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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; | |
628f6a4e BE |
209 | edge_iterator *stack; |
210 | edge_iterator ei, einext; | |
f8032688 MM |
211 | int sp; |
212 | /* Start block (ENTRY_BLOCK_PTR for forward problem, EXIT_BLOCK for backward | |
213 | problem). */ | |
214 | basic_block en_block; | |
215 | /* Ending block. */ | |
216 | basic_block ex_block; | |
217 | ||
628f6a4e | 218 | stack = xmalloc ((n_basic_blocks + 3) * sizeof (edge_iterator)); |
f8032688 MM |
219 | sp = 0; |
220 | ||
221 | /* Initialize our border blocks, and the first edge. */ | |
222 | if (reverse) | |
223 | { | |
628f6a4e | 224 | ei = ei_start (bb->preds); |
f8032688 MM |
225 | en_block = EXIT_BLOCK_PTR; |
226 | ex_block = ENTRY_BLOCK_PTR; | |
227 | } | |
228 | else | |
229 | { | |
628f6a4e | 230 | ei = ei_start (bb->succs); |
f8032688 MM |
231 | en_block = ENTRY_BLOCK_PTR; |
232 | ex_block = EXIT_BLOCK_PTR; | |
233 | } | |
234 | ||
235 | /* When the stack is empty we break out of this loop. */ | |
236 | while (1) | |
237 | { | |
238 | basic_block bn; | |
239 | ||
240 | /* This loop traverses edges e in depth first manner, and fills the | |
241 | stack. */ | |
628f6a4e | 242 | while (!ei_end_p (ei)) |
f8032688 | 243 | { |
628f6a4e | 244 | e = ei_edge (ei); |
f8032688 MM |
245 | |
246 | /* Deduce from E the current and the next block (BB and BN), and the | |
247 | next edge. */ | |
248 | if (reverse) | |
249 | { | |
250 | bn = e->src; | |
251 | ||
252 | /* If the next node BN is either already visited or a border | |
253 | block the current edge is useless, and simply overwritten | |
254 | with the next edge out of the current node. */ | |
0b17ab2f | 255 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 | 256 | { |
628f6a4e | 257 | ei_next (&ei); |
f8032688 MM |
258 | continue; |
259 | } | |
260 | bb = e->dest; | |
628f6a4e | 261 | einext = ei_start (bn->preds); |
f8032688 MM |
262 | } |
263 | else | |
264 | { | |
265 | bn = e->dest; | |
0b17ab2f | 266 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 | 267 | { |
628f6a4e | 268 | ei_next (&ei); |
f8032688 MM |
269 | continue; |
270 | } | |
271 | bb = e->src; | |
628f6a4e | 272 | einext = ei_start (bn->succs); |
f8032688 MM |
273 | } |
274 | ||
ced3f397 | 275 | gcc_assert (bn != en_block); |
f8032688 MM |
276 | |
277 | /* Fill the DFS tree info calculatable _before_ recursing. */ | |
278 | if (bb != en_block) | |
0b17ab2f | 279 | my_i = di->dfs_order[bb->index]; |
f8032688 | 280 | else |
d55bc081 | 281 | my_i = di->dfs_order[last_basic_block]; |
0b17ab2f | 282 | child_i = di->dfs_order[bn->index] = di->dfsnum++; |
f8032688 MM |
283 | di->dfs_to_bb[child_i] = bn; |
284 | di->dfs_parent[child_i] = my_i; | |
285 | ||
286 | /* Save the current point in the CFG on the stack, and recurse. */ | |
628f6a4e BE |
287 | stack[sp++] = ei; |
288 | ei = einext; | |
f8032688 MM |
289 | } |
290 | ||
291 | if (!sp) | |
292 | break; | |
628f6a4e | 293 | ei = stack[--sp]; |
f8032688 MM |
294 | |
295 | /* OK. The edge-list was exhausted, meaning normally we would | |
296 | end the recursion. After returning from the recursive call, | |
297 | there were (may be) other statements which were run after a | |
298 | child node was completely considered by DFS. Here is the | |
299 | point to do it in the non-recursive variant. | |
300 | E.g. The block just completed is in e->dest for forward DFS, | |
301 | the block not yet completed (the parent of the one above) | |
302 | in e->src. This could be used e.g. for computing the number of | |
303 | descendants or the tree depth. */ | |
628f6a4e | 304 | ei_next (&ei); |
f8032688 MM |
305 | } |
306 | free (stack); | |
307 | } | |
308 | ||
309 | /* The main entry for calculating the DFS tree or forest. DI is our working | |
310 | structure and REVERSE is true, if we are interested in the reverse flow | |
311 | graph. In that case the result is not necessarily a tree but a forest, | |
312 | because there may be nodes from which the EXIT_BLOCK is unreachable. */ | |
313 | ||
314 | static void | |
7080f735 | 315 | calc_dfs_tree (struct dom_info *di, enum cdi_direction reverse) |
f8032688 MM |
316 | { |
317 | /* The first block is the ENTRY_BLOCK (or EXIT_BLOCK if REVERSE). */ | |
318 | basic_block begin = reverse ? EXIT_BLOCK_PTR : ENTRY_BLOCK_PTR; | |
d55bc081 | 319 | di->dfs_order[last_basic_block] = di->dfsnum; |
f8032688 MM |
320 | di->dfs_to_bb[di->dfsnum] = begin; |
321 | di->dfsnum++; | |
322 | ||
323 | calc_dfs_tree_nonrec (di, begin, reverse); | |
324 | ||
325 | if (reverse) | |
326 | { | |
327 | /* In the post-dom case we may have nodes without a path to EXIT_BLOCK. | |
328 | They are reverse-unreachable. In the dom-case we disallow such | |
26e0e410 RH |
329 | nodes, but in post-dom we have to deal with them. |
330 | ||
331 | There are two situations in which this occurs. First, noreturn | |
332 | functions. Second, infinite loops. In the first case we need to | |
333 | pretend that there is an edge to the exit block. In the second | |
334 | case, we wind up with a forest. We need to process all noreturn | |
335 | blocks before we know if we've got any infinite loops. */ | |
336 | ||
e0082a72 | 337 | basic_block b; |
26e0e410 RH |
338 | bool saw_unconnected = false; |
339 | ||
e0082a72 | 340 | FOR_EACH_BB_REVERSE (b) |
f8032688 | 341 | { |
628f6a4e | 342 | if (EDGE_COUNT (b->succs) > 0) |
26e0e410 RH |
343 | { |
344 | if (di->dfs_order[b->index] == 0) | |
345 | saw_unconnected = true; | |
346 | continue; | |
347 | } | |
348 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
0b17ab2f | 349 | di->dfs_order[b->index] = di->dfsnum; |
f8032688 | 350 | di->dfs_to_bb[di->dfsnum] = b; |
26e0e410 | 351 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; |
f8032688 MM |
352 | di->dfsnum++; |
353 | calc_dfs_tree_nonrec (di, b, reverse); | |
354 | } | |
26e0e410 RH |
355 | |
356 | if (saw_unconnected) | |
357 | { | |
358 | FOR_EACH_BB_REVERSE (b) | |
359 | { | |
360 | if (di->dfs_order[b->index]) | |
361 | continue; | |
362 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
363 | di->dfs_order[b->index] = di->dfsnum; | |
364 | di->dfs_to_bb[di->dfsnum] = b; | |
365 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; | |
366 | di->dfsnum++; | |
367 | calc_dfs_tree_nonrec (di, b, reverse); | |
368 | } | |
369 | } | |
f8032688 MM |
370 | } |
371 | ||
372 | di->nodes = di->dfsnum - 1; | |
373 | ||
374 | /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. */ | |
ced3f397 | 375 | gcc_assert (di->nodes == (unsigned int) n_basic_blocks + 1); |
f8032688 MM |
376 | } |
377 | ||
378 | /* Compress the path from V to the root of its set and update path_min at the | |
379 | same time. After compress(di, V) set_chain[V] is the root of the set V is | |
380 | in and path_min[V] is the node with the smallest key[] value on the path | |
381 | from V to that root. */ | |
382 | ||
383 | static void | |
7080f735 | 384 | compress (struct dom_info *di, TBB v) |
f8032688 MM |
385 | { |
386 | /* Btw. It's not worth to unrecurse compress() as the depth is usually not | |
387 | greater than 5 even for huge graphs (I've not seen call depth > 4). | |
388 | Also performance wise compress() ranges _far_ behind eval(). */ | |
389 | TBB parent = di->set_chain[v]; | |
390 | if (di->set_chain[parent]) | |
391 | { | |
392 | compress (di, parent); | |
393 | if (di->key[di->path_min[parent]] < di->key[di->path_min[v]]) | |
394 | di->path_min[v] = di->path_min[parent]; | |
395 | di->set_chain[v] = di->set_chain[parent]; | |
396 | } | |
397 | } | |
398 | ||
399 | /* Compress the path from V to the set root of V if needed (when the root has | |
400 | changed since the last call). Returns the node with the smallest key[] | |
401 | value on the path from V to the root. */ | |
402 | ||
403 | static inline TBB | |
7080f735 | 404 | eval (struct dom_info *di, TBB v) |
f8032688 MM |
405 | { |
406 | /* The representant of the set V is in, also called root (as the set | |
407 | representation is a tree). */ | |
408 | TBB rep = di->set_chain[v]; | |
409 | ||
410 | /* V itself is the root. */ | |
411 | if (!rep) | |
412 | return di->path_min[v]; | |
413 | ||
414 | /* Compress only if necessary. */ | |
415 | if (di->set_chain[rep]) | |
416 | { | |
417 | compress (di, v); | |
418 | rep = di->set_chain[v]; | |
419 | } | |
420 | ||
421 | if (di->key[di->path_min[rep]] >= di->key[di->path_min[v]]) | |
422 | return di->path_min[v]; | |
423 | else | |
424 | return di->path_min[rep]; | |
425 | } | |
426 | ||
427 | /* This essentially merges the two sets of V and W, giving a single set with | |
428 | the new root V. The internal representation of these disjoint sets is a | |
429 | balanced tree. Currently link(V,W) is only used with V being the parent | |
430 | of W. */ | |
431 | ||
432 | static void | |
7080f735 | 433 | link_roots (struct dom_info *di, TBB v, TBB w) |
f8032688 MM |
434 | { |
435 | TBB s = w; | |
436 | ||
437 | /* Rebalance the tree. */ | |
438 | while (di->key[di->path_min[w]] < di->key[di->path_min[di->set_child[s]]]) | |
439 | { | |
440 | if (di->set_size[s] + di->set_size[di->set_child[di->set_child[s]]] | |
441 | >= 2 * di->set_size[di->set_child[s]]) | |
442 | { | |
443 | di->set_chain[di->set_child[s]] = s; | |
444 | di->set_child[s] = di->set_child[di->set_child[s]]; | |
445 | } | |
446 | else | |
447 | { | |
448 | di->set_size[di->set_child[s]] = di->set_size[s]; | |
449 | s = di->set_chain[s] = di->set_child[s]; | |
450 | } | |
451 | } | |
452 | ||
453 | di->path_min[s] = di->path_min[w]; | |
454 | di->set_size[v] += di->set_size[w]; | |
455 | if (di->set_size[v] < 2 * di->set_size[w]) | |
456 | { | |
457 | TBB tmp = s; | |
458 | s = di->set_child[v]; | |
459 | di->set_child[v] = tmp; | |
460 | } | |
461 | ||
462 | /* Merge all subtrees. */ | |
463 | while (s) | |
464 | { | |
465 | di->set_chain[s] = v; | |
466 | s = di->set_child[s]; | |
467 | } | |
468 | } | |
469 | ||
470 | /* This calculates the immediate dominators (or post-dominators if REVERSE is | |
471 | true). DI is our working structure and should hold the DFS forest. | |
472 | On return the immediate dominator to node V is in di->dom[V]. */ | |
473 | ||
474 | static void | |
7080f735 | 475 | calc_idoms (struct dom_info *di, enum cdi_direction reverse) |
f8032688 MM |
476 | { |
477 | TBB v, w, k, par; | |
478 | basic_block en_block; | |
628f6a4e BE |
479 | edge_iterator ei, einext; |
480 | ||
f8032688 MM |
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]; | |
628f6a4e | 491 | edge e; |
f8032688 MM |
492 | |
493 | par = di->dfs_parent[v]; | |
494 | k = v; | |
628f6a4e BE |
495 | |
496 | ei = (reverse) ? ei_start (bb->succs) : ei_start (bb->preds); | |
497 | ||
f8032688 | 498 | if (reverse) |
26e0e410 | 499 | { |
26e0e410 RH |
500 | /* If this block has a fake edge to exit, process that first. */ |
501 | if (bitmap_bit_p (di->fake_exit_edge, bb->index)) | |
502 | { | |
628f6a4e BE |
503 | einext = ei; |
504 | einext.index = 0; | |
26e0e410 RH |
505 | goto do_fake_exit_edge; |
506 | } | |
507 | } | |
f8032688 MM |
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. */ | |
628f6a4e | 513 | while (!ei_end_p (ei)) |
f8032688 MM |
514 | { |
515 | TBB k1; | |
516 | basic_block b; | |
517 | ||
628f6a4e BE |
518 | e = ei_edge (ei); |
519 | b = (reverse) ? e->dest : e->src; | |
520 | einext = ei; | |
521 | ei_next (&einext); | |
522 | ||
f8032688 | 523 | if (b == en_block) |
26e0e410 RH |
524 | { |
525 | do_fake_exit_edge: | |
526 | k1 = di->dfs_order[last_basic_block]; | |
527 | } | |
f8032688 | 528 | else |
0b17ab2f | 529 | k1 = di->dfs_order[b->index]; |
f8032688 MM |
530 | |
531 | /* Call eval() only if really needed. If k1 is above V in DFS tree, | |
532 | then we know, that eval(k1) == k1 and key[k1] == k1. */ | |
533 | if (k1 > v) | |
534 | k1 = di->key[eval (di, k1)]; | |
535 | if (k1 < k) | |
536 | k = k1; | |
628f6a4e BE |
537 | |
538 | ei = einext; | |
f8032688 MM |
539 | } |
540 | ||
541 | di->key[v] = k; | |
542 | link_roots (di, par, v); | |
543 | di->next_bucket[v] = di->bucket[k]; | |
544 | di->bucket[k] = v; | |
545 | ||
546 | /* Transform semidominators into dominators. */ | |
547 | for (w = di->bucket[par]; w; w = di->next_bucket[w]) | |
548 | { | |
549 | k = eval (di, w); | |
550 | if (di->key[k] < di->key[w]) | |
551 | di->dom[w] = k; | |
552 | else | |
553 | di->dom[w] = par; | |
554 | } | |
555 | /* We don't need to cleanup next_bucket[]. */ | |
556 | di->bucket[par] = 0; | |
557 | v--; | |
558 | } | |
559 | ||
a1f300c0 | 560 | /* Explicitly define the dominators. */ |
f8032688 MM |
561 | di->dom[1] = 0; |
562 | for (v = 2; v <= di->nodes; v++) | |
563 | if (di->dom[v] != di->key[v]) | |
564 | di->dom[v] = di->dom[di->dom[v]]; | |
565 | } | |
566 | ||
d47cc544 SB |
567 | /* Assign dfs numbers starting from NUM to NODE and its sons. */ |
568 | ||
569 | static void | |
570 | assign_dfs_numbers (struct et_node *node, int *num) | |
571 | { | |
572 | struct et_node *son; | |
573 | ||
574 | node->dfs_num_in = (*num)++; | |
575 | ||
576 | if (node->son) | |
577 | { | |
578 | assign_dfs_numbers (node->son, num); | |
579 | for (son = node->son->right; son != node->son; son = son->right) | |
6de9cd9a | 580 | assign_dfs_numbers (son, num); |
d47cc544 | 581 | } |
f8032688 | 582 | |
d47cc544 SB |
583 | node->dfs_num_out = (*num)++; |
584 | } | |
f8032688 | 585 | |
5d3cc252 | 586 | /* Compute the data necessary for fast resolving of dominator queries in a |
d47cc544 | 587 | static dominator tree. */ |
f8032688 | 588 | |
d47cc544 SB |
589 | static void |
590 | compute_dom_fast_query (enum cdi_direction dir) | |
591 | { | |
592 | int num = 0; | |
593 | basic_block bb; | |
594 | ||
ced3f397 | 595 | gcc_assert (dom_computed[dir] >= DOM_NO_FAST_QUERY); |
d47cc544 SB |
596 | |
597 | if (dom_computed[dir] == DOM_OK) | |
598 | return; | |
599 | ||
600 | FOR_ALL_BB (bb) | |
601 | { | |
602 | if (!bb->dom[dir]->father) | |
6de9cd9a | 603 | assign_dfs_numbers (bb->dom[dir], &num); |
d47cc544 SB |
604 | } |
605 | ||
606 | dom_computed[dir] = DOM_OK; | |
607 | } | |
608 | ||
609 | /* The main entry point into this module. DIR is set depending on whether | |
610 | we want to compute dominators or postdominators. */ | |
611 | ||
612 | void | |
613 | calculate_dominance_info (enum cdi_direction dir) | |
f8032688 MM |
614 | { |
615 | struct dom_info di; | |
355be0dc JH |
616 | basic_block b; |
617 | ||
d47cc544 SB |
618 | if (dom_computed[dir] == DOM_OK) |
619 | return; | |
355be0dc | 620 | |
d47cc544 SB |
621 | if (dom_computed[dir] != DOM_NO_FAST_QUERY) |
622 | { | |
623 | if (dom_computed[dir] != DOM_NONE) | |
6de9cd9a DN |
624 | free_dominance_info (dir); |
625 | ||
ced3f397 | 626 | gcc_assert (!n_bbs_in_dom_tree[dir]); |
f8032688 | 627 | |
d47cc544 SB |
628 | FOR_ALL_BB (b) |
629 | { | |
630 | b->dom[dir] = et_new_tree (b); | |
631 | } | |
6de9cd9a | 632 | n_bbs_in_dom_tree[dir] = n_basic_blocks + 2; |
f8032688 | 633 | |
26e0e410 | 634 | init_dom_info (&di, dir); |
d47cc544 SB |
635 | calc_dfs_tree (&di, dir); |
636 | calc_idoms (&di, dir); | |
355be0dc | 637 | |
d47cc544 SB |
638 | FOR_EACH_BB (b) |
639 | { | |
640 | TBB d = di.dom[di.dfs_order[b->index]]; | |
641 | ||
642 | if (di.dfs_to_bb[d]) | |
643 | et_set_father (b->dom[dir], di.dfs_to_bb[d]->dom[dir]); | |
644 | } | |
e0082a72 | 645 | |
d47cc544 SB |
646 | free_dom_info (&di); |
647 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
648 | } |
649 | ||
d47cc544 | 650 | compute_dom_fast_query (dir); |
355be0dc JH |
651 | } |
652 | ||
d47cc544 | 653 | /* Free dominance information for direction DIR. */ |
355be0dc | 654 | void |
d47cc544 | 655 | free_dominance_info (enum cdi_direction dir) |
355be0dc JH |
656 | { |
657 | basic_block bb; | |
658 | ||
d47cc544 SB |
659 | if (!dom_computed[dir]) |
660 | return; | |
661 | ||
662 | FOR_ALL_BB (bb) | |
663 | { | |
664 | delete_from_dominance_info (dir, bb); | |
665 | } | |
666 | ||
6de9cd9a | 667 | /* If there are any nodes left, something is wrong. */ |
ced3f397 | 668 | gcc_assert (!n_bbs_in_dom_tree[dir]); |
6de9cd9a | 669 | |
d47cc544 | 670 | dom_computed[dir] = DOM_NONE; |
355be0dc JH |
671 | } |
672 | ||
673 | /* Return the immediate dominator of basic block BB. */ | |
674 | basic_block | |
d47cc544 | 675 | get_immediate_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 676 | { |
d47cc544 SB |
677 | struct et_node *node = bb->dom[dir]; |
678 | ||
ced3f397 | 679 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
680 | |
681 | if (!node->father) | |
682 | return NULL; | |
683 | ||
6de9cd9a | 684 | return node->father->data; |
355be0dc JH |
685 | } |
686 | ||
687 | /* Set the immediate dominator of the block possibly removing | |
688 | existing edge. NULL can be used to remove any edge. */ | |
689 | inline void | |
d47cc544 SB |
690 | set_immediate_dominator (enum cdi_direction dir, basic_block bb, |
691 | basic_block dominated_by) | |
355be0dc | 692 | { |
d47cc544 SB |
693 | struct et_node *node = bb->dom[dir]; |
694 | ||
ced3f397 | 695 | gcc_assert (dom_computed[dir]); |
355be0dc | 696 | |
d47cc544 | 697 | if (node->father) |
355be0dc | 698 | { |
d47cc544 | 699 | if (node->father->data == dominated_by) |
6de9cd9a | 700 | return; |
d47cc544 | 701 | et_split (node); |
355be0dc | 702 | } |
d47cc544 SB |
703 | |
704 | if (dominated_by) | |
705 | et_set_father (node, dominated_by->dom[dir]); | |
706 | ||
707 | if (dom_computed[dir] == DOM_OK) | |
708 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
709 | } |
710 | ||
5d3cc252 | 711 | /* Store all basic blocks immediately dominated by BB into BBS and return |
d47cc544 | 712 | their number. */ |
355be0dc | 713 | int |
d47cc544 | 714 | get_dominated_by (enum cdi_direction dir, basic_block bb, basic_block **bbs) |
355be0dc | 715 | { |
d47cc544 SB |
716 | int n; |
717 | struct et_node *node = bb->dom[dir], *son = node->son, *ason; | |
718 | ||
ced3f397 | 719 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
720 | |
721 | if (!son) | |
722 | { | |
723 | *bbs = NULL; | |
724 | return 0; | |
725 | } | |
726 | ||
727 | for (ason = son->right, n = 1; ason != son; ason = ason->right) | |
728 | n++; | |
729 | ||
730 | *bbs = xmalloc (n * sizeof (basic_block)); | |
731 | (*bbs)[0] = son->data; | |
732 | for (ason = son->right, n = 1; ason != son; ason = ason->right) | |
733 | (*bbs)[n++] = ason->data; | |
355be0dc | 734 | |
355be0dc JH |
735 | return n; |
736 | } | |
737 | ||
42759f1e ZD |
738 | /* Find all basic blocks that are immediately dominated (in direction DIR) |
739 | by some block between N_REGION ones stored in REGION, except for blocks | |
740 | in the REGION itself. The found blocks are stored to DOMS and their number | |
741 | is returned. */ | |
742 | ||
743 | unsigned | |
744 | get_dominated_by_region (enum cdi_direction dir, basic_block *region, | |
745 | unsigned n_region, basic_block *doms) | |
746 | { | |
747 | unsigned n_doms = 0, i; | |
748 | basic_block dom; | |
749 | ||
750 | for (i = 0; i < n_region; i++) | |
751 | region[i]->rbi->duplicated = 1; | |
752 | for (i = 0; i < n_region; i++) | |
753 | for (dom = first_dom_son (dir, region[i]); | |
754 | dom; | |
755 | dom = next_dom_son (dir, dom)) | |
756 | if (!dom->rbi->duplicated) | |
757 | doms[n_doms++] = dom; | |
758 | for (i = 0; i < n_region; i++) | |
759 | region[i]->rbi->duplicated = 0; | |
760 | ||
761 | return n_doms; | |
762 | } | |
763 | ||
355be0dc JH |
764 | /* Redirect all edges pointing to BB to TO. */ |
765 | void | |
d47cc544 SB |
766 | redirect_immediate_dominators (enum cdi_direction dir, basic_block bb, |
767 | basic_block to) | |
355be0dc | 768 | { |
d47cc544 SB |
769 | struct et_node *bb_node = bb->dom[dir], *to_node = to->dom[dir], *son; |
770 | ||
ced3f397 | 771 | gcc_assert (dom_computed[dir]); |
355be0dc | 772 | |
d47cc544 SB |
773 | if (!bb_node->son) |
774 | return; | |
775 | ||
776 | while (bb_node->son) | |
355be0dc | 777 | { |
d47cc544 SB |
778 | son = bb_node->son; |
779 | ||
780 | et_split (son); | |
781 | et_set_father (son, to_node); | |
355be0dc | 782 | } |
d47cc544 SB |
783 | |
784 | if (dom_computed[dir] == DOM_OK) | |
785 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
786 | } |
787 | ||
788 | /* Find first basic block in the tree dominating both BB1 and BB2. */ | |
789 | basic_block | |
d47cc544 | 790 | nearest_common_dominator (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
355be0dc | 791 | { |
ced3f397 | 792 | gcc_assert (dom_computed[dir]); |
d47cc544 | 793 | |
355be0dc JH |
794 | if (!bb1) |
795 | return bb2; | |
796 | if (!bb2) | |
797 | return bb1; | |
d47cc544 SB |
798 | |
799 | return et_nca (bb1->dom[dir], bb2->dom[dir])->data; | |
355be0dc JH |
800 | } |
801 | ||
802 | /* Return TRUE in case BB1 is dominated by BB2. */ | |
803 | bool | |
d47cc544 | 804 | dominated_by_p (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
6de9cd9a | 805 | { |
d47cc544 SB |
806 | struct et_node *n1 = bb1->dom[dir], *n2 = bb2->dom[dir]; |
807 | ||
ced3f397 | 808 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
809 | |
810 | if (dom_computed[dir] == DOM_OK) | |
811 | return (n1->dfs_num_in >= n2->dfs_num_in | |
6de9cd9a | 812 | && n1->dfs_num_out <= n2->dfs_num_out); |
d47cc544 SB |
813 | |
814 | return et_below (n1, n2); | |
355be0dc JH |
815 | } |
816 | ||
817 | /* Verify invariants of dominator structure. */ | |
818 | void | |
d47cc544 | 819 | verify_dominators (enum cdi_direction dir) |
355be0dc JH |
820 | { |
821 | int err = 0; | |
822 | basic_block bb; | |
823 | ||
ced3f397 | 824 | gcc_assert (dom_computed[dir]); |
d47cc544 | 825 | |
355be0dc JH |
826 | FOR_EACH_BB (bb) |
827 | { | |
828 | basic_block dom_bb; | |
df485d80 | 829 | basic_block imm_bb; |
355be0dc | 830 | |
d47cc544 | 831 | dom_bb = recount_dominator (dir, bb); |
df485d80 FCE |
832 | imm_bb = get_immediate_dominator (dir, bb); |
833 | if (dom_bb != imm_bb) | |
f8032688 | 834 | { |
df485d80 FCE |
835 | if ((dom_bb == NULL) || (imm_bb == NULL)) |
836 | error ("dominator of %d status unknown", bb->index); | |
08fb229e FCE |
837 | else |
838 | error ("dominator of %d should be %d, not %d", | |
df485d80 | 839 | bb->index, dom_bb->index, imm_bb->index); |
355be0dc JH |
840 | err = 1; |
841 | } | |
842 | } | |
e7bd94cc ZD |
843 | |
844 | if (dir == CDI_DOMINATORS | |
845 | && dom_computed[dir] >= DOM_NO_FAST_QUERY) | |
846 | { | |
847 | FOR_EACH_BB (bb) | |
848 | { | |
849 | if (!dominated_by_p (dir, bb, ENTRY_BLOCK_PTR)) | |
850 | { | |
851 | error ("ENTRY does not dominate bb %d", bb->index); | |
852 | err = 1; | |
853 | } | |
854 | } | |
855 | } | |
856 | ||
ced3f397 | 857 | gcc_assert (!err); |
355be0dc JH |
858 | } |
859 | ||
738ed977 ZD |
860 | /* Determine immediate dominator (or postdominator, according to DIR) of BB, |
861 | assuming that dominators of other blocks are correct. We also use it to | |
862 | recompute the dominators in a restricted area, by iterating it until it | |
71cc389b | 863 | reaches a fixed point. */ |
738ed977 | 864 | |
355be0dc | 865 | basic_block |
d47cc544 | 866 | recount_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 867 | { |
738ed977 ZD |
868 | basic_block dom_bb = NULL; |
869 | edge e; | |
628f6a4e | 870 | edge_iterator ei; |
355be0dc | 871 | |
ced3f397 | 872 | gcc_assert (dom_computed[dir]); |
d47cc544 | 873 | |
738ed977 ZD |
874 | if (dir == CDI_DOMINATORS) |
875 | { | |
628f6a4e | 876 | FOR_EACH_EDGE (e, ei, bb->preds) |
738ed977 | 877 | { |
e7bd94cc ZD |
878 | /* Ignore the predecessors that either are not reachable from |
879 | the entry block, or whose dominator was not determined yet. */ | |
880 | if (!dominated_by_p (dir, e->src, ENTRY_BLOCK_PTR)) | |
881 | continue; | |
882 | ||
738ed977 ZD |
883 | if (!dominated_by_p (dir, e->src, bb)) |
884 | dom_bb = nearest_common_dominator (dir, dom_bb, e->src); | |
885 | } | |
886 | } | |
887 | else | |
888 | { | |
628f6a4e | 889 | FOR_EACH_EDGE (e, ei, bb->succs) |
738ed977 ZD |
890 | { |
891 | if (!dominated_by_p (dir, e->dest, bb)) | |
892 | dom_bb = nearest_common_dominator (dir, dom_bb, e->dest); | |
893 | } | |
894 | } | |
f8032688 | 895 | |
738ed977 | 896 | return dom_bb; |
355be0dc JH |
897 | } |
898 | ||
899 | /* Iteratively recount dominators of BBS. The change is supposed to be local | |
900 | and not to grow further. */ | |
901 | void | |
d47cc544 | 902 | iterate_fix_dominators (enum cdi_direction dir, basic_block *bbs, int n) |
355be0dc JH |
903 | { |
904 | int i, changed = 1; | |
905 | basic_block old_dom, new_dom; | |
906 | ||
ced3f397 | 907 | gcc_assert (dom_computed[dir]); |
d47cc544 | 908 | |
e7bd94cc ZD |
909 | for (i = 0; i < n; i++) |
910 | set_immediate_dominator (dir, bbs[i], NULL); | |
911 | ||
355be0dc JH |
912 | while (changed) |
913 | { | |
914 | changed = 0; | |
915 | for (i = 0; i < n; i++) | |
916 | { | |
d47cc544 SB |
917 | old_dom = get_immediate_dominator (dir, bbs[i]); |
918 | new_dom = recount_dominator (dir, bbs[i]); | |
355be0dc JH |
919 | if (old_dom != new_dom) |
920 | { | |
921 | changed = 1; | |
d47cc544 | 922 | set_immediate_dominator (dir, bbs[i], new_dom); |
355be0dc | 923 | } |
f8032688 MM |
924 | } |
925 | } | |
e7bd94cc ZD |
926 | |
927 | for (i = 0; i < n; i++) | |
ced3f397 | 928 | gcc_assert (get_immediate_dominator (dir, bbs[i])); |
355be0dc | 929 | } |
f8032688 | 930 | |
355be0dc | 931 | void |
d47cc544 | 932 | add_to_dominance_info (enum cdi_direction dir, basic_block bb) |
355be0dc | 933 | { |
ced3f397 NS |
934 | gcc_assert (dom_computed[dir]); |
935 | gcc_assert (!bb->dom[dir]); | |
d47cc544 | 936 | |
6de9cd9a DN |
937 | n_bbs_in_dom_tree[dir]++; |
938 | ||
d47cc544 SB |
939 | bb->dom[dir] = et_new_tree (bb); |
940 | ||
941 | if (dom_computed[dir] == DOM_OK) | |
942 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
943 | } |
944 | ||
945 | void | |
d47cc544 SB |
946 | delete_from_dominance_info (enum cdi_direction dir, basic_block bb) |
947 | { | |
ced3f397 | 948 | gcc_assert (dom_computed[dir]); |
d47cc544 SB |
949 | |
950 | et_free_tree (bb->dom[dir]); | |
951 | bb->dom[dir] = NULL; | |
6de9cd9a | 952 | n_bbs_in_dom_tree[dir]--; |
d47cc544 SB |
953 | |
954 | if (dom_computed[dir] == DOM_OK) | |
955 | dom_computed[dir] = DOM_NO_FAST_QUERY; | |
956 | } | |
957 | ||
958 | /* Returns the first son of BB in the dominator or postdominator tree | |
959 | as determined by DIR. */ | |
960 | ||
961 | basic_block | |
962 | first_dom_son (enum cdi_direction dir, basic_block bb) | |
355be0dc | 963 | { |
d47cc544 SB |
964 | struct et_node *son = bb->dom[dir]->son; |
965 | ||
966 | return son ? son->data : NULL; | |
967 | } | |
968 | ||
969 | /* Returns the next dominance son after BB in the dominator or postdominator | |
970 | tree as determined by DIR, or NULL if it was the last one. */ | |
971 | ||
972 | basic_block | |
973 | next_dom_son (enum cdi_direction dir, basic_block bb) | |
974 | { | |
975 | struct et_node *next = bb->dom[dir]->right; | |
976 | ||
977 | return next->father->son == next ? NULL : next->data; | |
355be0dc JH |
978 | } |
979 | ||
980 | void | |
d47cc544 | 981 | debug_dominance_info (enum cdi_direction dir) |
355be0dc JH |
982 | { |
983 | basic_block bb, bb2; | |
984 | FOR_EACH_BB (bb) | |
d47cc544 | 985 | if ((bb2 = get_immediate_dominator (dir, bb))) |
355be0dc | 986 | fprintf (stderr, "%i %i\n", bb->index, bb2->index); |
f8032688 | 987 | } |