Write an ARMv8 assembly program to compute the sum of squares of first n even natural numbers and store the sum. Write an ARMv8 assembly function to compute and use the function to compute the sum of squares of first n even natural numbers. The input n is in X20 and is 64-bit, non-zero positive integer less than 1001. Store the sum in X21. Assume all the registers are used by the caller function to store some data before calling the function. Do not use the divide instruction. Assemble, test, and simulate the assembly code using DS-5 simulator.

Please comment the assembly code.