单片机频率计程序设计报错c275expression with possibly no effect

问题遇到的现象和发生背景

4848894.c(21): warning C275: expression with possibly no effect
4848894.c(25): warning C275: expression with possibly no effect
4848894.c(30): warning C275: expression with possibly no effect
4848894.c(35): warning C275: expression with possibly no effect
4848894.c(40): warning C275: expression with possibly no effect
4848894.c(45): warning C275: expression with possibly no effect
4848894.c(49): warning C275: expression with possibly no effect
4848894.c(88): warning C294: unreachable code

问题相关代码，请勿粘贴截图

#include <REGX51.H>
signed char code table[10]={0xa0,0xbb,0x62,0x2a,0x39,0x2c,0x24,0xba,0x20,0x28};
char Ledbuffer[8]="";
unsigned char temp,f,times,yc,FH,FL;
void delay(unsigned int n)
{
unsigned char j,k;
for(j=0;j<n;j++)
for(k=0;k<500;k++);
}
void timer()
{
TMOD=0x51;
ET0=ET1=1;
EA=1;
TR0=TR1=1;
}
void caizi()
{
temp=f;
Ledbuffer[7]=table[temp%10];temp/10;
if(temp==0)
Ledbuffer[6]=0xff;
else
{Ledbuffer[6]=table[temp%10];temp/10;
if(temp==0)
Ledbuffer[5]=0xff;
else
{
Ledbuffer[5]=table[temp%10];temp/10;
if(temp==0)
Ledbuffer[4]=0xff;
else
{
Ledbuffer[4]=table[temp%10];temp/10;
if(temp==0)
Ledbuffer[3]=0xff;
else
{
Ledbuffer[3]=table[temp%10];temp/10;
if(temp==0)
Ledbuffer[2]=0xff;
else
{
Ledbuffer[2]=table[temp%10];temp/10;
if(temp==0)
Ledbuffer[1]=0xff;
else{
Ledbuffer[1]=table[temp%10];temp/10;
if(temp==0)
Ledbuffer[0]=0xff;
else
Ledbuffer[0]=table[temp%10];
}
}
}
}
}
}

}
void leddisplay()
{
unsigned char x;
for(x=0;x<8;x++)
{P0=Ledbuffer[x],P2=0x80>>x;delay(1);}
}
void TO_interserve() interrupt 1 using 1
{
TH0=15535/256;
TL0=15535%256;
times++;
if(times==20)
{times=0;
FH=TH1;
FL=TL1;
f=yc65536+FH256+FL;
}
}
void T1_interserve() interrupt 3 using 2
{yc++;
}
void main()
{
timer();
while(1);
{
caizi();
leddisplay();
}
}

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果

变量f和yc定义的时候加上volatile。