Re: [PATCH 2/5] [gfortran] Translate allocate directive (OpenMP 5.0).

[Jakub Jelinek <jakub@redhat.com>]

On Thu, Jan 13, 2022 at 02:53:17PM +0000, Hafiz Abid Qadeer wrote:
> gcc/fortran/ChangeLog:
> 
> 	* trans-openmp.c (gfc_trans_omp_clauses): Handle OMP_LIST_ALLOCATOR.
> 	(gfc_trans_omp_allocate): New function.
> 	(gfc_trans_omp_directive): Handle EXEC_OMP_ALLOCATE.
> 
> gcc/ChangeLog:
> 
> 	* tree-pretty-print.c (dump_omp_clause): Handle OMP_CLAUSE_ALLOCATOR.
> 	(dump_generic_node): Handle OMP_ALLOCATE.
> 	* tree.def (OMP_ALLOCATE): New.
> 	* tree.h (OMP_ALLOCATE_CLAUSES): Likewise.
> 	(OMP_ALLOCATE_DECL): Likewise.
> 	(OMP_ALLOCATE_ALLOCATOR): Likewise.
> 	* tree.c (omp_clause_num_ops): Add entry for OMP_CLAUSE_ALLOCATOR.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gfortran.dg/gomp/allocate-6.f90: New test.

There is another issue besides what I wrote in my last review,
and I'm afraid I don't know what to do about it, hoping Tobias
has some ideas.
The problem is that without the allocate-stmt associated allocate directive,
Fortran allocatables are easily always allocated with malloc and freed with
free.  The deallocation can be implicit through reallocation, or explicit
deallocate statement etc.
But when some allocatables are now allocated with a different
allocator (when allocate-stmt associated allocate directive is used),
some allocatables are allocated with malloc and others with GOMP_alloc
but we need to free them with the corresponding allocator based on how
they were allocated, what has been allocated with malloc should be
deallocated with free, what has been allocated with GOMP_alloc should be
deallocated with GOMP_free.
The deallocation can be done in a completely different TU from where it has
been allocated, in theory it could be also not compiled with -fopenmp, etc.
So, I'm afraid we need to store somewhere whether we used malloc or
GOMP_alloc for the allocation (say somewhere in the array descriptor and for
other stuff somewhere on the side?) and slow down all code that needs
deallocation to check that bit (or say we don't support
deallocation/reallocation of OpenMP allocated allocatables without -fopenmp
on the deallocation TU and only slow down -fopenmp compiled code)?

Tobias, thoughts on this?

	Jakub