Detecting and analyzing code clones in HDL

In this paper, we study code clones in hardware description languages (HDLs) in comparison with general programming languages. For this purpose, we have developed a method for detecting code clones in Verilog HDL. A key idea of the proposed method is to convert the Verilog HDL code into the pseudo C++ code, which is then processed by an existing code clone detector for C++. We conducted an experiment on 10 open source hardware products described in Verilog HDL, where we succeeded in detecting nearly 1,800 clone sets with approximately 80% precision. We compared code clones in Verilog HDL with those in Java/C based on the metrics to identify the differences among languages. We identified patterns on how code clones are created in Verilog HDL, which include cases for increasing stability and capability of parallel processing of the circuit.