;;; In copy propagation, we manipulate sets of TNs. We only consider TNs whose
;;; sole write is by a MOVE VOP. This allows us to use a degenerate version of
;;; reaching definitions: since each such TN has only one definition, the TN
;;; In copy propagation, we manipulate sets of TNs. We only consider TNs whose
;;; sole write is by a MOVE VOP. This allows us to use a degenerate version of
;;; reaching definitions: since each such TN has only one definition, the TN