linux-kernel - Re: [PATCH] x86: bpf_jit_comp: Reduce is

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Message-Id: <20141209.145712.712673313891632719.davem@davemloft.net>
Date:	Tue, 09 Dec 2014 14:57:12 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	joe@...ches.com
Cc:	alexei.starovoitov@...il.com, lambert.quentin@...il.com,
	kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	kaber@...sh.net, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: bpf_jit_comp: Reduce is_ereg() code size

From: Joe Perches <joe@...ches.com>
Date: Thu, 04 Dec 2014 15:00:48 -0800

> 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@...ches.com>

Applied.
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