A method for resolving overlaps in the cell placement (placement
legalization) during the physical design phase of an integrated chip
design is described. This problem arises in several contexts within the
physical design automation area including global and detailed placement,
physical synthesis, and ECO (Engineering Change Order) mode for
timing/design closure The method involves capturing a view of a given
placement, solving a global two-dimensional area migration model and
locally perturbing the cells to resolve the overlaps with minimal changes
to the given placement. The method first captures a two-dimensional view
of the placement including blockage-space, free-space and the given
location of cells by defining physical regions. The desired global area
migration across the physical regions of the placement image is
determined such that it satisfies area capacity-demand constraints. The
method also provides moving the cells between physical regions along
previously computed directions of migration to minimize the movement
cost. Also provided is an approximate method to model the movement of
multi-row high cells.