If Compy Swarm leaves the battlefield before its triggered ability resolves, the token will still enter the battlefield as a copy of Compy Swarm, using Compy Swarm's copiable values from when it was last on the battlefield.

The token copy will have Compy Swarm's ability. It will also be able to create copies of itself.

The token copy won't copy counters or damage marked on Compy Swarm, nor will it copy other effects that have changed Compy Swarm's power, toughness, types, color, and so on. Normally, this means the token will simply be a Compy Swarm, but if any copy effects have affected the original Compy Swarm, the token will take those into account.