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

["Ludovic Courtès" <ludo@gnu.org>]

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!