Re: [gentoo-dev] Gentoo i486 support

[Mike Gilbert <floppym@gentoo.org>]

On Wed, Aug 22, 2018 at 8:26 AM Ben Kohler <bkohler@gentoo.org> wrote:
>
> Hi guys,
>
> For some time now, we've been shipping broken i486 stage3s that do not
> run on pre-i686 hardware [1].  Due to a change in catalyst [2], we no
> longer set CXXFLAGS in the default make.conf, so the x86 profiles' (imho
> wrong/broken) defaults [3] kick in.
>
> I'd like to get this fixed, and I see 3 possible solutions, listed in
> order of my own preference:
>
> 1) Adjust x86 profile defaults to drop the problematic -march=i686.
> This would be more in line with amd64 profiles (et al), which set no
> -march value so it can run on any hardware for this arch.

Based on a quick test, running i686-pc-linuc-gnu-gcc without passing
-march seems to be equivalent to passing "-mtune=generic -march=i686".
So, you'll get code that will only run on i686, but has "generic"
tuning (whatever that means).

I don't think that will make a noticeable difference on user systems.
Most Gentoo people probably override this to some more specific CPU
model via CFLAGS in make.conf anyway.

So +1 from me on removing -march=i686 from the x86 arch profile.