why software's speed is so slowly run on nios II

hello,my code is like this

word1=1;

word2=2;

word3=3;

word4=4;

word5=5;

//from this

check_sum=(word1&0x0000ffff)+(word1>>16)

+(word2&0x0000ffff)+(word2>>16)

+(word3&0x0000ffff)+(word3>>16)

+(word4&0x0000ffff)+(word4>>16)

(word5&0x0000ffff)+(word5>>16);

while(check_sum>>16)

check_sum=(check_sum&0x0000ffff)+(check_sum>>16);

if(check_sum==0x0000ffff)

errflag=0;

else

errflag=1;

//end this

I had found do check_sum need about 100 cycles with Nios/f and _g3 .is it true ?

In addition £¬if a=3,the data isn't in cache ,how many cycles will spend?