Optimizations for leaf objects #385
Description
Leaf objects are objects that do not contain any reference (they do not reference other objects, thus 'leaf' in the graph). For leaf objects, we do not need to scan them.
We can simply use address segragation for leaf objects, e.g. provide a space specifically for leaf objects. If locality is a concern, we can use tagged pointer for leaf objects with double mapping (mapping two address ranges to the same physical memory, and the two addresses only have 1 bit difference in one of the high-order bits).