gcc 4.3.0 i386 default question

[Richard Guenther]

On Wed, Mar 12, 2008 at 4:23 PM, Joel Sherrill
<joel.sherrill@oarcorp.com> wrote:
> Hi,
>
>  Did the default i386 CPU model that gcc generates
>  code for change between 4.2.x and 4.3.0?  I didn't
>  see anything in the release notes that jumps out at
>  me about this.
>
>  Using i386-rtems4.9 as the target, I was running
>  code compiled by gcc 4.3.0 on a  vanilla i386 and
>  was getting illegal instruction  exceptions.  I looked
>  at the assembly and noticed instructions which were
>  not on the i386.  Obviosuly, when I added -mtune=i386
>  and the issue went away.
>
>  This probably impacts no one on a GNU/Linux computer
>  since very few of those are base i386's anymore.  Just
>  venerable embedded systems. :)

-mtune doesn't change the instruction set, -march/-mcpu does.
So this is probably a bug in the instruction predicates.  What
is the illegal instruction gcc emits?

Richard.