pub fn pretty_print(&self) -> String {
        let mut result = String::new();
        result.push_str("Weld Compiler:\n");
        let mut total = Duration::milliseconds(0);
        for &(ref name, ref dur) in self.weld_times.iter() {
            result.push_str(&format!(
                "\t{}: {:.3} ms\n",
                name,
                CompilationStats::format_time(dur)
            ));
            total = total + *dur;
        }
        result.push_str(&format!(
            "\t\x1b[0;32mWeld Compiler Total\x1b[0m {} ms\n",
            CompilationStats::format_time(&total)
        ));

        let mut total = Duration::milliseconds(0);
        result.push_str("Weld Optimization Passes:\n");
        for &(ref name, ref dur) in self.pass_times.iter() {
            result.push_str(&format!(
                "\t{}: {:.3} ms\n",
                name,
                CompilationStats::format_time(dur)
            ));
            total = total + *dur;
        }
        result.push_str(&format!(
            "\t\x1b[0;32mWeld Optimization Passes Total\x1b[0m {} ms\n",
            CompilationStats::format_time(&total)
        ));

        let mut total = Duration::milliseconds(0);
        result.push_str("LLVM:\n");
        for &(ref name, ref dur) in self.llvm_times.iter() {
            result.push_str(&format!(
                "\t{}: {:.3} ms\n",
                name,
                CompilationStats::format_time(dur)
            ));
            total = total + *dur;
        }
        result.push_str(&format!(
            "\t\x1b[0;32mLLVM Total\x1b[0m {} ms\n",
            CompilationStats::format_time(&total)
        ));

        result
    }
Returns pretty-printed statistics stored in `self`.
weld/src/util/stats.rs