Techniques for optimizing program code through property merging are described. In an embodiment, a compiler identifies, from a plurality of properties of a particular data object that are referenced by the program code, one or more candidate sets of properties that are eligible for merging. For a respective candidate set of properties of the one or more candidate set of properties, the compiler determines whether to merge different properties of the particular data object that belong to the respective candidate set of properties. After determining to merge the different properties, a particular data structure is generated, within the memory of a computing device, that stores the different properties of the particular data object that belong to the respective candidate set.