Cretonne Code Generator

Cretonne is a low-level retargetable code generator. It translates a target-independent intermediate representation into executable machine code.

For more information, see the documentation.

Status

Cretonne 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. Cretonne currently supports the System V AMD64 ABI calling convention used on many platforms, but does not yet support the Windows x64 calling convention. The performance of code produced by Cretonne is not yet impressive, though we have plans to fix that.

The core codegen crates have minimal dependencies, support no_std mode, and do not require any host floating-point support.

Cretonne 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.

Cretonne's APIs are not yet stable.

Cretonne currently supports Rust 1.22.1 and later. We intend to always support the latest stable Rust. And, we currently support the version of Rust in the latest Ubuntu LTS, although whether we will always do so is not yet determined. Cretonne requires Python 2.7 or Python 3 to build.

Planned uses

Cretonne 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:

Building Cretonne

Cretonne is using the Cargo package manager format. First, ensure you have installed a current stable rust (stable, beta, and nightly should all work, but only stable and beta are tested consistently). Then, change the working directory to your clone of cretonne and run:

cargo build

This will create a target/debug directory where you can find the generated binary.

To build the optimized binary for release:

cargo build --release

You can then run tests with:

./test-all.sh

You may need to install the wat2wasm tool from the wabt project in order to run all of the WebAssembly tests. Tests requiring wat2wasm are ignored if the tool is not installed.

Building with no_std

The following crates support no_std:

cretonne-entity
cretonne-codegen
cretonne-frontend
cretonne-native
cretonne-wasm
cretonne-module
cretonne-simplejit
cretonne

To use no_std mode, disable the std feature and enable the core feature. This currently requires nightly rust.

For example, to build cretonne-codegen:

cd lib/codegen
cargo build --no-default-features --features core

Or, when using cretonne-codegen as a dependency (in Cargo.toml):

[dependency.cretonne-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 cretonne 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.

Building the documentation

To build the Cretonne documentation, you need the Sphinx documentation generator:

$ pip install sphinx sphinx-autobuild sphinx_rtd_theme
$ cd cretonne/docs
$ make html
$ open _build/html/index.html