US Patent 7747659 Garbage collector with eager read barrier

A garbage collection system that needs to meet real-time requirements uses an eager read barrier that performs a forwarding operation as soon as a quantity is loaded. The barrier maintains a to-space invariant by including a forwarding pointer in the header of objects to be moved or accessed that normally points to the object itself. However, if the object has been moved, the forwarding pointer points to the new object location. The eager read barrier maintains the registers and stack cells such that the registers and stack cells always point into to-space. Barrier-sinking and common sub-expression elimination are used to minimize the overhead associated with the read barrier.