Rules Reference's page

...(not sure how that works in the case of a weapon with multiple physical damage types)!

When a weapon has multiple damage types, it either does all types at the same time ("B and P" e.g. morningstar) or the wielder can choose the damage type ("P or S" e.g. dagger). In either case, as long as the weapon can deal a single type of damage that bypasses DR, the attack bypasses DR.

Of course, if you're unaware of the DR, and you're wielding an "or" weapon, it's possible to choose the wrong type (slashing a skeleton, oops).

Type: Weapons are classified according to the type of damage they deal: B for bludgeoning, P for piercing, or S for slashing. Some monsters may be resistant or immune to attacks from certain types of weapons.

Some weapons deal damage of multiple types. If a weapon causes two types of damage, the type it deals is not half one type and half another; all damage caused is of both types. Therefore, a creature would have to be immune to both types of damage to ignore any of the damage caused by such a weapon.

In other cases, a weapon can deal either of two types of damage. In a situation where the damage type is significant, the wielder can choose which type of damage to deal with such a weapon.