1. A data processing method comprising employing at least one processor to perform the steps of: receiving high-level source code containing a reference to an internal field of a data structure; and from the high-level source code, generating a low-level language memory access instruction for the internal field, the low-level language memory access instruction including an identifier of a memory address offset of the internal field relative to a base address of the data structure, and an identifier of a field bitspan within a word, wherein the field bitspan defines an intra-byte field start position and a field length, and wherein the identifier of the memory address offset and the identifier of the field bitspan are not necessarily distinct.