2 * liveness.c: liveness analysis
5 * Dietmar Maurer (dietmar@ximian.com)
7 * (C) 2002 Ximian, Inc.
11 #include <mono/metadata/debug-helpers.h>
13 static void mono_linear_scan2 (MonoCompile *cfg, GList *vars, GList *regs, regmask_t *used_mask);
16 mono_varlist_insert_sorted (MonoCompile *cfg, GList *list, MonoMethodVar *mv, int sort_type)
21 return g_list_prepend (NULL, mv);
23 for (l = list; l; l = l->next) {
24 MonoMethodVar *v1 = l->data;
27 if (mv->spill_costs >= v1->spill_costs) {
28 list = g_list_insert_before (list, l, mv);
31 } else if (sort_type == 1) {
32 if (mv->range.last_use.abs_pos <= v1->range.last_use.abs_pos) {
33 list = g_list_insert_before (list, l, mv);
37 if (mv->range.first_use.abs_pos <= v1->range.first_use.abs_pos) {
38 list = g_list_insert_before (list, l, mv);
44 list = g_list_append (list, mv);
50 compare_by_first_use_func (gconstpointer a, gconstpointer b)
52 MonoMethodVar *v1 = (MonoMethodVar*)a;
53 MonoMethodVar *v2 = (MonoMethodVar*)b;
55 return v1->range.first_use.abs_pos - v2->range.first_use.abs_pos;
59 mono_varlist_sort (MonoCompile *cfg, GList *list, int sort_type)
62 return g_list_sort (list, compare_by_first_use_func);
64 g_assert_not_reached ();
69 // #define DEBUG_LSCAN
72 mono_linear_scan (MonoCompile *cfg, GList *vars, GList *regs, regmask_t *used_mask)
74 GList *l, *a, *active = NULL;
75 MonoMethodVar *vmv, *amv;
76 int max_regs, n_regvars;
77 int gains [sizeof (regmask_t) * 8];
78 regmask_t used_regs = 0;
81 if (vars && (((MonoMethodVar*)vars->data)->interval != NULL)) {
82 mono_linear_scan2 (cfg, vars, regs, used_mask);
89 printf ("Linears scan for %s\n", mono_method_full_name (cfg->method, TRUE));
93 for (l = vars; l; l = l->next) {
95 printf ("VAR %d %08x %08x C%d\n", vmv->idx, vmv->range.first_use.abs_pos,
96 vmv->range.last_use.abs_pos, vmv->spill_costs);
99 max_regs = g_list_length (regs);
101 for (l = regs; l; l = l->next) {
102 int regnum = GPOINTER_TO_INT (l->data);
103 g_assert (regnum < G_N_ELEMENTS (gains));
108 for (l = vars; l; l = l->next) {
112 printf ("START %2d %08x %08x\n", vmv->idx, vmv->range.first_use.abs_pos,
113 vmv->range.last_use.abs_pos);
115 /* expire old intervals in active */
116 if (!cfg->disable_reuse_registers) {
118 amv = (MonoMethodVar *)active->data;
120 if (amv->range.last_use.abs_pos > vmv->range.first_use.abs_pos)
124 printf ("EXPIR %2d %08x %08x C%d R%d\n", amv->idx, amv->range.first_use.abs_pos,
125 amv->range.last_use.abs_pos, amv->spill_costs, amv->reg);
127 active = g_list_delete_link (active, active);
128 regs = g_list_prepend (regs, GINT_TO_POINTER (amv->reg));
129 gains [amv->reg] += amv->spill_costs;
133 if (active && g_list_length (active) == max_regs) {
136 a = g_list_nth (active, max_regs - 1);
137 amv = (MonoMethodVar *)a->data;
139 if ((cost_driven && amv->spill_costs < vmv->spill_costs) ||
140 (!cost_driven && amv->range.last_use.abs_pos > vmv->range.last_use.abs_pos)) {
143 active = g_list_delete_link (active, a);
146 active = mono_varlist_insert_sorted (cfg, active, vmv, 2);
148 active = mono_varlist_insert_sorted (cfg, active, vmv, 1);
151 printf ("SPILL0 %2d %08x %08x C%d\n", amv->idx,
152 amv->range.first_use.abs_pos, amv->range.last_use.abs_pos,
157 printf ("SPILL1 %2d %08x %08x C%d\n", vmv->idx,
158 vmv->range.first_use.abs_pos, vmv->range.last_use.abs_pos,
164 /* assign register */
168 vmv->reg = GPOINTER_TO_INT (regs->data);
170 used_regs |= 1LL << vmv->reg;
172 regs = g_list_delete_link (regs, regs);
175 printf ("ADD %2d %08x %08x C%d R%d\n", vmv->idx,
176 vmv->range.first_use.abs_pos, vmv->range.last_use.abs_pos,
177 vmv->spill_costs, vmv->reg);
179 active = mono_varlist_insert_sorted (cfg, active, vmv, TRUE);
184 for (a = active; a; a = a->next) {
185 amv = (MonoMethodVar *)a->data;
186 printf ("ACT %2d %08x %08x C%d R%d\n", amv->idx, amv->range.first_use.abs_pos,
187 amv->range.last_use.abs_pos, amv->spill_costs, amv->reg);
193 for (a = active; a; a = a->next) {
194 amv = (MonoMethodVar *)a->data;
195 gains [amv->reg] += amv->spill_costs;
199 for (l = vars; l; l = l->next) {
203 if ((gains [vmv->reg] > mono_arch_regalloc_cost (cfg, vmv)) && (cfg->varinfo [vmv->idx]->opcode != OP_REGVAR)) {
204 if (cfg->verbose_level > 2) {
205 printf ("ALLOCATED R%d(%d) TO HREG %d COST %d\n", cfg->varinfo [vmv->idx]->dreg, vmv->idx, vmv->reg, vmv->spill_costs);
207 cfg->varinfo [vmv->idx]->opcode = OP_REGVAR;
208 cfg->varinfo [vmv->idx]->dreg = vmv->reg;
211 if (cfg->verbose_level > 2)
212 printf ("COSTLY: R%d C%d C%d %s\n", vmv->idx, vmv->spill_costs, mono_arch_regalloc_cost (cfg, vmv), mono_arch_regname (vmv->reg));
217 if (vmv->reg == -1) {
218 if (cfg->verbose_level > 2)
219 printf ("NOT REGVAR: %d\n", vmv->idx);
223 mono_jit_stats.regvars += n_regvars;
225 /* Compute used regs */
227 for (l = vars; l; l = l->next) {
231 used_regs |= 1LL << vmv->reg;
234 *used_mask |= used_regs;
237 if (cfg->verbose_level > 2)
238 printf ("EXIT: final used mask: %08x\n", *used_mask);
242 g_list_free (active);
247 compare_by_interval_start_pos_func (gconstpointer a, gconstpointer b)
249 MonoMethodVar *v1 = (MonoMethodVar*)a;
250 MonoMethodVar *v2 = (MonoMethodVar*)b;
254 else if (v1->interval->range && v2->interval->range)
255 return v1->interval->range->from - v2->interval->range->from;
256 else if (v1->interval->range)
263 #define LSCAN_DEBUG(a) do { a; } while (0)
265 #define LSCAN_DEBUG(a)
268 /* FIXME: This is x86 only */
269 static inline guint32
270 regalloc_cost (MonoCompile *cfg, MonoMethodVar *vmv)
272 MonoInst *ins = cfg->varinfo [vmv->idx];
274 /* Load if it is an argument */
275 return (ins->opcode == OP_ARG) ? 1 : 0;
279 mono_linear_scan2 (MonoCompile *cfg, GList *vars, GList *regs, regmask_t *used_mask)
281 GList *unhandled, *active, *inactive, *l;
283 gint32 free_pos [sizeof (regmask_t) * 8];
284 gint32 gains [sizeof (regmask_t) * 8];
285 regmask_t used_regs = 0;
286 int n_regs, n_regvars, i;
288 for (l = vars; l; l = l->next) {
290 LSCAN_DEBUG (printf ("VAR R%d %08x %08x C%d\n", cfg->varinfo [vmv->idx]->dreg, vmv->range.first_use.abs_pos,
291 vmv->range.last_use.abs_pos, vmv->spill_costs));
294 LSCAN_DEBUG (printf ("Linear Scan 2 for %s:\n", mono_method_full_name (cfg->method, TRUE)));
296 n_regs = g_list_length (regs);
297 memset (gains, 0, n_regs * sizeof (gint32));
298 unhandled = g_list_sort (g_list_copy (vars), compare_by_interval_start_pos_func);
303 MonoMethodVar *current = unhandled->data;
304 int pos, reg, max_free_pos;
307 unhandled = g_list_delete_link (unhandled, unhandled);
309 LSCAN_DEBUG (printf ("Processing R%d: ", cfg->varinfo [current->idx]->dreg));
310 LSCAN_DEBUG (mono_linterval_print (current->interval));
311 LSCAN_DEBUG (printf ("\n"));
313 if (!current->interval->range)
316 pos = current->interval->range->from;
318 /* Check for intervals in active which expired or inactive */
320 /* FIXME: Optimize this */
323 for (l = active; l != NULL; l = l->next) {
324 MonoMethodVar *v = (MonoMethodVar*)l->data;
326 if (v->interval->last_range->to < pos) {
327 active = g_list_delete_link (active, l);
328 LSCAN_DEBUG (printf ("Interval R%d has expired\n", cfg->varinfo [v->idx]->dreg));
332 else if (!mono_linterval_covers (v->interval, pos)) {
333 inactive = g_list_append (inactive, v);
334 active = g_list_delete_link (active, l);
335 LSCAN_DEBUG (printf ("Interval R%d became inactive\n", cfg->varinfo [v->idx]->dreg));
342 /* Check for intervals in inactive which expired or active */
344 /* FIXME: Optimize this */
347 for (l = inactive; l != NULL; l = l->next) {
348 MonoMethodVar *v = (MonoMethodVar*)l->data;
350 if (v->interval->last_range->to < pos) {
351 inactive = g_list_delete_link (inactive, l);
352 LSCAN_DEBUG (printf ("\tInterval R%d has expired\n", cfg->varinfo [v->idx]->dreg));
356 else if (mono_linterval_covers (v->interval, pos)) {
357 active = g_list_append (active, v);
358 inactive = g_list_delete_link (inactive, l);
359 LSCAN_DEBUG (printf ("\tInterval R%d became active\n", cfg->varinfo [v->idx]->dreg));
366 /* Find a register for the current interval */
367 for (i = 0; i < n_regs; ++i)
368 free_pos [i] = ((gint32)0x7fffffff);
370 for (l = active; l != NULL; l = l->next) {
371 MonoMethodVar *v = (MonoMethodVar*)l->data;
374 free_pos [v->reg] = 0;
375 LSCAN_DEBUG (printf ("\threg %d is busy (cost %d)\n", v->reg, v->spill_costs));
379 for (l = inactive; l != NULL; l = l->next) {
380 MonoMethodVar *v = (MonoMethodVar*)l->data;
381 gint32 intersect_pos;
384 intersect_pos = mono_linterval_get_intersect_pos (current->interval, v->interval);
385 if (intersect_pos != -1) {
386 free_pos [v->reg] = intersect_pos;
387 LSCAN_DEBUG (printf ("\threg %d becomes free at %d\n", v->reg, intersect_pos));
394 for (i = 0; i < n_regs; ++i)
395 if (free_pos [i] > max_free_pos) {
397 max_free_pos = free_pos [i];
400 g_assert (reg != -1);
402 if (free_pos [reg] >= current->interval->last_range->to) {
403 /* Register available for whole interval */
405 LSCAN_DEBUG (printf ("\tAssigned hreg %d to R%d\n", reg, cfg->varinfo [current->idx]->dreg));
407 active = g_list_append (active, current);
408 gains [current->reg] += current->spill_costs;
412 * free_pos [reg] > 0 means there is a register available for parts
413 * of the interval, so splitting it is possible. This is not yet
414 * supported, so we spill in this case too.
417 /* Spill an interval */
419 /* FIXME: Optimize the selection of the interval */
422 GList *min_spill_pos;
425 * This favors registers with big spill costs, thus larger liveness ranges,
426 * thus actually leading to worse code size.
428 guint32 min_spill_value = G_MAXINT32;
430 for (l = active; l != NULL; l = l->next) {
431 vmv = (MonoMethodVar*)l->data;
433 if (vmv->spill_costs < min_spill_value) {
435 min_spill_value = vmv->spill_costs;
439 /* Spill either the first active or the current interval */
440 min_spill_pos = active;
442 vmv = (MonoMethodVar*)min_spill_pos->data;
443 if (vmv->spill_costs < current->spill_costs) {
444 // if (vmv->interval->last_range->to < current->interval->last_range->to) {
445 gains [vmv->reg] -= vmv->spill_costs;
447 LSCAN_DEBUG (printf ("\tSpilled R%d\n", cfg->varinfo [vmv->idx]->dreg));
448 active = g_list_delete_link (active, min_spill_pos);
451 LSCAN_DEBUG (printf ("\tSpilled current (cost %d)\n", current->spill_costs));
454 LSCAN_DEBUG (printf ("\tSpilled current\n"));
458 /* Decrease the gains by the cost of saving+restoring the register */
459 for (i = 0; i < n_regs; ++i) {
461 /* FIXME: This is x86 only */
462 gains [i] -= cfg->method->save_lmf ? 1 : 2;
468 /* Do the actual register assignment */
470 for (l = vars; l; l = l->next) {
474 int reg_index = vmv->reg;
476 /* During allocation, vmv->reg is an index into the regs list */
477 vmv->reg = GPOINTER_TO_INT (g_list_nth_data (regs, vmv->reg));
479 if ((gains [reg_index] > regalloc_cost (cfg, vmv)) && (cfg->varinfo [vmv->idx]->opcode != OP_REGVAR)) {
480 if (cfg->verbose_level > 2)
481 printf ("REGVAR R%d G%d C%d %s\n", cfg->varinfo [vmv->idx]->dreg, gains [reg_index], regalloc_cost (cfg, vmv), mono_arch_regname (vmv->reg));
482 cfg->varinfo [vmv->idx]->opcode = OP_REGVAR;
483 cfg->varinfo [vmv->idx]->dreg = vmv->reg;
487 if (cfg->verbose_level > 2)
488 printf ("COSTLY: %s R%d G%d C%d %s\n", mono_method_full_name (cfg->method, TRUE), cfg->varinfo [vmv->idx]->dreg, gains [reg_index], regalloc_cost (cfg, vmv), mono_arch_regname (vmv->reg));
494 mono_jit_stats.regvars += n_regvars;
496 /* Compute used regs */
498 for (l = vars; l; l = l->next) {
502 used_regs |= 1LL << vmv->reg;
505 *used_mask |= used_regs;
507 g_list_free (active);
508 g_list_free (inactive);