Optimization by a compiler can be executed with many different methods. The defence company Saab provided us with a mission, to see if we could optimize their code with the help of the GCC compiler and its optimization flags. For this thesis we have conducted a study of the optimization flags to decrease the worst case execution time. The first step to assemble an effective base of flags was reading the documentation for the flags. We then tested the different flags and analysed them. In the end we ended up with four chosen sets that we saw fitted to be discussed and analyzed further. The results did not live up to our expectations, as we thought the flags would optimize the execution time. The flags int he majority of cases gave an, although small, increase of the execution time. We only had one set where the flags gave us a decrease, which we called the Expensive Optimization.With these results we can conclude that Saab do not need to change their existing set of optimization flags to optimize their compiler further.