Status of the DLX backend for GCC?

Status of the DLX backend for GCC?

[Gerald Pfeifer]

At http://www.gnu.org/software/gcc/extensions.html we have a reference
to the DLX port of GCC, which corresponds to the DLX machine described
in "Computer Architecture: A Quantitative Approach" by Hennessy and 
Patterson.

Sadly, the link to http://www-mount.ee.umn.edu/~okeefe/mcerg/gcc-dlx.html 
doesn't work and I failed to find a replacement page.  Any pointers?

On the binutils side I see that Nikolaos has been listed as a maintainer, 
so there may be hope? :-)  Otherwise I'm afraid we'll have to remove our
reference to the DLX port.

Gerald

Re: Status of the DLX backend for GCC?

[nkavv]

Hi Gerald and friends

(what follows is a copy of a message sent earlier today to Gerald)

> At http://www.gnu.org/software/gcc/extensions.html we have a reference
> to the DLX port of GCC, which corresponds to the DLX machine described
> in "Computer Architecture: A Quantitative Approach" by Hennessy and
> Patterson.

First of all, i will be happy to help, and if applicable to submit my own DLX
backend.

Over the previous years, I had downloaded and used both a really archaic
gcc-1.09 DLX backend as well as the one you refer too. They are both in a sad
state of affairs, but the gcc-2.7.2.1 (AFAICR) was usable.

Since i wanted to use a DLX cross-compiler for embedded system development (and
to produce objects for the ArchC -- http://www.archc.org -- simulator
infrastructure), I coded my own DLX backend for GCC. I developed it around
September-October 2006, first for the 3.3.1 release and then updated its state
for the 3.4.4.

This backend is usable (i used it quite a lot) and has the following features
and non-features :)

- no proper handling of 64-bit moves
- no support for soft-float
- a couple of additions to the "standard" DLX ISA, a select (conditional move)
instructions for partial predication, inspired by the Machine-SUIF select IR
instruction. This one really works well (was adapted from MIPS32 movn, movz).

If there is interest, i can submit the backend (where exactly in the cvs tree?)
and with the help of the community can fix the 64-bit moves issue, plus add
soft-floating.

> On the binutils side I see that Nikolaos has been listed as a maintainer,
> so there may be hope? :-)  Otherwise I'm afraid we'll have to remove our
> reference to the DLX port.

Actually, I had stepped up as a binutils DLX maintainer for more-less the same
reasons. I work on my own soft processors for FPGA-based embedded systems and
DLX is a reference for comparisons.

I'm having a small sabbatical from late Feb. to May 10 during which i will
mostly polish my software projects. I can submit the backend in next days
(prior 5-6 January) and fix most issues prior May 10 (joining the army for
9-month military service :)

Kind regards
Nikolaos Kavvadias

PS: My own version of the binutils DLX port supports the "select" instruction. I
should submit this as well.

Re: Status of the DLX backend for GCC?

[Serge Belyshev]

nkavv@physics.auth.gr writes:

> Over the previous years, I had downloaded and used both a really archaic
> gcc-1.09 DLX backend as well as the one you refer too. They are both in a sad
> state of affairs, but the gcc-2.7.2.1 (AFAICR) was usable.
>

Offtopic: if you still have such an old gcc-1.09 (?) release around, please make
it available so it can be uploaded here: ftp://sourceware.org/pub/gcc/old-releases/

Re: Status of the DLX backend for GCC?

[nkavv]

> Offtopic: if you still have such an old gcc-1.09 (?) release around, please
> make
> it available so it can be uploaded here:
> ftp://sourceware.org/pub/gcc/old-releases/

Oops, reality check :)

My glibc version for DLX is 1.09. The GCC version seems to be either 1.37.1 or
more probably 1.39. Which i think you already have ^_^

Nikolaos Kavvadias

PS: Nice repo of old releases!

Re: Status of the DLX backend for GCC?

[Gerald Pfeifer]

Hi Nikolaos,

On Sun, 30 Dec 2007, nkavv@physics.auth.gr wrote:
> Over the previous years, I had downloaded and used both a really archaic 
> gcc-1.09 DLX backend as well as the one you refer too. They are both in 
> a sad state of affairs, but the gcc-2.7.2.1 (AFAICR) was usable.

do you have a working download location for the latter?  Right now,
http://www.gnu.org/software/gcc/extensions.html has a broken link
and I'd like to address this if possible.

> I coded my own DLX backend for GCC. I developed it around 
> September-October 2006, first for the 3.3.1 release and then updated
> its state for the 3.4.4.
> [...]
> If there is interest, i can submit the backend (where exactly in the
> cvs tree?) and with the help of the community can fix the 64-bit moves 
> issue, plus add soft-floating.

I'm not able to approve a change like this (that's left to some others
here), but if you'd like to put this up for download somewhere and submit
a patch against http://www.gnu.org/software/gcc/extensions.html to give
it more exposure, that would a very good first step!

For details on how to submit a patch against current GCC sources, our
page at http://gcc.gnu.org/contribute.html should provide a good overview.

Cheers,
Gerald

Re: Status of the DLX backend for GCC?

[nkavv]

Hi Gerald

> do you have a working download location for the latter?  Right now,
> http://www.gnu.org/software/gcc/extensions.html has a broken link
> and I'd like to address this if possible.

The dlx backend was in gcc-2.7.2.3 (it is a 2.7.2.3 actually :) distribution
from this site:
http://www2.ucsc.edu/courses/cmps111-elm/dlx/tarballs/dlx-gcc.tgz

While this was a publicly available download 3 or 4 years ago (from a previous
site of the same author), it seems that the author forbids access to third
parties.

I have my own copy and if appropriate, i could upload it to my academic webpage.

> > I coded my own DLX backend for GCC.
> > If there is interest, i can submit the backend...
>
> I'm not able to approve a change like this (that's left to some others
> here), but if you'd like to put this up for download somewhere and submit
> a patch against http://www.gnu.org/software/gcc/extensions.html to give
> it more exposure, that would a very good first step!

I will submit a patch for mentioning my external location (adding DLX support to
the gcc-3.4.3/4) to the extensions.html page.


Kind regards
Nikolaos Kavvadias

Re: Status of the DLX backend for GCC?

[Peter Bergner]

On Sun, 2007-12-30 at 10:16 +0100, Gerald Pfeifer wrote:
> At http://www.gnu.org/software/gcc/extensions.html we have a reference
> to the DLX port of GCC, which corresponds to the DLX machine described
> in "Computer Architecture: A Quantitative Approach" by Hennessy and 
> Patterson.
> 
> Sadly, the link to http://www-mount.ee.umn.edu/~okeefe/mcerg/gcc-dlx.html 
> doesn't work and I failed to find a replacement page.  Any pointers?
> 
> On the binutils side I see that Nikolaos has been listed as a maintainer, 
> so there may be hope? :-)  Otherwise I'm afraid we'll have to remove our
> reference to the DLX port.
> 
> Gerald

Hi Gerald,

What is it exactly you're looking for on that page?  That web page was from
my old research group, so if there's something in particular you're looking
for, I can try poking some of the people to see whether they still have the
files.  FYI, Aaron Sawdey who now works for IBM doing performance work wrote
that GCC-DLX port.

I'll note that Matt O'keefe who was our research advisor no longer works
at the University of Minnesota so that's why the pages no longer work.


Peter

Re: Status of the DLX backend for GCC?

[Gerald Pfeifer]

[ Oops, somehow I had missed this... ]

On Fri, 4 Jan 2008, Peter Bergner wrote:
>> At http://www.gnu.org/software/gcc/extensions.html we have a reference
>> to the DLX port of GCC, which corresponds to the DLX machine described
>> in "Computer Architecture: A Quantitative Approach" by Hennessy and 
>> Patterson.
>> 
>> Sadly, the link to http://www-mount.ee.umn.edu/~okeefe/mcerg/gcc-dlx.html 
>> doesn't work and I failed to find a replacement page.  Any pointers?
> What is it exactly you're looking for on that page?  That web page was 
> from my old research group, so if there's something in particular you're 
> looking for, I can try poking some of the people to see whether they 
> still have the files.  FYI, Aaron Sawdey who now works for IBM doing 
> performance work wrote that GCC-DLX port.
> 
> I'll note that Matt O'keefe who was our research advisor no longer works
> at the University of Minnesota so that's why the pages no longer work.

Thanks for the background on this, Peter, and the background on this
site disappearing.

The reason I asked was that we have that reference from our site to that
URL and I failed to find any replacement so far.  The first two hits that
I get in Google actually are mails by you in the gcc archives. ;-)

I guess we'll just have to remove that reference?

Gerald

Re: Status of the DLX backend for GCC?

[Peter Bergner]

On Sat, 2008-10-04 at 18:48 +0200, Gerald Pfeifer wrote:
> Thanks for the background on this, Peter, and the background on this
> site disappearing.
> 
> The reason I asked was that we have that reference from our site to that
> URL and I failed to find any replacement so far.  The first two hits that
> I get in Google actually are mails by you in the gcc archives. ;-)
> 
> I guess we'll just have to remove that reference?

I talked with Aaron Sawdey and he still had the tarballs which he has
given me.  Let me go through a build process with them to make sure they
still build and then I'll post them somewhere you can link to.

Peter

[wwwdocs] Re: Status of the DLX backend for GCC?

[Gerald Pfeifer]

On Tue, 7 Oct 2008, Peter Bergner wrote:
>> The reason I asked was that we have that reference from our site to that
>> URL and I failed to find any replacement so far.  The first two hits that
>> I get in Google actually are mails by you in the gcc archives. ;-)
>> 
>> I guess we'll just have to remove that reference?
> I talked with Aaron Sawdey and he still had the tarballs which he has
> given me.  Let me go through a build process with them to make sure they
> still build and then I'll post them somewhere you can link to.

It seems this hasn't made it to the top of your list, and I can understand 
that.  Let's not spend time on this, I'd say.  Today I realized that the 
DLX emulator also faces a similar fate and only builds with GCC 2.95, so 
let's just remove the reference.  Clearly interest is minimal.

The patch below is what I committed now.  Thanks again for the background
you provided, Peter!

Gerald

Index: extensions.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/extensions.html,v
retrieving revision 1.44
diff -u -3 -p -r1.44 extensions.html
--- extensions.html	25 Jan 2009 16:35:21 -0000	1.44
+++ extensions.html	28 Feb 2009 22:44:35 -0000
@@ -12,9 +12,6 @@ reason or the other, did not (yet) make 
 tree. Please direct feedback and bugreports to their respective
 maintainers, not our mailing lists.</p>
 
-<h2><a href="http://www-mount.ee.umn.edu/~okeefe/mcerg/gcc-dlx.html">DLX port</a></h2>
-<p>A GCC Machine Description for the DLX machine described in Computer
-Architecture: A Quantitative Approach by Hennessy and Patterson.</p>
 
 <h2><a href="http://pdp10.nocrew.org/gcc/">PDP-10 port</a></h2>
 <p>This is an experimental port of GCC to the DEC PDP-10