Re: LLVM 16 (opaque pointers)

On Thu, Oct 19, 2023 at 6:20 AM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> Interestingly, a new problem just showed up on the the RHEL9 s390x
> machine "lora", where a previously reported problem [1] apparently
> re-appeared. It complains about incompatible layout, previously
> blamed on mismatch between clang and LLVM versions. I can see that
> its clang is v15 from clues in the conflig log, but I don't know which
> version of LLVM is being used. However, I see now that --with-llvm
> was literally just turned on, so there is no reason to think that this
> would have worked before or this work is relevant. Strange though --
> we must be able to JIT further than that on s390x because we have
> crash reports in other threads (ie we made it past this and into other
> more advanced brokenness).

I see that Mark has also just enabled --with-llvm on some POWER Linux
animals, and they have failed in various ways. The failures are
strangely lacking in detail. It seems we didn't have coverage before,
and I recall that there were definitely versions of LLVM that *didn't*
work for our usage in the past, which I'll need to dredge out of the
archives. I will try to get onto a cfarm POWER machine and see if I
can reproduce that, before and after these commits, and whose bug is
it etc.

I doubt I can get anywhere near an s390x though, and we definitely had
pre-existing problems on that arch.