Cranelift Code Generator
Cranelift has moved
The cranelift source code now lives in the wasmtime
repository
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.
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.
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"]
Cranelift's documentation is published online.
To build the documentation locally, you need the Sphinx documentation
generator as well as Python 3::
$ pip install sphinx sphinx-autobuild sphinx_rtd_theme
$ cd cranelift/docs
$ make html
$ open _build/html/index.html
Editor Support
Editor support for working with Cranelift IR (clif) files: