3 * File name: ir/ana/irdom.c
4 * Purpose: Construct and access dominator / post dominator tree.
5 * Author: Goetz Lindenmaier
6 * Modified by: Michael Beck, Rubino Geiss
9 * Copyright: (c) 2002-2003 Universitaet Karlsruhe
10 * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
32 #include "irgraph_t.h" /* To access state field. */
39 #define get_dom_info(bl) (&(bl)->attr.block.dom)
40 #define get_pdom_info(bl) (&(bl)->attr.block.pdom)
42 /*--------------------------------------------------------------------*/
43 /** Accessing the dominator and post dominator data structures **/
44 /*--------------------------------------------------------------------*/
46 ir_node *get_Block_idom(const ir_node *bl) {
48 if (get_Block_dom_depth(bl) == -1) {
49 /* This block is not reachable from Start */
52 return get_dom_info(bl)->idom;
55 void set_Block_idom(ir_node *bl, ir_node *n) {
56 dom_info *bli = get_dom_info(bl);
58 assert(get_irn_op(bl) == op_Block);
60 /* Set the immediate dominator of bl to n */
64 * If we don't set the root of the dominator tree
65 * Append bl to the dominates queue of n.
68 dom_info *ni = get_dom_info(n);
70 bli->next = ni->first;
75 ir_node *get_Block_ipostdom(const ir_node *bl) {
77 if (get_Block_postdom_depth(bl) == -1) {
78 /* This block is not reachable from Start */
81 return get_pdom_info(bl)->idom;
84 void set_Block_ipostdom(ir_node *bl, ir_node *n) {
85 dom_info *bli = get_pdom_info(bl);
87 assert(get_irn_op(bl) == op_Block);
89 /* Set the immediate post dominator of bl to n */
93 * If we don't set the root of the post dominator tree
94 * Append bl to the post dominates queue of n.
97 dom_info *ni = get_pdom_info(n);
99 bli->next = ni->first;
104 int get_Block_dom_pre_num(const ir_node *bl) {
105 assert(get_irn_op(bl) == op_Block);
106 return get_dom_info(bl)->pre_num;
109 void set_Block_dom_pre_num(ir_node *bl, int num) {
110 assert(get_irn_op(bl) == op_Block);
111 get_dom_info(bl)->pre_num = num;
114 int get_Block_dom_depth(const ir_node *bl) {
115 assert(get_irn_op(bl) == op_Block);
116 return get_dom_info(bl)->dom_depth;
119 void set_Block_dom_depth(ir_node *bl, int depth) {
120 assert(get_irn_op(bl) == op_Block);
121 get_dom_info(bl)->dom_depth = depth;
125 int get_Block_postdom_pre_num(const ir_node *bl) {
126 assert(get_irn_op(bl) == op_Block);
127 return get_pdom_info(bl)->pre_num;
130 void set_Block_postdom_pre_num(ir_node *bl, int num) {
131 assert(get_irn_op(bl) == op_Block);
132 get_pdom_info(bl)->pre_num = num;
135 int get_Block_postdom_depth(const ir_node *bl) {
136 assert(get_irn_op(bl) == op_Block);
137 return get_pdom_info(bl)->dom_depth;
140 void set_Block_postdom_depth(ir_node *bl, int depth) {
141 assert(get_irn_op(bl) == op_Block);
142 get_pdom_info(bl)->dom_depth = depth;
145 unsigned get_Block_dom_tree_pre_num(const ir_node *bl)
147 assert(is_Block(bl));
148 return get_dom_info(bl)->tree_pre_num;
151 unsigned get_Block_dom_max_subtree_pre_num(const ir_node *bl)
153 assert(is_Block(bl));
154 return get_dom_info(bl)->max_subtree_pre_num;
157 unsigned get_Block_pdom_tree_pre_num(const ir_node *bl)
159 assert(is_Block(bl));
160 return get_pdom_info(bl)->tree_pre_num;
163 unsigned get_Block_pdom_max_subtree_pre_num(const ir_node *bl)
165 assert(is_Block(bl));
166 return get_pdom_info(bl)->max_subtree_pre_num;
169 /* Check, if a block dominates another block. */
170 int block_dominates(const ir_node *a, const ir_node *b)
172 const dom_info *ai, *bi;
174 if (is_Block(a) && is_Block(b)) {
175 ai = get_dom_info(a);
176 bi = get_dom_info(b);
177 return bi->tree_pre_num - ai->tree_pre_num
178 <= ai->max_subtree_pre_num - ai->tree_pre_num;
184 /* Returns the smallest common dominator block of two nodes. */
185 ir_node *node_smallest_common_dominator(ir_node *a, ir_node *b) {
186 ir_node *bl_a = is_Block(a) ? a : get_nodes_block(a);
187 ir_node *bl_b = is_Block(b) ? b : get_nodes_block(b);
188 ir_node *dom_bl = NULL;
190 /* Check if block of a dominates block of b */
191 if (block_dominates(bl_a, bl_b))
193 /* Check if block of b dominates block of a */
194 else if (block_dominates(bl_b, bl_a))
197 /* walk up dominator tree and search for first block dominating a and b */
199 bl_a = get_Block_idom(bl_a);
201 assert(! is_Bad(bl_a) && "block is dead?");
203 if (block_dominates(bl_a, bl_b))
211 /* Returns the smallest common dominator block of all users of a node. */
212 ir_node *node_users_smallest_common_dominator(ir_node *irn, int handle_phi) {
213 int n, j, i = 0, success;
214 ir_node **user_blocks, *dom_bl;
215 const ir_edge_t *edge;
217 assert(! is_Block(irn) && "WRONG USAGE of node_users_smallest_common_dominator");
218 assert(edges_activated(get_irn_irg(irn)) && "need edges activated");
220 n = get_irn_n_edges(irn);
222 /* get array to hold all block of the node users */
223 NEW_ARR_A(ir_node *, user_blocks, n);
224 foreach_out_edge(irn, edge) {
225 ir_node *src = get_edge_src_irn(edge);
227 if (is_Phi(src) && handle_phi) {
228 /* get the corresponding cfg predecessor block if phi handling requested */
229 j = get_irn_pred_pos(src, irn);
230 assert(j >= 0 && "kaputt");
231 user_blocks[i++] = get_Block_cfgpred_block(get_nodes_block(src), j);
234 user_blocks[i++] = is_Block(src) ? src : get_nodes_block(src);
237 /* in case of only one user: return the block of the user */
239 return user_blocks[0];
242 /* search the smallest block dominating all user blocks */
244 dom_bl = node_smallest_common_dominator(user_blocks[i], user_blocks[i + 1]);
247 /* check if this block dominates all remaining blocks as well */
248 for (j = i + 2; j < n; j++) {
249 if (! block_dominates(dom_bl, user_blocks[j]))
256 /* inherit the dominator block of the first (i + 1) users */
257 user_blocks[++i] = dom_bl;
260 assert(success && "no block found dominating all users");
266 /* Get the first node in the list of nodes dominated by a given block. */
267 ir_node *get_Block_dominated_first(const ir_node *bl)
269 assert(is_Block(bl));
270 return get_dom_info(bl)->first;
273 /* Get the next node in a list of nodes which are dominated by some
275 ir_node *get_Block_dominated_next(const ir_node *bl)
277 assert(is_Block(bl));
278 return get_dom_info(bl)->next;
281 /* Check, if a block post dominates another block. */
282 int block_postdominates(const ir_node *a, const ir_node *b)
284 const dom_info *ai, *bi;
286 if (is_Block(a) && is_Block(b)) {
287 ai = get_pdom_info(a);
288 bi = get_pdom_info(b);
289 return bi->tree_pre_num - ai->tree_pre_num
290 <= ai->max_subtree_pre_num - ai->tree_pre_num;
296 /* Get the first node in the list of nodes post dominated by a given block. */
297 ir_node *get_Block_postdominated_first(const ir_node *bl)
299 assert(is_Block(bl));
300 return get_pdom_info(bl)->first;
303 /* Get the next node in a list of nodes which are post dominated by some
305 ir_node *get_Block_postdominated_next(const ir_node *bl)
307 assert(is_Block(bl));
308 return get_pdom_info(bl)->next;
311 /* Visit all nodes in the dominator subtree of a given node. */
312 void dom_tree_walk(ir_node *bl, irg_walk_func *pre,
313 irg_walk_func *post, void *env)
320 dominates_for_each(bl, p) {
321 dom_tree_walk(p, pre, post, env);
328 /* Visit all nodes in the post dominator subtree of a given node. */
329 void postdom_tree_walk(ir_node *bl, irg_walk_func *pre,
330 irg_walk_func *post, void *env)
337 postdominates_for_each(bl, p) {
338 postdom_tree_walk(p, pre, post, env);
345 /* Walk over the dominator tree of an irg starting at the root. */
346 void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
347 irg_walk_func *post, void *env)
349 /* The root of the dominator tree should be the Start block. */
350 ir_node *root = get_irg_start_block(irg);
352 assert(irg->dom_state == dom_consistent
353 && "The dominators of the irg must be consistent");
354 assert(root && "The start block of the graph is NULL?");
355 assert(get_dom_info(root)->idom == NULL
356 && "The start node in the graph must be the root of the dominator tree");
357 dom_tree_walk(root, pre, post, env);
360 /* Walk over the post dominator tree of an irg starting at the root. */
361 void postdom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
362 irg_walk_func *post, void *env)
364 /* The root of the dominator tree should be the End block. */
365 ir_node *root = get_irg_end_block(irg);
367 assert(irg->pdom_state == dom_consistent
368 && "The dominators of the irg must be consistent");
369 assert(root && "The end block of the graph is NULL?");
370 assert(get_pdom_info(root)->idom == NULL
371 && "The End block node in the graph must be the root of the post dominator tree");
372 postdom_tree_walk(root, pre, post, env);
376 static void assign_tree_dom_pre_order(ir_node *bl, void *data)
378 unsigned *num = data;
379 dom_info *bi = get_dom_info(bl);
381 bi->tree_pre_num = (*num)++;
384 static void assign_tree_dom_pre_order_max(ir_node *bl, void *data)
386 dom_info *bi = get_dom_info(bl);
389 unsigned children = 0;
391 for(p = bi->first; p; p = get_dom_info(p)->next) {
392 unsigned max_p = get_dom_info(p)->max_subtree_pre_num;
393 max = max > max_p ? max : max_p;
397 bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
398 assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
401 static void assign_tree_postdom_pre_order(ir_node *bl, void *data)
403 unsigned *num = data;
404 dom_info *bi = get_pdom_info(bl);
406 bi->tree_pre_num = (*num)++;
409 static void assign_tree_postdom_pre_order_max(ir_node *bl, void *data)
411 dom_info *bi = get_pdom_info(bl);
414 unsigned children = 0;
416 for(p = bi->first; p; p = get_pdom_info(p)->next) {
417 unsigned max_p = get_pdom_info(p)->max_subtree_pre_num;
418 max = max > max_p ? max : max_p;
422 bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
423 assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
426 /*--------------------------------------------------------------------*/
427 /* Building and Removing the dominator data structure */
428 /*--------------------------------------------------------------------*/
431 * count the number of blocks and clears the post dominance info
433 static void count_and_init_blocks_pdom(ir_node *bl, void *env) {
434 int *n_blocks = (int *) env;
437 memset(get_pdom_info(bl), 0, sizeof(dom_info));
438 set_Block_ipostdom(bl, NULL);
439 set_Block_postdom_pre_num(bl, -1);
440 set_Block_postdom_depth(bl, -1);
443 /** temporary type used while constructing the dominator / post dominator tree. */
444 typedef struct tmp_dom_info {
445 ir_node *block; /**< backlink */
447 struct tmp_dom_info *semi; /**< semidominator */
448 struct tmp_dom_info *parent;
449 struct tmp_dom_info *label; /**< used for LINK and EVAL */
450 struct tmp_dom_info *ancestor;/**< used for LINK and EVAL */
451 struct tmp_dom_info *dom; /**< After step 3, if the semidominator of w is
452 its immediate dominator, then w->dom is the
453 immediate dominator of w. Otherwise w->dom
454 is a vertex v whose number is smaller than
455 w and whose immediate dominator is also w's
456 immediate dominator. After step 4, w->dom
457 is the immediate dominator of w. */
458 struct tmp_dom_info *bucket; /**< set of vertices with same semidominator */
461 /** Struct to pass info through walker. */
469 * Walks Blocks along the out data structure. If recursion started with
470 * Start block misses control dead blocks.
472 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
473 tmp_dom_info *tdi_list, int *used) {
477 assert(is_Block(bl));
478 if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
480 mark_Block_block_visited(bl);
481 set_Block_dom_pre_num(bl, *used);
483 tdi = &tdi_list[*used];
488 tdi->ancestor = NULL;
490 tdi->parent = parent;
494 for (i = get_Block_n_cfg_outs_ka(bl) - 1; i >= 0; --i) {
495 ir_node *pred = get_Block_cfg_out_ka(bl, i);
496 assert(is_Block(pred));
497 init_tmp_dom_info(pred, tdi, tdi_list, used);
502 * Walks Blocks along the control flow. If recursion started with
503 * End block misses blocks in endless loops.
505 static void init_tmp_pdom_info(ir_node *bl, tmp_dom_info *parent,
506 tmp_dom_info *tdi_list, int* used) {
510 assert(is_Block(bl));
511 if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
513 mark_Block_block_visited(bl);
514 set_Block_postdom_pre_num(bl, *used);
516 tdi = &tdi_list[*used];
521 tdi->ancestor = NULL;
523 tdi->parent = parent;
527 for (i = get_Block_n_cfgpreds(bl) - 1; i >= 0; --i) {
528 ir_node *pred = get_Block_cfgpred_block(bl, i);
531 assert(is_Block(pred));
532 init_tmp_pdom_info(pred, tdi, tdi_list, used);
535 /* Handle keep-alives. Note that the preprocessing
536 in init_construction() had already killed all
537 phantom keep-alive edges. All remaining block keep-alives
538 are really edges to endless loops.
540 if (bl == get_irg_end_block(current_ir_graph)) {
541 ir_node *end = get_irg_end(current_ir_graph);
543 for (i = get_irn_arity(end) - 1; i >= 0; --i) {
544 ir_node *pred = get_irn_n(end, i);
547 init_tmp_pdom_info(pred, tdi, tdi_list, used);
552 static void dom_compress(tmp_dom_info *v)
554 assert (v->ancestor);
555 if (v->ancestor->ancestor) {
556 dom_compress (v->ancestor);
557 if (v->ancestor->label->semi < v->label->semi) {
558 v->label = v->ancestor->label;
560 v->ancestor = v->ancestor->ancestor;
565 * if V is a root, return v, else return the vertex u, not being the
566 * root, with minimum u->semi on the path from v to its root.
568 INLINE static tmp_dom_info *dom_eval (tmp_dom_info *v)
570 if (!v->ancestor) return v;
575 /** make V W's ancestor */
576 INLINE static void dom_link(tmp_dom_info *v, tmp_dom_info *w)
582 * Walker: count the number of blocks and clears the dominance info
584 static void count_and_init_blocks_dom(ir_node *bl, void *env) {
585 int *n_blocks = (int *) env;
588 memset(get_dom_info(bl), 0, sizeof(dom_info));
589 set_Block_idom(bl, NULL);
590 set_Block_dom_pre_num(bl, -1);
591 set_Block_dom_depth(bl, -1);
595 * Initialize the dominance/postdominance construction:
597 * - count the number of blocks
598 * - clear the dominance info
599 * - remove Block-keepalives of live blocks to reduce
600 * the number of "phantom" block edges
602 * @param irg the graph
603 * @param pre a walker function that will be called for every block in the graph
605 static int init_construction(ir_graph *irg, irg_walk_func *pre) {
606 ir_graph *rem = current_ir_graph;
611 current_ir_graph = irg;
613 /* this visits only the reachable blocks */
614 irg_block_walk(get_irg_end_block(irg), pre, NULL, &n_blocks);
616 /* now visit the unreachable (from End) Blocks and remove unnecessary keep-alives */
617 end = get_irg_end(irg);
618 arity = get_End_n_keepalives(end);
619 if (arity) { /* we have keep-alives */
623 NEW_ARR_A(ir_node *, in, arity);
624 for (i = j = 0; i < arity; i++) {
625 ir_node *pred = get_End_keepalive(end, i);
627 if (get_irn_op(pred) == op_Block) {
628 if (Block_not_block_visited(pred)) {
629 /* we found a endless loop */
630 dec_irg_block_visited(irg);
631 irg_block_walk(pred, pre, NULL, &n_blocks);
639 /* we kill some Block keep-alives */
640 set_End_keepalives(end, j, in);
641 set_irg_outs_inconsistent(irg);
645 current_ir_graph = rem;
650 /* Computes the dominator trees. Sets a flag in irg to "dom_consistent".
651 If the control flow of the graph is changed this flag must be set to
652 "dom_inconsistent". */
653 void compute_doms(ir_graph *irg) {
654 ir_graph *rem = current_ir_graph;
655 int n_blocks, used, i, j;
656 tmp_dom_info *tdi_list; /* Ein Golf? */
658 current_ir_graph = irg;
660 /* Update graph state */
661 assert(get_irg_phase_state(irg) != phase_building);
662 irg->dom_state = dom_consistent;
664 /* Count the number of blocks in the graph. */
665 n_blocks = init_construction(irg, count_and_init_blocks_dom);
667 /* Memory for temporary information. */
668 tdi_list = xcalloc(n_blocks, sizeof(tdi_list[0]));
670 /* We need the out data structure. */
671 assure_irg_outs(irg);
673 /* this with a standard walker as passing the parent to the sons isn't
676 inc_irg_block_visited(irg);
677 init_tmp_dom_info(get_irg_start_block(irg), NULL, tdi_list, &used);
678 /* If not all blocks are reachable from Start by out edges this assertion
680 assert(used == n_blocks && "Precondition for dom construction violated"); */
684 for (i = n_blocks-1; i > 0; i--) { /* Don't iterate the root, it's done. */
686 tmp_dom_info *w = &tdi_list[i];
690 irn_arity = get_irn_arity(w->block);
691 for (j = 0; j < irn_arity; j++) {
692 ir_node *pred = get_Block_cfgpred_block(w->block, j);
695 if (is_Bad(pred) || (get_Block_dom_pre_num (pred) == -1))
696 continue; /* control-dead */
698 u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
699 if (u->semi < w->semi) w->semi = u->semi;
702 /* handle keep-alives if we are at the end block */
703 if (w->block == get_irg_end_block(irg)) {
704 ir_node *end = get_irg_end(irg);
706 irn_arity = get_irn_arity(end);
707 for (j = 0; j < irn_arity; j++) {
708 ir_node *pred = get_irn_n(end, j);
711 if (is_no_Block(pred))
714 if (get_Block_dom_pre_num(pred) == -1)
715 continue; /* control-dead */
717 u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
718 if (u->semi < w->semi) w->semi = u->semi;
722 /* Add w to w->semi's bucket. w is in exactly one bucket, so
723 buckets can been implemented as linked lists. */
724 w->bucket = w->semi->bucket;
727 dom_link (w->parent, w);
730 while (w->parent->bucket) {
732 v = w->parent->bucket;
733 /* remove v from w->parent->bucket */
734 w->parent->bucket = v->bucket;
738 if (u->semi < v->semi)
745 tdi_list[0].dom = NULL;
746 set_Block_idom(tdi_list[0].block, NULL);
747 set_Block_dom_depth(tdi_list[0].block, 1);
748 for (i = 1; i < n_blocks; i++) {
749 tmp_dom_info *w = &tdi_list[i];
751 if (w->dom != w->semi) w->dom = w->dom->dom;
752 set_Block_idom(w->block, w->dom->block);
753 set_Block_dom_depth(w->block, get_Block_dom_depth(w->dom->block) + 1);
758 current_ir_graph = rem;
760 /* Do a walk over the tree and assign the tree pre orders. */
762 unsigned tree_pre_order = 0;
763 dom_tree_walk_irg(irg, assign_tree_dom_pre_order,
764 assign_tree_dom_pre_order_max, &tree_pre_order);
768 void assure_doms(ir_graph *irg) {
769 if (get_irg_dom_state(irg) != dom_consistent)
773 void free_dom(ir_graph *irg) {
774 /* Update graph state */
775 assert(get_irg_phase_state(current_ir_graph) != phase_building);
776 current_ir_graph->dom_state = dom_none;
778 /* With the implementation right now there is nothing to free,
779 but better call it anyways... */
782 /* Computes the post dominator trees. Sets a flag in irg to "dom_consistent".
783 If the control flow of the graph is changed this flag must be set to
784 "dom_inconsistent". */
785 void compute_postdoms(ir_graph *irg) {
786 ir_graph *rem = current_ir_graph;
787 int n_blocks, used, i, j;
788 tmp_dom_info *tdi_list;
790 current_ir_graph = irg;
792 /* Update graph state */
793 assert(get_irg_phase_state(irg) != phase_building);
794 irg->pdom_state = dom_consistent;
796 /* Count the number of blocks in the graph. */
797 n_blocks = init_construction(irg, count_and_init_blocks_pdom);
799 /* Memory for temporary information. */
800 tdi_list = xcalloc(n_blocks, sizeof(tdi_list[0]));
802 /* We need the out data structure. */
803 assure_irg_outs(irg);
805 /* this with a standard walker as passing the parent to the sons isn't
808 inc_irg_block_visited(irg);
809 init_tmp_pdom_info(get_irg_end_block(irg), NULL, tdi_list, &used);
810 /* If not all blocks are reachable from End by cfg edges this assertion
812 assert(used == n_blocks && "Precondition for dom construction violated"); */
816 for (i = n_blocks-1; i > 0; i--) { /* Don't iterate the root, it's done. */
818 tmp_dom_info *w = &tdi_list[i];
822 irn_arity = get_Block_n_cfg_outs_ka(w->block);
823 for (j = 0; j < irn_arity; j++) {
824 ir_node *succ = get_Block_cfg_out_ka(w->block, j);
827 if (get_Block_postdom_pre_num (succ) == -1)
828 continue; /* endless-loop */
830 u = dom_eval (&tdi_list[get_Block_postdom_pre_num(succ)]);
831 if (u->semi < w->semi) w->semi = u->semi;
833 /* Add w to w->semi's bucket. w is in exactly one bucket, so
834 buckets can be implemented as linked lists. */
835 w->bucket = w->semi->bucket;
838 dom_link (w->parent, w);
841 while (w->parent->bucket) {
843 v = w->parent->bucket;
844 /* remove v from w->parent->bucket */
845 w->parent->bucket = v->bucket;
849 if (u->semi < v->semi)
856 tdi_list[0].dom = NULL;
857 set_Block_ipostdom(tdi_list[0].block, NULL);
858 set_Block_postdom_depth(tdi_list[0].block, 1);
859 for (i = 1; i < n_blocks; i++) {
860 tmp_dom_info *w = &tdi_list[i];
862 if (w->dom != w->semi) w->dom = w->dom->dom;
863 set_Block_ipostdom(w->block, w->dom->block);
864 set_Block_postdom_depth(w->block, get_Block_postdom_depth(w->dom->block) + 1);
871 /* Do a walk over the tree and assign the tree pre orders. */
873 unsigned tree_pre_order = 0;
874 postdom_tree_walk_irg(irg, assign_tree_postdom_pre_order,
875 assign_tree_postdom_pre_order_max, &tree_pre_order);
879 void assure_postdoms(ir_graph *irg) {
880 if (get_irg_postdom_state(irg) != dom_consistent)
881 compute_postdoms(irg);
884 void free_postdom(ir_graph *irg) {
885 /* Update graph state */
886 assert(get_irg_phase_state(current_ir_graph) != phase_building);
887 current_ir_graph->pdom_state = dom_none;
889 /* With the implementation right now there is nothing to free,
890 but better call it anyways... */