Re: Rustc unsoundness on i386

[Fabian Grünbichler <fabian@gruenbichler.email>]

On November 23, 2024 9:03:26 PM GMT+01:00, "Jeremy Bícha" <jeremy.bicha@canonical.com> wrote:
>On Sat, Nov 23, 2024 at 1:57 PM Bastien Roucariès <rouca@debian.org> wrote:
>>
>> Le samedi 23 novembre 2024, 18:29:04 UTC Andrey Rakhmatullin a écrit :
>> > On Sat, Nov 23, 2024 at 03:14:42PM +0100, Fabian Grünbichler wrote:
>> > > B) bump the i386 baseline in Debian to require SSE2, and stop disabling SSE2 there in rustc
>>
>> It will break I suppose imagemagick on i386 and scientific software testsuite
>>
>> i386 means FPU so excess precision.
>>
>> SSE is good and even better but excess precision is worked arround thus FTBFS
>
>Debian's i386 already has excess precision:
>https://wiki.debian.org/ArchitectureSpecificsMemo#i386
>
>If you mean something else, could you be… more precise?

Its very much possible that things relying on x87 floats on i386 will need to adapt if some underlying implementation switches to SSE, just like the inverse happens now (like testsuites expecting SSE behaviour/results that need to be adapted to x87).

I don't think that is a problem per se. And you can still use x87 floats if those work for your package, even if we go down that road. Well not with rust, but given that those are apparently broken already anyway...