fcddb9ca81
* x64: Refactor `Amode` computation in ISLE This commit replaces the previous computation of `Amode` with a different set of rules that are intended to achieve the same purpose but are structured differently. The motivation for this commit is going to become more relevant in the next commit where `lea` will be used for the `iadd` instruction, possibly, on x64. When doing so it caused a stack overflow in the test suite during the compilation phase of a wasm module, namely as part of the `amode_add` function. This function is recursively defined in terms of itself and recurses as deep as the deepest `iadd`-chain in a program. A particular test in our test suite has a 10k-long chain of `iadd` which ended up causing a stack overflow in debug mode. This stack overflow is caused because the `amode_add` helper in ISLE unconditionally peels all the `iadd` nodes away and looks at all of them, even if most end up in intermediate registers along the way. Given that structure I couldn't find a way to easily abort the recursion. The new `to_amode` helper is structured in a similar fashion but attempts to instead only recurse far enough to fold items into the final `Amode` instead of recursing through items which themselves don't end up in the `Amode`. Put another way previously the `amode_add` helper might emit `x64_add` instructions, but it no longer does that. This goal of this commit is to preserve all the original `Amode` optimizations, however. For some parts, though, it relies more on egraph optimizations to run since if an `iadd` is 10k deep it doesn't try to find a constant buried 9k levels inside there to fold into the `Amode`. The hope, though, is that with egraphs having run already it's shuffled constants to the right most of the time and already folded any possible together. * x64: Add `lea`-based lowering for `iadd` This commit adds a rule for the lowering of `iadd` to use `lea` for 32 and 64-bit addition. The theoretical benefit of `lea` over the `add` instruction is that the `lea` variant can emulate a 3-operand instruction which doesn't destructively modify on of its operands. Additionally the `lea` operation can fold in other components such as constant additions and shifts. In practice, however, if `lea` is unconditionally used instead of `iadd` it ends up losing 10% performance on a local `meshoptimizer` benchmark. My best guess as to what's going on here is that my CPU's dedicated units for address computation are all overloaded while the ALUs are basically idle in a memory-intensive loop. Previously when the ALU was used for `add` and the address units for stores/loads it in theory pipelined things better (most of this is me shooting in the dark). To prevent the performance loss here I've updated the lowering of `iadd` to conditionally sometimes use `lea` and sometimes use `add` depending on how "complicated" the `Amode` is. Simple ones like `a + b` or `a + $imm` continue to use `add` (and its subsequent hypothetical extra `mov` necessary into the result). More complicated ones like `a + b + $imm` or `a + b << c + $imm` use `lea` as it can remove the need for extra instructions. Locally at least this fixes the performance loss relative to unconditionally using `lea`. One note is that this adds an `OperandSize` argument to the `MInst::LoadEffectiveAddress` variant to add an encoding for 32-bit `lea` in addition to the preexisting 64-bit encoding. * Conditionally use `lea` based on regalloc
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 (locally) 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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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.
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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.
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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.
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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.
Languages supported by the Bytecode Alliance:
- 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
Languages supported by the community:
- Elixir - the
wasmexhex package
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.