Index: llvm/trunk/CMakeLists.txt
===================================================================
--- llvm/trunk/CMakeLists.txt
+++ llvm/trunk/CMakeLists.txt
@@ -40,6 +40,12 @@
                   "host compiler, pass -Thost=x64 on the CMake command line.")
 endif()
 
+if (CMAKE_GENERATOR STREQUAL "Xcode" AND NOT CMAKE_OSX_ARCHITECTURES)
+  # Some CMake features like object libraries get confused if you don't
+  # explicitly specify an architecture setting with the Xcode generator.
+  set(CMAKE_OSX_ARCHITECTURES "x86_64")
+endif()
+
 project(LLVM
   VERSION ${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}
   LANGUAGES C CXX ASM)
Index: llvm/trunk/cmake/modules/AddLLVM.cmake
===================================================================
--- llvm/trunk/cmake/modules/AddLLVM.cmake
+++ llvm/trunk/cmake/modules/AddLLVM.cmake
@@ -433,7 +433,12 @@
       ${ALL_FILES}
       )
     llvm_update_compile_flags(${obj_name})
-    set(ALL_FILES "$<TARGET_OBJECTS:${obj_name}>")
+    if(CMAKE_GENERATOR STREQUAL "Xcode")
+      set(DUMMY_FILE ${CMAKE_CURRENT_BINARY_DIR}/Dummy.c)
+      file(WRITE ${DUMMY_FILE} "// This file intentionally empty\n")
+      set_property(SOURCE ${DUMMY_FILE} APPEND_STRING PROPERTY COMPILE_FLAGS "-Wno-empty-translation-unit")
+    endif()
+    set(ALL_FILES "$<TARGET_OBJECTS:${obj_name}>" ${DUMMY_FILE})
 
     # Do add_dependencies(obj) later due to CMake issue 14747.
     list(APPEND objlibs ${obj_name})