Detecting Full Initialization Points of Objects to Support Code Refactorings

A common need of refactorings that involve object allocations is to determine precisely the program points at which objects allocated at a given allocation site become fully initialized. In this paper we formalize the notion of full initialization points (FIPs) of allocation sites, and present a static analysis to determine precisely these program points. While this analysis can benefit several allocation-site refactorings, to demonstrate its usefulness we select two specific refactorings in this paper - object sharing refactoring and immutability refactoring. By introducing code to cache and share objects at the FIPs suggested by our analysis, object-sharing refactoring was able to obtain a mean memory savings of 11.4% on a set of real Java benchmarks. Immutability refactoring guided by our analysis achieved a mean runtime speedup of 1.6X compared to performing the same refactoring using a baseline approach.

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