Re: JIT crash introduced by 6185c9737c with LLVM 14

The following query causes a crash on an optimized build using LLVM 14:

create table t(i int);
set jit_above_cost=0;
select count(*) from t;

I bisected the crash to 6185c9737c.

Regards,
Jeff Davis

Hi Jeff,

On Fri, Jun 14, 2024 at 1:25 PM Jeff Davis <jeff(at)j-davis(dot)com> wrot>
> The following query causes a crash on an optimized build using LLVM 14:
>
> create table t(i int);
> set jit_above_cost=0;
> select count(*) from t;
>
> I bisected the crash to 6185c9737c.

Thanks for the report. Will look into it.

--
Thanks, Amit Langote

Hi Jeff,

On Fri, Jun 14, 2024 at 2:57 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> On Fri, Jun 14, 2024 at 1:25 PM Jeff Davis <jeff(at)j-davis(dot)com> wrot>
> > The following query causes a crash on an optimized build using LLVM 14:
> >
> > create table t(i int);
> > set jit_above_cost=0;
> > select count(*) from t;
> >
> > I bisected the crash to 6185c9737c.
>
> Thanks for the report. Will look into it.

Would you please share more details about the crash (llvm build
attributes, etc.) as I'm unable to reproduce this crash with
libLLVM-14.so that I built from sources that I got at [1]. No luck
even after building with -DLLVM_ENABLE_ASSERTIONS=ON. I'm building PG
HEAD with --buildtype=release.

--
Thanks, Amit Langote

[1] https://github.com/llvm/llvm-project/releases/tag/llvmorg-14.0.6

Hi,

On Mon, Jun 17, 2024 at 6:32 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> Hi Jeff,
>
> On Fri, Jun 14, 2024 at 2:57 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> > On Fri, Jun 14, 2024 at 1:25 PM Jeff Davis <jeff(at)j-davis(dot)com> wrot>
> > > The following query causes a crash on an optimized build using LLVM 14:
> > >
> > > create table t(i int);
> > > set jit_above_cost=0;
> > > select count(*) from t;
> > >
> > > I bisected the crash to 6185c9737c.
> >
> > Thanks for the report. Will look into it.
>
> Would you please share more details about the crash (llvm build
> attributes, etc.) as I'm unable to reproduce this crash with
> libLLVM-14.so that I built from sources that I got at [1]. No luck
> even after building with -DLLVM_ENABLE_ASSERTIONS=ON. I'm building PG
> HEAD with --buildtype=release.

Also, could you please check if the crash still occurs after applying
the attached patch which removes the changes that 6185c9737c made to
files under src/backend/jit?

(My colleague David Rowley offered to test it on a raspberrypi and on
a x86_64 machine with libLLVM-14.so, but sees no crash using those
steps.)

--
Thanks, Amit Langote

On Tue, 2024-06-18 at 15:11 +0900, Amit Langote wrote:
> Also, could you please check if the crash still occurs after applying
> the attached patch which removes the changes that 6185c9737c made to
> files under src/backend/jit?
>
> (My colleague David Rowley offered to test it on a raspberrypi and on
> a x86_64 machine with libLLVM-14.so, but sees no crash using those
> steps.)

My testcase was wrong because I was installing into the same
destination directory each time when bisecting (that shortcut normally
works but can cause problems with LLVM changes). When I install into a
fresh directory, it works.

There may (or may not) have been some bug in my original larger case,
but I'll have to re-investigate, and in any case I don't think your
commit was a problem.

Regards,
Jeff Davis

On Wed, Jun 19, 2024 at 3:20 AM Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> There may (or may not) have been some bug in my original larger case,
> but I'll have to re-investigate, and in any case I don't think your
> commit was a problem.

There are some unresolved reports of crashes on ARM CPUs using LLVM 14
in particular. What is your CPU?

On Wed, Jun 19, 2024 at 11:03:11AM +1200, Thomas Munro wrote:
> On Wed, Jun 19, 2024 at 3:20 AM Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
>> There may (or may not) have been some bug in my original larger case,
>> but I'll have to re-investigate, and in any case I don't think your
>> commit was a problem.

Okay, for now I have removed Amit's name as owner of this open item.

> There are some unresolved reports of crashes on ARM CPUs using LLVM 14
> in particular. What is your CPU?

But it looks like we still have something new to v17 in this case, so
the item it still around, pending more investigation.
--
Michael

On Wed, Jun 19, 2024 at 8:52 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> On Wed, Jun 19, 2024 at 11:03:11AM +1200, Thomas Munro wrote:
> > On Wed, Jun 19, 2024 at 3:20 AM Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> >> There may (or may not) have been some bug in my original larger case,
> >> but I'll have to re-investigate, and in any case I don't think your
> >> commit was a problem.

Ok, thanks.

> Okay, for now I have removed Amit's name as owner of this open item.
>
> > There are some unresolved reports of crashes on ARM CPUs using LLVM 14
> > in particular. What is your CPU?
>
> But it looks like we still have something new to v17 in this case, so
> the item it still around, pending more investigation.

+1. I was about to mark it as resolved, but this makes sense.

--
Thanks, Amit Langote