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4 * This file is part of libFirm.
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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
26 * Heuristic for minimizing copies using a queue which holds 'qnodes' not yet
27 * examined. A qnode has a 'target color', nodes out of the opt unit and
28 * a 'conflict graph'. 'Conflict graph' = "Interference graph' + 'conflict edges'
29 * A 'max indep set' is determined from these. We try to color this mis using a
30 * color-exchanging mechanism. Occuring conflicts are modeled with 'conflict edges'
31 * and the qnode is reinserted in the queue. The first qnode colored without
32 * conflicts is the best one.
38 #include "raw_bitset.h"
41 #include "becopyopt_t.h"
42 #include "becopystat.h"
43 #include "beintlive_t.h"
47 DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)
49 /** Defines an invalid register index. */
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) (hash_irn(c.n1) ^ hash_irn(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 node 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 be_lv_t *lv = be_get_irg_liveness(env->irg);
100 return be_values_interfere(lv, a, b);
104 static int set_cmp_conflict_t(const void *x, const void *y, size_t size)
106 const conflict_t *xx = (const conflict_t*)x;
107 const conflict_t *yy = (const conflict_t*)y;
110 return xx->n1 != yy->n1 || xx->n2 != yy->n2;
114 * If a local pinned conflict occurs, a new edge in the conflict graph is added.
115 * The next maximum independent set build, will regard it.
117 static inline void qnode_add_conflict(const qnode_t *qn, const ir_node *n1, const ir_node *n2)
120 DBG((dbg, LEVEL_4, "\t %+F -- %+F\n", n1, n2));
122 if (get_irn_idx(n1) < get_irn_idx(n2)) {
129 (void)set_insert(conflict_t, qn->conflicts, &c, sizeof(c), HASH_CONFLICT(c));
133 * Checks if two nodes are in a conflict.
135 static inline int qnode_are_conflicting(const qnode_t *qn, const ir_node *n1, const ir_node *n2)
138 /* search for live range interference */
139 if (n1!=n2 && nodes_interfere(qn->ou->co->cenv, n1, n2))
141 /* search for recoloring conflicts */
142 if (get_irn_idx(n1) < get_irn_idx(n2)) {
149 return set_find(conflict_t, qn->conflicts, &c, sizeof(c), HASH_CONFLICT(c)) != 0;
152 static int set_cmp_node_stat_t(const void *x, const void *y, size_t size)
155 return ((const node_stat_t*)x)->irn != ((const node_stat_t*)y)->irn;
159 * Finds a node status entry of a node if existent. Otherwise return NULL
161 static inline const node_stat_t *qnode_find_node(const qnode_t *qn, ir_node *irn)
165 return set_find(node_stat_t, qn->changed_nodes, &find, sizeof(find), hash_irn(irn));
169 * Finds a node status entry of a node if existent. Otherwise it will return
170 * an initialized new entry for this node.
172 static inline node_stat_t *qnode_find_or_insert_node(const qnode_t *qn, ir_node *irn)
176 find.new_color = NO_COLOR;
177 find.pinned_local = 0;
178 return set_insert(node_stat_t, qn->changed_nodes, &find, sizeof(find), hash_irn(irn));
182 * Returns the virtual color of a node if set before, else returns the real color.
184 static inline int qnode_get_new_color(const qnode_t *qn, ir_node *irn)
186 const node_stat_t *found = qnode_find_node(qn, irn);
188 return found->new_color;
190 return get_irn_col(irn);
194 * Sets the virtual color of a node.
196 static inline void qnode_set_new_color(const qnode_t *qn, ir_node *irn, int color)
198 node_stat_t *found = qnode_find_or_insert_node(qn, irn);
199 found->new_color = color;
200 DBG((dbg, LEVEL_3, "\t col(%+F) := %d\n", irn, color));
204 * Checks if a node is local pinned. A node is local pinned, iff it belongs
205 * to the same optimization unit and has been optimized before the current
208 static inline int qnode_is_pinned_local(const qnode_t *qn, ir_node *irn)
210 const node_stat_t *found = qnode_find_node(qn, irn);
212 return found->pinned_local;
218 * Local-pins a node, so optimizations of further nodes of the same opt unit
219 * can handle situations in which a color change would undo prior optimizations.
221 static inline void qnode_pin_local(const qnode_t *qn, ir_node *irn)
223 node_stat_t *found = qnode_find_or_insert_node(qn, irn);
224 found->pinned_local = 1;
225 if (found->new_color == NO_COLOR)
226 found->new_color = get_irn_col(irn);
231 * Possible return values of qnode_color_irn()
233 #define CHANGE_SAVE NULL
234 #define CHANGE_IMPOSSIBLE (ir_node *)1
237 * Performs virtual re-coloring of node @p n to color @p col. Virtual colors of
238 * other nodes are changed too, as required to preserve correctness. Function is
239 * aware of local and global pinning. Recursive.
241 * If irn == trigger the color @p col must be used. (the first recoloring)
242 * If irn != trigger an arbitrary free color may be used. If no color is free, @p col is used.
244 * @param irn The node to set the color for
245 * @param col The color to set
246 * @param trigger The irn that caused the wish to change the color of the irn
247 * External callers must call with trigger = irn
249 * @return CHANGE_SAVE iff setting the color is possible, with all transitive effects.
250 * CHANGE_IMPOSSIBLE iff conflicts with reg-constraintsis occured.
251 * Else the first conflicting ir_node encountered is returned.
254 static ir_node *qnode_color_irn(const qnode_t *qn, ir_node *irn, int col, const ir_node *trigger)
256 copy_opt_t *co = qn->ou->co;
257 const be_chordal_env_t *chordal_env = co->cenv;
258 const arch_register_class_t *cls = co->cls;
259 int irn_col = qnode_get_new_color(qn, irn);
260 ir_node *sub_res, *curr;
261 be_ifg_t *ifg = chordal_env->ifg;
262 neighbours_iter_t iter;
263 const arch_register_req_t *req;
265 DBG((dbg, LEVEL_3, "\t %+F \tcaused col(%+F) \t%2d --> %2d\n", trigger, irn, irn_col, col));
267 /* If the target color is already set do nothing */
268 if (irn_col == col) {
269 DBG((dbg, LEVEL_3, "\t %+F same color\n", irn));
273 /* If the irn is pinned, changing color is impossible */
274 if (pset_find_ptr(pinned_global, irn) || qnode_is_pinned_local(qn, irn)) {
275 DBG((dbg, LEVEL_3, "\t %+F conflicting\n", irn));
279 req = arch_get_irn_register_req(irn);
280 #ifdef SEARCH_FREE_COLORS
281 /* If we resolve conflicts (recursive calls) we can use any unused color.
282 * In case of the first call @p col must be used.
284 if (irn != trigger) {
285 bitset_t *free_cols = bitset_alloca(cls->n_regs);
289 /* Get all possible colors */
290 bitset_copy(free_cols, co->cenv->allocatable_regs);
292 /* Exclude colors not assignable to the irn */
293 if (arch_register_req_is(req, limited)) {
294 bitset_t *limited = bitset_alloca(cls->n_regs);
295 rbitset_copy_to_bitset(req->limited, limited);
296 bitset_and(free_cols, limited);
299 /* Exclude the color of the irn, because it must _change_ its color */
300 bitset_clear(free_cols, irn_col);
302 /* Exclude all colors used by adjacent nodes */
303 be_ifg_foreach_neighbour(ifg, &iter, irn, curr)
304 bitset_clear(free_cols, qnode_get_new_color(qn, curr));
306 free_col = bitset_next_set(free_cols, 0);
308 if (free_col != -1) {
309 qnode_set_new_color(qn, irn, free_col);
313 #endif /* SEARCH_FREE_COLORS */
315 /* If target color is not allocatable changing color is impossible */
316 if (!arch_reg_is_allocatable(req, arch_register_for_index(cls, col))) {
317 DBG((dbg, LEVEL_3, "\t %+F impossible\n", irn));
318 return CHANGE_IMPOSSIBLE;
322 * If we arrive here changing color may be possible, but there may be conflicts.
323 * Try to color all conflicting nodes 'curr' with the color of the irn itself.
325 be_ifg_foreach_neighbour(ifg, &iter, irn, curr) {
326 DBG((dbg, LEVEL_3, "\t Confl %+F(%d)\n", curr, qnode_get_new_color(qn, curr)));
327 if (qnode_get_new_color(qn, curr) == col && curr != trigger) {
328 sub_res = qnode_color_irn(qn, curr, irn_col, irn);
329 if (sub_res != CHANGE_SAVE) {
330 be_ifg_neighbours_break(&iter);
337 * If we arrive here, all conflicts were resolved.
338 * So it is save to change this irn
340 qnode_set_new_color(qn, irn, col);
346 * Tries to set the colors for all members of this queue node;
347 * to the target color qn->color
348 * @returns 1 iff all members colors could be set
351 static int qnode_try_color(const qnode_t *qn)
354 for (i=0; i<qn->mis_size; ++i) {
355 ir_node *test_node, *confl_node;
357 test_node = qn->mis[i];
358 DBG((dbg, LEVEL_3, "\t Testing %+F\n", test_node));
359 confl_node = qnode_color_irn(qn, test_node, qn->color, test_node);
361 if (confl_node == CHANGE_SAVE) {
362 DBG((dbg, LEVEL_3, "\t Save --> pin local\n"));
363 qnode_pin_local(qn, test_node);
364 } else if (confl_node == CHANGE_IMPOSSIBLE) {
365 DBG((dbg, LEVEL_3, "\t Impossible --> remove from qnode\n"));
366 qnode_add_conflict(qn, test_node, test_node);
369 if (qnode_is_pinned_local(qn, confl_node)) {
370 /* changing test_node would change back a node of current ou */
371 if (confl_node == qn->ou->nodes[0]) {
372 /* Adding a conflict edge between testnode and conflnode
373 * would introduce a root -- arg interference.
374 * So remove the arg of the qn */
375 DBG((dbg, LEVEL_3, "\t Conflicting local with phi --> remove from qnode\n"));
376 qnode_add_conflict(qn, test_node, test_node);
378 DBG((dbg, LEVEL_3, "\t Conflicting local --> add conflict\n"));
379 qnode_add_conflict(qn, confl_node, test_node);
382 if (pset_find_ptr(pinned_global, confl_node)) {
383 /* changing test_node would change back a node of a prior ou */
384 DBG((dbg, LEVEL_3, "\t Conflicting global --> remove from qnode\n"));
385 qnode_add_conflict(qn, test_node, test_node);
394 * Determines a maximum weighted independent set with respect to
395 * the interference and conflict edges of all nodes in a qnode.
397 static inline void qnode_max_ind_set(qnode_t *qn, const unit_t *ou)
399 ir_node **safe, **unsafe;
400 int i, o, safe_count, safe_costs, unsafe_count, *unsafe_costs;
401 bitset_t *curr, *best;
402 int next, curr_weight, best_weight = 0;
404 /* assign the nodes into two groups.
405 * safe: node has no interference, hence it is in every max stable set.
406 * unsafe: node has an interference
408 safe = ALLOCAN(ir_node*, ou->node_count - 1);
411 unsafe = ALLOCAN(ir_node*, ou->node_count - 1);
412 unsafe_costs = ALLOCAN(int, ou->node_count - 1);
414 for (i=1; i<ou->node_count; ++i) {
416 for (o=1; o<ou->node_count; ++o) {
417 if (qnode_are_conflicting(qn, ou->nodes[i], ou->nodes[o])) {
419 unsafe_costs[unsafe_count] = ou->costs[i];
420 unsafe[unsafe_count] = ou->nodes[i];
428 safe_costs += ou->costs[i];
429 safe[safe_count++] = ou->nodes[i];
435 /* now compute the best set out of the unsafe nodes*/
436 best = bitset_alloca(unsafe_count);
438 if (unsafe_count > MIS_HEUR_TRIGGER) {
439 /* Heuristic: Greedy trial and error form index 0 to unsafe_count-1 */
440 for (i=0; i<unsafe_count; ++i) {
442 /* check if it is a stable set */
443 for (o=bitset_next_set(best, 0); o!=-1 && o<=i; o=bitset_next_set(best, o+1))
444 if (qnode_are_conflicting(qn, unsafe[i], unsafe[o])) {
445 bitset_clear(best, i); /* clear the bit and try next one */
449 /* compute the weight */
450 bitset_foreach(best, pos)
451 best_weight += unsafe_costs[pos];
453 /* Exact Algorithm: Brute force */
454 curr = bitset_alloca(unsafe_count);
455 bitset_set_all(curr);
456 while (!bitset_is_empty(curr)) {
457 /* check if curr is a stable set */
458 for (i=bitset_next_set(curr, 0); i!=-1; i=bitset_next_set(curr, i+1))
459 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) */
460 if (qnode_are_conflicting(qn, unsafe[i], unsafe[o]))
463 /* if we arrive here, we have a stable set */
464 /* compute the weight of the stable set*/
466 bitset_foreach(curr, pos)
467 curr_weight += unsafe_costs[pos];
470 if (curr_weight > best_weight) {
471 best_weight = curr_weight;
472 bitset_copy(best, curr);
480 /* transfer the best set into the qn */
481 qn->mis_size = 1+safe_count+bitset_popcount(best);
482 qn->mis_costs = safe_costs+best_weight;
483 qn->mis[0] = ou->nodes[0]; /* the root is always in a max stable set */
485 for (i=0; i<safe_count; ++i)
486 qn->mis[next++] = safe[i];
487 bitset_foreach(best, pos)
488 qn->mis[next++] = unsafe[pos];
492 * Creates a new qnode
494 static inline qnode_t *new_qnode(const unit_t *ou, int color)
496 qnode_t *qn = XMALLOC(qnode_t);
499 qn->mis = XMALLOCN(ir_node*, ou->node_count);
500 qn->conflicts = new_set(set_cmp_conflict_t, SLOTS_CONFLICTS);
501 qn->changed_nodes = new_set(set_cmp_node_stat_t, SLOTS_CHANGED_NODES);
506 * Frees space used by a queue node
508 static inline void free_qnode(qnode_t *qn)
510 del_set(qn->conflicts);
511 del_set(qn->changed_nodes);
517 * Inserts a qnode in the sorted queue of the optimization unit. Queue is
518 * ordered by field 'size' (the size of the mis) in decreasing order.
520 static inline void ou_insert_qnode(unit_t *ou, qnode_t *qn)
522 struct list_head *lh;
524 if (qnode_are_conflicting(qn, ou->nodes[0], ou->nodes[0])) {
525 /* root node is not in qnode */
530 qnode_max_ind_set(qn, ou);
531 /* do the insertion */
532 DBG((dbg, LEVEL_4, "\t Insert qnode color %d with cost %d\n", qn->color, qn->mis_costs));
534 while (lh->next != &ou->queue) {
535 qnode_t *curr = list_entry_queue(lh->next);
536 if (curr->mis_costs <= qn->mis_costs)
540 list_add(&qn->queue, lh);
544 * Tries to re-allocate colors of nodes in this opt unit, to achieve lower
545 * costs of copy instructions placed during SSA-destruction and lowering.
546 * Works only for opt units with exactly 1 root node, which is the
547 * case for approximately 80% of all phi classes and 100% of register constrained
548 * nodes. (All other phi classes are reduced to this case.)
550 static void ou_optimize(unit_t *ou)
552 qnode_t *curr = NULL;
553 const arch_register_req_t *req;
554 bitset_t const* allocatable_regs;
559 DBG((dbg, LEVEL_1, "\tOptimizing unit:\n"));
560 for (i=0; i<ou->node_count; ++i)
561 DBG((dbg, LEVEL_1, "\t %+F\n", ou->nodes[i]));
564 INIT_LIST_HEAD(&ou->queue);
566 req = arch_get_irn_register_req(ou->nodes[0]);
567 allocatable_regs = ou->co->cenv->allocatable_regs;
568 n_regs = req->cls->n_regs;
569 if (arch_register_req_is(req, limited)) {
570 unsigned const* limited = req->limited;
572 for (idx = 0; idx != n_regs; ++idx) {
573 if (!bitset_is_set(allocatable_regs, idx))
575 if (!rbitset_is_set(limited, idx))
578 ou_insert_qnode(ou, new_qnode(ou, idx));
581 for (idx = 0; idx != n_regs; ++idx) {
582 if (!bitset_is_set(allocatable_regs, idx))
585 ou_insert_qnode(ou, new_qnode(ou, idx));
591 assert(!list_empty(&ou->queue));
592 /* get head of queue */
593 curr = list_entry_queue(ou->queue.next);
594 list_del(&curr->queue);
595 DBG((dbg, LEVEL_2, "\t Examine qnode color %d with cost %d\n", curr->color, curr->mis_costs));
598 if (qnode_try_color(curr))
601 /* no success, so re-insert */
602 del_set(curr->changed_nodes);
603 curr->changed_nodes = new_set(set_cmp_node_stat_t, SLOTS_CHANGED_NODES);
604 ou_insert_qnode(ou, curr);
607 /* apply the best found qnode */
608 if (curr->mis_size >= 2) {
609 int root_col = qnode_get_new_color(curr, ou->nodes[0]);
610 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));
611 /* globally pin root and all args which have the same color */
612 pset_insert_ptr(pinned_global, ou->nodes[0]);
613 for (i=1; i<ou->node_count; ++i) {
614 ir_node *irn = ou->nodes[i];
615 int nc = qnode_get_new_color(curr, irn);
616 if (nc != NO_COLOR && nc == root_col)
617 pset_insert_ptr(pinned_global, irn);
620 /* set color of all changed nodes */
621 foreach_set(curr->changed_nodes, node_stat_t, ns) {
622 /* NO_COLOR is possible, if we had an undo */
623 if (ns->new_color != NO_COLOR) {
624 DBG((dbg, LEVEL_1, "\t color(%+F) := %d\n", ns->irn, ns->new_color));
625 set_irn_col(ou->co->cls, ns->irn, ns->new_color);
630 /* free best qnode (curr) and queue */
632 list_for_each_entry_safe(qnode_t, curr, tmp, &ou->queue, queue)
637 * Solves the problem using a heuristic approach
638 * Uses the OU data structure
640 int co_solve_heuristic(copy_opt_t *co)
644 pinned_global = pset_new_ptr(SLOTS_PINNED_GLOBAL);
645 list_for_each_entry(unit_t, curr, &co->units, units)
646 if (curr->node_count > 1)
649 del_pset(pinned_global);
653 BE_REGISTER_MODULE_CONSTRUCTOR(be_init_copyheur)
654 void be_init_copyheur(void)
656 static co_algo_info copyheur = {
657 co_solve_heuristic, 0
660 be_register_copyopt("heur1", ©heur);
661 FIRM_DBG_REGISTER(dbg, "ir.be.copyoptheur");