On Saturday, July 26, 2025, Frederick Virchanza Gotham wrote:

>
> The opcode + operand to compare a register value with 0xFFFFFFFFFFFFFFFF
> is a few more bytes. Plus the 'jump' instructions have optimised forms such
> as 'jump if zero' and 'jump if non-zero' which are perfect for branching on
> nullptr.
>


We could actually use these optimized instructions for all bits one simply
by flipping all the bits before comparing:

     not rdi // flip all one's to all zero's
     test rdi, rdi
     jz target_label