Re: Patches to fix optimizer bug & C++ exceptions for GCC VAX backend

[Jan-Benedict Glaw <jbglaw at lug-owl dot de>]

On Fri, 2016-04-01 12:06:20 -0700, Jake Hamby <jehamby420@me.com> wrote:
> I apologize for the poor quality of the initial version of the patch
> that I submitted. I think I may have also mangled it by not

Don't apologize!  Posting work early enables others to comment on it.
GCC is a highly complex beast; nobody will produce a perfectly looking
patch on their first try.

[...]

> To be honest, my hope by sending out my work now, even in such a
> rough state, would be to try to avoid deprecating the GCC port to
> VAX, if only because: 1) there doesn't seem to be a compelling
> reason to remove support for it since it doesn't use any really old
> code paths that aren't also used by other backends (e.g. m68k and
> Atmel AVR use cc0, IBM S/390 uses non-IEEE FP formats), so it
> doesn't seem to be preventing any optimizations or code refactoring
> elsewhere in GCC that I could see, 2) even though NetBSD could
> continue to support VAX GCC, I noticed in the ChangeLogs that
> whenever somebody has made a change to a definition that affects the
> backends, they're usually very good about updating all of the
> backends so that they continue to compile, at least. So leaving the
> VAX backend in the tree would be beneficial from a maintenance
> standpoint for users of it, 3) the VAX backend is perhaps somewhat
> useful as a test case for GCC because so many unusual RTX standard
> instructions were obviously defined *for* it (although x86 defines a
> lot of them, too), although my interest is personally in preserving
> an interesting piece of computer history, and for nostalgia
> purposes.

As of now, ther VAX backend isn't near deprecation IMO. There'a
maintainer (Matt), who did quite a revamp a few years ago bringing the
VAX backend quite forward.  I also quite care for that backend and the
Build Robot I'm running is primarily(!) running to detect VAX
breakages early. (In fact, quite often Matt and I communicate over
submitted patches to the VAX backend.)

> I sent an earlier email to port-vax suggesting that future
> discussions of this project aren't relevant to gcc-patches, but I
> did want to get it on a few people's radar on the NetBSD side and
> try to solicit a bit of help on the questions I had as to how to
> avoid having to add that hack to gcc/except.c to make the optimizer
> not delete the insns. All of the other stuff can be worked on in
> NetBSD-current and avoid bothering the 99% of people who subscribe
> to gcc-patches who have no interest in the VAX backend.

You should /for sure/ bother the gcc-patches people! Please keep
Cc'ing patches to that mailing list.

MfG, JBG

-- 
      Jan-Benedict Glaw      jbglaw@lug-owl.de              +49-172-7608481
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