Targeted Control-flow Transformations for Mitigating Path Explosion in Dynamic Symbolic Execution

Dynamic symbolic execution (DSE) suffers from path explosion problem when the target program has many conditional branches. Classical approach for managing the path explosion problem is dynamic state merging. Dynamic state merging combines similar symbolic program states together to avoid the exponential growth of states in DSE. However, state merging still requires solver invocations at each branch point of the program even when both paths of the branch is feasible and, the best path search strategy for DSE may not create the best state merging opportunities. Some drawbacks of state merging can be mitigated by compile-time state merging i.e. branch elimination by converting control-flow into data-flow. In this paper, we propose a non-semantics preserving but failure-preserving compiler technique for removing expensive symbolic branches in a program to improve the scalability of DSE. We develop a framework for detecting spurious bugs that can be inserted by our transformation. Finally, we show that our transformation can significantly improve the performance of exhaustive DSE on variety of benchmarks and helps in achieving more coverage in a large real-world subjects within a limited time budget.