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  * Replaces ins with optimized opcodes.
  46  * Returns TRUE if additional vregs were allocated.
  47  */
  48 static gboolean
  49 mono_strength_reduction_ins (MonoCompile *cfg, MonoBasicBlock *bb, MonoInst *ins, const char **spec)
  50 {
  51         gboolean allocated_vregs = FALSE;
  52
  53         /* FIXME: Add long/float */
  54         switch (ins->opcode) {
  55         case OP_MOVE:
  56         case OP_XMOVE:
  57                 if (ins->dreg == ins->sreg1) {
  58                         MONO_DELETE_INS (bb, ins);
  59                 }
  60                 break;
  61         case OP_ADD_IMM:
  62         case OP_IADD_IMM:
  63         case OP_SUB_IMM:
  64         case OP_ISUB_IMM:
  65 #if SIZEOF_REGISTER == 8
  66         case OP_LADD_IMM:
  67         case OP_LSUB_IMM:
  68 #endif
  69                 if (ins->inst_imm == 0) {
  70                         ins->opcode = OP_MOVE;
  71                 }
  72                 break;
  73         case OP_MUL_IMM:
  74         case OP_IMUL_IMM:
  75 #if SIZEOF_REGISTER == 8
  76         case OP_LMUL_IMM:
  77 #endif
  78                 if (ins->inst_imm == 0) {
  79                         ins->opcode = (ins->opcode == OP_LMUL_IMM) ? OP_I8CONST : OP_ICONST;
  80                         ins->inst_c0 = 0;
  81                         ins->sreg1 = -1;
  82                 } else if (ins->inst_imm == 1) {
  83                         ins->opcode = OP_MOVE;
  84                 } else if ((ins->opcode == OP_IMUL_IMM) && (ins->inst_imm == -1)) {
  85                         ins->opcode = OP_INEG;
  86                 } else if ((ins->opcode == OP_LMUL_IMM) && (ins->inst_imm == -1)) {
  87                         ins->opcode = OP_LNEG;
  88                 } else {
  89                         int power2 = mono_is_power_of_two (ins->inst_imm);
  90                         if (power2 >= 0) {
  91                                 ins->opcode = (ins->opcode == OP_MUL_IMM) ? OP_SHL_IMM : ((ins->opcode == OP_LMUL_IMM) ? OP_LSHL_IMM : OP_ISHL_IMM);
  92                                 ins->inst_imm = power2;
  93                         }
  94                 }
  95                 break;
  96         case OP_IREM_UN_IMM:
  97         case OP_IDIV_UN_IMM: {
  98                 int c = ins->inst_imm;
  99                 int power2 = mono_is_power_of_two (c);
 100
 101                 if (power2 >= 0) {
 102                         if (ins->opcode == OP_IREM_UN_IMM) {
 103                                 ins->opcode = OP_IAND_IMM;
 104                                 ins->sreg2 = -1;
 105                                 ins->inst_imm = (1 << power2) - 1;
 106                         } else if (ins->opcode == OP_IDIV_UN_IMM) {
 107                                 ins->opcode = OP_ISHR_UN_IMM;
 108                                 ins->sreg2 = -1;
 109                                 ins->inst_imm = power2;
 110                         }
 111                 }
 112                 break;
 113         }
 114         case OP_IDIV_IMM: {
 115                 int c = ins->inst_imm;
 116                 int power2 = mono_is_power_of_two (c);
 117                 MonoInst *tmp1, *tmp2, *tmp3, *tmp4;
 118
 119                 /* FIXME: Move this elsewhere cause its hard to implement it here */
 120                 if (power2 == 1) {
 121                         int r1 = mono_alloc_ireg (cfg);
 122
 123                         NEW_BIALU_IMM (cfg, tmp1, OP_ISHR_UN_IMM, r1, ins->sreg1, 31);
 124                         mono_bblock_insert_after_ins (bb, ins, tmp1);
 125                         NEW_BIALU (cfg, tmp2, OP_IADD, r1, r1, ins->sreg1);
 126                         mono_bblock_insert_after_ins (bb, tmp1, tmp2);
 127                         NEW_BIALU_IMM (cfg, tmp3, OP_ISHR_IMM, ins->dreg, r1, 1);
 128                         mono_bblock_insert_after_ins (bb, tmp2, tmp3);
 129
 130                         NULLIFY_INS (ins);
 131                         allocated_vregs = TRUE;
 132                 } else if (power2 > 0 && power2 < 31) {
 133                         int r1 = mono_alloc_ireg (cfg);
 134
 135                         NEW_BIALU_IMM (cfg, tmp1, OP_ISHR_IMM, r1, ins->sreg1, 31);
 136                         mono_bblock_insert_after_ins (bb, ins, tmp1);
 137                         NEW_BIALU_IMM (cfg, tmp2, OP_ISHR_UN_IMM, r1, r1, (32 - power2));
 138                         mono_bblock_insert_after_ins (bb, tmp1, tmp2);
 139                         NEW_BIALU (cfg, tmp3, OP_IADD, r1, r1, ins->sreg1);
 140                         mono_bblock_insert_after_ins (bb, tmp2, tmp3);
 141                         NEW_BIALU_IMM (cfg, tmp4, OP_ISHR_IMM, ins->dreg, r1, power2);
 142                         mono_bblock_insert_after_ins (bb, tmp3, tmp4);
 143
 144                         NULLIFY_INS (ins);
 145                         allocated_vregs = TRUE;
 146                 }
 147                 break;
 148         }
 149         default:
 150                 break;
 151         }
 152
 153         *spec = INS_INFO (ins->opcode);
 154         return allocated_vregs;
 155 }
 156
 157 /*
 158  * mono_local_cprop:
 159  *
 160  *  A combined local copy and constant propagation pass.
 161  */
 162 void
 163 mono_local_cprop (MonoCompile *cfg)
 164 {
 165         MonoBasicBlock *bb;
 166         MonoInst **defs;
 167         gint32 *def_index;
 168         int max;
 169         int filter = FILTER_IL_SEQ_POINT;
 170
 171 restart:
 172
 173         max = cfg->next_vreg;
 174         defs = (MonoInst **)mono_mempool_alloc (cfg->mempool, sizeof (MonoInst*) * cfg->next_vreg);
 175         def_index = (gint32 *)mono_mempool_alloc (cfg->mempool, sizeof (guint32) * cfg->next_vreg);
 176
 177         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
 178                 MonoInst *ins;
 179                 int ins_index;
 180                 int last_call_index;
 181
 182                 /* Manually init the defs entries used by the bblock */
 183                 MONO_BB_FOR_EACH_INS (bb, ins) {
 184                         int sregs [MONO_MAX_SRC_REGS];
 185                         int num_sregs, i;
 186
 187                         if ((ins->dreg != -1) && (ins->dreg < max)) {
 188                                 defs [ins->dreg] = NULL;
 189 #if SIZEOF_REGISTER == 4
 190                                 defs [ins->dreg + 1] = NULL;
 191 #endif
 192                         }
 193
 194                         num_sregs = mono_inst_get_src_registers (ins, sregs);
 195                         for (i = 0; i < num_sregs; ++i) {
 196                                 int sreg = sregs [i];
 197                                 if (sreg < max) {
 198                                         defs [sreg] = NULL;
 199 #if SIZEOF_REGISTER == 4
 200                                         defs [sreg + 1] = NULL;
 201 #endif
 202                                 }
 203                         }
 204                 }
 205
 206                 ins_index = 0;
 207                 last_call_index = -1;
 208                 MONO_BB_FOR_EACH_INS (bb, ins) {
 209                         const char *spec = INS_INFO (ins->opcode);
 210                         int regtype, srcindex, sreg;
 211                         int num_sregs;
 212                         int sregs [MONO_MAX_SRC_REGS];
 213
 214                         if (ins->opcode == OP_NOP) {
 215                                 MONO_DELETE_INS (bb, ins);
 216                                 continue;
 217                         }
 218
 219                         g_assert (ins->opcode > MONO_CEE_LAST);
 220
 221                         /* FIXME: Optimize this */
 222                         if (ins->opcode == OP_LDADDR) {
 223                                 MonoInst *var = (MonoInst *)ins->inst_p0;
 224
 225                                 defs [var->dreg] = NULL;
 226                                 /*
 227                                 if (!MONO_TYPE_ISSTRUCT (var->inst_vtype))
 228                                         break;
 229                                 */
 230                         }
 231
 232                         if (MONO_IS_STORE_MEMBASE (ins)) {
 233                                 sreg = ins->dreg;
 234                                 regtype = 'i';
 235
 236                                 if ((regtype == 'i') && (sreg != -1) && defs [sreg]) {
 237                                         MonoInst *def = defs [sreg];
 238
 239                                         if ((def->opcode == OP_MOVE) && (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg])) && !vreg_is_volatile (cfg, def->sreg1)) {
 240                                                 int vreg = def->sreg1;
 241                                                 if (cfg->verbose_level > 2) printf ("CCOPY: R%d -> R%d\n", sreg, vreg);
 242                                                 ins->dreg = vreg;
 243                                         }
 244                                 }
 245                         }
 246
 247                         num_sregs = mono_inst_get_src_registers (ins, sregs);
 248                         for (srcindex = 0; srcindex < num_sregs; ++srcindex) {
 249                                 MonoInst *def;
 250
 251                                 mono_inst_get_src_registers (ins, sregs);
 252
 253                                 regtype = spec [MONO_INST_SRC1 + srcindex];
 254                                 sreg = sregs [srcindex];
 255
 256                                 if ((regtype == ' ') || (sreg == -1) || (!defs [sreg]))
 257                                         continue;
 258
 259                                 def = defs [sreg];
 260
 261                                 /* Copy propagation */
 262                                 /*
 263                                  * The first check makes sure the source of the copy did not change since
 264                                  * the copy was made.
 265                                  * The second check avoids volatile variables.
 266                                  * The third check avoids copy propagating local vregs through a call,
 267                                  * since the lvreg will be spilled
 268                                  * The fourth check avoids copy propagating a vreg in cases where
 269                                  * it would be eliminated anyway by reverse copy propagation later,
 270                                  * because propagating it would create another use for it, thus making
 271                                  * it impossible to use reverse copy propagation.
 272                                  */
 273                                 /* Enabling this for floats trips up the fp stack */
 274                                 /*
 275                                  * Enabling this for floats on amd64 seems to cause a failure in
 276                                  * basic-math.cs, most likely because it gets rid of some r8->r4
 277                                  * conversions.
 278                                  */
 279                                 if (MONO_IS_MOVE (def) &&
 280                                         (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg])) &&
 281                                         !vreg_is_volatile (cfg, def->sreg1) &&
 282                                         /* This avoids propagating local vregs across calls */
 283                                         ((get_vreg_to_inst (cfg, def->sreg1) || !defs [def->sreg1] || (def_index [def->sreg1] >= last_call_index) || (def->opcode == OP_VMOVE))) &&
 284                                         !(defs [def->sreg1] && mono_inst_next (defs [def->sreg1], filter) == def) &&
 285                                         (!MONO_ARCH_USE_FPSTACK || (def->opcode != OP_FMOVE)) &&
 286                                         (def->opcode != OP_FMOVE)) {
 287                                         int vreg = def->sreg1;
 288
 289                                         if (cfg->verbose_level > 2) printf ("CCOPY/2: R%d -> R%d\n", sreg, vreg);
 290                                         sregs [srcindex] = vreg;
 291                                         mono_inst_set_src_registers (ins, sregs);
 292
 293                                         /* Allow further iterations */
 294                                         srcindex = -1;
 295                                         continue;
 296                                 }
 297
 298                                 /* Constant propagation */
 299                                 /* FIXME: Make is_inst_imm a macro */
 300                                 /* FIXME: Make is_inst_imm take an opcode argument */
 301                                 /* is_inst_imm is only needed for binops */
 302                                 if ((((def->opcode == OP_ICONST) || ((sizeof (gpointer) == 8) && (def->opcode == OP_I8CONST))) &&
 303                                          (((srcindex == 0) && (ins->sreg2 == -1)) || mono_arch_is_inst_imm (def->inst_c0))) ||
 304                                         (!MONO_ARCH_USE_FPSTACK && (def->opcode == OP_R8CONST))) {
 305                                         guint32 opcode2;
 306
 307                                         /* srcindex == 1 -> binop, ins->sreg2 == -1 -> unop */
 308                                         if ((srcindex == 1) && (ins->sreg1 != -1) && defs [ins->sreg1] && (defs [ins->sreg1]->opcode == OP_ICONST) && defs [ins->sreg2]) {
 309                                                 /* Both arguments are constants, perform cfold */
 310                                                 mono_constant_fold_ins (cfg, ins, defs [ins->sreg1], defs [ins->sreg2], TRUE);
 311                                         } else if ((srcindex == 0) && (ins->sreg2 != -1) && defs [ins->sreg2]) {
 312                                                 /* Arg 1 is constant, swap arguments if possible */
 313                                                 int opcode = ins->opcode;
 314                                                 mono_constant_fold_ins (cfg, ins, defs [ins->sreg1], defs [ins->sreg2], TRUE);
 315                                                 if (ins->opcode != opcode) {
 316                                                         /* Allow further iterations */
 317                                                         srcindex = -1;
 318                                                         continue;
 319                                                 }
 320                                         } else if ((srcindex == 0) && (ins->sreg2 == -1)) {
 321                                                 /* Constant unop, perform cfold */
 322                                                 mono_constant_fold_ins (cfg, ins, defs [ins->sreg1], NULL, TRUE);
 323                                         }
 324
 325                                         opcode2 = mono_op_to_op_imm (ins->opcode);
 326                                         if ((opcode2 != -1) && mono_arch_is_inst_imm (def->inst_c0) && ((srcindex == 1) || (ins->sreg2 == -1))) {
 327                                                 ins->opcode = opcode2;
 328                                                 if ((def->opcode == OP_I8CONST) && (sizeof (gpointer) == 4)) {
 329                                                         ins->inst_ls_word = def->inst_ls_word;
 330                                                         ins->inst_ms_word = def->inst_ms_word;
 331                                                 } else {
 332                                                         ins->inst_imm = def->inst_c0;
 333                                                 }
 334                                                 sregs [srcindex] = -1;
 335                                                 mono_inst_set_src_registers (ins, sregs);
 336
 337                                                 if ((opcode2 == OP_VOIDCALL) || (opcode2 == OP_CALL) || (opcode2 == OP_LCALL) || (opcode2 == OP_FCALL))
 338                                                         ((MonoCallInst*)ins)->fptr = (gpointer)ins->inst_imm;
 339
 340                                                 /* Allow further iterations */
 341                                                 srcindex = -1;
 342                                                 continue;
 343                                         }
 344                                         else {
 345                                                 /* Special cases */
 346 #if defined(TARGET_X86) || defined(TARGET_AMD64)
 347                                                 if ((ins->opcode == OP_X86_LEA) && (srcindex == 1)) {
 348 #if SIZEOF_REGISTER == 8
 349                                                         /* FIXME: Use OP_PADD_IMM when the new JIT is done */
 350                                                         ins->opcode = OP_LADD_IMM;
 351 #else
 352                                                         ins->opcode = OP_ADD_IMM;
 353 #endif
 354                                                         ins->inst_imm += def->inst_c0 << ins->backend.shift_amount;
 355                                                         ins->sreg2 = -1;
 356                                                 }
 357 #endif
 358                                                 opcode2 = mono_load_membase_to_load_mem (ins->opcode);
 359                                                 if ((srcindex == 0) && (opcode2 != -1) && mono_arch_is_inst_imm (def->inst_c0)) {
 360                                                         ins->opcode = opcode2;
 361                                                         ins->inst_imm = def->inst_c0 + ins->inst_offset;
 362                                                         ins->sreg1 = -1;
 363                                                 }
 364                                         }
 365                                 }
 366                                 else if (((def->opcode == OP_ADD_IMM) || (def->opcode == OP_LADD_IMM)) && (MONO_IS_LOAD_MEMBASE (ins) || MONO_ARCH_IS_OP_MEMBASE (ins->opcode))) {
 367                                         /* ADD_IMM is created by spill_global_vars */
 368                                         /*
 369                                          * We have to guarantee that def->sreg1 haven't changed since def->dreg
 370                                          * was defined. cfg->frame_reg is assumed to remain constant.
 371                                          */
 372                                         if ((def->sreg1 == cfg->frame_reg) || ((mono_inst_next (def, filter) == ins) && (def->dreg != def->sreg1))) {
 373                                                 ins->inst_basereg = def->sreg1;
 374                                                 ins->inst_offset += def->inst_imm;
 375                                         }
 376                                 } else if ((ins->opcode == OP_ISUB_IMM) && (def->opcode == OP_IADD_IMM) && (mono_inst_next (def, filter) == ins) && (def->dreg != def->sreg1)) {
 377                                         ins->sreg1 = def->sreg1;
 378                                         ins->inst_imm -= def->inst_imm;
 379                                 } else if ((ins->opcode == OP_IADD_IMM) && (def->opcode == OP_ISUB_IMM) && (mono_inst_next (def, filter) == ins) && (def->dreg != def->sreg1)) {
 380                                         ins->sreg1 = def->sreg1;
 381                                         ins->inst_imm -= def->inst_imm;
 382                                 } else if (ins->opcode == OP_STOREI1_MEMBASE_REG &&
 383                                                    (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)) &&
 384                                                    (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg]))) {
 385                                         /* Avoid needless sign extension */
 386                                         ins->sreg1 = def->sreg1;
 387                                 } else if (ins->opcode == OP_STOREI2_MEMBASE_REG &&
 388                                                    (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)) &&
 389                                                    (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg]))) {
 390                                         /* Avoid needless sign extension */
 391                                         ins->sreg1 = def->sreg1;
 392                                 }
 393                         }
 394
 395                         /* Do strength reduction here */
 396                         if (mono_strength_reduction_ins (cfg, bb, ins, &spec))
 397                                 goto restart;
 398
 399                         if (spec [MONO_INST_DEST] != ' ') {
 400                                 MonoInst *def = defs [ins->dreg];
 401
 402                                 if (def && (def->opcode == OP_ADD_IMM) && (def->sreg1 == cfg->frame_reg) && (MONO_IS_STORE_MEMBASE (ins))) {
 403                                         /* ADD_IMM is created by spill_global_vars */
 404                                         /* cfg->frame_reg is assumed to remain constant */
 405                                         ins->inst_destbasereg = def->sreg1;
 406                                         ins->inst_offset += def->inst_imm;
 407                                 }
 408                         }
 409
 410                         if ((spec [MONO_INST_DEST] != ' ') && !MONO_IS_STORE_MEMBASE (ins) && !vreg_is_volatile (cfg, ins->dreg)) {
 411                                 defs [ins->dreg] = ins;
 412                                 def_index [ins->dreg] = ins_index;
 413                         }
 414
 415                         if (MONO_IS_CALL (ins))
 416                                 last_call_index = ins_index;
 417
 418                         ins_index ++;
 419                 }
 420         }
 421 }
 422
 423 static inline gboolean
 424 reg_is_softreg_no_fpstack (int reg, const char spec)
 425 {
 426         return (spec == 'i' && reg >= MONO_MAX_IREGS)
 427                 || ((spec == 'f' && reg >= MONO_MAX_FREGS) && !MONO_ARCH_USE_FPSTACK)
 428 #ifdef MONO_ARCH_SIMD_INTRINSICS
 429                 || (spec == 'x' && reg >= MONO_MAX_XREGS)
 430 #endif
 431                 || (spec == 'v');
 432 }
 433
 434 static inline gboolean
 435 reg_is_softreg (int reg, const char spec)
 436 {
 437         return (spec == 'i' && reg >= MONO_MAX_IREGS)
 438                 || (spec == 'f' && reg >= MONO_MAX_FREGS)
 439 #ifdef MONO_ARCH_SIMD_INTRINSICS
 440                 || (spec == 'x' && reg >= MONO_MAX_XREGS)
 441 #endif
 442                 || (spec == 'v');
 443 }
 444
 445 static inline gboolean
 446 mono_is_simd_accessor (MonoInst *ins)
 447 {
 448         switch (ins->opcode) {
 449 #ifdef MONO_ARCH_SIMD_INTRINSICS
 450         case OP_INSERT_I1:
 451         case OP_INSERT_I2:
 452         case OP_INSERT_I4:
 453         case OP_INSERT_I8:
 454         case OP_INSERT_R4:
 455         case OP_INSERT_R8:
 456
 457         case OP_INSERTX_U1_SLOW:
 458         case OP_INSERTX_I4_SLOW:
 459         case OP_INSERTX_R4_SLOW:
 460         case OP_INSERTX_R8_SLOW:
 461         case OP_INSERTX_I8_SLOW:
 462                 return TRUE;
 463 #endif
 464         default:
 465                 return FALSE;
 466         }
 467 }
 468
 469 /**
 470  * mono_local_deadce:
 471  *
 472  *   Get rid of the dead assignments to local vregs like the ones created by the
 473  * copyprop pass.
 474  */
 475 void
 476 mono_local_deadce (MonoCompile *cfg)
 477 {
 478         MonoBasicBlock *bb;
 479         MonoInst *ins, *prev;
 480         MonoBitSet *used, *defined;
 481
 482         //mono_print_code (cfg, "BEFORE LOCAL-DEADCE");
 483
 484         /*
 485          * Assignments to global vregs can't be eliminated so this pass must come
 486          * after the handle_global_vregs () pass.
 487          */
 488
 489         used = mono_bitset_mp_new_noinit (cfg->mempool, cfg->next_vreg + 1);
 490         defined = mono_bitset_mp_new_noinit (cfg->mempool, cfg->next_vreg + 1);
 491
 492         /* First pass: collect liveness info */
 493         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
 494                 /* Manually init the defs entries used by the bblock */
 495                 MONO_BB_FOR_EACH_INS (bb, ins) {
 496                         const char *spec = INS_INFO (ins->opcode);
 497                         int sregs [MONO_MAX_SRC_REGS];
 498                         int num_sregs, i;
 499
 500                         if (spec [MONO_INST_DEST] != ' ') {
 501                                 mono_bitset_clear_fast (used, ins->dreg);
 502                                 mono_bitset_clear_fast (defined, ins->dreg);
 503 #if SIZEOF_REGISTER == 4
 504                                 /* Regpairs */
 505                                 mono_bitset_clear_fast (used, ins->dreg + 1);
 506                                 mono_bitset_clear_fast (defined, ins->dreg + 1);
 507 #endif
 508                         }
 509                         num_sregs = mono_inst_get_src_registers (ins, sregs);
 510                         for (i = 0; i < num_sregs; ++i) {
 511                                 mono_bitset_clear_fast (used, sregs [i]);
 512 #if SIZEOF_REGISTER == 4
 513                                 mono_bitset_clear_fast (used, sregs [i] + 1);
 514 #endif
 515                         }
 516                 }
 517
 518                 /*
 519                  * Make a reverse pass over the instruction list
 520                  */
 521                 MONO_BB_FOR_EACH_INS_REVERSE_SAFE (bb, prev, ins) {
 522                         const char *spec = INS_INFO (ins->opcode);
 523                         int sregs [MONO_MAX_SRC_REGS];
 524                         int num_sregs, i;
 525                         MonoInst *prev_f = mono_inst_prev (ins, FILTER_NOP | FILTER_IL_SEQ_POINT);
 526
 527                         if (ins->opcode == OP_NOP) {
 528                                 MONO_DELETE_INS (bb, ins);
 529                                 continue;
 530                         }
 531
 532                         g_assert (ins->opcode > MONO_CEE_LAST);
 533
 534                         if (MONO_IS_NON_FP_MOVE (ins) && prev_f) {
 535                                 MonoInst *def;
 536                                 const char *spec2;
 537
 538                                 def = prev_f;
 539                                 spec2 = INS_INFO (def->opcode);
 540
 541                                 /*
 542                                  * Perform a limited kind of reverse copy propagation, i.e.
 543                                  * transform B <- FOO; A <- B into A <- FOO
 544                                  * This isn't copyprop, not deadce, but it can only be performed
 545                                  * after handle_global_vregs () has run.
 546                                  */
 547                                 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)) {
 548                                         if (cfg->verbose_level > 2) {
 549                                                 printf ("\tReverse copyprop in BB%d on ", bb->block_num);
 550                                                 mono_print_ins (ins);
 551                                         }
 552
 553                                         def->dreg = ins->dreg;
 554                                         MONO_DELETE_INS (bb, ins);
 555                                         spec = INS_INFO (ins->opcode);
 556                                 }
 557                         }
 558
 559                         /* Enabling this on x86 could screw up the fp stack */
 560                         if (reg_is_softreg_no_fpstack (ins->dreg, spec [MONO_INST_DEST])) {
 561                                 /*
 562                                  * Assignments to global vregs can only be eliminated if there is another
 563                                  * assignment to the same vreg later in the same bblock.
 564                                  */
 565                                 if (!mono_bitset_test_fast (used, ins->dreg) &&
 566                                         (!get_vreg_to_inst (cfg, ins->dreg) || (!bb->extended && !vreg_is_volatile (cfg, ins->dreg) && mono_bitset_test_fast (defined, ins->dreg))) &&
 567                                         MONO_INS_HAS_NO_SIDE_EFFECT (ins)) {
 568                                         /* Happens with CMOV instructions */
 569                                         if (prev_f && prev_f->opcode == OP_ICOMPARE_IMM) {
 570                                                 MonoInst *prev = prev_f;
 571                                                 /*
 572                                                  * Can't use DELETE_INS since that would interfere with the
 573                                                  * FOR_EACH_INS loop.
 574                                                  */
 575                                                 NULLIFY_INS (prev);
 576                                         }
 577                                         //printf ("DEADCE: "); mono_print_ins (ins);
 578                                         MONO_DELETE_INS (bb, ins);
 579                                         spec = INS_INFO (ins->opcode);
 580                                 }
 581
 582                                 if (spec [MONO_INST_DEST] != ' ')
 583                                         mono_bitset_clear_fast (used, ins->dreg);
 584                         }
 585
 586                         if (spec [MONO_INST_DEST] != ' ')
 587                                 mono_bitset_set_fast (defined, ins->dreg);
 588                         num_sregs = mono_inst_get_src_registers (ins, sregs);
 589                         for (i = 0; i < num_sregs; ++i)
 590                                 mono_bitset_set_fast (used, sregs [i]);
 591                         if (MONO_IS_STORE_MEMBASE (ins))
 592                                 mono_bitset_set_fast (used, ins->dreg);
 593
 594                         if (MONO_IS_CALL (ins)) {
 595                                 MonoCallInst *call = (MonoCallInst*)ins;
 596                                 GSList *l;
 597
 598                                 if (call->out_ireg_args) {
 599                                         for (l = call->out_ireg_args; l; l = l->next) {
 600                                                 guint32 regpair, reg;
 601
 602                                                 regpair = (guint32)(gssize)(l->data);
 603                                                 reg = regpair & 0xffffff;
 604
 605                                                 mono_bitset_set_fast (used, reg);
 606                                         }
 607                                 }
 608
 609                                 if (call->out_freg_args) {
 610                                         for (l = call->out_freg_args; l; l = l->next) {
 611                                                 guint32 regpair, reg;
 612
 613                                                 regpair = (guint32)(gssize)(l->data);
 614                                                 reg = regpair & 0xffffff;
 615
 616                                                 mono_bitset_set_fast (used, reg);
 617                                         }
 618                                 }
 619                         }
 620                 }
 621         }
 622
 623         //mono_print_code (cfg, "AFTER LOCAL-DEADCE");
 624 }
 625
 626 #endif /* DISABLE_JIT */