From: Torbjorn Granlund <t...@gmplib.org> Date: Sat, 13 Apr 2013 15:40:38 +0200
> I spotted a comment in gcc, > > ;; Even on V9 we use this call sequence with a stub, instead of "rd %pc, ..." > ;; because the RDPC instruction is extremely expensive and incurs a complete > ;; instruction pipeline flush. > > which perhaps answers my question. But is that true in general or for > some sparcv9 implementations? It would be nice to avoid these long > insns sequences where they can be avoided. "rd %pc" is very expensive on every single chip I've tried it on. It tends to flush the entire pipeline, which for example means a minimum of 9 cycles on Ultra1&2. _______________________________________________ gmp-devel mailing list gmp-devel@gmplib.org http://gmplib.org/mailman/listinfo/gmp-devel
