Re: [Patch]GCC11 - Fortran: combined directives - order(concurrent) not on distribute (was: Re: [Patch] Fortran/OpenMP: unconstrained/reproducible ordered modifier)

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Sep 20, 2021 at 05:01:32PM +0200, Tobias Burnus wrote:
> On 20.09.21 11:55, Jakub Jelinek via Fortran wrote:
> > So the FE was splitting the order clause to distribute already before,
> > perhaps we should undo that for gcc 11 which doesn't claim any OpenMP 5.1
> > support.
> > The difference is e.g. the distribute parallel do order(concurrent) copyin(thr)
> > case which used to be ok in 5.0 and is not in 5.1.
> 
> Well, if I try with GCC 11:
> 
> void f(int *a)
> {
> int  i;
> static int thr;
> #pragma omp threadprivate (thr)
> #pragma omp distribute parallel for order(concurrent) copyin(thr)
>   for (i = 0; i < 10; ++i)
>    {
>     thr = 5;
>     a[i] = thr;
>    }
> }
> 
> I get with gcc (+ gfortran):
>   error: threadprivate variable ‘thr’ used in a region with ‘order(concurrent)’ clause
> I might have misunderstood the example.

Sure, even before you couldn't use it in the region body, because
order(concurrent) was split to worksharing-loop.
The testcase that used to be accepted and is now rejected is e.g.

int thr;
#pragma omp threadprivate (thr)

void
foo (void)
{
  int i;
#pragma omp distribute parallel for order(concurrent) copyin(thr)
  for (i = 0; i < 10; ++i)
   ;
}

While copyin without actually using the threadprivate var in the body
might look weird, in some cases it might be useful if the threadprivate
variable is used in some following parallel region.

> OK for GCC 11, only?
> 
> Tobias
> 
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> GCC11 - Fortran: combined directives - order(concurrent) not on distribute
> 
> While OpenMP 5.1 and GCC 12 permits 'order(concurrent)' on distribute,
> OpenMP 5.0 and GCC 11 don't. This patch for GCC 11 ensures the clause also
> does not end up on 'distribute' when splitting combined directives.
> 
> gcc/fortran/ChangeLog:
> 
> 	* trans-openmp.c (gfc_split_omp_clauses): Don't put 'order(concurrent)'
> 	on 'distribute' for combined directives, matching OpenMP 5.0
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gfortran.dg/gomp/distribute-order-concurrent.f90: New test.

Ok, thanks.

	Jakub