rustc_codegen_gcc VS gcc-rust

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)