Is the register keyword still used?

Question

Just came across the register keyword in C++ and I wondered as this seems a good idea (keeping certain variables in a register) surely the compiler does this by default?

Answer 1

Probably the only remotely serious use for the register keyword left is a GCC extension that allows you to use a hard-coded hardware register without inline assembly:

register int* foo asm("a5");

This will mean that any access to foo will affect the CPU register a5.

This extension of course has little use outside of very low-level code.