On Sat, Nov 21, 2020 at 11:23 AM David Edelsohn <[email protected]> wrote: > > On Sat, Nov 21, 2020 at 10:57 AM Jeffrey Walton <[email protected]> wrote: > > > > On Sat, Nov 21, 2020 at 10:20 AM David Edelsohn <[email protected]> wrote: > > > > > > Please don't target Power7. Please target Power9, or at least Power8. > > > > > > The PPC64LE Linux ABI specifies Power8 as the minimum ISA. > > > > > > Power ISA 2.07 is Power8. ISA 3.0 is Power9. ISA 3.1 is Power10. > > > > Small nit... PowerMac G4's and G5's still have a strong following. > > There's a lot of activity on Debian's PowerPC list. > > > > The G4's and G5's provide Altivec acceleration and the old gcc > > compiler even accepts -mcpu=power4. > > > > ChaCha is a simple algorithm that benefits from Altivec, even when you > > manage the 64-bit additions/carries in a 32x4 vector arrangement. > > Small nit: G4 and G5 Macs are not Power7. If an implementation of a > cipher targets Power7, it still can use ISA instructions not supported > by PowerMacs. If you want to provide an additional implementation for > pure Altivec, that's fine.
Correct. > There is a vocal group of Debian PowerPC users. I greatly appreciate > support and advocacy. But the number of actual users is very small. > And it's highly unlikely that those users will run ChaCha cipher in > production. The ChaCha implementation is new, not maintaining > existing support. > > If Niels wants to implement an optimized version of a cipher on Power > that will be useful in production environments and applied in global > businesses, I would recommend that he target Power9. A new, > high-performance implementation will be deployed on new systems for > new applications or new versions of applications. When you said the library should not target POWER7, and only target POWER8 and POWER9, I took that to mean the library should not target POWER7 and below. Altivec and POWER4 is a fine target given the user base. It will even run on POWER7. An Altivec version of ChaCha is an easy implementation. There are no pain points in implementing it. Jeff _______________________________________________ nettle-bugs mailing list [email protected] http://lists.lysator.liu.se/mailman/listinfo/nettle-bugs
