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 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 from 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.
39 #include "raw_bitset.h"
42 #include "becopyopt_t.h"
43 #include "becopystat.h"
44 #include "beintlive_t.h"
47 DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)
49 #define SEARCH_FREE_COLORS
51 #define SLOTS_PINNED_GLOBAL 64
52 #define SLOTS_CONFLICTS 8
53 #define SLOTS_CHANGED_NODES 32
55 #define list_entry_queue(lh) list_entry(lh, qnode_t, queue)
56 #define HASH_CONFLICT(c) (hash_irn(c.n1) ^ hash_irn(c.n2))
59 * Modeling additional conflicts between nodes. NOT live range interference
61 typedef struct _conflict_t {
62 const ir_node *n1, *n2;
66 * If an irn is changed, the changes first get stored in a node_stat_t,
67 * to allow undo of changes (=drop new data) in case of conflicts.
69 typedef struct _node_stat_t {
76 * Represents a node in the optimization queue.
78 typedef struct _qnode_t {
79 struct list_head queue; /**< chaining of unit_t->queue */
80 const unit_t *ou; /**< the opt unit this node belongs to */
81 int color; /**< target color */
82 set *conflicts; /**< contains conflict_t's. All internal conflicts */
83 int mis_costs; /**< costs of nodes/copies in the mis. */
84 int mis_size; /**< size of the array below */
85 ir_node **mis; /**< the nodes of unit_t->nodes[] being part of the max independent set */
86 set *changed_nodes; /**< contains node_stat_t's. */
89 static pset *pinned_global; /**< optimized nodes should not be altered any more */
91 static INLINE int nodes_interfere(const be_chordal_env_t *env, const ir_node *a, const ir_node *b)
94 return be_ifg_connected(env->ifg, a, b);
96 return values_interfere(env->birg, a, b);
99 static int set_cmp_conflict_t(const void *x, const void *y, size_t size) {
100 const conflict_t *xx = x;
101 const conflict_t *yy = y;
104 return xx->n1 != yy->n1 || xx->n2 != yy->n2;
108 * If a local pinned conflict occurs, a new edge in the conflict graph is added.
109 * The next maximum independent set build, will regard it.
111 static INLINE void qnode_add_conflict(const qnode_t *qn, const ir_node *n1, const ir_node *n2) {
113 DBG((dbg, LEVEL_4, "\t %+F -- %+F\n", n1, n2));
115 if (get_irn_idx(n1) < get_irn_idx(n2)) {
122 set_insert(qn->conflicts, &c, sizeof(c), HASH_CONFLICT(c));
126 * Checks if two nodes are in a conflict.
128 static INLINE int qnode_are_conflicting(const qnode_t *qn, const ir_node *n1, const ir_node *n2) {
130 /* search for live range interference */
131 if (n1!=n2 && nodes_interfere(qn->ou->co->cenv, n1, n2))
133 /* search for recoloring conflicts */
134 if (get_irn_idx(n1) < get_irn_idx(n2)) {
141 return set_find(qn->conflicts, &c, sizeof(c), HASH_CONFLICT(c)) != 0;
144 static int set_cmp_node_stat_t(const void *x, const void *y, size_t size) {
146 return ((const node_stat_t*)x)->irn != ((const node_stat_t*)y)->irn;
150 * Finds a node status entry of a node if existent. Otherwise return NULL
152 static INLINE const node_stat_t *qnode_find_node(const qnode_t *qn, ir_node *irn) {
155 return set_find(qn->changed_nodes, &find, sizeof(find), hash_irn(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), hash_irn(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 const node_stat_t *found = qnode_find_node(qn, irn);
176 return found->new_color;
178 return get_irn_col(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 const 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(irn);
216 * Possible return values of qnode_color_irn()
218 #define CHANGE_SAVE NULL
219 #define CHANGE_IMPOSSIBLE (ir_node *)1
222 * Performs virtual re-coloring of node @p n to color @p col. Virtual colors of
223 * other nodes are changed too, as required to preserve correctness. Function is
224 * aware of local and global pinning. Recursive.
226 * If irn == trigger the color @p col must be used. (the first recoloring)
227 * If irn != trigger an arbitrary free color may be used. If no color is free, @p col is used.
229 * @param irn The node to set the color for
230 * @param col The color to set
231 * @param trigger The irn that caused the wish to change the color of the irn
232 * External callers must call with trigger = irn
234 * @return CHANGE_SAVE iff setting the color is possible, with all transitive effects.
235 * CHANGE_IMPOSSIBLE iff conflicts with reg-constraintsis occured.
236 * Else the first conflicting ir_node encountered is returned.
239 static ir_node *qnode_color_irn(const qnode_t *qn, ir_node *irn, int col, const ir_node *trigger) {
240 copy_opt_t *co = qn->ou->co;
241 const be_chordal_env_t *chordal_env = co->cenv;
242 const arch_register_class_t *cls = co->cls;
243 int irn_col = qnode_get_new_color(qn, irn);
244 ir_node *sub_res, *curr;
245 be_ifg_t *ifg = chordal_env->ifg;
246 void *iter = be_ifg_neighbours_iter_alloca(ifg);
249 DBG((dbg, LEVEL_3, "\t %+F \tcaused col(%+F) \t%2d --> %2d\n", trigger, irn, irn_col, col));
251 /* If the target color is already set do nothing */
252 if (irn_col == col) {
253 DBG((dbg, LEVEL_3, "\t %+F same color\n", irn));
257 /* If the irn is pinned, changing color is impossible */
258 if (pset_find_ptr(pinned_global, irn) || qnode_is_pinned_local(qn, irn)) {
259 DBG((dbg, LEVEL_3, "\t %+F conflicting\n", irn));
263 #ifdef SEARCH_FREE_COLORS
264 /* If we resolve conflicts (recursive calls) we can use any unused color.
265 * In case of the first call @p col must be used.
267 if (irn != trigger) {
268 bitset_t *free_cols = bitset_alloca(cls->n_regs);
269 const arch_register_req_t *req;
273 /* Get all possible colors */
274 bitset_copy(free_cols, co->cenv->ignore_colors);
275 bitset_flip_all(free_cols);
277 /* Exclude colors not assignable to the irn */
278 req = arch_get_register_req(irn, -1);
279 if (arch_register_req_is(req, limited)) {
280 bitset_t *limited = bitset_alloca(cls->n_regs);
281 rbitset_copy_to_bitset(req->limited, limited);
282 bitset_and(free_cols, limited);
285 /* Exclude the color of the irn, because it must _change_ its color */
286 bitset_clear(free_cols, irn_col);
288 /* Exclude all colors used by adjacent nodes */
289 be_ifg_foreach_neighbour(ifg, iter, irn, curr)
290 bitset_clear(free_cols, qnode_get_new_color(qn, curr));
292 free_col = bitset_next_set(free_cols, 0);
294 if (free_col != -1) {
295 qnode_set_new_color(qn, irn, free_col);
299 #endif /* SEARCH_FREE_COLORS */
301 /* If target color is not allocatable changing color is impossible */
302 if (!arch_reg_is_allocatable(irn, -1, arch_register_for_index(cls, col))) {
303 DBG((dbg, LEVEL_3, "\t %+F impossible\n", irn));
304 return CHANGE_IMPOSSIBLE;
308 * If we arrive here changing color may be possible, but there may be conflicts.
309 * Try to color all conflicting nodes 'curr' with the color of the irn itself.
311 be_ifg_foreach_neighbour(ifg, iter, irn, curr) {
312 DBG((dbg, LEVEL_3, "\t Confl %+F(%d)\n", curr, qnode_get_new_color(qn, curr)));
313 if (qnode_get_new_color(qn, curr) == col && curr != trigger) {
314 sub_res = qnode_color_irn(qn, curr, irn_col, irn);
315 if (sub_res != CHANGE_SAVE) {
316 be_ifg_neighbours_break(ifg, iter);
323 * If we arrive here, all conflicts were resolved.
324 * So it is save to change this irn
326 qnode_set_new_color(qn, irn, col);
332 * Tries to set the colors for all members of this queue node;
333 * to the target color qn->color
334 * @returns 1 iff all members colors could be set
337 static int qnode_try_color(const qnode_t *qn) {
339 for (i=0; i<qn->mis_size; ++i) {
340 ir_node *test_node, *confl_node;
342 test_node = qn->mis[i];
343 DBG((dbg, LEVEL_3, "\t Testing %+F\n", test_node));
344 confl_node = qnode_color_irn(qn, test_node, qn->color, test_node);
346 if (confl_node == CHANGE_SAVE) {
347 DBG((dbg, LEVEL_3, "\t Save --> pin local\n"));
348 qnode_pin_local(qn, test_node);
349 } else if (confl_node == CHANGE_IMPOSSIBLE) {
350 DBG((dbg, LEVEL_3, "\t Impossible --> remove from qnode\n"));
351 qnode_add_conflict(qn, test_node, test_node);
354 if (qnode_is_pinned_local(qn, confl_node)) {
355 /* changing test_node would change back a node of current ou */
356 if (confl_node == qn->ou->nodes[0]) {
357 /* Adding a conflict edge between testnode and conflnode
358 * would introduce a root -- arg interference.
359 * So remove the arg of the qn */
360 DBG((dbg, LEVEL_3, "\t Conflicting local with phi --> remove from qnode\n"));
361 qnode_add_conflict(qn, test_node, test_node);
363 DBG((dbg, LEVEL_3, "\t Conflicting local --> add conflict\n"));
364 qnode_add_conflict(qn, confl_node, test_node);
367 if (pset_find_ptr(pinned_global, confl_node)) {
368 /* changing test_node would change back a node of a prior ou */
369 DBG((dbg, LEVEL_3, "\t Conflicting global --> remove from qnode\n"));
370 qnode_add_conflict(qn, test_node, test_node);
379 * Determines a maximum weighted independent set with respect to
380 * the interference and conflict edges of all nodes in a qnode.
382 static INLINE void qnode_max_ind_set(qnode_t *qn, const unit_t *ou) {
383 ir_node **safe, **unsafe;
384 int i, o, safe_count, safe_costs, unsafe_count, *unsafe_costs;
385 bitset_t *curr, *best;
387 int max, next, curr_weight, best_weight = 0;
389 /* assign the nodes into two groups.
390 * safe: node has no interference, hence it is in every max stable set.
391 * unsafe: node has an interference
393 safe = alloca((ou->node_count-1) * sizeof(*safe));
396 unsafe = alloca((ou->node_count-1) * sizeof(*unsafe));
397 unsafe_costs = alloca((ou->node_count-1) * sizeof(*unsafe_costs));
399 for(i=1; i<ou->node_count; ++i) {
401 for(o=1; o<ou->node_count; ++o) {
402 if (qnode_are_conflicting(qn, ou->nodes[i], ou->nodes[o])) {
404 unsafe_costs[unsafe_count] = ou->costs[i];
405 unsafe[unsafe_count] = ou->nodes[i];
413 safe_costs += ou->costs[i];
414 safe[safe_count++] = ou->nodes[i];
420 /* now compute the best set out of the unsafe nodes*/
421 best = bitset_alloca(unsafe_count);
423 if (unsafe_count > MIS_HEUR_TRIGGER) {
424 /* Heuristic: Greedy trial and error form index 0 to unsafe_count-1 */
425 for (i=0; i<unsafe_count; ++i) {
427 /* check if it is a stable set */
428 for (o=bitset_next_set(best, 0); o!=-1 && o<=i; o=bitset_next_set(best, o+1))
429 if (qnode_are_conflicting(qn, unsafe[i], unsafe[o])) {
430 bitset_clear(best, i); /* clear the bit and try next one */
434 /* compute the weight */
435 bitset_foreach(best, pos)
436 best_weight += unsafe_costs[pos];
438 /* Exact Algorithm: Brute force */
439 curr = bitset_alloca(unsafe_count);
440 bitset_set_all(curr);
441 while ((max = bitset_popcnt(curr)) != 0) {
442 /* check if curr is a stable set */
443 for (i=bitset_next_set(curr, 0); i!=-1; i=bitset_next_set(curr, i+1))
444 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) */
445 if (qnode_are_conflicting(qn, unsafe[i], unsafe[o]))
448 /* if we arrive here, we have a stable set */
449 /* compute the weigth of the stable set*/
451 bitset_foreach(curr, pos)
452 curr_weight += unsafe_costs[pos];
455 if (curr_weight > best_weight) {
456 best_weight = curr_weight;
457 bitset_copy(best, curr);
465 /* transfer the best set into the qn */
466 qn->mis_size = 1+safe_count+bitset_popcnt(best);
467 qn->mis_costs = safe_costs+best_weight;
468 qn->mis[0] = ou->nodes[0]; /* the root is always in a max stable set */
470 for (i=0; i<safe_count; ++i)
471 qn->mis[next++] = safe[i];
472 bitset_foreach(best, pos)
473 qn->mis[next++] = unsafe[pos];
477 * Creates a new qnode
479 static INLINE qnode_t *new_qnode(const unit_t *ou, int color) {
480 qnode_t *qn = XMALLOC(qnode_t);
483 qn->mis = XMALLOCN(ir_node*, ou->node_count);
484 qn->conflicts = new_set(set_cmp_conflict_t, SLOTS_CONFLICTS);
485 qn->changed_nodes = new_set(set_cmp_node_stat_t, SLOTS_CHANGED_NODES);
490 * Frees space used by a queue node
492 static INLINE void free_qnode(qnode_t *qn) {
493 del_set(qn->conflicts);
494 del_set(qn->changed_nodes);
500 * Inserts a qnode in the sorted queue of the optimization unit. Queue is
501 * ordered by field 'size' (the size of the mis) in decreasing order.
503 static INLINE void ou_insert_qnode(unit_t *ou, qnode_t *qn) {
504 struct list_head *lh;
506 if (qnode_are_conflicting(qn, ou->nodes[0], ou->nodes[0])) {
507 /* root node is not in qnode */
512 qnode_max_ind_set(qn, ou);
513 /* do the insertion */
514 DBG((dbg, LEVEL_4, "\t Insert qnode color %d with cost %d\n", qn->color, qn->mis_costs));
516 while (lh->next != &ou->queue) {
517 qnode_t *curr = list_entry_queue(lh->next);
518 if (curr->mis_costs <= qn->mis_costs)
522 list_add(&qn->queue, lh);
526 * Tries to re-allocate colors of nodes in this opt unit, to achieve lower
527 * costs of copy instructions placed during SSA-destruction and lowering.
528 * Works only for opt units with exactly 1 root node, which is the
529 * case for approximately 80% of all phi classes and 100% of register constrained
530 * nodes. (All other phi classes are reduced to this case.)
532 static void ou_optimize(unit_t *ou) {
534 qnode_t *curr = NULL, *tmp;
535 const arch_register_class_t *cls = ou->co->cls;
537 bitset_t *pos_regs = bitset_alloca(cls->n_regs);
539 DBG((dbg, LEVEL_1, "\tOptimizing unit:\n"));
540 for (i=0; i<ou->node_count; ++i)
541 DBG((dbg, LEVEL_1, "\t %+F\n", ou->nodes[i]));
544 INIT_LIST_HEAD(&ou->queue);
546 arch_get_allocatable_regs(ou->nodes[0], -1, pos_regs);
548 /* exclude ignore colors */
549 bitset_andnot(pos_regs, ou->co->cenv->ignore_colors);
551 assert(bitset_popcnt(pos_regs) != 0 && "No register is allowed for this node !!?");
553 /* create new qnode */
554 bitset_foreach(pos_regs, idx)
555 ou_insert_qnode(ou, new_qnode(ou, idx));
559 assert(!list_empty(&ou->queue));
560 /* get head of queue */
561 curr = list_entry_queue(ou->queue.next);
562 list_del(&curr->queue);
563 DBG((dbg, LEVEL_2, "\t Examine qnode color %d with cost %d\n", curr->color, curr->mis_costs));
566 if (qnode_try_color(curr))
569 /* no success, so re-insert */
570 del_set(curr->changed_nodes);
571 curr->changed_nodes = new_set(set_cmp_node_stat_t, SLOTS_CHANGED_NODES);
572 ou_insert_qnode(ou, curr);
575 /* apply the best found qnode */
576 if (curr->mis_size >= 2) {
578 int root_col = qnode_get_new_color(curr, ou->nodes[0]);
579 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));
580 /* globally pin root and all args which have the same color */
581 pset_insert_ptr(pinned_global, ou->nodes[0]);
582 for (i=1; i<ou->node_count; ++i) {
583 ir_node *irn = ou->nodes[i];
584 int nc = qnode_get_new_color(curr, irn);
585 if (nc != NO_COLOR && nc == root_col)
586 pset_insert_ptr(pinned_global, irn);
589 /* set color of all changed nodes */
590 for (ns = set_first(curr->changed_nodes); ns; ns = set_next(curr->changed_nodes)) {
591 /* NO_COLOR is possible, if we had an undo */
592 if (ns->new_color != NO_COLOR) {
593 DBG((dbg, LEVEL_1, "\t color(%+F) := %d\n", ns->irn, ns->new_color));
594 set_irn_col(ou->co, ns->irn, ns->new_color);
599 /* free best qnode (curr) and queue */
601 list_for_each_entry_safe(qnode_t, curr, tmp, &ou->queue, queue)
605 int co_solve_heuristic(copy_opt_t *co) {
607 FIRM_DBG_REGISTER(dbg, "ir.be.copyoptheur");
611 pinned_global = pset_new_ptr(SLOTS_PINNED_GLOBAL);
612 list_for_each_entry(unit_t, curr, &co->units, units)
613 if (curr->node_count > 1)
616 del_pset(pinned_global);