Comment by mikepurvis

C++20 is gaining the [[likely]] attribute for guiding the predictor in a portable way:

http://eel.is/c++draft/dcl.attr.likelihood

Prior to this it was also possible, but required compiler-specific macros like GCC's __builtin_expect, which is used all over the kernel:

https://github.com/torvalds/linux/search?q=__builtin_expect