Pointer Bit Manipulation: Unlocking Hidden Performance with Unused Bits

A 64-bit pointer can address far more memory than even the most powerful supercomputers need. This article explores pointer tagging, a clever technique leveraging unused bits in pointers (typically in the upper and lower ranges) to store extra data, such as type information or flags. This improves memory efficiency and performance by reducing cache misses and streamlining dynamic polymorphism. The article illustrates this with a C++ implementation, demonstrating how to pack and unpack data within pointers and showcasing its application in abstract syntax trees and other complex data structures.