Re: [openacc] acc loop updates in fortran

[Jakub Jelinek <jakub@redhat.com>]

On Wed, Nov 04, 2015 at 06:15:14PM +0100, Thomas Schwinge wrote:
> > --- a/gcc/fortran/openmp.c
> > +++ b/gcc/fortran/openmp.c
> 
> > @@ -3028,6 +3015,22 @@ resolve_omp_clauses (gfc_code *code, gfc_omp_clauses *omp_clauses,
> >  	n->sym->mark = 1;
> >      }
> >  
> > +  /* OpenACC reductions.  */
> > +  if (openacc)
> > +    {
> > +      for (n = omp_clauses->lists[OMP_LIST_REDUCTION]; n; n = n->next)
> > +	n->sym->mark = 0;
> 
> Maybe I'm just confugsed, but if setting all these to zero here...
> 
> > +
> > +      for (n = omp_clauses->lists[OMP_LIST_REDUCTION]; n; n = n->next)
> > +	{
> > +	  if (n->sym->mark)
> > +	    gfc_error ("Symbol %qs present on multiple clauses at %L",
> > +		       n->sym->name, &n->where);
> > +	  else
> > +	    n->sym->mark = 1;
> 
> ... won't this just always run into the "else" branch?

The point is to check if some symbol isn't present multiple times in
reduction clause(s).  So the first loop clears the flag as it could have
arbitrary values, and the second loop will diagnose an error if n->sym
is present multiple times in the list.  reduction(+: a, b, a) and the like.
In C/C++ FE we use bitmaps for this, in Fortran FE we have mark
field for those purposes.

	Jakub