2 * Copyright (C) 1995-2008 University of Karlsruhe. All right reserved.
4 * This file is part of libFirm.
6 * This file may be distributed and/or modified under the terms of the
7 * GNU General Public License version 2 as published by the Free Software
8 * Foundation and appearing in the file LICENSE.GPL included in the
9 * packaging of this file.
11 * Licensees holding valid libFirm Professional Edition licenses may use
12 * this file in accordance with the libFirm Commercial License.
13 * Agreement provided with the Software.
15 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
16 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * @brief Construct and access dominator / post dominator tree.
23 * @author Goetz Lindenmaier, Michael Beck, Rubino Geiss
36 #include "irgraph_t.h"
43 #define get_dom_info(bl) (&(bl)->attr.block.dom)
44 #define get_pdom_info(bl) (&(bl)->attr.block.pdom)
46 /*--------------------------------------------------------------------*/
47 /** Accessing the dominator and post dominator data structures **/
48 /*--------------------------------------------------------------------*/
50 ir_node *get_Block_idom(const ir_node *bl)
53 if (get_Block_dom_depth(bl) == -1) {
54 /* This block is not reachable from Start */
57 return get_dom_info(bl)->idom;
60 void set_Block_idom(ir_node *bl, ir_node *n)
62 ir_dom_info *bli = get_dom_info(bl);
66 /* Set the immediate dominator of bl to n */
70 * If we don't set the root of the dominator tree
71 * Append bl to the dominates queue of n.
74 ir_dom_info *ni = get_dom_info(n);
76 bli->next = ni->first;
81 ir_node *get_Block_ipostdom(const ir_node *bl)
84 if (get_Block_postdom_depth(bl) == -1) {
85 /* This block is not reachable from Start */
88 return get_pdom_info(bl)->idom;
91 void set_Block_ipostdom(ir_node *bl, ir_node *n)
93 ir_dom_info *bli = get_pdom_info(bl);
97 /* Set the immediate post dominator of bl to n */
101 * If we don't set the root of the post dominator tree
102 * Append bl to the post dominates queue of n.
105 ir_dom_info *ni = get_pdom_info(n);
107 bli->next = ni->first;
112 int get_Block_dom_pre_num(const ir_node *bl)
114 assert(is_Block(bl));
115 return get_dom_info(bl)->pre_num;
118 void set_Block_dom_pre_num(ir_node *bl, int num)
120 assert(is_Block(bl));
121 get_dom_info(bl)->pre_num = num;
124 int get_Block_dom_depth(const ir_node *bl)
126 assert(is_Block(bl));
127 return get_dom_info(bl)->dom_depth;
130 void set_Block_dom_depth(ir_node *bl, int depth)
132 assert(is_Block(bl));
133 get_dom_info(bl)->dom_depth = depth;
137 int get_Block_postdom_pre_num(const ir_node *bl)
139 assert(is_Block(bl));
140 return get_pdom_info(bl)->pre_num;
143 void set_Block_postdom_pre_num(ir_node *bl, int num)
145 assert(is_Block(bl));
146 get_pdom_info(bl)->pre_num = num;
149 int get_Block_postdom_depth(const ir_node *bl)
151 assert(is_Block(bl));
152 return get_pdom_info(bl)->dom_depth;
155 void set_Block_postdom_depth(ir_node *bl, int depth)
157 assert(is_Block(bl));
158 get_pdom_info(bl)->dom_depth = depth;
161 unsigned get_Block_dom_tree_pre_num(const ir_node *bl)
163 assert(is_Block(bl));
164 return get_dom_info(bl)->tree_pre_num;
167 unsigned get_Block_dom_max_subtree_pre_num(const ir_node *bl)
169 assert(is_Block(bl));
170 return get_dom_info(bl)->max_subtree_pre_num;
173 unsigned get_Block_pdom_tree_pre_num(const ir_node *bl)
175 assert(is_Block(bl));
176 return get_pdom_info(bl)->tree_pre_num;
179 unsigned get_Block_pdom_max_subtree_pre_num(const ir_node *bl)
181 assert(is_Block(bl));
182 return get_pdom_info(bl)->max_subtree_pre_num;
185 /* Check, if a block dominates another block. */
186 int block_dominates(const ir_node *a, const ir_node *b)
188 const ir_dom_info *ai, *bi;
190 if (is_Block(a) && is_Block(b)) {
191 ai = get_dom_info(a);
192 bi = get_dom_info(b);
193 return bi->tree_pre_num - ai->tree_pre_num
194 <= ai->max_subtree_pre_num - ai->tree_pre_num;
200 /* Check, if a block strictly dominates another block. */
201 int block_strictly_dominates(const ir_node *a, const ir_node *b)
203 return (a != b) && block_dominates(a, b);
206 /* Returns the smallest common dominator block of two nodes. */
207 ir_node *node_smallest_common_dominator(ir_node *a, ir_node *b)
209 ir_node *bl_a = is_Block(a) ? a : get_nodes_block(a);
210 ir_node *bl_b = is_Block(b) ? b : get_nodes_block(b);
211 ir_node *dom_bl = NULL;
213 /* Check if block of a dominates block of b */
214 if (block_dominates(bl_a, bl_b))
216 /* Check if block of b dominates block of a */
217 else if (block_dominates(bl_b, bl_a))
220 /* walk up dominator tree and search for first block dominating a and b */
222 bl_a = get_Block_idom(bl_a);
224 assert(! is_Bad(bl_a) && "block is dead?");
226 if (block_dominates(bl_a, bl_b))
234 /* Returns the smallest common dominator block of all users of a node. */
235 ir_node *node_users_smallest_common_dominator(ir_node *irn, int handle_phi)
237 int n, j, i = 0, success;
238 ir_node **user_blocks, *dom_bl;
239 const ir_edge_t *edge;
241 assert(! is_Block(irn) && "WRONG USAGE of node_users_smallest_common_dominator");
242 assert(edges_activated(get_irn_irg(irn)) && "need edges activated");
244 n = get_irn_n_edges(irn);
246 /* get array to hold all block of the node users */
247 NEW_ARR_A(ir_node *, user_blocks, n);
248 foreach_out_edge(irn, edge) {
249 ir_node *src = get_edge_src_irn(edge);
251 if (is_Phi(src) && handle_phi) {
252 /* get the corresponding cfg predecessor block if phi handling requested */
253 j = get_edge_src_pos(edge);
254 assert(j >= 0 && "kaputt");
255 user_blocks[i++] = get_Block_cfgpred_block(get_nodes_block(src), j);
258 user_blocks[i++] = is_Block(src) ? src : get_nodes_block(src);
261 assert(i == n && "get_irn_n_edges probably broken");
263 /* in case of only one user: return the block of the user */
265 return user_blocks[0];
268 /* search the smallest block dominating all user blocks */
270 dom_bl = node_smallest_common_dominator(user_blocks[i], user_blocks[i + 1]);
273 /* check if this block dominates all remaining blocks as well */
274 for (j = i + 2; j < n; j++) {
275 if (! block_dominates(dom_bl, user_blocks[j]))
282 /* inherit the dominator block of the first (i + 1) users */
283 user_blocks[++i] = dom_bl;
286 assert(success && "no block found dominating all users");
292 /* Get the first node in the list of nodes dominated by a given block. */
293 ir_node *get_Block_dominated_first(const ir_node *bl)
295 assert(is_Block(bl));
296 return get_dom_info(bl)->first;
299 /* Get the next node in a list of nodes which are dominated by some
301 ir_node *get_Block_dominated_next(const ir_node *bl)
303 assert(is_Block(bl));
304 return get_dom_info(bl)->next;
307 /* Check, if a block post dominates another block. */
308 int block_postdominates(const ir_node *a, const ir_node *b)
310 const ir_dom_info *ai, *bi;
312 if (is_Block(a) && is_Block(b)) {
313 ai = get_pdom_info(a);
314 bi = get_pdom_info(b);
315 return bi->tree_pre_num - ai->tree_pre_num
316 <= ai->max_subtree_pre_num - ai->tree_pre_num;
322 /* Check, if a block strictly dominates another block. */
323 int block_strictly_postdominates(const ir_node *a, const ir_node *b)
325 return (a != b) && block_postdominates(a, b);
329 /* Get the first node in the list of nodes post dominated by a given block. */
330 ir_node *get_Block_postdominated_first(const ir_node *bl)
332 assert(is_Block(bl));
333 return get_pdom_info(bl)->first;
336 /* Get the next node in a list of nodes which are post dominated by some
338 ir_node *get_Block_postdominated_next(const ir_node *bl)
340 assert(is_Block(bl));
341 return get_pdom_info(bl)->next;
344 /* Visit all nodes in the dominator subtree of a given node. */
345 void dom_tree_walk(ir_node *bl, irg_walk_func *pre,
346 irg_walk_func *post, void *env)
353 dominates_for_each(bl, p) {
354 dom_tree_walk(p, pre, post, env);
361 /* Visit all nodes in the post dominator subtree of a given node. */
362 void postdom_tree_walk(ir_node *bl, irg_walk_func *pre,
363 irg_walk_func *post, void *env)
370 postdominates_for_each(bl, p) {
371 postdom_tree_walk(p, pre, post, env);
378 /* Walk over the dominator tree of an irg starting at the root. */
379 void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
380 irg_walk_func *post, void *env)
382 /* The root of the dominator tree should be the Start block. */
383 ir_node *root = get_irg_start_block(irg);
385 assert(irg->dom_state == dom_consistent
386 && "The dominators of the irg must be consistent");
387 assert(root && "The start block of the graph is NULL?");
388 assert(get_dom_info(root)->idom == NULL
389 && "The start node in the graph must be the root of the dominator tree");
390 dom_tree_walk(root, pre, post, env);
393 /* Walk over the post dominator tree of an irg starting at the root. */
394 void postdom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
395 irg_walk_func *post, void *env)
397 /* The root of the dominator tree should be the End block. */
398 ir_node *root = get_irg_end_block(irg);
400 assert(irg->pdom_state == dom_consistent
401 && "The dominators of the irg must be consistent");
402 assert(root && "The end block of the graph is NULL?");
403 assert(get_pdom_info(root)->idom == NULL
404 && "The End block node in the graph must be the root of the post dominator tree");
405 postdom_tree_walk(root, pre, post, env);
409 static void assign_tree_dom_pre_order(ir_node *bl, void *data)
411 unsigned *num = data;
412 ir_dom_info *bi = get_dom_info(bl);
414 bi->tree_pre_num = (*num)++;
417 static void assign_tree_dom_pre_order_max(ir_node *bl, void *data)
419 ir_dom_info *bi = get_dom_info(bl);
422 unsigned children = 0;
425 for (p = bi->first; p; p = get_dom_info(p)->next) {
426 unsigned max_p = get_dom_info(p)->max_subtree_pre_num;
427 max = max > max_p ? max : max_p;
431 bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
432 assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
435 static void assign_tree_postdom_pre_order(ir_node *bl, void *data)
437 unsigned *num = data;
438 ir_dom_info *bi = get_pdom_info(bl);
440 bi->tree_pre_num = (*num)++;
443 static void assign_tree_postdom_pre_order_max(ir_node *bl, void *data)
445 ir_dom_info *bi = get_pdom_info(bl);
448 unsigned children = 0;
451 for (p = bi->first; p; p = get_pdom_info(p)->next) {
452 unsigned max_p = get_pdom_info(p)->max_subtree_pre_num;
453 max = max > max_p ? max : max_p;
457 bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
458 assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
461 /*--------------------------------------------------------------------*/
462 /* Building and Removing the dominator data structure */
463 /*--------------------------------------------------------------------*/
466 * count the number of blocks and clears the post dominance info
468 static void count_and_init_blocks_pdom(ir_node *bl, void *env)
470 int *n_blocks = (int *) env;
472 if (is_Block_dead(bl))
477 memset(get_pdom_info(bl), 0, sizeof(ir_dom_info));
478 set_Block_ipostdom(bl, NULL);
479 set_Block_postdom_pre_num(bl, -1);
480 set_Block_postdom_depth(bl, -1);
483 /** temporary type used while constructing the dominator / post dominator tree. */
484 typedef struct tmp_dom_info {
485 ir_node *block; /**< backlink */
487 struct tmp_dom_info *semi; /**< semidominator */
488 struct tmp_dom_info *parent;
489 struct tmp_dom_info *label; /**< used for LINK and EVAL */
490 struct tmp_dom_info *ancestor;/**< used for LINK and EVAL */
491 struct tmp_dom_info *dom; /**< After step 3, if the semidominator of w is
492 its immediate dominator, then w->dom is the
493 immediate dominator of w. Otherwise w->dom
494 is a vertex v whose number is smaller than
495 w and whose immediate dominator is also w's
496 immediate dominator. After step 4, w->dom
497 is the immediate dominator of w. */
498 struct tmp_dom_info *bucket; /**< set of vertices with same semidominator */
501 /** Struct to pass info through walker. */
509 * Walks Blocks along the out data structure. If recursion started with
510 * Start block misses control dead blocks.
512 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
513 tmp_dom_info *tdi_list, int *used, int n_blocks)
518 if (is_Block_dead(bl))
521 assert(is_Block(bl));
522 if (Block_block_visited(bl))
524 mark_Block_block_visited(bl);
525 set_Block_dom_pre_num(bl, *used);
527 assert(*used < n_blocks);
528 tdi = &tdi_list[*used];
533 tdi->ancestor = NULL;
535 tdi->parent = parent;
539 for (i = get_Block_n_cfg_outs_ka(bl) - 1; i >= 0; --i) {
540 ir_node *pred = get_Block_cfg_out_ka(bl, i);
541 /* can happen for half-optimized dead code (I've seen this in student
546 init_tmp_dom_info(pred, tdi, tdi_list, used, n_blocks);
551 * Walks Blocks along the control flow. If recursion started with
552 * End block misses blocks in endless loops.
554 static void init_tmp_pdom_info(ir_node *bl, tmp_dom_info *parent,
555 tmp_dom_info *tdi_list, int* used, int n_blocks)
560 if (is_Block_dead(bl))
563 assert(is_Block(bl));
564 if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
566 mark_Block_block_visited(bl);
567 set_Block_postdom_pre_num(bl, *used);
569 assert(*used < n_blocks);
570 tdi = &tdi_list[*used];
575 tdi->ancestor = NULL;
577 tdi->parent = parent;
581 for (i = get_Block_n_cfgpreds(bl) - 1; i >= 0; --i) {
582 ir_node *pred = get_Block_cfgpred_block(bl, i);
585 assert(is_Block(pred));
586 init_tmp_pdom_info(pred, tdi, tdi_list, used, n_blocks);
589 /* Handle keep-alives. Note that the preprocessing
590 in init_construction() had already killed all
591 phantom keep-alive edges. All remaining block keep-alives
592 are really edges to endless loops.
594 if (bl == get_irg_end_block(current_ir_graph)) {
595 ir_node *end = get_irg_end(current_ir_graph);
597 for (i = get_irn_arity(end) - 1; i >= 0; --i) {
598 ir_node *pred = get_irn_n(end, i);
601 init_tmp_pdom_info(pred, tdi, tdi_list, used, n_blocks);
606 static void dom_compress(tmp_dom_info *v)
608 assert (v->ancestor);
609 if (v->ancestor->ancestor) {
610 dom_compress (v->ancestor);
611 if (v->ancestor->label->semi < v->label->semi) {
612 v->label = v->ancestor->label;
614 v->ancestor = v->ancestor->ancestor;
619 * if V is a root, return v, else return the vertex u, not being the
620 * root, with minimum u->semi on the path from v to its root.
622 inline static tmp_dom_info *dom_eval(tmp_dom_info *v)
624 if (!v->ancestor) return v;
629 /** make V W's ancestor */
630 inline static void dom_link(tmp_dom_info *v, tmp_dom_info *w)
636 * Walker: count the number of blocks and clears the dominance info
638 static void count_and_init_blocks_dom(ir_node *bl, void *env)
640 int *n_blocks = (int *) env;
641 if (is_Block_dead(bl))
646 memset(get_dom_info(bl), 0, sizeof(ir_dom_info));
647 set_Block_idom(bl, NULL);
648 set_Block_dom_pre_num(bl, -1);
649 set_Block_dom_depth(bl, -1);
652 /* Computes the dominator trees. Sets a flag in irg to "dom_consistent".
653 If the control flow of the graph is changed this flag must be set to
654 "dom_inconsistent". */
655 void compute_doms(ir_graph *irg)
657 ir_graph *rem = current_ir_graph;
658 int n_blocks, used, i, j;
659 tmp_dom_info *tdi_list; /* Ein Golf? */
661 current_ir_graph = irg;
663 /* Update graph state */
664 assert(get_irg_phase_state(irg) != phase_building);
665 irg->dom_state = dom_consistent;
667 /* Count the number of blocks in the graph. */
669 irg_block_walk_graph(irg, count_and_init_blocks_dom, NULL, &n_blocks);
671 /* Memory for temporary information. */
672 tdi_list = XMALLOCNZ(tmp_dom_info, n_blocks);
674 /* We need the out data structure. */
675 assure_irg_outs(irg);
677 /* this with a standard walker as passing the parent to the sons isn't
680 inc_irg_block_visited(irg);
681 init_tmp_dom_info(get_irg_start_block(irg), NULL, tdi_list, &used, n_blocks);
682 /* If not all blocks are reachable from Start by out edges this assertion
684 assert(used == n_blocks && "Precondition for dom construction violated"); */
685 assert(used <= n_blocks && "Precondition for dom construction violated");
689 for (i = n_blocks-1; i > 0; i--) { /* Don't iterate the root, it's done. */
691 tmp_dom_info *w = &tdi_list[i];
695 irn_arity = get_irn_arity(w->block);
696 for (j = 0; j < irn_arity; j++) {
697 ir_node *pred = get_Block_cfgpred_block(w->block, j);
700 if (is_Bad(pred) || (get_Block_dom_pre_num (pred) == -1))
701 continue; /* control-dead */
703 u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
704 if (u->semi < w->semi) w->semi = u->semi;
707 /* handle keep-alives if we are at the end block */
708 if (w->block == get_irg_end_block(irg)) {
709 ir_node *end = get_irg_end(irg);
711 irn_arity = get_irn_arity(end);
712 for (j = 0; j < irn_arity; j++) {
713 ir_node *pred = get_irn_n(end, j);
716 if (is_no_Block(pred) || get_Block_dom_pre_num(pred) == -1)
717 continue; /* control-dead */
719 u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
720 if (u->semi < w->semi) w->semi = u->semi;
724 /* Add w to w->semi's bucket. w is in exactly one bucket, so
725 buckets can been implemented as linked lists. */
726 w->bucket = w->semi->bucket;
729 dom_link (w->parent, w);
732 while (w->parent->bucket) {
734 v = w->parent->bucket;
735 /* remove v from w->parent->bucket */
736 w->parent->bucket = v->bucket;
740 if (u->semi < v->semi)
747 tdi_list[0].dom = NULL;
748 set_Block_idom(tdi_list[0].block, NULL);
749 set_Block_dom_depth(tdi_list[0].block, 1);
750 for (i = 1; i < n_blocks; i++) {
751 tmp_dom_info *w = &tdi_list[i];
755 continue; /* control dead */
757 if (w->dom != w->semi) w->dom = w->dom->dom;
758 set_Block_idom(w->block, w->dom->block);
760 /* blocks dominated by dead one's are still dead */
761 depth = get_Block_dom_depth(w->dom->block);
764 set_Block_dom_depth(w->block, depth);
770 /* Do a walk over the tree and assign the tree pre orders. */
772 unsigned tree_pre_order = 0;
773 dom_tree_walk_irg(irg, assign_tree_dom_pre_order,
774 assign_tree_dom_pre_order_max, &tree_pre_order);
776 current_ir_graph = rem;
779 void assure_doms(ir_graph *irg)
781 if (get_irg_dom_state(irg) != dom_consistent)
785 void free_dom(ir_graph *irg)
787 /* Update graph state */
788 assert(get_irg_phase_state(irg) != phase_building);
789 irg->dom_state = dom_none;
791 /* With the implementation right now there is nothing to free,
792 but better call it anyways... */
795 /* Computes the post dominator trees. Sets a flag in irg to "dom_consistent".
796 If the control flow of the graph is changed this flag must be set to
797 "dom_inconsistent". */
798 void compute_postdoms(ir_graph *irg)
800 ir_graph *rem = current_ir_graph;
801 int n_blocks, used, i, j;
802 tmp_dom_info *tdi_list;
804 current_ir_graph = irg;
806 /* Update graph state */
807 assert(get_irg_phase_state(irg) != phase_building);
808 irg->pdom_state = dom_consistent;
810 /* Count the number of blocks in the graph. */
812 irg_block_walk_graph(irg, count_and_init_blocks_pdom, NULL, &n_blocks);
814 /* Memory for temporary information. */
815 tdi_list = XMALLOCNZ(tmp_dom_info, n_blocks);
817 /* We need the out data structure. */
818 assure_irg_outs(irg);
820 /* this with a standard walker as passing the parent to the sons isn't
823 inc_irg_block_visited(irg);
824 init_tmp_pdom_info(get_irg_end_block(irg), NULL, tdi_list, &used, n_blocks);
825 /* If not all blocks are reachable from End by cfg edges this assertion
827 assert(used == n_blocks && "Precondition for dom construction violated"); */
831 for (i = n_blocks-1; i > 0; i--) { /* Don't iterate the root, it's done. */
833 tmp_dom_info *w = &tdi_list[i];
837 irn_arity = get_Block_n_cfg_outs_ka(w->block);
838 for (j = 0; j < irn_arity; j++) {
839 ir_node *succ = get_Block_cfg_out_ka(w->block, j);
842 if (get_Block_postdom_pre_num (succ) == -1)
843 continue; /* endless-loop */
845 u = dom_eval (&tdi_list[get_Block_postdom_pre_num(succ)]);
846 if (u->semi < w->semi) w->semi = u->semi;
848 /* Add w to w->semi's bucket. w is in exactly one bucket, so
849 buckets can be implemented as linked lists. */
850 w->bucket = w->semi->bucket;
853 dom_link (w->parent, w);
856 while (w->parent->bucket) {
858 v = w->parent->bucket;
859 /* remove v from w->parent->bucket */
860 w->parent->bucket = v->bucket;
864 if (u->semi < v->semi)
871 tdi_list[0].dom = NULL;
872 set_Block_ipostdom(tdi_list[0].block, NULL);
873 set_Block_postdom_depth(tdi_list[0].block, 1);
874 for (i = 1; i < n_blocks; i++) {
875 tmp_dom_info *w = &tdi_list[i];
877 if (w->dom != w->semi) w->dom = w->dom->dom;
878 set_Block_ipostdom(w->block, w->dom->block);
879 set_Block_postdom_depth(w->block, get_Block_postdom_depth(w->dom->block) + 1);
885 /* Do a walk over the tree and assign the tree pre orders. */
887 unsigned tree_pre_order = 0;
888 postdom_tree_walk_irg(irg, assign_tree_postdom_pre_order,
889 assign_tree_postdom_pre_order_max, &tree_pre_order);
891 current_ir_graph = rem;
894 void assure_postdoms(ir_graph *irg)
896 if (get_irg_postdom_state(irg) != dom_consistent)
897 compute_postdoms(irg);
900 void free_postdom(ir_graph *irg)
902 /* Update graph state */
903 assert(get_irg_phase_state(irg) != phase_building);
904 irg->pdom_state = dom_none;
906 /* With the implementation right now there is nothing to free,
907 but better call it anyways... */