[discuss] When is RBX used for base pointer?

[Michael Matz]

Hi,

On Wed, 13 Feb 2008, H.J. Lu wrote:

> Our proposal is at
> 
> http://gcc.gnu.org/ml/gcc/2007-12/msg00567.html
> 
> For most cases, we can align stack with RBP/RSP. But
> we need an extra register when there is dynamic stack
> allocation or nested functions. It has to be callee-saved
> to work with setjmp/longjmp.

I'm probably missing something, but why does it have to be a fixed 
register at all?  Why not simply saying "a free callee-saved register"?


Ciao,
Michael.