Optimizations using global code motion for Java just-in-time compilers

制度:新 ; 文部省報告番号:乙1877号 ; 学位の種類:博士(情報科学) ; 授与年月日:2004/3/4 ; 早大学位記番号:新380

Effective sign extension elimination

Computer designs are shifting from 32-bit architectures to 64-bit architectures, while most of the programs available today are still designed for 32-bit architectures. Java™, for example, specifies the frequently used “int ” as a 32-bit data type. If such Java programs are executed on a 64-bit architecture, many 32-bit values must be sign-extended to 64-bit values for integer operations. This causes serious performance overhead. In this paper, we present a fast and effective algorithm for eliminating sign extensions. We implemented this algorithm in the IBM Java Just-in-Time (JIT) compiler for IA-64™. Our experimental results show that our algorithm effectively eliminates the majority of sign extensions. They also show that it significantly improves performance, while it increases JIT compilation time by only 0.11%. We implemented our algorithm for programs in Java, but it can be applied to any language requiring sign extensions