IRust VS rustc_codegen_cranelift

irust?

Something I've been thinking a lot about for Rust is what can and should a REPL experience be for a compiled language (ie what are reasonable compromises).

There seem to be two repls that haven't gotten much traction:

- https://github.com/google/evcxr/blob/main/evcxr_repl/README....

- https://github.com/sigmaSd/IRust

There have been little and big nits that have held me back from wanting to push these further, including

- Bad defaults (having to opt-in to panic handling)

- Command syntax feeling out of place and likely not beginner friendly

- Limits on variable preservation

- Lack of introspection (at least irust as `:type`)

So far I've been punting on wanting to improve this area by instead focusing on polishing up a rust script solution in the hopes of getting it merged: https://github.com/epage/cargo-script-mvs

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/...