anchor.diff:              (let #+x86 ((rax sb-vm::eax-tn)
                           (rcx sb-vm::ecx-tn)
                           (rdi sb-vm::edi-tn))
  +                 #-x86 ()
                 #+x86
                 (progn
                   (unless (sb-vm::location= fill-word rax)
  
positive.code:          (defmacro ,memset-name (ptr index n-words fill-word
                                   &key
                                     (scale +fixnum-zero-mask+1+) (offset 0))
             (let ((memset-fun ',%memset-name))
               `(,memset-fun ,ptr ,index ,n-words ,fill-word ,scale ,offset)))))))
  
  
  
  
negative.code:             (let #+x86 ((rcx sb-vm::ecx-tn)
                          (rsi sb-vm::esi-tn)
                          (rdi sb-vm::edi-tn))
                   #-x86 ()
                #+x86
                (progn
                  (unless (sb-vm::location= n-words rcx)
  