tail id prev' (G.ZTail m t) rest = tail id (mid m : prev') t rest
tail id prev' (G.ZLast G.LastExit) rest = exit id prev' rest
tail id prev' (G.ZLast (G.LastOther l)) rest = last id prev' l rest
mid (MidComment s) = CmmComment s
mid (MidAssign l r) = CmmAssign l r
mid (MidStore l r) = CmmStore l r
tail id prev' (G.ZTail m t) rest = tail id (mid m : prev') t rest
tail id prev' (G.ZLast G.LastExit) rest = exit id prev' rest
tail id prev' (G.ZLast (G.LastOther l)) rest = last id prev' l rest
mid (MidComment s) = CmmComment s
mid (MidAssign l r) = CmmAssign l r
mid (MidStore l r) = CmmStore l r