simplify.c

   1 /*
   2  * Simplify - do instruction simplification before CSE
   3  *
   4  * Copyright (C) 2004 Linus Torvalds
   5  */
   6
   7 #include <assert.h>
   8
   9 #include "parse.h"
  10 #include "expression.h"
  11 #include "linearize.h"
  12 #include "flow.h"
  13 #include "symbol.h"
  14
  15 /* Find the trivial parent for a phi-source */
  16 static struct basic_block *phi_parent(struct basic_block *source, pseudo_t pseudo)
  17 {
  18         /* Can't go upwards if the pseudo is defined in the bb it came from.. */
  19         if (pseudo->type == PSEUDO_REG) {
  20                 struct instruction *def = pseudo->def;
  21                 if (def->bb == source)
  22                         return source;
  23         }
  24         if (bb_list_size(source->children) != 1 || bb_list_size(source->parents) != 1)
  25                 return source;
  26         return first_basic_block(source->parents);
  27 }
  28
  29 static int if_convert_phi(struct instruction *insn)
  30 {
  31         pseudo_t array[3];
  32         struct basic_block *parents[3];
  33         struct basic_block *bb, *bb1, *bb2, *source;
  34         struct instruction *br;
  35         pseudo_t p1, p2;
  36
  37         bb = insn->bb;
  38         if (linearize_ptr_list((struct ptr_list *)insn->phi_list, (void **)array, 3) != 2)
  39                 return 0;
  40         if (linearize_ptr_list((struct ptr_list *)bb->parents, (void **)parents, 3) != 2)
  41                 return 0;
  42         p1 = array[0]->def->src1;
  43         bb1 = array[0]->def->bb;
  44         p2 = array[1]->def->src1;
  45         bb2 = array[1]->def->bb;
  46
  47         /* Only try the simple "direct parents" case */
  48         if ((bb1 != parents[0] || bb2 != parents[1]) &&
  49             (bb1 != parents[1] || bb2 != parents[0]))
  50                 return 0;
  51
  52         /*
  53          * See if we can find a common source for this..
  54          */
  55         source = phi_parent(bb1, p1);
  56         if (source != phi_parent(bb2, p2))
  57                 return 0;
  58
  59         /*
  60          * Cool. We now know that 'source' is the exclusive
  61          * parent of both phi-nodes, so the exit at the
  62          * end of it fully determines which one it is, and
  63          * we can turn it into a select.
  64          *
  65          * HOWEVER, right now we only handle regular
  66          * conditional branches. No multijumps or computed
  67          * stuff. Verify that here.
  68          */
  69         br = last_instruction(source->insns);
  70         if (!br || br->opcode != OP_BR)
  71                 return 0;
  72
  73         assert(br->cond);
  74         assert(br->bb_false);
  75
  76         /*
  77          * We're in business. Match up true/false with p1/p2.
  78          */
  79         if (br->bb_true == bb2 || br->bb_false == bb1) {
  80                 pseudo_t p = p1;
  81                 p1 = p2;
  82                 p2 = p;
  83         }
  84
  85         /*
  86          * OK, we can now replace that last
  87          *
  88          *      br cond, a, b
  89          *
  90          * with the sequence
  91          *
  92          *      setcc cond
  93          *      select pseudo, p1, p2
  94          *      br cond, a, b
  95          *
  96          * and remove the phi-node. If it then
  97          * turns out that 'a' or 'b' is entirely
  98          * empty (common case), and now no longer
  99          * a phi-source, we'll be able to simplify
 100          * the conditional branch too.
 101          */
 102         insert_select(source, br, insn, p1, p2);
 103         kill_instruction(insn);
 104         return REPEAT_CSE;
 105 }
 106
 107 static int clean_up_phi(struct instruction *insn)
 108 {
 109         pseudo_t phi;
 110         struct instruction *last;
 111         int same;
 112
 113         last = NULL;
 114         same = 1;
 115         FOR_EACH_PTR(insn->phi_list, phi) {
 116                 struct instruction *def;
 117                 if (phi == VOID)
 118                         continue;
 119                 def = phi->def;
 120                 if (def->src1 == VOID || !def->bb)
 121                         continue;
 122                 if (last) {
 123                         if (last->src1 != def->src1)
 124                                 same = 0;
 125                         continue;
 126                 }
 127                 last = def;
 128         } END_FOR_EACH_PTR(phi);
 129
 130         if (same) {
 131                 pseudo_t pseudo = last ? last->src1 : VOID;
 132                 convert_instruction_target(insn, pseudo);
 133                 kill_instruction(insn);
 134                 return REPEAT_CSE;
 135         }
 136
 137         return if_convert_phi(insn);
 138 }
 139
 140 static int delete_pseudo_user_list_entry(struct pseudo_user_list **list, pseudo_t *entry, int count)
 141 {
 142         struct pseudo_user *pu;
 143
 144         FOR_EACH_PTR(*list, pu) {
 145                 if (pu->userp == entry) {
 146                         DELETE_CURRENT_PTR(pu);
 147                         if (!--count)
 148                                 goto out;
 149                 }
 150         } END_FOR_EACH_PTR(pu);
 151         assert(count <= 0);
 152 out:
 153         pack_ptr_list((struct ptr_list **)list);
 154         return count;
 155 }
 156
 157 static inline void remove_usage(pseudo_t p, pseudo_t *usep)
 158 {
 159         if (has_use_list(p)) {
 160                 delete_pseudo_user_list_entry(&p->users, usep, 1);
 161                 if (!p->users)
 162                         kill_instruction(p->def);
 163         }
 164 }
 165
 166 void kill_use(pseudo_t *usep)
 167 {
 168         if (usep) {
 169                 pseudo_t p = *usep;
 170                 *usep = VOID;
 171                 remove_usage(p, usep);
 172         }
 173 }
 174
 175 static void kill_use_list(struct pseudo_list *list)
 176 {
 177         pseudo_t p;
 178         FOR_EACH_PTR(list, p) {
 179                 if (p == VOID)
 180                         continue;
 181                 kill_use(THIS_ADDRESS(p));
 182         } END_FOR_EACH_PTR(p);
 183 }
 184
 185 /*
 186  * kill an instruction:
 187  * - remove it from its bb
 188  * - remove the usage of all its operands
 189  * If forse is zero, the normal case, the function only for
 190  * instructions free of (possible) side-effects. Otherwise
 191  * the function does that unconditionally (must only be used
 192  * for unreachable instructions.
 193  */
 194 void kill_insn(struct instruction *insn, int force)
 195 {
 196         if (!insn || !insn->bb)
 197                 return;
 198
 199         switch (insn->opcode) {
 200         case OP_SEL:
 201         case OP_RANGE:
 202                 kill_use(&insn->src3);
 203                 /* fall through */
 204
 205         case OP_BINARY ... OP_BINCMP_END:
 206                 kill_use(&insn->src2);
 207                 /* fall through */
 208
 209         case OP_CAST:
 210         case OP_SCAST:
 211         case OP_FPCAST:
 212         case OP_PTRCAST:
 213         case OP_SETVAL:
 214         case OP_NOT: case OP_NEG:
 215         case OP_SLICE:
 216                 kill_use(&insn->src1);
 217                 break;
 218
 219         case OP_PHI:
 220                 kill_use_list(insn->phi_list);
 221                 break;
 222         case OP_PHISOURCE:
 223                 kill_use(&insn->phi_src);
 224                 break;
 225
 226         case OP_SYMADDR:
 227                 repeat_phase |= REPEAT_SYMBOL_CLEANUP;
 228                 break;
 229
 230         case OP_BR:
 231                 if (!insn->bb_true || !insn->bb_false)
 232                         break;
 233                 /* fall through */
 234
 235         case OP_COMPUTEDGOTO:
 236                 kill_use(&insn->cond);
 237                 break;
 238
 239         case OP_CALL:
 240                 if (!force) {
 241                         /* a "pure" function can be killed too */
 242                         if (!(insn->func->type == PSEUDO_SYM))
 243                                 return;
 244                         if (!(insn->func->sym->ctype.modifiers & MOD_PURE))
 245                                 return;
 246                 }
 247                 kill_use_list(insn->arguments);
 248                 if (insn->func->type == PSEUDO_REG)
 249                         kill_use(&insn->func);
 250                 break;
 251
 252         case OP_LOAD:
 253                 if (!force && insn->type->ctype.modifiers & MOD_VOLATILE)
 254                         return;
 255                 kill_use(&insn->src);
 256                 break;
 257
 258         case OP_STORE:
 259                 if (!force)
 260                         return;
 261                 kill_use(&insn->src);
 262                 kill_use(&insn->target);
 263                 break;
 264
 265         case OP_ENTRY:
 266                 /* ignore */
 267                 return;
 268
 269         default:
 270                 break;
 271         }
 272
 273         insn->bb = NULL;
 274         repeat_phase |= REPEAT_CSE;
 275         return;
 276 }
 277
 278 /*
 279  * Kill trivially dead instructions
 280  */
 281 static int dead_insn(struct instruction *insn, pseudo_t *src1, pseudo_t *src2, pseudo_t *src3)
 282 {
 283         struct pseudo_user *pu;
 284         FOR_EACH_PTR(insn->target->users, pu) {
 285                 if (*pu->userp != VOID)
 286                         return 0;
 287         } END_FOR_EACH_PTR(pu);
 288
 289         insn->bb = NULL;
 290         kill_use(src1);
 291         kill_use(src2);
 292         kill_use(src3);
 293         return REPEAT_CSE;
 294 }
 295
 296 static inline int constant(pseudo_t pseudo)
 297 {
 298         return pseudo->type == PSEUDO_VAL;
 299 }
 300
 301 static int replace_with_pseudo(struct instruction *insn, pseudo_t pseudo)
 302 {
 303         convert_instruction_target(insn, pseudo);
 304
 305         switch (insn->opcode) {
 306         case OP_SEL:
 307         case OP_RANGE:
 308                 kill_use(&insn->src3);
 309         case OP_BINARY ... OP_BINCMP_END:
 310                 kill_use(&insn->src2);
 311         case OP_NOT:
 312         case OP_NEG:
 313         case OP_SYMADDR:
 314         case OP_CAST:
 315         case OP_SCAST:
 316         case OP_FPCAST:
 317         case OP_PTRCAST:
 318                 kill_use(&insn->src1);
 319                 break;
 320
 321         default:
 322                 assert(0);
 323         }
 324         insn->bb = NULL;
 325         return REPEAT_CSE;
 326 }
 327
 328 static unsigned int value_size(long long value)
 329 {
 330         value >>= 8;
 331         if (!value)
 332                 return 8;
 333         value >>= 8;
 334         if (!value)
 335                 return 16;
 336         value >>= 16;
 337         if (!value)
 338                 return 32;
 339         return 64;
 340 }
 341
 342 /*
 343  * Try to determine the maximum size of bits in a pseudo.
 344  *
 345  * Right now this only follow casts and constant values, but we
 346  * could look at things like logical 'and' instructions etc.
 347  */
 348 static unsigned int operand_size(struct instruction *insn, pseudo_t pseudo)
 349 {
 350         unsigned int size = insn->size;
 351
 352         if (pseudo->type == PSEUDO_REG) {
 353                 struct instruction *src = pseudo->def;
 354                 if (src && src->opcode == OP_CAST && src->orig_type) {
 355                         unsigned int orig_size = src->orig_type->bit_size;
 356                         if (orig_size < size)
 357                                 size = orig_size;
 358                 }
 359         }
 360         if (pseudo->type == PSEUDO_VAL) {
 361                 unsigned int orig_size = value_size(pseudo->value);
 362                 if (orig_size < size)
 363                         size = orig_size;
 364         }
 365         return size;
 366 }
 367
 368 static int simplify_asr(struct instruction *insn, pseudo_t pseudo, long long value)
 369 {
 370         unsigned int size = operand_size(insn, pseudo);
 371
 372         if (value >= size) {
 373                 warning(insn->pos, "right shift by bigger than source value");
 374                 return replace_with_pseudo(insn, value_pseudo(0));
 375         }
 376         if (!value)
 377                 return replace_with_pseudo(insn, pseudo);
 378         return 0;
 379 }
 380
 381 static int simplify_mul_div(struct instruction *insn, long long value)
 382 {
 383         unsigned long long sbit = 1ULL << (insn->size - 1);
 384         unsigned long long bits = sbit | (sbit - 1);
 385
 386         if (value == 1)
 387                 return replace_with_pseudo(insn, insn->src1);
 388
 389         switch (insn->opcode) {
 390         case OP_MULS:
 391         case OP_MULU:
 392                 if (value == 0)
 393                         return replace_with_pseudo(insn, insn->src2);
 394         /* Fall through */
 395         case OP_DIVS:
 396                 if (!(value & sbit))    // positive
 397                         break;
 398
 399                 value |= ~bits;
 400                 if (value == -1) {
 401                         insn->opcode = OP_NEG;
 402                         return REPEAT_CSE;
 403                 }
 404         }
 405
 406         return 0;
 407 }
 408
 409 static int compare_opcode(int opcode, int inverse)
 410 {
 411         if (!inverse)
 412                 return opcode;
 413
 414         switch (opcode) {
 415         case OP_SET_EQ: return OP_SET_NE;
 416         case OP_SET_NE: return OP_SET_EQ;
 417
 418         case OP_SET_LT: return OP_SET_GE;
 419         case OP_SET_LE: return OP_SET_GT;
 420         case OP_SET_GT: return OP_SET_LE;
 421         case OP_SET_GE: return OP_SET_LT;
 422
 423         case OP_SET_A:  return OP_SET_BE;
 424         case OP_SET_AE: return OP_SET_B;
 425         case OP_SET_B:  return OP_SET_AE;
 426         case OP_SET_BE: return OP_SET_A;
 427
 428         default:
 429                 return opcode;
 430         }
 431 }
 432
 433 static int simplify_seteq_setne(struct instruction *insn, long long value)
 434 {
 435         struct instruction *def = insn->src1->def;
 436         pseudo_t src1, src2;
 437         int inverse;
 438         int opcode;
 439
 440         if (value != 0 && value != 1)
 441                 return 0;
 442
 443         if (!def)
 444                 return 0;
 445
 446         inverse = (insn->opcode == OP_SET_NE) == value;
 447         opcode = def->opcode;
 448         switch (opcode) {
 449         case OP_BINCMP ... OP_BINCMP_END:
 450                 // Convert:
 451                 //      setcc.n %t <- %a, %b
 452                 //      setne.m %r <- %t, $0
 453                 // into:
 454                 //      setcc.n %t <- %a, %b
 455                 //      setcc.m %r <- %a, $b
 456                 // and similar for setne/eq ... 0/1
 457                 src1 = def->src1;
 458                 src2 = def->src2;
 459                 remove_usage(insn->src1, &insn->src1);
 460                 insn->opcode = compare_opcode(opcode, inverse);
 461                 use_pseudo(insn, src1, &insn->src1);
 462                 use_pseudo(insn, src2, &insn->src2);
 463                 return REPEAT_CSE;
 464
 465         default:
 466                 return 0;
 467         }
 468 }
 469
 470 static int simplify_constant_rightside(struct instruction *insn)
 471 {
 472         long long value = insn->src2->value;
 473
 474         switch (insn->opcode) {
 475         case OP_OR_BOOL:
 476                 if (value == 1)
 477                         return replace_with_pseudo(insn, insn->src2);
 478                 goto case_neutral_zero;
 479
 480         case OP_SUB:
 481                 if (value) {
 482                         insn->opcode = OP_ADD;
 483                         insn->src2 = value_pseudo(-value);
 484                         return REPEAT_CSE;
 485                 }
 486         /* Fall through */
 487         case OP_ADD:
 488         case OP_OR: case OP_XOR:
 489         case OP_SHL:
 490         case OP_LSR:
 491         case_neutral_zero:
 492                 if (!value)
 493                         return replace_with_pseudo(insn, insn->src1);
 494                 return 0;
 495         case OP_ASR:
 496                 return simplify_asr(insn, insn->src1, value);
 497
 498         case OP_MODU: case OP_MODS:
 499                 if (value == 1)
 500                         return replace_with_pseudo(insn, value_pseudo(0));
 501                 return 0;
 502
 503         case OP_DIVU: case OP_DIVS:
 504         case OP_MULU: case OP_MULS:
 505                 return simplify_mul_div(insn, value);
 506
 507         case OP_AND_BOOL:
 508                 if (value == 1)
 509                         return replace_with_pseudo(insn, insn->src1);
 510         /* Fall through */
 511         case OP_AND:
 512                 if (!value)
 513                         return replace_with_pseudo(insn, insn->src2);
 514                 return 0;
 515
 516         case OP_SET_NE:
 517         case OP_SET_EQ:
 518                 return simplify_seteq_setne(insn, value);
 519         }
 520         return 0;
 521 }
 522
 523 static int simplify_constant_leftside(struct instruction *insn)
 524 {
 525         long long value = insn->src1->value;
 526
 527         switch (insn->opcode) {
 528         case OP_ADD: case OP_OR: case OP_XOR:
 529                 if (!value)
 530                         return replace_with_pseudo(insn, insn->src2);
 531                 return 0;
 532
 533         case OP_SHL:
 534         case OP_LSR: case OP_ASR:
 535         case OP_AND:
 536         case OP_MULU: case OP_MULS:
 537                 if (!value)
 538                         return replace_with_pseudo(insn, insn->src1);
 539                 return 0;
 540         }
 541         return 0;
 542 }
 543
 544 static int simplify_constant_binop(struct instruction *insn)
 545 {
 546         /* FIXME! Verify signs and sizes!! */
 547         long long left = insn->src1->value;
 548         long long right = insn->src2->value;
 549         unsigned long long ul, ur;
 550         long long res, mask, bits;
 551
 552         mask = 1ULL << (insn->size-1);
 553         bits = mask | (mask-1);
 554
 555         if (left & mask)
 556                 left |= ~bits;
 557         if (right & mask)
 558                 right |= ~bits;
 559         ul = left & bits;
 560         ur = right & bits;
 561
 562         switch (insn->opcode) {
 563         case OP_ADD:
 564                 res = left + right;
 565                 break;
 566         case OP_SUB:
 567                 res = left - right;
 568                 break;
 569         case OP_MULU:
 570                 res = ul * ur;
 571                 break;
 572         case OP_MULS:
 573                 res = left * right;
 574                 break;
 575         case OP_DIVU:
 576                 if (!ur)
 577                         return 0;
 578                 res = ul / ur;
 579                 break;
 580         case OP_DIVS:
 581                 if (!right)
 582                         return 0;
 583                 if (left == mask && right == -1)
 584                         return 0;
 585                 res = left / right;
 586                 break;
 587         case OP_MODU:
 588                 if (!ur)
 589                         return 0;
 590                 res = ul % ur;
 591                 break;
 592         case OP_MODS:
 593                 if (!right)
 594                         return 0;
 595                 if (left == mask && right == -1)
 596                         return 0;
 597                 res = left % right;
 598                 break;
 599         case OP_SHL:
 600                 res = left << right;
 601                 break;
 602         case OP_LSR:
 603                 res = ul >> ur;
 604                 break;
 605         case OP_ASR:
 606                 res = left >> right;
 607                 break;
 608        /* Logical */
 609         case OP_AND:
 610                 res = left & right;
 611                 break;
 612         case OP_OR:
 613                 res = left | right;
 614                 break;
 615         case OP_XOR:
 616                 res = left ^ right;
 617                 break;
 618         case OP_AND_BOOL:
 619                 res = left && right;
 620                 break;
 621         case OP_OR_BOOL:
 622                 res = left || right;
 623                 break;
 624
 625         /* Binary comparison */
 626         case OP_SET_EQ:
 627                 res = left == right;
 628                 break;
 629         case OP_SET_NE:
 630                 res = left != right;
 631                 break;
 632         case OP_SET_LE:
 633                 res = left <= right;
 634                 break;
 635         case OP_SET_GE:
 636                 res = left >= right;
 637                 break;
 638         case OP_SET_LT:
 639                 res = left < right;
 640                 break;
 641         case OP_SET_GT:
 642                 res = left > right;
 643                 break;
 644         case OP_SET_B:
 645                 res = ul < ur;
 646                 break;
 647         case OP_SET_A:
 648                 res = ul > ur;
 649                 break;
 650         case OP_SET_BE:
 651                 res = ul <= ur;
 652                 break;
 653         case OP_SET_AE:
 654                 res = ul >= ur;
 655                 break;
 656         default:
 657                 return 0;
 658         }
 659         res &= bits;
 660
 661         replace_with_pseudo(insn, value_pseudo(res));
 662         return REPEAT_CSE;
 663 }
 664
 665 static int simplify_binop_same_args(struct instruction *insn, pseudo_t arg)
 666 {
 667         switch (insn->opcode) {
 668         case OP_SET_NE:
 669         case OP_SET_LT: case OP_SET_GT:
 670         case OP_SET_B:  case OP_SET_A:
 671                 if (Wtautological_compare)
 672                         warning(insn->pos, "self-comparison always evaluates to false");
 673         case OP_SUB:
 674         case OP_XOR:
 675                 return replace_with_pseudo(insn, value_pseudo(0));
 676
 677         case OP_SET_EQ:
 678         case OP_SET_LE: case OP_SET_GE:
 679         case OP_SET_BE: case OP_SET_AE:
 680                 if (Wtautological_compare)
 681                         warning(insn->pos, "self-comparison always evaluates to true");
 682                 return replace_with_pseudo(insn, value_pseudo(1));
 683
 684         case OP_AND:
 685         case OP_OR:
 686                 return replace_with_pseudo(insn, arg);
 687
 688         case OP_AND_BOOL:
 689         case OP_OR_BOOL:
 690                 remove_usage(arg, &insn->src2);
 691                 insn->src2 = value_pseudo(0);
 692                 insn->opcode = OP_SET_NE;
 693                 return REPEAT_CSE;
 694
 695         default:
 696                 break;
 697         }
 698
 699         return 0;
 700 }
 701
 702 static int simplify_binop(struct instruction *insn)
 703 {
 704         if (dead_insn(insn, &insn->src1, &insn->src2, NULL))
 705                 return REPEAT_CSE;
 706         if (constant(insn->src1)) {
 707                 if (constant(insn->src2))
 708                         return simplify_constant_binop(insn);
 709                 return simplify_constant_leftside(insn);
 710         }
 711         if (constant(insn->src2))
 712                 return simplify_constant_rightside(insn);
 713         if (insn->src1 == insn->src2)
 714                 return simplify_binop_same_args(insn, insn->src1);
 715         return 0;
 716 }
 717
 718 static void switch_pseudo(struct instruction *insn1, pseudo_t *pp1, struct instruction *insn2, pseudo_t *pp2)
 719 {
 720         pseudo_t p1 = *pp1, p2 = *pp2;
 721
 722         use_pseudo(insn1, p2, pp1);
 723         use_pseudo(insn2, p1, pp2);
 724         remove_usage(p1, pp1);
 725         remove_usage(p2, pp2);
 726 }
 727
 728 static int canonical_order(pseudo_t p1, pseudo_t p2)
 729 {
 730         /* symbol/constants on the right */
 731         if (p1->type == PSEUDO_VAL)
 732                 return p2->type == PSEUDO_VAL;
 733
 734         if (p1->type == PSEUDO_SYM)
 735                 return p2->type == PSEUDO_SYM || p2->type == PSEUDO_VAL;
 736
 737         return 1;
 738 }
 739
 740 static int simplify_commutative_binop(struct instruction *insn)
 741 {
 742         if (!canonical_order(insn->src1, insn->src2)) {
 743                 switch_pseudo(insn, &insn->src1, insn, &insn->src2);
 744                 return REPEAT_CSE;
 745         }
 746         return 0;
 747 }
 748
 749 static inline int simple_pseudo(pseudo_t pseudo)
 750 {
 751         return pseudo->type == PSEUDO_VAL || pseudo->type == PSEUDO_SYM;
 752 }
 753
 754 static int simplify_associative_binop(struct instruction *insn)
 755 {
 756         struct instruction *def;
 757         pseudo_t pseudo = insn->src1;
 758
 759         if (!simple_pseudo(insn->src2))
 760                 return 0;
 761         if (pseudo->type != PSEUDO_REG)
 762                 return 0;
 763         def = pseudo->def;
 764         if (def == insn)
 765                 return 0;
 766         if (def->opcode != insn->opcode)
 767                 return 0;
 768         if (!simple_pseudo(def->src2))
 769                 return 0;
 770         if (ptr_list_size((struct ptr_list *)def->target->users) != 1)
 771                 return 0;
 772         switch_pseudo(def, &def->src1, insn, &insn->src2);
 773         return REPEAT_CSE;
 774 }
 775
 776 static int simplify_constant_unop(struct instruction *insn)
 777 {
 778         long long val = insn->src1->value;
 779         long long res, mask;
 780
 781         switch (insn->opcode) {
 782         case OP_NOT:
 783                 res = ~val;
 784                 break;
 785         case OP_NEG:
 786                 res = -val;
 787                 break;
 788         default:
 789                 return 0;
 790         }
 791         mask = 1ULL << (insn->size-1);
 792         res &= mask | (mask-1);
 793
 794         replace_with_pseudo(insn, value_pseudo(res));
 795         return REPEAT_CSE;
 796 }
 797
 798 static int simplify_unop(struct instruction *insn)
 799 {
 800         if (dead_insn(insn, &insn->src1, NULL, NULL))
 801                 return REPEAT_CSE;
 802         if (constant(insn->src1))
 803                 return simplify_constant_unop(insn);
 804
 805         switch (insn->opcode) {
 806                 struct instruction *def;
 807
 808         case OP_NOT:
 809                 def = insn->src->def;
 810                 if (def && def->opcode == OP_NOT)
 811                         return replace_with_pseudo(insn, def->src);
 812                 break;
 813         case OP_NEG:
 814                 def = insn->src->def;
 815                 if (def && def->opcode == OP_NEG)
 816                         return replace_with_pseudo(insn, def->src);
 817                 break;
 818         default:
 819                 return 0;
 820         }
 821         return 0;
 822 }
 823
 824 static int simplify_one_memop(struct instruction *insn, pseudo_t orig)
 825 {
 826         pseudo_t addr = insn->src;
 827         pseudo_t new, off;
 828
 829         if (addr->type == PSEUDO_REG) {
 830                 struct instruction *def = addr->def;
 831                 if (def->opcode == OP_SYMADDR && def->src) {
 832                         kill_use(&insn->src);
 833                         use_pseudo(insn, def->src, &insn->src);
 834                         return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
 835                 }
 836                 if (def->opcode == OP_ADD) {
 837                         new = def->src1;
 838                         off = def->src2;
 839                         if (constant(off))
 840                                 goto offset;
 841                         new = off;
 842                         off = def->src1;
 843                         if (constant(off))
 844                                 goto offset;
 845                         return 0;
 846                 }
 847         }
 848         return 0;
 849
 850 offset:
 851         /* Invalid code */
 852         if (new == orig) {
 853                 if (new == VOID)
 854                         return 0;
 855                 new = VOID;
 856                 warning(insn->pos, "crazy programmer");
 857         }
 858         insn->offset += off->value;
 859         use_pseudo(insn, new, &insn->src);
 860         remove_usage(addr, &insn->src);
 861         return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
 862 }
 863
 864 /*
 865  * We walk the whole chain of adds/subs backwards. That's not
 866  * only more efficient, but it allows us to find loops.
 867  */
 868 static int simplify_memop(struct instruction *insn)
 869 {
 870         int one, ret = 0;
 871         pseudo_t orig = insn->src;
 872
 873         do {
 874                 one = simplify_one_memop(insn, orig);
 875                 ret |= one;
 876         } while (one);
 877         return ret;
 878 }
 879
 880 static long long get_cast_value(long long val, int old_size, int new_size, int sign)
 881 {
 882         long long mask;
 883
 884         if (sign && new_size > old_size) {
 885                 mask = 1 << (old_size-1);
 886                 if (val & mask)
 887                         val |= ~(mask | (mask-1));
 888         }
 889         mask = 1 << (new_size-1);
 890         return val & (mask | (mask-1));
 891 }
 892
 893 static int simplify_cast(struct instruction *insn)
 894 {
 895         struct symbol *orig_type;
 896         int orig_size, size;
 897         pseudo_t src;
 898
 899         if (dead_insn(insn, &insn->src, NULL, NULL))
 900                 return REPEAT_CSE;
 901
 902         orig_type = insn->orig_type;
 903         if (!orig_type)
 904                 return 0;
 905
 906         /* Keep casts with pointer on either side (not only case of OP_PTRCAST) */
 907         if (is_ptr_type(orig_type) || is_ptr_type(insn->type))
 908                 return 0;
 909
 910         orig_size = orig_type->bit_size;
 911         size = insn->size;
 912         src = insn->src;
 913
 914         /* A cast of a constant? */
 915         if (constant(src)) {
 916                 int sign = orig_type->ctype.modifiers & MOD_SIGNED;
 917                 long long val = get_cast_value(src->value, orig_size, size, sign);
 918                 src = value_pseudo(val);
 919                 goto simplify;
 920         }
 921
 922         /* A cast of a "and" might be a no-op.. */
 923         if (src->type == PSEUDO_REG) {
 924                 struct instruction *def = src->def;
 925                 if (def->opcode == OP_AND && def->size >= size) {
 926                         pseudo_t val = def->src2;
 927                         if (val->type == PSEUDO_VAL) {
 928                                 unsigned long long value = val->value;
 929                                 if (!(value >> (size-1)))
 930                                         goto simplify;
 931                         }
 932                 }
 933         }
 934
 935         if (size == orig_size) {
 936                 int op = (orig_type->ctype.modifiers & MOD_SIGNED) ? OP_SCAST : OP_CAST;
 937                 if (insn->opcode == op)
 938                         goto simplify;
 939                 if (insn->opcode == OP_FPCAST && is_float_type(orig_type))
 940                         goto simplify;
 941         }
 942
 943         return 0;
 944
 945 simplify:
 946         return replace_with_pseudo(insn, src);
 947 }
 948
 949 static int simplify_select(struct instruction *insn)
 950 {
 951         pseudo_t cond, src1, src2;
 952
 953         if (dead_insn(insn, &insn->src1, &insn->src2, &insn->src3))
 954                 return REPEAT_CSE;
 955
 956         cond = insn->src1;
 957         src1 = insn->src2;
 958         src2 = insn->src3;
 959         if (constant(cond) || src1 == src2) {
 960                 pseudo_t *kill, take;
 961                 kill_use(&insn->src1);
 962                 take = cond->value ? src1 : src2;
 963                 kill = cond->value ? &insn->src3 : &insn->src2;
 964                 kill_use(kill);
 965                 replace_with_pseudo(insn, take);
 966                 return REPEAT_CSE;
 967         }
 968         if (constant(src1) && constant(src2)) {
 969                 long long val1 = src1->value;
 970                 long long val2 = src2->value;
 971
 972                 /* The pair 0/1 is special - replace with SETNE/SETEQ */
 973                 if ((val1 | val2) == 1) {
 974                         int opcode = OP_SET_EQ;
 975                         if (val1) {
 976                                 src1 = src2;
 977                                 opcode = OP_SET_NE;
 978                         }
 979                         insn->opcode = opcode;
 980                         /* insn->src1 is already cond */
 981                         insn->src2 = src1; /* Zero */
 982                         return REPEAT_CSE;
 983                 }
 984         }
 985         return 0;
 986 }
 987
 988 static int is_in_range(pseudo_t src, long long low, long long high)
 989 {
 990         long long value;
 991
 992         switch (src->type) {
 993         case PSEUDO_VAL:
 994                 value = src->value;
 995                 return value >= low && value <= high;
 996         default:
 997                 return 0;
 998         }
 999 }
1000
1001 static int simplify_range(struct instruction *insn)
1002 {
1003         pseudo_t src1, src2, src3;
1004
1005         src1 = insn->src1;
1006         src2 = insn->src2;
1007         src3 = insn->src3;
1008         if (src2->type != PSEUDO_VAL || src3->type != PSEUDO_VAL)
1009                 return 0;
1010         if (is_in_range(src1, src2->value, src3->value)) {
1011                 kill_instruction(insn);
1012                 return REPEAT_CSE;
1013         }
1014         return 0;
1015 }
1016
1017 /*
1018  * Simplify "set_ne/eq $0 + br"
1019  */
1020 static int simplify_cond_branch(struct instruction *br, pseudo_t cond, struct instruction *def, pseudo_t *pp)
1021 {
1022         use_pseudo(br, *pp, &br->cond);
1023         remove_usage(cond, &br->cond);
1024         if (def->opcode == OP_SET_EQ) {
1025                 struct basic_block *true = br->bb_true;
1026                 struct basic_block *false = br->bb_false;
1027                 br->bb_false = true;
1028                 br->bb_true = false;
1029         }
1030         return REPEAT_CSE;
1031 }
1032
1033 static int simplify_branch(struct instruction *insn)
1034 {
1035         pseudo_t cond = insn->cond;
1036
1037         if (!cond)
1038                 return 0;
1039
1040         /* Constant conditional */
1041         if (constant(cond)) {
1042                 insert_branch(insn->bb, insn, cond->value ? insn->bb_true : insn->bb_false);
1043                 return REPEAT_CSE;
1044         }
1045
1046         /* Same target? */
1047         if (insn->bb_true == insn->bb_false) {
1048                 struct basic_block *bb = insn->bb;
1049                 struct basic_block *target = insn->bb_false;
1050                 remove_bb_from_list(&target->parents, bb, 1);
1051                 remove_bb_from_list(&bb->children, target, 1);
1052                 insn->bb_false = NULL;
1053                 kill_use(&insn->cond);
1054                 insn->cond = NULL;
1055                 return REPEAT_CSE;
1056         }
1057
1058         /* Conditional on a SETNE $0 or SETEQ $0 */
1059         if (cond->type == PSEUDO_REG) {
1060                 struct instruction *def = cond->def;
1061
1062                 if (def->opcode == OP_SET_NE || def->opcode == OP_SET_EQ) {
1063                         if (constant(def->src1) && !def->src1->value)
1064                                 return simplify_cond_branch(insn, cond, def, &def->src2);
1065                         if (constant(def->src2) && !def->src2->value)
1066                                 return simplify_cond_branch(insn, cond, def, &def->src1);
1067                 }
1068                 if (def->opcode == OP_SEL) {
1069                         if (constant(def->src2) && constant(def->src3)) {
1070                                 long long val1 = def->src2->value;
1071                                 long long val2 = def->src3->value;
1072                                 if (!val1 && !val2) {
1073                                         insert_branch(insn->bb, insn, insn->bb_false);
1074                                         return REPEAT_CSE;
1075                                 }
1076                                 if (val1 && val2) {
1077                                         insert_branch(insn->bb, insn, insn->bb_true);
1078                                         return REPEAT_CSE;
1079                                 }
1080                                 if (val2) {
1081                                         struct basic_block *true = insn->bb_true;
1082                                         struct basic_block *false = insn->bb_false;
1083                                         insn->bb_false = true;
1084                                         insn->bb_true = false;
1085                                 }
1086                                 use_pseudo(insn, def->src1, &insn->cond);
1087                                 remove_usage(cond, &insn->cond);
1088                                 return REPEAT_CSE;
1089                         }
1090                 }
1091                 if (def->opcode == OP_CAST || def->opcode == OP_SCAST) {
1092                         int orig_size = def->orig_type ? def->orig_type->bit_size : 0;
1093                         if (def->size > orig_size) {
1094                                 use_pseudo(insn, def->src, &insn->cond);
1095                                 remove_usage(cond, &insn->cond);
1096                                 return REPEAT_CSE;
1097                         }
1098                 }
1099         }
1100         return 0;
1101 }
1102
1103 static int simplify_switch(struct instruction *insn)
1104 {
1105         pseudo_t cond = insn->cond;
1106         long long val;
1107         struct multijmp *jmp;
1108
1109         if (!constant(cond))
1110                 return 0;
1111         val = insn->cond->value;
1112
1113         FOR_EACH_PTR(insn->multijmp_list, jmp) {
1114                 /* Default case */
1115                 if (jmp->begin > jmp->end)
1116                         goto found;
1117                 if (val >= jmp->begin && val <= jmp->end)
1118                         goto found;
1119         } END_FOR_EACH_PTR(jmp);
1120         warning(insn->pos, "Impossible case statement");
1121         return 0;
1122
1123 found:
1124         insert_branch(insn->bb, insn, jmp->target);
1125         return REPEAT_CSE;
1126 }
1127
1128 int simplify_instruction(struct instruction *insn)
1129 {
1130         if (!insn->bb)
1131                 return 0;
1132         switch (insn->opcode) {
1133         case OP_ADD: case OP_MULS:
1134         case OP_AND: case OP_OR: case OP_XOR:
1135         case OP_AND_BOOL: case OP_OR_BOOL:
1136                 if (simplify_binop(insn))
1137                         return REPEAT_CSE;
1138                 if (simplify_commutative_binop(insn))
1139                         return REPEAT_CSE;
1140                 return simplify_associative_binop(insn);
1141
1142         case OP_MULU:
1143         case OP_SET_EQ: case OP_SET_NE:
1144                 if (simplify_binop(insn))
1145                         return REPEAT_CSE;
1146                 return simplify_commutative_binop(insn);
1147
1148         case OP_SUB:
1149         case OP_DIVU: case OP_DIVS:
1150         case OP_MODU: case OP_MODS:
1151         case OP_SHL:
1152         case OP_LSR: case OP_ASR:
1153         case OP_SET_LE: case OP_SET_GE:
1154         case OP_SET_LT: case OP_SET_GT:
1155         case OP_SET_B:  case OP_SET_A:
1156         case OP_SET_BE: case OP_SET_AE:
1157                 return simplify_binop(insn);
1158
1159         case OP_NOT: case OP_NEG:
1160                 return simplify_unop(insn);
1161         case OP_LOAD: case OP_STORE:
1162                 return simplify_memop(insn);
1163         case OP_SYMADDR:
1164                 if (dead_insn(insn, NULL, NULL, NULL))
1165                         return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
1166                 return replace_with_pseudo(insn, insn->symbol);
1167         case OP_CAST:
1168         case OP_SCAST:
1169         case OP_FPCAST:
1170         case OP_PTRCAST:
1171                 return simplify_cast(insn);
1172         case OP_PHI:
1173                 if (dead_insn(insn, NULL, NULL, NULL)) {
1174                         kill_use_list(insn->phi_list);
1175                         return REPEAT_CSE;
1176                 }
1177                 return clean_up_phi(insn);
1178         case OP_PHISOURCE:
1179                 if (dead_insn(insn, &insn->phi_src, NULL, NULL))
1180                         return REPEAT_CSE;
1181                 break;
1182         case OP_SEL:
1183                 return simplify_select(insn);
1184         case OP_BR:
1185                 return simplify_branch(insn);
1186         case OP_SWITCH:
1187                 return simplify_switch(insn);
1188         case OP_RANGE:
1189                 return simplify_range(insn);
1190         }
1191         return 0;
1192 }