Write a function that returns the sum of its two parameters. The parameters and return values are both 64-bit integers. 64-bit operands are passed in two consecutive registers. Thus, the first parameter is in r4 and r5, while the second parameter is in r6 and r7, with the return value returned in r2 and r3.
long long add64 (long long a, long long b);
Expected solution length: Around 5 lines.
Write your solution here