2 * Copyright (C) 1995-2008 University of Karlsruhe. All right reserved.
4 * This file is part of libFirm.
6 * This file may be distributed and/or modified under the terms of the
7 * GNU General Public License version 2 as published by the Free Software
8 * Foundation and appearing in the file LICENSE.GPL included in the
9 * packaging of this file.
11 * Licensees holding valid libFirm Professional Edition licenses may use
12 * this file in accordance with the libFirm Commercial License.
13 * Agreement provided with the Software.
15 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
16 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * @brief SSA construction for a set of nodes
23 * @author Sebastian Hack, Daniel Grund, Matthias Braun, Christian Wuerdig
27 * The problem: Given a value and a set of "copies" that are known to
28 * represent the same abstract value, rewire all usages of the original value
29 * to their closest copy while introducing phis as necessary.
31 * Algorithm: Mark all blocks in the iterated dominance frontiers of the value
32 * and it's copies. Link the copies ordered by dominance to the blocks. Then
33 * we search for each use all definitions in the current block, if none is
34 * found, then we search one in the immediate dominator. If we are in a block
35 * of the dominance frontier, create a phi and do the same search for all
38 * A copy in this context means, that you want to introduce several new
39 * abstract values (in Firm: nodes) for which you know, that they
40 * represent the same concrete value. This is the case if you
46 * This function reroutes all uses of the original value to the copies in the
47 * corresponding dominance subtrees and creates Phi functions where necessary.
53 #include "bessaconstr.h"
55 #include "besched_t.h"
56 #include "beintlive_t.h"
67 #include "iredges_t.h"
69 DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)
72 * Checks that low <= what < hi.
74 static INLINE int is_inside(unsigned what, unsigned low, unsigned hi)
76 return what - low < hi;
80 * Calculates the iterated dominance frontier of a set of blocks. Marks the
81 * blocks as visited. Sets the link fields of the blocks in the dominance
82 * frontier to the block itself.
85 void mark_iterated_dominance_frontiers(const be_ssa_construction_env_t *env)
87 stat_ev_cnt_decl(blocks);
88 DBG((dbg, LEVEL_3, "Dominance Frontier:"));
90 while (!waitq_empty(env->worklist)) {
92 ir_node *block = waitq_get(env->worklist);
93 ir_node **domfront = be_get_dominance_frontier(env->domfronts, block);
94 int domfront_len = ARR_LEN(domfront);
96 for (i = 0; i < domfront_len; ++i) {
97 ir_node *y = domfront[i];
98 if (Block_block_visited(y))
102 * It makes no sense to add phi-functions to blocks
103 * that are not dominated by any definition;
104 * all uses are dominated, hence the paths reaching the uses
105 * have to stay in the dominance subtrees of the given definitions.
108 if (!is_inside(get_Block_dom_tree_pre_num(y), env->min_dom, env->max_dom))
111 if (!irn_visited(y)) {
112 set_irn_link(y, NULL);
113 waitq_put(env->worklist, y);
116 DBG((dbg, LEVEL_3, " %+F", y));
117 mark_Block_block_visited(y);
118 stat_ev_cnt_inc(blocks);
121 stat_ev_tim_pop("bessaconstr_idf_time");
122 stat_ev_cnt_done(blocks, "bessaconstr_idf_blocks");
123 DBG((dbg, LEVEL_3, "\n"));
127 ir_node *search_def_end_of_block(be_ssa_construction_env_t *env,
131 ir_node *create_phi(be_ssa_construction_env_t *env, ir_node *block,
134 int i, n_preds = get_Block_n_cfgpreds(block);
135 ir_graph *irg = get_irn_irg(block);
137 ir_node **ins = alloca(n_preds * sizeof(ins[0]));
141 for(i = 0; i < n_preds; ++i) {
142 ins[i] = new_r_Unknown(irg, env->mode);
144 phi = new_r_Phi(irg, block, n_preds, ins, env->mode);
145 if(env->new_phis != NULL) {
146 ARR_APP1(ir_node*, env->new_phis, phi);
149 if(env->mode != mode_M) {
150 sched_add_after(block, phi);
153 DBG((dbg, LEVEL_2, "\tcreating phi %+F in %+F\n", phi, block));
154 set_irn_link(link_with, phi);
155 mark_irn_visited(block);
157 for(i = 0; i < n_preds; ++i) {
158 ir_node *pred_block = get_Block_cfgpred_block(block, i);
159 ir_node *pred_def = search_def_end_of_block(env, pred_block);
161 set_irn_n(phi, i, pred_def);
168 ir_node *get_def_at_idom(be_ssa_construction_env_t *env, ir_node *block)
170 ir_node *dom = get_Block_idom(block);
172 return search_def_end_of_block(env, dom);
176 ir_node *search_def_end_of_block(be_ssa_construction_env_t *env, ir_node *block)
178 if(irn_visited(block)) {
179 assert(get_irn_link(block) != NULL);
180 return get_irn_link(block);
181 } else if(Block_block_visited(block)) {
182 return create_phi(env, block, block);
184 ir_node *def = get_def_at_idom(env, block);
185 mark_irn_visited(block);
186 set_irn_link(block, def);
192 ir_node *search_def(be_ssa_construction_env_t *env, ir_node *at)
194 ir_node *block = get_nodes_block(at);
198 DBG((dbg, LEVEL_3, "\t...searching def at %+F\n", at));
200 /* no defs in the current block we can do the normal searching */
201 if(!irn_visited(block) && !Block_block_visited(block)) {
202 DBG((dbg, LEVEL_3, "\t...continue at idom\n"));
203 return get_def_at_idom(env, block);
206 /* there are defs in the current block, walk the linked list to find
207 the one immediately dominating us
210 def = get_irn_link(node);
212 if(!value_dominates(at, def)) {
213 DBG((dbg, LEVEL_3, "\t...found dominating def %+F\n", def));
218 def = get_irn_link(node);
221 /* block in dominance frontier? create a phi then */
222 if(Block_block_visited(block)) {
223 DBG((dbg, LEVEL_3, "\t...create phi at block %+F\n", block));
224 assert(!is_Phi(node));
225 return create_phi(env, block, node);
228 DBG((dbg, LEVEL_3, "\t...continue at idom (after checking block)\n"));
229 return get_def_at_idom(env, block);
233 void update_domzone(be_ssa_construction_env_t *env, const ir_node *bl)
235 int start = get_Block_dom_tree_pre_num(bl);
236 int end = get_Block_dom_max_subtree_pre_num(bl) + 1;
238 env->min_dom = MIN(env->min_dom, start);
239 env->max_dom = MAX(env->max_dom, end);
243 * Adds a definition into the link field of the block. The definitions are
244 * sorted by dominance. A non-visited block means no definition has been
248 void introduce_def_at_block(ir_node *block, ir_node *def)
250 if(irn_visited(block)) {
251 ir_node *node = block;
252 ir_node *current_def;
255 current_def = get_irn_link(node);
256 if(current_def == def) {
257 /* already in block */
260 if(current_def == NULL)
262 if(value_dominates(current_def, def))
267 set_irn_link(node, def);
268 set_irn_link(def, current_def);
270 set_irn_link(block, def);
271 set_irn_link(def, NULL);
272 mark_irn_visited(block);
276 void be_ssa_construction_init(be_ssa_construction_env_t *env, be_irg_t *birg)
278 ir_graph *irg = be_get_birg_irg(birg);
279 ir_node *sb = get_irg_start_block(irg);
280 int n_blocks = get_Block_dom_max_subtree_pre_num(sb);
282 stat_ev_ctx_push_fobj("bessaconstr", irg);
286 stat_ev_dbl("bessaconstr_n_blocks", n_blocks);
288 memset(env, 0, sizeof(env[0]));
289 be_assure_dom_front(birg);
292 env->domfronts = be_get_birg_dom_front(birg);
293 env->new_phis = NEW_ARR_F(ir_node*, 0);
294 env->worklist = new_waitq();
295 env->min_dom = INT_MAX;
298 set_using_irn_visited(irg);
299 set_using_block_visited(irg);
300 set_using_irn_link(irg);
302 /* we use the visited flag to indicate blocks in the dominance frontier
303 * and blocks that already have the relevant value at the end calculated */
304 inc_irg_visited(irg);
305 /* We use the block visited flag to indicate blocks in the dominance
306 * frontier of some values (and this potentially needing phis) */
307 inc_irg_block_visited(irg);
310 void be_ssa_construction_destroy(be_ssa_construction_env_t *env)
312 stat_ev_int("bessaconstr_phis", ARR_LEN(env->new_phis));
313 del_waitq(env->worklist);
314 DEL_ARR_F(env->new_phis);
316 clear_using_irn_visited(env->irg);
317 clear_using_block_visited(env->irg);
318 clear_using_irn_link(env->irg);
320 stat_ev_tim_pop("bessaconstr_total_time");
321 stat_ev_ctx_pop("bessaconstr");
324 void be_ssa_construction_add_copy(be_ssa_construction_env_t *env,
329 assert(env->iterated_domfront_calculated == 0);
331 if(env->mode == NULL) {
332 env->mode = get_irn_mode(copy);
334 assert(env->mode == get_irn_mode(copy));
337 block = get_nodes_block(copy);
339 if(!irn_visited(block)) {
340 waitq_put(env->worklist, block);
342 introduce_def_at_block(block, copy);
343 update_domzone(env, block);
346 void be_ssa_construction_add_copies(be_ssa_construction_env_t *env,
347 ir_node **copies, size_t copies_len)
351 assert(env->iterated_domfront_calculated == 0);
353 if(env->mode == NULL) {
354 env->mode = get_irn_mode(copies[0]);
357 for(i = 0; i < copies_len; ++i) {
358 ir_node *copy = copies[i];
359 ir_node *block = get_nodes_block(copy);
361 assert(env->mode == get_irn_mode(copy));
362 if(!irn_visited(block)) {
363 waitq_put(env->worklist, block);
365 introduce_def_at_block(block, copy);
366 update_domzone(env, block);
370 void be_ssa_construction_set_ignore_uses(be_ssa_construction_env_t *env,
371 const ir_nodeset_t *ignore_uses)
373 env->ignore_uses = ignore_uses;
376 ir_node **be_ssa_construction_get_new_phis(be_ssa_construction_env_t *env)
378 return env->new_phis;
381 void be_ssa_construction_fix_users_array(be_ssa_construction_env_t *env,
382 ir_node **nodes, size_t nodes_len)
384 stat_ev_cnt_decl(uses);
385 const ir_edge_t *edge, *next;
388 BE_TIMER_PUSH(t_ssa_constr);
390 if(!env->iterated_domfront_calculated) {
391 mark_iterated_dominance_frontiers(env);
392 env->iterated_domfront_calculated = 1;
395 stat_ev_int("bessaconstr_domzone", env->max_dom - env->min_dom);
397 for(i = 0; i < nodes_len; ++i) {
398 ir_node *value = nodes[i];
401 * Search the valid def for each use and set it.
403 foreach_out_edge_safe(value, edge, next) {
404 ir_node *use = get_edge_src_irn(edge);
406 int pos = get_edge_src_pos(edge);
409 if(env->ignore_uses != NULL &&
410 ir_nodeset_contains(env->ignore_uses, use))
416 ir_node *block = get_nodes_block(use);
417 ir_node *predblock = get_Block_cfgpred_block(block, pos);
418 at = sched_last(predblock);
421 def = search_def(env, at);
424 panic("no definition found for %+F at position %d\n", use, pos);
427 DBG((dbg, LEVEL_2, "\t%+F(%d) -> %+F\n", use, pos, def));
428 set_irn_n(use, pos, def);
429 stat_ev_cnt_inc(uses);
432 BE_TIMER_POP(t_ssa_constr);
434 stat_ev_tim_pop("bessaconstr_fix_time");
435 stat_ev_cnt_done(uses, "bessaconstr_uses");
438 void be_ssa_construction_fix_users(be_ssa_construction_env_t *env, ir_node *value)
440 be_ssa_construction_fix_users_array(env, &value, 1);
444 void be_ssa_construction_update_liveness_phis(be_ssa_construction_env_t *env,
449 BE_TIMER_PUSH(t_ssa_constr);
451 n = ARR_LEN(env->new_phis);
452 for(i = 0; i < n; ++i) {
453 ir_node *phi = env->new_phis[i];
454 be_liveness_introduce(lv, phi);
457 BE_TIMER_POP(t_ssa_constr);
460 void be_init_ssaconstr(void)
462 FIRM_DBG_REGISTER(dbg, "firm.be.ssaconstr");
465 BE_REGISTER_MODULE_CONSTRUCTOR(be_init_ssaconstr);