rustc_codegen_gcc VS rustc_codegen_cranelift

It's true that if this project succeeds, that would be an outcome, but it's probably worth noting that you'd really only have to add support for the GCC backend to do that, and not reimplement the frontend as well (parsing, type checking, lifetime checking, etc.). There's an unrelated project working to do that: https://github.com/antoyo/rustc_codegen_gcc that would likely yield those same benefits for less effort.

platform support (may improve soon)

Here's the gcc backend for rustc here https://github.com/antoyo/rustc_codegen_gcc Since this just swaps the optimizer/codegen module and reuses all the other stuff from rustc it needs less work and can already compile many valid rust programs.

I'd like to use the rustc_codegen_gcc backend to compile some Rust programs, but I'm confused about how to install and use the patched libgccjit dependency. I've downloaded the fork provided but don't know where to go from there.

I was being a little sloppy and mixing together "actual embedded hardware" with "extensions for applications written in other languages" in my head. I think your point about LLVM is still accurate, though I hear peeps about different projects working on GCC support from time to time.

This doesn't have anything to do with using GCC to compile rust, but instead using rustc to compile Rust using the GCC backend. You can do that today by using the linked project, rustc_codegen_gcc, which is intended to be integrated into rustc at some point in the (hopefully near) future.

Rather than mrustc you should probably look at rustc_codegen_gcc which uses gcc as a backend to rustc (WIP) or GCC Rust which tries to implement a rust frontend for gcc (also WIP). I think rustc_codegen_gcc looks the most promising at the moment

Libgccjit AOT Codegen for Rustc\ (2 comments)

Windows is supported. See https://github.com/rust-lang/rustc_codegen_cranelift/issues/....

> When this happens, it seems like it'll be possible to get the LLVM bits out of the bootstrap process and lead to a fully self-hosted Rust.

What do you mean by "when this happens"? GP's point is that this has already happened: the Cranelift backend is feature-complete from the perspective of the language [0], except for inline assembly and unwinding on panic. It was merged into the upstream compiler in 2020 [1], and a compiler built with only the Cranelift backend is perfectly capable of building another compiler. LLVM hasn't been a necessary component of the Rust compiler for quite some time.

[0] https://github.com/bjorn3/rustc_codegen_cranelift

[1] https://github.com/rust-lang/rust/pull/77975

Note that the Cranelift codegen will eventually become standard for debug builds to speed them up.

Maybe one day we'll have rustc b3 backend like what they did with Cranelift

Additionally, there is gcc codegen for rustc (https://github.com/rust-lang/rustc_codegen_gcc), which is not a compiler per se, but an alternative code generator, with more architectures supported and other nice things. It's also coming along, but there's still a lot of work to do there too. There's also Cranelift codegen (https://github.com/bjorn3/rustc_codegen_cranelift), which is designed to make debug builds faster, but this is not as exciting/useful as the other 2.

For the instant reloading, that's in Sycamore, so you should speak to its devs, but as for the alternative compiler backend, it's not my project, but it uses Cranelift and works pretty well! See https://github.com/bjorn3/rustc_codegen_cranelift for details.

The more immediate goal of "distribute the cranelift backend as a rustup component" has been making good progress and seems like it might happen relatively soon https://github.com/bjorn3/rustc_codegen_cranelift/milestone/...