Date: Tue, 30 Jul 2013 12:16:15 -0400 From: John Baldwin <jhb@freebsd.org> To: Matthew Fleming <mdf@freebsd.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, Dimitry Andric <dim@freebsd.org> Subject: Re: svn commit: r253802 - head/contrib/llvm/tools/clang/lib/Headers Message-ID: <201307301216.15235.jhb@freebsd.org> In-Reply-To: <CAMBSHm8xDvWsKJiLAzPF8azMKLHq3WWWQ3X1d6-6nJSAppux9Q@mail.gmail.com> References: <201307301233.r6UCXLT8012177@svn.freebsd.org> <CAMBSHm8xDvWsKJiLAzPF8azMKLHq3WWWQ3X1d6-6nJSAppux9Q@mail.gmail.com>
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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: > > > Author: dim > > Date: Tue Jul 30 12:33:21 2013 > > New Revision: 253802 > > URL: http://svnweb.freebsd.org/changeset/base/253802 > > > > Log: > > Pull in r186696 from upstream clang trunk: > > > > This patch implements __get_cpuid_max() as an inline and __cpuid() > > and __cpuid_count() as macros to be compatible with GCC's cpuid.h. > > It also adds bit_<foo> constants for the various feature bits as > > described in version 039 (May 2011) of Intel's SDM Volume 2 in the > > description of the CPUID instruction. The list of bit_<foo> > > constants is a bit exhaustive (GCC doesn't do near this many). More > > bits could be added from a newer version of SDM if desired. > > > > Patch by John Baldwin! > > > > This should fix several ports which depend on this functionality being > > available. > > > > MFC after: 1 week > > > > Modified: > > head/contrib/llvm/tools/clang/lib/Headers/cpuid.h > > > > Modified: head/contrib/llvm/tools/clang/lib/Headers/cpuid.h > > > > ============================================================================== > > --- head/contrib/llvm/tools/clang/lib/Headers/cpuid.h Tue Jul 30 > > 12:17:45 2013 (r253801) > > +++ head/contrib/llvm/tools/clang/lib/Headers/cpuid.h Tue Jul 30 > > 12:33:21 2013 (r253802) > > +/* PIC on i386 uses %ebx, so preserve it. */ > > +#if __i386__ > > +#define __cpuid(__level, __eax, __ebx, __ecx, __edx) \ > > + __asm(" pushl %%ebx\n" \ > > + " cpuid\n" \ > > + " mov %%ebx,%1\n" \ > > + " popl %%ebx" \ > > + : "=a"(__eax), "=r" (__ebx), "=c"(__ecx), "=d"(__edx) \ > > + : "0"(__level)) > > + > > +#define __cpuid_count(__level, __count, __eax, __ebx, __ecx, __edx) \ > > + __asm(" pushl %%ebx\n" \ > > + " cpuid\n" \ > > + " mov %%ebx,%1\n" \ > > + " popl %%ebx" \ > > + : "=a"(__eax), "=r" (__ebx), "=c"(__ecx), "=d"(__edx) \ > > + : "0"(__level), "2"(__count)) > > +#else > > +#define __cpuid(__level, __eax, __ebx, __ecx, __edx) \ > > + __asm("cpuid" : "=a"(__eax), "=b" (__ebx), "=c"(__ecx), "=d"(__edx) \ > > + : "0"(__level)) > > + > > +#define __cpuid_count(__level, __count, __eax, __ebx, __ecx, __edx) \ > > + __asm("cpuid" : "=a"(__eax), "=b" (__ebx), "=c"(__ecx), "=d"(__edx) \ > > + : "0"(__level), "2"(__count)) > > +#endif > > > > 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. -- John Baldwin
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