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[OMP_OFFLOAD_LLVM] Undefined references to .omp_offloading symbols #1399

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dmikushin opened this issue Jun 28, 2023 · 3 comments
Open

[OMP_OFFLOAD_LLVM] Undefined references to .omp_offloading symbols #1399

dmikushin opened this issue Jun 28, 2023 · 3 comments

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@dmikushin
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dmikushin commented Jun 28, 2023 •
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By testing

flang -O2 -fopenmp -fopenmp-targets=x86_64 /openmp-offload-example/src/example.f90 -o /openmp-offload-example/build/example

I get a linking error:

/usr/bin/ld: /tmp/example-49d1c7.o:(.rodata 0x0): undefined reference to `.omp_offloading.img_start.nvptx64-nvidia-cuda'
/usr/bin/ld: /tmp/example-49d1c7.o:(.rodata 0x8): undefined reference to `.omp_offloading.img_end.nvptx64-nvidia-cuda'
/usr/bin/ld: /tmp/example-49d1c7.o:(.rodata 0x10): undefined reference to `.omp_offloading.entries_begin'
/usr/bin/ld: /tmp/example-49d1c7.o:(.rodata 0x18): undefined reference to `.omp_offloading.entries_end'
/usr/bin/ld: /tmp/example-49d1c7.o:(.rodata 0x30): undefined reference to `.omp_offloading.entries_begin'
/usr/bin/ld: /tmp/example-49d1c7.o:(.rodata 0x38): undefined reference to `.omp_offloading.entries_end'

Instead of following my -fopenmp-targets=x86_64 command, Flang gives me offloading to NVIDIA. "I no longer have a motorcycle, but the habit remains" (c)
@dmikushin
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dmikushin commented Jun 29, 2023 •
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Today I grepped the whole LLVM repository history for img_start entries with

git rev-list --all | parallel --bar -P 16 git show | grep "img_start"

And found zero occurrences. If it existed, it should pop up at least in the tests. Perhaps, it means the OpenMP linking in Flang was done against PGI's internal fork of LLVM, which is not a part of this project anymore.

Does anyone have a clue? If not, I will match my Fortran example with C example side by side to find the proper naming of OpenMP symbols.

@bryanpkc
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@shivaramaarao Any clue?

@bryanpkc
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@sscalpone

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