A receiving node in a computer system that includes a plurality of types of execution units receives an active message from a sending node. The receiving node compiles an intermediate language message handler corresponding to the active message into a machine instruction set architecture (ISA) message handler and the receiver executes the ISA message handler on a selected one of the execution units. If the active message handler is not available at the receiver, the sender sends an intermediate language version of the message handler to the receiving node. The execution unit selected to execute the message handler is chosen based on a field in the active message or on runtime criteria in the receiving system.