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
  14 /* Find the trivial parent for a phi-source */
  15 static struct basic_block *phi_parent(struct basic_block *source, pseudo_t pseudo)
  16 {
  17         /* Can't go upwards if the pseudo is defined in the bb it came from.. */
  18         if (pseudo->type == PSEUDO_REG) {
  19                 struct instruction *def = pseudo->def;
  20                 if (def->bb == source)
  21                         return source;
  22         }
  23         if (bb_list_size(source->children) != 1 || bb_list_size(source->parents) != 1)
  24                 return source;
  25         return first_basic_block(source->parents);
  26 }
  27
  28 static void clear_phi(struct instruction *insn)
  29 {
  30         pseudo_t phi;
  31
  32         insn->bb = NULL;
  33         FOR_EACH_PTR(insn->phi_list, phi) {
  34                 *THIS_ADDRESS(phi) = VOID;
  35         } END_FOR_EACH_PTR(phi);
  36 }
  37
  38 static int if_convert_phi(struct instruction *insn)
  39 {
  40         pseudo_t array[3];
  41         struct basic_block *parents[3];
  42         struct basic_block *bb, *bb1, *bb2, *source;
  43         struct instruction *br;
  44         pseudo_t p1, p2;
  45
  46         bb = insn->bb;
  47         if (linearize_ptr_list((struct ptr_list *)insn->phi_list, (void **)array, 3) != 2)
  48                 return 0;
  49         if (linearize_ptr_list((struct ptr_list *)bb->parents, (void **)parents, 3) != 2)
  50                 return 0;
  51         p1 = array[0]->def->src1;
  52         bb1 = array[0]->def->bb;
  53         p2 = array[1]->def->src1;
  54         bb2 = array[1]->def->bb;
  55
  56         /* Only try the simple "direct parents" case */
  57         if ((bb1 != parents[0] || bb2 != parents[1]) &&
  58             (bb1 != parents[1] || bb2 != parents[0]))
  59                 return 0;
  60
  61         /*
  62          * See if we can find a common source for this..
  63          */
  64         source = phi_parent(bb1, p1);
  65         if (source != phi_parent(bb2, p2))
  66                 return 0;
  67
  68         /*
  69          * Cool. We now know that 'source' is the exclusive
  70          * parent of both phi-nodes, so the exit at the
  71          * end of it fully determines which one it is, and
  72          * we can turn it into a select.
  73          *
  74          * HOWEVER, right now we only handle regular
  75          * conditional branches. No multijumps or computed
  76          * stuff. Verify that here.
  77          */
  78         br = last_instruction(source->insns);
  79         if (!br || br->opcode != OP_BR)
  80                 return 0;
  81
  82         assert(br->cond);
  83         assert(br->bb_false);
  84
  85         /*
  86          * We're in business. Match up true/false with p1/p2.
  87          */
  88         if (br->bb_true == bb2 || br->bb_false == bb1) {
  89                 pseudo_t p = p1;
  90                 p1 = p2;
  91                 p2 = p;
  92         }
  93
  94         /*
  95          * Ok, we can now replace that last
  96          *
  97          *      br cond, a, b
  98          *
  99          * with the sequence
 100          *
 101          *      setcc cond
 102          *      select pseudo, p1, p2
 103          *      br cond, a, b
 104          *
 105          * and remove the phi-node. If it then
 106          * turns out that 'a' or 'b' is entirely
 107          * empty (common case), and now no longer
 108          * a phi-source, we'll be able to simplify
 109          * the conditional branch too.
 110          */
 111         insert_select(source, br, insn, p1, p2);
 112         clear_phi(insn);
 113         return REPEAT_CSE;
 114 }
 115
 116 static int clean_up_phi(struct instruction *insn)
 117 {
 118         pseudo_t phi;
 119         struct instruction *last;
 120         int same;
 121
 122         last = NULL;
 123         same = 1;
 124         FOR_EACH_PTR(insn->phi_list, phi) {
 125                 struct instruction *def;
 126                 if (phi == VOID)
 127                         continue;
 128                 def = phi->def;
 129                 if (def->src1 == VOID || !def->bb)
 130                         continue;
 131                 if (last) {
 132                         if (last->src1 != def->src1)
 133                                 same = 0;
 134                         continue;
 135                 }
 136                 last = def;
 137         } END_FOR_EACH_PTR(phi);
 138
 139         if (same) {
 140                 pseudo_t pseudo = last ? last->src1 : VOID;
 141                 convert_instruction_target(insn, pseudo);
 142                 clear_phi(insn);
 143                 return REPEAT_CSE;
 144         }
 145
 146         return if_convert_phi(insn);
 147 }
 148
 149 static inline void remove_usage(pseudo_t p, pseudo_t *usep)
 150 {
 151         if (has_use_list(p)) {
 152                 delete_ptr_list_entry((struct ptr_list **)&p->users, usep, 1);
 153                 if (!p->users)
 154                         kill_instruction(p->def);
 155         }
 156 }
 157
 158 void kill_use(pseudo_t *usep)
 159 {
 160         if (usep) {
 161                 pseudo_t p = *usep;
 162                 *usep = VOID;
 163                 remove_usage(p, usep);
 164         }
 165 }
 166
 167 void kill_instruction(struct instruction *insn)
 168 {
 169         if (!insn || !insn->bb)
 170                 return;
 171
 172         switch (insn->opcode) {
 173         case OP_BINARY ... OP_BINCMP_END:
 174                 insn->bb = NULL;
 175                 kill_use(&insn->src1);
 176                 kill_use(&insn->src2);
 177                 repeat_phase |= REPEAT_CSE;
 178                 return;
 179
 180         case OP_NOT: case OP_NEG:
 181                 insn->bb = NULL;
 182                 kill_use(&insn->src1);
 183                 repeat_phase |= REPEAT_CSE;
 184                 return;
 185
 186         case OP_PHI:
 187                 insn->bb = NULL;
 188                 repeat_phase |= REPEAT_CSE;
 189                 return;
 190
 191          case OP_SETVAL:
 192                 insn->bb = NULL;
 193                 repeat_phase |= REPEAT_CSE;
 194                 if (insn->symbol)
 195                         repeat_phase |= REPEAT_SYMBOL_CLEANUP;
 196                 return;
 197         }
 198 }
 199
 200 /*
 201  * Kill trivially dead instructions
 202  */
 203 static int dead_insn(struct instruction *insn, pseudo_t *src1, pseudo_t *src2, pseudo_t *src3)
 204 {
 205         pseudo_t *usep;
 206         FOR_EACH_PTR(insn->target->users, usep) {
 207                 if (*usep != VOID)
 208                         return 0;
 209         } END_FOR_EACH_PTR(usep);
 210
 211         insn->bb = NULL;
 212         kill_use(src1);
 213         kill_use(src2);
 214         kill_use(src3);
 215         return REPEAT_CSE;
 216 }
 217
 218 static inline int constant(pseudo_t pseudo)
 219 {
 220         return pseudo->type == PSEUDO_VAL;
 221 }
 222
 223 static int replace_with_pseudo(struct instruction *insn, pseudo_t pseudo)
 224 {
 225         convert_instruction_target(insn, pseudo);
 226         insn->bb = NULL;
 227         return REPEAT_CSE;
 228 }
 229
 230 static int simplify_constant_rightside(struct instruction *insn)
 231 {
 232         long long value = insn->src2->value;
 233
 234         switch (insn->opcode) {
 235         case OP_SUB:
 236                 if (value) {
 237                         insn->opcode = OP_ADD;
 238                         insn->src2 = value_pseudo(-value);
 239                         return REPEAT_CSE;
 240                 }
 241         /* Fallthrough */
 242         case OP_ADD:
 243         case OP_OR: case OP_XOR:
 244         case OP_SHL: case OP_SHR:
 245                 if (!value)
 246                         return replace_with_pseudo(insn, insn->src1);
 247                 return 0;
 248
 249         case OP_AND: case OP_MUL:
 250                 if (!value)
 251                         return replace_with_pseudo(insn, insn->src2);
 252                 return 0;
 253         }
 254         return 0;
 255 }
 256
 257 static int simplify_constant_leftside(struct instruction *insn)
 258 {
 259         long long value = insn->src1->value;
 260
 261         switch (insn->opcode) {
 262         case OP_ADD: case OP_OR: case OP_XOR:
 263                 if (!value)
 264                         return replace_with_pseudo(insn, insn->src2);
 265                 return 0;
 266
 267         case OP_SHL: case OP_SHR:
 268         case OP_AND: case OP_MUL:
 269                 if (!value)
 270                         return replace_with_pseudo(insn, insn->src1);
 271                 return 0;
 272         }
 273         return 0;
 274 }
 275
 276 static int simplify_constant_binop(struct instruction *insn)
 277 {
 278         /* FIXME! Verify signs and sizes!! */
 279         long long left = insn->src1->value;
 280         long long right = insn->src2->value;
 281         long long res, mask;
 282
 283         switch (insn->opcode) {
 284         case OP_ADD:
 285                 res = left + right;
 286                 break;
 287         case OP_SUB:
 288                 res = left - right;
 289                 break;
 290         case OP_MUL:
 291                 /* FIXME! Check sign! */
 292                 res = left * right;
 293                 break;
 294         case OP_DIV:
 295                 if (!right)
 296                         return 0;
 297                 /* FIXME! Check sign! */
 298                 res = left / right;
 299                 break;
 300         case OP_MOD:
 301                 if (!right)
 302                         return 0;
 303                 /* FIXME! Check sign! */
 304                 res = left % right;
 305                 break;
 306         case OP_SHL:
 307                 res = left << right;
 308                 break;
 309         case OP_SHR:
 310                 /* FIXME! Check sign! */
 311                 res = left >> right;
 312                 break;
 313        /* Logical */
 314         case OP_AND:
 315                 res = left & right;
 316                 break;
 317         case OP_OR:
 318                 res = left | right;
 319                 break;
 320         case OP_XOR:
 321                 res = left ^ right;
 322                 break;
 323         case OP_AND_BOOL:
 324                 res = left && right;
 325                 break;
 326         case OP_OR_BOOL:
 327                 res = left || right;
 328                 break;
 329
 330         /* Binary comparison */
 331         case OP_SET_EQ:
 332                 res = left == right;
 333                 break;
 334         case OP_SET_NE:
 335                 res = left != right;
 336                 break;
 337         case OP_SET_LE:
 338                 /* FIXME! Check sign! */
 339                 res = left <= right;
 340                 break;
 341         case OP_SET_GE:
 342                 /* FIXME! Check sign! */
 343                 res = left >= right;
 344                 break;
 345         case OP_SET_LT:
 346                 /* FIXME! Check sign! */
 347                 res = left < right;
 348                 break;
 349         case OP_SET_GT:
 350                 /* FIXME! Check sign! */
 351                 res = left > right;
 352                 break;
 353         case OP_SET_B:
 354                 /* FIXME! Check sign! */
 355                 res = (unsigned long long) left < (unsigned long long) right;
 356                 break;
 357         case OP_SET_A:
 358                 /* FIXME! Check sign! */
 359                 res = (unsigned long long) left > (unsigned long long) right;
 360                 break;
 361         case OP_SET_BE:
 362                 /* FIXME! Check sign! */
 363                 res = (unsigned long long) left <= (unsigned long long) right;
 364                 break;
 365         case OP_SET_AE:
 366                 /* FIXME! Check sign! */
 367                 res = (unsigned long long) left >= (unsigned long long) right;
 368                 break;
 369         default:
 370                 return 0;
 371         }
 372         mask = 1ULL << (insn->size-1);
 373         res &= mask | (mask-1);
 374
 375         /* FIXME!! Sign??? */
 376         replace_with_pseudo(insn, value_pseudo(res));
 377         return REPEAT_CSE;
 378 }
 379
 380 static int simplify_binop(struct instruction *insn)
 381 {
 382         if (dead_insn(insn, &insn->src1, &insn->src2, NULL))
 383                 return REPEAT_CSE;
 384         if (constant(insn->src1)) {
 385                 if (constant(insn->src2))
 386                         return simplify_constant_binop(insn);
 387                 return simplify_constant_leftside(insn);
 388         }
 389         if (constant(insn->src2))
 390                 return simplify_constant_rightside(insn);
 391         return 0;
 392 }
 393
 394 static int simplify_constant_unop(struct instruction *insn)
 395 {
 396         return 0;
 397 }
 398
 399 static int simplify_unop(struct instruction *insn)
 400 {
 401         if (dead_insn(insn, &insn->src1, NULL, NULL))
 402                 return REPEAT_CSE;
 403         if (constant(insn->src1))
 404                 return simplify_constant_unop(insn);
 405         return 0;
 406 }
 407
 408 static int simplify_one_memop(struct instruction *insn, pseudo_t orig)
 409 {
 410         pseudo_t addr = insn->src;
 411         pseudo_t new, off;
 412
 413         if (addr->type == PSEUDO_REG) {
 414                 struct instruction *def = addr->def;
 415                 if (def->opcode == OP_SETVAL && def->src) {
 416                         kill_use(&insn->src);
 417                         use_pseudo(def->src, &insn->src);
 418                         return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
 419                 }
 420                 if (def->opcode == OP_ADD) {
 421                         new = def->src1;
 422                         off = def->src2;
 423                         if (constant(off))
 424                                 goto offset;
 425                         new = off;
 426                         off = def->src1;
 427                         if (constant(off))
 428                                 goto offset;
 429                         return 0;
 430                 }
 431         }
 432         return 0;
 433
 434 offset:
 435         /* Invalid code */
 436         if (new == orig) {
 437                 if (new == VOID)
 438                         return 0;
 439                 new = VOID;
 440                 warning(insn->bb->pos, "crazy programmer");
 441         }
 442         insn->offset += off->value;
 443         use_pseudo(new, &insn->src);
 444         remove_usage(addr, &insn->src);
 445         return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
 446 }
 447
 448 /*
 449  * We walk the whole chain of adds/subs backwards. That's not
 450  * only more efficient, but it allows us to find looops.
 451  */
 452 static int simplify_memop(struct instruction *insn)
 453 {
 454         int one, ret = 0;
 455         pseudo_t orig = insn->src;
 456
 457         do {
 458                 one = simplify_one_memop(insn, orig);
 459                 ret |= one;
 460         } while (one);
 461         return ret;
 462 }
 463
 464 static int simplify_cast(struct instruction *insn)
 465 {
 466         int orig_size;
 467
 468         if (dead_insn(insn, &insn->src, NULL, NULL))
 469                 return REPEAT_CSE;
 470         if (insn->opcode == OP_PTRCAST)
 471                 return 0;
 472         orig_size = insn->orig_type ? insn->orig_type->bit_size : 0;
 473         if (orig_size < 0)
 474                 orig_size = 0;
 475         if (insn->size != orig_size)
 476                 return 0;
 477         return replace_with_pseudo(insn, insn->src);
 478 }
 479
 480 static int simplify_select(struct instruction *insn)
 481 {
 482         pseudo_t cond, src1, src2;
 483
 484         if (dead_insn(insn, &insn->src1, &insn->src2, &insn->src3))
 485                 return REPEAT_CSE;
 486
 487         cond = insn->src1;
 488         src1 = insn->src2;
 489         src2 = insn->src3;
 490         if (constant(cond) || src1 == src2) {
 491                 pseudo_t *kill, take;
 492                 kill_use(&insn->src1);
 493                 take = cond->value ? src1 : src2;
 494                 kill = cond->value ? &insn->src3 : &insn->src2;
 495                 kill_use(kill);
 496                 replace_with_pseudo(insn, take);
 497                 return REPEAT_CSE;
 498         }
 499         if (constant(src1) && constant(src2)) {
 500                 long long val1 = src1->value;
 501                 long long val2 = src2->value;
 502
 503                 /* The pair 0/1 is special - replace with SETNE/SETEQ */
 504                 if ((val1 | val2) == 1) {
 505                         int opcode = OP_SET_EQ;
 506                         if (val1) {
 507                                 src1 = src2;
 508                                 opcode = OP_SET_NE;
 509                         }
 510                         insn->opcode = opcode;
 511                         /* insn->src1 is already cond */
 512                         insn->src2 = src1; /* Zero */
 513                         return REPEAT_CSE;
 514                 }
 515         }
 516         return 0;
 517 }
 518
 519 /*
 520  * Simplify "set_ne/eq $0 + br"
 521  */
 522 static int simplify_cond_branch(struct instruction *br, pseudo_t cond, struct instruction *def, pseudo_t *pp)
 523 {
 524         use_pseudo(*pp, &br->cond);
 525         remove_usage(cond, &br->cond);
 526         if (def->opcode == OP_SET_EQ) {
 527                 struct basic_block *true = br->bb_true;
 528                 struct basic_block *false = br->bb_false;
 529                 br->bb_false = true;
 530                 br->bb_true = false;
 531         }
 532         return REPEAT_CSE;
 533 }
 534
 535 static int simplify_branch(struct instruction *insn)
 536 {
 537         pseudo_t cond = insn->cond;
 538
 539         if (!cond)
 540                 return 0;
 541
 542         /* Constant conditional */
 543         if (constant(cond)) {
 544                 insert_branch(insn->bb, insn, cond->value ? insn->bb_true : insn->bb_false);
 545                 return REPEAT_CSE;
 546         }
 547
 548         /* Conditional on a SETNE $0 or SETEQ $0 */
 549         if (cond->type == PSEUDO_REG) {
 550                 struct instruction *def = cond->def;
 551
 552                 if (def->opcode == OP_SET_NE || def->opcode == OP_SET_EQ) {
 553                         if (constant(def->src1) && !def->src1->value)
 554                                 return simplify_cond_branch(insn, cond, def, &def->src2);
 555                         if (constant(def->src2) && !def->src2->value)
 556                                 return simplify_cond_branch(insn, cond, def, &def->src1);
 557                 }
 558                 if (def->opcode == OP_SEL) {
 559                         if (constant(def->src2) && constant(def->src3)) {
 560                                 long long val1 = def->src2->value;
 561                                 long long val2 = def->src3->value;
 562                                 if (!val1 && !val2) {
 563                                         insert_branch(insn->bb, insn, insn->bb_false);
 564                                         return REPEAT_CSE;
 565                                 }
 566                                 if (val1 && val2) {
 567                                         insert_branch(insn->bb, insn, insn->bb_true);
 568                                         return REPEAT_CSE;
 569                                 }
 570                                 if (val2) {
 571                                         struct basic_block *true = insn->bb_true;
 572                                         struct basic_block *false = insn->bb_false;
 573                                         insn->bb_false = true;
 574                                         insn->bb_true = false;
 575                                 }
 576                                 use_pseudo(def->src1, &insn->cond);
 577                                 remove_usage(cond, &insn->cond);
 578                                 return REPEAT_CSE;
 579                         }
 580                 }
 581         }
 582         return 0;
 583 }
 584
 585 static int simplify_switch(struct instruction *insn)
 586 {
 587         pseudo_t cond = insn->cond;
 588         long long val;
 589         struct multijmp *jmp;
 590
 591         if (!constant(cond))
 592                 return 0;
 593         val = insn->cond->value;
 594
 595         FOR_EACH_PTR(insn->multijmp_list, jmp) {
 596                 /* Default case */
 597                 if (jmp->begin > jmp->end)
 598                         goto found;
 599                 if (val >= jmp->begin && val <= jmp->end)
 600                         goto found;
 601         } END_FOR_EACH_PTR(jmp);
 602         warning(insn->bb->pos, "Impossible case statement");
 603         return 0;
 604
 605 found:
 606         insert_branch(insn->bb, insn, jmp->target);
 607         return REPEAT_CSE;
 608 }
 609
 610 int simplify_instruction(struct instruction *insn)
 611 {
 612         if (!insn->bb)
 613                 return 0;
 614         switch (insn->opcode) {
 615         case OP_BINARY ... OP_BINCMP_END:
 616                 return simplify_binop(insn);
 617
 618         case OP_NOT: case OP_NEG:
 619                 return simplify_unop(insn);
 620         case OP_LOAD: case OP_STORE:
 621                 return simplify_memop(insn);
 622         case OP_SETVAL:
 623                 if (dead_insn(insn, NULL, NULL, NULL))
 624                         return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
 625                 break;
 626         case OP_PTRCAST:
 627         case OP_CAST:
 628                 return simplify_cast(insn);
 629         case OP_PHI:
 630                 if (dead_insn(insn, NULL, NULL, NULL)) {
 631                         clear_phi(insn);
 632                         return REPEAT_CSE;
 633                 }
 634                 return clean_up_phi(insn);
 635         case OP_PHISOURCE:
 636                 if (dead_insn(insn, &insn->src1, NULL, NULL))
 637                         return REPEAT_CSE;
 638                 break;
 639         case OP_SEL:
 640                 return simplify_select(insn);
 641         case OP_BR:
 642                 return simplify_branch(insn);
 643         case OP_SWITCH:
 644                 return simplify_switch(insn);
 645         }
 646         return 0;
 647 }