It can be dangerous to use a table saw to cut logs. With a normal lumbar, there is a flat area that can be used to create stability during the cutting process. However, logs are completely round, making them unstable and able to roll and bounce when trying to cut. Logs straight from the forest won't have been treated and will have retained dirt and sap, which further affects the blade of the table saw.  These are good reasons not to use your table saw to cut logs, however, it is still possible. If you decide to cut your logs on a table saw, do so carefully and don't rush. It is best to split large logs as the cut depth is limited to the saw blade depth. It's also worth using a sort of jig so you can secure the log in order to help it pass through the blade.  It's useful to remember that you can break or bend saw blades whilst cutting logs, so ensure the logs are kept small to prevent damage.