控制high-level 优化操作在cells，hierarchical pins，references，designs，library cells。
set_compile_directives
object_list
[-delete_unloaded_gate true | false]删除unloaded gates
[-constant_propagation true | false]允许constant 传递通过cells 或者hier pins指定在object_list中，当为true时。
[-phase_inversion true | false]在boundary 优化过程中允许inverters 跨hier boundary 移动
[-location_optimization true | false]
[-critical_path_resynthesis true | false]