How C++ virtual inheritance is implemented in compilers?

How the compilers implement the virtual inheritance?

In the following code:

class A {
  public:
    A(int) {}
};

class B : public virtual A {
  public:
    B() : A(1) {}
};

class C : public B {
  public:
    C() : A(3), B() {}
};

Does a compiler generate two instance of B::ctor function, one without A(1) call, and one with it? So when B::constructor is called from derived class's constructor the first instance is used, otherwise the second.