From: antirez <antirez@invece.org>
To: Jakob ?stergaard <jakob@unthought.net>,
antirez <antirez@invece.org>, Brian Gerst <bgerst@didntduck.org>,
linux-kernel@vger.kernel.org
Subject: Re: * 4 converted to << 2 for networking code
Date: Wed, 10 Jan 2001 18:25:46 +0100 [thread overview]
Message-ID: <20010110182546.U7498@prosa.it> (raw)
In-Reply-To: <20010110174859.R7498@prosa.it> <3A5C778C.CFB363F3@didntduck.org> <20010110180322.T7498@prosa.it> <20010110161146.A3252@unthought.net>
In-Reply-To: <20010110161146.A3252@unthought.net>; from jakob@unthought.net on Wed, Jan 10, 2001 at 04:11:46PM +0100
On Wed, Jan 10, 2001 at 04:11:46PM +0100, Jakob ?stergaard wrote:
> On most processors <<2 is slower than *4. It's outright stupid to
> write <<2 when we mean *4 in order to optimize for one out of a
> gazillion supported architectures - even more so when the compiler
> for the one CPU where <<2 is faster, will actually generate a shift
> instead of a multiply as a part of the standard optimization.
Hug, ok, so all the << 2 already in should be changed in *4.
My point is that it is better to use only << 2 or *4, selecting
the better form.
--
Salvatore Sanfilippo | <antirez@invece.org>
http://www.kyuzz.org/antirez | PGP: finger antirez@tella.alicom.com
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next prev parent reply other threads:[~2001-01-10 15:25 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-01-10 16:48 * 4 converted to << 2 for networking code antirez
2001-01-10 14:38 ` David S. Miller
2001-01-10 14:54 ` Brian Gerst
2001-01-10 17:03 ` antirez
2001-01-10 15:11 ` Jakob Østergaard
2001-01-10 15:18 ` Mike Harrold
2001-01-10 15:31 ` Chris Jones
2001-01-10 16:23 ` Jamie Lokier
2001-01-10 16:26 ` Mike Harrold
2001-01-10 17:25 ` antirez [this message]
2001-01-10 16:25 ` Pauline Middelink
2001-01-11 0:29 ` H. Peter Anvin
2001-01-10 22:21 ` Matthias Andree
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