5fa4d36b0d
* Add CLI flags for internal cranelift options This commit adds two flags to the `wasmtime` CLI: * `--enable-cranelift-debug-verifier` * `--enable-cranelift-nan-canonicalization` These previously weren't exposed from the command line but have been useful to me at least for reproducing slowdowns found during fuzzing on the CLI. * Disable Cranelift debug verifier when fuzzing This commit disables Cranelift's debug verifier for our fuzz targets. We've gotten a good number of timeouts on OSS-Fuzz and some I've recently had some discussion over at google/oss-fuzz#3944 about this issue and what we can do. The result of that discussion was that there are two primary ways we can speed up our fuzzers: * One is independent of Wasmtime, which is to tweak the flags used to compile code. The conclusion was that one flag was passed to LLVM which significantly increased runtime for very little benefit. This has now been disabled in rust-fuzz/cargo-fuzz#229. * The other way is to reduce the amount of debug checks we run while fuzzing wasmtime itself. To put this in perspective, a test case which took ~100ms to instantiate was taking 50 *seconds* to instantiate in the fuzz target. This 500x slowdown was caused by a ton of multiplicative factors, but two major contributors were NaN canonicalization and cranelift's debug verifier. I suspect the NaN canonicalization itself isn't too pricy but when paired with the debug verifier in float-heavy code it can create lots of IR to verify. This commit is specifically tackling this second point in an attempt to avoid slowing down our fuzzers too much. The intent here is that we'll disable the cranelift debug verifier for now but leave all other checks enabled. If the debug verifier gets a speed boost we can try re-enabling it, but otherwise it seems like for now it's otherwise not catching any bugs and creating lots of noise about timeouts that aren't relevant. It's not great that we have to turn off internal checks since that's what fuzzing is supposed to trigger, but given the timeout on OSS-Fuzz and the multiplicative effects of all the slowdowns we have when fuzzing, I'm not sure we can afford the massive slowdown of the debug verifier.
wasmtime
A standalone runtime for WebAssembly
A Bytecode Alliance project
Guide | Contributing | Website | Chat
Installation
The Wasmtime CLI can be installed on Linux and macOS with a small install script:
$ curl https://wasmtime.dev/install.sh -sSf | bash
Windows or otherwise interested users can download installers and binaries directly from the GitHub Releases page.
Example
If you've got the Rust compiler installed then you can take some Rust source code:
fn main() {
println!("Hello, world!");
}
and compile/run it with:
$ rustup target add wasm32-wasi
$ rustc hello.rs --target wasm32-wasi
$ wasmtime hello.wasm
Hello, world!
Features
-
Lightweight. Wasmtime is a standalone runtime for WebAssembly that scales with your needs. It fits on tiny chips as well as makes use of huge servers. Wasmtime can be embedded into almost any application too.
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Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code at runtime.
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Configurable. Whether you need to precompile your wasm ahead of time, generate code blazingly fast with Lightbeam, or interpret it at runtime, Wasmtime has you covered for all your wasm-executing needs.
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WASI. Wasmtime supports a rich set of APIs for interacting with the host environment through the WASI standard.
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Standards Compliant. Wasmtime passes the official WebAssembly test suite, implements the official C API of wasm, and implements future proposals to WebAssembly as well. Wasmtime developers are intimately engaged with the WebAssembly standards process all along the way too.
Language Support
You can use Wasmtime from a variety of different languages through embeddings of the implementation:
- Rust - the
wasmtimecrate - C - the
wasm.h,wasi.h, andwasmtime.hheaders - Python - the
wasmtimePyPI package - .NET - the
WasmtimeNuGet package - Go - the wasmtime-go repository
Documentation
📚 Read the Wasmtime guide here! 📚
The wasmtime guide is the best starting point to learn about what Wasmtime can do for you or help answer your questions about Wasmtime. If you're curious in contributing to Wasmtime, it can also help you do that!.
It's Wasmtime.