Java 10 introduces a new Just-In-Time (JIT) compiler interface for the JVM (Java Virtual Machine). This interface allows developers to plug in their own JIT compiler implementation and integrate it with the Java runtime environment.

What is a JIT Compiler?

The JIT compiler is a component of the JVM that dynamically compiles Java bytecode into native machine code at runtime, which improves the performance of Java applications. It analyzes the hot or frequently executed parts of the code and optimizes them for better execution efficiency.

Why Introduce a JIT Compiler Interface?

The JVM traditionally ships with its own default JIT compiler implementation, like C1 and C2 in HotSpot JVM. However, the default compiler may not cater to all the specific needs of every application or hardware platform.

By providing a JIT compiler interface, Java 10 enables developers to create their own custom JIT compiler, tailored for specific requirements such as performance optimizations or code size reduction. This way, developers can optimize JVM behavior according to their application’s unique characteristics.

The JVM JIT Compiler Interface API

The new JIT compiler interface in Java 10 is represented by the java.compiler module. It provides a set of classes and interfaces to support the creation and integration of custom JIT compilers.

One of the key elements of the JIT compiler interface is the HotSpotJVMCIRuntime class, which serves as the entry point for all interactions with the JIT compiler. It provides methods to compile Java methods, query compiled methods, and manage compiler threads.

Here’s an example code snippet that demonstrates how to use the HotSpotJVMCIRuntime class to compile a Java method using the custom JIT compiler:

import jdk.vm.ci.hotspot.HotSpotJVMCIRuntime;
import jdk.vm.ci.meta.ResolvedJavaMethod;

HotSpotJVMCIRuntime runtime = new HotSpotJVMCIRuntime();

// Get the ResolvedJavaMethod for the method to be compiled
ResolvedJavaMethod method = ...;

// Compile the method using the custom JIT compiler
runtime.compileMethod(method);

Configuring a Custom JIT Compiler

To configure a custom JIT compiler, you need to set the appropriate system properties. For example, you can use the -XX:Compiler flag to specify the class name of your custom JIT compiler implementation.

Here’s an example command line argument to configure a custom JIT compiler called CustomJITCompiler:

java -XX:Compiler=CustomJITCompiler MyApp

Conclusion

The introduction of the JVM JIT compiler interface in Java 10 empowers developers to create and integrate their own custom JIT compiler implementations. This provides greater flexibility in optimizing Java applications for specific use cases and hardware platforms. With the ability to tailor the JIT compiler, developers can achieve improved performance and efficiency in running their Java applications.

For more information, you can refer to the official documentation on the JVM JIT compiler interface in Java 10.

#java #JVM