[PATCH] x86: Use target("baseline-isas-only") in <cpuid.h>

[H.J. Lu]

On Mon, Aug 24, 2020 at 7:55 AM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> On Mon, Aug 24, 2020 at 3:23 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> > > Speaking of pragmas, these should be added outside cpuid.h, like:
> > >
> > > #pragma GCC push_options
> > > #pragma GCC target("general-regs-only")
> > >
> > > #include <cpuid.h>
> > >
> > > void cpuid_check ()
> > > ...
> > >
> > > #pragma GCC pop_options
> > >
> > > >footnote
> > >
> > > Nowadays, -march=native is mostly used outside generic target
> > > compilations, so for relevant avx512 targets, we still generate spills
> > > to mask regs. In future, we can review the setting of the tuning flag
> > > for a generic target in the same way as with SSE2 inter-reg moves.
> > >
> >
> > Florian raised an issue that we need to limit <cpuid.h> to the basic ISAs.
> > <cpuid.h> should be handled similarly to other intrinsic header files.
> > That is <cpuid.h> should use
> >
> > #pragma GCC push_options
> > #ifdef __x86_64__
> > #pragma GCC target("arch=x86-64")
> > #else
> > #pragma GCC target("arch=i386")
> > ...
> > #pragma GCC pop_options
> >
> > Here is a patch.  OK for master?
>
> -ENOPATCH
>
> However, how will this affect inlining? Every single function in
> cpuid.h is defined as static __inline, and due to target flags
> mismatch, it won't be inlined anymore. These inline functions are used
> in some bit testing functions, and to keep them inlined, these should
> also use the same options to avoid non-basic ISAs. This is the reason
> cpuid.h should be #included after pragma, together with bit testing
> functions, as shown above.
>

How about target("baseline-isas-only")? All CPUID functions are
inlined.


-- 
H.J.
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