Jean-Michaël Celerier via llvm-dev
2020-Oct-05 19:30 UTC
[llvm-dev] LLJIT: __{math}_finite symbols not resolved ?
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 >> >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20201005/eaf9659f/attachment.html>
Lang Hames via llvm-dev
2020-Oct-05 20:11 UTC
[llvm-dev] LLJIT: __{math}_finite symbols not resolved ?
Hi Jean-Michaël, Ok -- if you're linking against other symbols without issue then your setup sounds good. My first take is that if you're set up correctly then this should "just work", and this failure should be considered a bug, but I need to understand more about ELF indirect / versioned symbols before I can say that definitively. I usually develop on MacOS, but I'll set up a VM and see if I can reproduce this locally to get some more insight here. In the meantime one workaround would be to define absoluteSymbol entries for these functions: auto Err = J->getMainJITDylib().define( absoluteSymbols({ { J->mangleAndIntern("__log_finite"), pointerToJITTargetAddress(&__log_finite) }, { J->mangleAndIntern("__exp2_finite"), pointerToJITTargetAddress(&__exp2_finite) } })); -- Lang. On Mon, Oct 5, 2020 at 12:31 PM Jean-Michaël Celerier < jeanmichael.celerier at gmail.com> wrote:> 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 >>> >>-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20201005/c86a8204/attachment.html>
Jean-Michaël Celerier via llvm-dev
2020-Oct-05 22:23 UTC
[llvm-dev] LLJIT: __{math}_finite symbols not resolved ?
Hello, here is a repro which runs in a docker image. https://we.tl/t-O1EhIAOeOF To see the issue, run repro.sh It will first download a (big, sorry) centos:7 docker image with my build of LLVM-11 and build a simple lljit-based example. This example is called with some trivial .cpp which calls `cos`. When ran from *within the container* it works. When the same example, with the same bitcode input, runs from outside the container, it does not find this symbol, likely because the host (in my case Arch, I think you need a glibc-2.31 at least for that behaviour to be visible)'s glibc symbols became versioned. Removing either the -fmath-errno or -ffinite-math-only flag for the clang cpp -> bitcode invocation in build.sh fixes the issue (at the expense of potentially slower code). <http://www.jcelerier.name> Thanks for the hint, sadly it's not possible to take the address of __log_finite : what happens is that you call the function e.g. log() in your code, and either clang or some magic glibc header transforms that into __log_finite further down the pipeline (see e.g. the discussion in https://reviews.llvm.org/D74712 - sadly in my case I can't "upgrade" the headers used by my JIT SDK to glibc-2.31+ as it would mean that only people with very very recent distros would be able to run the code that's being jit-compiled. Thanks ! Jean-Michaël On Mon, Oct 5, 2020 at 10:11 PM Lang Hames <lhames at gmail.com> wrote:> Hi Jean-Michaël, > > Ok -- if you're linking against other symbols without issue then your > setup sounds good. > > My first take is that if you're set up correctly then this should "just > work", and this failure should be considered a bug, but I need to > understand more about ELF indirect / versioned symbols before I can say > that definitively. I usually develop on MacOS, but I'll set up a VM and see > if I can reproduce this locally to get some more insight here. > > In the meantime one workaround would be to define absoluteSymbol entries > for these functions: > > auto Err = J->getMainJITDylib().define( > absoluteSymbols({ > { J->mangleAndIntern("__log_finite"), > pointerToJITTargetAddress(&__log_finite) }, > { J->mangleAndIntern("__exp2_finite"), > pointerToJITTargetAddress(&__exp2_finite) } > })); > > -- Lang. > > On Mon, Oct 5, 2020 at 12:31 PM Jean-Michaël Celerier < > jeanmichael.celerier at gmail.com> wrote: > >> 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 >>>> >>>-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20201006/43399f58/attachment.html>
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