You can use the cranelift backend, written in Rust, if you prefer. Nothing about LLVM being the best choice by default has to do with the choice of implementation language.

Or more likely for something that needs to be high performance mrustc, but you obviously have to be careful there.

mrustc is written in C++, so I don't see how it's a counter to what the parent is proposing. I also don't know anything about mrustc's performance characteristics, I didn't think performance was a goal, but it's also been a while since I've checked in on it.

Oh right, I don't even know if there's a C compiler that's not written in C++ that can compile the output of mrustc anyway, so there's that.