APT: A Data Structure for Optimal Control Dependence Computation

The control dependence relation is used extensively in restructuring compilers. This relation is usually represented using the control dependence graph; unfortunately, the size of this data structure can be quadratic in the size of the program, even for some structured programs. In this paper, we introduce a data structure called the augmented postdominator tree (A’PT) which is constructed in space and time proportional to the size of the program, and which can answer control dependence queries in time proportional to the size of the output. Therefore, APT is an optimal representation of control dependence. We also show that using APT, we can compute SSA graphs, as well as sparse dataflow evaluator graphs, in time proportional to the size of the program. Finally, we put ATT in perspective by showing that it can be viewed as a factored representation of the control dependence graph in which jiltered search is used to answer queries.

• Type: Conference
• Year: 1995
• Where: PLDI
• Authors: Keshav Pingali, Gianfranco Bilardi
• Keywords: Control Dependence, Control Dependence Graph, Control Dependence Relation, PLDI 1995, Programming Languages