The simple cases are simple. However the complex cases get hard.

    mytype foo() {
       mytype one;
       ...
       if(something) {
          mytype two;
          ...
          return two;
       }
    return one;
    }

That one is not too hard either. `one` simply can't be NRVO'd as there is a runtime path in scope of it that doesn't return it. `two` can be (unless you hide some other return within ...).