Missing the AF_BUS

Actually, predicted function calls *are* nearly free on modern CPUs. Of course, function calls stuck deep inside conditionals are less likely to be successfully predicted as taken -- and unpredicted/mispredicted function calls (like all other mispredicted, non-speculated branches) are expensive as hell. However, these days I don't believe there is much more reason to be concerned about function calls than there is to be concerned about any other conditional. (Specialists in deep x86 lore, which I am very much not and who I am merely reiterating from dim and vague memory, are welcome to contradict me, and probably will!)