mono/mini/liveness.c

   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
  41 #define INLINE_SIZE 16
  42
  43 typedef struct {
  44         int capacity;
  45         gpointer data [INLINE_SIZE];
  46 } MonoPtrSet;
  47
  48 static void
  49 mono_ptrset_init (MonoPtrSet *set)
  50 {
  51         set->capacity = 0;
  52 }
  53
  54 static void
  55 mono_ptrset_destroy (MonoPtrSet *set)
  56 {
  57         if (set->capacity > INLINE_SIZE)
  58                 g_hash_table_destroy (set->data [0]);
  59 }
  60
  61 static void
  62 mono_ptrset_add (MonoPtrSet *set, gpointer val)
  63 {
  64         //switch to hashtable
  65         if (set->capacity == INLINE_SIZE) {
  66                 GHashTable *tmp = g_hash_table_new (NULL, NULL);
  67                 for (int i = 0; i < INLINE_SIZE; ++i)
  68                         g_hash_table_insert (tmp, set->data [i], set->data [i]);
  69                 set->data [0] = tmp;
  70                 ++set->capacity;
  71         }
  72
  73         if (set->capacity > INLINE_SIZE) {
  74                 g_hash_table_insert (set->data [0], val, val);
  75         } else {
  76                 set->data [set->capacity] = val;
  77                 ++set->capacity;
  78         }
  79 }
  80
  81 static gboolean
  82 mono_ptrset_contains (MonoPtrSet *set, gpointer val)
  83 {
  84         if (set->capacity <= INLINE_SIZE) {
  85                 for (int i = 0; i < set->capacity; ++i) {
  86                         if (set->data [i] == val)
  87                                 return TRUE;
  88                 }
  89                 return FALSE;
  90         }
  91
  92         return g_hash_table_lookup (set->data [0], val) != NULL;
  93 }
  94
  95
  96 static void
  97 optimize_initlocals (MonoCompile *cfg);
  98
  99 /* mono_bitset_mp_new:
 100  *
 101  * allocates a MonoBitSet inside a memory pool
 102  */
 103 static inline MonoBitSet*
 104 mono_bitset_mp_new (MonoMemPool *mp, guint32 size, guint32 max_size)
 105 {
 106         guint8 *mem = (guint8 *)mono_mempool_alloc0 (mp, size);
 107         return mono_bitset_mem_new (mem, max_size, MONO_BITSET_DONT_FREE);
 108 }
 109
 110 static inline MonoBitSet*
 111 mono_bitset_mp_new_noinit (MonoMemPool *mp, guint32 size, guint32 max_size)
 112 {
 113         guint8 *mem = (guint8 *)mono_mempool_alloc (mp, size);
 114         return mono_bitset_mem_new (mem, max_size, MONO_BITSET_DONT_FREE);
 115 }
 116
 117 G_GNUC_UNUSED static void
 118 mono_bitset_print (MonoBitSet *set)
 119 {
 120         int i;
 121         gboolean first = TRUE;
 122
 123         printf ("{");
 124         for (i = 0; i < mono_bitset_size (set); i++) {
 125
 126                 if (mono_bitset_test (set, i)) {
 127                         if (!first)
 128                                 printf (", ");
 129                         printf ("%d", i);
 130                         first = FALSE;
 131                 }
 132         }
 133         printf ("}\n");
 134 }
 135
 136 static void
 137 visit_bb (MonoCompile *cfg, MonoBasicBlock *bb, MonoPtrSet *visited)
 138 {
 139         int i;
 140         MonoInst *ins;
 141
 142         if (mono_ptrset_contains (visited, bb))
 143                 return;
 144
 145         for (ins = bb->code; ins; ins = ins->next) {
 146                 const char *spec = INS_INFO (ins->opcode);
 147                 int regtype, srcindex, sreg, num_sregs;
 148                 int sregs [MONO_MAX_SRC_REGS];
 149
 150                 if (ins->opcode == OP_NOP)
 151                         continue;
 152
 153                 /* DREG */
 154                 regtype = spec [MONO_INST_DEST];
 155                 g_assert (((ins->dreg == -1) && (regtype == ' ')) || ((ins->dreg != -1) && (regtype != ' ')));
 156
 157                 if ((ins->dreg != -1) && get_vreg_to_inst (cfg, ins->dreg)) {
 158                         MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 159                         int idx = var->inst_c0;
 160                         MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 161
 162                         cfg->varinfo [vi->idx]->flags |= MONO_INST_VOLATILE;
 163                         if (SIZEOF_REGISTER == 4 && (var->type == STACK_I8 || (var->type == STACK_R8 && COMPILE_SOFT_FLOAT (cfg)))) {
 164                                 /* Make the component vregs volatile as well (#612206) */
 165                                 get_vreg_to_inst (cfg, MONO_LVREG_LS (var->dreg))->flags |= MONO_INST_VOLATILE;
 166                                 get_vreg_to_inst (cfg, MONO_LVREG_MS (var->dreg))->flags |= MONO_INST_VOLATILE;
 167                         }
 168                 }
 169
 170                 /* SREGS */
 171                 num_sregs = mono_inst_get_src_registers (ins, sregs);
 172                 for (srcindex = 0; srcindex < num_sregs; ++srcindex) {
 173                         sreg = sregs [srcindex];
 174
 175                         g_assert (sreg != -1);
 176                         if (get_vreg_to_inst (cfg, sreg)) {
 177                                 MonoInst *var = get_vreg_to_inst (cfg, sreg);
 178                                 int idx = var->inst_c0;
 179                                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 180
 181                                 cfg->varinfo [vi->idx]->flags |= MONO_INST_VOLATILE;
 182                                 if (SIZEOF_REGISTER == 4 && (var->type == STACK_I8 || (var->type == STACK_R8 && COMPILE_SOFT_FLOAT (cfg)))) {
 183                                         /* Make the component vregs volatile as well (#612206) */
 184                                         get_vreg_to_inst (cfg, MONO_LVREG_LS (var->dreg))->flags |= MONO_INST_VOLATILE;
 185                                         get_vreg_to_inst (cfg, MONO_LVREG_MS (var->dreg))->flags |= MONO_INST_VOLATILE;
 186                                 }
 187                         }
 188                 }
 189         }
 190
 191         mono_ptrset_add (visited, bb);
 192
 193         /*
 194          * Need to visit all bblocks reachable from this one since they can be
 195          * reached during exception handling.
 196          */
 197         for (i = 0; i < bb->out_count; ++i) {
 198                 visit_bb (cfg, bb->out_bb [i], visited);
 199         }
 200 }
 201
 202 void
 203 mono_liveness_handle_exception_clauses (MonoCompile *cfg)
 204 {
 205         MonoBasicBlock *bb;
 206         MonoMethodHeader *header = cfg->header;
 207         MonoExceptionClause *clause, *clause2;
 208         int i, j;
 209         gboolean *outer_try;
 210
 211         /*
 212          * Determine which clauses are outer try clauses, i.e. they are not contained in any
 213          * other non-try clause.
 214          */
 215         outer_try = (gboolean *)mono_mempool_alloc0 (cfg->mempool, sizeof (gboolean) * header->num_clauses);
 216         for (i = 0; i < header->num_clauses; ++i)
 217                 outer_try [i] = TRUE;
 218         /* Iterate over the clauses backward, so outer clauses come first */
 219         /* This avoids doing an O(2) search, since we can determine when inner clauses end */
 220         for (i = header->num_clauses - 1; i >= 0; --i) {
 221                 clause = &header->clauses [i];
 222
 223                 if (clause->flags != 0) {
 224                         outer_try [i] = TRUE;
 225                         /* Iterate over inner clauses */
 226                         for (j = i - 1; j >= 0; --j) {
 227                                 clause2 = &header->clauses [j];
 228
 229                                 if (clause2->flags == 0 && MONO_OFFSET_IN_HANDLER (clause, clause2->try_offset)) {
 230                                         outer_try [j] = FALSE;
 231                                         break;
 232                                 }
 233                                 if (clause2->try_offset < clause->try_offset)
 234                                         /* End of inner clauses */
 235                                         break;
 236                         }
 237                 }
 238         }
 239
 240         MonoPtrSet visited;
 241         mono_ptrset_init (&visited);
 242         /*
 243          * Variables in exception handler register cannot be allocated to registers
 244          * so make them volatile. See bug #42136. This will not be neccessary when
 245          * the back ends could guarantee that the variables will be in the
 246          * correct registers when a handler is called.
 247          * This includes try blocks too, since a variable in a try block might be
 248          * accessed after an exception handler has been run.
 249          */
 250         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
 251
 252                 if (bb->region == -1)
 253                         continue;
 254
 255                 if (MONO_BBLOCK_IS_IN_REGION (bb, MONO_REGION_TRY) && outer_try [MONO_REGION_CLAUSE_INDEX (bb->region)])
 256                         continue;
 257
 258                 if (cfg->verbose_level > 2)
 259                         printf ("pessimize variables in bb %d.\n", bb->block_num);
 260
 261                 visit_bb (cfg, bb, &visited);
 262         }
 263         mono_ptrset_destroy (&visited);
 264 }
 265
 266 static inline void
 267 update_live_range (MonoMethodVar *var, int abs_pos)
 268 {
 269         if (var->range.first_use.abs_pos > abs_pos)
 270                 var->range.first_use.abs_pos = abs_pos;
 271
 272         if (var->range.last_use.abs_pos < abs_pos)
 273                 var->range.last_use.abs_pos = abs_pos;
 274 }
 275
 276 static void
 277 analyze_liveness_bb (MonoCompile *cfg, MonoBasicBlock *bb)
 278 {
 279         MonoInst *ins;
 280         int sreg, inst_num;
 281         MonoMethodVar *vars = cfg->vars;
 282         guint32 abs_pos = (bb->dfn << BB_ID_SHIFT);
 283
 284         /* Start inst_num from > 0, so last_use.abs_pos is only 0 for dead variables */
 285         for (inst_num = 2, ins = bb->code; ins; ins = ins->next, inst_num += 2) {
 286                 const char *spec = INS_INFO (ins->opcode);
 287                 int num_sregs, i;
 288                 int sregs [MONO_MAX_SRC_REGS];
 289
 290 #ifdef DEBUG_LIVENESS
 291                 if (cfg->verbose_level > 1) {
 292                         mono_print_ins_index (1, ins);
 293                 }
 294 #endif
 295
 296                 if (ins->opcode == OP_NOP)
 297                         continue;
 298
 299                 if (ins->opcode == OP_LDADDR) {
 300                         MonoInst *var = (MonoInst *)ins->inst_p0;
 301                         int idx = var->inst_c0;
 302                         MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 303
 304 #ifdef DEBUG_LIVENESS
 305                         if (cfg->verbose_level > 1)
 306                                 printf ("\tGEN: R%d(%d)\n", var->dreg, idx);
 307 #endif
 308                         update_live_range (&vars [idx], abs_pos + inst_num);
 309                         if (!mono_bitset_test_fast (bb->kill_set, idx))
 310                                 mono_bitset_set_fast (bb->gen_set, idx);
 311                         vi->spill_costs += SPILL_COST_INCREMENT;
 312                 }
 313
 314                 /* SREGs must come first, so MOVE r <- r is handled correctly */
 315                 num_sregs = mono_inst_get_src_registers (ins, sregs);
 316                 for (i = 0; i < num_sregs; ++i) {
 317                         sreg = sregs [i];
 318                         if ((spec [MONO_INST_SRC1 + i] != ' ') && get_vreg_to_inst (cfg, sreg)) {
 319                                 MonoInst *var = get_vreg_to_inst (cfg, sreg);
 320                                 int idx = var->inst_c0;
 321                                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 322
 323 #ifdef DEBUG_LIVENESS
 324                                 if (cfg->verbose_level > 1)
 325                                         printf ("\tGEN: R%d(%d)\n", sreg, idx);
 326 #endif
 327                                 update_live_range (&vars [idx], abs_pos + inst_num);
 328                                 if (!mono_bitset_test_fast (bb->kill_set, idx))
 329                                         mono_bitset_set_fast (bb->gen_set, idx);
 330                                 vi->spill_costs += SPILL_COST_INCREMENT;
 331                         }
 332                 }
 333
 334                 /* DREG */
 335                 if ((spec [MONO_INST_DEST] != ' ') && get_vreg_to_inst (cfg, ins->dreg)) {
 336                         MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 337                         int idx = var->inst_c0;
 338                         MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 339
 340                         if (MONO_IS_STORE_MEMBASE (ins)) {
 341                                 update_live_range (&vars [idx], abs_pos + inst_num);
 342                                 if (!mono_bitset_test_fast (bb->kill_set, idx))
 343                                         mono_bitset_set_fast (bb->gen_set, idx);
 344                                 vi->spill_costs += SPILL_COST_INCREMENT;
 345                         } else {
 346 #ifdef DEBUG_LIVENESS
 347                                 if (cfg->verbose_level > 1)
 348                                         printf ("\tKILL: R%d(%d)\n", ins->dreg, idx);
 349 #endif
 350                                 update_live_range (&vars [idx], abs_pos + inst_num + 1);
 351                                 mono_bitset_set_fast (bb->kill_set, idx);
 352                                 vi->spill_costs += SPILL_COST_INCREMENT;
 353                         }
 354                 }
 355         }
 356 }
 357
 358 /* generic liveness analysis code. CFG specific parts are
 359  * in update_gen_kill_set()
 360  */
 361 void
 362 mono_analyze_liveness (MonoCompile *cfg)
 363 {
 364         MonoBitSet *old_live_out_set;
 365         int i, j, max_vars = cfg->num_varinfo;
 366         int out_iter;
 367         gboolean *in_worklist;
 368         MonoBasicBlock **worklist;
 369         guint32 l_end;
 370         int bitsize;
 371
 372 #ifdef DEBUG_LIVENESS
 373         if (cfg->verbose_level > 1)
 374                 printf ("\nLIVENESS:\n");
 375 #endif
 376
 377         g_assert (!(cfg->comp_done & MONO_COMP_LIVENESS));
 378
 379         cfg->comp_done |= MONO_COMP_LIVENESS;
 380
 381         if (max_vars == 0)
 382                 return;
 383
 384         bitsize = mono_bitset_alloc_size (max_vars, 0);
 385
 386         for (i = 0; i < max_vars; i ++) {
 387                 MONO_VARINFO (cfg, i)->range.first_use.abs_pos = ~ 0;
 388                 MONO_VARINFO (cfg, i)->range.last_use .abs_pos =   0;
 389                 MONO_VARINFO (cfg, i)->spill_costs = 0;
 390         }
 391
 392         for (i = 0; i < cfg->num_bblocks; ++i) {
 393                 MonoBasicBlock *bb = cfg->bblocks [i];
 394
 395                 bb->gen_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
 396                 bb->kill_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
 397
 398 #ifdef DEBUG_LIVENESS
 399                 if (cfg->verbose_level > 1) {
 400                         printf ("BLOCK BB%d (", bb->block_num);
 401                         for (j = 0; j < bb->out_count; j++)
 402                                 printf ("BB%d, ", bb->out_bb [j]->block_num);
 403
 404                         printf ("):\n");
 405                 }
 406 #endif
 407
 408                 analyze_liveness_bb (cfg, bb);
 409
 410 #ifdef DEBUG_LIVENESS
 411                 if (cfg->verbose_level > 1) {
 412                         printf ("GEN  BB%d: ", bb->block_num); mono_bitset_print (bb->gen_set);
 413                         printf ("KILL BB%d: ", bb->block_num); mono_bitset_print (bb->kill_set);
 414                 }
 415 #endif
 416         }
 417
 418         old_live_out_set = mono_bitset_new (max_vars, 0);
 419         in_worklist = g_new0 (gboolean, cfg->num_bblocks + 1);
 420
 421         worklist = g_new (MonoBasicBlock *, cfg->num_bblocks + 1);
 422         l_end = 0;
 423
 424         /*
 425          * This is a backward dataflow analysis problem, so we process blocks in
 426          * decreasing dfn order, this speeds up the iteration.
 427          */
 428         for (i = 0; i < cfg->num_bblocks; i ++) {
 429                 MonoBasicBlock *bb = cfg->bblocks [i];
 430
 431                 worklist [l_end ++] = bb;
 432                 in_worklist [bb->dfn] = TRUE;
 433
 434                 /* Initialized later */
 435                 bb->live_in_set = NULL;
 436                 bb->live_out_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
 437         }
 438
 439         out_iter = 0;
 440
 441         if (cfg->verbose_level > 1)
 442                 printf ("\nITERATION:\n");
 443
 444         while (l_end != 0) {
 445                 MonoBasicBlock *bb = worklist [--l_end];
 446                 MonoBasicBlock *out_bb;
 447                 gboolean changed;
 448
 449                 in_worklist [bb->dfn] = FALSE;
 450
 451 #ifdef DEBUG_LIVENESS
 452                 if (cfg->verbose_level > 1) {
 453                         printf ("P: BB%d(%d): IN: ", bb->block_num, bb->dfn);
 454                         for (j = 0; j < bb->in_count; ++j)
 455                                 printf ("BB%d ", bb->in_bb [j]->block_num);
 456                         printf ("OUT:");
 457                         for (j = 0; j < bb->out_count; ++j)
 458                                 printf ("BB%d ", bb->out_bb [j]->block_num);
 459                         printf ("\n");
 460                 }
 461 #endif
 462
 463
 464                 if (bb->out_count == 0)
 465                         continue;
 466
 467                 out_iter ++;
 468
 469                 if (!bb->live_in_set) {
 470                         /* First pass over this bblock */
 471                         changed = TRUE;
 472                 }
 473                 else {
 474                         changed = FALSE;
 475                         mono_bitset_copyto_fast (bb->live_out_set, old_live_out_set);
 476                 }
 477
 478                 for (j = 0; j < bb->out_count; j++) {
 479                         out_bb = bb->out_bb [j];
 480
 481                         if (!out_bb->live_in_set) {
 482                                 out_bb->live_in_set = mono_bitset_mp_new_noinit (cfg->mempool, bitsize, max_vars);
 483
 484                                 mono_bitset_copyto_fast (out_bb->live_out_set, out_bb->live_in_set);
 485                                 mono_bitset_sub_fast (out_bb->live_in_set, out_bb->kill_set);
 486                                 mono_bitset_union_fast (out_bb->live_in_set, out_bb->gen_set);
 487                         }
 488
 489                         // FIXME: Do this somewhere else
 490                         if (bb->last_ins && bb->last_ins->opcode == OP_NOT_REACHED) {
 491                         } else {
 492                                 mono_bitset_union_fast (bb->live_out_set, out_bb->live_in_set);
 493                         }
 494                 }
 495
 496                 if (changed || !mono_bitset_equal (old_live_out_set, bb->live_out_set)) {
 497                         if (!bb->live_in_set)
 498                                 bb->live_in_set = mono_bitset_mp_new_noinit (cfg->mempool, bitsize, max_vars);
 499                         mono_bitset_copyto_fast (bb->live_out_set, bb->live_in_set);
 500                         mono_bitset_sub_fast (bb->live_in_set, bb->kill_set);
 501                         mono_bitset_union_fast (bb->live_in_set, bb->gen_set);
 502
 503                         for (j = 0; j < bb->in_count; j++) {
 504                                 MonoBasicBlock *in_bb = bb->in_bb [j];
 505                                 /*
 506                                  * Some basic blocks do not seem to be in the
 507                                  * cfg->bblocks array...
 508                                  */
 509                                 if (in_bb->gen_set && !in_worklist [in_bb->dfn]) {
 510 #ifdef DEBUG_LIVENESS
 511                                         if (cfg->verbose_level > 1)
 512                                                 printf ("\tADD: %d\n", in_bb->block_num);
 513 #endif
 514                                         /*
 515                                          * Put the block at the top of the stack, so it
 516                                          * will be processed right away.
 517                                          */
 518                                         worklist [l_end ++] = in_bb;
 519                                         in_worklist [in_bb->dfn] = TRUE;
 520                                 }
 521                         }
 522                 }
 523
 524                 if (G_UNLIKELY (cfg->verbose_level > 1)) {
 525                         printf ("\tLIVE IN  BB%d: ", bb->block_num);
 526                         mono_bitset_print (bb->live_in_set);
 527                 }
 528         }
 529
 530 #ifdef DEBUG_LIVENESS
 531         if (cfg->verbose_level > 1)
 532                 printf ("IT: %d %d.\n", cfg->num_bblocks, out_iter);
 533 #endif
 534
 535         mono_bitset_free (old_live_out_set);
 536
 537         g_free (worklist);
 538         g_free (in_worklist);
 539
 540         /* Compute live_in_set for bblocks skipped earlier */
 541         for (i = 0; i < cfg->num_bblocks; ++i) {
 542                 MonoBasicBlock *bb = cfg->bblocks [i];
 543
 544                 if (!bb->live_in_set) {
 545                         bb->live_in_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
 546
 547                         mono_bitset_copyto_fast (bb->live_out_set, bb->live_in_set);
 548                         mono_bitset_sub_fast (bb->live_in_set, bb->kill_set);
 549                         mono_bitset_union_fast (bb->live_in_set, bb->gen_set);
 550                 }
 551         }
 552
 553         for (i = 0; i < cfg->num_bblocks; ++i) {
 554                 MonoBasicBlock *bb = cfg->bblocks [i];
 555                 guint32 max;
 556                 guint32 abs_pos = (bb->dfn << BB_ID_SHIFT);
 557                 MonoMethodVar *vars = cfg->vars;
 558
 559                 if (!bb->live_out_set)
 560                         continue;
 561
 562                 max = ((max_vars + (BITS_PER_CHUNK -1)) / BITS_PER_CHUNK);
 563                 for (j = 0; j < max; ++j) {
 564                         gsize bits_in;
 565                         gsize bits_out;
 566                         int k;
 567
 568                         bits_in = mono_bitset_get_fast (bb->live_in_set, j);
 569                         bits_out = mono_bitset_get_fast (bb->live_out_set, j);
 570
 571                         k = (j * BITS_PER_CHUNK);
 572                         while ((bits_in || bits_out)) {
 573                                 if (bits_in & 1)
 574                                         update_live_range (&vars [k], abs_pos + 0);
 575                                 if (bits_out & 1)
 576                                         update_live_range (&vars [k], abs_pos + ((1 << BB_ID_SHIFT) - 1));
 577                                 bits_in >>= 1;
 578                                 bits_out >>= 1;
 579                                 k ++;
 580                         }
 581                 }
 582         }
 583
 584         /*
 585          * Arguments need to have their live ranges extended to the beginning of
 586          * the method to account for the arg reg/memory -> global register copies
 587          * in the prolog (bug #74992).
 588          */
 589
 590         for (i = 0; i < max_vars; i ++) {
 591                 MonoMethodVar *vi = MONO_VARINFO (cfg, i);
 592                 if (cfg->varinfo [vi->idx]->opcode == OP_ARG) {
 593                         if (vi->range.last_use.abs_pos == 0 && !(cfg->varinfo [vi->idx]->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT))) {
 594                                 /*
 595                                  * Can't eliminate the this variable in gshared code, since
 596                                  * it is needed during exception handling to identify the
 597                                  * method.
 598                                  * It is better to check for this here instead of marking the variable
 599                                  * VOLATILE, since that would prevent it from being allocated to
 600                                  * registers.
 601                                  */
 602                                  if (!cfg->disable_deadce_vars && !(cfg->gshared && mono_method_signature (cfg->method)->hasthis && cfg->varinfo [vi->idx] == cfg->args [0]))
 603                                          cfg->varinfo [vi->idx]->flags |= MONO_INST_IS_DEAD;
 604                         }
 605                         vi->range.first_use.abs_pos = 0;
 606                 }
 607         }
 608
 609 #ifdef DEBUG_LIVENESS
 610         if (cfg->verbose_level > 1) {
 611                 for (i = cfg->num_bblocks - 1; i >= 0; i--) {
 612                         MonoBasicBlock *bb = cfg->bblocks [i];
 613
 614                         printf ("LIVE IN  BB%d: ", bb->block_num);
 615                         mono_bitset_print (bb->live_in_set);
 616                         printf ("LIVE OUT BB%d: ", bb->block_num);
 617                         mono_bitset_print (bb->live_out_set);
 618                 }
 619
 620                 for (i = 0; i < max_vars; i ++) {
 621                         MonoMethodVar *vi = MONO_VARINFO (cfg, i);
 622
 623                         printf ("V%d: [0x%x - 0x%x]\n", i, vi->range.first_use.abs_pos, vi->range.last_use.abs_pos);
 624                 }
 625         }
 626 #endif
 627
 628         if (!cfg->disable_initlocals_opt)
 629                 optimize_initlocals (cfg);
 630
 631 #ifdef ENABLE_LIVENESS2
 632         /* This improves code size by about 5% but slows down compilation too much */
 633         if (cfg->compile_aot)
 634                 mono_analyze_liveness2 (cfg);
 635 #endif
 636 }
 637
 638 /**
 639  * optimize_initlocals:
 640  *
 641  * Try to optimize away some of the redundant initialization code inserted because of
 642  * 'locals init' using the liveness information.
 643  */
 644 static void
 645 optimize_initlocals (MonoCompile *cfg)
 646 {
 647         MonoBitSet *used;
 648         MonoInst *ins;
 649         MonoBasicBlock *initlocals_bb;
 650
 651         used = mono_bitset_new (cfg->next_vreg + 1, 0);
 652
 653         mono_bitset_clear_all (used);
 654         initlocals_bb = cfg->bb_entry->next_bb;
 655         for (ins = initlocals_bb->code; ins; ins = ins->next) {
 656                 int num_sregs, i;
 657                 int sregs [MONO_MAX_SRC_REGS];
 658
 659                 num_sregs = mono_inst_get_src_registers (ins, sregs);
 660                 for (i = 0; i < num_sregs; ++i)
 661                         mono_bitset_set_fast (used, sregs [i]);
 662
 663                 if (MONO_IS_STORE_MEMBASE (ins))
 664                         mono_bitset_set_fast (used, ins->dreg);
 665         }
 666
 667         for (ins = initlocals_bb->code; ins; ins = ins->next) {
 668                 const char *spec = INS_INFO (ins->opcode);
 669
 670                 /* Look for statements whose dest is not used in this bblock and not live on exit. */
 671                 if ((spec [MONO_INST_DEST] != ' ') && !MONO_IS_STORE_MEMBASE (ins)) {
 672                         MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 673
 674                         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))) {
 675                                 //printf ("DEAD: "); mono_print_ins (ins);
 676                                 if (cfg->disable_initlocals_opt_refs && var->type == STACK_OBJ)
 677                                         continue;
 678                                 if ((ins->opcode == OP_ICONST) || (ins->opcode == OP_I8CONST) || (ins->opcode == OP_R8CONST) || (ins->opcode == OP_R4CONST)) {
 679                                         NULLIFY_INS (ins);
 680                                         MONO_VARINFO (cfg, var->inst_c0)->spill_costs -= 1;
 681                                         /*
 682                                          * We should shorten the liveness interval of these vars as well, but
 683                                          * don't have enough info to do that.
 684                                          */
 685                                 }
 686                         }
 687                 }
 688         }
 689
 690         g_free (used);
 691 }
 692
 693 void
 694 mono_linterval_add_range (MonoCompile *cfg, MonoLiveInterval *interval, int from, int to)
 695 {
 696         MonoLiveRange2 *prev_range, *next_range, *new_range;
 697
 698         g_assert (to >= from);
 699
 700         /* Optimize for extending the first interval backwards */
 701         if (G_LIKELY (interval->range && (interval->range->from > from) && (interval->range->from == to))) {
 702                 interval->range->from = from;
 703                 return;
 704         }
 705
 706         /* Find a place in the list for the new range */
 707         prev_range = NULL;
 708         next_range = interval->range;
 709         while ((next_range != NULL) && (next_range->from <= from)) {
 710                 prev_range = next_range;
 711                 next_range = next_range->next;
 712         }
 713
 714         if (prev_range && prev_range->to == from) {
 715                 /* Merge with previous */
 716                 prev_range->to = to;
 717         } else if (next_range && next_range->from == to) {
 718                 /* Merge with previous */
 719                 next_range->from = from;
 720         } else {
 721                 /* Insert it */
 722                 new_range = (MonoLiveRange2 *)mono_mempool_alloc (cfg->mempool, sizeof (MonoLiveRange2));
 723                 new_range->from = from;
 724                 new_range->to = to;
 725                 new_range->next = NULL;
 726
 727                 if (prev_range)
 728                         prev_range->next = new_range;
 729                 else
 730                         interval->range = new_range;
 731                 if (next_range)
 732                         new_range->next = next_range;
 733                 else
 734                         interval->last_range = new_range;
 735         }
 736
 737         /* FIXME: Merge intersecting ranges */
 738 }
 739
 740 void
 741 mono_linterval_print (MonoLiveInterval *interval)
 742 {
 743         MonoLiveRange2 *range;
 744
 745         for (range = interval->range; range != NULL; range = range->next)
 746                 printf ("[%x-%x] ", range->from, range->to);
 747 }
 748
 749 void
 750 mono_linterval_print_nl (MonoLiveInterval *interval)
 751 {
 752         mono_linterval_print (interval);
 753         printf ("\n");
 754 }
 755
 756 /**
 757  * mono_linterval_convers:
 758  *
 759  *   Return whenever INTERVAL covers the position POS.
 760  */
 761 gboolean
 762 mono_linterval_covers (MonoLiveInterval *interval, int pos)
 763 {
 764         MonoLiveRange2 *range;
 765
 766         for (range = interval->range; range != NULL; range = range->next) {
 767                 if (pos >= range->from && pos <= range->to)
 768                         return TRUE;
 769                 if (range->from > pos)
 770                         return FALSE;
 771         }
 772
 773         return FALSE;
 774 }
 775
 776 /**
 777  * mono_linterval_get_intersect_pos:
 778  *
 779  *   Determine whenever I1 and I2 intersect, and if they do, return the first
 780  * point of intersection. Otherwise, return -1.
 781  */
 782 gint32
 783 mono_linterval_get_intersect_pos (MonoLiveInterval *i1, MonoLiveInterval *i2)
 784 {
 785         MonoLiveRange2 *r1, *r2;
 786
 787         /* FIXME: Optimize this */
 788         for (r1 = i1->range; r1 != NULL; r1 = r1->next) {
 789                 for (r2 = i2->range; r2 != NULL; r2 = r2->next) {
 790                         if (r2->to > r1->from && r2->from < r1->to) {
 791                                 if (r2->from <= r1->from)
 792                                         return r1->from;
 793                                 else
 794                                         return r2->from;
 795                         }
 796                 }
 797         }
 798
 799         return -1;
 800 }
 801
 802 /**
 803  * mono_linterval_split
 804  *
 805  *   Split L at POS and store the newly created intervals into L1 and L2. POS becomes
 806  * part of L2.
 807  */
 808 void
 809 mono_linterval_split (MonoCompile *cfg, MonoLiveInterval *interval, MonoLiveInterval **i1, MonoLiveInterval **i2, int pos)
 810 {
 811         MonoLiveRange2 *r;
 812
 813         g_assert (pos > interval->range->from && pos <= interval->last_range->to);
 814
 815         *i1 = (MonoLiveInterval *)mono_mempool_alloc0 (cfg->mempool, sizeof (MonoLiveInterval));
 816         *i2 = (MonoLiveInterval *)mono_mempool_alloc0 (cfg->mempool, sizeof (MonoLiveInterval));
 817
 818         for (r = interval->range; r; r = r->next) {
 819                 if (pos > r->to) {
 820                         /* Add it to the first child */
 821                         mono_linterval_add_range (cfg, *i1, r->from, r->to);
 822                 } else if (pos > r->from && pos <= r->to) {
 823                         /* Split at pos */
 824                         mono_linterval_add_range (cfg, *i1, r->from, pos - 1);
 825                         mono_linterval_add_range (cfg, *i2, pos, r->to);
 826                 } else {
 827                         /* Add it to the second child */
 828                         mono_linterval_add_range (cfg, *i2, r->from, r->to);
 829                 }
 830         }
 831 }
 832
 833 #if 1
 834 #define LIVENESS_DEBUG(a) do { if (cfg->verbose_level > 1) do { a; } while (0); } while (0)
 835 #define ENABLE_LIVENESS_DEBUG 1
 836 #else
 837 #define LIVENESS_DEBUG(a)
 838 #endif
 839
 840 #ifdef ENABLE_LIVENESS2
 841
 842 static inline void
 843 update_liveness2 (MonoCompile *cfg, MonoInst *ins, gboolean set_volatile, int inst_num, gint32 *last_use)
 844 {
 845         const char *spec = INS_INFO (ins->opcode);
 846         int sreg;
 847         int num_sregs, i;
 848         int sregs [MONO_MAX_SRC_REGS];
 849
 850         LIVENESS_DEBUG (printf ("\t%x: ", inst_num); mono_print_ins (ins));
 851
 852         if (ins->opcode == OP_NOP || ins->opcode == OP_IL_SEQ_POINT)
 853                 return;
 854
 855         /* DREG */
 856         if ((spec [MONO_INST_DEST] != ' ') && get_vreg_to_inst (cfg, ins->dreg)) {
 857                 MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 858                 int idx = var->inst_c0;
 859                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 860
 861                 if (MONO_IS_STORE_MEMBASE (ins)) {
 862                         if (last_use [idx] == 0) {
 863                                 LIVENESS_DEBUG (printf ("\tlast use of R%d set to %x\n", ins->dreg, inst_num));
 864                                 last_use [idx] = inst_num;
 865                         }
 866                 } else {
 867                         if (last_use [idx] > 0) {
 868                                 LIVENESS_DEBUG (printf ("\tadd range to R%d: [%x, %x)\n", ins->dreg, inst_num, last_use [idx]));
 869                                 mono_linterval_add_range (cfg, vi->interval, inst_num, last_use [idx]);
 870                                 last_use [idx] = 0;
 871                         }
 872                         else {
 873                                 /* Try dead code elimination */
 874                                 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)) {
 875                                         LIVENESS_DEBUG (printf ("\tdead def of R%d, eliminated\n", ins->dreg));
 876                                         NULLIFY_INS (ins);
 877                                         return;
 878                                 } else {
 879                                         int inst_num_add = 1;
 880                                         MonoInst *next = ins->next;
 881                                         while (next && next->opcode == OP_IL_SEQ_POINT) {
 882                                                 inst_num_add++;
 883                                                 next = next->next;
 884                                         }
 885
 886                                         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));
 887                                         mono_linterval_add_range (cfg, vi->interval, inst_num, inst_num + inst_num_add);
 888                                 }
 889                         }
 890                 }
 891         }
 892
 893         /* SREGs */
 894         num_sregs = mono_inst_get_src_registers (ins, sregs);
 895         for (i = 0; i < num_sregs; ++i) {
 896                 sreg = sregs [i];
 897                 if ((spec [MONO_INST_SRC1 + i] != ' ') && get_vreg_to_inst (cfg, sreg)) {
 898                         MonoInst *var = get_vreg_to_inst (cfg, sreg);
 899                         int idx = var->inst_c0;
 900
 901                         if (last_use [idx] == 0) {
 902                                 LIVENESS_DEBUG (printf ("\tlast use of R%d set to %x\n", sreg, inst_num));
 903                                 last_use [idx] = inst_num;
 904                         }
 905                 }
 906         }
 907 }
 908
 909 static void
 910 mono_analyze_liveness2 (MonoCompile *cfg)
 911 {
 912         int bnum, idx, i, j, nins, max, max_vars, block_from, block_to, pos;
 913         gint32 *last_use;
 914         static guint32 disabled = -1;
 915
 916         if (disabled == -1)
 917                 disabled = g_hasenv ("DISABLED");
 918
 919         if (disabled)
 920                 return;
 921
 922         if (cfg->num_bblocks >= (1 << (32 - BB_ID_SHIFT - 1)))
 923                 /* Ranges would overflow */
 924                 return;
 925
 926         for (bnum = cfg->num_bblocks - 1; bnum >= 0; --bnum) {
 927                 MonoBasicBlock *bb = cfg->bblocks [bnum];
 928                 MonoInst *ins;
 929
 930                 nins = 0;
 931                 for (nins = 0, ins = bb->code; ins; ins = ins->next, ++nins)
 932                         nins ++;
 933
 934                 if (nins >= ((1 << BB_ID_SHIFT) - 1))
 935                         /* Ranges would overflow */
 936                         return;
 937         }
 938
 939         LIVENESS_DEBUG (printf ("LIVENESS 2 %s\n", mono_method_full_name (cfg->method, TRUE)));
 940
 941         /*
 942         if (strstr (cfg->method->name, "test_") != cfg->method->name)
 943                 return;
 944         */
 945
 946         max_vars = cfg->num_varinfo;
 947         last_use = g_new0 (gint32, max_vars);
 948
 949         for (idx = 0; idx < max_vars; ++idx) {
 950                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 951
 952                 vi->interval = (MonoLiveInterval *)mono_mempool_alloc0 (cfg->mempool, sizeof (MonoLiveInterval));
 953         }
 954
 955         /*
 956          * Process bblocks in reverse order, so the addition of new live ranges
 957          * to the intervals is faster.
 958          */
 959         for (bnum = cfg->num_bblocks - 1; bnum >= 0; --bnum) {
 960                 MonoBasicBlock *bb = cfg->bblocks [bnum];
 961                 MonoInst *ins;
 962
 963                 block_from = (bb->dfn << BB_ID_SHIFT) + 1; /* so pos > 0 */
 964                 if (bnum < cfg->num_bblocks - 1)
 965                         /* Beginning of the next bblock */
 966                         block_to = (cfg->bblocks [bnum + 1]->dfn << BB_ID_SHIFT) + 1;
 967                 else
 968                         block_to = (bb->dfn << BB_ID_SHIFT) + ((1 << BB_ID_SHIFT) - 1);
 969
 970                 LIVENESS_DEBUG (printf ("LIVENESS BLOCK BB%d:\n", bb->block_num));
 971
 972                 memset (last_use, 0, max_vars * sizeof (gint32));
 973
 974                 /* For variables in bb->live_out, set last_use to block_to */
 975
 976                 max = ((max_vars + (BITS_PER_CHUNK -1)) / BITS_PER_CHUNK);
 977                 for (j = 0; j < max; ++j) {
 978                         gsize bits_out;
 979                         int k;
 980
 981                         bits_out = mono_bitset_get_fast (bb->live_out_set, j);
 982                         k = (j * BITS_PER_CHUNK);
 983                         while (bits_out) {
 984                                 if (bits_out & 1) {
 985                                         LIVENESS_DEBUG (printf ("Var R%d live at exit, set last_use to %x\n", cfg->varinfo [k]->dreg, block_to));
 986                                         last_use [k] = block_to;
 987                                 }
 988                                 bits_out >>= 1;
 989                                 k ++;
 990                         }
 991                 }
 992
 993                 if (cfg->ret)
 994                         last_use [cfg->ret->inst_c0] = block_to;
 995
 996                 pos = block_from + 1;
 997                 MONO_BB_FOR_EACH_INS (bb, ins) pos++;
 998
 999                 /* Process instructions backwards */
1000                 MONO_BB_FOR_EACH_INS_REVERSE (bb, ins) {
1001                         update_liveness2 (cfg, ins, FALSE, pos, last_use);
1002                         pos--;
1003                 }
1004
1005                 for (idx = 0; idx < max_vars; ++idx) {
1006                         MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
1007
1008                         if (last_use [idx] != 0) {
1009                                 /* Live at exit, not written -> live on enter */
1010                                 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]));
1011                                 mono_linterval_add_range (cfg, vi->interval, block_from, last_use [idx]);
1012                         }
1013                 }
1014         }
1015
1016         /*
1017          * Arguments need to have their live ranges extended to the beginning of
1018          * the method to account for the arg reg/memory -> global register copies
1019          * in the prolog (bug #74992).
1020          */
1021         for (i = 0; i < max_vars; i ++) {
1022                 MonoMethodVar *vi = MONO_VARINFO (cfg, i);
1023                 if (cfg->varinfo [vi->idx]->opcode == OP_ARG)
1024                         mono_linterval_add_range (cfg, vi->interval, 0, 1);
1025         }
1026
1027 #if 0
1028         for (idx = 0; idx < max_vars; ++idx) {
1029                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
1030
1031                 LIVENESS_DEBUG (printf ("LIVENESS R%d: ", cfg->varinfo [idx]->dreg));
1032                 LIVENESS_DEBUG (mono_linterval_print (vi->interval));
1033                 LIVENESS_DEBUG (printf ("\n"));
1034         }
1035 #endif
1036
1037         g_free (last_use);
1038 }
1039
1040 #endif
1041
1042 static inline void
1043 update_liveness_gc (MonoCompile *cfg, MonoBasicBlock *bb, MonoInst *ins, gint32 *last_use, MonoMethodVar **vreg_to_varinfo, GSList **callsites)
1044 {
1045         if (ins->opcode == OP_GC_LIVENESS_DEF || ins->opcode == OP_GC_LIVENESS_USE) {
1046                 int vreg = ins->inst_c1;
1047                 MonoMethodVar *vi = vreg_to_varinfo [vreg];
1048                 int idx = vi->idx;
1049                 int pc_offset = ins->backend.pc_offset;
1050
1051                 LIVENESS_DEBUG (printf ("\t%x: ", pc_offset); mono_print_ins (ins));
1052
1053                 if (ins->opcode == OP_GC_LIVENESS_DEF) {
1054                         if (last_use [idx] > 0) {
1055                                 LIVENESS_DEBUG (printf ("\tadd range to R%d: [%x, %x)\n", vreg, pc_offset, last_use [idx]));
1056                                 last_use [idx] = 0;
1057                         }
1058                 } else {
1059                         if (last_use [idx] == 0) {
1060                                 LIVENESS_DEBUG (printf ("\tlast use of R%d set to %x\n", vreg, pc_offset));
1061                                 last_use [idx] = pc_offset;
1062                         }
1063                 }
1064         } else if (ins->opcode == OP_GC_PARAM_SLOT_LIVENESS_DEF) {
1065                 GCCallSite *last;
1066
1067                 /* Add it to the last callsite */
1068                 g_assert (*callsites);
1069                 last = (GCCallSite *)(*callsites)->data;
1070                 last->param_slots = g_slist_prepend_mempool (cfg->mempool, last->param_slots, ins);
1071         } else if (ins->flags & MONO_INST_GC_CALLSITE) {
1072                 GCCallSite *callsite = (GCCallSite *)mono_mempool_alloc0 (cfg->mempool, sizeof (GCCallSite));
1073                 int i;
1074
1075                 LIVENESS_DEBUG (printf ("\t%x: ", ins->backend.pc_offset); mono_print_ins (ins));
1076                 LIVENESS_DEBUG (printf ("\t\tlive: "));
1077
1078                 callsite->bb = bb;
1079                 callsite->liveness = (guint8 *)mono_mempool_alloc0 (cfg->mempool, ALIGN_TO (cfg->num_varinfo, 8) / 8);
1080                 callsite->pc_offset = ins->backend.pc_offset;
1081                 for (i = 0; i < cfg->num_varinfo; ++i) {
1082                         if (last_use [i] != 0) {
1083                                 LIVENESS_DEBUG (printf ("R%d", MONO_VARINFO (cfg, i)->vreg));
1084                                 callsite->liveness [i / 8] |= (1 << (i % 8));
1085                         }
1086                 }
1087                 LIVENESS_DEBUG (printf ("\n"));
1088                 *callsites = g_slist_prepend_mempool (cfg->mempool, *callsites, callsite);
1089         }
1090 }
1091
1092 static inline int
1093 get_vreg_from_var (MonoCompile *cfg, MonoInst *var)
1094 {
1095         if (var->opcode == OP_REGVAR)
1096                 /* dreg contains a hreg, but inst_c0 still contains the var index */
1097                 return MONO_VARINFO (cfg, var->inst_c0)->vreg;
1098         else
1099                 /* dreg still contains the vreg */
1100                 return var->dreg;
1101 }
1102
1103 /*
1104  * mono_analyze_liveness_gc:
1105  *
1106  *   Compute liveness bitmaps for each call site.
1107  * This function is a modified version of mono_analyze_liveness2 ().
1108  */
1109 void
1110 mono_analyze_liveness_gc (MonoCompile *cfg)
1111 {
1112         int idx, i, j, nins, max, max_vars, block_from, block_to, pos, reverse_len;
1113         gint32 *last_use;
1114         MonoInst **reverse;
1115         MonoMethodVar **vreg_to_varinfo = NULL;
1116         MonoBasicBlock *bb;
1117         GSList *callsites;
1118
1119         LIVENESS_DEBUG (printf ("\n------------ GC LIVENESS: ----------\n"));
1120
1121         max_vars = cfg->num_varinfo;
1122         last_use = g_new0 (gint32, max_vars);
1123
1124         /*
1125          * var->inst_c0 no longer contains the variable index, so compute a mapping now.
1126          */
1127         vreg_to_varinfo = g_new0 (MonoMethodVar*, cfg->next_vreg);
1128         for (idx = 0; idx < max_vars; ++idx) {
1129                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
1130
1131                 vreg_to_varinfo [vi->vreg] = vi;
1132         }
1133
1134         reverse_len = 1024;
1135         reverse = (MonoInst **)mono_mempool_alloc (cfg->mempool, sizeof (MonoInst*) * reverse_len);
1136
1137         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
1138                 MonoInst *ins;
1139
1140                 block_from = bb->real_native_offset;
1141                 block_to = bb->native_offset + bb->native_length;
1142
1143                 LIVENESS_DEBUG (printf ("GC LIVENESS BB%d:\n", bb->block_num));
1144
1145                 if (!bb->code)
1146                         continue;
1147
1148                 memset (last_use, 0, max_vars * sizeof (gint32));
1149
1150                 /* For variables in bb->live_out, set last_use to block_to */
1151
1152                 max = ((max_vars + (BITS_PER_CHUNK -1)) / BITS_PER_CHUNK);
1153                 for (j = 0; j < max; ++j) {
1154                         gsize bits_out;
1155                         int k;
1156
1157                         if (!bb->live_out_set)
1158                                 /* The variables used in this bblock are volatile anyway */
1159                                 continue;
1160
1161                         bits_out = mono_bitset_get_fast (bb->live_out_set, j);
1162                         k = (j * BITS_PER_CHUNK);
1163                         while (bits_out) {
1164                                 if ((bits_out & 1) && cfg->varinfo [k]->flags & MONO_INST_GC_TRACK) {
1165                                         int vreg = get_vreg_from_var (cfg, cfg->varinfo [k]);
1166                                         LIVENESS_DEBUG (printf ("Var R%d live at exit, last_use set to %x.\n", vreg, block_to));
1167                                         last_use [k] = block_to;
1168                                 }
1169                                 bits_out >>= 1;
1170                                 k ++;
1171                         }
1172                 }
1173
1174                 for (nins = 0, pos = block_from, ins = bb->code; ins; ins = ins->next, ++nins, ++pos) {
1175                         if (nins >= reverse_len) {
1176                                 int new_reverse_len = reverse_len * 2;
1177                                 MonoInst **new_reverse = (MonoInst **)mono_mempool_alloc (cfg->mempool, sizeof (MonoInst*) * new_reverse_len);
1178                                 memcpy (new_reverse, reverse, sizeof (MonoInst*) * reverse_len);
1179                                 reverse = new_reverse;
1180                                 reverse_len = new_reverse_len;
1181                         }
1182
1183                         reverse [nins] = ins;
1184                 }
1185
1186                 /* Process instructions backwards */
1187                 callsites = NULL;
1188                 for (i = nins - 1; i >= 0; --i) {
1189                         MonoInst *ins = (MonoInst*)reverse [i];
1190
1191                         update_liveness_gc (cfg, bb, ins, last_use, vreg_to_varinfo, &callsites);
1192                 }
1193                 /* The callsites should already be sorted by pc offset because we added them backwards */
1194                 bb->gc_callsites = callsites;
1195         }
1196
1197         g_free (last_use);
1198         g_free (vreg_to_varinfo);
1199 }
1200
1201 #else /* !DISABLE_JIT */
1202
1203 MONO_EMPTY_SOURCE_FILE (liveness);
1204
1205 #endif /* !DISABLE_JIT */