159static int convert_code_r(struct block *);
160#ifdef BDEBUG
161static void opt_dump(struct block *);
162#endif
163
164static int n_blocks;
165struct block **blocks;
166static int n_edges;
167struct edge **edges;
168
169/*
170 * A bit vector set representation of the dominators.
171 * We round up the set size to the next power of two.
172 */
173static int nodewords;
174static int edgewords;
175struct block **levels;
176bpf_u_int32 *space;
177#define BITS_PER_WORD (8*sizeof(bpf_u_int32))
178/*
179 * True if a is in uset {p}
180 */
181#define SET_MEMBER(p, a) \
182((p)[(unsigned)(a) / BITS_PER_WORD] & (1 << ((unsigned)(a) % BITS_PER_WORD)))
183
184/*
185 * Add 'a' to uset p.
186 */
187#define SET_INSERT(p, a) \
188(p)[(unsigned)(a) / BITS_PER_WORD] |= (1 << ((unsigned)(a) % BITS_PER_WORD))
189
190/*
191 * Delete 'a' from uset p.
192 */
193#define SET_DELETE(p, a) \
194(p)[(unsigned)(a) / BITS_PER_WORD] &= ~(1 << ((unsigned)(a) % BITS_PER_WORD))
195
196/*
197 * a := a intersect b
198 */
199#define SET_INTERSECT(a, b, n)\
200{\
201 register bpf_u_int32 *_x = a, *_y = b;\
202 register int _n = n;\
203 while (--_n >= 0) *_x++ &= *_y++;\
204}
205
206/*
207 * a := a - b
208 */
209#define SET_SUBTRACT(a, b, n)\
210{\
211 register bpf_u_int32 *_x = a, *_y = b;\
212 register int _n = n;\
213 while (--_n >= 0) *_x++ &=~ *_y++;\
214}
215
216/*
217 * a := a union b
218 */
219#define SET_UNION(a, b, n)\
220{\
221 register bpf_u_int32 *_x = a, *_y = b;\
222 register int _n = n;\
223 while (--_n >= 0) *_x++ |= *_y++;\
224}
225
226static uset all_dom_sets;
227static uset all_closure_sets;
228static uset all_edge_sets;
229
230#ifndef MAX
231#define MAX(a,b) ((a)>(b)?(a):(b))
232#endif
233
234static void
235find_levels_r(b)
236 struct block *b;
237{
238 int level;
239
240 if (isMarked(b))
241 return;
242
243 Mark(b);
244 b->link = 0;
245
246 if (JT(b)) {
247 find_levels_r(JT(b));
248 find_levels_r(JF(b));
249 level = MAX(JT(b)->level, JF(b)->level) + 1;
250 } else
251 level = 0;
252 b->level = level;
253 b->link = levels[level];
254 levels[level] = b;
255}
256
257/*
258 * Level graph. The levels go from 0 at the leaves to
259 * N_LEVELS at the root. The levels[] array points to the
260 * first node of the level list, whose elements are linked
261 * with the 'link' field of the struct block.
262 */
263static void
264find_levels(root)
265 struct block *root;
266{
267 memset((char *)levels, 0, n_blocks * sizeof(*levels));
268 unMarkAll();
269 find_levels_r(root);
270}
271
272/*
273 * Find dominator relationships.
274 * Assumes graph has been leveled.
275 */
276static void
277find_dom(root)
278 struct block *root;
279{
280 int i;
281 struct block *b;
282 bpf_u_int32 *x;
283
284 /*
285 * Initialize sets to contain all nodes.
286 */
287 x = all_dom_sets;
288 i = n_blocks * nodewords;
289 while (--i >= 0)
290 *x++ = ~0;
291 /* Root starts off empty. */
292 for (i = nodewords; --i >= 0;)
293 root->dom[i] = 0;
294
295 /* root->level is the highest level no found. */
296 for (i = root->level; i >= 0; --i) {
297 for (b = levels[i]; b; b = b->link) {
298 SET_INSERT(b->dom, b->id);
299 if (JT(b) == 0)
300 continue;
301 SET_INTERSECT(JT(b)->dom, b->dom, nodewords);
302 SET_INTERSECT(JF(b)->dom, b->dom, nodewords);
303 }
304 }
305}
306
307static void
308propedom(ep)
309 struct edge *ep;
310{
311 SET_INSERT(ep->edom, ep->id);
312 if (ep->succ) {
313 SET_INTERSECT(ep->succ->et.edom, ep->edom, edgewords);
314 SET_INTERSECT(ep->succ->ef.edom, ep->edom, edgewords);
315 }
316}
317
318/*
319 * Compute edge dominators.
320 * Assumes graph has been leveled and predecessors established.
321 */
322static void
323find_edom(root)
324 struct block *root;
325{
326 int i;
327 uset x;
328 struct block *b;
329
330 x = all_edge_sets;
331 for (i = n_edges * edgewords; --i >= 0; )
332 x[i] = ~0;
333
334 /* root->level is the highest level no found. */
335 memset(root->et.edom, 0, edgewords * sizeof(*(uset)0));
336 memset(root->ef.edom, 0, edgewords * sizeof(*(uset)0));
337 for (i = root->level; i >= 0; --i) {
338 for (b = levels[i]; b != 0; b = b->link) {
339 propedom(&b->et);
340 propedom(&b->ef);
341 }
342 }
343}
344
345/*
346 * Find the backwards transitive closure of the flow graph. These sets
347 * are backwards in the sense that we find the set of nodes that reach
348 * a given node, not the set of nodes that can be reached by a node.
349 *
350 * Assumes graph has been leveled.
351 */
352static void
353find_closure(root)
354 struct block *root;
355{
356 int i;
357 struct block *b;
358
359 /*
360 * Initialize sets to contain no nodes.
361 */
362 memset((char *)all_closure_sets, 0,
363 n_blocks * nodewords * sizeof(*all_closure_sets));
364
365 /* root->level is the highest level no found. */
366 for (i = root->level; i >= 0; --i) {
367 for (b = levels[i]; b; b = b->link) {
368 SET_INSERT(b->closure, b->id);
369 if (JT(b) == 0)
370 continue;
371 SET_UNION(JT(b)->closure, b->closure, nodewords);
372 SET_UNION(JF(b)->closure, b->closure, nodewords);
373 }
374 }
375}
376
377/*
378 * Return the register number that is used by s. If A and X are both
379 * used, return AX_ATOM. If no register is used, return -1.
380 *
381 * The implementation should probably change to an array access.
382 */
383static int
384atomuse(s)
385 struct stmt *s;
386{
387 register int c = s->code;
388
389 if (c == NOP)
390 return -1;
391
392 switch (BPF_CLASS(c)) {
393
394 case BPF_RET:
395 return (BPF_RVAL(c) == BPF_A) ? A_ATOM :
396 (BPF_RVAL(c) == BPF_X) ? X_ATOM : -1;
397
398 case BPF_LD:
399 case BPF_LDX:
400 return (BPF_MODE(c) == BPF_IND) ? X_ATOM :
401 (BPF_MODE(c) == BPF_MEM) ? s->k : -1;
402
403 case BPF_ST:
404 return A_ATOM;
405
406 case BPF_STX:
407 return X_ATOM;
408
409 case BPF_JMP:
410 case BPF_ALU:
411 if (BPF_SRC(c) == BPF_X)
412 return AX_ATOM;
413 return A_ATOM;
414
415 case BPF_MISC:
416 return BPF_MISCOP(c) == BPF_TXA ? X_ATOM : A_ATOM;
417 }
418 abort();
419 /* NOTREACHED */
420}
421
422/*
423 * Return the register number that is defined by 's'. We assume that
424 * a single stmt cannot define more than one register. If no register
425 * is defined, return -1.
426 *
427 * The implementation should probably change to an array access.
428 */
429static int
430atomdef(s)
431 struct stmt *s;
432{
433 if (s->code == NOP)
434 return -1;
435
436 switch (BPF_CLASS(s->code)) {
437
438 case BPF_LD:
439 case BPF_ALU:
440 return A_ATOM;
441
442 case BPF_LDX:
443 return X_ATOM;
444
445 case BPF_ST:
446 case BPF_STX:
447 return s->k;
448
449 case BPF_MISC:
450 return BPF_MISCOP(s->code) == BPF_TAX ? X_ATOM : A_ATOM;
451 }
452 return -1;
453}
454
455/*
456 * Compute the sets of registers used, defined, and killed by 'b'.
457 *
458 * "Used" means that a statement in 'b' uses the register before any
459 * statement in 'b' defines it, i.e. it uses the value left in
460 * that register by a predecessor block of this block.
461 * "Defined" means that a statement in 'b' defines it.
462 * "Killed" means that a statement in 'b' defines it before any
463 * statement in 'b' uses it, i.e. it kills the value left in that
464 * register by a predecessor block of this block.
465 */
466static void
467compute_local_ud(b)
468 struct block *b;
469{
470 struct slist *s;
471 atomset def = 0, use = 0, kill = 0;
472 int atom;
473
474 for (s = b->stmts; s; s = s->next) {
475 if (s->s.code == NOP)
476 continue;
477 atom = atomuse(&s->s);
478 if (atom >= 0) {
479 if (atom == AX_ATOM) {
480 if (!ATOMELEM(def, X_ATOM))
481 use |= ATOMMASK(X_ATOM);
482 if (!ATOMELEM(def, A_ATOM))
483 use |= ATOMMASK(A_ATOM);
484 }
485 else if (atom < N_ATOMS) {
486 if (!ATOMELEM(def, atom))
487 use |= ATOMMASK(atom);
488 }
489 else
490 abort();
491 }
492 atom = atomdef(&s->s);
493 if (atom >= 0) {
494 if (!ATOMELEM(use, atom))
495 kill |= ATOMMASK(atom);
496 def |= ATOMMASK(atom);
497 }
498 }
499 if (BPF_CLASS(b->s.code) == BPF_JMP) {
500 /*
501 * XXX - what about RET?
502 */
503 atom = atomuse(&b->s);
504 if (atom >= 0) {
505 if (atom == AX_ATOM) {
506 if (!ATOMELEM(def, X_ATOM))
507 use |= ATOMMASK(X_ATOM);
508 if (!ATOMELEM(def, A_ATOM))
509 use |= ATOMMASK(A_ATOM);
510 }
511 else if (atom < N_ATOMS) {
512 if (!ATOMELEM(def, atom))
513 use |= ATOMMASK(atom);
514 }
515 else
516 abort();
517 }
518 }
519
520 b->def = def;
521 b->kill = kill;
522 b->in_use = use;
523}
524
525/*
526 * Assume graph is already leveled.
527 */
528static void
529find_ud(root)
530 struct block *root;
531{
532 int i, maxlevel;
533 struct block *p;
534
535 /*
536 * root->level is the highest level no found;
537 * count down from there.
538 */
539 maxlevel = root->level;
540 for (i = maxlevel; i >= 0; --i)
541 for (p = levels[i]; p; p = p->link) {
542 compute_local_ud(p);
543 p->out_use = 0;
544 }
545
546 for (i = 1; i <= maxlevel; ++i) {
547 for (p = levels[i]; p; p = p->link) {
548 p->out_use |= JT(p)->in_use | JF(p)->in_use;
549 p->in_use |= p->out_use &~ p->kill;
550 }
551 }
552}
553
554/*
555 * These data structures are used in a Cocke and Shwarz style
556 * value numbering scheme. Since the flowgraph is acyclic,
557 * exit values can be propagated from a node's predecessors
558 * provided it is uniquely defined.
559 */
560struct valnode {
561 int code;
562 int v0, v1;
563 int val;
564 struct valnode *next;
565};
566
567#define MODULUS 213
568static struct valnode *hashtbl[MODULUS];
569static int curval;
570static int maxval;
571
572/* Integer constants mapped with the load immediate opcode. */
573#define K(i) F(BPF_LD|BPF_IMM|BPF_W, i, 0L)
574
575struct vmapinfo {
576 int is_const;
577 bpf_int32 const_val;
578};
579
580struct vmapinfo *vmap;
581struct valnode *vnode_base;
582struct valnode *next_vnode;
583
584static void
585init_val()
586{
587 curval = 0;
588 next_vnode = vnode_base;
589 memset((char *)vmap, 0, maxval * sizeof(*vmap));
590 memset((char *)hashtbl, 0, sizeof hashtbl);
591}
592
593/* Because we really don't have an IR, this stuff is a little messy. */
594static int
595F(code, v0, v1)
596 int code;
597 int v0, v1;
598{
599 u_int hash;
600 int val;
601 struct valnode *p;
602
603 hash = (u_int)code ^ (v0 << 4) ^ (v1 << 8);
604 hash %= MODULUS;
605
606 for (p = hashtbl[hash]; p; p = p->next)
607 if (p->code == code && p->v0 == v0 && p->v1 == v1)
608 return p->val;
609
610 val = ++curval;
611 if (BPF_MODE(code) == BPF_IMM &&
612 (BPF_CLASS(code) == BPF_LD || BPF_CLASS(code) == BPF_LDX)) {
613 vmap[val].const_val = v0;
614 vmap[val].is_const = 1;
615 }
616 p = next_vnode++;
617 p->val = val;
618 p->code = code;
619 p->v0 = v0;
620 p->v1 = v1;
621 p->next = hashtbl[hash];
622 hashtbl[hash] = p;
623
624 return val;
625}
626
627static inline void
628vstore(s, valp, newval, alter)
629 struct stmt *s;
630 int *valp;
631 int newval;
632 int alter;
633{
634 if (alter && *valp == newval)
635 s->code = NOP;
636 else
637 *valp = newval;
638}
639
640static void
641fold_op(s, v0, v1)
642 struct stmt *s;
643 int v0, v1;
644{
645 bpf_u_int32 a, b;
646
647 a = vmap[v0].const_val;
648 b = vmap[v1].const_val;
649
650 switch (BPF_OP(s->code)) {
651 case BPF_ADD:
652 a += b;
653 break;
654
655 case BPF_SUB:
656 a -= b;
657 break;
658
659 case BPF_MUL:
660 a *= b;
661 break;
662
663 case BPF_DIV:
664 if (b == 0)
665 bpf_error("division by zero");
666 a /= b;
667 break;
668
669 case BPF_AND:
670 a &= b;
671 break;
672
673 case BPF_OR:
674 a |= b;
675 break;
676
677 case BPF_LSH:
678 a <<= b;
679 break;
680
681 case BPF_RSH:
682 a >>= b;
683 break;
684
685 case BPF_NEG:
686 a = -a;
687 break;
688
689 default:
690 abort();
691 }
692 s->k = a;
693 s->code = BPF_LD|BPF_IMM;
694 done = 0;
695}
696
697static inline struct slist *
698this_op(s)
699 struct slist *s;
700{
701 while (s != 0 && s->s.code == NOP)
702 s = s->next;
703 return s;
704}
705
706static void
707opt_not(b)
708 struct block *b;
709{
710 struct block *tmp = JT(b);
711
712 JT(b) = JF(b);
713 JF(b) = tmp;
714}
715
716static void
717opt_peep(b)
718 struct block *b;
719{
720 struct slist *s;
721 struct slist *next, *last;
722 int val;
723
724 s = b->stmts;
725 if (s == 0)
726 return;
727
728 last = s;
729 for (/*empty*/; /*empty*/; s = next) {
730 /*
731 * Skip over nops.
732 */
733 s = this_op(s);
734 if (s == 0)
735 break; /* nothing left in the block */
736
737 /*
738 * Find the next real instruction after that one
739 * (skipping nops).
740 */
741 next = this_op(s->next);
742 if (next == 0)
743 break; /* no next instruction */
744 last = next;
745
746 /*
747 * st M[k] --> st M[k]
748 * ldx M[k] tax
749 */
750 if (s->s.code == BPF_ST &&
751 next->s.code == (BPF_LDX|BPF_MEM) &&
752 s->s.k == next->s.k) {
753 done = 0;
754 next->s.code = BPF_MISC|BPF_TAX;
755 }
756 /*
757 * ld #k --> ldx #k
758 * tax txa
759 */
760 if (s->s.code == (BPF_LD|BPF_IMM) &&
761 next->s.code == (BPF_MISC|BPF_TAX)) {
762 s->s.code = BPF_LDX|BPF_IMM;
763 next->s.code = BPF_MISC|BPF_TXA;
764 done = 0;
765 }
766 /*
767 * This is an ugly special case, but it happens
768 * when you say tcp[k] or udp[k] where k is a constant.
769 */
770 if (s->s.code == (BPF_LD|BPF_IMM)) {
771 struct slist *add, *tax, *ild;
772
773 /*
774 * Check that X isn't used on exit from this
775 * block (which the optimizer might cause).
776 * We know the code generator won't generate
777 * any local dependencies.
778 */
779 if (ATOMELEM(b->out_use, X_ATOM))
780 continue;
781
782 /*
783 * Check that the instruction following the ldi
784 * is an addx, or it's an ldxms with an addx
785 * following it (with 0 or more nops between the
786 * ldxms and addx).
787 */
788 if (next->s.code != (BPF_LDX|BPF_MSH|BPF_B))
789 add = next;
790 else
791 add = this_op(next->next);
792 if (add == 0 || add->s.code != (BPF_ALU|BPF_ADD|BPF_X))
793 continue;
794
795 /*
796 * Check that a tax follows that (with 0 or more
797 * nops between them).
798 */
799 tax = this_op(add->next);
800 if (tax == 0 || tax->s.code != (BPF_MISC|BPF_TAX))
801 continue;
802
803 /*
804 * Check that an ild follows that (with 0 or more
805 * nops between them).
806 */
807 ild = this_op(tax->next);
808 if (ild == 0 || BPF_CLASS(ild->s.code) != BPF_LD ||
809 BPF_MODE(ild->s.code) != BPF_IND)
810 continue;
811 /*
812 * We want to turn this sequence:
813 *
814 * (004) ldi #0x2 {s}
815 * (005) ldxms [14] {next} -- optional
816 * (006) addx {add}
817 * (007) tax {tax}
818 * (008) ild [x+0] {ild}
819 *
820 * into this sequence:
821 *
822 * (004) nop
823 * (005) ldxms [14]
824 * (006) nop
825 * (007) nop
826 * (008) ild [x+2]
827 *
828 * XXX We need to check that X is not
829 * subsequently used, because we want to change
830 * what'll be in it after this sequence.
831 *
832 * We know we can eliminate the accumulator
833 * modifications earlier in the sequence since
834 * it is defined by the last stmt of this sequence
835 * (i.e., the last statement of the sequence loads
836 * a value into the accumulator, so we can eliminate
837 * earlier operations on the accumulator).
838 */
839 ild->s.k += s->s.k;
840 s->s.code = NOP;
841 add->s.code = NOP;
842 tax->s.code = NOP;
843 done = 0;
844 }
845 }
846 /*
847 * If the comparison at the end of a block is an equality
848 * comparison against a constant, and nobody uses the value
849 * we leave in the A register at the end of a block, and
850 * the operation preceding the comparison is an arithmetic
851 * operation, we can sometime optimize it away.
852 */
853 if (b->s.code == (BPF_JMP|BPF_JEQ|BPF_K) &&
854 !ATOMELEM(b->out_use, A_ATOM)) {
855 /*
856 * We can optimize away certain subtractions of the
857 * X register.
858 */
859 if (last->s.code == (BPF_ALU|BPF_SUB|BPF_X)) {
860 val = b->val[X_ATOM];
861 if (vmap[val].is_const) {
862 /*
863 * If we have a subtract to do a comparison,
864 * and the X register is a known constant,
865 * we can merge this value into the
866 * comparison:
867 *
868 * sub x -> nop
869 * jeq #y jeq #(x+y)
870 */
871 b->s.k += vmap[val].const_val;
872 last->s.code = NOP;
873 done = 0;
874 } else if (b->s.k == 0) {
875 /*
876 * If the X register isn't a constant,
877 * and the comparison in the test is
878 * against 0, we can compare with the
879 * X register, instead:
880 *
881 * sub x -> nop
882 * jeq #0 jeq x
883 */
884 last->s.code = NOP;
885 b->s.code = BPF_JMP|BPF_JEQ|BPF_X;
886 done = 0;
887 }
888 }
889 /*
890 * Likewise, a constant subtract can be simplified:
891 *
892 * sub #x -> nop
893 * jeq #y -> jeq #(x+y)
894 */
895 else if (last->s.code == (BPF_ALU|BPF_SUB|BPF_K)) {
896 last->s.code = NOP;
897 b->s.k += last->s.k;
898 done = 0;
899 }
900 /*
901 * And, similarly, a constant AND can be simplified
902 * if we're testing against 0, i.e.:
903 *
904 * and #k nop
905 * jeq #0 -> jset #k
906 */
907 else if (last->s.code == (BPF_ALU|BPF_AND|BPF_K) &&
908 b->s.k == 0) {
909 b->s.k = last->s.k;
910 b->s.code = BPF_JMP|BPF_K|BPF_JSET;
911 last->s.code = NOP;
912 done = 0;
913 opt_not(b);
914 }
915 }
916 /*
917 * jset #0 -> never
918 * jset #ffffffff -> always
919 */
920 if (b->s.code == (BPF_JMP|BPF_K|BPF_JSET)) {
921 if (b->s.k == 0)
922 JT(b) = JF(b);
923 if (b->s.k == 0xffffffff)
924 JF(b) = JT(b);
925 }
926 /*
927 * If we're comparing against the index register, and the index
928 * register is a known constant, we can just compare against that
929 * constant.
930 */
931 val = b->val[X_ATOM];
932 if (vmap[val].is_const && BPF_SRC(b->s.code) == BPF_X) {
933 bpf_int32 v = vmap[val].const_val;
934 b->s.code &= ~BPF_X;
935 b->s.k = v;
936 }
937 /*
938 * If the accumulator is a known constant, we can compute the
939 * comparison result.
940 */
941 val = b->val[A_ATOM];
942 if (vmap[val].is_const && BPF_SRC(b->s.code) == BPF_K) {
943 bpf_int32 v = vmap[val].const_val;
944 switch (BPF_OP(b->s.code)) {
945
946 case BPF_JEQ:
947 v = v == b->s.k;
948 break;
949
950 case BPF_JGT:
951 v = (unsigned)v > b->s.k;
952 break;
953
954 case BPF_JGE:
955 v = (unsigned)v >= b->s.k;
956 break;
957
958 case BPF_JSET:
959 v &= b->s.k;
960 break;
961
962 default:
963 abort();
964 }
965 if (JF(b) != JT(b))
966 done = 0;
967 if (v)
968 JF(b) = JT(b);
969 else
970 JT(b) = JF(b);
971 }
972}
973
974/*
975 * Compute the symbolic value of expression of 's', and update
976 * anything it defines in the value table 'val'. If 'alter' is true,
977 * do various optimizations. This code would be cleaner if symbolic
978 * evaluation and code transformations weren't folded together.
979 */
980static void
981opt_stmt(s, val, alter)
982 struct stmt *s;
983 int val[];
984 int alter;
985{
986 int op;
987 int v;
988
989 switch (s->code) {
990
991 case BPF_LD|BPF_ABS|BPF_W:
992 case BPF_LD|BPF_ABS|BPF_H:
993 case BPF_LD|BPF_ABS|BPF_B:
994 v = F(s->code, s->k, 0L);
995 vstore(s, &val[A_ATOM], v, alter);
996 break;
997
998 case BPF_LD|BPF_IND|BPF_W:
999 case BPF_LD|BPF_IND|BPF_H:
1000 case BPF_LD|BPF_IND|BPF_B:
1001 v = val[X_ATOM];
1002 if (alter && vmap[v].is_const) {
1003 s->code = BPF_LD|BPF_ABS|BPF_SIZE(s->code);
1004 s->k += vmap[v].const_val;
1005 v = F(s->code, s->k, 0L);
1006 done = 0;
1007 }
1008 else
1009 v = F(s->code, s->k, v);
1010 vstore(s, &val[A_ATOM], v, alter);
1011 break;
1012
1013 case BPF_LD|BPF_LEN:
1014 v = F(s->code, 0L, 0L);
1015 vstore(s, &val[A_ATOM], v, alter);
1016 break;
1017
1018 case BPF_LD|BPF_IMM:
1019 v = K(s->k);
1020 vstore(s, &val[A_ATOM], v, alter);
1021 break;
1022
1023 case BPF_LDX|BPF_IMM:
1024 v = K(s->k);
1025 vstore(s, &val[X_ATOM], v, alter);
1026 break;
1027
1028 case BPF_LDX|BPF_MSH|BPF_B:
1029 v = F(s->code, s->k, 0L);
1030 vstore(s, &val[X_ATOM], v, alter);
1031 break;
1032
1033 case BPF_ALU|BPF_NEG:
1034 if (alter && vmap[val[A_ATOM]].is_const) {
1035 s->code = BPF_LD|BPF_IMM;
1036 s->k = -vmap[val[A_ATOM]].const_val;
1037 val[A_ATOM] = K(s->k);
1038 }
1039 else
1040 val[A_ATOM] = F(s->code, val[A_ATOM], 0L);
1041 break;
1042
1043 case BPF_ALU|BPF_ADD|BPF_K:
1044 case BPF_ALU|BPF_SUB|BPF_K:
1045 case BPF_ALU|BPF_MUL|BPF_K:
1046 case BPF_ALU|BPF_DIV|BPF_K:
1047 case BPF_ALU|BPF_AND|BPF_K:
1048 case BPF_ALU|BPF_OR|BPF_K:
1049 case BPF_ALU|BPF_LSH|BPF_K:
1050 case BPF_ALU|BPF_RSH|BPF_K:
1051 op = BPF_OP(s->code);
1052 if (alter) {
1053 if (s->k == 0) {
1054 /* don't optimize away "sub #0"
1055 * as it may be needed later to
1056 * fixup the generated math code */
1057 if (op == BPF_ADD ||
1058 op == BPF_LSH || op == BPF_RSH ||
1059 op == BPF_OR) {
1060 s->code = NOP;
1061 break;
1062 }
1063 if (op == BPF_MUL || op == BPF_AND) {
1064 s->code = BPF_LD|BPF_IMM;
1065 val[A_ATOM] = K(s->k);
1066 break;
1067 }
1068 }
1069 if (vmap[val[A_ATOM]].is_const) {
1070 fold_op(s, val[A_ATOM], K(s->k));
1071 val[A_ATOM] = K(s->k);
1072 break;
1073 }
1074 }
1075 val[A_ATOM] = F(s->code, val[A_ATOM], K(s->k));
1076 break;
1077
1078 case BPF_ALU|BPF_ADD|BPF_X:
1079 case BPF_ALU|BPF_SUB|BPF_X:
1080 case BPF_ALU|BPF_MUL|BPF_X:
1081 case BPF_ALU|BPF_DIV|BPF_X:
1082 case BPF_ALU|BPF_AND|BPF_X:
1083 case BPF_ALU|BPF_OR|BPF_X:
1084 case BPF_ALU|BPF_LSH|BPF_X:
1085 case BPF_ALU|BPF_RSH|BPF_X:
1086 op = BPF_OP(s->code);
1087 if (alter && vmap[val[X_ATOM]].is_const) {
1088 if (vmap[val[A_ATOM]].is_const) {
1089 fold_op(s, val[A_ATOM], val[X_ATOM]);
1090 val[A_ATOM] = K(s->k);
1091 }
1092 else {
1093 s->code = BPF_ALU|BPF_K|op;
1094 s->k = vmap[val[X_ATOM]].const_val;
1095 done = 0;
1096 val[A_ATOM] =
1097 F(s->code, val[A_ATOM], K(s->k));
1098 }
1099 break;
1100 }
1101 /*
1102 * Check if we're doing something to an accumulator
1103 * that is 0, and simplify. This may not seem like
1104 * much of a simplification but it could open up further
1105 * optimizations.
1106 * XXX We could also check for mul by 1, etc.
1107 */
1108 if (alter && vmap[val[A_ATOM]].is_const
1109 && vmap[val[A_ATOM]].const_val == 0) {
1110 if (op == BPF_ADD || op == BPF_OR) {
1111 s->code = BPF_MISC|BPF_TXA;
1112 vstore(s, &val[A_ATOM], val[X_ATOM], alter);
1113 break;
1114 }
1115 else if (op == BPF_MUL || op == BPF_DIV ||
1116 op == BPF_AND || op == BPF_LSH || op == BPF_RSH) {
1117 s->code = BPF_LD|BPF_IMM;
1118 s->k = 0;
1119 vstore(s, &val[A_ATOM], K(s->k), alter);
1120 break;
1121 }
1122 else if (op == BPF_NEG) {
1123 s->code = NOP;
1124 break;
1125 }
1126 }
1127 val[A_ATOM] = F(s->code, val[A_ATOM], val[X_ATOM]);
1128 break;
1129
1130 case BPF_MISC|BPF_TXA:
1131 vstore(s, &val[A_ATOM], val[X_ATOM], alter);
1132 break;
1133
1134 case BPF_LD|BPF_MEM:
1135 v = val[s->k];
1136 if (alter && vmap[v].is_const) {
1137 s->code = BPF_LD|BPF_IMM;
1138 s->k = vmap[v].const_val;
1139 done = 0;
1140 }
1141 vstore(s, &val[A_ATOM], v, alter);
1142 break;
1143
1144 case BPF_MISC|BPF_TAX:
1145 vstore(s, &val[X_ATOM], val[A_ATOM], alter);
1146 break;
1147
1148 case BPF_LDX|BPF_MEM:
1149 v = val[s->k];
1150 if (alter && vmap[v].is_const) {
1151 s->code = BPF_LDX|BPF_IMM;
1152 s->k = vmap[v].const_val;
1153 done = 0;
1154 }
1155 vstore(s, &val[X_ATOM], v, alter);
1156 break;
1157
1158 case BPF_ST:
1159 vstore(s, &val[s->k], val[A_ATOM], alter);
1160 break;
1161
1162 case BPF_STX:
1163 vstore(s, &val[s->k], val[X_ATOM], alter);
1164 break;
1165 }
1166}
1167
1168static void
1169deadstmt(s, last)
1170 register struct stmt *s;
1171 register struct stmt *last[];
1172{
1173 register int atom;
1174
1175 atom = atomuse(s);
1176 if (atom >= 0) {
1177 if (atom == AX_ATOM) {
1178 last[X_ATOM] = 0;
1179 last[A_ATOM] = 0;
1180 }
1181 else
1182 last[atom] = 0;
1183 }
1184 atom = atomdef(s);
1185 if (atom >= 0) {
1186 if (last[atom]) {
1187 done = 0;
1188 last[atom]->code = NOP;
1189 }
1190 last[atom] = s;
1191 }
1192}
1193
1194static void
1195opt_deadstores(b)
1196 register struct block *b;
1197{
1198 register struct slist *s;
1199 register int atom;
1200 struct stmt *last[N_ATOMS];
1201
1202 memset((char *)last, 0, sizeof last);
1203
1204 for (s = b->stmts; s != 0; s = s->next)
1205 deadstmt(&s->s, last);
1206 deadstmt(&b->s, last);
1207
1208 for (atom = 0; atom < N_ATOMS; ++atom)
1209 if (last[atom] && !ATOMELEM(b->out_use, atom)) {
1210 last[atom]->code = NOP;
1211 done = 0;
1212 }
1213}
1214
1215static void
1216opt_blk(b, do_stmts)
1217 struct block *b;
1218 int do_stmts;
1219{
1220 struct slist *s;
1221 struct edge *p;
1222 int i;
1223 bpf_int32 aval, xval;
1224
1225#if 0
1226 for (s = b->stmts; s && s->next; s = s->next)
1227 if (BPF_CLASS(s->s.code) == BPF_JMP) {
1228 do_stmts = 0;
1229 break;
1230 }
1231#endif
1232
1233 /*
1234 * Initialize the atom values.
1235 */
1236 p = b->in_edges;
1237 if (p == 0) {
1238 /*
1239 * We have no predecessors, so everything is undefined
1240 * upon entry to this block.
1241 */
1242 memset((char *)b->val, 0, sizeof(b->val));
1243 } else {
1244 /*
1245 * Inherit values from our predecessors.
1246 *
1247 * First, get the values from the predecessor along the
1248 * first edge leading to this node.
1249 */
1250 memcpy((char *)b->val, (char *)p->pred->val, sizeof(b->val));
1251 /*
1252 * Now look at all the other nodes leading to this node.
1253 * If, for the predecessor along that edge, a register
1254 * has a different value from the one we have (i.e.,
1255 * control paths are merging, and the merging paths
1256 * assign different values to that register), give the
1257 * register the undefined value of 0.
1258 */
1259 while ((p = p->next) != NULL) {
1260 for (i = 0; i < N_ATOMS; ++i)
1261 if (b->val[i] != p->pred->val[i])
1262 b->val[i] = 0;
1263 }
1264 }
1265 aval = b->val[A_ATOM];
1266 xval = b->val[X_ATOM];
1267 for (s = b->stmts; s; s = s->next)
1268 opt_stmt(&s->s, b->val, do_stmts);
1269
1270 /*
1271 * This is a special case: if we don't use anything from this
1272 * block, and we load the accumulator or index register with a
1273 * value that is already there, or if this block is a return,
1274 * eliminate all the statements.
1275 *
1276 * XXX - what if it does a store?
1277 *
1278 * XXX - why does it matter whether we use anything from this
1279 * block? If the accumulator or index register doesn't change
1280 * its value, isn't that OK even if we use that value?
1281 *
1282 * XXX - if we load the accumulator with a different value,
1283 * and the block ends with a conditional branch, we obviously
1284 * can't eliminate it, as the branch depends on that value.
1285 * For the index register, the conditional branch only depends
1286 * on the index register value if the test is against the index
1287 * register value rather than a constant; if nothing uses the
1288 * value we put into the index register, and we're not testing
1289 * against the index register's value, and there aren't any
1290 * other problems that would keep us from eliminating this
1291 * block, can we eliminate it?
1292 */
1293 if (do_stmts &&
1294 ((b->out_use == 0 && aval != 0 && b->val[A_ATOM] == aval &&
1295 xval != 0 && b->val[X_ATOM] == xval) ||
1296 BPF_CLASS(b->s.code) == BPF_RET)) {
1297 if (b->stmts != 0) {
1298 b->stmts = 0;
1299 done = 0;
1300 }
1301 } else {
1302 opt_peep(b);
1303 opt_deadstores(b);
1304 }
1305 /*
1306 * Set up values for branch optimizer.
1307 */
1308 if (BPF_SRC(b->s.code) == BPF_K)
1309 b->oval = K(b->s.k);
1310 else
1311 b->oval = b->val[X_ATOM];
1312 b->et.code = b->s.code;
1313 b->ef.code = -b->s.code;
1314}
1315
1316/*
1317 * Return true if any register that is used on exit from 'succ', has
1318 * an exit value that is different from the corresponding exit value
1319 * from 'b'.
1320 */
1321static int
1322use_conflict(b, succ)
1323 struct block *b, *succ;
1324{
1325 int atom;
1326 atomset use = succ->out_use;
1327
1328 if (use == 0)
1329 return 0;
1330
1331 for (atom = 0; atom < N_ATOMS; ++atom)
1332 if (ATOMELEM(use, atom))
1333 if (b->val[atom] != succ->val[atom])
1334 return 1;
1335 return 0;
1336}
1337
1338static struct block *
1339fold_edge(child, ep)
1340 struct block *child;
1341 struct edge *ep;
1342{
1343 int sense;
1344 int aval0, aval1, oval0, oval1;
1345 int code = ep->code;
1346
1347 if (code < 0) {
1348 code = -code;
1349 sense = 0;
1350 } else
1351 sense = 1;
1352
1353 if (child->s.code != code)
1354 return 0;
1355
1356 aval0 = child->val[A_ATOM];
1357 oval0 = child->oval;
1358 aval1 = ep->pred->val[A_ATOM];
1359 oval1 = ep->pred->oval;
1360
1361 if (aval0 != aval1)
1362 return 0;
1363
1364 if (oval0 == oval1)
1365 /*
1366 * The operands of the branch instructions are
1367 * identical, so the result is true if a true
1368 * branch was taken to get here, otherwise false.
1369 */
1370 return sense ? JT(child) : JF(child);
1371
1372 if (sense && code == (BPF_JMP|BPF_JEQ|BPF_K))
1373 /*
1374 * At this point, we only know the comparison if we
1375 * came down the true branch, and it was an equality
1376 * comparison with a constant.
1377 *
1378 * I.e., if we came down the true branch, and the branch
1379 * was an equality comparison with a constant, we know the
1380 * accumulator contains that constant. If we came down
1381 * the false branch, or the comparison wasn't with a
1382 * constant, we don't know what was in the accumulator.
1383 *
1384 * We rely on the fact that distinct constants have distinct
1385 * value numbers.
1386 */
1387 return JF(child);
1388
1389 return 0;
1390}
1391
1392static void
1393opt_j(ep)
1394 struct edge *ep;
1395{
1396 register int i, k;
1397 register struct block *target;
1398
1399 if (JT(ep->succ) == 0)
1400 return;
1401
1402 if (JT(ep->succ) == JF(ep->succ)) {
1403 /*
1404 * Common branch targets can be eliminated, provided
1405 * there is no data dependency.
1406 */
1407 if (!use_conflict(ep->pred, ep->succ->et.succ)) {
1408 done = 0;
1409 ep->succ = JT(ep->succ);
1410 }
1411 }
1412 /*
1413 * For each edge dominator that matches the successor of this
1414 * edge, promote the edge successor to the its grandchild.
1415 *
1416 * XXX We violate the set abstraction here in favor a reasonably
1417 * efficient loop.
1418 */
1419 top:
1420 for (i = 0; i < edgewords; ++i) {
1421 register bpf_u_int32 x = ep->edom[i];
1422
1423 while (x != 0) {
1424 k = ffs(x) - 1;
1425 x &=~ (1 << k);
1426 k += i * BITS_PER_WORD;
1427
1428 target = fold_edge(ep->succ, edges[k]);
1429 /*
1430 * Check that there is no data dependency between
1431 * nodes that will be violated if we move the edge.
1432 */
1433 if (target != 0 && !use_conflict(ep->pred, target)) {
1434 done = 0;
1435 ep->succ = target;
1436 if (JT(target) != 0)
1437 /*
1438 * Start over unless we hit a leaf.
1439 */
1440 goto top;
1441 return;
1442 }
1443 }
1444 }
1445}
1446
1447
1448static void
1449or_pullup(b)
1450 struct block *b;
1451{
1452 int val, at_top;
1453 struct block *pull;
1454 struct block **diffp, **samep;
1455 struct edge *ep;
1456
1457 ep = b->in_edges;
1458 if (ep == 0)
1459 return;
1460
1461 /*
1462 * Make sure each predecessor loads the same value.
1463 * XXX why?
1464 */
1465 val = ep->pred->val[A_ATOM];
1466 for (ep = ep->next; ep != 0; ep = ep->next)
1467 if (val != ep->pred->val[A_ATOM])
1468 return;
1469
1470 if (JT(b->in_edges->pred) == b)
1471 diffp = &JT(b->in_edges->pred);
1472 else
1473 diffp = &JF(b->in_edges->pred);
1474
1475 at_top = 1;
1476 while (1) {
1477 if (*diffp == 0)
1478 return;
1479
1480 if (JT(*diffp) != JT(b))
1481 return;
1482
1483 if (!SET_MEMBER((*diffp)->dom, b->id))
1484 return;
1485
1486 if ((*diffp)->val[A_ATOM] != val)
1487 break;
1488
1489 diffp = &JF(*diffp);
1490 at_top = 0;
1491 }
1492 samep = &JF(*diffp);
1493 while (1) {
1494 if (*samep == 0)
1495 return;
1496
1497 if (JT(*samep) != JT(b))
1498 return;
1499
1500 if (!SET_MEMBER((*samep)->dom, b->id))
1501 return;
1502
1503 if ((*samep)->val[A_ATOM] == val)
1504 break;
1505
1506 /* XXX Need to check that there are no data dependencies
1507 between dp0 and dp1. Currently, the code generator
1508 will not produce such dependencies. */
1509 samep = &JF(*samep);
1510 }
1511#ifdef notdef
1512 /* XXX This doesn't cover everything. */
1513 for (i = 0; i < N_ATOMS; ++i)
1514 if ((*samep)->val[i] != pred->val[i])
1515 return;
1516#endif
1517 /* Pull up the node. */
1518 pull = *samep;
1519 *samep = JF(pull);
1520 JF(pull) = *diffp;
1521
1522 /*
1523 * At the top of the chain, each predecessor needs to point at the
1524 * pulled up node. Inside the chain, there is only one predecessor
1525 * to worry about.
1526 */
1527 if (at_top) {
1528 for (ep = b->in_edges; ep != 0; ep = ep->next) {
1529 if (JT(ep->pred) == b)
1530 JT(ep->pred) = pull;
1531 else
1532 JF(ep->pred) = pull;
1533 }
1534 }
1535 else
1536 *diffp = pull;
1537
1538 done = 0;
1539}
1540
1541static void
1542and_pullup(b)
1543 struct block *b;
1544{
1545 int val, at_top;
1546 struct block *pull;
1547 struct block **diffp, **samep;
1548 struct edge *ep;
1549
1550 ep = b->in_edges;
1551 if (ep == 0)
1552 return;
1553
1554 /*
1555 * Make sure each predecessor loads the same value.
1556 */
1557 val = ep->pred->val[A_ATOM];
1558 for (ep = ep->next; ep != 0; ep = ep->next)
1559 if (val != ep->pred->val[A_ATOM])
1560 return;
1561
1562 if (JT(b->in_edges->pred) == b)
1563 diffp = &JT(b->in_edges->pred);
1564 else
1565 diffp = &JF(b->in_edges->pred);
1566
1567 at_top = 1;
1568 while (1) {
1569 if (*diffp == 0)
1570 return;
1571
1572 if (JF(*diffp) != JF(b))
1573 return;
1574
1575 if (!SET_MEMBER((*diffp)->dom, b->id))
1576 return;
1577
1578 if ((*diffp)->val[A_ATOM] != val)
1579 break;
1580
1581 diffp = &JT(*diffp);
1582 at_top = 0;
1583 }
1584 samep = &JT(*diffp);
1585 while (1) {
1586 if (*samep == 0)
1587 return;
1588
1589 if (JF(*samep) != JF(b))
1590 return;
1591
1592 if (!SET_MEMBER((*samep)->dom, b->id))
1593 return;
1594
1595 if ((*samep)->val[A_ATOM] == val)
1596 break;
1597
1598 /* XXX Need to check that there are no data dependencies
1599 between diffp and samep. Currently, the code generator
1600 will not produce such dependencies. */
1601 samep = &JT(*samep);
1602 }
1603#ifdef notdef
1604 /* XXX This doesn't cover everything. */
1605 for (i = 0; i < N_ATOMS; ++i)
1606 if ((*samep)->val[i] != pred->val[i])
1607 return;
1608#endif
1609 /* Pull up the node. */
1610 pull = *samep;
1611 *samep = JT(pull);
1612 JT(pull) = *diffp;
1613
1614 /*
1615 * At the top of the chain, each predecessor needs to point at the
1616 * pulled up node. Inside the chain, there is only one predecessor
1617 * to worry about.
1618 */
1619 if (at_top) {
1620 for (ep = b->in_edges; ep != 0; ep = ep->next) {
1621 if (JT(ep->pred) == b)
1622 JT(ep->pred) = pull;
1623 else
1624 JF(ep->pred) = pull;
1625 }
1626 }
1627 else
1628 *diffp = pull;
1629
1630 done = 0;
1631}
1632
1633static void
1634opt_blks(root, do_stmts)
1635 struct block *root;
1636 int do_stmts;
1637{
1638 int i, maxlevel;
1639 struct block *p;
1640
1641 init_val();
1642 maxlevel = root->level;
1643
1644 find_inedges(root);
1645 for (i = maxlevel; i >= 0; --i)
1646 for (p = levels[i]; p; p = p->link)
1647 opt_blk(p, do_stmts);
1648
1649 if (do_stmts)
1650 /*
1651 * No point trying to move branches; it can't possibly
1652 * make a difference at this point.
1653 */
1654 return;
1655
1656 for (i = 1; i <= maxlevel; ++i) {
1657 for (p = levels[i]; p; p = p->link) {
1658 opt_j(&p->et);
1659 opt_j(&p->ef);
1660 }
1661 }
1662
1663 find_inedges(root);
1664 for (i = 1; i <= maxlevel; ++i) {
1665 for (p = levels[i]; p; p = p->link) {
1666 or_pullup(p);
1667 and_pullup(p);
1668 }
1669 }
1670}
1671
1672static inline void
1673link_inedge(parent, child)
1674 struct edge *parent;
1675 struct block *child;
1676{
1677 parent->next = child->in_edges;
1678 child->in_edges = parent;
1679}
1680
1681static void
1682find_inedges(root)
1683 struct block *root;
1684{
1685 int i;
1686 struct block *b;
1687
1688 for (i = 0; i < n_blocks; ++i)
1689 blocks[i]->in_edges = 0;
1690
1691 /*
1692 * Traverse the graph, adding each edge to the predecessor
1693 * list of its successors. Skip the leaves (i.e. level 0).
1694 */
1695 for (i = root->level; i > 0; --i) {
1696 for (b = levels[i]; b != 0; b = b->link) {
1697 link_inedge(&b->et, JT(b));
1698 link_inedge(&b->ef, JF(b));
1699 }
1700 }
1701}
1702
1703static void
1704opt_root(b)
1705 struct block **b;
1706{
1707 struct slist *tmp, *s;
1708
1709 s = (*b)->stmts;
1710 (*b)->stmts = 0;
1711 while (BPF_CLASS((*b)->s.code) == BPF_JMP && JT(*b) == JF(*b))
1712 *b = JT(*b);
1713
1714 tmp = (*b)->stmts;
1715 if (tmp != 0)
1716 sappend(s, tmp);
1717 (*b)->stmts = s;
1718
1719 /*
1720 * If the root node is a return, then there is no
1721 * point executing any statements (since the bpf machine
1722 * has no side effects).
1723 */
1724 if (BPF_CLASS((*b)->s.code) == BPF_RET)
1725 (*b)->stmts = 0;
1726}
1727
1728static void
1729opt_loop(root, do_stmts)
1730 struct block *root;
1731 int do_stmts;
1732{
1733
1734#ifdef BDEBUG
1735 if (dflag > 1) {
1736 printf("opt_loop(root, %d) begin\n", do_stmts);
1737 opt_dump(root);
1738 }
1739#endif
1740 do {
1741 done = 1;
1742 find_levels(root);
1743 find_dom(root);
1744 find_closure(root);
1745 find_ud(root);
1746 find_edom(root);
1747 opt_blks(root, do_stmts);
1748#ifdef BDEBUG
1749 if (dflag > 1) {
1750 printf("opt_loop(root, %d) bottom, done=%d\n", do_stmts, done);
1751 opt_dump(root);
1752 }
1753#endif
1754 } while (!done);
1755}
1756
1757/*
1758 * Optimize the filter code in its dag representation.
1759 */
1760void
1761bpf_optimize(rootp)
1762 struct block **rootp;
1763{
1764 struct block *root;
1765
1766 root = *rootp;
1767
1768 opt_init(root);
1769 opt_loop(root, 0);
1770 opt_loop(root, 1);
1771 intern_blocks(root);
1772#ifdef BDEBUG
1773 if (dflag > 1) {
1774 printf("after intern_blocks()\n");
1775 opt_dump(root);
1776 }
1777#endif
1778 opt_root(rootp);
1779#ifdef BDEBUG
1780 if (dflag > 1) {
1781 printf("after opt_root()\n");
1782 opt_dump(root);
1783 }
1784#endif
1785 opt_cleanup();
1786}
1787
1788static void
1789make_marks(p)
1790 struct block *p;
1791{
1792 if (!isMarked(p)) {
1793 Mark(p);
1794 if (BPF_CLASS(p->s.code) != BPF_RET) {
1795 make_marks(JT(p));
1796 make_marks(JF(p));
1797 }
1798 }
1799}
1800
1801/*
1802 * Mark code array such that isMarked(i) is true
1803 * only for nodes that are alive.
1804 */
1805static void
1806mark_code(p)
1807 struct block *p;
1808{
1809 cur_mark += 1;
1810 make_marks(p);
1811}
1812
1813/*
1814 * True iff the two stmt lists load the same value from the packet into
1815 * the accumulator.
1816 */
1817static int
1818eq_slist(x, y)
1819 struct slist *x, *y;
1820{
1821 while (1) {
1822 while (x && x->s.code == NOP)
1823 x = x->next;
1824 while (y && y->s.code == NOP)
1825 y = y->next;
1826 if (x == 0)
1827 return y == 0;
1828 if (y == 0)
1829 return x == 0;
1830 if (x->s.code != y->s.code || x->s.k != y->s.k)
1831 return 0;
1832 x = x->next;
1833 y = y->next;
1834 }
1835}
1836
1837static inline int
1838eq_blk(b0, b1)
1839 struct block *b0, *b1;
1840{
1841 if (b0->s.code == b1->s.code &&
1842 b0->s.k == b1->s.k &&
1843 b0->et.succ == b1->et.succ &&
1844 b0->ef.succ == b1->ef.succ)
1845 return eq_slist(b0->stmts, b1->stmts);
1846 return 0;
1847}
1848
1849static void
1850intern_blocks(root)
1851 struct block *root;
1852{
1853 struct block *p;
1854 int i, j;
1855 int done1; /* don't shadow global */
1856 top:
1857 done1 = 1;
1858 for (i = 0; i < n_blocks; ++i)
1859 blocks[i]->link = 0;
1860
1861 mark_code(root);
1862
1863 for (i = n_blocks - 1; --i >= 0; ) {
1864 if (!isMarked(blocks[i]))
1865 continue;
1866 for (j = i + 1; j < n_blocks; ++j) {
1867 if (!isMarked(blocks[j]))
1868 continue;
1869 if (eq_blk(blocks[i], blocks[j])) {
1870 blocks[i]->link = blocks[j]->link ?
1871 blocks[j]->link : blocks[j];
1872 break;
1873 }
1874 }
1875 }
1876 for (i = 0; i < n_blocks; ++i) {
1877 p = blocks[i];
1878 if (JT(p) == 0)
1879 continue;
1880 if (JT(p)->link) {
1881 done1 = 0;
1882 JT(p) = JT(p)->link;
1883 }
1884 if (JF(p)->link) {
1885 done1 = 0;
1886 JF(p) = JF(p)->link;
1887 }
1888 }
1889 if (!done1)
1890 goto top;
1891}
1892
1893static void
1894opt_cleanup()
1895{
1896 free((void *)vnode_base);
1897 free((void *)vmap);
1898 free((void *)edges);
1899 free((void *)space);
1900 free((void *)levels);
1901 free((void *)blocks);
1902}
1903
1904/*
1905 * Return the number of stmts in 's'.
1906 */
| 159static int convert_code_r(struct block *);
160#ifdef BDEBUG
161static void opt_dump(struct block *);
162#endif
163
164static int n_blocks;
165struct block **blocks;
166static int n_edges;
167struct edge **edges;
168
169/*
170 * A bit vector set representation of the dominators.
171 * We round up the set size to the next power of two.
172 */
173static int nodewords;
174static int edgewords;
175struct block **levels;
176bpf_u_int32 *space;
177#define BITS_PER_WORD (8*sizeof(bpf_u_int32))
178/*
179 * True if a is in uset {p}
180 */
181#define SET_MEMBER(p, a) \
182((p)[(unsigned)(a) / BITS_PER_WORD] & (1 << ((unsigned)(a) % BITS_PER_WORD)))
183
184/*
185 * Add 'a' to uset p.
186 */
187#define SET_INSERT(p, a) \
188(p)[(unsigned)(a) / BITS_PER_WORD] |= (1 << ((unsigned)(a) % BITS_PER_WORD))
189
190/*
191 * Delete 'a' from uset p.
192 */
193#define SET_DELETE(p, a) \
194(p)[(unsigned)(a) / BITS_PER_WORD] &= ~(1 << ((unsigned)(a) % BITS_PER_WORD))
195
196/*
197 * a := a intersect b
198 */
199#define SET_INTERSECT(a, b, n)\
200{\
201 register bpf_u_int32 *_x = a, *_y = b;\
202 register int _n = n;\
203 while (--_n >= 0) *_x++ &= *_y++;\
204}
205
206/*
207 * a := a - b
208 */
209#define SET_SUBTRACT(a, b, n)\
210{\
211 register bpf_u_int32 *_x = a, *_y = b;\
212 register int _n = n;\
213 while (--_n >= 0) *_x++ &=~ *_y++;\
214}
215
216/*
217 * a := a union b
218 */
219#define SET_UNION(a, b, n)\
220{\
221 register bpf_u_int32 *_x = a, *_y = b;\
222 register int _n = n;\
223 while (--_n >= 0) *_x++ |= *_y++;\
224}
225
226static uset all_dom_sets;
227static uset all_closure_sets;
228static uset all_edge_sets;
229
230#ifndef MAX
231#define MAX(a,b) ((a)>(b)?(a):(b))
232#endif
233
234static void
235find_levels_r(b)
236 struct block *b;
237{
238 int level;
239
240 if (isMarked(b))
241 return;
242
243 Mark(b);
244 b->link = 0;
245
246 if (JT(b)) {
247 find_levels_r(JT(b));
248 find_levels_r(JF(b));
249 level = MAX(JT(b)->level, JF(b)->level) + 1;
250 } else
251 level = 0;
252 b->level = level;
253 b->link = levels[level];
254 levels[level] = b;
255}
256
257/*
258 * Level graph. The levels go from 0 at the leaves to
259 * N_LEVELS at the root. The levels[] array points to the
260 * first node of the level list, whose elements are linked
261 * with the 'link' field of the struct block.
262 */
263static void
264find_levels(root)
265 struct block *root;
266{
267 memset((char *)levels, 0, n_blocks * sizeof(*levels));
268 unMarkAll();
269 find_levels_r(root);
270}
271
272/*
273 * Find dominator relationships.
274 * Assumes graph has been leveled.
275 */
276static void
277find_dom(root)
278 struct block *root;
279{
280 int i;
281 struct block *b;
282 bpf_u_int32 *x;
283
284 /*
285 * Initialize sets to contain all nodes.
286 */
287 x = all_dom_sets;
288 i = n_blocks * nodewords;
289 while (--i >= 0)
290 *x++ = ~0;
291 /* Root starts off empty. */
292 for (i = nodewords; --i >= 0;)
293 root->dom[i] = 0;
294
295 /* root->level is the highest level no found. */
296 for (i = root->level; i >= 0; --i) {
297 for (b = levels[i]; b; b = b->link) {
298 SET_INSERT(b->dom, b->id);
299 if (JT(b) == 0)
300 continue;
301 SET_INTERSECT(JT(b)->dom, b->dom, nodewords);
302 SET_INTERSECT(JF(b)->dom, b->dom, nodewords);
303 }
304 }
305}
306
307static void
308propedom(ep)
309 struct edge *ep;
310{
311 SET_INSERT(ep->edom, ep->id);
312 if (ep->succ) {
313 SET_INTERSECT(ep->succ->et.edom, ep->edom, edgewords);
314 SET_INTERSECT(ep->succ->ef.edom, ep->edom, edgewords);
315 }
316}
317
318/*
319 * Compute edge dominators.
320 * Assumes graph has been leveled and predecessors established.
321 */
322static void
323find_edom(root)
324 struct block *root;
325{
326 int i;
327 uset x;
328 struct block *b;
329
330 x = all_edge_sets;
331 for (i = n_edges * edgewords; --i >= 0; )
332 x[i] = ~0;
333
334 /* root->level is the highest level no found. */
335 memset(root->et.edom, 0, edgewords * sizeof(*(uset)0));
336 memset(root->ef.edom, 0, edgewords * sizeof(*(uset)0));
337 for (i = root->level; i >= 0; --i) {
338 for (b = levels[i]; b != 0; b = b->link) {
339 propedom(&b->et);
340 propedom(&b->ef);
341 }
342 }
343}
344
345/*
346 * Find the backwards transitive closure of the flow graph. These sets
347 * are backwards in the sense that we find the set of nodes that reach
348 * a given node, not the set of nodes that can be reached by a node.
349 *
350 * Assumes graph has been leveled.
351 */
352static void
353find_closure(root)
354 struct block *root;
355{
356 int i;
357 struct block *b;
358
359 /*
360 * Initialize sets to contain no nodes.
361 */
362 memset((char *)all_closure_sets, 0,
363 n_blocks * nodewords * sizeof(*all_closure_sets));
364
365 /* root->level is the highest level no found. */
366 for (i = root->level; i >= 0; --i) {
367 for (b = levels[i]; b; b = b->link) {
368 SET_INSERT(b->closure, b->id);
369 if (JT(b) == 0)
370 continue;
371 SET_UNION(JT(b)->closure, b->closure, nodewords);
372 SET_UNION(JF(b)->closure, b->closure, nodewords);
373 }
374 }
375}
376
377/*
378 * Return the register number that is used by s. If A and X are both
379 * used, return AX_ATOM. If no register is used, return -1.
380 *
381 * The implementation should probably change to an array access.
382 */
383static int
384atomuse(s)
385 struct stmt *s;
386{
387 register int c = s->code;
388
389 if (c == NOP)
390 return -1;
391
392 switch (BPF_CLASS(c)) {
393
394 case BPF_RET:
395 return (BPF_RVAL(c) == BPF_A) ? A_ATOM :
396 (BPF_RVAL(c) == BPF_X) ? X_ATOM : -1;
397
398 case BPF_LD:
399 case BPF_LDX:
400 return (BPF_MODE(c) == BPF_IND) ? X_ATOM :
401 (BPF_MODE(c) == BPF_MEM) ? s->k : -1;
402
403 case BPF_ST:
404 return A_ATOM;
405
406 case BPF_STX:
407 return X_ATOM;
408
409 case BPF_JMP:
410 case BPF_ALU:
411 if (BPF_SRC(c) == BPF_X)
412 return AX_ATOM;
413 return A_ATOM;
414
415 case BPF_MISC:
416 return BPF_MISCOP(c) == BPF_TXA ? X_ATOM : A_ATOM;
417 }
418 abort();
419 /* NOTREACHED */
420}
421
422/*
423 * Return the register number that is defined by 's'. We assume that
424 * a single stmt cannot define more than one register. If no register
425 * is defined, return -1.
426 *
427 * The implementation should probably change to an array access.
428 */
429static int
430atomdef(s)
431 struct stmt *s;
432{
433 if (s->code == NOP)
434 return -1;
435
436 switch (BPF_CLASS(s->code)) {
437
438 case BPF_LD:
439 case BPF_ALU:
440 return A_ATOM;
441
442 case BPF_LDX:
443 return X_ATOM;
444
445 case BPF_ST:
446 case BPF_STX:
447 return s->k;
448
449 case BPF_MISC:
450 return BPF_MISCOP(s->code) == BPF_TAX ? X_ATOM : A_ATOM;
451 }
452 return -1;
453}
454
455/*
456 * Compute the sets of registers used, defined, and killed by 'b'.
457 *
458 * "Used" means that a statement in 'b' uses the register before any
459 * statement in 'b' defines it, i.e. it uses the value left in
460 * that register by a predecessor block of this block.
461 * "Defined" means that a statement in 'b' defines it.
462 * "Killed" means that a statement in 'b' defines it before any
463 * statement in 'b' uses it, i.e. it kills the value left in that
464 * register by a predecessor block of this block.
465 */
466static void
467compute_local_ud(b)
468 struct block *b;
469{
470 struct slist *s;
471 atomset def = 0, use = 0, kill = 0;
472 int atom;
473
474 for (s = b->stmts; s; s = s->next) {
475 if (s->s.code == NOP)
476 continue;
477 atom = atomuse(&s->s);
478 if (atom >= 0) {
479 if (atom == AX_ATOM) {
480 if (!ATOMELEM(def, X_ATOM))
481 use |= ATOMMASK(X_ATOM);
482 if (!ATOMELEM(def, A_ATOM))
483 use |= ATOMMASK(A_ATOM);
484 }
485 else if (atom < N_ATOMS) {
486 if (!ATOMELEM(def, atom))
487 use |= ATOMMASK(atom);
488 }
489 else
490 abort();
491 }
492 atom = atomdef(&s->s);
493 if (atom >= 0) {
494 if (!ATOMELEM(use, atom))
495 kill |= ATOMMASK(atom);
496 def |= ATOMMASK(atom);
497 }
498 }
499 if (BPF_CLASS(b->s.code) == BPF_JMP) {
500 /*
501 * XXX - what about RET?
502 */
503 atom = atomuse(&b->s);
504 if (atom >= 0) {
505 if (atom == AX_ATOM) {
506 if (!ATOMELEM(def, X_ATOM))
507 use |= ATOMMASK(X_ATOM);
508 if (!ATOMELEM(def, A_ATOM))
509 use |= ATOMMASK(A_ATOM);
510 }
511 else if (atom < N_ATOMS) {
512 if (!ATOMELEM(def, atom))
513 use |= ATOMMASK(atom);
514 }
515 else
516 abort();
517 }
518 }
519
520 b->def = def;
521 b->kill = kill;
522 b->in_use = use;
523}
524
525/*
526 * Assume graph is already leveled.
527 */
528static void
529find_ud(root)
530 struct block *root;
531{
532 int i, maxlevel;
533 struct block *p;
534
535 /*
536 * root->level is the highest level no found;
537 * count down from there.
538 */
539 maxlevel = root->level;
540 for (i = maxlevel; i >= 0; --i)
541 for (p = levels[i]; p; p = p->link) {
542 compute_local_ud(p);
543 p->out_use = 0;
544 }
545
546 for (i = 1; i <= maxlevel; ++i) {
547 for (p = levels[i]; p; p = p->link) {
548 p->out_use |= JT(p)->in_use | JF(p)->in_use;
549 p->in_use |= p->out_use &~ p->kill;
550 }
551 }
552}
553
554/*
555 * These data structures are used in a Cocke and Shwarz style
556 * value numbering scheme. Since the flowgraph is acyclic,
557 * exit values can be propagated from a node's predecessors
558 * provided it is uniquely defined.
559 */
560struct valnode {
561 int code;
562 int v0, v1;
563 int val;
564 struct valnode *next;
565};
566
567#define MODULUS 213
568static struct valnode *hashtbl[MODULUS];
569static int curval;
570static int maxval;
571
572/* Integer constants mapped with the load immediate opcode. */
573#define K(i) F(BPF_LD|BPF_IMM|BPF_W, i, 0L)
574
575struct vmapinfo {
576 int is_const;
577 bpf_int32 const_val;
578};
579
580struct vmapinfo *vmap;
581struct valnode *vnode_base;
582struct valnode *next_vnode;
583
584static void
585init_val()
586{
587 curval = 0;
588 next_vnode = vnode_base;
589 memset((char *)vmap, 0, maxval * sizeof(*vmap));
590 memset((char *)hashtbl, 0, sizeof hashtbl);
591}
592
593/* Because we really don't have an IR, this stuff is a little messy. */
594static int
595F(code, v0, v1)
596 int code;
597 int v0, v1;
598{
599 u_int hash;
600 int val;
601 struct valnode *p;
602
603 hash = (u_int)code ^ (v0 << 4) ^ (v1 << 8);
604 hash %= MODULUS;
605
606 for (p = hashtbl[hash]; p; p = p->next)
607 if (p->code == code && p->v0 == v0 && p->v1 == v1)
608 return p->val;
609
610 val = ++curval;
611 if (BPF_MODE(code) == BPF_IMM &&
612 (BPF_CLASS(code) == BPF_LD || BPF_CLASS(code) == BPF_LDX)) {
613 vmap[val].const_val = v0;
614 vmap[val].is_const = 1;
615 }
616 p = next_vnode++;
617 p->val = val;
618 p->code = code;
619 p->v0 = v0;
620 p->v1 = v1;
621 p->next = hashtbl[hash];
622 hashtbl[hash] = p;
623
624 return val;
625}
626
627static inline void
628vstore(s, valp, newval, alter)
629 struct stmt *s;
630 int *valp;
631 int newval;
632 int alter;
633{
634 if (alter && *valp == newval)
635 s->code = NOP;
636 else
637 *valp = newval;
638}
639
640static void
641fold_op(s, v0, v1)
642 struct stmt *s;
643 int v0, v1;
644{
645 bpf_u_int32 a, b;
646
647 a = vmap[v0].const_val;
648 b = vmap[v1].const_val;
649
650 switch (BPF_OP(s->code)) {
651 case BPF_ADD:
652 a += b;
653 break;
654
655 case BPF_SUB:
656 a -= b;
657 break;
658
659 case BPF_MUL:
660 a *= b;
661 break;
662
663 case BPF_DIV:
664 if (b == 0)
665 bpf_error("division by zero");
666 a /= b;
667 break;
668
669 case BPF_AND:
670 a &= b;
671 break;
672
673 case BPF_OR:
674 a |= b;
675 break;
676
677 case BPF_LSH:
678 a <<= b;
679 break;
680
681 case BPF_RSH:
682 a >>= b;
683 break;
684
685 case BPF_NEG:
686 a = -a;
687 break;
688
689 default:
690 abort();
691 }
692 s->k = a;
693 s->code = BPF_LD|BPF_IMM;
694 done = 0;
695}
696
697static inline struct slist *
698this_op(s)
699 struct slist *s;
700{
701 while (s != 0 && s->s.code == NOP)
702 s = s->next;
703 return s;
704}
705
706static void
707opt_not(b)
708 struct block *b;
709{
710 struct block *tmp = JT(b);
711
712 JT(b) = JF(b);
713 JF(b) = tmp;
714}
715
716static void
717opt_peep(b)
718 struct block *b;
719{
720 struct slist *s;
721 struct slist *next, *last;
722 int val;
723
724 s = b->stmts;
725 if (s == 0)
726 return;
727
728 last = s;
729 for (/*empty*/; /*empty*/; s = next) {
730 /*
731 * Skip over nops.
732 */
733 s = this_op(s);
734 if (s == 0)
735 break; /* nothing left in the block */
736
737 /*
738 * Find the next real instruction after that one
739 * (skipping nops).
740 */
741 next = this_op(s->next);
742 if (next == 0)
743 break; /* no next instruction */
744 last = next;
745
746 /*
747 * st M[k] --> st M[k]
748 * ldx M[k] tax
749 */
750 if (s->s.code == BPF_ST &&
751 next->s.code == (BPF_LDX|BPF_MEM) &&
752 s->s.k == next->s.k) {
753 done = 0;
754 next->s.code = BPF_MISC|BPF_TAX;
755 }
756 /*
757 * ld #k --> ldx #k
758 * tax txa
759 */
760 if (s->s.code == (BPF_LD|BPF_IMM) &&
761 next->s.code == (BPF_MISC|BPF_TAX)) {
762 s->s.code = BPF_LDX|BPF_IMM;
763 next->s.code = BPF_MISC|BPF_TXA;
764 done = 0;
765 }
766 /*
767 * This is an ugly special case, but it happens
768 * when you say tcp[k] or udp[k] where k is a constant.
769 */
770 if (s->s.code == (BPF_LD|BPF_IMM)) {
771 struct slist *add, *tax, *ild;
772
773 /*
774 * Check that X isn't used on exit from this
775 * block (which the optimizer might cause).
776 * We know the code generator won't generate
777 * any local dependencies.
778 */
779 if (ATOMELEM(b->out_use, X_ATOM))
780 continue;
781
782 /*
783 * Check that the instruction following the ldi
784 * is an addx, or it's an ldxms with an addx
785 * following it (with 0 or more nops between the
786 * ldxms and addx).
787 */
788 if (next->s.code != (BPF_LDX|BPF_MSH|BPF_B))
789 add = next;
790 else
791 add = this_op(next->next);
792 if (add == 0 || add->s.code != (BPF_ALU|BPF_ADD|BPF_X))
793 continue;
794
795 /*
796 * Check that a tax follows that (with 0 or more
797 * nops between them).
798 */
799 tax = this_op(add->next);
800 if (tax == 0 || tax->s.code != (BPF_MISC|BPF_TAX))
801 continue;
802
803 /*
804 * Check that an ild follows that (with 0 or more
805 * nops between them).
806 */
807 ild = this_op(tax->next);
808 if (ild == 0 || BPF_CLASS(ild->s.code) != BPF_LD ||
809 BPF_MODE(ild->s.code) != BPF_IND)
810 continue;
811 /*
812 * We want to turn this sequence:
813 *
814 * (004) ldi #0x2 {s}
815 * (005) ldxms [14] {next} -- optional
816 * (006) addx {add}
817 * (007) tax {tax}
818 * (008) ild [x+0] {ild}
819 *
820 * into this sequence:
821 *
822 * (004) nop
823 * (005) ldxms [14]
824 * (006) nop
825 * (007) nop
826 * (008) ild [x+2]
827 *
828 * XXX We need to check that X is not
829 * subsequently used, because we want to change
830 * what'll be in it after this sequence.
831 *
832 * We know we can eliminate the accumulator
833 * modifications earlier in the sequence since
834 * it is defined by the last stmt of this sequence
835 * (i.e., the last statement of the sequence loads
836 * a value into the accumulator, so we can eliminate
837 * earlier operations on the accumulator).
838 */
839 ild->s.k += s->s.k;
840 s->s.code = NOP;
841 add->s.code = NOP;
842 tax->s.code = NOP;
843 done = 0;
844 }
845 }
846 /*
847 * If the comparison at the end of a block is an equality
848 * comparison against a constant, and nobody uses the value
849 * we leave in the A register at the end of a block, and
850 * the operation preceding the comparison is an arithmetic
851 * operation, we can sometime optimize it away.
852 */
853 if (b->s.code == (BPF_JMP|BPF_JEQ|BPF_K) &&
854 !ATOMELEM(b->out_use, A_ATOM)) {
855 /*
856 * We can optimize away certain subtractions of the
857 * X register.
858 */
859 if (last->s.code == (BPF_ALU|BPF_SUB|BPF_X)) {
860 val = b->val[X_ATOM];
861 if (vmap[val].is_const) {
862 /*
863 * If we have a subtract to do a comparison,
864 * and the X register is a known constant,
865 * we can merge this value into the
866 * comparison:
867 *
868 * sub x -> nop
869 * jeq #y jeq #(x+y)
870 */
871 b->s.k += vmap[val].const_val;
872 last->s.code = NOP;
873 done = 0;
874 } else if (b->s.k == 0) {
875 /*
876 * If the X register isn't a constant,
877 * and the comparison in the test is
878 * against 0, we can compare with the
879 * X register, instead:
880 *
881 * sub x -> nop
882 * jeq #0 jeq x
883 */
884 last->s.code = NOP;
885 b->s.code = BPF_JMP|BPF_JEQ|BPF_X;
886 done = 0;
887 }
888 }
889 /*
890 * Likewise, a constant subtract can be simplified:
891 *
892 * sub #x -> nop
893 * jeq #y -> jeq #(x+y)
894 */
895 else if (last->s.code == (BPF_ALU|BPF_SUB|BPF_K)) {
896 last->s.code = NOP;
897 b->s.k += last->s.k;
898 done = 0;
899 }
900 /*
901 * And, similarly, a constant AND can be simplified
902 * if we're testing against 0, i.e.:
903 *
904 * and #k nop
905 * jeq #0 -> jset #k
906 */
907 else if (last->s.code == (BPF_ALU|BPF_AND|BPF_K) &&
908 b->s.k == 0) {
909 b->s.k = last->s.k;
910 b->s.code = BPF_JMP|BPF_K|BPF_JSET;
911 last->s.code = NOP;
912 done = 0;
913 opt_not(b);
914 }
915 }
916 /*
917 * jset #0 -> never
918 * jset #ffffffff -> always
919 */
920 if (b->s.code == (BPF_JMP|BPF_K|BPF_JSET)) {
921 if (b->s.k == 0)
922 JT(b) = JF(b);
923 if (b->s.k == 0xffffffff)
924 JF(b) = JT(b);
925 }
926 /*
927 * If we're comparing against the index register, and the index
928 * register is a known constant, we can just compare against that
929 * constant.
930 */
931 val = b->val[X_ATOM];
932 if (vmap[val].is_const && BPF_SRC(b->s.code) == BPF_X) {
933 bpf_int32 v = vmap[val].const_val;
934 b->s.code &= ~BPF_X;
935 b->s.k = v;
936 }
937 /*
938 * If the accumulator is a known constant, we can compute the
939 * comparison result.
940 */
941 val = b->val[A_ATOM];
942 if (vmap[val].is_const && BPF_SRC(b->s.code) == BPF_K) {
943 bpf_int32 v = vmap[val].const_val;
944 switch (BPF_OP(b->s.code)) {
945
946 case BPF_JEQ:
947 v = v == b->s.k;
948 break;
949
950 case BPF_JGT:
951 v = (unsigned)v > b->s.k;
952 break;
953
954 case BPF_JGE:
955 v = (unsigned)v >= b->s.k;
956 break;
957
958 case BPF_JSET:
959 v &= b->s.k;
960 break;
961
962 default:
963 abort();
964 }
965 if (JF(b) != JT(b))
966 done = 0;
967 if (v)
968 JF(b) = JT(b);
969 else
970 JT(b) = JF(b);
971 }
972}
973
974/*
975 * Compute the symbolic value of expression of 's', and update
976 * anything it defines in the value table 'val'. If 'alter' is true,
977 * do various optimizations. This code would be cleaner if symbolic
978 * evaluation and code transformations weren't folded together.
979 */
980static void
981opt_stmt(s, val, alter)
982 struct stmt *s;
983 int val[];
984 int alter;
985{
986 int op;
987 int v;
988
989 switch (s->code) {
990
991 case BPF_LD|BPF_ABS|BPF_W:
992 case BPF_LD|BPF_ABS|BPF_H:
993 case BPF_LD|BPF_ABS|BPF_B:
994 v = F(s->code, s->k, 0L);
995 vstore(s, &val[A_ATOM], v, alter);
996 break;
997
998 case BPF_LD|BPF_IND|BPF_W:
999 case BPF_LD|BPF_IND|BPF_H:
1000 case BPF_LD|BPF_IND|BPF_B:
1001 v = val[X_ATOM];
1002 if (alter && vmap[v].is_const) {
1003 s->code = BPF_LD|BPF_ABS|BPF_SIZE(s->code);
1004 s->k += vmap[v].const_val;
1005 v = F(s->code, s->k, 0L);
1006 done = 0;
1007 }
1008 else
1009 v = F(s->code, s->k, v);
1010 vstore(s, &val[A_ATOM], v, alter);
1011 break;
1012
1013 case BPF_LD|BPF_LEN:
1014 v = F(s->code, 0L, 0L);
1015 vstore(s, &val[A_ATOM], v, alter);
1016 break;
1017
1018 case BPF_LD|BPF_IMM:
1019 v = K(s->k);
1020 vstore(s, &val[A_ATOM], v, alter);
1021 break;
1022
1023 case BPF_LDX|BPF_IMM:
1024 v = K(s->k);
1025 vstore(s, &val[X_ATOM], v, alter);
1026 break;
1027
1028 case BPF_LDX|BPF_MSH|BPF_B:
1029 v = F(s->code, s->k, 0L);
1030 vstore(s, &val[X_ATOM], v, alter);
1031 break;
1032
1033 case BPF_ALU|BPF_NEG:
1034 if (alter && vmap[val[A_ATOM]].is_const) {
1035 s->code = BPF_LD|BPF_IMM;
1036 s->k = -vmap[val[A_ATOM]].const_val;
1037 val[A_ATOM] = K(s->k);
1038 }
1039 else
1040 val[A_ATOM] = F(s->code, val[A_ATOM], 0L);
1041 break;
1042
1043 case BPF_ALU|BPF_ADD|BPF_K:
1044 case BPF_ALU|BPF_SUB|BPF_K:
1045 case BPF_ALU|BPF_MUL|BPF_K:
1046 case BPF_ALU|BPF_DIV|BPF_K:
1047 case BPF_ALU|BPF_AND|BPF_K:
1048 case BPF_ALU|BPF_OR|BPF_K:
1049 case BPF_ALU|BPF_LSH|BPF_K:
1050 case BPF_ALU|BPF_RSH|BPF_K:
1051 op = BPF_OP(s->code);
1052 if (alter) {
1053 if (s->k == 0) {
1054 /* don't optimize away "sub #0"
1055 * as it may be needed later to
1056 * fixup the generated math code */
1057 if (op == BPF_ADD ||
1058 op == BPF_LSH || op == BPF_RSH ||
1059 op == BPF_OR) {
1060 s->code = NOP;
1061 break;
1062 }
1063 if (op == BPF_MUL || op == BPF_AND) {
1064 s->code = BPF_LD|BPF_IMM;
1065 val[A_ATOM] = K(s->k);
1066 break;
1067 }
1068 }
1069 if (vmap[val[A_ATOM]].is_const) {
1070 fold_op(s, val[A_ATOM], K(s->k));
1071 val[A_ATOM] = K(s->k);
1072 break;
1073 }
1074 }
1075 val[A_ATOM] = F(s->code, val[A_ATOM], K(s->k));
1076 break;
1077
1078 case BPF_ALU|BPF_ADD|BPF_X:
1079 case BPF_ALU|BPF_SUB|BPF_X:
1080 case BPF_ALU|BPF_MUL|BPF_X:
1081 case BPF_ALU|BPF_DIV|BPF_X:
1082 case BPF_ALU|BPF_AND|BPF_X:
1083 case BPF_ALU|BPF_OR|BPF_X:
1084 case BPF_ALU|BPF_LSH|BPF_X:
1085 case BPF_ALU|BPF_RSH|BPF_X:
1086 op = BPF_OP(s->code);
1087 if (alter && vmap[val[X_ATOM]].is_const) {
1088 if (vmap[val[A_ATOM]].is_const) {
1089 fold_op(s, val[A_ATOM], val[X_ATOM]);
1090 val[A_ATOM] = K(s->k);
1091 }
1092 else {
1093 s->code = BPF_ALU|BPF_K|op;
1094 s->k = vmap[val[X_ATOM]].const_val;
1095 done = 0;
1096 val[A_ATOM] =
1097 F(s->code, val[A_ATOM], K(s->k));
1098 }
1099 break;
1100 }
1101 /*
1102 * Check if we're doing something to an accumulator
1103 * that is 0, and simplify. This may not seem like
1104 * much of a simplification but it could open up further
1105 * optimizations.
1106 * XXX We could also check for mul by 1, etc.
1107 */
1108 if (alter && vmap[val[A_ATOM]].is_const
1109 && vmap[val[A_ATOM]].const_val == 0) {
1110 if (op == BPF_ADD || op == BPF_OR) {
1111 s->code = BPF_MISC|BPF_TXA;
1112 vstore(s, &val[A_ATOM], val[X_ATOM], alter);
1113 break;
1114 }
1115 else if (op == BPF_MUL || op == BPF_DIV ||
1116 op == BPF_AND || op == BPF_LSH || op == BPF_RSH) {
1117 s->code = BPF_LD|BPF_IMM;
1118 s->k = 0;
1119 vstore(s, &val[A_ATOM], K(s->k), alter);
1120 break;
1121 }
1122 else if (op == BPF_NEG) {
1123 s->code = NOP;
1124 break;
1125 }
1126 }
1127 val[A_ATOM] = F(s->code, val[A_ATOM], val[X_ATOM]);
1128 break;
1129
1130 case BPF_MISC|BPF_TXA:
1131 vstore(s, &val[A_ATOM], val[X_ATOM], alter);
1132 break;
1133
1134 case BPF_LD|BPF_MEM:
1135 v = val[s->k];
1136 if (alter && vmap[v].is_const) {
1137 s->code = BPF_LD|BPF_IMM;
1138 s->k = vmap[v].const_val;
1139 done = 0;
1140 }
1141 vstore(s, &val[A_ATOM], v, alter);
1142 break;
1143
1144 case BPF_MISC|BPF_TAX:
1145 vstore(s, &val[X_ATOM], val[A_ATOM], alter);
1146 break;
1147
1148 case BPF_LDX|BPF_MEM:
1149 v = val[s->k];
1150 if (alter && vmap[v].is_const) {
1151 s->code = BPF_LDX|BPF_IMM;
1152 s->k = vmap[v].const_val;
1153 done = 0;
1154 }
1155 vstore(s, &val[X_ATOM], v, alter);
1156 break;
1157
1158 case BPF_ST:
1159 vstore(s, &val[s->k], val[A_ATOM], alter);
1160 break;
1161
1162 case BPF_STX:
1163 vstore(s, &val[s->k], val[X_ATOM], alter);
1164 break;
1165 }
1166}
1167
1168static void
1169deadstmt(s, last)
1170 register struct stmt *s;
1171 register struct stmt *last[];
1172{
1173 register int atom;
1174
1175 atom = atomuse(s);
1176 if (atom >= 0) {
1177 if (atom == AX_ATOM) {
1178 last[X_ATOM] = 0;
1179 last[A_ATOM] = 0;
1180 }
1181 else
1182 last[atom] = 0;
1183 }
1184 atom = atomdef(s);
1185 if (atom >= 0) {
1186 if (last[atom]) {
1187 done = 0;
1188 last[atom]->code = NOP;
1189 }
1190 last[atom] = s;
1191 }
1192}
1193
1194static void
1195opt_deadstores(b)
1196 register struct block *b;
1197{
1198 register struct slist *s;
1199 register int atom;
1200 struct stmt *last[N_ATOMS];
1201
1202 memset((char *)last, 0, sizeof last);
1203
1204 for (s = b->stmts; s != 0; s = s->next)
1205 deadstmt(&s->s, last);
1206 deadstmt(&b->s, last);
1207
1208 for (atom = 0; atom < N_ATOMS; ++atom)
1209 if (last[atom] && !ATOMELEM(b->out_use, atom)) {
1210 last[atom]->code = NOP;
1211 done = 0;
1212 }
1213}
1214
1215static void
1216opt_blk(b, do_stmts)
1217 struct block *b;
1218 int do_stmts;
1219{
1220 struct slist *s;
1221 struct edge *p;
1222 int i;
1223 bpf_int32 aval, xval;
1224
1225#if 0
1226 for (s = b->stmts; s && s->next; s = s->next)
1227 if (BPF_CLASS(s->s.code) == BPF_JMP) {
1228 do_stmts = 0;
1229 break;
1230 }
1231#endif
1232
1233 /*
1234 * Initialize the atom values.
1235 */
1236 p = b->in_edges;
1237 if (p == 0) {
1238 /*
1239 * We have no predecessors, so everything is undefined
1240 * upon entry to this block.
1241 */
1242 memset((char *)b->val, 0, sizeof(b->val));
1243 } else {
1244 /*
1245 * Inherit values from our predecessors.
1246 *
1247 * First, get the values from the predecessor along the
1248 * first edge leading to this node.
1249 */
1250 memcpy((char *)b->val, (char *)p->pred->val, sizeof(b->val));
1251 /*
1252 * Now look at all the other nodes leading to this node.
1253 * If, for the predecessor along that edge, a register
1254 * has a different value from the one we have (i.e.,
1255 * control paths are merging, and the merging paths
1256 * assign different values to that register), give the
1257 * register the undefined value of 0.
1258 */
1259 while ((p = p->next) != NULL) {
1260 for (i = 0; i < N_ATOMS; ++i)
1261 if (b->val[i] != p->pred->val[i])
1262 b->val[i] = 0;
1263 }
1264 }
1265 aval = b->val[A_ATOM];
1266 xval = b->val[X_ATOM];
1267 for (s = b->stmts; s; s = s->next)
1268 opt_stmt(&s->s, b->val, do_stmts);
1269
1270 /*
1271 * This is a special case: if we don't use anything from this
1272 * block, and we load the accumulator or index register with a
1273 * value that is already there, or if this block is a return,
1274 * eliminate all the statements.
1275 *
1276 * XXX - what if it does a store?
1277 *
1278 * XXX - why does it matter whether we use anything from this
1279 * block? If the accumulator or index register doesn't change
1280 * its value, isn't that OK even if we use that value?
1281 *
1282 * XXX - if we load the accumulator with a different value,
1283 * and the block ends with a conditional branch, we obviously
1284 * can't eliminate it, as the branch depends on that value.
1285 * For the index register, the conditional branch only depends
1286 * on the index register value if the test is against the index
1287 * register value rather than a constant; if nothing uses the
1288 * value we put into the index register, and we're not testing
1289 * against the index register's value, and there aren't any
1290 * other problems that would keep us from eliminating this
1291 * block, can we eliminate it?
1292 */
1293 if (do_stmts &&
1294 ((b->out_use == 0 && aval != 0 && b->val[A_ATOM] == aval &&
1295 xval != 0 && b->val[X_ATOM] == xval) ||
1296 BPF_CLASS(b->s.code) == BPF_RET)) {
1297 if (b->stmts != 0) {
1298 b->stmts = 0;
1299 done = 0;
1300 }
1301 } else {
1302 opt_peep(b);
1303 opt_deadstores(b);
1304 }
1305 /*
1306 * Set up values for branch optimizer.
1307 */
1308 if (BPF_SRC(b->s.code) == BPF_K)
1309 b->oval = K(b->s.k);
1310 else
1311 b->oval = b->val[X_ATOM];
1312 b->et.code = b->s.code;
1313 b->ef.code = -b->s.code;
1314}
1315
1316/*
1317 * Return true if any register that is used on exit from 'succ', has
1318 * an exit value that is different from the corresponding exit value
1319 * from 'b'.
1320 */
1321static int
1322use_conflict(b, succ)
1323 struct block *b, *succ;
1324{
1325 int atom;
1326 atomset use = succ->out_use;
1327
1328 if (use == 0)
1329 return 0;
1330
1331 for (atom = 0; atom < N_ATOMS; ++atom)
1332 if (ATOMELEM(use, atom))
1333 if (b->val[atom] != succ->val[atom])
1334 return 1;
1335 return 0;
1336}
1337
1338static struct block *
1339fold_edge(child, ep)
1340 struct block *child;
1341 struct edge *ep;
1342{
1343 int sense;
1344 int aval0, aval1, oval0, oval1;
1345 int code = ep->code;
1346
1347 if (code < 0) {
1348 code = -code;
1349 sense = 0;
1350 } else
1351 sense = 1;
1352
1353 if (child->s.code != code)
1354 return 0;
1355
1356 aval0 = child->val[A_ATOM];
1357 oval0 = child->oval;
1358 aval1 = ep->pred->val[A_ATOM];
1359 oval1 = ep->pred->oval;
1360
1361 if (aval0 != aval1)
1362 return 0;
1363
1364 if (oval0 == oval1)
1365 /*
1366 * The operands of the branch instructions are
1367 * identical, so the result is true if a true
1368 * branch was taken to get here, otherwise false.
1369 */
1370 return sense ? JT(child) : JF(child);
1371
1372 if (sense && code == (BPF_JMP|BPF_JEQ|BPF_K))
1373 /*
1374 * At this point, we only know the comparison if we
1375 * came down the true branch, and it was an equality
1376 * comparison with a constant.
1377 *
1378 * I.e., if we came down the true branch, and the branch
1379 * was an equality comparison with a constant, we know the
1380 * accumulator contains that constant. If we came down
1381 * the false branch, or the comparison wasn't with a
1382 * constant, we don't know what was in the accumulator.
1383 *
1384 * We rely on the fact that distinct constants have distinct
1385 * value numbers.
1386 */
1387 return JF(child);
1388
1389 return 0;
1390}
1391
1392static void
1393opt_j(ep)
1394 struct edge *ep;
1395{
1396 register int i, k;
1397 register struct block *target;
1398
1399 if (JT(ep->succ) == 0)
1400 return;
1401
1402 if (JT(ep->succ) == JF(ep->succ)) {
1403 /*
1404 * Common branch targets can be eliminated, provided
1405 * there is no data dependency.
1406 */
1407 if (!use_conflict(ep->pred, ep->succ->et.succ)) {
1408 done = 0;
1409 ep->succ = JT(ep->succ);
1410 }
1411 }
1412 /*
1413 * For each edge dominator that matches the successor of this
1414 * edge, promote the edge successor to the its grandchild.
1415 *
1416 * XXX We violate the set abstraction here in favor a reasonably
1417 * efficient loop.
1418 */
1419 top:
1420 for (i = 0; i < edgewords; ++i) {
1421 register bpf_u_int32 x = ep->edom[i];
1422
1423 while (x != 0) {
1424 k = ffs(x) - 1;
1425 x &=~ (1 << k);
1426 k += i * BITS_PER_WORD;
1427
1428 target = fold_edge(ep->succ, edges[k]);
1429 /*
1430 * Check that there is no data dependency between
1431 * nodes that will be violated if we move the edge.
1432 */
1433 if (target != 0 && !use_conflict(ep->pred, target)) {
1434 done = 0;
1435 ep->succ = target;
1436 if (JT(target) != 0)
1437 /*
1438 * Start over unless we hit a leaf.
1439 */
1440 goto top;
1441 return;
1442 }
1443 }
1444 }
1445}
1446
1447
1448static void
1449or_pullup(b)
1450 struct block *b;
1451{
1452 int val, at_top;
1453 struct block *pull;
1454 struct block **diffp, **samep;
1455 struct edge *ep;
1456
1457 ep = b->in_edges;
1458 if (ep == 0)
1459 return;
1460
1461 /*
1462 * Make sure each predecessor loads the same value.
1463 * XXX why?
1464 */
1465 val = ep->pred->val[A_ATOM];
1466 for (ep = ep->next; ep != 0; ep = ep->next)
1467 if (val != ep->pred->val[A_ATOM])
1468 return;
1469
1470 if (JT(b->in_edges->pred) == b)
1471 diffp = &JT(b->in_edges->pred);
1472 else
1473 diffp = &JF(b->in_edges->pred);
1474
1475 at_top = 1;
1476 while (1) {
1477 if (*diffp == 0)
1478 return;
1479
1480 if (JT(*diffp) != JT(b))
1481 return;
1482
1483 if (!SET_MEMBER((*diffp)->dom, b->id))
1484 return;
1485
1486 if ((*diffp)->val[A_ATOM] != val)
1487 break;
1488
1489 diffp = &JF(*diffp);
1490 at_top = 0;
1491 }
1492 samep = &JF(*diffp);
1493 while (1) {
1494 if (*samep == 0)
1495 return;
1496
1497 if (JT(*samep) != JT(b))
1498 return;
1499
1500 if (!SET_MEMBER((*samep)->dom, b->id))
1501 return;
1502
1503 if ((*samep)->val[A_ATOM] == val)
1504 break;
1505
1506 /* XXX Need to check that there are no data dependencies
1507 between dp0 and dp1. Currently, the code generator
1508 will not produce such dependencies. */
1509 samep = &JF(*samep);
1510 }
1511#ifdef notdef
1512 /* XXX This doesn't cover everything. */
1513 for (i = 0; i < N_ATOMS; ++i)
1514 if ((*samep)->val[i] != pred->val[i])
1515 return;
1516#endif
1517 /* Pull up the node. */
1518 pull = *samep;
1519 *samep = JF(pull);
1520 JF(pull) = *diffp;
1521
1522 /*
1523 * At the top of the chain, each predecessor needs to point at the
1524 * pulled up node. Inside the chain, there is only one predecessor
1525 * to worry about.
1526 */
1527 if (at_top) {
1528 for (ep = b->in_edges; ep != 0; ep = ep->next) {
1529 if (JT(ep->pred) == b)
1530 JT(ep->pred) = pull;
1531 else
1532 JF(ep->pred) = pull;
1533 }
1534 }
1535 else
1536 *diffp = pull;
1537
1538 done = 0;
1539}
1540
1541static void
1542and_pullup(b)
1543 struct block *b;
1544{
1545 int val, at_top;
1546 struct block *pull;
1547 struct block **diffp, **samep;
1548 struct edge *ep;
1549
1550 ep = b->in_edges;
1551 if (ep == 0)
1552 return;
1553
1554 /*
1555 * Make sure each predecessor loads the same value.
1556 */
1557 val = ep->pred->val[A_ATOM];
1558 for (ep = ep->next; ep != 0; ep = ep->next)
1559 if (val != ep->pred->val[A_ATOM])
1560 return;
1561
1562 if (JT(b->in_edges->pred) == b)
1563 diffp = &JT(b->in_edges->pred);
1564 else
1565 diffp = &JF(b->in_edges->pred);
1566
1567 at_top = 1;
1568 while (1) {
1569 if (*diffp == 0)
1570 return;
1571
1572 if (JF(*diffp) != JF(b))
1573 return;
1574
1575 if (!SET_MEMBER((*diffp)->dom, b->id))
1576 return;
1577
1578 if ((*diffp)->val[A_ATOM] != val)
1579 break;
1580
1581 diffp = &JT(*diffp);
1582 at_top = 0;
1583 }
1584 samep = &JT(*diffp);
1585 while (1) {
1586 if (*samep == 0)
1587 return;
1588
1589 if (JF(*samep) != JF(b))
1590 return;
1591
1592 if (!SET_MEMBER((*samep)->dom, b->id))
1593 return;
1594
1595 if ((*samep)->val[A_ATOM] == val)
1596 break;
1597
1598 /* XXX Need to check that there are no data dependencies
1599 between diffp and samep. Currently, the code generator
1600 will not produce such dependencies. */
1601 samep = &JT(*samep);
1602 }
1603#ifdef notdef
1604 /* XXX This doesn't cover everything. */
1605 for (i = 0; i < N_ATOMS; ++i)
1606 if ((*samep)->val[i] != pred->val[i])
1607 return;
1608#endif
1609 /* Pull up the node. */
1610 pull = *samep;
1611 *samep = JT(pull);
1612 JT(pull) = *diffp;
1613
1614 /*
1615 * At the top of the chain, each predecessor needs to point at the
1616 * pulled up node. Inside the chain, there is only one predecessor
1617 * to worry about.
1618 */
1619 if (at_top) {
1620 for (ep = b->in_edges; ep != 0; ep = ep->next) {
1621 if (JT(ep->pred) == b)
1622 JT(ep->pred) = pull;
1623 else
1624 JF(ep->pred) = pull;
1625 }
1626 }
1627 else
1628 *diffp = pull;
1629
1630 done = 0;
1631}
1632
1633static void
1634opt_blks(root, do_stmts)
1635 struct block *root;
1636 int do_stmts;
1637{
1638 int i, maxlevel;
1639 struct block *p;
1640
1641 init_val();
1642 maxlevel = root->level;
1643
1644 find_inedges(root);
1645 for (i = maxlevel; i >= 0; --i)
1646 for (p = levels[i]; p; p = p->link)
1647 opt_blk(p, do_stmts);
1648
1649 if (do_stmts)
1650 /*
1651 * No point trying to move branches; it can't possibly
1652 * make a difference at this point.
1653 */
1654 return;
1655
1656 for (i = 1; i <= maxlevel; ++i) {
1657 for (p = levels[i]; p; p = p->link) {
1658 opt_j(&p->et);
1659 opt_j(&p->ef);
1660 }
1661 }
1662
1663 find_inedges(root);
1664 for (i = 1; i <= maxlevel; ++i) {
1665 for (p = levels[i]; p; p = p->link) {
1666 or_pullup(p);
1667 and_pullup(p);
1668 }
1669 }
1670}
1671
1672static inline void
1673link_inedge(parent, child)
1674 struct edge *parent;
1675 struct block *child;
1676{
1677 parent->next = child->in_edges;
1678 child->in_edges = parent;
1679}
1680
1681static void
1682find_inedges(root)
1683 struct block *root;
1684{
1685 int i;
1686 struct block *b;
1687
1688 for (i = 0; i < n_blocks; ++i)
1689 blocks[i]->in_edges = 0;
1690
1691 /*
1692 * Traverse the graph, adding each edge to the predecessor
1693 * list of its successors. Skip the leaves (i.e. level 0).
1694 */
1695 for (i = root->level; i > 0; --i) {
1696 for (b = levels[i]; b != 0; b = b->link) {
1697 link_inedge(&b->et, JT(b));
1698 link_inedge(&b->ef, JF(b));
1699 }
1700 }
1701}
1702
1703static void
1704opt_root(b)
1705 struct block **b;
1706{
1707 struct slist *tmp, *s;
1708
1709 s = (*b)->stmts;
1710 (*b)->stmts = 0;
1711 while (BPF_CLASS((*b)->s.code) == BPF_JMP && JT(*b) == JF(*b))
1712 *b = JT(*b);
1713
1714 tmp = (*b)->stmts;
1715 if (tmp != 0)
1716 sappend(s, tmp);
1717 (*b)->stmts = s;
1718
1719 /*
1720 * If the root node is a return, then there is no
1721 * point executing any statements (since the bpf machine
1722 * has no side effects).
1723 */
1724 if (BPF_CLASS((*b)->s.code) == BPF_RET)
1725 (*b)->stmts = 0;
1726}
1727
1728static void
1729opt_loop(root, do_stmts)
1730 struct block *root;
1731 int do_stmts;
1732{
1733
1734#ifdef BDEBUG
1735 if (dflag > 1) {
1736 printf("opt_loop(root, %d) begin\n", do_stmts);
1737 opt_dump(root);
1738 }
1739#endif
1740 do {
1741 done = 1;
1742 find_levels(root);
1743 find_dom(root);
1744 find_closure(root);
1745 find_ud(root);
1746 find_edom(root);
1747 opt_blks(root, do_stmts);
1748#ifdef BDEBUG
1749 if (dflag > 1) {
1750 printf("opt_loop(root, %d) bottom, done=%d\n", do_stmts, done);
1751 opt_dump(root);
1752 }
1753#endif
1754 } while (!done);
1755}
1756
1757/*
1758 * Optimize the filter code in its dag representation.
1759 */
1760void
1761bpf_optimize(rootp)
1762 struct block **rootp;
1763{
1764 struct block *root;
1765
1766 root = *rootp;
1767
1768 opt_init(root);
1769 opt_loop(root, 0);
1770 opt_loop(root, 1);
1771 intern_blocks(root);
1772#ifdef BDEBUG
1773 if (dflag > 1) {
1774 printf("after intern_blocks()\n");
1775 opt_dump(root);
1776 }
1777#endif
1778 opt_root(rootp);
1779#ifdef BDEBUG
1780 if (dflag > 1) {
1781 printf("after opt_root()\n");
1782 opt_dump(root);
1783 }
1784#endif
1785 opt_cleanup();
1786}
1787
1788static void
1789make_marks(p)
1790 struct block *p;
1791{
1792 if (!isMarked(p)) {
1793 Mark(p);
1794 if (BPF_CLASS(p->s.code) != BPF_RET) {
1795 make_marks(JT(p));
1796 make_marks(JF(p));
1797 }
1798 }
1799}
1800
1801/*
1802 * Mark code array such that isMarked(i) is true
1803 * only for nodes that are alive.
1804 */
1805static void
1806mark_code(p)
1807 struct block *p;
1808{
1809 cur_mark += 1;
1810 make_marks(p);
1811}
1812
1813/*
1814 * True iff the two stmt lists load the same value from the packet into
1815 * the accumulator.
1816 */
1817static int
1818eq_slist(x, y)
1819 struct slist *x, *y;
1820{
1821 while (1) {
1822 while (x && x->s.code == NOP)
1823 x = x->next;
1824 while (y && y->s.code == NOP)
1825 y = y->next;
1826 if (x == 0)
1827 return y == 0;
1828 if (y == 0)
1829 return x == 0;
1830 if (x->s.code != y->s.code || x->s.k != y->s.k)
1831 return 0;
1832 x = x->next;
1833 y = y->next;
1834 }
1835}
1836
1837static inline int
1838eq_blk(b0, b1)
1839 struct block *b0, *b1;
1840{
1841 if (b0->s.code == b1->s.code &&
1842 b0->s.k == b1->s.k &&
1843 b0->et.succ == b1->et.succ &&
1844 b0->ef.succ == b1->ef.succ)
1845 return eq_slist(b0->stmts, b1->stmts);
1846 return 0;
1847}
1848
1849static void
1850intern_blocks(root)
1851 struct block *root;
1852{
1853 struct block *p;
1854 int i, j;
1855 int done1; /* don't shadow global */
1856 top:
1857 done1 = 1;
1858 for (i = 0; i < n_blocks; ++i)
1859 blocks[i]->link = 0;
1860
1861 mark_code(root);
1862
1863 for (i = n_blocks - 1; --i >= 0; ) {
1864 if (!isMarked(blocks[i]))
1865 continue;
1866 for (j = i + 1; j < n_blocks; ++j) {
1867 if (!isMarked(blocks[j]))
1868 continue;
1869 if (eq_blk(blocks[i], blocks[j])) {
1870 blocks[i]->link = blocks[j]->link ?
1871 blocks[j]->link : blocks[j];
1872 break;
1873 }
1874 }
1875 }
1876 for (i = 0; i < n_blocks; ++i) {
1877 p = blocks[i];
1878 if (JT(p) == 0)
1879 continue;
1880 if (JT(p)->link) {
1881 done1 = 0;
1882 JT(p) = JT(p)->link;
1883 }
1884 if (JF(p)->link) {
1885 done1 = 0;
1886 JF(p) = JF(p)->link;
1887 }
1888 }
1889 if (!done1)
1890 goto top;
1891}
1892
1893static void
1894opt_cleanup()
1895{
1896 free((void *)vnode_base);
1897 free((void *)vmap);
1898 free((void *)edges);
1899 free((void *)space);
1900 free((void *)levels);
1901 free((void *)blocks);
1902}
1903
1904/*
1905 * Return the number of stmts in 's'.
1906 */
|