llvm dev - Oct 2020 - LLJIT: __{math}_finite symbols not resolved ?

Hello,
when building code with -Ofast -ffinite-math-only -ffast-math, clang
generates calls to "finite" variants of math functions.

This has been the source of a fair amount of issues in a "normal",
non-JIT
pipeline, which seem to have been fixed over time - a simple fix being
recompiling the target app against the new glibc.
- https://bugs.llvm.org/show_bug.cgi?id=44842
- https://github.com/cms-sw/cmssw/issues/24935
- https://github.com/google/filament/issues/2146

But when going through LLJIT (tested with LLVM-10 & LLVM-11, on ArchLinux,
glibc-2.32) I still get

     Symbols not found: [ __log_finite, __exp2_finite ]

when trying to materialize my code.

What could be done for that ? "Recompiling" doesn't seem to fix
anything in
this case so it looks like LLJIT lacks the mechanism to understand the ELF
symbol indirection.

Thanks,
Jean-Michaël
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Hi Jean-Michaël,

How are you trying to provide those symbols to the JIT? Are you using a
DynamicLibrarySearchGenerator to reflect process symbols (or this specific
library's symbols) into the JIT?

I haven't looked at ELF symbol indirection before -- I'll need to read
up
on that before I can provide a sensible answer. It's quite likely that
RuntimeDyld doesn't support it yet though. Depending on what is required we
can either try to implement it there, or aim to fix it in the newer JITLink
linker -- a few people are working on an initial implementation of that at
the moment.

-- Lang.

On Mon, Oct 5, 2020 at 12:52 AM Jean-Michaël Celerier via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hello,
> when building code with -Ofast -ffinite-math-only -ffast-math, clang
> generates calls to "finite" variants of math functions.
>
> This has been the source of a fair amount of issues in a
"normal", non-JIT
> pipeline, which seem to have been fixed over time - a simple fix being
> recompiling the target app against the new glibc.
> - https://bugs.llvm.org/show_bug.cgi?id=44842
> - https://github.com/cms-sw/cmssw/issues/24935
> - https://github.com/google/filament/issues/2146
>
> But when going through LLJIT (tested with LLVM-10 & LLVM-11, on
ArchLinux,
> glibc-2.32) I still get
>
>      Symbols not found: [ __log_finite, __exp2_finite ]
>
> when trying to materialize my code.
>
> What could be done for that ? "Recompiling" doesn't seem to
fix anything
> in this case so it looks like LLJIT lacks the mechanism to understand the
> ELF symbol indirection.
>
> Thanks,
> Jean-Michaël
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Hello,
Right now I am just using a Generator to look for symbols in my process
(which links dynamically against libc / libm).
It seems to have no trouble finding every other libc / libm / libc++ / ...
symbol so I assumed that it was not necessary to specifically link against
libm where these __finite symbols reside:

  $ nm -D /usr/lib/libm.so.6 |  grep finite
  0000000000050540 T __acosf128_finite at GLIBC_2.26
  0000000000042f70 T __acosf_finite at GLIBC_2.15
  0000000000026940 i __acos_finite at GLIBC_2.15
  0000000000051000 T __acoshf128_finite at GLIBC_2.26
  0000000000043240 T __acoshf_finite at GLIBC_2.15
)
but maybe it needs some help on that regard ?

Thanks for your quick answer,

Jean-Michaël


On Mon, Oct 5, 2020 at 7:53 PM Lang Hames <lhames at gmail.com> wrote:
> Hi Jean-Michaël,
>
> How are you trying to provide those symbols to the JIT? Are you using a
> DynamicLibrarySearchGenerator to reflect process symbols (or this specific
> library's symbols) into the JIT?
>
> I haven't looked at ELF symbol indirection before -- I'll need to
read up
> on that before I can provide a sensible answer. It's quite likely that
> RuntimeDyld doesn't support it yet though. Depending on what is
required we
> can either try to implement it there, or aim to fix it in the newer JITLink
> linker -- a few people are working on an initial implementation of that at
> the moment.
>
> -- Lang.
>
> On Mon, Oct 5, 2020 at 12:52 AM Jean-Michaël Celerier via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hello,
>> when building code with -Ofast -ffinite-math-only -ffast-math, clang
>> generates calls to "finite" variants of math functions.
>>
>> This has been the source of a fair amount of issues in a
"normal",
>> non-JIT pipeline, which seem to have been fixed over time - a simple
fix
>> being recompiling the target app against the new glibc.
>> - https://bugs.llvm.org/show_bug.cgi?id=44842
>> - https://github.com/cms-sw/cmssw/issues/24935
>> - https://github.com/google/filament/issues/2146
>>
>> But when going through LLJIT (tested with LLVM-10 & LLVM-11, on
>> ArchLinux, glibc-2.32) I still get
>>
>>      Symbols not found: [ __log_finite, __exp2_finite ]
>>
>> when trying to materialize my code.
>>
>> What could be done for that ? "Recompiling" doesn't seem
to fix anything
>> in this case so it looks like LLJIT lacks the mechanism to understand
the
>> ELF symbol indirection.
>>
>> Thanks,
>> Jean-Michaël
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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