Re: No i686 kernel: Can we require SSE2 for i686?

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On 07/11/2017 10:26 PM, Florian Weimer wrote:
> I ran into this unannounced change:
> 
>   https://fedoraproject.org/wiki/Changes/Stop_Building_i686_Kernels
> 
> If this is accepted, all x86 hardware on which Fedora can run will
> support SSE2, and we should reflect that in the i686 build flags.

Current GCC does not seem to provide a way to enable SSE2 while
preserving stack alignment, but not requiring it for SSE2 access to
stack variables.  As a result, enabling SSE2 will break tons of
third-party software which is not compliant with the increased stack
alignment which was introduced as a silent, breaking change to the i386
psABI about 15 years ago.

I don't think it's worth fixing GCC because i386 support is legacy only
anyway, so I'd suggest to leave things as they are (and even scale back
the SSE2 use within glibc).

Thanks,
Florian
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