From: Chris Lattner <sabre@nondot.org>
To: Ian Lance Taylor <ian@airs.com>
Cc: gcc-help@gcc.gnu.org
Subject: Re: attribute aligned(4) ignored
Date: Tue, 26 Jul 2005 05:57:00 -0000 [thread overview]
Message-ID: <Pine.LNX.4.61.0507260051230.12411@nondot.org> (raw)
In-Reply-To: <m3pst6f8bf.fsf@gossamer.airs.com>
On Tue, 25 Jul 2005, Ian Lance Taylor wrote:
>> ... the struct maintains its 8-byte alignment even though nothing
>> inside of it requires 8-byte alignment any more.
>
> When I try that with a powerpc-eabi compiler, it appears to generates
> a struct with a size of 12 bytes and an alignment of 4 bytes. Do you
> not see that with a Darwin compiler? What target are you configuring
> for? What sources are you using?
This is a powerpc-darwin specific issue I believe. The Darwin ABI states
(roughly) that doubles have 4-byte alignment, unless they are the first
element of a structure (in which they have 8-byte alignment). I think
this is a holdover from AIX compatibility.
It is my guess that this ABI rule is overruling the user request, but I
don't really know how to go about verifying this, or working around it :(
-Chris
--
http://nondot.org/sabre/
http://llvm.org/
next prev parent reply other threads:[~2005-07-26 5:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-26 1:04 Chris Lattner
2005-07-26 3:22 ` Ian Lance Taylor
2005-07-26 4:58 ` Chris Lattner
2005-07-26 5:02 ` corey taylor
2005-07-26 5:04 ` Chris Lattner
2005-07-26 5:25 ` Ian Lance Taylor
2005-07-26 5:57 ` Chris Lattner [this message]
2005-07-26 6:27 ` Ian Lance Taylor
2005-07-26 6:44 ` Chris Lattner
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