Wasm2Sea Compiler

A WebAssembly to native code compiler using Binaryen and dstogov/ir.

Overview

Wasm2Sea translates WebAssembly bytecode to an intermediate representation (IR), then generates native code through the dstogov/ir backend. The project demonstrates a complete compilation pipeline from WASM to executable code.

Features

Implemented ✓

• Arithmetic Operations: add, sub, mul, div (signed/unsigned), rem
• Comparisons: eq, ne, lt, gt, le, ge (signed/unsigned), eqz
• Bitwise Operations: and, or, xor, shl, shr (arithmetic/logical)
• Local Variables: local.get, local.set, local.tee
• Control Flow:
  • Select (ternary operator)
  • If-else with complex branches
  • Nested conditionals

In Progress 🚧

• Loops: Loop structures parsed, execution not yet implemented

Planned 📋

• Block structures
• Function calls
• Memory operations
• Additional types (i64, f32, f64)

See TODO.md for complete list.

Building

Prerequisites

• CMake 3.10+
• C++17 compiler
• Binaryen library
• dstogov/ir framework

Compile

mkdir build && cd build
cmake ..
make

Usage

Basic Workflow

1. Write WebAssembly text format (.wat):

(module
  (func $add (export "test") (param i32 i32) (result i32)
    local.get 0
    local.get 1
    i32.add
  )
)

2. Compile to WASM:

wat2wasm add.wat -o add.wasm

3. Convert to IR:

./wasm2sea add.wasm

4. Generate and compile C code:

cd ../third_party/dstogov-ir
./ir_main ../../build/out.ir --emit-c out.c
cc -O2 out.c run_varargs_ffi.c -o a.out $(pkg-config --cflags --libs libffi)

5. Run:

./a.out 10 20  # Returns 30

Testing Script

Use the provided test script:

./test_wasm_ffi.sh test_add 10 20

Architecture

Pipeline Stages

1. wasm_reader: Parse WASM binary using Binaryen
2. wasm_lower: Lower to SSA-form ValueIR
3. ir_bridge: Convert to dstogov/ir graph
4. dstogov/ir: Generate native code

Key Design Decisions

• Visitor Pattern: Manual control over AST traversal for correct control flow handling
• SSA Form: Each value assigned once, simplifies optimization
• Label Management: WebAssembly labels converted to depth-based indexing
• PHI Nodes: Handle value merging at control flow joins

Known Quirks

• dstogov/ir converts GT(a,b) to LT(b,a) internally
• This affects PHI parameter ordering in control flow
• Select and if-else require different PHI orders as a result

Examples

See tests/ directory for examples:

• test_select.wat: Ternary operator
• test_if_else.wat: Conditional branches
• test_if_complex.wat: Complex branch logic
• test_loop_countdown.wat: Loop structure (parsing only)

Development

Running Tests

# Individual test
./test_wasm_ffi.sh test_name [args...]

# Example
./test_wasm_ffi.sh test_if_else 10 5  # Expected: 10

Debug Output

Uncomment debug prints in wasm_reader.cpp to see instruction sequence.

Adding New Operations

1. Add to WasmOp enum in wasm_instr.hpp
2. Handle in visitExpression in wasm_reader.cpp
3. Lower to ValueIR in wasm_lower.cpp
4. Map to dstogov/ir in ir_bridge.cpp

Project Status

This is a research/educational project demonstrating WebAssembly compilation. Current focus is on implementing loop support, which is the most complex remaining feature.

See PROGRESS.md for detailed status and TODO.md for roadmap.

License

[Add your license here]

References

• Binaryen
• dstogov/ir
• WebAssembly Specification