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