How is Rust compiled to machine code?

Question

I've recently been looking at the Rust programming language. How does it work? Rust code seems to be compiled into ELF or PE (etc) binaries, but I've not been able to find any information on how that's done? Is it compiled to an intermediate format then compiled the rest of the way with gxx for example? Any help (or links) would be really appreciated.

question from:https://stackoverflow.com/questions/43385142/how-is-rust-compiled-to-machine-code

Answer 1

The code-generation phase of the Rust compiler is mainly done by LLVM. LLVM is a set of tools for building a compiler, most notably used by the C[++] Compiler clang[++].

First, the Rust compiler (just like clang, for example) does all the Rust specific stuff like type and borrow checking; in the end, it generates LLVM-IR. IR stands for intermediate representation and it's... comparable to assembly, but a tiny bit more high level and most importantly: platform independent. Then the Rust compiler just calls ? LLVM and says:

Hey buddy, could you please take this IR and generate machine code for the current platform? That would be fantastic ? ? ?

To which LLVM responds:

?? Sure, no problem, new friend. Here is your highly optimized machine code for [e.g.] x86_64! ???

Afterwards they invite a few more friends to wrap it all up in a nice little [e.g.] ELF package and beautifully place it in the users file system. (and the user is like...)

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Information like this can be found in the official FAQ which contains a lot of interesting information anyway. For more in-depth details on the Rust compiler, you can read the "Rustc Guide". For this question, the chapter "High Level Overview" is pretty interesting.