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Re: gcc 4.3.0 i386 default question
- From: "Richard Guenther" <richard dot guenther at gmail dot com>
- To: "Joel Sherrill" <joel dot sherrill at oarcorp dot com>
- Cc: "GCC List" <gcc at gcc dot gnu dot org>
- Date: Wed, 12 Mar 2008 16:26:31 +0100
- Subject: Re: gcc 4.3.0 i386 default question
- References: <47D7F58E.firstname.lastname@example.org>
On Wed, Mar 12, 2008 at 4:23 PM, Joel Sherrill
> 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?