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22 * @brief Naiv spilling algorithm
23 * @author Matthias Braun
25 * @version $Id: bespillbelady.c 13913 2007-05-18 12:48:56Z matze $
27 * This implements a naiv spilling algorithm. It is design to produce similar
28 * effects to the spill decisions produced by traditional graph coloring
29 * 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.
42 #include "irnodeset.h"
45 #include "iredges_t.h"
49 #include "bespilloptions.h"
58 DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)
60 typedef struct daemel_env_t daemel_env_t;
62 spill_env_t *spill_env;
64 const arch_env_t *arch_env;
65 const arch_register_class_t *cls;
67 bitset_t *spilled_nodes;
70 typedef struct spill_candidate_t spill_candidate_t;
71 struct spill_candidate_t {
77 int compare_spill_candidates_desc(const void *d1, const void *d2)
79 const spill_candidate_t *c1 = d1;
80 const spill_candidate_t *c2 = d2;
82 return (int) (c1->costs - c2->costs);
86 double get_spill_costs(daemel_env_t *env, ir_node *node)
88 const ir_edge_t *edge;
89 spill_env_t *spill_env = env->spill_env;
90 double costs = be_get_spill_costs(spill_env, node, node);
92 foreach_out_edge(node, edge) {
93 ir_node *use = get_edge_src_irn(edge);
96 int in = get_edge_src_pos(edge);
97 ir_node *block = get_nodes_block(use);
99 costs += be_get_reload_costs_on_edge(spill_env, node, block, in);
101 costs += be_get_reload_costs(spill_env, node, use);
109 * spills a node by placing a reload before each usage
112 void spill_node(daemel_env_t *env, ir_node *node, ir_nodeset_t *nodes)
114 const ir_edge_t *edge;
115 spill_env_t *spill_env = env->spill_env;
116 const arch_register_class_t *cls = env->cls;
118 DBG((dbg, LEVEL_3, "\tspilling %+F\n", node));
120 foreach_out_edge(node, edge) {
121 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);
128 } else if(!be_is_Keep(use)) {
129 be_add_reload(spill_env, node, use, cls, 1);
133 bitset_set(env->spilled_nodes, get_irn_idx(node));
134 ir_nodeset_remove(nodes, node);
138 * spill @p n nodes from a nodeset. Removes the nodes from the nodeset and
139 * sets the spilled bits in env->spilled_nodes.
142 void do_spilling(daemel_env_t *env, ir_nodeset_t *nodes, ir_node *node)
144 size_t node_count = ir_nodeset_size(nodes);
145 size_t additional_defines = 0;
146 size_t reload_values = 0;
147 int registers = env->n_regs;
148 const arch_env_t *arch_env = env->arch_env;
149 const arch_register_class_t *cls = env->cls;
150 spill_candidate_t *candidates;
151 ir_nodeset_iterator_t iter;
156 const bitset_t *spilled_nodes = env->spilled_nodes;
158 /* mode_T nodes define several values at once. Count them */
159 if(get_irn_mode(node) == mode_T) {
160 ir_node *proj = sched_next(node);
162 while(is_Proj(proj)) {
163 if(arch_irn_consider_in_reg_alloc(arch_env, cls, proj)) {
164 ++additional_defines;
166 proj = sched_next(proj);
170 /* we might temporarily need registers for reloaded values */
171 arity = get_irn_arity(node);
172 for(i = 0; i < arity; ++i) {
173 ir_node *pred = get_irn_n(node, i);
174 if(bitset_is_set(spilled_nodes, get_irn_idx(pred)))
178 if(reload_values > additional_defines)
179 additional_defines = reload_values;
181 spills_needed = (node_count + additional_defines) - registers;
182 if(spills_needed <= 0)
184 DBG((dbg, LEVEL_2, "\tspills needed after %+F: %d\n", node, spills_needed));
186 candidates = malloc(node_count * sizeof(candidates[0]));
188 /* construct array with spill candidates and calculate their costs */
190 foreach_ir_nodeset(nodes, n, iter) {
191 spill_candidate_t *candidate = & candidates[i];
194 candidate->costs = get_spill_costs(env, n);
197 assert(i == node_count);
199 /* sort spill candidates */
200 qsort(candidates, node_count, sizeof(candidates[0]),
201 compare_spill_candidates_desc);
203 /* spill cheapest ones */
205 while(spills_needed > 0) {
206 spill_candidate_t *candidate = &candidates[cand_idx];
207 ir_node *cand_node = candidate->node;
211 if(cand_idx >= node_count) {
212 panic("can't spill enough values for node %+F\n", node);
215 /* make sure the node is not a use of the instruction */
217 for(i = 0; i < arity; ++i) {
218 ir_node *in = get_irn_n(node, i);
219 if(in == cand_node) {
228 spill_node(env, cand_node, nodes);
236 * similar to be_liveness_transfer.
237 * custom liveness transfer function, that doesn't place already spilled values
238 * into the liveness set
241 void liveness_transfer(daemel_env_t *env, ir_node *node, ir_nodeset_t *nodeset)
244 const arch_register_class_t *cls = env->cls;
245 const arch_env_t *arch_env = env->arch_env;
246 const bitset_t *bitset = env->spilled_nodes;
248 /* You should better break out of your loop when hitting the first phi
250 assert(!is_Phi(node) && "liveness_transfer produces invalid results for phi nodes");
252 if(arch_irn_consider_in_reg_alloc(arch_env, cls, node)) {
253 ir_nodeset_remove(nodeset, node);
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(arch_env, cls, op)
261 && !bitset_is_set(bitset, get_irn_idx(op))) {
262 ir_nodeset_insert(nodeset, op);
268 * make sure register pressure in a block is always equal or below the number
269 * of available registers
272 void spill_block(ir_node *block, void *data)
274 daemel_env_t *env = data;
275 const arch_env_t *arch_env = env->arch_env;
276 const arch_register_class_t *cls = env->cls;
277 const be_lv_t *lv = env->lv;
278 ir_nodeset_t live_nodes;
279 ir_nodeset_iterator_t iter;
281 bitset_t *spilled_nodes = env->spilled_nodes;
284 DBG((dbg, LEVEL_1, "spilling block %+F\n", block));
286 ir_nodeset_init(&live_nodes);
287 be_liveness_end_of_block_ir_nodeset(lv, arch_env, cls, block, &live_nodes);
289 foreach_ir_nodeset(&live_nodes, node, iter) {
290 DBG((dbg, LEVEL_2, "\t%+F is live-in... ", node));
291 if(bitset_is_set(spilled_nodes, get_irn_idx(node))) {
292 DBG((dbg, LEVEL_2, "but spilled; removing.\n"));
294 DBG((dbg, LEVEL_2, "keeping.\n"));
298 sched_foreach_reverse(block, node) {
302 if(is_Proj(node) || be_is_Keep(node)) {
303 liveness_transfer(env, node, &live_nodes);
307 do_spilling(env, &live_nodes, node);
308 liveness_transfer(env, node, &live_nodes);
310 do_spilling(env, &live_nodes, node);
313 int spilled_phis = 0;
314 sched_foreach(block, node) {
319 if(bitset_is_set(spilled_nodes, get_irn_idx(node))) {
323 int regpressure = ir_nodeset_size(&live_nodes) - spilled_phis;
324 int phi_spills_needed = regpressure - env->n_regs;
325 sched_foreach(block, node) {
328 if(phi_spills_needed <= 0)
331 if(bitset_is_set(spilled_nodes, get_irn_idx(node))) {
332 be_spill_phi(env->spill_env, node);
336 assert(phi_spills_needed <= 0);
338 ir_nodeset_destroy(&live_nodes);
341 void be_spill_daemel(be_irg_t *birg, const arch_register_class_t *cls)
344 ir_graph *irg = be_get_birg_irg(birg);
345 int n_regs = cls->n_regs - be_put_ignore_regs(birg, cls, NULL);
350 be_invalidate_liveness(birg);
351 be_assure_liveness(birg);
353 env.spill_env = be_new_spill_env(birg);
355 env.arch_env = be_get_birg_arch_env(birg);
357 env.lv = be_get_birg_liveness(birg);
358 env.spilled_nodes = bitset_malloc(get_irg_last_idx(irg));
360 irg_block_walk_graph(irg, spill_block, NULL, &env);
362 bitset_free(env.spilled_nodes);
364 be_insert_spills_reloads(env.spill_env);
366 be_delete_spill_env(env.spill_env);
369 void be_init_daemelspill(void)
371 static be_spiller_t daemel_spiller = {
375 be_register_spiller("daemel", &daemel_spiller);
376 FIRM_DBG_REGISTER(dbg, "ir.be.spilldaemel");
379 BE_REGISTER_MODULE_CONSTRUCTOR(be_init_doedelspill);