3 * File name: ir/ana/irdom.c
4 * Purpose: Construct and access dominator tree.
5 * Author: Goetz Lindenmaier
9 * Copyright: (c) 2002-2003 Universität Karlsruhe
10 * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
26 #include "irgraph_t.h" /* To access state field. */
30 #define get_dom_info(bl) (&(bl)->attr.block.dom)
33 /*--------------------------------------------------------------------*/
34 /** Accessing the dominator data structures **/
35 /*--------------------------------------------------------------------*/
37 ir_node *get_Block_idom(const ir_node *bl) {
39 if (get_Block_dom_depth(bl) == -1) {
40 /* This block is not reachable from Start */
43 return get_dom_info(bl)->idom;
46 void set_Block_idom(ir_node *bl, ir_node *n) {
47 dom_info *bli = get_dom_info(bl);
49 assert(get_irn_op(bl) == op_Block);
51 /* Set the immediate dominator of bl to n */
55 * If we don't set the root of the dominator tree
56 * Append bl to the dominates queue of n.
59 dom_info *ni = get_dom_info(n);
61 bli->next = ni->first;
66 int get_Block_pre_num(const ir_node *bl) {
67 assert(get_irn_op(bl) == op_Block);
68 return bl->attr.block.dom.pre_num;
71 void set_Block_pre_num(ir_node *bl, int num) {
72 assert(get_irn_op(bl) == op_Block);
73 bl->attr.block.dom.pre_num = num;
76 int get_Block_dom_depth(const ir_node *bl) {
77 assert(get_irn_op(bl) == op_Block);
78 return bl->attr.block.dom.dom_depth;
81 void set_Block_dom_depth(ir_node *bl, int depth) {
82 assert(get_irn_op(bl) == op_Block);
83 bl->attr.block.dom.dom_depth = depth;
86 unsigned get_Block_dom_tree_pre_num(const ir_node *bl)
89 return get_dom_info(bl)->tree_pre_num;
92 unsigned get_Block_dom_max_subtree_pre_num(const ir_node *bl)
95 return get_dom_info(bl)->max_subtree_pre_num;
98 int block_dominates(const ir_node *a, const ir_node *b)
100 const dom_info *ai, *bi;
102 assert(is_Block(a) && is_Block(b));
103 ai = get_dom_info(a);
104 bi = get_dom_info(b);
105 return bi->tree_pre_num - ai->tree_pre_num
106 <= ai->max_subtree_pre_num - ai->tree_pre_num;
109 ir_node *get_Block_dominated_first(const ir_node *bl)
111 assert(is_Block(bl));
112 return get_dom_info(bl)->first;
115 ir_node *get_Block_dominated_next(const ir_node *bl)
117 assert(is_Block(bl));
118 return get_dom_info(bl)->next;
121 void dom_tree_walk(ir_node *n, irg_walk_func *pre,
122 irg_walk_func *post, void *env)
126 assert(get_irn_irg(n)->dom_state == dom_consistent
127 && "The dominators of the irg must be consistent");
129 for(p = get_dom_info(p)->first; p; p = get_dom_info(p)->next) {
133 dom_tree_walk(p, pre, post, env);
140 void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
141 irg_walk_func *post, void *env)
143 /* The root of the dominator tree should be the start node. */
144 ir_node *root = get_irg_start_block(irg);
146 assert(irg->dom_state == dom_consistent
147 && "The dominators of the irg must be consistent");
148 assert(root && "The start block of the graph is NULL?");
149 assert(get_dom_info(root)->idom == NULL
150 && "The start node in the graph must be the root of the dominator tree");
151 dom_tree_walk(root, pre, post, env);
154 static void assign_tree_pre_order(ir_node *bl, void *data)
156 unsigned *num = data;
157 dom_info *bi = get_dom_info(bl);
158 bi->tree_pre_num = (*num)++;
161 static void assign_tree_pre_order_max(ir_node *bl, void *data)
163 dom_info *bi = get_dom_info(bl);
167 for(p = bi->first; p; p = get_dom_info(p)->next) {
168 unsigned max_p = get_dom_info(p)->max_subtree_pre_num;
169 max = max > max_p ? max : max_p;
172 bi->max_subtree_pre_num = max;
175 /*--------------------------------------------------------------------*/
176 /* Building and Removing the dominator datastructure */
177 /*--------------------------------------------------------------------*/
179 static void count_and_init_blocks(ir_node *bl, void *env) {
180 int *n_blocks = (int *) env;
183 set_Block_idom(bl, NULL);
184 set_Block_pre_num(bl, -1);
185 set_Block_dom_depth(bl, -1);
188 /* temporary type used while constructing the dominator tree. */
189 typedef struct tmp_dom_info {
190 ir_node *block; /* backlink */
192 struct tmp_dom_info *semi; /* semidominator */
193 struct tmp_dom_info *parent;
194 struct tmp_dom_info *label; /* used for LINK and EVAL */
195 struct tmp_dom_info *ancestor;/* used for LINK and EVAL */
196 struct tmp_dom_info *dom; /* After step 3, if the semidominator of w is
197 its immediate dominator, then w->dom is the
198 immediate dominator of w. Otherwise w->dom
199 is a vertex v whose number is smaller than
200 w and whose immediate dominator is also w's
201 immediate dominator. After step 4, w->dom
202 is the immediate dominator of w. */
203 struct tmp_dom_info *bucket; /* set of vertices with same semidominator */
206 /* Struct to pass info through walker. */
214 /* Walks Blocks along the out datastructure. If recursion started with
215 Start block misses control dead blocks. */
216 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
217 tmp_dom_info *tdi_list, int* used) {
221 assert(get_irn_op(bl) == op_Block);
222 if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
224 mark_Block_block_visited(bl);
225 set_Block_pre_num(bl, *used);
227 tdi = &tdi_list[*used];
232 tdi->ancestor = NULL;
234 tdi->parent = parent;
238 for(i = 0; i < get_Block_n_cfg_outs(bl); i++) {
239 ir_node *pred = get_Block_cfg_out(bl, i);
240 assert(get_irn_opcode(pred) == iro_Block);
241 init_tmp_dom_info(pred, tdi, tdi_list, used);
246 dom_compress (tmp_dom_info *v)
248 assert (v->ancestor);
249 if (v->ancestor->ancestor) {
250 dom_compress (v->ancestor);
251 if (v->ancestor->label->semi < v->label->semi) {
252 v->label = v->ancestor->label;
254 v->ancestor = v->ancestor->ancestor;
258 /* if V is a root, return v, else return the vertex u, not being the
259 root, with minimum u->semi on the path from v to its root. */
260 INLINE static tmp_dom_info*
261 dom_eval (tmp_dom_info *v)
263 if (!v->ancestor) return v;
268 /* make V W's ancestor */
270 dom_link (tmp_dom_info *v, tmp_dom_info *w)
275 /* Computes the dominator trees. Sets a flag in irg to "dom_consistent".
276 If the control flow of the graph is changed this flag must be set to
277 "dom_inconsistent". */
278 void compute_doms(ir_graph *irg) {
279 ir_graph *rem = current_ir_graph;
280 int n_blocks, used, i, j;
281 tmp_dom_info *tdi_list; /* Ein Golf? */
283 current_ir_graph = irg;
285 /* Update graph state */
286 assert(get_irg_phase_state(current_ir_graph) != phase_building);
287 current_ir_graph->dom_state = dom_consistent;
289 /* Count the number of blocks in the graph. */
291 irg_block_walk(get_irg_end(current_ir_graph), count_and_init_blocks, NULL, &n_blocks);
293 /* Memory for temporary information. */
294 tdi_list = xcalloc(n_blocks, sizeof(tdi_list[0]));
296 /* We need the out datastructure. */
297 if (current_ir_graph->outs_state != outs_consistent)
298 compute_outs(current_ir_graph);
300 /* this with a standard walker as passing the parent to the sons isn't
303 inc_irg_block_visited(current_ir_graph);
304 init_tmp_dom_info(get_irg_start_block(current_ir_graph), NULL, tdi_list, &used);
305 /* If not all blocks are reachable from Start by out edges this assertion
307 assert(used == n_blocks && "Precondition for dom construction violated"); */
311 for (i = n_blocks-1; i > 0; i--) { /* Don't iterate the root, it's done. */
313 tmp_dom_info *w = &tdi_list[i];
317 irn_arity = get_irn_arity(w->block);
318 for (j = 0; j < irn_arity; j++) {
319 ir_node *cf_op = get_Block_cfgpred(w->block, j);
320 ir_node *pred = get_nodes_block(cf_op);
323 if ((is_Bad(cf_op)) || (is_Bad(pred)) ||
324 (get_Block_pre_num (pred) == -1))
325 continue; /* control-dead */
327 u = dom_eval (&tdi_list[get_Block_pre_num(pred)]);
328 if (u->semi < w->semi) w->semi = u->semi;
330 /* Add w to w->semi's bucket. w is in exactly one bucket, so
331 buckets can ben implemented as linked lists. */
332 w->bucket = w->semi->bucket;
335 dom_link (w->parent, w);
338 while (w->parent->bucket) {
340 v = w->parent->bucket;
341 /* remove v from w->parent->bucket */
342 w->parent->bucket = v->bucket;
346 if (u->semi < v->semi)
353 tdi_list[0].dom = NULL;
354 set_Block_idom(tdi_list[0].block, NULL);
355 set_Block_dom_depth(tdi_list[0].block, 1);
356 for (i = 1; i < n_blocks; i++) {
357 tmp_dom_info *w = &tdi_list[i];
359 if (w->dom != w->semi) w->dom = w->dom->dom;
360 set_Block_idom(w->block, w->dom->block);
361 set_Block_dom_depth(w->block, get_Block_dom_depth(w->dom->block) + 1);
365 /* free(tdi_list); @@@ does not work !!?? */
366 current_ir_graph = rem;
368 /* Do a walk over the tree and assign the tree pre orders. */
370 unsigned tree_pre_order = 0;
371 dom_tree_walk_irg(irg, assign_tree_pre_order,
372 assign_tree_pre_order_max, &tree_pre_order);
376 void free_dom_and_peace(ir_graph *irg) {
377 /* Update graph state */
378 assert(get_irg_phase_state(current_ir_graph) != phase_building);
379 current_ir_graph->dom_state = dom_none;
381 /* With the implementation right now there is nothing to free,
382 but better call it anyways... */