diff options
Diffstat (limited to 'target/linux/etrax-2.6/image/e100boot/src/libpcap-0.4/optimize.c')
| -rw-r--r-- | target/linux/etrax-2.6/image/e100boot/src/libpcap-0.4/optimize.c | 2004 |
1 files changed, 2004 insertions, 0 deletions
diff --git a/target/linux/etrax-2.6/image/e100boot/src/libpcap-0.4/optimize.c b/target/linux/etrax-2.6/image/e100boot/src/libpcap-0.4/optimize.c new file mode 100644 index 0000000000..43d07d9dad --- /dev/null +++ b/target/linux/etrax-2.6/image/e100boot/src/libpcap-0.4/optimize.c @@ -0,0 +1,2004 @@ +/* + * Copyright (c) 1988, 1989, 1990, 1991, 1993, 1994, 1995, 1996 + * The Regents of the University of California. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that: (1) source code distributions + * retain the above copyright notice and this paragraph in its entirety, (2) + * distributions including binary code include the above copyright notice and + * this paragraph in its entirety in the documentation or other materials + * provided with the distribution, and (3) all advertising materials mentioning + * features or use of this software display the following acknowledgement: + * ``This product includes software developed by the University of California, + * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of + * the University nor the names of its contributors may be used to endorse + * or promote products derived from this software without specific prior + * written permission. + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED + * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. + * + * Optimization module for tcpdump intermediate representation. + */ +#ifndef lint +static const char rcsid[] = + "@(#) $Header: /usr/local/cvs/linux/tools/build/e100boot/libpcap-0.4/optimize.c,v 1.1 1999/08/26 10:05:23 johana Exp $ (LBL)"; +#endif + +#include <sys/types.h> +#include <sys/time.h> + +#include <stdio.h> +#include <stdlib.h> +#include <memory.h> + +#include "pcap-int.h" + +#include "gencode.h" + +#include "gnuc.h" +#ifdef HAVE_OS_PROTO_H +#include "os-proto.h" +#endif + +#ifdef BDEBUG +extern int dflag; +#endif + +#define A_ATOM BPF_MEMWORDS +#define X_ATOM (BPF_MEMWORDS+1) + +#define NOP -1 + +/* + * This define is used to represent *both* the accumulator and + * x register in use-def computations. + * Currently, the use-def code assumes only one definition per instruction. + */ +#define AX_ATOM N_ATOMS + +/* + * A flag to indicate that further optimization is needed. + * Iterative passes are continued until a given pass yields no + * branch movement. + */ +static int done; + +/* + * A block is marked if only if its mark equals the current mark. + * Rather than traverse the code array, marking each item, 'cur_mark' is + * incremented. This automatically makes each element unmarked. + */ +static int cur_mark; +#define isMarked(p) ((p)->mark == cur_mark) +#define unMarkAll() cur_mark += 1 +#define Mark(p) ((p)->mark = cur_mark) + +static void opt_init(struct block *); +static void opt_cleanup(void); + +static void make_marks(struct block *); +static void mark_code(struct block *); + +static void intern_blocks(struct block *); + +static int eq_slist(struct slist *, struct slist *); + +static void find_levels_r(struct block *); + +static void find_levels(struct block *); +static void find_dom(struct block *); +static void propedom(struct edge *); +static void find_edom(struct block *); +static void find_closure(struct block *); +static int atomuse(struct stmt *); +static int atomdef(struct stmt *); +static void compute_local_ud(struct block *); +static void find_ud(struct block *); +static void init_val(void); +static int F(int, int, int); +static inline void vstore(struct stmt *, int *, int, int); +static void opt_blk(struct block *, int); +static int use_conflict(struct block *, struct block *); +static void opt_j(struct edge *); +static void or_pullup(struct block *); +static void and_pullup(struct block *); +static void opt_blks(struct block *, int); +static inline void link_inedge(struct edge *, struct block *); +static void find_inedges(struct block *); +static void opt_root(struct block **); +static void opt_loop(struct block *, int); +static void fold_op(struct stmt *, int, int); +static inline struct slist *this_op(struct slist *); +static void opt_not(struct block *); +static void opt_peep(struct block *); +static void opt_stmt(struct stmt *, int[], int); +static void deadstmt(struct stmt *, struct stmt *[]); +static void opt_deadstores(struct block *); +static void opt_blk(struct block *, int); +static int use_conflict(struct block *, struct block *); +static void opt_j(struct edge *); +static struct block *fold_edge(struct block *, struct edge *); +static inline int eq_blk(struct block *, struct block *); +static int slength(struct slist *); +static int count_blocks(struct block *); +static void number_blks_r(struct block *); +static int count_stmts(struct block *); +static int convert_code_r(struct block *); +#ifdef BDEBUG +static void opt_dump(struct block *); +#endif + +static int n_blocks; +struct block **blocks; +static int n_edges; +struct edge **edges; + +/* + * A bit vector set representation of the dominators. + * We round up the set size to the next power of two. + */ +static int nodewords; +static int edgewords; +struct block **levels; +bpf_u_int32 *space; +#define BITS_PER_WORD (8*sizeof(bpf_u_int32)) +/* + * True if a is in uset {p} + */ +#define SET_MEMBER(p, a) \ +((p)[(unsigned)(a) / BITS_PER_WORD] & (1 << ((unsigned)(a) % BITS_PER_WORD))) + +/* + * Add 'a' to uset p. + */ +#define SET_INSERT(p, a) \ +(p)[(unsigned)(a) / BITS_PER_WORD] |= (1 << ((unsigned)(a) % BITS_PER_WORD)) + +/* + * Delete 'a' from uset p. + */ +#define SET_DELETE(p, a) \ +(p)[(unsigned)(a) / BITS_PER_WORD] &= ~(1 << ((unsigned)(a) % BITS_PER_WORD)) + +/* + * a := a intersect b + */ +#define SET_INTERSECT(a, b, n)\ +{\ + register bpf_u_int32 *_x = a, *_y = b;\ + register int _n = n;\ + while (--_n >= 0) *_x++ &= *_y++;\ +} + +/* + * a := a - b + */ +#define SET_SUBTRACT(a, b, n)\ +{\ + register bpf_u_int32 *_x = a, *_y = b;\ + register int _n = n;\ + while (--_n >= 0) *_x++ &=~ *_y++;\ +} + +/* + * a := a union b + */ +#define SET_UNION(a, b, n)\ +{\ + register bpf_u_int32 *_x = a, *_y = b;\ + register int _n = n;\ + while (--_n >= 0) *_x++ |= *_y++;\ +} + +static uset all_dom_sets; +static uset all_closure_sets; +static uset all_edge_sets; + +#ifndef MAX +#define MAX(a,b) ((a)>(b)?(a):(b)) +#endif + +static void +find_levels_r(b) + struct block *b; +{ + int level; + + if (isMarked(b)) + return; + + Mark(b); + b->link = 0; + + if (JT(b)) { + find_levels_r(JT(b)); + find_levels_r(JF(b)); + level = MAX(JT(b)->level, JF(b)->level) + 1; + } else + level = 0; + b->level = level; + b->link = levels[level]; + levels[level] = b; +} + +/* + * Level graph. The levels go from 0 at the leaves to + * N_LEVELS at the root. The levels[] array points to the + * first node of the level list, whose elements are linked + * with the 'link' field of the struct block. + */ +static void +find_levels(root) + struct block *root; +{ + memset((char *)levels, 0, n_blocks * sizeof(*levels)); + unMarkAll(); + find_levels_r(root); +} + +/* + * Find dominator relationships. + * Assumes graph has been leveled. + */ +static void +find_dom(root) + struct block *root; +{ + int i; + struct block *b; + bpf_u_int32 *x; + + /* + * Initialize sets to contain all nodes. + */ + x = all_dom_sets; + i = n_blocks * nodewords; + while (--i >= 0) + *x++ = ~0; + /* Root starts off empty. */ + for (i = nodewords; --i >= 0;) + root->dom[i] = 0; + + /* root->level is the highest level no found. */ + for (i = root->level; i >= 0; --i) { + for (b = levels[i]; b; b = b->link) { + SET_INSERT(b->dom, b->id); + if (JT(b) == 0) + continue; + SET_INTERSECT(JT(b)->dom, b->dom, nodewords); + SET_INTERSECT(JF(b)->dom, b->dom, nodewords); + } + } +} + +static void +propedom(ep) + struct edge *ep; +{ + SET_INSERT(ep->edom, ep->id); + if (ep->succ) { + SET_INTERSECT(ep->succ->et.edom, ep->edom, edgewords); + SET_INTERSECT(ep->succ->ef.edom, ep->edom, edgewords); + } +} + +/* + * Compute edge dominators. + * Assumes graph has been leveled and predecessors established. + */ +static void +find_edom(root) + struct block *root; +{ + int i; + uset x; + struct block *b; + + x = all_edge_sets; + for (i = n_edges * edgewords; --i >= 0; ) + x[i] = ~0; + + /* root->level is the highest level no found. */ + memset(root->et.edom, 0, edgewords * sizeof(*(uset)0)); + memset(root->ef.edom, 0, edgewords * sizeof(*(uset)0)); + for (i = root->level; i >= 0; --i) { + for (b = levels[i]; b != 0; b = b->link) { + propedom(&b->et); + propedom(&b->ef); + } + } +} + +/* + * Find the backwards transitive closure of the flow graph. These sets + * are backwards in the sense that we find the set of nodes that reach + * a given node, not the set of nodes that can be reached by a node. + * + * Assumes graph has been leveled. + */ +static void +find_closure(root) + struct block *root; +{ + int i; + struct block *b; + + /* + * Initialize sets to contain no nodes. + */ + memset((char *)all_closure_sets, 0, + n_blocks * nodewords * sizeof(*all_closure_sets)); + + /* root->level is the highest level no found. */ + for (i = root->level; i >= 0; --i) { + for (b = levels[i]; b; b = b->link) { + SET_INSERT(b->closure, b->id); + if (JT(b) == 0) + continue; + SET_UNION(JT(b)->closure, b->closure, nodewords); + SET_UNION(JF(b)->closure, b->closure, nodewords); + } + } +} + +/* + * Return the register number that is used by s. If A and X are both + * used, return AX_ATOM. If no register is used, return -1. + * + * The implementation should probably change to an array access. + */ +static int +atomuse(s) + struct stmt *s; +{ + register int c = s->code; + + if (c == NOP) + return -1; + + switch (BPF_CLASS(c)) { + + case BPF_RET: + return (BPF_RVAL(c) == BPF_A) ? A_ATOM : + (BPF_RVAL(c) == BPF_X) ? X_ATOM : -1; + + case BPF_LD: + case BPF_LDX: + return (BPF_MODE(c) == BPF_IND) ? X_ATOM : + (BPF_MODE(c) == BPF_MEM) ? s->k : -1; + + case BPF_ST: + return A_ATOM; + + case BPF_STX: + return X_ATOM; + + case BPF_JMP: + case BPF_ALU: + if (BPF_SRC(c) == BPF_X) + return AX_ATOM; + return A_ATOM; + + case BPF_MISC: + return BPF_MISCOP(c) == BPF_TXA ? X_ATOM : A_ATOM; + } + abort(); + /* NOTREACHED */ +} + +/* + * Return the register number that is defined by 's'. We assume that + * a single stmt cannot define more than one register. If no register + * is defined, return -1. + * + * The implementation should probably change to an array access. + */ +static int +atomdef(s) + struct stmt *s; +{ + if (s->code == NOP) + return -1; + + switch (BPF_CLASS(s->code)) { + + case BPF_LD: + case BPF_ALU: + return A_ATOM; + + case BPF_LDX: + return X_ATOM; + + case BPF_ST: + case BPF_STX: + return s->k; + + case BPF_MISC: + return BPF_MISCOP(s->code) == BPF_TAX ? X_ATOM : A_ATOM; + } + return -1; +} + +static void +compute_local_ud(b) + struct block *b; +{ + struct slist *s; + atomset def = 0, use = 0, kill = 0; + int atom; + + for (s = b->stmts; s; s = s->next) { + if (s->s.code == NOP) + continue; + atom = atomuse(&s->s); + if (atom >= 0) { + if (atom == AX_ATOM) { + if (!ATOMELEM(def, X_ATOM)) + use |= ATOMMASK(X_ATOM); + if (!ATOMELEM(def, A_ATOM)) + use |= ATOMMASK(A_ATOM); + } + else if (atom < N_ATOMS) { + if (!ATOMELEM(def, atom)) + use |= ATOMMASK(atom); + } + else + abort(); + } + atom = atomdef(&s->s); + if (atom >= 0) { + if (!ATOMELEM(use, atom)) + kill |= ATOMMASK(atom); + def |= ATOMMASK(atom); + } + } + if (!ATOMELEM(def, A_ATOM) && BPF_CLASS(b->s.code) == BPF_JMP) + use |= ATOMMASK(A_ATOM); + + b->def = def; + b->kill = kill; + b->in_use = use; +} + +/* + * Assume graph is already leveled. + */ +static void +find_ud(root) + struct block *root; +{ + int i, maxlevel; + struct block *p; + + /* + * root->level is the highest level no found; + * count down from there. + */ + maxlevel = root->level; + for (i = maxlevel; i >= 0; --i) + for (p = levels[i]; p; p = p->link) { + compute_local_ud(p); + p->out_use = 0; + } + + for (i = 1; i <= maxlevel; ++i) { + for (p = levels[i]; p; p = p->link) { + p->out_use |= JT(p)->in_use | JF(p)->in_use; + p->in_use |= p->out_use &~ p->kill; + } + } +} + +/* + * These data structures are used in a Cocke and Shwarz style + * value numbering scheme. Since the flowgraph is acyclic, + * exit values can be propagated from a node's predecessors + * provided it is uniquely defined. + */ +struct valnode { + int code; + int v0, v1; + int val; + struct valnode *next; +}; + +#define MODULUS 213 +static struct valnode *hashtbl[MODULUS]; +static int curval; +static int maxval; + +/* Integer constants mapped with the load immediate opcode. */ +#define K(i) F(BPF_LD|BPF_IMM|BPF_W, i, 0L) + +struct vmapinfo { + int is_const; + bpf_int32 const_val; +}; + +struct vmapinfo *vmap; +struct valnode *vnode_base; +struct valnode *next_vnode; + +static void +init_val() +{ + curval = 0; + next_vnode = vnode_base; + memset((char *)vmap, 0, maxval * sizeof(*vmap)); + memset((char *)hashtbl, 0, sizeof hashtbl); +} + +/* Because we really don't have an IR, this stuff is a little messy. */ +static int +F(code, v0, v1) + int code; + int v0, v1; +{ + u_int hash; + int val; + struct valnode *p; + + hash = (u_int)code ^ (v0 << 4) ^ (v1 << 8); + hash %= MODULUS; + + for (p = hashtbl[hash]; p; p = p->next) + if (p->code == code && p->v0 == v0 && p->v1 == v1) + return p->val; + + val = ++curval; + if (BPF_MODE(code) == BPF_IMM && + (BPF_CLASS(code) == BPF_LD || BPF_CLASS(code) == BPF_LDX)) { + vmap[val].const_val = v0; + vmap[val].is_const = 1; + } + p = next_vnode++; + p->val = val; + p->code = code; + p->v0 = v0; + p->v1 = v1; + p->next = hashtbl[hash]; + hashtbl[hash] = p; + + return val; +} + +static inline void +vstore(s, valp, newval, alter) + struct stmt *s; + int *valp; + int newval; + int alter; +{ + if (alter && *valp == newval) + s->code = NOP; + else + *valp = newval; +} + +static void +fold_op(s, v0, v1) + struct stmt *s; + int v0, v1; +{ + bpf_int32 a, b; + + a = vmap[v0].const_val; + b = vmap[v1].const_val; + + switch (BPF_OP(s->code)) { + case BPF_ADD: + a += b; + break; + + case BPF_SUB: + a -= b; + break; + + case BPF_MUL: + a *= b; + break; + + case BPF_DIV: + if (b == 0) + bpf_error("division by zero"); + a /= b; + break; + + case BPF_AND: + a &= b; + break; + + case BPF_OR: + a |= b; + break; + + case BPF_LSH: + a <<= b; + break; + + case BPF_RSH: + a >>= b; + break; + + case BPF_NEG: + a = -a; + break; + + default: + abort(); + } + s->k = a; + s->code = BPF_LD|BPF_IMM; + done = 0; +} + +static inline struct slist * +this_op(s) + struct slist *s; +{ + while (s != 0 && s->s.code == NOP) + s = s->next; + return s; +} + +static void +opt_not(b) + struct block *b; +{ + struct block *tmp = JT(b); + + JT(b) = JF(b); + JF(b) = tmp; +} + +static void +opt_peep(b) + struct block *b; +{ + struct slist *s; + struct slist *next, *last; + int val; + + s = b->stmts; + if (s == 0) + return; + + last = s; + while (1) { + s = this_op(s); + if (s == 0) + break; + next = this_op(s->next); + if (next == 0) + break; + last = next; + + /* + * st M[k] --> st M[k] + * ldx M[k] tax + */ + if (s->s.code == BPF_ST && + next->s.code == (BPF_LDX|BPF_MEM) && + s->s.k == next->s.k) { + done = 0; + next->s.code = BPF_MISC|BPF_TAX; + } + /* + * ld #k --> ldx #k + * tax txa + */ + if (s->s.code == (BPF_LD|BPF_IMM) && + next->s.code == (BPF_MISC|BPF_TAX)) { + s->s.code = BPF_LDX|BPF_IMM; + next->s.code = BPF_MISC|BPF_TXA; + done = 0; + } + /* + * This is an ugly special case, but it happens + * when you say tcp[k] or udp[k] where k is a constant. + */ + if (s->s.code == (BPF_LD|BPF_IMM)) { + struct slist *add, *tax, *ild; + + /* + * Check that X isn't used on exit from this + * block (which the optimizer might cause). + * We know the code generator won't generate + * any local dependencies. + */ + if (ATOMELEM(b->out_use, X_ATOM)) + break; + + if (next->s.code != (BPF_LDX|BPF_MSH|BPF_B)) + add = next; + else + add = this_op(next->next); + if (add == 0 || add->s.code != (BPF_ALU|BPF_ADD|BPF_X)) + break; + + tax = this_op(add->next); + if (tax == 0 || tax->s.code != (BPF_MISC|BPF_TAX)) + break; + + ild = this_op(tax->next); + if (ild == 0 || BPF_CLASS(ild->s.code) != BPF_LD || + BPF_MODE(ild->s.code) != BPF_IND) + break; + /* + * XXX We need to check that X is not + * subsequently used. We know we can eliminate the + * accumulator modifications since it is defined + * by the last stmt of this sequence. + * + * We want to turn this sequence: + * + * (004) ldi #0x2 {s} + * (005) ldxms [14] {next} -- optional + * (006) addx {add} + * (007) tax {tax} + * (008) ild [x+0] {ild} + * + * into this sequence: + * + * (004) nop + * (005) ldxms [14] + * (006) nop + * (007) nop + * (008) ild [x+2] + * + */ + ild->s.k += s->s.k; + s->s.code = NOP; + add->s.code = NOP; + tax->s.code = NOP; + done = 0; + } + s = next; + } + /* + * If we have a subtract to do a comparison, and the X register + * is a known constant, we can merge this value into the + * comparison. + */ + if (last->s.code == (BPF_ALU|BPF_SUB|BPF_X) && + !ATOMELEM(b->out_use, A_ATOM)) { + val = b->val[X_ATOM]; + if (vmap[val].is_const) { + int op; + + b->s.k += vmap[val].const_val; + op = BPF_OP(b->s.code); + if (op == BPF_JGT || op == BPF_JGE) { + struct block *t = JT(b); + JT(b) = JF(b); + JF(b) = t; + b->s.k += 0x80000000; + } + last->s.code = NOP; + done = 0; + } else if (b->s.k == 0) { + /* + * sub x -> nop + * j #0 j x + */ + last->s.code = NOP; + b->s.code = BPF_CLASS(b->s.code) | BPF_OP(b->s.code) | + BPF_X; + done = 0; + } + } + /* + * Likewise, a constant subtract can be simplified. + */ + else if (last->s.code == (BPF_ALU|BPF_SUB|BPF_K) && + !ATOMELEM(b->out_use, A_ATOM)) { + int op; + + b->s.k += last->s.k; + last->s.code = NOP; + op = BPF_OP(b->s.code); + if (op == BPF_JGT || op == BPF_JGE) { + struct block *t = JT(b); + JT(b) = JF(b); + JF(b) = t; + b->s.k += 0x80000000; + } + done = 0; + } + /* + * and #k nop + * jeq #0 -> jset #k + */ + if (last->s.code == (BPF_ALU|BPF_AND|BPF_K) && + !ATOMELEM(b->out_use, A_ATOM) && b->s.k == 0) { + b->s.k = last->s.k; + b->s.code = BPF_JMP|BPF_K|BPF_JSET; + last->s.code = NOP; + done = 0; + opt_not(b); + } + /* + * If the accumulator is a known constant, we can compute the + * comparison result. + */ + val = b->val[A_ATOM]; + if (vmap[val].is_const && BPF_SRC(b->s.code) == BPF_K) { + bpf_int32 v = vmap[val].const_val; + switch (BPF_OP(b->s.code)) { + + case BPF_JEQ: + v = v == b->s.k; + break; + + case BPF_JGT: + v = (unsigned)v > b->s.k; + break; + + case BPF_JGE: + v = (unsigned)v >= b->s.k; + break; + + case BPF_JSET: + v &= b->s.k; + break; + + default: + abort(); + } + if (JF(b) != JT(b)) + done = 0; + if (v) + JF(b) = JT(b); + else + JT(b) = JF(b); + } +} + +/* + * Compute the symbolic value of expression of 's', and update + * anything it defines in the value table 'val'. If 'alter' is true, + * do various optimizations. This code would be cleaner if symbolic + * evaluation and code transformations weren't folded together. + */ +static void +opt_stmt(s, val, alter) + struct stmt *s; + int val[]; + int alter; +{ + int op; + int v; + + switch (s->code) { + + case BPF_LD|BPF_ABS|BPF_W: + case BPF_LD|BPF_ABS|BPF_H: + case BPF_LD|BPF_ABS|BPF_B: + v = F(s->code, s->k, 0L); + vstore(s, &val[A_ATOM], v, alter); + break; + + case BPF_LD|BPF_IND|BPF_W: + case BPF_LD|BPF_IND|BPF_H: + case BPF_LD|BPF_IND|BPF_B: + v = val[X_ATOM]; + if (alter && vmap[v].is_const) { + s->code = BPF_LD|BPF_ABS|BPF_SIZE(s->code); + s->k += vmap[v].const_val; + v = F(s->code, s->k, 0L); + done = 0; + } + else + v = F(s->code, s->k, v); + vstore(s, &val[A_ATOM], v, alter); + break; + + case BPF_LD|BPF_LEN: + v = F(s->code, 0L, 0L); + vstore(s, &val[A_ATOM], v, alter); + break; + + case BPF_LD|BPF_IMM: + v = K(s->k); + vstore(s, &val[A_ATOM], v, alter); + break; + + case BPF_LDX|BPF_IMM: + v = K(s->k); + vstore(s, &val[X_ATOM], v, alter); + break; + + case BPF_LDX|BPF_MSH|BPF_B: + v = F(s->code, s->k, 0L); + vstore(s, &val[X_ATOM], v, alter); + break; + + case BPF_ALU|BPF_NEG: + if (alter && vmap[val[A_ATOM]].is_const) { + s->code = BPF_LD|BPF_IMM; + s->k = -vmap[val[A_ATOM]].const_val; + val[A_ATOM] = K(s->k); + } + else + val[A_ATOM] = F(s->code, val[A_ATOM], 0L); + break; + + case BPF_ALU|BPF_ADD|BPF_K: + case BPF_ALU|BPF_SUB|BPF_K: + case BPF_ALU|BPF_MUL|BPF_K: + case BPF_ALU|BPF_DIV|BPF_K: + case BPF_ALU|BPF_AND|BPF_K: + case BPF_ALU|BPF_OR|BPF_K: + case BPF_ALU|BPF_LSH|BPF_K: + case BPF_ALU|BPF_RSH|BPF_K: + op = BPF_OP(s->code); + if (alter) { + if (s->k == 0) { + if (op == BPF_ADD || op == BPF_SUB || + op == BPF_LSH || op == BPF_RSH || + op == BPF_OR) { + s->code = NOP; + break; + } + if (op == BPF_MUL || op == BPF_AND) { + s->code = BPF_LD|BPF_IMM; + val[A_ATOM] = K(s->k); + break; + } + } + if (vmap[val[A_ATOM]].is_const) { + fold_op(s, val[A_ATOM], K(s->k)); + val[A_ATOM] = K(s->k); + break; + } + } + val[A_ATOM] = F(s->code, val[A_ATOM], K(s->k)); + break; + + case BPF_ALU|BPF_ADD|BPF_X: + case BPF_ALU|BPF_SUB|BPF_X: + case BPF_ALU|BPF_MUL|BPF_X: + case BPF_ALU|BPF_DIV|BPF_X: + case BPF_ALU|BPF_AND|BPF_X: + case BPF_ALU|BPF_OR|BPF_X: + case BPF_ALU|BPF_LSH|BPF_X: + case BPF_ALU|BPF_RSH|BPF_X: + op = BPF_OP(s->code); + if (alter && vmap[val[X_ATOM]].is_const) { + if (vmap[val[A_ATOM]].is_const) { + fold_op(s, val[A_ATOM], val[X_ATOM]); + val[A_ATOM] = K(s->k); + } + else { + s->code = BPF_ALU|BPF_K|op; + s->k = vmap[val[X_ATOM]].const_val; + done = 0; + val[A_ATOM] = + F(s->code, val[A_ATOM], K(s->k)); + } + break; + } + /* + * Check if we're doing something to an accumulator + * that is 0, and simplify. This may not seem like + * much of a simplification but it could open up further + * optimizations. + * XXX We could also check for mul by 1, and -1, etc. + */ + if (alter && vmap[val[A_ATOM]].is_const + && vmap[val[A_ATOM]].const_val == 0) { + if (op == BPF_ADD || op == BPF_OR || + op == BPF_LSH || op == BPF_RSH || op == BPF_SUB) { + s->code = BPF_MISC|BPF_TXA; + vstore(s, &val[A_ATOM], val[X_ATOM], alter); + break; + } + else if (op == BPF_MUL || op == BPF_DIV || + op == BPF_AND) { + s->code = BPF_LD|BPF_IMM; + s->k = 0; + vstore(s, &val[A_ATOM], K(s->k), alter); + break; + } + else if (op == BPF_NEG) { + s->code = NOP; + break; + } + } + val[A_ATOM] = F(s->code, val[A_ATOM], val[X_ATOM]); + break; + + case BPF_MISC|BPF_TXA: + vstore(s, &val[A_ATOM], val[X_ATOM], alter); + break; + + case BPF_LD|BPF_MEM: + v = val[s->k]; + if (alter && vmap[v].is_const) { + s->code = BPF_LD|BPF_IMM; + s->k = vmap[v].const_val; + done = 0; + } + vstore(s, &val[A_ATOM], v, alter); + break; + + case BPF_MISC|BPF_TAX: + vstore(s, &val[X_ATOM], val[A_ATOM], alter); + break; + + case BPF_LDX|BPF_MEM: + v = val[s->k]; + if (alter && vmap[v].is_const) { + s->code = BPF_LDX|BPF_IMM; + s->k = vmap[v].const_val; + done = 0; + } + vstore(s, &val[X_ATOM], v, alter); + break; + + case BPF_ST: + vstore(s, &val[s->k], val[A_ATOM], alter); + break; + + case BPF_STX: + vstore(s, &val[s->k], val[X_ATOM], alter); + break; + } +} + +static void +deadstmt(s, last) + register struct stmt *s; + register struct stmt *last[]; +{ + register int atom; + + atom = atomuse(s); + if (atom >= 0) { + if (atom == AX_ATOM) { + last[X_ATOM] = 0; + last[A_ATOM] = 0; + } + else + last[atom] = 0; + } + atom = atomdef(s); + if (atom >= 0) { + if (last[atom]) { + done = 0; + last[atom]->code = NOP; + } + last[atom] = s; + } +} + +static void +opt_deadstores(b) + register struct block *b; +{ + register struct slist *s; + register int atom; + struct stmt *last[N_ATOMS]; + + memset((char *)last, 0, sizeof last); + + for (s = b->stmts; s != 0; s = s->next) + deadstmt(&s->s, last); + deadstmt(&b->s, last); + + for (atom = 0; atom < N_ATOMS; ++atom) + if (last[atom] && !ATOMELEM(b->out_use, atom)) { + last[atom]->code = NOP; + done = 0; + } +} + +static void +opt_blk(b, do_stmts) + struct block *b; + int do_stmts; +{ + struct slist *s; + struct edge *p; + int i; + bpf_int32 aval; + + /* + * Initialize the atom values. + * If we have no predecessors, everything is undefined. + * Otherwise, we inherent our values from our predecessors. + * If any register has an ambiguous value (i.e. control paths are + * merging) give it the undefined value of 0. + */ + p = b->in_edges; + if (p == 0) + memset((char *)b->val, 0, sizeof(b->val)); + else { + memcpy((char *)b->val, (char *)p->pred->val, sizeof(b->val)); + while ((p = p->next) != NULL) { + for (i = 0; i < N_ATOMS; ++i) + if (b->val[i] != p->pred->val[i]) + b->val[i] = 0; + } + } + aval = b->val[A_ATOM]; + for (s = b->stmts; s; s = s->next) + opt_stmt(&s->s, b->val, do_stmts); + + /* + * This is a special case: if we don't use anything from this + * block, and we load the accumulator with value that is + * already there, or if this block is a return, + * eliminate all the statements. + */ + if (do_stmts && + ((b->out_use == 0 && aval != 0 &&b->val[A_ATOM] == aval) || + BPF_CLASS(b->s.code) == BPF_RET)) { + if (b->stmts != 0) { + b->stmts = 0; + done = 0; + } + } else { + opt_peep(b); + opt_deadstores(b); + } + /* + * Set up values for branch optimizer. + */ + if (BPF_SRC(b->s.code) == BPF_K) + b->oval = K(b->s.k); + else + b->oval = b->val[X_ATOM]; + b->et.code = b->s.code; + b->ef.code = -b->s.code; +} + +/* + * Return true if any register that is used on exit from 'succ', has + * an exit value that is different from the corresponding exit value + * from 'b'. + */ +static int +use_conflict(b, succ) + struct block *b, *succ; +{ + int atom; + atomset use = succ->out_use; + + if (use == 0) + return 0; + + for (atom = 0; atom < N_ATOMS; ++atom) + if (ATOMELEM(use, atom)) + if (b->val[atom] != succ->val[atom]) + return 1; + return 0; +} + +static struct block * +fold_edge(child, ep) + struct block *child; + struct edge *ep; +{ + int sense; + int aval0, aval1, oval0, oval1; + int code = ep->code; + + if (code < 0) { + code = -code; + sense = 0; + } else + sense = 1; + + if (child->s.code != code) + return 0; + + aval0 = child->val[A_ATOM]; + oval0 = child->oval; + aval1 = ep->pred->val[A_ATOM]; + oval1 = ep->pred->oval; + + if (aval0 != aval1) + return 0; + + if (oval0 == oval1) + /* + * The operands are identical, so the + * result is true if a true branch was + * taken to get here, otherwise false. + */ + return sense ? JT(child) : JF(child); + + if (sense && code == (BPF_JMP|BPF_JEQ|BPF_K)) + /* + * At this point, we only know the comparison if we + * came down the true branch, and it was an equality + * comparison with a constant. We rely on the fact that + * distinct constants have distinct value numbers. + */ + return JF(child); + + return 0; +} + +static void +opt_j(ep) + struct edge *ep; +{ + register int i, k; + register struct block *target; + + if (JT(ep->succ) == 0) + return; + + if (JT(ep->succ) == JF(ep->succ)) { + /* + * Common branch targets can be eliminated, provided + * there is no data dependency. + */ + if (!use_conflict(ep->pred, ep->succ->et.succ)) { + done = 0; + ep->succ = JT(ep->succ); + } + } + /* + * For each edge dominator that matches the successor of this + * edge, promote the edge successor to the its grandchild. + * + * XXX We violate the set abstraction here in favor a reasonably + * efficient loop. + */ + top: + for (i = 0; i < edgewords; ++i) { + register bpf_u_int32 x = ep->edom[i]; + + while (x != 0) { + k = ffs(x) - 1; + x &=~ (1 << k); + k += i * BITS_PER_WORD; + + target = fold_edge(ep->succ, edges[k]); + /* + * Check that there is no data dependency between + * nodes that will be violated if we move the edge. + */ + if (target != 0 && !use_conflict(ep->pred, target)) { + done = 0; + ep->succ = target; + if (JT(target) != 0) + /* + * Start over unless we hit a leaf. + */ + goto top; + return; + } + } + } +} + + +static void +or_pullup(b) + struct block *b; +{ + int val, at_top; + struct block *pull; + struct block **diffp, **samep; + struct edge *ep; + + ep = b->in_edges; + if (ep == 0) + return; + + /* + * Make sure each predecessor loads the same value. + * XXX why? + */ + val = ep->pred->val[A_ATOM]; + for (ep = ep->next; ep != 0; ep = ep->next) + if (val != ep->pred->val[A_ATOM]) + return; + + if (JT(b->in_edges->pred) == b) + diffp = &JT(b->in_edges->pred); + else + diffp = &JF(b->in_edges->pred); + + at_top = 1; + while (1) { + if (*diffp == 0) + return; + + if (JT(*diffp) != JT(b)) + return; + + if (!SET_MEMBER((*diffp)->dom, b->id)) + return; + + if ((*diffp)->val[A_ATOM] != val) + break; + + diffp = &JF(*diffp); + at_top = 0; + } + samep = &JF(*diffp); + while (1) { + if (*samep == 0) + return; + + if (JT(*samep) != JT(b)) + return; + + if (!SET_MEMBER((*samep)->dom, b->id)) + return; + + if ((*samep)->val[A_ATOM] == val) + break; + + /* XXX Need to check that there are no data dependencies + between dp0 and dp1. Currently, the code generator + will not produce such dependencies. */ + samep = &JF(*samep); + } +#ifdef notdef + /* XXX This doesn't cover everything. */ + for (i = 0; i < N_ATOMS; ++i) + if ((*samep)->val[i] != pred->val[i]) + return; +#endif + /* Pull up the node. */ + pull = *samep; + *samep = JF(pull); + JF(pull) = *diffp; + + /* + * At the top of the chain, each predecessor needs to point at the + * pulled up node. Inside the chain, there is only one predecessor + * to worry about. + */ + if (at_top) { + for (ep = b->in_edges; ep != 0; ep = ep->next) { + if (JT(ep->pred) == b) + JT(ep->pred) = pull; + else + JF(ep->pred) = pull; + } + } + else + *diffp = pull; + + done = 0; +} + +static void +and_pullup(b) + struct block *b; +{ + int val, at_top; + struct block *pull; + struct block **diffp, **samep; + struct edge *ep; + + ep = b->in_edges; + if (ep == 0) + return; + + /* + * Make sure each predecessor loads the same value. + */ + val = ep->pred->val[A_ATOM]; + for (ep = ep->next; ep != 0; ep = ep->next) + if (val != ep->pred->val[A_ATOM]) + return; + + if (JT(b->in_edges->pred) == b) + diffp = &JT(b->in_edges->pred); + else + diffp = &JF(b->in_edges->pred); + + at_top = 1; + while (1) { + if (*diffp == 0) + return; + + if (JF(*diffp) != JF(b)) + return; + + if (!SET_MEMBER((*diffp)->dom, b->id)) + return; + + if ((*diffp)->val[A_ATOM] != val) + break; + + diffp = &JT(*diffp); + at_top = 0; + } + samep = &JT(*diffp); + while (1) { + if (*samep == 0) + return; + + if (JF(*samep) != JF(b)) + return; + + if (!SET_MEMBER((*samep)->dom, b->id)) + return; + + if ((*samep)->val[A_ATOM] == val) + break; + + /* XXX Need to check that there are no data dependencies + between diffp and samep. Currently, the code generator + will not produce such dependencies. */ + samep = &JT(*samep); + } +#ifdef notdef + /* XXX This doesn't cover everything. */ + for (i = 0; i < N_ATOMS; ++i) + if ((*samep)->val[i] != pred->val[i]) + return; +#endif + /* Pull up the node. */ + pull = *samep; + *samep = JT(pull); + JT(pull) = *diffp; + + /* + * At the top of the chain, each predecessor needs to point at the + * pulled up node. Inside the chain, there is only one predecessor + * to worry about. + */ + if (at_top) { + for (ep = b->in_edges; ep != 0; ep = ep->next) { + if (JT(ep->pred) == b) + JT(ep->pred) = pull; + else + JF(ep->pred) = pull; + } + } + else + *diffp = pull; + + done = 0; +} + +static void +opt_blks(root, do_stmts) + struct block *root; + int do_stmts; +{ + int i, maxlevel; + struct block *p; + + init_val(); + maxlevel = root->level; + for (i = maxlevel; i >= 0; --i) + for (p = levels[i]; p; p = p->link) + opt_blk(p, do_stmts); + + if (do_stmts) + /* + * No point trying to move branches; it can't possibly + * make a difference at this point. + */ + return; + + for (i = 1; i <= maxlevel; ++i) { + for (p = levels[i]; p; p = p->link) { + opt_j(&p->et); + opt_j(&p->ef); + } + } + for (i = 1; i <= maxlevel; ++i) { + for (p = levels[i]; p; p = p->link) { + or_pullup(p); + and_pullup(p); + } + } +} + +static inline void +link_inedge(parent, child) + struct edge *parent; + struct block *child; +{ + parent->next = child->in_edges; + child->in_edges = parent; +} + +static void +find_inedges(root) + struct block *root; +{ + int i; + struct block *b; + + for (i = 0; i < n_blocks; ++i) + blocks[i]->in_edges = 0; + + /* + * Traverse the graph, adding each edge to the predecessor + * list of its successors. Skip the leaves (i.e. level 0). + */ + for (i = root->level; i > 0; --i) { + for (b = levels[i]; b != 0; b = b->link) { + link_inedge(&b->et, JT(b)); + link_inedge(&b->ef, JF(b)); + } + } +} + +static void +opt_root(b) + struct block **b; +{ + struct slist *tmp, *s; + + s = (*b)->stmts; + (*b)->stmts = 0; + while (BPF_CLASS((*b)->s.code) == BPF_JMP && JT(*b) == JF(*b)) + *b = JT(*b); + + tmp = (*b)->stmts; + if (tmp != 0) + sappend(s, tmp); + (*b)->stmts = s; + + /* + * If the root node is a return, then there is no + * point executing any statements (since the bpf machine + * has no side effects). + */ + if (BPF_CLASS((*b)->s.code) == BPF_RET) + (*b)->stmts = 0; +} + +static void +opt_loop(root, do_stmts) + struct block *root; + int do_stmts; +{ + +#ifdef BDEBUG + if (dflag > 1) + opt_dump(root); +#endif + do { + done = 1; + find_levels(root); + find_dom(root); + find_closure(root); + find_inedges(root); + find_ud(root); + find_edom(root); + opt_blks(root, do_stmts); +#ifdef BDEBUG + if (dflag > 1) + opt_dump(root); +#endif + } while (!done); +} + +/* + * Optimize the filter code in its dag representation. + */ +void +bpf_optimize(rootp) + struct block **rootp; +{ + struct block *root; + + root = *rootp; + + opt_init(root); + opt_loop(root, 0); + opt_loop(root, 1); + intern_blocks(root); + opt_root(rootp); + opt_cleanup(); +} + +static void +make_marks(p) + struct block *p; +{ + if (!isMarked(p)) { + Mark(p); + if (BPF_CLASS(p->s.code) != BPF_RET) { + make_marks(JT(p)); + make_marks(JF(p)); + } + } +} + +/* + * Mark code array such that isMarked(i) is true + * only for nodes that are alive. + */ +static void +mark_code(p) + struct block *p; +{ + cur_mark += 1; + make_marks(p); +} + +/* + * True iff the two stmt lists load the same value from the packet into + * the accumulator. + */ +static int +eq_slist(x, y) + struct slist *x, *y; +{ + while (1) { + while (x && x->s.code == NOP) + x = x->next; + while (y && y->s.code == NOP) + y = y->next; + if (x == 0) + return y == 0; + if (y == 0) + return x == 0; + if (x->s.code != y->s.code || x->s.k != y->s.k) + return 0; + x = x->next; + y = y->next; + } +} + +static inline int +eq_blk(b0, b1) + struct block *b0, *b1; +{ + if (b0->s.code == b1->s.code && + b0->s.k == b1->s.k && + b0->et.succ == b1->et.succ && + b0->ef.succ == b1->ef.succ) + return eq_slist(b0->stmts, b1->stmts); + return 0; +} + +static void +intern_blocks(root) + struct block *root; +{ + struct block *p; + int i, j; + int done; + top: + done = 1; + for (i = 0; i < n_blocks; ++i) + blocks[i]->link = 0; + + mark_code(root); + + for (i = n_blocks - 1; --i >= 0; ) { + if (!isMarked(blocks[i])) + continue; + for (j = i + 1; j < n_blocks; ++j) { + if (!isMarked(blocks[j])) + continue; + if (eq_blk(blocks[i], blocks[j])) { + blocks[i]->link = blocks[j]->link ? + blocks[j]->link : blocks[j]; + break; + } + } + } + for (i = 0; i < n_blocks; ++i) { + p = blocks[i]; + if (JT(p) == 0) + continue; + if (JT(p)->link) { + done = 0; + JT(p) = JT(p)->link; + } + if (JF(p)->link) { + done = 0; + JF(p) = JF(p)->link; + } + } + if (!done) + goto top; +} + +static void +opt_cleanup() +{ + free((void *)vnode_base); + free((void *)vmap); + free((void *)edges); + free((void *)space); + free((void *)levels); + free((void *)blocks); +} + +/* + * Return the number of stmts in 's'. + */ +static int +slength(s) + struct slist *s; +{ + int n = 0; + + for (; s; s = s->next) + if (s->s.code != NOP) + ++n; + return n; +} + +/* + * Return the number of nodes reachable by 'p'. + * All nodes should be initially unmarked. + */ +static int +count_blocks(p) + struct block *p; +{ + if (p == 0 || isMarked(p)) + return 0; + Mark(p); + return count_blocks(JT(p)) + count_blocks(JF(p)) + 1; +} + +/* + * Do a depth first search on the flow graph, numbering the + * the basic blocks, and entering them into the 'blocks' array.` + */ +static void +number_blks_r(p) + struct block *p; +{ + int n; + + if (p == 0 || isMarked(p)) + return; + + Mark(p); + n = n_blocks++; + p->id = n; + blocks[n] = p; + + number_blks_r(JT(p)); + number_blks_r(JF(p)); +} + +/* + * Return the number of stmts in the flowgraph reachable by 'p'. + * The nodes should be unmarked before calling. + */ +static int +count_stmts(p) + struct block *p; +{ + int n; + + if (p == 0 || isMarked(p)) + return 0; + Mark(p); + n = count_stmts(JT(p)) + count_stmts(JF(p)); + return slength(p->stmts) + n + 1; +} + +/* + * Allocate memory. All allocation is done before optimization + * is begun. A linear bound on the size of all data structures is computed + * from the total number of blocks and/or statements. + */ +static void +opt_init(root) + struct block *root; +{ + bpf_u_int32 *p; + int i, n, max_stmts; + + /* + * First, count the blocks, so we can malloc an array to map + * block number to block. Then, put the blocks into the array. + */ + unMarkAll(); + n = count_blocks(root); + blocks = (struct block **)malloc(n * sizeof(*blocks)); + unMarkAll(); + n_blocks = 0; + number_blks_r(root); + + n_edges = 2 * n_blocks; + edges = (struct edge **)malloc(n_edges * sizeof(*edges)); + + /* + * The number of levels is bounded by the number of nodes. + */ + levels = (struct block **)malloc(n_blocks * sizeof(*levels)); + + edgewords = n_edges / (8 * sizeof(bpf_u_int32)) + 1; + nodewords = n_blocks / (8 * sizeof(bpf_u_int32)) + 1; + + /* XXX */ + space = (bpf_u_int32 *)malloc(2 * n_blocks * nodewords * sizeof(*space) + + n_edges * edgewords * sizeof(*space)); + p = space; + all_dom_sets = p; + for (i = 0; i < n; ++i) { + blocks[i]->dom = p; + p += nodewords; + } + all_closure_sets = p; + for (i = 0; i < n; ++i) { + blocks[i]->closure = p; + p += nodewords; + } + all_edge_sets = p; + for (i = 0; i < n; ++i) { + register struct block *b = blocks[i]; + + b->et.edom = p; + p += edgewords; + b->ef.edom = p; + p += edgewords; + b->et.id = i; + edges[i] = &b->et; + b->ef.id = n_blocks + i; + edges[n_blocks + i] = &b->ef; + b->et.pred = b; + b->ef.pred = b; + } + max_stmts = 0; + for (i = 0; i < n; ++i) + max_stmts += slength(blocks[i]->stmts) + 1; + /* + * We allocate at most 3 value numbers per statement, + * so this is an upper bound on the number of valnodes + * we'll need. + */ + maxval = 3 * max_stmts; + vmap = (struct vmapinfo *)malloc(maxval * sizeof(*vmap)); + vnode_base = (struct valnode *)malloc(maxval * sizeof(*vmap)); +} + +/* + * Some pointers used to convert the basic block form of the code, + * into the array form that BPF requires. 'fstart' will point to + * the malloc'd array while 'ftail' is used during the recursive traversal. + */ +static struct bpf_insn *fstart; +static struct bpf_insn *ftail; + +#ifdef BDEBUG +int bids[1000]; +#endif + +/* + * Returns true if successful. Returns false if a branch has + * an offset that is too large. If so, we have marked that + * branch so that on a subsequent iteration, it will be treated + * properly. + */ +static int +convert_code_r(p) + struct block *p; +{ + struct bpf_insn *dst; + struct slist *src; + int slen; + u_int off; + int extrajmps; /* number of extra jumps inserted */ + + if (p == 0 || isMarked(p)) + return (1); + Mark(p); + + if (convert_code_r(JF(p)) == 0) + return (0); + if (convert_code_r(JT(p)) == 0) + return (0); + + slen = slength(p->stmts); + dst = ftail -= (slen + 1 + p->longjt + p->longjf); + /* inflate length by any extra jumps */ + + p->offset = dst - fstart; + + for (src = p->stmts; src; src = src->next) { + if (src->s.code == NOP) + continue; + dst->code = (u_short)src->s.code; + dst->k = src->s.k; + ++dst; + } +#ifdef BDEBUG + bids[dst - fstart] = p->id + 1; +#endif + dst->code = (u_short)p->s.code; + dst->k = p->s.k; + if (JT(p)) { + extrajmps = 0; + off = JT(p)->offset - (p->offset + slen) - 1; + if (off >= 256) { + /* offset too large for branch, must add a jump */ + if (p->longjt == 0) { + /* mark this instruction and retry */ + p->longjt++; + return(0); + } + /* branch if T to following jump */ + dst->jt = extrajmps; + extrajmps++; + dst[extrajmps].code = BPF_JMP|BPF_JA; + dst[extrajmps].k = off - extrajmps; + } + else + dst->jt = off; + off = JF(p)->offset - (p->offset + slen) - 1; + if (off >= 256) { + /* offset too large for branch, must add a jump */ + if (p->longjf == 0) { + /* mark this instruction and retry */ + p->longjf++; + return(0); + } + /* branch if F to following jump */ + /* if two jumps are inserted, F goes to second one */ + dst->jf = extrajmps; + extrajmps++; + dst[extrajmps].code = BPF_JMP|BPF_JA; + dst[extrajmps].k = off - extrajmps; + } + else + dst->jf = off; + } + return (1); +} + + +/* + * Convert flowgraph intermediate representation to the + * BPF array representation. Set *lenp to the number of instructions. + */ +struct bpf_insn * +icode_to_fcode(root, lenp) + struct block *root; + int *lenp; +{ + int n; + struct bpf_insn *fp; + + /* + * Loop doing convert_codr_r() until no branches remain + * with too-large offsets. + */ + while (1) { + unMarkAll(); + n = *lenp = count_stmts(root); + + fp = (struct bpf_insn *)malloc(sizeof(*fp) * n); + memset((char *)fp, 0, sizeof(*fp) * n); + fstart = fp; + ftail = fp + n; + + unMarkAll(); + if (convert_code_r(root)) + break; + free(fp); + } + + return fp; +} + +#ifdef BDEBUG +static void +opt_dump(root) + struct block *root; +{ + struct bpf_program f; + + memset(bids, 0, sizeof bids); + f.bf_insns = icode_to_fcode(root, &f.bf_len); + bpf_dump(&f, 1); + putchar('\n'); + free((char *)f.bf_insns); +} +#endif |