mono/mini/local-propagation.c

   1 /*
   2  * local-propagation.c: Local constant, copy and tree propagation.
   3  *
   4  * To make some sense of the tree mover, read mono/docs/tree-mover.txt
   5  *
   6  * Author:
   7  *   Paolo Molaro (lupus@ximian.com)
   8  *   Dietmar Maurer (dietmar@ximian.com)
   9  *   Massimiliano Mantione (massi@ximian.com)
  10  *
  11  * (C) 2006 Novell, Inc.  http://www.novell.com
  12  * Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
  13  */
  14
  15 #include <config.h>
  16 #ifndef DISABLE_JIT
  17
  18 #include <string.h>
  19 #include <stdio.h>
  20 #ifdef HAVE_ALLOCA_H
  21 #include <alloca.h>
  22 #endif
  23
  24 #include <mono/metadata/debug-helpers.h>
  25 #include <mono/metadata/mempool.h>
  26 #include <mono/metadata/opcodes.h>
  27 #include "mini.h"
  28 #include "ir-emit.h"
  29
  30 #ifndef MONO_ARCH_IS_OP_MEMBASE
  31 #define MONO_ARCH_IS_OP_MEMBASE(opcode) FALSE
  32 #endif
  33
  34 static inline MonoBitSet*
  35 mono_bitset_mp_new_noinit (MonoMemPool *mp,  guint32 max_size)
  36 {
  37         int size = mono_bitset_alloc_size (max_size, 0);
  38         gpointer mem;
  39
  40         mem = mono_mempool_alloc (mp, size);
  41         return mono_bitset_mem_new (mem, max_size, MONO_BITSET_DONT_FREE);
  42 }
  43
  44 /*
  45  * mono_local_cprop:
  46  *
  47  *  A combined local copy and constant propagation pass.
  48  */
  49 void
  50 mono_local_cprop (MonoCompile *cfg)
  51 {
  52         MonoBasicBlock *bb;
  53         MonoInst **defs;
  54         gint32 *def_index;
  55         int max;
  56         int filter = FILTER_IL_SEQ_POINT;
  57
  58 restart:
  59
  60         max = cfg->next_vreg;
  61         defs = mono_mempool_alloc (cfg->mempool, sizeof (MonoInst*) * (cfg->next_vreg + 1));
  62         def_index = mono_mempool_alloc (cfg->mempool, sizeof (guint32) * (cfg->next_vreg + 1));
  63
  64         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
  65                 MonoInst *ins;
  66                 int ins_index;
  67                 int last_call_index;
  68
  69                 /* Manually init the defs entries used by the bblock */
  70                 MONO_BB_FOR_EACH_INS (bb, ins) {
  71                         int sregs [MONO_MAX_SRC_REGS];
  72                         int num_sregs, i;
  73
  74                         if ((ins->dreg != -1) && (ins->dreg < max)) {
  75                                 defs [ins->dreg] = NULL;
  76 #if SIZEOF_REGISTER == 4
  77                                 defs [ins->dreg + 1] = NULL;
  78 #endif
  79                         }
  80
  81                         num_sregs = mono_inst_get_src_registers (ins, sregs);
  82                         for (i = 0; i < num_sregs; ++i) {
  83                                 int sreg = sregs [i];
  84                                 if (sreg < max) {
  85                                         defs [sreg] = NULL;
  86 #if SIZEOF_REGISTER == 4
  87                                         defs [sreg + 1] = NULL;
  88 #endif
  89                                 }
  90                         }
  91                 }
  92
  93                 ins_index = 0;
  94                 last_call_index = -1;
  95                 MONO_BB_FOR_EACH_INS (bb, ins) {
  96                         const char *spec = INS_INFO (ins->opcode);
  97                         int regtype, srcindex, sreg;
  98                         int num_sregs;
  99                         int sregs [MONO_MAX_SRC_REGS];
 100
 101                         if (ins->opcode == OP_NOP) {
 102                                 MONO_DELETE_INS (bb, ins);
 103                                 continue;
 104                         }
 105
 106                         g_assert (ins->opcode > MONO_CEE_LAST);
 107
 108                         /* FIXME: Optimize this */
 109                         if (ins->opcode == OP_LDADDR) {
 110                                 MonoInst *var = ins->inst_p0;
 111
 112                                 defs [var->dreg] = NULL;
 113                                 /*
 114                                 if (!MONO_TYPE_ISSTRUCT (var->inst_vtype))
 115                                         break;
 116                                 */
 117                         }
 118
 119                         if (MONO_IS_STORE_MEMBASE (ins)) {
 120                                 sreg = ins->dreg;
 121                                 regtype = 'i';
 122
 123                                 if ((regtype == 'i') && (sreg != -1) && defs [sreg]) {
 124                                         MonoInst *def = defs [sreg];
 125
 126                                         if ((def->opcode == OP_MOVE) && (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg])) && !vreg_is_volatile (cfg, def->sreg1)) {
 127                                                 int vreg = def->sreg1;
 128                                                 if (cfg->verbose_level > 2) printf ("CCOPY: R%d -> R%d\n", sreg, vreg);
 129                                                 ins->dreg = vreg;
 130                                         }
 131                                 }
 132                         }
 133
 134                         num_sregs = mono_inst_get_src_registers (ins, sregs);
 135                         for (srcindex = 0; srcindex < num_sregs; ++srcindex) {
 136                                 MonoInst *def;
 137
 138                                 mono_inst_get_src_registers (ins, sregs);
 139
 140                                 regtype = spec [MONO_INST_SRC1 + srcindex];
 141                                 sreg = sregs [srcindex];
 142
 143                                 if ((regtype == ' ') || (sreg == -1) || (!defs [sreg]))
 144                                         continue;
 145
 146                                 def = defs [sreg];
 147
 148                                 /* Copy propagation */
 149                                 /*
 150                                  * The first check makes sure the source of the copy did not change since
 151                                  * the copy was made.
 152                                  * The second check avoids volatile variables.
 153                                  * The third check avoids copy propagating local vregs through a call,
 154                                  * since the lvreg will be spilled
 155                                  * The fourth check avoids copy propagating a vreg in cases where
 156                                  * it would be eliminated anyway by reverse copy propagation later,
 157                                  * because propagating it would create another use for it, thus making
 158                                  * it impossible to use reverse copy propagation.
 159                                  */
 160                                 /* Enabling this for floats trips up the fp stack */
 161                                 /*
 162                                  * Enabling this for floats on amd64 seems to cause a failure in
 163                                  * basic-math.cs, most likely because it gets rid of some r8->r4
 164                                  * conversions.
 165                                  */
 166                                 if (MONO_IS_MOVE (def) &&
 167                                         (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg])) &&
 168                                         !vreg_is_volatile (cfg, def->sreg1) &&
 169                                         /* This avoids propagating local vregs across calls */
 170                                         ((get_vreg_to_inst (cfg, def->sreg1) || !defs [def->sreg1] || (def_index [def->sreg1] >= last_call_index) || (def->opcode == OP_VMOVE))) &&
 171                                         !(defs [def->sreg1] && mono_inst_next (defs [def->sreg1], filter) == def) &&
 172                                         (!MONO_ARCH_USE_FPSTACK || (def->opcode != OP_FMOVE)) &&
 173                                         (def->opcode != OP_FMOVE)) {
 174                                         int vreg = def->sreg1;
 175
 176                                         if (cfg->verbose_level > 2) printf ("CCOPY/2: R%d -> R%d\n", sreg, vreg);
 177                                         sregs [srcindex] = vreg;
 178                                         mono_inst_set_src_registers (ins, sregs);
 179
 180                                         /* Allow further iterations */
 181                                         srcindex = -1;
 182                                         continue;
 183                                 }
 184
 185                                 /* Constant propagation */
 186                                 /* FIXME: Make is_inst_imm a macro */
 187                                 /* FIXME: Make is_inst_imm take an opcode argument */
 188                                 /* is_inst_imm is only needed for binops */
 189                                 if ((((def->opcode == OP_ICONST) || ((sizeof (gpointer) == 8) && (def->opcode == OP_I8CONST))) &&
 190                                          (((srcindex == 0) && (ins->sreg2 == -1)) || mono_arch_is_inst_imm (def->inst_c0))) ||
 191                                         (!MONO_ARCH_USE_FPSTACK && (def->opcode == OP_R8CONST))) {
 192                                         guint32 opcode2;
 193
 194                                         /* srcindex == 1 -> binop, ins->sreg2 == -1 -> unop */
 195                                         if ((srcindex == 1) && (ins->sreg1 != -1) && defs [ins->sreg1] && (defs [ins->sreg1]->opcode == OP_ICONST) && defs [ins->sreg2]) {
 196                                                 /* Both arguments are constants, perform cfold */
 197                                                 mono_constant_fold_ins (cfg, ins, defs [ins->sreg1], defs [ins->sreg2], TRUE);
 198                                         } else if ((srcindex == 0) && (ins->sreg2 != -1) && defs [ins->sreg2]) {
 199                                                 /* Arg 1 is constant, swap arguments if possible */
 200                                                 int opcode = ins->opcode;
 201                                                 mono_constant_fold_ins (cfg, ins, defs [ins->sreg1], defs [ins->sreg2], TRUE);
 202                                                 if (ins->opcode != opcode) {
 203                                                         /* Allow further iterations */
 204                                                         srcindex = -1;
 205                                                         continue;
 206                                                 }
 207                                         } else if ((srcindex == 0) && (ins->sreg2 == -1)) {
 208                                                 /* Constant unop, perform cfold */
 209                                                 mono_constant_fold_ins (cfg, ins, defs [ins->sreg1], NULL, TRUE);
 210                                         }
 211
 212                                         opcode2 = mono_op_to_op_imm (ins->opcode);
 213                                         if ((opcode2 != -1) && mono_arch_is_inst_imm (def->inst_c0) && ((srcindex == 1) || (ins->sreg2 == -1))) {
 214                                                 ins->opcode = opcode2;
 215                                                 if ((def->opcode == OP_I8CONST) && (sizeof (gpointer) == 4)) {
 216                                                         ins->inst_ls_word = def->inst_ls_word;
 217                                                         ins->inst_ms_word = def->inst_ms_word;
 218                                                 } else {
 219                                                         ins->inst_imm = def->inst_c0;
 220                                                 }
 221                                                 sregs [srcindex] = -1;
 222                                                 mono_inst_set_src_registers (ins, sregs);
 223
 224                                                 if ((opcode2 == OP_VOIDCALL) || (opcode2 == OP_CALL) || (opcode2 == OP_LCALL) || (opcode2 == OP_FCALL))
 225                                                         ((MonoCallInst*)ins)->fptr = (gpointer)ins->inst_imm;
 226
 227                                                 /* Allow further iterations */
 228                                                 srcindex = -1;
 229                                                 continue;
 230                                         }
 231                                         else {
 232                                                 /* Special cases */
 233 #if defined(TARGET_X86) || defined(TARGET_AMD64)
 234                                                 if ((ins->opcode == OP_X86_LEA) && (srcindex == 1)) {
 235 #if SIZEOF_REGISTER == 8
 236                                                         /* FIXME: Use OP_PADD_IMM when the new JIT is done */
 237                                                         ins->opcode = OP_LADD_IMM;
 238 #else
 239                                                         ins->opcode = OP_ADD_IMM;
 240 #endif
 241                                                         ins->inst_imm += def->inst_c0 << ins->backend.shift_amount;
 242                                                         ins->sreg2 = -1;
 243                                                 }
 244 #endif
 245                                                 opcode2 = mono_load_membase_to_load_mem (ins->opcode);
 246                                                 if ((srcindex == 0) && (opcode2 != -1) && mono_arch_is_inst_imm (def->inst_c0)) {
 247                                                         ins->opcode = opcode2;
 248                                                         ins->inst_imm = def->inst_c0 + ins->inst_offset;
 249                                                         ins->sreg1 = -1;
 250                                                 }
 251                                         }
 252                                 }
 253                                 else if (((def->opcode == OP_ADD_IMM) || (def->opcode == OP_LADD_IMM)) && (MONO_IS_LOAD_MEMBASE (ins) || MONO_ARCH_IS_OP_MEMBASE (ins->opcode))) {
 254                                         /* ADD_IMM is created by spill_global_vars */
 255                                         /*
 256                                          * We have to guarantee that def->sreg1 haven't changed since def->dreg
 257                                          * was defined. cfg->frame_reg is assumed to remain constant.
 258                                          */
 259                                         if ((def->sreg1 == cfg->frame_reg) || ((mono_inst_next (def, filter) == ins) && (def->dreg != def->sreg1))) {
 260                                                 ins->inst_basereg = def->sreg1;
 261                                                 ins->inst_offset += def->inst_imm;
 262                                         }
 263                                 } else if ((ins->opcode == OP_ISUB_IMM) && (def->opcode == OP_IADD_IMM) && (mono_inst_next (def, filter) == ins) && (def->dreg != def->sreg1)) {
 264                                         ins->sreg1 = def->sreg1;
 265                                         ins->inst_imm -= def->inst_imm;
 266                                 } else if ((ins->opcode == OP_IADD_IMM) && (def->opcode == OP_ISUB_IMM) && (mono_inst_next (def, filter) == ins) && (def->dreg != def->sreg1)) {
 267                                         ins->sreg1 = def->sreg1;
 268                                         ins->inst_imm -= def->inst_imm;
 269                                 } else if (ins->opcode == OP_STOREI1_MEMBASE_REG &&
 270                                                    (def->opcode == OP_ICONV_TO_U1 || def->opcode == OP_ICONV_TO_I1 || def->opcode == OP_SEXT_I4 || (SIZEOF_REGISTER == 8 && def->opcode == OP_LCONV_TO_U1)) &&
 271                                                    (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg]))) {
 272                                         /* Avoid needless sign extension */
 273                                         ins->sreg1 = def->sreg1;
 274                                 } else if (ins->opcode == OP_STOREI2_MEMBASE_REG &&
 275                                                    (def->opcode == OP_ICONV_TO_U2 || def->opcode == OP_ICONV_TO_I2 || def->opcode == OP_SEXT_I4 || (SIZEOF_REGISTER == 8 && def->opcode == OP_LCONV_TO_I2)) &&
 276                                                    (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg]))) {
 277                                         /* Avoid needless sign extension */
 278                                         ins->sreg1 = def->sreg1;
 279                                 }
 280                         }
 281
 282                         /* Do strength reduction here */
 283                         /* FIXME: Add long/float */
 284                         switch (ins->opcode) {
 285                         case OP_MOVE:
 286                         case OP_XMOVE:
 287                                 if (ins->dreg == ins->sreg1) {
 288                                         MONO_DELETE_INS (bb, ins);
 289                                         spec = INS_INFO (ins->opcode);
 290                                 }
 291                                 break;
 292                         case OP_ADD_IMM:
 293                         case OP_IADD_IMM:
 294                         case OP_SUB_IMM:
 295                         case OP_ISUB_IMM:
 296 #if SIZEOF_REGISTER == 8
 297                         case OP_LADD_IMM:
 298                         case OP_LSUB_IMM:
 299 #endif
 300                                 if (ins->inst_imm == 0) {
 301                                         ins->opcode = OP_MOVE;
 302                                         spec = INS_INFO (ins->opcode);
 303                                 }
 304                                 break;
 305                         case OP_MUL_IMM:
 306                         case OP_IMUL_IMM:
 307 #if SIZEOF_REGISTER == 8
 308                         case OP_LMUL_IMM:
 309 #endif
 310                                 if (ins->inst_imm == 0) {
 311                                         ins->opcode = (ins->opcode == OP_LMUL_IMM) ? OP_I8CONST : OP_ICONST;
 312                                         ins->inst_c0 = 0;
 313                                         ins->sreg1 = -1;
 314                                 } else if (ins->inst_imm == 1) {
 315                                         ins->opcode = OP_MOVE;
 316                                 } else if ((ins->opcode == OP_IMUL_IMM) && (ins->inst_imm == -1)) {
 317                                         ins->opcode = OP_INEG;
 318                                 } else if ((ins->opcode == OP_LMUL_IMM) && (ins->inst_imm == -1)) {
 319                                         ins->opcode = OP_LNEG;
 320                                 } else {
 321                                         int power2 = mono_is_power_of_two (ins->inst_imm);
 322                                         if (power2 >= 0) {
 323                                                 ins->opcode = (ins->opcode == OP_MUL_IMM) ? OP_SHL_IMM : ((ins->opcode == OP_LMUL_IMM) ? OP_LSHL_IMM : OP_ISHL_IMM);
 324                                                 ins->inst_imm = power2;
 325                                         }
 326                                 }
 327                                 spec = INS_INFO (ins->opcode);
 328                                 break;
 329                         case OP_IREM_UN_IMM:
 330                         case OP_IDIV_UN_IMM: {
 331                                 int c = ins->inst_imm;
 332                                 int power2 = mono_is_power_of_two (c);
 333
 334                                 if (power2 >= 0) {
 335                                         if (ins->opcode == OP_IREM_UN_IMM) {
 336                                                 ins->opcode = OP_IAND_IMM;
 337                                                 ins->sreg2 = -1;
 338                                                 ins->inst_imm = (1 << power2) - 1;
 339                                         } else if (ins->opcode == OP_IDIV_UN_IMM) {
 340                                                 ins->opcode = OP_ISHR_UN_IMM;
 341                                                 ins->sreg2 = -1;
 342                                                 ins->inst_imm = power2;
 343                                         }
 344                                 }
 345                                 spec = INS_INFO (ins->opcode);
 346                                 break;
 347                         }
 348                         case OP_IDIV_IMM: {
 349                                 int c = ins->inst_imm;
 350                                 int power2 = mono_is_power_of_two (c);
 351                                 MonoInst *tmp1, *tmp2, *tmp3, *tmp4;
 352
 353                                 /* FIXME: Move this elsewhere cause its hard to implement it here */
 354                                 if (power2 == 1) {
 355                                         int r1 = mono_alloc_ireg (cfg);
 356
 357                                         NEW_BIALU_IMM (cfg, tmp1, OP_ISHR_UN_IMM, r1, ins->sreg1, 31);
 358                                         mono_bblock_insert_after_ins (bb, ins, tmp1);
 359                                         NEW_BIALU (cfg, tmp2, OP_IADD, r1, r1, ins->sreg1);
 360                                         mono_bblock_insert_after_ins (bb, tmp1, tmp2);
 361                                         NEW_BIALU_IMM (cfg, tmp3, OP_ISHR_IMM, ins->dreg, r1, 1);
 362                                         mono_bblock_insert_after_ins (bb, tmp2, tmp3);
 363
 364                                         NULLIFY_INS (ins);
 365
 366                                         // We allocated a new vreg, so need to restart
 367                                         goto restart;
 368                                 } else if (power2 > 0) {
 369                                         int r1 = mono_alloc_ireg (cfg);
 370
 371                                         NEW_BIALU_IMM (cfg, tmp1, OP_ISHR_IMM, r1, ins->sreg1, 31);
 372                                         mono_bblock_insert_after_ins (bb, ins, tmp1);
 373                                         NEW_BIALU_IMM (cfg, tmp2, OP_ISHR_UN_IMM, r1, r1, (32 - power2));
 374                                         mono_bblock_insert_after_ins (bb, tmp1, tmp2);
 375                                         NEW_BIALU (cfg, tmp3, OP_IADD, r1, r1, ins->sreg1);
 376                                         mono_bblock_insert_after_ins (bb, tmp2, tmp3);
 377                                         NEW_BIALU_IMM (cfg, tmp4, OP_ISHR_IMM, ins->dreg, r1, power2);
 378                                         mono_bblock_insert_after_ins (bb, tmp3, tmp4);
 379
 380                                         NULLIFY_INS (ins);
 381
 382                                         // We allocated a new vreg, so need to restart
 383                                         goto restart;
 384                                 }
 385                                 break;
 386                         }
 387                         }
 388
 389                         if (spec [MONO_INST_DEST] != ' ') {
 390                                 MonoInst *def = defs [ins->dreg];
 391
 392                                 if (def && (def->opcode == OP_ADD_IMM) && (def->sreg1 == cfg->frame_reg) && (MONO_IS_STORE_MEMBASE (ins))) {
 393                                         /* ADD_IMM is created by spill_global_vars */
 394                                         /* cfg->frame_reg is assumed to remain constant */
 395                                         ins->inst_destbasereg = def->sreg1;
 396                                         ins->inst_offset += def->inst_imm;
 397                                 }
 398                         }
 399
 400                         if ((spec [MONO_INST_DEST] != ' ') && !MONO_IS_STORE_MEMBASE (ins) && !vreg_is_volatile (cfg, ins->dreg)) {
 401                                 defs [ins->dreg] = ins;
 402                                 def_index [ins->dreg] = ins_index;
 403                         }
 404
 405                         if (MONO_IS_CALL (ins))
 406                                 last_call_index = ins_index;
 407
 408                         ins_index ++;
 409                 }
 410         }
 411 }
 412
 413 static inline gboolean
 414 reg_is_softreg_no_fpstack (int reg, const char spec)
 415 {
 416         return (spec == 'i' && reg >= MONO_MAX_IREGS)
 417                 || ((spec == 'f' && reg >= MONO_MAX_FREGS) && !MONO_ARCH_USE_FPSTACK)
 418 #ifdef MONO_ARCH_SIMD_INTRINSICS
 419                 || (spec == 'x' && reg >= MONO_MAX_XREGS)
 420 #endif
 421                 || (spec == 'v');
 422 }
 423
 424 static inline gboolean
 425 reg_is_softreg (int reg, const char spec)
 426 {
 427         return (spec == 'i' && reg >= MONO_MAX_IREGS)
 428                 || (spec == 'f' && reg >= MONO_MAX_FREGS)
 429 #ifdef MONO_ARCH_SIMD_INTRINSICS
 430                 || (spec == 'x' && reg >= MONO_MAX_XREGS)
 431 #endif
 432                 || (spec == 'v');
 433 }
 434
 435 static inline gboolean
 436 mono_is_simd_accessor (MonoInst *ins)
 437 {
 438         switch (ins->opcode) {
 439 #ifdef MONO_ARCH_SIMD_INTRINSICS
 440         case OP_INSERT_I1:
 441         case OP_INSERT_I2:
 442         case OP_INSERT_I4:
 443         case OP_INSERT_I8:
 444         case OP_INSERT_R4:
 445         case OP_INSERT_R8:
 446
 447         case OP_INSERTX_U1_SLOW:
 448         case OP_INSERTX_I4_SLOW:
 449         case OP_INSERTX_R4_SLOW:
 450         case OP_INSERTX_R8_SLOW:
 451         case OP_INSERTX_I8_SLOW:
 452                 return TRUE;
 453 #endif
 454         default:
 455                 return FALSE;
 456         }
 457 }
 458
 459 /**
 460  * mono_local_deadce:
 461  *
 462  *   Get rid of the dead assignments to local vregs like the ones created by the
 463  * copyprop pass.
 464  */
 465 void
 466 mono_local_deadce (MonoCompile *cfg)
 467 {
 468         MonoBasicBlock *bb;
 469         MonoInst *ins, *prev;
 470         MonoBitSet *used, *defined;
 471
 472         //mono_print_code (cfg, "BEFORE LOCAL-DEADCE");
 473
 474         /*
 475          * Assignments to global vregs can't be eliminated so this pass must come
 476          * after the handle_global_vregs () pass.
 477          */
 478
 479         used = mono_bitset_mp_new_noinit (cfg->mempool, cfg->next_vreg + 1);
 480         defined = mono_bitset_mp_new_noinit (cfg->mempool, cfg->next_vreg + 1);
 481
 482         /* First pass: collect liveness info */
 483         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
 484                 /* Manually init the defs entries used by the bblock */
 485                 MONO_BB_FOR_EACH_INS (bb, ins) {
 486                         const char *spec = INS_INFO (ins->opcode);
 487                         int sregs [MONO_MAX_SRC_REGS];
 488                         int num_sregs, i;
 489
 490                         if (spec [MONO_INST_DEST] != ' ') {
 491                                 mono_bitset_clear_fast (used, ins->dreg);
 492                                 mono_bitset_clear_fast (defined, ins->dreg);
 493 #if SIZEOF_REGISTER == 4
 494                                 /* Regpairs */
 495                                 mono_bitset_clear_fast (used, ins->dreg + 1);
 496                                 mono_bitset_clear_fast (defined, ins->dreg + 1);
 497 #endif
 498                         }
 499                         num_sregs = mono_inst_get_src_registers (ins, sregs);
 500                         for (i = 0; i < num_sregs; ++i) {
 501                                 mono_bitset_clear_fast (used, sregs [i]);
 502 #if SIZEOF_REGISTER == 4
 503                                 mono_bitset_clear_fast (used, sregs [i] + 1);
 504 #endif
 505                         }
 506                 }
 507
 508                 /*
 509                  * Make a reverse pass over the instruction list
 510                  */
 511                 MONO_BB_FOR_EACH_INS_REVERSE_SAFE (bb, prev, ins) {
 512                         const char *spec = INS_INFO (ins->opcode);
 513                         int sregs [MONO_MAX_SRC_REGS];
 514                         int num_sregs, i;
 515                         MonoInst *prev_f = mono_inst_prev (ins, FILTER_NOP | FILTER_IL_SEQ_POINT);
 516
 517                         if (ins->opcode == OP_NOP) {
 518                                 MONO_DELETE_INS (bb, ins);
 519                                 continue;
 520                         }
 521
 522                         g_assert (ins->opcode > MONO_CEE_LAST);
 523
 524                         if (MONO_IS_NON_FP_MOVE (ins) && prev_f) {
 525                                 MonoInst *def;
 526                                 const char *spec2;
 527
 528                                 def = prev_f;
 529                                 spec2 = INS_INFO (def->opcode);
 530
 531                                 /*
 532                                  * Perform a limited kind of reverse copy propagation, i.e.
 533                                  * transform B <- FOO; A <- B into A <- FOO
 534                                  * This isn't copyprop, not deadce, but it can only be performed
 535                                  * after handle_global_vregs () has run.
 536                                  */
 537                                 if (!get_vreg_to_inst (cfg, ins->sreg1) && (spec2 [MONO_INST_DEST] != ' ') && (def->dreg == ins->sreg1) && !mono_bitset_test_fast (used, ins->sreg1) && !MONO_IS_STORE_MEMBASE (def) && reg_is_softreg (ins->sreg1, spec [MONO_INST_DEST]) && !mono_is_simd_accessor (def)) {
 538                                         if (cfg->verbose_level > 2) {
 539                                                 printf ("\tReverse copyprop in BB%d on ", bb->block_num);
 540                                                 mono_print_ins (ins);
 541                                         }
 542
 543                                         def->dreg = ins->dreg;
 544                                         MONO_DELETE_INS (bb, ins);
 545                                         spec = INS_INFO (ins->opcode);
 546                                 }
 547                         }
 548
 549                         /* Enabling this on x86 could screw up the fp stack */
 550                         if (reg_is_softreg_no_fpstack (ins->dreg, spec [MONO_INST_DEST])) {
 551                                 /*
 552                                  * Assignments to global vregs can only be eliminated if there is another
 553                                  * assignment to the same vreg later in the same bblock.
 554                                  */
 555                                 if (!mono_bitset_test_fast (used, ins->dreg) &&
 556                                         (!get_vreg_to_inst (cfg, ins->dreg) || (!bb->extended && !vreg_is_volatile (cfg, ins->dreg) && mono_bitset_test_fast (defined, ins->dreg))) &&
 557                                         MONO_INS_HAS_NO_SIDE_EFFECT (ins)) {
 558                                         /* Happens with CMOV instructions */
 559                                         if (prev_f && prev_f->opcode == OP_ICOMPARE_IMM) {
 560                                                 MonoInst *prev = prev_f;
 561                                                 /*
 562                                                  * Can't use DELETE_INS since that would interfere with the
 563                                                  * FOR_EACH_INS loop.
 564                                                  */
 565                                                 NULLIFY_INS (prev);
 566                                         }
 567                                         //printf ("DEADCE: "); mono_print_ins (ins);
 568                                         MONO_DELETE_INS (bb, ins);
 569                                         spec = INS_INFO (ins->opcode);
 570                                 }
 571
 572                                 if (spec [MONO_INST_DEST] != ' ')
 573                                         mono_bitset_clear_fast (used, ins->dreg);
 574                         }
 575
 576                         if (spec [MONO_INST_DEST] != ' ')
 577                                 mono_bitset_set_fast (defined, ins->dreg);
 578                         num_sregs = mono_inst_get_src_registers (ins, sregs);
 579                         for (i = 0; i < num_sregs; ++i)
 580                                 mono_bitset_set_fast (used, sregs [i]);
 581                         if (MONO_IS_STORE_MEMBASE (ins))
 582                                 mono_bitset_set_fast (used, ins->dreg);
 583
 584                         if (MONO_IS_CALL (ins)) {
 585                                 MonoCallInst *call = (MonoCallInst*)ins;
 586                                 GSList *l;
 587
 588                                 if (call->out_ireg_args) {
 589                                         for (l = call->out_ireg_args; l; l = l->next) {
 590                                                 guint32 regpair, reg;
 591
 592                                                 regpair = (guint32)(gssize)(l->data);
 593                                                 reg = regpair & 0xffffff;
 594
 595                                                 mono_bitset_set_fast (used, reg);
 596                                         }
 597                                 }
 598
 599                                 if (call->out_freg_args) {
 600                                         for (l = call->out_freg_args; l; l = l->next) {
 601                                                 guint32 regpair, reg;
 602
 603                                                 regpair = (guint32)(gssize)(l->data);
 604                                                 reg = regpair & 0xffffff;
 605
 606                                                 mono_bitset_set_fast (used, reg);
 607                                         }
 608                                 }
 609                         }
 610                 }
 611         }
 612
 613         //mono_print_code (cfg, "AFTER LOCAL-DEADCE");
 614 }
 615
 616 #endif /* DISABLE_JIT */