Skip to content

wasm-build.md

Latest commit

 

History

History
172 lines (120 loc) · 3.89 KB

wasm-build.md

File metadata and controls

172 lines (120 loc) · 3.89 KB

Building LOOM for WebAssembly (wasm32-wasip2)

This document describes how to build LOOM for WebAssembly using the wasm32-wasip2 target.

Prerequisites

  1. Rust toolchain with wasm32-wasip2 support:

    rustup target add wasm32-wasip2

  2. Bazel (for Bazel builds):

    • Bazel 6.0 or later
    • The wasm32-wasip2 toolchain is automatically registered via extra_target_triples

Building with Cargo

Development Build

cargo build --target wasm32-wasip2

Release Build (optimized for size)

cargo build --target wasm32-wasip2 --profile release-wasm

The release-wasm profile is configured for minimal WASM binary size:

  • opt-level = "z" - Optimize for size
  • lto = true - Enable link-time optimization
  • codegen-units = 1 - Single codegen unit for better optimization
  • strip = true - Strip debug symbols
  • panic = "abort" - Smaller panic handler

Building with Bazel

Build LOOM for WASM

# Build the WASM binary
bazel build //loom-cli:loom_wasm --platforms=@rules_rust//rust/platform:wasm

# Output will be in: bazel-bin/loom-cli/loom_wasm.wasm

Build with custom platform

For more control over the WASM build, you can define a custom platform:

# platforms/BUILD.bazel
platform(
    name = "wasm32_wasip2",
    constraint_values = [
        "@platforms//cpu:wasm32",
        "@platforms//os:wasi",
    ],
)

Then build with:

bazel build //loom-cli:loom_wasm --platforms=//platforms:wasm32_wasip2

Deployment

WebAssembly Component Model

LOOM is designed to work with the WebAssembly Component Model. To create a component:

# Install wasm-tools
cargo install wasm-tools

# Build LOOM as WASM
cargo build --target wasm32-wasip2 --release

# Create a component (if using WIT interface)
wasm-tools component new \
  target/wasm32-wasip2/release/loom.wasm \
  -o loom.component.wasm

Running LOOM WASM

You can run LOOM compiled to WASM using a WASI runtime:

# Using wasmtime
wasmtime target/wasm32-wasip2/release/loom.wasm optimize input.wasm -o output.wasm

# Using wasmer
wasmer run target/wasm32-wasip2/release/loom.wasm -- optimize input.wasm -o output.wasm

Size Optimization

The release-wasm profile produces binaries optimized for size. Additional optimizations:

Using wasm-opt

# Install Binaryen tools
npm install -g binaryen

# Optimize the WASM binary
wasm-opt -Oz target/wasm32-wasip2/release/loom.wasm -o loom.opt.wasm

# With aggressive optimizations
wasm-opt -Oz --enable-bulk-memory --enable-simd \
  target/wasm32-wasip2/release/loom.wasm \
  -o loom.opt.wasm

Using wasm-snip

Remove unused functions:

cargo install wasm-snip

wasm-snip target/wasm32-wasip2/release/loom.wasm \
  -o loom.snipped.wasm \
  --snip-rust-panicking-code

Troubleshooting

Missing wasm32-wasip2 target

If you get an error about missing wasm32-wasip2 target:

rustup target add wasm32-wasip2

Bazel build errors

If Bazel fails to find the WASM toolchain:

# Re-sync Bazel's Rust toolchains
bazel sync --configure

ISLE build script issues

The ISLE code generation happens during build. For WASM builds, ensure:

  • ISLE compiler runs on the host platform (not WASM)
  • Generated code is included in the build

Performance

WASM builds of LOOM can be run in:

  • Server-side WASI runtimes (Wasmtime, Wasmer, WasmEdge)
  • Browser environments (with WASI polyfill)
  • Edge computing platforms (Fastly Compute@Edge, Cloudflare Workers)

Expected performance:

  • ~2-3x slower than native for I/O-bound operations
  • ~1.5-2x slower for CPU-bound optimizations
  • Smaller deployment footprint (~1-2MB compressed)

Future Work

  • Component Model: Full WIT interface for LOOM as a component
  • WASI Preview 2: Migrate to newer WASI standard
  • JavaScript Bindings: NPM package for browser use
  • Edge Runtime: Optimized builds for edge platforms