Implicit altivec vs. linux kernel build

[Benjamin Herrenschmidt]

>   Surely it would be possible to use -ffixed-* options to reserve all the
> altivec registers and get precisely that effect?

Nah, I don't need to be that drastic. The RAID6 code is already in a
separate file that can have a specific additional set of compile flags,
so I can just enable altivec just for this file and make sure the
functions it provides are always called from the proper environment
(that is have the enable_kernel_altivec() call etc... be _outside_ of
that file).

Ben.