altivec instructions

altivec instructions

[Jim Terman]

We are trying to run a program that contains altivec instructions on a G4,
but the process keeps crashing (gdb will actually cause a kernal panic).
It looks like a bit in the MSR needs to be set.  What would be the best
way to modify the kernel to let this happen?

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Re: altivec instructions

[Tony Mantler]

At 12:52 PM -0600 1/24/00, Jim Terman wrote:
>We are trying to run a program that contains altivec instructions on a G4,
>but the process keeps crashing (gdb will actually cause a kernal panic).
>It looks like a bit in the MSR needs to be set.  What would be the best
>way to modify the kernel to let this happen?

Before you enable the MSR bit, you'll have to write altivec register saving
code for your kernel, the strategies for which were discussed a while back
on this mailing list, and should be available for your reading convinience
on the mailing list archive.

Following that, you'll have to check to be sure your code properly uses the
VRSAVE register, to avoid forward compatibility problems.


Once that's all done, your code should run just fine.


Cheers - Tony :)


--
Tony Mantler         Renaissance Nerd Extraordinaire         eek@escape.ca
Winnipeg, Manitoba, Canada                       http://www.escape.ca/~eek


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Re: altivec instructions

[Robert Neugebauer]

Wouldn't the 2.2 kernel patches for altivec instructions handle that. I
don't know if they were supported, but they worked on my G4 and haven't
caused any instability. I had found them somewhere on devel.linuxppc.org.

I can send them too you if you need.

Bob


On Mon, 24 Jan 2000, Tony Mantler wrote:

>
> At 12:52 PM -0600 1/24/00, Jim Terman wrote:
> >We are trying to run a program that contains altivec instructions on a G4,
> >but the process keeps crashing (gdb will actually cause a kernal panic).
> >It looks like a bit in the MSR needs to be set.  What would be the best
> >way to modify the kernel to let this happen?
>
> Before you enable the MSR bit, you'll have to write altivec register saving
> code for your kernel, the strategies for which were discussed a while back
> on this mailing list, and should be available for your reading convinience
> on the mailing list archive.
>
> Following that, you'll have to check to be sure your code properly uses the
> VRSAVE register, to avoid forward compatibility problems.
>
>
> Once that's all done, your code should run just fine.
>
>
> Cheers - Tony :)
>
>
> --
> Tony Mantler         Renaissance Nerd Extraordinaire         eek@escape.ca
> Winnipeg, Manitoba, Canada                       http://www.escape.ca/~eek
>
>


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Re: altivec instructions

[Tony Mantler]

At 4:16 PM -0600 1/24/00, Robert Neugebauer wrote:
>Wouldn't the 2.2 kernel patches for altivec instructions handle that. I
>don't know if they were supported, but they worked on my G4 and haven't
>caused any instability. I had found them somewhere on devel.linuxppc.org.
>
>I can send them too you if you need.
>
>Bob
[...]

*search, search* Ah, so there is a patch. I assume this is the one you're
referring to?
<http://devel.linuxppc.org/ftp/users/ajoshi/altivec-2.2.patch>

It might just be my imagination, but for some reason it doesn't look like
that patch actually touches any altivec registers other than the VRSAVE...

For a single altivec task on a UP system it might work, though.


While I'm on the subject, does GCC even have altivec support yet? It seems
I always miss all the important announcements... :)


Cheers - Tony :)


--
Tony Mantler         Renaissance Nerd Extraordinaire         eek@escape.ca
Winnipeg, Manitoba, Canada                       http://www.escape.ca/~eek


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