mono/mini/liveness.c

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