Re: Intel P6 vs P7 system call performance

Linus Torvalds
2002-12-17T18:40:59Z

On 17 Dec 2002, Alan Cox wrote:
>
> Is there any reason you can't just keep the linker out of the entire
> mess by generating
>
> .byte whatever
> .dword 0xFFFF0000
>
> instead of call ?

Alan, the problem is that there _is_ no such instruction as a "call
absolute".

There is only a "call relative" or "call indirect-absolute". So you either
have to indirect through memory or a register, or you have to fix up the
call at link-time.

Yeah, I know it sounds strange, but it makes sense. Absolute calls are
actually very unusual, and using relative calls is _usually_ the right
thing to do. It's only in cases like this that we really want to call a
specific address.

Linus