We present a new technique for removing unnecessary synchronization operations from statically compiled Java programs. Our approach improves upon current efforts based on escape analysis, as it can eliminate synchronization operations even on objects that escape their allocating threads. It makes use of a compact, equivalence-class-based representation that eliminates the need for fixed point operations during the analysis. We describe and evaluate the performance of an implementation in the Marmot native Java compiler. For the benchmark programs examined, the optimization removes 100% of the dynamic synchronization operations in single-threaded programs, and 0-99% in multi-threaded programs, at a low cost in additional compilation time and code growth.
|Published in||PLDI 2000|