netdev - Re: [PATCH net-next] x86: bpf_jit: small optimization in emit_bpf_tail

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Message-ID: <20170831143818.6s7lbu6ai7dqveah@ast-mbp.dhcp.thefacebook.com>
Date:   Thu, 31 Aug 2017 07:38:20 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH net-next] x86: bpf_jit: small optimization in
 emit_bpf_tail_call()

On Thu, Aug 31, 2017 at 04:53:42AM -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> Saves 4 bytes replacing following instructions :
> 
> lea rax, [rsi + rdx * 8 + offsetof(...)] 
> mov rax, qword ptr [rax]
> cmp rax, 0
> 
> by :
> 
> mov rax, [rsi + rdx * 8 + offsetof(...)] 
> test rax, rax
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Nicely spotted. Much appreciate it!
Acked-by: Alexei Starovoitov <ast@...nel.org>