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added section on cranelift codegen #801

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added section on cranelift codegen
MalekiRe Nov 4, 2023
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alice-i-cecile May 5, 2024
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3 changes: 3 additions & 0 deletions content/learn/book/getting-started/setup/_index.md
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Expand Up @@ -200,6 +200,9 @@ Bevy can be built just fine using default configuration on stable Rust. However

For more information, see [The rustup book: Overrides](https://rust-lang.github.io/rustup/overrides.html#the-toolchain-file).

* **Cranelift Codegen**: This uses a new nightly-only codegen that can be 300% faster than LLVM! However it only currently works on Linux and is generally still immature.
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30% is a more realistic average.

It works fine on Windows now and x86_64 macOS (arm64 macOS has some ABI issues)

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@janhohenheim janhohenheim Jul 3, 2024 •
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I could not get Bevy compiling on (intel) macOS with cranelift enabled. Specifically objc2 failed to build.
Windows works, but the installation process is a bit whackier and it may not play nice with sccache.
After my little investigation, it seems like the only platform where everything runs smoothly out of the box is still Linux.

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An issue for that at https://github.com/rust-lang/rustc_codegen_cranelift/issues would be appreciated.

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Sure! I'll post one tomorrow :)

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Update: there you go rust-lang/rustc_codegen_cranelift#1504
Let me know in that issue if there's anything I can try out to help debug it.

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Thanks!

[Cranelift codegen setup](https://bjorn3.github.io/2023/10/31/progress-report-oct-2023.html).
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Maybe link to the setup section of the readme instead? Unlike this page it will be kept up to date if the setup changes.

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Also it is possible to compile all dependencies with the LLVM backend and optimizations, but the main game crate with Cranelift to get much better runtime performance.

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@bjorn3 I've tried that before and ran into issues where I would get random segfaults.

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There were some abi incompatibilities in the past, but most should be fixed now.


* **Generic Sharing**: Allows crates to share monomorphized generic code instead of duplicating it. In some cases this allows us to "precompile" generic code so it doesn't affect iterative compiles. This is only available on nightly Rust.

To enable fast compiles, install the nightly rust compiler and LLD. Then copy the contents of [this file](https://github.com/bevyengine/bevy/blob/main/.cargo/config_fast_builds) to `YOUR_WORKSPACE/.cargo/config.toml`. For the project in this guide, that would be `my_bevy_game/.cargo/config.toml`.
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