Kernel handling of vector registers

[Torbjorn Granlund <tg@swox.com>]

I recently committed several GMP assembly functions for powerpc32
using Altivec registers and instructions.

I also reinstalled my system (a Pegasos2) recently, from an obsolete
snapshot I got from somebody on the net, to a much less obsolete
system.

With the new assembly code *and* with the new GNU/Linux installation,
the system fails intermittently in GMP's make check.  I don't know how
to debug such an intermittent failure.

The same GMP code works correctly on Mac OS X.

Debugging such an intermittent problem is close to impossible.

Do you know if the Linux kernel correctly handles Altivec registers
during context switch?  Does it require setting the VRSAVE special
register, BTW?  (I set it properly, since Mac OS X needs it, and
setting it shouldn't hurt.)

(The kernel on the system identifies itself as 2.6.12.)

-- 
Torbjörn