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         long long val = insn->src1->value;
 397         long long res, mask;
 398
 399         switch (insn->opcode) {
 400         case OP_NOT:
 401                 res = ~val;
 402                 break;
 403         case OP_NEG:
 404                 res = -val;
 405                 break;
 406         default:
 407                 return 0;
 408         }
 409         mask = 1ULL << (insn->size-1);
 410         res &= mask | (mask-1);
 411
 412         replace_with_pseudo(insn, value_pseudo(res));
 413         return REPEAT_CSE;
 414 }
 415
 416 static int simplify_unop(struct instruction *insn)
 417 {
 418         if (dead_insn(insn, &insn->src1, NULL, NULL))
 419                 return REPEAT_CSE;
 420         if (constant(insn->src1))
 421                 return simplify_constant_unop(insn);
 422         return 0;
 423 }
 424
 425 static int simplify_one_memop(struct instruction *insn, pseudo_t orig)
 426 {
 427         pseudo_t addr = insn->src;
 428         pseudo_t new, off;
 429
 430         if (addr->type == PSEUDO_REG) {
 431                 struct instruction *def = addr->def;
 432                 if (def->opcode == OP_SETVAL && def->src) {
 433                         kill_use(&insn->src);
 434                         use_pseudo(def->src, &insn->src);
 435                         return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
 436                 }
 437                 if (def->opcode == OP_ADD) {
 438                         new = def->src1;
 439                         off = def->src2;
 440                         if (constant(off))
 441                                 goto offset;
 442                         new = off;
 443                         off = def->src1;
 444                         if (constant(off))
 445                                 goto offset;
 446                         return 0;
 447                 }
 448         }
 449         return 0;
 450
 451 offset:
 452         /* Invalid code */
 453         if (new == orig) {
 454                 if (new == VOID)
 455                         return 0;
 456                 new = VOID;
 457                 warning(insn->bb->pos, "crazy programmer");
 458         }
 459         insn->offset += off->value;
 460         use_pseudo(new, &insn->src);
 461         remove_usage(addr, &insn->src);
 462         return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
 463 }
 464
 465 /*
 466  * We walk the whole chain of adds/subs backwards. That's not
 467  * only more efficient, but it allows us to find looops.
 468  */
 469 static int simplify_memop(struct instruction *insn)
 470 {
 471         int one, ret = 0;
 472         pseudo_t orig = insn->src;
 473
 474         do {
 475                 one = simplify_one_memop(insn, orig);
 476                 ret |= one;
 477         } while (one);
 478         return ret;
 479 }
 480
 481 static int simplify_cast(struct instruction *insn)
 482 {
 483         int orig_size;
 484
 485         if (dead_insn(insn, &insn->src, NULL, NULL))
 486                 return REPEAT_CSE;
 487         if (insn->opcode == OP_PTRCAST)
 488                 return 0;
 489         orig_size = insn->orig_type ? insn->orig_type->bit_size : 0;
 490         if (orig_size < 0)
 491                 orig_size = 0;
 492         if (insn->size != orig_size)
 493                 return 0;
 494         return replace_with_pseudo(insn, insn->src);
 495 }
 496
 497 static int simplify_select(struct instruction *insn)
 498 {
 499         pseudo_t cond, src1, src2;
 500
 501         if (dead_insn(insn, &insn->src1, &insn->src2, &insn->src3))
 502                 return REPEAT_CSE;
 503
 504         cond = insn->src1;
 505         src1 = insn->src2;
 506         src2 = insn->src3;
 507         if (constant(cond) || src1 == src2) {
 508                 pseudo_t *kill, take;
 509                 kill_use(&insn->src1);
 510                 take = cond->value ? src1 : src2;
 511                 kill = cond->value ? &insn->src3 : &insn->src2;
 512                 kill_use(kill);
 513                 replace_with_pseudo(insn, take);
 514                 return REPEAT_CSE;
 515         }
 516         if (constant(src1) && constant(src2)) {
 517                 long long val1 = src1->value;
 518                 long long val2 = src2->value;
 519
 520                 /* The pair 0/1 is special - replace with SETNE/SETEQ */
 521                 if ((val1 | val2) == 1) {
 522                         int opcode = OP_SET_EQ;
 523                         if (val1) {
 524                                 src1 = src2;
 525                                 opcode = OP_SET_NE;
 526                         }
 527                         insn->opcode = opcode;
 528                         /* insn->src1 is already cond */
 529                         insn->src2 = src1; /* Zero */
 530                         return REPEAT_CSE;
 531                 }
 532         }
 533         return 0;
 534 }
 535
 536 /*
 537  * Simplify "set_ne/eq $0 + br"
 538  */
 539 static int simplify_cond_branch(struct instruction *br, pseudo_t cond, struct instruction *def, pseudo_t *pp)
 540 {
 541         use_pseudo(*pp, &br->cond);
 542         remove_usage(cond, &br->cond);
 543         if (def->opcode == OP_SET_EQ) {
 544                 struct basic_block *true = br->bb_true;
 545                 struct basic_block *false = br->bb_false;
 546                 br->bb_false = true;
 547                 br->bb_true = false;
 548         }
 549         return REPEAT_CSE;
 550 }
 551
 552 static int simplify_branch(struct instruction *insn)
 553 {
 554         pseudo_t cond = insn->cond;
 555
 556         if (!cond)
 557                 return 0;
 558
 559         /* Constant conditional */
 560         if (constant(cond)) {
 561                 insert_branch(insn->bb, insn, cond->value ? insn->bb_true : insn->bb_false);
 562                 return REPEAT_CSE;
 563         }
 564
 565         /* Same target? */
 566         if (insn->bb_true == insn->bb_false) {
 567                 struct basic_block *bb = insn->bb;
 568                 struct basic_block *target = insn->bb_false;
 569                 remove_bb_from_list(&target->parents, bb, 1);
 570                 remove_bb_from_list(&bb->children, target, 1);
 571                 insn->bb_false = NULL;
 572                 kill_use(&insn->cond);
 573                 insn->cond = NULL;
 574                 return REPEAT_CSE;
 575         }
 576
 577         /* Conditional on a SETNE $0 or SETEQ $0 */
 578         if (cond->type == PSEUDO_REG) {
 579                 struct instruction *def = cond->def;
 580
 581                 if (def->opcode == OP_SET_NE || def->opcode == OP_SET_EQ) {
 582                         if (constant(def->src1) && !def->src1->value)
 583                                 return simplify_cond_branch(insn, cond, def, &def->src2);
 584                         if (constant(def->src2) && !def->src2->value)
 585                                 return simplify_cond_branch(insn, cond, def, &def->src1);
 586                 }
 587                 if (def->opcode == OP_SEL) {
 588                         if (constant(def->src2) && constant(def->src3)) {
 589                                 long long val1 = def->src2->value;
 590                                 long long val2 = def->src3->value;
 591                                 if (!val1 && !val2) {
 592                                         insert_branch(insn->bb, insn, insn->bb_false);
 593                                         return REPEAT_CSE;
 594                                 }
 595                                 if (val1 && val2) {
 596                                         insert_branch(insn->bb, insn, insn->bb_true);
 597                                         return REPEAT_CSE;
 598                                 }
 599                                 if (val2) {
 600                                         struct basic_block *true = insn->bb_true;
 601                                         struct basic_block *false = insn->bb_false;
 602                                         insn->bb_false = true;
 603                                         insn->bb_true = false;
 604                                 }
 605                                 use_pseudo(def->src1, &insn->cond);
 606                                 remove_usage(cond, &insn->cond);
 607                                 return REPEAT_CSE;
 608                         }
 609                 }
 610         }
 611         return 0;
 612 }
 613
 614 static int simplify_switch(struct instruction *insn)
 615 {
 616         pseudo_t cond = insn->cond;
 617         long long val;
 618         struct multijmp *jmp;
 619
 620         if (!constant(cond))
 621                 return 0;
 622         val = insn->cond->value;
 623
 624         FOR_EACH_PTR(insn->multijmp_list, jmp) {
 625                 /* Default case */
 626                 if (jmp->begin > jmp->end)
 627                         goto found;
 628                 if (val >= jmp->begin && val <= jmp->end)
 629                         goto found;
 630         } END_FOR_EACH_PTR(jmp);
 631         warning(insn->bb->pos, "Impossible case statement");
 632         return 0;
 633
 634 found:
 635         insert_branch(insn->bb, insn, jmp->target);
 636         return REPEAT_CSE;
 637 }
 638
 639 int simplify_instruction(struct instruction *insn)
 640 {
 641         if (!insn->bb)
 642                 return 0;
 643         switch (insn->opcode) {
 644         case OP_BINARY ... OP_BINCMP_END:
 645                 return simplify_binop(insn);
 646
 647         case OP_NOT: case OP_NEG:
 648                 return simplify_unop(insn);
 649         case OP_LOAD: case OP_STORE:
 650                 return simplify_memop(insn);
 651         case OP_SETVAL:
 652                 if (dead_insn(insn, NULL, NULL, NULL))
 653                         return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
 654                 break;
 655         case OP_PTRCAST:
 656         case OP_CAST:
 657                 return simplify_cast(insn);
 658         case OP_PHI:
 659                 if (dead_insn(insn, NULL, NULL, NULL)) {
 660                         clear_phi(insn);
 661                         return REPEAT_CSE;
 662                 }
 663                 return clean_up_phi(insn);
 664         case OP_PHISOURCE:
 665                 if (dead_insn(insn, &insn->phi_src, NULL, NULL))
 666                         return REPEAT_CSE;
 667                 break;
 668         case OP_SEL:
 669                 return simplify_select(insn);
 670         case OP_BR:
 671                 return simplify_branch(insn);
 672         case OP_SWITCH:
 673                 return simplify_switch(insn);
 674         }
 675         return 0;
 676 }