The simplest tool is to just grep for various constructs that copy or allocate. Clippy, the Rust linter, will find some of these (as well as other issues, some of which tend to cause performance problems).

The better tool is to profile the code, then optimize hotspots. There's a Rust Performance Book with a list of profilers known to work with Rust programs[1]. Rustc does support Profile Guided Optimization[2] which is often pretty good at speeding up the output even without any code changes.

[1] https://nnethercote.github.io/perf-book/profiling.html [2] https://doc.rust-lang.org/rustc/profile-guided-optimization....