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At control-flow join points, cranelift-frontend's SSA builder currently checks to see if only one definition of a variable reaches the current block. If so, it can eliminate the corresponding block parameter and use the original def directly. It implements this by turning the block parameter into an alias for the original value. However, it didn't resolve aliases during this check, except after it had already determined that there was only one definition. Resolving aliases first instead allows it to detect that more block parameters are redundant. And as more block parameters get converted to aliases, later blocks can see common definitions from further away, so this has a compounding effect. This also merges a special case, where there's exactly one unique non-sentinel definition but it's actually an alias for the sentinel, into the general case where all definitions are from the sentinel. As a result there's only one case that has to introduce a definition of the variable to zero. According to `valgrind --tool=dhat`, this is a significant memory savings. On the pulldown-cmark benchmark from Sightglass: - 15.3% (1.9MiB) less memory allocated at maximum heap - 4.1% (6.7MiB) less memory allocated in total - 9.8% (57MiB) fewer bytes read - 12.6% (36MiB) fewer bytes written - 5.4% fewer instructions retired - 1.04x faster by instructions retired (per Sightglass/perf) - 1.03x to 1.04x faster by CPU cycles (per Sightglass/perf) - 1.03 ± 0.01 times faster by CPU time (per hyperfine) - 1.04x faster by cache accesses (per Sightglass/perf) On the bz2 benchmark: - 1.06x faster by instructions retired (per Sightglass/perf) - 1.05x faster by CPU cycles (per Sightglass/perf) - 1.04 ± 0.01 times faster by CPU time (per hyperfine) - 1.02x to 1.03x faster by cache accesses (per Sightglass/perf) Even on the largest benchmark in Sightglass (spidermonkey.wasm), this is a measurable improvement: - 1.03x faster by instructions retired (per Sightglass/perf) - 1.02x faster by CPU cycles (per Sightglass/perf) - 1.02 ± 0.00 times faster by CPU time (per hyperfine) There was no significant difference in cache misses for any benchmark, according to Sightglass/perf.
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
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.