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# WIP Cranelift codegen backend for rust
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> ⚠⚠⚠ Certain kinds of FFI don't work yet. ⚠⚠⚠
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## Building
```bash
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$ git clone https://github.com/bjorn3/rustc_codegen_cranelift.git
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$ cd rustc_codegen_cranelift
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$ ./prepare.sh # download and patch sysroot src and install hyperfine for benchmarking
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$ ./test.sh --release
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```
## Usage
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`$cg_clif_dir` is the directory you cloned this repo into in the following instruction.
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### Cargo
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```bash
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$ CHANNEL="release" $cg_clif_dir/cargo.sh run
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```
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If you compiled cg_clif in debug mode (aka you didn't pass `--release` to `./test.sh` ) you should use `CHANNEL="debug"` instead or omit `CHANNEL="release"` completely.
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### Rustc
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> You should prefer using the Cargo method.
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```bash
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$ rustc +$(cat $cg_clif_dir/rust-toolchain) -Cpanic=abort -Zcodegen-backend=$cg_clif_dir/target/release/librustc_codegen_cranelift.so --sysroot $cg_clif_dir/build_sysroot/sysroot my_crate.rs
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```
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## Env vars
< dl >
< dt > CG_CLIF_JIT< / dt >
< dd > Enable JIT mode to immediately run a program instead of writing an executable file.< / dd >
< dt > CG_CLIF_JIT_ARGS< / dt >
< dd > When JIT mode is enable pass these arguments to the program.< / dd >
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< dt > CG_CLIF_INCR_CACHE_DISABLED< / dt >
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< dd > Don't cache object files in the incremental cache. Useful during development of cg_clif
to make it possible to use incremental mode for all analyses performed by rustc without caching
object files when their content should have been changed by a change to cg_clif.< / dd >
< dt > CG_CLIF_DISPLAY_CG_TIME< / dt >
< dd > Display the time it took to perform codegen for a crate< / dd >
< / dl >
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## Not yet supported
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* Good non-rust abi support ([several problems](https://github.com/bjorn3/rustc_codegen_cranelift/issues/10))
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* Checked binops ([some missing instructions in cranelift](https://github.com/bytecodealliance/wasmtime/issues/1044))
* Inline assembly ([no cranelift support](https://github.com/bytecodealliance/wasmtime/issues/1041), not coming soon)
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* SIMD ([tracked here](https://github.com/bjorn3/rustc_codegen_cranelift/issues/171), some basic things work)
