A coroutine call instruction.The instruction pops the top of stack into temporary register, pushes program counter onto the stack, and then puts the saved top of stack in the program counter.

• 一种协同程序访问指令，该指令把栈顶弹入临时寄存器，把程序计数器推入栈内，然后把保存的栈顶内容存入到程序计数器内。