Index: cmake/config-ix.cmake
===================================================================
--- cmake/config-ix.cmake
+++ cmake/config-ix.cmake
@@ -1,5 +1,6 @@
 include(CheckLibraryExists)
 include(CheckCXXCompilerFlag)
+include(CheckAtomic)
 
 # Check compiler flags
 
@@ -17,3 +18,7 @@
 check_library_exists(m ccos "" LIBCXX_HAS_M_LIB)
 check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)
 check_library_exists(gcc_s __gcc_personality_v0 "" LIBCXX_HAS_GCC_S_LIB)
+
+if (NOT HAVE_CXX_ATOMICS_WITHOUT_LIB)
+  set(LIBCXX_HAS_ATOMIC_LIB True)
+endif()
Index: lib/CMakeLists.txt
===================================================================
--- lib/CMakeLists.txt
+++ lib/CMakeLists.txt
@@ -79,6 +79,7 @@
 add_library_flags_if(LIBCXX_HAS_M_LIB m)
 add_library_flags_if(LIBCXX_HAS_RT_LIB rt)
 add_library_flags_if(LIBCXX_HAS_GCC_S_LIB gcc_s)
+add_library_flags_if(LIBCXX_HAS_ATOMIC_LIB atomic)
 
 # Setup flags.
 add_flags_if_supported(-fPIC)
Index: test/CMakeLists.txt
===================================================================
--- test/CMakeLists.txt
+++ test/CMakeLists.txt
@@ -15,6 +15,7 @@
 pythonize_bool(LIBCXX_BUILD_32_BITS)
 pythonize_bool(LIBCXX_GENERATE_COVERAGE)
 pythonize_bool(LIBCXXABI_USE_LLVM_UNWINDER)
+pythonize_bool(LIBCXX_HAS_ATOMIC_LIB)
 
 # The tests shouldn't link to any ABI library when it has been linked into
 # libc++ statically or via a linker script.
Index: test/libcxx/test/target_info.py
===================================================================
--- test/libcxx/test/target_info.py
+++ test/libcxx/test/target_info.py
@@ -172,6 +172,9 @@
             flags += ['-lunwind', '-ldl']
         else:
             flags += ['-lgcc_s', '-lgcc']
+        use_libatomic = self.full_config.get_lit_bool('use_libatomic', False)
+        if use_libatomic:
+            flags += ['-latomic']
         san = self.full_config.get_lit_conf('use_sanitizer', '').strip()
         if san:
             # The libraries and their order are taken from the
Index: test/lit.site.cfg.in
===================================================================
--- test/lit.site.cfg.in
+++ test/lit.site.cfg.in
@@ -20,6 +20,7 @@
 config.target_info              = "@LIBCXX_TARGET_INFO@"
 config.executor                 = "@LIBCXX_EXECUTOR@"
 config.llvm_unwinder            = "@LIBCXXABI_USE_LLVM_UNWINDER@"
+config.use_libatomic            = "@LIBCXX_HAS_ATOMIC_LIB@"
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@LIBCXX_SOURCE_DIR@/test/lit.cfg")