2 * Copyright (C) 1995-2007 University of Karlsruhe. All right reserved.
4 * This file is part of libFirm.
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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 First simple copy minimization heuristics.
23 * @author Daniel Grund
27 * Heuristic for minimizing copies using a queue which holds 'qnodes' not yet
28 * examined. A qnode has a 'target color', nodes out of the opt unit and
29 * a 'conflict graph'. 'Conflict graph' = "Interference graph' + 'conflict edges'
30 * A 'max indep set' is determined form these. We try to color this mis using a
31 * color-exchanging mechanism. Occuring conflicts are modeled with 'conflict edges'
32 * and the qnode is reinserted in the queue. The first qnode colored without
33 * conflicts is the best one.
41 #include "raw_bitset.h"
44 #include "becopyopt_t.h"
45 #include "becopystat.h"
46 #include "benodesets.h"
47 #include "beintlive_t.h"
50 DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)
52 #define SEARCH_FREE_COLORS
54 #define SLOTS_PINNED_GLOBAL 64
55 #define SLOTS_CONFLICTS 8
56 #define SLOTS_CHANGED_NODES 32
58 #define list_entry_queue(lh) list_entry(lh, qnode_t, queue)
59 #define HASH_CONFLICT(c) (nodeset_hash(c.n1) ^ nodeset_hash(c.n2))
62 * Modeling additional conflicts between nodes. NOT live range interference
64 typedef struct _conflict_t {
65 const ir_node *n1, *n2;
69 * If an irn is changed, the changes first get stored in a node_stat_t,
70 * to allow undo of changes (=drop new data) in case of conflicts.
72 typedef struct _node_stat_t {
79 * Represents a node in the optimization queue.
81 typedef struct _qnode_t {
82 struct list_head queue; /**< chaining of unit_t->queue */
83 const unit_t *ou; /**< the opt unit this qnode belongs to */
84 int color; /**< target color */
85 set *conflicts; /**< contains conflict_t's. All internal conflicts */
86 int mis_costs; /**< costs of nodes/copies in the mis. */
87 int mis_size; /**< size of the array below */
88 ir_node **mis; /**< the nodes of unit_t->nodes[] being part of the max independent set */
89 set *changed_nodes; /**< contains node_stat_t's. */
92 static pset *pinned_global; /**< optimized nodes should not be altered any more */
94 static INLINE int nodes_interfere(const be_chordal_env_t *env, const ir_node *a, const ir_node *b)
97 return be_ifg_connected(env->ifg, a, b);
99 return values_interfere(env->birg, a, b);
102 static int set_cmp_conflict_t(const void *x, const void *y, size_t size) {
103 const conflict_t *xx = x;
104 const conflict_t *yy = y;
105 return ! (xx->n1 == yy->n1 && xx->n2 == yy->n2);
109 * If a local pinned conflict occurs, a new edge in the conflict graph is added.
110 * The next maximum independent set build, will regard it.
112 static INLINE void qnode_add_conflict(const qnode_t *qn, const ir_node *n1, const ir_node *n2) {
114 DBG((dbg, LEVEL_4, "\t %+F -- %+F\n", n1, n2));
116 if ((int)n1 < (int)n2) {
123 set_insert(qn->conflicts, &c, sizeof(c), HASH_CONFLICT(c));
127 * Checks if two nodes are in a conflict.
129 static INLINE int qnode_are_conflicting(const qnode_t *qn, const ir_node *n1, const ir_node *n2) {
131 /* search for live range interference */
132 if (n1!=n2 && nodes_interfere(qn->ou->co->cenv, n1, n2))
134 /* search for recoloring conflicts */
135 if ((int)n1 < (int)n2) {
142 return (int) set_find(qn->conflicts, &c, sizeof(c), HASH_CONFLICT(c));
145 static int set_cmp_node_stat_t(const void *x, const void *y, size_t size) {
146 return ((node_stat_t *)x)->irn != ((node_stat_t *)y)->irn;
150 * Finds a node status entry of a node if existent. Otherwise return NULL
152 static INLINE node_stat_t *qnode_find_node(const qnode_t *qn, ir_node *irn) {
155 return set_find(qn->changed_nodes, &find, sizeof(find), nodeset_hash(irn));
159 * Finds a node status entry of a node if existent. Otherwise it will return
160 * an initialized new entry for this node.
162 static INLINE node_stat_t *qnode_find_or_insert_node(const qnode_t *qn, ir_node *irn) {
165 find.new_color = NO_COLOR;
166 find.pinned_local = 0;
167 return set_insert(qn->changed_nodes, &find, sizeof(find), nodeset_hash(irn));
171 * Returns the virtual color of a node if set before, else returns the real color.
173 static INLINE int qnode_get_new_color(const qnode_t *qn, ir_node *irn) {
174 node_stat_t *found = qnode_find_node(qn, irn);
176 return found->new_color;
178 return get_irn_col(qn->ou->co, irn);
182 * Sets the virtual color of a node.
184 static INLINE void qnode_set_new_color(const qnode_t *qn, ir_node *irn, int color) {
185 node_stat_t *found = qnode_find_or_insert_node(qn, irn);
186 found->new_color = color;
187 DBG((dbg, LEVEL_3, "\t col(%+F) := %d\n", irn, color));
191 * Checks if a node is local pinned. A node is local pinned, iff it belongs
192 * to the same optimization unit and has been optimized before the current
195 static INLINE int qnode_is_pinned_local(const qnode_t *qn, ir_node *irn) {
196 node_stat_t *found = qnode_find_node(qn, irn);
198 return found->pinned_local;
204 * Local-pins a node, so optimizations of further nodes of the same opt unit
205 * can handle situations in which a color change would undo prior optimizations.
207 static INLINE void qnode_pin_local(const qnode_t *qn, ir_node *irn) {
208 node_stat_t *found = qnode_find_or_insert_node(qn, irn);
209 found->pinned_local = 1;
210 if (found->new_color == NO_COLOR)
211 found->new_color = get_irn_col(qn->ou->co, irn);
216 * Possible return values of qnode_color_irn()
218 #define CHANGE_SAVE NULL
219 #define CHANGE_IMPOSSIBLE (ir_node *)1
220 #define is_conflicting_node(n) (((int)n) > 1)
223 * Performs virtual re-coloring of node @p n to color @p col. Virtual colors of
224 * other nodes are changed too, as required to preserve correctness. Function is
225 * aware of local and global pinning. Recursive.
227 * If irn == trigger the color @p col must be used. (the first recoloring)
228 * If irn != trigger an arbitrary free color may be used. If no color is free, @p col is used.
230 * @param irn The node to set the color for
231 * @param col The color to set
232 * @param trigger The irn that caused the wish to change the color of the irn
233 * External callers must call with trigger = irn
235 * @return CHANGE_SAVE iff setting the color is possible, with all transitive effects.
236 * CHANGE_IMPOSSIBLE iff conflicts with reg-constraintsis occured.
237 * Else the first conflicting ir_node encountered is returned.
240 static ir_node *qnode_color_irn(const qnode_t *qn, ir_node *irn, int col, const ir_node *trigger) {
241 copy_opt_t *co = qn->ou->co;
242 const be_chordal_env_t *chordal_env = co->cenv;
243 const arch_register_class_t *cls = co->cls;
244 const arch_env_t *arch_env = co->aenv;
245 int irn_col = qnode_get_new_color(qn, irn);
246 ir_node *sub_res, *curr;
247 be_ifg_t *ifg = chordal_env->ifg;
248 void *iter = be_ifg_neighbours_iter_alloca(ifg);
251 DBG((dbg, LEVEL_3, "\t %+F \tcaused col(%+F) \t%2d --> %2d\n", trigger, irn, irn_col, col));
253 /* If the target color is already set do nothing */
254 if (irn_col == col) {
255 DBG((dbg, LEVEL_3, "\t %+F same color\n", irn));
259 /* If the irn is pinned, changing color is impossible */
260 if (pset_find_ptr(pinned_global, irn) || qnode_is_pinned_local(qn, irn)) {
261 DBG((dbg, LEVEL_3, "\t %+F conflicting\n", irn));
265 #ifdef SEARCH_FREE_COLORS
266 /* If we resolve conflicts (recursive calls) we can use any unused color.
267 * In case of the first call @p col must be used.
269 if (irn != trigger) {
270 bitset_t *free_cols = bitset_alloca(cls->n_regs);
271 const arch_register_req_t *req;
275 /* Get all possible colors */
276 bitset_copy(free_cols, co->cenv->ignore_colors);
277 bitset_flip_all(free_cols);
279 /* Exclude colors not assignable to the irn */
280 req = arch_get_register_req(arch_env, irn, -1);
281 if (arch_register_req_is(req, limited)) {
282 bitset_t *limited = bitset_alloca(cls->n_regs);
283 rbitset_copy_to_bitset(req->limited, limited);
284 bitset_and(free_cols, limited);
287 /* Exclude the color of the irn, because it must _change_ its color */
288 bitset_clear(free_cols, irn_col);
290 /* Exclude all colors used by adjacent nodes */
291 be_ifg_foreach_neighbour(ifg, iter, irn, curr)
292 bitset_clear(free_cols, qnode_get_new_color(qn, curr));
294 free_col = bitset_next_set(free_cols, 0);
296 if (free_col != -1) {
297 qnode_set_new_color(qn, irn, free_col);
301 #endif /* SEARCH_FREE_COLORS */
303 /* If target color is not allocatable changing color is impossible */
304 if (!arch_reg_is_allocatable(arch_env, irn, -1, arch_register_for_index(cls, col))) {
305 DBG((dbg, LEVEL_3, "\t %+F impossible\n", irn));
306 return CHANGE_IMPOSSIBLE;
310 * If we arrive here changing color may be possible, but there may be conflicts.
311 * Try to color all conflicting nodes 'curr' with the color of the irn itself.
313 be_ifg_foreach_neighbour(ifg, iter, irn, curr) {
314 DBG((dbg, LEVEL_3, "\t Confl %+F(%d)\n", curr, qnode_get_new_color(qn, curr)));
315 if (qnode_get_new_color(qn, curr) == col && curr != trigger) {
316 sub_res = qnode_color_irn(qn, curr, irn_col, irn);
317 if (sub_res != CHANGE_SAVE) {
318 be_ifg_neighbours_break(ifg, iter);
325 * If we arrive here, all conflicts were resolved.
326 * So it is save to change this irn
328 qnode_set_new_color(qn, irn, col);
334 * Tries to set the colors for all members of this queue node;
335 * to the target color qn->color
336 * @returns 1 iff all members colors could be set
339 static int qnode_try_color(const qnode_t *qn) {
341 for (i=0; i<qn->mis_size; ++i) {
342 ir_node *test_node, *confl_node;
344 test_node = qn->mis[i];
345 DBG((dbg, LEVEL_3, "\t Testing %+F\n", test_node));
346 confl_node = qnode_color_irn(qn, test_node, qn->color, test_node);
348 if (confl_node == CHANGE_SAVE) {
349 DBG((dbg, LEVEL_3, "\t Save --> pin local\n"));
350 qnode_pin_local(qn, test_node);
351 } else if (confl_node == CHANGE_IMPOSSIBLE) {
352 DBG((dbg, LEVEL_3, "\t Impossible --> remove from qnode\n"));
353 qnode_add_conflict(qn, test_node, test_node);
355 if (qnode_is_pinned_local(qn, confl_node)) {
356 /* changing test_node would change back a node of current ou */
357 if (confl_node == qn->ou->nodes[0]) {
358 /* Adding a conflict edge between testnode and conflnode
359 * would introduce a root -- arg interference.
360 * So remove the arg of the qn */
361 DBG((dbg, LEVEL_3, "\t Conflicting local with phi --> remove from qnode\n"));
362 qnode_add_conflict(qn, test_node, test_node);
364 DBG((dbg, LEVEL_3, "\t Conflicting local --> add conflict\n"));
365 qnode_add_conflict(qn, confl_node, test_node);
368 if (pset_find_ptr(pinned_global, confl_node)) {
369 /* changing test_node would change back a node of a prior ou */
370 DBG((dbg, LEVEL_3, "\t Conflicting global --> remove from qnode\n"));
371 qnode_add_conflict(qn, test_node, test_node);
375 if (confl_node != CHANGE_SAVE)
382 * Determines a maximum weighted independent set with respect to
383 * the interference and conflict edges of all nodes in a qnode.
385 static INLINE void qnode_max_ind_set(qnode_t *qn, const unit_t *ou) {
386 ir_node **safe, **unsafe;
387 int i, o, safe_count, safe_costs, unsafe_count, *unsafe_costs;
388 bitset_t *curr, *best;
389 int max, next, pos, curr_weight, best_weight = 0;
391 /* assign the nodes into two groups.
392 * safe: node has no interference, hence it is in every max stable set.
393 * unsafe: node has an interference
395 safe = alloca((ou->node_count-1) * sizeof(*safe));
398 unsafe = alloca((ou->node_count-1) * sizeof(*unsafe));
399 unsafe_costs = alloca((ou->node_count-1) * sizeof(*unsafe_costs));
401 for(i=1; i<ou->node_count; ++i) {
403 for(o=1; o<ou->node_count; ++o) {
404 if (qnode_are_conflicting(qn, ou->nodes[i], ou->nodes[o])) {
406 unsafe_costs[unsafe_count] = ou->costs[i];
407 unsafe[unsafe_count] = ou->nodes[i];
415 safe_costs += ou->costs[i];
416 safe[safe_count++] = ou->nodes[i];
422 /* now compute the best set out of the unsafe nodes*/
423 best = bitset_alloca(unsafe_count);
425 if (unsafe_count > MIS_HEUR_TRIGGER) {
426 /* Heuristic: Greedy trial and error form index 0 to unsafe_count-1 */
427 for (i=0; i<unsafe_count; ++i) {
429 /* check if it is a stable set */
430 for (o=bitset_next_set(best, 0); o!=-1 && o<=i; o=bitset_next_set(best, o+1))
431 if (qnode_are_conflicting(qn, unsafe[i], unsafe[o])) {
432 bitset_clear(best, i); /* clear the bit and try next one */
436 /* compute the weight */
437 bitset_foreach(best, pos)
438 best_weight += unsafe_costs[pos];
440 /* Exact Algorithm: Brute force */
441 curr = bitset_alloca(unsafe_count);
442 bitset_set_all(curr);
443 while ((max = bitset_popcnt(curr)) != 0) {
444 /* check if curr is a stable set */
445 for (i=bitset_next_set(curr, 0); i!=-1; i=bitset_next_set(curr, i+1))
446 for (o=bitset_next_set(curr, i); o!=-1; o=bitset_next_set(curr, o+1)) /* !!!!! difference to ou_max_ind_set_costs(): NOT (curr, i+1) */
447 if (qnode_are_conflicting(qn, unsafe[i], unsafe[o]))
450 /* if we arrive here, we have a stable set */
451 /* compute the weigth of the stable set*/
453 bitset_foreach(curr, pos)
454 curr_weight += unsafe_costs[pos];
457 if (curr_weight > best_weight) {
458 best_weight = curr_weight;
459 bitset_copy(best, curr);
467 /* transfer the best set into the qn */
468 qn->mis_size = 1+safe_count+bitset_popcnt(best);
469 qn->mis_costs = safe_costs+best_weight;
470 qn->mis[0] = ou->nodes[0]; /* the root is always in a max stable set */
472 for (i=0; i<safe_count; ++i)
473 qn->mis[next++] = safe[i];
474 bitset_foreach(best, pos)
475 qn->mis[next++] = unsafe[pos];
479 * Creates a new qnode
481 static INLINE qnode_t *new_qnode(const unit_t *ou, int color) {
482 qnode_t *qn = xmalloc(sizeof(*qn));
485 qn->mis = xmalloc(ou->node_count * sizeof(*qn->mis));
486 qn->conflicts = new_set(set_cmp_conflict_t, SLOTS_CONFLICTS);
487 qn->changed_nodes = new_set(set_cmp_node_stat_t, SLOTS_CHANGED_NODES);
492 * Frees space used by a queue node
494 static INLINE void free_qnode(qnode_t *qn) {
495 del_set(qn->conflicts);
496 del_set(qn->changed_nodes);
502 * Inserts a qnode in the sorted queue of the optimization unit. Queue is
503 * ordered by field 'size' (the size of the mis) in decreasing order.
505 static INLINE void ou_insert_qnode(unit_t *ou, qnode_t *qn) {
506 struct list_head *lh;
508 if (qnode_are_conflicting(qn, ou->nodes[0], ou->nodes[0])) {
509 /* root node is not in qnode */
514 qnode_max_ind_set(qn, ou);
515 /* do the insertion */
516 DBG((dbg, LEVEL_4, "\t Insert qnode color %d with cost %d\n", qn->color, qn->mis_costs));
518 while (lh->next != &ou->queue) {
519 qnode_t *curr = list_entry_queue(lh->next);
520 if (curr->mis_costs <= qn->mis_costs)
524 list_add(&qn->queue, lh);
528 * Tries to re-allocate colors of nodes in this opt unit, to achieve lower
529 * costs of copy instructions placed during SSA-destruction and lowering.
530 * Works only for opt units with exactly 1 root node, which is the
531 * case for approximately 80% of all phi classes and 100% of register constrained
532 * nodes. (All other phi classes are reduced to this case.)
534 static void ou_optimize(unit_t *ou) {
536 qnode_t *curr = NULL, *tmp;
537 const arch_env_t *aenv = ou->co->aenv;
538 const arch_register_class_t *cls = ou->co->cls;
539 bitset_t *pos_regs = bitset_alloca(cls->n_regs);
541 DBG((dbg, LEVEL_1, "\tOptimizing unit:\n"));
542 for (i=0; i<ou->node_count; ++i)
543 DBG((dbg, LEVEL_1, "\t %+F\n", ou->nodes[i]));
546 INIT_LIST_HEAD(&ou->queue);
548 arch_get_allocatable_regs(aenv, ou->nodes[0], -1, pos_regs);
550 /* exclude ingore colors */
551 bitset_andnot(pos_regs, ou->co->cenv->ignore_colors);
553 assert(bitset_popcnt(pos_regs) != 0 && "No register is allowed for this node !!?");
555 /* create new qnode */
556 bitset_foreach(pos_regs, i)
557 ou_insert_qnode(ou, new_qnode(ou, i));
560 while (!list_empty(&ou->queue)) {
561 /* get head of queue */
562 curr = list_entry_queue(ou->queue.next);
563 list_del(&curr->queue);
564 DBG((dbg, LEVEL_2, "\t Examine qnode color %d with cost %d\n", curr->color, curr->mis_costs));
567 if (qnode_try_color(curr))
570 /* no success, so re-insert */
571 del_set(curr->changed_nodes);
572 curr->changed_nodes = new_set(set_cmp_node_stat_t, SLOTS_CHANGED_NODES);
573 ou_insert_qnode(ou, curr);
576 /* apply the best found qnode */
577 if (curr->mis_size >= 2) {
579 int root_col = qnode_get_new_color(curr, ou->nodes[0]);
580 DBG((dbg, LEVEL_1, "\t Best color: %d Costs: %d << %d << %d\n", curr->color, ou->min_nodes_costs, ou->all_nodes_costs - curr->mis_costs, ou->all_nodes_costs));
581 /* globally pin root and all args which have the same color */
582 pset_insert_ptr(pinned_global, ou->nodes[0]);
583 for (i=1; i<ou->node_count; ++i) {
584 ir_node *irn = ou->nodes[i];
585 int nc = qnode_get_new_color(curr, irn);
586 if (nc != NO_COLOR && nc == root_col)
587 pset_insert_ptr(pinned_global, irn);
590 /* set color of all changed nodes */
591 for (ns = set_first(curr->changed_nodes); ns; ns = set_next(curr->changed_nodes)) {
592 /* NO_COLOR is possible, if we had an undo */
593 if (ns->new_color != NO_COLOR) {
594 DBG((dbg, LEVEL_1, "\t color(%+F) := %d\n", ns->irn, ns->new_color));
595 set_irn_col(ou->co, ns->irn, ns->new_color);
600 /* free best qnode (curr) and queue */
602 list_for_each_entry_safe(qnode_t, curr, tmp, &ou->queue, queue)
606 int co_solve_heuristic(copy_opt_t *co) {
608 FIRM_DBG_REGISTER(dbg, "ir.be.copyoptheur");
612 pinned_global = pset_new_ptr(SLOTS_PINNED_GLOBAL);
613 list_for_each_entry(unit_t, curr, &co->units, units)
614 if (curr->node_count > 1)
617 del_pset(pinned_global);