@ -30,30 +30,56 @@ 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.
WebAssembly (MVP and various extensions like SIMD), although it needs to be
used within an external WebAssembly embedding such as Wasmtime to be part of a
complete WebAssembly implementation. It is also usable as a backend for
non-WebAssembly use cases: for example, there is an effort to build a [Rust
compiler backend] using Cranelift.
Cranelift is production-ready, and is used in production in several places, all
within the context of Wasmtime. It is carefully fuzzed as part of Wasmtime with
differential comparison against V8 and the executable Wasm spec, and the
register allocator is separately fuzzed with symbolic verification. There is an
active effort to formally verify Cranelift's instruction-selection backends. We
take security seriously and have a [security policy] as a part of Bytecode
Alliance.
Cranelift has three backends: x86-64, aarch64 (aka ARM64), and s390x (aka IBM
Z). All three backends fully support enough functionality for Wasm MVP, and
x86-64 and aarch64 fully support SIMD as well. On x86-64, Cranelift supports
both the System V AMD64 ABI calling convention used on many platforms and the
Windows x64 calling convention. On aarch64, Cranelift supports the standard
Linux calling convention and also has specific support for macOS (i.e., M1 /
Apple Silicon).
Cranelift's code quality is within range of competitiveness to browser JIT
engines' optimizing tiers. A [recent paper] includes third-party benchmarks of
Cranelift, driven by Wasmtime, against V8 and an LLVM-based Wasm engine, WAVM
(Fig 22). The speed of Cranelift's generated code is ~2% slower than that of
V8 (TurboFan), and ~14% slower than WAVM (LLVM). Its compilation speed, in the
same paper, is measured as approximately an order of magnitude faster than WAVM
(LLVM). We continue to work to improve both measures.
[Rust compiler backend]: https://github.com/bjorn3/rustc_codegen_cranelift
[security policy]: https://bytecodealliance.org/security
[recent paper]: https://arxiv.org/abs/2011.13127
The core codegen crates have minimal dependencies and are carefully written to
handle malicious or arbitrary compiler input: in particular, they do not use
callstack recursion.
Cranelift performs some basic mitigations for Spectre attacks on heap bounds
checks, table bounds checks, and indirect branch bounds checks; see
[#1032] for more.
[#1032]: https://github.com/bytecodealliance/wasmtime/issues/1032
Cranelift's APIs are not yet considered stable, though we do follow
semantic-versioning (semver) with minor-version patch releases.
Cranelift generally requires the latest stable Rust to build as a policy, and
is tested as such, but we can incorporate fixes for compilation with older Rust
versions on a best-effort basis.
Contributing
------------
@ -92,57 +118,6 @@ 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.
< details >
< summary > Building with no_std< / summary >
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\`:
``` {.sourceCode .sh}
cd cranelift-codegen
cargo build --no-default-features --features core
```
Or, when using cranelift-codegen as a dependency (in Cargo.toml):
``` {.sourceCode .}
[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.
< / details >
< details >
< summary > Log configuration< / summary >
Chris Fallin
2 years ago
GitHub