Design, Implementation, and Evaluation of Optimizations in a Just-In-Time Compiler Kazuaki Ishizaki, Motohiro Kawahito, et al

Design, Implementation, and Evaluation of Optimizations in a Just-In-Time Compiler

• Kazuaki Ishizaki, Motohiro Kawahito, et al.

• IBM Tokyo Research Laboratory

• Presentation By:

• Allen Chu

Outline

• Introduction

• Motivation

• JIT Optimizations

• Exception Elimination,
• Common Subexpression Elimination
• Type Inclusion Test

• Result

• Conclusion

Introduction

• Advantage and Disadvantage of Java

• Safety (Array-Bound Check)
• Reusability and Portability
• But It Is Slow

• Compiler for Java

• Compiler (byte code to native code)
• Just-In-Time Compiler

Motivation

• Regular Compiler Looses the Portability and Reusability of Code.

• Goal for JIT Compiler

• Preserve Safety and Reusability
• Translation Time of JIT Compiler + Execution Time of Native Code <= Running Time on JVM

JIT Compiler

• Translation occurs when new method is called.

Exception Check Elimination

• Null-Pointer Check Eliminated By Data Flow Analysis

• Array-Bound Check Eliminated By Propagating the Information of Checked Exception in Data Flow Analysis

• Keep Track of Indices and Range of Checked Indices.

Array-Bound Elimination (Cont.)

CSE

• Scalar Replacement Of Array Element

• Consecutive Array Access Using Interior Pointer

• Instance Variable Elimination

• Replace “this.variable”

CSE (Cont.)

CSE (Cont.)

Type Inclusion Test

Result - “Compress”

Result - Overall

Conclusion

• All Optimizations Do Not Improve Execution Speed All the Time

• Overall Combined Optimizations Do Improve Execution.