anchor.diff:  
   (defmethod emit-lap (backend-function (instruction x86-tail-call-instruction) uses defs)
     (call-argument-setup (call-arguments instruction))
  +  (maybe-log-missed-builtin (call-function instruction))
     (emit `(lap:mov64 :r13 (:function ,(call-function instruction))))
     (cond ((<= (length (call-arguments instruction)) 5)
            (emit `(lap:leave)
  
positive.code: (defun emit-gc-info (&rest metadata)
    (emit `(:gc :frame :layout ,*current-frame-layout* ,@metadata)))
  
  (defgeneric lap-prepass (backend-function instruction uses defs)
    (:method (backend-function instruction uses defs) nil))
  (defgeneric emit-lap (backend-function instruction uses defs))
  
negative.code:     (when (not (zerop n-stack-args))
        (emit `(lap:add64 :rsp ,(* n-stack-args 8))))))
  
  (defun maybe-log-missed-builtin (fn)
    (when (gethash fn mezzano.compiler.codegen.x86-64::*builtins*)
      (incf (gethash fn *missed-builtins* 0))))
  
  (defmethod emit-lap (backend-function (instruction call-instruction) uses defs)
    (call-argument-setup (call-arguments instruction))
    (maybe-log-missed-builtin (call-function instruction))
    (emit `(lap:mov64 :r13 (:function ,(call-function instruction)))
          `(lap:call (:object :r13 ,sys.int::+fref-entry-point+)))
    (call-argument-teardown (call-arguments instruction)))
  
  (defmethod emit-lap (backend-function (instruction call-multiple-instruction) uses defs)
    (call-argument-setup (call-arguments instruction))
    (maybe-log-missed-builtin (call-function instruction))
    (emit `(lap:mov64 :r13 (:function ,(call-function instruction)))
          `(lap:call (:object :r13 ,sys.int::+fref-entry-point+)))
    (emit-gc-info :multiple-values 0)
  