rename get_global_alloc to try_get_global_alloc

[rust.git] / Readme.md

diff --git a/Readme.md b/Readme.md
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--- a/Readme.md
+++ b/Readme.md
@@ -1,41 +1,75 @@
-# Work in progress cranelift codegen backend for rust
+# Cranelift codegen backend for rust
 
-> ⚠⚠⚠ This doesn't do much useful yet ⚠⚠⚠
+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).
+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.
 
-## Building
+## Building and testing
 
 ```bash
 $ git clone https://github.com/bjorn3/rustc_codegen_cranelift.git
 $ cd rustc_codegen_cranelift
-$ ./prepare.sh # download and patch sysroot src and install hyperfine for benchmarking
+$ ./y.rs prepare # download and patch sysroot src and install hyperfine for benchmarking
+$ ./y.rs build
+```
+
+To run the test suite replace the last command with:
+
+```bash
 $ ./test.sh
 ```
 
+This will implicitly build cg_clif too. Both `y.rs build` and `test.sh` accept a `--debug` argument to
+build in debug mode.
+
+Alternatively you can download a pre built version from [GHA]. It is listed in the artifacts section
+of workflow runs. Unfortunately due to GHA restrictions you need to be logged in to access it.
+
+[GHA]: https://github.com/bjorn3/rustc_codegen_cranelift/actions?query=branch%3Amaster+event%3Apush+is%3Asuccess
+
 ## Usage
 
-`$cg_clif_dir` is the directory you cloned this repo into in the following instruction.
+rustc_codegen_cranelift can be used as a near-drop-in replacement for `cargo build` or `cargo run` for existing projects.
+
+Assuming `$cg_clif_dir` is the directory you cloned this repo into and you followed the instructions (`y.rs prepare` and `y.rs build` or `test.sh`).
 
-### Rustc
+In the directory with your project (where you can do the usual `cargo build`), run:
 
 ```bash
-$ rustc -Cpanic=abort -Zcodegen-backend=$cg_clif_dir/target/debug/librustc_codegen_cranelift.so --sysroot $cg_clif_dir/build_sysroot/sysroot my_crate.rs
+$ $cg_clif_dir/build/cargo-clif build
 ```
 
-### Cargo
+This will build your project with rustc_codegen_cranelift instead of the usual LLVM backend.
 
-```bash
-$ RUSTFLAGS="-Cpanic=abort -Zcodegen-backend=$cg_clif_dir/target/debug/librustc_codegen_cranelift.dylib --sysroot $cg_clif_dir/build_sysroot/sysroot" cargo run
-```
+For additional ways to use rustc_codegen_cranelift like the JIT mode see [usage.md](docs/usage.md).
+
+## Configuration
+
+See the documentation on the `BackendConfig` struct in [config.rs](src/config.rs) for all
+configuration options.
 
 ## Not yet supported
 
-* Good non-rust abi support ([vectors 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))
+* Inline assembly ([no cranelift support](https://github.com/bytecodealliance/wasmtime/issues/1041))
+    * On Linux there is support for invoking an external assembler for `global_asm!` and `asm!`.
+      `llvm_asm!` will remain unimplemented forever. `asm!` doesn't yet support reg classes. You
+      have to specify specific registers instead.
 * SIMD ([tracked here](https://github.com/bjorn3/rustc_codegen_cranelift/issues/171), some basic things work)
 
-## Troubleshooting
+## License
+
+Licensed under either of
+
+  * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
+    http://www.apache.org/licenses/LICENSE-2.0)
+  * MIT license ([LICENSE-MIT](LICENSE-MIT) or
+    http://opensource.org/licenses/MIT)
+
+at your option.
 
-### Can't compile
+### Contribution
 
-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.
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you shall be dual licensed as above, without any
+additional terms or conditions.