From: Shaun Jackman <sjackman@gmail.com>
To: Carl Whitwell <carl.whitwell@gmail.com>
Cc: gcc@gcc.gnu.org
Subject: Re: memcpy to an unaligned address
Date: Fri, 05 Aug 2005 16:09:00 -0000 [thread overview]
Message-ID: <7f45d939050805090960ce261@mail.gmail.com> (raw)
In-Reply-To: <345be69105080501405eb8663e@mail.gmail.com>
On 8/5/05, Carl Whitwell <carl.whitwell@gmail.com> wrote:
> On 8/4/05, Shaun Jackman <sjackman@gmail.com> wrote:
> > Are you using an x86 host and an arm target?
>
> Actually no, my major concern at the time was the large quantity of
> legacy code with packed structures that we have on an embedded linux
> x86 system. I was just testing that we didn't have an issue there with
> the structure access.
The x86 includes hardware to fetch a word from an unaligned address by
fetching from two aligned address and shifting and combining to
produce the correct result. So, unaligned accesses on the x86 might
effect a slight performance hit, but they will still act correctly.
The ARM on the other hand does not include such hardware, so a load
instruction fetching from an unaligned address will behave
incorrectly. My primary concern is really just code correctness.
Cheers,
Shaun
next prev parent reply other threads:[~2005-08-05 16:09 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <345be691050804025955c0b4ab@mail.gmail.com>
2005-08-04 15:06 ` Shaun Jackman
2005-08-04 15:09 ` Christian Joensson
2005-08-05 8:41 ` Carl Whitwell
2005-08-05 16:09 ` Shaun Jackman [this message]
2005-08-02 17:32 Shaun Jackman
2005-08-02 17:43 ` Dave Korn
2005-08-02 19:13 ` Shaun Jackman
2005-08-02 19:19 ` Paul Koning
2005-08-02 19:26 ` Shaun Jackman
2005-08-02 19:40 ` Dave Korn
2005-08-02 19:48 ` Paul Koning
2005-08-02 20:15 ` Shaun Jackman
2005-08-02 20:29 ` Mike Stump
2005-08-02 20:38 ` Andrew Pinski
2005-08-02 20:45 ` Ian Lance Taylor
2005-08-02 21:30 ` Mike Stump
2005-08-02 21:34 ` Joe Buck
2005-08-03 18:00 ` Richard Henderson
2005-08-03 18:15 ` Shaun Jackman
2005-08-03 18:19 ` Dave Korn
2005-08-03 21:26 ` Richard Henderson
2005-08-04 4:42 ` Ian Lance Taylor
2005-08-04 12:40 ` Paul Koning
2005-08-02 20:46 ` Paul Koning
2005-08-02 22:17 ` Shaun Jackman
2005-08-03 17:16 ` Paul Koning
2005-08-02 22:26 ` Shaun Jackman
2005-08-02 22:29 ` Shaun Jackman
2005-08-02 21:05 ` Mike Stump
2005-08-02 21:11 ` Joe Buck
2005-08-02 22:15 ` Shaun Jackman
2005-08-02 22:12 ` Joe Buck
2005-08-02 20:29 ` Paul Koning
2005-08-02 17:48 ` Falk Hueffner
2005-08-02 18:03 ` Mike Stump
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