Add LANG_HOOKS_EMPTY_RECORD_P for C++ empty classhjl/pr60336/hook

Empty record should be returned and passed the same way in C and C++.
This patch adds LANG_HOOKS_EMPTY_RECORD_P for C++ empty class, which
defaults to return false.  For C++, LANG_HOOKS_EMPTY_RECORD_P is defined
to is_really_empty_class, which returns true for C++ empty classes.  For
LTO, we stream out a bit to indicate if a record is empty and we store
it in TYPE_LANG_FLAG_0 when streaming in.  Middle-end and x86
backend are updated to ignore empty records for parameter passing and
function value return.  Other targets may need similar changes.

get_ref_base_and_extent is changed to set bitsize to 0 for empty records
so that when ref_maybe_used_by_call_p_1 calls get_ref_base_and_extent to
get 0 as the maximum size on empty record.  Otherwise, find_tail_calls
won't perform tail call optimization for functions with empty record
parameters, as shown in g++.dg/pr60336-1.C and g++.dg/pr60336-2.C.

gcc/

	PR c++/60336
	PR middle-end/67239
	PR target/68355
	* calls.c (initialize_argument_information): Replace
	targetm.calls.function_arg, targetm.calls.function_incoming_arg
	and targetm.calls.function_arg_advance with function_arg,
	function_incoming_arg and function_arg_advance.
	(expand_call): Likewise.
	(emit_library_call_value_1): Likewise.
	(store_one_arg): Use 0 for empty record size.  Don't
	push 0 size argument onto stack.
	(must_pass_in_stack_var_size_or_pad): Return false for empty
	record.
	* dse.c (get_call_args): Replace targetm.calls.function_arg
	and targetm.calls.function_arg_advance with function_arg and
	function_arg_advance.
	* expr.c (block_move_libcall_safe_for_call_parm): Likewise.
	* function.c (aggregate_value_p): Replace
	targetm.calls.return_in_memory with return_in_memory.
	(assign_parm_find_entry_rtl): Replace
	targetm.calls.function_incoming_arg with function_incoming_arg.
	(assign_parms): Replace targetm.calls.function_arg_advance with
	function_arg_advance.
	(gimplify_parameters): Replace targetm.calls.function_arg_advance
	with function_arg_advance.
	(locate_and_pad_parm): Use 0 for empty record size.
	(function_arg_advance): New wrapper function.
	(function_arg): Likewise.
	(function_incoming_arg): Likewise.
	(return_in_memory): Likewise.
	* langhooks-def.h (LANG_HOOKS_EMPTY_RECORD_P): New.
	(LANG_HOOKS_DECLS): Add LANG_HOOKS_EMPTY_RECORD_P.
	* langhooks.h (lang_hooks_for_decls): Add empty_record_p.
	* lto-streamer.h (LTO_major_version): Increase by 1 to 6.
	* target.h (function_arg_advance): New prototype.
	(function_arg): Likewise.
	(function_incoming_arg): Likewise.
	(return_in_memory): Likewise.
	* targhooks.c: Include "langhooks.h".
	(std_gimplify_va_arg_expr): Use 0 for empty record size.
	* tree-dfa.c (get_ref_base_and_extent): Likewise.
	* tree-streamer-in.c (unpack_ts_base_value_fields): Stream in
	TYPE_LANG_FLAG_0.
	* tree-streamer-out.c: Include "langhooks.h".
	(pack_ts_base_value_fields): Stream out a bit to indicate if a
	record is empty.
	* var-tracking.c (prepare_call_arguments): Replace
	targetm.calls.function_arg and targetm.calls.function_arg_advance
	with function_arg and function_arg_advance.
	* config/i386/i386.c (ix86_gimplify_va_arg): Use 0 for empty
	record size.

gcc/cp/

	PR c++/60336
	PR middle-end/67239
	PR target/68355
	* class.c (is_empty_class): Changed to return bool and take
	const_tree.
	(is_really_empty_class): Changed to take const_tree.  Check
	if TYPE_BINFO is zero.
	* cp-tree.h (is_empty_class): Updated.
	(is_really_empty_class): Likewise.
	* cp-lang.c (LANG_HOOKS_EMPTY_RECORD_P): New.

gcc/lto/

	PR c++/60336
	PR middle-end/67239
	PR target/68355
	* lto-lang.c (lto_empty_record_p): New.
	(LANG_HOOKS_EMPTY_RECORD_P): Likewise.

gcc/testsuite/

	PR c++/60336
	PR middle-end/67239
	PR target/68355
	* g++.dg/abi/empty12.C: New test.
	* g++.dg/abi/empty12.h: Likewise.
	* g++.dg/abi/empty12a.c: Likewise.
	* g++.dg/pr60336-1.C: Likewise.
	* g++.dg/pr60336-2.C: Likewise.
	* g++.dg/pr68355.C: Likewise.

0 files changed, 0 insertions, 0 deletions