Are logic synthesis tools robust?

A systematic investigation is presented about the robustness of logic synthesis tools to equivalence-preserving transformations of the input Verilog file. We have developed a framework that: 1) parses Verilog behavioral models into an abstract syntax tree; 2) generates random equivalence-preserving transformations on the syntax tree, and; 3) writes the transformed design back in Verilog format. The original and the transformed Verilog descriptions are then checked for equivalence and synthesized. Results show that average (peak) improvements in area of 2:5%(11%) and length of the critical path of 4%(13%) are achievable. Indeed these figures are comparable to recent advancements in logic synthesis (achieve 4:9%(23%) 5%(24%) improvements area-wise, respectively), signaling a relevant lack of robustness in synthesis tools. This lack of robustness suggests that new synthesis algorithms should be evaluated by measuring the average improvement on several transformed files to assess their real contributions to the quality of the results.