Probing for native availability of isel from userspace

[Gabriel Paubert]

On Sun, Sep 23, 2012 at 03:46:06AM +0200, Segher Boessenkool wrote:
> Why does the kernel emulate this, btw?  I can see emulation is useful
> for running older binaries, for instructions that have been removed
> from the architecture; but for newly added instructions, or optional
> instructions, it hurts more than it helps?

Indeed. I also don't understand why mfpvr is emulated. That's the kind
of information that should be passed to the executables through auxiliary
vectors. After all, you can (or could at least) compile a kernel without
Altivec support and run it on a processor with Altivec.

Therefore, whether Altivec is supported or not, is a matter of
processor and kernel options. Provide this information through
the auxiliary vector and the problem is solved.

	Gabriel