Apparatus and method for incorporating driver sizing into buffer insertion using a delay penalty estimation technique

An apparatus and method for incorporating driver sizing into buffer insertion such that the two optimization techniques are performed simultaneously are provided. In particular, the apparatus and method extends van Ginneken's algorithm to handle driver sizing by treating a source node as a "driver library". With the apparatus and method, the circuit design is converted to a Steiner tree representation of the circuit design. Buffer insertion is performed on the Steiner tree using the van Ginneken algorithm to generate a first set of possible optimal solutions. For each solution in the first set, a driver of the same type as the original driver in the Steiner tree is selected from a driver library and virtually inserted into the solution. A delay penalty is retrieved for the selected driver. This delay penalty is then used along with the new driver's characteristics to generate a second set of solutions based on the first set of solutions. A determination is made as to whether there are other drivers of this type in the driver library. If so, the operation returns and a next driver of this driver type is selected. If not, the second set of solutions is traversed to identify a solution having a maximum slack.