[OpenMP] Remove -fno-experimental-isel from OMP testing

[greened]

Summary

The restrictions in GlobalISel that caused OMP testing to break have been fixed, so remove -fno-experimental-isel from testing runs. This fixes a couple of OMP test failures on AArch64.

[Hahnfeld]

Did you also implement frameaddress in GlobalISel (see llvm.org/PR40131)? Otherwise this won't make all tests work and it would be better to "fix" -fno-experimental-isel.

If the flag can really go away the change must also handle cmake/DetectTestCompiler/CMakeLists.txt and in particular make sure that -fno-experimental-isel is still passed for versions of Clang that require it when testing out-of-tree with older compilers.

[greened]

No, I haven't implemented frameaddress or done any GISel work at all. From our ML conversation, I was under the impression that the tests didn't need -fno-experimental-isel anymore.

http://lists.llvm.org/pipermail/llvm-dev/2018-December/128697.html

Specifically, "I was the one who originally added the flag to fix failures related to GlobalISel. This was because first versions of GlobalISel didn't know how to select 'blockaddress', but this should have been fixed"

And indeed, this change gets almost all of the OMPT tests passing for me.

If more work needs to be done then I can just abandon this revision. I don't have the cycles to hack on GISel at the moment.

[Hahnfeld]

Yeah, sorry about that: That message was before I got the chance to really look into the generated assembly. I posted my analysis in the referenced bug you reported (https://bugs.llvm.org/show_bug.cgi?id=40131#c6) and frameaddress is also missing from GlobalISel which is why some tests are still failing. Fortunately there is https://reviews.llvm.org/D56266 which should restore -fno-experimental-isel and turn all tests green again until somebody has time to fully address all issues related to GlobalISel.

[greened]

I believe https://reviews.llvm.org/D56266 is working for me.

cmake/OpenMPTesting.cmake

if (${OPENMP_STANDALONE_BUILD})
   endif()
 else()
   # Set the information that we know.
   set(OPENMP_TEST_COMPILER_ID "Clang")
   # Cannot use CLANG_VERSION because we are not guaranteed that this is already set.
   set(OPENMP_TEST_COMPILER_VERSION "${LLVM_VERSION}")
   set(OPENMP_TEST_COMPILER_VERSION_MAJOR "${LLVM_MAJOR_VERSION}")
   set(OPENMP_TEST_COMPILER_VERSION_MAJOR_MINOR "${LLVM_MAJOR_VERSION}.${LLVM_MINOR_VERSION}")
-  # TODO: Implement blockaddress in GlobalISel and remove this flag!
-  set(OPENMP_TEST_COMPILER_OPENMP_FLAGS "-fopenmp -fno-experimental-isel")
+  set(OPENMP_TEST_COMPILER_OPENMP_FLAGS "-fopenmp")
 endif()
 
 # Function to set compiler features for use in lit.
 function(set_test_compiler_features)
   if ("${OPENMP_TEST_COMPILER_ID}" STREQUAL "GNU")
     set(comp "gcc")
   elseif ("${OPENMP_TEST_COMPILER_ID}" STREQUAL "Intel")
     set(comp "icc")