i am arriving in Terminal 1 flying from Amsterdam to Shanghai and need to transfer to Terminal 2 headed to Manila the same day.

Although there are free shuttle buses between the terminals, I remember you still have to pass the immigration. Anyway, no need to get worried! Any passenger whose transit duration is within 24h is visa-free in the airport, so you can still use your single entry visa for another possible trip.
To better ensure the procedure, you can dial 021-96990 to ask.