From: Joe Perches <joe@perches•com>
To: Alexei Starovoitov <alexei.starovoitov@gmail•com>
Cc: Quentin Lambert <lambert.quentin@gmail•com>,
"David S. Miller" <davem@davemloft•net>,
Alexey Kuznetsov <kuznet@ms2•inr.ac.ru>,
James Morris <jmorris@namei•org>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6•org>,
Patrick McHardy <kaber@trash•net>,
Thomas Gleixner <tglx@linutronix•de>,
Ingo Molnar <mingo@redhat•com>, "H. Peter Anvin" <hpa@zytor•com>,
x86@kernel•org, "netdev@vger•kernel.org" <netdev@vger•kernel.org>,
"linux-kernel@vger•kernel.org" <linux-kernel@vger•kernel.org>
Subject: [PATCH] x86: bpf_jit_comp: Reduce is_ereg() code size
Date: Thu, 04 Dec 2014 15:00:48 -0800 [thread overview]
Message-ID: <1417734048.2721.22.camel@perches.com> (raw)
In-Reply-To: <CAADnVQKtYkKtsd9rUFm2yfMoh7F_SRFPVP8hpvSY00KpmB-NNg@mail.gmail.com>
Use the (1 << reg) & mask trick to reduce code size.
x86-64 size difference -O2 without profiling for various
gcc versions:
$ size arch/x86/net/bpf_jit_comp.o*
text data bss dec hex filename
9266 4 0 9270 2436 arch/x86/net/bpf_jit_comp.o.4.4.new
10042 4 0 10046 273e arch/x86/net/bpf_jit_comp.o.4.4.old
9109 4 0 9113 2399 arch/x86/net/bpf_jit_comp.o.4.6.new
9717 4 0 9721 25f9 arch/x86/net/bpf_jit_comp.o.4.6.old
8789 4 0 8793 2259 arch/x86/net/bpf_jit_comp.o.4.7.new
10245 4 0 10249 2809 arch/x86/net/bpf_jit_comp.o.4.7.old
9671 4 0 9675 25cb arch/x86/net/bpf_jit_comp.o.4.9.new
10679 4 0 10683 29bb arch/x86/net/bpf_jit_comp.o.4.9.old
Signed-off-by: Joe Perches <joe@perches•com>
---
compiled, untested by me, but per Alexei Starovoitov this passes
the test_bpf suite
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 3f62734..09e2cea 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -135,11 +135,11 @@ static const int reg2hex[] = {
*/
static inline bool is_ereg(u32 reg)
{
- if (reg == BPF_REG_5 || reg == AUX_REG ||
- (reg >= BPF_REG_7 && reg <= BPF_REG_9))
- return true;
- else
- return false;
+ return (1 << reg) & (BIT(BPF_REG_5) |
+ BIT(AUX_REG) |
+ BIT(BPF_REG_7) |
+ BIT(BPF_REG_8) |
+ BIT(BPF_REG_9));
}
/* add modifiers if 'reg' maps to x64 registers r8..r15 */
next prev parent reply other threads:[~2014-12-04 23:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-26 17:23 [PATCH] x86: bpf_jit_comp: simplify trivial boolean return Alexei Starovoitov
2014-11-26 18:02 ` Joe Perches
2014-12-04 23:00 ` Joe Perches [this message]
2014-12-04 23:12 ` [PATCH] x86: bpf_jit_comp: Reduce is_ereg() code size Alexei Starovoitov
2014-12-04 23:14 ` Eric Dumazet
2014-12-04 23:31 ` Alexei Starovoitov
2014-12-05 0:46 ` Eric Dumazet
2014-12-05 1:01 ` [PATCH] x86: bpf_jit_comp: Remove inline from static function definitions Joe Perches
2014-12-05 1:21 ` Alexei Starovoitov
2014-12-05 1:43 ` Joe Perches
2014-12-09 19:57 ` David Miller
2014-12-04 23:35 ` [PATCH] x86: bpf_jit_comp: Reduce is_ereg() code size Joe Perches
2014-12-09 19:57 ` David Miller
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