Trying to build OpenMP on Apple Silicon mac fails with link errors

Runtimes OpenMP
#1

Hello

Trying to build top of tree LLVM with openmp runtime on Apple Silicon Mac fails with the following link errors.

Undefined symbols for architecture arm64:
  "___divdc3", referenced from:
      ___kmpc_atomic_cmplx8_div in kmp_atomic.cpp.o
      ___kmpc_atomic_cmplx4_div_cmplx8 in kmp_atomic.cpp.o
      ___kmpc_atomic_cmplx8_div_cpt in kmp_atomic.cpp.o
      ___kmpc_atomic_cmplx10_div_cpt in kmp_atomic.cpp.o
  "___divsc3", referenced from:
      ___kmpc_atomic_cmplx4_div in kmp_atomic.cpp.o
      ___kmpc_atomic_cmplx4_div_cpt in kmp_atomic.cpp.o

Build command used

cmake -GNinja  ../llvm-project/llvm/ -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang" -DLLVM_ENABLE_RUNTIMES="openmp"  -DLLVM_TARGETS_TO_BUILD="X86;AArch64;AMDGPU;NVPTX" -DLLVM_ENABLE_ASSERTIONS=1 -DCLANG_OPENMP_NVPTX_DEFAULT_ARCH=sm_80 -DLIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES=35

It appears some of the builtins being used are not available?

#2

Firstly, I would be surprised if you get OpenMP offload to run on Apple Silicon. You could try to add compiler-rt. It contains the builtins.

#3

Thorsten,
“I would be surprised if you get OpenMP offload to run on Apple Silicon”, so would I, but that isn’t the point at hand, since kmp_atomic.cpp is not an offload file, it’s in the normal, host, runtime.
– Jim

#4

Sorry. The compilation error can probably be solved by adding compiler-rt to the build. The other issue is the attempt to try OpenMP target on Apple Silicon.

#5

This is going to be a waste of time and space.

#6

FWIW, I’m about to get my hands on an M2 processor. Some others and me will check how unreasonable offload on Apple Silicon really is :wink:

1 Like
#7

Hello, building compiler RT was all I needed do. As for why, satisfying my curiosity after seeing some cool talks in the dev meeting :slight_smile:

#8

https://compiler-rt.llvm.org also contains the builtins like your ___divsc3.

#9

I’m not sure why building OpenMP host runtime requires compiler-rt. That’s definitely not expected.

1 Like