[llvm-dev] LLJIT: __{math}_finite symbols not resolved ?

[Jean-Michaël Celerier via llvm-dev]

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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