Function templates
The more code resolved at compile time, the better.
Inlining
The compiler replaces the function call with the body of the function.
Branchless programming
Branchless programming removes the need for branch prediction, which removes branch misprediction entirely.
CRTP
The Curiously Recurring Template Pattern (CRTP) is static polymorphism, as opposed to virtual functions, which are dynamic polymorphism. CRTP has no runtime overhead. CRTP is preferable to virtual functions as well as Runtime Type Information (RTTI).