netdev - Re: [PATCH] x86: bpf_jit_comp: simplify trivial boolean return

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Message-ID: <1417021108.19695.5.camel@perches.com>
Date:	Wed, 26 Nov 2014 08:58:28 -0800
From:	Joe Perches <joe@...ches.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	Quentin Lambert <lambert.quentin@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: bpf_jit_comp: simplify trivial boolean return

On Wed, 2014-11-26 at 08:42 -0800, Alexei Starovoitov wrote:
> On Wed, Nov 26, 2014 at 1:18 AM, Quentin Lambert
> <lambert.quentin@...il.com> wrote:
> > Remove if then else statements preceding
> > boolean return.
[]
> > diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
[]
> > @@ -135,11 +135,9 @@ 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 (reg == BPF_REG_5 ||
> > +               reg == AUX_REG ||
> > +               (reg >= BPF_REG_7 && reg <= BPF_REG_9));
> 
> please remove extra () around the whole expression, and
> align in properly, and
> don't move reg==AUX_REG check to a different line.
> Subject is not warranted. I don't think it's a simplification.

It's not really a simplification,
gcc should emit the same object code.

> imo existing code is fine and I don't think the time spent
> reviewing such changes is worth it when there is no
> improvement in readability.

Is there any value in reordering these tests for frequency
or maybe using | instead of || to avoid multiple jumps?


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