What is the difference between caller save and callee save registers in terms of their impact on program performance and efficiency?

Caller save registers are saved and restored by the calling function, while callee save registers are saved and restored by the called function. Caller save registers can lead to faster function calls but may require more instructions to save and restore values. Callee save registers can lead to slower function calls but may result in better overall program efficiency by reducing the need for saving and restoring values frequently.