[Openmp-dev] Offloading build fails

[Itaru Kitayama via Openmp-dev]

I'm on POWER8, the nvcc version is below:

$ nvcc --version
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2018 NVIDIA Corporation
Built on Sat_Aug_25_21:10:00_CDT_2018
Cuda compilation tools, release 10.0, V10.0.130

Jon, I can't locate the file you mentioned in the latest trunk's openmp
project directory.


On Tue, Nov 5, 2019 at 8:05 AM Jon Chesterfield <
jonathanchesterfield at gmail.com> wrote:

> That's actually interesting in itself. Plus it's a problem with my change
> so I'm definitely on the hook to fix that one.
>
> I moved some inline functions (the symbols you're seeing) into a source
> file and that broke some builds. https://reviews.llvm.org/D69652. cc
> Alexey who reported the error earlier this evening.
>
> Nvcc 10 on x64 works for me with that change, some versions of nvcc on
> some architectures don't work. The workaround I'm suggesting is sed -i
> support.cu 's/INLINE/DEVICE/g', but without a local repro it's difficult
> to be sure what the effect is.
>
> I'd be very interested in what version of the nvcc toolchain you're using,
> and in whether replacing INLINE with DEVICE in deviceRTL/nvptx/src/
> support.cu fixes it. Alternatively, __forceinline__ to __inline__ in
> deviceRTL/nvptx/src/target_impl.h's definition of INLINE may fix things.
>
> Thanks,
>
> Jon
>
>
> On Mon, Nov 4, 2019 at 10:48 PM Itaru Kitayama <itaru.kitayama at gmail.com>
> wrote:
>
>> Switching to libc++ did not help much:
>> $ cat example.cpp
>> #include <iostream>
>> int main() {
>> #pragma omp target parallel for
>> for (int i=0;i<10;i++) {
>> }
>> }
>>
>> $ $ clang++ -fopenmp -fopenmp-targets=nvptx64 -stdlib=libc++ example.cpp
>> nvlink error   : Undefined reference to '_Z13checkSPMDModeP5ident' in
>> '/tmp/example-b3be69.cubin'
>> nvlink error   : Undefined reference to '_Z25GetLogicalThreadIdInBlockb'
>> in '/tmp/example-b3be69.cubin'
>> nvlink error   : Undefined reference to '_Z14GetOmpThreadIdib' in
>> '/tmp/example-b3be69.cubin'
>> nvlink error   : Undefined reference to '_Z21GetNumberOfOmpThreadsb' in
>> '/tmp/example-b3be69.cubin'
>> nvlink error   : Undefined reference to '_Z12GetOmpTeamIdv' in
>> '/tmp/example-b3be69.cubin'
>> nvlink error   : Undefined reference to '_Z19GetNumberOfOmpTeamsv' in
>> '/tmp/example-b3be69.cubin'
>> nvlink error   : Undefined reference to
>> '_Z22setExecutionParameters13ExecutionMode11RuntimeMode' in
>> '/tmp/example-b3be69.cubin'
>> nvlink error   : Undefined reference to '_Z18GetThreadIdInBlockv' in
>> '/tmp/example-b3be69.cubin'
>> nvlink error   : Undefined reference to '_Z25GetNumberOfThreadsInBlockv'
>> in '/tmp/example-b3be69.cubin'
>> nvlink error   : Undefined reference to '_Z9GetLaneIdv' in
>> '/tmp/example-b3be69.cubin'
>> nvlink error   : Undefined reference to '_Z9GetWarpIdv' in
>> '/tmp/example-b3be69.cubin'
>> clang-10: error: nvlink command failed with exit code 255 (use -v to see
>> invocation)
>>
>> Tested on POWER8
>>
>> On Tue, Nov 5, 2019 at 7:43 AM Jon Chesterfield <
>> jonathanchesterfield at gmail.com> wrote:
>>
>>> On Mon, Nov 4, 2019 at 10:16 PM Itaru Kitayama <itaru.kitayama at gmail.com>
>>> wrote:
>>>
>>>> Can you submit a patch to upstream? In the meantime, I workaround by
>>>> using libc++.
>>>>
>>>
>>> The 'right' fix is to stop cuda putting symbols in namespace std::, but
>>> that ship has sailed. Or possibly openmp variants as a future repair.
>>>
>>> I've 'raised a concern' on the guilty commit (
>>> https://reviews.llvm.org/rC361066) in the hope that someone else fixes
>>> it. My next step would probably be to propose a reverting commit and put
>>> the author of that patch down as reviewer.
>>>
>>> Cheers
>>>
>>> Jon
>>>
>>
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