[Bug c/80502] Provide macro to indicate OpenMP SIMD support

["egallager at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80502

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-08-01
                 CC|                            |egallager at gcc dot gnu.org
     Ever confirmed|0                           |1
           Severity|normal                      |enhancement

--- Comment #1 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Evan Nemerson from comment #0)
> Created attachment 41250 [details]
> define _OPENMP_SIMD when -fopenmp-simd or -fopenmp is passed
> 
> _OPENMP is (correctly) only defined for full OpenMP; when only -fopenmp-simd
> is used there doesn't seem to be any way to detect in the preprocessor that
> the compiler supports OpenMP SIMD pragmas.
> 
> It would be nice if there were a macro to determine whether they are
> supported so we could do something like
> 
>   #if (defined(_OPENMP) && (_OPENMP >= 201307L)) || \
>     (defined(_OPENMP_SIMD) && (_OPENMP_SIMD >= 201307L))
>   #pragma omp simd
>   #endif
> 
> AFAIK ICC is the only compiler with a feature like -fopenmp-simd (they call
> it -openmp-simd), and they don't define anything either.  I've reported the
> issue to them, but in the meantime it seems GCC can choose whatever it wants
> without creating any compatibility issues.  Defining _OPENMP_SIMD to the
> version of OpenMP supported (just like _OPENMP does) seems logicial to me. 
> I've attached a fairly trivial patch.

Patches go to the gcc-patches mailing list. Confirming as an enhancement.