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 /*--------------------------------------------------------------------*/
31 /** Accessing the dominator data structures **/
32 /*--------------------------------------------------------------------*/
34 ir_node *get_Block_idom(ir_node *bl) {
35 assert(get_irn_op(bl) == op_Block);
36 if (get_Block_dom_depth(bl) == -1) {
37 /* This block is not reachable from Start */
40 return bl->attr.block.dom.idom;
43 void set_Block_idom(ir_node *bl, ir_node *n) {
44 assert(get_irn_op(bl) == op_Block);
45 bl->attr.block.dom.idom = n;
48 int get_Block_pre_num(ir_node *bl) {
49 assert(get_irn_op(bl) == op_Block);
50 return bl->attr.block.dom.pre_num;
53 void set_Block_pre_num(ir_node *bl, int num) {
54 assert(get_irn_op(bl) == op_Block);
55 bl->attr.block.dom.pre_num = num;
58 int get_Block_dom_depth(ir_node *bl) {
59 assert(get_irn_op(bl) == op_Block);
60 return bl->attr.block.dom.dom_depth;
63 void set_Block_dom_depth(ir_node *bl, int depth) {
64 assert(get_irn_op(bl) == op_Block);
65 bl->attr.block.dom.dom_depth = depth;
70 /*--------------------------------------------------------------------*/
71 /* Building and Removing the dominator datastructure */
72 /*--------------------------------------------------------------------*/
74 static void count_and_init_blocks(ir_node *bl, void *env) {
75 int *n_blocks = (int *) env;
78 set_Block_idom(bl, NULL);
79 set_Block_pre_num(bl, -1);
80 set_Block_dom_depth(bl, -1);
83 /* temporary type used while constructing the dominator tree. */
84 typedef struct tmp_dom_info {
85 ir_node *block; /* backlink */
87 struct tmp_dom_info *semi; /* semidominator */
88 struct tmp_dom_info *parent;
89 struct tmp_dom_info *label; /* used for LINK and EVAL */
90 struct tmp_dom_info *ancestor;/* used for LINK and EVAL */
91 struct tmp_dom_info *dom; /* After step 3, if the semidominator of w is
92 its immediate dominator, then w->dom is the
93 immediate dominator of w. Otherwise w->dom
94 is a vertex v whose number is smaller than
95 w and whose immediate dominator is also w's
96 immediate dominator. After step 4, w->dom
97 is the immediate dominator of w. */
98 struct tmp_dom_info *bucket; /* set of vertices with same semidominator */
101 /* Struct to pass info through walker. */
109 /* Walks Blocks along the out datastructure. If recursion started with
110 Start block misses control dead blocks. */
111 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
112 tmp_dom_info *tdi_list, int* used) {
116 assert(get_irn_op(bl) == op_Block);
117 if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
119 mark_Block_block_visited(bl);
120 set_Block_pre_num(bl, *used);
122 tdi = &tdi_list[*used];
127 tdi->ancestor = NULL;
129 tdi->parent = parent;
133 for(i = 0; i < get_Block_n_cfg_outs(bl); i++) {
134 ir_node *pred = get_Block_cfg_out(bl, i);
135 assert(get_irn_opcode(pred) == iro_Block);
136 init_tmp_dom_info(pred, tdi, tdi_list, used);
141 dom_compress (tmp_dom_info *v)
143 assert (v->ancestor);
144 if (v->ancestor->ancestor) {
145 dom_compress (v->ancestor);
146 if (v->ancestor->label->semi < v->label->semi) {
147 v->label = v->ancestor->label;
149 v->ancestor = v->ancestor->ancestor;
153 /* if V is a root, return v, else return the vertex u, not being the
154 root, with minimum u->semi on the path from v to its root. */
155 INLINE static tmp_dom_info*
156 dom_eval (tmp_dom_info *v)
158 if (!v->ancestor) return v;
163 /* make V W's ancestor */
165 dom_link (tmp_dom_info *v, tmp_dom_info *w)
170 /* Computes the dominator trees. Sets a flag in irg to "dom_consistent".
171 If the control flow of the graph is changed this flag must be set to
172 "dom_inconsistent". */
173 void compute_doms(ir_graph *irg) {
174 ir_graph *rem = current_ir_graph;
175 int n_blocks, used, i, j;
176 tmp_dom_info *tdi_list; /* Ein Golf? */
178 current_ir_graph = irg;
180 /* Update graph state */
181 assert(get_irg_phase_state(current_ir_graph) != phase_building);
182 current_ir_graph->dom_state = dom_consistent;
184 /* Count the number of blocks in the graph. */
186 irg_block_walk(get_irg_end(current_ir_graph), count_and_init_blocks, NULL, &n_blocks);
188 /* Memory for temporary information. */
189 tdi_list = xmalloc(n_blocks * sizeof(tmp_dom_info));
190 memset(tdi_list, 0, n_blocks * sizeof(tmp_dom_info));
192 /* We need the out datastructure. */
193 if (current_ir_graph->outs_state != outs_consistent)
194 compute_outs(current_ir_graph);
196 /* this with a standard walker as passing the parent to the sons isn't
199 inc_irg_block_visited(current_ir_graph);
200 init_tmp_dom_info(get_irg_start_block(current_ir_graph), NULL, tdi_list, &used);
201 /* If not all blocks are reachable from Start by out edges this assertion
203 assert(used == n_blocks && "Precondition for dom construction violated"); */
207 for (i = n_blocks-1; i > 0; i--) { /* Don't iterate the root, it's done. */
209 tmp_dom_info *w = &tdi_list[i];
213 irn_arity = get_irn_arity(w->block);
214 for (j = 0; j < irn_arity; j++) {
215 ir_node *cf_op = get_Block_cfgpred(w->block, j);
216 ir_node *pred = get_nodes_block(cf_op);
219 if ((is_Bad(cf_op)) || (is_Bad(pred)) ||
220 (get_Block_pre_num (pred) == -1))
221 continue; /* control-dead */
223 u = dom_eval (&tdi_list[get_Block_pre_num(pred)]);
224 if (u->semi < w->semi) w->semi = u->semi;
226 /* Add w to w->semi's bucket. w is in exactly one bucket, so
227 buckets can ben implemented as linked lists. */
228 w->bucket = w->semi->bucket;
231 dom_link (w->parent, w);
234 while (w->parent->bucket) {
236 v = w->parent->bucket;
237 /* remove v from w->parent->bucket */
238 w->parent->bucket = v->bucket;
242 if (u->semi < v->semi)
249 tdi_list[0].dom = NULL;
250 set_Block_idom(tdi_list[0].block, NULL);
251 set_Block_dom_depth(tdi_list[0].block, 1);
252 for (i = 1; i < n_blocks; i++) {
253 tmp_dom_info *w = &tdi_list[i];
255 if (w->dom != w->semi) w->dom = w->dom->dom;
256 set_Block_idom(w->block, w->dom->block);
257 set_Block_dom_depth(w->block, get_Block_dom_depth(w->dom->block) + 1);
261 /* free(tdi_list); @@@ does not work !!?? */
262 current_ir_graph = rem;
265 void free_dom_and_peace(ir_graph *irg) {
266 /* Update graph state */
267 assert(get_irg_phase_state(current_ir_graph) != phase_building);
268 current_ir_graph->dom_state = dom_none;
270 /* With the implementation right now there is nothing to free,
271 but better call it anyways... */