| /* |
| * 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[] _U_ = |
| "@(#) $Header: /tcpdump/master/libpcap/optimize.c,v 1.91 2008-01-02 04:16:46 guy Exp $ (LBL)"; |
| #endif |
| |
| #ifdef HAVE_CONFIG_H |
| #include "config.h" |
| #endif |
| |
| #ifdef WIN32 |
| #include <pcap-stdinc.h> |
| #else /* WIN32 */ |
| #if HAVE_INTTYPES_H |
| #include <inttypes.h> |
| #elif HAVE_STDINT_H |
| #include <stdint.h> |
| #endif |
| #ifdef HAVE_SYS_BITYPES_H |
| #include <sys/bitypes.h> |
| #endif |
| #include <sys/types.h> |
| #endif /* WIN32 */ |
| |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <memory.h> |
| #include <string.h> |
| |
| #include <errno.h> |
| |
| #include "pcap-int.h" |
| |
| #include "gencode.h" |
| |
| #ifdef HAVE_OS_PROTO_H |
| #include "os-proto.h" |
| #endif |
| |
| #ifdef BDEBUG |
| extern int dflag; |
| #endif |
| |
| #if defined(MSDOS) && !defined(__DJGPP__) |
| extern int _w32_ffs (int mask); |
| #define ffs _w32_ffs |
| #endif |
| |
| #if defined(WIN32) && defined (_MSC_VER) |
| int ffs(int mask); |
| #endif |
| |
| /* |
| * Represents a deleted instruction. |
| */ |
| #define NOP -1 |
| |
| /* |
| * Register numbers for use-def values. |
| * 0 through BPF_MEMWORDS-1 represent the corresponding scratch memory |
| * location. A_ATOM is the accumulator and X_ATOM is the index |
| * register. |
| */ |
| #define A_ATOM BPF_MEMWORDS |
| #define X_ATOM (BPF_MEMWORDS+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 struct block *fold_edge(struct block *, struct edge *); |
| static inline int eq_blk(struct block *, struct block *); |
| static u_int slength(struct slist *); |
| static int count_blocks(struct block *); |
| static void number_blks_r(struct block *); |
| static u_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; |
| } |
| |
| /* |
| * Compute the sets of registers used, defined, and killed by 'b'. |
| * |
| * "Used" means that a statement in 'b' uses the register before any |
| * statement in 'b' defines it, i.e. it uses the value left in |
| * that register by a predecessor block of this block. |
| * "Defined" means that a statement in 'b' defines it. |
| * "Killed" means that a statement in 'b' defines it before any |
| * statement in 'b' uses it, i.e. it kills the value left in that |
| * register by a predecessor block of this block. |
| */ |
| 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 (BPF_CLASS(b->s.code) == BPF_JMP) { |
| /* |
| * XXX - what about RET? |
| */ |
| atom = atomuse(&b->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(); |
| } |
| } |
| |
| 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_u_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; |
| for (/*empty*/; /*empty*/; s = next) { |
| /* |
| * Skip over nops. |
| */ |
| s = this_op(s); |
| if (s == 0) |
| break; /* nothing left in the block */ |
| |
| /* |
| * Find the next real instruction after that one |
| * (skipping nops). |
| */ |
| next = this_op(s->next); |
| if (next == 0) |
| break; /* no next instruction */ |
| 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)) |
| continue; |
| |
| /* |
| * Check that the instruction following the ldi |
| * is an addx, or it's an ldxms with an addx |
| * following it (with 0 or more nops between the |
| * ldxms and addx). |
| */ |
| 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)) |
| continue; |
| |
| /* |
| * Check that a tax follows that (with 0 or more |
| * nops between them). |
| */ |
| tax = this_op(add->next); |
| if (tax == 0 || tax->s.code != (BPF_MISC|BPF_TAX)) |
| continue; |
| |
| /* |
| * Check that an ild follows that (with 0 or more |
| * nops between them). |
| */ |
| ild = this_op(tax->next); |
| if (ild == 0 || BPF_CLASS(ild->s.code) != BPF_LD || |
| BPF_MODE(ild->s.code) != BPF_IND) |
| continue; |
| /* |
| * 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] |
| * |
| * XXX We need to check that X is not |
| * subsequently used, because we want to change |
| * what'll be in it after this sequence. |
| * |
| * We know we can eliminate the accumulator |
| * modifications earlier in the sequence since |
| * it is defined by the last stmt of this sequence |
| * (i.e., the last statement of the sequence loads |
| * a value into the accumulator, so we can eliminate |
| * earlier operations on the accumulator). |
| */ |
| ild->s.k += s->s.k; |
| s->s.code = NOP; |
| add->s.code = NOP; |
| tax->s.code = NOP; |
| done = 0; |
| } |
| } |
| /* |
| * If the comparison at the end of a block is an equality |
| * comparison against a constant, and nobody uses the value |
| * we leave in the A register at the end of a block, and |
| * the operation preceding the comparison is an arithmetic |
| * operation, we can sometime optimize it away. |
| */ |
| if (b->s.code == (BPF_JMP|BPF_JEQ|BPF_K) && |
| !ATOMELEM(b->out_use, A_ATOM)) { |
| /* |
| * We can optimize away certain subtractions of the |
| * X register. |
| */ |
| if (last->s.code == (BPF_ALU|BPF_SUB|BPF_X)) { |
| val = b->val[X_ATOM]; |
| if (vmap[val].is_const) { |
| /* |
| * 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: |
| * |
| * sub x -> nop |
| * jeq #y jeq #(x+y) |
| */ |
| b->s.k += vmap[val].const_val; |
| last->s.code = NOP; |
| done = 0; |
| } else if (b->s.k == 0) { |
| /* |
| * If the X register isn't a constant, |
| * and the comparison in the test is |
| * against 0, we can compare with the |
| * X register, instead: |
| * |
| * sub x -> nop |
| * jeq #0 jeq x |
| */ |
| last->s.code = NOP; |
| b->s.code = BPF_JMP|BPF_JEQ|BPF_X; |
| done = 0; |
| } |
| } |
| /* |
| * Likewise, a constant subtract can be simplified: |
| * |
| * sub #x -> nop |
| * jeq #y -> jeq #(x+y) |
| */ |
| else if (last->s.code == (BPF_ALU|BPF_SUB|BPF_K)) { |
| last->s.code = NOP; |
| b->s.k += last->s.k; |
| done = 0; |
| } |
| /* |
| * And, similarly, a constant AND can be simplified |
| * if we're testing against 0, i.e.: |
| * |
| * and #k nop |
| * jeq #0 -> jset #k |
| */ |
| else if (last->s.code == (BPF_ALU|BPF_AND|BPF_K) && |
| 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); |
| } |
| } |
| /* |
| * jset #0 -> never |
| * jset #ffffffff -> always |
| */ |
| if (b->s.code == (BPF_JMP|BPF_K|BPF_JSET)) { |
| if (b->s.k == 0) |
| JT(b) = JF(b); |
| if (b->s.k == 0xffffffff) |
| JF(b) = JT(b); |
| } |
| /* |
| * If we're comparing against the index register, and the index |
| * register is a known constant, we can just compare against that |
| * constant. |
| */ |
| val = b->val[X_ATOM]; |
| if (vmap[val].is_const && BPF_SRC(b->s.code) == BPF_X) { |
| bpf_int32 v = vmap[val].const_val; |
| b->s.code &= ~BPF_X; |
| b->s.k = v; |
| } |
| /* |
| * 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) { |
| /* don't optimize away "sub #0" |
| * as it may be needed later to |
| * fixup the generated math code */ |
| if (op == BPF_ADD || |
| 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, etc. |
| */ |
| if (alter && vmap[val[A_ATOM]].is_const |
| && vmap[val[A_ATOM]].const_val == 0) { |
| if (op == BPF_ADD || op == BPF_OR) { |
| 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 || op == BPF_LSH || op == BPF_RSH) { |
| 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, xval; |
| |
| #if 0 |
| for (s = b->stmts; s && s->next; s = s->next) |
| if (BPF_CLASS(s->s.code) == BPF_JMP) { |
| do_stmts = 0; |
| break; |
| } |
| #endif |
| |
| /* |
| * Initialize the atom values. |
| */ |
| p = b->in_edges; |
| if (p == 0) { |
| /* |
| * We have no predecessors, so everything is undefined |
| * upon entry to this block. |
| */ |
| memset((char *)b->val, 0, sizeof(b->val)); |
| } else { |
| /* |
| * Inherit values from our predecessors. |
| * |
| * First, get the values from the predecessor along the |
| * first edge leading to this node. |
| */ |
| memcpy((char *)b->val, (char *)p->pred->val, sizeof(b->val)); |
| /* |
| * Now look at all the other nodes leading to this node. |
| * If, for the predecessor along that edge, a register |
| * has a different value from the one we have (i.e., |
| * control paths are merging, and the merging paths |
| * assign different values to that register), give the |
| * register the undefined value of 0. |
| */ |
| 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]; |
| xval = b->val[X_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 or index register with a |
| * value that is already there, or if this block is a return, |
| * eliminate all the statements. |
| * |
| * XXX - what if it does a store? |
| * |
| * XXX - why does it matter whether we use anything from this |
| * block? If the accumulator or index register doesn't change |
| * its value, isn't that OK even if we use that value? |
| * |
| * XXX - if we load the accumulator with a different value, |
| * and the block ends with a conditional branch, we obviously |
| * can't eliminate it, as the branch depends on that value. |
| * For the index register, the conditional branch only depends |
| * on the index register value if the test is against the index |
| * register value rather than a constant; if nothing uses the |
| * value we put into the index register, and we're not testing |
| * against the index register's value, and there aren't any |
| * other problems that would keep us from eliminating this |
| * block, can we eliminate it? |
| */ |
| if (do_stmts && |
| ((b->out_use == 0 && aval != 0 && b->val[A_ATOM] == aval && |
| xval != 0 && b->val[X_ATOM] == xval) || |
| 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 of the branch instructions 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. |
| * |
| * I.e., if we came down the true branch, and the branch |
| * was an equality comparison with a constant, we know the |
| * accumulator contains that constant. If we came down |
| * the false branch, or the comparison wasn't with a |
| * constant, we don't know what was in the accumulator. |
| * |
| * 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; |
| |
| find_inedges(root); |
| 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); |
| } |
| } |
| |
| find_inedges(root); |
| 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) { |
| printf("opt_loop(root, %d) begin\n", do_stmts); |
| opt_dump(root); |
| } |
| #endif |
| do { |
| done = 1; |
| find_levels(root); |
| find_dom(root); |
| find_closure(root); |
| find_ud(root); |
| find_edom(root); |
| opt_blks(root, do_stmts); |
| #ifdef BDEBUG |
| if (dflag > 1) { |
| printf("opt_loop(root, %d) bottom, done=%d\n", do_stmts, done); |
| 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); |
| #ifdef BDEBUG |
| if (dflag > 1) { |
| printf("after intern_blocks()\n"); |
| opt_dump(root); |
| } |
| #endif |
| opt_root(rootp); |
| #ifdef BDEBUG |
| if (dflag > 1) { |
| printf("after opt_root()\n"); |
| opt_dump(root); |
| } |
| #endif |
| 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 done1; /* don't shadow global */ |
| top: |
| done1 = 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) { |
| done1 = 0; |
| JT(p) = JT(p)->link; |
| } |
| if (JF(p)->link) { |
| done1 = 0; |
| JF(p) = JF(p)->link; |
| } |
| } |
| if (!done1) |
| 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 u_int |
| slength(s) |
| struct slist *s; |
| { |
| u_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. |
| * |
| * Note that "stmts" means "instructions", and that this includes |
| * |
| * side-effect statements in 'p' (slength(p->stmts)); |
| * |
| * statements in the true branch from 'p' (count_stmts(JT(p))); |
| * |
| * statements in the false branch from 'p' (count_stmts(JF(p))); |
| * |
| * the conditional jump itself (1); |
| * |
| * an extra long jump if the true branch requires it (p->longjt); |
| * |
| * an extra long jump if the false branch requires it (p->longjf). |
| */ |
| static u_int |
| count_stmts(p) |
| struct block *p; |
| { |
| u_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 + p->longjt + p->longjf; |
| } |
| |
| /* |
| * 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 **)calloc(n, sizeof(*blocks)); |
| if (blocks == NULL) |
| bpf_error("malloc"); |
| unMarkAll(); |
| n_blocks = 0; |
| number_blks_r(root); |
| |
| n_edges = 2 * n_blocks; |
| edges = (struct edge **)calloc(n_edges, sizeof(*edges)); |
| if (edges == NULL) |
| bpf_error("malloc"); |
| |
| /* |
| * The number of levels is bounded by the number of nodes. |
| */ |
| levels = (struct block **)calloc(n_blocks, sizeof(*levels)); |
| if (levels == NULL) |
| bpf_error("malloc"); |
| |
| 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)); |
| if (space == NULL) |
| bpf_error("malloc"); |
| 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 *)calloc(maxval, sizeof(*vmap)); |
| vnode_base = (struct valnode *)calloc(maxval, sizeof(*vnode_base)); |
| if (vmap == NULL || vnode_base == NULL) |
| bpf_error("malloc"); |
| } |
| |
| /* |
| * 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 */ |
| struct slist **offset = NULL; |
| |
| 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; |
| |
| /* generate offset[] for convenience */ |
| if (slen) { |
| offset = (struct slist **)calloc(slen, sizeof(struct slist *)); |
| if (!offset) { |
| bpf_error("not enough core"); |
| /*NOTREACHED*/ |
| } |
| } |
| src = p->stmts; |
| for (off = 0; off < slen && src; off++) { |
| #if 0 |
| printf("off=%d src=%x\n", off, src); |
| #endif |
| offset[off] = src; |
| src = src->next; |
| } |
| |
| off = 0; |
| 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; |
| |
| /* fill block-local relative jump */ |
| if (BPF_CLASS(src->s.code) != BPF_JMP || src->s.code == (BPF_JMP|BPF_JA)) { |
| #if 0 |
| if (src->s.jt || src->s.jf) { |
| bpf_error("illegal jmp destination"); |
| /*NOTREACHED*/ |
| } |
| #endif |
| goto filled; |
| } |
| if (off == slen - 2) /*???*/ |
| goto filled; |
| |
| { |
| int i; |
| int jt, jf; |
| const char *ljerr = "%s for block-local relative jump: off=%d"; |
| |
| #if 0 |
| printf("code=%x off=%d %x %x\n", src->s.code, |
| off, src->s.jt, src->s.jf); |
| #endif |
| |
| if (!src->s.jt || !src->s.jf) { |
| bpf_error(ljerr, "no jmp destination", off); |
| /*NOTREACHED*/ |
| } |
| |
| jt = jf = 0; |
| for (i = 0; i < slen; i++) { |
| if (offset[i] == src->s.jt) { |
| if (jt) { |
| bpf_error(ljerr, "multiple matches", off); |
| /*NOTREACHED*/ |
| } |
| |
| dst->jt = i - off - 1; |
| jt++; |
| } |
| if (offset[i] == src->s.jf) { |
| if (jf) { |
| bpf_error(ljerr, "multiple matches", off); |
| /*NOTREACHED*/ |
| } |
| dst->jf = i - off - 1; |
| jf++; |
| } |
| } |
| if (!jt || !jf) { |
| bpf_error(ljerr, "no destination found", off); |
| /*NOTREACHED*/ |
| } |
| } |
| filled: |
| ++dst; |
| ++off; |
| } |
| if (offset) |
| free(offset); |
| |
| #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. |
| * |
| * This routine does *NOT* leak the memory pointed to by fp. It *must |
| * not* do free(fp) before returning fp; doing so would make no sense, |
| * as the BPF array pointed to by the return value of icode_to_fcode() |
| * must be valid - it's being returned for use in a bpf_program structure. |
| * |
| * If it appears that icode_to_fcode() is leaking, the problem is that |
| * the program using pcap_compile() is failing to free the memory in |
| * the BPF program when it's done - the leak is in the program, not in |
| * the routine that happens to be allocating the memory. (By analogy, if |
| * a program calls fopen() without ever calling fclose() on the FILE *, |
| * it will leak the FILE structure; the leak is not in fopen(), it's in |
| * the program.) Change the program to use pcap_freecode() when it's |
| * done with the filter program. See the pcap man page. |
| */ |
| struct bpf_insn * |
| icode_to_fcode(root, lenp) |
| struct block *root; |
| u_int *lenp; |
| { |
| u_int n; |
| struct bpf_insn *fp; |
| |
| /* |
| * Loop doing convert_code_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); |
| if (fp == NULL) |
| bpf_error("malloc"); |
| memset((char *)fp, 0, sizeof(*fp) * n); |
| fstart = fp; |
| ftail = fp + n; |
| |
| unMarkAll(); |
| if (convert_code_r(root)) |
| break; |
| free(fp); |
| } |
| |
| return fp; |
| } |
| |
| /* |
| * Make a copy of a BPF program and put it in the "fcode" member of |
| * a "pcap_t". |
| * |
| * If we fail to allocate memory for the copy, fill in the "errbuf" |
| * member of the "pcap_t" with an error message, and return -1; |
| * otherwise, return 0. |
| */ |
| int |
| install_bpf_program(pcap_t *p, struct bpf_program *fp) |
| { |
| size_t prog_size; |
| |
| /* |
| * Validate the program. |
| */ |
| if (!bpf_validate(fp->bf_insns, fp->bf_len)) { |
| snprintf(p->errbuf, sizeof(p->errbuf), |
| "BPF program is not valid"); |
| return (-1); |
| } |
| |
| /* |
| * Free up any already installed program. |
| */ |
| pcap_freecode(&p->fcode); |
| |
| prog_size = sizeof(*fp->bf_insns) * fp->bf_len; |
| p->fcode.bf_len = fp->bf_len; |
| p->fcode.bf_insns = (struct bpf_insn *)malloc(prog_size); |
| if (p->fcode.bf_insns == NULL) { |
| snprintf(p->errbuf, sizeof(p->errbuf), |
| "malloc: %s", pcap_strerror(errno)); |
| return (-1); |
| } |
| memcpy(p->fcode.bf_insns, fp->bf_insns, prog_size); |
| return (0); |
| } |
| |
| #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 |