LOOM - Formally Verified WebAssembly Optimizer

A high-performance WebAssembly optimizer with formal verification support, featuring a comprehensive 12-phase optimization pipeline built with ISLE (Instruction Selection and Lowering Engine) and Z3 SMT solver integration.

✨ Features

🚀 Comprehensive Optimization Pipeline

• 12 optimization phases including constant folding, strength reduction, CSE, inlining, LICM, and DCE
• Declarative rules using ISLE DSL for maintainable optimizations
• Stateful dataflow analysis tracking locals and memory state
• Idempotent optimizations - safe to run multiple times

🔬 Formal Verification

• Z3 SMT-based verification proves optimization correctness via translation validation
• Property-based testing ensures idempotence and validity
• Counterexample generation for debugging failed optimizations
• Optional verification feature (build with --features verification)

⚡ Performance

• Ultra-fast: 10-30 µs optimization time for most modules
• Excellent compression: 80-95% binary size reduction
• Instruction optimization: 0-40% instruction count reduction (varies by code)
• Lightweight: Minimal dependencies, pure Rust implementation

🎯 Advanced Features

• Component Model support for modern WebAssembly
• wasm32-wasip2 build target support
• Comprehensive benchmarking with Criterion
• Full WAT and WASM format support

🏛️ Architecture

Loom is built with a modular architecture featuring a shared foundation:

• loom-shared: Core ISLE definitions and WebAssembly IR (stable API)
• loom-core: Optimization pipeline implementation
• loom-cli: Command-line interface and tooling
• loom-testing: Differential testing framework

The loom-shared crate provides a stable, reusable foundation that other WebAssembly tools can build upon. It contains:

• ISLE term definitions for all WebAssembly instructions
• Module IR (Module, Function, Instruction types)
• WASM parsing and encoding utilities
• Z3 verification infrastructure (optional)

This architecture enables both rapid prototyping in Loom and potential use in safety-critical applications through derived tools.

📖 See LOOM_SYNTH_ARCHITECTURE.md for detailed architecture documentation.

📦 Quick Start

Installation

# Build from source
git clone https://github.com/pulseengine/loom
cd loom
cargo build --release

# Binary at target/release/loom
./target/release/loom --help

Basic Usage

# Optimize WebAssembly module
loom optimize input.wasm -o output.wasm

# Show detailed statistics
loom optimize input.wat -o output.wasm --stats

# Run verification checks
loom optimize input.wasm -o output.wasm --verify

# Output as WAT text format
loom optimize input.wasm -o output.wat --wat

Example Output

🔧 LOOM Optimizer v0.1.0
Input: input.wasm
✓ Parsed in 234µs
⚡ Optimizing...
✓ Optimized in 0 ms

📊 Optimization Statistics
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Instructions: 24 → 20 (16.7% reduction)
Binary size:  797 → 92 bytes (88.5% reduction)
Constant folds: 3
Optimization time: 0 ms
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

✅ Optimization complete!

🏗️ 12-Phase Optimization Pipeline

Phase	Optimization	Example	Impact
1	Precompute	Global constant propagation	Enables folding
2	ISLE Folding	10 + 20 → 30	Compile-time evaluation
3	Strength Reduction	x * 8 → x << 3	2-3x speedup
4	CSE	Cache duplicate computations	Reduces redundancy
5	Function Inlining	Inline small functions	Call overhead removal
6	ISLE (Post-inline)	Fold exposed constants	Cross-function optimization
7	Code Folding	Flatten blocks	Control flow simplification
8	LICM	Hoist loop invariants	Loop speedup
9	Branch Simplify	Simplify conditionals	Fewer branches
10	DCE	Remove unreachable code	Code cleanup
11	Block Merge	Merge consecutive blocks	Reduce overhead
12	Vacuum & Locals	Remove unused variables	Final cleanup

📊 Benchmark Results

Performance (Criterion benchmarks)

Constant Folding:        8-11 µs
Strength Reduction:      10 µs
CSE:                     9-14 µs
Function Inlining:       16-18 µs
Full Pipeline:           19-28 µs
Parser:                  6.8 µs
Encoder:                 183 ns (!)

Real-World Results

Fixture	Instructions	Binary Size	Constant Folds
bench_bitops	24 → 20 (16.7%)	88.5% reduction	0
test_input	9 → 7 (22.2%)	81.6% reduction	1
fibonacci	12 → 12 (0%)	92.6% reduction	0
quicksort	Complex	92.5% reduction	0
game_logic	Complex	92.5% reduction	0

Key Insight: Binary size reductions are consistently excellent (80-93%), while instruction count improvements vary by code complexity.

🔬 Formal Verification

LOOM supports two verification modes:

1. Property-Based (Always Available)

loom optimize input.wasm -o output.wasm --verify

• Fast idempotence checks
• Constant folding validation
• ~5ms overhead

2. Z3 SMT Formal Proof (Optional)

# Install Z3
brew install z3  # macOS
sudo apt install z3  # Linux

# Build with verification
cargo build --release --features verification

# Verify with formal proof
./target/release/loom optimize input.wasm -o output.wasm --verify

Output:

🔬 Running Z3 SMT verification...
  ✅ Z3 verification passed: optimizations are semantically equivalent

Z3 verification proves mathematically that optimizations preserve program semantics via translation validation.

💡 Examples

Example 1: Strength Reduction

Input:

(module
  (func $optimize_me (param $x i32) (result i32)
    local.get $x
    i32.const 8
    i32.mul
  )
)

After Optimization:

(module
  (func $optimize_me (param $x i32) (result i32)
    local.get $x
    i32.const 3
    i32.shl  ;; 2-3x faster than multiply!
  )
)

Example 2: Constant Folding

Input:

(func $calculate (result i32)
  i32.const 10
  i32.const 20
  i32.add
  i32.const 5
  i32.mul
)

After Optimization:

(func $calculate (result i32)
  i32.const 150  ;; Computed at compile-time
)

Example 3: CSE

Input:

(func $duplicate (param $x i32) (result i32)
  local.get $x
  i32.const 4
  i32.mul
  local.get $x
  i32.const 4
  i32.mul  ;; Duplicate computation!
  i32.add
)

After Optimization:

(func $duplicate (param $x i32) (result i32)
  local.get $x
  i32.const 4
  i32.mul
  local.tee $temp
  local.get $temp  ;; Reuse cached result
  i32.add
)

🏛️ Architecture

                    ┌──────────────────┐
                    │  WebAssembly     │
                    │  (WAT or WASM)   │
                    └────────┬─────────┘
                             │
                             ▼
                    ┌──────────────────┐
                    │   wasmparser     │
                    │  Parse to AST    │
                    └────────┬─────────┘
                             │
                             ▼
                    ┌──────────────────┐
                    │  ISLE Terms      │
                    │  (IR)            │
                    └────────┬─────────┘
                             │
                             ▼
    ┌────────────────────────────────────────────┐
    │     12-Phase Optimization Pipeline         │
    │  ┌──────────────────────────────────────┐  │
    │  │ 1. Precompute                        │  │
    │  │ 2. ISLE Constant Folding             │  │
    │  │ 3. Strength Reduction                │  │
    │  │ 4. Common Subexpression Elimination  │  │
    │  │ 5. Function Inlining                 │  │
    │  │ 6. ISLE (Post-inline)                │  │
    │  │ 7. Code Folding                      │  │
    │  │ 8. Loop-Invariant Code Motion        │  │
    │  │ 9. Branch Simplification             │  │
    │  │ 10. Dead Code Elimination            │  │
    │  │ 11. Block Merging                    │  │
    │  │ 12. Vacuum & Simplify Locals         │  │
    │  └──────────────────────────────────────┘  │
    │              │                              │
    │              ▼                              │
    │  ┌──────────────────────────────────────┐  │
    │  │   Dataflow Analysis                  │  │
    │  │   (locals, memory state tracking)    │  │
    │  └──────────────────────────────────────┘  │
    └────────────────────────────────────────────┘
                             │
                             ▼
              ┌──────────────────────────┐
              │   Optional: Z3 SMT       │
              │   Verification           │
              └────────────┬─────────────┘
                           │
                           ▼
              ┌──────────────────────────┐
              │   wasm-encoder           │
              │   Encode to binary       │
              └────────────┬─────────────┘
                           │
                           ▼
              ┌──────────────────────────┐
              │  Optimized WebAssembly   │
              └──────────────────────────┘

📚 Documentation

User Guides

• Usage Guide - Complete CLI reference, examples, and best practices
• Quick Reference - Cheat sheet for common tasks
• Performance Comparison - LOOM vs wasm-opt benchmarks and analysis

Technical Documentation

• Architecture - Deep dive into the 12-phase pipeline and implementation
• Formal Verification Guide - Z3 SMT verification internals
• WASM Build Guide - Building LOOM to WebAssembly (wasm32-wasip2)
• Implementation Details - Technical implementation notes

For Contributors

• Contributing Guide - How to contribute to LOOM
• Design Documents - Individual optimization pass designs (CSE, DCE, LICM, etc.)

🧪 Testing

# Run all tests
cargo test

# Run optimization-specific tests
cargo test --test optimization_tests

# Run benchmarks
cargo bench

# Test on real fixtures
./target/release/loom optimize tests/fixtures/quicksort.wat -o /tmp/out.wasm --stats --verify

Test Status:

• ✅ 20/20 optimization tests passing (100%)
• ✅ 54/57 unit tests passing (95%)
• ✅ All benchmarks complete successfully

📁 Project Structure

loom/
├── loom-core/                # Core optimizer implementation
│   ├── src/lib.rs            # 12-phase pipeline, optimizations
│   ├── src/verify.rs         # Z3 verification module
│   ├── tests/                # Unit and integration tests
│   └── benches/              # Criterion performance benchmarks
├── loom-isle/                # ISLE term definitions and rules
│   ├── isle/                 # ISLE DSL files
│   └── src/lib.rs            # Rust integration
├── loom-cli/                 # Command-line interface
│   ├── src/main.rs           # CLI implementation
│   └── BUILD.bazel           # Bazel build rules
├── tests/fixtures/           # Real-world test cases
│   ├── fibonacci.wat
│   ├── quicksort.wat
│   ├── matrix_multiply.wat
│   └── ...
└── docs/                     # Comprehensive documentation
    ├── USAGE_GUIDE.md
    ├── QUICK_REFERENCE.md
    └── ...

🔧 Building

Standard Build

cargo build --release

With Z3 Verification

cargo build --release --features verification

WASM Build (wasm32-wasip2)

# Using Cargo
cargo build --release --target wasm32-wasip2

# Using Bazel
bazel build //loom-cli:loom_wasm --platforms=@rules_rust//rust/platform:wasm

See WASM_BUILD.md for details.

🚀 Use Cases

1. Production Deployment

# Optimize and verify before deployment
loom optimize app.wasm -o app.optimized.wasm --verify --stats

2. CI/CD Integration

- name: Optimize WebAssembly
  run: |
    loom optimize dist/*.wasm -o dist/*.wasm --stats --verify

3. Development Workflow

# Optimize during build
cargo build --target wasm32-unknown-unknown
loom optimize target/wasm32-unknown-unknown/release/app.wasm -o dist/app.wasm

4. Performance Analysis

# Compare before/after
ls -lh original.wasm optimized.wasm
loom optimize original.wasm -o optimized.wasm --stats

🎯 Optimization Patterns

Strength Reduction

• x * 2^n → x << n (2-3x faster)
• x / 2^n → x >> n (2-3x faster)
• x % 2^n → x & (2^n - 1) (2-3x faster)

Algebraic Simplification

• x | 0 → x
• x & -1 → x
• x ^ 0 → x
• x + 0 → x
• x * 1 → x

Constant Folding

• Compile-time evaluation of all constant expressions
• Propagation through local variables
• Cross-function constant propagation via inlining

🤝 Contributing

Contributions welcome! This project is under active development.

1. Check existing issues
2. Run tests: cargo test && cargo clippy
3. Follow Rust conventions
4. Add tests for new features
5. Update documentation

📜 License

Apache License 2.0

🙏 Acknowledgments

• ISLE DSL from Cranelift
• Z3 SMT Solver from Microsoft Research
• wasmparser & wasm-encoder from Bytecode Alliance

🔗 Related Projects

• Binaryen - Reference WebAssembly optimizer (C++)
• wasm-opt - Industry-standard optimizer
• Cranelift - High-performance code generator
• WRT - WebAssembly Component Model runtime

📈 Roadmap

Current Status (v0.1.0):

• ✅ 12-phase optimization pipeline
• ✅ Z3 formal verification
• ✅ Comprehensive benchmarking
• ✅ Component Model support
• ✅ wasm32-wasip2 build target

Coming Soon:

• 🚧 More aggressive LICM (arithmetic operations, global reads)
• 🚧 Profile-guided optimization
• 🚧 SIMD-specific optimizations
• 🚧 Inter-procedural analysis
• 🚧 Custom optimization passes

---

Built with ❤️ by PulseEngine