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