These instructions perform dynamic lookup of class and generic methods.
The class_method and super_method instructions must reference Swift native methods and always use vtable dispatch.
The objc_method and objc_super_method instructions must reference Objective-C methods (indicated by the foreignmarker on a method reference, as in #NSObject.description!1.foreign).
witness_method
https://github.com/apple/swift/blob/master/docs/SIL.rst#id129