In this paper, we present a pointer analysis that aims to enable the following optimizations for Java: loop-based dependence analysis in the presence of pointers and the identification of exception-free regions. The analysis computes a property called element-wise points-to (ewpt) mapping. An ewpt mapping summarizes precise points-to information for all instances of a pointer or all elements of an array of pointer type. This is done with the help of a single, compact representation. Such instance-wise and element-wise information is especially important for loop-based dependence analysis and for a language where multi-dimensional arrays axe implemented as arrays of pointers. We describe an iterative algorithm to compute ewpt mappings. We also present techniques to kill 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. In addition, all redundant null-pointer checks on array element accesses can be removed.
By: Peng Wu, Paul Feautriert, David Paduas, Zehra Sura
Published in: RC22240 in 2002
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