[PATCH 00/31] VAX: Bring the port up to date (yes, MODE_CC conversion is included)

[Maciej W. Rozycki]

On Mon, 23 Nov 2020, Paul Koning wrote:

> > Then there is a fix for the PDP11 backend addressing an issue I found in 
> > the handling of floating-point comparisons.  Unlike all the other changes 
> > this one has not been regression-tested, not even built as I have no idea 
> > how to prepare a development environment for a PDP11 target (also none of 
> > my VAX pieces is old enough to support PDP11 machine code execution).
> 
> I agree this is a correct change, interesting that it was missed before.  
> You'd expect some ICE issues from that mistake.  Perhaps there were and 
> I didn't realize the cause; the PDP11 test run is not yet fully clean.

 Nothing like that, I wouldn't expect an ICE here.  Just as none happened 
with the VAX backend before a test case made me realise a corresponding 
change was required.  It's just a pessimisation: the RTL simply doesn't 
match and the comparison to remove stays.

> I've hacked together a primitive newlib based "bare metal" execution 
> test setup that uses SIMH, but it's not a particularly clean setup.  
> And it hasn't been posted, I hope to be able to do that at some point.

 Hmm, I gather those systems are able to run some kind of BSD Unix: don't 
they support the r-commands which would allow you to run DejaGNU testing 
with a realistic environment PDP-11 hardware would be usually used with, 
possibly on actual hardware even?  I always feel a bit uneasy about the 
accuracy of any simulation (having suffered from bugs in QEMU causing 
false negatives in software verification).

 While I would expect old BSD libc to miss some of the C language features 
considered standard nowadays, I think at least the C GCC frontend runtime 
(libgcc.a) and the test suite do not overall rely on their presence, and 
any individual test cases that do can be easily excluded.

> Thanks for the fix.

 I take it as an approval and will apply the change then along with the 
rest of the series.  Thank you for your review.

  Maciej