a1c9b06cea
Previously, the x64 backend's ABI code would generate a sign-extending load when loading a less-than-64-bit integer from a spillslot. This is incorrect: e.g., for i32s > 0x80000000, this would result in all high bits set. This interacts poorly with another optimization. Normally, the invariant is that the high bits of a register holding a value of a certain type, beyond that type's bits, are undefined. However, as an optimization, we recognize and use the fact that on x86-64, 32-bit instructions zero the upper 32 bits. This allows us to elide a 32-to-64-bit zero-extend op (turning it into just a move, which can then sometimes disappear entirely due to register coalescing). If a spill and reload happen between the production of a 32-bit value from an instruction known to zero the upper bits and its use, then we will rely on zero upper bits that might actually be set by a sign-extend. This will result in incorrect execution. As a fix, we stick to a simple invariant: we always spill and reload a full 64 bits when handling integer registers on x64. This ensures that no bits are mangled.
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.
-
Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code at runtime.
-
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.
-
WASI. Wasmtime supports a rich set of APIs for interacting with the host environment through the WASI standard.
-
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-gorepository
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.