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f8032688 | 1 | /* Calculate (post)dominators in slightly super-linear time. |
fa10beec RW |
2 | Copyright (C) 2000, 2003, 2004, 2005, 2006, 2007, 2008 Free |
3 | Software Foundation, Inc. | |
f8032688 | 4 | Contributed by Michael Matz (matz@ifh.de). |
3a538a66 | 5 | |
1322177d | 6 | This file is part of GCC. |
3a538a66 | 7 | |
1322177d LB |
8 | GCC is free software; you can redistribute it and/or modify it |
9 | under the terms of the GNU General Public License as published by | |
9dcd6f09 | 10 | the Free Software Foundation; either version 3, or (at your option) |
f8032688 MM |
11 | any later version. |
12 | ||
1322177d LB |
13 | GCC is distributed in the hope that it will be useful, but WITHOUT |
14 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY | |
15 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public | |
16 | License for more details. | |
f8032688 MM |
17 | |
18 | You should have received a copy of the GNU General Public License | |
9dcd6f09 NC |
19 | along with GCC; see the file COPYING3. If not see |
20 | <http://www.gnu.org/licenses/>. */ | |
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" |
74c96e0c | 46 | #include "timevar.h" |
66f97d31 ZD |
47 | #include "vecprim.h" |
48 | #include "pointer-set.h" | |
49 | #include "graphds.h" | |
f8032688 | 50 | |
f8032688 MM |
51 | /* We name our nodes with integers, beginning with 1. Zero is reserved for |
52 | 'undefined' or 'end of list'. The name of each node is given by the dfs | |
53 | number of the corresponding basic block. Please note, that we include the | |
54 | artificial ENTRY_BLOCK (or EXIT_BLOCK in the post-dom case) in our lists to | |
24bd1a0b | 55 | support multiple entry points. Its dfs number is of course 1. */ |
f8032688 MM |
56 | |
57 | /* Type of Basic Block aka. TBB */ | |
58 | typedef unsigned int TBB; | |
59 | ||
60 | /* We work in a poor-mans object oriented fashion, and carry an instance of | |
61 | this structure through all our 'methods'. It holds various arrays | |
62 | reflecting the (sub)structure of the flowgraph. Most of them are of type | |
63 | TBB and are also indexed by TBB. */ | |
64 | ||
65 | struct dom_info | |
66 | { | |
67 | /* The parent of a node in the DFS tree. */ | |
68 | TBB *dfs_parent; | |
69 | /* For a node x key[x] is roughly the node nearest to the root from which | |
70 | exists a way to x only over nodes behind x. Such a node is also called | |
71 | semidominator. */ | |
72 | TBB *key; | |
73 | /* The value in path_min[x] is the node y on the path from x to the root of | |
74 | the tree x is in with the smallest key[y]. */ | |
75 | TBB *path_min; | |
76 | /* bucket[x] points to the first node of the set of nodes having x as key. */ | |
77 | TBB *bucket; | |
78 | /* And next_bucket[x] points to the next node. */ | |
79 | TBB *next_bucket; | |
80 | /* After the algorithm is done, dom[x] contains the immediate dominator | |
81 | of x. */ | |
82 | TBB *dom; | |
83 | ||
84 | /* The following few fields implement the structures needed for disjoint | |
85 | sets. */ | |
fa10beec | 86 | /* set_chain[x] is the next node on the path from x to the representative |
f8032688 MM |
87 | of the set containing x. If set_chain[x]==0 then x is a root. */ |
88 | TBB *set_chain; | |
89 | /* set_size[x] is the number of elements in the set named by x. */ | |
90 | unsigned int *set_size; | |
91 | /* set_child[x] is used for balancing the tree representing a set. It can | |
92 | be understood as the next sibling of x. */ | |
93 | TBB *set_child; | |
94 | ||
95 | /* If b is the number of a basic block (BB->index), dfs_order[b] is the | |
96 | number of that node in DFS order counted from 1. This is an index | |
97 | into most of the other arrays in this structure. */ | |
98 | TBB *dfs_order; | |
09da1532 | 99 | /* If x is the DFS-index of a node which corresponds with a basic block, |
f8032688 MM |
100 | dfs_to_bb[x] is that basic block. Note, that in our structure there are |
101 | more nodes that basic blocks, so only dfs_to_bb[dfs_order[bb->index]]==bb | |
102 | is true for every basic block bb, but not the opposite. */ | |
103 | basic_block *dfs_to_bb; | |
104 | ||
26e0e410 | 105 | /* This is the next free DFS number when creating the DFS tree. */ |
f8032688 MM |
106 | unsigned int dfsnum; |
107 | /* The number of nodes in the DFS tree (==dfsnum-1). */ | |
108 | unsigned int nodes; | |
26e0e410 RH |
109 | |
110 | /* Blocks with bits set here have a fake edge to EXIT. These are used | |
111 | to turn a DFS forest into a proper tree. */ | |
112 | bitmap fake_exit_edge; | |
f8032688 MM |
113 | }; |
114 | ||
26e0e410 | 115 | static void init_dom_info (struct dom_info *, enum cdi_direction); |
7080f735 | 116 | static void free_dom_info (struct dom_info *); |
2b28c07a JC |
117 | static void calc_dfs_tree_nonrec (struct dom_info *, basic_block, bool); |
118 | static void calc_dfs_tree (struct dom_info *, bool); | |
7080f735 AJ |
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); | |
2b28c07a | 122 | static void calc_idoms (struct dom_info *, bool); |
d47cc544 | 123 | void debug_dominance_info (enum cdi_direction); |
1fc3998d | 124 | void debug_dominance_tree (enum cdi_direction, basic_block); |
f8032688 MM |
125 | |
126 | /* Helper macro for allocating and initializing an array, | |
127 | for aesthetic reasons. */ | |
128 | #define init_ar(var, type, num, content) \ | |
3a538a66 KH |
129 | do \ |
130 | { \ | |
131 | unsigned int i = 1; /* Catch content == i. */ \ | |
132 | if (! (content)) \ | |
5ed6ace5 | 133 | (var) = XCNEWVEC (type, num); \ |
3a538a66 KH |
134 | else \ |
135 | { \ | |
5ed6ace5 | 136 | (var) = XNEWVEC (type, (num)); \ |
3a538a66 KH |
137 | for (i = 0; i < num; i++) \ |
138 | (var)[i] = (content); \ | |
139 | } \ | |
140 | } \ | |
141 | while (0) | |
f8032688 MM |
142 | |
143 | /* Allocate all needed memory in a pessimistic fashion (so we round up). | |
4912a07c | 144 | This initializes the contents of DI, which already must be allocated. */ |
f8032688 MM |
145 | |
146 | static void | |
26e0e410 | 147 | init_dom_info (struct dom_info *di, enum cdi_direction dir) |
f8032688 | 148 | { |
6fb5fa3c | 149 | /* We need memory for n_basic_blocks nodes. */ |
24bd1a0b | 150 | unsigned int num = n_basic_blocks; |
f8032688 MM |
151 | init_ar (di->dfs_parent, TBB, num, 0); |
152 | init_ar (di->path_min, TBB, num, i); | |
153 | init_ar (di->key, TBB, num, i); | |
154 | init_ar (di->dom, TBB, num, 0); | |
155 | ||
156 | init_ar (di->bucket, TBB, num, 0); | |
157 | init_ar (di->next_bucket, TBB, num, 0); | |
158 | ||
159 | init_ar (di->set_chain, TBB, num, 0); | |
160 | init_ar (di->set_size, unsigned int, num, 1); | |
161 | init_ar (di->set_child, TBB, num, 0); | |
162 | ||
d55bc081 | 163 | init_ar (di->dfs_order, TBB, (unsigned int) last_basic_block + 1, 0); |
f8032688 MM |
164 | init_ar (di->dfs_to_bb, basic_block, num, 0); |
165 | ||
166 | di->dfsnum = 1; | |
167 | di->nodes = 0; | |
26e0e410 | 168 | |
2b28c07a JC |
169 | switch (dir) |
170 | { | |
171 | case CDI_DOMINATORS: | |
172 | di->fake_exit_edge = NULL; | |
173 | break; | |
174 | case CDI_POST_DOMINATORS: | |
175 | di->fake_exit_edge = BITMAP_ALLOC (NULL); | |
176 | break; | |
177 | default: | |
178 | gcc_unreachable (); | |
179 | break; | |
180 | } | |
f8032688 MM |
181 | } |
182 | ||
183 | #undef init_ar | |
184 | ||
2b28c07a JC |
185 | /* Map dominance calculation type to array index used for various |
186 | dominance information arrays. This version is simple -- it will need | |
187 | to be modified, obviously, if additional values are added to | |
188 | cdi_direction. */ | |
189 | ||
190 | static unsigned int | |
191 | dom_convert_dir_to_idx (enum cdi_direction dir) | |
192 | { | |
193 | gcc_assert (dir == CDI_DOMINATORS || dir == CDI_POST_DOMINATORS); | |
194 | return dir - 1; | |
195 | } | |
196 | ||
f8032688 MM |
197 | /* Free all allocated memory in DI, but not DI itself. */ |
198 | ||
199 | static void | |
7080f735 | 200 | free_dom_info (struct dom_info *di) |
f8032688 MM |
201 | { |
202 | free (di->dfs_parent); | |
203 | free (di->path_min); | |
204 | free (di->key); | |
205 | free (di->dom); | |
206 | free (di->bucket); | |
207 | free (di->next_bucket); | |
208 | free (di->set_chain); | |
209 | free (di->set_size); | |
210 | free (di->set_child); | |
211 | free (di->dfs_order); | |
212 | free (di->dfs_to_bb); | |
8bdbfff5 | 213 | BITMAP_FREE (di->fake_exit_edge); |
f8032688 MM |
214 | } |
215 | ||
216 | /* The nonrecursive variant of creating a DFS tree. DI is our working | |
217 | structure, BB the starting basic block for this tree and REVERSE | |
218 | is true, if predecessors should be visited instead of successors of a | |
219 | node. After this is done all nodes reachable from BB were visited, have | |
220 | assigned their dfs number and are linked together to form a tree. */ | |
221 | ||
222 | static void | |
2b28c07a | 223 | calc_dfs_tree_nonrec (struct dom_info *di, basic_block bb, bool reverse) |
f8032688 | 224 | { |
f8032688 MM |
225 | /* We call this _only_ if bb is not already visited. */ |
226 | edge e; | |
227 | TBB child_i, my_i = 0; | |
628f6a4e BE |
228 | edge_iterator *stack; |
229 | edge_iterator ei, einext; | |
f8032688 MM |
230 | int sp; |
231 | /* Start block (ENTRY_BLOCK_PTR for forward problem, EXIT_BLOCK for backward | |
232 | problem). */ | |
233 | basic_block en_block; | |
234 | /* Ending block. */ | |
235 | basic_block ex_block; | |
236 | ||
5ed6ace5 | 237 | stack = XNEWVEC (edge_iterator, n_basic_blocks + 1); |
f8032688 MM |
238 | sp = 0; |
239 | ||
240 | /* Initialize our border blocks, and the first edge. */ | |
241 | if (reverse) | |
242 | { | |
628f6a4e | 243 | ei = ei_start (bb->preds); |
f8032688 MM |
244 | en_block = EXIT_BLOCK_PTR; |
245 | ex_block = ENTRY_BLOCK_PTR; | |
246 | } | |
247 | else | |
248 | { | |
628f6a4e | 249 | ei = ei_start (bb->succs); |
f8032688 MM |
250 | en_block = ENTRY_BLOCK_PTR; |
251 | ex_block = EXIT_BLOCK_PTR; | |
252 | } | |
253 | ||
254 | /* When the stack is empty we break out of this loop. */ | |
255 | while (1) | |
256 | { | |
257 | basic_block bn; | |
258 | ||
259 | /* This loop traverses edges e in depth first manner, and fills the | |
260 | stack. */ | |
628f6a4e | 261 | while (!ei_end_p (ei)) |
f8032688 | 262 | { |
628f6a4e | 263 | e = ei_edge (ei); |
f8032688 MM |
264 | |
265 | /* Deduce from E the current and the next block (BB and BN), and the | |
266 | next edge. */ | |
267 | if (reverse) | |
268 | { | |
269 | bn = e->src; | |
270 | ||
271 | /* If the next node BN is either already visited or a border | |
272 | block the current edge is useless, and simply overwritten | |
273 | with the next edge out of the current node. */ | |
0b17ab2f | 274 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 | 275 | { |
628f6a4e | 276 | ei_next (&ei); |
f8032688 MM |
277 | continue; |
278 | } | |
279 | bb = e->dest; | |
628f6a4e | 280 | einext = ei_start (bn->preds); |
f8032688 MM |
281 | } |
282 | else | |
283 | { | |
284 | bn = e->dest; | |
0b17ab2f | 285 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 | 286 | { |
628f6a4e | 287 | ei_next (&ei); |
f8032688 MM |
288 | continue; |
289 | } | |
290 | bb = e->src; | |
628f6a4e | 291 | einext = ei_start (bn->succs); |
f8032688 MM |
292 | } |
293 | ||
ced3f397 | 294 | gcc_assert (bn != en_block); |
f8032688 MM |
295 | |
296 | /* Fill the DFS tree info calculatable _before_ recursing. */ | |
297 | if (bb != en_block) | |
0b17ab2f | 298 | my_i = di->dfs_order[bb->index]; |
f8032688 | 299 | else |
d55bc081 | 300 | my_i = di->dfs_order[last_basic_block]; |
0b17ab2f | 301 | child_i = di->dfs_order[bn->index] = di->dfsnum++; |
f8032688 MM |
302 | di->dfs_to_bb[child_i] = bn; |
303 | di->dfs_parent[child_i] = my_i; | |
304 | ||
305 | /* Save the current point in the CFG on the stack, and recurse. */ | |
628f6a4e BE |
306 | stack[sp++] = ei; |
307 | ei = einext; | |
f8032688 MM |
308 | } |
309 | ||
310 | if (!sp) | |
311 | break; | |
628f6a4e | 312 | ei = stack[--sp]; |
f8032688 MM |
313 | |
314 | /* OK. The edge-list was exhausted, meaning normally we would | |
315 | end the recursion. After returning from the recursive call, | |
316 | there were (may be) other statements which were run after a | |
317 | child node was completely considered by DFS. Here is the | |
318 | point to do it in the non-recursive variant. | |
319 | E.g. The block just completed is in e->dest for forward DFS, | |
320 | the block not yet completed (the parent of the one above) | |
321 | in e->src. This could be used e.g. for computing the number of | |
322 | descendants or the tree depth. */ | |
628f6a4e | 323 | ei_next (&ei); |
f8032688 MM |
324 | } |
325 | free (stack); | |
326 | } | |
327 | ||
328 | /* The main entry for calculating the DFS tree or forest. DI is our working | |
329 | structure and REVERSE is true, if we are interested in the reverse flow | |
330 | graph. In that case the result is not necessarily a tree but a forest, | |
331 | because there may be nodes from which the EXIT_BLOCK is unreachable. */ | |
332 | ||
333 | static void | |
2b28c07a | 334 | calc_dfs_tree (struct dom_info *di, bool reverse) |
f8032688 MM |
335 | { |
336 | /* The first block is the ENTRY_BLOCK (or EXIT_BLOCK if REVERSE). */ | |
337 | basic_block begin = reverse ? EXIT_BLOCK_PTR : ENTRY_BLOCK_PTR; | |
d55bc081 | 338 | di->dfs_order[last_basic_block] = di->dfsnum; |
f8032688 MM |
339 | di->dfs_to_bb[di->dfsnum] = begin; |
340 | di->dfsnum++; | |
341 | ||
342 | calc_dfs_tree_nonrec (di, begin, reverse); | |
343 | ||
344 | if (reverse) | |
345 | { | |
346 | /* In the post-dom case we may have nodes without a path to EXIT_BLOCK. | |
347 | They are reverse-unreachable. In the dom-case we disallow such | |
26e0e410 RH |
348 | nodes, but in post-dom we have to deal with them. |
349 | ||
350 | There are two situations in which this occurs. First, noreturn | |
351 | functions. Second, infinite loops. In the first case we need to | |
352 | pretend that there is an edge to the exit block. In the second | |
353 | case, we wind up with a forest. We need to process all noreturn | |
354 | blocks before we know if we've got any infinite loops. */ | |
355 | ||
e0082a72 | 356 | basic_block b; |
26e0e410 RH |
357 | bool saw_unconnected = false; |
358 | ||
e0082a72 | 359 | FOR_EACH_BB_REVERSE (b) |
f8032688 | 360 | { |
628f6a4e | 361 | if (EDGE_COUNT (b->succs) > 0) |
26e0e410 RH |
362 | { |
363 | if (di->dfs_order[b->index] == 0) | |
364 | saw_unconnected = true; | |
365 | continue; | |
366 | } | |
367 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
0b17ab2f | 368 | di->dfs_order[b->index] = di->dfsnum; |
f8032688 | 369 | di->dfs_to_bb[di->dfsnum] = b; |
26e0e410 | 370 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; |
f8032688 MM |
371 | di->dfsnum++; |
372 | calc_dfs_tree_nonrec (di, b, reverse); | |
373 | } | |
26e0e410 RH |
374 | |
375 | if (saw_unconnected) | |
376 | { | |
377 | FOR_EACH_BB_REVERSE (b) | |
378 | { | |
379 | if (di->dfs_order[b->index]) | |
380 | continue; | |
381 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
382 | di->dfs_order[b->index] = di->dfsnum; | |
383 | di->dfs_to_bb[di->dfsnum] = b; | |
384 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; | |
385 | di->dfsnum++; | |
386 | calc_dfs_tree_nonrec (di, b, reverse); | |
387 | } | |
388 | } | |
f8032688 MM |
389 | } |
390 | ||
391 | di->nodes = di->dfsnum - 1; | |
392 | ||
24bd1a0b DB |
393 | /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. */ |
394 | gcc_assert (di->nodes == (unsigned int) n_basic_blocks - 1); | |
f8032688 MM |
395 | } |
396 | ||
397 | /* Compress the path from V to the root of its set and update path_min at the | |
398 | same time. After compress(di, V) set_chain[V] is the root of the set V is | |
399 | in and path_min[V] is the node with the smallest key[] value on the path | |
400 | from V to that root. */ | |
401 | ||
402 | static void | |
7080f735 | 403 | compress (struct dom_info *di, TBB v) |
f8032688 MM |
404 | { |
405 | /* Btw. It's not worth to unrecurse compress() as the depth is usually not | |
406 | greater than 5 even for huge graphs (I've not seen call depth > 4). | |
407 | Also performance wise compress() ranges _far_ behind eval(). */ | |
408 | TBB parent = di->set_chain[v]; | |
409 | if (di->set_chain[parent]) | |
410 | { | |
411 | compress (di, parent); | |
412 | if (di->key[di->path_min[parent]] < di->key[di->path_min[v]]) | |
413 | di->path_min[v] = di->path_min[parent]; | |
414 | di->set_chain[v] = di->set_chain[parent]; | |
415 | } | |
416 | } | |
417 | ||
418 | /* Compress the path from V to the set root of V if needed (when the root has | |
419 | changed since the last call). Returns the node with the smallest key[] | |
420 | value on the path from V to the root. */ | |
421 | ||
422 | static inline TBB | |
7080f735 | 423 | eval (struct dom_info *di, TBB v) |
f8032688 | 424 | { |
fa10beec | 425 | /* The representative of the set V is in, also called root (as the set |
f8032688 MM |
426 | representation is a tree). */ |
427 | TBB rep = di->set_chain[v]; | |
428 | ||
429 | /* V itself is the root. */ | |
430 | if (!rep) | |
431 | return di->path_min[v]; | |
432 | ||
433 | /* Compress only if necessary. */ | |
434 | if (di->set_chain[rep]) | |
435 | { | |
436 | compress (di, v); | |
437 | rep = di->set_chain[v]; | |
438 | } | |
439 | ||
440 | if (di->key[di->path_min[rep]] >= di->key[di->path_min[v]]) | |
441 | return di->path_min[v]; | |
442 | else | |
443 | return di->path_min[rep]; | |
444 | } | |
445 | ||
446 | /* This essentially merges the two sets of V and W, giving a single set with | |
447 | the new root V. The internal representation of these disjoint sets is a | |
448 | balanced tree. Currently link(V,W) is only used with V being the parent | |
449 | of W. */ | |
450 | ||
451 | static void | |
7080f735 | 452 | link_roots (struct dom_info *di, TBB v, TBB w) |
f8032688 MM |
453 | { |
454 | TBB s = w; | |
455 | ||
456 | /* Rebalance the tree. */ | |
457 | while (di->key[di->path_min[w]] < di->key[di->path_min[di->set_child[s]]]) | |
458 | { | |
459 | if (di->set_size[s] + di->set_size[di->set_child[di->set_child[s]]] | |
460 | >= 2 * di->set_size[di->set_child[s]]) | |
461 | { | |
462 | di->set_chain[di->set_child[s]] = s; | |
463 | di->set_child[s] = di->set_child[di->set_child[s]]; | |
464 | } | |
465 | else | |
466 | { | |
467 | di->set_size[di->set_child[s]] = di->set_size[s]; | |
468 | s = di->set_chain[s] = di->set_child[s]; | |
469 | } | |
470 | } | |
471 | ||
472 | di->path_min[s] = di->path_min[w]; | |
473 | di->set_size[v] += di->set_size[w]; | |
474 | if (di->set_size[v] < 2 * di->set_size[w]) | |
475 | { | |
476 | TBB tmp = s; | |
477 | s = di->set_child[v]; | |
478 | di->set_child[v] = tmp; | |
479 | } | |
480 | ||
481 | /* Merge all subtrees. */ | |
482 | while (s) | |
483 | { | |
484 | di->set_chain[s] = v; | |
485 | s = di->set_child[s]; | |
486 | } | |
487 | } | |
488 | ||
489 | /* This calculates the immediate dominators (or post-dominators if REVERSE is | |
490 | true). DI is our working structure and should hold the DFS forest. | |
491 | On return the immediate dominator to node V is in di->dom[V]. */ | |
492 | ||
493 | static void | |
2b28c07a | 494 | calc_idoms (struct dom_info *di, bool reverse) |
f8032688 MM |
495 | { |
496 | TBB v, w, k, par; | |
497 | basic_block en_block; | |
628f6a4e BE |
498 | edge_iterator ei, einext; |
499 | ||
f8032688 MM |
500 | if (reverse) |
501 | en_block = EXIT_BLOCK_PTR; | |
502 | else | |
503 | en_block = ENTRY_BLOCK_PTR; | |
504 | ||
505 | /* Go backwards in DFS order, to first look at the leafs. */ | |
506 | v = di->nodes; | |
507 | while (v > 1) | |
508 | { | |
509 | basic_block bb = di->dfs_to_bb[v]; | |
628f6a4e | 510 | edge e; |
f8032688 MM |
511 | |
512 | par = di->dfs_parent[v]; | |
513 | k = v; | |
628f6a4e BE |
514 | |
515 | ei = (reverse) ? ei_start (bb->succs) : ei_start (bb->preds); | |
516 | ||
f8032688 | 517 | if (reverse) |
26e0e410 | 518 | { |
26e0e410 RH |
519 | /* If this block has a fake edge to exit, process that first. */ |
520 | if (bitmap_bit_p (di->fake_exit_edge, bb->index)) | |
521 | { | |
628f6a4e BE |
522 | einext = ei; |
523 | einext.index = 0; | |
26e0e410 RH |
524 | goto do_fake_exit_edge; |
525 | } | |
526 | } | |
f8032688 MM |
527 | |
528 | /* Search all direct predecessors for the smallest node with a path | |
529 | to them. That way we have the smallest node with also a path to | |
530 | us only over nodes behind us. In effect we search for our | |
531 | semidominator. */ | |
628f6a4e | 532 | while (!ei_end_p (ei)) |
f8032688 MM |
533 | { |
534 | TBB k1; | |
535 | basic_block b; | |
536 | ||
628f6a4e BE |
537 | e = ei_edge (ei); |
538 | b = (reverse) ? e->dest : e->src; | |
539 | einext = ei; | |
540 | ei_next (&einext); | |
541 | ||
f8032688 | 542 | if (b == en_block) |
26e0e410 RH |
543 | { |
544 | do_fake_exit_edge: | |
545 | k1 = di->dfs_order[last_basic_block]; | |
546 | } | |
f8032688 | 547 | else |
0b17ab2f | 548 | k1 = di->dfs_order[b->index]; |
f8032688 MM |
549 | |
550 | /* Call eval() only if really needed. If k1 is above V in DFS tree, | |
551 | then we know, that eval(k1) == k1 and key[k1] == k1. */ | |
552 | if (k1 > v) | |
553 | k1 = di->key[eval (di, k1)]; | |
554 | if (k1 < k) | |
555 | k = k1; | |
628f6a4e BE |
556 | |
557 | ei = einext; | |
f8032688 MM |
558 | } |
559 | ||
560 | di->key[v] = k; | |
561 | link_roots (di, par, v); | |
562 | di->next_bucket[v] = di->bucket[k]; | |
563 | di->bucket[k] = v; | |
564 | ||
565 | /* Transform semidominators into dominators. */ | |
566 | for (w = di->bucket[par]; w; w = di->next_bucket[w]) | |
567 | { | |
568 | k = eval (di, w); | |
569 | if (di->key[k] < di->key[w]) | |
570 | di->dom[w] = k; | |
571 | else | |
572 | di->dom[w] = par; | |
573 | } | |
574 | /* We don't need to cleanup next_bucket[]. */ | |
575 | di->bucket[par] = 0; | |
576 | v--; | |
577 | } | |
578 | ||
a1f300c0 | 579 | /* Explicitly define the dominators. */ |
f8032688 MM |
580 | di->dom[1] = 0; |
581 | for (v = 2; v <= di->nodes; v++) | |
582 | if (di->dom[v] != di->key[v]) | |
583 | di->dom[v] = di->dom[di->dom[v]]; | |
584 | } | |
585 | ||
d47cc544 SB |
586 | /* Assign dfs numbers starting from NUM to NODE and its sons. */ |
587 | ||
588 | static void | |
589 | assign_dfs_numbers (struct et_node *node, int *num) | |
590 | { | |
591 | struct et_node *son; | |
592 | ||
593 | node->dfs_num_in = (*num)++; | |
594 | ||
595 | if (node->son) | |
596 | { | |
597 | assign_dfs_numbers (node->son, num); | |
598 | for (son = node->son->right; son != node->son; son = son->right) | |
6de9cd9a | 599 | assign_dfs_numbers (son, num); |
d47cc544 | 600 | } |
f8032688 | 601 | |
d47cc544 SB |
602 | node->dfs_num_out = (*num)++; |
603 | } | |
f8032688 | 604 | |
5d3cc252 | 605 | /* Compute the data necessary for fast resolving of dominator queries in a |
d47cc544 | 606 | static dominator tree. */ |
f8032688 | 607 | |
d47cc544 SB |
608 | static void |
609 | compute_dom_fast_query (enum cdi_direction dir) | |
610 | { | |
611 | int num = 0; | |
612 | basic_block bb; | |
2b28c07a | 613 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
d47cc544 | 614 | |
fce22de5 | 615 | gcc_assert (dom_info_available_p (dir)); |
d47cc544 | 616 | |
2b28c07a | 617 | if (dom_computed[dir_index] == DOM_OK) |
d47cc544 SB |
618 | return; |
619 | ||
620 | FOR_ALL_BB (bb) | |
621 | { | |
2b28c07a JC |
622 | if (!bb->dom[dir_index]->father) |
623 | assign_dfs_numbers (bb->dom[dir_index], &num); | |
d47cc544 SB |
624 | } |
625 | ||
2b28c07a | 626 | dom_computed[dir_index] = DOM_OK; |
d47cc544 SB |
627 | } |
628 | ||
629 | /* The main entry point into this module. DIR is set depending on whether | |
630 | we want to compute dominators or postdominators. */ | |
631 | ||
632 | void | |
633 | calculate_dominance_info (enum cdi_direction dir) | |
f8032688 MM |
634 | { |
635 | struct dom_info di; | |
355be0dc | 636 | basic_block b; |
2b28c07a JC |
637 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
638 | bool reverse = (dir == CDI_POST_DOMINATORS) ? true : false; | |
355be0dc | 639 | |
2b28c07a | 640 | if (dom_computed[dir_index] == DOM_OK) |
d47cc544 | 641 | return; |
355be0dc | 642 | |
74c96e0c | 643 | timevar_push (TV_DOMINANCE); |
fce22de5 | 644 | if (!dom_info_available_p (dir)) |
d47cc544 | 645 | { |
2b28c07a | 646 | gcc_assert (!n_bbs_in_dom_tree[dir_index]); |
f8032688 | 647 | |
d47cc544 SB |
648 | FOR_ALL_BB (b) |
649 | { | |
2b28c07a | 650 | b->dom[dir_index] = et_new_tree (b); |
d47cc544 | 651 | } |
2b28c07a | 652 | n_bbs_in_dom_tree[dir_index] = n_basic_blocks; |
f8032688 | 653 | |
26e0e410 | 654 | init_dom_info (&di, dir); |
2b28c07a JC |
655 | calc_dfs_tree (&di, reverse); |
656 | calc_idoms (&di, reverse); | |
355be0dc | 657 | |
d47cc544 SB |
658 | FOR_EACH_BB (b) |
659 | { | |
660 | TBB d = di.dom[di.dfs_order[b->index]]; | |
661 | ||
662 | if (di.dfs_to_bb[d]) | |
2b28c07a | 663 | et_set_father (b->dom[dir_index], di.dfs_to_bb[d]->dom[dir_index]); |
d47cc544 | 664 | } |
e0082a72 | 665 | |
d47cc544 | 666 | free_dom_info (&di); |
2b28c07a | 667 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; |
355be0dc JH |
668 | } |
669 | ||
d47cc544 | 670 | compute_dom_fast_query (dir); |
74c96e0c ZD |
671 | |
672 | timevar_pop (TV_DOMINANCE); | |
355be0dc JH |
673 | } |
674 | ||
d47cc544 | 675 | /* Free dominance information for direction DIR. */ |
355be0dc | 676 | void |
d47cc544 | 677 | free_dominance_info (enum cdi_direction dir) |
355be0dc JH |
678 | { |
679 | basic_block bb; | |
2b28c07a | 680 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
355be0dc | 681 | |
fce22de5 | 682 | if (!dom_info_available_p (dir)) |
d47cc544 SB |
683 | return; |
684 | ||
685 | FOR_ALL_BB (bb) | |
686 | { | |
2b28c07a JC |
687 | et_free_tree_force (bb->dom[dir_index]); |
688 | bb->dom[dir_index] = NULL; | |
d47cc544 | 689 | } |
5a6ccafd | 690 | et_free_pools (); |
d47cc544 | 691 | |
2b28c07a | 692 | n_bbs_in_dom_tree[dir_index] = 0; |
6de9cd9a | 693 | |
2b28c07a | 694 | dom_computed[dir_index] = DOM_NONE; |
355be0dc JH |
695 | } |
696 | ||
697 | /* Return the immediate dominator of basic block BB. */ | |
698 | basic_block | |
d47cc544 | 699 | get_immediate_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 700 | { |
2b28c07a JC |
701 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
702 | struct et_node *node = bb->dom[dir_index]; | |
d47cc544 | 703 | |
2b28c07a | 704 | gcc_assert (dom_computed[dir_index]); |
d47cc544 SB |
705 | |
706 | if (!node->father) | |
707 | return NULL; | |
708 | ||
f883e0a7 | 709 | return (basic_block) node->father->data; |
355be0dc JH |
710 | } |
711 | ||
712 | /* Set the immediate dominator of the block possibly removing | |
713 | existing edge. NULL can be used to remove any edge. */ | |
714 | inline void | |
d47cc544 SB |
715 | set_immediate_dominator (enum cdi_direction dir, basic_block bb, |
716 | basic_block dominated_by) | |
355be0dc | 717 | { |
2b28c07a JC |
718 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
719 | struct et_node *node = bb->dom[dir_index]; | |
720 | ||
721 | gcc_assert (dom_computed[dir_index]); | |
355be0dc | 722 | |
d47cc544 | 723 | if (node->father) |
355be0dc | 724 | { |
d47cc544 | 725 | if (node->father->data == dominated_by) |
6de9cd9a | 726 | return; |
d47cc544 | 727 | et_split (node); |
355be0dc | 728 | } |
d47cc544 SB |
729 | |
730 | if (dominated_by) | |
2b28c07a | 731 | et_set_father (node, dominated_by->dom[dir_index]); |
d47cc544 | 732 | |
2b28c07a JC |
733 | if (dom_computed[dir_index] == DOM_OK) |
734 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
735 | } |
736 | ||
66f97d31 ZD |
737 | /* Returns the list of basic blocks immediately dominated by BB, in the |
738 | direction DIR. */ | |
739 | VEC (basic_block, heap) * | |
740 | get_dominated_by (enum cdi_direction dir, basic_block bb) | |
355be0dc | 741 | { |
d47cc544 | 742 | int n; |
66f97d31 | 743 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
2b28c07a | 744 | struct et_node *node = bb->dom[dir_index], *son = node->son, *ason; |
66f97d31 ZD |
745 | VEC (basic_block, heap) *bbs = NULL; |
746 | ||
2b28c07a | 747 | gcc_assert (dom_computed[dir_index]); |
d47cc544 SB |
748 | |
749 | if (!son) | |
66f97d31 | 750 | return NULL; |
d47cc544 | 751 | |
f883e0a7 | 752 | VEC_safe_push (basic_block, heap, bbs, (basic_block) son->data); |
d47cc544 | 753 | for (ason = son->right, n = 1; ason != son; ason = ason->right) |
f883e0a7 | 754 | VEC_safe_push (basic_block, heap, bbs, (basic_block) ason->data); |
355be0dc | 755 | |
66f97d31 | 756 | return bbs; |
355be0dc JH |
757 | } |
758 | ||
66f97d31 ZD |
759 | /* Returns the list of basic blocks that are immediately dominated (in |
760 | direction DIR) by some block between N_REGION ones stored in REGION, | |
761 | except for blocks in the REGION itself. */ | |
762 | ||
763 | VEC (basic_block, heap) * | |
42759f1e | 764 | get_dominated_by_region (enum cdi_direction dir, basic_block *region, |
66f97d31 | 765 | unsigned n_region) |
42759f1e | 766 | { |
66f97d31 | 767 | unsigned i; |
42759f1e | 768 | basic_block dom; |
66f97d31 | 769 | VEC (basic_block, heap) *doms = NULL; |
42759f1e ZD |
770 | |
771 | for (i = 0; i < n_region; i++) | |
6580ee77 | 772 | region[i]->flags |= BB_DUPLICATED; |
42759f1e ZD |
773 | for (i = 0; i < n_region; i++) |
774 | for (dom = first_dom_son (dir, region[i]); | |
775 | dom; | |
776 | dom = next_dom_son (dir, dom)) | |
6580ee77 | 777 | if (!(dom->flags & BB_DUPLICATED)) |
66f97d31 | 778 | VEC_safe_push (basic_block, heap, doms, dom); |
42759f1e | 779 | for (i = 0; i < n_region; i++) |
6580ee77 | 780 | region[i]->flags &= ~BB_DUPLICATED; |
42759f1e | 781 | |
66f97d31 | 782 | return doms; |
42759f1e ZD |
783 | } |
784 | ||
355be0dc JH |
785 | /* Redirect all edges pointing to BB to TO. */ |
786 | void | |
d47cc544 SB |
787 | redirect_immediate_dominators (enum cdi_direction dir, basic_block bb, |
788 | basic_block to) | |
355be0dc | 789 | { |
2b28c07a JC |
790 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
791 | struct et_node *bb_node, *to_node, *son; | |
792 | ||
793 | bb_node = bb->dom[dir_index]; | |
794 | to_node = to->dom[dir_index]; | |
d47cc544 | 795 | |
2b28c07a | 796 | gcc_assert (dom_computed[dir_index]); |
355be0dc | 797 | |
d47cc544 SB |
798 | if (!bb_node->son) |
799 | return; | |
800 | ||
801 | while (bb_node->son) | |
355be0dc | 802 | { |
d47cc544 SB |
803 | son = bb_node->son; |
804 | ||
805 | et_split (son); | |
806 | et_set_father (son, to_node); | |
355be0dc | 807 | } |
d47cc544 | 808 | |
2b28c07a JC |
809 | if (dom_computed[dir_index] == DOM_OK) |
810 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
811 | } |
812 | ||
813 | /* Find first basic block in the tree dominating both BB1 and BB2. */ | |
814 | basic_block | |
d47cc544 | 815 | nearest_common_dominator (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
355be0dc | 816 | { |
2b28c07a JC |
817 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
818 | ||
819 | gcc_assert (dom_computed[dir_index]); | |
d47cc544 | 820 | |
355be0dc JH |
821 | if (!bb1) |
822 | return bb2; | |
823 | if (!bb2) | |
824 | return bb1; | |
d47cc544 | 825 | |
f883e0a7 | 826 | return (basic_block) et_nca (bb1->dom[dir_index], bb2->dom[dir_index])->data; |
355be0dc JH |
827 | } |
828 | ||
0bca51f0 DN |
829 | |
830 | /* Find the nearest common dominator for the basic blocks in BLOCKS, | |
831 | using dominance direction DIR. */ | |
832 | ||
833 | basic_block | |
834 | nearest_common_dominator_for_set (enum cdi_direction dir, bitmap blocks) | |
835 | { | |
836 | unsigned i, first; | |
837 | bitmap_iterator bi; | |
838 | basic_block dom; | |
839 | ||
840 | first = bitmap_first_set_bit (blocks); | |
841 | dom = BASIC_BLOCK (first); | |
842 | EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi) | |
843 | if (dom != BASIC_BLOCK (i)) | |
844 | dom = nearest_common_dominator (dir, dom, BASIC_BLOCK (i)); | |
845 | ||
846 | return dom; | |
847 | } | |
848 | ||
b629276a DB |
849 | /* Given a dominator tree, we can determine whether one thing |
850 | dominates another in constant time by using two DFS numbers: | |
851 | ||
852 | 1. The number for when we visit a node on the way down the tree | |
853 | 2. The number for when we visit a node on the way back up the tree | |
854 | ||
855 | You can view these as bounds for the range of dfs numbers the | |
856 | nodes in the subtree of the dominator tree rooted at that node | |
857 | will contain. | |
858 | ||
859 | The dominator tree is always a simple acyclic tree, so there are | |
860 | only three possible relations two nodes in the dominator tree have | |
861 | to each other: | |
862 | ||
863 | 1. Node A is above Node B (and thus, Node A dominates node B) | |
864 | ||
865 | A | |
866 | | | |
867 | C | |
868 | / \ | |
869 | B D | |
870 | ||
871 | ||
872 | In the above case, DFS_Number_In of A will be <= DFS_Number_In of | |
873 | B, and DFS_Number_Out of A will be >= DFS_Number_Out of B. This is | |
874 | because we must hit A in the dominator tree *before* B on the walk | |
875 | down, and we will hit A *after* B on the walk back up | |
876 | ||
d8701f02 | 877 | 2. Node A is below node B (and thus, node B dominates node A) |
b629276a DB |
878 | |
879 | ||
880 | B | |
881 | | | |
882 | A | |
883 | / \ | |
884 | C D | |
885 | ||
886 | In the above case, DFS_Number_In of A will be >= DFS_Number_In of | |
887 | B, and DFS_Number_Out of A will be <= DFS_Number_Out of B. | |
888 | ||
889 | This is because we must hit A in the dominator tree *after* B on | |
890 | the walk down, and we will hit A *before* B on the walk back up | |
891 | ||
892 | 3. Node A and B are siblings (and thus, neither dominates the other) | |
893 | ||
894 | C | |
895 | | | |
896 | D | |
897 | / \ | |
898 | A B | |
899 | ||
900 | In the above case, DFS_Number_In of A will *always* be <= | |
901 | DFS_Number_In of B, and DFS_Number_Out of A will *always* be <= | |
902 | DFS_Number_Out of B. This is because we will always finish the dfs | |
903 | walk of one of the subtrees before the other, and thus, the dfs | |
904 | numbers for one subtree can't intersect with the range of dfs | |
905 | numbers for the other subtree. If you swap A and B's position in | |
906 | the dominator tree, the comparison changes direction, but the point | |
907 | is that both comparisons will always go the same way if there is no | |
908 | dominance relationship. | |
909 | ||
910 | Thus, it is sufficient to write | |
911 | ||
912 | A_Dominates_B (node A, node B) | |
913 | { | |
914 | return DFS_Number_In(A) <= DFS_Number_In(B) | |
915 | && DFS_Number_Out (A) >= DFS_Number_Out(B); | |
916 | } | |
917 | ||
918 | A_Dominated_by_B (node A, node B) | |
919 | { | |
920 | return DFS_Number_In(A) >= DFS_Number_In(A) | |
921 | && DFS_Number_Out (A) <= DFS_Number_Out(B); | |
922 | } */ | |
0bca51f0 | 923 | |
355be0dc JH |
924 | /* Return TRUE in case BB1 is dominated by BB2. */ |
925 | bool | |
ed7a4b4b | 926 | dominated_by_p (enum cdi_direction dir, const_basic_block bb1, const_basic_block bb2) |
6de9cd9a | 927 | { |
2b28c07a JC |
928 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
929 | struct et_node *n1 = bb1->dom[dir_index], *n2 = bb2->dom[dir_index]; | |
930 | ||
931 | gcc_assert (dom_computed[dir_index]); | |
d47cc544 | 932 | |
2b28c07a | 933 | if (dom_computed[dir_index] == DOM_OK) |
d47cc544 | 934 | return (n1->dfs_num_in >= n2->dfs_num_in |
6de9cd9a | 935 | && n1->dfs_num_out <= n2->dfs_num_out); |
d47cc544 SB |
936 | |
937 | return et_below (n1, n2); | |
355be0dc JH |
938 | } |
939 | ||
f074ff6c ZD |
940 | /* Returns the entry dfs number for basic block BB, in the direction DIR. */ |
941 | ||
942 | unsigned | |
943 | bb_dom_dfs_in (enum cdi_direction dir, basic_block bb) | |
944 | { | |
2b28c07a JC |
945 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
946 | struct et_node *n = bb->dom[dir_index]; | |
f074ff6c | 947 | |
2b28c07a | 948 | gcc_assert (dom_computed[dir_index] == DOM_OK); |
f074ff6c ZD |
949 | return n->dfs_num_in; |
950 | } | |
951 | ||
952 | /* Returns the exit dfs number for basic block BB, in the direction DIR. */ | |
953 | ||
954 | unsigned | |
955 | bb_dom_dfs_out (enum cdi_direction dir, basic_block bb) | |
956 | { | |
2b28c07a JC |
957 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
958 | struct et_node *n = bb->dom[dir_index]; | |
f074ff6c | 959 | |
2b28c07a | 960 | gcc_assert (dom_computed[dir_index] == DOM_OK); |
f074ff6c ZD |
961 | return n->dfs_num_out; |
962 | } | |
963 | ||
355be0dc JH |
964 | /* Verify invariants of dominator structure. */ |
965 | void | |
d47cc544 | 966 | verify_dominators (enum cdi_direction dir) |
355be0dc JH |
967 | { |
968 | int err = 0; | |
1fc3998d ZD |
969 | basic_block bb, imm_bb, imm_bb_correct; |
970 | struct dom_info di; | |
971 | bool reverse = (dir == CDI_POST_DOMINATORS) ? true : false; | |
355be0dc | 972 | |
fce22de5 | 973 | gcc_assert (dom_info_available_p (dir)); |
d47cc544 | 974 | |
1fc3998d ZD |
975 | init_dom_info (&di, dir); |
976 | calc_dfs_tree (&di, reverse); | |
977 | calc_idoms (&di, reverse); | |
978 | ||
355be0dc JH |
979 | FOR_EACH_BB (bb) |
980 | { | |
1fc3998d ZD |
981 | imm_bb = get_immediate_dominator (dir, bb); |
982 | if (!imm_bb) | |
f8032688 | 983 | { |
66f97d31 | 984 | error ("dominator of %d status unknown", bb->index); |
355be0dc JH |
985 | err = 1; |
986 | } | |
66f97d31 | 987 | |
1fc3998d ZD |
988 | imm_bb_correct = di.dfs_to_bb[di.dom[di.dfs_order[bb->index]]]; |
989 | if (imm_bb != imm_bb_correct) | |
e7bd94cc | 990 | { |
66f97d31 | 991 | error ("dominator of %d should be %d, not %d", |
1fc3998d | 992 | bb->index, imm_bb_correct->index, imm_bb->index); |
66f97d31 | 993 | err = 1; |
e7bd94cc ZD |
994 | } |
995 | } | |
996 | ||
1fc3998d | 997 | free_dom_info (&di); |
ced3f397 | 998 | gcc_assert (!err); |
355be0dc JH |
999 | } |
1000 | ||
738ed977 ZD |
1001 | /* Determine immediate dominator (or postdominator, according to DIR) of BB, |
1002 | assuming that dominators of other blocks are correct. We also use it to | |
1003 | recompute the dominators in a restricted area, by iterating it until it | |
71cc389b | 1004 | reaches a fixed point. */ |
738ed977 | 1005 | |
355be0dc | 1006 | basic_block |
66f97d31 | 1007 | recompute_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 1008 | { |
2b28c07a | 1009 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
738ed977 ZD |
1010 | basic_block dom_bb = NULL; |
1011 | edge e; | |
628f6a4e | 1012 | edge_iterator ei; |
355be0dc | 1013 | |
2b28c07a | 1014 | gcc_assert (dom_computed[dir_index]); |
d47cc544 | 1015 | |
738ed977 ZD |
1016 | if (dir == CDI_DOMINATORS) |
1017 | { | |
628f6a4e | 1018 | FOR_EACH_EDGE (e, ei, bb->preds) |
738ed977 ZD |
1019 | { |
1020 | if (!dominated_by_p (dir, e->src, bb)) | |
1021 | dom_bb = nearest_common_dominator (dir, dom_bb, e->src); | |
1022 | } | |
1023 | } | |
1024 | else | |
1025 | { | |
628f6a4e | 1026 | FOR_EACH_EDGE (e, ei, bb->succs) |
738ed977 ZD |
1027 | { |
1028 | if (!dominated_by_p (dir, e->dest, bb)) | |
1029 | dom_bb = nearest_common_dominator (dir, dom_bb, e->dest); | |
1030 | } | |
1031 | } | |
f8032688 | 1032 | |
738ed977 | 1033 | return dom_bb; |
355be0dc JH |
1034 | } |
1035 | ||
66f97d31 ZD |
1036 | /* Use simple heuristics (see iterate_fix_dominators) to determine dominators |
1037 | of BBS. We assume that all the immediate dominators except for those of the | |
1038 | blocks in BBS are correct. If CONSERVATIVE is true, we also assume that the | |
1039 | currently recorded immediate dominators of blocks in BBS really dominate the | |
1040 | blocks. The basic blocks for that we determine the dominator are removed | |
1041 | from BBS. */ | |
1042 | ||
1043 | static void | |
1044 | prune_bbs_to_update_dominators (VEC (basic_block, heap) *bbs, | |
1045 | bool conservative) | |
1046 | { | |
1047 | unsigned i; | |
1048 | bool single; | |
1049 | basic_block bb, dom = NULL; | |
1050 | edge_iterator ei; | |
1051 | edge e; | |
1052 | ||
1053 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb);) | |
1054 | { | |
1055 | if (bb == ENTRY_BLOCK_PTR) | |
1056 | goto succeed; | |
1057 | ||
1058 | if (single_pred_p (bb)) | |
1059 | { | |
1060 | set_immediate_dominator (CDI_DOMINATORS, bb, single_pred (bb)); | |
1061 | goto succeed; | |
1062 | } | |
1063 | ||
1064 | if (!conservative) | |
1065 | goto fail; | |
1066 | ||
1067 | single = true; | |
1068 | dom = NULL; | |
1069 | FOR_EACH_EDGE (e, ei, bb->preds) | |
1070 | { | |
1071 | if (dominated_by_p (CDI_DOMINATORS, e->src, bb)) | |
1072 | continue; | |
1073 | ||
1074 | if (!dom) | |
1075 | dom = e->src; | |
1076 | else | |
1077 | { | |
1078 | single = false; | |
1079 | dom = nearest_common_dominator (CDI_DOMINATORS, dom, e->src); | |
1080 | } | |
1081 | } | |
1082 | ||
1083 | gcc_assert (dom != NULL); | |
1084 | if (single | |
1085 | || find_edge (dom, bb)) | |
1086 | { | |
1087 | set_immediate_dominator (CDI_DOMINATORS, bb, dom); | |
1088 | goto succeed; | |
1089 | } | |
1090 | ||
1091 | fail: | |
1092 | i++; | |
1093 | continue; | |
1094 | ||
1095 | succeed: | |
1096 | VEC_unordered_remove (basic_block, bbs, i); | |
1097 | } | |
1098 | } | |
1099 | ||
1100 | /* Returns root of the dominance tree in the direction DIR that contains | |
1101 | BB. */ | |
1102 | ||
1103 | static basic_block | |
1104 | root_of_dom_tree (enum cdi_direction dir, basic_block bb) | |
1105 | { | |
f883e0a7 | 1106 | return (basic_block) et_root (bb->dom[dom_convert_dir_to_idx (dir)])->data; |
66f97d31 ZD |
1107 | } |
1108 | ||
1109 | /* See the comment in iterate_fix_dominators. Finds the immediate dominators | |
1110 | for the sons of Y, found using the SON and BROTHER arrays representing | |
1111 | the dominance tree of graph G. BBS maps the vertices of G to the basic | |
1112 | blocks. */ | |
1113 | ||
1114 | static void | |
1115 | determine_dominators_for_sons (struct graph *g, VEC (basic_block, heap) *bbs, | |
1116 | int y, int *son, int *brother) | |
1117 | { | |
1118 | bitmap gprime; | |
1119 | int i, a, nc; | |
1120 | VEC (int, heap) **sccs; | |
1121 | basic_block bb, dom, ybb; | |
1122 | unsigned si; | |
1123 | edge e; | |
1124 | edge_iterator ei; | |
1125 | ||
1126 | if (son[y] == -1) | |
1127 | return; | |
1128 | if (y == (int) VEC_length (basic_block, bbs)) | |
1129 | ybb = ENTRY_BLOCK_PTR; | |
1130 | else | |
1131 | ybb = VEC_index (basic_block, bbs, y); | |
1132 | ||
1133 | if (brother[son[y]] == -1) | |
1134 | { | |
1135 | /* Handle the common case Y has just one son specially. */ | |
1136 | bb = VEC_index (basic_block, bbs, son[y]); | |
1137 | set_immediate_dominator (CDI_DOMINATORS, bb, | |
1138 | recompute_dominator (CDI_DOMINATORS, bb)); | |
1139 | identify_vertices (g, y, son[y]); | |
1140 | return; | |
1141 | } | |
1142 | ||
1143 | gprime = BITMAP_ALLOC (NULL); | |
1144 | for (a = son[y]; a != -1; a = brother[a]) | |
1145 | bitmap_set_bit (gprime, a); | |
1146 | ||
1147 | nc = graphds_scc (g, gprime); | |
1148 | BITMAP_FREE (gprime); | |
1149 | ||
1150 | sccs = XCNEWVEC (VEC (int, heap) *, nc); | |
1151 | for (a = son[y]; a != -1; a = brother[a]) | |
1152 | VEC_safe_push (int, heap, sccs[g->vertices[a].component], a); | |
1153 | ||
1154 | for (i = nc - 1; i >= 0; i--) | |
1155 | { | |
1156 | dom = NULL; | |
1157 | for (si = 0; VEC_iterate (int, sccs[i], si, a); si++) | |
1158 | { | |
1159 | bb = VEC_index (basic_block, bbs, a); | |
1160 | FOR_EACH_EDGE (e, ei, bb->preds) | |
1161 | { | |
1162 | if (root_of_dom_tree (CDI_DOMINATORS, e->src) != ybb) | |
1163 | continue; | |
1164 | ||
1165 | dom = nearest_common_dominator (CDI_DOMINATORS, dom, e->src); | |
1166 | } | |
1167 | } | |
1168 | ||
1169 | gcc_assert (dom != NULL); | |
1170 | for (si = 0; VEC_iterate (int, sccs[i], si, a); si++) | |
1171 | { | |
1172 | bb = VEC_index (basic_block, bbs, a); | |
1173 | set_immediate_dominator (CDI_DOMINATORS, bb, dom); | |
1174 | } | |
1175 | } | |
1176 | ||
1177 | for (i = 0; i < nc; i++) | |
1178 | VEC_free (int, heap, sccs[i]); | |
1179 | free (sccs); | |
1180 | ||
1181 | for (a = son[y]; a != -1; a = brother[a]) | |
1182 | identify_vertices (g, y, a); | |
1183 | } | |
1184 | ||
1185 | /* Recompute dominance information for basic blocks in the set BBS. The | |
1186 | function assumes that the immediate dominators of all the other blocks | |
1187 | in CFG are correct, and that there are no unreachable blocks. | |
1188 | ||
1189 | If CONSERVATIVE is true, we additionally assume that all the ancestors of | |
1190 | a block of BBS in the current dominance tree dominate it. */ | |
1191 | ||
355be0dc | 1192 | void |
66f97d31 ZD |
1193 | iterate_fix_dominators (enum cdi_direction dir, VEC (basic_block, heap) *bbs, |
1194 | bool conservative) | |
355be0dc | 1195 | { |
66f97d31 ZD |
1196 | unsigned i; |
1197 | basic_block bb, dom; | |
1198 | struct graph *g; | |
1199 | int n, y; | |
1200 | size_t dom_i; | |
1201 | edge e; | |
1202 | edge_iterator ei; | |
1203 | struct pointer_map_t *map; | |
1204 | int *parent, *son, *brother; | |
2b28c07a | 1205 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
355be0dc | 1206 | |
66f97d31 ZD |
1207 | /* We only support updating dominators. There are some problems with |
1208 | updating postdominators (need to add fake edges from infinite loops | |
1209 | and noreturn functions), and since we do not currently use | |
1210 | iterate_fix_dominators for postdominators, any attempt to handle these | |
1211 | problems would be unused, untested, and almost surely buggy. We keep | |
1212 | the DIR argument for consistency with the rest of the dominator analysis | |
1213 | interface. */ | |
1214 | gcc_assert (dir == CDI_DOMINATORS); | |
2b28c07a | 1215 | gcc_assert (dom_computed[dir_index]); |
d47cc544 | 1216 | |
66f97d31 ZD |
1217 | /* The algorithm we use takes inspiration from the following papers, although |
1218 | the details are quite different from any of them: | |
1219 | ||
1220 | [1] G. Ramalingam, T. Reps, An Incremental Algorithm for Maintaining the | |
1221 | Dominator Tree of a Reducible Flowgraph | |
1222 | [2] V. C. Sreedhar, G. R. Gao, Y.-F. Lee: Incremental computation of | |
1223 | dominator trees | |
1224 | [3] K. D. Cooper, T. J. Harvey and K. Kennedy: A Simple, Fast Dominance | |
1225 | Algorithm | |
1226 | ||
1227 | First, we use the following heuristics to decrease the size of the BBS | |
1228 | set: | |
1229 | a) if BB has a single predecessor, then its immediate dominator is this | |
1230 | predecessor | |
1231 | additionally, if CONSERVATIVE is true: | |
1232 | b) if all the predecessors of BB except for one (X) are dominated by BB, | |
1233 | then X is the immediate dominator of BB | |
1234 | c) if the nearest common ancestor of the predecessors of BB is X and | |
1235 | X -> BB is an edge in CFG, then X is the immediate dominator of BB | |
1236 | ||
1237 | Then, we need to establish the dominance relation among the basic blocks | |
1238 | in BBS. We split the dominance tree by removing the immediate dominator | |
0d52bcc1 | 1239 | edges from BBS, creating a forest F. We form a graph G whose vertices |
66f97d31 | 1240 | are BBS and ENTRY and X -> Y is an edge of G if there exists an edge |
0d52bcc1 | 1241 | X' -> Y in CFG such that X' belongs to the tree of the dominance forest |
66f97d31 ZD |
1242 | whose root is X. We then determine dominance tree of G. Note that |
1243 | for X, Y in BBS, X dominates Y in CFG if and only if X dominates Y in G. | |
1244 | In this step, we can use arbitrary algorithm to determine dominators. | |
1245 | We decided to prefer the algorithm [3] to the algorithm of | |
1246 | Lengauer and Tarjan, since the set BBS is usually small (rarely exceeding | |
1247 | 10 during gcc bootstrap), and [3] should perform better in this case. | |
1248 | ||
1249 | Finally, we need to determine the immediate dominators for the basic | |
1250 | blocks of BBS. If the immediate dominator of X in G is Y, then | |
1251 | the immediate dominator of X in CFG belongs to the tree of F rooted in | |
1252 | Y. We process the dominator tree T of G recursively, starting from leaves. | |
1253 | Suppose that X_1, X_2, ..., X_k are the sons of Y in T, and that the | |
1254 | subtrees of the dominance tree of CFG rooted in X_i are already correct. | |
1255 | Let G' be the subgraph of G induced by {X_1, X_2, ..., X_k}. We make | |
1256 | the following observations: | |
1257 | (i) the immediate dominator of all blocks in a strongly connected | |
1258 | component of G' is the same | |
1259 | (ii) if X has no predecessors in G', then the immediate dominator of X | |
1260 | is the nearest common ancestor of the predecessors of X in the | |
1261 | subtree of F rooted in Y | |
1262 | Therefore, it suffices to find the topological ordering of G', and | |
1263 | process the nodes X_i in this order using the rules (i) and (ii). | |
1264 | Then, we contract all the nodes X_i with Y in G, so that the further | |
1265 | steps work correctly. */ | |
1266 | ||
1267 | if (!conservative) | |
1268 | { | |
1269 | /* Split the tree now. If the idoms of blocks in BBS are not | |
1270 | conservatively correct, setting the dominators using the | |
1271 | heuristics in prune_bbs_to_update_dominators could | |
1272 | create cycles in the dominance "tree", and cause ICE. */ | |
1273 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb); i++) | |
1274 | set_immediate_dominator (CDI_DOMINATORS, bb, NULL); | |
1275 | } | |
1276 | ||
1277 | prune_bbs_to_update_dominators (bbs, conservative); | |
1278 | n = VEC_length (basic_block, bbs); | |
1279 | ||
1280 | if (n == 0) | |
1281 | return; | |
e7bd94cc | 1282 | |
66f97d31 | 1283 | if (n == 1) |
355be0dc | 1284 | { |
66f97d31 ZD |
1285 | bb = VEC_index (basic_block, bbs, 0); |
1286 | set_immediate_dominator (CDI_DOMINATORS, bb, | |
1287 | recompute_dominator (CDI_DOMINATORS, bb)); | |
1288 | return; | |
1289 | } | |
1290 | ||
1291 | /* Construct the graph G. */ | |
1292 | map = pointer_map_create (); | |
1293 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb); i++) | |
1294 | { | |
1295 | /* If the dominance tree is conservatively correct, split it now. */ | |
1296 | if (conservative) | |
1297 | set_immediate_dominator (CDI_DOMINATORS, bb, NULL); | |
1298 | *pointer_map_insert (map, bb) = (void *) (size_t) i; | |
1299 | } | |
1300 | *pointer_map_insert (map, ENTRY_BLOCK_PTR) = (void *) (size_t) n; | |
1301 | ||
1302 | g = new_graph (n + 1); | |
1303 | for (y = 0; y < g->n_vertices; y++) | |
1304 | g->vertices[y].data = BITMAP_ALLOC (NULL); | |
1305 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb); i++) | |
1306 | { | |
1307 | FOR_EACH_EDGE (e, ei, bb->preds) | |
355be0dc | 1308 | { |
66f97d31 ZD |
1309 | dom = root_of_dom_tree (CDI_DOMINATORS, e->src); |
1310 | if (dom == bb) | |
1311 | continue; | |
1312 | ||
1313 | dom_i = (size_t) *pointer_map_contains (map, dom); | |
1314 | ||
1315 | /* Do not include parallel edges to G. */ | |
f883e0a7 | 1316 | if (bitmap_bit_p ((bitmap) g->vertices[dom_i].data, i)) |
66f97d31 ZD |
1317 | continue; |
1318 | ||
f883e0a7 | 1319 | bitmap_set_bit ((bitmap) g->vertices[dom_i].data, i); |
66f97d31 | 1320 | add_edge (g, dom_i, i); |
f8032688 MM |
1321 | } |
1322 | } | |
66f97d31 ZD |
1323 | for (y = 0; y < g->n_vertices; y++) |
1324 | BITMAP_FREE (g->vertices[y].data); | |
1325 | pointer_map_destroy (map); | |
1326 | ||
1327 | /* Find the dominator tree of G. */ | |
1328 | son = XNEWVEC (int, n + 1); | |
1329 | brother = XNEWVEC (int, n + 1); | |
1330 | parent = XNEWVEC (int, n + 1); | |
1331 | graphds_domtree (g, n, parent, son, brother); | |
1332 | ||
1333 | /* Finally, traverse the tree and find the immediate dominators. */ | |
1334 | for (y = n; son[y] != -1; y = son[y]) | |
1335 | continue; | |
1336 | while (y != -1) | |
1337 | { | |
1338 | determine_dominators_for_sons (g, bbs, y, son, brother); | |
1339 | ||
1340 | if (brother[y] != -1) | |
1341 | { | |
1342 | y = brother[y]; | |
1343 | while (son[y] != -1) | |
1344 | y = son[y]; | |
1345 | } | |
1346 | else | |
1347 | y = parent[y]; | |
1348 | } | |
1349 | ||
1350 | free (son); | |
1351 | free (brother); | |
1352 | free (parent); | |
e7bd94cc | 1353 | |
66f97d31 | 1354 | free_graph (g); |
355be0dc | 1355 | } |
f8032688 | 1356 | |
355be0dc | 1357 | void |
d47cc544 | 1358 | add_to_dominance_info (enum cdi_direction dir, basic_block bb) |
355be0dc | 1359 | { |
2b28c07a JC |
1360 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1361 | ||
1362 | gcc_assert (dom_computed[dir_index]); | |
1363 | gcc_assert (!bb->dom[dir_index]); | |
d47cc544 | 1364 | |
2b28c07a | 1365 | n_bbs_in_dom_tree[dir_index]++; |
6de9cd9a | 1366 | |
2b28c07a | 1367 | bb->dom[dir_index] = et_new_tree (bb); |
d47cc544 | 1368 | |
2b28c07a JC |
1369 | if (dom_computed[dir_index] == DOM_OK) |
1370 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
1371 | } |
1372 | ||
1373 | void | |
d47cc544 SB |
1374 | delete_from_dominance_info (enum cdi_direction dir, basic_block bb) |
1375 | { | |
2b28c07a | 1376 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
d47cc544 | 1377 | |
2b28c07a | 1378 | gcc_assert (dom_computed[dir_index]); |
d47cc544 | 1379 | |
2b28c07a JC |
1380 | et_free_tree (bb->dom[dir_index]); |
1381 | bb->dom[dir_index] = NULL; | |
1382 | n_bbs_in_dom_tree[dir_index]--; | |
1383 | ||
1384 | if (dom_computed[dir_index] == DOM_OK) | |
1385 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
d47cc544 SB |
1386 | } |
1387 | ||
1388 | /* Returns the first son of BB in the dominator or postdominator tree | |
1389 | as determined by DIR. */ | |
1390 | ||
1391 | basic_block | |
1392 | first_dom_son (enum cdi_direction dir, basic_block bb) | |
355be0dc | 1393 | { |
2b28c07a JC |
1394 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1395 | struct et_node *son = bb->dom[dir_index]->son; | |
d47cc544 | 1396 | |
f883e0a7 | 1397 | return (basic_block) (son ? son->data : NULL); |
d47cc544 SB |
1398 | } |
1399 | ||
1400 | /* Returns the next dominance son after BB in the dominator or postdominator | |
1401 | tree as determined by DIR, or NULL if it was the last one. */ | |
1402 | ||
1403 | basic_block | |
1404 | next_dom_son (enum cdi_direction dir, basic_block bb) | |
1405 | { | |
2b28c07a JC |
1406 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1407 | struct et_node *next = bb->dom[dir_index]->right; | |
d47cc544 | 1408 | |
f883e0a7 | 1409 | return (basic_block) (next->father->son == next ? NULL : next->data); |
355be0dc JH |
1410 | } |
1411 | ||
2b28c07a JC |
1412 | /* Return dominance availability for dominance info DIR. */ |
1413 | ||
1414 | enum dom_state | |
1415 | dom_info_state (enum cdi_direction dir) | |
1416 | { | |
1417 | unsigned int dir_index = dom_convert_dir_to_idx (dir); | |
1418 | ||
1419 | return dom_computed[dir_index]; | |
1420 | } | |
1421 | ||
1422 | /* Set the dominance availability for dominance info DIR to NEW_STATE. */ | |
1423 | ||
1424 | void | |
1425 | set_dom_info_availability (enum cdi_direction dir, enum dom_state new_state) | |
1426 | { | |
1427 | unsigned int dir_index = dom_convert_dir_to_idx (dir); | |
1428 | ||
1429 | dom_computed[dir_index] = new_state; | |
1430 | } | |
1431 | ||
fce22de5 ZD |
1432 | /* Returns true if dominance information for direction DIR is available. */ |
1433 | ||
1434 | bool | |
1435 | dom_info_available_p (enum cdi_direction dir) | |
1436 | { | |
2b28c07a JC |
1437 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1438 | ||
1439 | return dom_computed[dir_index] != DOM_NONE; | |
fce22de5 ZD |
1440 | } |
1441 | ||
355be0dc | 1442 | void |
d47cc544 | 1443 | debug_dominance_info (enum cdi_direction dir) |
355be0dc JH |
1444 | { |
1445 | basic_block bb, bb2; | |
1446 | FOR_EACH_BB (bb) | |
d47cc544 | 1447 | if ((bb2 = get_immediate_dominator (dir, bb))) |
355be0dc | 1448 | fprintf (stderr, "%i %i\n", bb->index, bb2->index); |
f8032688 | 1449 | } |
1fc3998d ZD |
1450 | |
1451 | /* Prints to stderr representation of the dominance tree (for direction DIR) | |
cea618ac | 1452 | rooted in ROOT, indented by INDENT tabulators. If INDENT_FIRST is false, |
1fc3998d ZD |
1453 | the first line of the output is not indented. */ |
1454 | ||
1455 | static void | |
1456 | debug_dominance_tree_1 (enum cdi_direction dir, basic_block root, | |
1457 | unsigned indent, bool indent_first) | |
1458 | { | |
1459 | basic_block son; | |
1460 | unsigned i; | |
1461 | bool first = true; | |
1462 | ||
1463 | if (indent_first) | |
1464 | for (i = 0; i < indent; i++) | |
1465 | fprintf (stderr, "\t"); | |
1466 | fprintf (stderr, "%d\t", root->index); | |
1467 | ||
1468 | for (son = first_dom_son (dir, root); | |
1469 | son; | |
1470 | son = next_dom_son (dir, son)) | |
1471 | { | |
1472 | debug_dominance_tree_1 (dir, son, indent + 1, !first); | |
1473 | first = false; | |
1474 | } | |
1475 | ||
1476 | if (first) | |
1477 | fprintf (stderr, "\n"); | |
1478 | } | |
1479 | ||
1480 | /* Prints to stderr representation of the dominance tree (for direction DIR) | |
1481 | rooted in ROOT. */ | |
1482 | ||
1483 | void | |
1484 | debug_dominance_tree (enum cdi_direction dir, basic_block root) | |
1485 | { | |
1486 | debug_dominance_tree_1 (dir, root, 0, false); | |
1487 | } |