notes/pl/cpp/tricks/cpp-devirtualization.txt

class Base
{
  typedef void (*FP)();
  typedef int (*FPGet) (const Base &);
  typedef void (*FPSet) (Base &, int);

  static FP vtbl[totalMethods][totalClasses];

  uint8_t tag;
public:
  int get() const {
    return ((FPGet)(vtbl[0][tag]))(*this);
  }
  void set(int x) {
    ((FPSet)vtbl[1][tag])(*this, x);
  }
};

// double index is just a single address calculation.