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.
21 #include "irgraph_t.h" /* To access state field. */
24 /**********************************************************************/
25 /** Accessing the dominator data structures **/
26 /**********************************************************************/
28 ir_node *get_Block_idom(ir_node *bl) {
29 assert(get_irn_op(bl) == op_Block);
30 return bl->attr.block.dom.idom;
33 void set_Block_idom(ir_node *bl, ir_node *n) {
34 assert(get_irn_op(bl) == op_Block);
35 bl->attr.block.dom.idom = n;
38 int get_Block_pre_num(ir_node *bl) {
39 assert(get_irn_op(bl) == op_Block);
40 return bl->attr.block.dom.pre_num;
43 void set_Block_pre_num(ir_node *bl, int num) {
44 assert(get_irn_op(bl) == op_Block);
45 bl->attr.block.dom.pre_num = num;
48 int get_Block_dom_depth(ir_node *bl) {
49 assert(get_irn_op(bl) == op_Block);
50 return bl->attr.block.dom.dom_depth;
53 void set_Block_dom_depth(ir_node *bl, int depth) {
54 assert(get_irn_op(bl) == op_Block);
55 bl->attr.block.dom.dom_depth = depth;
60 /**********************************************************************/
61 /** Building and Removing the dominator datasturcture **/
76 /**********************************************************************/
78 static void count_and_init_blocks(ir_node *bl, void *env) {
79 int *n_blocks = (int *) env;
82 set_Block_idom(bl, NULL);
83 set_Block_pre_num(bl, -1);
84 set_Block_dom_depth(bl, -1);
87 /* temporary type used while constructing the dominator tree. */
88 typedef struct tmp_dom_info {
89 ir_node *block; /* backlink */
91 struct tmp_dom_info *semi; /* semidominator */
92 struct tmp_dom_info *parent;
93 struct tmp_dom_info *label; /* used for LINK and EVAL */
94 struct tmp_dom_info *ancestor;/* used for LINK and EVAL */
95 struct tmp_dom_info *dom; /* After step 3, if the semidominator of w is
96 its immediate dominator, then w->dom is the
97 immediate dominator of w. Otherwise w->dom
98 is a vertex v whose number is smaller than
99 w and whose immediate dominator is also w's
100 immediate dominator. After step 4, w->dom
101 is the immediate dominator of w. */
102 struct tmp_dom_info *bucket; /* set of vertices with same semidominator */
105 /* Struct to pass info through walker. */
113 /* Walks Blocks along the out datastructure. If recursion started with
114 Start block misses control dead blocks. */
115 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
116 tmp_dom_info *tdi_list, int* used) {
120 assert(get_irn_op(bl) == op_Block);
121 if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
123 mark_Block_block_visited(bl);
124 set_Block_pre_num(bl, *used);
126 tdi = &tdi_list[*used];
131 tdi->ancestor = NULL;
133 tdi->parent = parent;
137 for(i = 0; i < get_Block_n_cfg_outs(bl); i++) {
138 ir_node *pred = get_Block_cfg_out(bl, i);
139 assert(get_irn_opcode(pred) == iro_Block);
140 init_tmp_dom_info(pred, tdi, tdi_list, used);
145 dom_compress (tmp_dom_info *v)
147 assert (v->ancestor);
148 if (v->ancestor->ancestor) {
149 dom_compress (v->ancestor);
150 if (v->ancestor->label->semi < v->label->semi) {
151 v->label = v->ancestor->label;
153 v->ancestor = v->ancestor->ancestor;
157 /* if V is a root, return v, else return the vertex u, not being the
158 root, with minimum u->semi on the path from v to its root. */
159 INLINE static tmp_dom_info*
160 dom_eval (tmp_dom_info *v)
162 if (!v->ancestor) return v;
167 /* make V W's ancestor */
169 dom_link (tmp_dom_info *v, tmp_dom_info *w)
174 /* Computes the dominator trees. Sets a flag in irg to "dom_consistent".
175 If the control flow of the graph is changed this flag must be set to
176 "dom_inconsistent". */
177 void compute_doms(ir_graph *irg) {
178 ir_graph *rem = current_ir_graph;
179 int n_blocks, used, i, j;
180 tmp_dom_info *tdi_list; /* Ein Golf? */
182 current_ir_graph = irg;
184 /* Update graph state */
185 assert(get_irg_phase_state(current_ir_graph) != phase_building);
186 current_ir_graph->dom_state = dom_consistent;
188 /* Count the number of blocks in the graph. */
190 irg_block_walk(get_irg_end(current_ir_graph), count_and_init_blocks, NULL, &n_blocks);
192 /* Memory for temporary information. */
193 tdi_list = (tmp_dom_info *) calloc(n_blocks, sizeof(tmp_dom_info));
195 /* We need the out datastructure. */
196 if (current_ir_graph->outs_state != outs_consistent)
197 compute_outs(current_ir_graph);
200 this with a standard walker as passing the parent to the sons isn't
203 inc_irg_block_visited(current_ir_graph);
204 init_tmp_dom_info(get_irg_start_block(current_ir_graph), NULL, tdi_list, &used);
205 /* If not all blocks are reachable from Start by out edges this assertion
207 assert(used == n_blocks && "Precondition for dom construction violated"); */
211 for (i = n_blocks-1; i > 0; i--) { /* Don't iterate the root, it's done. */
212 tmp_dom_info *w = &tdi_list[i];
216 for (j = 0; j < get_irn_arity(w->block); j++) {
217 ir_node *pred = get_nodes_Block(get_Block_cfgpred(w->block, j));
220 if ((is_Bad(get_Block_cfgpred(w->block, j))) ||
221 (get_Block_pre_num (pred) == -1))
222 continue; /* control-dead */
224 u = dom_eval (&tdi_list[get_Block_pre_num(pred)]);
225 if (u->semi < w->semi) w->semi = u->semi;
227 /* Add w to w->semi's bucket. w is in exactly one bucket, so
228 buckets can ben implemented as linked lists. */
229 w->bucket = w->semi->bucket;
232 dom_link (w->parent, w);
235 while (w->parent->bucket) {
237 v = w->parent->bucket;
238 /* remove v from w->parent->bucket */
239 w->parent->bucket = v->bucket;
243 if (u->semi < v->semi)
250 tdi_list[0].dom = NULL;
251 set_Block_idom(tdi_list[0].block, NULL);
252 set_Block_dom_depth(tdi_list[0].block, 1);
253 for (i = 1; i < n_blocks; i++) {
254 tmp_dom_info *w = &tdi_list[i];
256 if (w->dom != w->semi) w->dom = w->dom->dom;
257 set_Block_idom(w->block, w->dom->block);
258 set_Block_dom_depth(w->block, get_Block_dom_depth(w->dom->block) + 1);
262 /* free(tdi_list); @@@ does not work !!?? */
263 current_ir_graph = rem;
266 void free_dom_and_peace(ir_graph *irg) {
267 /* Update graph state */
268 assert(get_irg_phase_state(current_ir_graph) != phase_building);
269 current_ir_graph->dom_state = no_dom;
271 /* With the implementation right now there is nothing to free,
272 but better call it anyways... */