Date: Wed, 31 Jul 2013 14:21:42 +0200 From: Dimitry Andric <dim@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, Matthew Fleming <mdf@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org> Subject: Re: svn commit: r253802 - head/contrib/llvm/tools/clang/lib/Headers Message-ID: <A7A9F3E9-AFB6-44C3-8B3F-E28F813229F5@freebsd.org> In-Reply-To: <201307301216.15235.jhb@freebsd.org> References: <201307301233.r6UCXLT8012177@svn.freebsd.org> <CAMBSHm8xDvWsKJiLAzPF8azMKLHq3WWWQ3X1d6-6nJSAppux9Q@mail.gmail.com> <201307301216.15235.jhb@freebsd.org>
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On Jul 30, 2013, at 18:16, John Baldwin <jhb@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 <dim@freebsd.org> = wrote: >>=20 >>> 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). >=20 > Note that this is used in userland and the kernel. >=20 >> 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? >=20 > 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=20 two). Similarly, __pie__ and __PIE__ are defined as 1 for -fpie, and as 2 for -fPIE. -Dimitry
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