Bug#1095863: release.debian.org: Raising the i386 baseline for Trixie to include SSE2/MMX

[Samuel Thibault <sthibault@debian.org>]

Simon McVittie, le jeu. 13 févr. 2025 16:32:30 +0000, a ecrit:
> The options as I see them, *including* the options that I would personally
> prefer to rule out, are:
> 
> - Status quo: don't change anything. As Fabian says, Rust code on i386
>   will sometimes be miscompiled and might crash.
> 
> - Raise baseline to i686+SSE2+MMX and make gcc require/assume this
> 
> - Raise "official" baseline to i686+SSE2+MMX, leave gcc producing
>   code that would have worked with the previous baseline by default,
>   but rustc/LLVM may require/assume i686+SSE2+MMX

Are rustc and LLVM necessarily coupled? AIUI the rustc baseline is
configured in rustc itself, in
./compiler/rustc_target/src/spec/targets/i686_unknown_linux_gnu.rs :

    base.cpu = "pentiumpro".into();

vs

    base.cpu = "pentium4".into();

So we could raise the baseline only in rustc.

> - Officially keep current baseline, intentionally violate the baseline in
>   rustc (and maybe LLVM?) so that rustc produces working code, and
>   have the release team announce that the resulting baseline violations
>   are not to be considered RC bugs
> 
> - Do a transition to remove all Rust code from i386
> 
> - Remove i386 completely, re-introduce the equivalent of ia32-libs so we
>   can still provide 32-bit Wine and Mesa
>   (I'm mentioning this for completeness but I suspect the release team
>   would veto this, because nobody liked ia32-libs)
> 
> - Remove i386 completely, no more 32-bit Wine, no more ability to
>   install Steam, etc.

Samuel