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

[Florian Weimer]

* H. J. Lu:


> Here is the patch with CPU_FEATURE_USABLE only.  OK for master
> branch?

Thanks.  Recently, the matter of special-casing code inside target
clones came up on the glibc list:

  <https://gcc.gnu.org/ml/gcc-help/2018-10/msg00118.html>

Do you think it might be possible to eventually turn some results for
CPU_FEATURE_USABLE in target clones into compile-time constants because
the compiler knows the results of the feature selection in the
automatically generated IFUNC resolver?

Thanks,
Florian