diff --git a/cmake/DetectTestCompiler/CMakeLists.txt b/cmake/DetectTestCompiler/CMakeLists.txt
index 82d287b..c2f408c 100644
--- a/cmake/DetectTestCompiler/CMakeLists.txt
+++ b/cmake/DetectTestCompiler/CMakeLists.txt
@@ -1,11 +1,14 @@
 cmake_minimum_required(VERSION 2.8)
 project(DetectTestCompiler C CXX)
 
+include(CheckCCompilerFlag)
+include(CheckCXXCompilerFlag)
+
 function(write_compiler_information lang)
   set(information "${CMAKE_${lang}_COMPILER}")
   set(information "${information}\\;${CMAKE_${lang}_COMPILER_ID}")
   set(information "${information}\\;${CMAKE_${lang}_COMPILER_VERSION}")
-  set(information "${information}\\;${OpenMP_${lang}_FLAGS}")
+  set(information "${information}\\;${${lang}_FLAGS}")
   file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/${lang}CompilerInformation.txt ${information})
 endfunction(write_compiler_information)
 
@@ -15,5 +18,22 @@
   set(OpenMP_CXX_FLAGS "-fopenmp")
 endif()
 
+set(C_FLAGS ${flags} ${OpenMP_C_FLAGS})
+set(CXX_FLAGS ${flags} ${OpenMP_CXX_FLAGS})
+
+# TODO: Implement blockaddress in GlobalISel and remove this flag!
+if (CMAKE_C_COMPILER_ID STREQUAL "Clang")
+  check_c_compiler_flag("-fno-experimental-isel" C_HAS_EXPERIMENTAL_ISEL_FLAG)
+  check_cxx_compiler_flag("-fno-experimental-isel" CXX_HAS_EXPERIMENTAL_ISEL_FLAG)
+  macro(add_experimental_isel_flag lang)
+    if (${lang}_HAS_EXPERIMENTAL_ISEL_FLAG)
+      set(${lang}_FLAGS "-fno-experimental-isel ${${lang}_FLAGS}")
+    endif()
+  endmacro(add_experimental_isel_flag)
+
+  add_experimental_isel_flag(C)
+  add_experimental_isel_flag(CXX)
+endif()
+
 write_compiler_information(C)
 write_compiler_information(CXX)
diff --git a/cmake/OpenMPTesting.cmake b/cmake/OpenMPTesting.cmake
index 1cff9ec..165435f 100644
--- a/cmake/OpenMPTesting.cmake
+++ b/cmake/OpenMPTesting.cmake
@@ -117,7 +117,8 @@
   # 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_OPENMP_FLAGS "-fopenmp")
+  # TODO: Implement blockaddress in GlobalISel and remove this flag!
+  set(OPENMP_TEST_COMPILER_OPENMP_FLAGS "-fopenmp -fno-experimental-isel")
 endif()
 
 # Function to set compiler features for use in lit.