private MultiMap<Instruction, Instruction> calcBackwardMap() {
    MultiMap<Instruction, Instruction> result = MultiMap.create();
    for (Instruction instruction : myInstructions) {
      for (Instruction next : myForwardMap.get(instruction)) {
        result.putValue(next, instruction);
      }
    }
    return result;
  }
private MultiMap<Instruction, Instruction> calcBackwardMap()