找不到库函数问题

# include<reg52.h>
# include<instrins.h>
# define led P2

void delay(int a)
{
 while(a--);

 }
 
 void main()
{
   int i=0;
   led=0xfe;
    delay(50000);
   while(1)
  {
   for(i=0;i<7;++i)
   {
      led=_crol_(led,1);
      delay(50000);
      }
      for(i=0;i<7;++i)
   {
      led=_cror_(led,1);
      delay(50000);
      }
        
      }
      }
      
   
 大家帮我看一下这个为什么运行会出现: warning C318: can't open file 'instrins.h'