A clip-cull-viewport (CCV) unit manages information associated with vertices of a primitive as the primitive passes through the CCV unit. The CCV unit includes an index cache and a cache-status table. Vertices of a received primitive are stored in locations within the index cache based on attribute and index fields of the primitive. If a vertex is a reused vertex of another primitive that matches a valid entry in the cache-status table and if the primitive survives being culled, the valid entry in the cache-status table is preserved, the attribute field of the primitive is set to indicate that the vertex is a reused vertex, and the primitive is sent to an output interface for a downstream unit. Otherwise, the attribute field is set to indicate that the vertex is not reused, and the primitive is sent to the output interface for the downstream unit.