Register allocation error

[mateoconlechuga]

This code:

short foo(unsigned char *data, unsigned long a, unsigned char b)
{
    short var = a / 2 + b;

    for (unsigned char i = 0; i < 8; i += 2)
    {
        var += data[i];
    }

    return var;
}

Results in error: ran out of registers during register allocation when any optimization level is used.