When assigning a net to a region, only the instances driven by the net are assigned to the region.
Assigning nets to a region allows you to control the net delays of logic connected to certain nets in the design. You can adjust the size of the region to pack logic more closely together, hence, improving its net delays.
To assign a net to a region:
In the Regions tab of the Hierarchy window, right-click a region and choose Assign/Unassign from the right-click menu.
The Assign Instances to Region dialog box appears with the name of the selected region in the Region name field. The dialog box displays all of the macros that you can assign to the selected region.
To display a subset of the unassigned instances, you can create and apply filters.
To filter the unassigned instances list by a net name, enter it in the text box to the left of the Filter button, select Connected to nets matching pattern, and then click Filter.
The Unassigned Instances list displays only macros assigned to the net name you specified. For example, enter add_count_clk to display only macros assigned to the net named add_count_clk.
To assign specific instances, select one or more instances in the Unassigned Instances list box, and click Assign.
To select all instances, click Assign All.
Click OK.
Note: The total number of instances that you can assign, as well as the number of currently selected unassigned instances, appears under the list box.