PLC004: No legal global assignment could be found. Some global nets have shared instances, requiring them to be assigned to overlapping global regions.

Automatic global net placement cannot find a legal assignment because of shared instance violation. A shared instance is a common load of two or more nets. If two global nets have common loads, both nets must be on global resources that can reach their shared loads. As a result, the nets must be assigned to overlapping regions.

Action

Use PDC to assign the nets manually and run compile again. Compile inserts buffers if two nets with shared instances are assigned to different regions (i.e., two distinct quadrant global regions).