Re: robustness vs. conservative GC

[Fergus Henderson <fjh at cs dot mu dot oz dot au>]

On 30-Jul-2001, dewar@gnat.com <dewar@gnat.com> wrote:
> <<  Any scheme for doing exact GC without cooperation from the compiler
>   back-end needs to store pointers in a known location on the stack, rather
>   than in registers, so that they can be updated when objects are moved.
>   This denies the back-end compiler freedom to put such pointers in
>   registers.  Register allocation obviously has a big effect on performance.
> >>
> 
> I don't accept that, and there are most certainly counter examples to 
> this claim (e.g. IBM mainframe SPITBOL). It is fine to have pointers in
> registers, providing that you have sufficient information to track them
> down, i.e. know where the register values are saved.

I said "without cooperation from the compiler back-end".

I don't see how you can obtain that sufficient information
without cooperation from the compiler back-end.

-- 
Fergus Henderson <fjh@cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.