I use AVR Rust and have dumped the resulting assembly output and I was suitably impressed. It optimized the living daylights out of the code and the resulting assembly was amazingly short and did exactly what you'd expect. It didn't really waste any stack space or RAM. It's truly amazing to see modern rust running on an 8 bit CPU in such a reasonable way (of course it also helps to write in an 8 bit friendly way, like using u8 or i8 for things that don't need to be big), but it's also nice to know I can just use a 64 bit int and it'll do whatever it has to do to work.