There's no need to load the 64-bit immediate into a temporary register.
x64 will sign-extend 32-bit immediates to 64 bits, giving us the exact
value we need in this case.
48 C7 C0 00 00 FF FF mov rax,0FFFFFFFFFFFF0000h
48 21 C2 and rdx,rax
48 81 E2 00 00 FF FF and rdx,0FFFFFFFFFFFF0000h