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From: Pavel Machek <pavel@ucw.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Ralf Baechle <ralf@linux-mips.org>,
	Atsushi Nemoto <anemo@mba.ocn.ne.jp>,
	linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Optimize generic get_unaligned / put_unaligned implementations.
Date: Tue, 20 Feb 2007 13:50:46 +0000	[thread overview]
Message-ID: <20070220135046.GE3945@ucw.cz> (raw)
In-Reply-To: <20070215172720.3e9ce464.akpm@linux-foundation.org>

Hi!

> > > hm.  So if I have
> > > 
> > > 	struct bar {
> > > 		unsigned long b;
> > > 	} __attribute__((packed));
> > > 
> > > 	struct foo {
> > > 		unsigned long u;
> > > 		struct bar b;
> > > 	};
> > > 
> > > then the compiler can see that foo.b.b is well-aligned, regardless of the
> > > packedness.
> > > 
> > > Plus some crazy people compile the kernel with icc (or at least they used
> > > to).  What happens there?
> > 
> > A quick grep for __attribute__((packed)) and __packed find around 900 hits,
> > I'd probably find more if I'd look for syntactical variations.  Some hits
> > are in arch/{i386,x86_64,ia64}.  At a glance it seems hard to configure a
> > useful x86 kernel that doesn't involve any packed attribute.  I take that
> > as statistical proof that icc either has doesn't really work for building
> > the kernel or groks packing.  Any compiler not implementing gcc extensions
> > is lost at building the kernel but that's old news.
> > 
> 
> No, icc surely supports attribute(packed).  My point is that we shouldn't
> rely upon the gcc info file for this, because other compilers can (or
> could) be used to build the kernel.

Well, icc should be gcc compatible. If it is not, it is icc bug.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

      parent reply	other threads:[~2007-02-20 14:00 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20050830104056.GA4710@linux-mips.org>
     [not found] ` <20060306.203218.69025300.nemoto@toshiba-tops.co.jp>
2006-03-07  1:05   ` [PATCH] 64bit unaligned access on 32bit kernel Andrew Morton
2006-03-07  2:03     ` Atsushi Nemoto
2006-03-07 18:09     ` Ralf Baechle
2006-03-08  4:58       ` Atsushi Nemoto
2006-03-08  5:12         ` Andrew Morton
2007-02-14 21:42     ` [PATCH] Optimize generic get_unaligned / put_unaligned implementations Ralf Baechle
2007-02-15  4:39       ` Andrew Morton
2007-02-15  8:35         ` Marcel Holtmann
2007-02-15 14:34         ` Ralf Baechle
2007-02-15 21:53           ` Andrew Morton
2007-02-15 22:18             ` Ralf Baechle
2007-02-15 23:05               ` Jeremy Fitzhardinge
2007-02-15 23:38               ` Andrew Morton
2007-02-16  0:13                 ` Jeremy Fitzhardinge
2007-02-16  0:43                 ` Ralf Baechle
2007-02-16  1:27                   ` Andrew Morton
2007-02-16  1:59                     ` Ralf Baechle
2007-02-20 13:50                     ` Pavel Machek [this message]

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