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                         if (SIZEOF_REGISTER == 4 && (var->type == STACK_I8 || (var->type == STACK_R8 && COMPILE_SOFT_FLOAT (cfg)))) {
  98                                 /* Make the component vregs volatile as well (#612206) */
  99                                 get_vreg_to_inst (cfg, var->dreg + 1)->flags |= MONO_INST_VOLATILE;
 100                                 get_vreg_to_inst (cfg, var->dreg + 2)->flags |= MONO_INST_VOLATILE;
 101                         }
 102                 }
 103
 104                 /* SREGS */
 105                 num_sregs = mono_inst_get_src_registers (ins, sregs);
 106                 for (srcindex = 0; srcindex < num_sregs; ++srcindex) {
 107                         sreg = sregs [srcindex];
 108
 109                         g_assert (sreg != -1);
 110                         if (get_vreg_to_inst (cfg, sreg)) {
 111                                 MonoInst *var = get_vreg_to_inst (cfg, sreg);
 112                                 int idx = var->inst_c0;
 113                                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 114
 115                                 cfg->varinfo [vi->idx]->flags |= MONO_INST_VOLATILE;
 116                                 if (SIZEOF_REGISTER == 4 && (var->type == STACK_I8 || (var->type == STACK_R8 && COMPILE_SOFT_FLOAT (cfg)))) {
 117                                         /* Make the component vregs volatile as well (#612206) */
 118                                         get_vreg_to_inst (cfg, var->dreg + 1)->flags |= MONO_INST_VOLATILE;
 119                                         get_vreg_to_inst (cfg, var->dreg + 2)->flags |= MONO_INST_VOLATILE;
 120                                 }
 121                         }
 122                 }
 123         }
 124
 125         *visited = g_slist_append (*visited, bb);
 126
 127         /*
 128          * Need to visit all bblocks reachable from this one since they can be
 129          * reached during exception handling.
 130          */
 131         for (i = 0; i < bb->out_count; ++i) {
 132                 visit_bb (cfg, bb->out_bb [i], visited);
 133         }
 134 }
 135
 136 void
 137 mono_liveness_handle_exception_clauses (MonoCompile *cfg)
 138 {
 139         MonoBasicBlock *bb;
 140         GSList *visited = NULL;
 141
 142         /*
 143          * Variables in exception handler register cannot be allocated to registers
 144          * so make them volatile. See bug #42136. This will not be neccessary when
 145          * the back ends could guarantee that the variables will be in the
 146          * correct registers when a handler is called.
 147          * This includes try blocks too, since a variable in a try block might be
 148          * accessed after an exception handler has been run.
 149          */
 150         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
 151
 152                 if (bb->region == -1 || MONO_BBLOCK_IS_IN_REGION (bb, MONO_REGION_TRY))
 153                         continue;
 154
 155                 visit_bb (cfg, bb, &visited);
 156         }
 157         g_slist_free (visited);
 158 }
 159
 160 static inline void
 161 update_live_range (MonoMethodVar *var, int abs_pos)
 162 {
 163         if (var->range.first_use.abs_pos > abs_pos)
 164                 var->range.first_use.abs_pos = abs_pos;
 165
 166         if (var->range.last_use.abs_pos < abs_pos)
 167                 var->range.last_use.abs_pos = abs_pos;
 168 }
 169
 170 static void
 171 analyze_liveness_bb (MonoCompile *cfg, MonoBasicBlock *bb)
 172 {
 173         MonoInst *ins;
 174         int sreg, inst_num;
 175         MonoMethodVar *vars = cfg->vars;
 176         guint32 abs_pos = (bb->dfn << 16);
 177
 178         for (inst_num = 0, ins = bb->code; ins; ins = ins->next, inst_num += 2) {
 179                 const char *spec = INS_INFO (ins->opcode);
 180                 int num_sregs, i;
 181                 int sregs [MONO_MAX_SRC_REGS];
 182
 183 #ifdef DEBUG_LIVENESS
 184                 if (cfg->verbose_level > 1) {
 185                         printf ("\t");
 186                         mono_print_ins (ins);
 187                 }
 188 #endif
 189
 190                 if (ins->opcode == OP_NOP)
 191                         continue;
 192
 193                 if (ins->opcode == OP_LDADDR) {
 194                         MonoInst *var = ins->inst_p0;
 195                         int idx = var->inst_c0;
 196                         MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 197
 198 #ifdef DEBUG_LIVENESS
 199                         if (cfg->verbose_level > 1)
 200                                 printf ("\tGEN: R%d(%d)\n", var->dreg, idx);
 201 #endif
 202                         update_live_range (&vars [idx], abs_pos + inst_num);
 203                         if (!mono_bitset_test_fast (bb->kill_set, idx))
 204                                 mono_bitset_set_fast (bb->gen_set, idx);
 205                         vi->spill_costs += SPILL_COST_INCREMENT;
 206                 }
 207
 208                 /* SREGs must come first, so MOVE r <- r is handled correctly */
 209                 num_sregs = mono_inst_get_src_registers (ins, sregs);
 210                 for (i = 0; i < num_sregs; ++i) {
 211                         sreg = sregs [i];
 212                         if ((spec [MONO_INST_SRC1 + i] != ' ') && get_vreg_to_inst (cfg, sreg)) {
 213                                 MonoInst *var = get_vreg_to_inst (cfg, sreg);
 214                                 int idx = var->inst_c0;
 215                                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 216
 217 #ifdef DEBUG_LIVENESS
 218                                 if (cfg->verbose_level > 1)
 219                                         printf ("\tGEN: R%d(%d)\n", sreg, idx);
 220 #endif
 221                                 update_live_range (&vars [idx], abs_pos + inst_num);
 222                                 if (!mono_bitset_test_fast (bb->kill_set, idx))
 223                                         mono_bitset_set_fast (bb->gen_set, idx);
 224                                 vi->spill_costs += SPILL_COST_INCREMENT;
 225                         }
 226                 }
 227
 228                 /* DREG */
 229                 if ((spec [MONO_INST_DEST] != ' ') && get_vreg_to_inst (cfg, ins->dreg)) {
 230                         MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 231                         int idx = var->inst_c0;
 232                         MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 233
 234                         if (MONO_IS_STORE_MEMBASE (ins)) {
 235                                 update_live_range (&vars [idx], abs_pos + inst_num);
 236                                 if (!mono_bitset_test_fast (bb->kill_set, idx))
 237                                         mono_bitset_set_fast (bb->gen_set, idx);
 238                                 vi->spill_costs += SPILL_COST_INCREMENT;
 239                         } else {
 240 #ifdef DEBUG_LIVENESS
 241                                 if (cfg->verbose_level > 1)
 242                                         printf ("\tKILL: R%d(%d)\n", ins->dreg, idx);
 243 #endif
 244                                 update_live_range (&vars [idx], abs_pos + inst_num + 1);
 245                                 mono_bitset_set_fast (bb->kill_set, idx);
 246                                 vi->spill_costs += SPILL_COST_INCREMENT;
 247                         }
 248                 }
 249         }
 250 }
 251
 252 /* generic liveness analysis code. CFG specific parts are
 253  * in update_gen_kill_set()
 254  */
 255 void
 256 mono_analyze_liveness (MonoCompile *cfg)
 257 {
 258         MonoBitSet *old_live_out_set;
 259         int i, j, max_vars = cfg->num_varinfo;
 260         int out_iter;
 261         gboolean *in_worklist;
 262         MonoBasicBlock **worklist;
 263         guint32 l_end;
 264         int bitsize;
 265
 266 #ifdef DEBUG_LIVENESS
 267         if (cfg->verbose_level > 1)
 268                 printf ("\nLIVENESS:\n");
 269 #endif
 270
 271         g_assert (!(cfg->comp_done & MONO_COMP_LIVENESS));
 272
 273         cfg->comp_done |= MONO_COMP_LIVENESS;
 274
 275         if (max_vars == 0)
 276                 return;
 277
 278         bitsize = mono_bitset_alloc_size (max_vars, 0);
 279
 280         for (i = 0; i < max_vars; i ++) {
 281                 MONO_VARINFO (cfg, i)->range.first_use.abs_pos = ~ 0;
 282                 MONO_VARINFO (cfg, i)->range.last_use .abs_pos =   0;
 283                 MONO_VARINFO (cfg, i)->spill_costs = 0;
 284         }
 285
 286         for (i = 0; i < cfg->num_bblocks; ++i) {
 287                 MonoBasicBlock *bb = cfg->bblocks [i];
 288
 289                 bb->gen_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
 290                 bb->kill_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
 291
 292 #ifdef DEBUG_LIVENESS
 293                 if (cfg->verbose_level > 1) {
 294                         printf ("BLOCK BB%d (", bb->block_num);
 295                         for (j = 0; j < bb->out_count; j++)
 296                                 printf ("BB%d, ", bb->out_bb [j]->block_num);
 297
 298                         printf ("):\n");
 299                 }
 300 #endif
 301
 302                 analyze_liveness_bb (cfg, bb);
 303
 304 #ifdef DEBUG_LIVENESS
 305                 if (cfg->verbose_level > 1) {
 306                         printf ("GEN  BB%d: ", bb->block_num); mono_bitset_print (bb->gen_set);
 307                         printf ("KILL BB%d: ", bb->block_num); mono_bitset_print (bb->kill_set);
 308                 }
 309 #endif
 310         }
 311
 312         old_live_out_set = mono_bitset_new (max_vars, 0);
 313         in_worklist = g_new0 (gboolean, cfg->num_bblocks + 1);
 314
 315         worklist = g_new (MonoBasicBlock *, cfg->num_bblocks + 1);
 316         l_end = 0;
 317
 318         /*
 319          * This is a backward dataflow analysis problem, so we process blocks in
 320          * decreasing dfn order, this speeds up the iteration.
 321          */
 322         for (i = 0; i < cfg->num_bblocks; i ++) {
 323                 MonoBasicBlock *bb = cfg->bblocks [i];
 324
 325                 worklist [l_end ++] = bb;
 326                 in_worklist [bb->dfn] = TRUE;
 327
 328                 /* Initialized later */
 329                 bb->live_in_set = NULL;
 330                 bb->live_out_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
 331         }
 332
 333         out_iter = 0;
 334
 335         if (cfg->verbose_level > 1)
 336                 printf ("\nITERATION:\n");
 337
 338         while (l_end != 0) {
 339                 MonoBasicBlock *bb = worklist [--l_end];
 340                 MonoBasicBlock *out_bb;
 341                 gboolean changed;
 342
 343                 in_worklist [bb->dfn] = FALSE;
 344
 345 #ifdef DEBUG_LIVENESS
 346                 if (cfg->verbose_level > 1) {
 347                         printf ("P: BB%d(%d): IN: ", bb->block_num, bb->dfn);
 348                         for (j = 0; j < bb->in_count; ++j)
 349                                 printf ("BB%d ", bb->in_bb [j]->block_num);
 350                         printf ("OUT:");
 351                         for (j = 0; j < bb->out_count; ++j)
 352                                 printf ("BB%d ", bb->out_bb [j]->block_num);
 353                         printf ("\n");
 354                 }
 355 #endif
 356
 357
 358                 if (bb->out_count == 0)
 359                         continue;
 360
 361                 out_iter ++;
 362
 363                 if (!bb->live_in_set) {
 364                         /* First pass over this bblock */
 365                         changed = TRUE;
 366                 }
 367                 else {
 368                         changed = FALSE;
 369                         mono_bitset_copyto_fast (bb->live_out_set, old_live_out_set);
 370                 }
 371
 372                 for (j = 0; j < bb->out_count; j++) {
 373                         out_bb = bb->out_bb [j];
 374
 375                         if (!out_bb->live_in_set) {
 376                                 out_bb->live_in_set = mono_bitset_mp_new_noinit (cfg->mempool, bitsize, max_vars);
 377
 378                                 mono_bitset_copyto_fast (out_bb->live_out_set, out_bb->live_in_set);
 379                                 mono_bitset_sub_fast (out_bb->live_in_set, out_bb->kill_set);
 380                                 mono_bitset_union_fast (out_bb->live_in_set, out_bb->gen_set);
 381                         }
 382
 383                         // FIXME: Do this somewhere else
 384                         if (bb->last_ins && bb->last_ins->opcode == OP_NOT_REACHED) {
 385                         } else {
 386                                 mono_bitset_union_fast (bb->live_out_set, out_bb->live_in_set);
 387                         }
 388                 }
 389
 390                 if (changed || !mono_bitset_equal (old_live_out_set, bb->live_out_set)) {
 391                         if (!bb->live_in_set)
 392                                 bb->live_in_set = mono_bitset_mp_new_noinit (cfg->mempool, bitsize, max_vars);
 393                         mono_bitset_copyto_fast (bb->live_out_set, bb->live_in_set);
 394                         mono_bitset_sub_fast (bb->live_in_set, bb->kill_set);
 395                         mono_bitset_union_fast (bb->live_in_set, bb->gen_set);
 396
 397                         for (j = 0; j < bb->in_count; j++) {
 398                                 MonoBasicBlock *in_bb = bb->in_bb [j];
 399                                 /*
 400                                  * Some basic blocks do not seem to be in the
 401                                  * cfg->bblocks array...
 402                                  */
 403                                 if (in_bb->gen_set && !in_worklist [in_bb->dfn]) {
 404 #ifdef DEBUG_LIVENESS
 405                                         if (cfg->verbose_level > 1)
 406                                                 printf ("\tADD: %d\n", in_bb->block_num);
 407 #endif
 408                                         /*
 409                                          * Put the block at the top of the stack, so it
 410                                          * will be processed right away.
 411                                          */
 412                                         worklist [l_end ++] = in_bb;
 413                                         in_worklist [in_bb->dfn] = TRUE;
 414                                 }
 415                         }
 416                 }
 417
 418                 if (G_UNLIKELY (cfg->verbose_level > 1)) {
 419                         printf ("\tLIVE IN  BB%d: ", bb->block_num);
 420                         mono_bitset_print (bb->live_in_set);
 421                 }
 422         }
 423
 424 #ifdef DEBUG_LIVENESS
 425         if (cfg->verbose_level > 1)
 426                 printf ("IT: %d %d.\n", cfg->num_bblocks, out_iter);
 427 #endif
 428
 429         mono_bitset_free (old_live_out_set);
 430
 431         g_free (worklist);
 432         g_free (in_worklist);
 433
 434         /* Compute live_in_set for bblocks skipped earlier */
 435         for (i = 0; i < cfg->num_bblocks; ++i) {
 436                 MonoBasicBlock *bb = cfg->bblocks [i];
 437
 438                 if (!bb->live_in_set) {
 439                         bb->live_in_set = mono_bitset_mp_new (cfg->mempool, bitsize, max_vars);
 440
 441                         mono_bitset_copyto_fast (bb->live_out_set, bb->live_in_set);
 442                         mono_bitset_sub_fast (bb->live_in_set, bb->kill_set);
 443                         mono_bitset_union_fast (bb->live_in_set, bb->gen_set);
 444                 }
 445         }
 446
 447         for (i = 0; i < cfg->num_bblocks; ++i) {
 448                 MonoBasicBlock *bb = cfg->bblocks [i];
 449                 guint32 rem, max;
 450                 guint32 abs_pos = (bb->dfn << 16);
 451                 MonoMethodVar *vars = cfg->vars;
 452
 453                 if (!bb->live_out_set)
 454                         continue;
 455
 456                 rem = max_vars % BITS_PER_CHUNK;
 457                 max = ((max_vars + (BITS_PER_CHUNK -1)) / BITS_PER_CHUNK);
 458                 for (j = 0; j < max; ++j) {
 459                         gsize bits_in;
 460                         gsize bits_out;
 461                         int k;
 462
 463                         bits_in = mono_bitset_get_fast (bb->live_in_set, j);
 464                         bits_out = mono_bitset_get_fast (bb->live_out_set, j);
 465
 466                         k = (j * BITS_PER_CHUNK);
 467                         while ((bits_in || bits_out)) {
 468                                 if (bits_in & 1)
 469                                         update_live_range (&vars [k], abs_pos + 0);
 470                                 if (bits_out & 1)
 471                                         update_live_range (&vars [k], abs_pos + 0xffff);
 472                                 bits_in >>= 1;
 473                                 bits_out >>= 1;
 474                                 k ++;
 475                         }
 476                 }
 477         }
 478
 479         /*
 480          * Arguments need to have their live ranges extended to the beginning of
 481          * the method to account for the arg reg/memory -> global register copies
 482          * in the prolog (bug #74992).
 483          */
 484
 485         for (i = 0; i < max_vars; i ++) {
 486                 MonoMethodVar *vi = MONO_VARINFO (cfg, i);
 487                 if (cfg->varinfo [vi->idx]->opcode == OP_ARG) {
 488                         if (vi->range.last_use.abs_pos == 0 && !(cfg->varinfo [vi->idx]->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT))) {
 489                                 /*
 490                                  * Can't eliminate the this variable in gshared code, since
 491                                  * it is needed during exception handling to identify the
 492                                  * method.
 493                                  * It is better to check for this here instead of marking the variable
 494                                  * VOLATILE, since that would prevent it from being allocated to
 495                                  * registers.
 496                                  */
 497                                  if (!cfg->disable_deadce_vars && !(cfg->generic_sharing_context && mono_method_signature (cfg->method)->hasthis && cfg->varinfo [vi->idx] == cfg->args [0]))
 498                                          cfg->varinfo [vi->idx]->flags |= MONO_INST_IS_DEAD;
 499                         }
 500                         vi->range.first_use.abs_pos = 0;
 501                 }
 502         }
 503
 504 #ifdef DEBUG_LIVENESS
 505         if (cfg->verbose_level > 1) {
 506                 for (i = cfg->num_bblocks - 1; i >= 0; i--) {
 507                         MonoBasicBlock *bb = cfg->bblocks [i];
 508
 509                         printf ("LIVE IN  BB%d: ", bb->block_num);
 510                         mono_bitset_print (bb->live_in_set);
 511                         printf ("LIVE OUT BB%d: ", bb->block_num);
 512                         mono_bitset_print (bb->live_out_set);
 513                 }
 514
 515                 for (i = 0; i < max_vars; i ++) {
 516                         MonoMethodVar *vi = MONO_VARINFO (cfg, i);
 517
 518                         printf ("V%d: [0x%x - 0x%x]\n", i, vi->range.first_use.abs_pos, vi->range.last_use.abs_pos);
 519                 }
 520         }
 521 #endif
 522
 523         if (!cfg->disable_initlocals_opt)
 524                 optimize_initlocals (cfg);
 525
 526 #ifdef ENABLE_LIVENESS2
 527         /* This improves code size by about 5% but slows down compilation too much */
 528         if (cfg->compile_aot)
 529                 mono_analyze_liveness2 (cfg);
 530 #endif
 531 }
 532
 533 /**
 534  * optimize_initlocals:
 535  *
 536  * Try to optimize away some of the redundant initialization code inserted because of
 537  * 'locals init' using the liveness information.
 538  */
 539 static void
 540 optimize_initlocals (MonoCompile *cfg)
 541 {
 542         MonoBitSet *used;
 543         MonoInst *ins;
 544         MonoBasicBlock *initlocals_bb;
 545
 546         used = mono_bitset_new (cfg->next_vreg + 1, 0);
 547
 548         mono_bitset_clear_all (used);
 549         initlocals_bb = cfg->bb_entry->next_bb;
 550         for (ins = initlocals_bb->code; ins; ins = ins->next) {
 551                 int num_sregs, i;
 552                 int sregs [MONO_MAX_SRC_REGS];
 553
 554                 num_sregs = mono_inst_get_src_registers (ins, sregs);
 555                 for (i = 0; i < num_sregs; ++i)
 556                         mono_bitset_set_fast (used, sregs [i]);
 557
 558                 if (MONO_IS_STORE_MEMBASE (ins))
 559                         mono_bitset_set_fast (used, ins->dreg);
 560         }
 561
 562         for (ins = initlocals_bb->code; ins; ins = ins->next) {
 563                 const char *spec = INS_INFO (ins->opcode);
 564
 565                 /* Look for statements whose dest is not used in this bblock and not live on exit. */
 566                 if ((spec [MONO_INST_DEST] != ' ') && !MONO_IS_STORE_MEMBASE (ins)) {
 567                         MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 568
 569                         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))) {
 570                                 //printf ("DEAD: "); mono_print_ins (ins);
 571                                 if (cfg->disable_initlocals_opt_refs && var->type == STACK_OBJ)
 572                                         continue;
 573                                 if ((ins->opcode == OP_ICONST) || (ins->opcode == OP_I8CONST) || (ins->opcode == OP_R8CONST)) {
 574                                         NULLIFY_INS (ins);
 575                                         MONO_VARINFO (cfg, var->inst_c0)->spill_costs -= 1;
 576                                         /*
 577                                          * We should shorten the liveness interval of these vars as well, but
 578                                          * don't have enough info to do that.
 579                                          */
 580                                 }
 581                         }
 582                 }
 583         }
 584
 585         g_free (used);
 586 }
 587
 588 void
 589 mono_linterval_add_range (MonoCompile *cfg, MonoLiveInterval *interval, int from, int to)
 590 {
 591         MonoLiveRange2 *prev_range, *next_range, *new_range;
 592
 593         g_assert (to >= from);
 594
 595         /* Optimize for extending the first interval backwards */
 596         if (G_LIKELY (interval->range && (interval->range->from > from) && (interval->range->from == to))) {
 597                 interval->range->from = from;
 598                 return;
 599         }
 600
 601         /* Find a place in the list for the new range */
 602         prev_range = NULL;
 603         next_range = interval->range;
 604         while ((next_range != NULL) && (next_range->from <= from)) {
 605                 prev_range = next_range;
 606                 next_range = next_range->next;
 607         }
 608
 609         if (prev_range && prev_range->to == from) {
 610                 /* Merge with previous */
 611                 prev_range->to = to;
 612         } else if (next_range && next_range->from == to) {
 613                 /* Merge with previous */
 614                 next_range->from = from;
 615         } else {
 616                 /* Insert it */
 617                 new_range = mono_mempool_alloc (cfg->mempool, sizeof (MonoLiveRange2));
 618                 new_range->from = from;
 619                 new_range->to = to;
 620                 new_range->next = NULL;
 621
 622                 if (prev_range)
 623                         prev_range->next = new_range;
 624                 else
 625                         interval->range = new_range;
 626                 if (next_range)
 627                         new_range->next = next_range;
 628                 else
 629                         interval->last_range = new_range;
 630         }
 631
 632         /* FIXME: Merge intersecting ranges */
 633 }
 634
 635 void
 636 mono_linterval_print (MonoLiveInterval *interval)
 637 {
 638         MonoLiveRange2 *range;
 639
 640         for (range = interval->range; range != NULL; range = range->next)
 641                 printf ("[%x-%x] ", range->from, range->to);
 642 }
 643
 644 void
 645 mono_linterval_print_nl (MonoLiveInterval *interval)
 646 {
 647         mono_linterval_print (interval);
 648         printf ("\n");
 649 }
 650
 651 /**
 652  * mono_linterval_convers:
 653  *
 654  *   Return whenever INTERVAL covers the position POS.
 655  */
 656 gboolean
 657 mono_linterval_covers (MonoLiveInterval *interval, int pos)
 658 {
 659         MonoLiveRange2 *range;
 660
 661         for (range = interval->range; range != NULL; range = range->next) {
 662                 if (pos >= range->from && pos <= range->to)
 663                         return TRUE;
 664                 if (range->from > pos)
 665                         return FALSE;
 666         }
 667
 668         return FALSE;
 669 }
 670
 671 /**
 672  * mono_linterval_get_intersect_pos:
 673  *
 674  *   Determine whenever I1 and I2 intersect, and if they do, return the first
 675  * point of intersection. Otherwise, return -1.
 676  */
 677 gint32
 678 mono_linterval_get_intersect_pos (MonoLiveInterval *i1, MonoLiveInterval *i2)
 679 {
 680         MonoLiveRange2 *r1, *r2;
 681
 682         /* FIXME: Optimize this */
 683         for (r1 = i1->range; r1 != NULL; r1 = r1->next) {
 684                 for (r2 = i2->range; r2 != NULL; r2 = r2->next) {
 685                         if (r2->to > r1->from && r2->from < r1->to) {
 686                                 if (r2->from <= r1->from)
 687                                         return r1->from;
 688                                 else
 689                                         return r2->from;
 690                         }
 691                 }
 692         }
 693
 694         return -1;
 695 }
 696
 697 /**
 698  * mono_linterval_split
 699  *
 700  *   Split L at POS and store the newly created intervals into L1 and L2. POS becomes
 701  * part of L2.
 702  */
 703 void
 704 mono_linterval_split (MonoCompile *cfg, MonoLiveInterval *interval, MonoLiveInterval **i1, MonoLiveInterval **i2, int pos)
 705 {
 706         MonoLiveRange2 *r;
 707
 708         g_assert (pos > interval->range->from && pos <= interval->last_range->to);
 709
 710         *i1 = mono_mempool_alloc0 (cfg->mempool, sizeof (MonoLiveInterval));
 711         *i2 = mono_mempool_alloc0 (cfg->mempool, sizeof (MonoLiveInterval));
 712
 713         for (r = interval->range; r; r = r->next) {
 714                 if (pos > r->to) {
 715                         /* Add it to the first child */
 716                         mono_linterval_add_range (cfg, *i1, r->from, r->to);
 717                 } else if (pos > r->from && pos <= r->to) {
 718                         /* Split at pos */
 719                         mono_linterval_add_range (cfg, *i1, r->from, pos - 1);
 720                         mono_linterval_add_range (cfg, *i2, pos, r->to);
 721                 } else {
 722                         /* Add it to the second child */
 723                         mono_linterval_add_range (cfg, *i2, r->from, r->to);
 724                 }
 725         }
 726 }
 727
 728 #ifdef ENABLE_LIVENESS2
 729
 730 #if 0
 731 #define LIVENESS_DEBUG(a) do { a; } while (0)
 732 #else
 733 #define LIVENESS_DEBUG(a)
 734 #endif
 735
 736 static inline void
 737 update_liveness2 (MonoCompile *cfg, MonoInst *ins, gboolean set_volatile, int inst_num, gint32 *last_use)
 738 {
 739         const char *spec = INS_INFO (ins->opcode);
 740         int sreg;
 741         int num_sregs, i;
 742         int sregs [MONO_MAX_SRC_REGS];
 743
 744         LIVENESS_DEBUG (printf ("\t%x: ", inst_num); mono_print_ins (ins));
 745
 746         if (ins->opcode == OP_NOP)
 747                 return;
 748
 749         /* DREG */
 750         if ((spec [MONO_INST_DEST] != ' ') && get_vreg_to_inst (cfg, ins->dreg)) {
 751                 MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 752                 int idx = var->inst_c0;
 753                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 754
 755                 if (MONO_IS_STORE_MEMBASE (ins)) {
 756                         if (last_use [idx] == 0) {
 757                                 LIVENESS_DEBUG (printf ("\tlast use of R%d set to %x\n", ins->dreg, inst_num));
 758                                 last_use [idx] = inst_num;
 759                         }
 760                 } else {
 761                         if (last_use [idx] > 0) {
 762                                 LIVENESS_DEBUG (printf ("\tadd range to R%d: [%x, %x)\n", ins->dreg, inst_num, last_use [idx]));
 763                                 mono_linterval_add_range (cfg, vi->interval, inst_num, last_use [idx]);
 764                                 last_use [idx] = 0;
 765                         }
 766                         else {
 767                                 /* Try dead code elimination */
 768                                 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)) {
 769                                         LIVENESS_DEBUG (printf ("\tdead def of R%d, eliminated\n", ins->dreg));
 770                                         ins->opcode = OP_NOP;
 771                                         ins->dreg = -1;
 772                                         MONO_INST_NULLIFY_SREGS (ins);
 773                                         return;
 774                                 }
 775
 776                                 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));
 777                                 mono_linterval_add_range (cfg, vi->interval, inst_num, inst_num + 1);
 778                         }
 779                 }
 780         }
 781
 782         /* SREGs */
 783         num_sregs = mono_inst_get_src_registers (ins, sregs);
 784         for (i = 0; i < num_sregs; ++i) {
 785                 sreg = sregs [i];
 786                 if ((spec [MONO_INST_SRC1 + i] != ' ') && get_vreg_to_inst (cfg, sreg)) {
 787                         MonoInst *var = get_vreg_to_inst (cfg, sreg);
 788                         int idx = var->inst_c0;
 789
 790                         if (last_use [idx] == 0) {
 791                                 LIVENESS_DEBUG (printf ("\tlast use of R%d set to %x\n", sreg, inst_num));
 792                                 last_use [idx] = inst_num;
 793                         }
 794                 }
 795         }
 796 }
 797
 798 static void
 799 mono_analyze_liveness2 (MonoCompile *cfg)
 800 {
 801         int bnum, idx, i, j, nins, rem, max, max_vars, block_from, block_to, pos, reverse_len;
 802         gint32 *last_use;
 803         static guint32 disabled = -1;
 804         MonoInst **reverse;
 805
 806         if (disabled == -1)
 807                 disabled = getenv ("DISABLED") != NULL;
 808
 809         if (disabled)
 810                 return;
 811
 812         LIVENESS_DEBUG (printf ("LIVENESS 2 %s\n", mono_method_full_name (cfg->method, TRUE)));
 813
 814         /*
 815         if (strstr (cfg->method->name, "test_") != cfg->method->name)
 816                 return;
 817         */
 818
 819         max_vars = cfg->num_varinfo;
 820         last_use = g_new0 (gint32, max_vars);
 821
 822         reverse_len = 1024;
 823         reverse = mono_mempool_alloc (cfg->mempool, sizeof (MonoInst*) * reverse_len);
 824
 825         for (idx = 0; idx < max_vars; ++idx) {
 826                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 827
 828                 vi->interval = mono_mempool_alloc0 (cfg->mempool, sizeof (MonoLiveInterval));
 829         }
 830
 831         /*
 832          * Process bblocks in reverse order, so the addition of new live ranges
 833          * to the intervals is faster.
 834          */
 835         for (bnum = cfg->num_bblocks - 1; bnum >= 0; --bnum) {
 836                 MonoBasicBlock *bb = cfg->bblocks [bnum];
 837                 MonoInst *ins;
 838
 839                 block_from = (bb->dfn << 16) + 1; /* so pos > 0 */
 840                 if (bnum < cfg->num_bblocks - 1)
 841                         /* Beginning of the next bblock */
 842                         block_to = (cfg->bblocks [bnum + 1]->dfn << 16) + 1;
 843                 else
 844                         block_to = (bb->dfn << 16) + 0xffff;
 845
 846                 LIVENESS_DEBUG (printf ("LIVENESS BLOCK BB%d:\n", bb->block_num));
 847
 848                 memset (last_use, 0, max_vars * sizeof (gint32));
 849
 850                 /* For variables in bb->live_out, set last_use to block_to */
 851
 852                 rem = max_vars % BITS_PER_CHUNK;
 853                 max = ((max_vars + (BITS_PER_CHUNK -1)) / BITS_PER_CHUNK);
 854                 for (j = 0; j < max; ++j) {
 855                         gsize bits_out;
 856                         int k;
 857
 858                         bits_out = mono_bitset_get_fast (bb->live_out_set, j);
 859                         k = (j * BITS_PER_CHUNK);
 860                         while (bits_out) {
 861                                 if (bits_out & 1) {
 862                                         LIVENESS_DEBUG (printf ("Var R%d live at exit, set last_use to %x\n", cfg->varinfo [k]->dreg, block_to));
 863                                         last_use [k] = block_to;
 864                                 }
 865                                 bits_out >>= 1;
 866                                 k ++;
 867                         }
 868                 }
 869
 870                 if (cfg->ret)
 871                         last_use [cfg->ret->inst_c0] = block_to;
 872
 873                 for (nins = 0, pos = block_from, ins = bb->code; ins; ins = ins->next, ++nins, ++pos) {
 874                         if (nins >= reverse_len) {
 875                                 int new_reverse_len = reverse_len * 2;
 876                                 MonoInst **new_reverse = mono_mempool_alloc (cfg->mempool, sizeof (MonoInst*) * new_reverse_len);
 877                                 memcpy (new_reverse, reverse, sizeof (MonoInst*) * reverse_len);
 878                                 reverse = new_reverse;
 879                                 reverse_len = new_reverse_len;
 880                         }
 881
 882                         reverse [nins] = ins;
 883                 }
 884
 885                 /* Process instructions backwards */
 886                 for (i = nins - 1; i >= 0; --i) {
 887                         MonoInst *ins = (MonoInst*)reverse [i];
 888
 889                         update_liveness2 (cfg, ins, FALSE, pos, last_use);
 890
 891                         pos --;
 892                 }
 893
 894                 for (idx = 0; idx < max_vars; ++idx) {
 895                         MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 896
 897                         if (last_use [idx] != 0) {
 898                                 /* Live at exit, not written -> live on enter */
 899                                 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]));
 900                                 mono_linterval_add_range (cfg, vi->interval, block_from, last_use [idx]);
 901                         }
 902                 }
 903         }
 904
 905         /*
 906          * Arguments need to have their live ranges extended to the beginning of
 907          * the method to account for the arg reg/memory -> global register copies
 908          * in the prolog (bug #74992).
 909          */
 910         for (i = 0; i < max_vars; i ++) {
 911                 MonoMethodVar *vi = MONO_VARINFO (cfg, i);
 912                 if (cfg->varinfo [vi->idx]->opcode == OP_ARG)
 913                         mono_linterval_add_range (cfg, vi->interval, 0, 1);
 914         }
 915
 916 #if 0
 917         for (idx = 0; idx < max_vars; ++idx) {
 918                 MonoMethodVar *vi = MONO_VARINFO (cfg, idx);
 919
 920                 LIVENESS_DEBUG (printf ("LIVENESS R%d: ", cfg->varinfo [idx]->dreg));
 921                 LIVENESS_DEBUG (mono_linterval_print (vi->interval));
 922                 LIVENESS_DEBUG (printf ("\n"));
 923         }
 924 #endif
 925
 926         g_free (last_use);
 927 }
 928
 929 #endif