Function optimizations_used 

pub fn optimizations_used(source: &str) -> Vec<&'static str>

Which optimizations actually FIRE for source: an optimization is “used” when disabling it (via a file-level ## No <X> decorator) changes the generated Rust. Lets the benchmarks UI show, per program, which optimizations it USES vs the full set it CAN use. O(number of optimizations) compiles — intended for per-benchmark, not hot-path, use. Returns the decorator keywords of the firing optimizations (in registry order).