Re: V6 [PATCH] x86: Add <sys/platform/x86.h>

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Oct 25, 2018 at 11:11 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On 10/25/18, Florian Weimer <fweimer@redhat.com> wrote:
> > * H. J. Lu:
> >
> >> /* CPU_FEATURE_USABLE evaluates to true if the feature is usable.  */
> >>  #define CPU_FEATURE_USABLE(name)                                  \
> >>    ((need_arch_feature_##name                                      \
> >>      && (x86_get_arch_feature (index_arch_##name##_Usable)         \
> >>    & (bit_arch_##name##_Usable)) != 0)                             \
> >>     || (!need_arch_feature_##name                               \
> >>         && (x86_get_cpuid_registers (index_cpu_##name)->reg_##name \
> >>          & (bit_cpu_##name)) != 0))
> >
> > I still think this is wrong.  This should be a const function, with a
> > single argument, returning bool, so that we do not expose the internal
>
> The only things exposed are
>
> enum
>   {
>     /* The integer bit array index for the first set of internal feature
>        bits.  */
>     FEATURE_INDEX_1 = 0,
>     FEATURE_INDEX_2,
>     /* The current maximum size of the feature integer bit array.  */
>     FEATURE_INDEX_MAX
>   };
>
> enum
>   {
>     COMMON_CPUID_INDEX_1 = 0,
>     COMMON_CPUID_INDEX_7,
>     COMMON_CPUID_INDEX_80000001,
>     /* Keep the following line at the end.  */
>     COMMON_CPUID_INDEX_MAX
>   };
>
> struct cpuid_registers
>   {
>     unsigned int eax;
>     unsigned int ebx;
>     unsigned int ecx;
>     unsigned int edx;
>   };
>
> following the conventions of C/C++.
>
> > implementation.  It will also be possible to use this function from Ada,
> > Fortran, and so on.  This is not possible with a preprocessor macro.
>
> This is designed for C/C++.  This is never intended for Fortran nor
> Ada.  If there are requests for Fortran or Ada, we can investigate different
> approaches for them.
>
> Any other comments?

I'd like to add this C/C++ feature to glibc.  If there is no objection, I will
check it in tomorrow.

-- 
H.J.