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 Global Value Numbering Partial Redundancy Elimination
23 * (VanDrunen Hosking 2004)
24 * @author Michael Beck
30 #include "iroptimize.h"
39 #include "irnodemap.h"
40 #include "irnodeset.h"
42 #include "iropt_dbg.h"
46 #include "irgraph_t.h"
50 /** Additional info we need for every block. */
51 typedef struct block_info {
52 ir_valueset_t *exp_gen; /**< The set of expression per block. */
53 ir_valueset_t *avail_out; /**< The Avail_out set for a block. */
54 ir_valueset_t *antic_in; /**< The Antic_in set for a block. */
55 ir_valueset_t *new_set; /**< The set of all new values for a block. */
56 ir_node *avail; /**< The get_map(avail, block) result. */
57 ir_node *block; /**< The Block of the block info. */
58 struct block_info *next; /**< Links all entries, so we can recover the sets easily. */
59 int not_found; /**< Non-zero, if avail was not found in this block. */
63 * A pair of nodes that must be exchanged.
64 * We must defer the exchange because our hash-sets cannot
65 * find an already replace node else.
67 typedef struct elim_pair {
68 ir_node *old_node; /**< The old node that will be replaced. */
69 ir_node *new_node; /**< The new node. */
70 struct elim_pair *next; /**< Links all entries in a list. */
71 int reason; /**< The reason for the replacement. */
74 /** The environment for the GVN-PRE algorithm */
75 typedef struct pre_env {
76 struct obstack *obst; /**< The obstack to allocate on. */
77 ir_node *start_block; /**< The start block of the current graph. */
78 ir_node *end_block; /**< The end block of the current graph */
79 block_info *list; /**< Links all block info entries for easier recovery. */
80 elim_pair *pairs; /**< A list of node pairs that must be eliminated. */
81 unsigned last_idx; /**< last node index of "old" nodes, all higher indexes are newly created once. */
82 char changes; /**< Non-zero, if calculation of Antic_in has changed. */
83 char first_iter; /**< non-zero for first iteration */
86 static ir_nodemap_t value_map;
88 /** The debug module handle. */
89 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
91 /* ---------- Functions for Value sets ---------- */
93 /** computes dst = dst \/ src for value sets */
94 static void value_union(ir_valueset_t *dst, ir_valueset_t *src)
96 ir_valueset_iterator_t iter;
97 ir_node *value, *expr;
99 foreach_valueset(src, value, expr, iter) {
100 ir_valueset_insert(dst, value, expr);
105 /* ---------- Functions for Values ---------- */
108 * Add a node e representing the value v to the set.
110 * @param e a node representing an expression
111 * @param v a node representing a value
113 * @return the final value for the expression e
115 static ir_node *add(ir_node *e, ir_node *v)
118 ir_node *pred = get_Proj_pred(v);
119 ir_node *v_pred = identify_remember(pred);
121 if (v_pred != pred) {
122 /* must create a new value here */
123 v = new_r_Proj(v_pred, get_irn_mode(v), get_Proj_proj(v));
126 v = identify_remember(v);
127 ir_nodemap_insert(&value_map, e, v);
132 * Lookup a value in a value set.
134 * @param e a node representing an expression
136 * @return a node representing the value or NULL if
137 * the given expression is not available
139 static ir_node *lookup(ir_node *e)
141 ir_node *value = ir_nodemap_get(&value_map, e);
143 return identify_remember(value);
148 * Return the block info of a block.
150 * @param block the block
152 static block_info *get_block_info(ir_node *block)
154 return get_irn_link(block);
155 } /* get_block_info */
158 * Allocate a block info for a block.
160 * @param block the block
161 * @param env the environment
163 static void alloc_blk_info(ir_node *block, pre_env *env)
165 block_info *info = OALLOC(env->obst, block_info);
167 set_irn_link(block, info);
168 info->exp_gen = ir_valueset_new(16);
169 info->avail_out = ir_valueset_new(16);
170 info->antic_in = ir_valueset_new(16);
171 info->new_set = NULL;
174 info->next = env->list;
177 } /* alloc_blk_info */
180 * Returns non-zero if a node is movable and a possible candidate for PRE.
184 static int is_nice_value(ir_node *n)
189 n = get_Proj_pred(n);
190 if (get_irn_pinned(n) == op_pin_state_pinned)
192 mode = get_irn_mode(n);
193 if (!mode_is_data(mode)) {
194 if (! is_Div(n) && ! is_Mod(n) && ! is_DivMod(n))
196 if (! is_NoMem(get_fragile_op_mem(n)))
200 } /* is_nice_value */
206 * @param set the set to dump
207 * @param txt a text to describe the set
208 * @param block the owner block of the set
210 static void dump_value_set(ir_valueset_t *set, char *txt, ir_node *block)
212 ir_valueset_iterator_t iter;
213 ir_node *value, *expr;
216 DB((dbg, LEVEL_2, "%s(%+F) = {\n", txt, block));
218 foreach_valueset(set, value, expr, iter) {
220 DB((dbg, LEVEL_2, "\n"));
222 DB((dbg, LEVEL_2, " %+F(%+F),", expr, value));
224 DB((dbg, LEVEL_2, " %+F,", expr));
227 DB((dbg, LEVEL_2, "\n}\n"));
228 } /* dump_value_set */
231 #define dump_value_set(set, txt, block)
232 #endif /* DEBUG_libfirm */
235 * Topological walker. Allocates block info for every block and place nodes in topological
236 * order into the nodes set.
238 static void topo_walker(ir_node *irn, void *ctx)
246 /* the topological walker ensures that blocks are visited before anything else */
247 alloc_blk_info(irn, env);
250 /* GVN step: remember the value */
251 value = add(irn, irn);
253 /* no need to put constants into the sets: they are always redundant */
254 if (! is_nice_value(irn) || is_irn_constlike(irn))
257 /* Do not put mode_T nodes info the sets, or PhiT will be created
258 (which are not allowed in Firm). Instead, put the Proj's here only. */
259 if (get_irn_mode(irn) == mode_T)
262 /* place this node into the set of possible nodes of its block */
263 block = get_nodes_block(irn);
264 info = get_block_info(block);
266 ir_valueset_insert(info->exp_gen, value, irn);
270 * Computes Avail_out(block):
272 * Avail_in(block) = Avail_out(dom(block))
273 * Avail_out(block) = Avail_in(block) \/ Nodes(block)
276 * This function must be called in the top-down dominance order:
277 * Then, it computes Leader(Nodes(block)) instead of Nodes(block) !
279 * @param block the block
280 * @param ctx walker context
282 static void compute_avail_top_down(ir_node *block, void *ctx)
285 block_info *dom_info;
286 block_info *info = get_block_info(block);
289 /* we don't need the end block Avail */
290 if (block == env->end_block)
294 * First add all nodes from the dominator.
295 * This must be done to ensure that Antic_out contains the leader
296 * for every node. The root has no dominator.
298 if (block != env->start_block) {
299 dom_blk = get_Block_idom(block);
300 assert(is_Block(dom_blk));
302 dom_info = get_block_info(dom_blk);
305 value_union(info->avail_out, dom_info->avail_out);
307 value_union(info->avail_out, info->exp_gen);
309 dump_value_set(info->avail_out, "Avail_out", block);
310 } /* compute_avail_top_down */
313 * check if a node n is clean in block block.
316 * @param block the block
317 * @param set a value set, containing the already processed predecessors
319 static int is_clean_in_block(ir_node *n, ir_node *block, ir_valueset_t *set)
326 if (! is_nice_value(n))
329 for (i = get_irn_arity(n) - 1; i >= 0; --i) {
330 ir_node *pred = get_irn_n(n, i);
333 if (get_nodes_block(pred) != block)
339 if (! is_nice_value(pred))
342 value = lookup(pred);
345 if (! ir_valueset_lookup(set, value))
349 } /* is_clean_in_block */
352 * Implements phi_translate. Translate a expression above a Phi.
354 * @param node the node
355 * @param block the block in which the node is translated
356 * @param pos the input number of the destination block
357 * @param translated the valueset containing the other already translated nodes
359 * @return a node representing the translated value
361 static ir_node *phi_translate(ir_node *node, ir_node *block, int pos, ir_valueset_t *translated)
367 if (get_nodes_block(node) == block) {
368 /* a Phi inside our block */
369 return get_Phi_pred(node, pos);
371 /* already outside */
375 arity = get_irn_arity(node);
377 /* check if the node has at least one Phi predecessor */
378 for (i = 0; i < arity; ++i) {
379 ir_node *pred = get_irn_n(node, i);
380 ir_node *leader = lookup(pred);
383 leader = leader != NULL ? leader : pred;
384 trans = ir_valueset_lookup(translated, leader);
386 if ((trans != NULL && trans != leader) || (is_Phi(leader) && get_nodes_block(leader) == block))
390 /* no translation needed */
395 get_irn_dbg_info(node),
397 get_nodes_block(node),
402 /* We need the attribute copy here, because the Hash value of a
403 node might depend on that. */
404 copy_node_attr(current_ir_graph, node, nn);
406 for (i = 0; i < arity; ++i) {
407 ir_node *pred = get_irn_n(node, i);
408 ir_node *leader = lookup(pred);
411 leader = leader != NULL ? leader : pred;
412 trans = ir_valueset_lookup(translated, leader);
416 if (is_Phi(trans) && get_nodes_block(trans) == block)
417 set_irn_n(nn, i, get_Phi_pred(trans, pos));
419 set_irn_n(nn, i, trans);
421 nn = optimize_node(nn);
423 } /* phi_translate */
426 * Block-walker, computes Antic_in(block).
428 * @param block the block
429 * @param ctx the walker environment
431 static void compute_antic(ir_node *block, void *ctx)
434 block_info *succ_info;
435 block_info *info = get_block_info(block);
436 ir_node *succ, *value, *expr;
438 ir_valueset_iterator_t iter;
440 /* no need for computations in start block */
441 if (block == env->start_block)
444 size = ir_valueset_size(info->antic_in);
446 /* the end block has no successor */
447 if (block != env->end_block) {
451 * This step puts all generated expression from the current
452 * current block into Antic_in.
453 * It is enough to do this in the first iteration only, because
454 * the set info->exp_gen is not changed anymore.
456 if (env->first_iter) {
457 foreach_valueset(info->exp_gen, value, expr, iter) {
458 ir_valueset_insert(info->antic_in, value, expr);
462 n_succ = get_Block_n_cfg_outs(block);
466 /* find blocks position in succ's block predecessors */
467 succ = get_Block_cfg_out(block, 0);
468 pos = get_Block_cfgpred_pos(succ, block);
471 succ_info = get_block_info(succ);
472 /* translate into list: we cannot insert into a set we iterate
473 * and succ might be equal to block for endless loops */
474 foreach_valueset(succ_info->antic_in, value, expr, iter) {
475 ir_node *trans = phi_translate(expr, succ, pos, info->antic_in);
477 if (is_clean_in_block(trans, block, info->antic_in))
478 ir_valueset_insert(info->antic_in, value, trans);
480 } else { /* n_succ > 1 */
482 block_info *succ0_info;
487 /* Select a successor to compute the disjoint of all Nodes
488 sets, it might be useful to select the block with the
489 smallest number of nodes. For simplicity we choose the
491 succ0 = get_Block_cfg_out(block, 0);
492 succ0_info = get_block_info(succ0);
493 foreach_valueset(succ0_info->antic_in, value, expr, iter) {
494 /* we need the disjoint */
495 for (i = 1; i < n_succ; ++i) {
496 ir_node *succ = get_Block_cfg_out(block, i);
497 block_info *succ_info = get_block_info(succ);
498 if (ir_valueset_lookup(succ_info->antic_in, value) == NULL)
502 /* we found a value that is common in all Antic_in(succ(b)),
503 put it in Antic_in(b) if the value is NOT already represented. */
504 if (is_clean_in_block(expr, block, info->antic_in))
505 ir_valueset_insert(info->antic_in, value, expr);
511 /* we do not need a clean here, because we ensure that only cleaned nodes are in exp_gen
512 * and all other sets */
514 dump_value_set(info->antic_in, "Antic_in", block);
515 if (size != ir_valueset_size(info->antic_in)) {
516 /* the Antic_in set has changed */
519 } /* compute_antic */
522 * Perform insertion of partially redundant values.
523 * For every Block node, do the following:
524 * 1. Propagate the NEW_SETS of the dominator into the current block.
525 * If the block has multiple predecessors,
526 * 2a. Iterate over the ANTIC expressions for the block to see if
527 * any of them are partially redundant.
528 * 2b. If so, insert them into the necessary predecessors to make
529 * the expression fully redundant.
530 * 2c. Insert a new Phi merging the values of the predecessors.
531 * 2d. Insert the new Phi, and the new expressions, into the
534 * @param block the block
535 * @param ctx the walker environment
537 static void insert_nodes(ir_node *block, void *ctx)
540 ir_node *value, *expr, *idom, *first_s, *worklist;
541 block_info *curr_info, *idom_info;
542 int pos, arity = get_irn_arity(block);
543 int all_same, by_some, updated;
544 ir_valueset_iterator_t iter;
546 /* ensure that even the start block has a new_set */
547 curr_info = get_block_info(block);
548 if (curr_info->new_set)
549 ir_valueset_del(curr_info->new_set);
550 curr_info->new_set = ir_valueset_new(16);
552 if (block == env->start_block)
555 idom = get_Block_idom(block);
556 idom_info = get_block_info(idom);
558 /* update the new_sets */
560 dump_value_set(idom_info->new_set, "[New Set]", idom);
561 foreach_valueset(idom_info->new_set, value, expr, iter) {
562 ir_valueset_insert(curr_info->new_set, value, expr);
563 updated |= ir_valueset_replace(curr_info->avail_out, value, expr);
566 dump_value_set(curr_info->avail_out, "Updated [Avail_out]", block);
572 /* convert the set into a list. This allows the removal of
573 * elements from the set */
575 foreach_valueset(curr_info->antic_in, value, expr, iter) {
578 /* If the value was already computed in the dominator, then
579 it is totally redundant. Hence we have nothing to insert. */
580 if (ir_valueset_lookup(idom_info->avail_out, value)) {
581 // DB((dbg, LEVEL_2, "Found %+F from block %+F avail in dom %+F\n", v, block, idom));
590 /* for all predecessor blocks */
591 for (pos = 0; pos < arity; ++pos) {
592 block_info *pred_info;
593 ir_node *pred_blk = get_Block_cfgpred_block(block, pos);
594 ir_node *e_prime, *v_prime, *e_dprime;
596 /* ignore bad blocks. */
597 if (is_Bad(pred_blk))
600 e_prime = phi_translate(expr, block, pos, curr_info->avail_out);
601 v_prime = lookup(e_prime);
605 pred_info = get_block_info(pred_blk);
606 e_dprime = ir_valueset_lookup(pred_info->avail_out, v_prime);
608 if (e_dprime == NULL) {
609 pred_info->avail = e_prime;
610 pred_info->not_found = 1;
613 pred_info->avail = e_dprime;
614 pred_info->not_found = 0;
615 mode = get_irn_mode(e_dprime);
620 else if (first_s != e_dprime)
623 DB((dbg, LEVEL_2, "Found %+F from block %+F as %+F in pred %+F\n", expr, block, e_dprime, pred_blk));
627 /* If it's not the same value already existing along every predecessor, and
628 it's defined by some predecessor, it is partially redundant. */
629 if (! all_same && by_some) {
630 ir_node *phi, *l, **in;
632 DB((dbg, LEVEL_1, "Partial redundant %+F from block %+F found\n", expr, block));
634 in = XMALLOCN(ir_node*, arity);
635 /* for all predecessor blocks */
636 for (pos = 0; pos < arity; ++pos) {
637 ir_node *pred_blk = get_Block_cfgpred_block(block, pos);
638 block_info *pred_info = get_block_info(pred_blk);
640 /* ignore bad blocks. */
641 if (is_Bad(pred_blk)) {
642 ir_graph *irg = get_irn_irg(pred_blk);
643 in[pos] = new_r_Bad(irg);
647 /* ignore blocks that already have the expression */
648 if (pred_info->not_found) {
649 ir_node *e_prime = pred_info->avail;
651 if (!is_Phi(e_prime)) {
652 ir_node *proj_pred = NULL;
653 if (is_Proj(e_prime)) {
654 ir_node *pred = get_Proj_pred(e_prime);
655 mode = get_irn_mode(pred);
657 get_irn_dbg_info(pred),
658 current_ir_graph, pred_blk,
662 get_irn_in(pred) + 1);
663 copy_node_attr(current_ir_graph, pred, nn);
665 DB((dbg, LEVEL_1, "New node %+F in block %+F created\n", nn, pred_blk));
668 mode = get_irn_mode(e_prime);
670 get_irn_dbg_info(e_prime),
671 current_ir_graph, pred_blk,
674 get_irn_arity(e_prime),
675 get_irn_in(e_prime) + 1);
676 copy_node_attr(current_ir_graph, e_prime, nn);
677 if (proj_pred != NULL) {
678 set_Proj_pred(nn, proj_pred);
681 DB((dbg, LEVEL_1, "New node %+F in block %+F created\n", nn, pred_blk));
684 l = add(expr, value);
686 ir_valueset_insert(pred_info->avail_out, add(nn, l), nn);
687 pred_info->avail = nn;
690 in[pos] = pred_info->avail;
692 phi = new_r_Phi(block, arity, in, mode);
695 l = add(expr, value);
698 ir_valueset_replace(curr_info->avail_out, value, phi);
699 ir_valueset_insert(curr_info->new_set, value, phi);
701 DB((dbg, LEVEL_1, "New %+F for redundant %+F created\n", phi, expr));
702 ir_valueset_remove_iterator(curr_info->antic_in, &iter);
705 } /* node_set_foreach */
709 * Walker, change nodes by its value if different.
711 * We cannot do the changes right here, as this would change
712 * the hash values of the nodes in the avail_out set!
714 * @param irn the node
715 * @param ctx the walker environment
717 static void eliminate(ir_node *irn, void *ctx)
721 if (!is_Block(irn)) {
722 ir_node *block = get_nodes_block(irn);
723 block_info *bl = get_block_info(block);
724 ir_node *value = lookup(irn);
727 ir_node *expr = ir_valueset_lookup(bl->avail_out, value);
729 if (expr != NULL && expr != irn) {
730 elim_pair *p = OALLOC(env->obst, elim_pair);
734 p->next = env->pairs;
735 p->reason = get_irn_idx(expr) >= env->last_idx ? FS_OPT_GVN_PARTLY : FS_OPT_GVN_FULLY;
743 * Do all the recorded changes and optimize
744 * newly created Phi's.
746 * @param pairs list of elimination pairs
748 static void eliminate_nodes(elim_pair *pairs)
752 for (p = pairs; p != NULL; p = p->next) {
753 /* might be already changed */
754 p->new_node = skip_Id(p->new_node);
756 DB((dbg, LEVEL_2, "Replacing %+F by %+F\n", p->old_node, p->new_node));
758 * PRE tends to create Phi(self, self, ... , x, self, self, ...)
759 * which we can optimize here
761 if (is_Phi(p->new_node)) {
765 for (i = get_irn_arity(p->new_node) - 1; i >= 0; --i) {
766 ir_node *pred = get_irn_n(p->new_node, i);
768 if (pred != p->old_node) {
777 exchange(p->new_node, res);
781 DBG_OPT_GVN_PRE(p->old_node, p->new_node, p->reason);
782 exchange(p->old_node, p->new_node);
784 } /* eliminate_nodes */
787 * Argh: Endless loops cause problems, because the
788 * insert algorithm did not terminate. We get translated nodes that
789 * references the origin. These nodes are translated again and again...
791 * The current fix is to use post-dominance. This simple ignores
792 * endless loops, i.e. we cannot optimize them.
794 void do_gvn_pre(ir_graph *irg)
798 optimization_state_t state;
800 unsigned antic_iter, insert_iter;
801 ir_node *value, *expr;
803 /* register a debug mask */
804 FIRM_DBG_REGISTER(dbg, "firm.opt.gvn_pre");
806 /* edges will crash if enabled due to our allocate on other obstack trick */
807 edges_deactivate(irg);
810 ir_nodemap_init(&value_map);
815 a_env.start_block = get_irg_start_block(irg);
816 a_env.end_block = get_irg_end_block(irg);
819 /* critical edges MUST be removed */
820 remove_critical_cf_edges(irg);
822 /* we need dominator for Antic_out calculation */
824 assure_postdoms(irg);
825 /* we get all nodes of a block by following outs */
826 assure_irg_outs(irg);
829 * Switch on GCSE. We need it to correctly compute
830 * the value of a node, which is independent from
833 save_optimization_state(&state);
834 set_opt_global_cse(1);
836 DB((dbg, LEVEL_1, "Doing GVN-PRE for %+F\n", irg));
838 /* allocate block info for all blocks */
839 irg_walk_blkwise_dom_top_down(irg, NULL, topo_walker, &a_env);
841 /* clean the exp_gen set. Doing this here saves the cleanup in the iteration. */
842 for (bl_info = a_env.list; bl_info != NULL; bl_info = bl_info->next) {
843 ir_valueset_iterator_t iter;
845 foreach_valueset(bl_info->exp_gen, value, expr, iter) {
846 if (!is_clean_in_block(expr, bl_info->block, bl_info->exp_gen))
847 ir_valueset_remove_iterator(bl_info->exp_gen, &iter);
850 /* compute the available value sets for all blocks */
851 dom_tree_walk_irg(irg, compute_avail_top_down, NULL, &a_env);
853 /* compute the anticipated value sets for all blocks */
855 a_env.first_iter = 1;
857 /* we use the visited flag to mark non-clean nodes */
858 inc_irg_visited(irg);
860 DB((dbg, LEVEL_1, "Antic_in Iteration %d starts ...\n", ++antic_iter));
862 postdom_tree_walk_irg(irg, compute_antic, NULL, &a_env);
863 a_env.first_iter = 0;
864 DB((dbg, LEVEL_1, "------------------------\n"));
865 } while (a_env.changes != 0);
867 /* compute redundant expressions */
869 a_env.last_idx = get_irg_last_idx(irg);
871 DB((dbg, LEVEL_1, "Insert Iteration %d starts ...\n", ++insert_iter));
873 dom_tree_walk_irg(irg, insert_nodes, NULL, &a_env);
874 DB((dbg, LEVEL_1, "------------------------\n"));
875 } while (a_env.changes != 0);
877 /* last step: eliminate nodes */
878 irg_walk_graph(irg, NULL, eliminate, &a_env);
879 eliminate_nodes(a_env.pairs);
881 /* clean up: delete all sets */
882 for (bl_info = a_env.list; bl_info != NULL; bl_info = bl_info->next) {
883 ir_valueset_del(bl_info->exp_gen);
884 ir_valueset_del(bl_info->avail_out);
885 ir_valueset_del(bl_info->antic_in);
886 if (bl_info->new_set)
887 ir_valueset_del(bl_info->new_set);
889 ir_nodemap_destroy(&value_map);
890 obstack_free(&obst, NULL);
892 /* pin the graph again: This is needed due to the use of set_opt_global_cse(1) */
893 set_irg_pinned(irg, op_pin_state_pinned);
894 restore_optimization_state(&state);
897 set_irg_outs_inconsistent(irg);
898 set_irg_loopinfo_inconsistent(irg);
902 /* Creates an ir_graph pass for do_gvn_pre. */
903 ir_graph_pass_t *do_gvn_pre_pass(const char *name)
905 return def_graph_pass(name ? name : "gvn_pre", do_gvn_pre);
906 } /* do_gvn_pre_pass */