不懂流水灯的设计keil 编译的warning !!~求指导~谢谢

#include<reg52.h>
#define uint unsigned int
sbit D1=P1^0;
void delay(uint z);
void main()
{
while(1)
{
D1=0;
delay(10);
D1=1;
delay(10);
}
}
void delay(uint z)
{