On Sat, Nov 21, 2020 at 11:32 AM Jeffrey Walton <[email protected]> wrote: > > 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.
Nettle can target any processors and ISA levels that it wishes. Niels wrote: > I would like to target Power 7 for the chacha code. I responded that Power9 (or at least Power8) would be preferred. If Niels wants the implementation to impact production deployments and increase the use of Nettle for cryptography on Power systems, I recommend that he target a more recent level of the ISA. He can target Power7, and Power4, and pure Altivec as well. Thanks, David _______________________________________________ nettle-bugs mailing list [email protected] http://lists.lysator.liu.se/mailman/listinfo/nettle-bugs
