There are a number of specializations of CALL_FUNCTION that make sense:

• Calls to a Python function where the arguments and parameters match exactly.
• Calls to a Python function with keyword arguments, or defaults, when the argument shuffle can be pre-computed.
• Calls to builtin functions.
• Calls to specific builtin functions, specifically len and instance.
• Calls to type with a single argument.
• Instantiation of a "normal" class, that is a class that does not redefine __new__ and whose metaclass is type.