On Thursday 19 March 2009 14:31:55 Gonzalo Tornaria wrote: > On Wed, Mar 18, 2009 at 10:44 PM, Bill Hart <goodwillh...@googlemail.com> wrote: > > Wait, how does it currently decide which ABI to use? Does configure > > decide that aside from what config.guess says. > > Yes, except config.guess may change it (but it shouldn't, as we > discussed before this causes compilation failure, e.g. in a kvm > virtual cpu which reports wrong cpuid).
At the moment a kvm cpuid would be unrecognized , and so would default to x86_64 the base architecture . If the kvm doesn't virtualize cpu then a better choice may be K8 or core2 depending on the host cpu, do we know what it does and whether is may return some info we can use to choose a better path. > > > I thought I recalled that this is why Gonzalo and I had nocona. > > The choice was made to match tuning options in gcc; from some gcc > manpage, the options for p4 where "pentium4", "prescott" and "nocona", > and the man page said "nocona" was for the p4 chips with 64 bit > support --- iow, I assumed the "nocona" tuning option would be the > only good one for 64 bit p4, but that may not be the case. > > Anyway, the point was, using the same name as gcc to avoid a mapping > from cpu naming to gcc tuning options, but this is just another > mapping which can be written, as long as the cpu names are > fine-grained enough to get advantage of gcc tuning. > You still have to write the same mapping regardless of weather the names match or not , so we can call them what we want(nearly) > e.g. calling "core2" a pentium D is not good, because -mtune=nocona > gives better results than -mtune=core2 as shown by the benchmarks I > posted in a different thread. > > Gonzalo > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "mpir-devel" group. To post to this group, send email to mpir-devel@googlegroups.com To unsubscribe from this group, send email to mpir-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/mpir-devel?hl=en -~----------~----~----~----~------~----~------~--~---
