Make tests unsupported if libatomic cannot be found.

[twoh]

Summary

As https://reviews.llvm.org/rL336467 appends -latomic when -fopenmp is given, openmp unit tests are failing if libatomic cannot be found. This diff makes unit tests unsupported if there's no libatomic.

• Test

From the build dir

[~/llvms/upstream-git/build-Release] grep -r LIBOMP_HAVE_LIBATOMIC .
./CMakeCache.txt:LIBOMP_HAVE_LIBATOMIC:INTERNAL=

suggests that libatomic cannot be found. Without the diff,

[~/llvms/upstream-git/build-Release] ninja check-openmp
...
    libomp :: worksharing/single/omp_single.c
    libomp :: worksharing/single/omp_single_copyprivate.c
    libomp :: worksharing/single/omp_single_nowait.c
    libomp :: worksharing/single/omp_single_private.c

  Expected Passes    : 2
  Expected Failures  : 1
  Unsupported Tests  : 2
  Unexpected Failures: 166

With the diff,

[~/llvms/upstream-git/build-Release] ninja check-openmp
[0/1] Running OpenMP tests
Testing Time: 0.16s
  Expected Passes    : 2
  Unsupported Tests  : 169

[Hahnfeld]

@ABataev does this mean that Clang will now require libatomic even if there is no OpenMP atomic construct? I remember documentation saying that the user has to link atomic libraries when needed...

runtime/test/lit.cfg

56–57

I think what you want to test here is whether you are compiling with Clang? If so, please use config.test_c_compiler or config.test_compiler_features.

[twoh]

runtime/test/lit.cfg

56–57

Thanks for the comment! I couldn't quite get it why are you thinking that I want to check if the compiler is clang. Following https://reviews.llvm.org/rL336467, -latomic is added if -fopenmp is given, so that's what I'm checking here. Don't all test cases here assume that they are compiling with clang?

[Hahnfeld]

In D49386#1163854, @Hahnfeld wrote:

@ABataev does this mean that Clang will now require libatomic even if there is no OpenMP atomic construct? I remember documentation saying that the user has to link atomic libraries when needed...

(I've replied on cfe-commits to the commit that introduced linking of -latomic because I don't think it's a good idea.)

runtime/test/lit.cfg

56–57

No, the tests can be run with GCC, Intel Compiler and maybe others. The test in its current form is pointless because all OpenMP tests get -fopenmp.

[twoh]

Addressing comments from @Hahnfeld. Thanks!

[Hahnfeld]

This shouldn't be needed anymore, I reverted the relevant commit in rC337722 after discussion on cfe-commits.

@twoh Which distribution are you using that doesn't have libatomic? If possible you might want to explain your situation in https://bugs.llvm.org/show_bug.cgi?id=38026, thanks.

runtime/test/lit.cfg

config.test_flags = " -I " + config.test_source_root + \
     " " + config.test_extra_flags
 
 # extra libraries
 libs = ""
 if config.has_libm:
     libs += " -lm"
 if config.has_libatomic:
     libs += " -latomic"
+elif 'clang' in config.test_compiler_features:
+    config.unsupported = True
 
 # Allow XFAIL to work
 config.target_triple = [ ]
 for feature in config.test_compiler_features:
     config.available_features.add(feature)
 
 # Setup environment to find dynamic library at runtime
 append_dynamic_library_path(config.library_dir)