I'm the one who added the warnings in rustc (that will eventually become hard
errors) that show up when disabling SSE2 on our primary x86-32 targets. Happy to
answer any questions you may have about that!
As a Rust compiler developer and Debian user, I'd love to see Debian no longer
ship a patched rustc that uses a configuration which we cannot support with
reasonable effort. :) So having the baseline raised here would be amazing -- if
I had known that this is even an option, I'd have tried to push for it sooner.
:D That would remove a significant portability hazard from the Rust ecosystem.
It's one thing to have people opt-in to a tier 3 target and then get strange
behavior; it's another thing entirely for people to "apt install rustc" and get
strange behavior.
The lack of support in Rust, as already mentioned, is due to lack of support in
LLVM, which I would say is ultimately due to general lack of interest in making
a platform with such quirky behavior work well in today's world where basically
everything implements IEEE FP semantics (at the expected precision levels).
Someone would have to put in that work, but the community of people keeping
non-SSE2 x86-32 alive do not seem to have the capacity for that, unfortunately.
If you need to keep the patch for Trixie, and if you want to ship Rust 1.86 in
Trixie, the patch will need updating due to
<https://github.com/rust-lang/rust/pull/137037>. I left some comments
specifically for distributions in the code to hopefully help with that; again
let me know if you have any questions.
Kind regards,
Ralf
