X-Git-Url: https://git.tcpdump.org/libpcap/blobdiff_plain/ae7216eb6094534d2a3a739d8867feb33a9fd25e..c6ea3652f55b9d1ab1c0c94f5f8ba0c0bca64a9d:/optimize.c?ds=inline diff --git a/optimize.c b/optimize.c index 4115cb55..ad2fdb31 100644 --- a/optimize.c +++ b/optimize.c @@ -21,9 +21,7 @@ * Optimization module for BPF code intermediate representation. */ -#ifdef HAVE_CONFIG_H #include -#endif #include @@ -119,7 +117,7 @@ pcap_set_print_dot_graph(int value) #define lowest_set_bit(mask) ((u_int)__builtin_ctz(mask)) #elif defined(_MSC_VER) /* - * Visual Studio; we support only 2005 and later, so use + * Visual Studio; we support only 2015 and later, so use * _BitScanForward(). */ #include @@ -142,33 +140,14 @@ lowest_set_bit(int mask) return (u_int)bit; } #else -/* - * None of the above. - * Use a perfect-hash-function-based function. - */ -static u_int -lowest_set_bit(int mask) -{ - unsigned int v = (unsigned int)mask; - - static const u_int MultiplyDeBruijnBitPosition[32] = { - 0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8, - 31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9 - }; - - /* - * We strip off all but the lowermost set bit (v & ~v), - * and perform a minimal perfect hash on it to look up the - * number of low-order zero bits in a table. - * - * See: - * - * http://7ooo.mooo.com/text/ComputingTrailingZerosHOWTO.pdf - * - * http://supertech.csail.mit.edu/papers/debruijn.pdf - */ - return (MultiplyDeBruijnBitPosition[((v & -v) * 0x077CB531U) >> 27]); -} + /* + * POSIX.1-2001 says ffs() is in . Every supported non-Windows OS + * (including Linux with musl libc and uclibc-ng) has the header and (except + * HP-UX) declares the function there. HP-UX declares the function in + * , which has already been included. + */ + #include + #define lowest_set_bit(mask) ((u_int)(ffs((mask)) - 1)) #endif /* @@ -850,11 +829,11 @@ fold_op(opt_state_t *opt_state, struct stmt *s, bpf_u_int32 v0, bpf_u_int32 v1) } s->k = a; s->code = BPF_LD|BPF_IMM; + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } static inline struct slist * @@ -910,12 +889,12 @@ opt_peep(opt_state_t *opt_state, struct block *b) if (s->s.code == BPF_ST && next->s.code == (BPF_LDX|BPF_MEM) && s->s.k == next->s.k) { + opt_state->done = 0; + next->s.code = BPF_MISC|BPF_TAX; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; - next->s.code = BPF_MISC|BPF_TAX; } /* * ld #k --> ldx #k @@ -925,11 +904,11 @@ opt_peep(opt_state_t *opt_state, struct block *b) next->s.code == (BPF_MISC|BPF_TAX)) { s->s.code = BPF_LDX|BPF_IMM; next->s.code = BPF_MISC|BPF_TXA; + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } /* * This is an ugly special case, but it happens @@ -1008,11 +987,11 @@ opt_peep(opt_state_t *opt_state, struct block *b) s->s.code = NOP; add->s.code = NOP; tax->s.code = NOP; + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } } /* @@ -1042,11 +1021,11 @@ opt_peep(opt_state_t *opt_state, struct block *b) */ b->s.k += opt_state->vmap[val].const_val; last->s.code = NOP; + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } else if (b->s.k == 0) { /* * If the X register isn't a constant, @@ -1059,11 +1038,11 @@ opt_peep(opt_state_t *opt_state, struct block *b) */ last->s.code = NOP; b->s.code = BPF_JMP|BPF_JEQ|BPF_X; + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } } /* @@ -1075,11 +1054,11 @@ opt_peep(opt_state_t *opt_state, struct block *b) else if (last->s.code == (BPF_ALU|BPF_SUB|BPF_K)) { last->s.code = NOP; b->s.k += last->s.k; + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } /* * And, similarly, a constant AND can be simplified @@ -1093,12 +1072,12 @@ opt_peep(opt_state_t *opt_state, struct block *b) b->s.k = last->s.k; b->s.code = BPF_JMP|BPF_K|BPF_JSET; last->s.code = NOP; + opt_state->done = 0; + opt_not(b); /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; - opt_not(b); } } /* @@ -1151,11 +1130,11 @@ opt_peep(opt_state_t *opt_state, struct block *b) abort(); } if (JF(b) != JT(b)) { + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } if (v) JF(b) = JT(b); @@ -1193,11 +1172,11 @@ opt_stmt(opt_state_t *opt_state, struct stmt *s, bpf_u_int32 val[], int alter) s->code = BPF_LD|BPF_ABS|BPF_SIZE(s->code); s->k += opt_state->vmap[v].const_val; v = F(opt_state, s->code, s->k, 0L); + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } else v = F(opt_state, s->code, s->k, v); @@ -1324,13 +1303,13 @@ opt_stmt(opt_state_t *opt_state, struct stmt *s, bpf_u_int32 val[], int alter) s->k > 31) opt_error(opt_state, "shift by more than 31 bits"); + opt_state->done = 0; + val[A_ATOM] = + F(opt_state, s->code, val[A_ATOM], K(s->k)); /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; - val[A_ATOM] = - F(opt_state, s->code, val[A_ATOM], K(s->k)); } break; } @@ -1372,11 +1351,11 @@ opt_stmt(opt_state_t *opt_state, struct stmt *s, bpf_u_int32 val[], int alter) if (alter && opt_state->vmap[v].is_const) { s->code = BPF_LD|BPF_IMM; s->k = opt_state->vmap[v].const_val; + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } vstore(s, &val[A_ATOM], v, alter); break; @@ -1390,11 +1369,11 @@ opt_stmt(opt_state_t *opt_state, struct stmt *s, bpf_u_int32 val[], int alter) if (alter && opt_state->vmap[v].is_const) { s->code = BPF_LDX|BPF_IMM; s->k = opt_state->vmap[v].const_val; + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } vstore(s, &val[X_ATOM], v, alter); break; @@ -1426,12 +1405,12 @@ deadstmt(opt_state_t *opt_state, register struct stmt *s, register struct stmt * atom = atomdef(s); if (atom >= 0) { if (last[atom]) { + opt_state->done = 0; + last[atom]->code = NOP; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; - last[atom]->code = NOP; } last[atom] = s; } @@ -1453,11 +1432,17 @@ opt_deadstores(opt_state_t *opt_state, register struct block *b) for (atom = 0; atom < N_ATOMS; ++atom) if (last[atom] && !ATOMELEM(b->out_use, atom)) { last[atom]->code = NOP; + /* + * The store was removed as it's dead, + * so the value stored into now has + * an unknown value. + */ + vstore(0, &b->val[atom], VAL_UNKNOWN, 0); + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } } @@ -1547,11 +1532,11 @@ opt_blk(opt_state_t *opt_state, struct block *b, int do_stmts) BPF_CLASS(b->s.code) == BPF_RET)) { if (b->stmts != 0) { b->stmts = 0; + opt_state->done = 0; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 1; - opt_state->done = 0; } } else { opt_peep(opt_state, b); @@ -1719,12 +1704,13 @@ opt_j(opt_state_t *opt_state, struct edge *ep) * Make this edge go to the block to * which the successor of that edge * goes. - * - * XXX - optimizer loop detection. */ - opt_state->non_branch_movement_performed = 1; opt_state->done = 0; ep->succ = JT(ep->succ); + /* + * XXX - optimizer loop detection. + */ + opt_state->non_branch_movement_performed = 1; } } /* @@ -2189,11 +2175,11 @@ opt_loop(opt_state_t *opt_state, struct icode *ic, int do_stmts) */ int loop_count = 0; for (;;) { - opt_state->done = 1; /* * XXX - optimizer loop detection. */ opt_state->non_branch_movement_performed = 0; + opt_state->done = 1; find_levels(opt_state, ic); find_dom(opt_state, ic->root); find_closure(opt_state, ic->root); @@ -2264,7 +2250,6 @@ bpf_optimize(struct icode *ic, char *errbuf) memset(&opt_state, 0, sizeof(opt_state)); opt_state.errbuf = errbuf; - opt_state.non_branch_movement_performed = 0; if (setjmp(opt_state.top_ctx)) { opt_cleanup(&opt_state); return -1;