Performance potential of optimization phase selection during dynamic JIT compilation

Abstract

Phase selection is the process of customizing the applied set of compiler optimization phases for individual functions or programs to improve performance of generated code. Researchers have recently developed novel feature-vector based heuristic techniques to perform phase selection during online JIT compilation. While these heuristics improve program startup speed, steady-state performance was not seen to benefit over the default fixed single sequence baseline. Unfortunately, it is still not conclusively known whether this lack of steady-state performance gain is due to a failure of existing online phase selection heuristics, or because there is, indeed, little or no speedup to be gained by phase selection in online JIT environments. The goal of this work is to resolve this question, while examining the phase selection related behavior of optimizations, and assessing and improving the effectiveness of existing heuristic solutions.