An integrated tool which allows layouts for cells to be generated using a combination of synthesis, migration and manual approaches. In an embodiment, a compaction tool of a migration engine/module is used to perform incremental compaction. Various utilities are developed to enable the use of the compaction tool. For example, when using synthesis to generate layout for a new combinational cell, a utility to generate inputs to the migration engine from pre-compaction representation of the synthesis tool is provided according to an aspect of the present invention. Another utility generates a device table indicating the manner in which each component of a pre-existing layout needs to be modified to generate a layout consistent with a target netlist. The device table and the pre-existing layout can be provided as an input to the migration engine to perform incremental compaction.