e4b7c8a737
* Cranelift: fix #3953: rework single/multiple-use logic in lowering. This PR addresses the longstanding issue with loads trying to merge into compares on x86-64, and more generally, with the lowering framework falsely recognizing "single uses" of one op by another (which would normally allow merging of side-effecting ops like loads) when there is *indirect* duplication. To fix this, we replace the direct `value_uses` count with a transitive notion of uniqueness (not unlike Rust's `&`/`&mut` and how a `&mut` downgrades to `&` when accessed through another `&`!). A value is used multiple times transitively if it has multiple direct uses, or is used by another op that is used multiple times transitively. The canonical example of badness is: ``` v1 := load v2 := ifcmp v1, ... v3 := selectif v2, ... v4 := selectif v2, ... ``` both `v3` and `v4` effectively merge the `ifcmp` (`v2`), so even though the use of `v1` is "unique", it is codegenned twice. This is why we ~~can't have nice things~~ can't merge loads into compares (#3953). There is quite a subtle and interesting design space around this problem and how we might solve it. See the long doc-comment on `ValueUseState` in this PR for more justification for the particular design here. In particular, this design deliberately simplifies a bit relative to an "optimal" solution: some uses can *become* unique depending on merging, but we don't design our data structures for such updates because that would require significant extra costly tracking (some sort of transitive refcounting). For example, in the above, if `selectif` somehow did not merge `ifcmp`, then we would only codegen the `ifcmp` once into its result register (and use that register twice); then the load *is* uniquely used, and could be merged. But that requires transitioning from "multiple use" back to "unique use" with careful tracking as we do pattern-matching, which I've chosen to make out-of-scope here for now. In practice, I don't think it will matter too much (and we can always improve later). With this PR, we can now re-enable load-op merging for compares. A subsequent commit does this. * Update x64 backend to allow load-op merging for `cmp`. * Update filetests. * Add test for cmp-mem merging on x64. * Comment fixes. * Rework ValueUseState analysis for better performance. * Update s390x filetest: iadd_ifcout cannot merge loads anymore because it has multiple outputs (ValueUseState limitation) * Address review comments.
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
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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, 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 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.