Enhance the DWARF back-end to emit proper descriptions for
variable-length records as well as variant parts in records.

In order to achieve this, generate DWARF expressions ("location
descriptions" in dwarf2out's parlance) for size and data member location
attributes.  Also match QUAL_UNION_TYPE data types as variant parts,
assuming the formers appear only to implement the latters (which is the
case at the moment: only the Ada front-end emits them).

Note that very few debuggers can handle these descriptions (GDB does not
yet), so in order to ease the the transition enable these only when
-fgnat-encodings=minimal.

gcc/ada/ChangeLog:

	* gcc-interface/decl.c (gnat_to_gnu_entity): Disable ___XVS GNAT
	encodings when -fgnat-encodings=minimal.
	(components_to_record): Disable ___XVE, ___XVN, ___XVU and
	___XVZ GNAT encodings when -fgnat-encodings=minimal.
	* gcc-interface/utils.c (maybe_pad_type): Disable __XVS GNAT
	encodings when -fgnat-encodings=minimal.

gcc/ChangeLog:

	* debug.h (struct gcc_debug_hooks): Add a new size_function
	hook.
	* debug.c (do_nothing_debug_hooks): Set the size_function field
	to no-op.
	* dbxout.c (dbx_debug_hooks, xcoff_debug_hooks): Likewise.
	* sdbout.c (sdb_debug_hooks): Likewise.
	* vmsdbgout.c (vmsdbg_debug_hooks): Likewise.
	* stor-layout.c (finalize_size_functions): Let the debug info
	back-end know about the implementation of size functions.
	* dwarf2out.h (dw_discr_list_ref): New typedef.
	(enum dw_val_class): Add value classes for discriminant values
	and discriminant lists.
	(struct dw_discr_value): New structure.
	(struct dw_val_node): Add discriminant values and discriminant
	lists to the union.
	(struct dw_loc_descr_node): Add frame_offset_rel and
	dw_loc_frame_offset (only for checking) fields to handle DWARF
	procedures generation.
	(struct dw_discr_list_node): New structure.
	* dwarf2out.c (dwarf2out_size_function): New.
	(dwarf2_debug_hooks): Set the size_function field to
	dwarf2out_size_function.
	(dwarf2_lineno_debug_hooks): Set the size_function field to
	no-op.
	(new_loc_descr): Initialize the
	dw_loc_frame_offset field.
	(dwarf_proc_stack_usage_map): New.
	(dw_val_equal_p): Handle discriminants.
	(size_of_discr_value): New.
	(size_of_discr_list): New.
	(size_of_die): Handle discriminants.
	(add_loc_descr_to_each): New.
	(add_loc_list): New.
	(print_discr_value): New.
	(print_dw_val): Handle discriminants.
	(value_format): Handle discriminants.
	(output_discr_value): New.
	(output_die): Handle discriminants.
	(output_loc_operands): Handle DW_OP_call2 and DW_OP_call4.
	(uint_loc_descriptor): New.
	(uint_comparison_loc_list): New.
	(loc_list_from_uint_comparison): New.
	(add_discr_value): New.
	(add_discr_list): New.
	(AT_discr_list): New.
	(loc_descr_to_next_no_op): New.
	(free_loc_descr): New.
	(loc_descr_without_nops): New.
	(struct loc_descr_context): Add a dpi field.
	(struct dwarf_procedure_info): New helper structure.
	(new_dwarf_proc_die): New.
	(is_handled_procedure_type): New.
	(resolve_args_picking_1): New.
	(resolve_args_picking): New.
	(function_to_dwarf_procedure): New.
	(copy_dwarf_procedure): New.
	(copy_dwarf_procs_ref_in_attrs): New.
	(copy_dwarf_procs_ref_in_dies): New.
	(break_out_comdat_types): Copy DWARF procedures along with the
	types that reference them.
	(loc_list_from_tree): Rename into loc_list_from_tree_1.  Handle
	CALL_EXPR in the cases suitable for DWARF procedures.  Handle
	for PARM_DECL when generating a location description for a DWARF
	procedure.  Handle big unsigned INTEGER_CST nodes.  Handle
	NON_LVALUE_EXPR, EXACT_DIV_EXPR and all unsigned comparison
	operators.  Add a wrapper for loc_list_from_tree that strips
	DW_OP_nop operations from the result.
	(type_byte_size): New.
	(struct vlr_context): New helper structure.
	(field_byte_offset): Change signature to return either a
	constant offset or a location description for dynamic ones.
	Handle dynamic byte offsets with constant bit offsets and handle
	fields in variant parts.
	(add_data_member_location): Change signature to handle dynamic
	member offsets and fields in variant parts.  Update call to
	field_byte_offset.  Handle location lists.  Emit a variable data
	member location only when -fgnat-encodings=minimal.
	(add_bound_info): Emit self-referential bounds only when
	-fgnat-encodings=minimal.
	(add_byte_size_attribute): Use type_byte_size in order to handle
	dynamic type sizes.  Emit variable byte size only when
	-fgnat-encodings=minimal and when the target DWARF version
	allows them.
	(add_bit_offset_attribute): Change signature to handle
	variable-length records.  Update call to field_byte_offset.
	(gen_descr_array_type_die): Update call to gen_field_die.
	Update loc_descr_context literal.
	(gen_type_die_for_member): Likewise.
	(gen_subprogram_die): Update calls to get_decl_die.
	(gen_field_die): Change signature to handle variable-length
	records.  Update calls to add_bit_offset_attribute and
	add_data_member_location_attribute.
	(gen_inheritance_die): Update call to
	add_data_member_location_attribute.
	(gen_decl_die): Change signature to handle variable-length
	records.  Update call to gen_field_die.
	(gen_inheritance_die): Change signature to handle
	variable-length records.  Update call to
	add_data_member_location_attribute.
	(is_variant_part): New.
	(analyze_discr_in_predicate): New.
	(get_discr_value): New.
	(analyze_variants_discr): New.
	(gen_variant_part): New.
	(gen_member_die): Update calls to gen_decl_die.  Call instead
	gen_variant_part for variant parts.
	(gen_type_die_with_usage): Update calls to gen_decl_die.
	(process_scope_var): Likewise.
	(force_decl_die): Likewise.
	(declare_in_namespace): Likewise.
	(dwarf2out_decl): Likewise.
	(prune_unused_types_walk_loc_descr): New.
	(prune_unused_types_walk_attribs): Mark DIEs referenced by
	location descriptions and loc. descr. lists.
	(prune_unused_types_walk): Don't mark DWARF procedures by
	default.  Mark variant parts since nothing is supposed to
	reference them.
	(dwarf2out_init): Allocate dwarf_proc_stack_usage_map.
	(dwarf2out_c_finalize): Deallocate and reset
	dwarf_proc_stack_usage_map.

gcc/testsuite/ChangeLog:

	* gnat.dg/specs/debug1.ads: Update the expected number of
	DW_AT_artificial attribute in compiler output.

From-SVN: r231762