docs: def _kill(self, live_defs, variable, code_loc):
          """
          Kill previous defs. `addr_list` is a list of normalized addresses.
          """
  
          # Case 1: address perfectly match, we kill
          # Case 2: a is a subset of the original address
          # Case 3: a is a superset of the original address
  
          live_defs[variable] = { code_loc }
          l.debug("XX CodeLoc %s kills variable %s", code_loc, variable)