"I find life…long"

In the film version of John Fowles's novel The Magus (1965), "Conchis" (Anthony Quinn) recites a poem for "Urfe" (Michael Caine) that he claims is from the T'ang Dynasty:

Here at the frontier there are falling leaves.
Although my neighbours are all barbarians, and you,
You are a thousand miles away,
There are always two cups on my table.

But no such poem exists -- at least not from that era. What does exist are a couple of poems that, when combined, might supply it.