On Monday, February 09, 2015 04:55:52 PM Jung-uk Kim wrote: > On 02/09/2015 16:08, John Baldwin wrote: > > On Monday, February 09, 2015 09:03:24 PM John Baldwin wrote: > >> Author: jhb Date: Mon Feb 9 21:03:23 2015 New Revision: 278474 > >> URL: https://svnweb.freebsd.org/changeset/base/278474 > >> > >> Log: Use __builtin_popcnt() to implement a BIT_COUNT() operation > >> for bitsets and use this to implement CPU_COUNT() to count the > >> number of CPUs in a cpuset. > >> > >> MFC after: 2 weeks > > > > Yes, __builtin_popcnt() works with GCC 4.2. It should also allow > > the compiler to DTRT in userland uses of this if -msse4.2 is > > enabled. > > Back in 2012, when I submitted a similar patch, bde noted > __builtin_popcount*() cannot be used with GCC 4.2 for *kernel* because > it emits a library call. > > http://docs.freebsd.org/cgi/mid.cgi?20121116171923.L1135 > > FYI...
Weird, I though I built a kernel with this in a tree that uses it in the igb(4) driver. We need a CPU_COUNT() no matter what, but if this emits a library call under GCC I will need to add the call. We could also adopt your bitcount header, though I think it is more consistent to keep the loop in BIT_COUNT() and use something that emulates popcountl() rather than directly using bitcount() in BIT_COUNT() (primarily because the rest of sys/bitset.h is structured that way: explicit loops in sys/bitset.h itself). -- John Baldwin _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
