Abstract. Run-time exception checking is required by the Java Language Specification (JLS). Though providing higher software reliability, that mechanism negatively affects performance of Java programs, especially those computationally intensive. This paper pursues loop versioning, a simple program transformation which often helps to avoid the checking overhead. Basing upon the Java Memory Model precisely defined in JLS, the work proposes a set of sufficient conditions for applicability of loop versioning. Scalable intra-and interprocedural analyses that efficiently check fulfilment of the conditions are also described. Implemented in Excelsior JET, an ahead-of-time compiler for Java, the developed technique results in significant performance improvements on some computational benchmarks.

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