1. A method in a data processing system for atomically updating a first bit field in a second bit environment, wherein the first bit field word size exceeds the word size supported by the second bit environment, the method comprising: executing a load and reserve indexed instruction in response to a determination that a data request applies to a first bit object in a second bit execution environment, wherein the load and reserve indexed instruction creates a reservation for a memory location; decomposing the first bit object into low-order bits and high-order bits; preserving the low-order bits in a low-order word in a first register; preserving the high-order bits in a low-order word in a second register, wherein the high-order bits are preserved to allow for returning the original value of the first bit object in the second bit execution environment when the reservation is lost; executing a store conditional indexed instruction, wherein the store conditional indexed instruction stores a result to the memory location if the reservation has remained valid; and reconstructing the first bit object with the low-order bits and the high-order bits if the reservation is lost.