03463458e4
In #5031, we removed `bool` types from CLIF, using integers instead for "truthy" values. This greatly simplified the IR, and was generally an improvement. However, because x86's `SETcc` instruction sets only the low 8 bits of a register, we chose to use `i8` types as the result of `icmp` and `fcmp`, to avoid the need for a masking operation when materializing the result. Unfortunately this means that uses of truthy values often now have `uextend` operations, especially when coming from Wasm (where truthy values are naturally `i32`-typed). For example, where we previously had `(brz (icmp ...))`, we now have `(brz (uextend (icmp ...)))`. It's arguable whether or not we should switch to `i32` truthy values -- in most cases we can avoid materializing a value that's immediately used for a branch or select, so a mask would in most cases be unnecessary, and it would be a win at the IR level -- but irrespective of that, this change *did* regress our generated code quality: our backends had patterns for e.g. `(brz (icmp ...))` but not with the `uextend`, so we were *always* materializing truthy values. Many blocks thus ended with "cmp; setcc; cmp; test; branch" rather than "cmp; branch". In #5391 we noticed this and fixed it on x64, but it was a general problem on aarch64 and riscv64 as well. This PR introduces a `maybe_uextend` extractor that "looks through" uextends, and uses it where we consume truthy values, thus fixing the regression. This PR also adds compile filetests to ensure we don't regress again. The riscv64 backend has not been updated here because doing so appears to trigger another issue in its branch handling; fixing that is TBD.
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
-
Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code either at runtime or ahead-of-time. Wasmtime is optimized for efficient instantiation, low-overhead calls between the embedder and wasm, and scalability of concurrent instances.
-
Secure. Wasmtime's development is strongly focused on correctness and security. Building on top of Rust's runtime safety guarantees, each Wasmtime feature goes through careful review and consideration via an RFC process. Once features are designed and implemented, they undergo 24/7 fuzzing donated by Google's OSS Fuzz. As features stabilize they become part of a release, and when things go wrong we have a well-defined security policy in place to quickly mitigate and patch any issues. We follow best practices for defense-in-depth and integrate protections and mitigations for issues like Spectre. Finally, we're working to push the state-of-the-art by collaborating with academic researchers to formally verify critical parts of Wasmtime and Cranelift.
-
Configurable. Wasmtime uses sensible defaults, but can also be configured to provide more fine-grained control over things like CPU and memory consumption. Whether you want to run Wasmtime in a tiny environment or on massive servers with many concurrent instances, we've got you covered.
-
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, CMake orwasmtimeConan package - C++ - the
wasmtime-cpprepository or usewasmtime-cppConan package - Python - the
wasmtimePyPI package - .NET - the
WasmtimeNuGet package - Go - the
wasmtime-gorepository - Ruby - the
wasmtimegem
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.