Re: gcc compiler for pdp10

["J.C. Pizarro" <jcpiza at gmail dot com>]

On Fri, 18 Apr 2008 21:56:38 -0400, Alan Lehotsky <apl@alum.mit.edu> wrote:
>Martin,
>
>I did a port of GCC to the Analog Devices SHARC chip. I ended up
supporting 3 >kinds of pointers for this chip (two for address
>spaces and one for byte pointers - the chip itself is only word
addressable >(although words can be from 16 to 48 bits in size
>depending on what memory is being accessed.)
>
>I also worked on the Bliss-36 compiler at DEC, so I'm well acquainted
with the >PDP10 architecture.
>
>I don't have access to any 10/20 HW, but I'd be happy to act as a
>reviewer/advisor to your changes.
>
>Al Lehotsky
>
>On Apr 18, 2008, at 20:21, Martin Chaney wrote:
>>
>>    Hi,
>>
>>    I'm am the proprietor of a gcc compiler for the PDP10 architecture.
>>
>>    (This is a compiler previously worked on by Lars Brinkhoff who
left XKL some >>while before I joined XKL. It's possible some of you
may have been familiar with >>him or the compiler from that time.)
>>
>>    The compiler is currently in a state where it is synched with
the both the 4.3 >>and 4.4 branches, and it passes the testsuite tests
(with the exception of some >>I've flagged as expected failures for
the pdp10).
>>
>>    My employer is happy to release my work on the gcc compiler back
to the >>gcc community and I've sent in a request for the necessary
forms.
>>
>>    The PDP10 architecture is unusual in various ways that
distinguish it from >>the mainstream architectures supported by the
gcc compiler and this has >>made the development of this compiler a
significant task. Undoubtedly I've >>made customizations in
inappropriate ways. I'm seeking contacts with people >>who might be
able to advise me on how to cleanup my implementation to >>reduce the
amount of #ifdef __PDP10_H__ I've sprinkled liberally throughout the
>>source. Also, if its possible to get simple changes made to prevent
breaking >>my PDP10 version and that are otherwise innocuous that
would be wonderful. >>For example, the PDP10 word size is 36 bits;
Fairly recently people have taken >>to writing code that assumes word
size is a power of 2 even when it's >>straightforward to write in a
manner that doesn't make that assumption.
>>
>>    Considering the large number of files customized to get the
PDP10 compiler >>working, I'm not sure whether it's possible to get it
to build directly from the gcc >>trunk, but it would be nice to work
toward that goal.
>>
>>    Some other things which distinguish the PDP10 architecture from
>>assumptions in the gcc code base include: its variety of formats of
pointers >>only one of which can be viewed as an integer and that one
is capable of >>referencing only word aligned data, a functional
difference between signed and >>unsigned integers, and peculiarities
to the use of PDP10 byte arrays which are >>very difficult to
describe.
>>
>>    Any help or advise would be appreciated.
>>
>>    Martin Chaney
>>    XKL, LLC

In http://pdp-10.trailing-edge.com/  there are ~6.5GB
about PDP10 files where inside ~1.5GB are tapes in tap.bz2 format.

It's a lot of obsolete software of more >20 years ago,
it's only for hobbies because you won't find archaic 36 bit machines,
and all the current modern machines are 32 and 64 bit.