Formally specifying memory consistency models and automatically generating executable specifications

Memory ordering properties of shared memory multiprocessors are more subtle and less well understood than cache coherence. These properties tend to be processor or platform specific and are not always formally specified. It is difficult to compare even those platforms whose memory ordering properties have been clearly specified as each such platform is usually specified in its own definitional framework. We present a generic and formal specification scheme to specify any realistic memory consistency model that gives an intuitive undertstanding to architects, and implementors of platforms whose memory model is being defined and also a common definitional framework to compare memory models. Another contribution of the paper is to generate an executable specification automatically, given the specification of any memory consistency model expressed in our newly defined framework. This alternative specification can be used to generate all possible outcomes of small assembly-language multiprocessor programs in a given memory model, which is very helpful for understanding the subtleties of the model. The executable specification can also check the correctness of assembly language programs including synchronization routines.