init_ar (di->set_child, TBB, num, 0); | |
165 | ||
d55bc081 | 166 | init_ar (di->dfs_order, TBB, (unsigned int) last_basic_block + 1, 0); |
f8032688 MM |
167 | init_ar (di->dfs_to_bb, basic_block, num, 0); |
168 | ||
169 | di->dfsnum = 1; | |
170 | di->nodes = 0; | |
26e0e410 RH |
171 | |
172 | di->fake_exit_edge = dir ? BITMAP_XMALLOC () : NULL; | |
f8032688 MM |
173 | } |
174 | ||
175 | #undef init_ar | |
176 | ||
177 | /* Free all allocated memory in DI, but not DI itself. */ | |
178 | ||
179 | static void | |
7080f735 | 180 | free_dom_info (struct dom_info *di) |
f8032688 MM |
181 | { |
182 | free (di->dfs_parent); | |
183 | free (di->path_min); | |
184 | free (di->key); | |
185 | free (di->dom); | |
186 | free (di->bucket); | |
187 | free (di->next_bucket); | |
188 | free (di->set_chain); | |
189 | free (di->set_size); | |
190 | free (di->set_child); | |
191 | free (di->dfs_order); | |
192 | free (di->dfs_to_bb); | |
26e0e410 | 193 | BITMAP_XFREE (di->fake_exit_edge); |
f8032688 MM |
194 | } |
195 | ||
196 | /* The nonrecursive variant of creating a DFS tree. DI is our working | |
197 | structure, BB the starting basic block for this tree and REVERSE | |
198 | is true, if predecessors should be visited instead of successors of a | |
199 | node. After this is done all nodes reachable from BB were visited, have | |
200 | assigned their dfs number and are linked together to form a tree. */ | |
201 | ||
202 | static void | |
26e0e410 RH |
203 | calc_dfs_tree_nonrec (struct dom_info *di, basic_block bb, |
204 | enum cdi_direction reverse) | |
f8032688 | 205 | { |
f8032688 MM |
206 | /* We call this _only_ if bb is not already visited. */ |
207 | edge e; | |
208 | TBB child_i, my_i = 0; | |
209 | edge *stack; | |
210 | int sp; | |
211 | /* Start block (ENTRY_BLOCK_PTR for forward problem, EXIT_BLOCK for backward | |
212 | problem). */ | |
213 | basic_block en_block; | |
214 | /* Ending block. */ | |
215 | basic_block ex_block; | |
216 | ||
703ad42b | 217 | stack = xmalloc ((n_basic_blocks + 3) * sizeof (edge)); |
f8032688 MM |
218 | sp = 0; |
219 | ||
220 | /* Initialize our border blocks, and the first edge. */ | |
221 | if (reverse) | |
222 | { | |
223 | e = bb->pred; | |
224 | en_block = EXIT_BLOCK_PTR; | |
225 | ex_block = ENTRY_BLOCK_PTR; | |
226 | } | |
227 | else | |
228 | { | |
229 | e = bb->succ; | |
230 | en_block = ENTRY_BLOCK_PTR; | |
231 | ex_block = EXIT_BLOCK_PTR; | |
232 | } | |
233 | ||
234 | /* When the stack is empty we break out of this loop. */ | |
235 | while (1) | |
236 | { | |
237 | basic_block bn; | |
238 | ||
239 | /* This loop traverses edges e in depth first manner, and fills the | |
240 | stack. */ | |
241 | while (e) | |
242 | { | |
243 | edge e_next; | |
244 | ||
245 | /* Deduce from E the current and the next block (BB and BN), and the | |
246 | next edge. */ | |
247 | if (reverse) | |
248 | { | |
249 | bn = e->src; | |
250 | ||
251 | /* If the next node BN is either already visited or a border | |
252 | block the current edge is useless, and simply overwritten | |
253 | with the next edge out of the current node. */ | |
0b17ab2f | 254 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 MM |
255 | { |
256 | e = e->pred_next; | |
257 | continue; | |
258 | } | |
259 | bb = e->dest; | |
260 | e_next = bn->pred; | |
261 | } | |
262 | else | |
263 | { | |
264 | bn = e->dest; | |
0b17ab2f | 265 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 MM |
266 | { |
267 | e = e->succ_next; | |
268 | continue; | |
269 | } | |
270 | bb = e->src; | |
271 | e_next = bn->succ; | |
272 | } | |
273 | ||
ced3f397 | 274 | gcc_assert (bn != en_block); |
f8032688 MM |
275 | |
276 | /* Fill the DFS tree info calculatable _before_ recursing. */ | |
277 | if (bb != en_block) | |
0b17ab2f | 278 | my_i = di->dfs_order[bb->index]; |
f8032688 | 279 | else |
d55bc081 | 280 | my_i = di->dfs_order[last_basic_block]; |
0b17ab2f | 281 | child_i = di->dfs_order[bn->index] = di->dfsnum++; |
f8032688 MM |
282 | di->dfs_to_bb[child_i] = bn; |
283 | di->dfs_parent[child_i] = my_i; | |
284 | ||
285 | /* Save the current point in the CFG on the stack, and recurse. */ | |
286 | stack[sp++] = e; | |
287 | e = e_next; | |
288 | } | |
289 | ||
290 | if (!sp) | |
291 | break; | |
292 | e = stack[--sp]; | |
293 | ||
294 | /* OK. The edge-list was exhausted, meaning normally we would | |
295 | end the recursion. After returning from the recursive call, | |
296 | there were (may be) other statements which were run after a | |
297 | child node was completely considered by DFS. Here is the | |
298 | point to do it in the non-recursive variant. | |
299 | E.g. The block just completed is in e->dest for forward DFS, | |
300 | the block not yet completed (the parent of the one above) | |
301 | in e->src. This could be used e.g. for computing the number of | |
302 | descendants or the tree depth. */ | |
303 | if (reverse) | |
304 | e = e->pred_next; | |
305 | else | |
306 | e = e->succ_next; | |
307 | } | |
308 | free (stack); | |
309 | } | |
310 | ||
311 | /* The main entry for calculating the DFS tree or forest. DI is our working | |
312 | structure and REVERSE is true, if we are interested in the reverse flow | |
313 | graph. In that case the result is not necessarily a tree but a forest, | |
314 | because there may be nodes from which the EXIT_BLOCK is unreachable. */ | |
315 | ||
316 | static void | |
7080f735 | 317 | calc_dfs_tree (struct dom_info *di, enum cdi_direction reverse) |
f8032688 MM |
318 | { |
319 | /* The first block is the ENTRY_BLOCK (or EXIT_BLOCK if REVERSE). */ | |
320 | basic_block begin = reverse ? EXIT_BLOCK_PTR : ENTRY_BLOCK_PTR; | |
d55bc081 | 321 | di->dfs_order[last_basic_block] = di->dfsnum; |
f8032688 MM |
322 | di->dfs_to_bb[di->dfsnum] = begin; |
323 | di->dfsnum++; | |
324 | ||
325 | calc_dfs_tree_nonrec (di, begin, reverse); | |
326 | ||
327 | if (reverse) | |
328 | { | |
329 | /* In the post-dom case we may have nodes without a path to EXIT_BLOCK. | |
330 | They are reverse-unreachable. In the dom-case we disallow such | |
26e0e410 RH |
331 | nodes, but in post-dom we have to deal with them. |
332 | ||
333 | There are two situations in which this occurs. First, noreturn | |
334 | functions. Second, infinite loops. In the first case we need to | |
335 | pretend that there is an edge to the exit block. In the second | |
336 | case, we wind up with a forest. We need to process all noreturn | |
337 | blocks before we know if we've got any infinite loops. */ | |
338 | ||
e0082a72 | 339 | basic_block b; |
26e0e410 RH |
340 | bool saw_unconnected = false; |
341 | ||
e0082a72 | 342 | FOR_EACH_BB_REVERSE (b) |
f8032688 | 343 | { |
26e0e410 RH |
344 | if (b->succ) |
345 | { | |
346 | if (di->dfs_order[b->index] == 0) | |
347 | saw_unconnected = true; | |
348 | continue; | |
349 | } | |
350 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
0b17ab2f | 351 | di->dfs_order[b->index] = di->dfsnum; |
f8032688 | 352 | di->dfs_to_bb[di->dfsnum] = b; |
26e0e410 | 353 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; |
f8032688 MM |
354 | di->dfsnum++; |
355 | calc_dfs_tree_nonrec (di, b, reverse); | |
356 | } | |
26e0e410 RH |
357 | |
358 | if (saw_unconnected) | |
359 | { | |
360 | FOR_EACH_BB_REVERSE (b) | |
361 | { | |
362 | if (di->dfs_order[b->index]) | |
363 | continue; | |
364 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
365 | di->dfs_order[b->index] = di->dfsnum; | |
366 | di->dfs_to_bb[di->dfsnum] = b; | |
367 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; | |
368 | di->dfsnum++; | |
369 | calc_dfs_tree_nonrec (di, b, reverse); | |
370 | } | |
371 | } | |
f8032688 MM |
372 | } |
373 | ||
374 | di->nodes = di->dfsnum - 1; | |
375 | ||
376 | /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. */ | |
ced3f397 | 377 | gcc_assert (di->nodes == (unsigned int) n_basic_blocks + 1); |
f8032688 MM |
378 | } |
379 | ||
380 | /* Compress the path from V to the root of its set and update path_min at the | |
381 | same time. After compress(di, V) set_chain[V] is the root of the set V is | |
382 | in and path_min[V] is the node with the smallest key[] value on the path | |
383 | from V to that root. */ | |
384 | ||
385 | static void | |
7080f735 | 386 | compress (struct dom_info *di, TBB v) |
f8032688 MM |
387 | { |
388 | /* Btw. It's not worth to unrecurse compress() as the depth is usually not | |
389 | greater than 5 even for huge graphs (I've not seen call depth > 4). | |
390 | Also performance wise compress() ranges _far_ behind eval(). */ | |
391 | TBB parent = di->set_chain[v]; | |
392 | if (di->set_chain[parent]) | |
393 | { | |
394 | compress (di, parent); | |
395 | if (di->key[di->path_min[parent]] < di->key[di->path_min[v]]) | |
396 | di->path_min[v] = di->path_min[parent]; | |
397 | di->set_chain[v] = di->set_chain[parent]; | |
398 | } | |
399 | } | |
400 | ||
401 | /* Compress the path from V to the set root of V if needed (when the root has | |
402 | changed since the last call). Returns the node with the smallest key[] | |
403 | value on the path from V to the root. */ | |
404 | ||
405 | static inline TBB | |
7080f735 | 406 | eval (struct dom_info *di, TBB v) |
f8032688 MM |
407 | { |
408 | /* The representant of the set V is in, also called root (as the set | |
409 | representation is a tree). */ | |
410 | TBB rep = di->set_chain[v]; | |
411 | ||
412 | /* V itself is the root. */ | |
413 | if (!rep) | |
414 | return di->path_min[v]; | |
415 | ||
416 | /* Compress only if necessary. */ | |
417 | if (di->set_chain[rep]) | |
418 | { | |
419 | compress (di, v); | |
420 | rep = di->set_chain[v]; | |
421 | } | |
422 | ||
423 | if (di->key[di->path_min[rep]] >= di->key[di->path_min[v]]) | |
424 | return di->path_min[v]; | |
425 | else | |
426 | return di->path_min[rep]; | |
427 | } | |
428 | ||
429 | /* This essentially merges the two sets of V and W, giving a single set with | |
430 | the new root V. The internal representation of these disjoint sets is a | |
431 | balanced tree. Currently link(V,W) is only used with V being the parent | |
432 | of W. */ | |
433 | ||
434 | static void | |
7080f735 | 435 | link_roots (struct dom_info *di, TBB v, TBB w) |
f8032688 MM |
436 | { |
437 | TBB s = w; | |
438 | ||
439 | /* Rebalance the tree. */ | |
440 | while (di->key[di->path_min[w]] < di->key[di->path_min[di->set_child[s]]]) | |
441 | { | |
442 | if (di->set_size[s] + di->set_size[di->set_child[di->set_child[s]]] | |
443 | >= 2 * di->set_size[di->set_child[s]]) | |
444 | { | |
445 | di->set_chain[di->set_child[s]] = s; | |
446 | di->set_child[s] = di->set_child[di->set_child[s]]; | |
447 | } | |
448 | else | |
449 | { | |
450 | di->set_size[di->set_child[s]] = di->set_size[s]; | |
451 | s = di->set_chain[s] = di->set_child[s]; | |
452 | } | |
453 | } | |
454 | ||
455 | di->path_min[s] = di->path_min[w]; | |
456 | di->set_size[v] += di->set_size[w]; | |
457 | if (di->set_size[v] < 2 * di->set_size[w]) | |
458 | { | |
459 | TBB tmp = s; | |
460 | s = di->set_child[v]; | |
461 | di->set_child[v] = tmp; | |
462 | } | |
463 | ||
464 | /* Merge all subtrees. */ | |
465 | while (s) | |
466 | { | |
467 | di->set_chain[s] = v; | |
468 | s = di->set_child[s]; | |
469 | } | |
470 | } | |
471 | ||
472 | /* This calculates the immediate dominators (or post-dominators if REVERSE is | |
473 | true). DI is our working structure and should hold the DFS forest. | |
474 | On return the immediate dominator to node V is in di->dom[V]. */ | |
475 | ||
476 | static void | |
7080f735 | 477 | calc_idoms (struct dom_info *di, enum cdi_direction reverse) |
f8032688 MM |
478 | { |
479 | TBB v, w, k, par; | |
480 | basic_block en_block; | |
481 | if (reverse) | |
482 | en_block = EXIT_BLOCK_PTR; | |
483 | else | |
484 | en_block = ENTRY_BLOCK_PTR; | |
485 | ||
486 | /* Go backwards in DFS order, to first look at the leafs. */ | |
487 | v = di->nodes; | |
488 | while (v > 1) | |
489 | { | |
490 | basic_block bb = di->dfs_to_bb[v]; | |
491 | edge e, e_next; | |
492 | ||
493 | par = di->dfs_parent[v]; | |
494 | k = v; | |
495 | if (reverse) | |
26e0e410 RH |
496 | { |
497 | e = bb->succ; | |
498 | ||
499 | /* If this block has a fake edge to exit, process that first. */ | |
500 | if (bitmap_bit_p (di->fake_exit_edge, bb->index)) | |
501 | { | |
502 | e_next = e; | |
503 | goto do_fake_exit_edge; | |
504 | } | |
505 | } | |
f8032688 MM |
506 | else |
507 | e = bb->pred; | |
508 | ||
509 | /* Search all direct predecessors for the smallest node with a path | |
510 | to them. That way we have the smallest node with also a path to | |
511 | us only over nodes behind us. In effect we search for our | |
512 | semidominator. */ | |
26e0e410 | 513 | for (; e ; e = e_next) |
f8032688 MM |
514 | { |
515 | TBB k1; | |
516 | basic_block b; | |
517 | ||
518 | if (reverse) | |
519 | { | |
520 | b = e->dest; | |
521 | e_next = e->succ_next; | |
522 | } | |
523 | else | |
524 | { | |
525 | b = e->src; | |
526 | e_next = e->pred_next; | |
527 | } | |
528 | if (b == en_block) | |
26e0e410 RH |
529 | { |
530 | do_fake_exit_edge: | |
531 | k1 = di->dfs_order[last_basic_block]; | |
532 | } | |
f8032688 | 533 | else |
0b17ab2f | 534 | k1 = di->dfs_order[b->index]; |
f8032688 MM |
535 | |
536 | /* Call eval() only if really needed. If k1 is above V in DFS tree, | |
537 | then we know, that eval(k1) == k1 and key[k1] == k1. */ | |
538 | if (k1 > v) | |
539 | k1 = di->key[eval (di, k1)]; | |
540 | if (k1 < k) | |
541 | k = k1; | |
542 | } | |
543 | ||
544 | di->key[v] = k; | |
545 | link_roots (di, par, v); | |
546 | di->next_bucket[v] = di->bucket[k]; | |
547 | di->bucket[k] = v; | |
548 | ||
549 | /* Transform semidominators into dominators. */ | |
550 | for (w = di->bucket[par]; w; w = di->next_bucket[w]) | |
551 | { | |
552 | k = eval (di, w); | |
553 | if (di->key[k] < di->key[w]) | |
554 | di->dom[w] = k; | |
555 | else | |
556 | di->dom[w] = par; | |
557 | } | |
558 | /* We don't need to cleanup next_bucket[]. */ | |
559 | di->bucket[par] = 0; | |
560 | v--; | |
561 | } | |
562 | ||
a1f300c0 | 563 | /* Explicitly define the dominators. */ |
f8032688 MM |
564 | di->dom[1] = 0; |
565 | for (v = 2; v <= di->nodes; v++) | |
566 | if (di->dom[v] != di->key[v]) | |
567 | di->dom[v] = di->dom[di->dom[v]]; | |
568 | } | |
569 | ||
d47cc544 SB |
570 | /* Assign dfs numbers starting from NUM to NODE and its sons. */ |
571 | ||
572 | static void | |
573 | assign_dfs_numbers (struct et_node *node, int *num) | |
574 | { | |
575 | struct et_node *son; | |
576 | ||
577 | node->dfs_num_in = (*num)++; | |
578 | ||
579 | if (node->son) | |
580 | { | |
581 | assign_dfs_numbers (node->son, num); | |
582 | for (son = node->son->right; son != node->son; son = son->right) | |
6de9cd9a | 583 | assign_dfs_numbers (son, num); |
d47cc544 | 584 | } |
f8032688 | 585 | |
d47cc544 SB |
586 | node->dfs_num_out = (*num)++; |
587 | } | |
f8032688 | 588 | |
5d3cc252 | 589 | /* Compute the data necessary for fast resolving of dominator queries in a |
d47cc544 | 590 | static dominator tree. */ |
f8032688 | 591 | |
d47cc544 SB |
592 | static void |
593 | compute_dom_fast_query (enum cdi_direction dir) | |
594 | { | |
595 | int num = 0; | |
596 | basic_block bb; | |
597 | ||
ced3f397 | 598 | gcc_assert (dom_computed[dir] >= DOM_NO_FAST_QUERY); |
d47cc544 SB |
599 | |
600 | if (dom_computed[dir] == DOM_OK) | |
601 | return; | |
602 | ||
603 | FOR_ALL_BB (bb) | |
604 | { | |
605 | if (!bb->dom[dir]->father) | |
6de9cd9a | 606 | assign_dfs_numbers (bb->dom[dir], &num); |
d47cc544 SB |
607 | } |
608 | ||
609 | dom_computed[dir] = DOM_OK; | |
610 | } | |
611 | ||
612 | /* The main entry point into this module. DIR is set depending on whether | |
613 | we want to compute dominators or postdominators. */ | |
614 | ||
615 | void | |
616 | calculate_dominance_info (enum cdi_direction dir) | |
f8032688 MM |
617 | { |
618 | struct dom_info di; | |
355be0dc JH |
619 | basic_block b; |
620 | ||
d47cc544 SB |
621 | if (dom_computed[dir] == DOM_OK) |
622 | return; | |
355be0dc | 623 | |
d47cc544 SB |
624 | if (dom_computed[dir] != DOM_NO_FAST_QUERY) |
625 | { | |
626 | if (dom_computed[dir] != DOM_NONE) | |
6de9cd9a DN |
627 | free_dominance_info (dir); |
628 | ||
ced3f397 | 629 | gcc_assert (!n_bbs_in_dom_tree[dir]); |
f8032688 | 630 | |
d47cc544 SB |
631 | FOR_ALL_BB (b) |
632 | { | |
633 | b->dom[dir] = et_new_tree (b); | |
634 | } | |
6de9cd9a | 635 | n_bbs_in_dom_tree[dir] = n_basic_blocks + 2; |
f8032688 | 636 | |
26e0e410 | 637 | init_dom_info (&di, dir); |
d47cc544 SB |
638 | calc_dfs_tree (&di, dir); |
639 | calc_idoms (&di, dir); | |
355be0dc | 640 | |
d47cc544 SB |
641 | FOR_EACH_BB (b) |
642 | { | |
643 | TBB d = di.dom[di.dfs_order[b->index]]; | |
644 | ||
645 | if (di.dfs_to_bb[d]) | |
646 | et_set_father (b->dom[dir], di.dfs_to_bb[d]->dom[dir]); | |
647 | } | |
e0082a72 | 648 | |
d47cc544 SB |
649 | free_dom_info (&di); |
650 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
651 | } |
652 | ||
d47cc544 | 653 | compute_dom_fast_query (dir); |
355be0dc JH |
654 | } |
655 | ||
d47cc544 | 656 | /* Free dominance information for direction DIR. */ |
355be0dc | 657 | void |
d47cc544 | 658 | free_dominance_info (enum cdi_direction dir) |
355be0dc JH |
659 | { |
660 | basic_block bb; | |
661 | ||
d47cc544 SB |
662 | if (!dom_computed[dir]) |
663 | return; | |
664 | ||
665 | FOR_ALL_BB (bb) | |
666 | { | |
667 | delete_from_dominance_info (dir, bb); | |
668 | } | |
669 | ||
6de9cd9a | 670 | /* If there are any nodes left, something is wrong. */ |
ced3f397 | 671 | gcc_assert (!n_bbs_in_dom_tree[dir]); |
6de9cd9a | 672 | |
d47cc544 | 673 | dom_computed[dir] = DOM_NONE; |
355be0dc JH |
674 | } |
675 | ||
676 | /* Return the immediate dominator of basic block BB. */ | |
677 | basic_block | |
d47cc544 | 678 | get_immediate_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 679 | { |
d47cc544 SB |
680 | struct et_node *node = bb->dom[dir]; |
681 | ||
ced3f397 | 682 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
683 | |
684 | if (!node->father) | |
685 | return NULL; | |
686 | ||
6de9cd9a | 687 | return node->father->data; |
355be0dc JH |
688 | } |
689 | ||
690 | /* Set the immediate dominator of the block possibly removing | |
691 | existing edge. NULL can be used to remove any edge. */ | |
692 | inline void | |
d47cc544 SB |
693 | set_immediate_dominator (enum cdi_direction dir, basic_block bb, |
694 | basic_block dominated_by) | |
355be0dc | 695 | { |
d47cc544 SB |
696 | struct et_node *node = bb->dom[dir]; |
697 | ||
ced3f397 | 698 | gcc_assert (dom_computed[dir]); |
355be0dc | 699 | |
d47cc544 | 700 | if (node->father) |
355be0dc | 701 | { |
d47cc544 | 702 | if (node->father->data == dominated_by) |
6de9cd9a | 703 | return; |
d47cc544 | 704 | et_split (node); |
355be0dc | 705 | } |
d47cc544 SB |
706 | |
707 | if (dominated_by) | |
708 | et_set_father (node, dominated_by->dom[dir]); | |
709 | ||
710 | if (dom_computed[dir] == DOM_OK) | |
711 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
712 | } |
713 | ||
5d3cc252 | 714 | /* Store all basic blocks immediately dominated by BB into BBS and return |
d47cc544 | 715 | their number. */ |
355be0dc | 716 | int |
d47cc544 | 717 | get_dominated_by (enum cdi_direction dir, basic_block bb, basic_block **bbs) |
355be0dc | 718 | { |
d47cc544 SB |
719 | int n; |
720 | struct et_node *node = bb->dom[dir], *son = node->son, *ason; | |
721 | ||
ced3f397 | 722 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
723 | |
724 | if (!son) | |
725 | { | |
726 | *bbs = NULL; | |
727 | return 0; | |
728 | } | |
729 | ||
730 | for (ason = son->right, n = 1; ason != son; ason = ason->right) | |
731 | n++; | |
732 | ||
733 | *bbs = xmalloc (n * sizeof (basic_block)); | |
734 | (*bbs)[0] = son->data; | |
735 | for (ason = son->right, n = 1; ason != son; ason = ason->right) | |
736 | (*bbs)[n++] = ason->data; | |
355be0dc | 737 | |
355be0dc JH |
738 | return n; |
739 | } | |
740 | ||
741 | /* Redirect all edges pointing to BB to TO. */ | |
742 | void | |
d47cc544 SB |
743 | redirect_immediate_dominators (enum cdi_direction dir, basic_block bb, |
744 | basic_block to) | |
355be0dc | 745 | { |
d47cc544 SB |
746 | struct et_node *bb_node = bb->dom[dir], *to_node = to->dom[dir], *son; |
747 | ||
ced3f397 | 748 | gcc_assert (dom_computed[dir]); |
355be0dc | 749 | |
d47cc544 SB |
750 | if (!bb_node->son) |
751 | return; | |
752 | ||
753 | while (bb_node->son) | |
355be0dc | 754 | { |
d47cc544 SB |
755 | son = bb_node->son; |
756 | ||
757 | et_split (son); | |
758 | et_set_father (son, to_node); | |
355be0dc | 759 | } |
d47cc544 SB |
760 | |
761 | if (dom_computed[dir] == DOM_OK) | |
762 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
763 | } |
764 | ||
765 | /* Find first basic block in the tree dominating both BB1 and BB2. */ | |
766 | basic_block | |
d47cc544 | 767 | nearest_common_dominator (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
355be0dc | 768 | { |
ced3f397 | 769 | gcc_assert (dom_computed[dir]); |
d47cc544 | 770 | |
355be0dc JH |
771 | if (!bb1) |
772 | return bb2; | |
773 | if (!bb2) | |
774 | return bb1; | |
d47cc544 SB |
775 | |
776 | return et_nca (bb1->dom[dir], bb2->dom[dir])->data; | |
355be0dc JH |
777 | } |
778 | ||
779 | /* Return TRUE in case BB1 is dominated by BB2. */ | |
780 | bool | |
d47cc544 | 781 | dominated_by_p (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
6de9cd9a | 782 | { |
d47cc544 SB |
783 | struct et_node *n1 = bb1->dom[dir], *n2 = bb2->dom[dir]; |
784 | ||
ced3f397 | 785 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
786 | |
787 | if (dom_computed[dir] == DOM_OK) | |
788 | return (n1->dfs_num_in >= n2->dfs_num_in | |
6de9cd9a | 789 | && n1->dfs_num_out <= n2->dfs_num_out); |
d47cc544 SB |
790 | |
791 | return et_below (n1, n2); | |
355be0dc JH |
792 | } |
793 | ||
794 | /* Verify invariants of dominator structure. */ | |
795 | void | |
d47cc544 | 796 | verify_dominators (enum cdi_direction dir) |
355be0dc JH |
797 | { |
798 | int err = 0; | |
799 | basic_block bb; | |
800 | ||
ced3f397 | 801 | gcc_assert (dom_computed[dir]); |
d47cc544 | 802 | |
355be0dc JH |
803 | FOR_EACH_BB (bb) |
804 | { | |
805 | basic_block dom_bb; | |
806 | ||
d47cc544 SB |
807 | dom_bb = recount_dominator (dir, bb); |
808 | if (dom_bb != get_immediate_dominator (dir, bb)) | |
f8032688 | 809 | { |
355be0dc | 810 | error ("dominator of %d should be %d, not %d", |
d47cc544 | 811 | bb->index, dom_bb->index, get_immediate_dominator(dir, bb)->index); |
355be0dc JH |
812 | err = 1; |
813 | } | |
814 | } | |
e7bd94cc ZD |
815 | |
816 | if (dir == CDI_DOMINATORS | |
817 | && dom_computed[dir] >= DOM_NO_FAST_QUERY) | |
818 | { | |
819 | FOR_EACH_BB (bb) | |
820 | { | |
821 | if (!dominated_by_p (dir, bb, ENTRY_BLOCK_PTR)) | |
822 | { | |
823 | error ("ENTRY does not dominate bb %d", bb->index); | |
824 | err = 1; | |
825 | } | |
826 | } | |
827 | } | |
828 | ||
ced3f397 | 829 | gcc_assert (!err); |
355be0dc JH |
830 | } |
831 | ||
738ed977 ZD |
832 | /* Determine immediate dominator (or postdominator, according to DIR) of BB, |
833 | assuming that dominators of other blocks are correct. We also use it to | |
834 | recompute the dominators in a restricted area, by iterating it until it | |
71cc389b | 835 | reaches a fixed point. */ |
738ed977 | 836 | |
355be0dc | 837 | basic_block |
d47cc544 | 838 | recount_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 839 | { |
738ed977 ZD |
840 | basic_block dom_bb = NULL; |
841 | edge e; | |
355be0dc | 842 | |
ced3f397 | 843 | gcc_assert (dom_computed[dir]); |
d47cc544 | 844 | |
738ed977 ZD |
845 | if (dir == CDI_DOMINATORS) |
846 | { | |
847 | for (e = bb->pred; e; e = e->pred_next) | |
848 | { | |
e7bd94cc ZD |
849 | /* Ignore the predecessors that either are not reachable from |
850 | the entry block, or whose dominator was not determined yet. */ | |
851 | if (!dominated_by_p (dir, e->src, ENTRY_BLOCK_PTR)) | |
852 | continue; | |
853 | ||
738ed977 ZD |
854 | if (!dominated_by_p (dir, e->src, bb)) |
855 | dom_bb = nearest_common_dominator (dir, dom_bb, e->src); | |
856 | } | |
857 | } | |
858 | else | |
859 | { | |
860 | for (e = bb->succ; e; e = e->succ_next) | |
861 | { | |
862 | if (!dominated_by_p (dir, e->dest, bb)) | |
863 | dom_bb = nearest_common_dominator (dir, dom_bb, e->dest); | |
864 | } | |
865 | } | |
f8032688 | 866 | |
738ed977 | 867 | return dom_bb; |
355be0dc JH |
868 | } |
869 | ||
870 | /* Iteratively recount dominators of BBS. The change is supposed to be local | |
871 | and not to grow further. */ | |
872 | void | |
d47cc544 | 873 | iterate_fix_dominators (enum cdi_direction dir, basic_block *bbs, int n) |
355be0dc JH |
874 | { |
875 | int i, changed = 1; | |
876 | basic_block old_dom, new_dom; | |
877 | ||
ced3f397 | 878 | gcc_assert (dom_computed[dir]); |
d47cc544 | 879 | |
e7bd94cc ZD |
880 | for (i = 0; i < n; i++) |
881 | set_immediate_dominator (dir, bbs[i], NULL); | |
882 | ||
355be0dc JH |
883 | while (changed) |
884 | { | |
885 | changed = 0; | |
886 | for (i = 0; i < n; i++) | |
887 | { | |
d47cc544 SB |
888 | old_dom = get_immediate_dominator (dir, bbs[i]); |
889 | new_dom = recount_dominator (dir, bbs[i]); | |
355be0dc JH |
890 | if (old_dom != new_dom) |
891 | { | |
892 | changed = 1; | |
d47cc544 | 893 | set_immediate_dominator (dir, bbs[i], new_dom); |
355be0dc | 894 | } |
f8032688 MM |
895 | } |
896 | } | |
e7bd94cc ZD |
897 | |
898 | for (i = 0; i < n; i++) | |
ced3f397 | 899 | gcc_assert (get_immediate_dominator (dir, bbs[i])); |
355be0dc | 900 | } |
f8032688 | 901 | |
355be0dc | 902 | void |
d47cc544 | 903 | add_to_dominance_info (enum cdi_direction dir, basic_block bb) |
355be0dc | 904 | { |
ced3f397 NS |
905 | gcc_assert (dom_computed[dir]); |
906 | gcc_assert (!bb->dom[dir]); | |
d47cc544 | 907 | |
6de9cd9a DN |
908 | n_bbs_in_dom_tree[dir]++; |
909 | ||
d47cc544 SB |
910 | bb->dom[dir] = et_new_tree (bb); |
911 | ||
912 | if (dom_computed[dir] == DOM_OK) | |
913 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
914 | } |
915 | ||
916 | void | |
d47cc544 SB |
917 | delete_from_dominance_info (enum cdi_direction dir, basic_block bb) |
918 | { | |
ced3f397 | 919 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
920 | |
921 | et_free_tree (bb->dom[dir]); | |
922 | bb->dom[dir] = NULL; | |
6de9cd9a | 923 | n_bbs_in_dom_tree[dir]--; |
d47cc544 SB |
924 | |
925 | if (dom_computed[dir] == DOM_OK) | |
926 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
927 | } | |
928 | ||
929 | /* Returns the first son of BB in the dominator or postdominator tree | |
930 | as determined by DIR. */ | |
931 | ||
932 | basic_block | |
933 | first_dom_son (enum cdi_direction dir, basic_block bb) | |
355be0dc | 934 | { |
d47cc544 SB |
935 | struct et_node *son = bb->dom[dir]->son; |
936 | ||
937 | return son ? son->data : NULL; | |
938 | } | |
939 | ||
940 | /* Returns the next dominance son after BB in the dominator or postdominator | |
941 | tree as determined by DIR, or NULL if it was the last one. */ | |
942 | ||
943 | basic_block | |
944 | next_dom_son (enum cdi_direction dir, basic_block bb) | |
945 | { | |
946 | struct et_node *next = bb->dom[dir]->right; | |
947 | ||
948 | return next->father->son == next ? NULL : next->data; | |
355be0dc JH |
949 | } |
950 | ||
951 | void | |
d47cc544 | 952 | debug_dominance_info (enum cdi_direction dir) |
355be0dc JH |
953 | { |
954 | basic_block bb, bb2; | |
955 | FOR_EACH_BB (bb) | |
d47cc544 | 956 | if ((bb2 = get_immediate_dominator (dir, bb))) |
355be0dc | 957 | fprintf (stderr, "%i %i\n", bb->index, bb2->index); |
f8032688 | 958 | } |