anchor.diff:          (inst sub count 1)
           (inst jmp :nz repeat))
   
  -      (progn
         (inst movdqa x0 (nth-xmm-mem state 0))
         (inst movdqa x1 (nth-xmm-mem state 1))
         (inst movdqa x2 (nth-xmm-mem state 2))
  
positive.code:         (inst sub count 1)
          (inst jmp :nz repeat))
  
        (progn
        (inst movdqa x0 (nth-xmm-mem state 0))
        (inst movdqa x1 (nth-xmm-mem state 1))
        (inst movdqa x2 (nth-xmm-mem state 2))
  
negative.code:       (inst movdqa (nth-xmm-mem buffer 0) x0)
        (inst movdqa (nth-xmm-mem buffer 1) x1)
        (inst movdqa (nth-xmm-mem buffer 2) x2)
        (inst movdqa (nth-xmm-mem buffer 3) x3))))
  
  #+x86-64
  (define-vop (chacha-core-fast)
  