c82326a1ae
The `peepmatic-automata` crate builds and queries finite-state transducer automata. A transducer is a type of automata that has not only an input that it accepts or rejects, but also an output. While regular automata check whether an input string is in the set that the automata accepts, a transducer maps the input strings to values. A regular automata is sort of a compressed, immutable set, and a transducer is sort of a compressed, immutable key-value dictionary. A [trie] compresses a set of strings or map from a string to a value by sharing prefixes of the input string. Automata and transducers can compress even better: they can share both prefixes and suffixes. [*Index 1,600,000,000 Keys with Automata and Rust* by Andrew Gallant (aka burntsushi)][burntsushi-blog-post] is a top-notch introduction. If you're looking for a general-purpose transducers crate in Rust you're probably looking for [the `fst` crate][fst-crate]. While this implementation is fully generic and has no dependencies, its feature set is specific to `peepmatic`'s needs: * We need to associate extra data with each state: the match operation to evaluate next. * We can't provide the full input string up front, so this crate must support incremental lookups. This is because the peephole optimizer is computing the input string incrementally and dynamically: it looks at the current state's match operation, evaluates it, and then uses the result as the next character of the input string. * We also support incremental insertion and output when building the transducer. This is necessary because we don't want to emit output values that bind a match on an optimization's left-hand side's pattern (for example) until after we've succeeded in matching it, which might not happen until we've reached the n^th state. * We need to support generic output values. The `fst` crate only supports `u64` outputs, while we need to build up an optimization's right-hand side instructions. This implementation is based on [*Direct Construction of Minimal Acyclic Subsequential Transducers* by Mihov and Maurel][paper]. That means that keys must be inserted in lexicographic order during construction. [trie]: https://en.wikipedia.org/wiki/Trie [burntsushi-blog-post]: https://blog.burntsushi.net/transducers/#ordered-maps [fst-crate]: https://crates.io/crates/fst [paper]: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.24.3698&rep=rep1&type=pdf
Cranelift Code Generator
A Bytecode Alliance project
Cranelift is a low-level retargetable code generator. It translates a target-independent intermediate representation into executable machine code.
For more information, see the documentation.
For an example of how to use the JIT, see the SimpleJIT Demo, which implements a toy language.
For an example of how to use Cranelift to run WebAssembly code, see Wasmtime, which implements a standalone, embeddable, VM using Cranelift.
Status
Cranelift currently supports enough functionality to run a wide variety of programs, including all the functionality needed to execute WebAssembly MVP functions, although it needs to be used within an external WebAssembly embedding to be part of a complete WebAssembly implementation.
The x86-64 backend is currently the most complete and stable; other architectures are in various stages of development. Cranelift currently supports both the System V AMD64 ABI calling convention used on many platforms and the Windows x64 calling convention. The performance of code produced by Cranelift is not yet impressive, though we have plans to fix that.
The core codegen crates have minimal dependencies, support no_std mode (see below), and do not require any host floating-point support, and do not use callstack recursion.
Cranelift does not yet perform mitigations for Spectre or related security issues, though it may do so in the future. It does not currently make any security-relevant instruction timing guarantees. It has seen a fair amount of testing and fuzzing, although more work is needed before it would be ready for a production use case.
Cranelift's APIs are not yet stable.
Cranelift currently requires Rust 1.37 or later to build.
Contributing
If you're interested in contributing to Cranelift: thank you! We have a [contributing guide] which will help you getting involved in the Cranelift project.
Planned uses
Cranelift is designed to be a code generator for WebAssembly, but it is general enough to be useful elsewhere too. The initial planned uses that affected its design are:
- WebAssembly compiler for the SpiderMonkey engine in Firefox.
- Backend for the IonMonkey JavaScript JIT compiler in Firefox.
- Debug build backend for the Rust compiler.
- Wasmtime non-Web wasm engine.
Building Cranelift
Cranelift uses a conventional Cargo build process.
Cranelift consists of a collection of crates, and uses a Cargo
Workspace,
so for some cargo commands, such as cargo test, the --all is needed
to tell cargo to visit all of the crates.
test-all.sh at the top level is a script which runs all the cargo
tests and also performs code format, lint, and documentation checks.
Building with no_std
The following crates support `no_std`, although they do depend on liballoc:
- cranelift-entity
- cranelift-bforest
- cranelift-codegen
- cranelift-frontend
- cranelift-native
- cranelift-wasm
- cranelift-module
- cranelift-preopt
- cranelift
To use no_std mode, disable the std feature and enable the core feature. This currently requires nightly rust.
For example, to build `cranelift-codegen`:
cd cranelift-codegen
cargo build --no-default-features --features core
Or, when using cranelift-codegen as a dependency (in Cargo.toml):
[dependency.cranelift-codegen]
...
default-features = false
features = ["core"]
no_std support is currently "best effort". We won't try to break it, and we'll accept patches fixing problems, however we don't expect all developers to build and test no_std when submitting patches. Accordingly, the ./test-all.sh script does not test no_std.
There is a separate ./test-no_std.sh script that tests the no_std support in packages which support it.
It's important to note that cranelift still needs liballoc to compile. Thus, whatever environment is used must implement an allocator.
Also, to allow the use of HashMaps with no_std, an external crate called hashmap_core is pulled in (via the core feature). This is mostly the same as std::collections::HashMap, except that it doesn't have DOS protection. Just something to think about.
Log configuration
Cranelift uses the log crate to log messages at various levels. It doesn't
specify any maximal logging level, so embedders can choose what it should be;
however, this can have an impact of Cranelift's code size. You can use log
features to reduce the maximum logging level. For instance if you want to limit
the level of logging to warn messages and above in release mode:
[dependency.log]
...
features = ["release_max_level_warn"]
Editor Support
Editor support for working with Cranelift IR (clif) files: