Instance-wise points-to analysis for loop-based dependence testing

Abstract

We present a points-to analysis that aims at enabling loop-based dependence analysis in the presence of Java references. The analysis is based on an abstraction called element-wise points-to (ewpt) mapping. An ewpt mapping summarizes, in a compact representation, the relation between a pointer and the heap object it points to, for every instance of the pointer inside a loop and for every array element directly accessible through this pointer. Such instance-wise and element-wise information is especially important for loop-based dependence analyses and for a language where multi-dimensional arrays are implemented as arrays of pointers. We describe an iterative algorithm to compute ewpt mappings. We also present techniques to remove objects from ewpt mappings for destructive updates. The points-to algorithm was implemented and evaluated on a set of benchmark programs. We demonstrate that ewpt information can significantly improve the precision of dependence analysis. In many cases, the dependence analysis reports no false dependences due to array accesses.