Details of Function Call

1. For each argument, use genarith to compute the argument. If needed, move the result from the register returned by genarith to %xmm0 and mark the genarith register unused.

2. For each volatile register that is in use, save it

3. Call the function

4. For each volatile register that is in use, restore it

5. Return the function result register ( %xmm0, %eax or %rax) as the result of genarith.