rustc_codegen_cranelift VS gccrs

> I wonder if how much value there is in skipping LLVM in favor of having a JIT optimized linked in instead. For release builds it would get you a reasonable proxy if it optimized decently while still retaining better debugability.

Rust is in the process of building out the cranelift backend. Cranelift was originally built to be a JIT compiler. The hope is that this can become the debug build compiler.

https://github.com/rust-lang/rustc_codegen_cranelift

There's no reason? Are you sure about this?

I think you mean there could theoretically be an interpreted Rust, but I don't think anyone has ever made a prototype of a Rust interpreter.

The closest is probably rust-analyzer (the official language server), that maintains internal state and reacts to changes you make, but it doesn't create an executable artifact.

The other is probably the Cranelift Backend (https://github.com/rust-lang/rustc_codegen_cranelift), which can produce debug builds quickly.

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.

Why? It depends on what you want to replace, but the Rust project has a long history of using tools written in other languages. Python is used a lot in build tooling, bors-ng was written in Elixir, llvm is written in c, ... gcc-rs doesn't contain a lot of rust code either, it's purely other languages according to https://github.com/Rust-GCC/gccrs

Fundamentally, if a tool is good and provides benefits then why not use it? You'll be met with concerns about maintainability if you just airdrop something written in Ada/SPARK but that's fair - just as it was fair that the introduction of Rust in the linux kernel was indeed met with concerns about maintainability. It seems that those were resolved to the satisfcation of the group that decides things and the cost/benefit balance was considered net positive.

I agree with the sentiment somewhat. Some rust libraries are dying, while some great new ones thrive (recently found iroh is getting up to speed). Everyone wants to write a game engine or some fun project and then abandon it, but no one wants to write a game. No application software has really "cemented" itself in the global ecosystem. Except for maybe ripgrep?

I would like to see support for more compilers (https://rust-gcc.github.io/), more interoperability with C/C++, better support for cross-compilation. Maybe less reliance on crates.io, static linking, and permissive licenses.

Still, I see Rust as the natural progression from C++.

The community has been very supportive of the gccrs (https://github.com/Rust-GCC/gccrs) project, which is the main project to write a Rust compiler written in C.

There is a Rust front-end for GCC that is under active development [1]. If the chip vendors are not willing to develop and upstream a LLVM back-end then they can feel free to start contributing to it.

[1] https://rust-gcc.github.io/

That's why gccrs doesn't even consider lifetime checking a part of the language (they plan to use Polonius, too).

There's ongoing work on a Rust front-end for GCC (https://github.com/Rust-GCC/gccrs). Bit barebones right now -- ie, even core doesn't compile -- but there's funding, demand, and regular progress, so it'll only get better from there. Once gccrs can compile core, it should be ready to compile most of Rust, and thus if you've taught the calling conventions for C to GCC, you're golden.

I recommend checking out the GCC Rust frontend project.