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f8032688 | 1 | /* Calculate (post)dominators in slightly super-linear time. |
6fb5fa3c | 2 | Copyright (C) 2000, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc. |
f8032688 | 3 | Contributed by Michael Matz (matz@ifh.de). |
3a538a66 | 4 | |
1322177d | 5 | This file is part of GCC. |
3a538a66 | 6 | |
1322177d LB |
7 | GCC is free software; you can redistribute it and/or modify it |
8 | under the terms of the GNU General Public License as published by | |
f8032688 MM |
9 | the Free Software Foundation; either version 2, or (at your option) |
10 | any later version. | |
11 | ||
1322177d LB |
12 | GCC is distributed in the hope that it will be useful, but WITHOUT |
13 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY | |
14 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public | |
15 | License for more details. | |
f8032688 MM |
16 | |
17 | You should have received a copy of the GNU General Public License | |
1322177d | 18 | along with GCC; see the file COPYING. If not, write to the Free |
366ccddb KC |
19 | Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA |
20 | 02110-1301, USA. */ | |
f8032688 MM |
21 | |
22 | /* This file implements the well known algorithm from Lengauer and Tarjan | |
23 | to compute the dominators in a control flow graph. A basic block D is said | |
24 | to dominate another block X, when all paths from the entry node of the CFG | |
25 | to X go also over D. The dominance relation is a transitive reflexive | |
26 | relation and its minimal transitive reduction is a tree, called the | |
27 | dominator tree. So for each block X besides the entry block exists a | |
28 | block I(X), called the immediate dominator of X, which is the parent of X | |
29 | in the dominator tree. | |
30 | ||
a1f300c0 | 31 | The algorithm computes this dominator tree implicitly by computing for |
f8032688 | 32 | each block its immediate dominator. We use tree balancing and path |
f3b569ca | 33 | compression, so it's the O(e*a(e,v)) variant, where a(e,v) is the very |
f8032688 MM |
34 | slowly growing functional inverse of the Ackerman function. */ |
35 | ||
36 | #include "config.h" | |
37 | #include "system.h" | |
4977bab6 ZW |
38 | #include "coretypes.h" |
39 | #include "tm.h" | |
f8032688 MM |
40 | #include "rtl.h" |
41 | #include "hard-reg-set.h" | |
7932a3db | 42 | #include "obstack.h" |
f8032688 | 43 | #include "basic-block.h" |
4c714dd4 | 44 | #include "toplev.h" |
355be0dc | 45 | #include "et-forest.h" |
74c96e0c | 46 | #include "timevar.h" |
66f97d31 ZD |
47 | #include "vecprim.h" |
48 | #include "pointer-set.h" | |
49 | #include "graphds.h" | |
f8032688 | 50 | |
d47cc544 | 51 | /* Whether the dominators and the postdominators are available. */ |
2b28c07a | 52 | static enum dom_state dom_computed[2]; |
f8032688 MM |
53 | |
54 | /* We name our nodes with integers, beginning with 1. Zero is reserved for | |
55 | 'undefined' or 'end of list'. The name of each node is given by the dfs | |
56 | number of the corresponding basic block. Please note, that we include the | |
57 | artificial ENTRY_BLOCK (or EXIT_BLOCK in the post-dom case) in our lists to | |
24bd1a0b | 58 | support multiple entry points. Its dfs number is of course 1. */ |
f8032688 MM |
59 | |
60 | /* Type of Basic Block aka. TBB */ | |
61 | typedef unsigned int TBB; | |
62 | ||
63 | /* We work in a poor-mans object oriented fashion, and carry an instance of | |
64 | this structure through all our 'methods'. It holds various arrays | |
65 | reflecting the (sub)structure of the flowgraph. Most of them are of type | |
66 | TBB and are also indexed by TBB. */ | |
67 | ||
68 | struct dom_info | |
69 | { | |
70 | /* The parent of a node in the DFS tree. */ | |
71 | TBB *dfs_parent; | |
72 | /* For a node x key[x] is roughly the node nearest to the root from which | |
73 | exists a way to x only over nodes behind x. Such a node is also called | |
74 | semidominator. */ | |
75 | TBB *key; | |
76 | /* The value in path_min[x] is the node y on the path from x to the root of | |
77 | the tree x is in with the smallest key[y]. */ | |
78 | TBB *path_min; | |
79 | /* bucket[x] points to the first node of the set of nodes having x as key. */ | |
80 | TBB *bucket; | |
81 | /* And next_bucket[x] points to the next node. */ | |
82 | TBB *next_bucket; | |
83 | /* After the algorithm is done, dom[x] contains the immediate dominator | |
84 | of x. */ | |
85 | TBB *dom; | |
86 | ||
87 | /* The following few fields implement the structures needed for disjoint | |
88 | sets. */ | |
89 | /* set_chain[x] is the next node on the path from x to the representant | |
90 | of the set containing x. If set_chain[x]==0 then x is a root. */ | |
91 | TBB *set_chain; | |
92 | /* set_size[x] is the number of elements in the set named by x. */ | |
93 | unsigned int *set_size; | |
94 | /* set_child[x] is used for balancing the tree representing a set. It can | |
95 | be understood as the next sibling of x. */ | |
96 | TBB *set_child; | |
97 | ||
98 | /* If b is the number of a basic block (BB->index), dfs_order[b] is the | |
99 | number of that node in DFS order counted from 1. This is an index | |
100 | into most of the other arrays in this structure. */ | |
101 | TBB *dfs_order; | |
09da1532 | 102 | /* If x is the DFS-index of a node which corresponds with a basic block, |
f8032688 MM |
103 | dfs_to_bb[x] is that basic block. Note, that in our structure there are |
104 | more nodes that basic blocks, so only dfs_to_bb[dfs_order[bb->index]]==bb | |
105 | is true for every basic block bb, but not the opposite. */ | |
106 | basic_block *dfs_to_bb; | |
107 | ||
26e0e410 | 108 | /* This is the next free DFS number when creating the DFS tree. */ |
f8032688 MM |
109 | unsigned int dfsnum; |
110 | /* The number of nodes in the DFS tree (==dfsnum-1). */ | |
111 | unsigned int nodes; | |
26e0e410 RH |
112 | |
113 | /* Blocks with bits set here have a fake edge to EXIT. These are used | |
114 | to turn a DFS forest into a proper tree. */ | |
115 | bitmap fake_exit_edge; | |
f8032688 MM |
116 | }; |
117 | ||
26e0e410 | 118 | static void init_dom_info (struct dom_info *, enum cdi_direction); |
7080f735 | 119 | static void free_dom_info (struct dom_info *); |
2b28c07a JC |
120 | static void calc_dfs_tree_nonrec (struct dom_info *, basic_block, bool); |
121 | static void calc_dfs_tree (struct dom_info *, bool); | |
7080f735 AJ |
122 | static void compress (struct dom_info *, TBB); |
123 | static TBB eval (struct dom_info *, TBB); | |
124 | static void link_roots (struct dom_info *, TBB, TBB); | |
2b28c07a | 125 | static void calc_idoms (struct dom_info *, bool); |
d47cc544 | 126 | void debug_dominance_info (enum cdi_direction); |
1fc3998d | 127 | void debug_dominance_tree (enum cdi_direction, basic_block); |
f8032688 | 128 | |
6de9cd9a DN |
129 | /* Keeps track of the*/ |
130 | static unsigned n_bbs_in_dom_tree[2]; | |
131 | ||
f8032688 MM |
132 | /* Helper macro for allocating and initializing an array, |
133 | for aesthetic reasons. */ | |
134 | #define init_ar(var, type, num, content) \ | |
3a538a66 KH |
135 | do \ |
136 | { \ | |
137 | unsigned int i = 1; /* Catch content == i. */ \ | |
138 | if (! (content)) \ | |
5ed6ace5 | 139 | (var) = XCNEWVEC (type, num); \ |
3a538a66 KH |
140 | else \ |
141 | { \ | |
5ed6ace5 | 142 | (var) = XNEWVEC (type, (num)); \ |
3a538a66 KH |
143 | for (i = 0; i < num; i++) \ |
144 | (var)[i] = (content); \ | |
145 | } \ | |
146 | } \ | |
147 | while (0) | |
f8032688 MM |
148 | |
149 | /* Allocate all needed memory in a pessimistic fashion (so we round up). | |
4912a07c | 150 | This initializes the contents of DI, which already must be allocated. */ |
f8032688 MM |
151 | |
152 | static void | |
26e0e410 | 153 | init_dom_info (struct dom_info *di, enum cdi_direction dir) |
f8032688 | 154 | { |
6fb5fa3c | 155 | /* We need memory for n_basic_blocks nodes. */ |
24bd1a0b | 156 | unsigned int num = n_basic_blocks; |
f8032688 MM |
157 | init_ar (di->dfs_parent, TBB, num, 0); |
158 | init_ar (di->path_min, TBB, num, i); | |
159 | init_ar (di->key, TBB, num, i); | |
160 | init_ar (di->dom, TBB, num, 0); | |
161 | ||
162 | init_ar (di->bucket, TBB, num, 0); | |
163 | init_ar (di->next_bucket, TBB, num, 0); | |
164 | ||
165 | init_ar (di->set_chain, TBB, num, 0); | |
166 | init_ar (di->set_size, unsigned int, num, 1); | |
167 | init_ar (di->set_child, TBB, num, 0); | |
168 | ||
d55bc081 | 169 | init_ar (di->dfs_order, TBB, (unsigned int) last_basic_block + 1, 0); |
f8032688 MM |
170 | init_ar (di->dfs_to_bb, basic_block, num, 0); |
171 | ||
172 | di->dfsnum = 1; | |
173 | di->nodes = 0; | |
26e0e410 | 174 | |
2b28c07a JC |
175 | switch (dir) |
176 | { | |
177 | case CDI_DOMINATORS: | |
178 | di->fake_exit_edge = NULL; | |
179 | break; | |
180 | case CDI_POST_DOMINATORS: | |
181 | di->fake_exit_edge = BITMAP_ALLOC (NULL); | |
182 | break; | |
183 | default: | |
184 | gcc_unreachable (); | |
185 | break; | |
186 | } | |
f8032688 MM |
187 | } |
188 | ||
189 | #undef init_ar | |
190 | ||
2b28c07a JC |
191 | /* Map dominance calculation type to array index used for various |
192 | dominance information arrays. This version is simple -- it will need | |
193 | to be modified, obviously, if additional values are added to | |
194 | cdi_direction. */ | |
195 | ||
196 | static unsigned int | |
197 | dom_convert_dir_to_idx (enum cdi_direction dir) | |
198 | { | |
199 | gcc_assert (dir == CDI_DOMINATORS || dir == CDI_POST_DOMINATORS); | |
200 | return dir - 1; | |
201 | } | |
202 | ||
f8032688 MM |
203 | /* Free all allocated memory in DI, but not DI itself. */ |
204 | ||
205 | static void | |
7080f735 | 206 | free_dom_info (struct dom_info *di) |
f8032688 MM |
207 | { |
208 | free (di->dfs_parent); | |
209 | free (di->path_min); | |
210 | free (di->key); | |
211 | free (di->dom); | |
212 | free (di->bucket); | |
213 | free (di->next_bucket); | |
214 | free (di->set_chain); | |
215 | free (di->set_size); | |
216 | free (di->set_child); | |
217 | free (di->dfs_order); | |
218 | free (di->dfs_to_bb); | |
8bdbfff5 | 219 | BITMAP_FREE (di->fake_exit_edge); |
f8032688 MM |
220 | } |
221 | ||
222 | /* The nonrecursive variant of creating a DFS tree. DI is our working | |
223 | structure, BB the starting basic block for this tree and REVERSE | |
224 | is true, if predecessors should be visited instead of successors of a | |
225 | node. After this is done all nodes reachable from BB were visited, have | |
226 | assigned their dfs number and are linked together to form a tree. */ | |
227 | ||
228 | static void | |
2b28c07a | 229 | calc_dfs_tree_nonrec (struct dom_info *di, basic_block bb, bool reverse) |
f8032688 | 230 | { |
f8032688 MM |
231 | /* We call this _only_ if bb is not already visited. */ |
232 | edge e; | |
233 | TBB child_i, my_i = 0; | |
628f6a4e BE |
234 | edge_iterator *stack; |
235 | edge_iterator ei, einext; | |
f8032688 MM |
236 | int sp; |
237 | /* Start block (ENTRY_BLOCK_PTR for forward problem, EXIT_BLOCK for backward | |
238 | problem). */ | |
239 | basic_block en_block; | |
240 | /* Ending block. */ | |
241 | basic_block ex_block; | |
242 | ||
5ed6ace5 | 243 | stack = XNEWVEC (edge_iterator, n_basic_blocks + 1); |
f8032688 MM |
244 | sp = 0; |
245 | ||
246 | /* Initialize our border blocks, and the first edge. */ | |
247 | if (reverse) | |
248 | { | |
628f6a4e | 249 | ei = ei_start (bb->preds); |
f8032688 MM |
250 | en_block = EXIT_BLOCK_PTR; |
251 | ex_block = ENTRY_BLOCK_PTR; | |
252 | } | |
253 | else | |
254 | { | |
628f6a4e | 255 | ei = ei_start (bb->succs); |
f8032688 MM |
256 | en_block = ENTRY_BLOCK_PTR; |
257 | ex_block = EXIT_BLOCK_PTR; | |
258 | } | |
259 | ||
260 | /* When the stack is empty we break out of this loop. */ | |
261 | while (1) | |
262 | { | |
263 | basic_block bn; | |
264 | ||
265 | /* This loop traverses edges e in depth first manner, and fills the | |
266 | stack. */ | |
628f6a4e | 267 | while (!ei_end_p (ei)) |
f8032688 | 268 | { |
628f6a4e | 269 | e = ei_edge (ei); |
f8032688 MM |
270 | |
271 | /* Deduce from E the current and the next block (BB and BN), and the | |
272 | next edge. */ | |
273 | if (reverse) | |
274 | { | |
275 | bn = e->src; | |
276 | ||
277 | /* If the next node BN is either already visited or a border | |
278 | block the current edge is useless, and simply overwritten | |
279 | with the next edge out of the current node. */ | |
0b17ab2f | 280 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 | 281 | { |
628f6a4e | 282 | ei_next (&ei); |
f8032688 MM |
283 | continue; |
284 | } | |
285 | bb = e->dest; | |
628f6a4e | 286 | einext = ei_start (bn->preds); |
f8032688 MM |
287 | } |
288 | else | |
289 | { | |
290 | bn = e->dest; | |
0b17ab2f | 291 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 | 292 | { |
628f6a4e | 293 | ei_next (&ei); |
f8032688 MM |
294 | continue; |
295 | } | |
296 | bb = e->src; | |
628f6a4e | 297 | einext = ei_start (bn->succs); |
f8032688 MM |
298 | } |
299 | ||
ced3f397 | 300 | gcc_assert (bn != en_block); |
f8032688 MM |
301 | |
302 | /* Fill the DFS tree info calculatable _before_ recursing. */ | |
303 | if (bb != en_block) | |
0b17ab2f | 304 | my_i = di->dfs_order[bb->index]; |
f8032688 | 305 | else |
d55bc081 | 306 | my_i = di->dfs_order[last_basic_block]; |
0b17ab2f | 307 | child_i = di->dfs_order[bn->index] = di->dfsnum++; |
f8032688 MM |
308 | di->dfs_to_bb[child_i] = bn; |
309 | di->dfs_parent[child_i] = my_i; | |
310 | ||
311 | /* Save the current point in the CFG on the stack, and recurse. */ | |
628f6a4e BE |
312 | stack[sp++] = ei; |
313 | ei = einext; | |
f8032688 MM |
314 | } |
315 | ||
316 | if (!sp) | |
317 | break; | |
628f6a4e | 318 | ei = stack[--sp]; |
f8032688 MM |
319 | |
320 | /* OK. The edge-list was exhausted, meaning normally we would | |
321 | end the recursion. After returning from the recursive call, | |
322 | there were (may be) other statements which were run after a | |
323 | child node was completely considered by DFS. Here is the | |
324 | point to do it in the non-recursive variant. | |
325 | E.g. The block just completed is in e->dest for forward DFS, | |
326 | the block not yet completed (the parent of the one above) | |
327 | in e->src. This could be used e.g. for computing the number of | |
328 | descendants or the tree depth. */ | |
628f6a4e | 329 | ei_next (&ei); |
f8032688 MM |
330 | } |
331 | free (stack); | |
332 | } | |
333 | ||
334 | /* The main entry for calculating the DFS tree or forest. DI is our working | |
335 | structure and REVERSE is true, if we are interested in the reverse flow | |
336 | graph. In that case the result is not necessarily a tree but a forest, | |
337 | because there may be nodes from which the EXIT_BLOCK is unreachable. */ | |
338 | ||
339 | static void | |
2b28c07a | 340 | calc_dfs_tree (struct dom_info *di, bool reverse) |
f8032688 MM |
341 | { |
342 | /* The first block is the ENTRY_BLOCK (or EXIT_BLOCK if REVERSE). */ | |
343 | basic_block begin = reverse ? EXIT_BLOCK_PTR : ENTRY_BLOCK_PTR; | |
d55bc081 | 344 | di->dfs_order[last_basic_block] = di->dfsnum; |
f8032688 MM |
345 | di->dfs_to_bb[di->dfsnum] = begin; |
346 | di->dfsnum++; | |
347 | ||
348 | calc_dfs_tree_nonrec (di, begin, reverse); | |
349 | ||
350 | if (reverse) | |
351 | { | |
352 | /* In the post-dom case we may have nodes without a path to EXIT_BLOCK. | |
353 | They are reverse-unreachable. In the dom-case we disallow such | |
26e0e410 RH |
354 | nodes, but in post-dom we have to deal with them. |
355 | ||
356 | There are two situations in which this occurs. First, noreturn | |
357 | functions. Second, infinite loops. In the first case we need to | |
358 | pretend that there is an edge to the exit block. In the second | |
359 | case, we wind up with a forest. We need to process all noreturn | |
360 | blocks before we know if we've got any infinite loops. */ | |
361 | ||
e0082a72 | 362 | basic_block b; |
26e0e410 RH |
363 | bool saw_unconnected = false; |
364 | ||
e0082a72 | 365 | FOR_EACH_BB_REVERSE (b) |
f8032688 | 366 | { |
628f6a4e | 367 | if (EDGE_COUNT (b->succs) > 0) |
26e0e410 RH |
368 | { |
369 | if (di->dfs_order[b->index] == 0) | |
370 | saw_unconnected = true; | |
371 | continue; | |
372 | } | |
373 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
0b17ab2f | 374 | di->dfs_order[b->index] = di->dfsnum; |
f8032688 | 375 | di->dfs_to_bb[di->dfsnum] = b; |
26e0e410 | 376 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; |
f8032688 MM |
377 | di->dfsnum++; |
378 | calc_dfs_tree_nonrec (di, b, reverse); | |
379 | } | |
26e0e410 RH |
380 | |
381 | if (saw_unconnected) | |
382 | { | |
383 | FOR_EACH_BB_REVERSE (b) | |
384 | { | |
385 | if (di->dfs_order[b->index]) | |
386 | continue; | |
387 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
388 | di->dfs_order[b->index] = di->dfsnum; | |
389 | di->dfs_to_bb[di->dfsnum] = b; | |
390 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; | |
391 | di->dfsnum++; | |
392 | calc_dfs_tree_nonrec (di, b, reverse); | |
393 | } | |
394 | } | |
f8032688 MM |
395 | } |
396 | ||
397 | di->nodes = di->dfsnum - 1; | |
398 | ||
24bd1a0b DB |
399 | /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. */ |
400 | gcc_assert (di->nodes == (unsigned int) n_basic_blocks - 1); | |
f8032688 MM |
401 | } |
402 | ||
403 | /* Compress the path from V to the root of its set and update path_min at the | |
404 | same time. After compress(di, V) set_chain[V] is the root of the set V is | |
405 | in and path_min[V] is the node with the smallest key[] value on the path | |
406 | from V to that root. */ | |
407 | ||
408 | static void | |
7080f735 | 409 | compress (struct dom_info *di, TBB v) |
f8032688 MM |
410 | { |
411 | /* Btw. It's not worth to unrecurse compress() as the depth is usually not | |
412 | greater than 5 even for huge graphs (I've not seen call depth > 4). | |
413 | Also performance wise compress() ranges _far_ behind eval(). */ | |
414 | TBB parent = di->set_chain[v]; | |
415 | if (di->set_chain[parent]) | |
416 | { | |
417 | compress (di, parent); | |
418 | if (di->key[di->path_min[parent]] < di->key[di->path_min[v]]) | |
419 | di->path_min[v] = di->path_min[parent]; | |
420 | di->set_chain[v] = di->set_chain[parent]; | |
421 | } | |
422 | } | |
423 | ||
424 | /* Compress the path from V to the set root of V if needed (when the root has | |
425 | changed since the last call). Returns the node with the smallest key[] | |
426 | value on the path from V to the root. */ | |
427 | ||
428 | static inline TBB | |
7080f735 | 429 | eval (struct dom_info *di, TBB v) |
f8032688 MM |
430 | { |
431 | /* The representant of the set V is in, also called root (as the set | |
432 | representation is a tree). */ | |
433 | TBB rep = di->set_chain[v]; | |
434 | ||
435 | /* V itself is the root. */ | |
436 | if (!rep) | |
437 | return di->path_min[v]; | |
438 | ||
439 | /* Compress only if necessary. */ | |
440 | if (di->set_chain[rep]) | |
441 | { | |
442 | compress (di, v); | |
443 | rep = di->set_chain[v]; | |
444 | } | |
445 | ||
446 | if (di->key[di->path_min[rep]] >= di->key[di->path_min[v]]) | |
447 | return di->path_min[v]; | |
448 | else | |
449 | return di->path_min[rep]; | |
450 | } | |
451 | ||
452 | /* This essentially merges the two sets of V and W, giving a single set with | |
453 | the new root V. The internal representation of these disjoint sets is a | |
454 | balanced tree. Currently link(V,W) is only used with V being the parent | |
455 | of W. */ | |
456 | ||
457 | static void | |
7080f735 | 458 | link_roots (struct dom_info *di, TBB v, TBB w) |
f8032688 MM |
459 | { |
460 | TBB s = w; | |
461 | ||
462 | /* Rebalance the tree. */ | |
463 | while (di->key[di->path_min[w]] < di->key[di->path_min[di->set_child[s]]]) | |
464 | { | |
465 | if (di->set_size[s] + di->set_size[di->set_child[di->set_child[s]]] | |
466 | >= 2 * di->set_size[di->set_child[s]]) | |
467 | { | |
468 | di->set_chain[di->set_child[s]] = s; | |
469 | di->set_child[s] = di->set_child[di->set_child[s]]; | |
470 | } | |
471 | else | |
472 | { | |
473 | di->set_size[di->set_child[s]] = di->set_size[s]; | |
474 | s = di->set_chain[s] = di->set_child[s]; | |
475 | } | |
476 | } | |
477 | ||
478 | di->path_min[s] = di->path_min[w]; | |
479 | di->set_size[v] += di->set_size[w]; | |
480 | if (di->set_size[v] < 2 * di->set_size[w]) | |
481 | { | |
482 | TBB tmp = s; | |
483 | s = di->set_child[v]; | |
484 | di->set_child[v] = tmp; | |
485 | } | |
486 | ||
487 | /* Merge all subtrees. */ | |
488 | while (s) | |
489 | { | |
490 | di->set_chain[s] = v; | |
491 | s = di->set_child[s]; | |
492 | } | |
493 | } | |
494 | ||
495 | /* This calculates the immediate dominators (or post-dominators if REVERSE is | |
496 | true). DI is our working structure and should hold the DFS forest. | |
497 | On return the immediate dominator to node V is in di->dom[V]. */ | |
498 | ||
499 | static void | |
2b28c07a | 500 | calc_idoms (struct dom_info *di, bool reverse) |
f8032688 MM |
501 | { |
502 | TBB v, w, k, par; | |
503 | basic_block en_block; | |
628f6a4e BE |
504 | edge_iterator ei, einext; |
505 | ||
f8032688 MM |
506 | if (reverse) |
507 | en_block = EXIT_BLOCK_PTR; | |
508 | else | |
509 | en_block = ENTRY_BLOCK_PTR; | |
510 | ||
511 | /* Go backwards in DFS order, to first look at the leafs. */ | |
512 | v = di->nodes; | |
513 | while (v > 1) | |
514 | { | |
515 | basic_block bb = di->dfs_to_bb[v]; | |
628f6a4e | 516 | edge e; |
f8032688 MM |
517 | |
518 | par = di->dfs_parent[v]; | |
519 | k = v; | |
628f6a4e BE |
520 | |
521 | ei = (reverse) ? ei_start (bb->succs) : ei_start (bb->preds); | |
522 | ||
f8032688 | 523 | if (reverse) |
26e0e410 | 524 | { |
26e0e410 RH |
525 | /* If this block has a fake edge to exit, process that first. */ |
526 | if (bitmap_bit_p (di->fake_exit_edge, bb->index)) | |
527 | { | |
628f6a4e BE |
528 | einext = ei; |
529 | einext.index = 0; | |
26e0e410 RH |
530 | goto do_fake_exit_edge; |
531 | } | |
532 | } | |
f8032688 MM |
533 | |
534 | /* Search all direct predecessors for the smallest node with a path | |
535 | to them. That way we have the smallest node with also a path to | |
536 | us only over nodes behind us. In effect we search for our | |
537 | semidominator. */ | |
628f6a4e | 538 | while (!ei_end_p (ei)) |
f8032688 MM |
539 | { |
540 | TBB k1; | |
541 | basic_block b; | |
542 | ||
628f6a4e BE |
543 | e = ei_edge (ei); |
544 | b = (reverse) ? e->dest : e->src; | |
545 | einext = ei; | |
546 | ei_next (&einext); | |
547 | ||
f8032688 | 548 | if (b == en_block) |
26e0e410 RH |
549 | { |
550 | do_fake_exit_edge: | |
551 | k1 = di->dfs_order[last_basic_block]; | |
552 | } | |
f8032688 | 553 | else |
0b17ab2f | 554 | k1 = di->dfs_order[b->index]; |
f8032688 MM |
555 | |
556 | /* Call eval() only if really needed. If k1 is above V in DFS tree, | |
557 | then we know, that eval(k1) == k1 and key[k1] == k1. */ | |
558 | if (k1 > v) | |
559 | k1 = di->key[eval (di, k1)]; | |
560 | if (k1 < k) | |
561 | k = k1; | |
628f6a4e BE |
562 | |
563 | ei = einext; | |
f8032688 MM |
564 | } |
565 | ||
566 | di->key[v] = k; | |
567 | link_roots (di, par, v); | |
568 | di->next_bucket[v] = di->bucket[k]; | |
569 | di->bucket[k] = v; | |
570 | ||
571 | /* Transform semidominators into dominators. */ | |
572 | for (w = di->bucket[par]; w; w = di->next_bucket[w]) | |
573 | { | |
574 | k = eval (di, w); | |
575 | if (di->key[k] < di->key[w]) | |
576 | di->dom[w] = k; | |
577 | else | |
578 | di->dom[w] = par; | |
579 | } | |
580 | /* We don't need to cleanup next_bucket[]. */ | |
581 | di->bucket[par] = 0; | |
582 | v--; | |
583 | } | |
584 | ||
a1f300c0 | 585 | /* Explicitly define the dominators. */ |
f8032688 MM |
586 | di->dom[1] = 0; |
587 | for (v = 2; v <= di->nodes; v++) | |
588 | if (di->dom[v] != di->key[v]) | |
589 | di->dom[v] = di->dom[di->dom[v]]; | |
590 | } | |
591 | ||
d47cc544 SB |
592 | /* Assign dfs numbers starting from NUM to NODE and its sons. */ |
593 | ||
594 | static void | |
595 | assign_dfs_numbers (struct et_node *node, int *num) | |
596 | { | |
597 | struct et_node *son; | |
598 | ||
599 | node->dfs_num_in = (*num)++; | |
600 | ||
601 | if (node->son) | |
602 | { | |
603 | assign_dfs_numbers (node->son, num); | |
604 | for (son = node->son->right; son != node->son; son = son->right) | |
6de9cd9a | 605 | assign_dfs_numbers (son, num); |
d47cc544 | 606 | } |
f8032688 | 607 | |
d47cc544 SB |
608 | node->dfs_num_out = (*num)++; |
609 | } | |
f8032688 | 610 | |
5d3cc252 | 611 | /* Compute the data necessary for fast resolving of dominator queries in a |
d47cc544 | 612 | static dominator tree. */ |
f8032688 | 613 | |
d47cc544 SB |
614 | static void |
615 | compute_dom_fast_query (enum cdi_direction dir) | |
616 | { | |
617 | int num = 0; | |
618 | basic_block bb; | |
2b28c07a | 619 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
d47cc544 | 620 | |
fce22de5 | 621 | gcc_assert (dom_info_available_p (dir)); |
d47cc544 | 622 | |
2b28c07a | 623 | if (dom_computed[dir_index] == DOM_OK) |
d47cc544 SB |
624 | return; |
625 | ||
626 | FOR_ALL_BB (bb) | |
627 | { | |
2b28c07a JC |
628 | if (!bb->dom[dir_index]->father) |
629 | assign_dfs_numbers (bb->dom[dir_index], &num); | |
d47cc544 SB |
630 | } |
631 | ||
2b28c07a | 632 | dom_computed[dir_index] = DOM_OK; |
d47cc544 SB |
633 | } |
634 | ||
635 | /* The main entry point into this module. DIR is set depending on whether | |
636 | we want to compute dominators or postdominators. */ | |
637 | ||
638 | void | |
639 | calculate_dominance_info (enum cdi_direction dir) | |
f8032688 MM |
640 | { |
641 | struct dom_info di; | |
355be0dc | 642 | basic_block b; |
2b28c07a JC |
643 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
644 | bool reverse = (dir == CDI_POST_DOMINATORS) ? true : false; | |
355be0dc | 645 | |
2b28c07a | 646 | if (dom_computed[dir_index] == DOM_OK) |
d47cc544 | 647 | return; |
355be0dc | 648 | |
74c96e0c | 649 | timevar_push (TV_DOMINANCE); |
fce22de5 | 650 | if (!dom_info_available_p (dir)) |
d47cc544 | 651 | { |
2b28c07a | 652 | gcc_assert (!n_bbs_in_dom_tree[dir_index]); |
f8032688 | 653 | |
d47cc544 SB |
654 | FOR_ALL_BB (b) |
655 | { | |
2b28c07a | 656 | b->dom[dir_index] = et_new_tree (b); |
d47cc544 | 657 | } |
2b28c07a | 658 | n_bbs_in_dom_tree[dir_index] = n_basic_blocks; |
f8032688 | 659 | |
26e0e410 | 660 | init_dom_info (&di, dir); |
2b28c07a JC |
661 | calc_dfs_tree (&di, reverse); |
662 | calc_idoms (&di, reverse); | |
355be0dc | 663 | |
d47cc544 SB |
664 | FOR_EACH_BB (b) |
665 | { | |
666 | TBB d = di.dom[di.dfs_order[b->index]]; | |
667 | ||
668 | if (di.dfs_to_bb[d]) | |
2b28c07a | 669 | et_set_father (b->dom[dir_index], di.dfs_to_bb[d]->dom[dir_index]); |
d47cc544 | 670 | } |
e0082a72 | 671 | |
d47cc544 | 672 | free_dom_info (&di); |
2b28c07a | 673 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; |
355be0dc JH |
674 | } |
675 | ||
d47cc544 | 676 | compute_dom_fast_query (dir); |
74c96e0c ZD |
677 | |
678 | timevar_pop (TV_DOMINANCE); | |
355be0dc JH |
679 | } |
680 | ||
d47cc544 | 681 | /* Free dominance information for direction DIR. */ |
355be0dc | 682 | void |
d47cc544 | 683 | free_dominance_info (enum cdi_direction dir) |
355be0dc JH |
684 | { |
685 | basic_block bb; | |
2b28c07a | 686 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
355be0dc | 687 | |
fce22de5 | 688 | if (!dom_info_available_p (dir)) |
d47cc544 SB |
689 | return; |
690 | ||
691 | FOR_ALL_BB (bb) | |
692 | { | |
2b28c07a JC |
693 | et_free_tree_force (bb->dom[dir_index]); |
694 | bb->dom[dir_index] = NULL; | |
d47cc544 | 695 | } |
5a6ccafd | 696 | et_free_pools (); |
d47cc544 | 697 | |
2b28c07a | 698 | n_bbs_in_dom_tree[dir_index] = 0; |
6de9cd9a | 699 | |
2b28c07a | 700 | dom_computed[dir_index] = DOM_NONE; |
355be0dc JH |
701 | } |
702 | ||
703 | /* Return the immediate dominator of basic block BB. */ | |
704 | basic_block | |
d47cc544 | 705 | get_immediate_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 706 | { |
2b28c07a JC |
707 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
708 | struct et_node *node = bb->dom[dir_index]; | |
d47cc544 | 709 | |
2b28c07a | 710 | gcc_assert (dom_computed[dir_index]); |
d47cc544 SB |
711 | |
712 | if (!node->father) | |
713 | return NULL; | |
714 | ||
6de9cd9a | 715 | return node->father->data; |
355be0dc JH |
716 | } |
717 | ||
718 | /* Set the immediate dominator of the block possibly removing | |
719 | existing edge. NULL can be used to remove any edge. */ | |
720 | inline void | |
d47cc544 SB |
721 | set_immediate_dominator (enum cdi_direction dir, basic_block bb, |
722 | basic_block dominated_by) | |
355be0dc | 723 | { |
2b28c07a JC |
724 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
725 | struct et_node *node = bb->dom[dir_index]; | |
726 | ||
727 | gcc_assert (dom_computed[dir_index]); | |
355be0dc | 728 | |
d47cc544 | 729 | if (node->father) |
355be0dc | 730 | { |
d47cc544 | 731 | if (node->father->data == dominated_by) |
6de9cd9a | 732 | return; |
d47cc544 | 733 | et_split (node); |
355be0dc | 734 | } |
d47cc544 SB |
735 | |
736 | if (dominated_by) | |
2b28c07a | 737 | et_set_father (node, dominated_by->dom[dir_index]); |
d47cc544 | 738 | |
2b28c07a JC |
739 | if (dom_computed[dir_index] == DOM_OK) |
740 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
741 | } |
742 | ||
66f97d31 ZD |
743 | /* Returns the list of basic blocks immediately dominated by BB, in the |
744 | direction DIR. */ | |
745 | VEC (basic_block, heap) * | |
746 | get_dominated_by (enum cdi_direction dir, basic_block bb) | |
355be0dc | 747 | { |
d47cc544 | 748 | int n; |
66f97d31 | 749 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
2b28c07a | 750 | struct et_node *node = bb->dom[dir_index], *son = node->son, *ason; |
66f97d31 ZD |
751 | VEC (basic_block, heap) *bbs = NULL; |
752 | ||
2b28c07a | 753 | gcc_assert (dom_computed[dir_index]); |
d47cc544 SB |
754 | |
755 | if (!son) | |
66f97d31 | 756 | return NULL; |
d47cc544 | 757 | |
66f97d31 | 758 | VEC_safe_push (basic_block, heap, bbs, son->data); |
d47cc544 | 759 | for (ason = son->right, n = 1; ason != son; ason = ason->right) |
66f97d31 | 760 | VEC_safe_push (basic_block, heap, bbs, ason->data); |
355be0dc | 761 | |
66f97d31 | 762 | return bbs; |
355be0dc JH |
763 | } |
764 | ||
66f97d31 ZD |
765 | /* Returns the list of basic blocks that are immediately dominated (in |
766 | direction DIR) by some block between N_REGION ones stored in REGION, | |
767 | except for blocks in the REGION itself. */ | |
768 | ||
769 | VEC (basic_block, heap) * | |
42759f1e | 770 | get_dominated_by_region (enum cdi_direction dir, basic_block *region, |
66f97d31 | 771 | unsigned n_region) |
42759f1e | 772 | { |
66f97d31 | 773 | unsigned i; |
42759f1e | 774 | basic_block dom; |
66f97d31 | 775 | VEC (basic_block, heap) *doms = NULL; |
42759f1e ZD |
776 | |
777 | for (i = 0; i < n_region; i++) | |
6580ee77 | 778 | region[i]->flags |= BB_DUPLICATED; |
42759f1e ZD |
779 | for (i = 0; i < n_region; i++) |
780 | for (dom = first_dom_son (dir, region[i]); | |
781 | dom; | |
782 | dom = next_dom_son (dir, dom)) | |
6580ee77 | 783 | if (!(dom->flags & BB_DUPLICATED)) |
66f97d31 | 784 | VEC_safe_push (basic_block, heap, doms, dom); |
42759f1e | 785 | for (i = 0; i < n_region; i++) |
6580ee77 | 786 | region[i]->flags &= ~BB_DUPLICATED; |
42759f1e | 787 | |
66f97d31 | 788 | return doms; |
42759f1e ZD |
789 | } |
790 | ||
355be0dc JH |
791 | /* Redirect all edges pointing to BB to TO. */ |
792 | void | |
d47cc544 SB |
793 | redirect_immediate_dominators (enum cdi_direction dir, basic_block bb, |
794 | basic_block to) | |
355be0dc | 795 | { |
2b28c07a JC |
796 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
797 | struct et_node *bb_node, *to_node, *son; | |
798 | ||
799 | bb_node = bb->dom[dir_index]; | |
800 | to_node = to->dom[dir_index]; | |
d47cc544 | 801 | |
2b28c07a | 802 | gcc_assert (dom_computed[dir_index]); |
355be0dc | 803 | |
d47cc544 SB |
804 | if (!bb_node->son) |
805 | return; | |
806 | ||
807 | while (bb_node->son) | |
355be0dc | 808 | { |
d47cc544 SB |
809 | son = bb_node->son; |
810 | ||
811 | et_split (son); | |
812 | et_set_father (son, to_node); | |
355be0dc | 813 | } |
d47cc544 | 814 | |
2b28c07a JC |
815 | if (dom_computed[dir_index] == DOM_OK) |
816 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
817 | } |
818 | ||
819 | /* Find first basic block in the tree dominating both BB1 and BB2. */ | |
820 | basic_block | |
d47cc544 | 821 | nearest_common_dominator (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
355be0dc | 822 | { |
2b28c07a JC |
823 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
824 | ||
825 | gcc_assert (dom_computed[dir_index]); | |
d47cc544 | 826 | |
355be0dc JH |
827 | if (!bb1) |
828 | return bb2; | |
829 | if (!bb2) | |
830 | return bb1; | |
d47cc544 | 831 | |
2b28c07a | 832 | return et_nca (bb1->dom[dir_index], bb2->dom[dir_index])->data; |
355be0dc JH |
833 | } |
834 | ||
0bca51f0 DN |
835 | |
836 | /* Find the nearest common dominator for the basic blocks in BLOCKS, | |
837 | using dominance direction DIR. */ | |
838 | ||
839 | basic_block | |
840 | nearest_common_dominator_for_set (enum cdi_direction dir, bitmap blocks) | |
841 | { | |
842 | unsigned i, first; | |
843 | bitmap_iterator bi; | |
844 | basic_block dom; | |
845 | ||
846 | first = bitmap_first_set_bit (blocks); | |
847 | dom = BASIC_BLOCK (first); | |
848 | EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi) | |
849 | if (dom != BASIC_BLOCK (i)) | |
850 | dom = nearest_common_dominator (dir, dom, BASIC_BLOCK (i)); | |
851 | ||
852 | return dom; | |
853 | } | |
854 | ||
b629276a DB |
855 | /* Given a dominator tree, we can determine whether one thing |
856 | dominates another in constant time by using two DFS numbers: | |
857 | ||
858 | 1. The number for when we visit a node on the way down the tree | |
859 | 2. The number for when we visit a node on the way back up the tree | |
860 | ||
861 | You can view these as bounds for the range of dfs numbers the | |
862 | nodes in the subtree of the dominator tree rooted at that node | |
863 | will contain. | |
864 | ||
865 | The dominator tree is always a simple acyclic tree, so there are | |
866 | only three possible relations two nodes in the dominator tree have | |
867 | to each other: | |
868 | ||
869 | 1. Node A is above Node B (and thus, Node A dominates node B) | |
870 | ||
871 | A | |
872 | | | |
873 | C | |
874 | / \ | |
875 | B D | |
876 | ||
877 | ||
878 | In the above case, DFS_Number_In of A will be <= DFS_Number_In of | |
879 | B, and DFS_Number_Out of A will be >= DFS_Number_Out of B. This is | |
880 | because we must hit A in the dominator tree *before* B on the walk | |
881 | down, and we will hit A *after* B on the walk back up | |
882 | ||
d8701f02 | 883 | 2. Node A is below node B (and thus, node B dominates node A) |
b629276a DB |
884 | |
885 | ||
886 | B | |
887 | | | |
888 | A | |
889 | / \ | |
890 | C D | |
891 | ||
892 | In the above case, DFS_Number_In of A will be >= DFS_Number_In of | |
893 | B, and DFS_Number_Out of A will be <= DFS_Number_Out of B. | |
894 | ||
895 | This is because we must hit A in the dominator tree *after* B on | |
896 | the walk down, and we will hit A *before* B on the walk back up | |
897 | ||
898 | 3. Node A and B are siblings (and thus, neither dominates the other) | |
899 | ||
900 | C | |
901 | | | |
902 | D | |
903 | / \ | |
904 | A B | |
905 | ||
906 | In the above case, DFS_Number_In of A will *always* be <= | |
907 | DFS_Number_In of B, and DFS_Number_Out of A will *always* be <= | |
908 | DFS_Number_Out of B. This is because we will always finish the dfs | |
909 | walk of one of the subtrees before the other, and thus, the dfs | |
910 | numbers for one subtree can't intersect with the range of dfs | |
911 | numbers for the other subtree. If you swap A and B's position in | |
912 | the dominator tree, the comparison changes direction, but the point | |
913 | is that both comparisons will always go the same way if there is no | |
914 | dominance relationship. | |
915 | ||
916 | Thus, it is sufficient to write | |
917 | ||
918 | A_Dominates_B (node A, node B) | |
919 | { | |
920 | return DFS_Number_In(A) <= DFS_Number_In(B) | |
921 | && DFS_Number_Out (A) >= DFS_Number_Out(B); | |
922 | } | |
923 | ||
924 | A_Dominated_by_B (node A, node B) | |
925 | { | |
926 | return DFS_Number_In(A) >= DFS_Number_In(A) | |
927 | && DFS_Number_Out (A) <= DFS_Number_Out(B); | |
928 | } */ | |
0bca51f0 | 929 | |
355be0dc JH |
930 | /* Return TRUE in case BB1 is dominated by BB2. */ |
931 | bool | |
d47cc544 | 932 | dominated_by_p (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
6de9cd9a | 933 | { |
2b28c07a JC |
934 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
935 | struct et_node *n1 = bb1->dom[dir_index], *n2 = bb2->dom[dir_index]; | |
936 | ||
937 | gcc_assert (dom_computed[dir_index]); | |
d47cc544 | 938 | |
2b28c07a | 939 | if (dom_computed[dir_index] == DOM_OK) |
d47cc544 | 940 | return (n1->dfs_num_in >= n2->dfs_num_in |
6de9cd9a | 941 | && n1->dfs_num_out <= n2->dfs_num_out); |
d47cc544 SB |
942 | |
943 | return et_below (n1, n2); | |
355be0dc JH |
944 | } |
945 | ||
f074ff6c ZD |
946 | /* Returns the entry dfs number for basic block BB, in the direction DIR. */ |
947 | ||
948 | unsigned | |
949 | bb_dom_dfs_in (enum cdi_direction dir, basic_block bb) | |
950 | { | |
2b28c07a JC |
951 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
952 | struct et_node *n = bb->dom[dir_index]; | |
f074ff6c | 953 | |
2b28c07a | 954 | gcc_assert (dom_computed[dir_index] == DOM_OK); |
f074ff6c ZD |
955 | return n->dfs_num_in; |
956 | } | |
957 | ||
958 | /* Returns the exit dfs number for basic block BB, in the direction DIR. */ | |
959 | ||
960 | unsigned | |
961 | bb_dom_dfs_out (enum cdi_direction dir, basic_block bb) | |
962 | { | |
2b28c07a JC |
963 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
964 | struct et_node *n = bb->dom[dir_index]; | |
f074ff6c | 965 | |
2b28c07a | 966 | gcc_assert (dom_computed[dir_index] == DOM_OK); |
f074ff6c ZD |
967 | return n->dfs_num_out; |
968 | } | |
969 | ||
355be0dc JH |
970 | /* Verify invariants of dominator structure. */ |
971 | void | |
d47cc544 | 972 | verify_dominators (enum cdi_direction dir) |
355be0dc JH |
973 | { |
974 | int err = 0; | |
1fc3998d ZD |
975 | basic_block bb, imm_bb, imm_bb_correct; |
976 | struct dom_info di; | |
977 | bool reverse = (dir == CDI_POST_DOMINATORS) ? true : false; | |
355be0dc | 978 | |
fce22de5 | 979 | gcc_assert (dom_info_available_p (dir)); |
d47cc544 | 980 | |
1fc3998d ZD |
981 | init_dom_info (&di, dir); |
982 | calc_dfs_tree (&di, reverse); | |
983 | calc_idoms (&di, reverse); | |
984 | ||
355be0dc JH |
985 | FOR_EACH_BB (bb) |
986 | { | |
1fc3998d ZD |
987 | imm_bb = get_immediate_dominator (dir, bb); |
988 | if (!imm_bb) | |
f8032688 | 989 | { |
66f97d31 | 990 | error ("dominator of %d status unknown", bb->index); |
355be0dc JH |
991 | err = 1; |
992 | } | |
66f97d31 | 993 | |
1fc3998d ZD |
994 | imm_bb_correct = di.dfs_to_bb[di.dom[di.dfs_order[bb->index]]]; |
995 | if (imm_bb != imm_bb_correct) | |
e7bd94cc | 996 | { |
66f97d31 | 997 | error ("dominator of %d should be %d, not %d", |
1fc3998d | 998 | bb->index, imm_bb_correct->index, imm_bb->index); |
66f97d31 | 999 | err = 1; |
e7bd94cc ZD |
1000 | } |
1001 | } | |
1002 | ||
1fc3998d | 1003 | free_dom_info (&di); |
ced3f397 | 1004 | gcc_assert (!err); |
355be0dc JH |
1005 | } |
1006 | ||
738ed977 ZD |
1007 | /* Determine immediate dominator (or postdominator, according to DIR) of BB, |
1008 | assuming that dominators of other blocks are correct. We also use it to | |
1009 | recompute the dominators in a restricted area, by iterating it until it | |
71cc389b | 1010 | reaches a fixed point. */ |
738ed977 | 1011 | |
355be0dc | 1012 | basic_block |
66f97d31 | 1013 | recompute_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 1014 | { |
2b28c07a | 1015 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
738ed977 ZD |
1016 | basic_block dom_bb = NULL; |
1017 | edge e; | |
628f6a4e | 1018 | edge_iterator ei; |
355be0dc | 1019 | |
2b28c07a | 1020 | gcc_assert (dom_computed[dir_index]); |
d47cc544 | 1021 | |
738ed977 ZD |
1022 | if (dir == CDI_DOMINATORS) |
1023 | { | |
628f6a4e | 1024 | FOR_EACH_EDGE (e, ei, bb->preds) |
738ed977 ZD |
1025 | { |
1026 | if (!dominated_by_p (dir, e->src, bb)) | |
1027 | dom_bb = nearest_common_dominator (dir, dom_bb, e->src); | |
1028 | } | |
1029 | } | |
1030 | else | |
1031 | { | |
628f6a4e | 1032 | FOR_EACH_EDGE (e, ei, bb->succs) |
738ed977 ZD |
1033 | { |
1034 | if (!dominated_by_p (dir, e->dest, bb)) | |
1035 | dom_bb = nearest_common_dominator (dir, dom_bb, e->dest); | |
1036 | } | |
1037 | } | |
f8032688 | 1038 | |
738ed977 | 1039 | return dom_bb; |
355be0dc JH |
1040 | } |
1041 | ||
66f97d31 ZD |
1042 | /* Use simple heuristics (see iterate_fix_dominators) to determine dominators |
1043 | of BBS. We assume that all the immediate dominators except for those of the | |
1044 | blocks in BBS are correct. If CONSERVATIVE is true, we also assume that the | |
1045 | currently recorded immediate dominators of blocks in BBS really dominate the | |
1046 | blocks. The basic blocks for that we determine the dominator are removed | |
1047 | from BBS. */ | |
1048 | ||
1049 | static void | |
1050 | prune_bbs_to_update_dominators (VEC (basic_block, heap) *bbs, | |
1051 | bool conservative) | |
1052 | { | |
1053 | unsigned i; | |
1054 | bool single; | |
1055 | basic_block bb, dom = NULL; | |
1056 | edge_iterator ei; | |
1057 | edge e; | |
1058 | ||
1059 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb);) | |
1060 | { | |
1061 | if (bb == ENTRY_BLOCK_PTR) | |
1062 | goto succeed; | |
1063 | ||
1064 | if (single_pred_p (bb)) | |
1065 | { | |
1066 | set_immediate_dominator (CDI_DOMINATORS, bb, single_pred (bb)); | |
1067 | goto succeed; | |
1068 | } | |
1069 | ||
1070 | if (!conservative) | |
1071 | goto fail; | |
1072 | ||
1073 | single = true; | |
1074 | dom = NULL; | |
1075 | FOR_EACH_EDGE (e, ei, bb->preds) | |
1076 | { | |
1077 | if (dominated_by_p (CDI_DOMINATORS, e->src, bb)) | |
1078 | continue; | |
1079 | ||
1080 | if (!dom) | |
1081 | dom = e->src; | |
1082 | else | |
1083 | { | |
1084 | single = false; | |
1085 | dom = nearest_common_dominator (CDI_DOMINATORS, dom, e->src); | |
1086 | } | |
1087 | } | |
1088 | ||
1089 | gcc_assert (dom != NULL); | |
1090 | if (single | |
1091 | || find_edge (dom, bb)) | |
1092 | { | |
1093 | set_immediate_dominator (CDI_DOMINATORS, bb, dom); | |
1094 | goto succeed; | |
1095 | } | |
1096 | ||
1097 | fail: | |
1098 | i++; | |
1099 | continue; | |
1100 | ||
1101 | succeed: | |
1102 | VEC_unordered_remove (basic_block, bbs, i); | |
1103 | } | |
1104 | } | |
1105 | ||
1106 | /* Returns root of the dominance tree in the direction DIR that contains | |
1107 | BB. */ | |
1108 | ||
1109 | static basic_block | |
1110 | root_of_dom_tree (enum cdi_direction dir, basic_block bb) | |
1111 | { | |
1112 | return et_root (bb->dom[dom_convert_dir_to_idx (dir)])->data; | |
1113 | } | |
1114 | ||
1115 | /* See the comment in iterate_fix_dominators. Finds the immediate dominators | |
1116 | for the sons of Y, found using the SON and BROTHER arrays representing | |
1117 | the dominance tree of graph G. BBS maps the vertices of G to the basic | |
1118 | blocks. */ | |
1119 | ||
1120 | static void | |
1121 | determine_dominators_for_sons (struct graph *g, VEC (basic_block, heap) *bbs, | |
1122 | int y, int *son, int *brother) | |
1123 | { | |
1124 | bitmap gprime; | |
1125 | int i, a, nc; | |
1126 | VEC (int, heap) **sccs; | |
1127 | basic_block bb, dom, ybb; | |
1128 | unsigned si; | |
1129 | edge e; | |
1130 | edge_iterator ei; | |
1131 | ||
1132 | if (son[y] == -1) | |
1133 | return; | |
1134 | if (y == (int) VEC_length (basic_block, bbs)) | |
1135 | ybb = ENTRY_BLOCK_PTR; | |
1136 | else | |
1137 | ybb = VEC_index (basic_block, bbs, y); | |
1138 | ||
1139 | if (brother[son[y]] == -1) | |
1140 | { | |
1141 | /* Handle the common case Y has just one son specially. */ | |
1142 | bb = VEC_index (basic_block, bbs, son[y]); | |
1143 | set_immediate_dominator (CDI_DOMINATORS, bb, | |
1144 | recompute_dominator (CDI_DOMINATORS, bb)); | |
1145 | identify_vertices (g, y, son[y]); | |
1146 | return; | |
1147 | } | |
1148 | ||
1149 | gprime = BITMAP_ALLOC (NULL); | |
1150 | for (a = son[y]; a != -1; a = brother[a]) | |
1151 | bitmap_set_bit (gprime, a); | |
1152 | ||
1153 | nc = graphds_scc (g, gprime); | |
1154 | BITMAP_FREE (gprime); | |
1155 | ||
1156 | sccs = XCNEWVEC (VEC (int, heap) *, nc); | |
1157 | for (a = son[y]; a != -1; a = brother[a]) | |
1158 | VEC_safe_push (int, heap, sccs[g->vertices[a].component], a); | |
1159 | ||
1160 | for (i = nc - 1; i >= 0; i--) | |
1161 | { | |
1162 | dom = NULL; | |
1163 | for (si = 0; VEC_iterate (int, sccs[i], si, a); si++) | |
1164 | { | |
1165 | bb = VEC_index (basic_block, bbs, a); | |
1166 | FOR_EACH_EDGE (e, ei, bb->preds) | |
1167 | { | |
1168 | if (root_of_dom_tree (CDI_DOMINATORS, e->src) != ybb) | |
1169 | continue; | |
1170 | ||
1171 | dom = nearest_common_dominator (CDI_DOMINATORS, dom, e->src); | |
1172 | } | |
1173 | } | |
1174 | ||
1175 | gcc_assert (dom != NULL); | |
1176 | for (si = 0; VEC_iterate (int, sccs[i], si, a); si++) | |
1177 | { | |
1178 | bb = VEC_index (basic_block, bbs, a); | |
1179 | set_immediate_dominator (CDI_DOMINATORS, bb, dom); | |
1180 | } | |
1181 | } | |
1182 | ||
1183 | for (i = 0; i < nc; i++) | |
1184 | VEC_free (int, heap, sccs[i]); | |
1185 | free (sccs); | |
1186 | ||
1187 | for (a = son[y]; a != -1; a = brother[a]) | |
1188 | identify_vertices (g, y, a); | |
1189 | } | |
1190 | ||
1191 | /* Recompute dominance information for basic blocks in the set BBS. The | |
1192 | function assumes that the immediate dominators of all the other blocks | |
1193 | in CFG are correct, and that there are no unreachable blocks. | |
1194 | ||
1195 | If CONSERVATIVE is true, we additionally assume that all the ancestors of | |
1196 | a block of BBS in the current dominance tree dominate it. */ | |
1197 | ||
355be0dc | 1198 | void |
66f97d31 ZD |
1199 | iterate_fix_dominators (enum cdi_direction dir, VEC (basic_block, heap) *bbs, |
1200 | bool conservative) | |
355be0dc | 1201 | { |
66f97d31 ZD |
1202 | unsigned i; |
1203 | basic_block bb, dom; | |
1204 | struct graph *g; | |
1205 | int n, y; | |
1206 | size_t dom_i; | |
1207 | edge e; | |
1208 | edge_iterator ei; | |
1209 | struct pointer_map_t *map; | |
1210 | int *parent, *son, *brother; | |
2b28c07a | 1211 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
355be0dc | 1212 | |
66f97d31 ZD |
1213 | /* We only support updating dominators. There are some problems with |
1214 | updating postdominators (need to add fake edges from infinite loops | |
1215 | and noreturn functions), and since we do not currently use | |
1216 | iterate_fix_dominators for postdominators, any attempt to handle these | |
1217 | problems would be unused, untested, and almost surely buggy. We keep | |
1218 | the DIR argument for consistency with the rest of the dominator analysis | |
1219 | interface. */ | |
1220 | gcc_assert (dir == CDI_DOMINATORS); | |
2b28c07a | 1221 | gcc_assert (dom_computed[dir_index]); |
d47cc544 | 1222 | |
66f97d31 ZD |
1223 | /* The algorithm we use takes inspiration from the following papers, although |
1224 | the details are quite different from any of them: | |
1225 | ||
1226 | [1] G. Ramalingam, T. Reps, An Incremental Algorithm for Maintaining the | |
1227 | Dominator Tree of a Reducible Flowgraph | |
1228 | [2] V. C. Sreedhar, G. R. Gao, Y.-F. Lee: Incremental computation of | |
1229 | dominator trees | |
1230 | [3] K. D. Cooper, T. J. Harvey and K. Kennedy: A Simple, Fast Dominance | |
1231 | Algorithm | |
1232 | ||
1233 | First, we use the following heuristics to decrease the size of the BBS | |
1234 | set: | |
1235 | a) if BB has a single predecessor, then its immediate dominator is this | |
1236 | predecessor | |
1237 | additionally, if CONSERVATIVE is true: | |
1238 | b) if all the predecessors of BB except for one (X) are dominated by BB, | |
1239 | then X is the immediate dominator of BB | |
1240 | c) if the nearest common ancestor of the predecessors of BB is X and | |
1241 | X -> BB is an edge in CFG, then X is the immediate dominator of BB | |
1242 | ||
1243 | Then, we need to establish the dominance relation among the basic blocks | |
1244 | in BBS. We split the dominance tree by removing the immediate dominator | |
0d52bcc1 | 1245 | edges from BBS, creating a forest F. We form a graph G whose vertices |
66f97d31 | 1246 | are BBS and ENTRY and X -> Y is an edge of G if there exists an edge |
0d52bcc1 | 1247 | X' -> Y in CFG such that X' belongs to the tree of the dominance forest |
66f97d31 ZD |
1248 | whose root is X. We then determine dominance tree of G. Note that |
1249 | for X, Y in BBS, X dominates Y in CFG if and only if X dominates Y in G. | |
1250 | In this step, we can use arbitrary algorithm to determine dominators. | |
1251 | We decided to prefer the algorithm [3] to the algorithm of | |
1252 | Lengauer and Tarjan, since the set BBS is usually small (rarely exceeding | |
1253 | 10 during gcc bootstrap), and [3] should perform better in this case. | |
1254 | ||
1255 | Finally, we need to determine the immediate dominators for the basic | |
1256 | blocks of BBS. If the immediate dominator of X in G is Y, then | |
1257 | the immediate dominator of X in CFG belongs to the tree of F rooted in | |
1258 | Y. We process the dominator tree T of G recursively, starting from leaves. | |
1259 | Suppose that X_1, X_2, ..., X_k are the sons of Y in T, and that the | |
1260 | subtrees of the dominance tree of CFG rooted in X_i are already correct. | |
1261 | Let G' be the subgraph of G induced by {X_1, X_2, ..., X_k}. We make | |
1262 | the following observations: | |
1263 | (i) the immediate dominator of all blocks in a strongly connected | |
1264 | component of G' is the same | |
1265 | (ii) if X has no predecessors in G', then the immediate dominator of X | |
1266 | is the nearest common ancestor of the predecessors of X in the | |
1267 | subtree of F rooted in Y | |
1268 | Therefore, it suffices to find the topological ordering of G', and | |
1269 | process the nodes X_i in this order using the rules (i) and (ii). | |
1270 | Then, we contract all the nodes X_i with Y in G, so that the further | |
1271 | steps work correctly. */ | |
1272 | ||
1273 | if (!conservative) | |
1274 | { | |
1275 | /* Split the tree now. If the idoms of blocks in BBS are not | |
1276 | conservatively correct, setting the dominators using the | |
1277 | heuristics in prune_bbs_to_update_dominators could | |
1278 | create cycles in the dominance "tree", and cause ICE. */ | |
1279 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb); i++) | |
1280 | set_immediate_dominator (CDI_DOMINATORS, bb, NULL); | |
1281 | } | |
1282 | ||
1283 | prune_bbs_to_update_dominators (bbs, conservative); | |
1284 | n = VEC_length (basic_block, bbs); | |
1285 | ||
1286 | if (n == 0) | |
1287 | return; | |
e7bd94cc | 1288 | |
66f97d31 | 1289 | if (n == 1) |
355be0dc | 1290 | { |
66f97d31 ZD |
1291 | bb = VEC_index (basic_block, bbs, 0); |
1292 | set_immediate_dominator (CDI_DOMINATORS, bb, | |
1293 | recompute_dominator (CDI_DOMINATORS, bb)); | |
1294 | return; | |
1295 | } | |
1296 | ||
1297 | /* Construct the graph G. */ | |
1298 | map = pointer_map_create (); | |
1299 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb); i++) | |
1300 | { | |
1301 | /* If the dominance tree is conservatively correct, split it now. */ | |
1302 | if (conservative) | |
1303 | set_immediate_dominator (CDI_DOMINATORS, bb, NULL); | |
1304 | *pointer_map_insert (map, bb) = (void *) (size_t) i; | |
1305 | } | |
1306 | *pointer_map_insert (map, ENTRY_BLOCK_PTR) = (void *) (size_t) n; | |
1307 | ||
1308 | g = new_graph (n + 1); | |
1309 | for (y = 0; y < g->n_vertices; y++) | |
1310 | g->vertices[y].data = BITMAP_ALLOC (NULL); | |
1311 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb); i++) | |
1312 | { | |
1313 | FOR_EACH_EDGE (e, ei, bb->preds) | |
355be0dc | 1314 | { |
66f97d31 ZD |
1315 | dom = root_of_dom_tree (CDI_DOMINATORS, e->src); |
1316 | if (dom == bb) | |
1317 | continue; | |
1318 | ||
1319 | dom_i = (size_t) *pointer_map_contains (map, dom); | |
1320 | ||
1321 | /* Do not include parallel edges to G. */ | |
1322 | if (bitmap_bit_p (g->vertices[dom_i].data, i)) | |
1323 | continue; | |
1324 | ||
1325 | bitmap_set_bit (g->vertices[dom_i].data, i); | |
1326 | add_edge (g, dom_i, i); | |
f8032688 MM |
1327 | } |
1328 | } | |
66f97d31 ZD |
1329 | for (y = 0; y < g->n_vertices; y++) |
1330 | BITMAP_FREE (g->vertices[y].data); | |
1331 | pointer_map_destroy (map); | |
1332 | ||
1333 | /* Find the dominator tree of G. */ | |
1334 | son = XNEWVEC (int, n + 1); | |
1335 | brother = XNEWVEC (int, n + 1); | |
1336 | parent = XNEWVEC (int, n + 1); | |
1337 | graphds_domtree (g, n, parent, son, brother); | |
1338 | ||
1339 | /* Finally, traverse the tree and find the immediate dominators. */ | |
1340 | for (y = n; son[y] != -1; y = son[y]) | |
1341 | continue; | |
1342 | while (y != -1) | |
1343 | { | |
1344 | determine_dominators_for_sons (g, bbs, y, son, brother); | |
1345 | ||
1346 | if (brother[y] != -1) | |
1347 | { | |
1348 | y = brother[y]; | |
1349 | while (son[y] != -1) | |
1350 | y = son[y]; | |
1351 | } | |
1352 | else | |
1353 | y = parent[y]; | |
1354 | } | |
1355 | ||
1356 | free (son); | |
1357 | free (brother); | |
1358 | free (parent); | |
e7bd94cc | 1359 | |
66f97d31 | 1360 | free_graph (g); |
355be0dc | 1361 | } |
f8032688 | 1362 | |
355be0dc | 1363 | void |
d47cc544 | 1364 | add_to_dominance_info (enum cdi_direction dir, basic_block bb) |
355be0dc | 1365 | { |
2b28c07a JC |
1366 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1367 | ||
1368 | gcc_assert (dom_computed[dir_index]); | |
1369 | gcc_assert (!bb->dom[dir_index]); | |
d47cc544 | 1370 | |
2b28c07a | 1371 | n_bbs_in_dom_tree[dir_index]++; |
6de9cd9a | 1372 | |
2b28c07a | 1373 | bb->dom[dir_index] = et_new_tree (bb); |
d47cc544 | 1374 | |
2b28c07a JC |
1375 | if (dom_computed[dir_index] == DOM_OK) |
1376 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
1377 | } |
1378 | ||
1379 | void | |
d47cc544 SB |
1380 | delete_from_dominance_info (enum cdi_direction dir, basic_block bb) |
1381 | { | |
2b28c07a | 1382 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
d47cc544 | 1383 | |
2b28c07a | 1384 | gcc_assert (dom_computed[dir_index]); |
d47cc544 | 1385 | |
2b28c07a JC |
1386 | et_free_tree (bb->dom[dir_index]); |
1387 | bb->dom[dir_index] = NULL; | |
1388 | n_bbs_in_dom_tree[dir_index]--; | |
1389 | ||
1390 | if (dom_computed[dir_index] == DOM_OK) | |
1391 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
d47cc544 SB |
1392 | } |
1393 | ||
1394 | /* Returns the first son of BB in the dominator or postdominator tree | |
1395 | as determined by DIR. */ | |
1396 | ||
1397 | basic_block | |
1398 | first_dom_son (enum cdi_direction dir, basic_block bb) | |
355be0dc | 1399 | { |
2b28c07a JC |
1400 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1401 | struct et_node *son = bb->dom[dir_index]->son; | |
d47cc544 SB |
1402 | |
1403 | return son ? son->data : NULL; | |
1404 | } | |
1405 | ||
1406 | /* Returns the next dominance son after BB in the dominator or postdominator | |
1407 | tree as determined by DIR, or NULL if it was the last one. */ | |
1408 | ||
1409 | basic_block | |
1410 | next_dom_son (enum cdi_direction dir, basic_block bb) | |
1411 | { | |
2b28c07a JC |
1412 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1413 | struct et_node *next = bb->dom[dir_index]->right; | |
d47cc544 SB |
1414 | |
1415 | return next->father->son == next ? NULL : next->data; | |
355be0dc JH |
1416 | } |
1417 | ||
2b28c07a JC |
1418 | /* Return dominance availability for dominance info DIR. */ |
1419 | ||
1420 | enum dom_state | |
1421 | dom_info_state (enum cdi_direction dir) | |
1422 | { | |
1423 | unsigned int dir_index = dom_convert_dir_to_idx (dir); | |
1424 | ||
1425 | return dom_computed[dir_index]; | |
1426 | } | |
1427 | ||
1428 | /* Set the dominance availability for dominance info DIR to NEW_STATE. */ | |
1429 | ||
1430 | void | |
1431 | set_dom_info_availability (enum cdi_direction dir, enum dom_state new_state) | |
1432 | { | |
1433 | unsigned int dir_index = dom_convert_dir_to_idx (dir); | |
1434 | ||
1435 | dom_computed[dir_index] = new_state; | |
1436 | } | |
1437 | ||
fce22de5 ZD |
1438 | /* Returns true if dominance information for direction DIR is available. */ |
1439 | ||
1440 | bool | |
1441 | dom_info_available_p (enum cdi_direction dir) | |
1442 | { | |
2b28c07a JC |
1443 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1444 | ||
1445 | return dom_computed[dir_index] != DOM_NONE; | |
fce22de5 ZD |
1446 | } |
1447 | ||
355be0dc | 1448 | void |
d47cc544 | 1449 | debug_dominance_info (enum cdi_direction dir) |
355be0dc JH |
1450 | { |
1451 | basic_block bb, bb2; | |
1452 | FOR_EACH_BB (bb) | |
d47cc544 | 1453 | if ((bb2 = get_immediate_dominator (dir, bb))) |
355be0dc | 1454 | fprintf (stderr, "%i %i\n", bb->index, bb2->index); |
f8032688 | 1455 | } |
1fc3998d ZD |
1456 | |
1457 | /* Prints to stderr representation of the dominance tree (for direction DIR) | |
1458 | rooted in ROOT, indented by INDENT tabelators. If INDENT_FIRST is false, | |
1459 | the first line of the output is not indented. */ | |
1460 | ||
1461 | static void | |
1462 | debug_dominance_tree_1 (enum cdi_direction dir, basic_block root, | |
1463 | unsigned indent, bool indent_first) | |
1464 | { | |
1465 | basic_block son; | |
1466 | unsigned i; | |
1467 | bool first = true; | |
1468 | ||
1469 | if (indent_first) | |
1470 | for (i = 0; i < indent; i++) | |
1471 | fprintf (stderr, "\t"); | |
1472 | fprintf (stderr, "%d\t", root->index); | |
1473 | ||
1474 | for (son = first_dom_son (dir, root); | |
1475 | son; | |
1476 | son = next_dom_son (dir, son)) | |
1477 | { | |
1478 | debug_dominance_tree_1 (dir, son, indent + 1, !first); | |
1479 | first = false; | |
1480 | } | |
1481 | ||
1482 | if (first) | |
1483 | fprintf (stderr, "\n"); | |
1484 | } | |
1485 | ||
1486 | /* Prints to stderr representation of the dominance tree (for direction DIR) | |
1487 | rooted in ROOT. */ | |
1488 | ||
1489 | void | |
1490 | debug_dominance_tree (enum cdi_direction dir, basic_block root) | |
1491 | { | |
1492 | debug_dominance_tree_1 (dir, root, 0, false); | |
1493 | } |