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authorDaniel Borkmann <daniel@iogearbox.net>2018-02-24 01:07:58 +0100
committerAlexei Starovoitov <ast@kernel.org>2018-02-23 22:50:00 -0800
commit88e69a1fcc1e67dec3025af64736a84532528242 (patch)
tree3b7969431a064be0e3079257d01f895bf5692f97 /arch/x86/net
parentee07862f7b4594d390b978f6636a6a6191632ab3 (diff)
downloadlinux-88e69a1fcc1e67dec3025af64736a84532528242.tar.bz2
bpf, x64: save one byte per shl/shr/sar when imm is 1
When we shift by one, we can use a different encoding where imm is not explicitly needed, which saves 1 byte per such op. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'arch/x86/net')
-rw-r--r--arch/x86/net/bpf_jit_comp.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 4923d92f918d..4bc36bd1b97a 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -640,7 +640,11 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
case BPF_RSH: b3 = 0xE8; break;
case BPF_ARSH: b3 = 0xF8; break;
}
- EMIT3(0xC1, add_1reg(b3, dst_reg), imm32);
+
+ if (imm32 == 1)
+ EMIT2(0xD1, add_1reg(b3, dst_reg));
+ else
+ EMIT3(0xC1, add_1reg(b3, dst_reg), imm32);
break;
case BPF_ALU | BPF_LSH | BPF_X: