MetaIR

MetaIR is a graph-based intermediate representation (IR) for JVM bytecode, built on Cliff Click's Sea-of-Nodes concept. The framework leverages the Java Class-File API introduced in Java 24 (JEP 484).

Key Features

• Analysis: Transform and inspect existing JVM bytecode
• Visualization: Debug functionality for graph representation
• Optimization: Built-in peephole optimizations for graph reduction
• Integration: Built-in integration with JUnit Platform
• Cross-Compilation: Foundation framework for cross-compiler development

Technical Details

• Built on Java Class-File API (JEP 484)
• Implements Sea-of-Nodes IR design
• Further examples and documentation: SeaOfNodes/Simple

• 🚧 Scheduling logic for machine code transformation is under development.
• 🚧 Exception handling is under development.

Credits

• An excellent tutorial about the Class-File API: Build A Compiler With The Java Class-File API by Dr. James Hamilton

Example new instance creation

A simple Java example with constructor invoke, demonstrating the use of the JUnit Platform integration:

import de.mirkosertic.metair.ir.test.MetaIRTest;

@MetaIRTest
public class NewInstanceTest {

    public void newInstance() {
        new NewInstanceTest();
    }
}

Class-File API Debug YAML:

- method name: newInstance
  flags: [PUBLIC]
  method type: ()V
  attributes: [Code]
  code:
  max stack: 2
  max locals: 1
  attributes: [LineNumberTable, LocalVariableTable]
  line numbers:
  - {start: 0, line number: 12}
  - {start: 8, line number: 13}
  local variables:
  - {start: 0, end: 9, slot: 0, name: this, type: Lde/mirkosertic/metair/ir/examples/NewInstanceTest;}
  //stack map frame @0: {locals: [de/mirkosertic/metair/ir/examples/NewInstanceTest], stack: []}
  0: {opcode: NEW, type: de/mirkosertic/metair/ir/examples/NewInstanceTest}
  3: {opcode: DUP}
  4: {opcode: INVOKESPECIAL, owner: de/mirkosertic/metair/ir/examples/NewInstanceTest, method name: <init>, method type: ()V}
  7: {opcode: POP}
  8: {opcode: RETURN}

Generated IR (raw and unoptimized):

A full set of examples can be found in the MetaIR Test Suite. Each directory corresponds to a single testcase, and you will find the Class-File API Debug YAML and the generated IR (raw and unoptimized) as well in dot(graphviz) notation and as SVG images.

JVM instructions not implemented

🚧 These instructions are discontinued and will be removed in the future, so MetaIR will not support them for now.

/**
 * (Discontinued) Jump subroutine; last used in major version {@value
 * ClassFile#JAVA_6_VERSION}.
 *
 * @jvms 4.9.1 Static Constraints
 * @jvms 6.5.jsr <em>jsr</em>
 * @see Kind#DISCONTINUED_JSR
 */
JSR(RawBytecodeHelper.JSR, 3, Kind.DISCONTINUED_JSR),

/**
 * (Discontinued) Return from subroutine; last used in major version
 * {@value ClassFile#JAVA_6_VERSION}.
 *
 * @jvms 4.9.1 Static Constraints
 * @jvms 6.5.ret <em>ret</em>
 * @see Kind#DISCONTINUED_RET
 */
RET(RawBytecodeHelper.RET, 2, Kind.DISCONTINUED_RET),

/**
 * (Discontinued) Jump subroutine (wide index); last used in major
 * version {@value ClassFile#JAVA_6_VERSION}.
 *
 * @jvms 4.9.1 Static Constraints
 * @jvms 6.5.jsr_w <em>jsr_w</em>
 * @see Kind#DISCONTINUED_JSR
 */
JSR_W(RawBytecodeHelper.JSR_W, 5, Kind.DISCONTINUED_JSR),

/**
 * (Discontinued) Return from subroutine (wide index); last used in major
 * version {@value ClassFile#JAVA_6_VERSION}.
 * This is a {@linkplain #isWide() wide}-modified pseudo-opcode.
 *
 * @jvms 4.9.1 Static Constraints
 * @jvms 6.5.wide <em>wide</em>
 * @jvms 6.5.ret <em>ret</em>
 * @see Kind#DISCONTINUED_RET
 */
RET_W((RawBytecodeHelper.WIDE << 8) | RawBytecodeHelper.RET, 4, Kind.DISCONTINUED_RET),