On Tue, Aug 1, 2017 at 1:02 AM, Florian Weimer <fweimer(a)redhat.com> wrote:
On 07/11/2017 10:26 PM, Florian Weimer wrote:
> I ran into this unannounced change:
> 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).
I think it's worth filing the GCC bug report. The GCC developers
should fix this issue.
It may still be worth scaling back SSE2 support in 32-bit glibc, though.