On Tue, Apr 10, 2018 at 02:55:43PM +0200, Richard Biener wrote:
> > And the easiest solution is in the Fortran FE based on some flag
> > (e.g. -mveclibabi=glibc) through a target hook add
> > __attribute__((__simd__ ("notinbranch")))
> > to the builtins like __builtin_sin etc. that have them in the
> > glibc header (x86_64 -m64 and -ffast-math only):
> >
> > # undef __DECL_SIMD_cos
> > # define __DECL_SIMD_cos __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_cosf
> > # define __DECL_SIMD_cosf __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_sin
> > # define __DECL_SIMD_sin __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_sinf
> > # define __DECL_SIMD_sinf __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_sincos
> > # define __DECL_SIMD_sincos __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_sincosf
> > # define __DECL_SIMD_sincosf __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_log
> > # define __DECL_SIMD_log __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_logf
> > # define __DECL_SIMD_logf __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_exp
> > # define __DECL_SIMD_exp __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_expf
> > # define __DECL_SIMD_expf __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_pow
> > # define __DECL_SIMD_pow __DECL_SIMD_x86_64
> > # undef __DECL_SIMD_powf
> > # define __DECL_SIMD_powf __DECL_SIMD_x86_64
> >
> > The sincos/sincosf stuff is questionable, because some glibc versions
> > implement it incorrectly and the simd ("notinbranch") attribute isn't that
> > useful for it anyway, we'd want to use extra clauses so that it doesn't need
> > to do scatter stores.
>
> I wonder if it is possible for glibc to ship a "module" for fortran instead
> containing the appropriate declarations and gfortran auto-include that
> (if present).
Then we'd run into module binary format changing every release, so hard for
glibc to ship that.
Another thing is how would we express it in the module,
we could just use OpenMP syntax,
interface
function sin(x) bind(C,name="__builtin_sin") result(res)
import
!$omp declare simd notinbranch
real(c_double) :: res
real(c_double),value :: x
end function
end interface
but we'd need to temporarily enable OpenMP while parsing that module.
I see Fortran now supports already
!GCC$ attributes stdcall, fastcall::test
Could we support
!GCC$ attributes simd
and
!GCC$ attributes simd('notinbranch')
too?
Jakub
