+if( NOT CMAKE_SOURCE_DIR STREQUAL CMAKE_BINARY_DIR )
+ file(GLOB_RECURSE
+ tablegenned_files_on_include_dir
+ "${LLVM_MAIN_SRC_DIR}/include/llvm/*.gen")
+ file(GLOB_RECURSE
+ tablegenned_files_on_lib_dir
+ "${LLVM_MAIN_SRC_DIR}/lib/Target/*.inc")
+ if( tablegenned_files_on_include_dir OR tablegenned_files_on_lib_dir)
+ message(FATAL_ERROR "Apparently there is a previous in-source build,
+probably as the result of running `configure' and `make' on
+${LLVM_MAIN_SRC_DIR}.
+This may cause problems. The suspicious files are:
+${tablegenned_files_on_lib_dir}
+${tablegenned_files_on_include_dir}
+Please clean the source directory.")
+ endif()
+endif()
+