A Fully Automatic Hierarchical Compactor

A fully automatic hierarchical compactor has been developed to translate hierarchical, symbolic cell designs into artwork. The hierarchical compactor takes advantage of the fact that a typical hierarchical design uses the same cell in several different places. Each cell is first examined in all of its contexts. The leaf-cell compactor next compacts each leaf-cell to its minimum possible size in its worst-case environment. The last step is to abut instances of the cells according to the original symbolic layout; some grid line spacings may be increased to avoid breaking wires. The compactor is implemented as a set of rule-driven procedures that find all technology dependent information in technology description files. The result of this strategy is a technology-independent compactor that produces compact, error-free artwork.