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Date:	Thu, 30 Sep 2010 07:16:48 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	"Pekka Savola (ipv6)" <pekkas@...core.fi>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: code cleanups

Le jeudi 30 septembre 2010 à 10:24 +0800, Changli Gao a écrit :
> Compare operations are more readable, and compilers generate the same code
> for the both.
> 

You have a buggy compiler then.

I know this code is ugly, but please keep it as is, dont add conditional
branches on hot paths.

Thanks

> Use the macros fl4_* to shrink the length of the lines.
> 
> Signed-off-by: Changli Gao <xiaosuo@...il.com>
> ---
>  net/ipv4/af_inet.c |    7 +++----
>  net/ipv4/route.c   |   27 ++++++++++++---------------
>  2 files changed, 15 insertions(+), 19 deletions(-)
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index f581f77..ef26640 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -1338,10 +1338,9 @@ static struct sk_buff **inet_gro_receive(struct sk_buff **head,
>  
>  		iph2 = ip_hdr(p);
>  
> -		if ((iph->protocol ^ iph2->protocol) |
> -		    (iph->tos ^ iph2->tos) |
> -		    ((__force u32)iph->saddr ^ (__force u32)iph2->saddr) |
> -		    ((__force u32)iph->daddr ^ (__force u32)iph2->daddr)) {
> +		if (iph->protocol != iph2->protocol || iph->tos != iph2->tos ||
> +		    (__force u32)iph->saddr != (__force u32)iph2->saddr ||
> +		    (__force u32)iph->daddr != (__force u32)iph2->daddr) {
>  			NAPI_GRO_CB(p)->same_flow = 0;
>  			continue;
>  		}
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index 98beda4..6b00fde 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -683,19 +683,18 @@ static inline bool rt_caching(const struct net *net)
>  static inline bool compare_hash_inputs(const struct flowi *fl1,
>  					const struct flowi *fl2)
>  {
> -	return ((((__force u32)fl1->nl_u.ip4_u.daddr ^ (__force u32)fl2->nl_u.ip4_u.daddr) |
> -		((__force u32)fl1->nl_u.ip4_u.saddr ^ (__force u32)fl2->nl_u.ip4_u.saddr) |
> -		(fl1->iif ^ fl2->iif)) == 0);
> +	return (__force u32)fl1->fl4_dst == (__force u32)fl2->fl4_dst &&
> +	       (__force u32)fl1->fl4_src == (__force u32)fl2->fl4_src &&
> +	       fl1->iif == fl2->iif;
>  }
>  
>  static inline int compare_keys(struct flowi *fl1, struct flowi *fl2)
>  {
> -	return (((__force u32)fl1->nl_u.ip4_u.daddr ^ (__force u32)fl2->nl_u.ip4_u.daddr) |
> -		((__force u32)fl1->nl_u.ip4_u.saddr ^ (__force u32)fl2->nl_u.ip4_u.saddr) |
> -		(fl1->mark ^ fl2->mark) |
> -		(*(u16 *)&fl1->nl_u.ip4_u.tos ^ *(u16 *)&fl2->nl_u.ip4_u.tos) |
> -		(fl1->oif ^ fl2->oif) |
> -		(fl1->iif ^ fl2->iif)) == 0;
> +	return (__force u32)fl1->fl4_dst == (__force u32)fl2->fl4_dst &&
> +	       (__force u32)fl1->fl4_src == (__force u32)fl2->fl4_src &&
> +	       fl1->mark == fl2->mark &&
> +	       *(u16 *)&fl1->fl4_tos == *(u16 *)&fl2->fl4_tos &&
> +	       fl1->oif == fl2->oif && fl1->iif == fl2->iif;
>  }
>  
>  static inline int compare_netns(struct rtable *rt1, struct rtable *rt2)
> @@ -2286,12 +2285,10 @@ int ip_route_input_common(struct sk_buff *skb, __be32 daddr, __be32 saddr,
>  
>  	for (rth = rcu_dereference(rt_hash_table[hash].chain); rth;
>  	     rth = rcu_dereference(rth->dst.rt_next)) {
> -		if ((((__force u32)rth->fl.fl4_dst ^ (__force u32)daddr) |
> -		     ((__force u32)rth->fl.fl4_src ^ (__force u32)saddr) |
> -		     (rth->fl.iif ^ iif) |
> -		     rth->fl.oif |
> -		     (rth->fl.fl4_tos ^ tos)) == 0 &&
> -		    rth->fl.mark == skb->mark &&
> +		if ((__force u32)rth->fl.fl4_dst == (__force u32)daddr &&
> +		    (__force u32)rth->fl.fl4_src == (__force u32)saddr &&
> +		    rth->fl.iif == iif && rth->fl.oif == 0 &&
> +		    rth->fl.fl4_tos == tos && rth->fl.mark == skb->mark &&
>  		    net_eq(dev_net(rth->dst.dev), net) &&
>  		    !rt_is_expired(rth)) {
>  			if (noref) {
> --
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