About g++ optimization

[address@hidden]

for(int i = 0; i < f(n); ++ i) {
...
}

If I have the above "for" statement and I compile it with -O3, will the
function "f(n)" be optimized such that f(n) will only be evaluated
once. Or I have to factor "f(n)" outside the loop to make sure that it
only be evaluated once?

Thanks,
Peng