@Override
	public AssignAction clone(ParamListStandard newResource) throws InvalidInputException {
		return new HiddenReturnAssign(newResource, retCode);
	}
Allocate the return value as an input parameter

A pointer to where the return value is to be stored is passed in as an input parameter.
This action signals this by returning one of
  - HIDDENRET_PTRPARAM         - indicating the pointer is allocated as a normal input parameter
  - HIDDENRET_SPECIALREG       - indicating the pointer is passed in a dedicated register
  - HIDDENRET_SPECIALREG_VOID

Usually, if a hidden return input is present, the normal register used for return
will also hold the pointer at the point(s) where the function returns.  A signal of
HIDDENRET_SPECIALREG_VOID indicates the normal return register is not used to pass back
the pointer.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/lang/protorules/HiddenReturnAssign.java