Reader set encoding for directory of shared cache memory in multiprocessor system

In a multiprocessor system comprising

• a plurality of processors running speculative threads in parallel;
• and
• at least one cache shared by the processors,
• a method comprising:
• in a control unit of the cache, maintaining a dynamic record of read accesses to the cache, the record comprising for each cache line a format specification indication specifying a reader encoding format responsive to occurrence of a type of read access, said type including transactional memory (TM), thread level speculation (TLS) and rollback, the record comprises an identification of which speculative thread or threads has read a particular cache line, said identification in the form of a field that encodes thread identification numbers of a group of threads, wherein each bit of said field represents a group of IDs, an aggregate of all IDs is represented as the aggregate of all bits of the field;
• and a bit set in the field representing the cache line has been read by at least one ID of a corresponding group;
• directing memory accesses for a same physical address from any of the processors through a same memory addressing scheme of the control unit;
• abrogating recordation of portions of lines read responsive to one or more of:
• more than two speculative TM threads have read from the line, a mix of TM and TLS threads have read from the line, and TLS threads from different domains have read from the line;
• and
• performing conflict checking for all the processors of the system using the record to locate potential conflicts.