An interesting way to increase the performance of many C++ projects is to enable link-time optimization (LTO). During compilation, your compiler doesn't know how the code will get linked with other object files or libraries. Many opportunities to optimize arise only at this point: when linking, your tools can see the bigger picture of how the parts of your program interact with each other. By enabling LTO, you can sometimes grab a significant improvement in performance with very little cost. In CMake projects, you can enable LTO by setting either the global CMAKE_INTERPROCEDURAL_OPTIMIZATION flag or by setting the INTERPROCEDURAL_OPTIMIZATION property on your targets.
One drawback of using LTO is that it makes the building process longer. Sometimes a lot longer. To mitigate this cost for developers, you may want to only enable this optimization for builds that undergo performance testing or are meant to be released.
