It's entirely likely that you could write faster Rust in the same (nigh-infinite) time it'd take to write equally safe C. I intentionally avoided that comparison though. If you take a normal 10min function in C, it's going to compile into something reasonable and run fast. If you take the same 10min rust function, the language surface area is so much larger that there's a much higher chance that it won't.
Here's a more concrete, albeit irrelevant in practice example from writing most things in both languages:
Implemented in Rust over generic T, you need Wrapping<T> or the equivalent num_traits traits. The implementations for these take borrowed references. Rustc is pretty good at ensuring this becomes pass by value under the hood, but it's imperfect. I found instances of it failing in the test disassembly, even though an implementation for this never has to touch anything but registers. That's performance work that wouldn't have existed in C/C++ for these particular types.
Here's a more concrete, albeit irrelevant in practice example from writing most things in both languages:
https://news.ycombinator.com/item?id=42342382#42352053
Implemented in Rust over generic T, you need Wrapping<T> or the equivalent num_traits traits. The implementations for these take borrowed references. Rustc is pretty good at ensuring this becomes pass by value under the hood, but it's imperfect. I found instances of it failing in the test disassembly, even though an implementation for this never has to touch anything but registers. That's performance work that wouldn't have existed in C/C++ for these particular types.