Depends on the domain.

For single threaded applications, as fast is the goal. There is potential for it to be faster due to stronger restrictions around pointers.

Multithreaded code is slated to be faster mainly because rust provides safety for patterns that would be difficult to do right in C++ (see servo css handling).

That is to say, you could do the same thing in C++, but getting it right is harder to do.

Concurrency patterns that are difficult to execute in the decades old codebase of Firefox, which also happens to be a browser aka nightmare of complexity.

The same environmental conditions don't apply to other software and it's perfectly possible to write blazing fast multithreaded software in C++. In fact that's SOP.