1 /* Calculate (post)dominators in slightly super-linear time.
2 Copyright (C) 2000, 2003, 2004 Free Software Foundation, Inc.
3 Contributed by Michael Matz (matz@ifh.de).
5 This file is part of GCC.
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
9 the Free Software Foundation; either version 2, or (at your option)
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.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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.
31 The algorithm computes this dominator tree implicitly by computing for
32 each block its immediate dominator. We use tree balancing and path
33 compression, so its the O(e*a(e,v)) variant, where a(e,v) is the very
34 slowly growing functional inverse of the Ackerman function. */
38 #include "coretypes.h"
41 #include "hard-reg-set.h"
42 #include "basic-block.h"
44 #include "et-forest.h"
46 /* Whether the dominators and the postdominators are available. */
47 enum dom_state dom_computed[2];
49 /* We name our nodes with integers, beginning with 1. Zero is reserved for
50 'undefined' or 'end of list'. The name of each node is given by the dfs
51 number of the corresponding basic block. Please note, that we include the
52 artificial ENTRY_BLOCK (or EXIT_BLOCK in the post-dom case) in our lists to
53 support multiple entry points. As it has no real basic block index we use
54 'last_basic_block' for that. Its dfs number is of course 1. */
56 /* Type of Basic Block aka. TBB */
57 typedef unsigned int TBB;
59 /* We work in a poor-mans object oriented fashion, and carry an instance of
60 this structure through all our 'methods'. It holds various arrays
61 reflecting the (sub)structure of the flowgraph. Most of them are of type
62 TBB and are also indexed by TBB. */
66 /* The parent of a node in the DFS tree. */
68 /* For a node x key[x] is roughly the node nearest to the root from which
69 exists a way to x only over nodes behind x. Such a node is also called
72 /* The value in path_min[x] is the node y on the path from x to the root of
73 the tree x is in with the smallest key[y]. */
75 /* bucket[x] points to the first node of the set of nodes having x as key. */
77 /* And next_bucket[x] points to the next node. */
79 /* After the algorithm is done, dom[x] contains the immediate dominator
83 /* The following few fields implement the structures needed for disjoint
85 /* set_chain[x] is the next node on the path from x to the representant
86 of the set containing x. If set_chain[x]==0 then x is a root. */
88 /* set_size[x] is the number of elements in the set named by x. */
89 unsigned int *set_size;
90 /* set_child[x] is used for balancing the tree representing a set. It can
91 be understood as the next sibling of x. */
94 /* If b is the number of a basic block (BB->index), dfs_order[b] is the
95 number of that node in DFS order counted from 1. This is an index
96 into most of the other arrays in this structure. */
98 /* If x is the DFS-index of a node which corresponds with a basic block,
99 dfs_to_bb[x] is that basic block. Note, that in our structure there are
100 more nodes that basic blocks, so only dfs_to_bb[dfs_order[bb->index]]==bb
101 is true for every basic block bb, but not the opposite. */
102 basic_block *dfs_to_bb;
104 /* This is the next free DFS number when creating the DFS tree. */
106 /* The number of nodes in the DFS tree (==dfsnum-1). */
109 /* Blocks with bits set here have a fake edge to EXIT. These are used
110 to turn a DFS forest into a proper tree. */
111 bitmap fake_exit_edge;
114 static void init_dom_info (struct dom_info *, enum cdi_direction);
115 static void free_dom_info (struct dom_info *);
116 static void calc_dfs_tree_nonrec (struct dom_info *, basic_block,
118 static void calc_dfs_tree (struct dom_info *, enum cdi_direction);
119 static void compress (struct dom_info *, TBB);
120 static TBB eval (struct dom_info *, TBB);
121 static void link_roots (struct dom_info *, TBB, TBB);
122 static void calc_idoms (struct dom_info *, enum cdi_direction);
123 void debug_dominance_info (enum cdi_direction);
125 /* Keeps track of the*/
126 static unsigned n_bbs_in_dom_tree[2];
128 /* Helper macro for allocating and initializing an array,
129 for aesthetic reasons. */
130 #define init_ar(var, type, num, content) \
133 unsigned int i = 1; /* Catch content == i. */ \
135 (var) = xcalloc ((num), sizeof (type)); \
138 (var) = xmalloc ((num) * sizeof (type)); \
139 for (i = 0; i < num; i++) \
140 (var)[i] = (content); \
145 /* Allocate all needed memory in a pessimistic fashion (so we round up).
146 This initializes the contents of DI, which already must be allocated. */
149 init_dom_info (struct dom_info *di, enum cdi_direction dir)
151 /* We need memory for n_basic_blocks nodes and the ENTRY_BLOCK or
153 unsigned int num = n_basic_blocks + 1 + 1;
154 init_ar (di->dfs_parent, TBB, num, 0);
155 init_ar (di->path_min, TBB, num, i);
156 init_ar (di->key, TBB, num, i);
157 init_ar (di->dom, TBB, num, 0);
159 init_ar (di->bucket, TBB, num, 0);
160 init_ar (di->next_bucket, TBB, num, 0);
162 init_ar (di->set_chain, TBB, num, 0);
163 init_ar (di->set_size, unsigned int, num, 1);
164 init_ar (di->set_child, TBB, num, 0);
166 init_ar (di->dfs_order, TBB, (unsigned int) last_basic_block + 1, 0);
167 init_ar (di->dfs_to_bb, basic_block, num, 0);
172 di->fake_exit_edge = dir ? BITMAP_XMALLOC () : NULL;
177 /* Free all allocated memory in DI, but not DI itself. */
180 free_dom_info (struct dom_info *di)
182 free (di->dfs_parent);
187 free (di->next_bucket);
188 free (di->set_chain);
190 free (di->set_child);
191 free (di->dfs_order);
192 free (di->dfs_to_bb);
193 BITMAP_XFREE (di->fake_exit_edge);
196 /* The nonrecursive variant of creating a DFS tree. DI is our working
197 structure, BB the starting basic block for this tree and REVERSE
198 is true, if predecessors should be visited instead of successors of a
199 node. After this is done all nodes reachable from BB were visited, have
200 assigned their dfs number and are linked together to form a tree. */
203 calc_dfs_tree_nonrec (struct dom_info *di, basic_block bb,
204 enum cdi_direction reverse)
206 /* We call this _only_ if bb is not already visited. */
208 TBB child_i, my_i = 0;
211 /* Start block (ENTRY_BLOCK_PTR for forward problem, EXIT_BLOCK for backward
213 basic_block en_block;
215 basic_block ex_block;
217 stack = xmalloc ((n_basic_blocks + 3) * sizeof (edge));
220 /* Initialize our border blocks, and the first edge. */
224 en_block = EXIT_BLOCK_PTR;
225 ex_block = ENTRY_BLOCK_PTR;
230 en_block = ENTRY_BLOCK_PTR;
231 ex_block = EXIT_BLOCK_PTR;
234 /* When the stack is empty we break out of this loop. */
239 /* This loop traverses edges e in depth first manner, and fills the
245 /* Deduce from E the current and the next block (BB and BN), and the
251 /* If the next node BN is either already visited or a border
252 block the current edge is useless, and simply overwritten
253 with the next edge out of the current node. */
254 if (bn == ex_block || di->dfs_order[bn->index])
265 if (bn == ex_block || di->dfs_order[bn->index])
274 gcc_assert (bn != en_block);
276 /* Fill the DFS tree info calculatable _before_ recursing. */
278 my_i = di->dfs_order[bb->index];
280 my_i = di->dfs_order[last_basic_block];
281 child_i = di->dfs_order[bn->index] = di->dfsnum++;
282 di->dfs_to_bb[child_i] = bn;
283 di->dfs_parent[child_i] = my_i;
285 /* Save the current point in the CFG on the stack, and recurse. */
294 /* OK. The edge-list was exhausted, meaning normally we would
295 end the recursion. After returning from the recursive call,
296 there were (may be) other statements which were run after a
297 child node was completely considered by DFS. Here is the
298 point to do it in the non-recursive variant.
299 E.g. The block just completed is in e->dest for forward DFS,
300 the block not yet completed (the parent of the one above)
301 in e->src. This could be used e.g. for computing the number of
302 descendants or the tree depth. */
311 /* The main entry for calculating the DFS tree or forest. DI is our working
312 structure and REVERSE is true, if we are interested in the reverse flow
313 graph. In that case the result is not necessarily a tree but a forest,
314 because there may be nodes from which the EXIT_BLOCK is unreachable. */
317 calc_dfs_tree (struct dom_info *di, enum cdi_direction reverse)
319 /* The first block is the ENTRY_BLOCK (or EXIT_BLOCK if REVERSE). */
320 basic_block begin = reverse ? EXIT_BLOCK_PTR : ENTRY_BLOCK_PTR;
321 di->dfs_order[last_basic_block] = di->dfsnum;
322 di->dfs_to_bb[di->dfsnum] = begin;
325 calc_dfs_tree_nonrec (di, begin, reverse);
329 /* In the post-dom case we may have nodes without a path to EXIT_BLOCK.
330 They are reverse-unreachable. In the dom-case we disallow such
331 nodes, but in post-dom we have to deal with them.
333 There are two situations in which this occurs. First, noreturn
334 functions. Second, infinite loops. In the first case we need to
335 pretend that there is an edge to the exit block. In the second
336 case, we wind up with a forest. We need to process all noreturn
337 blocks before we know if we've got any infinite loops. */
340 bool saw_unconnected = false;
342 FOR_EACH_BB_REVERSE (b)
346 if (di->dfs_order[b->index] == 0)
347 saw_unconnected = true;
350 bitmap_set_bit (di->fake_exit_edge, b->index);
351 di->dfs_order[b->index] = di->dfsnum;
352 di->dfs_to_bb[di->dfsnum] = b;
353 di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block];
355 calc_dfs_tree_nonrec (di, b, reverse);
360 FOR_EACH_BB_REVERSE (b)
362 if (di->dfs_order[b->index])
364 bitmap_set_bit (di->fake_exit_edge, b->index);
365 di->dfs_order[b->index] = di->dfsnum;
366 di->dfs_to_bb[di->dfsnum] = b;
367 di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block];
369 calc_dfs_tree_nonrec (di, b, reverse);
374 di->nodes = di->dfsnum - 1;
376 /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. */
377 gcc_assert (di->nodes == (unsigned int) n_basic_blocks + 1);
380 /* Compress the path from V to the root of its set and update path_min at the
381 same time. After compress(di, V) set_chain[V] is the root of the set V is
382 in and path_min[V] is the node with the smallest key[] value on the path
383 from V to that root. */
386 compress (struct dom_info *di, TBB v)
388 /* Btw. It's not worth to unrecurse compress() as the depth is usually not
389 greater than 5 even for huge graphs (I've not seen call depth > 4).
390 Also performance wise compress() ranges _far_ behind eval(). */
391 TBB parent = di->set_chain[v];
392 if (di->set_chain[parent])
394 compress (di, parent);
395 if (di->key[di->path_min[parent]] < di->key[di->path_min[v]])
396 di->path_min[v] = di->path_min[parent];
397 di->set_chain[v] = di->set_chain[parent];
401 /* Compress the path from V to the set root of V if needed (when the root has
402 changed since the last call). Returns the node with the smallest key[]
403 value on the path from V to the root. */
406 eval (struct dom_info *di, TBB v)
408 /* The representant of the set V is in, also called root (as the set
409 representation is a tree). */
410 TBB rep = di->set_chain[v];
412 /* V itself is the root. */
414 return di->path_min[v];
416 /* Compress only if necessary. */
417 if (di->set_chain[rep])
420 rep = di->set_chain[v];
423 if (di->key[di->path_min[rep]] >= di->key[di->path_min[v]])
424 return di->path_min[v];
426 return di->path_min[rep];
429 /* This essentially merges the two sets of V and W, giving a single set with
430 the new root V. The internal representation of these disjoint sets is a
431 balanced tree. Currently link(V,W) is only used with V being the parent
435 link_roots (struct dom_info *di, TBB v, TBB w)
439 /* Rebalance the tree. */
440 while (di->key[di->path_min[w]] < di->key[di->path_min[di->set_child[s]]])
442 if (di->set_size[s] + di->set_size[di->set_child[di->set_child[s]]]
443 >= 2 * di->set_size[di->set_child[s]])
445 di->set_chain[di->set_child[s]] = s;
446 di->set_child[s] = di->set_child[di->set_child[s]];
450 di->set_size[di->set_child[s]] = di->set_size[s];
451 s = di->set_chain[s] = di->set_child[s];
455 di->path_min[s] = di->path_min[w];
456 di->set_size[v] += di->set_size[w];
457 if (di->set_size[v] < 2 * di->set_size[w])
460 s = di->set_child[v];
461 di->set_child[v] = tmp;
464 /* Merge all subtrees. */
467 di->set_chain[s] = v;
468 s = di->set_child[s];
472 /* This calculates the immediate dominators (or post-dominators if REVERSE is
473 true). DI is our working structure and should hold the DFS forest.
474 On return the immediate dominator to node V is in di->dom[V]. */
477 calc_idoms (struct dom_info *di, enum cdi_direction reverse)
480 basic_block en_block;
482 en_block = EXIT_BLOCK_PTR;
484 en_block = ENTRY_BLOCK_PTR;
486 /* Go backwards in DFS order, to first look at the leafs. */
490 basic_block bb = di->dfs_to_bb[v];
493 par = di->dfs_parent[v];
499 /* If this block has a fake edge to exit, process that first. */
500 if (bitmap_bit_p (di->fake_exit_edge, bb->index))
503 goto do_fake_exit_edge;
509 /* Search all direct predecessors for the smallest node with a path
510 to them. That way we have the smallest node with also a path to
511 us only over nodes behind us. In effect we search for our
513 for (; e ; e = e_next)
521 e_next = e->succ_next;
526 e_next = e->pred_next;
531 k1 = di->dfs_order[last_basic_block];
534 k1 = di->dfs_order[b->index];
536 /* Call eval() only if really needed. If k1 is above V in DFS tree,
537 then we know, that eval(k1) == k1 and key[k1] == k1. */
539 k1 = di->key[eval (di, k1)];
545 link_roots (di, par, v);
546 di->next_bucket[v] = di->bucket[k];
549 /* Transform semidominators into dominators. */
550 for (w = di->bucket[par]; w; w = di->next_bucket[w])
553 if (di->key[k] < di->key[w])
558 /* We don't need to cleanup next_bucket[]. */
563 /* Explicitly define the dominators. */
565 for (v = 2; v <= di->nodes; v++)
566 if (di->dom[v] != di->key[v])
567 di->dom[v] = di->dom[di->dom[v]];
570 /* Assign dfs numbers starting from NUM to NODE and its sons. */
573 assign_dfs_numbers (struct et_node *node, int *num)
577 node->dfs_num_in = (*num)++;
581 assign_dfs_numbers (node->son, num);
582 for (son = node->son->right; son != node->son; son = son->right)
583 assign_dfs_numbers (son, num);
586 node->dfs_num_out = (*num)++;
589 /* Compute the data necessary for fast resolving of dominator queries in a
590 static dominator tree. */
593 compute_dom_fast_query (enum cdi_direction dir)
598 gcc_assert (dom_computed[dir] >= DOM_NO_FAST_QUERY);
600 if (dom_computed[dir] == DOM_OK)
605 if (!bb->dom[dir]->father)
606 assign_dfs_numbers (bb->dom[dir], &num);
609 dom_computed[dir] = DOM_OK;
612 /* The main entry point into this module. DIR is set depending on whether
613 we want to compute dominators or postdominators. */
616 calculate_dominance_info (enum cdi_direction dir)
621 if (dom_computed[dir] == DOM_OK)
624 if (dom_computed[dir] != DOM_NO_FAST_QUERY)
626 if (dom_computed[dir] != DOM_NONE)
627 free_dominance_info (dir);
629 gcc_assert (!n_bbs_in_dom_tree[dir]);
633 b->dom[dir] = et_new_tree (b);
635 n_bbs_in_dom_tree[dir] = n_basic_blocks + 2;
637 init_dom_info (&di, dir);
638 calc_dfs_tree (&di, dir);
639 calc_idoms (&di, dir);
643 TBB d = di.dom[di.dfs_order[b->index]];
646 et_set_father (b->dom[dir], di.dfs_to_bb[d]->dom[dir]);
650 dom_computed[dir] = DOM_NO_FAST_QUERY;
653 compute_dom_fast_query (dir);
656 /* Free dominance information for direction DIR. */
658 free_dominance_info (enum cdi_direction dir)
662 if (!dom_computed[dir])
667 delete_from_dominance_info (dir, bb);
670 /* If there are any nodes left, something is wrong. */
671 gcc_assert (!n_bbs_in_dom_tree[dir]);
673 dom_computed[dir] = DOM_NONE;
676 /* Return the immediate dominator of basic block BB. */
678 get_immediate_dominator (enum cdi_direction dir, basic_block bb)
680 struct et_node *node = bb->dom[dir];
682 gcc_assert (dom_computed[dir]);
687 return node->father->data;
690 /* Set the immediate dominator of the block possibly removing
691 existing edge. NULL can be used to remove any edge. */
693 set_immediate_dominator (enum cdi_direction dir, basic_block bb,
694 basic_block dominated_by)
696 struct et_node *node = bb->dom[dir];
698 gcc_assert (dom_computed[dir]);
702 if (node->father->data == dominated_by)
708 et_set_father (node, dominated_by->dom[dir]);
710 if (dom_computed[dir] == DOM_OK)
711 dom_computed[dir] = DOM_NO_FAST_QUERY;
714 /* Store all basic blocks immediately dominated by BB into BBS and return
717 get_dominated_by (enum cdi_direction dir, basic_block bb, basic_block **bbs)
720 struct et_node *node = bb->dom[dir], *son = node->son, *ason;
722 gcc_assert (dom_computed[dir]);
730 for (ason = son->right, n = 1; ason != son; ason = ason->right)
733 *bbs = xmalloc (n * sizeof (basic_block));
734 (*bbs)[0] = son->data;
735 for (ason = son->right, n = 1; ason != son; ason = ason->right)
736 (*bbs)[n++] = ason->data;
741 /* Find all basic blocks that are immediately dominated (in direction DIR)
742 by some block between N_REGION ones stored in REGION, except for blocks
743 in the REGION itself. The found blocks are stored to DOMS and their number
747 get_dominated_by_region (enum cdi_direction dir, basic_block *region,
748 unsigned n_region, basic_block *doms)
750 unsigned n_doms = 0, i;
753 for (i = 0; i < n_region; i++)
754 region[i]->rbi->duplicated = 1;
755 for (i = 0; i < n_region; i++)
756 for (dom = first_dom_son (dir, region[i]);
758 dom = next_dom_son (dir, dom))
759 if (!dom->rbi->duplicated)
760 doms[n_doms++] = dom;
761 for (i = 0; i < n_region; i++)
762 region[i]->rbi->duplicated = 0;
767 /* Redirect all edges pointing to BB to TO. */
769 redirect_immediate_dominators (enum cdi_direction dir, basic_block bb,
772 struct et_node *bb_node = bb->dom[dir], *to_node = to->dom[dir], *son;
774 gcc_assert (dom_computed[dir]);
784 et_set_father (son, to_node);
787 if (dom_computed[dir] == DOM_OK)
788 dom_computed[dir] = DOM_NO_FAST_QUERY;
791 /* Find first basic block in the tree dominating both BB1 and BB2. */
793 nearest_common_dominator (enum cdi_direction dir, basic_block bb1, basic_block bb2)
795 gcc_assert (dom_computed[dir]);
802 return et_nca (bb1->dom[dir], bb2->dom[dir])->data;
805 /* Return TRUE in case BB1 is dominated by BB2. */
807 dominated_by_p (enum cdi_direction dir, basic_block bb1, basic_block bb2)
809 struct et_node *n1 = bb1->dom[dir], *n2 = bb2->dom[dir];
811 gcc_assert (dom_computed[dir]);
813 if (dom_computed[dir] == DOM_OK)
814 return (n1->dfs_num_in >= n2->dfs_num_in
815 && n1->dfs_num_out <= n2->dfs_num_out);
817 return et_below (n1, n2);
820 /* Verify invariants of dominator structure. */
822 verify_dominators (enum cdi_direction dir)
827 gcc_assert (dom_computed[dir]);
833 dom_bb = recount_dominator (dir, bb);
834 if (dom_bb != get_immediate_dominator (dir, bb))
836 error ("dominator of %d should be %d, not %d",
837 bb->index, dom_bb->index, get_immediate_dominator(dir, bb)->index);
842 if (dir == CDI_DOMINATORS
843 && dom_computed[dir] >= DOM_NO_FAST_QUERY)
847 if (!dominated_by_p (dir, bb, ENTRY_BLOCK_PTR))
849 error ("ENTRY does not dominate bb %d", bb->index);
858 /* Determine immediate dominator (or postdominator, according to DIR) of BB,
859 assuming that dominators of other blocks are correct. We also use it to
860 recompute the dominators in a restricted area, by iterating it until it
861 reaches a fixed point. */
864 recount_dominator (enum cdi_direction dir, basic_block bb)
866 basic_block dom_bb = NULL;
869 gcc_assert (dom_computed[dir]);
871 if (dir == CDI_DOMINATORS)
873 for (e = bb->pred; e; e = e->pred_next)
875 /* Ignore the predecessors that either are not reachable from
876 the entry block, or whose dominator was not determined yet. */
877 if (!dominated_by_p (dir, e->src, ENTRY_BLOCK_PTR))
880 if (!dominated_by_p (dir, e->src, bb))
881 dom_bb = nearest_common_dominator (dir, dom_bb, e->src);
886 for (e = bb->succ; e; e = e->succ_next)
888 if (!dominated_by_p (dir, e->dest, bb))
889 dom_bb = nearest_common_dominator (dir, dom_bb, e->dest);
896 /* Iteratively recount dominators of BBS. The change is supposed to be local
897 and not to grow further. */
899 iterate_fix_dominators (enum cdi_direction dir, basic_block *bbs, int n)
902 basic_block old_dom, new_dom;
904 gcc_assert (dom_computed[dir]);
906 for (i = 0; i < n; i++)
907 set_immediate_dominator (dir, bbs[i], NULL);
912 for (i = 0; i < n; i++)
914 old_dom = get_immediate_dominator (dir, bbs[i]);
915 new_dom = recount_dominator (dir, bbs[i]);
916 if (old_dom != new_dom)
919 set_immediate_dominator (dir, bbs[i], new_dom);
924 for (i = 0; i < n; i++)
925 gcc_assert (get_immediate_dominator (dir, bbs[i]));
929 add_to_dominance_info (enum cdi_direction dir, basic_block bb)
931 gcc_assert (dom_computed[dir]);
932 gcc_assert (!bb->dom[dir]);
934 n_bbs_in_dom_tree[dir]++;
936 bb->dom[dir] = et_new_tree (bb);
938 if (dom_computed[dir] == DOM_OK)
939 dom_computed[dir] = DOM_NO_FAST_QUERY;
943 delete_from_dominance_info (enum cdi_direction dir, basic_block bb)
945 gcc_assert (dom_computed[dir]);
947 et_free_tree (bb->dom[dir]);
949 n_bbs_in_dom_tree[dir]--;
951 if (dom_computed[dir] == DOM_OK)
952 dom_computed[dir] = DOM_NO_FAST_QUERY;
955 /* Returns the first son of BB in the dominator or postdominator tree
956 as determined by DIR. */
959 first_dom_son (enum cdi_direction dir, basic_block bb)
961 struct et_node *son = bb->dom[dir]->son;
963 return son ? son->data : NULL;
966 /* Returns the next dominance son after BB in the dominator or postdominator
967 tree as determined by DIR, or NULL if it was the last one. */
970 next_dom_son (enum cdi_direction dir, basic_block bb)
972 struct et_node *next = bb->dom[dir]->right;
974 return next->father->son == next ? NULL : next->data;
978 debug_dominance_info (enum cdi_direction dir)
982 if ((bb2 = get_immediate_dominator (dir, bb)))
983 fprintf (stderr, "%i %i\n", bb->index, bb2->index);