[bug#69581] [PATCH 05/11] guix: cpu: Enable tuning for i686-linux.

[Efraim Flashner]

On Wed, Mar 06, 2024 at 07:05:03PM +0100, Ludovic Courtès wrote:
> Efraim Flashner <efraim@flashner.co.il> skribis:
> 
> > * gnu/packages/gcc.scm (gcc-7, gcc-10, gcc-11, gcc-12, gcc-13)
> > [properties]: In compiler-cpu-architectures use the
> > x86_64-micro-architectures list for i686.
> > * guix/cpu.scm (cpu->gcc-architecture): Expand the x86_64 case to also
> > support i686.
> 
> [...]
> 
> > +++ b/gnu/packages/gcc.scm
> > @@ -673,6 +673,7 @@ (define-public gcc-7
> >       `((compiler-cpu-architectures
> >          ("aarch64" ,@%gcc-7.5-aarch64-micro-architectures)
> >          ("armhf" ,@%gcc-7.5-armhf-micro-architectures)
> > +        ("i686" ,@%gcc-7.5-x86_64-micro-architectures)
> >          ("x86_64" ,@%gcc-7.5-x86_64-micro-architectures))
> 
> Wait, that wouldn’t work on an actual i686 CPU, right?
> 
> I was surprised to see that GCC built for i686 accepts those flags:
> 
>   guix shell -s i686-linux gcc-toolchain -- gcc -march=skylake /tmp/t.c
>   guix shell -s i686-linux gcc-toolchain -- gcc -march=x86-64-v4 /tmp/t.c
> 
> If GCC agrees, so be it.  LGTM!

I checked with `guix build foo --system=i686-linux --tune=znver2` and
everything just worked. That's definitely a Guix special, since we don't
have multilib support.

-- 
Efraim Flashner   <efraim@flashner.co.il>   רנשלפ םירפא
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