Yes, in principle a compiler is free to generate arbitrarily horrendous code regardless of what you ask it to do.
In practice, non-virtual function calls are reliably compiled to fairly efficient code while virtual calls are much less reliable.
In practice, non-virtual function calls are reliably compiled to fairly efficient code while virtual calls are much less reliable.
Like I said, this echoes the conventional wisdom that most C++ developers seem to retain. The compiler landscape has changed since that wisdom was formed, since the advent of LTO and devirtualization optimizations.
I’ve seen it simplify patches of code here and there, and that does apply to the trivial examples given in the post this topic links to - a function call involving a known child class. But add some basic real-world complexity and it quickly gets too complex for the optimiser to prove that it knows for sure what child class it is dealing with.