#12873: Clear MMX state in i686 longjmp()
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Reporter: jdemeyer | Owner: jdemeyer
Type: defect | Status: new
Priority: major | Milestone: sage-5.0
Component: c_lib | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Jeroen Demeyer | Merged in:
Dependencies: | Stopgaps:
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Description changed by jdemeyer:
Old description:
> The libc `setjmp`/`longjmp` functions on i686 hardware do not fully
> restore the x87 FPU state, in particular when MMX instructions have been
> used. The proposed solution is to execute the `EMMS` instruction before
> `longjmp()`. For more context, see #12777 where this bug was discovered.
New description:
The libc `setjmp`/`longjmp` functions on i686 hardware do not fully
restore the x87 FPU state, in particular when MMX instructions have been
used. The proposed solution is to execute the `EMMS` instruction before
`longjmp()`. For more context, see #12777 where this bug was discovered.
To see the problem in action, compile [attachment:emms.c] on i686 hardware
with
{{{
gcc -lm -march=native -m32 -mfpmath=387 emms.c -o emms
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12873#comment:4>
Sage <http://www.sagemath.org>
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