> One solution to both of these problems I have thought about, but do not work at a low enough level to know if it is already a thing, is an opcode for unlikely

> One solution to both of these problems I have thought about, but do not work at a low enough level to know if it is already a thing, is an opcode for unlikely branches. x86 actually does have jump instructions with branch prediction hints, but surprisingly modern CPUs will completely ignore those hints. Perhaps they never really caused large enough performance improvements to be worthwhile, or something. > In this particular case, it would also involve a way of signalling to the compiler (or the compiler inferring), [...] This functionality does exist, and Linux does make use of them. See the macros likely() and unlikely() at http://lxr.free-electrons.com/source/include/linux/compiler.h#L131 http://lxr.free-electrons.com/source/include/linux/compiler....