re PR rtl-optimization/36419 (Wrong unwind info with -Os -fasynchronous-unwind-tables)

re PR rtl-optimization/36419 (Wrong unwind info with -Os -fasynchronous-unwind-tables)

	PR rtl-optimization/36419
	* dwarf2out.c (barrier_args_size): New variable.
	(compute_barrier_args_size, compute_barrier_args_size_1): New
	functions.
	(dwarf2out_stack_adjust): For BARRIERs call compute_barrier_args_size
	if not called yet in the current function, use barrier_args_size
	array to find the new args_size value.
	(dwarf2out_frame_debug): Free and clear barrier_args_size.

	* g++.dg/eh/async-unwind2.C: New test.

From-SVN: r138427