Automated Iterative Pipelining for ASIC Design

We describe an automated pipelining approach for optimally balanced pipeline implementation that achieves low area cost as well as meeting timing requirements. Most previous automatic pipelining methods have focused on Instruction Set Architecture (ISA)-based designs and the main goal of such methods generally has been maximizing performance as measured in terms of instructions per clock (IPC). By contrast, we focus on datapath-oriented designs (e.g., DSP filters for image or communication processing applications) in ASIC design flows. The goal of the proposed pipelining approach is to find the optimally pipelined design that not only meets the user-specified target clock frequency, but also seeks to minimize area cost of a given design. Unlike most previous approaches, the proposed methods incorporate the use of accurate area and timing information (iteratively achieved by synthesizing every interim pipelined design) to achieve higher accuracy during design exploration. When compared with exhaustive design exploration that considers all possible pipeline patterns, the two heuristic pipelining methods presented here involve only a small area penalty (typically under 5%) while offering dramatically reduced computational complexity. Experimental validation is performed with commercial ASIC design tools and described for applications including polynomial function evaluation, FIR filters, matrix multiplication, and discrete wavelet transform filter designs with a 90nm standard cell library.