1 /**
2 * \file
3 * liveness analysis
4 *
5 * Author:
6 * Dietmar Maurer (dietmar@ximian.com)
7 *
8 * (C) 2002 Ximian, Inc.
9 * Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
10 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
11 */
12
13 #include <config.h>
14 #include <mono/utils/mono-compiler.h>
15
16 #ifndef DISABLE_JIT
17
18 #include "mini.h"
19
20 #define SPILL_COST_INCREMENT (1 << (bb->nesting << 1))
21
22 #define DEBUG_LIVENESS
23
24 #define BITS_PER_CHUNK MONO_BITSET_BITS_PER_CHUNK
25
26 #define BB_ID_SHIFT 18
27
28 /*
29 * The liveness2 pass can't handle long vars on 32 bit platforms because the component
30 * vars have the same 'idx'.
31 */
32 #if SIZEOF_REGISTER == 8
33 #define ENABLE_LIVENESS2
34 #endif
35
36 #ifdef ENABLE_LIVENESS2
37 static void mono_analyze_liveness2 (MonoCompile *cfg);
38 #endif
39
40 static void
41 optimize_initlocals (MonoCompile *cfg);
42
43 /* mono_bitset_mp_new:
44 *
45 * allocates a MonoBitSet inside a memory pool
46 */
47 static inline MonoBitSet*
mono_bitset_mp_new(MonoMemPool * mp,guint32 size,guint32 max_size)48 mono_bitset_mp_new (MonoMemPool *mp, guint32 size, guint32 max_size)
49 {
50 guint8 *mem = (guint8 *)mono_mempool_alloc0 (mp, size);
51 return mono_bitset_mem_new (mem, max_size, MONO_BITSET_DONT_FREE);
52 }
53
54 static inline MonoBitSet*
mono_bitset_mp_new_noinit(MonoMemPool * mp,guint32 size,guint32 max_size)55 mono_bitset_mp_new_noinit (MonoMemPool *mp, guint32 size, guint32 max_size)
56 {
57 guint8 *mem = (guint8 *)mono_mempool_alloc (mp, size);
58 return mono_bitset_mem_new (mem, max_size, MONO_BITSET_DONT_FREE);
59 }
60
61 G_GNUC_UNUSED static void
mono_bitset_print(MonoBitSet * set)62 mono_bitset_print (MonoBitSet *set)
63 {
64 int i;
65 gboolean first = TRUE;
66
67 printf ("{");
68 for (i = 0; i < mono_bitset_size (set); i++) {
69
70 if (mono_bitset_test (set, i)) {
71 if (!first)
72 printf (", ");
73 printf ("%d", i);
74 first = FALSE;
75 }
76 }
77 printf ("}\n");
78 }
79
80 static void
visit_bb(MonoCompile * cfg,MonoBasicBlock * bb,GSList ** visited)81 visit_bb (MonoCompile *cfg, MonoBasicBlock *bb, GSList **visited)
82 {
83 int i;
84 MonoInst *ins;
85
86 if (g_slist_find (*visited, bb))
87 return;
88
89 for (ins = bb->code; ins; ins = ins->next) {
90 const char *spec = INS_INFO (ins->opcode);
91 int regtype, srcindex, sreg, num_sregs;
92 int sregs [MONO_MAX_SRC_REGS];
93
94 if (ins->opcode == OP_NOP)
95 continue;
96
97 /* DREG */
98 regtype = spec [MONO_INST_DEST];
99 g_assert (((ins->dreg == -1) && (regtype == ' ')) || ((ins->dreg != -1) && (regtype != ' ')));
100
101 if ((ins->dreg != -1) && get_vreg_to_inst (cfg, ins->dreg)) {
102 MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
103 int idx = var->inst_c0;
104 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
105
106 cfg->varinfo [vi->idx]->flags |= MONO_INST_VOLATILE;
107 if (SIZEOF_REGISTER == 4 && (var->type == STACK_I8 || (var->type == STACK_R8 && COMPILE_SOFT_FLOAT (cfg)))) {
108 /* Make the component vregs volatile as well (#612206) */
109 get_vreg_to_inst (cfg, MONO_LVREG_LS (var->dreg))->flags |= MONO_INST_VOLATILE;
110 get_vreg_to_inst (cfg, MONO_LVREG_MS (var->dreg))->flags |= MONO_INST_VOLATILE;
111 }
112 }
113
114 /* SREGS */
115 num_sregs = mono_inst_get_src_registers (ins, sregs);
116 for (srcindex = 0; srcindex < num_sregs; ++srcindex) {
117 sreg = sregs [srcindex];
118
119 g_assert (sreg != -1);
120 if (get_vreg_to_inst (cfg, sreg)) {
121 MonoInst *var = get_vreg_to_inst (cfg, sreg);
122 int idx = var->inst_c0;
123 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
124
125 cfg->varinfo [vi->idx]->flags |= MONO_INST_VOLATILE;
126 if (SIZEOF_REGISTER == 4 && (var->type == STACK_I8 || (var->type == STACK_R8 && COMPILE_SOFT_FLOAT (cfg)))) {
127 /* Make the component vregs volatile as well (#612206) */
128 get_vreg_to_inst (cfg, MONO_LVREG_LS (var->dreg))->flags |= MONO_INST_VOLATILE;
129 get_vreg_to_inst (cfg, MONO_LVREG_MS (var->dreg))->flags |= MONO_INST_VOLATILE;
130 }
131 }
132 }
133 }
134
135 *visited = g_slist_append (*visited, bb);
136
137 /*
138 * Need to visit all bblocks reachable from this one since they can be
139 * reached during exception handling.
140 */
141 for (i = 0; i < bb->out_count; ++i) {
142 visit_bb (cfg, bb->out_bb [i], visited);
143 }
144 }
145
146 void
mono_liveness_handle_exception_clauses(MonoCompile * cfg)147 mono_liveness_handle_exception_clauses (MonoCompile *cfg)
148 {
149 MonoBasicBlock *bb;
150 GSList *visited = NULL;
151 MonoMethodHeader *header = cfg->header;
152 MonoExceptionClause *clause, *clause2;
153 int i, j;
154 gboolean *outer_try;
155
156 /*
157 * Determine which clauses are outer try clauses, i.e. they are not contained in any
158 * other non-try clause.
159 */
160 outer_try = (gboolean *)mono_mempool_alloc0 (cfg->mempool, sizeof (gboolean) * header->num_clauses);
161 for (i = 0; i < header->num_clauses; ++i)
162 outer_try [i] = TRUE;
163 /* Iterate over the clauses backward, so outer clauses come first */
164 /* This avoids doing an O(2) search, since we can determine when inner clauses end */
165 for (i = header->num_clauses - 1; i >= 0; --i) {
166 clause = &header->clauses [i];
167
168 if (clause->flags != 0) {
169 outer_try [i] = TRUE;
170 /* Iterate over inner clauses */
171 for (j = i - 1; j >= 0; --j) {
172 clause2 = &header->clauses [j];
173
174 if (clause2->flags == 0 && MONO_OFFSET_IN_HANDLER (clause, clause2->try_offset)) {
175 outer_try [j] = FALSE;
176 break;
177 }
178 if (clause2->try_offset < clause->try_offset)
179 /* End of inner clauses */
180 break;
181 }
182 }
183 }
184
185 /*
186 * Variables in exception handler register cannot be allocated to registers
187 * so make them volatile. See bug #42136. This will not be neccessary when
188 * the back ends could guarantee that the variables will be in the
189 * correct registers when a handler is called.
190 * This includes try blocks too, since a variable in a try block might be
191 * accessed after an exception handler has been run.
192 */
193 for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
194
195 if (bb->region == -1)
196 continue;
197
198 if (MONO_BBLOCK_IS_IN_REGION (bb, MONO_REGION_TRY) && outer_try [MONO_REGION_CLAUSE_INDEX (bb->region)])
199 continue;
200
201 if (cfg->verbose_level > 2)
202 printf ("pessimize variables in bb %d.\n", bb->block_num);
203
204 visit_bb (cfg, bb, &visited);
205 }
206 g_slist_free (visited);
207 }
208
209 static inline void
update_live_range(MonoMethodVar * var,int abs_pos)210 update_live_range (MonoMethodVar *var, int abs_pos)
211 {
212 if (var->range.first_use.abs_pos > abs_pos)
213 var->range.first_use.abs_pos = abs_pos;
214
215 if (var->range.last_use.abs_pos < abs_pos)
216 var->range.last_use.abs_pos = abs_pos;
217 }
218
219 static void
analyze_liveness_bb(MonoCompile * cfg,MonoBasicBlock * bb)220 analyze_liveness_bb (MonoCompile *cfg, MonoBasicBlock *bb)
221 {
222 MonoInst *ins;
223 int sreg, inst_num;
224 MonoMethodVar *vars = cfg->vars;
225 guint32 abs_pos = (bb->dfn << BB_ID_SHIFT);
226
227 /* Start inst_num from > 0, so last_use.abs_pos is only 0 for dead variables */
228 for (inst_num = 2, ins = bb->code; ins; ins = ins->next, inst_num += 2) {
229 const char *spec = INS_INFO (ins->opcode);
230 int num_sregs, i;
231 int sregs [MONO_MAX_SRC_REGS];
232
233 #ifdef DEBUG_LIVENESS
234 if (cfg->verbose_level > 1) {
235 mono_print_ins_index (1, ins);
236 }
237 #endif
238
239 if (ins->opcode == OP_NOP)
240 continue;
241
242 if (ins->opcode == OP_LDADDR) {
243 MonoInst *var = (MonoInst *)ins->inst_p0;
244 int idx = var->inst_c0;
245 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
246
247 #ifdef DEBUG_LIVENESS
248 if (cfg->verbose_level > 1)
249 printf ("\tGEN: R%d(%d)\n", var->dreg, idx);
250 #endif
251 update_live_range (&vars [idx], abs_pos + inst_num);
252 if (!mono_bitset_test_fast (bb->kill_set, idx))
253 mono_bitset_set_fast (bb->gen_set, idx);
254 vi->spill_costs += SPILL_COST_INCREMENT;
255 }
256
257 /* SREGs must come first, so MOVE r <- r is handled correctly */
258 num_sregs = mono_inst_get_src_registers (ins, sregs);
259 for (i = 0; i < num_sregs; ++i) {
260 sreg = sregs [i];
261 if ((spec [MONO_INST_SRC1 + i] != ' ') && get_vreg_to_inst (cfg, sreg)) {
262 MonoInst *var = get_vreg_to_inst (cfg, sreg);
263 int idx = var->inst_c0;
264 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
265
266 #ifdef DEBUG_LIVENESS
267 if (cfg->verbose_level > 1)
268 printf ("\tGEN: R%d(%d)\n", sreg, idx);
269 #endif
270 update_live_range (&vars [idx], abs_pos + inst_num);
271 if (!mono_bitset_test_fast (bb->kill_set, idx))
272 mono_bitset_set_fast (bb->gen_set, idx);
273 vi->spill_costs += SPILL_COST_INCREMENT;
274 }
275 }
276
277 /* DREG */
278 if ((spec [MONO_INST_DEST] != ' ') && get_vreg_to_inst (cfg, ins->dreg)) {
279 MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
280 int idx = var->inst_c0;
281 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
282
283 if (MONO_IS_STORE_MEMBASE (ins)) {
284 update_live_range (&vars [idx], abs_pos + inst_num);
285 if (!mono_bitset_test_fast (bb->kill_set, idx))
286 mono_bitset_set_fast (bb->gen_set, idx);
287 vi->spill_costs += SPILL_COST_INCREMENT;
288 } else {
289 #ifdef DEBUG_LIVENESS
290 if (cfg->verbose_level > 1)
291 printf ("\tKILL: R%d(%d)\n", ins->dreg, idx);
292 #endif
293 update_live_range (&vars [idx], abs_pos + inst_num + 1);
294 mono_bitset_set_fast (bb->kill_set, idx);
295 vi->spill_costs += SPILL_COST_INCREMENT;
296 }
297 }
298 }
299 }
300
301 /* generic liveness analysis code. CFG specific parts are
302 * in update_gen_kill_set()
303 */
304 void
mono_analyze_liveness(MonoCompile * cfg)305 mono_analyze_liveness (MonoCompile *cfg)
306 {
307 MonoBitSet *old_live_out_set;
308 int i, j, max_vars = cfg->num_varinfo;
309 int out_iter;
310 gboolean *in_worklist;
311 MonoBasicBlock **worklist;
312 guint32 l_end;
313 int bitsize;
314
315 #ifdef DEBUG_LIVENESS
316 if (cfg->verbose_level > 1)
317 printf ("\nLIVENESS:\n");
318 #endif
319
320 g_assert (!(cfg->comp_done & MONO_COMP_LIVENESS));
321
322 cfg->comp_done |= MONO_COMP_LIVENESS;
323
324 if (max_vars == 0)
325 return;
326
327 bitsize = mono_bitset_alloc_size (max_vars, 0);
328
329 for (i = 0; i < max_vars; i ++) {
330 MONO_VARINFO (cfg, i)->range.first_use.abs_pos = ~ 0;
331 MONO_VARINFO (cfg, i)->range.last_use .abs_pos = 0;
332 MONO_VARINFO (cfg, i)->spill_costs = 0;
333 }
334
335 for (i = 0; i < cfg->num_bblocks; ++i) {
336 MonoBasicBlock *bb = cfg->bblocks [i];
337
338 bb->gen_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
339 bb->kill_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
340
341 #ifdef DEBUG_LIVENESS
342 if (cfg->verbose_level > 1) {
343 printf ("BLOCK BB%d (", bb->block_num);
344 for (j = 0; j < bb->out_count; j++)
345 printf ("BB%d, ", bb->out_bb [j]->block_num);
346
347 printf ("):\n");
348 }
349 #endif
350
351 analyze_liveness_bb (cfg, bb);
352
353 #ifdef DEBUG_LIVENESS
354 if (cfg->verbose_level > 1) {
355 printf ("GEN BB%d: ", bb->block_num); mono_bitset_print (bb->gen_set);
356 printf ("KILL BB%d: ", bb->block_num); mono_bitset_print (bb->kill_set);
357 }
358 #endif
359 }
360
361 old_live_out_set = mono_bitset_new (max_vars, 0);
362 in_worklist = g_new0 (gboolean, cfg->num_bblocks + 1);
363
364 worklist = g_new (MonoBasicBlock *, cfg->num_bblocks + 1);
365 l_end = 0;
366
367 /*
368 * This is a backward dataflow analysis problem, so we process blocks in
369 * decreasing dfn order, this speeds up the iteration.
370 */
371 for (i = 0; i < cfg->num_bblocks; i ++) {
372 MonoBasicBlock *bb = cfg->bblocks [i];
373
374 worklist [l_end ++] = bb;
375 in_worklist [bb->dfn] = TRUE;
376
377 /* Initialized later */
378 bb->live_in_set = NULL;
379 bb->live_out_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
380 }
381
382 out_iter = 0;
383
384 if (cfg->verbose_level > 1)
385 printf ("\nITERATION:\n");
386
387 while (l_end != 0) {
388 MonoBasicBlock *bb = worklist [--l_end];
389 MonoBasicBlock *out_bb;
390 gboolean changed;
391
392 in_worklist [bb->dfn] = FALSE;
393
394 #ifdef DEBUG_LIVENESS
395 if (cfg->verbose_level > 1) {
396 printf ("P: BB%d(%d): IN: ", bb->block_num, bb->dfn);
397 for (j = 0; j < bb->in_count; ++j)
398 printf ("BB%d ", bb->in_bb [j]->block_num);
399 printf ("OUT:");
400 for (j = 0; j < bb->out_count; ++j)
401 printf ("BB%d ", bb->out_bb [j]->block_num);
402 printf ("\n");
403 }
404 #endif
405
406
407 if (bb->out_count == 0)
408 continue;
409
410 out_iter ++;
411
412 if (!bb->live_in_set) {
413 /* First pass over this bblock */
414 changed = TRUE;
415 }
416 else {
417 changed = FALSE;
418 mono_bitset_copyto_fast (bb->live_out_set, old_live_out_set);
419 }
420
421 for (j = 0; j < bb->out_count; j++) {
422 out_bb = bb->out_bb [j];
423
424 if (!out_bb->live_in_set) {
425 out_bb->live_in_set = mono_bitset_mp_new_noinit (cfg->mempool, bitsize, max_vars);
426
427 mono_bitset_copyto_fast (out_bb->live_out_set, out_bb->live_in_set);
428 mono_bitset_sub_fast (out_bb->live_in_set, out_bb->kill_set);
429 mono_bitset_union_fast (out_bb->live_in_set, out_bb->gen_set);
430 }
431
432 // FIXME: Do this somewhere else
433 if (bb->last_ins && bb->last_ins->opcode == OP_NOT_REACHED) {
434 } else {
435 mono_bitset_union_fast (bb->live_out_set, out_bb->live_in_set);
436 }
437 }
438
439 if (changed || !mono_bitset_equal (old_live_out_set, bb->live_out_set)) {
440 if (!bb->live_in_set)
441 bb->live_in_set = mono_bitset_mp_new_noinit (cfg->mempool, bitsize, max_vars);
442 mono_bitset_copyto_fast (bb->live_out_set, bb->live_in_set);
443 mono_bitset_sub_fast (bb->live_in_set, bb->kill_set);
444 mono_bitset_union_fast (bb->live_in_set, bb->gen_set);
445
446 for (j = 0; j < bb->in_count; j++) {
447 MonoBasicBlock *in_bb = bb->in_bb [j];
448 /*
449 * Some basic blocks do not seem to be in the
450 * cfg->bblocks array...
451 */
452 if (in_bb->gen_set && !in_worklist [in_bb->dfn]) {
453 #ifdef DEBUG_LIVENESS
454 if (cfg->verbose_level > 1)
455 printf ("\tADD: %d\n", in_bb->block_num);
456 #endif
457 /*
458 * Put the block at the top of the stack, so it
459 * will be processed right away.
460 */
461 worklist [l_end ++] = in_bb;
462 in_worklist [in_bb->dfn] = TRUE;
463 }
464 }
465 }
466
467 if (G_UNLIKELY (cfg->verbose_level > 1)) {
468 printf ("\tLIVE IN BB%d: ", bb->block_num);
469 mono_bitset_print (bb->live_in_set);
470 }
471 }
472
473 #ifdef DEBUG_LIVENESS
474 if (cfg->verbose_level > 1)
475 printf ("IT: %d %d.\n", cfg->num_bblocks, out_iter);
476 #endif
477
478 mono_bitset_free (old_live_out_set);
479
480 g_free (worklist);
481 g_free (in_worklist);
482
483 /* Compute live_in_set for bblocks skipped earlier */
484 for (i = 0; i < cfg->num_bblocks; ++i) {
485 MonoBasicBlock *bb = cfg->bblocks [i];
486
487 if (!bb->live_in_set) {
488 bb->live_in_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
489
490 mono_bitset_copyto_fast (bb->live_out_set, bb->live_in_set);
491 mono_bitset_sub_fast (bb->live_in_set, bb->kill_set);
492 mono_bitset_union_fast (bb->live_in_set, bb->gen_set);
493 }
494 }
495
496 for (i = 0; i < cfg->num_bblocks; ++i) {
497 MonoBasicBlock *bb = cfg->bblocks [i];
498 guint32 max;
499 guint32 abs_pos = (bb->dfn << BB_ID_SHIFT);
500 MonoMethodVar *vars = cfg->vars;
501
502 if (!bb->live_out_set)
503 continue;
504
505 max = ((max_vars + (BITS_PER_CHUNK -1)) / BITS_PER_CHUNK);
506 for (j = 0; j < max; ++j) {
507 gsize bits_in;
508 gsize bits_out;
509 int k;
510
511 bits_in = mono_bitset_get_fast (bb->live_in_set, j);
512 bits_out = mono_bitset_get_fast (bb->live_out_set, j);
513
514 k = (j * BITS_PER_CHUNK);
515 while ((bits_in || bits_out)) {
516 if (bits_in & 1)
517 update_live_range (&vars [k], abs_pos + 0);
518 if (bits_out & 1)
519 update_live_range (&vars [k], abs_pos + ((1 << BB_ID_SHIFT) - 1));
520 bits_in >>= 1;
521 bits_out >>= 1;
522 k ++;
523 }
524 }
525 }
526
527 /*
528 * Arguments need to have their live ranges extended to the beginning of
529 * the method to account for the arg reg/memory -> global register copies
530 * in the prolog (bug #74992).
531 */
532
533 for (i = 0; i < max_vars; i ++) {
534 MonoMethodVar *vi = MONO_VARINFO (cfg, i);
535 if (cfg->varinfo [vi->idx]->opcode == OP_ARG) {
536 if (vi->range.last_use.abs_pos == 0 && !(cfg->varinfo [vi->idx]->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT))) {
537 /*
538 * Can't eliminate the this variable in gshared code, since
539 * it is needed during exception handling to identify the
540 * method.
541 * It is better to check for this here instead of marking the variable
542 * VOLATILE, since that would prevent it from being allocated to
543 * registers.
544 */
545 if (!cfg->disable_deadce_vars && !(cfg->gshared && mono_method_signature (cfg->method)->hasthis && cfg->varinfo [vi->idx] == cfg->args [0]))
546 cfg->varinfo [vi->idx]->flags |= MONO_INST_IS_DEAD;
547 }
548 vi->range.first_use.abs_pos = 0;
549 }
550 }
551
552 #ifdef DEBUG_LIVENESS
553 if (cfg->verbose_level > 1) {
554 for (i = cfg->num_bblocks - 1; i >= 0; i--) {
555 MonoBasicBlock *bb = cfg->bblocks [i];
556
557 printf ("LIVE IN BB%d: ", bb->block_num);
558 mono_bitset_print (bb->live_in_set);
559 printf ("LIVE OUT BB%d: ", bb->block_num);
560 mono_bitset_print (bb->live_out_set);
561 }
562
563 for (i = 0; i < max_vars; i ++) {
564 MonoMethodVar *vi = MONO_VARINFO (cfg, i);
565
566 printf ("V%d: [0x%x - 0x%x]\n", i, vi->range.first_use.abs_pos, vi->range.last_use.abs_pos);
567 }
568 }
569 #endif
570
571 if (!cfg->disable_initlocals_opt)
572 optimize_initlocals (cfg);
573
574 #ifdef ENABLE_LIVENESS2
575 /* This improves code size by about 5% but slows down compilation too much */
576 if (cfg->compile_aot)
577 mono_analyze_liveness2 (cfg);
578 #endif
579 }
580
581 /**
582 * optimize_initlocals:
583 *
584 * Try to optimize away some of the redundant initialization code inserted because of
585 * 'locals init' using the liveness information.
586 */
587 static void
optimize_initlocals(MonoCompile * cfg)588 optimize_initlocals (MonoCompile *cfg)
589 {
590 MonoBitSet *used;
591 MonoInst *ins;
592 MonoBasicBlock *initlocals_bb;
593
594 used = mono_bitset_new (cfg->next_vreg + 1, 0);
595
596 mono_bitset_clear_all (used);
597 initlocals_bb = cfg->bb_entry->next_bb;
598 for (ins = initlocals_bb->code; ins; ins = ins->next) {
599 int num_sregs, i;
600 int sregs [MONO_MAX_SRC_REGS];
601
602 num_sregs = mono_inst_get_src_registers (ins, sregs);
603 for (i = 0; i < num_sregs; ++i)
604 mono_bitset_set_fast (used, sregs [i]);
605
606 if (MONO_IS_STORE_MEMBASE (ins))
607 mono_bitset_set_fast (used, ins->dreg);
608 }
609
610 for (ins = initlocals_bb->code; ins; ins = ins->next) {
611 const char *spec = INS_INFO (ins->opcode);
612
613 /* Look for statements whose dest is not used in this bblock and not live on exit. */
614 if ((spec [MONO_INST_DEST] != ' ') && !MONO_IS_STORE_MEMBASE (ins)) {
615 MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
616
617 if (var && !mono_bitset_test_fast (used, ins->dreg) && !mono_bitset_test_fast (initlocals_bb->live_out_set, var->inst_c0) && (var != cfg->ret) && !(var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT))) {
618 //printf ("DEAD: "); mono_print_ins (ins);
619 if (cfg->disable_initlocals_opt_refs && var->type == STACK_OBJ)
620 continue;
621 if ((ins->opcode == OP_ICONST) || (ins->opcode == OP_I8CONST) || (ins->opcode == OP_R8CONST) || (ins->opcode == OP_R4CONST)) {
622 NULLIFY_INS (ins);
623 MONO_VARINFO (cfg, var->inst_c0)->spill_costs -= 1;
624 /*
625 * We should shorten the liveness interval of these vars as well, but
626 * don't have enough info to do that.
627 */
628 }
629 }
630 }
631 }
632
633 g_free (used);
634 }
635
636 void
mono_linterval_add_range(MonoCompile * cfg,MonoLiveInterval * interval,int from,int to)637 mono_linterval_add_range (MonoCompile *cfg, MonoLiveInterval *interval, int from, int to)
638 {
639 MonoLiveRange2 *prev_range, *next_range, *new_range;
640
641 g_assert (to >= from);
642
643 /* Optimize for extending the first interval backwards */
644 if (G_LIKELY (interval->range && (interval->range->from > from) && (interval->range->from == to))) {
645 interval->range->from = from;
646 return;
647 }
648
649 /* Find a place in the list for the new range */
650 prev_range = NULL;
651 next_range = interval->range;
652 while ((next_range != NULL) && (next_range->from <= from)) {
653 prev_range = next_range;
654 next_range = next_range->next;
655 }
656
657 if (prev_range && prev_range->to == from) {
658 /* Merge with previous */
659 prev_range->to = to;
660 } else if (next_range && next_range->from == to) {
661 /* Merge with previous */
662 next_range->from = from;
663 } else {
664 /* Insert it */
665 new_range = (MonoLiveRange2 *)mono_mempool_alloc (cfg->mempool, sizeof (MonoLiveRange2));
666 new_range->from = from;
667 new_range->to = to;
668 new_range->next = NULL;
669
670 if (prev_range)
671 prev_range->next = new_range;
672 else
673 interval->range = new_range;
674 if (next_range)
675 new_range->next = next_range;
676 else
677 interval->last_range = new_range;
678 }
679
680 /* FIXME: Merge intersecting ranges */
681 }
682
683 void
mono_linterval_print(MonoLiveInterval * interval)684 mono_linterval_print (MonoLiveInterval *interval)
685 {
686 MonoLiveRange2 *range;
687
688 for (range = interval->range; range != NULL; range = range->next)
689 printf ("[%x-%x] ", range->from, range->to);
690 }
691
692 void
mono_linterval_print_nl(MonoLiveInterval * interval)693 mono_linterval_print_nl (MonoLiveInterval *interval)
694 {
695 mono_linterval_print (interval);
696 printf ("\n");
697 }
698
699 /**
700 * mono_linterval_convers:
701 *
702 * Return whenever INTERVAL covers the position POS.
703 */
704 gboolean
mono_linterval_covers(MonoLiveInterval * interval,int pos)705 mono_linterval_covers (MonoLiveInterval *interval, int pos)
706 {
707 MonoLiveRange2 *range;
708
709 for (range = interval->range; range != NULL; range = range->next) {
710 if (pos >= range->from && pos <= range->to)
711 return TRUE;
712 if (range->from > pos)
713 return FALSE;
714 }
715
716 return FALSE;
717 }
718
719 /**
720 * mono_linterval_get_intersect_pos:
721 *
722 * Determine whenever I1 and I2 intersect, and if they do, return the first
723 * point of intersection. Otherwise, return -1.
724 */
725 gint32
mono_linterval_get_intersect_pos(MonoLiveInterval * i1,MonoLiveInterval * i2)726 mono_linterval_get_intersect_pos (MonoLiveInterval *i1, MonoLiveInterval *i2)
727 {
728 MonoLiveRange2 *r1, *r2;
729
730 /* FIXME: Optimize this */
731 for (r1 = i1->range; r1 != NULL; r1 = r1->next) {
732 for (r2 = i2->range; r2 != NULL; r2 = r2->next) {
733 if (r2->to > r1->from && r2->from < r1->to) {
734 if (r2->from <= r1->from)
735 return r1->from;
736 else
737 return r2->from;
738 }
739 }
740 }
741
742 return -1;
743 }
744
745 /**
746 * mono_linterval_split
747 *
748 * Split L at POS and store the newly created intervals into L1 and L2. POS becomes
749 * part of L2.
750 */
751 void
mono_linterval_split(MonoCompile * cfg,MonoLiveInterval * interval,MonoLiveInterval ** i1,MonoLiveInterval ** i2,int pos)752 mono_linterval_split (MonoCompile *cfg, MonoLiveInterval *interval, MonoLiveInterval **i1, MonoLiveInterval **i2, int pos)
753 {
754 MonoLiveRange2 *r;
755
756 g_assert (pos > interval->range->from && pos <= interval->last_range->to);
757
758 *i1 = (MonoLiveInterval *)mono_mempool_alloc0 (cfg->mempool, sizeof (MonoLiveInterval));
759 *i2 = (MonoLiveInterval *)mono_mempool_alloc0 (cfg->mempool, sizeof (MonoLiveInterval));
760
761 for (r = interval->range; r; r = r->next) {
762 if (pos > r->to) {
763 /* Add it to the first child */
764 mono_linterval_add_range (cfg, *i1, r->from, r->to);
765 } else if (pos > r->from && pos <= r->to) {
766 /* Split at pos */
767 mono_linterval_add_range (cfg, *i1, r->from, pos - 1);
768 mono_linterval_add_range (cfg, *i2, pos, r->to);
769 } else {
770 /* Add it to the second child */
771 mono_linterval_add_range (cfg, *i2, r->from, r->to);
772 }
773 }
774 }
775
776 #if 1
777 #define LIVENESS_DEBUG(a) do { if (cfg->verbose_level > 1) do { a; } while (0); } while (0)
778 #define ENABLE_LIVENESS_DEBUG 1
779 #else
780 #define LIVENESS_DEBUG(a)
781 #endif
782
783 #ifdef ENABLE_LIVENESS2
784
785 static inline void
update_liveness2(MonoCompile * cfg,MonoInst * ins,gboolean set_volatile,int inst_num,gint32 * last_use)786 update_liveness2 (MonoCompile *cfg, MonoInst *ins, gboolean set_volatile, int inst_num, gint32 *last_use)
787 {
788 const char *spec = INS_INFO (ins->opcode);
789 int sreg;
790 int num_sregs, i;
791 int sregs [MONO_MAX_SRC_REGS];
792
793 LIVENESS_DEBUG (printf ("\t%x: ", inst_num); mono_print_ins (ins));
794
795 if (ins->opcode == OP_NOP || ins->opcode == OP_IL_SEQ_POINT)
796 return;
797
798 /* DREG */
799 if ((spec [MONO_INST_DEST] != ' ') && get_vreg_to_inst (cfg, ins->dreg)) {
800 MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
801 int idx = var->inst_c0;
802 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
803
804 if (MONO_IS_STORE_MEMBASE (ins)) {
805 if (last_use [idx] == 0) {
806 LIVENESS_DEBUG (printf ("\tlast use of R%d set to %x\n", ins->dreg, inst_num));
807 last_use [idx] = inst_num;
808 }
809 } else {
810 if (last_use [idx] > 0) {
811 LIVENESS_DEBUG (printf ("\tadd range to R%d: [%x, %x)\n", ins->dreg, inst_num, last_use [idx]));
812 mono_linterval_add_range (cfg, vi->interval, inst_num, last_use [idx]);
813 last_use [idx] = 0;
814 }
815 else {
816 /* Try dead code elimination */
817 if (!cfg->disable_deadce_vars && (var != cfg->ret) && !(var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT)) && ((ins->opcode == OP_ICONST) || (ins->opcode == OP_I8CONST) || (ins->opcode == OP_R8CONST)) && !(var->flags & MONO_INST_VOLATILE)) {
818 LIVENESS_DEBUG (printf ("\tdead def of R%d, eliminated\n", ins->dreg));
819 NULLIFY_INS (ins);
820 return;
821 } else {
822 int inst_num_add = 1;
823 MonoInst *next = ins->next;
824 while (next && next->opcode == OP_IL_SEQ_POINT) {
825 inst_num_add++;
826 next = next->next;
827 }
828
829 LIVENESS_DEBUG (printf ("\tdead def of R%d, add range to R%d: [%x, %x]\n", ins->dreg, ins->dreg, inst_num, inst_num + inst_num_add));
830 mono_linterval_add_range (cfg, vi->interval, inst_num, inst_num + inst_num_add);
831 }
832 }
833 }
834 }
835
836 /* SREGs */
837 num_sregs = mono_inst_get_src_registers (ins, sregs);
838 for (i = 0; i < num_sregs; ++i) {
839 sreg = sregs [i];
840 if ((spec [MONO_INST_SRC1 + i] != ' ') && get_vreg_to_inst (cfg, sreg)) {
841 MonoInst *var = get_vreg_to_inst (cfg, sreg);
842 int idx = var->inst_c0;
843
844 if (last_use [idx] == 0) {
845 LIVENESS_DEBUG (printf ("\tlast use of R%d set to %x\n", sreg, inst_num));
846 last_use [idx] = inst_num;
847 }
848 }
849 }
850 }
851
852 static void
mono_analyze_liveness2(MonoCompile * cfg)853 mono_analyze_liveness2 (MonoCompile *cfg)
854 {
855 int bnum, idx, i, j, nins, max, max_vars, block_from, block_to, pos;
856 gint32 *last_use;
857 static guint32 disabled = -1;
858
859 if (disabled == -1)
860 disabled = g_hasenv ("DISABLED");
861
862 if (disabled)
863 return;
864
865 if (cfg->num_bblocks >= (1 << (32 - BB_ID_SHIFT - 1)))
866 /* Ranges would overflow */
867 return;
868
869 for (bnum = cfg->num_bblocks - 1; bnum >= 0; --bnum) {
870 MonoBasicBlock *bb = cfg->bblocks [bnum];
871 MonoInst *ins;
872
873 nins = 0;
874 for (nins = 0, ins = bb->code; ins; ins = ins->next, ++nins)
875 nins ++;
876
877 if (nins >= ((1 << BB_ID_SHIFT) - 1))
878 /* Ranges would overflow */
879 return;
880 }
881
882 LIVENESS_DEBUG (printf ("LIVENESS 2 %s\n", mono_method_full_name (cfg->method, TRUE)));
883
884 /*
885 if (strstr (cfg->method->name, "test_") != cfg->method->name)
886 return;
887 */
888
889 max_vars = cfg->num_varinfo;
890 last_use = g_new0 (gint32, max_vars);
891
892 for (idx = 0; idx < max_vars; ++idx) {
893 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
894
895 vi->interval = (MonoLiveInterval *)mono_mempool_alloc0 (cfg->mempool, sizeof (MonoLiveInterval));
896 }
897
898 /*
899 * Process bblocks in reverse order, so the addition of new live ranges
900 * to the intervals is faster.
901 */
902 for (bnum = cfg->num_bblocks - 1; bnum >= 0; --bnum) {
903 MonoBasicBlock *bb = cfg->bblocks [bnum];
904 MonoInst *ins;
905
906 block_from = (bb->dfn << BB_ID_SHIFT) + 1; /* so pos > 0 */
907 if (bnum < cfg->num_bblocks - 1)
908 /* Beginning of the next bblock */
909 block_to = (cfg->bblocks [bnum + 1]->dfn << BB_ID_SHIFT) + 1;
910 else
911 block_to = (bb->dfn << BB_ID_SHIFT) + ((1 << BB_ID_SHIFT) - 1);
912
913 LIVENESS_DEBUG (printf ("LIVENESS BLOCK BB%d:\n", bb->block_num));
914
915 memset (last_use, 0, max_vars * sizeof (gint32));
916
917 /* For variables in bb->live_out, set last_use to block_to */
918
919 max = ((max_vars + (BITS_PER_CHUNK -1)) / BITS_PER_CHUNK);
920 for (j = 0; j < max; ++j) {
921 gsize bits_out;
922 int k;
923
924 bits_out = mono_bitset_get_fast (bb->live_out_set, j);
925 k = (j * BITS_PER_CHUNK);
926 while (bits_out) {
927 if (bits_out & 1) {
928 LIVENESS_DEBUG (printf ("Var R%d live at exit, set last_use to %x\n", cfg->varinfo [k]->dreg, block_to));
929 last_use [k] = block_to;
930 }
931 bits_out >>= 1;
932 k ++;
933 }
934 }
935
936 if (cfg->ret)
937 last_use [cfg->ret->inst_c0] = block_to;
938
939 pos = block_from + 1;
940 MONO_BB_FOR_EACH_INS (bb, ins) pos++;
941
942 /* Process instructions backwards */
943 MONO_BB_FOR_EACH_INS_REVERSE (bb, ins) {
944 update_liveness2 (cfg, ins, FALSE, pos, last_use);
945 pos--;
946 }
947
948 for (idx = 0; idx < max_vars; ++idx) {
949 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
950
951 if (last_use [idx] != 0) {
952 /* Live at exit, not written -> live on enter */
953 LIVENESS_DEBUG (printf ("Var R%d live at enter, add range to R%d: [%x, %x)\n", cfg->varinfo [idx]->dreg, cfg->varinfo [idx]->dreg, block_from, last_use [idx]));
954 mono_linterval_add_range (cfg, vi->interval, block_from, last_use [idx]);
955 }
956 }
957 }
958
959 /*
960 * Arguments need to have their live ranges extended to the beginning of
961 * the method to account for the arg reg/memory -> global register copies
962 * in the prolog (bug #74992).
963 */
964 for (i = 0; i < max_vars; i ++) {
965 MonoMethodVar *vi = MONO_VARINFO (cfg, i);
966 if (cfg->varinfo [vi->idx]->opcode == OP_ARG)
967 mono_linterval_add_range (cfg, vi->interval, 0, 1);
968 }
969
970 #if 0
971 for (idx = 0; idx < max_vars; ++idx) {
972 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
973
974 LIVENESS_DEBUG (printf ("LIVENESS R%d: ", cfg->varinfo [idx]->dreg));
975 LIVENESS_DEBUG (mono_linterval_print (vi->interval));
976 LIVENESS_DEBUG (printf ("\n"));
977 }
978 #endif
979
980 g_free (last_use);
981 }
982
983 #endif
984
985 #define ALIGN_TO(val,align) ((((guint64)val) + ((align) - 1)) & ~((align) - 1))
986
987 static inline void
update_liveness_gc(MonoCompile * cfg,MonoBasicBlock * bb,MonoInst * ins,gint32 * last_use,MonoMethodVar ** vreg_to_varinfo,GSList ** callsites)988 update_liveness_gc (MonoCompile *cfg, MonoBasicBlock *bb, MonoInst *ins, gint32 *last_use, MonoMethodVar **vreg_to_varinfo, GSList **callsites)
989 {
990 if (ins->opcode == OP_GC_LIVENESS_DEF || ins->opcode == OP_GC_LIVENESS_USE) {
991 int vreg = ins->inst_c1;
992 MonoMethodVar *vi = vreg_to_varinfo [vreg];
993 int idx = vi->idx;
994 int pc_offset = ins->backend.pc_offset;
995
996 LIVENESS_DEBUG (printf ("\t%x: ", pc_offset); mono_print_ins (ins));
997
998 if (ins->opcode == OP_GC_LIVENESS_DEF) {
999 if (last_use [idx] > 0) {
1000 LIVENESS_DEBUG (printf ("\tadd range to R%d: [%x, %x)\n", vreg, pc_offset, last_use [idx]));
1001 last_use [idx] = 0;
1002 }
1003 } else {
1004 if (last_use [idx] == 0) {
1005 LIVENESS_DEBUG (printf ("\tlast use of R%d set to %x\n", vreg, pc_offset));
1006 last_use [idx] = pc_offset;
1007 }
1008 }
1009 } else if (ins->opcode == OP_GC_PARAM_SLOT_LIVENESS_DEF) {
1010 GCCallSite *last;
1011
1012 /* Add it to the last callsite */
1013 g_assert (*callsites);
1014 last = (GCCallSite *)(*callsites)->data;
1015 last->param_slots = g_slist_prepend_mempool (cfg->mempool, last->param_slots, ins);
1016 } else if (ins->flags & MONO_INST_GC_CALLSITE) {
1017 GCCallSite *callsite = (GCCallSite *)mono_mempool_alloc0 (cfg->mempool, sizeof (GCCallSite));
1018 int i;
1019
1020 LIVENESS_DEBUG (printf ("\t%x: ", ins->backend.pc_offset); mono_print_ins (ins));
1021 LIVENESS_DEBUG (printf ("\t\tlive: "));
1022
1023 callsite->bb = bb;
1024 callsite->liveness = (guint8 *)mono_mempool_alloc0 (cfg->mempool, ALIGN_TO (cfg->num_varinfo, 8) / 8);
1025 callsite->pc_offset = ins->backend.pc_offset;
1026 for (i = 0; i < cfg->num_varinfo; ++i) {
1027 if (last_use [i] != 0) {
1028 LIVENESS_DEBUG (printf ("R%d", MONO_VARINFO (cfg, i)->vreg));
1029 callsite->liveness [i / 8] |= (1 << (i % 8));
1030 }
1031 }
1032 LIVENESS_DEBUG (printf ("\n"));
1033 *callsites = g_slist_prepend_mempool (cfg->mempool, *callsites, callsite);
1034 }
1035 }
1036
1037 static inline int
get_vreg_from_var(MonoCompile * cfg,MonoInst * var)1038 get_vreg_from_var (MonoCompile *cfg, MonoInst *var)
1039 {
1040 if (var->opcode == OP_REGVAR)
1041 /* dreg contains a hreg, but inst_c0 still contains the var index */
1042 return MONO_VARINFO (cfg, var->inst_c0)->vreg;
1043 else
1044 /* dreg still contains the vreg */
1045 return var->dreg;
1046 }
1047
1048 /*
1049 * mono_analyze_liveness_gc:
1050 *
1051 * Compute liveness bitmaps for each call site.
1052 * This function is a modified version of mono_analyze_liveness2 ().
1053 */
1054 void
mono_analyze_liveness_gc(MonoCompile * cfg)1055 mono_analyze_liveness_gc (MonoCompile *cfg)
1056 {
1057 int idx, i, j, nins, max, max_vars, block_from, block_to, pos, reverse_len;
1058 gint32 *last_use;
1059 MonoInst **reverse;
1060 MonoMethodVar **vreg_to_varinfo = NULL;
1061 MonoBasicBlock *bb;
1062 GSList *callsites;
1063
1064 LIVENESS_DEBUG (printf ("\n------------ GC LIVENESS: ----------\n"));
1065
1066 max_vars = cfg->num_varinfo;
1067 last_use = g_new0 (gint32, max_vars);
1068
1069 /*
1070 * var->inst_c0 no longer contains the variable index, so compute a mapping now.
1071 */
1072 vreg_to_varinfo = g_new0 (MonoMethodVar*, cfg->next_vreg);
1073 for (idx = 0; idx < max_vars; ++idx) {
1074 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
1075
1076 vreg_to_varinfo [vi->vreg] = vi;
1077 }
1078
1079 reverse_len = 1024;
1080 reverse = (MonoInst **)mono_mempool_alloc (cfg->mempool, sizeof (MonoInst*) * reverse_len);
1081
1082 for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
1083 MonoInst *ins;
1084
1085 block_from = bb->real_native_offset;
1086 block_to = bb->native_offset + bb->native_length;
1087
1088 LIVENESS_DEBUG (printf ("GC LIVENESS BB%d:\n", bb->block_num));
1089
1090 if (!bb->code)
1091 continue;
1092
1093 memset (last_use, 0, max_vars * sizeof (gint32));
1094
1095 /* For variables in bb->live_out, set last_use to block_to */
1096
1097 max = ((max_vars + (BITS_PER_CHUNK -1)) / BITS_PER_CHUNK);
1098 for (j = 0; j < max; ++j) {
1099 gsize bits_out;
1100 int k;
1101
1102 if (!bb->live_out_set)
1103 /* The variables used in this bblock are volatile anyway */
1104 continue;
1105
1106 bits_out = mono_bitset_get_fast (bb->live_out_set, j);
1107 k = (j * BITS_PER_CHUNK);
1108 while (bits_out) {
1109 if ((bits_out & 1) && cfg->varinfo [k]->flags & MONO_INST_GC_TRACK) {
1110 int vreg = get_vreg_from_var (cfg, cfg->varinfo [k]);
1111 LIVENESS_DEBUG (printf ("Var R%d live at exit, last_use set to %x.\n", vreg, block_to));
1112 last_use [k] = block_to;
1113 }
1114 bits_out >>= 1;
1115 k ++;
1116 }
1117 }
1118
1119 for (nins = 0, pos = block_from, ins = bb->code; ins; ins = ins->next, ++nins, ++pos) {
1120 if (nins >= reverse_len) {
1121 int new_reverse_len = reverse_len * 2;
1122 MonoInst **new_reverse = (MonoInst **)mono_mempool_alloc (cfg->mempool, sizeof (MonoInst*) * new_reverse_len);
1123 memcpy (new_reverse, reverse, sizeof (MonoInst*) * reverse_len);
1124 reverse = new_reverse;
1125 reverse_len = new_reverse_len;
1126 }
1127
1128 reverse [nins] = ins;
1129 }
1130
1131 /* Process instructions backwards */
1132 callsites = NULL;
1133 for (i = nins - 1; i >= 0; --i) {
1134 MonoInst *ins = (MonoInst*)reverse [i];
1135
1136 update_liveness_gc (cfg, bb, ins, last_use, vreg_to_varinfo, &callsites);
1137 }
1138 /* The callsites should already be sorted by pc offset because we added them backwards */
1139 bb->gc_callsites = callsites;
1140 }
1141
1142 g_free (last_use);
1143 g_free (vreg_to_varinfo);
1144 }
1145
1146 #else /* !DISABLE_JIT */
1147
1148 MONO_EMPTY_SOURCE_FILE (liveness);
1149
1150 #endif /* !DISABLE_JIT */
1151