linux-mips
[Top] [All Lists]

Re: [PATCH] Optimize generic get_unaligned / put_unaligned implementatio

To: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] Optimize generic get_unaligned / put_unaligned implementations.
From: Jeremy Fitzhardinge <jeremy@goop.org>
Date: Thu, 15 Feb 2007 16:13:41 -0800
Cc: Ralf Baechle <ralf@linux-mips.org>, Atsushi Nemoto <anemo@mba.ocn.ne.jp>, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
In-reply-to: <20070215153823.239fd616.akpm@linux-foundation.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20050830104056.GA4710@linux-mips.org> <20060306.203218.69025300.nemoto@toshiba-tops.co.jp> <20060306170552.0aab29c5.akpm@osdl.org> <20070214214226.GA17899@linux-mips.org> <20070214203903.8d013170.akpm@linux-foundation.org> <20070215143441.GA18155@linux-mips.org> <20070215135358.020781dd.akpm@linux-foundation.org> <20070215221839.GA14103@linux-mips.org> <20070215153823.239fd616.akpm@linux-foundation.org>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Thunderbird 1.5.0.9 (X11/20070212)
Andrew Morton wrote:
> 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.

In Ralf's code, the structure is anonymous, and is used to declare a
pointer type, which is initialized from a void *.  So I think the
compiler isn't allowed to assume anything about its alignment.

    J

<Prev in Thread] Current Thread [Next in Thread>