An effective floorplanning algorithm in mixed mode placement integrated with rectilinear-shaped optimization for soft blocks

Mixed mode placement (MMP) problem can be successfully solved by combining floorplanning and cell based placement according to circuit's hierarchy. Floorplanning is the key design stage for achieving optimum performance if virtual blocks (VB: Soft Block) in floorplanning are not restricted to only have rectangular shapes. In this paper, an effective floorplanning algorithm RSF used in MMP is presented to perform the rectilinear-shaped optimization for VBs. Our approach allows VBs to transform into rectilinear shapes without overlaps and selects the optimum shapes for them during topology optimization of normal floorplanning. It is based on the dead-space block assignment and pin allocation during the process of packing. It depends on the theoretic analysis on lower bound of net wire length in half perimeter mode which makes RSF result in shorter total wire length in floorplanning. Applied in MMP, RSF can improve the final performance of MMP.