Optimizing Nop-shadows Typestate Analysis by Filtering Interferential Configurations

Nop-shadows Analysis (NSA) is an efficient static typestate analysis, which can be used to eliminate unnecessary monitoring instrumentations for runtime monitors. In this paper, we propose two optimizations to improve the precision of NSA. Both of the optimizations filter interferential configurations when determining whether a monitoring instrumentation is necessary. We have implemented our optimization methods in Clara and conducted extensive experiments on the DaCapo benchmark. The experimental results indicate that the optimized NSA can further remove unnecessary instrumentations after the original NSA in more than half of the cases, without a significant overhead. In addition, for two cases, all the instrumentations are removed, which implies the program is proved to satisfy the typestate property.