Segment register support for the i386

[Denis Chertykov]

Richard Henderson <rth@cygnus.com> writes:

> On Mon, Dec 27, 1999 at 05:55:06AM -0700, Jeffrey A Law wrote:
> > Yes CSE and other passes would all have to know about this kind of
> > stuff.  Though I don't think it would be that nasty since a seg + offset
> > pointer would have a different mode than just an offset pointer.
> > 
> > The tougher problem is the general infrastructure to have pointers of
> > differing sizes, supporting partial mode arithmetic, and ABI issues with
> > segment/space registers.
> 
> As pointed out in other mail, Mark wasn't looking for 48-bit pointers,
> rather different address spaces.  Conceptually, this is actually much
> more like the `__X' and `__Y' address spaces from DSP-land, and I have
> proposed in the past treating them similarly.
> 
> I believe my original thought was to do this with extra modes, so that
> you'd have P_Xmode and P_Ymode (P_GSmode and P_FSmode in the x86 case)
> to disambiguate the different address spaces.

It's a good solution for harvard architectures too.
(DSP's and micro controllers)
Something like PCODEmode and PDATAmode.

Denis.