15.7.6.1 Use Logic Regions to Localize Placement of Logic Blocks

If you partitioned your design into several modules, and some of these modules contain regular structures (such as arithmetic logic, register arrays, counters, or multiplexors), place these modules into Logic regions. These logic functions have a good amount of both local connectivity and regularity to their structure, which makes them good candidates for regions. Interconnects between your regions now become interconnects between hierarchical blocks in your design. Floorplan your regions so there is a smooth horizontal or vertical data flow between each Logic region.