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wasmi is an efficient WebAssembly interpreter with low-overhead and support
for embedded environment such as WebAssembly itself.
At Parity we are using wasmi in Substrate
as the execution engine for our WebAssembly based smart contracts.
Furthermore we run wasmi within the Substrate runtime which is a WebAssembly
environment itself and driven via Wasmtime at the time of this writing.
As such wasmi's implementation requires a high degree of correctness and
Wasm specification conformance.
Since wasmi is relatively lightweight compared to other Wasm virtual machines
such as Wasmtime it is also a decent option for initial prototyping.
The following list states some of the distinct features of wasmi.
- Primarily concerned about
- correct and deterministic WebAssembly execution.
- WebAssembly specification compliance.
- Can itself be compiled to and executed via WebAssembly.
- Low-overhead and cross-platform WebAssembly runtime.
- Loosely mirrors the Wasmtime API to act as a drop-in solution.
The new wasmi_v1 engine supports a variety of WebAssembly proposals and will support even more of them in the future.
| WebAssembly Proposal | Status | Comment |
|---|---|---|
mutable-global |
✅ | |
saturating-float-to-int |
✅ | |
sign-extension |
✅ | |
multi-value |
✅ | |
reference-types |
⌛ | Planned but not yet implemented. Low priority. |
bulk-memory |
⌛ | Planned but not yet implemented. Low priority. |
simd |
❌ | No support is planned for wasmi. |
tail-calls |
⌛ | Not yet part of the Wasm standard but support in wasmi is planned. Low priority. |
Clone wasmi from our official repository and then build using the standard cargo procedure:
git clone https://github.com/paritytech/wasmi.git
cd wasmi
cargo build
In order to test wasmi you need to initialize and update the Git submodules using:
git submodule update --init --recursive
Alternatively you can provide --recursive flag to git clone command while cloning the repository:
git clone https://github.com/paritytech/wasmi.git ---recursive
After Git submodules have been initialized and updated you can test using:
cargo test --workspace
Before pushing a PR to our repository we would like you to execute the
ci.sh script that can be found in the repository's root folder.
Supported platforms are primarily Linux, MacOS, Windows and WebAssembly.
Use the following command in order to produce a WebAssembly build:
cargo build --no-default-features --target wasm32-unknown-unknown
In order to reap the most performance out of wasmi we highly recommended
to compile the wasmi crate using the following Cargo profile:
[profile.release]
lto = "fat"
codegen-units = 1When compiling for the WebAssembly target we highly recommend to post-optimize
wasmi using Binaryen's wasm-opt tool since our experiments displayed a
80-100% performance improvements when executed under Wasmtime and also
slightly smaller Wasm binaries.
In order to benchmark wasmi use the following command:
cargo bench
Note: Benchmarks can be filtered by compile_and_validate,
instantiate and execute flags given to cargo bench.
For example cargo bench execute will only execute the benchmark
tests that test the performance of WebAssembly execution.
wasmi is primarily distributed under the terms of both the MIT
license and the APACHE license (Version 2.0), at your choice.
See LICENSE-APACHE and LICENSE-MIT for details.
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in wasmi by you, as defined in the APACHE 2.0 license, shall be
dual licensed as above, without any additional terms or conditions.