KEIL用C语言加入PUSH，POP

在keil C51中，直接调用库函数：
＃include<intrins.h> // 其中包含了对部分汇编指令的调用申明

_nop_(); // 产生一条NOP指令
_push_(acc); // 产生一条push指令

以下是intrins.h的内容
/*--------------------------------------------------------------------------
INTRINS.H

Intrinsic functions for C51.
Copyright (c) 1988-2004 Keil Elektronik GmbH and Keil Software, Inc.
All rights reserved.
--------------------------------------------------------------------------*/

#ifndef __INTRINS_H__
#define __INTRINS_H__

extern void _nop_ (void);
extern bit _testbit_ (bit);
extern unsigned char _cror_ (unsigned char, unsigned char);
extern unsigned int _iror_ (unsigned int, unsigned char);
extern unsigned long _lror_ (unsigned long, unsigned char);
extern unsigned char _crol_ (unsigned char, unsigned char);
extern unsigned int _irol_ (unsigned int, unsigned char);
extern unsigned