code: public ValueType getInstance(Instruction ins, ConstantPoolGen cpg) throws DataflowAnalysisException {
          return getStackValue(getInstanceStackLocation(ins, cpg));
      }
docs: Get the value corresponding to the object instance used in the given
  instruction. This relies on the observation that in instructions which
  use an object instance (such as getfield, invokevirtual, etc.), the
  object instance is the first operand used by the instruction.
  
  @param ins
  the instruction
  @param cpg
  the ConstantPoolGen for the method