Harris played in only one game last season, the last one of the regular season against Minnesota. He was signed last year by the Lions to compete to start at right guard, a job that was won by rookie Larry Warford. Harris previously started 42 of 76 games for the Tennessee Titans.
Irvin played in six games as a reserve last season in Dallas. He has played in 24 career games, all as a backup, for the Cowboys, Tampa Bay, Jacksonville and Carolina. The Panthers selected him in the third round of the 2009 NFL draft out of Georgia.
The moves were announced Tuesday.