class Time {
  public:
  float value;

  Time(float f):value{f}{}
  Time operator +(Time b) const
  { return value + b.value; }
  operator float() const
  { return value; }
};

float f(float a, float b)
{ return a + b; }

float g(Time a, Time b)
{ return a + b; }


Result: (with gcc.godbolt.org)
f(float, float):
    addss   %xmm1, %xmm0
    ret
g(Time, Time):
    addss   %xmm1, %xmm0
    ret