Corner stitching for simple rectilinear shapes [VLSI layouts]

This paper extends the corner-stitching data structure proposed by Ousterhout (1984) for manipulating rectangular objects in very large scale integration (VLSI) layouts to L-shaped objects. This provides additional flexibility in the design of very large scale integration (VLSI) circuits. Our technique is fundamentally different from Ousterhout's and other extensions to the corner stitching data structure in that it modifies the underlying topology of the data structure. This gives rise to differences in the implementation of operations on the data structure. Our data structure is guaranteed to require less memory than the original data structure. Experiments show that our data structure required about 15%-17% less memory than the original data structure on VLSI layouts but was slower by a factor of two to eight. Extensions of corner stitching to T- and Z-shaped tiles are also described.