On Jul 13, 10:54 am, Jason <ja...@njkfrudils.plus.com> wrote: > On Wednesday 13 July 2011 10:06:50 Jason wrote: > > > Hi > > > New karasub/add for nehalem , I did do a re-shuffle and it was pretty much > > optimal , but the feedin/winddown code killed it ,
This has been and still is a problem , when you get close to the machines limit the feedin and winddown code can effect the speed of the inner loop , so when I try an find a good inner loop I really need to have the correct feedin and winddown code around it. If I'm changing the pipelining this is difficult(but compilers can do it) . Also the calling conventions and the call.ret code really should be the same , I'll modify my optimizer for these call/ret differences , hopefully this will make things more predictable and will also mean I can tune windows 64 code on a linux box and at some stage I'll adapt speed.c etc so that we can speed test in linux as well so at the mo this is > > just the existing K10 code with the inc's replaced by an add and lea's , > > just do a diff. > > Going to a 3-way unroll on karasub free's up 2 registers which we can use > > to store the carrys therefore the false dependence is gone and the latency > > bound is much reduced , but in practice I couldn't find anything better :( > > , and storing the carry in a mem location was even worse. > > > I expect the other Intel chips will benefit as well from inc's to lea's , > > I'll check it out later. > > > Jason > > Hi > > I added two new asm functions for the K8/K10 > > mpn_double(mp_ptr rp,mp_size_t n) > > mpn_half(mp_ptr rp,mp_size_t n) > > which are inplace left and right shifts by 1 , these functions can be used > unconditionally as they fall back via macro's to lshift1 or even lshift > > On the K8/K10 they are 30% faster than our existing lshift1/rshift1 running at > the optimal 1.0 cycle per word. > > I'll add the relevant C code later today , as I've only done a few quick tests > on them so far. > > Jason -- 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.
