Re: [patch] OpenMP/Fortran: Implement omp allocators/allocate for ptr/allocatables

[Jakub Jelinek <jakub@redhat.com>]

On Sat, Dec 09, 2023 at 12:19:10PM +0100, Thomas Schwinge wrote:
> > --- a/gcc/omp-builtins.def
> > +++ b/gcc/omp-builtins.def
> > @@ -467,6 +467,9 @@ DEF_GOMP_BUILTIN (BUILT_IN_GOMP_WORKSHARE_TASK_REDUCTION_UNREGISTER,
> >  DEF_GOMP_BUILTIN (BUILT_IN_GOMP_ALLOC,
> >                 "GOMP_alloc", BT_FN_PTR_SIZE_SIZE_PTRMODE,
> >                 ATTR_ALLOC_WARN_UNUSED_RESULT_SIZE_2_NOTHROW_LIST)
> > +DEF_GOMP_BUILTIN (BUILT_IN_GOMP_REALLOC,
> > +               "omp_realloc", BT_FN_PTR_PTR_SIZE_PTRMODE_PTRMODE,
> > +               ATTR_ALLOC_WARN_UNUSED_RESULT_SIZE_2_NOTHROW_LEAF_LIST)
> >  DEF_GOMP_BUILTIN (BUILT_IN_GOMP_FREE,
> >                 "GOMP_free", BT_FN_VOID_PTR_PTRMODE, ATTR_NOTHROW_LEAF_LIST)
> >  DEF_GOMP_BUILTIN (BUILT_IN_GOMP_WARNING, "GOMP_warning",
> 
> Should this either be 'BUILT_IN_OMP_REALLOC' ('OMP' instead of 'GOMP'),
> or otherwise a 'GOMP_realloc' be added to 'libgomp/allocator.c', like for
> 'GOMP_alloc', 'GOMP_free'; 'ialias_call'ing the respective 'omp_[...]'
> functions?  (Verbatim 'omp_realloc' also mentioned in the comment before
> 'gcc/fortran/trans-openmp.cc:gfc_omp_call_is_alloc'.)

There were 3 reasons to add GOMP_alloc (and 1 for GOMP_free):
1) when it was added, omp_aligned_alloc was still not exported from the
   library because we thought we shouldn't expose 5.1 features until we
   have 5.0 implemented (then changed mind)
2) unline omp_aligned_alloc, GOMP_alloc issues fatal error on allocation
   failure
3) the omp_* functions have omp_allocator_handle_t arguments, which is hard
   to provide for builtins (I think this is the only reason for GOMP_free
   addition, maybe together with wanting those to be paired)

Now, 1) is a non-issue anymore, I don't know what Fortran wants for
allocation failures, if it is better to have diagnostics on the libgomp side
or if wants to emit it inline.  And yes, 3) would be an argument to add
GOMP_realloc.

	Jakub