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f8032688 | 1 | /* Calculate (post)dominators in slightly super-linear time. |
c8d3e15a | 2 | Copyright (C) 2000, 2003, 2004, 2005 Free Software Foundation, Inc. |
f8032688 | 3 | Contributed by Michael Matz (matz@ifh.de). |
3a538a66 | 4 | |
1322177d | 5 | This file is part of GCC. |
3a538a66 | 6 | |
1322177d LB |
7 | GCC is free software; you can redistribute it and/or modify it |
8 | under the terms of the GNU General Public License as published by | |
f8032688 MM |
9 | the Free Software Foundation; either version 2, or (at your option) |
10 | any later version. | |
11 | ||
1322177d LB |
12 | GCC is distributed in the hope that it will be useful, but WITHOUT |
13 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY | |
14 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public | |
15 | License for more details. | |
f8032688 MM |
16 | |
17 | You should have received a copy of the GNU General Public License | |
1322177d | 18 | along with GCC; see the file COPYING. If not, write to the Free |
366ccddb KC |
19 | Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA |
20 | 02110-1301, USA. */ | |
f8032688 MM |
21 | |
22 | /* This file implements the well known algorithm from Lengauer and Tarjan | |
23 | to compute the dominators in a control flow graph. A basic block D is said | |
24 | to dominate another block X, when all paths from the entry node of the CFG | |
25 | to X go also over D. The dominance relation is a transitive reflexive | |
26 | relation and its minimal transitive reduction is a tree, called the | |
27 | dominator tree. So for each block X besides the entry block exists a | |
28 | block I(X), called the immediate dominator of X, which is the parent of X | |
29 | in the dominator tree. | |
30 | ||
a1f300c0 | 31 | The algorithm computes this dominator tree implicitly by computing for |
f8032688 | 32 | each block its immediate dominator. We use tree balancing and path |
f3b569ca | 33 | compression, so it's the O(e*a(e,v)) variant, where a(e,v) is the very |
f8032688 MM |
34 | slowly growing functional inverse of the Ackerman function. */ |
35 | ||
36 | #include "config.h" | |
37 | #include "system.h" | |
4977bab6 ZW |
38 | #include "coretypes.h" |
39 | #include "tm.h" | |
f8032688 MM |
40 | #include "rtl.h" |
41 | #include "hard-reg-set.h" | |
7932a3db | 42 | #include "obstack.h" |
f8032688 | 43 | #include "basic-block.h" |
4c714dd4 | 44 | #include "toplev.h" |
355be0dc | 45 | #include "et-forest.h" |
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 | { |
24bd1a0b | 155 | unsigned int num = n_basic_blocks; |
f8032688 MM |
156 | init_ar (di->dfs_parent, TBB, num, 0); |
157 | init_ar (di->path_min, TBB, num, i); | |
158 | init_ar (di->key, TBB, num, i); | |
159 | init_ar (di->dom, TBB, num, 0); | |
160 | ||
161 | init_ar (di->bucket, TBB, num, 0); | |
162 | init_ar (di->next_bucket, TBB, num, 0); | |
163 | ||
164 | init_ar (di->set_chain, TBB, num, 0); | |
165 | init_ar (di->set_size, unsigned int, num, 1); | |
166 | init_ar (di->set_child, TBB, num, 0); | |
167 | ||
d55bc081 | 168 | init_ar (di->dfs_order, TBB, (unsigned int) last_basic_block + 1, 0); |
f8032688 MM |
169 | init_ar (di->dfs_to_bb, basic_block, num, 0); |
170 | ||
171 | di->dfsnum = 1; | |
172 | di->nodes = 0; | |
26e0e410 | 173 | |
2b28c07a JC |
174 | switch (dir) |
175 | { | |
176 | case CDI_DOMINATORS: | |
177 | di->fake_exit_edge = NULL; | |
178 | break; | |
179 | case CDI_POST_DOMINATORS: | |
180 | di->fake_exit_edge = BITMAP_ALLOC (NULL); | |
181 | break; | |
182 | default: | |
183 | gcc_unreachable (); | |
184 | break; | |
185 | } | |
f8032688 MM |
186 | } |
187 | ||
188 | #undef init_ar | |
189 | ||
2b28c07a JC |
190 | /* Map dominance calculation type to array index used for various |
191 | dominance information arrays. This version is simple -- it will need | |
192 | to be modified, obviously, if additional values are added to | |
193 | cdi_direction. */ | |
194 | ||
195 | static unsigned int | |
196 | dom_convert_dir_to_idx (enum cdi_direction dir) | |
197 | { | |
198 | gcc_assert (dir == CDI_DOMINATORS || dir == CDI_POST_DOMINATORS); | |
199 | return dir - 1; | |
200 | } | |
201 | ||
f8032688 MM |
202 | /* Free all allocated memory in DI, but not DI itself. */ |
203 | ||
204 | static void | |
7080f735 | 205 | free_dom_info (struct dom_info *di) |
f8032688 MM |
206 | { |
207 | free (di->dfs_parent); | |
208 | free (di->path_min); | |
209 | free (di->key); | |
210 | free (di->dom); | |
211 | free (di->bucket); | |
212 | free (di->next_bucket); | |
213 | free (di->set_chain); | |
214 | free (di->set_size); | |
215 | free (di->set_child); | |
216 | free (di->dfs_order); | |
217 | free (di->dfs_to_bb); | |
8bdbfff5 | 218 | BITMAP_FREE (di->fake_exit_edge); |
f8032688 MM |
219 | } |
220 | ||
221 | /* The nonrecursive variant of creating a DFS tree. DI is our working | |
222 | structure, BB the starting basic block for this tree and REVERSE | |
223 | is true, if predecessors should be visited instead of successors of a | |
224 | node. After this is done all nodes reachable from BB were visited, have | |
225 | assigned their dfs number and are linked together to form a tree. */ | |
226 | ||
227 | static void | |
2b28c07a | 228 | calc_dfs_tree_nonrec (struct dom_info *di, basic_block bb, bool reverse) |
f8032688 | 229 | { |
f8032688 MM |
230 | /* We call this _only_ if bb is not already visited. */ |
231 | edge e; | |
232 | TBB child_i, my_i = 0; | |
628f6a4e BE |
233 | edge_iterator *stack; |
234 | edge_iterator ei, einext; | |
f8032688 MM |
235 | int sp; |
236 | /* Start block (ENTRY_BLOCK_PTR for forward problem, EXIT_BLOCK for backward | |
237 | problem). */ | |
238 | basic_block en_block; | |
239 | /* Ending block. */ | |
240 | basic_block ex_block; | |
241 | ||
5ed6ace5 | 242 | stack = XNEWVEC (edge_iterator, n_basic_blocks + 1); |
f8032688 MM |
243 | sp = 0; |
244 | ||
245 | /* Initialize our border blocks, and the first edge. */ | |
246 | if (reverse) | |
247 | { | |
628f6a4e | 248 | ei = ei_start (bb->preds); |
f8032688 MM |
249 | en_block = EXIT_BLOCK_PTR; |
250 | ex_block = ENTRY_BLOCK_PTR; | |
251 | } | |
252 | else | |
253 | { | |
628f6a4e | 254 | ei = ei_start (bb->succs); |
f8032688 MM |
255 | en_block = ENTRY_BLOCK_PTR; |
256 | ex_block = EXIT_BLOCK_PTR; | |
257 | } | |
258 | ||
259 | /* When the stack is empty we break out of this loop. */ | |
260 | while (1) | |
261 | { | |
262 | basic_block bn; | |
263 | ||
264 | /* This loop traverses edges e in depth first manner, and fills the | |
265 | stack. */ | |
628f6a4e | 266 | while (!ei_end_p (ei)) |
f8032688 | 267 | { |
628f6a4e | 268 | e = ei_edge (ei); |
f8032688 MM |
269 | |
270 | /* Deduce from E the current and the next block (BB and BN), and the | |
271 | next edge. */ | |
272 | if (reverse) | |
273 | { | |
274 | bn = e->src; | |
275 | ||
276 | /* If the next node BN is either already visited or a border | |
277 | block the current edge is useless, and simply overwritten | |
278 | with the next edge out of the current node. */ | |
0b17ab2f | 279 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 | 280 | { |
628f6a4e | 281 | ei_next (&ei); |
f8032688 MM |
282 | continue; |
283 | } | |
284 | bb = e->dest; | |
628f6a4e | 285 | einext = ei_start (bn->preds); |
f8032688 MM |
286 | } |
287 | else | |
288 | { | |
289 | bn = e->dest; | |
0b17ab2f | 290 | if (bn == ex_block || di->dfs_order[bn->index]) |
f8032688 | 291 | { |
628f6a4e | 292 | ei_next (&ei); |
f8032688 MM |
293 | continue; |
294 | } | |
295 | bb = e->src; | |
628f6a4e | 296 | einext = ei_start (bn->succs); |
f8032688 MM |
297 | } |
298 | ||
ced3f397 | 299 | gcc_assert (bn != en_block); |
f8032688 MM |
300 | |
301 | /* Fill the DFS tree info calculatable _before_ recursing. */ | |
302 | if (bb != en_block) | |
0b17ab2f | 303 | my_i = di->dfs_order[bb->index]; |
f8032688 | 304 | else |
d55bc081 | 305 | my_i = di->dfs_order[last_basic_block]; |
0b17ab2f | 306 | child_i = di->dfs_order[bn->index] = di->dfsnum++; |
f8032688 MM |
307 | di->dfs_to_bb[child_i] = bn; |
308 | di->dfs_parent[child_i] = my_i; | |
309 | ||
310 | /* Save the current point in the CFG on the stack, and recurse. */ | |
628f6a4e BE |
311 | stack[sp++] = ei; |
312 | ei = einext; | |
f8032688 MM |
313 | } |
314 | ||
315 | if (!sp) | |
316 | break; | |
628f6a4e | 317 | ei = stack[--sp]; |
f8032688 MM |
318 | |
319 | /* OK. The edge-list was exhausted, meaning normally we would | |
320 | end the recursion. After returning from the recursive call, | |
321 | there were (may be) other statements which were run after a | |
322 | child node was completely considered by DFS. Here is the | |
323 | point to do it in the non-recursive variant. | |
324 | E.g. The block just completed is in e->dest for forward DFS, | |
325 | the block not yet completed (the parent of the one above) | |
326 | in e->src. This could be used e.g. for computing the number of | |
327 | descendants or the tree depth. */ | |
628f6a4e | 328 | ei_next (&ei); |
f8032688 MM |
329 | } |
330 | free (stack); | |
331 | } | |
332 | ||
333 | /* The main entry for calculating the DFS tree or forest. DI is our working | |
334 | structure and REVERSE is true, if we are interested in the reverse flow | |
335 | graph. In that case the result is not necessarily a tree but a forest, | |
336 | because there may be nodes from which the EXIT_BLOCK is unreachable. */ | |
337 | ||
338 | static void | |
2b28c07a | 339 | calc_dfs_tree (struct dom_info *di, bool reverse) |
f8032688 MM |
340 | { |
341 | /* The first block is the ENTRY_BLOCK (or EXIT_BLOCK if REVERSE). */ | |
342 | basic_block begin = reverse ? EXIT_BLOCK_PTR : ENTRY_BLOCK_PTR; | |
d55bc081 | 343 | di->dfs_order[last_basic_block] = di->dfsnum; |
f8032688 MM |
344 | di->dfs_to_bb[di->dfsnum] = begin; |
345 | di->dfsnum++; | |
346 | ||
347 | calc_dfs_tree_nonrec (di, begin, reverse); | |
348 | ||
349 | if (reverse) | |
350 | { | |
351 | /* In the post-dom case we may have nodes without a path to EXIT_BLOCK. | |
352 | They are reverse-unreachable. In the dom-case we disallow such | |
26e0e410 RH |
353 | nodes, but in post-dom we have to deal with them. |
354 | ||
355 | There are two situations in which this occurs. First, noreturn | |
356 | functions. Second, infinite loops. In the first case we need to | |
357 | pretend that there is an edge to the exit block. In the second | |
358 | case, we wind up with a forest. We need to process all noreturn | |
359 | blocks before we know if we've got any infinite loops. */ | |
360 | ||
e0082a72 | 361 | basic_block b; |
26e0e410 RH |
362 | bool saw_unconnected = false; |
363 | ||
e0082a72 | 364 | FOR_EACH_BB_REVERSE (b) |
f8032688 | 365 | { |
628f6a4e | 366 | if (EDGE_COUNT (b->succs) > 0) |
26e0e410 RH |
367 | { |
368 | if (di->dfs_order[b->index] == 0) | |
369 | saw_unconnected = true; | |
370 | continue; | |
371 | } | |
372 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
0b17ab2f | 373 | di->dfs_order[b->index] = di->dfsnum; |
f8032688 | 374 | di->dfs_to_bb[di->dfsnum] = b; |
26e0e410 | 375 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; |
f8032688 MM |
376 | di->dfsnum++; |
377 | calc_dfs_tree_nonrec (di, b, reverse); | |
378 | } | |
26e0e410 RH |
379 | |
380 | if (saw_unconnected) | |
381 | { | |
382 | FOR_EACH_BB_REVERSE (b) | |
383 | { | |
384 | if (di->dfs_order[b->index]) | |
385 | continue; | |
386 | bitmap_set_bit (di->fake_exit_edge, b->index); | |
387 | di->dfs_order[b->index] = di->dfsnum; | |
388 | di->dfs_to_bb[di->dfsnum] = b; | |
389 | di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; | |
390 | di->dfsnum++; | |
391 | calc_dfs_tree_nonrec (di, b, reverse); | |
392 | } | |
393 | } | |
f8032688 MM |
394 | } |
395 | ||
396 | di->nodes = di->dfsnum - 1; | |
397 | ||
24bd1a0b DB |
398 | /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. */ |
399 | gcc_assert (di->nodes == (unsigned int) n_basic_blocks - 1); | |
f8032688 MM |
400 | } |
401 | ||
402 | /* Compress the path from V to the root of its set and update path_min at the | |
403 | same time. After compress(di, V) set_chain[V] is the root of the set V is | |
404 | in and path_min[V] is the node with the smallest key[] value on the path | |
405 | from V to that root. */ | |
406 | ||
407 | static void | |
7080f735 | 408 | compress (struct dom_info *di, TBB v) |
f8032688 MM |
409 | { |
410 | /* Btw. It's not worth to unrecurse compress() as the depth is usually not | |
411 | greater than 5 even for huge graphs (I've not seen call depth > 4). | |
412 | Also performance wise compress() ranges _far_ behind eval(). */ | |
413 | TBB parent = di->set_chain[v]; | |
414 | if (di->set_chain[parent]) | |
415 | { | |
416 | compress (di, parent); | |
417 | if (di->key[di->path_min[parent]] < di->key[di->path_min[v]]) | |
418 | di->path_min[v] = di->path_min[parent]; | |
419 | di->set_chain[v] = di->set_chain[parent]; | |
420 | } | |
421 | } | |
422 | ||
423 | /* Compress the path from V to the set root of V if needed (when the root has | |
424 | changed since the last call). Returns the node with the smallest key[] | |
425 | value on the path from V to the root. */ | |
426 | ||
427 | static inline TBB | |
7080f735 | 428 | eval (struct dom_info *di, TBB v) |
f8032688 MM |
429 | { |
430 | /* The representant of the set V is in, also called root (as the set | |
431 | representation is a tree). */ | |
432 | TBB rep = di->set_chain[v]; | |
433 | ||
434 | /* V itself is the root. */ | |
435 | if (!rep) | |
436 | return di->path_min[v]; | |
437 | ||
438 | /* Compress only if necessary. */ | |
439 | if (di->set_chain[rep]) | |
440 | { | |
441 | compress (di, v); | |
442 | rep = di->set_chain[v]; | |
443 | } | |
444 | ||
445 | if (di->key[di->path_min[rep]] >= di->key[di->path_min[v]]) | |
446 | return di->path_min[v]; | |
447 | else | |
448 | return di->path_min[rep]; | |
449 | } | |
450 | ||
451 | /* This essentially merges the two sets of V and W, giving a single set with | |
452 | the new root V. The internal representation of these disjoint sets is a | |
453 | balanced tree. Currently link(V,W) is only used with V being the parent | |
454 | of W. */ | |
455 | ||
456 | static void | |
7080f735 | 457 | link_roots (struct dom_info *di, TBB v, TBB w) |
f8032688 MM |
458 | { |
459 | TBB s = w; | |
460 | ||
461 | /* Rebalance the tree. */ | |
462 | while (di->key[di->path_min[w]] < di->key[di->path_min[di->set_child[s]]]) | |
463 | { | |
464 | if (di->set_size[s] + di->set_size[di->set_child[di->set_child[s]]] | |
465 | >= 2 * di->set_size[di->set_child[s]]) | |
466 | { | |
467 | di->set_chain[di->set_child[s]] = s; | |
468 | di->set_child[s] = di->set_child[di->set_child[s]]; | |
469 | } | |
470 | else | |
471 | { | |
472 | di->set_size[di->set_child[s]] = di->set_size[s]; | |
473 | s = di->set_chain[s] = di->set_child[s]; | |
474 | } | |
475 | } | |
476 | ||
477 | di->path_min[s] = di->path_min[w]; | |
478 | di->set_size[v] += di->set_size[w]; | |
479 | if (di->set_size[v] < 2 * di->set_size[w]) | |
480 | { | |
481 | TBB tmp = s; | |
482 | s = di->set_child[v]; | |
483 | di->set_child[v] = tmp; | |
484 | } | |
485 | ||
486 | /* Merge all subtrees. */ | |
487 | while (s) | |
488 | { | |
489 | di->set_chain[s] = v; | |
490 | s = di->set_child[s]; | |
491 | } | |
492 | } | |
493 | ||
494 | /* This calculates the immediate dominators (or post-dominators if REVERSE is | |
495 | true). DI is our working structure and should hold the DFS forest. | |
496 | On return the immediate dominator to node V is in di->dom[V]. */ | |
497 | ||
498 | static void | |
2b28c07a | 499 | calc_idoms (struct dom_info *di, bool reverse) |
f8032688 MM |
500 | { |
501 | TBB v, w, k, par; | |
502 | basic_block en_block; | |
628f6a4e BE |
503 | edge_iterator ei, einext; |
504 | ||
f8032688 MM |
505 | if (reverse) |
506 | en_block = EXIT_BLOCK_PTR; | |
507 | else | |
508 | en_block = ENTRY_BLOCK_PTR; | |
509 | ||
510 | /* Go backwards in DFS order, to first look at the leafs. */ | |
511 | v = di->nodes; | |
512 | while (v > 1) | |
513 | { | |
514 | basic_block bb = di->dfs_to_bb[v]; | |
628f6a4e | 515 | edge e; |
f8032688 MM |
516 | |
517 | par = di->dfs_parent[v]; | |
518 | k = v; | |
628f6a4e BE |
519 | |
520 | ei = (reverse) ? ei_start (bb->succs) : ei_start (bb->preds); | |
521 | ||
f8032688 | 522 | if (reverse) |
26e0e410 | 523 | { |
26e0e410 RH |
524 | /* If this block has a fake edge to exit, process that first. */ |
525 | if (bitmap_bit_p (di->fake_exit_edge, bb->index)) | |
526 | { | |
628f6a4e BE |
527 | einext = ei; |
528 | einext.index = 0; | |
26e0e410 RH |
529 | goto do_fake_exit_edge; |
530 | } | |
531 | } | |
f8032688 MM |
532 | |
533 | /* Search all direct predecessors for the smallest node with a path | |
534 | to them. That way we have the smallest node with also a path to | |
535 | us only over nodes behind us. In effect we search for our | |
536 | semidominator. */ | |
628f6a4e | 537 | while (!ei_end_p (ei)) |
f8032688 MM |
538 | { |
539 | TBB k1; | |
540 | basic_block b; | |
541 | ||
628f6a4e BE |
542 | e = ei_edge (ei); |
543 | b = (reverse) ? e->dest : e->src; | |
544 | einext = ei; | |
545 | ei_next (&einext); | |
546 | ||
f8032688 | 547 | if (b == en_block) |
26e0e410 RH |
548 | { |
549 | do_fake_exit_edge: | |
550 | k1 = di->dfs_order[last_basic_block]; | |
551 | } | |
f8032688 | 552 | else |
0b17ab2f | 553 | k1 = di->dfs_order[b->index]; |
f8032688 MM |
554 | |
555 | /* Call eval() only if really needed. If k1 is above V in DFS tree, | |
556 | then we know, that eval(k1) == k1 and key[k1] == k1. */ | |
557 | if (k1 > v) | |
558 | k1 = di->key[eval (di, k1)]; | |
559 | if (k1 < k) | |
560 | k = k1; | |
628f6a4e BE |
561 | |
562 | ei = einext; | |
f8032688 MM |
563 | } |
564 | ||
565 | di->key[v] = k; | |
566 | link_roots (di, par, v); | |
567 | di->next_bucket[v] = di->bucket[k]; | |
568 | di->bucket[k] = v; | |
569 | ||
570 | /* Transform semidominators into dominators. */ | |
571 | for (w = di->bucket[par]; w; w = di->next_bucket[w]) | |
572 | { | |
573 | k = eval (di, w); | |
574 | if (di->key[k] < di->key[w]) | |
575 | di->dom[w] = k; | |
576 | else | |
577 | di->dom[w] = par; | |
578 | } | |
579 | /* We don't need to cleanup next_bucket[]. */ | |
580 | di->bucket[par] = 0; | |
581 | v--; | |
582 | } | |
583 | ||
a1f300c0 | 584 | /* Explicitly define the dominators. */ |
f8032688 MM |
585 | di->dom[1] = 0; |
586 | for (v = 2; v <= di->nodes; v++) | |
587 | if (di->dom[v] != di->key[v]) | |
588 | di->dom[v] = di->dom[di->dom[v]]; | |
589 | } | |
590 | ||
d47cc544 SB |
591 | /* Assign dfs numbers starting from NUM to NODE and its sons. */ |
592 | ||
593 | static void | |
594 | assign_dfs_numbers (struct et_node *node, int *num) | |
595 | { | |
596 | struct et_node *son; | |
597 | ||
598 | node->dfs_num_in = (*num)++; | |
599 | ||
600 | if (node->son) | |
601 | { | |
602 | assign_dfs_numbers (node->son, num); | |
603 | for (son = node->son->right; son != node->son; son = son->right) | |
6de9cd9a | 604 | assign_dfs_numbers (son, num); |
d47cc544 | 605 | } |
f8032688 | 606 | |
d47cc544 SB |
607 | node->dfs_num_out = (*num)++; |
608 | } | |
f8032688 | 609 | |
5d3cc252 | 610 | /* Compute the data necessary for fast resolving of dominator queries in a |
d47cc544 | 611 | static dominator tree. */ |
f8032688 | 612 | |
d47cc544 SB |
613 | static void |
614 | compute_dom_fast_query (enum cdi_direction dir) | |
615 | { | |
616 | int num = 0; | |
617 | basic_block bb; | |
2b28c07a | 618 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
d47cc544 | 619 | |
fce22de5 | 620 | gcc_assert (dom_info_available_p (dir)); |
d47cc544 | 621 | |
2b28c07a | 622 | if (dom_computed[dir_index] == DOM_OK) |
d47cc544 SB |
623 | return; |
624 | ||
625 | FOR_ALL_BB (bb) | |
626 | { | |
2b28c07a JC |
627 | if (!bb->dom[dir_index]->father) |
628 | assign_dfs_numbers (bb->dom[dir_index], &num); | |
d47cc544 SB |
629 | } |
630 | ||
2b28c07a | 631 | dom_computed[dir_index] = DOM_OK; |
d47cc544 SB |
632 | } |
633 | ||
634 | /* The main entry point into this module. DIR is set depending on whether | |
635 | we want to compute dominators or postdominators. */ | |
636 | ||
637 | void | |
638 | calculate_dominance_info (enum cdi_direction dir) | |
f8032688 MM |
639 | { |
640 | struct dom_info di; | |
355be0dc | 641 | basic_block b; |
2b28c07a JC |
642 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
643 | bool reverse = (dir == CDI_POST_DOMINATORS) ? true : false; | |
355be0dc | 644 | |
2b28c07a | 645 | if (dom_computed[dir_index] == DOM_OK) |
d47cc544 | 646 | return; |
355be0dc | 647 | |
74c96e0c | 648 | timevar_push (TV_DOMINANCE); |
fce22de5 | 649 | if (!dom_info_available_p (dir)) |
d47cc544 | 650 | { |
2b28c07a | 651 | gcc_assert (!n_bbs_in_dom_tree[dir_index]); |
f8032688 | 652 | |
d47cc544 SB |
653 | FOR_ALL_BB (b) |
654 | { | |
2b28c07a | 655 | b->dom[dir_index] = et_new_tree (b); |
d47cc544 | 656 | } |
2b28c07a | 657 | n_bbs_in_dom_tree[dir_index] = n_basic_blocks; |
f8032688 | 658 | |
26e0e410 | 659 | init_dom_info (&di, dir); |
2b28c07a JC |
660 | calc_dfs_tree (&di, reverse); |
661 | calc_idoms (&di, reverse); | |
355be0dc | 662 | |
d47cc544 SB |
663 | FOR_EACH_BB (b) |
664 | { | |
665 | TBB d = di.dom[di.dfs_order[b->index]]; | |
666 | ||
667 | if (di.dfs_to_bb[d]) | |
2b28c07a | 668 | et_set_father (b->dom[dir_index], di.dfs_to_bb[d]->dom[dir_index]); |
d47cc544 | 669 | } |
e0082a72 | 670 | |
d47cc544 | 671 | free_dom_info (&di); |
2b28c07a | 672 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; |
355be0dc JH |
673 | } |
674 | ||
d47cc544 | 675 | compute_dom_fast_query (dir); |
74c96e0c ZD |
676 | |
677 | timevar_pop (TV_DOMINANCE); | |
355be0dc JH |
678 | } |
679 | ||
d47cc544 | 680 | /* Free dominance information for direction DIR. */ |
355be0dc | 681 | void |
d47cc544 | 682 | free_dominance_info (enum cdi_direction dir) |
355be0dc JH |
683 | { |
684 | basic_block bb; | |
2b28c07a | 685 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
355be0dc | 686 | |
fce22de5 | 687 | if (!dom_info_available_p (dir)) |
d47cc544 SB |
688 | return; |
689 | ||
690 | FOR_ALL_BB (bb) | |
691 | { | |
2b28c07a JC |
692 | et_free_tree_force (bb->dom[dir_index]); |
693 | bb->dom[dir_index] = NULL; | |
d47cc544 | 694 | } |
5a6ccafd | 695 | et_free_pools (); |
d47cc544 | 696 | |
2b28c07a | 697 | n_bbs_in_dom_tree[dir_index] = 0; |
6de9cd9a | 698 | |
2b28c07a | 699 | dom_computed[dir_index] = DOM_NONE; |
355be0dc JH |
700 | } |
701 | ||
702 | /* Return the immediate dominator of basic block BB. */ | |
703 | basic_block | |
d47cc544 | 704 | get_immediate_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 705 | { |
2b28c07a JC |
706 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
707 | struct et_node *node = bb->dom[dir_index]; | |
d47cc544 | 708 | |
2b28c07a | 709 | gcc_assert (dom_computed[dir_index]); |
d47cc544 SB |
710 | |
711 | if (!node->father) | |
712 | return NULL; | |
713 | ||
6de9cd9a | 714 | return node->father->data; |
355be0dc JH |
715 | } |
716 | ||
717 | /* Set the immediate dominator of the block possibly removing | |
718 | existing edge. NULL can be used to remove any edge. */ | |
719 | inline void | |
d47cc544 SB |
720 | set_immediate_dominator (enum cdi_direction dir, basic_block bb, |
721 | basic_block dominated_by) | |
355be0dc | 722 | { |
2b28c07a JC |
723 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
724 | struct et_node *node = bb->dom[dir_index]; | |
725 | ||
726 | gcc_assert (dom_computed[dir_index]); | |
355be0dc | 727 | |
d47cc544 | 728 | if (node->father) |
355be0dc | 729 | { |
d47cc544 | 730 | if (node->father->data == dominated_by) |
6de9cd9a | 731 | return; |
d47cc544 | 732 | et_split (node); |
355be0dc | 733 | } |
d47cc544 SB |
734 | |
735 | if (dominated_by) | |
2b28c07a | 736 | et_set_father (node, dominated_by->dom[dir_index]); |
d47cc544 | 737 | |
2b28c07a JC |
738 | if (dom_computed[dir_index] == DOM_OK) |
739 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
740 | } |
741 | ||
66f97d31 ZD |
742 | /* Returns the list of basic blocks immediately dominated by BB, in the |
743 | direction DIR. */ | |
744 | VEC (basic_block, heap) * | |
745 | get_dominated_by (enum cdi_direction dir, basic_block bb) | |
355be0dc | 746 | { |
d47cc544 | 747 | int n; |
66f97d31 | 748 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
2b28c07a | 749 | struct et_node *node = bb->dom[dir_index], *son = node->son, *ason; |
66f97d31 ZD |
750 | VEC (basic_block, heap) *bbs = NULL; |
751 | ||
2b28c07a | 752 | gcc_assert (dom_computed[dir_index]); |
d47cc544 SB |
753 | |
754 | if (!son) | |
66f97d31 | 755 | return NULL; |
d47cc544 | 756 | |
66f97d31 | 757 | VEC_safe_push (basic_block, heap, bbs, son->data); |
d47cc544 | 758 | for (ason = son->right, n = 1; ason != son; ason = ason->right) |
66f97d31 | 759 | VEC_safe_push (basic_block, heap, bbs, ason->data); |
355be0dc | 760 | |
66f97d31 | 761 | return bbs; |
355be0dc JH |
762 | } |
763 | ||
66f97d31 ZD |
764 | /* Returns the list of basic blocks that are immediately dominated (in |
765 | direction DIR) by some block between N_REGION ones stored in REGION, | |
766 | except for blocks in the REGION itself. */ | |
767 | ||
768 | VEC (basic_block, heap) * | |
42759f1e | 769 | get_dominated_by_region (enum cdi_direction dir, basic_block *region, |
66f97d31 | 770 | unsigned n_region) |
42759f1e | 771 | { |
66f97d31 | 772 | unsigned i; |
42759f1e | 773 | basic_block dom; |
66f97d31 | 774 | VEC (basic_block, heap) *doms = NULL; |
42759f1e ZD |
775 | |
776 | for (i = 0; i < n_region; i++) | |
6580ee77 | 777 | region[i]->flags |= BB_DUPLICATED; |
42759f1e ZD |
778 | for (i = 0; i < n_region; i++) |
779 | for (dom = first_dom_son (dir, region[i]); | |
780 | dom; | |
781 | dom = next_dom_son (dir, dom)) | |
6580ee77 | 782 | if (!(dom->flags & BB_DUPLICATED)) |
66f97d31 | 783 | VEC_safe_push (basic_block, heap, doms, dom); |
42759f1e | 784 | for (i = 0; i < n_region; i++) |
6580ee77 | 785 | region[i]->flags &= ~BB_DUPLICATED; |
42759f1e | 786 | |
66f97d31 | 787 | return doms; |
42759f1e ZD |
788 | } |
789 | ||
355be0dc JH |
790 | /* Redirect all edges pointing to BB to TO. */ |
791 | void | |
d47cc544 SB |
792 | redirect_immediate_dominators (enum cdi_direction dir, basic_block bb, |
793 | basic_block to) | |
355be0dc | 794 | { |
2b28c07a JC |
795 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
796 | struct et_node *bb_node, *to_node, *son; | |
797 | ||
798 | bb_node = bb->dom[dir_index]; | |
799 | to_node = to->dom[dir_index]; | |
d47cc544 | 800 | |
2b28c07a | 801 | gcc_assert (dom_computed[dir_index]); |
355be0dc | 802 | |
d47cc544 SB |
803 | if (!bb_node->son) |
804 | return; | |
805 | ||
806 | while (bb_node->son) | |
355be0dc | 807 | { |
d47cc544 SB |
808 | son = bb_node->son; |
809 | ||
810 | et_split (son); | |
811 | et_set_father (son, to_node); | |
355be0dc | 812 | } |
d47cc544 | 813 | |
2b28c07a JC |
814 | if (dom_computed[dir_index] == DOM_OK) |
815 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
816 | } |
817 | ||
818 | /* Find first basic block in the tree dominating both BB1 and BB2. */ | |
819 | basic_block | |
d47cc544 | 820 | nearest_common_dominator (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
355be0dc | 821 | { |
2b28c07a JC |
822 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
823 | ||
824 | gcc_assert (dom_computed[dir_index]); | |
d47cc544 | 825 | |
355be0dc JH |
826 | if (!bb1) |
827 | return bb2; | |
828 | if (!bb2) | |
829 | return bb1; | |
d47cc544 | 830 | |
2b28c07a | 831 | return et_nca (bb1->dom[dir_index], bb2->dom[dir_index])->data; |
355be0dc JH |
832 | } |
833 | ||
0bca51f0 DN |
834 | |
835 | /* Find the nearest common dominator for the basic blocks in BLOCKS, | |
836 | using dominance direction DIR. */ | |
837 | ||
838 | basic_block | |
839 | nearest_common_dominator_for_set (enum cdi_direction dir, bitmap blocks) | |
840 | { | |
841 | unsigned i, first; | |
842 | bitmap_iterator bi; | |
843 | basic_block dom; | |
844 | ||
845 | first = bitmap_first_set_bit (blocks); | |
846 | dom = BASIC_BLOCK (first); | |
847 | EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi) | |
848 | if (dom != BASIC_BLOCK (i)) | |
849 | dom = nearest_common_dominator (dir, dom, BASIC_BLOCK (i)); | |
850 | ||
851 | return dom; | |
852 | } | |
853 | ||
b629276a DB |
854 | /* Given a dominator tree, we can determine whether one thing |
855 | dominates another in constant time by using two DFS numbers: | |
856 | ||
857 | 1. The number for when we visit a node on the way down the tree | |
858 | 2. The number for when we visit a node on the way back up the tree | |
859 | ||
860 | You can view these as bounds for the range of dfs numbers the | |
861 | nodes in the subtree of the dominator tree rooted at that node | |
862 | will contain. | |
863 | ||
864 | The dominator tree is always a simple acyclic tree, so there are | |
865 | only three possible relations two nodes in the dominator tree have | |
866 | to each other: | |
867 | ||
868 | 1. Node A is above Node B (and thus, Node A dominates node B) | |
869 | ||
870 | A | |
871 | | | |
872 | C | |
873 | / \ | |
874 | B D | |
875 | ||
876 | ||
877 | In the above case, DFS_Number_In of A will be <= DFS_Number_In of | |
878 | B, and DFS_Number_Out of A will be >= DFS_Number_Out of B. This is | |
879 | because we must hit A in the dominator tree *before* B on the walk | |
880 | down, and we will hit A *after* B on the walk back up | |
881 | ||
d8701f02 | 882 | 2. Node A is below node B (and thus, node B dominates node A) |
b629276a DB |
883 | |
884 | ||
885 | B | |
886 | | | |
887 | A | |
888 | / \ | |
889 | C D | |
890 | ||
891 | In the above case, DFS_Number_In of A will be >= DFS_Number_In of | |
892 | B, and DFS_Number_Out of A will be <= DFS_Number_Out of B. | |
893 | ||
894 | This is because we must hit A in the dominator tree *after* B on | |
895 | the walk down, and we will hit A *before* B on the walk back up | |
896 | ||
897 | 3. Node A and B are siblings (and thus, neither dominates the other) | |
898 | ||
899 | C | |
900 | | | |
901 | D | |
902 | / \ | |
903 | A B | |
904 | ||
905 | In the above case, DFS_Number_In of A will *always* be <= | |
906 | DFS_Number_In of B, and DFS_Number_Out of A will *always* be <= | |
907 | DFS_Number_Out of B. This is because we will always finish the dfs | |
908 | walk of one of the subtrees before the other, and thus, the dfs | |
909 | numbers for one subtree can't intersect with the range of dfs | |
910 | numbers for the other subtree. If you swap A and B's position in | |
911 | the dominator tree, the comparison changes direction, but the point | |
912 | is that both comparisons will always go the same way if there is no | |
913 | dominance relationship. | |
914 | ||
915 | Thus, it is sufficient to write | |
916 | ||
917 | A_Dominates_B (node A, node B) | |
918 | { | |
919 | return DFS_Number_In(A) <= DFS_Number_In(B) | |
920 | && DFS_Number_Out (A) >= DFS_Number_Out(B); | |
921 | } | |
922 | ||
923 | A_Dominated_by_B (node A, node B) | |
924 | { | |
925 | return DFS_Number_In(A) >= DFS_Number_In(A) | |
926 | && DFS_Number_Out (A) <= DFS_Number_Out(B); | |
927 | } */ | |
0bca51f0 | 928 | |
355be0dc JH |
929 | /* Return TRUE in case BB1 is dominated by BB2. */ |
930 | bool | |
d47cc544 | 931 | dominated_by_p (enum cdi_direction dir, basic_block bb1, basic_block bb2) |
6de9cd9a | 932 | { |
2b28c07a JC |
933 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
934 | struct et_node *n1 = bb1->dom[dir_index], *n2 = bb2->dom[dir_index]; | |
935 | ||
936 | gcc_assert (dom_computed[dir_index]); | |
d47cc544 | 937 | |
2b28c07a | 938 | if (dom_computed[dir_index] == DOM_OK) |
d47cc544 | 939 | return (n1->dfs_num_in >= n2->dfs_num_in |
6de9cd9a | 940 | && n1->dfs_num_out <= n2->dfs_num_out); |
d47cc544 SB |
941 | |
942 | return et_below (n1, n2); | |
355be0dc JH |
943 | } |
944 | ||
f074ff6c ZD |
945 | /* Returns the entry dfs number for basic block BB, in the direction DIR. */ |
946 | ||
947 | unsigned | |
948 | bb_dom_dfs_in (enum cdi_direction dir, basic_block bb) | |
949 | { | |
2b28c07a JC |
950 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
951 | struct et_node *n = bb->dom[dir_index]; | |
f074ff6c | 952 | |
2b28c07a | 953 | gcc_assert (dom_computed[dir_index] == DOM_OK); |
f074ff6c ZD |
954 | return n->dfs_num_in; |
955 | } | |
956 | ||
957 | /* Returns the exit dfs number for basic block BB, in the direction DIR. */ | |
958 | ||
959 | unsigned | |
960 | bb_dom_dfs_out (enum cdi_direction dir, basic_block bb) | |
961 | { | |
2b28c07a JC |
962 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
963 | struct et_node *n = bb->dom[dir_index]; | |
f074ff6c | 964 | |
2b28c07a | 965 | gcc_assert (dom_computed[dir_index] == DOM_OK); |
f074ff6c ZD |
966 | return n->dfs_num_out; |
967 | } | |
968 | ||
355be0dc JH |
969 | /* Verify invariants of dominator structure. */ |
970 | void | |
d47cc544 | 971 | verify_dominators (enum cdi_direction dir) |
355be0dc JH |
972 | { |
973 | int err = 0; | |
1fc3998d ZD |
974 | basic_block bb, imm_bb, imm_bb_correct; |
975 | struct dom_info di; | |
976 | bool reverse = (dir == CDI_POST_DOMINATORS) ? true : false; | |
355be0dc | 977 | |
fce22de5 | 978 | gcc_assert (dom_info_available_p (dir)); |
d47cc544 | 979 | |
1fc3998d ZD |
980 | init_dom_info (&di, dir); |
981 | calc_dfs_tree (&di, reverse); | |
982 | calc_idoms (&di, reverse); | |
983 | ||
355be0dc JH |
984 | FOR_EACH_BB (bb) |
985 | { | |
1fc3998d ZD |
986 | imm_bb = get_immediate_dominator (dir, bb); |
987 | if (!imm_bb) | |
f8032688 | 988 | { |
66f97d31 | 989 | error ("dominator of %d status unknown", bb->index); |
355be0dc JH |
990 | err = 1; |
991 | } | |
66f97d31 | 992 | |
1fc3998d ZD |
993 | imm_bb_correct = di.dfs_to_bb[di.dom[di.dfs_order[bb->index]]]; |
994 | if (imm_bb != imm_bb_correct) | |
e7bd94cc | 995 | { |
66f97d31 | 996 | error ("dominator of %d should be %d, not %d", |
1fc3998d | 997 | bb->index, imm_bb_correct->index, imm_bb->index); |
66f97d31 | 998 | err = 1; |
e7bd94cc ZD |
999 | } |
1000 | } | |
1001 | ||
1fc3998d | 1002 | free_dom_info (&di); |
ced3f397 | 1003 | gcc_assert (!err); |
355be0dc JH |
1004 | } |
1005 | ||
738ed977 ZD |
1006 | /* Determine immediate dominator (or postdominator, according to DIR) of BB, |
1007 | assuming that dominators of other blocks are correct. We also use it to | |
1008 | recompute the dominators in a restricted area, by iterating it until it | |
71cc389b | 1009 | reaches a fixed point. */ |
738ed977 | 1010 | |
355be0dc | 1011 | basic_block |
66f97d31 | 1012 | recompute_dominator (enum cdi_direction dir, basic_block bb) |
355be0dc | 1013 | { |
2b28c07a | 1014 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
738ed977 ZD |
1015 | basic_block dom_bb = NULL; |
1016 | edge e; | |
628f6a4e | 1017 | edge_iterator ei; |
355be0dc | 1018 | |
2b28c07a | 1019 | gcc_assert (dom_computed[dir_index]); |
d47cc544 | 1020 | |
738ed977 ZD |
1021 | if (dir == CDI_DOMINATORS) |
1022 | { | |
628f6a4e | 1023 | FOR_EACH_EDGE (e, ei, bb->preds) |
738ed977 ZD |
1024 | { |
1025 | if (!dominated_by_p (dir, e->src, bb)) | |
1026 | dom_bb = nearest_common_dominator (dir, dom_bb, e->src); | |
1027 | } | |
1028 | } | |
1029 | else | |
1030 | { | |
628f6a4e | 1031 | FOR_EACH_EDGE (e, ei, bb->succs) |
738ed977 ZD |
1032 | { |
1033 | if (!dominated_by_p (dir, e->dest, bb)) | |
1034 | dom_bb = nearest_common_dominator (dir, dom_bb, e->dest); | |
1035 | } | |
1036 | } | |
f8032688 | 1037 | |
738ed977 | 1038 | return dom_bb; |
355be0dc JH |
1039 | } |
1040 | ||
66f97d31 ZD |
1041 | /* Use simple heuristics (see iterate_fix_dominators) to determine dominators |
1042 | of BBS. We assume that all the immediate dominators except for those of the | |
1043 | blocks in BBS are correct. If CONSERVATIVE is true, we also assume that the | |
1044 | currently recorded immediate dominators of blocks in BBS really dominate the | |
1045 | blocks. The basic blocks for that we determine the dominator are removed | |
1046 | from BBS. */ | |
1047 | ||
1048 | static void | |
1049 | prune_bbs_to_update_dominators (VEC (basic_block, heap) *bbs, | |
1050 | bool conservative) | |
1051 | { | |
1052 | unsigned i; | |
1053 | bool single; | |
1054 | basic_block bb, dom = NULL; | |
1055 | edge_iterator ei; | |
1056 | edge e; | |
1057 | ||
1058 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb);) | |
1059 | { | |
1060 | if (bb == ENTRY_BLOCK_PTR) | |
1061 | goto succeed; | |
1062 | ||
1063 | if (single_pred_p (bb)) | |
1064 | { | |
1065 | set_immediate_dominator (CDI_DOMINATORS, bb, single_pred (bb)); | |
1066 | goto succeed; | |
1067 | } | |
1068 | ||
1069 | if (!conservative) | |
1070 | goto fail; | |
1071 | ||
1072 | single = true; | |
1073 | dom = NULL; | |
1074 | FOR_EACH_EDGE (e, ei, bb->preds) | |
1075 | { | |
1076 | if (dominated_by_p (CDI_DOMINATORS, e->src, bb)) | |
1077 | continue; | |
1078 | ||
1079 | if (!dom) | |
1080 | dom = e->src; | |
1081 | else | |
1082 | { | |
1083 | single = false; | |
1084 | dom = nearest_common_dominator (CDI_DOMINATORS, dom, e->src); | |
1085 | } | |
1086 | } | |
1087 | ||
1088 | gcc_assert (dom != NULL); | |
1089 | if (single | |
1090 | || find_edge (dom, bb)) | |
1091 | { | |
1092 | set_immediate_dominator (CDI_DOMINATORS, bb, dom); | |
1093 | goto succeed; | |
1094 | } | |
1095 | ||
1096 | fail: | |
1097 | i++; | |
1098 | continue; | |
1099 | ||
1100 | succeed: | |
1101 | VEC_unordered_remove (basic_block, bbs, i); | |
1102 | } | |
1103 | } | |
1104 | ||
1105 | /* Returns root of the dominance tree in the direction DIR that contains | |
1106 | BB. */ | |
1107 | ||
1108 | static basic_block | |
1109 | root_of_dom_tree (enum cdi_direction dir, basic_block bb) | |
1110 | { | |
1111 | return et_root (bb->dom[dom_convert_dir_to_idx (dir)])->data; | |
1112 | } | |
1113 | ||
1114 | /* See the comment in iterate_fix_dominators. Finds the immediate dominators | |
1115 | for the sons of Y, found using the SON and BROTHER arrays representing | |
1116 | the dominance tree of graph G. BBS maps the vertices of G to the basic | |
1117 | blocks. */ | |
1118 | ||
1119 | static void | |
1120 | determine_dominators_for_sons (struct graph *g, VEC (basic_block, heap) *bbs, | |
1121 | int y, int *son, int *brother) | |
1122 | { | |
1123 | bitmap gprime; | |
1124 | int i, a, nc; | |
1125 | VEC (int, heap) **sccs; | |
1126 | basic_block bb, dom, ybb; | |
1127 | unsigned si; | |
1128 | edge e; | |
1129 | edge_iterator ei; | |
1130 | ||
1131 | if (son[y] == -1) | |
1132 | return; | |
1133 | if (y == (int) VEC_length (basic_block, bbs)) | |
1134 | ybb = ENTRY_BLOCK_PTR; | |
1135 | else | |
1136 | ybb = VEC_index (basic_block, bbs, y); | |
1137 | ||
1138 | if (brother[son[y]] == -1) | |
1139 | { | |
1140 | /* Handle the common case Y has just one son specially. */ | |
1141 | bb = VEC_index (basic_block, bbs, son[y]); | |
1142 | set_immediate_dominator (CDI_DOMINATORS, bb, | |
1143 | recompute_dominator (CDI_DOMINATORS, bb)); | |
1144 | identify_vertices (g, y, son[y]); | |
1145 | return; | |
1146 | } | |
1147 | ||
1148 | gprime = BITMAP_ALLOC (NULL); | |
1149 | for (a = son[y]; a != -1; a = brother[a]) | |
1150 | bitmap_set_bit (gprime, a); | |
1151 | ||
1152 | nc = graphds_scc (g, gprime); | |
1153 | BITMAP_FREE (gprime); | |
1154 | ||
1155 | sccs = XCNEWVEC (VEC (int, heap) *, nc); | |
1156 | for (a = son[y]; a != -1; a = brother[a]) | |
1157 | VEC_safe_push (int, heap, sccs[g->vertices[a].component], a); | |
1158 | ||
1159 | for (i = nc - 1; i >= 0; i--) | |
1160 | { | |
1161 | dom = NULL; | |
1162 | for (si = 0; VEC_iterate (int, sccs[i], si, a); si++) | |
1163 | { | |
1164 | bb = VEC_index (basic_block, bbs, a); | |
1165 | FOR_EACH_EDGE (e, ei, bb->preds) | |
1166 | { | |
1167 | if (root_of_dom_tree (CDI_DOMINATORS, e->src) != ybb) | |
1168 | continue; | |
1169 | ||
1170 | dom = nearest_common_dominator (CDI_DOMINATORS, dom, e->src); | |
1171 | } | |
1172 | } | |
1173 | ||
1174 | gcc_assert (dom != NULL); | |
1175 | for (si = 0; VEC_iterate (int, sccs[i], si, a); si++) | |
1176 | { | |
1177 | bb = VEC_index (basic_block, bbs, a); | |
1178 | set_immediate_dominator (CDI_DOMINATORS, bb, dom); | |
1179 | } | |
1180 | } | |
1181 | ||
1182 | for (i = 0; i < nc; i++) | |
1183 | VEC_free (int, heap, sccs[i]); | |
1184 | free (sccs); | |
1185 | ||
1186 | for (a = son[y]; a != -1; a = brother[a]) | |
1187 | identify_vertices (g, y, a); | |
1188 | } | |
1189 | ||
1190 | /* Recompute dominance information for basic blocks in the set BBS. The | |
1191 | function assumes that the immediate dominators of all the other blocks | |
1192 | in CFG are correct, and that there are no unreachable blocks. | |
1193 | ||
1194 | If CONSERVATIVE is true, we additionally assume that all the ancestors of | |
1195 | a block of BBS in the current dominance tree dominate it. */ | |
1196 | ||
355be0dc | 1197 | void |
66f97d31 ZD |
1198 | iterate_fix_dominators (enum cdi_direction dir, VEC (basic_block, heap) *bbs, |
1199 | bool conservative) | |
355be0dc | 1200 | { |
66f97d31 ZD |
1201 | unsigned i; |
1202 | basic_block bb, dom; | |
1203 | struct graph *g; | |
1204 | int n, y; | |
1205 | size_t dom_i; | |
1206 | edge e; | |
1207 | edge_iterator ei; | |
1208 | struct pointer_map_t *map; | |
1209 | int *parent, *son, *brother; | |
2b28c07a | 1210 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
355be0dc | 1211 | |
66f97d31 ZD |
1212 | /* We only support updating dominators. There are some problems with |
1213 | updating postdominators (need to add fake edges from infinite loops | |
1214 | and noreturn functions), and since we do not currently use | |
1215 | iterate_fix_dominators for postdominators, any attempt to handle these | |
1216 | problems would be unused, untested, and almost surely buggy. We keep | |
1217 | the DIR argument for consistency with the rest of the dominator analysis | |
1218 | interface. */ | |
1219 | gcc_assert (dir == CDI_DOMINATORS); | |
2b28c07a | 1220 | gcc_assert (dom_computed[dir_index]); |
d47cc544 | 1221 | |
66f97d31 ZD |
1222 | /* The algorithm we use takes inspiration from the following papers, although |
1223 | the details are quite different from any of them: | |
1224 | ||
1225 | [1] G. Ramalingam, T. Reps, An Incremental Algorithm for Maintaining the | |
1226 | Dominator Tree of a Reducible Flowgraph | |
1227 | [2] V. C. Sreedhar, G. R. Gao, Y.-F. Lee: Incremental computation of | |
1228 | dominator trees | |
1229 | [3] K. D. Cooper, T. J. Harvey and K. Kennedy: A Simple, Fast Dominance | |
1230 | Algorithm | |
1231 | ||
1232 | First, we use the following heuristics to decrease the size of the BBS | |
1233 | set: | |
1234 | a) if BB has a single predecessor, then its immediate dominator is this | |
1235 | predecessor | |
1236 | additionally, if CONSERVATIVE is true: | |
1237 | b) if all the predecessors of BB except for one (X) are dominated by BB, | |
1238 | then X is the immediate dominator of BB | |
1239 | c) if the nearest common ancestor of the predecessors of BB is X and | |
1240 | X -> BB is an edge in CFG, then X is the immediate dominator of BB | |
1241 | ||
1242 | Then, we need to establish the dominance relation among the basic blocks | |
1243 | in BBS. We split the dominance tree by removing the immediate dominator | |
1244 | edges from BBS, creating a forrest F. We form a graph G whose vertices | |
1245 | are BBS and ENTRY and X -> Y is an edge of G if there exists an edge | |
1246 | X' -> Y in CFG such that X' belongs to the tree of the dominance forrest | |
1247 | whose root is X. We then determine dominance tree of G. Note that | |
1248 | for X, Y in BBS, X dominates Y in CFG if and only if X dominates Y in G. | |
1249 | In this step, we can use arbitrary algorithm to determine dominators. | |
1250 | We decided to prefer the algorithm [3] to the algorithm of | |
1251 | Lengauer and Tarjan, since the set BBS is usually small (rarely exceeding | |
1252 | 10 during gcc bootstrap), and [3] should perform better in this case. | |
1253 | ||
1254 | Finally, we need to determine the immediate dominators for the basic | |
1255 | blocks of BBS. If the immediate dominator of X in G is Y, then | |
1256 | the immediate dominator of X in CFG belongs to the tree of F rooted in | |
1257 | Y. We process the dominator tree T of G recursively, starting from leaves. | |
1258 | Suppose that X_1, X_2, ..., X_k are the sons of Y in T, and that the | |
1259 | subtrees of the dominance tree of CFG rooted in X_i are already correct. | |
1260 | Let G' be the subgraph of G induced by {X_1, X_2, ..., X_k}. We make | |
1261 | the following observations: | |
1262 | (i) the immediate dominator of all blocks in a strongly connected | |
1263 | component of G' is the same | |
1264 | (ii) if X has no predecessors in G', then the immediate dominator of X | |
1265 | is the nearest common ancestor of the predecessors of X in the | |
1266 | subtree of F rooted in Y | |
1267 | Therefore, it suffices to find the topological ordering of G', and | |
1268 | process the nodes X_i in this order using the rules (i) and (ii). | |
1269 | Then, we contract all the nodes X_i with Y in G, so that the further | |
1270 | steps work correctly. */ | |
1271 | ||
1272 | if (!conservative) | |
1273 | { | |
1274 | /* Split the tree now. If the idoms of blocks in BBS are not | |
1275 | conservatively correct, setting the dominators using the | |
1276 | heuristics in prune_bbs_to_update_dominators could | |
1277 | create cycles in the dominance "tree", and cause ICE. */ | |
1278 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb); i++) | |
1279 | set_immediate_dominator (CDI_DOMINATORS, bb, NULL); | |
1280 | } | |
1281 | ||
1282 | prune_bbs_to_update_dominators (bbs, conservative); | |
1283 | n = VEC_length (basic_block, bbs); | |
1284 | ||
1285 | if (n == 0) | |
1286 | return; | |
e7bd94cc | 1287 | |
66f97d31 | 1288 | if (n == 1) |
355be0dc | 1289 | { |
66f97d31 ZD |
1290 | bb = VEC_index (basic_block, bbs, 0); |
1291 | set_immediate_dominator (CDI_DOMINATORS, bb, | |
1292 | recompute_dominator (CDI_DOMINATORS, bb)); | |
1293 | return; | |
1294 | } | |
1295 | ||
1296 | /* Construct the graph G. */ | |
1297 | map = pointer_map_create (); | |
1298 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb); i++) | |
1299 | { | |
1300 | /* If the dominance tree is conservatively correct, split it now. */ | |
1301 | if (conservative) | |
1302 | set_immediate_dominator (CDI_DOMINATORS, bb, NULL); | |
1303 | *pointer_map_insert (map, bb) = (void *) (size_t) i; | |
1304 | } | |
1305 | *pointer_map_insert (map, ENTRY_BLOCK_PTR) = (void *) (size_t) n; | |
1306 | ||
1307 | g = new_graph (n + 1); | |
1308 | for (y = 0; y < g->n_vertices; y++) | |
1309 | g->vertices[y].data = BITMAP_ALLOC (NULL); | |
1310 | for (i = 0; VEC_iterate (basic_block, bbs, i, bb); i++) | |
1311 | { | |
1312 | FOR_EACH_EDGE (e, ei, bb->preds) | |
355be0dc | 1313 | { |
66f97d31 ZD |
1314 | dom = root_of_dom_tree (CDI_DOMINATORS, e->src); |
1315 | if (dom == bb) | |
1316 | continue; | |
1317 | ||
1318 | dom_i = (size_t) *pointer_map_contains (map, dom); | |
1319 | ||
1320 | /* Do not include parallel edges to G. */ | |
1321 | if (bitmap_bit_p (g->vertices[dom_i].data, i)) | |
1322 | continue; | |
1323 | ||
1324 | bitmap_set_bit (g->vertices[dom_i].data, i); | |
1325 | add_edge (g, dom_i, i); | |
f8032688 MM |
1326 | } |
1327 | } | |
66f97d31 ZD |
1328 | for (y = 0; y < g->n_vertices; y++) |
1329 | BITMAP_FREE (g->vertices[y].data); | |
1330 | pointer_map_destroy (map); | |
1331 | ||
1332 | /* Find the dominator tree of G. */ | |
1333 | son = XNEWVEC (int, n + 1); | |
1334 | brother = XNEWVEC (int, n + 1); | |
1335 | parent = XNEWVEC (int, n + 1); | |
1336 | graphds_domtree (g, n, parent, son, brother); | |
1337 | ||
1338 | /* Finally, traverse the tree and find the immediate dominators. */ | |
1339 | for (y = n; son[y] != -1; y = son[y]) | |
1340 | continue; | |
1341 | while (y != -1) | |
1342 | { | |
1343 | determine_dominators_for_sons (g, bbs, y, son, brother); | |
1344 | ||
1345 | if (brother[y] != -1) | |
1346 | { | |
1347 | y = brother[y]; | |
1348 | while (son[y] != -1) | |
1349 | y = son[y]; | |
1350 | } | |
1351 | else | |
1352 | y = parent[y]; | |
1353 | } | |
1354 | ||
1355 | free (son); | |
1356 | free (brother); | |
1357 | free (parent); | |
e7bd94cc | 1358 | |
66f97d31 | 1359 | free_graph (g); |
355be0dc | 1360 | } |
f8032688 | 1361 | |
355be0dc | 1362 | void |
d47cc544 | 1363 | add_to_dominance_info (enum cdi_direction dir, basic_block bb) |
355be0dc | 1364 | { |
2b28c07a JC |
1365 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1366 | ||
1367 | gcc_assert (dom_computed[dir_index]); | |
1368 | gcc_assert (!bb->dom[dir_index]); | |
d47cc544 | 1369 | |
2b28c07a | 1370 | n_bbs_in_dom_tree[dir_index]++; |
6de9cd9a | 1371 | |
2b28c07a | 1372 | bb->dom[dir_index] = et_new_tree (bb); |
d47cc544 | 1373 | |
2b28c07a JC |
1374 | if (dom_computed[dir_index] == DOM_OK) |
1375 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
355be0dc JH |
1376 | } |
1377 | ||
1378 | void | |
d47cc544 SB |
1379 | delete_from_dominance_info (enum cdi_direction dir, basic_block bb) |
1380 | { | |
2b28c07a | 1381 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
d47cc544 | 1382 | |
2b28c07a | 1383 | gcc_assert (dom_computed[dir_index]); |
d47cc544 | 1384 | |
2b28c07a JC |
1385 | et_free_tree (bb->dom[dir_index]); |
1386 | bb->dom[dir_index] = NULL; | |
1387 | n_bbs_in_dom_tree[dir_index]--; | |
1388 | ||
1389 | if (dom_computed[dir_index] == DOM_OK) | |
1390 | dom_computed[dir_index] = DOM_NO_FAST_QUERY; | |
d47cc544 SB |
1391 | } |
1392 | ||
1393 | /* Returns the first son of BB in the dominator or postdominator tree | |
1394 | as determined by DIR. */ | |
1395 | ||
1396 | basic_block | |
1397 | first_dom_son (enum cdi_direction dir, basic_block bb) | |
355be0dc | 1398 | { |
2b28c07a JC |
1399 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1400 | struct et_node *son = bb->dom[dir_index]->son; | |
d47cc544 SB |
1401 | |
1402 | return son ? son->data : NULL; | |
1403 | } | |
1404 | ||
1405 | /* Returns the next dominance son after BB in the dominator or postdominator | |
1406 | tree as determined by DIR, or NULL if it was the last one. */ | |
1407 | ||
1408 | basic_block | |
1409 | next_dom_son (enum cdi_direction dir, basic_block bb) | |
1410 | { | |
2b28c07a JC |
1411 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1412 | struct et_node *next = bb->dom[dir_index]->right; | |
d47cc544 SB |
1413 | |
1414 | return next->father->son == next ? NULL : next->data; | |
355be0dc JH |
1415 | } |
1416 | ||
2b28c07a JC |
1417 | /* Return dominance availability for dominance info DIR. */ |
1418 | ||
1419 | enum dom_state | |
1420 | dom_info_state (enum cdi_direction dir) | |
1421 | { | |
1422 | unsigned int dir_index = dom_convert_dir_to_idx (dir); | |
1423 | ||
1424 | return dom_computed[dir_index]; | |
1425 | } | |
1426 | ||
1427 | /* Set the dominance availability for dominance info DIR to NEW_STATE. */ | |
1428 | ||
1429 | void | |
1430 | set_dom_info_availability (enum cdi_direction dir, enum dom_state new_state) | |
1431 | { | |
1432 | unsigned int dir_index = dom_convert_dir_to_idx (dir); | |
1433 | ||
1434 | dom_computed[dir_index] = new_state; | |
1435 | } | |
1436 | ||
fce22de5 ZD |
1437 | /* Returns true if dominance information for direction DIR is available. */ |
1438 | ||
1439 | bool | |
1440 | dom_info_available_p (enum cdi_direction dir) | |
1441 | { | |
2b28c07a JC |
1442 | unsigned int dir_index = dom_convert_dir_to_idx (dir); |
1443 | ||
1444 | return dom_computed[dir_index] != DOM_NONE; | |
fce22de5 ZD |
1445 | } |
1446 | ||
355be0dc | 1447 | void |
d47cc544 | 1448 | debug_dominance_info (enum cdi_direction dir) |
355be0dc JH |
1449 | { |
1450 | basic_block bb, bb2; | |
1451 | FOR_EACH_BB (bb) | |
d47cc544 | 1452 | if ((bb2 = get_immediate_dominator (dir, bb))) |
355be0dc | 1453 | fprintf (stderr, "%i %i\n", bb->index, bb2->index); |
f8032688 | 1454 | } |
1fc3998d ZD |
1455 | |
1456 | /* Prints to stderr representation of the dominance tree (for direction DIR) | |
1457 | rooted in ROOT, indented by INDENT tabelators. If INDENT_FIRST is false, | |
1458 | the first line of the output is not indented. */ | |
1459 | ||
1460 | static void | |
1461 | debug_dominance_tree_1 (enum cdi_direction dir, basic_block root, | |
1462 | unsigned indent, bool indent_first) | |
1463 | { | |
1464 | basic_block son; | |
1465 | unsigned i; | |
1466 | bool first = true; | |
1467 | ||
1468 | if (indent_first) | |
1469 | for (i = 0; i < indent; i++) | |
1470 | fprintf (stderr, "\t"); | |
1471 | fprintf (stderr, "%d\t", root->index); | |
1472 | ||
1473 | for (son = first_dom_son (dir, root); | |
1474 | son; | |
1475 | son = next_dom_son (dir, son)) | |
1476 | { | |
1477 | debug_dominance_tree_1 (dir, son, indent + 1, !first); | |
1478 | first = false; | |
1479 | } | |
1480 | ||
1481 | if (first) | |
1482 | fprintf (stderr, "\n"); | |
1483 | } | |
1484 | ||
1485 | /* Prints to stderr representation of the dominance tree (for direction DIR) | |
1486 | rooted in ROOT. */ | |
1487 | ||
1488 | void | |
1489 | debug_dominance_tree (enum cdi_direction dir, basic_block root) | |
1490 | { | |
1491 | debug_dominance_tree_1 (dir, root, 0, false); | |
1492 | } |