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Re: [INET] Optimise away a branch in IP_ECN_set_ce

To: herbert@xxxxxxxxxxxxxxxxxxx, acme@xxxxxxxxxxxxxxxx
Subject: Re: [INET] Optimise away a branch in IP_ECN_set_ce
From: YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@xxxxxxxxxxxxxx>
Date: Thu, 09 Sep 2004 09:36:25 +0900 (JST)
Cc: davem@xxxxxxxxxx, netdev@xxxxxxxxxxx, yoshfuji@xxxxxxxxxxxxxx
In-reply-to: <200409082127.57827.acme@xxxxxxxxxxxxxxxx>
Organization: USAGI Project
References: <20040909000330.GA5581@xxxxxxxxxxxxxxxxxxx> <20040909.092428.125540781.yoshfuji@xxxxxxxxxxxxxx> <200409082127.57827.acme@xxxxxxxxxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
In article <200409082127.57827.acme@xxxxxxxxxxxxxxxx> (at Wed, 8 Sep 2004 
21:27:57 -0300), Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxx> says:

> Em Qua 08 Set 2004 21:24, YOSHIFUJI Hideaki / 吉藤英明 escreveu:
> > In article <20040909000330.GA5581@xxxxxxxxxxxxxxxxxxx> (at Thu, 9 Sep 2004 
> 10:03:31 +1000), Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> says:
> > > +       u32 ecn = (iph->tos + 1) & INET_ECN_MASK;
> > >
> > > + /*
> > > +  * The following gives us:
> > > +  * INET_ECN_ECT_1 => check += __constant_htons(0xFFFD)
> > > +  * INET_ECN_ECT_0 => check += __constant_htons(0xFFFE)
> > > +  */
> > > + if (__constant_htons(1) != 1)
> > > +  ecn <<= 8;
> > > + check += __constant_htons(0xFFFB) + ecn;
> > > +
> > >   iph->check = check + (check>=0xFFFF);
> > >   iph->tos |= INET_ECN_CE;
> > >  }
> >
> > s/__constant_htons/htons/g here, please.
> 
> For Herbert understanding: the generated code is the same in this case. :)

Yes, thanks.
And, we don't use __const_{hton,ntoh}{s,l}() unless it is really required.
e.g. variable initializer

--yoshfuji

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