1 # WIP Cranelift codegen backend for rust
3 > ⚠⚠⚠ Certain kinds of FFI don't work yet. ⚠⚠⚠
5 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/master/cranelift). This has the potential to improve compilation times in debug mode. If your project doesn't use any of the things listed under "Not yet supported", it should work fine. If not please open an issue.
10 $ git clone https://github.com/bjorn3/rustc_codegen_cranelift.git
11 $ cd rustc_codegen_cranelift
12 $ ./prepare.sh # download and patch sysroot src and install hyperfine for benchmarking
18 rustc_codegen_cranelift can be used as a near-drop-in replacement for `cargo build` or `cargo run` for existing projects.
20 Assuming `$cg_clif_dir` is the directory you cloned this repo into and you followed the instructions (`prepare.sh` and `test.sh`).
24 In the directory with your project (where you can do the usual `cargo build`), run:
27 $ $cg_clif_dir/cargo.sh run
30 This should build and run your project with rustc_codegen_cranelift instead of the usual LLVM backend.
32 If you compiled cg_clif in debug mode (aka you didn't pass `--release` to `./test.sh`) you should set `CHANNEL="debug"`.
36 > You should prefer using the Cargo method.
39 $ $cg_clif_dir/target/release/cg_clif my_crate.rs
44 In jit mode cg_clif will immediately execute your code without creating an executable file.
46 > This requires all dependencies to be available as dynamic library.
47 > The jit mode will probably need cargo integration to make this possible.
50 $ $cg_clif_dir/cargo.sh jit
56 $ $cg_clif_dir/target/release/cg_clif --jit my_crate.rs
61 These are a few functions that allow you to easily run rust code from the shell using cg_clif as jit.
64 function jit_naked() {
65 echo "$@" | $cg_clif_dir/target/release/cg_clif - --jit
69 jit_naked "fn main() { $@ }"
73 jit 'println!("0x{:x}", ' $@ ');';
79 [see env_vars.md](docs/env_vars.md)
83 * Good non-rust abi support ([several problems](https://github.com/bjorn3/rustc_codegen_cranelift/issues/10))
84 * Inline assembly ([no cranelift support](https://github.com/bytecodealliance/wasmtime/issues/1041)
85 * On Linux there is support for invoking an external assembler for `global_asm!` and `asm!`.
86 `llvm_asm!` will remain unimplemented forever. `asm!` doesn't yet support reg classes. You
87 have to specify specific registers instead.
88 * SIMD ([tracked here](https://github.com/bjorn3/rustc_codegen_cranelift/issues/171), some basic things work)