Convert the below C code snippet to ARMv8 assembly code. Assume variables a, b, and c are stored in registers X20, X21, and X22 respectively and the array x is stored as a static array in the data section. Assume all the values are 64-bits and are unsigned integers. Do not use divide and multiply instructions in your code.

a = b - c;

x[2] = a + x[1];

x[a] = x[2] + 4*x[b];

x[2*b] = x[a] + x[c/2];