openmp: Add support for non-VLA {,first}private allocate on omp task

openmp: Add support for non-VLA {,first}private allocate on omp task

This patch adds support for custom allocators on private/firstprivate
clauses for task (and taskloop) constructs.  Private didn't need anything
special, but firstprivate if it is passed by reference needs the GOMP_alloc
calls in the copyfn and GOMP_free in the task body.

2020-11-14  Jakub Jelinek  <jakub@redhat.com>

	* gimplify.c (gimplify_omp_for): Add OMP_CLAUSE_ALLOCATE_ALLOCATOR
	decls as firstprivate on task clauses even when allocate clause
	decl is not lastprivate.
	* omp-low.c (install_var_field): Don't dereference omp_is_reference
	types if mask is 33 rather than 1.
	(scan_sharing_clauses): Populate allocate_map even for task
	constructs.  For now remove it back for variables mentioned in
	reduction and in_reduction clauses on task/taskloop constructs
	or on VLA task firstprivates.  For firstprivate on task construct,
	install the var field into field_map with by_ref and 33 instead
	of false and 1 if mentioned in allocate clause.
	(lower_private_allocate): Set TREE_THIS_NOTRAP on the created
	MEM_REF.
	(lower_rec_input_clauses): Handle allocate for task firstprivatized
	non-VLA variables.
	(create_task_copyfn): Likewise.

	* testsuite/libgomp.c-c++-common/allocate-1.c (struct S): New type.
	(foo): Add tests for non-VLA private and firstprivate clauses on
	omp task.
	(bar): Likewise.  Remove taking of address from private/firstprivate
	variables.
	* testsuite/libgomp.c++/allocate-1.C (struct S): New type.
	(foo): Add p, q, px and s arguments.  Add tests for array reductions
	and for non-VLA private and firstprivate clauses on omp task.
	(bar): Removed.
	(main): Adjust foo caller.  Don't call bar.