mono/mini/branch-opts.c

   1 /*
   2  * branch-opts.c: Branch optimizations support
   3  *
   4  * Authors:
   5  *   Patrik Torstensson (Patrik.Torstesson at gmail.com)
   6  *
   7  * (C) 2005 Ximian, Inc.  http://www.ximian.com
   8  */
   9  #include "mini.h"
  10
  11 #ifndef DISABLE_JIT
  12
  13
  14 /*
  15  * Returns true if @bb is a basic block which falls through the next block.
  16  * TODO verify if it helps to check if the bb last ins is a branch to its successor.
  17  */
  18 static gboolean
  19 mono_bb_is_fall_through (MonoCompile *cfg, MonoBasicBlock *bb)
  20 {
  21         return  bb->next_bb && bb->next_bb->region == bb->region && /*fall throught between regions is not really interesting or useful*/
  22                         (bb->last_ins == NULL || !MONO_IS_BRANCH_OP (bb->last_ins)); /*and the last op can't be a branch too*/
  23 }
  24
  25 /*
  26  * Used by the arch code to replace the exception handling
  27  * with a direct branch. This is safe to do if the
  28  * exception object isn't used, no rethrow statement and
  29  * no filter statement (verify).
  30  *
  31  */
  32 MonoInst *
  33 mono_branch_optimize_exception_target (MonoCompile *cfg, MonoBasicBlock *bb, const char * exname)
  34 {
  35         MonoMethod *method = cfg->method;
  36         MonoMethodHeader *header = mono_method_get_header (method);
  37         MonoExceptionClause *clause;
  38         MonoClass *exclass;
  39         int i;
  40
  41         if (!(cfg->opt & MONO_OPT_EXCEPTION))
  42                 return NULL;
  43
  44         if (bb->region == -1 || !MONO_BBLOCK_IS_IN_REGION (bb, MONO_REGION_TRY))
  45                 return NULL;
  46
  47         exclass = mono_class_from_name (mono_get_corlib (), "System", exname);
  48         /* search for the handler */
  49         for (i = 0; i < header->num_clauses; ++i) {
  50                 clause = &header->clauses [i];
  51                 if (MONO_OFFSET_IN_CLAUSE (clause, bb->real_offset)) {
  52                         if (clause->flags == MONO_EXCEPTION_CLAUSE_NONE && clause->data.catch_class && mono_class_is_assignable_from (clause->data.catch_class, exclass)) {
  53                                 MonoBasicBlock *tbb;
  54
  55                                 /* get the basic block for the handler and
  56                                  * check if the exception object is used.
  57                                  * Flag is set during method_to_ir due to
  58                                  * pop-op is optmized away in codegen (burg).
  59                                  */
  60                                 tbb = cfg->cil_offset_to_bb [clause->handler_offset];
  61                                 if (tbb && tbb->flags & BB_EXCEPTION_DEAD_OBJ && !(tbb->flags & BB_EXCEPTION_UNSAFE)) {
  62                                         MonoBasicBlock *targetbb = tbb;
  63                                         gboolean unsafe = FALSE;
  64
  65                                         /* Check if this catch clause is ok to optimize by
  66                                          * looking for the BB_EXCEPTION_UNSAFE in every BB that
  67                                          * belongs to the same region.
  68                                          *
  69                                          * UNSAFE flag is set during method_to_ir (OP_RETHROW)
  70                                          */
  71                                         while (!unsafe && tbb->next_bb && tbb->region == tbb->next_bb->region) {
  72                                                 if (tbb->next_bb->flags & BB_EXCEPTION_UNSAFE)  {
  73                                                         unsafe = TRUE;
  74                                                         break;
  75                                                 }
  76                                                 tbb = tbb->next_bb;
  77                                         }
  78
  79                                         if (!unsafe) {
  80                                                 MonoInst *jump;
  81
  82                                                 /* Create dummy inst to allow easier integration in
  83                                                  * arch dependent code (opcode ignored)
  84                                                  */
  85                                                 MONO_INST_NEW (cfg, jump, OP_BR);
  86
  87                                                 /* Allocate memory for our branch target */
  88                                                 jump->inst_i1 = mono_mempool_alloc0 (cfg->mempool, sizeof (MonoInst));
  89                                                 jump->inst_true_bb = targetbb;
  90
  91                                                 if (cfg->verbose_level > 2)
  92                                                         g_print ("found exception to optimize - returning branch to BB%d (%s) (instead of throw) for method %s:%s\n", targetbb->block_num, clause->data.catch_class->name, cfg->method->klass->name, cfg->method->name);
  93
  94                                                 return jump;
  95                                         }
  96
  97                                         return NULL;
  98                                 } else {
  99                                         /* Branching to an outer clause could skip inner clauses */
 100                                         return NULL;
 101                                 }
 102                         } else {
 103                                 /* Branching to an outer clause could skip inner clauses */
 104                                 return NULL;
 105                         }
 106                 }
 107         }
 108
 109         return NULL;
 110 }
 111
 112 static const int int_cmov_opcodes [] = {
 113         OP_CMOV_IEQ,
 114         OP_CMOV_INE_UN,
 115         OP_CMOV_ILE,
 116         OP_CMOV_IGE,
 117         OP_CMOV_ILT,
 118         OP_CMOV_IGT,
 119         OP_CMOV_ILE_UN,
 120         OP_CMOV_IGE_UN,
 121         OP_CMOV_ILT_UN,
 122         OP_CMOV_IGT_UN
 123 };
 124
 125 static const int long_cmov_opcodes [] = {
 126         OP_CMOV_LEQ,
 127         OP_CMOV_LNE_UN,
 128         OP_CMOV_LLE,
 129         OP_CMOV_LGE,
 130         OP_CMOV_LLT,
 131         OP_CMOV_LGT,
 132         OP_CMOV_LLE_UN,
 133         OP_CMOV_LGE_UN,
 134         OP_CMOV_LLT_UN,
 135         OP_CMOV_LGT_UN
 136 };
 137
 138 static int
 139 br_to_br_un (int opcode)
 140 {
 141         switch (opcode) {
 142         case OP_IBGT:
 143                 return OP_IBGT_UN;
 144                 break;
 145         case OP_IBLE:
 146                 return OP_IBLE_UN;
 147                 break;
 148         case OP_LBGT:
 149                 return OP_LBGT_UN;
 150                 break;
 151         case OP_LBLE:
 152                 return OP_LBLE_UN;
 153                 break;
 154         default:
 155                 g_assert_not_reached ();
 156                 return -1;
 157         }
 158 }
 159
 160 /**
 161  * mono_replace_ins:
 162  *
 163  *   Replace INS with its decomposition which is stored in a series of bblocks starting
 164  * at FIRST_BB and ending at LAST_BB. On enter, PREV points to the predecessor of INS.
 165  * On return, it will be set to the last ins of the decomposition.
 166  */
 167 void
 168 mono_replace_ins (MonoCompile *cfg, MonoBasicBlock *bb, MonoInst *ins, MonoInst **prev, MonoBasicBlock *first_bb, MonoBasicBlock *last_bb)
 169 {
 170         MonoInst *next = ins->next;
 171
 172         if (next && next->opcode == OP_NOP) {
 173                 /* Avoid NOPs following branches */
 174                 ins->next = next->next;
 175                 next = next->next;
 176         }
 177
 178         if (first_bb == last_bb) {
 179                 /*
 180                  * Only one replacement bb, merge the code into
 181                  * the current bb.
 182                  */
 183
 184                 /* Delete links between the first_bb and its successors */
 185                 while (first_bb->out_count)
 186                         mono_unlink_bblock (cfg, first_bb, first_bb->out_bb [0]);
 187
 188                 /* Head */
 189                 if (*prev) {
 190                         (*prev)->next = first_bb->code;
 191                         first_bb->code->prev = (*prev);
 192                 } else {
 193                         bb->code = first_bb->code;
 194                 }
 195
 196                 /* Tail */
 197                 last_bb->last_ins->next = next;
 198                 if (next)
 199                         next->prev = last_bb->last_ins;
 200                 else
 201                         bb->last_ins = last_bb->last_ins;
 202                 *prev = last_bb->last_ins;
 203                 bb->has_array_access |= first_bb->has_array_access;
 204         } else {
 205                 int i, count;
 206                 MonoBasicBlock **tmp_bblocks, *tmp;
 207                 MonoInst *last;
 208
 209                 /* Multiple BBs */
 210
 211                 /* Set region */
 212                 for (tmp = first_bb; tmp; tmp = tmp->next_bb)
 213                         tmp->region = bb->region;
 214
 215                 /* Split the original bb */
 216                 if (ins->next)
 217                         ins->next->prev = NULL;
 218                 ins->next = NULL;
 219                 bb->last_ins = ins;
 220
 221                 /* Merge the second part of the original bb into the last bb */
 222                 if (last_bb->last_ins) {
 223                         last_bb->last_ins->next = next;
 224                         if (next)
 225                                 next->prev = last_bb->last_ins;
 226                 } else {
 227                         last_bb->code = next;
 228                 }
 229                 last_bb->has_array_access |= bb->has_array_access;
 230
 231                 if (next) {
 232                         for (last = next; last->next != NULL; last = last->next)
 233                                 ;
 234                         last_bb->last_ins = last;
 235                 }
 236
 237                 for (i = 0; i < bb->out_count; ++i)
 238                         mono_link_bblock (cfg, last_bb, bb->out_bb [i]);
 239
 240                 /* Merge the first (dummy) bb to the original bb */
 241                 if (*prev) {
 242                         (*prev)->next = first_bb->code;
 243                         first_bb->code->prev = (*prev);
 244                 } else {
 245                         bb->code = first_bb->code;
 246                 }
 247                 bb->last_ins = first_bb->last_ins;
 248                 bb->has_array_access |= first_bb->has_array_access;
 249
 250                 /* Delete the links between the original bb and its successors */
 251                 tmp_bblocks = bb->out_bb;
 252                 count = bb->out_count;
 253                 for (i = 0; i < count; ++i)
 254                         mono_unlink_bblock (cfg, bb, tmp_bblocks [i]);
 255
 256                 /* Add links between the original bb and the first_bb's successors */
 257                 for (i = 0; i < first_bb->out_count; ++i) {
 258                         MonoBasicBlock *out_bb = first_bb->out_bb [i];
 259
 260                         mono_link_bblock (cfg, bb, out_bb);
 261                 }
 262                 /* Delete links between the first_bb and its successors */
 263                 for (i = 0; i < bb->out_count; ++i) {
 264                         MonoBasicBlock *out_bb = bb->out_bb [i];
 265
 266                         mono_unlink_bblock (cfg, first_bb, out_bb);
 267                 }
 268                 last_bb->next_bb = bb->next_bb;
 269                 bb->next_bb = first_bb->next_bb;
 270
 271                 *prev = NULL;
 272         }
 273 }
 274
 275 void
 276 mono_if_conversion (MonoCompile *cfg)
 277 {
 278 #ifdef MONO_ARCH_HAVE_CMOV_OPS
 279         MonoBasicBlock *bb;
 280         gboolean changed = FALSE;
 281
 282         if (!(cfg->opt & MONO_OPT_CMOV))
 283                 return;
 284
 285         // FIXME: Make this work with extended bblocks
 286
 287         /*
 288          * This pass requires somewhat optimized IR code so it should be run after
 289          * local cprop/deadce. Also, it should be run before dominator computation, since
 290          * it changes control flow.
 291          */
 292         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
 293                 MonoBasicBlock *bb1, *bb2;
 294
 295         restart:
 296                 /* Look for the IR code generated from cond ? a : b
 297                  * which is:
 298                  * BB:
 299                  * b<cond> [BB1BB2]
 300                  * BB1:
 301                  * <var> <- <a>
 302                  * br BB3
 303                  * BB2:
 304                  * <var> <- <b>
 305                  * br BB3
 306                  */
 307                 if (!(bb->out_count == 2 && !bb->extended))
 308                         continue;
 309
 310                 bb1 = bb->out_bb [0];
 311                 bb2 = bb->out_bb [1];
 312
 313                 if (bb1->in_count == 1 && bb2->in_count == 1 && bb1->out_count == 1 && bb2->out_count == 1 && bb1->out_bb [0] == bb2->out_bb [0]) {
 314                         MonoInst *compare, *branch, *ins1, *ins2, *cmov, *move, *tmp;
 315                         MonoBasicBlock *true_bb, *false_bb;
 316                         gboolean simple, ret;
 317                         int dreg, tmp_reg;
 318                         CompType comp_type;
 319
 320                         if (bb->last_ins && (bb->last_ins->opcode == OP_BR_REG || bb->last_ins->opcode == OP_BR))
 321                                 continue;
 322
 323                         /* Find the compare instruction */
 324                         if (!bb->last_ins || !bb->last_ins->prev)
 325                                 continue;
 326                         branch = bb->last_ins;
 327                         compare = branch->prev;
 328
 329                         if (!MONO_IS_COND_BRANCH_OP (branch))
 330                                 /* This can happen if a cond branch is optimized away */
 331                                 continue;
 332
 333                         true_bb = branch->inst_true_bb;
 334                         false_bb = branch->inst_false_bb;
 335
 336                         /*
 337                          * Check that bb1 and bb2 are 'simple' and both assign to the same
 338                          * variable.
 339                          */
 340                         /* FIXME: Get rid of the nops earlier */
 341                         ins1 = true_bb->code;
 342                         while (ins1 && ins1->opcode == OP_NOP)
 343                                 ins1 = ins1->next;
 344                         ins2 = false_bb->code;
 345                         while (ins2 && ins2->opcode == OP_NOP)
 346                                 ins2 = ins2->next;
 347                         if (!(ins1 && ins2 && ins1->dreg == ins2->dreg && ins1->dreg != -1))
 348                                 continue;
 349
 350                         simple = TRUE;
 351                         for (tmp = ins1->next; tmp; tmp = tmp->next)
 352                                 if (!((tmp->opcode == OP_NOP) || (tmp->opcode == OP_BR)))
 353                                         simple = FALSE;
 354
 355                         for (tmp = ins2->next; tmp; tmp = tmp->next)
 356                                 if (!((tmp->opcode == OP_NOP) || (tmp->opcode == OP_BR)))
 357                                         simple = FALSE;
 358
 359                         if (!simple)
 360                                 continue;
 361
 362                         /* We move ins1/ins2 before the compare so they should have no side effect */
 363                         if (!(MONO_INS_HAS_NO_SIDE_EFFECT (ins1) && MONO_INS_HAS_NO_SIDE_EFFECT (ins2)))
 364                                 continue;
 365
 366                         /* Moving ins1/ins2 could change the comparison */
 367                         /* FIXME: */
 368                         if (!((compare->sreg1 != ins1->dreg) && (compare->sreg2 != ins1->dreg)))
 369                                 continue;
 370
 371                         /* FIXME: */
 372                         comp_type = mono_opcode_to_type (branch->opcode, compare->opcode);
 373                         if (!((comp_type == CMP_TYPE_I) || (comp_type == CMP_TYPE_L)))
 374                                 continue;
 375
 376                         /* FIXME: */
 377                         /* ins->type might not be set */
 378                         if (INS_INFO (ins1->opcode) [MONO_INST_DEST] != 'i')
 379                                 continue;
 380
 381                         if (cfg->verbose_level > 2) {
 382                                 printf ("\tBranch -> CMove optimization in BB%d on\n", bb->block_num);
 383                                 printf ("\t\t"); mono_print_ins (compare);
 384                                 printf ("\t\t"); mono_print_ins (compare->next);
 385                                 printf ("\t\t"); mono_print_ins (ins1);
 386                                 printf ("\t\t"); mono_print_ins (ins2);
 387                         }
 388
 389                         changed = TRUE;
 390
 391                         //printf ("HIT!\n");
 392
 393                         /* Assignments to the return register must remain at the end of bbs */
 394                         if (cfg->ret)
 395                                 ret = ins1->dreg == cfg->ret->dreg;
 396                         else
 397                                 ret = FALSE;
 398
 399                         tmp_reg = mono_alloc_dreg (cfg, STACK_I4);
 400                         dreg = ins1->dreg;
 401
 402                         /* Rewrite ins1 to emit to tmp_reg */
 403                         ins1->dreg = tmp_reg;
 404
 405                         if (ret) {
 406                                 dreg = mono_alloc_dreg (cfg, STACK_I4);
 407                                 ins2->dreg = dreg;
 408                         }
 409
 410                         /* Remove ins1/ins2 from bb1/bb2 */
 411                         MONO_REMOVE_INS (true_bb, ins1);
 412                         MONO_REMOVE_INS (false_bb, ins2);
 413
 414                         /* Move ins1 and ins2 before the comparison */
 415                         /* ins1 comes first to avoid ins1 overwriting an argument of ins2 */
 416                         mono_bblock_insert_before_ins (bb, compare, ins2);
 417                         mono_bblock_insert_before_ins (bb, ins2, ins1);
 418
 419                         /* Add cmov instruction */
 420                         MONO_INST_NEW (cfg, cmov, OP_NOP);
 421                         cmov->dreg = dreg;
 422                         cmov->sreg1 = dreg;
 423                         cmov->sreg2 = tmp_reg;
 424                         switch (mono_opcode_to_type (branch->opcode, compare->opcode)) {
 425                         case CMP_TYPE_I:
 426                                 cmov->opcode = int_cmov_opcodes [mono_opcode_to_cond (branch->opcode)];
 427                                 break;
 428                         case CMP_TYPE_L:
 429                                 cmov->opcode = long_cmov_opcodes [mono_opcode_to_cond (branch->opcode)];
 430                                 break;
 431                         default:
 432                                 g_assert_not_reached ();
 433                         }
 434                         mono_bblock_insert_after_ins (bb, compare, cmov);
 435
 436                         if (ret) {
 437                                 /* Add an extra move */
 438                                 MONO_INST_NEW (cfg, move, OP_MOVE);
 439                                 move->dreg = cfg->ret->dreg;
 440                                 move->sreg1 = dreg;
 441                                 mono_bblock_insert_after_ins (bb, cmov, move);
 442                         }
 443
 444                         /* Rewrite the branch */
 445                         branch->opcode = OP_BR;
 446                         branch->inst_target_bb = true_bb->out_bb [0];
 447                         mono_link_bblock (cfg, bb, branch->inst_target_bb);
 448
 449                         /* Reorder bblocks */
 450                         mono_unlink_bblock (cfg, bb, true_bb);
 451                         mono_unlink_bblock (cfg, bb, false_bb);
 452                         mono_unlink_bblock (cfg, true_bb, true_bb->out_bb [0]);
 453                         mono_unlink_bblock (cfg, false_bb, false_bb->out_bb [0]);
 454                         mono_remove_bblock (cfg, true_bb);
 455                         mono_remove_bblock (cfg, false_bb);
 456
 457                         /* Merge bb and its successor if possible */
 458                         if ((bb->out_bb [0]->in_count == 1) && (bb->out_bb [0] != cfg->bb_exit) &&
 459                                 (bb->region == bb->out_bb [0]->region)) {
 460                                 mono_merge_basic_blocks (cfg, bb, bb->out_bb [0]);
 461                                 goto restart;
 462                         }
 463                 }
 464
 465                 /* Look for the IR code generated from if (cond) <var> <- <a>
 466                  * which is:
 467                  * BB:
 468                  * b<cond> [BB1BB2]
 469                  * BB1:
 470                  * <var> <- <a>
 471                  * br BB2
 472                  */
 473
 474                 if ((bb2->in_count == 1 && bb2->out_count == 1 && bb2->out_bb [0] == bb1) ||
 475                         (bb1->in_count == 1 && bb1->out_count == 1 && bb1->out_bb [0] == bb2)) {
 476                         MonoInst *compare, *branch, *ins1, *cmov, *tmp;
 477                         gboolean simple;
 478                         int dreg, tmp_reg;
 479                         CompType comp_type;
 480                         CompRelation cond;
 481                         MonoBasicBlock *next_bb, *code_bb;
 482
 483                         /* code_bb is the bblock containing code, next_bb is the successor bblock */
 484                         if (bb2->in_count == 1 && bb2->out_count == 1 && bb2->out_bb [0] == bb1) {
 485                                 code_bb = bb2;
 486                                 next_bb = bb1;
 487                         } else {
 488                                 code_bb = bb1;
 489                                 next_bb = bb2;
 490                         }
 491
 492                         ins1 = code_bb->code;
 493
 494                         if (!ins1)
 495                                 continue;
 496
 497                         /* Check that code_bb is simple */
 498                         simple = TRUE;
 499                         for (tmp = ins1->next; tmp; tmp = tmp->next)
 500                                 if (!((tmp->opcode == OP_NOP) || (tmp->opcode == OP_BR)))
 501                                         simple = FALSE;
 502
 503                         if (!simple)
 504                                 continue;
 505
 506                         /* We move ins1 before the compare so it should have no side effect */
 507                         if (!MONO_INS_HAS_NO_SIDE_EFFECT (ins1))
 508                                 continue;
 509
 510                         if (bb->last_ins && bb->last_ins->opcode == OP_BR_REG)
 511                                 continue;
 512
 513                         /* Find the compare instruction */
 514
 515                         if (!bb->last_ins || !bb->last_ins->prev)
 516                                 continue;
 517                         branch = bb->last_ins;
 518                         compare = branch->prev;
 519
 520                         if (!MONO_IS_COND_BRANCH_OP (branch))
 521                                 /* This can happen if a cond branch is optimized away */
 522                                 continue;
 523
 524                         /* FIXME: */
 525                         comp_type = mono_opcode_to_type (branch->opcode, compare->opcode);
 526                         if (!((comp_type == CMP_TYPE_I) || (comp_type == CMP_TYPE_L)))
 527                                 continue;
 528
 529                         /* FIXME: */
 530                         /* ins->type might not be set */
 531                         if (INS_INFO (ins1->opcode) [MONO_INST_DEST] != 'i')
 532                                 continue;
 533
 534                         /* FIXME: */
 535                         if (cfg->ret && ins1->dreg == cfg->ret->dreg)
 536                                 continue;
 537
 538                         if (cfg->verbose_level > 2) {
 539                                 printf ("\tBranch -> CMove optimization (2) in BB%d on\n", bb->block_num);
 540                                 printf ("\t\t"); mono_print_ins (compare);
 541                                 printf ("\t\t"); mono_print_ins (compare->next);
 542                                 printf ("\t\t"); mono_print_ins (ins1);
 543                         }
 544
 545                         changed = TRUE;
 546
 547                         //printf ("HIT!\n");
 548
 549                         tmp_reg = mono_alloc_dreg (cfg, STACK_I4);
 550                         dreg = ins1->dreg;
 551
 552                         /* Rewrite ins1 to emit to tmp_reg */
 553                         ins1->dreg = tmp_reg;
 554
 555                         /* Remove ins1 from code_bb */
 556                         MONO_REMOVE_INS (code_bb, ins1);
 557
 558                         /* Move ins1 before the comparison */
 559                         mono_bblock_insert_before_ins (bb, compare, ins1);
 560
 561                         /* Add cmov instruction */
 562                         MONO_INST_NEW (cfg, cmov, OP_NOP);
 563                         cmov->dreg = dreg;
 564                         cmov->sreg1 = dreg;
 565                         cmov->sreg2 = tmp_reg;
 566                         cond = mono_opcode_to_cond (branch->opcode);
 567                         if (branch->inst_false_bb == code_bb)
 568                                 cond = mono_negate_cond (cond);
 569                         switch (mono_opcode_to_type (branch->opcode, compare->opcode)) {
 570                         case CMP_TYPE_I:
 571                                 cmov->opcode = int_cmov_opcodes [cond];
 572                                 break;
 573                         case CMP_TYPE_L:
 574                                 cmov->opcode = long_cmov_opcodes [cond];
 575                                 break;
 576                         default:
 577                                 g_assert_not_reached ();
 578                         }
 579                         mono_bblock_insert_after_ins (bb, compare, cmov);
 580
 581                         /* Rewrite the branch */
 582                         branch->opcode = OP_BR;
 583                         branch->inst_target_bb = next_bb;
 584                         mono_link_bblock (cfg, bb, branch->inst_target_bb);
 585
 586                         /* Nullify the branch at the end of code_bb */
 587                         if (code_bb->code) {
 588                                 branch = code_bb->code;
 589                                 MONO_DELETE_INS (code_bb, branch);
 590                         }
 591
 592                         /* Reorder bblocks */
 593                         mono_unlink_bblock (cfg, bb, code_bb);
 594                         mono_unlink_bblock (cfg, code_bb, next_bb);
 595
 596                         /* Merge bb and its successor if possible */
 597                         if ((bb->out_bb [0]->in_count == 1) && (bb->out_bb [0] != cfg->bb_exit) &&
 598                                 (bb->region == bb->out_bb [0]->region)) {
 599                                 mono_merge_basic_blocks (cfg, bb, bb->out_bb [0]);
 600
 601                                 /*
 602                                  * bbn might have fallen through to the next bb without a branch,
 603                                  * have to add one now (#474718).
 604                                  * FIXME: Maybe need to do this more generally in
 605                                  * merge_basic_blocks () ?
 606                                  */
 607                                 if (!(bb->last_ins && MONO_IS_BRANCH_OP (bb->last_ins)) && bb->out_count) {
 608                                         MONO_INST_NEW (cfg, ins1, OP_BR);
 609                                         ins1->inst_target_bb = bb->out_bb [0];
 610                                         MONO_ADD_INS (bb, ins1);
 611                                 }
 612                                 goto restart;
 613                         }
 614                 }
 615         }
 616
 617         /*
 618          * Optimize checks like: if (v < 0 || v > limit) by changing then to unsigned
 619          * compares. This isn't really if conversion, but it easier to do here than in
 620          * optimize_branches () since the IR is already optimized.
 621          */
 622         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
 623                 MonoBasicBlock *bb1, *bb2, *true_bb, *false_bb, *next_bb;
 624                 MonoInst *branch1, *branch2, *compare1, *ins;
 625
 626                 /* Look for the IR code generated from if (<var> < 0 || v > <limit>)
 627                  * after branch opts which is:
 628                  * BB:
 629                  * icompare_imm R [0]
 630                  * int_blt [BB1BB2]
 631                  * BB2:
 632                  * icompare_imm R [<limit>]
 633                  * int_ble [BB3BB1]
 634                  */
 635                 if (!(bb->out_count == 2 && !bb->extended))
 636                         continue;
 637
 638                 bb1 = bb->out_bb [0];
 639                 bb2 = bb->out_bb [1];
 640
 641                 // FIXME: Add more cases
 642
 643                 /* Check structure */
 644                 if (!(bb1->in_count == 2 && bb1->in_bb [0] == bb && bb1->in_bb [1] == bb2 && bb2->in_count == 1 && bb2->out_count == 2))
 645                         continue;
 646
 647                 next_bb = bb2;
 648
 649                 /* Check first branch */
 650                 branch1 = bb->last_ins;
 651                 if (!(branch1 && ((branch1->opcode == OP_IBLT) || (branch1->opcode == OP_LBLT)) && (branch1->inst_false_bb == next_bb)))
 652                         continue;
 653
 654                 true_bb = branch1->inst_true_bb;
 655
 656                 /* Check second branch */
 657                 branch2 = next_bb->last_ins;
 658                 if (!branch2)
 659                         continue;
 660
 661                 /* mcs sometimes generates inverted branches */
 662                 if (((branch2->opcode == OP_IBGT) || (branch2->opcode == OP_LBGT)) && branch2->inst_true_bb == branch1->inst_true_bb)
 663                         false_bb = branch2->inst_false_bb;
 664                 else if (((branch2->opcode == OP_IBLE) || (branch2->opcode == OP_LBLE)) && branch2->inst_false_bb == branch1->inst_true_bb)
 665                         false_bb = branch2->inst_true_bb;
 666                 else
 667                         continue;
 668
 669                 /* Check first compare */
 670                 compare1 = bb->last_ins->prev;
 671                 if (!(compare1 && ((compare1->opcode == OP_ICOMPARE_IMM) || (compare1->opcode == OP_LCOMPARE_IMM)) && compare1->inst_imm == 0))
 672                         continue;
 673
 674                 /* Check second bblock */
 675                 ins = next_bb->code;
 676                 if (!ins)
 677                         continue;
 678                 if (((ins->opcode == OP_ICOMPARE_IMM) || (ins->opcode == OP_LCOMPARE_IMM)) && ins->sreg1 == compare1->sreg1 && ins->next == branch2) {
 679                         /* The second arg must be positive */
 680                         if (ins->inst_imm < 0)
 681                                 continue;
 682                 } else if (((ins->opcode == OP_LDLEN) || (ins->opcode == OP_STRLEN)) && ins->dreg != compare1->sreg1 && ins->next && ins->next->opcode == OP_ICOMPARE && ins->next->sreg1 == compare1->sreg1 && ins->next->sreg2 == ins->dreg && ins->next->next == branch2) {
 683                         /* Another common case: if (index < 0 || index > arr.Length) */
 684                 } else {
 685                         continue;
 686                 }
 687
 688                 if (cfg->verbose_level > 2) {
 689                         printf ("\tSigned->unsigned compare optimization in BB%d on\n", bb->block_num);
 690                         printf ("\t\t"); mono_print_ins (compare1);
 691                         printf ("\t\t"); mono_print_ins (compare1->next);
 692                         printf ("\t\t"); mono_print_ins (ins);
 693                 }
 694
 695                 /* Rewrite the first compare+branch */
 696                 MONO_DELETE_INS (bb, compare1);
 697                 branch1->opcode = OP_BR;
 698                 mono_unlink_bblock (cfg, bb, branch1->inst_true_bb);
 699                 mono_unlink_bblock (cfg, bb, branch1->inst_false_bb);
 700                 branch1->inst_target_bb = next_bb;
 701                 mono_link_bblock (cfg, bb, next_bb);
 702
 703                 /* Rewrite the second branch */
 704                 branch2->opcode = br_to_br_un (branch2->opcode);
 705
 706                 mono_merge_basic_blocks (cfg, bb, next_bb);
 707         }
 708
 709 #if 0
 710         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
 711                 MonoBasicBlock *bb1, *bb2;
 712                 MonoInst *prev, *compare, *branch, *ins1, *ins2, *cmov, *move, *tmp;
 713                 gboolean simple, ret;
 714                 int dreg, tmp_reg;
 715                 CompType comp_type;
 716
 717                 /* Look for the IR code generated from if (cond) <var> <- <a>
 718                  * after branch opts which is:
 719                  * BB:
 720                  * compare
 721                  * b<cond> [BB1]
 722                  * <var> <- <a>
 723                  * BB1:
 724                  */
 725                 if (!(bb->out_count == 1 && bb->extended && bb->code && bb->code->next && bb->code->next->next))
 726                         continue;
 727
 728                 mono_print_bb (bb, "");
 729
 730                 /* Find the compare instruction */
 731                 prev = NULL;
 732                 compare = bb->code;
 733                 g_assert (compare);
 734                 while (compare->next->next && compare->next->next != bb->last_ins) {
 735                         prev = compare;
 736                         compare = compare->next;
 737                 }
 738                 branch = compare->next;
 739                 if (!MONO_IS_COND_BRANCH_OP (branch))
 740                         continue;
 741         }
 742 #endif
 743
 744         if (changed) {
 745                 if (cfg->opt & MONO_OPT_BRANCH)
 746                         mono_optimize_branches (cfg);
 747                 /* Merging bblocks could make some variables local */
 748                 mono_handle_global_vregs (cfg);
 749                 if (cfg->opt & (MONO_OPT_CONSPROP | MONO_OPT_COPYPROP))
 750                         mono_local_cprop (cfg);
 751                 if (cfg->opt & MONO_OPT_DEADCE)
 752                         mono_local_deadce (cfg);
 753         }
 754 #endif
 755 }
 756
 757 void
 758 mono_nullify_basic_block (MonoBasicBlock *bb)
 759 {
 760         bb->in_count = 0;
 761         bb->out_count = 0;
 762         bb->in_bb = NULL;
 763         bb->out_bb = NULL;
 764         bb->next_bb = NULL;
 765         bb->code = bb->last_ins = NULL;
 766         bb->cil_code = NULL;
 767 }
 768
 769 static void
 770 replace_out_block (MonoBasicBlock *bb, MonoBasicBlock *orig,  MonoBasicBlock *repl)
 771 {
 772         int i;
 773
 774         for (i = 0; i < bb->out_count; i++) {
 775                 MonoBasicBlock *ob = bb->out_bb [i];
 776                 if (ob == orig) {
 777                         if (!repl) {
 778                                 if (bb->out_count > 1) {
 779                                         bb->out_bb [i] = bb->out_bb [bb->out_count - 1];
 780                                 }
 781                                 bb->out_count--;
 782                         } else {
 783                                 bb->out_bb [i] = repl;
 784                         }
 785                 }
 786         }
 787 }
 788
 789 static void
 790 replace_in_block (MonoBasicBlock *bb, MonoBasicBlock *orig, MonoBasicBlock *repl)
 791 {
 792         int i;
 793
 794         for (i = 0; i < bb->in_count; i++) {
 795                 MonoBasicBlock *ib = bb->in_bb [i];
 796                 if (ib == orig) {
 797                         if (!repl) {
 798                                 if (bb->in_count > 1) {
 799                                         bb->in_bb [i] = bb->in_bb [bb->in_count - 1];
 800                                 }
 801                                 bb->in_count--;
 802                         } else {
 803                                 bb->in_bb [i] = repl;
 804                         }
 805                 }
 806         }
 807 }
 808
 809 static void
 810 replace_out_block_in_code (MonoBasicBlock *bb, MonoBasicBlock *orig, MonoBasicBlock *repl) {
 811         MonoInst *ins;
 812
 813         for (ins = bb->code; ins != NULL; ins = ins->next) {
 814                 switch (ins->opcode) {
 815                 case OP_BR:
 816                         if (ins->inst_target_bb == orig)
 817                                 ins->inst_target_bb = repl;
 818                         break;
 819                 case OP_CALL_HANDLER:
 820                         if (ins->inst_target_bb == orig)
 821                                 ins->inst_target_bb = repl;
 822                         break;
 823                 case OP_SWITCH: {
 824                         int i;
 825                         int n = GPOINTER_TO_INT (ins->klass);
 826                         for (i = 0; i < n; i++ ) {
 827                                 if (ins->inst_many_bb [i] == orig)
 828                                         ins->inst_many_bb [i] = repl;
 829                         }
 830                         break;
 831                 }
 832                 default:
 833                         if (MONO_IS_COND_BRANCH_OP (ins)) {
 834                                 if (ins->inst_true_bb == orig)
 835                                         ins->inst_true_bb = repl;
 836                                 if (ins->inst_false_bb == orig)
 837                                         ins->inst_false_bb = repl;
 838                         } else if (MONO_IS_JUMP_TABLE (ins)) {
 839                                 int i;
 840                                 MonoJumpInfoBBTable *table = MONO_JUMP_TABLE_FROM_INS (ins);
 841                                 for (i = 0; i < table->table_size; i++ ) {
 842                                         if (table->table [i] == orig)
 843                                                 table->table [i] = repl;
 844                                 }
 845                         }
 846
 847                         break;
 848                 }
 849         }
 850 }
 851
 852 /**
 853   * Check if a bb is useless (is just made of NOPs and ends with an
 854   * unconditional branch, or nothing).
 855   * If it is so, unlink it from the CFG and nullify it, and return TRUE.
 856   * Otherwise, return FALSE;
 857   */
 858 static gboolean
 859 remove_block_if_useless (MonoCompile *cfg, MonoBasicBlock *bb, MonoBasicBlock *previous_bb) {
 860         MonoBasicBlock *target_bb = NULL;
 861         MonoInst *inst;
 862
 863         /* Do not touch handlers */
 864         if (bb->region != -1) {
 865                 bb->not_useless = TRUE;
 866                 return FALSE;
 867         }
 868
 869         MONO_BB_FOR_EACH_INS (bb, inst) {
 870                 switch (inst->opcode) {
 871                 case OP_NOP:
 872                         break;
 873                 case OP_BR:
 874                         target_bb = inst->inst_target_bb;
 875                         break;
 876                 default:
 877                         bb->not_useless = TRUE;
 878                         return FALSE;
 879                 }
 880         }
 881
 882         if (target_bb == NULL) {
 883                 if ((bb->out_count == 1) && (bb->out_bb [0] == bb->next_bb)) {
 884                         target_bb = bb->next_bb;
 885                 } else {
 886                         /* Do not touch empty BBs that do not "fall through" to their next BB (like the exit BB) */
 887                         return FALSE;
 888                 }
 889         }
 890
 891         /* Do not touch BBs following a switch (they are the "default" branch) */
 892         if ((previous_bb->last_ins != NULL) && (previous_bb->last_ins->opcode == OP_SWITCH)) {
 893                 return FALSE;
 894         }
 895
 896         /* Do not touch BBs following the entry BB and jumping to something that is not */
 897         /* thiry "next" bb (the entry BB cannot contain the branch) */
 898         if ((previous_bb == cfg->bb_entry) && (bb->next_bb != target_bb)) {
 899                 return FALSE;
 900         }
 901
 902         /*
 903          * Do not touch BBs following a try block as the code in
 904          * mini_method_compile needs them to compute the length of the try block.
 905          */
 906         if (MONO_BBLOCK_IS_IN_REGION (previous_bb, MONO_REGION_TRY))
 907                 return FALSE;
 908
 909         /* Check that there is a target BB, and that bb is not an empty loop (Bug 75061) */
 910         if ((target_bb != NULL) && (target_bb != bb)) {
 911                 int i;
 912
 913                 if (cfg->verbose_level > 1) {
 914                         printf ("remove_block_if_useless, removed BB%d\n", bb->block_num);
 915                 }
 916
 917                 /* unlink_bblock () modifies the bb->in_bb array so can't use a for loop here */
 918                 while (bb->in_count) {
 919                         MonoBasicBlock *in_bb = bb->in_bb [0];
 920                         mono_unlink_bblock (cfg, in_bb, bb);
 921                         mono_link_bblock (cfg, in_bb, target_bb);
 922                         replace_out_block_in_code (in_bb, bb, target_bb);
 923                 }
 924
 925                 mono_unlink_bblock (cfg, bb, target_bb);
 926                 if (previous_bb != cfg->bb_entry && mono_bb_is_fall_through (cfg, previous_bb)) {
 927                         for (i = 0; i < previous_bb->out_count; i++) {
 928                                 if (previous_bb->out_bb [i] == target_bb) {
 929                                         MonoInst *jump;
 930                                         MONO_INST_NEW (cfg, jump, OP_BR);
 931                                         MONO_ADD_INS (previous_bb, jump);
 932                                         jump->cil_code = previous_bb->cil_code;
 933                                         jump->inst_target_bb = target_bb;
 934                                         break;
 935                                 }
 936                         }
 937                 }
 938
 939                 previous_bb->next_bb = bb->next_bb;
 940                 mono_nullify_basic_block (bb);
 941
 942                 return TRUE;
 943         } else {
 944                 return FALSE;
 945         }
 946 }
 947
 948 void
 949 mono_merge_basic_blocks (MonoCompile *cfg, MonoBasicBlock *bb, MonoBasicBlock *bbn)
 950 {
 951         MonoInst *inst;
 952         MonoBasicBlock *prev_bb;
 953         int i;
 954
 955         bb->has_array_access |= bbn->has_array_access;
 956         bb->extended |= bbn->extended;
 957
 958         mono_unlink_bblock (cfg, bb, bbn);
 959         for (i = 0; i < bbn->out_count; ++i)
 960                 mono_link_bblock (cfg, bb, bbn->out_bb [i]);
 961         while (bbn->out_count)
 962                 mono_unlink_bblock (cfg, bbn, bbn->out_bb [0]);
 963
 964         /* Handle the branch at the end of the bb */
 965         if (bb->has_call_handler) {
 966                 for (inst = bb->code; inst != NULL; inst = inst->next) {
 967                         if (inst->opcode == OP_CALL_HANDLER) {
 968                                 g_assert (inst->inst_target_bb == bbn);
 969                                 NULLIFY_INS (inst);
 970                         }
 971                 }
 972         }
 973         if (bb->has_jump_table) {
 974                 for (inst = bb->code; inst != NULL; inst = inst->next) {
 975                         if (MONO_IS_JUMP_TABLE (inst)) {
 976                                 int i;
 977                                 MonoJumpInfoBBTable *table = MONO_JUMP_TABLE_FROM_INS (inst);
 978                                 for (i = 0; i < table->table_size; i++ ) {
 979                                         /* Might be already NULL from a previous merge */
 980                                         if (table->table [i])
 981                                                 g_assert (table->table [i] == bbn);
 982                                         table->table [i] = NULL;
 983                                 }
 984                                 /* Can't nullify this as later instructions depend on it */
 985                         }
 986                 }
 987         }
 988         if (bb->last_ins && MONO_IS_COND_BRANCH_OP (bb->last_ins)) {
 989                 g_assert (bb->last_ins->inst_false_bb == bbn);
 990                 bb->last_ins->inst_false_bb = NULL;
 991                 bb->extended = TRUE;
 992         } else if (bb->last_ins && MONO_IS_BRANCH_OP (bb->last_ins)) {
 993                 NULLIFY_INS (bb->last_ins);
 994         }
 995
 996         bb->has_call_handler |= bbn->has_call_handler;
 997         bb->has_jump_table |= bbn->has_jump_table;
 998
 999         if (bb->last_ins) {
1000                 if (bbn->code) {
1001                         bb->last_ins->next = bbn->code;
1002                         bbn->code->prev = bb->last_ins;
1003                         bb->last_ins = bbn->last_ins;
1004                 }
1005         } else {
1006                 bb->code = bbn->code;
1007                 bb->last_ins = bbn->last_ins;
1008         }
1009
1010         for (prev_bb = cfg->bb_entry; prev_bb && prev_bb->next_bb != bbn; prev_bb = prev_bb->next_bb)
1011                 ;
1012         if (prev_bb) {
1013                 prev_bb->next_bb = bbn->next_bb;
1014         } else {
1015                 /* bbn might not be in the bb list yet */
1016                 if (bb->next_bb == bbn)
1017                         bb->next_bb = bbn->next_bb;
1018         }
1019         mono_nullify_basic_block (bbn);
1020
1021         /*
1022          * If bbn fell through to its next bblock, have to add a branch, since bb
1023          * will not fall though to the same bblock (#513931).
1024          */
1025         if (bb->last_ins && bb->out_count == 1 && bb->out_bb [0] != bb->next_bb && !MONO_IS_BRANCH_OP (bb->last_ins)) {
1026                 MONO_INST_NEW (cfg, inst, OP_BR);
1027                 inst->inst_target_bb = bb->out_bb [0];
1028                 MONO_ADD_INS (bb, inst);
1029         }
1030 }
1031
1032 static void
1033 move_basic_block_to_end (MonoCompile *cfg, MonoBasicBlock *bb)
1034 {
1035         MonoBasicBlock *bbn, *next;
1036
1037         next = bb->next_bb;
1038
1039         /* Find the previous */
1040         for (bbn = cfg->bb_entry; bbn->next_bb && bbn->next_bb != bb; bbn = bbn->next_bb)
1041                 ;
1042         if (bbn->next_bb) {
1043                 bbn->next_bb = bb->next_bb;
1044         }
1045
1046         /* Find the last */
1047         for (bbn = cfg->bb_entry; bbn->next_bb; bbn = bbn->next_bb)
1048                 ;
1049         bbn->next_bb = bb;
1050         bb->next_bb = NULL;
1051
1052         /* Add a branch */
1053         if (next && (!bb->last_ins || ((bb->last_ins->opcode != OP_NOT_REACHED) && (bb->last_ins->opcode != OP_BR) && (bb->last_ins->opcode != OP_BR_REG) && (!MONO_IS_COND_BRANCH_OP (bb->last_ins))))) {
1054                 MonoInst *ins;
1055
1056                 MONO_INST_NEW (cfg, ins, OP_BR);
1057                 MONO_ADD_INS (bb, ins);
1058                 mono_link_bblock (cfg, bb, next);
1059                 ins->inst_target_bb = next;
1060         }
1061 }
1062
1063 /*
1064  * mono_remove_block:
1065  *
1066  *   Remove BB from the control flow graph
1067  */
1068 void
1069 mono_remove_bblock (MonoCompile *cfg, MonoBasicBlock *bb)
1070 {
1071         MonoBasicBlock *tmp_bb;
1072
1073         for (tmp_bb = cfg->bb_entry; tmp_bb && tmp_bb->next_bb != bb; tmp_bb = tmp_bb->next_bb)
1074                 ;
1075
1076         g_assert (tmp_bb);
1077         tmp_bb->next_bb = bb->next_bb;
1078 }
1079
1080 void
1081 mono_remove_critical_edges (MonoCompile *cfg)
1082 {
1083         MonoBasicBlock *bb;
1084         MonoBasicBlock *previous_bb;
1085
1086         if (cfg->verbose_level > 3) {
1087                 for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
1088                         int i;
1089                         printf ("remove_critical_edges, BEFORE BB%d (in:", bb->block_num);
1090                         for (i = 0; i < bb->in_count; i++) {
1091                                 printf (" %d", bb->in_bb [i]->block_num);
1092                         }
1093                         printf (") (out:");
1094                         for (i = 0; i < bb->out_count; i++) {
1095                                 printf (" %d", bb->out_bb [i]->block_num);
1096                         }
1097                         printf (")");
1098                         if (bb->last_ins != NULL) {
1099                                 printf (" ");
1100                                 mono_print_ins (bb->last_ins);
1101                         }
1102                         printf ("\n");
1103                 }
1104         }
1105
1106         for (previous_bb = cfg->bb_entry, bb = previous_bb->next_bb; bb != NULL; previous_bb = previous_bb->next_bb, bb = bb->next_bb) {
1107                 if (bb->in_count > 1) {
1108                         int in_bb_index;
1109                         for (in_bb_index = 0; in_bb_index < bb->in_count; in_bb_index++) {
1110                                 MonoBasicBlock *in_bb = bb->in_bb [in_bb_index];
1111                                 /*
1112                                  * Have to remove non-critical edges whose source ends with a BR_REG
1113                                  * ins too, since inserting a computation before the BR_REG could
1114                                  * overwrite the sreg1 of the ins.
1115                                  */
1116                                 if ((in_bb->out_count > 1) || (in_bb->out_count == 1 && in_bb->last_ins && in_bb->last_ins->opcode == OP_BR_REG)) {
1117                                         MonoBasicBlock *new_bb = mono_mempool_alloc0 ((cfg)->mempool, sizeof (MonoBasicBlock));
1118                                         new_bb->block_num = cfg->num_bblocks++;
1119 //                                      new_bb->real_offset = bb->real_offset;
1120                                         new_bb->region = bb->region;
1121
1122                                         /* Do not alter the CFG while altering the BB list */
1123                                         if (mono_bb_is_fall_through (cfg, previous_bb)) {
1124                                                 if (previous_bb != cfg->bb_entry) {
1125                                                         int i;
1126                                                         /* Make sure previous_bb really falls through bb */
1127                                                         for (i = 0; i < previous_bb->out_count; i++) {
1128                                                                 if (previous_bb->out_bb [i] == bb) {
1129                                                                         MonoInst *jump;
1130                                                                         MONO_INST_NEW (cfg, jump, OP_BR);
1131                                                                         MONO_ADD_INS (previous_bb, jump);
1132                                                                         jump->cil_code = previous_bb->cil_code;
1133                                                                         jump->inst_target_bb = bb;
1134                                                                         break;
1135                                                                 }
1136                                                         }
1137                                                 } else {
1138                                                         /* We cannot add any inst to the entry BB, so we must */
1139                                                         /* put a new BB in the middle to hold the OP_BR */
1140                                                         MonoInst *jump;
1141                                                         MonoBasicBlock *new_bb_after_entry = mono_mempool_alloc0 ((cfg)->mempool, sizeof (MonoBasicBlock));
1142                                                         new_bb_after_entry->block_num = cfg->num_bblocks++;
1143 //                                                      new_bb_after_entry->real_offset = bb->real_offset;
1144                                                         new_bb_after_entry->region = bb->region;
1145
1146                                                         MONO_INST_NEW (cfg, jump, OP_BR);
1147                                                         MONO_ADD_INS (new_bb_after_entry, jump);
1148                                                         jump->cil_code = bb->cil_code;
1149                                                         jump->inst_target_bb = bb;
1150
1151                                                         mono_unlink_bblock (cfg, previous_bb, bb);
1152                                                         mono_link_bblock (cfg, new_bb_after_entry, bb);
1153                                                         mono_link_bblock (cfg, previous_bb, new_bb_after_entry);
1154
1155                                                         previous_bb->next_bb = new_bb_after_entry;
1156                                                         previous_bb = new_bb_after_entry;
1157
1158                                                         if (cfg->verbose_level > 2) {
1159                                                                 printf ("remove_critical_edges, added helper BB%d jumping to BB%d\n", new_bb_after_entry->block_num, bb->block_num);
1160                                                         }
1161                                                 }
1162                                         }
1163
1164                                         /* Insert new_bb in the BB list */
1165                                         previous_bb->next_bb = new_bb;
1166                                         new_bb->next_bb = bb;
1167                                         previous_bb = new_bb;
1168
1169                                         /* Setup in_bb and out_bb */
1170                                         new_bb->in_bb = mono_mempool_alloc ((cfg)->mempool, sizeof (MonoBasicBlock*));
1171                                         new_bb->in_bb [0] = in_bb;
1172                                         new_bb->in_count = 1;
1173                                         new_bb->out_bb = mono_mempool_alloc ((cfg)->mempool, sizeof (MonoBasicBlock*));
1174                                         new_bb->out_bb [0] = bb;
1175                                         new_bb->out_count = 1;
1176
1177                                         /* Relink in_bb and bb to (from) new_bb */
1178                                         replace_out_block (in_bb, bb, new_bb);
1179                                         replace_out_block_in_code (in_bb, bb, new_bb);
1180                                         replace_in_block (bb, in_bb, new_bb);
1181
1182                                         if (cfg->verbose_level > 2) {
1183                                                 printf ("remove_critical_edges, removed critical edge from BB%d to BB%d (added BB%d)\n", in_bb->block_num, bb->block_num, new_bb->block_num);
1184                                         }
1185                                 }
1186                         }
1187                 }
1188         }
1189
1190         if (cfg->verbose_level > 3) {
1191                 for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
1192                         int i;
1193                         printf ("remove_critical_edges, AFTER BB%d (in:", bb->block_num);
1194                         for (i = 0; i < bb->in_count; i++) {
1195                                 printf (" %d", bb->in_bb [i]->block_num);
1196                         }
1197                         printf (") (out:");
1198                         for (i = 0; i < bb->out_count; i++) {
1199                                 printf (" %d", bb->out_bb [i]->block_num);
1200                         }
1201                         printf (")");
1202                         if (bb->last_ins != NULL) {
1203                                 printf (" ");
1204                                 mono_print_ins (bb->last_ins);
1205                         }
1206                         printf ("\n");
1207                 }
1208         }
1209 }
1210
1211 /*
1212  * Optimizes the branches on the Control Flow Graph
1213  *
1214  */
1215 void
1216 mono_optimize_branches (MonoCompile *cfg)
1217 {
1218         int i, changed = FALSE;
1219         MonoBasicBlock *bb, *bbn;
1220         guint32 niterations;
1221
1222         /*
1223          * Some crazy loops could cause the code below to go into an infinite
1224          * loop, see bug #53003 for an example. To prevent this, we put an upper
1225          * bound on the number of iterations.
1226          */
1227         if (cfg->num_bblocks > 1000)
1228                 niterations = cfg->num_bblocks * 2;
1229         else
1230                 niterations = 1000;
1231
1232         do {
1233                 MonoBasicBlock *previous_bb;
1234                 changed = FALSE;
1235                 niterations --;
1236
1237                 /* we skip the entry block (exit is handled specially instead ) */
1238                 for (previous_bb = cfg->bb_entry, bb = cfg->bb_entry->next_bb; bb; previous_bb = bb, bb = bb->next_bb) {
1239                         /* dont touch code inside exception clauses */
1240                         if (bb->region != -1)
1241                                 continue;
1242
1243                         if (!bb->not_useless && remove_block_if_useless (cfg, bb, previous_bb)) {
1244                                 changed = TRUE;
1245                                 continue;
1246                         }
1247
1248                         if ((bbn = bb->next_bb) && bbn->in_count == 0 && bbn != cfg->bb_exit && bb->region == bbn->region) {
1249                                 if (cfg->verbose_level > 2)
1250                                         g_print ("nullify block triggered %d\n", bbn->block_num);
1251
1252                                 bb->next_bb = bbn->next_bb;
1253
1254                                 for (i = 0; i < bbn->out_count; i++)
1255                                         replace_in_block (bbn->out_bb [i], bbn, NULL);
1256
1257                                 mono_nullify_basic_block (bbn);
1258                                 changed = TRUE;
1259                         }
1260
1261                         if (bb->out_count == 1) {
1262                                 bbn = bb->out_bb [0];
1263
1264                                 /* conditional branches where true and false targets are the same can be also replaced with OP_BR */
1265                                 if (bb->last_ins && (bb->last_ins->opcode != OP_BR) && MONO_IS_COND_BRANCH_OP (bb->last_ins)) {
1266                                         bb->last_ins->opcode = OP_BR;
1267                                         bb->last_ins->inst_target_bb = bb->last_ins->inst_true_bb;
1268                                         changed = TRUE;
1269                                         if (cfg->verbose_level > 2)
1270                                                 g_print ("cond branch removal triggered in %d %d\n", bb->block_num, bb->out_count);
1271                                 }
1272
1273                                 if (bb->region == bbn->region && bb->next_bb == bbn) {
1274                                         /* the block are in sequence anyway ... */
1275
1276                                         /* branches to the following block can be removed */
1277                                         if (bb->last_ins && bb->last_ins->opcode == OP_BR) {
1278                                                 bb->last_ins->opcode = OP_NOP;
1279                                                 changed = TRUE;
1280                                                 if (cfg->verbose_level > 2)
1281                                                         g_print ("br removal triggered %d -> %d\n", bb->block_num, bbn->block_num);
1282                                         }
1283
1284                                         if (bbn->in_count == 1 && !bb->extended) {
1285                                                 if (bbn != cfg->bb_exit) {
1286                                                         if (cfg->verbose_level > 2)
1287                                                                 g_print ("block merge triggered %d -> %d\n", bb->block_num, bbn->block_num);
1288                                                         mono_merge_basic_blocks (cfg, bb, bbn);
1289                                                         changed = TRUE;
1290                                                         continue;
1291                                                 }
1292
1293                                                 //mono_print_bb_code (bb);
1294                                         }
1295                                 }
1296                         }
1297
1298                         if ((bbn = bb->next_bb) && bbn->in_count == 0 && bbn != cfg->bb_exit && bb->region == bbn->region) {
1299                                 if (cfg->verbose_level > 2) {
1300                                         g_print ("nullify block triggered %d\n", bbn->block_num);
1301                                 }
1302                                 bb->next_bb = bbn->next_bb;
1303
1304                                 for (i = 0; i < bbn->out_count; i++)
1305                                         replace_in_block (bbn->out_bb [i], bbn, NULL);
1306
1307                                 mono_nullify_basic_block (bbn);
1308                                 changed = TRUE;
1309                                 continue;
1310                         }
1311
1312                         if (bb->out_count == 1) {
1313                                 bbn = bb->out_bb [0];
1314
1315                                 if (bb->last_ins && bb->last_ins->opcode == OP_BR) {
1316                                         bbn = bb->last_ins->inst_target_bb;
1317                                         if (bb->region == bbn->region && bbn->code && bbn->code->opcode == OP_BR &&
1318                                                 bbn->code->inst_target_bb != bbn &&
1319                                             bbn->code->inst_target_bb->region == bb->region) {
1320
1321                                                 if (cfg->verbose_level > 2)
1322                                                         g_print ("branch to branch triggered %d -> %d -> %d\n", bb->block_num, bbn->block_num, bbn->code->inst_target_bb->block_num);
1323
1324                                                 replace_in_block (bbn, bb, NULL);
1325                                                 replace_out_block (bb, bbn, bbn->code->inst_target_bb);
1326                                                 mono_link_bblock (cfg, bb, bbn->code->inst_target_bb);
1327                                                 bb->last_ins->inst_target_bb = bbn->code->inst_target_bb;
1328                                                 changed = TRUE;
1329                                                 continue;
1330                                         }
1331                                 }
1332                         } else if (bb->out_count == 2) {
1333                                 if (bb->last_ins && MONO_IS_COND_BRANCH_NOFP (bb->last_ins)) {
1334                                         int branch_result;
1335                                         MonoBasicBlock *taken_branch_target = NULL, *untaken_branch_target = NULL;
1336
1337                                         if (bb->last_ins->flags & MONO_INST_CFOLD_TAKEN)
1338                                                 branch_result = BRANCH_TAKEN;
1339                                         else if (bb->last_ins->flags & MONO_INST_CFOLD_NOT_TAKEN)
1340                                                 branch_result = BRANCH_NOT_TAKEN;
1341                                         else
1342                                                 branch_result = BRANCH_UNDEF;
1343
1344                                         if (branch_result == BRANCH_TAKEN) {
1345                                                 taken_branch_target = bb->last_ins->inst_true_bb;
1346                                                 untaken_branch_target = bb->last_ins->inst_false_bb;
1347                                         } else if (branch_result == BRANCH_NOT_TAKEN) {
1348                                                 taken_branch_target = bb->last_ins->inst_false_bb;
1349                                                 untaken_branch_target = bb->last_ins->inst_true_bb;
1350                                         }
1351                                         if (taken_branch_target) {
1352                                                 /* if mono_eval_cond_branch () is ever taken to handle
1353                                                  * non-constant values to compare, issue a pop here.
1354                                                  */
1355                                                 bb->last_ins->opcode = OP_BR;
1356                                                 bb->last_ins->inst_target_bb = taken_branch_target;
1357                                                 if (!bb->extended)
1358                                                         mono_unlink_bblock (cfg, bb, untaken_branch_target);
1359                                                 changed = TRUE;
1360                                                 continue;
1361                                         }
1362                                         bbn = bb->last_ins->inst_true_bb;
1363                                         if (bb->region == bbn->region && bbn->code && bbn->code->opcode == OP_BR &&
1364                                             bbn->code->inst_target_bb->region == bb->region) {
1365                                                 if (cfg->verbose_level > 2)
1366                                                         g_print ("cbranch1 to branch triggered %d -> (%d) %d (0x%02x)\n",
1367                                                                  bb->block_num, bbn->block_num, bbn->code->inst_target_bb->block_num,
1368                                                                  bbn->code->opcode);
1369
1370                                                 /*
1371                                                  * Unlink, then relink bblocks to avoid various
1372                                                  * tricky situations when the two targets of the branch
1373                                                  * are equal, or will become equal after the change.
1374                                                  */
1375                                                 mono_unlink_bblock (cfg, bb, bb->last_ins->inst_true_bb);
1376                                                 mono_unlink_bblock (cfg, bb, bb->last_ins->inst_false_bb);
1377
1378                                                 bb->last_ins->inst_true_bb = bbn->code->inst_target_bb;
1379
1380                                                 mono_link_bblock (cfg, bb, bb->last_ins->inst_true_bb);
1381                                                 mono_link_bblock (cfg, bb, bb->last_ins->inst_false_bb);
1382
1383                                                 changed = TRUE;
1384                                                 continue;
1385                                         }
1386
1387                                         bbn = bb->last_ins->inst_false_bb;
1388                                         if (bbn && bb->region == bbn->region && bbn->code && bbn->code->opcode == OP_BR &&
1389                                             bbn->code->inst_target_bb->region == bb->region) {
1390                                                 if (cfg->verbose_level > 2)
1391                                                         g_print ("cbranch2 to branch triggered %d -> (%d) %d (0x%02x)\n",
1392                                                                  bb->block_num, bbn->block_num, bbn->code->inst_target_bb->block_num,
1393                                                                  bbn->code->opcode);
1394
1395                                                 mono_unlink_bblock (cfg, bb, bb->last_ins->inst_true_bb);
1396                                                 mono_unlink_bblock (cfg, bb, bb->last_ins->inst_false_bb);
1397
1398                                                 bb->last_ins->inst_false_bb = bbn->code->inst_target_bb;
1399
1400                                                 mono_link_bblock (cfg, bb, bb->last_ins->inst_true_bb);
1401                                                 mono_link_bblock (cfg, bb, bb->last_ins->inst_false_bb);
1402
1403                                                 changed = TRUE;
1404                                                 continue;
1405                                         }
1406
1407                                         bbn = bb->last_ins->inst_false_bb;
1408                                         /*
1409                                          * If bb is an extended bb, it could contain an inside branch to bbn.
1410                                          * FIXME: Enable the optimization if that is not true.
1411                                          * If bblocks_linked () is true, then merging bb and bbn
1412                                          * would require addition of an extra branch at the end of bbn
1413                                          * slowing down loops.
1414                                          */
1415                                         if (bbn && bb->region == bbn->region && bbn->in_count == 1 && cfg->enable_extended_bblocks && bbn != cfg->bb_exit && !bb->extended && !bbn->out_of_line && !mono_bblocks_linked (bbn, bb)) {
1416                                                 g_assert (bbn->in_bb [0] == bb);
1417                                                 if (cfg->verbose_level > 2)
1418                                                         g_print ("merge false branch target triggered BB%d -> BB%d\n", bb->block_num, bbn->block_num);
1419                                                 mono_merge_basic_blocks (cfg, bb, bbn);
1420                                                 changed = TRUE;
1421                                                 continue;
1422                                         }
1423                                 }
1424
1425                                 if (bb->last_ins && MONO_IS_COND_BRANCH_NOFP (bb->last_ins)) {
1426                                         if (bb->last_ins->inst_false_bb && bb->last_ins->inst_false_bb->out_of_line && (bb->region == bb->last_ins->inst_false_bb->region) && !cfg->disable_out_of_line_bblocks) {
1427                                                 /* Reverse the branch */
1428                                                 bb->last_ins->opcode = mono_reverse_branch_op (bb->last_ins->opcode);
1429                                                 bbn = bb->last_ins->inst_false_bb;
1430                                                 bb->last_ins->inst_false_bb = bb->last_ins->inst_true_bb;
1431                                                 bb->last_ins->inst_true_bb = bbn;
1432
1433                                                 move_basic_block_to_end (cfg, bb->last_ins->inst_true_bb);
1434                                                 if (cfg->verbose_level > 2)
1435                                                         g_print ("cbranch to throw block triggered %d.\n",
1436                                                                          bb->block_num);
1437                                         }
1438                                 }
1439                         }
1440                 }
1441         } while (changed && (niterations > 0));
1442 }
1443
1444 #endif /* DISABLE_JIT */