1 /* Copyright (C) 2002 by Universitaet Karlsruhe
4 * Authors: Goetz Lindenmaier
6 * irdom.c --- Dominator tree.
16 #include "irgraph_t.h" /* To access state field. */
19 /**********************************************************************/
20 /** Accessing the dominator datastructures **/
21 /**********************************************************************/
23 ir_node *get_Block_idom(ir_node *bl) {
24 assert(get_irn_op(bl) == op_Block);
25 return bl->attr.block.dom.idom;
28 void set_Block_idom(ir_node *bl, ir_node *n) {
29 assert(get_irn_op(bl) == op_Block);
30 bl->attr.block.dom.idom = n;
33 int get_Block_pre_num(ir_node *bl) {
34 assert(get_irn_op(bl) == op_Block);
35 return bl->attr.block.dom.pre_num;
38 void set_Block_pre_num(ir_node *bl, int num) {
39 assert(get_irn_op(bl) == op_Block);
40 bl->attr.block.dom.pre_num = num;
43 int get_Block_dom_depth(ir_node *bl) {
44 assert(get_irn_op(bl) == op_Block);
45 return bl->attr.block.dom.dom_depth;
48 void set_Block_dom_depth(ir_node *bl, int depth) {
49 assert(get_irn_op(bl) == op_Block);
50 bl->attr.block.dom.dom_depth = depth;
55 /**********************************************************************/
56 /** Building and Removing the dominator datasturcture **/
71 /**********************************************************************/
73 static void count_and_init_blocks(ir_node *bl, void *env) {
74 int *n_blocks = (int *) env;
77 set_Block_idom(bl, NULL);
78 set_Block_pre_num(bl, -1);
79 set_Block_dom_depth(bl, -1);
82 /* temporary type used while constructing the dominator tree. */
83 typedef struct tmp_dom_info {
84 ir_node *block; /* backlink */
86 struct tmp_dom_info *semi; /* semidominator */
87 struct tmp_dom_info *parent;
88 struct tmp_dom_info *label; /* used for LINK and EVAL */
89 struct tmp_dom_info *ancestor;/* used for LINK and EVAL */
90 struct tmp_dom_info *dom; /* After step 3, if the semidominator of w is
91 its immediate dominator, then w->dom is the
92 immediate dominator of w. Otherwise w->dom
93 is a vertex v whose number is smaller than
94 w and whose immediate dominator is also w's
95 immediate dominator. After step 4, w->dom
96 is the immediate dominator of w. */
97 struct tmp_dom_info *bucket; /* set of vertices with same semidominator */
100 /* Struct to pass info through walker. */
108 /* Walks Blocks along the out datastructure. If recursion started with
109 Start block misses control dead blocks. */
110 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
111 tmp_dom_info *tdi_list, int* used) {
115 assert(get_irn_op(bl) == op_Block);
116 if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
118 mark_Block_block_visited(bl);
119 set_Block_pre_num(bl, *used);
121 tdi = &tdi_list[*used];
126 tdi->ancestor = NULL;
128 tdi->parent = parent;
132 for(i = 0; i < get_Block_n_cfg_outs(bl); i++) {
133 ir_node *pred = get_Block_cfg_out(bl, i);
134 assert(get_irn_opcode(pred) == iro_Block);
135 init_tmp_dom_info(pred, tdi, tdi_list, used);
140 dom_compress (tmp_dom_info *v)
142 assert (v->ancestor);
143 if (v->ancestor->ancestor) {
144 dom_compress (v->ancestor);
145 if (v->ancestor->label->semi < v->label->semi) {
146 v->label = v->ancestor->label;
148 v->ancestor = v->ancestor->ancestor;
152 /* if V is a root, return v, else return the vertex u, not being the
153 root, with minimum u->semi on the path from v to its root. */
154 INLINE static tmp_dom_info*
155 dom_eval (tmp_dom_info *v)
157 if (!v->ancestor) return v;
162 /* make V W's ancestor */
164 dom_link (tmp_dom_info *v, tmp_dom_info *w)
169 /* Computes the dominator trees. Sets a flag in irg to "dom_consistent".
170 If the control flow of the graph is changed this flag must be set to
171 "dom_inconsistent". */
172 void compute_doms(ir_graph *irg) {
173 ir_graph *rem = current_ir_graph;
174 int n_blocks, used, i, j;
175 tmp_dom_info *tdi_list; /* Ein Golf? */
177 current_ir_graph = irg;
179 /* Update graph state */
180 assert(get_irg_phase_state(current_ir_graph) != phase_building);
181 current_ir_graph->dom_state = dom_consistent;
183 /* Count the number of blocks in the graph. */
185 irg_block_walk(get_irg_end(current_ir_graph), count_and_init_blocks, NULL, &n_blocks);
187 /* Memory for temporary information. */
188 tdi_list = (tmp_dom_info *) calloc(n_blocks, sizeof(tmp_dom_info));
190 /* We need the out datastructure. */
191 if (current_ir_graph->outs_state != outs_consistent)
192 compute_outs(current_ir_graph);
195 this with a standard walker as passing the parent to the sons isn't
198 inc_irg_block_visited(current_ir_graph);
199 init_tmp_dom_info(get_irg_start_block(current_ir_graph), NULL, tdi_list, &used);
200 /* If not all blocks are reachable from Start by out edges this assertion
202 assert(used == n_blocks && "Precondition for dom construction violated"); */
206 for (i = n_blocks-1; i > 0; i--) { /* Don't iterate the root, it's done. */
207 tmp_dom_info *w = &tdi_list[i];
211 for (j = 0; j < get_irn_arity(w->block); j++) {
212 ir_node *pred = get_nodes_Block(get_Block_cfgpred(w->block, j));
215 if ((is_Bad(get_Block_cfgpred(w->block, j))) ||
216 (get_Block_pre_num (pred) == -1))
217 continue; /* control-dead */
219 u = dom_eval (&tdi_list[get_Block_pre_num(pred)]);
220 if (u->semi < w->semi) w->semi = u->semi;
222 /* Add w to w->semi's bucket. w is in exactly one bucket, so
223 buckets can ben implemented as linked lists. */
224 w->bucket = w->semi->bucket;
227 dom_link (w->parent, w);
230 while (w->parent->bucket) {
232 v = w->parent->bucket;
233 /* remove v from w->parent->bucket */
234 w->parent->bucket = v->bucket;
238 if (u->semi < v->semi)
245 tdi_list[0].dom = NULL;
246 set_Block_idom(tdi_list[0].block, NULL);
247 set_Block_dom_depth(tdi_list[0].block, 1);
248 for (i = 1; i < n_blocks; i++) {
249 tmp_dom_info *w = &tdi_list[i];
251 if (w->dom != w->semi) w->dom = w->dom->dom;
252 set_Block_idom(w->block, w->dom->block);
253 set_Block_dom_depth(w->block, get_Block_dom_depth(w->dom->block) + 1);
257 /* free(tdi_list); @@@ does not work !!?? */
258 current_ir_graph = rem;
261 void free_dom_and_peace(ir_graph *irg) {
262 /* Update graph state */
263 assert(get_irg_phase_state(current_ir_graph) != phase_building);
264 current_ir_graph->dom_state = no_dom;
266 /* With the implementation right now there is nothing to free,
267 but better call it anyways... */