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,
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.