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 Naive spilling algorithm
23 * @author Matthias Braun
25 * @version $Id: bespillbelady.c 13913 2007-05-18 12:48:56Z matze $
27 * This implements a naive spilling algorithm. It is designed to produce
28 * similar effects to the spill decisions produced by traditional graph
29 * coloring register allocators that spill while they are coloring the graph.
31 * This spiller walks over all blocks and looks for places with too high
32 * register pressure where it spills the values that are cheapest to spill.
33 * Spilling in this context means placing a spill instruction behind the
34 * definition of the value and a reload before each usage.
40 #include "irnodeset.h"
43 #include "iredges_t.h"
48 #include "bespillutil.h"
57 DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)
59 static spill_env_t *spill_env;
61 static const arch_register_class_t *cls;
62 static const be_lv_t *lv;
63 static bitset_t *spilled_nodes;
65 typedef struct spill_candidate_t spill_candidate_t;
66 struct spill_candidate_t {
71 static int compare_spill_candidates_desc(const void *d1, const void *d2)
73 const spill_candidate_t *c1 = d1;
74 const spill_candidate_t *c2 = d2;
76 return (int) (c1->costs - c2->costs);
79 static double get_spill_costs(ir_node *node)
81 const ir_edge_t *edge;
82 ir_node *spill_place = skip_Proj(node);
83 double costs = be_get_spill_costs(spill_env, node,
86 foreach_out_edge(node, edge) {
87 ir_node *use = get_edge_src_irn(edge);
89 /* keeps should be directly below the node */
90 if (be_is_Keep(use)) {
95 int in = get_edge_src_pos(edge);
96 ir_node *block = get_nodes_block(use);
98 costs += be_get_reload_costs_on_edge(spill_env, node, block, in);
100 costs += be_get_reload_costs(spill_env, node, use);
108 * spills a node by placing a reload before each usage
110 static void spill_node(ir_node *node)
112 const ir_edge_t *edge;
114 DBG((dbg, LEVEL_3, "\tspilling %+F\n", node));
116 foreach_out_edge(node, edge) {
117 ir_node *use = get_edge_src_irn(edge);
124 int in = get_edge_src_pos(edge);
125 ir_node *block = get_nodes_block(use);
127 be_add_reload_on_edge(spill_env, node, block, in, cls, 1);
129 be_add_reload(spill_env, node, use, cls, 1);
133 bitset_set(spilled_nodes, get_irn_idx(node));
136 static unsigned get_value_width(const ir_node *node)
138 const arch_register_req_t *req = arch_get_register_req_out(node);
143 * spill @p n nodes from a nodeset. Removes the nodes from the nodeset and
144 * sets the spilled bits in spilled_nodes.
146 static void do_spilling(ir_nodeset_t *live_nodes, ir_node *node)
148 size_t n_live_nodes = ir_nodeset_size(live_nodes);
149 size_t values_defined = 0;
150 size_t free_regs_needed = 0;
151 spill_candidate_t *candidates;
152 ir_nodeset_iterator_t iter;
159 be_foreach_definition(node, cls, value,
160 assert(req_->width >= 1);
161 values_defined += req_->width;
164 /* we need registers for the non-live argument values */
165 arity = get_irn_arity(node);
166 for (i = 0; i < arity; ++i) {
167 ir_node *pred = get_irn_n(node, i);
168 if (arch_irn_consider_in_reg_alloc(cls, pred)
169 && !ir_nodeset_contains(live_nodes, pred)) {
170 free_regs_needed += get_value_width(pred);
174 /* we can reuse all reloaded values for the defined values, but we might
175 * need even more registers */
176 if (values_defined > free_regs_needed)
177 free_regs_needed = values_defined;
179 spills_needed = (n_live_nodes + free_regs_needed) - n_regs;
180 if (spills_needed <= 0)
182 DBG((dbg, LEVEL_2, "\tspills needed after %+F: %d\n", node, spills_needed));
184 candidates = ALLOCAN(spill_candidate_t, n_live_nodes);
186 /* construct array with spill candidates and calculate their costs */
188 foreach_ir_nodeset(live_nodes, n, iter) {
189 spill_candidate_t *candidate = & candidates[i];
191 assert(!bitset_is_set(spilled_nodes, get_irn_idx(n)));
194 candidate->costs = get_spill_costs(n);
197 assert(i == n_live_nodes);
199 /* sort spill candidates */
200 qsort(candidates, n_live_nodes, sizeof(candidates[0]),
201 compare_spill_candidates_desc);
203 /* spill cheapest ones */
205 while (spills_needed > 0) {
207 spill_candidate_t *candidate;
210 if (cand_idx >= n_live_nodes) {
211 panic("can't spill enough values for node %+F", node);
214 candidate = &candidates[cand_idx];
215 cand_node = candidate->node;
218 if (arch_irn_is(skip_Proj_const(cand_node), dont_spill))
221 /* make sure the node is not an argument of the instruction */
222 for (i = 0; i < arity; ++i) {
223 ir_node *in = get_irn_n(node, i);
224 if (in == cand_node) {
232 spill_node(cand_node);
233 ir_nodeset_remove(live_nodes, cand_node);
234 spills_needed -= get_value_width(cand_node);
239 * removes all values from the nodeset that are defined by node
241 static void remove_defs(ir_node *node, ir_nodeset_t *nodeset)
244 /* You must break out of your loop when hitting the first phi function. */
245 assert(!is_Phi(node));
247 be_foreach_definition(node, cls, value,
248 ir_nodeset_remove(nodeset, value);
252 static void add_uses(ir_node *node, ir_nodeset_t *nodeset)
256 arity = get_irn_arity(node);
257 for (i = 0; i < arity; ++i) {
258 ir_node *op = get_irn_n(node, i);
260 if (arch_irn_consider_in_reg_alloc(cls, op) &&
261 !bitset_is_set(spilled_nodes, get_irn_idx(op))) {
262 ir_nodeset_insert(nodeset, op);
267 static __attribute__((unused))
268 void print_nodeset(ir_nodeset_t *nodeset)
270 ir_nodeset_iterator_t iter;
273 foreach_ir_nodeset(nodeset, node, iter) {
274 ir_fprintf(stderr, "%+F ", node);
276 fprintf(stderr, "\n");
280 * make sure register pressure in a block is always equal or below the number
281 * of available registers
283 static void spill_block(ir_node *block, void *data)
285 ir_nodeset_t live_nodes;
286 ir_nodeset_iterator_t iter;
288 int n_phi_values_spilled;
290 int live_nodes_pressure;
291 int phi_spills_needed;
294 DBG((dbg, LEVEL_1, "spilling block %+F\n", block));
296 /* construct set of live nodes at end of block */
297 ir_nodeset_init(&live_nodes);
298 be_liveness_end_of_block(lv, cls, block, &live_nodes);
300 /* remove already spilled nodes from liveset */
301 foreach_ir_nodeset(&live_nodes, node, iter) {
302 DBG((dbg, LEVEL_2, "\t%+F is live-end... ", node));
303 if (bitset_is_set(spilled_nodes, get_irn_idx(node))) {
304 DBG((dbg, LEVEL_2, "but spilled; removing.\n"));
305 ir_nodeset_remove_iterator(&live_nodes, &iter);
307 DBG((dbg, LEVEL_2, "keeping.\n"));
311 /* walk schedule backwards and spill until register pressure is fine at
313 sched_foreach_reverse(block, node) {
317 remove_defs(node, &live_nodes);
318 do_spilling(&live_nodes, node);
319 add_uses(node, &live_nodes);
322 /* until now only the values of some phis have been spilled the phis itself
323 * are still there and occupy registers, so we need to count them and might
324 * have to spill some of them. */
325 n_phi_values_spilled = 0;
326 sched_foreach(block, node) {
330 if (bitset_is_set(spilled_nodes, get_irn_idx(node))) {
331 n_phi_values_spilled += get_value_width(node);
335 live_nodes_pressure = 0;
336 foreach_ir_nodeset(&live_nodes, node, iter) {
337 live_nodes_pressure += get_value_width(node);
340 /* calculate how many of the phis need to be spilled */
341 regpressure = live_nodes_pressure + n_phi_values_spilled;
342 phi_spills_needed = regpressure - n_regs;
343 DBG((dbg, LEVEL_3, "Regpressure before phis: %d phispills: %d\n",
344 regpressure, phi_spills_needed));
346 /* spill as many phis as needed */
347 /* TODO: we should really estimate costs of the phi spill as well...
348 * and preferably spill phis with lower costs... */
349 sched_foreach(block, node) {
352 if (phi_spills_needed <= 0)
355 if (!bitset_is_set(spilled_nodes, get_irn_idx(node)))
358 be_spill_phi(spill_env, node);
359 phi_spills_needed -= get_value_width(node);
361 assert(phi_spills_needed <= 0);
363 ir_nodeset_destroy(&live_nodes);
366 static void be_spill_daemel(ir_graph *irg, const arch_register_class_t *new_cls)
368 n_regs = new_cls->n_regs - be_put_ignore_regs(irg, new_cls, NULL);
372 be_liveness_assure_sets(be_assure_liveness(irg));
374 spill_env = be_new_spill_env(irg);
376 lv = be_get_irg_liveness(irg);
377 spilled_nodes = bitset_malloc(get_irg_last_idx(irg));
379 DBG((dbg, LEVEL_1, "*** RegClass %s\n", cls->name));
381 irg_block_walk_graph(irg, spill_block, NULL, NULL);
383 bitset_free(spilled_nodes);
385 be_insert_spills_reloads(spill_env);
386 be_delete_spill_env(spill_env);
389 BE_REGISTER_MODULE_CONSTRUCTOR(be_init_daemelspill);
390 void be_init_daemelspill(void)
392 static be_spiller_t daemel_spiller = {
396 be_register_spiller("daemel", &daemel_spiller);
397 FIRM_DBG_REGISTER(dbg, "firm.be.spilldaemel");