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. */
25 /*--------------------------------------------------------------------*/
26 /** Accessing the dominator data structures **/
27 /*--------------------------------------------------------------------*/
29 ir_node *get_Block_idom(ir_node *bl) {
30 assert(get_irn_op(bl) == op_Block);
31 if (get_Block_dom_depth(bl) == -1) {
32 /* This block is not reachable from Start */
35 return bl->attr.block.dom.idom;
38 void set_Block_idom(ir_node *bl, ir_node *n) {
39 assert(get_irn_op(bl) == op_Block);
40 bl->attr.block.dom.idom = n;
43 int get_Block_pre_num(ir_node *bl) {
44 assert(get_irn_op(bl) == op_Block);
45 return bl->attr.block.dom.pre_num;
48 void set_Block_pre_num(ir_node *bl, int num) {
49 assert(get_irn_op(bl) == op_Block);
50 bl->attr.block.dom.pre_num = num;
53 int get_Block_dom_depth(ir_node *bl) {
54 assert(get_irn_op(bl) == op_Block);
55 return bl->attr.block.dom.dom_depth;
58 void set_Block_dom_depth(ir_node *bl, int depth) {
59 assert(get_irn_op(bl) == op_Block);
60 bl->attr.block.dom.dom_depth = depth;
65 /*--------------------------------------------------------------------*/
66 /* Building and Removing the dominator datastructure */
67 /*--------------------------------------------------------------------*/
69 static void count_and_init_blocks(ir_node *bl, void *env) {
70 int *n_blocks = (int *) env;
73 set_Block_idom(bl, NULL);
74 set_Block_pre_num(bl, -1);
75 set_Block_dom_depth(bl, -1);
78 /* temporary type used while constructing the dominator tree. */
79 typedef struct tmp_dom_info {
80 ir_node *block; /* backlink */
82 struct tmp_dom_info *semi; /* semidominator */
83 struct tmp_dom_info *parent;
84 struct tmp_dom_info *label; /* used for LINK and EVAL */
85 struct tmp_dom_info *ancestor;/* used for LINK and EVAL */
86 struct tmp_dom_info *dom; /* After step 3, if the semidominator of w is
87 its immediate dominator, then w->dom is the
88 immediate dominator of w. Otherwise w->dom
89 is a vertex v whose number is smaller than
90 w and whose immediate dominator is also w's
91 immediate dominator. After step 4, w->dom
92 is the immediate dominator of w. */
93 struct tmp_dom_info *bucket; /* set of vertices with same semidominator */
96 /* Struct to pass info through walker. */
104 /* Walks Blocks along the out datastructure. If recursion started with
105 Start block misses control dead blocks. */
106 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
107 tmp_dom_info *tdi_list, int* used) {
111 assert(get_irn_op(bl) == op_Block);
112 if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
114 mark_Block_block_visited(bl);
115 set_Block_pre_num(bl, *used);
117 tdi = &tdi_list[*used];
122 tdi->ancestor = NULL;
124 tdi->parent = parent;
128 for(i = 0; i < get_Block_n_cfg_outs(bl); i++) {
129 ir_node *pred = get_Block_cfg_out(bl, i);
130 assert(get_irn_opcode(pred) == iro_Block);
131 init_tmp_dom_info(pred, tdi, tdi_list, used);
136 dom_compress (tmp_dom_info *v)
138 assert (v->ancestor);
139 if (v->ancestor->ancestor) {
140 dom_compress (v->ancestor);
141 if (v->ancestor->label->semi < v->label->semi) {
142 v->label = v->ancestor->label;
144 v->ancestor = v->ancestor->ancestor;
148 /* if V is a root, return v, else return the vertex u, not being the
149 root, with minimum u->semi on the path from v to its root. */
150 INLINE static tmp_dom_info*
151 dom_eval (tmp_dom_info *v)
153 if (!v->ancestor) return v;
158 /* make V W's ancestor */
160 dom_link (tmp_dom_info *v, tmp_dom_info *w)
165 /* Computes the dominator trees. Sets a flag in irg to "dom_consistent".
166 If the control flow of the graph is changed this flag must be set to
167 "dom_inconsistent". */
168 void compute_doms(ir_graph *irg) {
169 ir_graph *rem = current_ir_graph;
170 int n_blocks, used, i, j;
171 tmp_dom_info *tdi_list; /* Ein Golf? */
173 current_ir_graph = irg;
175 /* Update graph state */
176 assert(get_irg_phase_state(current_ir_graph) != phase_building);
177 current_ir_graph->dom_state = dom_consistent;
179 /* Count the number of blocks in the graph. */
181 irg_block_walk(get_irg_end(current_ir_graph), count_and_init_blocks, NULL, &n_blocks);
183 /* Memory for temporary information. */
184 tdi_list = (tmp_dom_info *) calloc(n_blocks, sizeof(tmp_dom_info));
186 /* We need the out datastructure. */
187 if (current_ir_graph->outs_state != outs_consistent)
188 compute_outs(current_ir_graph);
190 /* this with a standard walker as passing the parent to the sons isn't
193 inc_irg_block_visited(current_ir_graph);
194 init_tmp_dom_info(get_irg_start_block(current_ir_graph), NULL, tdi_list, &used);
195 /* If not all blocks are reachable from Start by out edges this assertion
197 assert(used == n_blocks && "Precondition for dom construction violated"); */
201 for (i = n_blocks-1; i > 0; i--) { /* Don't iterate the root, it's done. */
203 tmp_dom_info *w = &tdi_list[i];
207 irn_arity = get_irn_arity(w->block);
208 for (j = 0; j < irn_arity; j++) {
209 ir_node *cf_op = get_Block_cfgpred(w->block, j);
210 ir_node *pred = get_nodes_block(cf_op);
213 if ((is_Bad(cf_op)) || (is_Bad(pred)) ||
214 (get_Block_pre_num (pred) == -1))
215 continue; /* control-dead */
217 u = dom_eval (&tdi_list[get_Block_pre_num(pred)]);
218 if (u->semi < w->semi) w->semi = u->semi;
220 /* Add w to w->semi's bucket. w is in exactly one bucket, so
221 buckets can ben implemented as linked lists. */
222 w->bucket = w->semi->bucket;
225 dom_link (w->parent, w);
228 while (w->parent->bucket) {
230 v = w->parent->bucket;
231 /* remove v from w->parent->bucket */
232 w->parent->bucket = v->bucket;
236 if (u->semi < v->semi)
243 tdi_list[0].dom = NULL;
244 set_Block_idom(tdi_list[0].block, NULL);
245 set_Block_dom_depth(tdi_list[0].block, 1);
246 for (i = 1; i < n_blocks; i++) {
247 tmp_dom_info *w = &tdi_list[i];
249 if (w->dom != w->semi) w->dom = w->dom->dom;
250 set_Block_idom(w->block, w->dom->block);
251 set_Block_dom_depth(w->block, get_Block_dom_depth(w->dom->block) + 1);
255 /* free(tdi_list); @@@ does not work !!?? */
256 current_ir_graph = rem;
259 void free_dom_and_peace(ir_graph *irg) {
260 /* Update graph state */
261 assert(get_irg_phase_state(current_ir_graph) != phase_building);
262 current_ir_graph->dom_state = dom_none;
264 /* With the implementation right now there is nothing to free,
265 but better call it anyways... */