Hacker News Reader

My experience with MSVC and ICC is similar - O3 is often worse than O2, and a lot of the time Os is actually the fastest (and smallest).

MSVC has /O1 and /O2 (and /Os), but not /O3. See https://docs.microsoft.com/en-us/cpp/build/reference/compile... . (I work on MSVC's STL.)