The complexity of copy constant detection in parallel programs

Abstract

Despite of the well-known state-explosion problem, certain simple but important data-flow analysis problems known as gen/kill problems can be solved effciently and completely for parallel programs with a shared state [7,6,2,3,13]. This paper shows that, in all probability, these surprising results cannot be generalized to significantly larger classes of data-flow analysis problems. More specifically, we study the complexity of detecting copy constants in parallel programs, a problem that may be seen as representing the next level of diffculty of data-flow problems beyond gen/kill problems. We show that already the intraprocedural problem for loop-free parallel programs is co-NP-complete and that the interprocedural problem is even PSPACE-hard.