code: private void checkUnconditionalDerefDatabase(Location location, ValueNumberFrame vnaFrame, UnconditionalValueDerefSet fact)
              throws DataflowAnalysisException {
          ConstantPoolGen constantPool = methodGen.getConstantPool();
  
          for (ValueNumber vn : checkUnconditionalDerefDatabase(location, vnaFrame, constantPool,
                  invDataflow.getFactAtLocation(location), typeDataflow)) {
              fact.addDeref(vn, location);
          }
      }
docs: Check method call at given location to see if it unconditionally
  dereferences a parameter. Mark any such arguments as derefs.
  
  @param location
  the Location of the method call
  @param vnaFrame
  ValueNumberFrame at the Location
  @param fact
  the dataflow value to modify
  @throws DataflowAnalysisException