Programmable unit for metadata processing

A system and method for metadata processing that can be used to encode an arbitrary number of security policies for code running on a stored-program processor. This disclosure adds metadata to every word in the system and adds a metadata processing unit that works in parallel with data flow to enforce an arbitrary set of policies, such that metadata is unbounded and software programmable to be applicable to a wide range of metadata processing policies. This instant disclosure is applicable to a wide range of uses including safety, security, and synchronization.