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From: Ingo Oeser <netdev@axxeo.de>
To: Wang Chen <wangchen@cn.fujitsu.com>
Cc: "David S. Miller" <davem@davemloft.net>, NETDEV <netdev@vger.kernel.org>
Subject: Re: [PATCH 1/2] ipmr: delete redundant variable
Date: Wed, 23 Jul 2008 14:05:39 +0200	[thread overview]
Message-ID: <200807231405.39515.netdev@axxeo.de> (raw)
In-Reply-To: <4886FB56.20905@cn.fujitsu.com>

Hi Wand Chen,

Wang Chen schrieb:
> But "accessing entry of table by index" is always allowed,
> right?
> If the complier makes such pointer which spills a register with
> the multiply/shift, the simple code as following is bug too:
> i = table[100].field;
> But it shouldn't, right :)

I'm NOT telling you, that your transformation is introducing a BUG.
It is semantically perfectly equivalent.

I'm trying to tell you, that it might not led to the same or better 
performance and might thus be not worth it.

But please check the generated assembly yourself on a CISC and RISC
machine to get an idea of the effects. It will be a nice learning 
experience I enjoyed myself already.


Best Regards

Ingo Oeser

  reply	other threads:[~2008-07-23 12:05 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-07-23  1:45 [PATCH 1/2] ipmr: delete redundant variable Wang Chen
2008-07-23  8:03 ` Ingo Oeser
2008-07-23  9:35   ` Wang Chen
2008-07-23 12:05     ` Ingo Oeser [this message]
2008-07-23 15:16       ` Wang Chen
2008-07-24  7:37       ` Wang Chen
2008-07-25 17:36         ` Ingo Oeser

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