Incremental Computation of Dominator Trees

Data flow analysis based on an incremental approach may require that the dominator tree be correctly maintained at all times [CR88]. Previous solutions to the problem of incrementally maintaining dominator trees were restricted to reducible flowgraphs [RR94, CR88]. In this paper we present a new algorithm for incrementally maintaining the dominator tree of an arbitrary flowgraph, either reducible or irreducible, based on a program representation called the DJ-graph [SG95, SGL94a]. For the case where an edge is inserted, our algorithm is also faster than previous approaches (in the worst case). For the deletion case, our algorithm is likely to run fast on the average cases. 1 Introduction In the past few years, Static Single Assignment (SSA) form [CFR + 89, CFR + 91], Sparse Evaluation Graphs (SEG) [CCF91], and other related intermediate representations have been successfully used for efficient data flow analysis and program transformations [CLZ86, RWZ88, AWZ88, WZ85, WCES94]. Cons..