From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Fri, 27 Feb 2015 22:21:30 +0100
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Message-ID: <20150227212130.GP434@hermes.click-hack.org>
References: <54F0CF9E.1040707@siemens.com>
 <20150227202724.GL434@hermes.click-hack.org>
 <54F0D599.8090009@siemens.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <54F0D599.8090009@siemens.com>
Subject: Re: [Xenomai] [RFC] Consolidated exception prologue/epiloge for x86
 and ARM
List-Id: Discussions about the Xenomai project <xenomai.xenomai.org>
List-Unsubscribe: <http://www.xenomai.org/mailman/options/xenomai>,
 <mailto:xenomai-request@xenomai.org?subject=unsubscribe>
List-Archive: <http://www.xenomai.org/pipermail/xenomai/>
List-Post: <mailto:xenomai@xenomai.org>
List-Help: <mailto:xenomai-request@xenomai.org?subject=help>
List-Subscribe: <http://www.xenomai.org/mailman/listinfo/xenomai>,
 <mailto:xenomai-request@xenomai.org?subject=subscribe>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Xenomai <xenomai@xenomai.org>

On Fri, Feb 27, 2015 at 09:37:45PM +0100, Jan Kiszka wrote:
> On 2015-02-27 21:27, Gilles Chanteperdrix wrote:
> > On Fri, Feb 27, 2015 at 09:12:14PM +0100, Jan Kiszka wrote:
> >> Hi,
> >>
> >> just pushed a first implementation of the general model that I proposed
> >> for exception handling. You can find it at
> >>
> >> http://git.xenomai.org/ipipe-jki.git/log/?h=queues/trap-rework
> > 
> > Also, the clean way to pass virtual + physical flags is to use
> > arch_mangle_bits. Using two longs (potentially 128 bits then) is
> > completely useless since one of the longs simply has one significant
> > bit.
> 
> The costs of mangling is higher than using two regs for passing that
> data as-is, both binary and LOC-wise (tried it). Plus the code is more
> readable.

That is false on ARM. On ARM gcc does not pass structs by values in
registers. The values get passed on stack.

-- 
					    Gilles.