PDP-11 GCC back-end, was Re: [HECnet] Raspberry Pi + SIMH VAX?

[Paul_Koning at Dell.com]

On Jun 6, 2012, at 9:21 PM, Dave McGuire wrote:

On 06/06/2012 09:01 PM, Paul_Koning at Dell.com wrote:
Strange that gcc has so much trouble for VAX.   I thought that had gotten a fair amount of care & feeding lately.

pdp11, that's a different story, though I do try to do some more bits from time to time...

Are you working on that??   I recently ran across this page:

http://www.diane-neisius.de/pdp11/index_E.html

...in which a very enthusiastic person got it running some time ago,
but with some pretty significant restrictions.

I'd truly love to see the PDP-11 GCC back-end be resurrected and made
to be fully functional.   It may have a very limited appeal, but I
already use GCC-based cross-compilers for many different architectures
in both my work and recreational activities (both mostly ARM7), and
would love to be able to do some bare-metal PDP-11 work with GCC as well.

If you're working on this, allow me to voice my heartfelt support for
this effort!

                    -Dave

Thanks.   Yes, pdp11 for gcc is an actual maintained port, given that I volunteered to be the port maintainer.   I've done work to clean it up, in spurts.   At this point it usually generates good code. I actually have it pass a fair fraction of the GCC test suite (execution, not just compilation).   Still there are issues; for example, the AC4/AC5 handling is not 100%.   But at least simple mistakes like assuming that BIC does the "and" operation have been cured.   :-)

You can grab a recent GCC (say, 4.7.0, or gcc trunk) and configure it --target=pdp11-aout, and that will build you a GCC that produces pdp11 code (standalone as opposed to for a particular OS).   Binutils can also be configured that way, and if you have that, then you can have GNU tools compile, assemble, and link for you.   

One unfortunate thing is that the pdp11-bsd2 flavor was removed some time ago; I haven't looked into what it would take to bring it back.   (I have near-zero experience with BSD 2.)

	paul