In the IDF, the HD.ISOLATED property is added and enabled for each user-created wrapper that needs to be isolated from each other. All other modules that do not require isolation do not get this property added. Such modules get optimized to the top level and have no place and route restrictions beyond keeping the fence intact. At this point in the design flow, this property is added on each wrapper, so synthesis knows which hierarchy is isolated, preventing optimization across isolation boundaries.
Figure 1. Adding Property HD.ISOLATED
Figure 2. Enabling HD.ISOLATED
