+(defun ref-good-for-dx-p (ref)
+ (let* ((lvar (ref-lvar ref))
+ (dest (when lvar (lvar-dest lvar))))
+ (and (combination-p dest)
+ (eq :known (combination-kind dest))
+ (awhen (combination-fun-info dest)
+ (or (ir1-attributep (fun-info-attributes it) dx-safe)
+ (and (not (combination-lvar dest))
+ (awhen (fun-info-result-arg it)
+ (eql lvar (nth it (combination-args dest))))))))))
+