May-happen-in-parallel analysis with static vector clocks

May-Happen-in-Parallel (MHP) analysis computes whether two statements in a multi-threaded program may execute concurrently or not. It works as a basis for many analyses and optimization techniques of concurrent programs. This paper proposes a novel approach for MHP analysis, by statically computing vector clocks. Static vector clocks extend the classic vector clocks algorithm to handle the complex control flow structures in static analysis, and we have developed an efficient context-sensitive algorithm to compute them. To the best of our knowledge, this is the first attempt to compute vector clocks statically. Using static vector clocks, we can drastically improve the efficiency of existing MHP analyses, without loss of precision: the performance speedup can be up to 1828X, with a much smaller memory footprint (reduced by up to 150X). We have implemented our analysis in a static data race detector, and experimental results show that our MHP analysis can help remove up to 88% of spurious data race pairs.