2 * This file is part of libFirm.
3 * Copyright (C) 2012 University of Karlsruhe.
8 * @brief Methods to compute when a value will be used again.
9 * @author Sebastian Hack, Matthias Braun
25 #include "irgraph_t.h"
26 #include "iredges_t.h"
39 #define UNKNOWN_OUTERMOST_LOOP ((unsigned)-1)
41 typedef struct be_use_t {
44 unsigned outermost_loop;
50 * The "uses" environment.
53 set *uses; /**< cache: contains all computed uses so far. */
54 ir_graph *irg; /**< the graph for this environment. */
55 const be_lv_t *lv; /**< the liveness for the graph. */
56 ir_visited_t visited_counter; /**< current search counter. */
57 DEBUG_ONLY(firm_dbg_module_t *dbg; /**< debug module for debug messages. */)
61 * Set-compare two uses.
63 static int cmp_use(const void *a, const void *b, size_t n)
65 const be_use_t *p = (const be_use_t*)a;
66 const be_use_t *q = (const be_use_t*)b;
69 return !(p->block == q->block && p->node == q->node);
72 static be_next_use_t get_next_use(be_uses_t *env, ir_node *from,
73 const ir_node *def, int skip_from_uses);
76 * Return the use for the given definition in the given block if exists,
79 * @param env the uses environment
80 * @param block the block we search the use in
81 * @param def the definition of the value we are searching
83 static const be_use_t *get_or_set_use_block(be_uses_t *env,
87 unsigned hash = hash_combine(hash_irn(block), hash_irn(def));
93 result = set_find(be_use_t, env->uses, &temp, sizeof(temp), hash);
96 // insert templ first as we might end in a loop in the get_next_use
98 temp.next_use = USES_INFINITY;
99 temp.outermost_loop = UNKNOWN_OUTERMOST_LOOP;
101 result = set_insert(be_use_t, env->uses, &temp, sizeof(temp), hash);
104 if (result->outermost_loop == UNKNOWN_OUTERMOST_LOOP && result->visited < env->visited_counter) {
105 be_next_use_t next_use;
107 result->visited = env->visited_counter;
108 next_use = get_next_use(env, sched_first(block), def, 0);
109 if (next_use.outermost_loop != UNKNOWN_OUTERMOST_LOOP) {
110 result->next_use = next_use.time;
111 result->outermost_loop = next_use.outermost_loop;
112 DBG((env->dbg, LEVEL_5, "Setting nextuse of %+F in block %+F to %u (outermostloop %d)\n",
113 def, block, result->next_use, result->outermost_loop));
121 * Check if a value of the given definition is used in the given block
124 * @param block the block to check
125 * @param def the definition of the value
127 * @return non-zero if the value is used in the given block as a Phi argument
128 * in one of its successor blocks.
130 static int be_is_phi_argument(const ir_node *block, const ir_node *def)
132 if (get_irn_n_edges_kind(block, EDGE_KIND_BLOCK) < 1)
135 ir_node *const succ_block = get_first_block_succ(block);
137 if (get_Block_n_cfgpreds(succ_block) <= 1) {
138 /* no Phis in the successor */
142 /* find the index of block in its successor */
143 int const i = get_Block_cfgpred_pos(succ_block, block);
146 /* iterate over the Phi nodes in the successor and check if def is
147 * one of its arguments */
148 sched_foreach(succ_block, node) {
152 /* found first non-Phi node, we can stop the search here */
156 arg = get_irn_n(node, i);
165 * Retrieve the scheduled index (the "step") of this node in its
168 * @param node the node
170 static inline unsigned get_step(const ir_node *node)
172 return (unsigned)PTR_TO_INT(get_irn_link(node));
176 * Set the scheduled index (the "step") of this node in its
179 * @param node the node
180 * @param step the scheduled index of the node
182 static inline void set_step(ir_node *node, unsigned step)
184 set_irn_link(node, INT_TO_PTR(step));
188 * Find the next use of a value defined by def, starting at node from.
190 * @param env the uses environment
191 * @param from the node at which we should start the search
192 * @param def the definition of the value
193 * @param skip_from_uses if non-zero, ignore from uses
195 static be_next_use_t get_next_use(be_uses_t *env, ir_node *from,
196 const ir_node *def, int skip_from_uses)
199 ir_node *block = get_nodes_block(from);
200 ir_node *next_use_node;
203 unsigned next_use_step;
205 assert(skip_from_uses == 0 || skip_from_uses == 1);
206 if (skip_from_uses) {
207 from = sched_next(from);
210 next_use_node = NULL;
211 next_use_step = INT_MAX;
212 timestep = get_step(from);
213 foreach_out_edge(def, edge) {
215 node = get_edge_src_irn(edge);
219 if (get_nodes_block(node) != block)
224 node_step = get_step(node);
225 if (node_step < timestep)
227 if (node_step < next_use_step) {
228 next_use_node = node;
229 next_use_step = node_step;
233 if (next_use_node != NULL) {
234 be_next_use_t result;
235 result.time = next_use_step - timestep + skip_from_uses;
236 result.outermost_loop = get_loop_depth(get_irn_loop(block));
237 result.before = next_use_node;
241 node = sched_last(block);
242 step = get_step(node) + 1 + timestep + skip_from_uses;
244 if (be_is_phi_argument(block, def)) {
245 // TODO we really should continue searching the uses of the phi,
246 // as a phi isn't a real use that implies a reload (because we could
247 // easily spill the whole phi)
249 be_next_use_t result;
251 result.outermost_loop = get_loop_depth(get_irn_loop(block));
252 result.before = block;
257 unsigned next_use = USES_INFINITY;
258 unsigned outermost_loop;
259 be_next_use_t result;
260 ir_loop *loop = get_irn_loop(block);
261 unsigned loopdepth = get_loop_depth(loop);
262 int found_visited = 0;
265 result.before = NULL;
266 outermost_loop = loopdepth;
267 foreach_block_succ(block, edge) {
269 const ir_node *succ_block = get_edge_src_irn(edge);
273 DBG((env->dbg, LEVEL_5, "Checking succ of block %+F: %+F (for use of %+F)\n", block, succ_block, def));
274 if (!be_is_live_in(env->lv, succ_block, def)) {
275 //next_use = USES_INFINITY;
276 DBG((env->dbg, LEVEL_5, " not live in\n"));
280 use = get_or_set_use_block(env, succ_block, def);
281 DBG((env->dbg, LEVEL_5, "Found %u (loopdepth %u) (we're in block %+F)\n", use->next_use,
282 use->outermost_loop, block));
283 if (USES_IS_INFINITE(use->next_use)) {
284 if (use->outermost_loop == UNKNOWN_OUTERMOST_LOOP) {
291 use_dist = use->next_use;
293 succ_loop = get_irn_loop(succ_block);
294 if (get_loop_depth(succ_loop) < loopdepth) {
295 unsigned factor = (loopdepth - get_loop_depth(succ_loop)) * 5000;
296 DBG((env->dbg, LEVEL_5, "Increase usestep because of loop out edge %d -> %d (%u)\n", factor));
297 // TODO we should use the number of nodes in the loop or so...
301 if (use_dist < next_use) {
303 outermost_loop = use->outermost_loop;
304 result.before = use->node;
308 if (loopdepth < outermost_loop)
309 outermost_loop = loopdepth;
311 result.time = next_use + step;
312 result.outermost_loop = outermost_loop;
314 if (!found_use && found_visited) {
315 // the current result is correct for the current search, but isn't
316 // generally correct, so mark it
317 result.outermost_loop = UNKNOWN_OUTERMOST_LOOP;
319 DBG((env->dbg, LEVEL_5, "Result: %d (outerloop: %u)\n", result.time, result.outermost_loop));
324 be_next_use_t be_get_next_use(be_uses_t *env, ir_node *from,
325 const ir_node *def, int skip_from_uses)
327 ++env->visited_counter;
328 return get_next_use(env, from, def, skip_from_uses);
332 * Pre-block walker, set the step number for every scheduled node
333 * in increasing order.
335 * After this, two scheduled nodes can be easily compared for the
336 * "scheduled earlier in block" property.
338 static void set_sched_step_walker(ir_node *block, void *data)
343 sched_foreach(block, node) {
344 set_step(node, step);
351 be_uses_t *be_begin_uses(ir_graph *irg, const be_lv_t *lv)
353 be_uses_t *env = XMALLOC(be_uses_t);
357 //set_using_irn_link(irg);
359 /* precalculate sched steps */
360 irg_block_walk_graph(irg, set_sched_step_walker, NULL, NULL);
362 env->uses = new_set(cmp_use, 512);
365 env->visited_counter = 0;
366 FIRM_DBG_REGISTER(env->dbg, "firm.be.uses");
371 void be_end_uses(be_uses_t *env)
373 //clear_using_irn_link(env->irg);