We have seen in a previous post that switch statements are more complex than they seem. The compiler is able to implement them as a decision tree (even though maybe it shouldn't). Is that everything it can do?
In this post, I'll focus on gcc. All optimizations, except the bitset lowering, translate to clang. I'll be using the -O3 optimization flag unless indicated otherwise.
Let us start with a simple example. A function that takes two integers x and val. Depending on the value of x, it calls a corresponding function (f0, f1, and so forth) with val as an argument and returns the result. Were we to implement this manually, we'd would use an array of function pointers, where the input serves as the index into the array.
