-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 On 02/09/2015 17:12, John Baldwin wrote: > 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).
I think you should back it out for now and move the discussion to arch or hackers. I gave it up at the time but you may have better luck. :-) FYI, the following was the last version of my patch at the time. https://people.freebsd.org/~jkim/bitcount5.diff Jung-uk Kim -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJU2TRdAAoJEHyflib82/FGUK8H/jnrTqxqw6k5mK2hL3jslBuK yAQKlfCV+pq3jJm6Ixqxk9vszZUwAMw02mPhxkHEPAB4vzZnnhH18u5cOrB1r7MA NFTva6UKoo5F00GO0yKyK9rGaHXxuoSGjdntEckYJuFxZ8Zh9K1dYIRXGW42f55c JEK9aU8uVtFTov8RF0pVGDqiezWJRGlTrftDwq8tUHfv8pJG2p0Z9rfLYsP1DTx2 fMcb7iz6IIQKO2aUYytXv8UdqkA2VtwOGrqC0nLTL4RF5bC5i61WHRJYxNWJ5+sV XQx9cXutkNIIj7IHIw2kpyvx0ynZGIN/jwpBy0d58aq3jv2wQhzk/F1ID51guNk= =uINd -----END PGP SIGNATURE----- _______________________________________________ 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"
