[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: FOSDEM thoughts


On Tue, 26 Feb 2008, Finn Thain wrote:

> On Mon, 25 Feb 2008, Christian T. Steigies wrote:
> > > Getting the coldfire port working would be nice, yes... I believe that 
> > > would bring in fresh blood and a general boost for debian-68k/cf...
> > 
> > We had a discussion with Aurelien, Geert and Sven about coldfire. The 
> > consensus was that we should not make cf a separate port, since we would 
> > probably loose all m68k developers in that case. I personally am 
> > interested in cf only if it can help m68k,
> That is my interest too. But surely that argues against your first 
> statement about losing developers?

As much as I understand to keep as much as possible common, I don't have 
much hope if I look at it from the technical perspective. IMO a common 
port would have too much restrictions and neither could use any of the 
advantages either architecture has to offer.

> What concerns me is that both 680x0 and CF code would be compromised if 
> one port were to try to support both.
> I don't know if anyone can confirm this example, but it looks like no-one 
> gets to use div without adding compatibility code,
> http://acp.atari.org/articles/mcf5407eval/mcf5407eval.html#Modifications%20of%20the%20MiNT%20kernel

CF doesn't have the divul.l instruction, it has a remu.l instruction, 
which unfortuately has the same opcode as divul.l (so the some machine 
instruction will return quotient/remainder on m68k, but only the 
remainder on CF).
The trick used there produces a signed and an unsigned divide, so that gcc 
won't merge both operations into a single instruction.

bye, Roman

Reply to: