[llvm] r273585 - Preserve DebugInfo when replacing values in DAGCombiner

[Nirav Davé via llvm-commits]

Apparently we're transferring debug values later in the ReplaceAllUsesWith
than the other N versions. I still don't see how we're getting bad Debug
Values, but this may fix it. Can you try this patch?

-Nirav

On Tue, Jul 26, 2016 at 9:51 AM, Nirav Davé <niravd at google.com> wrote:

> Not yet. I've run it for multiple days in multiple contexts but it never
> crashes for me.
>
> I've been working on it from first principles but aside from that minor
> patch I sent you that slightly cleans up usage, I haven't found anything
> that could be labelled as wrong. Most upsettingly, none of the Debug Values
> in question have ever been freed at the time of the crash; They're
> allocated in a bumpptr allocator which defers freeing until after we're
> done with SelectionDAG.
>
> -Nirav
>
>
> On Jul 26, 2016 07:38, "Ismail Donmez" <ismail at i10z.com> wrote:
> >
> > Any luck with reproducing? This bug affects us really badly, we are
> > unable to produce a snapshot more than a month now :(
> >
> > ismail
> >
> > On Fri, Jul 22, 2016 at 9:57 AM, Ismail Donmez <ismail at i10z.com> wrote:
> > > Hi Nirav,
> > >
> > > On Thu, Jul 21, 2016 at 10:37 PM, Nirav Davé <niravd at google.com>
> wrote:
> > >> Ismall:
> > >>
> > >> I'm still having problems finding reproducing this corruption
> locally, but I
> > >> may have a patch. Can you check if this works?
> > >> If it doesn't, maybe you can spot what I'm doing wrong in my
> reproduction
> > >> steps.
> > >
> > > Sadly the patch didn't help. What I did to reproduce the crash was
> > > running the reproducer script from
> > > https://llvm.org/bugs/show_bug.cgi?id=28613 in a tight loop like:
> > >
> > > while true; do ./Loop-blabla.sh && sleep 1; done
> > >
> > > After it crashes I used the core file with gdb to debug. Of course
> > > you'll still need to export MALLOC_CHECK_ and MALLOC_PERTURB_
> > > beforehand.
> > >
> > > Regards,
> > > ismail
>
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