This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: Change x86 prefix order
- From: "H. J. Lu" <hjl at lucon dot org>
- To: Randy Dunlap <rdunlap at xenotime dot net>
- Cc: gcc at gcc dot gnu dot org, GNU C Library <libc-alpha at sources dot redhat dot com>, linux kernel <linux-kernel at vger dot kernel dot org>
- Date: Wed, 6 Dec 2006 09:00:30 -0800
- Subject: Re: Change x86 prefix order
- References: <20061206070014.GA535@lucon.org> <20061206084317.4c0ef28d.rdunlap@xenotime.net>
On Wed, Dec 06, 2006 at 08:43:17AM -0800, Randy Dunlap wrote:
> On Tue, 5 Dec 2006 23:00:14 -0800 H. J. Lu wrote:
>
> > On x86, the order of prefix SEG_PREFIX, ADDR_PREFIX, DATA_PREFIX and
> > LOCKREP_PREFIX isn't fixed. Currently, gas generates
> >
> > LOCKREP_PREFIX ADDR_PREFIX DATA_PREFIX SEG_PREFIX
> >
> > I will check in a patch:
> >
> > http://sourceware.org/ml/binutils/2006-12/msg00054.html
> >
> > tomorrow and change gas to generate
> >
> > SEG_PREFIX ADDR_PREFIX DATA_PREFIX LOCKREP_PREFIX
>
> Hi,
> Could you provide a "why" for this in addition to the
> "what", please?
LOCKREP_PREFIX is also used as SIMD prefix. DATA_PREFIX can be used as
either SIMD prefix or data size prefix for SIMD instructions. The new
order
SEG_PREFIX ADDR_PREFIX DATA_PREFIX LOCKREP_PREFIX
will make SIMD prefixes close to SIMD opcode.
H.J.