1 # Cranelift codegen backend for rust
3 The goal of this project is to create an alternative codegen backend for the rust compiler based on [Cranelift](https://github.com/bytecodealliance/wasmtime/blob/main/cranelift).
4 This has the potential to improve compilation times in debug mode.
5 If your project doesn't use any of the things listed under "Not yet supported", it should work fine.
6 If not please open an issue.
8 ## Building and testing
11 $ git clone https://github.com/bjorn3/rustc_codegen_cranelift.git
12 $ cd rustc_codegen_cranelift
13 $ ./prepare.sh # download and patch sysroot src and install hyperfine for benchmarking
17 To run the test suite replace the last command with:
23 This will implicitly build cg_clif too. Both `build.sh` and `test.sh` accept a `--debug` argument to
26 Alternatively you can download a pre built version from [GHA]. It is listed in the artifacts section
27 of workflow runs. Unfortunately due to GHA restrictions you need to be logged in to access it.
29 [GHA]: https://github.com/bjorn3/rustc_codegen_cranelift/actions?query=branch%3Amaster+event%3Apush+is%3Asuccess
33 rustc_codegen_cranelift can be used as a near-drop-in replacement for `cargo build` or `cargo run` for existing projects.
35 Assuming `$cg_clif_dir` is the directory you cloned this repo into and you followed the instructions (`prepare.sh` and `build.sh` or `test.sh`).
39 In the directory with your project (where you can do the usual `cargo build`), run:
42 $ $cg_clif_dir/build/cargo.sh run
45 This should build and run your project with rustc_codegen_cranelift instead of the usual LLVM backend.
49 > You should prefer using the Cargo method.
52 $ $cg_clif_dir/build/bin/cg_clif my_crate.rs
57 In jit mode cg_clif will immediately execute your code without creating an executable file.
59 > This requires all dependencies to be available as dynamic library.
60 > The jit mode will probably need cargo integration to make this possible.
63 $ $cg_clif_dir/build/cargo.sh jit
69 $ $cg_clif_dir/build/bin/cg_clif -Cllvm-args=mode=jit -Cprefer-dynamic my_crate.rs
72 There is also an experimental lazy jit mode. In this mode functions are only compiled once they are
73 first called. It currently does not work with multi-threaded programs. When a not yet compiled
74 function is called from another thread than the main thread, you will get an ICE.
77 $ $cg_clif_dir/build/cargo.sh lazy-jit
82 These are a few functions that allow you to easily run rust code from the shell using cg_clif as jit.
85 function jit_naked() {
86 echo "$@" | $cg_clif_dir/build/bin/cg_clif - -Cllvm-args=mode=jit -Cprefer-dynamic
90 jit_naked "fn main() { $@ }"
94 jit 'println!("0x{:x}", ' $@ ');';
100 [see env_vars.md](docs/env_vars.md)
104 * Inline assembly ([no cranelift support](https://github.com/bytecodealliance/wasmtime/issues/1041))
105 * On Linux there is support for invoking an external assembler for `global_asm!` and `asm!`.
106 `llvm_asm!` will remain unimplemented forever. `asm!` doesn't yet support reg classes. You
107 have to specify specific registers instead.
108 * SIMD ([tracked here](https://github.com/bjorn3/rustc_codegen_cranelift/issues/171), some basic things work)