Loop based code motion

[kirstenmg]

To be on par with peggy, we should implement loop based code motion.

Example:

original:

int x = 0;
while (x < 3) {
    x += 1;
}
return x * 5;

optimized:

int x = 0;
while (x < 15) {
    x += 5;
}
return x;