Index: llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
@@ -96,6 +96,9 @@
 set(LLVM_PLUGIN_EXT ${CMAKE_SHARED_LIBRARY_SUFFIX})
 
 if(APPLE)
+  if(LLVM_ENABLE_LLD AND LLVM_ENABLE_LTO)
+    message(FATAL_ERROR "lld does not support LTO on Darwin")
+  endif()
   # Darwin-specific linker flags for loadable modules.
   set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -Wl,-flat_namespace -Wl,-undefined -Wl,suppress")
 endif()