This various a lot between compilers. Clang for example treats O3 perf regressions a bugs In many cases at least) and is a bit more reasonable with O3 on. GCC g

This various a lot between compilers. Clang for example treats O3 perf regressions a bugs In many cases at least) and is a bit more reasonable with O3 on. GCC goes full mad max and you don't know what it's going to do.