2 * Copyright (C) 1995-2007 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. The
33 * we search for each use all 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 search do the same search for
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"
66 #include "iredges_t.h"
68 DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)
70 static INLINE int is_inside(unsigned what, unsigned low, unsigned hi)
72 return what - low < hi;
76 * Calculates the iterated dominance frontier of a set of blocks. Marks the
77 * blocks as visited. Sets the link fields of the blocks in the dominance
78 * frontier to the block itself.
81 void mark_iterated_dominance_frontiers(const be_ssa_construction_env_t *env)
83 stat_ev_cnt_decl(blocks);
84 DBG((dbg, LEVEL_3, "Dominance Frontier:"));
86 while (!pdeq_empty(env->worklist)) {
88 ir_node *block = waitq_get(env->worklist);
89 ir_node **domfront = be_get_dominance_frontier(env->domfronts, block);
90 int domfront_len = ARR_LEN(domfront);
92 for (i = 0; i < domfront_len; ++i) {
93 ir_node *y = domfront[i];
94 if (Block_block_visited(y))
98 * It makes no sense to add phi-functions to blocks
99 * that are not dominated by any definition;
100 * all uses are dominated, hence the paths reaching the uses
101 * have to stay in the dominance subtrees of the given definitions.
104 if (!is_inside(get_Block_dom_tree_pre_num(y), env->min_dom, env->max_dom))
107 if (!irn_visited(y)) {
108 set_irn_link(y, NULL);
109 waitq_put(env->worklist, y);
112 DBG((dbg, LEVEL_3, " %+F", y));
113 mark_Block_block_visited(y);
114 stat_ev_cnt_inc(blocks);
117 stat_ev_tim_pop("bessaconstr_idf_time");
118 stat_ev_cnt_done(blocks, "bessaconstr_idf_blocks");
119 DBG((dbg, LEVEL_3, "\n"));
123 ir_node *search_def_end_of_block(be_ssa_construction_env_t *env,
127 ir_node *create_phi(be_ssa_construction_env_t *env, ir_node *block,
130 int i, n_preds = get_Block_n_cfgpreds(block);
131 ir_graph *irg = get_irn_irg(block);
133 ir_node **ins = alloca(n_preds * sizeof(ins[0]));
137 for(i = 0; i < n_preds; ++i) {
138 ins[i] = new_r_Unknown(irg, env->mode);
140 phi = new_r_Phi(irg, block, n_preds, ins, env->mode);
141 if(env->new_phis != NULL) {
142 ARR_APP1(ir_node*, env->new_phis, phi);
145 if(env->mode != mode_M) {
146 sched_add_after(block, phi);
149 DBG((dbg, LEVEL_2, "\tcreating phi %+F in %+F\n", phi, block));
150 set_irn_link(link_with, phi);
151 mark_irn_visited(block);
153 for(i = 0; i < n_preds; ++i) {
154 ir_node *pred_block = get_Block_cfgpred_block(block, i);
155 ir_node *pred_def = search_def_end_of_block(env, pred_block);
157 set_irn_n(phi, i, pred_def);
164 ir_node *get_def_at_idom(be_ssa_construction_env_t *env, ir_node *block)
166 ir_node *dom = get_Block_idom(block);
168 return search_def_end_of_block(env, dom);
172 ir_node *search_def_end_of_block(be_ssa_construction_env_t *env, ir_node *block)
174 if(irn_visited(block)) {
175 assert(get_irn_link(block) != NULL);
176 return get_irn_link(block);
177 } else if(Block_block_visited(block)) {
178 return create_phi(env, block, block);
180 ir_node *def = get_def_at_idom(env, block);
181 mark_irn_visited(block);
182 set_irn_link(block, def);
188 ir_node *search_def(be_ssa_construction_env_t *env, ir_node *at)
190 ir_node *block = get_nodes_block(at);
194 DBG((dbg, LEVEL_3, "\t...searching def at %+F\n", at));
196 /* no defs in the current block we can do the normal searching */
197 if(!irn_visited(block) && !Block_block_visited(block)) {
198 DBG((dbg, LEVEL_3, "\t...continue at idom\n"));
199 return get_def_at_idom(env, block);
202 /* there are defs in the current block, walk the linked list to find
203 the one immediately dominating us
206 def = get_irn_link(node);
208 if(!value_dominates(at, def)) {
209 DBG((dbg, LEVEL_3, "\t...found dominating def %+F\n", def));
214 def = get_irn_link(node);
217 /* block in dominance frontier? create a phi then */
218 if(Block_block_visited(block)) {
219 DBG((dbg, LEVEL_3, "\t...create phi at block %+F\n", block));
220 assert(!is_Phi(node));
221 return create_phi(env, block, node);
224 DBG((dbg, LEVEL_3, "\t...continue at idom (after checking block)\n"));
225 return get_def_at_idom(env, block);
229 void update_domzone(be_ssa_construction_env_t *env, const ir_node *bl)
231 int start = get_Block_dom_tree_pre_num(bl);
232 int end = get_Block_dom_max_subtree_pre_num(bl) + 1;
234 env->min_dom = MIN(env->min_dom, start);
235 env->max_dom = MAX(env->max_dom, end);
239 * Adds a definition into the link field of the block. The definitions are
240 * sorted by dominance. A non-visited block means no definition has been
244 void introduce_def_at_block(ir_node *block, ir_node *def)
246 if(irn_visited(block)) {
247 ir_node *node = block;
248 ir_node *current_def;
251 current_def = get_irn_link(node);
252 if(current_def == def) {
253 /* already in block */
256 if(current_def == NULL)
258 if(value_dominates(current_def, def))
263 set_irn_link(node, def);
264 set_irn_link(def, current_def);
266 set_irn_link(block, def);
267 set_irn_link(def, NULL);
268 mark_irn_visited(block);
272 void be_ssa_construction_init(be_ssa_construction_env_t *env, be_irg_t *birg)
274 ir_graph *irg = be_get_birg_irg(birg);
275 ir_node *sb = get_irg_start_block(irg);
276 int n_blocks = get_Block_dom_max_subtree_pre_num(sb);
278 stat_ev_ctx_push_fobj("bessaconstr", irg);
282 stat_ev_dbl("bessaconstr_n_blocks", n_blocks);
284 memset(env, 0, sizeof(env[0]));
285 be_assure_dom_front(birg);
288 env->domfronts = be_get_birg_dom_front(birg);
289 env->new_phis = NEW_ARR_F(ir_node*, 0);
290 env->worklist = new_waitq();
291 env->min_dom = INT_MAX;
294 set_using_visited(irg);
295 set_using_block_visited(irg);
296 set_using_irn_link(irg);
298 /* we use the visited flag to indicate blocks in the dominance frontier
299 * and blocks that already have the relevant value at the end calculated */
300 inc_irg_visited(irg);
301 /* We use the block visited flag to indicate blocks in the dominance
302 * frontier of some values (and this potentially needing phis) */
303 inc_irg_block_visited(irg);
306 void be_ssa_construction_destroy(be_ssa_construction_env_t *env)
308 stat_ev_int("bessaconstr_phis", ARR_LEN(env->new_phis));
309 del_waitq(env->worklist);
310 DEL_ARR_F(env->new_phis);
312 clear_using_visited(env->irg);
313 clear_using_block_visited(env->irg);
314 clear_using_irn_link(env->irg);
316 stat_ev_tim_pop("bessaconstr_total_time");
317 stat_ev_ctx_pop("bessaconstr");
320 void be_ssa_construction_add_copy(be_ssa_construction_env_t *env,
325 assert(env->iterated_domfront_calculated == 0);
327 if(env->mode == NULL) {
328 env->mode = get_irn_mode(copy);
330 assert(env->mode == get_irn_mode(copy));
333 block = get_nodes_block(copy);
335 if(!irn_visited(block)) {
336 waitq_put(env->worklist, block);
338 introduce_def_at_block(block, copy);
339 update_domzone(env, block);
342 void be_ssa_construction_add_copies(be_ssa_construction_env_t *env,
343 ir_node **copies, size_t copies_len)
347 assert(env->iterated_domfront_calculated == 0);
349 if(env->mode == NULL) {
350 env->mode = get_irn_mode(copies[0]);
353 for(i = 0; i < copies_len; ++i) {
354 ir_node *copy = copies[i];
355 ir_node *block = get_nodes_block(copy);
357 assert(env->mode == get_irn_mode(copy));
358 if(!irn_visited(block)) {
359 waitq_put(env->worklist, block);
361 introduce_def_at_block(block, copy);
362 update_domzone(env, block);
366 void be_ssa_construction_set_ignore_uses(be_ssa_construction_env_t *env,
367 const ir_nodeset_t *ignore_uses)
369 env->ignore_uses = ignore_uses;
372 ir_node **be_ssa_construction_get_new_phis(be_ssa_construction_env_t *env)
374 return env->new_phis;
377 void be_ssa_construction_fix_users_array(be_ssa_construction_env_t *env,
378 ir_node **nodes, size_t nodes_len)
380 stat_ev_cnt_decl(uses);
381 const ir_edge_t *edge, *next;
384 if(!env->iterated_domfront_calculated) {
385 mark_iterated_dominance_frontiers(env);
386 env->iterated_domfront_calculated = 1;
389 stat_ev_int("bessaconstr_domzone", env->max_dom - env->min_dom);
391 for(i = 0; i < nodes_len; ++i) {
392 ir_node *value = nodes[i];
395 * Search the valid def for each use and set it.
397 foreach_out_edge_safe(value, edge, next) {
398 ir_node *use = get_edge_src_irn(edge);
400 int pos = get_edge_src_pos(edge);
403 if(env->ignore_uses != NULL &&
404 ir_nodeset_contains(env->ignore_uses, use))
410 ir_node *block = get_nodes_block(use);
411 ir_node *predblock = get_Block_cfgpred_block(block, pos);
412 at = sched_last(predblock);
415 def = search_def(env, at);
418 panic("no definition found for %+F at position %d\n", use, pos);
421 DBG((dbg, LEVEL_2, "\t%+F(%d) -> %+F\n", use, pos, def));
422 set_irn_n(use, pos, def);
423 stat_ev_cnt_inc(uses);
426 stat_ev_tim_pop("bessaconstr_fix_time");
427 stat_ev_cnt_done(uses, "bessaconstr_uses");
430 void be_ssa_construction_fix_users(be_ssa_construction_env_t *env, ir_node *value)
432 be_ssa_construction_fix_users_array(env, &value, 1);
436 void be_ssa_construction_update_liveness_phis(be_ssa_construction_env_t *env,
441 n = ARR_LEN(env->new_phis);
442 for(i = 0; i < n; ++i) {
443 ir_node *phi = env->new_phis[i];
444 be_liveness_introduce(lv, phi);
448 void be_init_ssaconstr(void)
450 FIRM_DBG_REGISTER(dbg, "firm.be.ssaconstr");
453 BE_REGISTER_MODULE_CONSTRUCTOR(be_init_ssaconstr);