Exploring GCC support

[spacekatia]

considering that gcc has quite an extensive range of backends, we might want to look out for projects that would allow rust to be compiled trough gcc, be it Rust-gcc frontends or llvm-gcc IR translation layers, or compiling to C as an intermediary step

[jonas-schievink]

Links to projects of that kind:

• https://github.com/sapir/gcc-rust/tree/rust – rustc MIR->GIMPLE codegen backend
• https://github.com/redbrain/gccrs – Rust frontend for GCC (in C/C++)
• https://github.com/JuliaComputing/llvm-cbe – LLVM backend emitting C code

Related: I suspect that writing a Cranelift backend might be vastly easier than writing an LLVM backend, so that's another route that could be explored to target more architectures. There's a cranelift backend for rustc here and it actually works for some nontrivial programs (but still has plenty of bugs).

[IGBC]

from that list I think llvm-cbe is the most promising.

I am quick to dismiss cranelift as it has no asm support, something needed for most old targets. I looked into its creators, and it seems asm support is out of scope for the bytecodealliance

[thejpster]

Does mrustc count here? Rust -> C -> GCC -> ASM seems a workable approach for many applications.

[jonas-schievink]

Sure, that's how the ESP32 is/was targeted with Rust. It seems to be a huge pain though.

[IGBC]

Which project is used there seem to be a few transpiler projects