Missing time when using timer

Question

I have set up Timer2 to count every tick at 16MHz, or 62.5ns per tick. Then I run the following code:

int t = 0;
 for (int i=0;i<64;i++){
 data[4*i] = TCNT2;
 data[4*i+1] = TCNT2;
 byte now = data[4*i+1];
 byte last = data[4*i];
 t += now > last? (long)(now-last) : 256 -(long)(last-now);
 data[4*i+2] = TCNT2;
 data[4*i+3] = TCNT2; 
 }
}
for (int i=0;i<255;i++){
 Serial.println(data[i]-data[i+1]);
}

and I get the output: "4 4 4 11" (repeated) which makes sense, 4 clock cycles to read TCNT2 and write it to the correct place in data and 11 cycles when also evaluating the loop condition. However, I can't understand when the variable t is updated. I have tried running with and without t and both give the same timings. From my (obviously lacking) understanding updating a variable is at minimum one instruction, so how can it do it under one clock cycle? Am I misunderstanding what one instruction is or does the TCNT2 counter for the timer not update accurately here?

Answer 1

Ops, I just realized it's the compiler working it's magic. I never used t, thus the compiler said "Wtf is this guy doing, this t is useless and I'll remove it!". When I used t I got sensible results.