Minimal-JVM

Code for the JVM->LLVM JIT Compiler (Proof-of-Concept) is here: https://github.com/LouisJenkinsCS/LLVM-JVM

What is it?

A 'toy' JVM interpreter written in Haskell. Currently, it is considered a 'toy' in that it is not the intention of the author for this to be used as a viable JVM compared to others such as Hotspot or Oracle's implementations. This is being developed purely for educational purposes, and as such, I may or may not diverge from the JVM specification.

Why Haskell

Mind you that this is purely educational, and while I do admit that Haskell may NOT be the best language for an interpreter, I chose Haskell because I love challenges. Haskell is infamous for being difficult to learn, and so I figured it would be fun to do so.

There is no particular logical reasons for as to why I chose Haskell beyond this. However, I would say that Haskell would definitely be better for a JIT Compilation virtual machine instead of an interpreter, and as such I plan to make those overhauls in the future (given the time).

How did this project come to be?

This project originally was for a computer science course, called the "Organization of Programming Languages", and so I figured, why not knock out two birds with one stone by not only teaching myself a new language, a new paradigm, and to learn more about how languages are implemented?

Progress

Class Files

• Parse .class file into data structure representation
• Implement support for minimal attributes, (I.E: Code attribute)
• Implement support for all attributes

Runtime Environment

• Create a stack frame representation
• Create a heap with minimal garbage collection
• Implement bootstrap class loader for runtime

ByteCode

• Implement load and store operations
• Implement arithmetic operations
• Implement conditionals + goto jumps
• Implement all instructions

Misc. Details

The Virtual Machine implements small stubs for certain method calls that simulate the runtime, such as System.out.println, and as well as appending to a StringBuilder.