On Jul 30, 2013, at 18:16, John Baldwin <j...@freebsd.org> wrote: > On Tuesday, July 30, 2013 10:09:35 am Matthew Fleming wrote: >> On Tue, Jul 30, 2013 at 5:33 AM, Dimitry Andric <d...@freebsd.org> wrote: >> >>> Author: dim >>> Date: Tue Jul 30 12:33:21 2013 >>> New Revision: 253802 >>> URL: http://svnweb.freebsd.org/changeset/base/253802 ... >> PIC mode on amd64 also uses %ebx. The difference is that FreeBSD makefiles >> set -fPIC for i386 kernel compile but not amd64. Locally we use -fPIC for >> amd64 (it was added 6 years ago to our environment because it gave better >> kernel debugging). > > Note that this is used in userland and the kernel. > >> Anyways, is there some way to detect PIC mode and use that to decide >> whether to use %ebx for the cpuid instruction, rather than using i386? > > Does clang supply a reliable #define to indicate that PIC is in use? If not, > then this should use the PIC path always to be safe.
Just like gcc, clang defines both __pic__ and __PIC__ as 1 for -fpic, and as 2 for -fPIC (though on x86, there is no difference between the two). Similarly, __pie__ and __PIE__ are defined as 1 for -fpie, and as 2 for -fPIE. -Dimitry _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
