JuliaVM OSS

Overview

JuliaVM OSS (v0.6.7) is a minimal, fully static pipeline for executing a Julia subset. It uses a four-stage pipeline (Parser → Lowering → Compiler → VM) that accepts Julia syntax, determines feature support during lowering, compiles Core IR into bytecode, and executes bytecode in a deterministic stack-based VM. No JIT—fully App Store compliant.

Pure Rust Implementation: The entire pipeline is implemented in pure Rust with no C dependencies, making it fully portable across all platforms including iOS, macOS, Linux, WebAssembly, and Android.

95 percent of the code was written with the support of AI agents such as Claude Code, Codex, and Cursor.

Prerequisite

Install Rust from here:

$ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

We expect we can use cargo and rustc commands.

Architecture

Julia source (any valid syntax)
    ↓
Parser (Pure Rust) → CST with spans
    ↓
Lowering (CST → Core IR) → Supported: Core IR | Unsupported: Error with hint
    ↓
Compiler (Core IR → Bytecode)
    ↓
VM (executes bytecode) → Results or RuntimeError

Layer-by-Layer Breakdown

1. Parser Layer (Never Fails)

• Parses any valid Julia syntax using the pure Rust parser
• No C dependencies - fully portable across all platforms
• Produces a Concrete Syntax Tree (CST) with source spans
• Accepts everything: macros, modules, using, eval, etc.
• Key principle: The parser never rejects code—it always produces a tree

2. Lowering Layer (The Gatekeeper)

• Converts CST nodes to Core IR (our minimal representation)
• Supported features → Core IR nodes (Block, If, While, For, Call, etc.)
• Unsupported features → UnsupportedFeature error with:
  • Source span (exact line/column location)
  • Error kind (e.g., "MacroNotSupported", "TypeNotSupported")
  • Helpful hint message
• This is where we decide: "Can this code run on our VM?"

3. Compiler Layer (IR → Bytecode)

• Transforms Core IR into stack-based bytecode
• Instruction set includes:
  • Data: PushI64, PushF64, LoadI64, StoreI64
  • Arithmetic: AddI64, MulF64, DivF64, SqrtF64
  • Control: Jump, JumpIfZero, Call, Return
  • Arrays: ArrayNew, ArrayGet, ArraySet, ArrayPush
  • Matrix: MatMul (matrix-vector, matrix-matrix)
• Optimizes local variable access and control flow

4. VM Layer (Stack-based Interpreter)

• No JIT—pure interpreter executing bytecode sequentially
• Typed value stack: I64, F64, Str, Array, Complex, Nothing
• Deterministic execution: Uses seedable PRNG (currently StableRNG/LehmerRNG, Xoshiro256++ also supported)
• Output capture: Intercepts println() calls and captures to string
• Error handling: Runtime errors (division by zero, index out of bounds, etc.)

Running the CLI REPL

The JuliaVM OSS includes an interactive Julia-like REPL for terminal use.

Running without Installation

cd subset_julia_vm

# Run the REPL
cargo run --bin sjulia --features repl --release

Installing sjulia CLI

Install the sjulia command globally using cargo install:

# From the repository root
cargo install --path subset_julia_vm --features repl

This installs sjulia to ~/.cargo/bin/. Ensure this directory is in your PATH.

After installation, you can run sjulia from anywhere:

sjulia                    # Start interactive REPL
sjulia path/to/file.jl    # Execute a Julia file
sjulia -e '1+1'  # Execute code string

REPL Features

   ╔═╗╔═╗╔╦╗╔═╗╔═╗╔═╗╔╦╗╔═╗  (Colorful Monokai logo!)
   ║ ╦║ ║║║║╠═╣║ ╦║ ║║║║╠═╣
   ╚═╝╚═╝╩ ╩╩ ╩╚═╝╚═╝╩ ╩╩ ╩
   ╦╔═╦ ╦╦ ╦╦╔═╦╔═╦ ╦╦ ╦
   ╠╩╗╚╦╝║ ║╠╩╗╠╩╗╚╦╝║ ║
   ╩ ╩ ╩ ╚═╝╩ ╩╩ ╩ ╩ ╚═╝

julia> x = 10
10

julia> x * 2
20

julia> \alpha<Tab>    # LaTeX completion → α
julia> α = 3.14
3.14

Keyboard Shortcuts:

• Tab - Insert 4 spaces, or complete LaTeX (e.g., \alpha → α)
• Up/Down - Navigate history
• Ctrl-C - Cancel current input
• Ctrl-D - Exit

Building for WebAssembly

See subset_julia_vm_web/README.md to learn more.

Ahead-of-Time (AoT) Compilation

The JuliaVM OSS includes an AoT compiler that compiles Julia code to native Rust code.

AoT Compilation Workflow

$ cargo run --release --bin juliar --features aot -- ./examples/mandelbrot.jl -o output.rs
$ rustc -O output.rs -o output_binary \
    --extern subset_julia_vm_runtime="$(ls target/release/deps/libsubset_julia_vm_runtime-*.rlib | head -1)" \
    -L target/release/deps
$ ./output_binary
Mandelbrot Set (50x25):

                              .
                              . .
                              .+
                             ###+.
                        .   .####.
                       .#++#########....
                      ..##############.
            .        ..################..
             ...... .##################.
            .#######.###################
          ...##########################.
#####################################..
          ...##########################.
            .#######.###################
             ...... .##################.
            .        ..################..
                      ..##############.
                       .#++#########....
                        .   .####.
                             ###+.
                              .+
                              . .
                              .