Module Name: src
Committed By: alnsn
Date: Fri Jul 4 21:32:08 UTC 2014
Modified Files:
src/sys/net: bpfjit.c
Log Message:
Add optimization hints. They replace nscratches and ncopfuncs and improve
readability.
To generate a diff of this commit:
cvs rdiff -u -r1.19 -r1.20 src/sys/net/bpfjit.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/net/bpfjit.c
diff -u src/sys/net/bpfjit.c:1.19 src/sys/net/bpfjit.c:1.20
--- src/sys/net/bpfjit.c:1.19 Tue Jul 1 16:18:55 2014
+++ src/sys/net/bpfjit.c Fri Jul 4 21:32:08 2014
@@ -1,4 +1,4 @@
-/* $NetBSD: bpfjit.c,v 1.19 2014/07/01 16:18:55 alnsn Exp $ */
+/* $NetBSD: bpfjit.c,v 1.20 2014/07/04 21:32:08 alnsn Exp $ */
/*-
* Copyright (c) 2011-2014 Alexander Nasonov.
@@ -31,9 +31,9 @@
#include <sys/cdefs.h>
#ifdef _KERNEL
-__KERNEL_RCSID(0, "$NetBSD: bpfjit.c,v 1.19 2014/07/01 16:18:55 alnsn Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bpfjit.c,v 1.20 2014/07/04 21:32:08 alnsn Exp $");
#else
-__RCSID("$NetBSD: bpfjit.c,v 1.19 2014/07/01 16:18:55 alnsn Exp $");
+__RCSID("$NetBSD: bpfjit.c,v 1.20 2014/07/04 21:32:08 alnsn Exp $");
#endif
#include <sys/types.h>
@@ -120,6 +120,16 @@ __RCSID("$NetBSD: bpfjit.c,v 1.19 2014/0
#define GET_MEMWORDS(bc) (GET_EXTWORDS(bc) ? GET_EXTWORDS(bc) : BPF_MEMWORDS)
/*
+ * Optimization hints.
+ */
+typedef unsigned int bpfjit_hint_t;
+#define BJ_HINT_LDW 0x01 /* 32-bit packet read */
+#define BJ_HINT_IND 0x02 /* packet read at a variable offset */
+#define BJ_HINT_COP 0x04 /* BPF_COP or BPF_COPX instruction */
+#define BJ_HINT_XREG 0x08 /* BJ_XREG is needed */
+#define BJ_HINT_LDX 0x10 /* BPF_LDX instruction */
+
+/*
* Datatype for Array Bounds Check Elimination (ABC) pass.
*/
typedef uint64_t bpfjit_abc_length_t;
@@ -232,6 +242,32 @@ bpfjit_modcmd(modcmd_t cmd, void *arg)
}
#endif
+/*
+ * Return a number of scratch regiters to pass
+ * to sljit_emit_enter() function.
+ */
+static sljit_si
+nscratches(bpfjit_hint_t hints)
+{
+ sljit_si rv = 2;
+
+ if (hints & BJ_HINT_LDW)
+ rv = 3; /* uses BJ_TMP2REG */
+
+ if (hints & BJ_HINT_COP)
+ rv = 3; /* calls copfunc with three arguments */
+
+ if (hints & BJ_HINT_XREG)
+ rv = 4; /* uses BJ_XREG */
+
+#ifdef _KERNEL
+ if (hints & BJ_HINT_LDX)
+ rv = 5; /* uses BJ_TMP3REG */
+#endif
+
+ return rv;
+}
+
static uint32_t
read_width(const struct bpf_insn *pc)
{
@@ -1163,7 +1199,7 @@ optimize_init(struct bpfjit_insn_data *i
static bool
optimize_pass1(const bpf_ctx_t *bc, const struct bpf_insn *insns,
struct bpfjit_insn_data *insn_dat, size_t insn_count,
- bpf_memword_init_t *initmask, int *nscratches, int *ncopfuncs)
+ bpf_memword_init_t *initmask, bpfjit_hint_t *hints)
{
struct bpfjit_jump *jtf;
size_t i;
@@ -1174,8 +1210,7 @@ optimize_pass1(const bpf_ctx_t *bc, cons
const size_t memwords = GET_MEMWORDS(bc);
- *ncopfuncs = 0;
- *nscratches = 2;
+ *hints = 0;
*initmask = BJ_INIT_NOBITS;
unreachable = false;
@@ -1203,22 +1238,16 @@ optimize_pass1(const bpf_ctx_t *bc, cons
continue;
case BPF_LD:
- if (BPF_MODE(insns[i].code) == BPF_IND ||
- BPF_MODE(insns[i].code) == BPF_ABS) {
- if (BPF_MODE(insns[i].code) == BPF_IND &&
- *nscratches < 4) {
- /* uses BJ_XREG */
- *nscratches = 4;
- }
- if (*nscratches < 3 &&
- read_width(&insns[i]) == 4) {
- /* uses BJ_TMP2REG */
- *nscratches = 3;
- }
+ if ((BPF_MODE(insns[i].code) == BPF_IND ||
+ BPF_MODE(insns[i].code) == BPF_ABS) &&
+ read_width(&insns[i]) == 4) {
+ *hints |= BJ_HINT_LDW;
}
- if (BPF_MODE(insns[i].code) == BPF_IND)
+ if (BPF_MODE(insns[i].code) == BPF_IND) {
+ *hints |= BJ_HINT_XREG | BJ_HINT_IND;
*initmask |= invalid & BJ_INIT_XBIT;
+ }
if (BPF_MODE(insns[i].code) == BPF_MEM &&
(uint32_t)insns[i].k < memwords) {
@@ -1229,13 +1258,7 @@ optimize_pass1(const bpf_ctx_t *bc, cons
continue;
case BPF_LDX:
-#if defined(_KERNEL)
- /* uses BJ_TMP3REG */
- *nscratches = 5;
-#endif
- /* uses BJ_XREG */
- if (*nscratches < 4)
- *nscratches = 4;
+ *hints |= BJ_HINT_XREG | BJ_HINT_LDX;
if (BPF_MODE(insns[i].code) == BPF_MEM &&
(uint32_t)insns[i].k < memwords) {
@@ -1254,10 +1277,7 @@ optimize_pass1(const bpf_ctx_t *bc, cons
continue;
case BPF_STX:
- /* uses BJ_XREG */
- if (*nscratches < 4)
- *nscratches = 4;
-
+ *hints |= BJ_HINT_XREG;
*initmask |= invalid & BJ_INIT_XBIT;
if ((uint32_t)insns[i].k < memwords)
@@ -1270,11 +1290,8 @@ optimize_pass1(const bpf_ctx_t *bc, cons
if (insns[i].code != (BPF_ALU|BPF_NEG) &&
BPF_SRC(insns[i].code) == BPF_X) {
+ *hints |= BJ_HINT_XREG;
*initmask |= invalid & BJ_INIT_XBIT;
- /* uses BJ_XREG */
- if (*nscratches < 4)
- *nscratches = 4;
-
}
invalid &= ~BJ_INIT_ABIT;
@@ -1283,35 +1300,23 @@ optimize_pass1(const bpf_ctx_t *bc, cons
case BPF_MISC:
switch (BPF_MISCOP(insns[i].code)) {
case BPF_TAX: // X <- A
- /* uses BJ_XREG */
- if (*nscratches < 4)
- *nscratches = 4;
-
+ *hints |= BJ_HINT_XREG;
*initmask |= invalid & BJ_INIT_ABIT;
invalid &= ~BJ_INIT_XBIT;
continue;
case BPF_TXA: // A <- X
- /* uses BJ_XREG */
- if (*nscratches < 4)
- *nscratches = 4;
-
+ *hints |= BJ_HINT_XREG;
*initmask |= invalid & BJ_INIT_XBIT;
invalid &= ~BJ_INIT_ABIT;
continue;
case BPF_COPX:
- /* uses BJ_XREG */
- if (*nscratches < 4)
- *nscratches = 4;
+ *hints |= BJ_HINT_XREG;
/* FALLTHROUGH */
case BPF_COP:
- /* calls copfunc with three arguments */
- if (*nscratches < 3)
- *nscratches = 3;
-
- (*ncopfuncs)++;
+ *hints |= BJ_HINT_COP;
*initmask |= invalid & BJ_INIT_ABIT;
invalid &= ~BJ_INIT_ABIT;
continue;
@@ -1483,15 +1488,13 @@ optimize_pass3(const struct bpf_insn *in
static bool
optimize(const bpf_ctx_t *bc, const struct bpf_insn *insns,
struct bpfjit_insn_data *insn_dat, size_t insn_count,
- bpf_memword_init_t *initmask, int *nscratches, int *ncopfuncs)
+ bpf_memword_init_t *initmask, bpfjit_hint_t *hints)
{
optimize_init(insn_dat, insn_count);
- if (!optimize_pass1(bc, insns, insn_dat, insn_count,
- initmask, nscratches, ncopfuncs)) {
+ if (!optimize_pass1(bc, insns, insn_dat, insn_count, initmask, hints))
return false;
- }
optimize_pass2(bc, insns, insn_dat, insn_count);
optimize_pass3(insns, insn_dat, insn_count);
@@ -2037,7 +2040,7 @@ bpfjit_generate_code(const bpf_ctx_t *bc
/* optimization related */
bpf_memword_init_t initmask;
- int nscratches, ncopfuncs;
+ bpfjit_hint_t hints;
/* memory store location for initial zero initialization */
sljit_si mem_reg;
@@ -2063,10 +2066,8 @@ bpfjit_generate_code(const bpf_ctx_t *bc
if (insn_dat == NULL)
goto fail;
- if (!optimize(bc, insns, insn_dat, insn_count,
- &initmask, &nscratches, &ncopfuncs)) {
+ if (!optimize(bc, insns, insn_dat, insn_count, &initmask, &hints))
goto fail;
- }
compiler = sljit_create_compiler();
if (compiler == NULL)
@@ -2077,11 +2078,11 @@ bpfjit_generate_code(const bpf_ctx_t *bc
#endif
status = sljit_emit_enter(compiler,
- 2, nscratches, 3, sizeof(struct bpfjit_stack));
+ 2, nscratches(hints), 3, sizeof(struct bpfjit_stack));
if (status != SLJIT_SUCCESS)
goto fail;
- if (ncopfuncs > 0) {
+ if (hints & BJ_HINT_COP) {
/* save ctx argument */
status = sljit_emit_op1(compiler,
SLJIT_MOV_P,
