openmp: Implement allocate clause in omp lowering.

openmp: Implement allocate clause in omp lowering.

For now, task/taskloop constructs aren't handled and C/C++ array reductions
and reductions with task or inscan modifiers need further work.
Instead of calling omp_alloc/omp_free (where the former doesn't have
alignment argument and omp_aligned_alloc is 5.1 only feature), this calls
GOMP_alloc/GOMP_free, so that the library can fail if it would fall back
into NULL (exception is zero length allocations).

2020-11-12  Jakub Jelinek  <jakub@redhat.com>

gcc/
	* builtin-types.def (BT_FN_PTR_SIZE_SIZE_PTRMODE): New function type.
	* omp-builtins.def (BUILT_IN_GOACC_DECLARE): Move earlier.
	(BUILT_IN_GOMP_ALLOC, BUILT_IN_GOMP_FREE): New builtins.
	* gimplify.c (gimplify_scan_omp_clauses): Force allocator into a
	decl if it is not NULL, INTEGER_CST or decl.
	(gimplify_adjust_omp_clauses): Clear GOVD_EXPLICIT on explicit clauses
	which are being removed.  Remove allocate clauses for variables not seen
	if they are private, firstprivate or linear too.  Call
	omp_notice_variable on the allocator otherwise.
	(gimplify_omp_for): Handle iterator vars mentioned in allocate clauses
	similarly to non-is_gimple_reg iterators.
	* omp-low.c (struct omp_context): Add allocate_map field.
	(delete_omp_context): Delete it.
	(scan_sharing_clauses): Fill it from allocate clauses.  Remove it
	if mentioned also in shared clause.
	(lower_private_allocate): New function.
	(lower_rec_input_clauses): Handle allocate clause for privatized
	variables, except for task/taskloop, C/C++ array reductions for now
	and task/inscan variables.
	(lower_send_shared_vars): Don't consider variables in allocate_map
	as shared.
	* omp-expand.c (expand_omp_for_generic, expand_omp_for_static_nochunk,
	expand_omp_for_static_chunk): Use expand_omp_build_assign instead of
	gimple_build_assign + gsi_insert_after.
	* builtins.c (builtin_fnspec): Handle BUILTIN_GOMP_ALLOC and
	BUILTIN_GOMP_FREE.
	* tree-ssa-ccp.c (evaluate_stmt): Handle BUILTIN_GOMP_ALLOC.
	* tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Handle
	BUILTIN_GOMP_ALLOC.
	(mark_all_reaching_defs_necessary_1): Handle BUILTIN_GOMP_ALLOC
	and BUILTIN_GOMP_FREE.
	(propagate_necessity): Likewise.
gcc/fortran/
	* f95-lang.c (ATTR_ALLOC_WARN_UNUSED_RESULT_SIZE_2_NOTHROW_LIST):
	Define.
	(gfc_init_builtin_functions): Add alloc_size and warn_unused_result
	attributes to __builtin_GOMP_alloc.
	* types.def (BT_PTRMODE): New primitive type.
	(BT_FN_VOID_PTR_PTRMODE, BT_FN_PTR_SIZE_SIZE_PTRMODE): New function
	types.
libgomp/
	* libgomp.map (GOMP_alloc, GOMP_free): Export at GOMP_5.0.1.
	* omp.h.in (omp_alloc): Add malloc and alloc_size attributes.
	* libgomp_g.h (GOMP_alloc, GOMP_free): Declare.
	* allocator.c (omp_aligned_alloc): New for now static function,
	add alignment argument and handle it.
	(omp_alloc): Reimplement using omp_aligned_alloc.
	(GOMP_alloc, GOMP_free): New functions.
	(omp_free): Add ialias.
	* testsuite/libgomp.c-c++-common/allocate-1.c: New test.
	* testsuite/libgomp.c++/allocate-1.C: New test.