Micro-architecture Pipelining Optimization with Throughput-Aware Floorplanning

For modern processor designs in nanometer technologies, both block and interconnect pipelining are needed to achieve multi-gigahertz clock frequency, but previous approaches consider block pipelining and interconnect pipelining separately. For example, all recent works on wire pipelining assume pre-pipelined components and consider only inserting pipeline stages on point-to-point wire or bus connections. To the best of our knowledge, this paper is the first that considers block pipelining and interconnect pipelining simultaneously. We optimize multiple critical paths or loops in the micro-architecture and insert the pipelines stages optimally in the blocks and wires of these loops to meet the clock frequency requirement. We propose two approaches to this problem. The first approach is based on mixed integer linear programming (MILP) which is theoretically guaranteed to produce the optimal solution, and the second one is an efficient graph-based algorithm that produces near-optimal solutions. Experimental results show that simultaneous block and interconnect pipelining leads to more than 20% improvement over wire-pipelining alone on the overall processor performance. Moreover, the graph-based approach gives solutions very close to the MILP results ( 2% more than MILP results on average) but in a much shorter runtime.