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Re: Adding soft-registers
- From: Eric Botcazou <ebotcazou at libertysurf dot fr>
- To: James Dessart <james at skwirl dot ca>
- Cc: Stephane Carrez <stcarrez at nerim dot fr>,gcc at gcc dot gnu dot org
- Date: Fri, 9 Jan 2004 09:01:42 +0100
- Subject: Re: Adding soft-registers
- References: <Pine.LNX.4.10.10401081617280.15627-100000@coatl.skwirl.ca>
> There is a difference, a rather big one, in the direct mode. The HC11 and
> HC12s only address page 0. The 6809 has a register to configure which 256
> byte page that the direct mode points at.
I agree with Stephane that this is not signicant from GCC viewpoint.
> So the page 0 implementation that those ports use is limited. What would
> be nice is a run-time configured page that contains the registers. The
> direct page register could be configured in the runtime, and the compiled
> code wouldn't know the difference. The problem is that the segment that
> would be used would need to be on a page boundary... I'm not sure the
> assembler or linker are properly set up to do that sort of thing in a
> memory-efficient way. What do you think, Eric?
Nothing worth mentioning. I have never really investigated playing with the
DP register.
> Other than me, you're probably the one who's played with those tools the
> most, and perhaps the author. :)
Not that much. And by that time, I was new to GCC so I was already very
happy to have sort of a working compiler :-)
I think that, if you want to enhance the 6809 port, you should consider
switching to the HC11/HC12 back-end, instead of trying to re-implement
similar constructs. It is much more complete and up-to-date. And you could
still ask your questions in French :-)
--
Eric Botcazou