Frontend versus backend

[Serentty]

I was talking to Centril about this project, and he suggested that it would make more sense to structure it as a codegen target for the Rust compiler instead of a GCC frontend. These were his words, specifically:

also, I think that the perspective "gcc frontend" is a mistake -- I think a "gcc backend" makes more sense in that if this project wants to be viable, it should really be a rustc_codegen_gcc crate

I'm not familiar with compiler internals and have no opinion on this myself, but given that Centril is a central figure in the development of Rust, I figured it would be a good idea to pass this on.

[sapir]

Thanks!

I'm not sure I understand, though. I think it's really both a frontend for gcc and a backend for rustc. But do you mean that it should use librustc_codegen_ssa?

[bjorn3]

I think he means that you use can execute rustc with an extra flag instead of gcc with a rust file to use gcc-rust. This makes it easier to support cargo.

In cg_clif I use -Zcodegen-backend to load a .so as backend. That .so file just needs to provide a __rustc_codegen_backend symbol: https://github.com/bjorn3/rustc_codegen_cranelift/blob/6652f466efc93a8706c07cda0502fd487ce8219d/src/lib.rs#L286

[sapir]

My impression of gcc so far is that doing this without libgccjit would be difficult, and in any case it might not integrate as well with gcc.

[bjorn3]

That is unfortunate.