Re: PPC64 Illegal Instruction
On Sun, Mar 03, 2019 at 09:21:20PM +0100, John Paul Adrian Glaubitz wrote:
> On 3/3/19 9:12 PM, Noah Wolfe wrote:
> > Really? I thought that since the PowerPC 970 is built on POWER4, that would be the baseline.
> It's alright, I confused POWER4 and POWER5. There are just too many POWERs.
>
> Either way, Michael found the problem and the x265 maintainer already made
> some changes which will alleviate the issue. Although I'm not sure I like the
> idea of disabling AltiVec altogether. But maybe AltiVec in x265 is POWER8+
> only.
No, the difference is VSX. Altivec is the same instruction set, whether
on G4, G5, Power5 and later (IBM Power4 did not have Altivec, Power5 did,
VSX was added to Power7).
G5 or PPC970 is actually closer to Power5 from this point of view.
To support everything you would ideally need 3 versions (or 3
libraries):
- no vector instructions (basic Power4)
- Altivec (G5, P5, P6)
- VSX (P7 and later)
However, the big jump for performance is likely provided by Altivec.
Do you really want to support base Power4 (no Altivec) or not?
If not, a single version (Altivec and no VSX) is probably the simplest.
Gabriel
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