mono/mini/ssa.c

   1 /*
   2  * ssa.c: Static single assign form support for the JIT compiler.
   3  *
   4  * Author:
   5  *    Dietmar Maurer (dietmar@ximian.com)
   6  *
   7  * (C) 2003 Ximian, Inc.
   8  * Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
   9  */
  10 #include <config.h>
  11 #include <string.h>
  12 #include <mono/metadata/debug-helpers.h>
  13 #include <mono/metadata/mempool.h>
  14 #include <mono/metadata/mempool-internals.h>
  15
  16 #ifndef DISABLE_JIT
  17
  18 #include "mini.h"
  19 #ifdef HAVE_ALLOCA_H
  20 #include <alloca.h>
  21 #endif
  22
  23 #define USE_ORIGINAL_VARS
  24 #define CREATE_PRUNED_SSA
  25
  26 //#define DEBUG_SSA 1
  27
  28 #define NEW_PHI(cfg,dest,val) do {      \
  29                 (dest) = mono_mempool_alloc0 ((cfg)->mempool, sizeof (MonoInst));       \
  30                 (dest)->opcode = OP_PHI;        \
  31                 (dest)->inst_c0 = (val);        \
  32         (dest)->dreg = (dest)->sreg1 = (dest)->sreg2 = -1; \
  33         } while (0)
  34
  35 typedef struct {
  36         MonoBasicBlock *bb;
  37         MonoInst *inst;
  38 } MonoVarUsageInfo;
  39
  40 static void
  41 unlink_target (MonoBasicBlock *bb, MonoBasicBlock *target)
  42 {
  43         int i;
  44
  45         for (i = 0; i < bb->out_count; i++) {
  46                 if (bb->out_bb [i] == target) {
  47                         bb->out_bb [i] = bb->out_bb [--bb->out_count];
  48                         break;
  49                 }
  50         }
  51         for (i = 0; i < target->in_count; i++) {
  52                 if (target->in_bb [i] == bb) {
  53                         target->in_bb [i] = target->in_bb [--target->in_count];
  54                         break;
  55
  56                 }
  57         }
  58 }
  59
  60 static void
  61 unlink_unused_bblocks (MonoCompile *cfg)
  62 {
  63         int i, j;
  64         MonoBasicBlock *bb;
  65
  66         g_assert (cfg->comp_done & MONO_COMP_REACHABILITY);
  67
  68         if (G_UNLIKELY (cfg->verbose_level > 1))
  69                 printf ("\nUNLINK UNUSED BBLOCKS:\n");
  70
  71         for (bb = cfg->bb_entry; bb && bb->next_bb;) {
  72                 if (!(bb->next_bb->flags & BB_REACHABLE)) {
  73                         bb->next_bb = bb->next_bb->next_bb;
  74                 } else
  75                         bb = bb->next_bb;
  76         }
  77
  78         for (i = 1; i < cfg->num_bblocks; i++) {
  79                 bb = cfg->bblocks [i];
  80
  81                 if (!(bb->flags & BB_REACHABLE)) {
  82                         for (j = 0; j < bb->in_count; j++) {
  83                                 unlink_target (bb->in_bb [j], bb);
  84                         }
  85                         for (j = 0; j < bb->out_count; j++) {
  86                                 unlink_target (bb, bb->out_bb [j]);
  87                         }
  88                         if (G_UNLIKELY (cfg->verbose_level > 1))
  89                                 printf ("\tUnlinked BB%d\n", bb->block_num);
  90                 }
  91
  92         }
  93 }
  94
  95 /**
  96  * remove_bb_from_phis:
  97  *
  98  *   Remove BB from the PHI statements in TARGET.
  99  */
 100 static void
 101 remove_bb_from_phis (MonoCompile *cfg, MonoBasicBlock *bb, MonoBasicBlock *target)
 102 {
 103         MonoInst *ins;
 104         int i, j;
 105
 106         for (i = 0; i < target->in_count; i++) {
 107                 if (target->in_bb [i] == bb) {
 108                         break;
 109                 }
 110         }
 111         g_assert (i < target->in_count);
 112
 113         for (ins = target->code; ins; ins = ins->next) {
 114                 if (MONO_IS_PHI (ins)) {
 115                         for (j = i; j < ins->inst_phi_args [0] - 1; ++j)
 116                                 ins->inst_phi_args [j + 1] = ins->inst_phi_args [j + 2];
 117                         ins->inst_phi_args [0] --;
 118                 }
 119                 else
 120                         break;
 121         }
 122 }
 123
 124 static inline int
 125 op_phi_to_move (int opcode)
 126 {
 127         switch (opcode) {
 128         case OP_PHI:
 129                 return OP_MOVE;
 130         case OP_FPHI:
 131                 return OP_FMOVE;
 132         case OP_VPHI:
 133                 return OP_VMOVE;
 134         case OP_XPHI:
 135                 return OP_XMOVE;
 136         default:
 137                 g_assert_not_reached ();
 138         }
 139
 140         return -1;
 141 }
 142
 143 static inline void
 144 record_use (MonoCompile *cfg, MonoInst *var, MonoBasicBlock *bb, MonoInst *ins)
 145 {
 146         MonoMethodVar *info;
 147         MonoVarUsageInfo *ui = mono_mempool_alloc (cfg->mempool, sizeof (MonoVarUsageInfo));
 148
 149         info = MONO_VARINFO (cfg, var->inst_c0);
 150
 151         ui->bb = bb;
 152         ui->inst = ins;
 153         info->uses = g_list_prepend_mempool (cfg->mempool, info->uses, ui);
 154 }
 155
 156 typedef struct {
 157         MonoInst *var;
 158         int idx;
 159 } RenameInfo;
 160
 161 /**
 162  * mono_ssa_rename_vars:
 163  *
 164  *  Implement renaming of SSA variables. Also compute def-use information in parallel.
 165  * @stack_history points to an area of memory which can be used for storing changes
 166  * made to the stack, so they can be reverted later.
 167  */
 168 static void
 169 mono_ssa_rename_vars (MonoCompile *cfg, int max_vars, MonoBasicBlock *bb, gboolean *originals_used, MonoInst **stack,   guint32 *lvreg_stack, gboolean *lvreg_defined, RenameInfo *stack_history, int stack_history_size)
 170 {
 171         MonoInst *ins, *new_var;
 172         int i, j, idx;
 173         GSList *tmp;
 174         int stack_history_len = 0;
 175
 176         if (cfg->verbose_level >= 4)
 177                 printf ("\nRENAME VARS BLOCK %d:\n", bb->block_num);
 178
 179         /* First pass: Create new vars */
 180         for (ins = bb->code; ins; ins = ins->next) {
 181                 const char *spec = INS_INFO (ins->opcode);
 182                 int num_sregs;
 183                 int sregs [MONO_MAX_SRC_REGS];
 184
 185 #ifdef DEBUG_SSA
 186                 printf ("\tProcessing "); mono_print_ins (ins);
 187 #endif
 188                 if (ins->opcode == OP_NOP)
 189                         continue;
 190
 191                 /* SREGs */
 192                 num_sregs = mono_inst_get_src_registers (ins, sregs);
 193                 for (i = 0; i < num_sregs; ++i) {
 194                         if (spec [MONO_INST_SRC1 + i] != ' ') {
 195                                 MonoInst *var = get_vreg_to_inst (cfg, sregs [i]);
 196                                 if (var && !(var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT))) {
 197                                         int idx = var->inst_c0;
 198                                         if (stack [idx]) {
 199                                                 if (var->opcode != OP_ARG)
 200                                                         g_assert (stack [idx]);
 201                                                 sregs [i] = stack [idx]->dreg;
 202                                                 record_use (cfg, stack [idx], bb, ins);
 203                                         }
 204                                         else
 205                                                 record_use (cfg, var, bb, ins);
 206                                 }
 207                                 else if (G_UNLIKELY (!var && lvreg_stack [sregs [i]]))
 208                                         sregs [i] = lvreg_stack [sregs [i]];
 209                         }
 210                 }
 211                 mono_inst_set_src_registers (ins, sregs);
 212
 213                 if (MONO_IS_STORE_MEMBASE (ins)) {
 214                         MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 215                         if (var && !(var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT))) {
 216                                 int idx = var->inst_c0;
 217                                 if (stack [idx]) {
 218                                         if (var->opcode != OP_ARG)
 219                                                 g_assert (stack [idx]);
 220                                         ins->dreg = stack [idx]->dreg;
 221                                         record_use (cfg, stack [idx], bb, ins);
 222                                 }
 223                                 else
 224                                         record_use (cfg, var, bb, ins);
 225                         }
 226                         else if (G_UNLIKELY (!var && lvreg_stack [ins->dreg]))
 227                                 ins->dreg = lvreg_stack [ins->dreg];
 228                 }
 229
 230                 /* DREG */
 231                 if ((spec [MONO_INST_DEST] != ' ') && !MONO_IS_STORE_MEMBASE (ins)) {
 232                         MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 233                         MonoMethodVar *info;
 234
 235                         if (var && !(var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT))) {
 236                                 idx = var->inst_c0;
 237                                 g_assert (idx < max_vars);
 238
 239                                 if (var->opcode == OP_ARG)
 240                                         originals_used [idx] = TRUE;
 241
 242                                 /* FIXME: */
 243                                 g_assert (stack_history_len < stack_history_size);
 244                                 stack_history [stack_history_len].var = stack [idx];
 245                                 stack_history [stack_history_len].idx = idx;
 246                                 stack_history_len ++;
 247
 248                                 if (originals_used [idx]) {
 249                                         new_var = mono_compile_create_var (cfg, var->inst_vtype, OP_LOCAL);
 250                                         new_var->flags = var->flags;
 251                                         MONO_VARINFO (cfg, new_var->inst_c0)->reg = idx;
 252
 253                                         if (cfg->verbose_level >= 4)
 254                                                 printf ("  R%d -> R%d\n", var->dreg, new_var->dreg);
 255
 256                                         stack [idx] = new_var;
 257
 258                                         ins->dreg = new_var->dreg;
 259                                         var = new_var;
 260                                 }
 261                                 else {
 262                                         stack [idx] = var;
 263                                         originals_used [idx] = TRUE;
 264                                 }
 265
 266                                 info = MONO_VARINFO (cfg, var->inst_c0);
 267                                 info->def = ins;
 268                                 info->def_bb = bb;
 269                         }
 270                         else if (G_UNLIKELY (!var && lvreg_defined [ins->dreg] && (ins->dreg >= MONO_MAX_IREGS))) {
 271                                 /* Perform renaming for local vregs */
 272                                 lvreg_stack [ins->dreg] = vreg_is_ref (cfg, ins->dreg) ? mono_alloc_ireg_ref (cfg) : mono_alloc_preg (cfg);
 273                                 ins->dreg = lvreg_stack [ins->dreg];
 274                         }
 275                         else
 276                                 lvreg_defined [ins->dreg] = TRUE;
 277                 }
 278
 279 #ifdef DEBUG_SSA
 280                 printf ("\tAfter processing "); mono_print_ins (ins);
 281 #endif
 282
 283         }
 284
 285         /* Rename PHI arguments in succeeding bblocks */
 286         for (i = 0; i < bb->out_count; i++) {
 287                 MonoBasicBlock *n = bb->out_bb [i];
 288
 289                 for (j = 0; j < n->in_count; j++)
 290                         if (n->in_bb [j] == bb)
 291                                 break;
 292
 293                 for (ins = n->code; ins; ins = ins->next) {
 294                         if (MONO_IS_PHI (ins)) {
 295                                 idx = ins->inst_c0;
 296                                 if (stack [idx])
 297                                         new_var = stack [idx];
 298                                 else
 299                                         new_var = cfg->varinfo [idx];
 300 #ifdef DEBUG_SSA
 301                                 printf ("FOUND PHI %d (%d, %d)\n", idx, j, new_var->inst_c0);
 302 #endif
 303                                 ins->inst_phi_args [j + 1] = new_var->dreg;
 304                                 record_use (cfg,  new_var, n, ins);
 305                                 if (G_UNLIKELY (cfg->verbose_level >= 4))
 306                                         printf ("\tAdd PHI R%d <- R%d to BB%d\n", ins->dreg, new_var->dreg, n->block_num);
 307                         }
 308                         else
 309                                 /* The phi nodes are at the beginning of the bblock */
 310                                 break;
 311                 }
 312         }
 313
 314         if (bb->dominated) {
 315                 for (tmp = bb->dominated; tmp; tmp = tmp->next) {
 316                         mono_ssa_rename_vars (cfg, max_vars, (MonoBasicBlock *)tmp->data, originals_used, stack, lvreg_stack, lvreg_defined, stack_history + stack_history_len, stack_history_size - stack_history_len);
 317                 }
 318         }
 319
 320         /* Restore stack */
 321         for (i = stack_history_len - 1; i >= 0; i--) {
 322                 stack [stack_history [i].idx] = stack_history [i].var;
 323         }
 324
 325         cfg->comp_done |= MONO_COMP_SSA_DEF_USE;
 326 }
 327
 328 void
 329 mono_ssa_compute (MonoCompile *cfg)
 330 {
 331         int i, j, idx, bitsize;
 332         MonoBitSet *set;
 333         MonoMethodVar *vinfo = g_new0 (MonoMethodVar, cfg->num_varinfo);
 334         MonoInst *ins, **stack;
 335         guint8 *buf, *buf_start;
 336         RenameInfo *stack_history;
 337         int stack_history_size;
 338         gboolean *originals;
 339         guint32 *lvreg_stack;
 340         gboolean *lvreg_defined;
 341
 342         g_assert (!(cfg->comp_done & MONO_COMP_SSA));
 343
 344         g_assert (!cfg->disable_ssa);
 345
 346         if (cfg->verbose_level >= 4)
 347                 printf ("\nCOMPUTE SSA %d (R%d-)\n\n", cfg->num_varinfo, cfg->next_vreg);
 348
 349 #ifdef CREATE_PRUNED_SSA
 350         /* we need liveness for pruned SSA */
 351         if (!(cfg->comp_done & MONO_COMP_LIVENESS))
 352                 mono_analyze_liveness (cfg);
 353 #endif
 354
 355         mono_compile_dominator_info (cfg, MONO_COMP_DOM | MONO_COMP_IDOM | MONO_COMP_DFRONTIER);
 356
 357         bitsize = mono_bitset_alloc_size (cfg->num_bblocks, 0);
 358         buf = buf_start = g_malloc0 (mono_bitset_alloc_size (cfg->num_bblocks, 0) * cfg->num_varinfo);
 359
 360         for (i = 0; i < cfg->num_varinfo; ++i) {
 361                 vinfo [i].def_in = mono_bitset_mem_new (buf, cfg->num_bblocks, 0);
 362                 buf += bitsize;
 363                 vinfo [i].idx = i;
 364                 /* implicit reference at start */
 365                 if (cfg->varinfo [i]->opcode == OP_ARG)
 366                         mono_bitset_set_fast (vinfo [i].def_in, 0);
 367         }
 368
 369         for (i = 0; i < cfg->num_bblocks; ++i) {
 370                 MONO_BB_FOR_EACH_INS (cfg->bblocks [i], ins) {
 371                         if (ins->opcode == OP_NOP)
 372                                 continue;
 373
 374                         if (!MONO_IS_STORE_MEMBASE (ins) && get_vreg_to_inst (cfg, ins->dreg)) {
 375                                 mono_bitset_set_fast (vinfo [get_vreg_to_inst (cfg, ins->dreg)->inst_c0].def_in, i);
 376                         }
 377                 }
 378         }
 379
 380         /* insert phi functions */
 381         for (i = 0; i < cfg->num_varinfo; ++i) {
 382                 MonoInst *var = cfg->varinfo [i];
 383
 384 #if SIZEOF_REGISTER == 4
 385                 if (var->type == STACK_I8 && !COMPILE_LLVM (cfg))
 386                         continue;
 387 #endif
 388                 if (var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT))
 389                         continue;
 390
 391                 /* Most variables have only one definition */
 392                 if (mono_bitset_count (vinfo [i].def_in) <= 1)
 393                         continue;
 394
 395                 set = mono_compile_iterated_dfrontier (cfg, vinfo [i].def_in);
 396
 397                 if (cfg->verbose_level >= 4) {
 398                         if (mono_bitset_count (set) > 0) {
 399                                 printf ("\tR%d needs PHI functions in ", var->dreg);
 400                                 mono_blockset_print (cfg, set, "", -1);
 401                         }
 402                 }
 403
 404                 mono_bitset_foreach_bit (set, idx, cfg->num_bblocks) {
 405                         MonoBasicBlock *bb = cfg->bblocks [idx];
 406
 407                         /* fixme: create pruned SSA? we would need liveness information for that */
 408
 409                         if (bb == cfg->bb_exit && !COMPILE_LLVM (cfg))
 410                                 continue;
 411
 412                         if ((cfg->comp_done & MONO_COMP_LIVENESS) && !mono_bitset_test_fast (bb->live_in_set, i)) {
 413                                 //printf ("%d is not live in BB%d %s\n", i, bb->block_num, mono_method_full_name (cfg->method, TRUE));
 414                                 continue;
 415                         }
 416
 417                         NEW_PHI (cfg, ins, i);
 418
 419                         switch (var->type) {
 420                         case STACK_I4:
 421                         case STACK_I8:
 422                         case STACK_PTR:
 423                         case STACK_MP:
 424                         case STACK_OBJ:
 425                                 ins->opcode = OP_PHI;
 426                                 break;
 427                         case STACK_R8:
 428                                 ins->opcode = OP_FPHI;
 429                                 break;
 430                         case STACK_VTYPE:
 431                                 ins->opcode = MONO_CLASS_IS_SIMD (cfg, var->klass) ? OP_XPHI : OP_VPHI;
 432                                 break;
 433                         }
 434
 435                         if (var->inst_vtype->byref)
 436                                 ins->klass = mono_defaults.int_class;
 437                         else
 438                                 ins->klass = var->klass;
 439
 440                         ins->inst_phi_args =  mono_mempool_alloc0 (cfg->mempool, sizeof (int) * (cfg->bblocks [idx]->in_count + 1));
 441                         ins->inst_phi_args [0] = cfg->bblocks [idx]->in_count;
 442
 443                         /* For debugging */
 444                         for (j = 0; j < cfg->bblocks [idx]->in_count; ++j)
 445                                 ins->inst_phi_args [j + 1] = -1;
 446
 447                         ins->dreg = cfg->varinfo [i]->dreg;
 448
 449                         mono_bblock_insert_before_ins (bb, bb->code, ins);
 450
 451 #ifdef DEBUG_SSA
 452                         printf ("ADD PHI BB%d %s\n", cfg->bblocks [idx]->block_num, mono_method_full_name (cfg->method, TRUE));
 453 #endif
 454                 }
 455         }
 456
 457         /* free the stuff */
 458         g_free (vinfo);
 459         g_free (buf_start);
 460
 461         /* Renaming phase */
 462
 463         stack = alloca (sizeof (MonoInst *) * cfg->num_varinfo);
 464         memset (stack, 0, sizeof (MonoInst *) * cfg->num_varinfo);
 465
 466         lvreg_stack = g_new0 (guint32, cfg->next_vreg);
 467         lvreg_defined = g_new0 (gboolean, cfg->next_vreg);
 468         stack_history_size = 10240;
 469         stack_history = g_new (RenameInfo, stack_history_size);
 470         originals = g_new0 (gboolean, cfg->num_varinfo);
 471         mono_ssa_rename_vars (cfg, cfg->num_varinfo, cfg->bb_entry, originals, stack, lvreg_stack, lvreg_defined, stack_history, stack_history_size);
 472         g_free (stack_history);
 473         g_free (originals);
 474         g_free (lvreg_stack);
 475         g_free (lvreg_defined);
 476
 477         if (cfg->verbose_level >= 4)
 478                 printf ("\nEND COMPUTE SSA.\n\n");
 479
 480         cfg->comp_done |= MONO_COMP_SSA;
 481 }
 482
 483 void
 484 mono_ssa_remove (MonoCompile *cfg)
 485 {
 486         MonoInst *ins, *var, *move;
 487         int bbindex, i, j, first;
 488
 489         g_assert (cfg->comp_done & MONO_COMP_SSA);
 490
 491         for (i = 0; i < cfg->num_bblocks; ++i) {
 492                 MonoBasicBlock *bb = cfg->bblocks [i];
 493
 494                 if (cfg->verbose_level >= 4)
 495                         printf ("\nREMOVE SSA %d:\n", bb->block_num);
 496
 497                 for (ins = bb->code; ins; ins = ins->next) {
 498                         if (MONO_IS_PHI (ins)) {
 499                                 g_assert (ins->inst_phi_args [0] == bb->in_count);
 500                                 var = get_vreg_to_inst (cfg, ins->dreg);
 501
 502                                 /* Check for PHI nodes where all the inputs are the same */
 503                                 first = ins->inst_phi_args [1];
 504
 505                                 for (j = 1; j < bb->in_count; ++j)
 506                                         if (first != ins->inst_phi_args [j + 1])
 507                                                 break;
 508
 509                                 if ((bb->in_count > 1) && (j == bb->in_count)) {
 510                                         ins->opcode = op_phi_to_move (ins->opcode);
 511                                         if (ins->opcode == OP_VMOVE)
 512                                                 g_assert (ins->klass);
 513                                         ins->sreg1 = first;
 514                                 } else {
 515                                         for (j = 0; j < bb->in_count; j++) {
 516                                                 MonoBasicBlock *pred = bb->in_bb [j];
 517                                                 int sreg = ins->inst_phi_args [j + 1];
 518
 519                                                 if (cfg->verbose_level >= 4)
 520                                                         printf ("\tADD R%d <- R%d in BB%d\n", var->dreg, sreg, pred->block_num);
 521                                                 if (var->dreg != sreg) {
 522                                                         MONO_INST_NEW (cfg, move, op_phi_to_move (ins->opcode));
 523                                                         if (move->opcode == OP_VMOVE) {
 524                                                                 g_assert (ins->klass);
 525                                                                 move->klass = ins->klass;
 526                                                         }
 527                                                         move->dreg = var->dreg;
 528                                                         move->sreg1 = sreg;
 529                                                         mono_add_ins_to_end (pred, move);
 530                                                 }
 531                                         }
 532
 533                                         ins->opcode = OP_NOP;
 534                                         ins->dreg = -1;
 535                                 }
 536                         }
 537                 }
 538         }
 539
 540         if (cfg->verbose_level >= 4) {
 541                 for (i = 0; i < cfg->num_bblocks; ++i) {
 542                         MonoBasicBlock *bb = cfg->bblocks [i];
 543
 544                         mono_print_bb (bb, "AFTER REMOVE SSA:");
 545                 }
 546         }
 547
 548         /*
 549          * Removal of SSA form introduces many copies. To avoid this, we tyry to coalesce
 550          * the variables if possible. Since the newly introduced SSA variables don't
 551          * have overlapping live ranges (because we don't do agressive optimization), we
 552          * can coalesce them into the original variable.
 553          */
 554
 555         for (bbindex = 0; bbindex < cfg->num_bblocks; ++bbindex) {
 556                 MonoBasicBlock *bb = cfg->bblocks [bbindex];
 557
 558                 for (ins = bb->code; ins; ins = ins->next) {
 559                         const char *spec = INS_INFO (ins->opcode);
 560                         int num_sregs;
 561                         int sregs [MONO_MAX_SRC_REGS];
 562
 563                         if (ins->opcode == OP_NOP)
 564                                 continue;
 565
 566                         if (spec [MONO_INST_DEST] != ' ') {
 567                                 MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 568
 569                                 if (var) {
 570                                         MonoMethodVar *vmv = MONO_VARINFO (cfg, var->inst_c0);
 571
 572                                         /*
 573                                          * The third condition avoids coalescing with variables eliminated
 574                                          * during deadce.
 575                                          */
 576                                         if ((vmv->reg != -1) && (vmv->idx != vmv->reg) && (MONO_VARINFO (cfg, vmv->reg)->reg != -1)) {
 577                                                 printf ("COALESCE: R%d -> R%d\n", ins->dreg, cfg->varinfo [vmv->reg]->dreg);
 578                                                 ins->dreg = cfg->varinfo [vmv->reg]->dreg;
 579                                         }
 580                                 }
 581                         }
 582
 583                         num_sregs = mono_inst_get_src_registers (ins, sregs);
 584                         for (i = 0; i < num_sregs; ++i) {
 585                                 MonoInst *var = get_vreg_to_inst (cfg, sregs [i]);
 586
 587                                 if (var) {
 588                                         MonoMethodVar *vmv = MONO_VARINFO (cfg, var->inst_c0);
 589
 590                                         if ((vmv->reg != -1) && (vmv->idx != vmv->reg) && (MONO_VARINFO (cfg, vmv->reg)->reg != -1)) {
 591                                                 printf ("COALESCE: R%d -> R%d\n", sregs [i], cfg->varinfo [vmv->reg]->dreg);
 592                                                 sregs [i] = cfg->varinfo [vmv->reg]->dreg;
 593                                         }
 594                                 }
 595                         }
 596                         mono_inst_set_src_registers (ins, sregs);
 597                 }
 598         }
 599
 600         for (i = 0; i < cfg->num_varinfo; ++i) {
 601                 MONO_VARINFO (cfg, i)->reg = -1;
 602         }
 603
 604         if (cfg->comp_done & MONO_COMP_REACHABILITY)
 605                 unlink_unused_bblocks (cfg);
 606
 607         cfg->comp_done &= ~MONO_COMP_LIVENESS;
 608
 609         cfg->comp_done &= ~MONO_COMP_SSA;
 610 }
 611
 612 static void
 613 mono_ssa_create_def_use (MonoCompile *cfg)
 614 {
 615         MonoBasicBlock *bb;
 616         MonoInst *ins;
 617         int i;
 618
 619         g_assert (!(cfg->comp_done & MONO_COMP_SSA_DEF_USE));
 620
 621         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
 622                 for (ins = bb->code; ins; ins = ins->next) {
 623                         const char *spec = INS_INFO (ins->opcode);
 624                         MonoMethodVar *info;
 625                         int num_sregs;
 626                         int sregs [MONO_MAX_SRC_REGS];
 627
 628                         if (ins->opcode == OP_NOP)
 629                                 continue;
 630
 631                         /* SREGs */
 632                         num_sregs = mono_inst_get_src_registers (ins, sregs);
 633                         for (i = 0; i < num_sregs; ++i) {
 634                                 MonoInst *var = get_vreg_to_inst (cfg, sregs [i]);
 635                                 if (var && !(var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT)))
 636                                         record_use (cfg, var, bb, ins);
 637                         }
 638
 639                         if (MONO_IS_STORE_MEMBASE (ins)) {
 640                                 MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 641                                 if (var && !(var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT)))
 642                                         record_use (cfg, var, bb, ins);
 643                         }
 644
 645                         if (MONO_IS_PHI (ins)) {
 646                                 for (i = ins->inst_phi_args [0]; i > 0; i--) {
 647                                         g_assert (ins->inst_phi_args [i] != -1);
 648                                         record_use (cfg,  get_vreg_to_inst (cfg, ins->inst_phi_args [i]), bb, ins);
 649                                 }
 650                         }
 651
 652                         /* DREG */
 653                         if ((spec [MONO_INST_DEST] != ' ') && !MONO_IS_STORE_MEMBASE (ins)) {
 654                                 MonoInst *var = get_vreg_to_inst (cfg, ins->dreg);
 655
 656                                 if (var && !(var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT))) {
 657                                         info = MONO_VARINFO (cfg, var->inst_c0);
 658                                         info->def = ins;
 659                                         info->def_bb = bb;
 660                                 }
 661                         }
 662                 }
 663         }
 664
 665         cfg->comp_done |= MONO_COMP_SSA_DEF_USE;
 666 }
 667
 668 static void
 669 mono_ssa_copyprop (MonoCompile *cfg)
 670 {
 671         int i, index;
 672         GList *l;
 673
 674         g_assert ((cfg->comp_done & MONO_COMP_SSA_DEF_USE));
 675
 676         for (index = 0; index < cfg->num_varinfo; ++index) {
 677                 MonoInst *var = cfg->varinfo [index];
 678                 MonoMethodVar *info = MONO_VARINFO (cfg, index);
 679
 680                 if (info->def && (MONO_IS_MOVE (info->def))) {
 681                         MonoInst *var2 = get_vreg_to_inst (cfg, info->def->sreg1);
 682
 683                         if (var2 && !(var2->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT)) && MONO_VARINFO (cfg, var2->inst_c0)->def && (!MONO_IS_PHI (MONO_VARINFO (cfg, var2->inst_c0)->def))) {
 684                                 /* Rewrite all uses of var to be uses of var2 */
 685                                 int dreg = var->dreg;
 686                                 int sreg1 = var2->dreg;
 687
 688                                 l = info->uses;
 689                                 while (l) {
 690                                         MonoVarUsageInfo *u = (MonoVarUsageInfo*)l->data;
 691                                         MonoInst *ins = u->inst;
 692                                         GList *next = l->next;
 693                                         int num_sregs;
 694                                         int sregs [MONO_MAX_SRC_REGS];
 695
 696                                         num_sregs = mono_inst_get_src_registers (ins, sregs);
 697                                         for (i = 0; i < num_sregs; ++i) {
 698                                                 if (sregs [i] == dreg)
 699                                                         break;
 700                                         }
 701                                         if (i < num_sregs) {
 702                                                 g_assert (sregs [i] == dreg);
 703                                                 sregs [i] = sreg1;
 704                                                 mono_inst_set_src_registers (ins, sregs);
 705                                         } else if (MONO_IS_STORE_MEMBASE (ins) && ins->dreg == dreg) {
 706                                                 ins->dreg = sreg1;
 707                                         } else if (MONO_IS_PHI (ins)) {
 708                                                 for (i = ins->inst_phi_args [0]; i > 0; i--) {
 709                                                         int sreg = ins->inst_phi_args [i];
 710                                                         if (sreg == var->dreg)
 711                                                                 break;
 712                                                 }
 713                                                 g_assert (i > 0);
 714                                                 ins->inst_phi_args [i] = sreg1;
 715                                         }
 716                                         else
 717                                                 g_assert_not_reached ();
 718
 719                                         record_use (cfg, var2, u->bb, ins);
 720
 721                                         l = next;
 722                                 }
 723
 724                                 info->uses = NULL;
 725                         }
 726                 }
 727         }
 728
 729         if (cfg->verbose_level >= 4) {
 730                 MonoBasicBlock *bb;
 731
 732                 for (bb = cfg->bb_entry; bb; bb = bb->next_bb)
 733                         mono_print_bb (bb, "AFTER SSA COPYPROP");
 734         }
 735 }
 736
 737 static int
 738 evaluate_ins (MonoCompile *cfg, MonoInst *ins, MonoInst **res, MonoInst **carray)
 739 {
 740         MonoInst *args [MONO_MAX_SRC_REGS];
 741         int rs [MONO_MAX_SRC_REGS];
 742         MonoInst *c0;
 743         gboolean const_args = TRUE;
 744         const char *spec = INS_INFO (ins->opcode);
 745         int num_sregs, i;
 746         int sregs [MONO_MAX_SRC_REGS];
 747
 748         /* Short-circuit this */
 749         if (ins->opcode == OP_ICONST) {
 750                 *res = ins;
 751                 return 1;
 752         }
 753
 754         if (ins->opcode == OP_NOP)
 755                 return 2;
 756
 757         num_sregs = mono_inst_get_src_registers (ins, sregs);
 758         for (i = 0; i < MONO_MAX_SRC_REGS; ++i)
 759                 args [i] = NULL;
 760         for (i = 0; i < num_sregs; ++i) {
 761                 MonoInst *var = get_vreg_to_inst (cfg, sregs [i]);
 762
 763                 rs [i] = 2;
 764                 args [i] = carray [sregs [i]];
 765                 if (args [i])
 766                         rs [i] = 1;
 767                 else if (var && !(var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT)))
 768                         rs [i] = MONO_VARINFO (cfg, var->inst_c0)->cpstate;
 769                 if (rs [i] != 1)
 770                         const_args = FALSE;
 771         }
 772
 773         c0 = NULL;
 774
 775         if (num_sregs > 0 && const_args) {
 776                 g_assert (num_sregs <= 2);
 777                 if ((spec [MONO_INST_DEST] != ' ') && carray [ins->dreg]) {
 778                         // Cached value
 779                         *res = carray [ins->dreg];
 780                         return 1;
 781                 }
 782                 c0 = mono_constant_fold_ins (cfg, ins, args [0], args [1], FALSE);
 783                 if (c0) {
 784                         if (G_UNLIKELY (cfg->verbose_level > 1)) {
 785                                 printf ("\t cfold -> ");
 786                                 mono_print_ins (c0);
 787                         }
 788                         *res = c0;
 789                         return 1;
 790                 }
 791                 else
 792                         /* Can't cfold this ins */
 793                         return 2;
 794         }
 795
 796         if (num_sregs == 0)
 797                 return 2;
 798         for (i = 0; i < num_sregs; ++i) {
 799                 if (rs [i] == 2)
 800                         return 2;
 801         }
 802         return 0;
 803 }
 804
 805 static inline void
 806 change_varstate (MonoCompile *cfg, GList **cvars, MonoMethodVar *info, int state, MonoInst *c0, MonoInst **carray)
 807 {
 808         if (info->cpstate >= state)
 809                 return;
 810
 811         info->cpstate = state;
 812
 813         if (G_UNLIKELY (cfg->verbose_level > 1))
 814                 printf ("\tState of R%d set to %d\n", cfg->varinfo [info->idx]->dreg, info->cpstate);
 815
 816         if (state == 1)
 817                 g_assert (c0);
 818
 819         carray [cfg->varinfo [info->idx]->dreg] = c0;
 820
 821         if (!g_list_find (*cvars, info)) {
 822                 *cvars = g_list_prepend (*cvars, info);
 823         }
 824 }
 825
 826 static inline void
 827 add_cprop_bb (MonoCompile *cfg, MonoBasicBlock *bb, GList **bblist)
 828 {
 829         if (G_UNLIKELY (cfg->verbose_level > 1))
 830                 printf ("\tAdd BB%d to worklist\n", bb->block_num);
 831
 832     if (!(bb->flags &  BB_REACHABLE)) {
 833             bb->flags |= BB_REACHABLE;
 834                 *bblist = g_list_prepend (*bblist, bb);
 835         }
 836 }
 837
 838 static void
 839 visit_inst (MonoCompile *cfg, MonoBasicBlock *bb, MonoInst *ins, GList **cvars, GList **bblist, MonoInst **carray)
 840 {
 841         const char *spec = INS_INFO (ins->opcode);
 842
 843         if (ins->opcode == OP_NOP)
 844                 return;
 845
 846         if (cfg->verbose_level > 1)
 847                 mono_print_ins (ins);
 848
 849         /* FIXME: Support longs/floats */
 850         /* FIXME: Work on vregs as well */
 851
 852         if (MONO_IS_PHI (ins)) {
 853                 MonoMethodVar *info = MONO_VARINFO (cfg, get_vreg_to_inst (cfg, ins->dreg)->inst_c0);
 854                 MonoInst *c0 = NULL;
 855                 int j;
 856
 857                 for (j = 1; j <= ins->inst_phi_args [0]; j++) {
 858                         MonoInst *var = get_vreg_to_inst (cfg, ins->inst_phi_args [j]);
 859                         MonoMethodVar *mv = MONO_VARINFO (cfg, var->inst_c0);
 860                         MonoInst *src = mv->def;
 861
 862                         if (mv->def_bb && !(mv->def_bb->flags & BB_REACHABLE))
 863                                 continue;
 864
 865                         if (!mv->def || !src || mv->cpstate == 2) {
 866                                 change_varstate (cfg, cvars, info, 2, NULL, carray);
 867                                 break;
 868                         }
 869
 870                         if (mv->cpstate == 0)
 871                                 continue;
 872
 873                         g_assert (carray [var->dreg]);
 874
 875                         if (!c0)
 876                                 c0 = carray [var->dreg];
 877
 878                         /* FIXME: */
 879                         if (c0->opcode != OP_ICONST) {
 880                                 change_varstate (cfg, cvars, info, 2, NULL, carray);
 881                                 break;
 882                         }
 883
 884                         if (carray [var->dreg]->inst_c0 != c0->inst_c0) {
 885                                 change_varstate (cfg, cvars, info, 2, NULL, carray);
 886                                 break;
 887                         }
 888                 }
 889
 890                 if (c0 && info->cpstate < 1) {
 891                         change_varstate (cfg, cvars, info, 1, c0, carray);
 892
 893                         g_assert (c0->opcode == OP_ICONST);
 894                 }
 895         }
 896         else if (!MONO_IS_STORE_MEMBASE (ins) && ((spec [MONO_INST_SRC1] != ' ') || (spec [MONO_INST_SRC2] != ' ') || (spec [MONO_INST_DEST] != ' '))) {
 897                 MonoInst *var, *c0;
 898                 int state;
 899
 900                 if (spec [MONO_INST_DEST] !=  ' ')
 901                         var = get_vreg_to_inst (cfg, ins->dreg);
 902                 else
 903                         var = NULL;
 904
 905                 c0 = NULL;
 906                 state = evaluate_ins (cfg, ins, &c0, carray);
 907
 908                 if (var && !(var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT))) {
 909                         MonoMethodVar *info = MONO_VARINFO (cfg, var->inst_c0);
 910
 911                         if (info->cpstate < 2) {
 912                                 if (state == 1)
 913                                         change_varstate (cfg, cvars, info, 1, c0, carray);
 914                                 else if (state == 2)
 915                                         change_varstate (cfg, cvars, info, 2, NULL, carray);
 916                         }
 917                 }
 918                 else if (!var && (ins->dreg != -1)) {
 919                         /*
 920                          * We don't record def-use information for local vregs since it would be
 921                          * expensive. Instead, we depend on the fact that all uses of the vreg are in
 922                          * the same bblock, so they will be examined after the definition.
 923                          * FIXME: This isn't true if the ins is visited through an SSA edge.
 924                          */
 925                         if (c0) {
 926                                 carray [ins->dreg] = c0;
 927                         } else {
 928                                 if (carray [ins->dreg]) {
 929                                         /*
 930                                          * The state of the vreg changed from constant to non-constant
 931                                          * -> need to rescan the whole bblock.
 932                                          */
 933                                         carray [ins->dreg] = NULL;
 934                                         /* FIXME: Speed this up */
 935
 936                                         if (!g_list_find (*bblist, bb))
 937                                                 *bblist = g_list_prepend (*bblist, bb);
 938                                 }
 939                         }
 940                 }
 941
 942                 if (MONO_IS_JUMP_TABLE (ins)) {
 943                         int i;
 944                         MonoJumpInfoBBTable *table = MONO_JUMP_TABLE_FROM_INS (ins);
 945
 946                         if (!ins->next || ins->next->opcode != OP_PADD) {
 947                                 /* The PADD was optimized away */
 948                                 /* FIXME: handle this as well */
 949                                 for (i = 0; i < table->table_size; i++)
 950                                         if (table->table [i])
 951                                                 add_cprop_bb (cfg, table->table [i], bblist);
 952                                 return;
 953                         }
 954
 955                         g_assert (ins->next->opcode == OP_PADD);
 956                         g_assert (ins->next->sreg1 == ins->dreg);
 957
 958                         if (carray [ins->next->sreg2]) {
 959 #if SIZEOF_REGISTER == 8
 960                                 int idx = carray [ins->next->sreg2]->inst_c0 >> 3;
 961 #else
 962                                 int idx = carray [ins->next->sreg2]->inst_c0 >> 2;
 963 #endif
 964                                 if ((idx < 0) || (idx >= table->table_size))
 965                                         /* Out-of-range, no branch is executed */
 966                                         return;
 967                                 else
 968                                         if (table->table [idx])
 969                                                 add_cprop_bb (cfg, table->table [idx], bblist);
 970                         }
 971                         else {
 972                                 for (i = 0; i < table->table_size; i++)
 973                                         if (table->table [i])
 974                                                 add_cprop_bb (cfg, table->table [i], bblist);
 975                         }
 976                 }
 977
 978                 if (ins->opcode == OP_SWITCH) {
 979                         int i;
 980                         MonoJumpInfoBBTable *table = ins->inst_p0;
 981
 982                         for (i = 0; i < table->table_size; i++)
 983                                 if (table->table [i])
 984                                         add_cprop_bb (cfg, table->table [i], bblist);
 985                 }
 986
 987                 /* Handle COMPARE+BRCOND pairs */
 988                 if (ins->next && MONO_IS_COND_BRANCH_OP (ins->next)) {
 989                         if (c0) {
 990                                 g_assert (c0->opcode == OP_ICONST);
 991
 992                                 if (c0->inst_c0)
 993                                         ins->next->flags |= MONO_INST_CFOLD_TAKEN;
 994                                 else
 995                                         ins->next->flags |= MONO_INST_CFOLD_NOT_TAKEN;
 996                         }
 997                         else {
 998                                 ins->next->flags &= ~(MONO_INST_CFOLD_TAKEN | MONO_INST_CFOLD_NOT_TAKEN);
 999                         }
1000
1001                         visit_inst (cfg, bb, ins->next, cvars, bblist, carray);
1002                 }
1003         } else if (ins->opcode == OP_BR) {
1004                 add_cprop_bb (cfg, ins->inst_target_bb, bblist);
1005         } else if (MONO_IS_COND_BRANCH_OP (ins)) {
1006                 if (ins->flags & MONO_INST_CFOLD_TAKEN) {
1007                         add_cprop_bb (cfg, ins->inst_true_bb, bblist);
1008                 } else if (ins->flags & MONO_INST_CFOLD_NOT_TAKEN) {
1009                         if (ins->inst_false_bb)
1010                                 add_cprop_bb (cfg, ins->inst_false_bb, bblist);
1011         } else {
1012                         add_cprop_bb (cfg, ins->inst_true_bb, bblist);
1013                         if (ins->inst_false_bb)
1014                                 add_cprop_bb (cfg, ins->inst_false_bb, bblist);
1015                 }
1016         }
1017 }
1018
1019 /**
1020  * fold_ins:
1021  *
1022  *   Replace INS with its constant value, if it exists
1023  */
1024 static void
1025 fold_ins (MonoCompile *cfg, MonoBasicBlock *bb, MonoInst *ins, MonoInst **carray)
1026 {
1027         const char *spec = INS_INFO (ins->opcode);
1028         int opcode2;
1029         int num_sregs = mono_inst_get_num_src_registers (ins);
1030
1031         if ((ins->opcode != OP_NOP) && (ins->dreg != -1) && !MONO_IS_STORE_MEMBASE (ins)) {
1032                 if (carray [ins->dreg] && (spec [MONO_INST_DEST] == 'i') && (ins->dreg >= MONO_MAX_IREGS)) {
1033                         /* Perform constant folding */
1034                         /* FIXME: */
1035                         g_assert (carray [ins->dreg]->opcode == OP_ICONST);
1036                         ins->opcode = OP_ICONST;
1037                         ins->inst_c0 = carray [ins->dreg]->inst_c0;
1038                         MONO_INST_NULLIFY_SREGS (ins);
1039                 } else if (num_sregs == 2 && carray [ins->sreg2]) {
1040                         /* Perform op->op_imm conversion */
1041                         opcode2 = mono_op_to_op_imm (ins->opcode);
1042                         if (opcode2 != -1) {
1043                                 ins->opcode = opcode2;
1044                                 ins->inst_imm = carray [ins->sreg2]->inst_c0;
1045                                 ins->sreg2 = -1;
1046
1047                                 if ((opcode2 == OP_VOIDCALL) || (opcode2 == OP_CALL) || (opcode2 == OP_LCALL) || (opcode2 == OP_FCALL))
1048                                         ((MonoCallInst*)ins)->fptr = (gpointer)ins->inst_imm;
1049                         }
1050                 } else {
1051                         /* FIXME: Handle 3 op insns */
1052                 }
1053
1054                 if (MONO_IS_JUMP_TABLE (ins)) {
1055                         int i;
1056                         MonoJumpInfoBBTable *table = MONO_JUMP_TABLE_FROM_INS (ins);
1057
1058                         if (!ins->next || ins->next->opcode != OP_PADD) {
1059                                 /* The PADD was optimized away */
1060                                 /* FIXME: handle this as well */
1061                                 return;
1062                         }
1063
1064                         g_assert (ins->next->opcode == OP_PADD);
1065                         g_assert (ins->next->sreg1 == ins->dreg);
1066                         g_assert (ins->next->next->opcode == OP_LOAD_MEMBASE);
1067
1068                         if (carray [ins->next->sreg2]) {
1069                                 /* Convert to a simple branch */
1070 #if SIZEOF_REGISTER == 8
1071                                 int idx = carray [ins->next->sreg2]->inst_c0 >> 3;
1072 #else
1073                                 int idx = carray [ins->next->sreg2]->inst_c0 >> 2;
1074 #endif
1075
1076                                 if (!((idx >= 0) && (idx < table->table_size))) {
1077                                         /* Out of range, eliminate the whole switch */
1078                                         for (i = 0; i < table->table_size; ++i) {
1079                                                 remove_bb_from_phis (cfg, bb, table->table [i]);
1080                                                 mono_unlink_bblock (cfg, bb, table->table [i]);
1081                                         }
1082
1083                                         NULLIFY_INS (ins);
1084                                         NULLIFY_INS (ins->next);
1085                                         NULLIFY_INS (ins->next->next);
1086                                         if (ins->next->next->next)
1087                                                 NULLIFY_INS (ins->next->next->next);
1088
1089                                         return;
1090                                 }
1091
1092                                 if (!ins->next->next->next || ins->next->next->next->opcode != OP_BR_REG) {
1093                                         /* A one-way switch which got optimized away */
1094                                         if (G_UNLIKELY (cfg->verbose_level > 1)) {
1095                                                 printf ("\tNo cfold on ");
1096                                                 mono_print_ins (ins);
1097                                         }
1098                                         return;
1099                                 }
1100
1101                                 if (G_UNLIKELY (cfg->verbose_level > 1)) {
1102                                         printf ("\tcfold on ");
1103                                         mono_print_ins (ins);
1104                                 }
1105
1106                                 /* Unlink target bblocks */
1107                                 for (i = 0; i < table->table_size; ++i) {
1108                                         if (i != idx) {
1109                                                 remove_bb_from_phis (cfg, bb, table->table [i]);
1110                                                 mono_unlink_bblock (cfg, bb, table->table [i]);
1111                                         }
1112                                 }
1113
1114                                 /* Change the OP_BR_REG to a simple branch */
1115                                 ins->next->next->next->opcode = OP_BR;
1116                                 ins->next->next->next->inst_target_bb = table->table [idx];
1117                                 ins->next->next->next->sreg1 = -1;
1118
1119                                 /* Nullify the other instructions */
1120                                 NULLIFY_INS (ins);
1121                                 NULLIFY_INS (ins->next);
1122                                 NULLIFY_INS (ins->next->next);
1123                         }
1124                 }
1125         }
1126         else if (MONO_IS_COND_BRANCH_OP (ins)) {
1127                 if (ins->flags & MONO_INST_CFOLD_TAKEN) {
1128                         remove_bb_from_phis (cfg, bb, ins->inst_false_bb);
1129                         mono_unlink_bblock (cfg, bb, ins->inst_false_bb);
1130                         ins->opcode = OP_BR;
1131                         ins->inst_target_bb = ins->inst_true_bb;
1132                 } else if (ins->flags & MONO_INST_CFOLD_NOT_TAKEN) {
1133                         remove_bb_from_phis (cfg, bb, ins->inst_true_bb);
1134                         mono_unlink_bblock (cfg, bb, ins->inst_true_bb);
1135                         ins->opcode = OP_BR;
1136                         ins->inst_target_bb = ins->inst_false_bb;
1137                 }
1138         }
1139 }
1140
1141 void
1142 mono_ssa_cprop (MonoCompile *cfg)
1143 {
1144         MonoInst **carray;
1145         MonoBasicBlock *bb;
1146         GList *bblock_list, *cvars;
1147         GList *tmp;
1148         int i;
1149         //printf ("SIMPLE OPTS BB%d %s\n", bb->block_num, mono_method_full_name (cfg->method, TRUE));
1150
1151         carray = g_new0 (MonoInst*, cfg->next_vreg);
1152
1153         if (!(cfg->comp_done & MONO_COMP_SSA_DEF_USE))
1154                 mono_ssa_create_def_use (cfg);
1155
1156         bblock_list = g_list_prepend (NULL, cfg->bb_entry);
1157         cfg->bb_entry->flags |= BB_REACHABLE;
1158
1159         memset (carray, 0, sizeof (MonoInst *) * cfg->num_varinfo);
1160
1161         for (i = 0; i < cfg->num_varinfo; i++) {
1162                 MonoMethodVar *info = MONO_VARINFO (cfg, i);
1163                 if (!info->def)
1164                         info->cpstate = 2;
1165         }
1166
1167         for (bb = cfg->bb_entry->next_bb; bb; bb = bb->next_bb) {
1168                 /*
1169                  * FIXME: This should be bb->flags & BB_FLAG_EXCEPTION_HANDLER, but
1170                  * that would still allow unreachable try's to be removed.
1171                  */
1172                 if (bb->region)
1173                         add_cprop_bb (cfg, bb, &bblock_list);
1174         }
1175
1176         cvars = NULL;
1177
1178         while (bblock_list) {
1179                 MonoInst *inst;
1180
1181                 bb = (MonoBasicBlock *)bblock_list->data;
1182
1183                 bblock_list = g_list_delete_link (bblock_list, bblock_list);
1184
1185                 g_assert (bb->flags &  BB_REACHABLE);
1186
1187                 /*
1188                  * Some bblocks are linked to 2 others even through they fall through to the
1189                  * next bblock.
1190                  */
1191                 if (!(bb->last_ins && MONO_IS_BRANCH_OP (bb->last_ins))) {
1192                         for (i = 0; i < bb->out_count; ++i)
1193                                 add_cprop_bb (cfg, bb->out_bb [i], &bblock_list);
1194                 }
1195
1196                 if (cfg->verbose_level > 1)
1197                         printf ("\nSSA CONSPROP BB%d:\n", bb->block_num);
1198
1199                 for (inst = bb->code; inst; inst = inst->next) {
1200                         visit_inst (cfg, bb, inst, &cvars, &bblock_list, carray);
1201                 }
1202
1203                 while (cvars) {
1204                         MonoMethodVar *info = (MonoMethodVar *)cvars->data;
1205                         cvars = g_list_delete_link (cvars, cvars);
1206
1207                         for (tmp = info->uses; tmp; tmp = tmp->next) {
1208                                 MonoVarUsageInfo *ui = (MonoVarUsageInfo *)tmp->data;
1209                                 if (!(ui->bb->flags & BB_REACHABLE))
1210                                         continue;
1211                                 visit_inst (cfg, ui->bb, ui->inst, &cvars, &bblock_list, carray);
1212                         }
1213                 }
1214         }
1215
1216         for (bb = cfg->bb_entry->next_bb; bb; bb = bb->next_bb) {
1217                 MonoInst *inst;
1218                 for (inst = bb->code; inst; inst = inst->next) {
1219                         fold_ins (cfg, bb, inst, carray);
1220                 }
1221         }
1222
1223         g_free (carray);
1224
1225         cfg->comp_done |= MONO_COMP_REACHABILITY;
1226
1227         /* fixme: we should update usage infos during cprop, instead of computing it again */
1228         cfg->comp_done &=  ~MONO_COMP_SSA_DEF_USE;
1229         for (i = 0; i < cfg->num_varinfo; i++) {
1230                 MonoMethodVar *info = MONO_VARINFO (cfg, i);
1231                 info->def = NULL;
1232                 info->uses = NULL;
1233         }
1234 }
1235
1236 static inline void
1237 add_to_dce_worklist (MonoCompile *cfg, MonoMethodVar *var, MonoMethodVar *use, GList **wl)
1238 {
1239         GList *tmp;
1240
1241         *wl = g_list_prepend_mempool (cfg->mempool, *wl, use);
1242
1243         for (tmp = use->uses; tmp; tmp = tmp->next) {
1244                 MonoVarUsageInfo *ui = (MonoVarUsageInfo *)tmp->data;
1245                 if (ui->inst == var->def) {
1246                         /* from the mempool */
1247                         use->uses = g_list_remove_link (use->uses, tmp);
1248                         break;
1249                 }
1250         }
1251 }
1252
1253 void
1254 mono_ssa_deadce (MonoCompile *cfg)
1255 {
1256         int i;
1257         GList *work_list;
1258
1259         g_assert (cfg->comp_done & MONO_COMP_SSA);
1260
1261         //printf ("DEADCE %s\n", mono_method_full_name (cfg->method, TRUE));
1262
1263         if (!(cfg->comp_done & MONO_COMP_SSA_DEF_USE))
1264                 mono_ssa_create_def_use (cfg);
1265
1266         mono_ssa_copyprop (cfg);
1267
1268         work_list = NULL;
1269         for (i = 0; i < cfg->num_varinfo; i++) {
1270                 MonoMethodVar *info = MONO_VARINFO (cfg, i);
1271                 work_list = g_list_prepend_mempool (cfg->mempool, work_list, info);
1272         }
1273
1274         while (work_list) {
1275                 MonoMethodVar *info = (MonoMethodVar *)work_list->data;
1276                 work_list = g_list_remove_link (work_list, work_list);
1277
1278                 /*
1279                  * The second part of the condition happens often when PHI nodes have their dreg
1280                  * as one of their arguments due to the fact that we use the original vars.
1281                  */
1282                 if (info->def && (!info->uses || ((info->uses->next == NULL) && (((MonoVarUsageInfo*)info->uses->data)->inst == info->def)))) {
1283                         MonoInst *def = info->def;
1284
1285                         /* Eliminating FMOVE could screw up the fp stack */
1286                         if (MONO_IS_MOVE (def) && (!MONO_ARCH_USE_FPSTACK || (def->opcode != OP_FMOVE))) {
1287                                 MonoInst *src_var = get_vreg_to_inst (cfg, def->sreg1);
1288                                 if (src_var && !(src_var->flags & (MONO_INST_VOLATILE|MONO_INST_INDIRECT)))
1289                                         add_to_dce_worklist (cfg, info, MONO_VARINFO (cfg, src_var->inst_c0), &work_list);
1290                                 def->opcode = OP_NOP;
1291                                 def->dreg = def->sreg1 = def->sreg2 = -1;
1292                                 info->reg = -1;
1293                         } else if ((def->opcode == OP_ICONST) || (def->opcode == OP_I8CONST) || MONO_IS_ZERO (def)) {
1294                                 def->opcode = OP_NOP;
1295                                 def->dreg = def->sreg1 = def->sreg2 = -1;
1296                                 info->reg = -1;
1297                         } else if (MONO_IS_PHI (def)) {
1298                                 int j;
1299                                 for (j = def->inst_phi_args [0]; j > 0; j--) {
1300                                         MonoMethodVar *u = MONO_VARINFO (cfg, get_vreg_to_inst (cfg, def->inst_phi_args [j])->inst_c0);
1301                                         add_to_dce_worklist (cfg, info, u, &work_list);
1302                                 }
1303                                 def->opcode = OP_NOP;
1304                                 def->dreg = def->sreg1 = def->sreg2 = -1;
1305                                 info->reg = -1;
1306                         }
1307                         else if (def->opcode == OP_NOP) {
1308                         }
1309                         //else
1310                         //mono_print_ins (def);
1311                 }
1312
1313         }
1314 }
1315
1316 #if 0
1317 void
1318 mono_ssa_strength_reduction (MonoCompile *cfg)
1319 {
1320         MonoBasicBlock *bb;
1321         int i;
1322
1323         g_assert (cfg->comp_done & MONO_COMP_SSA);
1324         g_assert (cfg->comp_done & MONO_COMP_LOOPS);
1325         g_assert (cfg->comp_done & MONO_COMP_SSA_DEF_USE);
1326
1327         for (bb = cfg->bb_entry->next_bb; bb; bb = bb->next_bb) {
1328                 GList *lp = bb->loop_blocks;
1329
1330                 if (lp) {
1331                         MonoBasicBlock *h = (MonoBasicBlock *)lp->data;
1332
1333                         /* we only consider loops with 2 in bblocks */
1334                         if (!h->in_count == 2)
1335                                 continue;
1336
1337                         for (i = 0; i < cfg->num_varinfo; i++) {
1338                                 MonoMethodVar *info = MONO_VARINFO (cfg, i);
1339
1340                                 if (info->def && info->def->ssa_op == MONO_SSA_STORE &&
1341                                     info->def->inst_i0->opcode == OP_LOCAL && g_list_find (lp, info->def_bb)) {
1342                                         MonoInst *v = info->def->inst_i1;
1343
1344
1345                                         printf ("FOUND %d in %s\n", info->idx, mono_method_full_name (cfg->method, TRUE));
1346                                 }
1347                         }
1348                 }
1349         }
1350 }
1351 #endif
1352
1353 #endif /* DISABLE_JIT */