optimize.c revision 75107
1/* 2 * Copyright (c) 1988, 1989, 1990, 1991, 1993, 1994, 1995, 1996 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that: (1) source code distributions 7 * retain the above copyright notice and this paragraph in its entirety, (2) 8 * distributions including binary code include the above copyright notice and 9 * this paragraph in its entirety in the documentation or other materials 10 * provided with the distribution, and (3) all advertising materials mentioning 11 * features or use of this software display the following acknowledgement: 12 * ``This product includes software developed by the University of California, 13 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of 14 * the University nor the names of its contributors may be used to endorse 15 * or promote products derived from this software without specific prior 16 * written permission. 17 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED 18 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF 19 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 20 * 21 * Optimization module for tcpdump intermediate representation. 22 */ 23#ifndef lint 24static const char rcsid[] = 25 "@(#) $Header: /tcpdump/master/libpcap/optimize.c,v 1.67 2000/11/19 13:37:20 itojun Exp $ (LBL)"; 26#endif 27 28#ifdef HAVE_CONFIG_H 29#include "config.h" 30#endif 31 32#include <sys/types.h> 33#include <sys/time.h> 34 35#include <stdio.h> 36#include <stdlib.h> 37#include <memory.h> 38 39#include <errno.h> 40 41#include "pcap-int.h" 42 43#include "gencode.h" 44 45#ifdef HAVE_OS_PROTO_H 46#include "os-proto.h" 47#endif 48 49#ifdef BDEBUG 50extern int dflag; 51#endif 52 53#define A_ATOM BPF_MEMWORDS 54#define X_ATOM (BPF_MEMWORDS+1) 55 56#define NOP -1 57 58/* 59 * This define is used to represent *both* the accumulator and 60 * x register in use-def computations. 61 * Currently, the use-def code assumes only one definition per instruction. 62 */ 63#define AX_ATOM N_ATOMS 64 65/* 66 * A flag to indicate that further optimization is needed. 67 * Iterative passes are continued until a given pass yields no 68 * branch movement. 69 */ 70static int done; 71 72/* 73 * A block is marked if only if its mark equals the current mark. 74 * Rather than traverse the code array, marking each item, 'cur_mark' is 75 * incremented. This automatically makes each element unmarked. 76 */ 77static int cur_mark; 78#define isMarked(p) ((p)->mark == cur_mark) 79#define unMarkAll() cur_mark += 1 80#define Mark(p) ((p)->mark = cur_mark) 81 82static void opt_init(struct block *); 83static void opt_cleanup(void); 84 85static void make_marks(struct block *); 86static void mark_code(struct block *); 87 88static void intern_blocks(struct block *); 89 90static int eq_slist(struct slist *, struct slist *); 91 92static void find_levels_r(struct block *); 93 94static void find_levels(struct block *); 95static void find_dom(struct block *); 96static void propedom(struct edge *); 97static void find_edom(struct block *); 98static void find_closure(struct block *); 99static int atomuse(struct stmt *); 100static int atomdef(struct stmt *); 101static void compute_local_ud(struct block *); 102static void find_ud(struct block *); 103static void init_val(void); 104static int F(int, int, int); 105static inline void vstore(struct stmt *, int *, int, int); 106static void opt_blk(struct block *, int); 107static int use_conflict(struct block *, struct block *); 108static void opt_j(struct edge *); 109static void or_pullup(struct block *); 110static void and_pullup(struct block *); 111static void opt_blks(struct block *, int); 112static inline void link_inedge(struct edge *, struct block *); 113static void find_inedges(struct block *); 114static void opt_root(struct block **); 115static void opt_loop(struct block *, int); 116static void fold_op(struct stmt *, int, int); 117static inline struct slist *this_op(struct slist *); 118static void opt_not(struct block *); 119static void opt_peep(struct block *); 120static void opt_stmt(struct stmt *, int[], int); 121static void deadstmt(struct stmt *, struct stmt *[]); 122static void opt_deadstores(struct block *); 123static void opt_blk(struct block *, int); 124static int use_conflict(struct block *, struct block *); 125static void opt_j(struct edge *); 126static struct block *fold_edge(struct block *, struct edge *); 127static inline int eq_blk(struct block *, struct block *); 128static int slength(struct slist *); 129static int count_blocks(struct block *); 130static void number_blks_r(struct block *); 131static int count_stmts(struct block *); 132static int convert_code_r(struct block *); 133#ifdef BDEBUG 134static void opt_dump(struct block *); 135#endif 136 137static int n_blocks; 138struct block **blocks; 139static int n_edges; 140struct edge **edges; 141 142/* 143 * A bit vector set representation of the dominators. 144 * We round up the set size to the next power of two. 145 */ 146static int nodewords; 147static int edgewords; 148struct block **levels; 149bpf_u_int32 *space; 150#define BITS_PER_WORD (8*sizeof(bpf_u_int32)) 151/* 152 * True if a is in uset {p} 153 */ 154#define SET_MEMBER(p, a) \ 155((p)[(unsigned)(a) / BITS_PER_WORD] & (1 << ((unsigned)(a) % BITS_PER_WORD))) 156 157/* 158 * Add 'a' to uset p. 159 */ 160#define SET_INSERT(p, a) \ 161(p)[(unsigned)(a) / BITS_PER_WORD] |= (1 << ((unsigned)(a) % BITS_PER_WORD)) 162 163/* 164 * Delete 'a' from uset p. 165 */ 166#define SET_DELETE(p, a) \ 167(p)[(unsigned)(a) / BITS_PER_WORD] &= ~(1 << ((unsigned)(a) % BITS_PER_WORD)) 168 169/* 170 * a := a intersect b 171 */ 172#define SET_INTERSECT(a, b, n)\ 173{\ 174 register bpf_u_int32 *_x = a, *_y = b;\ 175 register int _n = n;\ 176 while (--_n >= 0) *_x++ &= *_y++;\ 177} 178 179/* 180 * a := a - b 181 */ 182#define SET_SUBTRACT(a, b, n)\ 183{\ 184 register bpf_u_int32 *_x = a, *_y = b;\ 185 register int _n = n;\ 186 while (--_n >= 0) *_x++ &=~ *_y++;\ 187} 188 189/* 190 * a := a union b 191 */ 192#define SET_UNION(a, b, n)\ 193{\ 194 register bpf_u_int32 *_x = a, *_y = b;\ 195 register int _n = n;\ 196 while (--_n >= 0) *_x++ |= *_y++;\ 197} 198 199static uset all_dom_sets; 200static uset all_closure_sets; 201static uset all_edge_sets; 202 203#ifndef MAX 204#define MAX(a,b) ((a)>(b)?(a):(b)) 205#endif 206 207static void 208find_levels_r(b) 209 struct block *b; 210{ 211 int level; 212 213 if (isMarked(b)) 214 return; 215 216 Mark(b); 217 b->link = 0; 218 219 if (JT(b)) { 220 find_levels_r(JT(b)); 221 find_levels_r(JF(b)); 222 level = MAX(JT(b)->level, JF(b)->level) + 1; 223 } else 224 level = 0; 225 b->level = level; 226 b->link = levels[level]; 227 levels[level] = b; 228} 229 230/* 231 * Level graph. The levels go from 0 at the leaves to 232 * N_LEVELS at the root. The levels[] array points to the 233 * first node of the level list, whose elements are linked 234 * with the 'link' field of the struct block. 235 */ 236static void 237find_levels(root) 238 struct block *root; 239{ 240 memset((char *)levels, 0, n_blocks * sizeof(*levels)); 241 unMarkAll(); 242 find_levels_r(root); 243} 244 245/* 246 * Find dominator relationships. 247 * Assumes graph has been leveled. 248 */ 249static void 250find_dom(root) 251 struct block *root; 252{ 253 int i; 254 struct block *b; 255 bpf_u_int32 *x; 256 257 /* 258 * Initialize sets to contain all nodes. 259 */ 260 x = all_dom_sets; 261 i = n_blocks * nodewords; 262 while (--i >= 0) 263 *x++ = ~0; 264 /* Root starts off empty. */ 265 for (i = nodewords; --i >= 0;) 266 root->dom[i] = 0; 267 268 /* root->level is the highest level no found. */ 269 for (i = root->level; i >= 0; --i) { 270 for (b = levels[i]; b; b = b->link) { 271 SET_INSERT(b->dom, b->id); 272 if (JT(b) == 0) 273 continue; 274 SET_INTERSECT(JT(b)->dom, b->dom, nodewords); 275 SET_INTERSECT(JF(b)->dom, b->dom, nodewords); 276 } 277 } 278} 279 280static void 281propedom(ep) 282 struct edge *ep; 283{ 284 SET_INSERT(ep->edom, ep->id); 285 if (ep->succ) { 286 SET_INTERSECT(ep->succ->et.edom, ep->edom, edgewords); 287 SET_INTERSECT(ep->succ->ef.edom, ep->edom, edgewords); 288 } 289} 290 291/* 292 * Compute edge dominators. 293 * Assumes graph has been leveled and predecessors established. 294 */ 295static void 296find_edom(root) 297 struct block *root; 298{ 299 int i; 300 uset x; 301 struct block *b; 302 303 x = all_edge_sets; 304 for (i = n_edges * edgewords; --i >= 0; ) 305 x[i] = ~0; 306 307 /* root->level is the highest level no found. */ 308 memset(root->et.edom, 0, edgewords * sizeof(*(uset)0)); 309 memset(root->ef.edom, 0, edgewords * sizeof(*(uset)0)); 310 for (i = root->level; i >= 0; --i) { 311 for (b = levels[i]; b != 0; b = b->link) { 312 propedom(&b->et); 313 propedom(&b->ef); 314 } 315 } 316} 317 318/* 319 * Find the backwards transitive closure of the flow graph. These sets 320 * are backwards in the sense that we find the set of nodes that reach 321 * a given node, not the set of nodes that can be reached by a node. 322 * 323 * Assumes graph has been leveled. 324 */ 325static void 326find_closure(root) 327 struct block *root; 328{ 329 int i; 330 struct block *b; 331 332 /* 333 * Initialize sets to contain no nodes. 334 */ 335 memset((char *)all_closure_sets, 0, 336 n_blocks * nodewords * sizeof(*all_closure_sets)); 337 338 /* root->level is the highest level no found. */ 339 for (i = root->level; i >= 0; --i) { 340 for (b = levels[i]; b; b = b->link) { 341 SET_INSERT(b->closure, b->id); 342 if (JT(b) == 0) 343 continue; 344 SET_UNION(JT(b)->closure, b->closure, nodewords); 345 SET_UNION(JF(b)->closure, b->closure, nodewords); 346 } 347 } 348} 349 350/* 351 * Return the register number that is used by s. If A and X are both 352 * used, return AX_ATOM. If no register is used, return -1. 353 * 354 * The implementation should probably change to an array access. 355 */ 356static int 357atomuse(s) 358 struct stmt *s; 359{ 360 register int c = s->code; 361 362 if (c == NOP) 363 return -1; 364 365 switch (BPF_CLASS(c)) { 366 367 case BPF_RET: 368 return (BPF_RVAL(c) == BPF_A) ? A_ATOM : 369 (BPF_RVAL(c) == BPF_X) ? X_ATOM : -1; 370 371 case BPF_LD: 372 case BPF_LDX: 373 return (BPF_MODE(c) == BPF_IND) ? X_ATOM : 374 (BPF_MODE(c) == BPF_MEM) ? s->k : -1; 375 376 case BPF_ST: 377 return A_ATOM; 378 379 case BPF_STX: 380 return X_ATOM; 381 382 case BPF_JMP: 383 case BPF_ALU: 384 if (BPF_SRC(c) == BPF_X) 385 return AX_ATOM; 386 return A_ATOM; 387 388 case BPF_MISC: 389 return BPF_MISCOP(c) == BPF_TXA ? X_ATOM : A_ATOM; 390 } 391 abort(); 392 /* NOTREACHED */ 393} 394 395/* 396 * Return the register number that is defined by 's'. We assume that 397 * a single stmt cannot define more than one register. If no register 398 * is defined, return -1. 399 * 400 * The implementation should probably change to an array access. 401 */ 402static int 403atomdef(s) 404 struct stmt *s; 405{ 406 if (s->code == NOP) 407 return -1; 408 409 switch (BPF_CLASS(s->code)) { 410 411 case BPF_LD: 412 case BPF_ALU: 413 return A_ATOM; 414 415 case BPF_LDX: 416 return X_ATOM; 417 418 case BPF_ST: 419 case BPF_STX: 420 return s->k; 421 422 case BPF_MISC: 423 return BPF_MISCOP(s->code) == BPF_TAX ? X_ATOM : A_ATOM; 424 } 425 return -1; 426} 427 428static void 429compute_local_ud(b) 430 struct block *b; 431{ 432 struct slist *s; 433 atomset def = 0, use = 0, kill = 0; 434 int atom; 435 436 for (s = b->stmts; s; s = s->next) { 437 if (s->s.code == NOP) 438 continue; 439 atom = atomuse(&s->s); 440 if (atom >= 0) { 441 if (atom == AX_ATOM) { 442 if (!ATOMELEM(def, X_ATOM)) 443 use |= ATOMMASK(X_ATOM); 444 if (!ATOMELEM(def, A_ATOM)) 445 use |= ATOMMASK(A_ATOM); 446 } 447 else if (atom < N_ATOMS) { 448 if (!ATOMELEM(def, atom)) 449 use |= ATOMMASK(atom); 450 } 451 else 452 abort(); 453 } 454 atom = atomdef(&s->s); 455 if (atom >= 0) { 456 if (!ATOMELEM(use, atom)) 457 kill |= ATOMMASK(atom); 458 def |= ATOMMASK(atom); 459 } 460 } 461 if (!ATOMELEM(def, A_ATOM) && BPF_CLASS(b->s.code) == BPF_JMP) 462 use |= ATOMMASK(A_ATOM); 463 464 b->def = def; 465 b->kill = kill; 466 b->in_use = use; 467} 468 469/* 470 * Assume graph is already leveled. 471 */ 472static void 473find_ud(root) 474 struct block *root; 475{ 476 int i, maxlevel; 477 struct block *p; 478 479 /* 480 * root->level is the highest level no found; 481 * count down from there. 482 */ 483 maxlevel = root->level; 484 for (i = maxlevel; i >= 0; --i) 485 for (p = levels[i]; p; p = p->link) { 486 compute_local_ud(p); 487 p->out_use = 0; 488 } 489 490 for (i = 1; i <= maxlevel; ++i) { 491 for (p = levels[i]; p; p = p->link) { 492 p->out_use |= JT(p)->in_use | JF(p)->in_use; 493 p->in_use |= p->out_use &~ p->kill; 494 } 495 } 496} 497 498/* 499 * These data structures are used in a Cocke and Shwarz style 500 * value numbering scheme. Since the flowgraph is acyclic, 501 * exit values can be propagated from a node's predecessors 502 * provided it is uniquely defined. 503 */ 504struct valnode { 505 int code; 506 int v0, v1; 507 int val; 508 struct valnode *next; 509}; 510 511#define MODULUS 213 512static struct valnode *hashtbl[MODULUS]; 513static int curval; 514static int maxval; 515 516/* Integer constants mapped with the load immediate opcode. */ 517#define K(i) F(BPF_LD|BPF_IMM|BPF_W, i, 0L) 518 519struct vmapinfo { 520 int is_const; 521 bpf_int32 const_val; 522}; 523 524struct vmapinfo *vmap; 525struct valnode *vnode_base; 526struct valnode *next_vnode; 527 528static void 529init_val() 530{ 531 curval = 0; 532 next_vnode = vnode_base; 533 memset((char *)vmap, 0, maxval * sizeof(*vmap)); 534 memset((char *)hashtbl, 0, sizeof hashtbl); 535} 536 537/* Because we really don't have an IR, this stuff is a little messy. */ 538static int 539F(code, v0, v1) 540 int code; 541 int v0, v1; 542{ 543 u_int hash; 544 int val; 545 struct valnode *p; 546 547 hash = (u_int)code ^ (v0 << 4) ^ (v1 << 8); 548 hash %= MODULUS; 549 550 for (p = hashtbl[hash]; p; p = p->next) 551 if (p->code == code && p->v0 == v0 && p->v1 == v1) 552 return p->val; 553 554 val = ++curval; 555 if (BPF_MODE(code) == BPF_IMM && 556 (BPF_CLASS(code) == BPF_LD || BPF_CLASS(code) == BPF_LDX)) { 557 vmap[val].const_val = v0; 558 vmap[val].is_const = 1; 559 } 560 p = next_vnode++; 561 p->val = val; 562 p->code = code; 563 p->v0 = v0; 564 p->v1 = v1; 565 p->next = hashtbl[hash]; 566 hashtbl[hash] = p; 567 568 return val; 569} 570 571static inline void 572vstore(s, valp, newval, alter) 573 struct stmt *s; 574 int *valp; 575 int newval; 576 int alter; 577{ 578 if (alter && *valp == newval) 579 s->code = NOP; 580 else 581 *valp = newval; 582} 583 584static void 585fold_op(s, v0, v1) 586 struct stmt *s; 587 int v0, v1; 588{ 589 bpf_int32 a, b; 590 591 a = vmap[v0].const_val; 592 b = vmap[v1].const_val; 593 594 switch (BPF_OP(s->code)) { 595 case BPF_ADD: 596 a += b; 597 break; 598 599 case BPF_SUB: 600 a -= b; 601 break; 602 603 case BPF_MUL: 604 a *= b; 605 break; 606 607 case BPF_DIV: 608 if (b == 0) 609 bpf_error("division by zero"); 610 a /= b; 611 break; 612 613 case BPF_AND: 614 a &= b; 615 break; 616 617 case BPF_OR: 618 a |= b; 619 break; 620 621 case BPF_LSH: 622 a <<= b; 623 break; 624 625 case BPF_RSH: 626 a >>= b; 627 break; 628 629 case BPF_NEG: 630 a = -a; 631 break; 632 633 default: 634 abort(); 635 } 636 s->k = a; 637 s->code = BPF_LD|BPF_IMM; 638 done = 0; 639} 640 641static inline struct slist * 642this_op(s) 643 struct slist *s; 644{ 645 while (s != 0 && s->s.code == NOP) 646 s = s->next; 647 return s; 648} 649 650static void 651opt_not(b) 652 struct block *b; 653{ 654 struct block *tmp = JT(b); 655 656 JT(b) = JF(b); 657 JF(b) = tmp; 658} 659 660static void 661opt_peep(b) 662 struct block *b; 663{ 664 struct slist *s; 665 struct slist *next, *last; 666 int val; 667 668 s = b->stmts; 669 if (s == 0) 670 return; 671 672 last = s; 673 while (1) { 674 s = this_op(s); 675 if (s == 0) 676 break; 677 next = this_op(s->next); 678 if (next == 0) 679 break; 680 last = next; 681 682 /* 683 * st M[k] --> st M[k] 684 * ldx M[k] tax 685 */ 686 if (s->s.code == BPF_ST && 687 next->s.code == (BPF_LDX|BPF_MEM) && 688 s->s.k == next->s.k) { 689 done = 0; 690 next->s.code = BPF_MISC|BPF_TAX; 691 } 692 /* 693 * ld #k --> ldx #k 694 * tax txa 695 */ 696 if (s->s.code == (BPF_LD|BPF_IMM) && 697 next->s.code == (BPF_MISC|BPF_TAX)) { 698 s->s.code = BPF_LDX|BPF_IMM; 699 next->s.code = BPF_MISC|BPF_TXA; 700 done = 0; 701 } 702 /* 703 * This is an ugly special case, but it happens 704 * when you say tcp[k] or udp[k] where k is a constant. 705 */ 706 if (s->s.code == (BPF_LD|BPF_IMM)) { 707 struct slist *add, *tax, *ild; 708 709 /* 710 * Check that X isn't used on exit from this 711 * block (which the optimizer might cause). 712 * We know the code generator won't generate 713 * any local dependencies. 714 */ 715 if (ATOMELEM(b->out_use, X_ATOM)) 716 break; 717 718 if (next->s.code != (BPF_LDX|BPF_MSH|BPF_B)) 719 add = next; 720 else 721 add = this_op(next->next); 722 if (add == 0 || add->s.code != (BPF_ALU|BPF_ADD|BPF_X)) 723 break; 724 725 tax = this_op(add->next); 726 if (tax == 0 || tax->s.code != (BPF_MISC|BPF_TAX)) 727 break; 728 729 ild = this_op(tax->next); 730 if (ild == 0 || BPF_CLASS(ild->s.code) != BPF_LD || 731 BPF_MODE(ild->s.code) != BPF_IND) 732 break; 733 /* 734 * XXX We need to check that X is not 735 * subsequently used. We know we can eliminate the 736 * accumulator modifications since it is defined 737 * by the last stmt of this sequence. 738 * 739 * We want to turn this sequence: 740 * 741 * (004) ldi #0x2 {s} 742 * (005) ldxms [14] {next} -- optional 743 * (006) addx {add} 744 * (007) tax {tax} 745 * (008) ild [x+0] {ild} 746 * 747 * into this sequence: 748 * 749 * (004) nop 750 * (005) ldxms [14] 751 * (006) nop 752 * (007) nop 753 * (008) ild [x+2] 754 * 755 */ 756 ild->s.k += s->s.k; 757 s->s.code = NOP; 758 add->s.code = NOP; 759 tax->s.code = NOP; 760 done = 0; 761 } 762 s = next; 763 } 764 /* 765 * If we have a subtract to do a comparison, and the X register 766 * is a known constant, we can merge this value into the 767 * comparison. 768 */ 769 if (last->s.code == (BPF_ALU|BPF_SUB|BPF_X) && 770 !ATOMELEM(b->out_use, A_ATOM)) { 771 val = b->val[X_ATOM]; 772 if (vmap[val].is_const) { 773 int op; 774 775 b->s.k += vmap[val].const_val; 776 op = BPF_OP(b->s.code); 777 if (op == BPF_JGT || op == BPF_JGE) { 778 struct block *t = JT(b); 779 JT(b) = JF(b); 780 JF(b) = t; 781 b->s.k += 0x80000000; 782 } 783 last->s.code = NOP; 784 done = 0; 785 } else if (b->s.k == 0) { 786 /* 787 * sub x -> nop 788 * j #0 j x 789 */ 790 last->s.code = NOP; 791 b->s.code = BPF_CLASS(b->s.code) | BPF_OP(b->s.code) | 792 BPF_X; 793 done = 0; 794 } 795 } 796 /* 797 * Likewise, a constant subtract can be simplified. 798 */ 799 else if (last->s.code == (BPF_ALU|BPF_SUB|BPF_K) && 800 !ATOMELEM(b->out_use, A_ATOM)) { 801 int op; 802 803 b->s.k += last->s.k; 804 last->s.code = NOP; 805 op = BPF_OP(b->s.code); 806 if (op == BPF_JGT || op == BPF_JGE) { 807 struct block *t = JT(b); 808 JT(b) = JF(b); 809 JF(b) = t; 810 b->s.k += 0x80000000; 811 } 812 done = 0; 813 } 814 /* 815 * and #k nop 816 * jeq #0 -> jset #k 817 */ 818 if (last->s.code == (BPF_ALU|BPF_AND|BPF_K) && 819 !ATOMELEM(b->out_use, A_ATOM) && b->s.k == 0) { 820 b->s.k = last->s.k; 821 b->s.code = BPF_JMP|BPF_K|BPF_JSET; 822 last->s.code = NOP; 823 done = 0; 824 opt_not(b); 825 } 826 /* 827 * If the accumulator is a known constant, we can compute the 828 * comparison result. 829 */ 830 val = b->val[A_ATOM]; 831 if (vmap[val].is_const && BPF_SRC(b->s.code) == BPF_K) { 832 bpf_int32 v = vmap[val].const_val; 833 switch (BPF_OP(b->s.code)) { 834 835 case BPF_JEQ: 836 v = v == b->s.k; 837 break; 838 839 case BPF_JGT: 840 v = (unsigned)v > b->s.k; 841 break; 842 843 case BPF_JGE: 844 v = (unsigned)v >= b->s.k; 845 break; 846 847 case BPF_JSET: 848 v &= b->s.k; 849 break; 850 851 default: 852 abort(); 853 } 854 if (JF(b) != JT(b)) 855 done = 0; 856 if (v) 857 JF(b) = JT(b); 858 else 859 JT(b) = JF(b); 860 } 861} 862 863/* 864 * Compute the symbolic value of expression of 's', and update 865 * anything it defines in the value table 'val'. If 'alter' is true, 866 * do various optimizations. This code would be cleaner if symbolic 867 * evaluation and code transformations weren't folded together. 868 */ 869static void 870opt_stmt(s, val, alter) 871 struct stmt *s; 872 int val[]; 873 int alter; 874{ 875 int op; 876 int v; 877 878 switch (s->code) { 879 880 case BPF_LD|BPF_ABS|BPF_W: 881 case BPF_LD|BPF_ABS|BPF_H: 882 case BPF_LD|BPF_ABS|BPF_B: 883 v = F(s->code, s->k, 0L); 884 vstore(s, &val[A_ATOM], v, alter); 885 break; 886 887 case BPF_LD|BPF_IND|BPF_W: 888 case BPF_LD|BPF_IND|BPF_H: 889 case BPF_LD|BPF_IND|BPF_B: 890 v = val[X_ATOM]; 891 if (alter && vmap[v].is_const) { 892 s->code = BPF_LD|BPF_ABS|BPF_SIZE(s->code); 893 s->k += vmap[v].const_val; 894 v = F(s->code, s->k, 0L); 895 done = 0; 896 } 897 else 898 v = F(s->code, s->k, v); 899 vstore(s, &val[A_ATOM], v, alter); 900 break; 901 902 case BPF_LD|BPF_LEN: 903 v = F(s->code, 0L, 0L); 904 vstore(s, &val[A_ATOM], v, alter); 905 break; 906 907 case BPF_LD|BPF_IMM: 908 v = K(s->k); 909 vstore(s, &val[A_ATOM], v, alter); 910 break; 911 912 case BPF_LDX|BPF_IMM: 913 v = K(s->k); 914 vstore(s, &val[X_ATOM], v, alter); 915 break; 916 917 case BPF_LDX|BPF_MSH|BPF_B: 918 v = F(s->code, s->k, 0L); 919 vstore(s, &val[X_ATOM], v, alter); 920 break; 921 922 case BPF_ALU|BPF_NEG: 923 if (alter && vmap[val[A_ATOM]].is_const) { 924 s->code = BPF_LD|BPF_IMM; 925 s->k = -vmap[val[A_ATOM]].const_val; 926 val[A_ATOM] = K(s->k); 927 } 928 else 929 val[A_ATOM] = F(s->code, val[A_ATOM], 0L); 930 break; 931 932 case BPF_ALU|BPF_ADD|BPF_K: 933 case BPF_ALU|BPF_SUB|BPF_K: 934 case BPF_ALU|BPF_MUL|BPF_K: 935 case BPF_ALU|BPF_DIV|BPF_K: 936 case BPF_ALU|BPF_AND|BPF_K: 937 case BPF_ALU|BPF_OR|BPF_K: 938 case BPF_ALU|BPF_LSH|BPF_K: 939 case BPF_ALU|BPF_RSH|BPF_K: 940 op = BPF_OP(s->code); 941 if (alter) { 942 if (s->k == 0) { 943 if (op == BPF_ADD || op == BPF_SUB || 944 op == BPF_LSH || op == BPF_RSH || 945 op == BPF_OR) { 946 s->code = NOP; 947 break; 948 } 949 if (op == BPF_MUL || op == BPF_AND) { 950 s->code = BPF_LD|BPF_IMM; 951 val[A_ATOM] = K(s->k); 952 break; 953 } 954 } 955 if (vmap[val[A_ATOM]].is_const) { 956 fold_op(s, val[A_ATOM], K(s->k)); 957 val[A_ATOM] = K(s->k); 958 break; 959 } 960 } 961 val[A_ATOM] = F(s->code, val[A_ATOM], K(s->k)); 962 break; 963 964 case BPF_ALU|BPF_ADD|BPF_X: 965 case BPF_ALU|BPF_SUB|BPF_X: 966 case BPF_ALU|BPF_MUL|BPF_X: 967 case BPF_ALU|BPF_DIV|BPF_X: 968 case BPF_ALU|BPF_AND|BPF_X: 969 case BPF_ALU|BPF_OR|BPF_X: 970 case BPF_ALU|BPF_LSH|BPF_X: 971 case BPF_ALU|BPF_RSH|BPF_X: 972 op = BPF_OP(s->code); 973 if (alter && vmap[val[X_ATOM]].is_const) { 974 if (vmap[val[A_ATOM]].is_const) { 975 fold_op(s, val[A_ATOM], val[X_ATOM]); 976 val[A_ATOM] = K(s->k); 977 } 978 else { 979 s->code = BPF_ALU|BPF_K|op; 980 s->k = vmap[val[X_ATOM]].const_val; 981 done = 0; 982 val[A_ATOM] = 983 F(s->code, val[A_ATOM], K(s->k)); 984 } 985 break; 986 } 987 /* 988 * Check if we're doing something to an accumulator 989 * that is 0, and simplify. This may not seem like 990 * much of a simplification but it could open up further 991 * optimizations. 992 * XXX We could also check for mul by 1, and -1, etc. 993 */ 994 if (alter && vmap[val[A_ATOM]].is_const 995 && vmap[val[A_ATOM]].const_val == 0) { 996 if (op == BPF_ADD || op == BPF_OR || 997 op == BPF_LSH || op == BPF_RSH || op == BPF_SUB) { 998 s->code = BPF_MISC|BPF_TXA; 999 vstore(s, &val[A_ATOM], val[X_ATOM], alter); 1000 break; 1001 } 1002 else if (op == BPF_MUL || op == BPF_DIV || 1003 op == BPF_AND) { 1004 s->code = BPF_LD|BPF_IMM; 1005 s->k = 0; 1006 vstore(s, &val[A_ATOM], K(s->k), alter); 1007 break; 1008 } 1009 else if (op == BPF_NEG) { 1010 s->code = NOP; 1011 break; 1012 } 1013 } 1014 val[A_ATOM] = F(s->code, val[A_ATOM], val[X_ATOM]); 1015 break; 1016 1017 case BPF_MISC|BPF_TXA: 1018 vstore(s, &val[A_ATOM], val[X_ATOM], alter); 1019 break; 1020 1021 case BPF_LD|BPF_MEM: 1022 v = val[s->k]; 1023 if (alter && vmap[v].is_const) { 1024 s->code = BPF_LD|BPF_IMM; 1025 s->k = vmap[v].const_val; 1026 done = 0; 1027 } 1028 vstore(s, &val[A_ATOM], v, alter); 1029 break; 1030 1031 case BPF_MISC|BPF_TAX: 1032 vstore(s, &val[X_ATOM], val[A_ATOM], alter); 1033 break; 1034 1035 case BPF_LDX|BPF_MEM: 1036 v = val[s->k]; 1037 if (alter && vmap[v].is_const) { 1038 s->code = BPF_LDX|BPF_IMM; 1039 s->k = vmap[v].const_val; 1040 done = 0; 1041 } 1042 vstore(s, &val[X_ATOM], v, alter); 1043 break; 1044 1045 case BPF_ST: 1046 vstore(s, &val[s->k], val[A_ATOM], alter); 1047 break; 1048 1049 case BPF_STX: 1050 vstore(s, &val[s->k], val[X_ATOM], alter); 1051 break; 1052 } 1053} 1054 1055static void 1056deadstmt(s, last) 1057 register struct stmt *s; 1058 register struct stmt *last[]; 1059{ 1060 register int atom; 1061 1062 atom = atomuse(s); 1063 if (atom >= 0) { 1064 if (atom == AX_ATOM) { 1065 last[X_ATOM] = 0; 1066 last[A_ATOM] = 0; 1067 } 1068 else 1069 last[atom] = 0; 1070 } 1071 atom = atomdef(s); 1072 if (atom >= 0) { 1073 if (last[atom]) { 1074 done = 0; 1075 last[atom]->code = NOP; 1076 } 1077 last[atom] = s; 1078 } 1079} 1080 1081static void 1082opt_deadstores(b) 1083 register struct block *b; 1084{ 1085 register struct slist *s; 1086 register int atom; 1087 struct stmt *last[N_ATOMS]; 1088 1089 memset((char *)last, 0, sizeof last); 1090 1091 for (s = b->stmts; s != 0; s = s->next) 1092 deadstmt(&s->s, last); 1093 deadstmt(&b->s, last); 1094 1095 for (atom = 0; atom < N_ATOMS; ++atom) 1096 if (last[atom] && !ATOMELEM(b->out_use, atom)) { 1097 last[atom]->code = NOP; 1098 done = 0; 1099 } 1100} 1101 1102static void 1103opt_blk(b, do_stmts) 1104 struct block *b; 1105 int do_stmts; 1106{ 1107 struct slist *s; 1108 struct edge *p; 1109 int i; 1110 bpf_int32 aval; 1111 1112#if 0 1113 for (s = b->stmts; s && s->next; s = s->next) 1114 if (BPF_CLASS(s->s.code) == BPF_JMP) { 1115 do_stmts = 0; 1116 break; 1117 } 1118#endif 1119 1120 /* 1121 * Initialize the atom values. 1122 * If we have no predecessors, everything is undefined. 1123 * Otherwise, we inherent our values from our predecessors. 1124 * If any register has an ambiguous value (i.e. control paths are 1125 * merging) give it the undefined value of 0. 1126 */ 1127 p = b->in_edges; 1128 if (p == 0) 1129 memset((char *)b->val, 0, sizeof(b->val)); 1130 else { 1131 memcpy((char *)b->val, (char *)p->pred->val, sizeof(b->val)); 1132 while ((p = p->next) != NULL) { 1133 for (i = 0; i < N_ATOMS; ++i) 1134 if (b->val[i] != p->pred->val[i]) 1135 b->val[i] = 0; 1136 } 1137 } 1138 aval = b->val[A_ATOM]; 1139 for (s = b->stmts; s; s = s->next) 1140 opt_stmt(&s->s, b->val, do_stmts); 1141 1142 /* 1143 * This is a special case: if we don't use anything from this 1144 * block, and we load the accumulator with value that is 1145 * already there, or if this block is a return, 1146 * eliminate all the statements. 1147 */ 1148 if (do_stmts && 1149 ((b->out_use == 0 && aval != 0 &&b->val[A_ATOM] == aval) || 1150 BPF_CLASS(b->s.code) == BPF_RET)) { 1151 if (b->stmts != 0) { 1152 b->stmts = 0; 1153 done = 0; 1154 } 1155 } else { 1156 opt_peep(b); 1157 opt_deadstores(b); 1158 } 1159 /* 1160 * Set up values for branch optimizer. 1161 */ 1162 if (BPF_SRC(b->s.code) == BPF_K) 1163 b->oval = K(b->s.k); 1164 else 1165 b->oval = b->val[X_ATOM]; 1166 b->et.code = b->s.code; 1167 b->ef.code = -b->s.code; 1168} 1169 1170/* 1171 * Return true if any register that is used on exit from 'succ', has 1172 * an exit value that is different from the corresponding exit value 1173 * from 'b'. 1174 */ 1175static int 1176use_conflict(b, succ) 1177 struct block *b, *succ; 1178{ 1179 int atom; 1180 atomset use = succ->out_use; 1181 1182 if (use == 0) 1183 return 0; 1184 1185 for (atom = 0; atom < N_ATOMS; ++atom) 1186 if (ATOMELEM(use, atom)) 1187 if (b->val[atom] != succ->val[atom]) 1188 return 1; 1189 return 0; 1190} 1191 1192static struct block * 1193fold_edge(child, ep) 1194 struct block *child; 1195 struct edge *ep; 1196{ 1197 int sense; 1198 int aval0, aval1, oval0, oval1; 1199 int code = ep->code; 1200 1201 if (code < 0) { 1202 code = -code; 1203 sense = 0; 1204 } else 1205 sense = 1; 1206 1207 if (child->s.code != code) 1208 return 0; 1209 1210 aval0 = child->val[A_ATOM]; 1211 oval0 = child->oval; 1212 aval1 = ep->pred->val[A_ATOM]; 1213 oval1 = ep->pred->oval; 1214 1215 if (aval0 != aval1) 1216 return 0; 1217 1218 if (oval0 == oval1) 1219 /* 1220 * The operands are identical, so the 1221 * result is true if a true branch was 1222 * taken to get here, otherwise false. 1223 */ 1224 return sense ? JT(child) : JF(child); 1225 1226 if (sense && code == (BPF_JMP|BPF_JEQ|BPF_K)) 1227 /* 1228 * At this point, we only know the comparison if we 1229 * came down the true branch, and it was an equality 1230 * comparison with a constant. We rely on the fact that 1231 * distinct constants have distinct value numbers. 1232 */ 1233 return JF(child); 1234 1235 return 0; 1236} 1237 1238static void 1239opt_j(ep) 1240 struct edge *ep; 1241{ 1242 register int i, k; 1243 register struct block *target; 1244 1245 if (JT(ep->succ) == 0) 1246 return; 1247 1248 if (JT(ep->succ) == JF(ep->succ)) { 1249 /* 1250 * Common branch targets can be eliminated, provided 1251 * there is no data dependency. 1252 */ 1253 if (!use_conflict(ep->pred, ep->succ->et.succ)) { 1254 done = 0; 1255 ep->succ = JT(ep->succ); 1256 } 1257 } 1258 /* 1259 * For each edge dominator that matches the successor of this 1260 * edge, promote the edge successor to the its grandchild. 1261 * 1262 * XXX We violate the set abstraction here in favor a reasonably 1263 * efficient loop. 1264 */ 1265 top: 1266 for (i = 0; i < edgewords; ++i) { 1267 register bpf_u_int32 x = ep->edom[i]; 1268 1269 while (x != 0) { 1270 k = ffs(x) - 1; 1271 x &=~ (1 << k); 1272 k += i * BITS_PER_WORD; 1273 1274 target = fold_edge(ep->succ, edges[k]); 1275 /* 1276 * Check that there is no data dependency between 1277 * nodes that will be violated if we move the edge. 1278 */ 1279 if (target != 0 && !use_conflict(ep->pred, target)) { 1280 done = 0; 1281 ep->succ = target; 1282 if (JT(target) != 0) 1283 /* 1284 * Start over unless we hit a leaf. 1285 */ 1286 goto top; 1287 return; 1288 } 1289 } 1290 } 1291} 1292 1293 1294static void 1295or_pullup(b) 1296 struct block *b; 1297{ 1298 int val, at_top; 1299 struct block *pull; 1300 struct block **diffp, **samep; 1301 struct edge *ep; 1302 1303 ep = b->in_edges; 1304 if (ep == 0) 1305 return; 1306 1307 /* 1308 * Make sure each predecessor loads the same value. 1309 * XXX why? 1310 */ 1311 val = ep->pred->val[A_ATOM]; 1312 for (ep = ep->next; ep != 0; ep = ep->next) 1313 if (val != ep->pred->val[A_ATOM]) 1314 return; 1315 1316 if (JT(b->in_edges->pred) == b) 1317 diffp = &JT(b->in_edges->pred); 1318 else 1319 diffp = &JF(b->in_edges->pred); 1320 1321 at_top = 1; 1322 while (1) { 1323 if (*diffp == 0) 1324 return; 1325 1326 if (JT(*diffp) != JT(b)) 1327 return; 1328 1329 if (!SET_MEMBER((*diffp)->dom, b->id)) 1330 return; 1331 1332 if ((*diffp)->val[A_ATOM] != val) 1333 break; 1334 1335 diffp = &JF(*diffp); 1336 at_top = 0; 1337 } 1338 samep = &JF(*diffp); 1339 while (1) { 1340 if (*samep == 0) 1341 return; 1342 1343 if (JT(*samep) != JT(b)) 1344 return; 1345 1346 if (!SET_MEMBER((*samep)->dom, b->id)) 1347 return; 1348 1349 if ((*samep)->val[A_ATOM] == val) 1350 break; 1351 1352 /* XXX Need to check that there are no data dependencies 1353 between dp0 and dp1. Currently, the code generator 1354 will not produce such dependencies. */ 1355 samep = &JF(*samep); 1356 } 1357#ifdef notdef 1358 /* XXX This doesn't cover everything. */ 1359 for (i = 0; i < N_ATOMS; ++i) 1360 if ((*samep)->val[i] != pred->val[i]) 1361 return; 1362#endif 1363 /* Pull up the node. */ 1364 pull = *samep; 1365 *samep = JF(pull); 1366 JF(pull) = *diffp; 1367 1368 /* 1369 * At the top of the chain, each predecessor needs to point at the 1370 * pulled up node. Inside the chain, there is only one predecessor 1371 * to worry about. 1372 */ 1373 if (at_top) { 1374 for (ep = b->in_edges; ep != 0; ep = ep->next) { 1375 if (JT(ep->pred) == b) 1376 JT(ep->pred) = pull; 1377 else 1378 JF(ep->pred) = pull; 1379 } 1380 } 1381 else 1382 *diffp = pull; 1383 1384 done = 0; 1385} 1386 1387static void 1388and_pullup(b) 1389 struct block *b; 1390{ 1391 int val, at_top; 1392 struct block *pull; 1393 struct block **diffp, **samep; 1394 struct edge *ep; 1395 1396 ep = b->in_edges; 1397 if (ep == 0) 1398 return; 1399 1400 /* 1401 * Make sure each predecessor loads the same value. 1402 */ 1403 val = ep->pred->val[A_ATOM]; 1404 for (ep = ep->next; ep != 0; ep = ep->next) 1405 if (val != ep->pred->val[A_ATOM]) 1406 return; 1407 1408 if (JT(b->in_edges->pred) == b) 1409 diffp = &JT(b->in_edges->pred); 1410 else 1411 diffp = &JF(b->in_edges->pred); 1412 1413 at_top = 1; 1414 while (1) { 1415 if (*diffp == 0) 1416 return; 1417 1418 if (JF(*diffp) != JF(b)) 1419 return; 1420 1421 if (!SET_MEMBER((*diffp)->dom, b->id)) 1422 return; 1423 1424 if ((*diffp)->val[A_ATOM] != val) 1425 break; 1426 1427 diffp = &JT(*diffp); 1428 at_top = 0; 1429 } 1430 samep = &JT(*diffp); 1431 while (1) { 1432 if (*samep == 0) 1433 return; 1434 1435 if (JF(*samep) != JF(b)) 1436 return; 1437 1438 if (!SET_MEMBER((*samep)->dom, b->id)) 1439 return; 1440 1441 if ((*samep)->val[A_ATOM] == val) 1442 break; 1443 1444 /* XXX Need to check that there are no data dependencies 1445 between diffp and samep. Currently, the code generator 1446 will not produce such dependencies. */ 1447 samep = &JT(*samep); 1448 } 1449#ifdef notdef 1450 /* XXX This doesn't cover everything. */ 1451 for (i = 0; i < N_ATOMS; ++i) 1452 if ((*samep)->val[i] != pred->val[i]) 1453 return; 1454#endif 1455 /* Pull up the node. */ 1456 pull = *samep; 1457 *samep = JT(pull); 1458 JT(pull) = *diffp; 1459 1460 /* 1461 * At the top of the chain, each predecessor needs to point at the 1462 * pulled up node. Inside the chain, there is only one predecessor 1463 * to worry about. 1464 */ 1465 if (at_top) { 1466 for (ep = b->in_edges; ep != 0; ep = ep->next) { 1467 if (JT(ep->pred) == b) 1468 JT(ep->pred) = pull; 1469 else 1470 JF(ep->pred) = pull; 1471 } 1472 } 1473 else 1474 *diffp = pull; 1475 1476 done = 0; 1477} 1478 1479static void 1480opt_blks(root, do_stmts) 1481 struct block *root; 1482 int do_stmts; 1483{ 1484 int i, maxlevel; 1485 struct block *p; 1486 1487 init_val(); 1488 maxlevel = root->level; 1489 1490 find_inedges(root); 1491 for (i = maxlevel; i >= 0; --i) 1492 for (p = levels[i]; p; p = p->link) 1493 opt_blk(p, do_stmts); 1494 1495 if (do_stmts) 1496 /* 1497 * No point trying to move branches; it can't possibly 1498 * make a difference at this point. 1499 */ 1500 return; 1501 1502 for (i = 1; i <= maxlevel; ++i) { 1503 for (p = levels[i]; p; p = p->link) { 1504 opt_j(&p->et); 1505 opt_j(&p->ef); 1506 } 1507 } 1508 1509 find_inedges(root); 1510 for (i = 1; i <= maxlevel; ++i) { 1511 for (p = levels[i]; p; p = p->link) { 1512 or_pullup(p); 1513 and_pullup(p); 1514 } 1515 } 1516} 1517 1518static inline void 1519link_inedge(parent, child) 1520 struct edge *parent; 1521 struct block *child; 1522{ 1523 parent->next = child->in_edges; 1524 child->in_edges = parent; 1525} 1526 1527static void 1528find_inedges(root) 1529 struct block *root; 1530{ 1531 int i; 1532 struct block *b; 1533 1534 for (i = 0; i < n_blocks; ++i) 1535 blocks[i]->in_edges = 0; 1536 1537 /* 1538 * Traverse the graph, adding each edge to the predecessor 1539 * list of its successors. Skip the leaves (i.e. level 0). 1540 */ 1541 for (i = root->level; i > 0; --i) { 1542 for (b = levels[i]; b != 0; b = b->link) { 1543 link_inedge(&b->et, JT(b)); 1544 link_inedge(&b->ef, JF(b)); 1545 } 1546 } 1547} 1548 1549static void 1550opt_root(b) 1551 struct block **b; 1552{ 1553 struct slist *tmp, *s; 1554 1555 s = (*b)->stmts; 1556 (*b)->stmts = 0; 1557 while (BPF_CLASS((*b)->s.code) == BPF_JMP && JT(*b) == JF(*b)) 1558 *b = JT(*b); 1559 1560 tmp = (*b)->stmts; 1561 if (tmp != 0) 1562 sappend(s, tmp); 1563 (*b)->stmts = s; 1564 1565 /* 1566 * If the root node is a return, then there is no 1567 * point executing any statements (since the bpf machine 1568 * has no side effects). 1569 */ 1570 if (BPF_CLASS((*b)->s.code) == BPF_RET) 1571 (*b)->stmts = 0; 1572} 1573 1574static void 1575opt_loop(root, do_stmts) 1576 struct block *root; 1577 int do_stmts; 1578{ 1579 1580#ifdef BDEBUG 1581 if (dflag > 1) 1582 opt_dump(root); 1583#endif 1584 do { 1585 done = 1; 1586 find_levels(root); 1587 find_dom(root); 1588 find_closure(root); 1589 find_ud(root); 1590 find_edom(root); 1591 opt_blks(root, do_stmts); 1592#ifdef BDEBUG 1593 if (dflag > 1) 1594 opt_dump(root); 1595#endif 1596 } while (!done); 1597} 1598 1599/* 1600 * Optimize the filter code in its dag representation. 1601 */ 1602void 1603bpf_optimize(rootp) 1604 struct block **rootp; 1605{ 1606 struct block *root; 1607 1608 root = *rootp; 1609 1610 opt_init(root); 1611 opt_loop(root, 0); 1612 opt_loop(root, 1); 1613 intern_blocks(root); 1614 opt_root(rootp); 1615 opt_cleanup(); 1616} 1617 1618static void 1619make_marks(p) 1620 struct block *p; 1621{ 1622 if (!isMarked(p)) { 1623 Mark(p); 1624 if (BPF_CLASS(p->s.code) != BPF_RET) { 1625 make_marks(JT(p)); 1626 make_marks(JF(p)); 1627 } 1628 } 1629} 1630 1631/* 1632 * Mark code array such that isMarked(i) is true 1633 * only for nodes that are alive. 1634 */ 1635static void 1636mark_code(p) 1637 struct block *p; 1638{ 1639 cur_mark += 1; 1640 make_marks(p); 1641} 1642 1643/* 1644 * True iff the two stmt lists load the same value from the packet into 1645 * the accumulator. 1646 */ 1647static int 1648eq_slist(x, y) 1649 struct slist *x, *y; 1650{ 1651 while (1) { 1652 while (x && x->s.code == NOP) 1653 x = x->next; 1654 while (y && y->s.code == NOP) 1655 y = y->next; 1656 if (x == 0) 1657 return y == 0; 1658 if (y == 0) 1659 return x == 0; 1660 if (x->s.code != y->s.code || x->s.k != y->s.k) 1661 return 0; 1662 x = x->next; 1663 y = y->next; 1664 } 1665} 1666 1667static inline int 1668eq_blk(b0, b1) 1669 struct block *b0, *b1; 1670{ 1671 if (b0->s.code == b1->s.code && 1672 b0->s.k == b1->s.k && 1673 b0->et.succ == b1->et.succ && 1674 b0->ef.succ == b1->ef.succ) 1675 return eq_slist(b0->stmts, b1->stmts); 1676 return 0; 1677} 1678 1679static void 1680intern_blocks(root) 1681 struct block *root; 1682{ 1683 struct block *p; 1684 int i, j; 1685 int done; 1686 top: 1687 done = 1; 1688 for (i = 0; i < n_blocks; ++i) 1689 blocks[i]->link = 0; 1690 1691 mark_code(root); 1692 1693 for (i = n_blocks - 1; --i >= 0; ) { 1694 if (!isMarked(blocks[i])) 1695 continue; 1696 for (j = i + 1; j < n_blocks; ++j) { 1697 if (!isMarked(blocks[j])) 1698 continue; 1699 if (eq_blk(blocks[i], blocks[j])) { 1700 blocks[i]->link = blocks[j]->link ? 1701 blocks[j]->link : blocks[j]; 1702 break; 1703 } 1704 } 1705 } 1706 for (i = 0; i < n_blocks; ++i) { 1707 p = blocks[i]; 1708 if (JT(p) == 0) 1709 continue; 1710 if (JT(p)->link) { 1711 done = 0; 1712 JT(p) = JT(p)->link; 1713 } 1714 if (JF(p)->link) { 1715 done = 0; 1716 JF(p) = JF(p)->link; 1717 } 1718 } 1719 if (!done) 1720 goto top; 1721} 1722 1723static void 1724opt_cleanup() 1725{ 1726 free((void *)vnode_base); 1727 free((void *)vmap); 1728 free((void *)edges); 1729 free((void *)space); 1730 free((void *)levels); 1731 free((void *)blocks); 1732} 1733 1734/* 1735 * Return the number of stmts in 's'. 1736 */ 1737static int 1738slength(s) 1739 struct slist *s; 1740{ 1741 int n = 0; 1742 1743 for (; s; s = s->next) 1744 if (s->s.code != NOP) 1745 ++n; 1746 return n; 1747} 1748 1749/* 1750 * Return the number of nodes reachable by 'p'. 1751 * All nodes should be initially unmarked. 1752 */ 1753static int 1754count_blocks(p) 1755 struct block *p; 1756{ 1757 if (p == 0 || isMarked(p)) 1758 return 0; 1759 Mark(p); 1760 return count_blocks(JT(p)) + count_blocks(JF(p)) + 1; 1761} 1762 1763/* 1764 * Do a depth first search on the flow graph, numbering the 1765 * the basic blocks, and entering them into the 'blocks' array.` 1766 */ 1767static void 1768number_blks_r(p) 1769 struct block *p; 1770{ 1771 int n; 1772 1773 if (p == 0 || isMarked(p)) 1774 return; 1775 1776 Mark(p); 1777 n = n_blocks++; 1778 p->id = n; 1779 blocks[n] = p; 1780 1781 number_blks_r(JT(p)); 1782 number_blks_r(JF(p)); 1783} 1784 1785/* 1786 * Return the number of stmts in the flowgraph reachable by 'p'. 1787 * The nodes should be unmarked before calling. 1788 * 1789 * Note that "stmts" means "instructions", and that this includes 1790 * 1791 * side-effect statements in 'p' (slength(p->stmts)); 1792 * 1793 * statements in the true branch from 'p' (count_stmts(JT(p))); 1794 * 1795 * statements in the false branch from 'p' (count_stmts(JF(p))); 1796 * 1797 * the conditional jump itself (1); 1798 * 1799 * an extra long jump if the true branch requires it (p->longjt); 1800 * 1801 * an extra long jump if the false branch requires it (p->longjf). 1802 */ 1803static int 1804count_stmts(p) 1805 struct block *p; 1806{ 1807 int n; 1808 1809 if (p == 0 || isMarked(p)) 1810 return 0; 1811 Mark(p); 1812 n = count_stmts(JT(p)) + count_stmts(JF(p)); 1813 return slength(p->stmts) + n + 1 + p->longjt + p->longjf; 1814} 1815 1816/* 1817 * Allocate memory. All allocation is done before optimization 1818 * is begun. A linear bound on the size of all data structures is computed 1819 * from the total number of blocks and/or statements. 1820 */ 1821static void 1822opt_init(root) 1823 struct block *root; 1824{ 1825 bpf_u_int32 *p; 1826 int i, n, max_stmts; 1827 1828 /* 1829 * First, count the blocks, so we can malloc an array to map 1830 * block number to block. Then, put the blocks into the array. 1831 */ 1832 unMarkAll(); 1833 n = count_blocks(root); 1834 blocks = (struct block **)malloc(n * sizeof(*blocks)); 1835 unMarkAll(); 1836 n_blocks = 0; 1837 number_blks_r(root); 1838 1839 n_edges = 2 * n_blocks; 1840 edges = (struct edge **)malloc(n_edges * sizeof(*edges)); 1841 1842 /* 1843 * The number of levels is bounded by the number of nodes. 1844 */ 1845 levels = (struct block **)malloc(n_blocks * sizeof(*levels)); 1846 1847 edgewords = n_edges / (8 * sizeof(bpf_u_int32)) + 1; 1848 nodewords = n_blocks / (8 * sizeof(bpf_u_int32)) + 1; 1849 1850 /* XXX */ 1851 space = (bpf_u_int32 *)malloc(2 * n_blocks * nodewords * sizeof(*space) 1852 + n_edges * edgewords * sizeof(*space)); 1853 p = space; 1854 all_dom_sets = p; 1855 for (i = 0; i < n; ++i) { 1856 blocks[i]->dom = p; 1857 p += nodewords; 1858 } 1859 all_closure_sets = p; 1860 for (i = 0; i < n; ++i) { 1861 blocks[i]->closure = p; 1862 p += nodewords; 1863 } 1864 all_edge_sets = p; 1865 for (i = 0; i < n; ++i) { 1866 register struct block *b = blocks[i]; 1867 1868 b->et.edom = p; 1869 p += edgewords; 1870 b->ef.edom = p; 1871 p += edgewords; 1872 b->et.id = i; 1873 edges[i] = &b->et; 1874 b->ef.id = n_blocks + i; 1875 edges[n_blocks + i] = &b->ef; 1876 b->et.pred = b; 1877 b->ef.pred = b; 1878 } 1879 max_stmts = 0; 1880 for (i = 0; i < n; ++i) 1881 max_stmts += slength(blocks[i]->stmts) + 1; 1882 /* 1883 * We allocate at most 3 value numbers per statement, 1884 * so this is an upper bound on the number of valnodes 1885 * we'll need. 1886 */ 1887 maxval = 3 * max_stmts; 1888 vmap = (struct vmapinfo *)malloc(maxval * sizeof(*vmap)); 1889 vnode_base = (struct valnode *)malloc(maxval * sizeof(*vnode_base)); 1890} 1891 1892/* 1893 * Some pointers used to convert the basic block form of the code, 1894 * into the array form that BPF requires. 'fstart' will point to 1895 * the malloc'd array while 'ftail' is used during the recursive traversal. 1896 */ 1897static struct bpf_insn *fstart; 1898static struct bpf_insn *ftail; 1899 1900#ifdef BDEBUG 1901int bids[1000]; 1902#endif 1903 1904/* 1905 * Returns true if successful. Returns false if a branch has 1906 * an offset that is too large. If so, we have marked that 1907 * branch so that on a subsequent iteration, it will be treated 1908 * properly. 1909 */ 1910static int 1911convert_code_r(p) 1912 struct block *p; 1913{ 1914 struct bpf_insn *dst; 1915 struct slist *src; 1916 int slen; 1917 u_int off; 1918 int extrajmps; /* number of extra jumps inserted */ 1919 struct slist **offset = NULL; 1920 1921 if (p == 0 || isMarked(p)) 1922 return (1); 1923 Mark(p); 1924 1925 if (convert_code_r(JF(p)) == 0) 1926 return (0); 1927 if (convert_code_r(JT(p)) == 0) 1928 return (0); 1929 1930 slen = slength(p->stmts); 1931 dst = ftail -= (slen + 1 + p->longjt + p->longjf); 1932 /* inflate length by any extra jumps */ 1933 1934 p->offset = dst - fstart; 1935 1936 /* generate offset[] for convenience */ 1937 if (slen) { 1938 offset = (struct slist **)calloc(sizeof(struct slist *), slen); 1939 if (!offset) { 1940 bpf_error("not enough core"); 1941 /*NOTREACHED*/ 1942 } 1943 } 1944 src = p->stmts; 1945 for (off = 0; off < slen && src; off++) { 1946#if 0 1947 printf("off=%d src=%x\n", off, src); 1948#endif 1949 offset[off] = src; 1950 src = src->next; 1951 } 1952 1953 off = 0; 1954 for (src = p->stmts; src; src = src->next) { 1955 if (src->s.code == NOP) 1956 continue; 1957 dst->code = (u_short)src->s.code; 1958 dst->k = src->s.k; 1959 1960 /* fill block-local relative jump */ 1961 if (BPF_CLASS(src->s.code) != BPF_JMP || src->s.code == (BPF_JMP|BPF_JA)) { 1962#if 0 1963 if (src->s.jt || src->s.jf) { 1964 bpf_error("illegal jmp destination"); 1965 /*NOTREACHED*/ 1966 } 1967#endif 1968 goto filled; 1969 } 1970 if (off == slen - 2) /*???*/ 1971 goto filled; 1972 1973 { 1974 int i; 1975 int jt, jf; 1976 char *ljerr = "%s for block-local relative jump: off=%d"; 1977 1978#if 0 1979 printf("code=%x off=%d %x %x\n", src->s.code, 1980 off, src->s.jt, src->s.jf); 1981#endif 1982 1983 if (!src->s.jt || !src->s.jf) { 1984 bpf_error(ljerr, "no jmp destination", off); 1985 /*NOTREACHED*/ 1986 } 1987 1988 jt = jf = 0; 1989 for (i = 0; i < slen; i++) { 1990 if (offset[i] == src->s.jt) { 1991 if (jt) { 1992 bpf_error(ljerr, "multiple matches", off); 1993 /*NOTREACHED*/ 1994 } 1995 1996 dst->jt = i - off - 1; 1997 jt++; 1998 } 1999 if (offset[i] == src->s.jf) { 2000 if (jf) { 2001 bpf_error(ljerr, "multiple matches", off); 2002 /*NOTREACHED*/ 2003 } 2004 dst->jf = i - off - 1; 2005 jf++; 2006 } 2007 } 2008 if (!jt || !jf) { 2009 bpf_error(ljerr, "no destination found", off); 2010 /*NOTREACHED*/ 2011 } 2012 } 2013filled: 2014 ++dst; 2015 ++off; 2016 } 2017 if (offset) 2018 free(offset); 2019 2020#ifdef BDEBUG 2021 bids[dst - fstart] = p->id + 1; 2022#endif 2023 dst->code = (u_short)p->s.code; 2024 dst->k = p->s.k; 2025 if (JT(p)) { 2026 extrajmps = 0; 2027 off = JT(p)->offset - (p->offset + slen) - 1; 2028 if (off >= 256) { 2029 /* offset too large for branch, must add a jump */ 2030 if (p->longjt == 0) { 2031 /* mark this instruction and retry */ 2032 p->longjt++; 2033 return(0); 2034 } 2035 /* branch if T to following jump */ 2036 dst->jt = extrajmps; 2037 extrajmps++; 2038 dst[extrajmps].code = BPF_JMP|BPF_JA; 2039 dst[extrajmps].k = off - extrajmps; 2040 } 2041 else 2042 dst->jt = off; 2043 off = JF(p)->offset - (p->offset + slen) - 1; 2044 if (off >= 256) { 2045 /* offset too large for branch, must add a jump */ 2046 if (p->longjf == 0) { 2047 /* mark this instruction and retry */ 2048 p->longjf++; 2049 return(0); 2050 } 2051 /* branch if F to following jump */ 2052 /* if two jumps are inserted, F goes to second one */ 2053 dst->jf = extrajmps; 2054 extrajmps++; 2055 dst[extrajmps].code = BPF_JMP|BPF_JA; 2056 dst[extrajmps].k = off - extrajmps; 2057 } 2058 else 2059 dst->jf = off; 2060 } 2061 return (1); 2062} 2063 2064 2065/* 2066 * Convert flowgraph intermediate representation to the 2067 * BPF array representation. Set *lenp to the number of instructions. 2068 */ 2069struct bpf_insn * 2070icode_to_fcode(root, lenp) 2071 struct block *root; 2072 int *lenp; 2073{ 2074 int n; 2075 struct bpf_insn *fp; 2076 2077 /* 2078 * Loop doing convert_codr_r() until no branches remain 2079 * with too-large offsets. 2080 */ 2081 while (1) { 2082 unMarkAll(); 2083 n = *lenp = count_stmts(root); 2084 2085 fp = (struct bpf_insn *)malloc(sizeof(*fp) * n); 2086 memset((char *)fp, 0, sizeof(*fp) * n); 2087 fstart = fp; 2088 ftail = fp + n; 2089 2090 unMarkAll(); 2091 if (convert_code_r(root)) 2092 break; 2093 free(fp); 2094 } 2095 2096 return fp; 2097} 2098 2099/* 2100 * Make a copy of a BPF program and put it in the "fcode" member of 2101 * a "pcap_t". 2102 * 2103 * If we fail to allocate memory for the copy, fill in the "errbuf" 2104 * member of the "pcap_t" with an error message, and return -1; 2105 * otherwise, return 0. 2106 */ 2107int 2108install_bpf_program(pcap_t *p, struct bpf_program *fp) 2109{ 2110 size_t prog_size; 2111 2112 /* 2113 * Free up any already installed program. 2114 */ 2115 pcap_freecode(&p->fcode); 2116 2117 prog_size = sizeof(*fp->bf_insns) * fp->bf_len; 2118 p->fcode.bf_len = fp->bf_len; 2119 p->fcode.bf_insns = (struct bpf_insn *)malloc(prog_size); 2120 if (p->fcode.bf_insns == NULL) { 2121 snprintf(p->errbuf, sizeof(p->errbuf), 2122 "malloc: %s", pcap_strerror(errno)); 2123 return (-1); 2124 } 2125 memcpy(p->fcode.bf_insns, fp->bf_insns, prog_size); 2126 return (0); 2127} 2128 2129#ifdef BDEBUG 2130static void 2131opt_dump(root) 2132 struct block *root; 2133{ 2134 struct bpf_program f; 2135 2136 memset(bids, 0, sizeof bids); 2137 f.bf_insns = icode_to_fcode(root, &f.bf_len); 2138 bpf_dump(&f, 1); 2139 putchar('\n'); 2140 free((char *)f.bf_insns); 2141} 2142#endif 2143