rust/Readme.md
2019-01-26 17:03:35 +01:00

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# Work in progress cranelift codegen backend for rust
> ⚠⚠⚠ This doesn't do much useful yet ⚠⚠⚠
## Building
```bash
$ git clone https://github.com/bjorn3/rustc_codegen_cranelift.git
$ cd rustc_codegen_cranelift
$ ./prepare.sh # downloads and patches sysroot src and installs hyperfine for benchmarking
$ ./test.sh
```
## Usage
`$cg_clif_dir` is the directory you cloned this repo into in the following instruction.
### Rustc
```bash
$ rustc -Cpanic=abort -Zcodegen-backend=$cg_clif_dir/target/debug/librustc_codegen_cranelift.so my_crate.rs
```
### Cargo
```bash
$ RUSTFLAGS="-Cpanic=abort -Zcodegen-backend=$cg_clif_dir/target/debug/librustc_codegen_cranelift.dylib --sysroot $cg_clif_dir/build_sysroot/sysroot" cargo run
```
## Not yet supported
* Good non-rust abi support ([scalar pair and vector are passed by-ref](https://github.com/bjorn3/rustc_codegen_cranelift/issues/10))
* Checked binops ([some missing instructions in cranelift](https://github.com/CraneStation/cranelift/issues/460))
* Inline assembly ([no cranelift support](https://github.com/CraneStation/cranelift/issues/444))
* Varargs ([no cranelift support](https://github.com/CraneStation/cranelift/issues/212))
* libstd (needs varargs and some other stuff) ([tracked here](https://github.com/bjorn3/rustc_codegen_cranelift/issues/146))
* u128 and i128 ([no cranelift support](https://github.com/CraneStation/cranelift/issues/354))
* SIMD ([tracked here](https://github.com/bjorn3/rustc_codegen_cranelift/issues/171))
## Troubleshooting
### Can't compile
Try updating your nightly compiler. You can try to use an nightly a day or two older if updating rustc doesn't fix it. If you still can't compile it, please fill an issue.
### error[E0463]: can't find crate for `std` while compiling a no_std crate
If you use `RUSTFLAGS` to pass `-Zcodegen-backend` to rustc, cargo will compile `build-dependencies` with those flags too. Because this project doesn't support libstd yet, that will result in an error. I don't know of any way to fix this. :(