1. A computer program product for executing a load instruction for loading data from an adapter, said computer program product comprising: a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: obtaining, by a processor coupled to the adapter, a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction comprising: an opcode field identifying a load from adapter instruction; a first field identifying a first location at which data fetched from the adapter will be loaded; a second field identifying a second location, the contents of which include a function handle identifying the adapter, a designation of an address space within the adapter from which data is to be loaded, and an offset within the address space; and executing, by the processor, the machine instruction, the executing comprising: using the function handle to obtain a function table entry associated with the adapter, the function table entry stored in memory associated with the processor; determining a data address of the adapter using at least one of information in the function table entry and the offset; and fetching data from a specific location in the address space identified by the designation of the address space, the specific location identified by the data address determined based on execution of the machine instruction by the processor.