From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Harvey Harrison <harvey.harrison@gmail.com>,
Al Viro <viro@ftp.linux.org.uk>,
mchehab@infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] or51132.c: unaligned
Date: Tue, 20 May 2008 17:55:38 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.1.10.0805201752230.3081@woody.linux-foundation.org> (raw)
In-Reply-To: <20080521004548.GD28946@ZenIV.linux.org.uk>
On Wed, 21 May 2008, Al Viro wrote:
> On Tue, May 20, 2008 at 05:41:12PM -0700, Harvey Harrison wrote:
>
> > > + return buf[0] | (buf[1] << 8);
> >
> > return get_unaligned_le16(buf);
>
> And the point of that would be?
Perhaps better code generation?
I didn't look what
buf[0] | (buf[1] << 8)
generates, but on x86, get_unaligned_le16() should just boil down to
*(unsigned short *)buf
which is certainly going to mostly generate better code (smaller, faster)
than at least the most likely and straigthforward of the former.
(Just checked. Gcc is not smart enough to make those two loads plus a
shift be one word load. At least not my version)
Linus
next prev parent reply other threads:[~2008-05-21 0:56 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-21 0:33 [PATCH] or51132.c: unaligned Al Viro
2008-05-21 0:41 ` Harvey Harrison
2008-05-21 0:45 ` Al Viro
2008-05-21 0:51 ` Harvey Harrison
2008-05-21 0:56 ` Al Viro
2008-05-21 0:55 ` Linus Torvalds [this message]
2008-05-21 1:18 ` Al Viro
2008-05-21 2:02 ` Linus Torvalds
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