This White Paper is an introduction to porting existing code to the A64 instruction set supported by ARMv8-A processors like the Cortex-A53 and Cortex-A57 from ARM. It will also be useful for those writing new code for these platforms.
Why 64-bit? It seems that is a question with many answers! For some, it will be the need to address more than 4GB of memory, for others the need for wider registers and greater accuracy of 64-bit data
processing, for still others the attraction of a larger register set.
Whatever your reason for looking to move to 64-bit, it is likely that you will have a body of legacy software which will need porting as well as new code which needs writing. This paper is designed to help with both processes.
We’ll start with a quick look at the evolution of the ARM architecture which has brought 64-bit to reality.