Relief for retpoline pain

In compilers this is called devirtualization and recent GCC versions can do this automatically for C++ at least. Java's JIT does this too and it's one of the biggest advantages of JIT over AOT as it knows for real what can and cannot be called and what is the distribution of probabilities of targets. A very smart compiler could in theory recognize the pattern in C and optimize it too, but since this is not a concept of the language itself, I wouldn't count on it really.