Comment by michidk

I was able to shave off one additional byte with this:

  ...
  xor rax, rax       ; = 0
  inc rax            ; = 1 - syscall: sys_write
  mov rdi, rax       ; copy 1 - file descriptor: stdout
  lea rsi, [rel msg] ; pointer to message
  mov rdx, 14        ; message length
  syscall
  ...

  $ nasm -f bin -o elf elf.asm; wc -c elf; ./elf
  166 elf
  Hello, World!

So I guess NASM already optimizes this quite well

However, using the stack-based instructions as xpasky hinted at:

  ...
  push 1             ; syscall: sys_write
  pop rax
  pop rdi       ; copy 1 - file descriptor: stdout
  lea rsi, [rel msg] ; pointer to message
  push 14            ; message length
  pop rdx
  syscall
  ...

I get down to 159 bytes! I updated the article to reflect that