Re: Debian ports for RiscPC, ARM710, etc.
On Mon, Sep 28, 1998 at 10:37:58AM -0700, Jim Pick wrote:
>
> Philip Blundell <pb@nexus.co.uk> writes:
>
> > >Most of the things should work - but on a StrongARM RiscPC only. Since
> > >I've got an ARM710 there'll be no chance using the binary packages on my
> > >system.
> >
> > Once everything is working on StrongARM it will be a no-brainer operation to
> > recompile everything with the right CFLAGS for ARM710. In fact the NetWinder
> > packages won't even work on a StrongARM RiscPC because of the halfword
> > problem. They should be OK out of the box on an EBSA or similar.
>
> I'm wondering what we should do for the Debian port to support more
> machines than just the NetWinder.
>
> Right now, we've built gcc with the --with-cpu=strongarm option, and
> we are compiling all the packages with the normal CFLAGS options.
> We're using the Corel patched gcc right now, but plan on moving to
> Philip's egcs.
>
> So I suppose we are building binaries that use the halfword
> instructions. Is that correct?
Yes. You can always objdump --disassemble |grep LDRH to check ;-)
> In the interests of portability, what would be the performance cost if
> we somehow compiled things without the halfword instructions? Do all
> apps benefit, or just some specific ones? Corel is using them for
> their RPM-based distribution, so I have assumed that there is a
> significant performance difference.
I don't think there's too much of a performance issue. One or two
additional instructions per short loaded, two extra ones per short
stored.
> As Philip says, it would be a no-brainer to create additional
> debian-arm distributions which have been compiled to use different
> instruction sets, since they can share the same source (actually, all
> Debian architectures use the same source). ie. We could have an
> "arm-riscpc" distribution, and maybe even an "arm-710" (??)
> distribution for older machines. Of course, this is only going to
> happen if there is enough interest.
you'd almost certainly want to use arm6 as the baseline - arm710 doesn't
have anything that needs changing in userland.
> If anybody wants me to, I could build a chroot image and a set of
> packages that have been compiled to use a different instruction set
> and put them on my FTP site.
>
> Is anybody interested in such a thing? There isn't much point in me
> doing it if nobody is going to try it, since I don't have the hardware
> to test it on.
Yes, I'm willing to test..
> I suppose I can lookup what flags to use from the source for the
> Linux/ARM distribution. Or maybe somebody could tell me?
It was -m6 for gcc 2.7, but egcs & gcc 2.8 moved to -march=3.
Or something similar, my GCC docs are out of date right now and I can't
test easily.
--
Matthew Wilcox <willy@bofh.ai>
"I decry the current tendency to seek patents on algorithms. There are
better ways to earn a living than to prevent other people from making use of
one's contributions to computer science." -- Donald E. Knuth, TAoCP vol 3
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