4.3 Resolving top.v and Block Instantiations
Libero integrates your top.v file and block file if there is no
            definition for the block file in top.v. For example:
- Import your 
top.v(File > Import HDL Sources Files) that contains instantiations but no definition of<block1>. - Import
                    
<block1>(File > Import > Blocks). 
Libero resolves the hierarchy for you and puts <block1> under
                top.v.
