2 * liveness.c: liveness analysis
5 * Dietmar Maurer (dietmar@ximian.com)
7 * (C) 2002 Ximian, Inc.
11 #include <mono/metadata/debug-helpers.h>
15 static void mono_linear_scan2 (MonoCompile *cfg, GList *vars, GList *regs, regmask_t *used_mask);
18 mono_varlist_insert_sorted (MonoCompile *cfg, GList *list, MonoMethodVar *mv, int sort_type)
23 return g_list_prepend (NULL, mv);
25 for (l = list; l; l = l->next) {
26 MonoMethodVar *v1 = (MonoMethodVar *)l->data;
29 if (mv->spill_costs >= v1->spill_costs) {
30 list = g_list_insert_before (list, l, mv);
33 } else if (sort_type == 1) {
34 if (mv->range.last_use.abs_pos <= v1->range.last_use.abs_pos) {
35 list = g_list_insert_before (list, l, mv);
39 if (mv->range.first_use.abs_pos <= v1->range.first_use.abs_pos) {
40 list = g_list_insert_before (list, l, mv);
46 list = g_list_append (list, mv);
52 compare_by_first_use_func (gconstpointer a, gconstpointer b)
54 MonoMethodVar *v1 = (MonoMethodVar*)a;
55 MonoMethodVar *v2 = (MonoMethodVar*)b;
57 return v1->range.first_use.abs_pos - v2->range.first_use.abs_pos;
61 mono_varlist_sort (MonoCompile *cfg, GList *list, int sort_type)
64 return g_list_sort (list, compare_by_first_use_func);
66 g_assert_not_reached ();
71 // #define DEBUG_LSCAN
74 mono_linear_scan (MonoCompile *cfg, GList *vars, GList *regs, regmask_t *used_mask)
76 GList *l, *a, *active = NULL;
77 MonoMethodVar *vmv, *amv;
78 int max_regs, n_regvars;
79 int gains [sizeof (regmask_t) * 8];
80 regmask_t used_regs = 0;
83 if (!cfg->disable_reuse_registers && vars && (((MonoMethodVar*)vars->data)->interval != NULL)) {
84 mono_linear_scan2 (cfg, vars, regs, used_mask);
92 printf ("Linears scan for %s\n", mono_method_full_name (cfg->method, TRUE));
96 for (l = vars; l; l = l->next) {
98 printf ("VAR %d %08x %08x C%d\n", vmv->idx, vmv->range.first_use.abs_pos,
99 vmv->range.last_use.abs_pos, vmv->spill_costs);
102 max_regs = g_list_length (regs);
104 for (l = regs; l; l = l->next) {
105 int regnum = GPOINTER_TO_INT (l->data);
106 g_assert (regnum < G_N_ELEMENTS (gains));
111 for (l = vars; l; l = l->next) {
112 vmv = (MonoMethodVar *)l->data;
115 printf ("START %2d %08x %08x\n", vmv->idx, vmv->range.first_use.abs_pos,
116 vmv->range.last_use.abs_pos);
118 /* expire old intervals in active */
119 if (!cfg->disable_reuse_registers) {
121 amv = (MonoMethodVar *)active->data;
123 if (amv->range.last_use.abs_pos > vmv->range.first_use.abs_pos)
127 printf ("EXPIR %2d %08x %08x C%d R%d\n", amv->idx, amv->range.first_use.abs_pos,
128 amv->range.last_use.abs_pos, amv->spill_costs, amv->reg);
130 active = g_list_delete_link (active, active);
131 regs = g_list_prepend (regs, GINT_TO_POINTER (amv->reg));
132 gains [amv->reg] += amv->spill_costs;
136 if (active && g_list_length (active) == max_regs) {
139 a = g_list_nth (active, max_regs - 1);
140 amv = (MonoMethodVar *)a->data;
142 if ((cost_driven && amv->spill_costs < vmv->spill_costs) ||
143 (!cost_driven && amv->range.last_use.abs_pos > vmv->range.last_use.abs_pos)) {
146 active = g_list_delete_link (active, a);
149 active = mono_varlist_insert_sorted (cfg, active, vmv, 2);
151 active = mono_varlist_insert_sorted (cfg, active, vmv, 1);
154 printf ("SPILL0 %2d %08x %08x C%d\n", amv->idx,
155 amv->range.first_use.abs_pos, amv->range.last_use.abs_pos,
160 printf ("SPILL1 %2d %08x %08x C%d\n", vmv->idx,
161 vmv->range.first_use.abs_pos, vmv->range.last_use.abs_pos,
167 /* assign register */
171 vmv->reg = GPOINTER_TO_INT (regs->data);
173 used_regs |= 1LL << vmv->reg;
175 regs = g_list_delete_link (regs, regs);
178 printf ("ADD %2d %08x %08x C%d R%d\n", vmv->idx,
179 vmv->range.first_use.abs_pos, vmv->range.last_use.abs_pos,
180 vmv->spill_costs, vmv->reg);
182 active = mono_varlist_insert_sorted (cfg, active, vmv, TRUE);
187 for (a = active; a; a = a->next) {
188 amv = (MonoMethodVar *)a->data;
189 printf ("ACT %2d %08x %08x C%d R%d\n", amv->idx, amv->range.first_use.abs_pos,
190 amv->range.last_use.abs_pos, amv->spill_costs, amv->reg);
196 for (a = active; a; a = a->next) {
197 amv = (MonoMethodVar *)a->data;
198 gains [amv->reg] += amv->spill_costs;
202 for (l = vars; l; l = l->next) {
203 vmv = (MonoMethodVar *)l->data;
206 if ((gains [vmv->reg] > mono_arch_regalloc_cost (cfg, vmv)) && (cfg->varinfo [vmv->idx]->opcode != OP_REGVAR)) {
207 if (cfg->verbose_level > 2) {
208 printf ("ALLOCATED R%d(%d) TO HREG %d COST %d\n", cfg->varinfo [vmv->idx]->dreg, vmv->idx, vmv->reg, vmv->spill_costs);
210 cfg->varinfo [vmv->idx]->opcode = OP_REGVAR;
211 cfg->varinfo [vmv->idx]->dreg = vmv->reg;
214 if (cfg->verbose_level > 2)
215 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));
220 if (vmv->reg == -1) {
221 if (cfg->verbose_level > 2)
222 printf ("NOT REGVAR: %d\n", vmv->idx);
226 cfg->stat_n_regvars = n_regvars;
228 /* Compute used regs */
230 for (l = vars; l; l = l->next) {
231 vmv = (MonoMethodVar *)l->data;
234 used_regs |= 1LL << vmv->reg;
237 *used_mask |= used_regs;
240 if (cfg->verbose_level > 2)
241 printf ("EXIT: final used mask: %08x\n", *used_mask);
245 g_list_free (active);
250 compare_by_interval_start_pos_func (gconstpointer a, gconstpointer b)
252 MonoMethodVar *v1 = (MonoMethodVar*)a;
253 MonoMethodVar *v2 = (MonoMethodVar*)b;
257 else if (v1->interval->range && v2->interval->range)
258 return v1->interval->range->from - v2->interval->range->from;
259 else if (v1->interval->range)
266 #define LSCAN_DEBUG(a) do { a; } while (0)
268 #define LSCAN_DEBUG(a)
271 /* FIXME: This is x86 only */
272 static inline guint32
273 regalloc_cost (MonoCompile *cfg, MonoMethodVar *vmv)
275 MonoInst *ins = cfg->varinfo [vmv->idx];
277 /* Load if it is an argument */
278 return (ins->opcode == OP_ARG) ? 1 : 0;
282 mono_linear_scan2 (MonoCompile *cfg, GList *vars, GList *regs, regmask_t *used_mask)
284 GList *unhandled, *active, *inactive, *l;
286 gint32 free_pos [sizeof (regmask_t) * 8];
287 gint32 gains [sizeof (regmask_t) * 8];
288 regmask_t used_regs = 0;
289 int n_regs, n_regvars, i;
291 for (l = vars; l; l = l->next) {
292 vmv = (MonoMethodVar *)l->data;
293 LSCAN_DEBUG (printf ("VAR R%d %08x %08x C%d\n", cfg->varinfo [vmv->idx]->dreg, vmv->range.first_use.abs_pos,
294 vmv->range.last_use.abs_pos, vmv->spill_costs));
297 LSCAN_DEBUG (printf ("Linear Scan 2 for %s:\n", mono_method_full_name (cfg->method, TRUE)));
299 n_regs = g_list_length (regs);
300 memset (gains, 0, n_regs * sizeof (gint32));
301 unhandled = g_list_sort (g_list_copy (vars), compare_by_interval_start_pos_func);
306 MonoMethodVar *current = (MonoMethodVar *)unhandled->data;
307 int pos, reg, max_free_pos;
310 unhandled = g_list_delete_link (unhandled, unhandled);
312 LSCAN_DEBUG (printf ("Processing R%d: ", cfg->varinfo [current->idx]->dreg));
313 LSCAN_DEBUG (mono_linterval_print (current->interval));
314 LSCAN_DEBUG (printf ("\n"));
316 if (!current->interval->range)
319 pos = current->interval->range->from;
321 /* Check for intervals in active which expired or inactive */
323 /* FIXME: Optimize this */
326 for (l = active; l != NULL; l = l->next) {
327 MonoMethodVar *v = (MonoMethodVar*)l->data;
329 if (v->interval->last_range->to < pos) {
330 active = g_list_delete_link (active, l);
331 LSCAN_DEBUG (printf ("Interval R%d has expired\n", cfg->varinfo [v->idx]->dreg));
335 else if (!mono_linterval_covers (v->interval, pos)) {
336 inactive = g_list_append (inactive, v);
337 active = g_list_delete_link (active, l);
338 LSCAN_DEBUG (printf ("Interval R%d became inactive\n", cfg->varinfo [v->idx]->dreg));
345 /* Check for intervals in inactive which expired or active */
347 /* FIXME: Optimize this */
350 for (l = inactive; l != NULL; l = l->next) {
351 MonoMethodVar *v = (MonoMethodVar*)l->data;
353 if (v->interval->last_range->to < pos) {
354 inactive = g_list_delete_link (inactive, l);
355 LSCAN_DEBUG (printf ("\tInterval R%d has expired\n", cfg->varinfo [v->idx]->dreg));
359 else if (mono_linterval_covers (v->interval, pos)) {
360 active = g_list_append (active, v);
361 inactive = g_list_delete_link (inactive, l);
362 LSCAN_DEBUG (printf ("\tInterval R%d became active\n", cfg->varinfo [v->idx]->dreg));
369 /* Find a register for the current interval */
370 for (i = 0; i < n_regs; ++i)
371 free_pos [i] = ((gint32)0x7fffffff);
373 for (l = active; l != NULL; l = l->next) {
374 MonoMethodVar *v = (MonoMethodVar*)l->data;
377 free_pos [v->reg] = 0;
378 LSCAN_DEBUG (printf ("\threg %d is busy (cost %d)\n", v->reg, v->spill_costs));
382 for (l = inactive; l != NULL; l = l->next) {
383 MonoMethodVar *v = (MonoMethodVar*)l->data;
384 gint32 intersect_pos;
387 intersect_pos = mono_linterval_get_intersect_pos (current->interval, v->interval);
388 if (intersect_pos != -1) {
389 free_pos [v->reg] = intersect_pos;
390 LSCAN_DEBUG (printf ("\threg %d becomes free at %d\n", v->reg, intersect_pos));
397 for (i = 0; i < n_regs; ++i)
398 if (free_pos [i] > max_free_pos) {
400 max_free_pos = free_pos [i];
403 g_assert (reg != -1);
405 if (free_pos [reg] >= current->interval->last_range->to) {
406 /* Register available for whole interval */
408 LSCAN_DEBUG (printf ("\tAssigned hreg %d to R%d\n", reg, cfg->varinfo [current->idx]->dreg));
410 active = g_list_append (active, current);
411 gains [current->reg] += current->spill_costs;
415 * free_pos [reg] > 0 means there is a register available for parts
416 * of the interval, so splitting it is possible. This is not yet
417 * supported, so we spill in this case too.
420 /* Spill an interval */
422 /* FIXME: Optimize the selection of the interval */
425 GList *min_spill_pos;
428 * This favors registers with big spill costs, thus larger liveness ranges,
429 * thus actually leading to worse code size.
431 guint32 min_spill_value = G_MAXINT32;
433 for (l = active; l != NULL; l = l->next) {
434 vmv = (MonoMethodVar*)l->data;
436 if (vmv->spill_costs < min_spill_value) {
438 min_spill_value = vmv->spill_costs;
442 /* Spill either the first active or the current interval */
443 min_spill_pos = active;
445 vmv = (MonoMethodVar*)min_spill_pos->data;
446 if (vmv->spill_costs < current->spill_costs) {
447 // if (vmv->interval->last_range->to < current->interval->last_range->to) {
448 gains [vmv->reg] -= vmv->spill_costs;
450 LSCAN_DEBUG (printf ("\tSpilled R%d\n", cfg->varinfo [vmv->idx]->dreg));
451 active = g_list_delete_link (active, min_spill_pos);
454 LSCAN_DEBUG (printf ("\tSpilled current (cost %d)\n", current->spill_costs));
457 LSCAN_DEBUG (printf ("\tSpilled current\n"));
461 /* Decrease the gains by the cost of saving+restoring the register */
462 for (i = 0; i < n_regs; ++i) {
464 /* FIXME: This is x86 only */
465 gains [i] -= cfg->method->save_lmf ? 1 : 2;
471 /* Do the actual register assignment */
473 for (l = vars; l; l = l->next) {
474 vmv = (MonoMethodVar *)l->data;
477 int reg_index = vmv->reg;
479 /* During allocation, vmv->reg is an index into the regs list */
480 vmv->reg = GPOINTER_TO_INT (g_list_nth_data (regs, vmv->reg));
482 if ((gains [reg_index] > regalloc_cost (cfg, vmv)) && (cfg->varinfo [vmv->idx]->opcode != OP_REGVAR)) {
483 if (cfg->verbose_level > 2)
484 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));
485 cfg->varinfo [vmv->idx]->opcode = OP_REGVAR;
486 cfg->varinfo [vmv->idx]->dreg = vmv->reg;
490 if (cfg->verbose_level > 2)
491 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));
497 cfg->stat_n_regvars = n_regvars;
499 /* Compute used regs */
501 for (l = vars; l; l = l->next) {
502 vmv = (MonoMethodVar *)l->data;
505 used_regs |= 1LL << vmv->reg;
508 *used_mask |= used_regs;
510 g_list_free (active);
511 g_list_free (inactive);
514 #endif /* #ifndef DISABLE_JIT */