[Issue]: flang-new: runtime and math functions don't link for OpenMP target regions

[VeeEM]

Problem Description

I get many linker errors for OpenMP target regions when offloading to GPU. Symbols from libFortranRuntime show as undefined and so do some math intrinsics like cosh.

There are some other math intrinsics that do link successfully, like tanh.

@sfantao

Operating System

SUSE Linux Enterprise Server 15 SP5 (Cray OS on LUMI)

CPU

AMD EPYC 7742 64-Core

GPU

AMD Instinct MI250X

ROCm Version

ROCm 6.2.2

ROCm Component

flang

Steps to Reproduce

flang-new --version
AMD AFAR drop #4.0 9/28/24 flang-new version 20.0.0git (ssh://gerritgit/lightning/ec/llvm-project amd-feature/atd-fortran/2024.09.28 24385 1ad3ac337fa4b1a5a7621a4c5480028b54fffada)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /pfs/lustrep3/scratch/project_462000394/amd-sw/rocm-afar/5891/lib/llvm/bin
Build config: +assertions

$ cat link.F90 
program link
implicit none
real :: r
real, dimension(5) :: xs

!$omp target map(xs, r)
xs = 2
xs = modulo(xs, 3)
r = cosh(r)
r = tanh(r)
!$omp end target

end program

flang-new -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa --offload-arch=gfx90a -fdefault-real-8 link.F90
ld.lld: error: undefined symbol: _FortranAAssign
>>> referenced by /tmp/a.out.amdgcn.gfx90a-6a405a.img.lto.o:(__omp_offloading_54bbb604_5101b8ee__QQmain_l6)
>>> referenced by /tmp/a.out.amdgcn.gfx90a-6a405a.img.lto.o:(__omp_offloading_54bbb604_5101b8ee__QQmain_l6)

ld.lld: error: undefined symbol: _FortranAModuloReal8
>>> referenced by /tmp/a.out.amdgcn.gfx90a-6a405a.img.lto.o:(__omp_offloading_54bbb604_5101b8ee__QQmain_l6)
>>> referenced by /tmp/a.out.amdgcn.gfx90a-6a405a.img.lto.o:(__omp_offloading_54bbb604_5101b8ee__QQmain_l6)

ld.lld: error: undefined symbol: cosh
>>> referenced by /tmp/a.out.amdgcn.gfx90a-6a405a.img.lto.o:(__omp_offloading_54bbb604_5101b8ee__QQmain_l6)
>>> referenced by /tmp/a.out.amdgcn.gfx90a-6a405a.img.lto.o:(__omp_offloading_54bbb604_5101b8ee__QQmain_l6)
clang: error: ld.lld command failed with exit code 1 (use -v to see invocation)
/pfs/lustrep3/scratch/project_462000394/amd-sw/rocm-afar/5891/lib/llvm/bin/clang-linker-wrapper: error: 'clang' failed
flang-new: error: linker command failed with exit code 1 (use -v to see invocation)

(Optional for Linux users) Output of /opt/rocm/bin/rocminfo --support

No response

Additional Information

No response

[bcornille]

In the user guide we have documented that adding -lFortranRuntimeHostDevice to the link line will resolve these link issues. As noted, using this device version of the FortranRuntime will result in low performance but allow linking and running of user programs. We however very much appreciate the reports of what functionality is needed by user codes from the runtime so the runtime calls can be circumvented. E.g. one would expect cosh to be able to be lowered directly without a call to the Fortran runtime.

[bcornille]

Math functions may alternatively require -lm when linking.