dwarf2out.c (compute_barrier_args_size): Set barrier_args_size for labels for which it hasn't been set yet.

	* dwarf2out.c (compute_barrier_args_size): Set barrier_args_size
	for labels for which it hasn't been set yet.  If it has been set,
	stop walking insns and continue with next worklist item.
	(dwarf2out_stack_adjust): Don't call compute_barrier_args_size
	if the only BARRIER is at the very end of a function.

From-SVN: r138537