Comment by _0w8t

When there are more bits in a pointer than NaN 52 bits allows, the trick is to replace pointers with indexes from the start of JS heap. This is not efficient even with arrangement like having heap aligned, say, on 4GB or even more granular address so to get the full pointer one just use bit operation, not an add. But if one wants efficiency, then make sure that types in the code is stable and JIT will generate type-specific code.