Index: llvm/trunk/CMakeLists.txt
===================================================================
--- llvm/trunk/CMakeLists.txt
+++ llvm/trunk/CMakeLists.txt
@@ -182,6 +182,7 @@
 endif()
 
 option(LLVM_ENABLE_CXX11 "Compile with C++11 enabled." OFF)
+option(LLVM_ENABLE_LIBCXX "Use libc++ if available." OFF)
 option(LLVM_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
 option(LLVM_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
 
Index: llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
@@ -253,6 +253,13 @@
     check_cxx_compiler_flag("-std=c++11" CXX_SUPPORTS_CXX11)
     append_if(CXX_SUPPORTS_CXX11 "-std=c++11" CMAKE_CXX_FLAGS)
   endif (LLVM_ENABLE_CXX11)
+  if(LLVM_ENABLE_LIBCXX)
+    check_cxx_compiler_flag("-stdlib=libc++" CXX_SUPPORTS_STDLIB)
+    append_if(CXX_SUPPORTS_STDLIB "-stdlib=libc++" CMAKE_CXX_FLAGS)
+    append_if(CXX_SUPPORTS_STDLIB "-stdlib=libc++" CMAKE_EXE_LINKER_FLAGS)
+    append_if(CXX_SUPPORTS_STDLIB "-stdlib=libc++" CMAKE_SHARED_LINKER_FLAGS)
+    append_if(CXX_SUPPORTS_STDLIB "-stdlib=libc++" CMAKE_MODULE_LINKER_FLAGS)
+  endif ()
 endif( MSVC )
 
 macro(append_common_sanitizer_flags)