Java Just-In-Time Compiler in hand-held system 指導教授 單智君老師 指導教授 單智君老師 李政仲 張淳恩 王信安

Outline Problem Description Motivation Goal State of the Art Background Proposal Schedule Reference

Problem Description 為了能 platform-independent ， Java 會先把 source code 轉成 bytecode ，由 JVM 裡的 interpreter 轉成適 合該平台的 machine code 。但是 interpreter 很慢， 於是把比較常用的 bytecode 先用 JIT compiler 處理， 下次遇到相同部份的便可直接呼叫使用，以節省時間。 在 hand-held 的平台下，通常記憶體跟處理速度都會 受限制， JIT compiler 的處理方法也會跟一般 J2SE 不太一樣。

Motivation Early Java implementations relied on interpretation, leading to poor performance compared to compiled programs. Interpreting bytecodes is slow. In software, the JVM (Java Virtual Machine) interpreter must fetch, decode, and then execute each bytecode in turn, which spends very much time. 現在 hand-held 漸漸的支援網路，當 DL 一個 java 程式 ( 多半為 GAME) ，我們希望能使處理 速度加快。

Goal Try to improve Java program performance with JIT (Just-In-Time) compilation techniques rather than interpretation in KVM. 將對 JIT compiler in KVM 作最佳化，使得能用 size 最小的 JIT compiler 達到最快的處理速度。

JAVA 應用運作流程

State of the Art Sun ’ s JIT technique for J2SE –The use of the operand stack constrains the order of evaluation specified by the bytecodes. More efficient orderings may be possible with a register-based processor. –The best choice of machine instructions for a particular bytecode may depend on how the result of that bytecode is used. –The bytecodes may include redundant operations.

Background Java programming language Java Virtual Machine architecture Kilobyte Virtual Machine (J2ME) Mixed-mode Bytecode Execution Compiler and Interpreter design

Java2 Edition 平台和目標市場

Proposal Method inline

Schedule February ~ June paper reading July ~ December programming implementation

Reference “ 深入嵌入式 Java 虛擬機器 Inside KVM” “Inside the Java 2 Virtual Machine”, by Bill Venners “Compiling Java Just in Time”, IEEE Micro “Mixed-mode Bytecode Execution”