If in doubt, always call your vet or the Animal Poison Line immediately.
Dogs need some sodium in their diet but excessive salt causes sodium ion poisoning. It draws water out of cells and into the bloodstream, leading to dehydration, brain swelling, and in severe cases seizures and death. Salted crisps, pretzels, and other snacks are the most common source.
Ensure fresh water is available. If large amounts were eaten, contact your vet.