Once the callee has finished processing, it restores SP from BP if it had allocated local stack space, then pops the previous value of BP, and returns via RETF.

• 一旦被调用函数完成了处理，且如果它曾经分配了局部堆栈空间的话，它将从BP中恢复SP的值，然后把以前的BP值压出堆栈，并通过RETF返回。