472b1b2e8a
Fixes #3468. If a program has many instances of the pattern "goto next; next:" in a row (i.e., no-op branches to the fallthrough address), the branch simplification in `MachBuffer` would remove them all, as expected. However, in order to work correctly, the algorithm needs to track all labels that alias the current buffer tail, so that they can be adjusted later if another branch chomp occurs. When many thousands of this branch-to-next pattern occur, many thousands of labels will reference the current buffer tail, and this list of thousands of labels will be shuffled between the branch metadata struct and the "labels at tail" struct as branches are appended and then chomped immediately. It's possible that with smarter data structure design, we could somehow share the list of labels -- e.g., a single array of all labels, in order they are bound, with ranges of indices in this array used to represent lists of labels (actually, that seems like a better design in general); but let's leave that to future optimization work. For now, we can avoid the quadratic behavior by just "giving up" if the list is too long; it's always valid to not optimize a branch. It is very unlikely that the "normal" case will have more than 100 "goto next" branches in a row, so this should not have any perf impact; if it does, we will leave 1 out of every 100 such branches un-optimized in a long sequence of thousands. This takes total compilation time down on my machine from ~300ms to ~72ms for the `foo.wasm` case in #3441. For reference, the old backend (now removed), built from arbitrarily-chosen-1-year-old commit `c7fcc344`, takes 158ms, so we're ~twice as fast, which is what I would expect.
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, 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.
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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 or usewasmtimeConan package - [C++] - the
wasmtime-cpprepository or usewasmtime-cppConan package - 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.