On Fri, May 30, 2025, at 11:13 PM, Stefan Monnier wrote: >>>I just confirmed now that downgrading to the version of `sqv` in >>>Debian stable (which also downgraded `apt` and `apt-utils`) brings the >>>system back to a usable state. >> >> The architecture baseline for i386 was raised. > > According to https://wiki.debian.org/ArchitectureSpecificsMemo#i386-1 > [ FWIW, it was difficult to find that page, because the natural search > terms like "baseline" are missing. ]: > > - i686 since Debian 12 'bookworm'. There's no MMX nor SSE. > - Before that, "almost" i686 (no "long NOP"/NOPL) since Debian 9 > 'stretch' (gcc-6 6.1.1-1). > - Before that, i586 since gcc-4.9 4.9-20140411-1 (2014). > - Before that, i486 since gcc-4.1 4.1ds7-0exp7 (2006). > - Before that, i386.
That page is not yet updated for Trixie, see below. > Whereas my processor is a Pentium-III (mobile), i.e. an evolution of the > Pentium-II itself an evolution of the famous Pentium Pro (aka *the* > original i686). It has SSE but not SSE2 which only came a bit later. > > [ The vast majority of CPUs after i686 are already supported via amd64, > so I don't understand what would be the benefit of raising the baseline > even further. ] See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1095863 and https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1095862 (and related/cloned LLVM bugs and upstream references) for details. The TL;DR gist: LLVM (which rustc uses as codegen backend) is broken for non-SSE2 targets with no intention upstream of fixing it, so Trixie+ will use targets which include/require SSE2 for what Debian calls i386 (which is called i686 by LLVM and rustc, but might otherwise be called i786 if that term ever had taken off ;)).
