Compressed diff from
```
git show d21664cce1db8debe2528f36b1fbd2b8af9c9401 87dac7da68ea1e0adac78c59ef1891dcf9632b67 3a0f6e699bb6d96dc62dce6faef20ac26cf103fd
```
with the purpose of avoiding linker errors arising in the polly-flavoured clang.

diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index a02c2a5a23f..faf8f561faa 100644
--- llvm/CMakeLists.txt
+++ llvm/CMakeLists.txt
@@ -1069,6 +1069,7 @@ endif()
 # after all targets are created.
 include(LLVMDistributionSupport)
 llvm_distribution_add_targets()
+process_llvm_pass_plugins(GEN_CONFIG)
 
 # This allows us to deploy the Universal CRT DLLs by passing -DCMAKE_INSTALL_UCRT_LIBRARIES=ON to CMake
 if (MSVC AND CMAKE_HOST_SYSTEM_NAME STREQUAL "Windows" AND CMAKE_INSTALL_UCRT_LIBRARIES)
@@ -1093,5 +1094,3 @@ endif()
 if (LLVM_INCLUDE_UTILS AND LLVM_INCLUDE_TOOLS)
   add_subdirectory(utils/llvm-locstats)
 endif()
-
-process_llvm_pass_plugins()
diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
index fd69786544a..8fbb33a22fd 100644
--- llvm/cmake/modules/AddLLVM.cmake
+++ llvm/cmake/modules/AddLLVM.cmake
@@ -884,53 +884,71 @@ function(add_llvm_pass_plugin name)
     if (TARGET intrinsics_gen)
       add_dependencies(obj.${name} intrinsics_gen)
     endif()
-    message(STATUS "Registering ${name} as a pass plugin (static build: ${LLVM_${name_upper}_LINK_INTO_TOOLS})")
-    set_property(GLOBAL APPEND PROPERTY LLVM_COMPILE_EXTENSIONS ${name})
+    set_property(GLOBAL APPEND PROPERTY LLVM_STATIC_EXTENSIONS ${name})
   elseif(NOT ARG_NO_MODULE)
     add_llvm_library(${name} MODULE ${ARG_UNPARSED_ARGUMENTS})
   else()
     add_llvm_library(${name} OBJECT ${ARG_UNPARSED_ARGUMENTS})
   endif()
+  message(STATUS "Registering ${name} as a pass plugin (static build: ${LLVM_${name_upper}_LINK_INTO_TOOLS})")
 
 endfunction(add_llvm_pass_plugin)
 
-# Generate X Macro file for extension handling. It provides a
-# HANDLE_EXTENSION(extension_namespace, ExtensionProject) call for each extension
-# allowing client code to define HANDLE_EXTENSION to have a specific code be run for
-# each extension.
+# process_llvm_pass_plugins([GEN_CONFIG])
+#
+# Correctly set lib dependencies between plugins and tools, based on tools
+# registered with the ENABLE_PLUGINS option.
+#
+# if GEN_CONFIG option is set, also generate X Macro file for extension
+# handling. It provides a HANDLE_EXTENSION(extension_namespace, ExtensionProject)
+# call for each extension allowing client code to define
+# HANDLE_EXTENSION to have a specific code be run for each extension.
 #
-# Also correctly set lib dependencies between plugins and tools.
 function(process_llvm_pass_plugins)
-  get_property(LLVM_EXTENSIONS GLOBAL PROPERTY LLVM_COMPILE_EXTENSIONS)
-  file(WRITE "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "//extension handlers\n")
-  foreach(llvm_extension ${LLVM_EXTENSIONS})
-    string(TOLOWER ${llvm_extension} llvm_extension_lower)
-
-    string(TOUPPER ${llvm_extension} llvm_extension_upper)
-    string(SUBSTRING ${llvm_extension_upper} 0 1 llvm_extension_upper_first)
-    string(SUBSTRING ${llvm_extension_lower} 1 -1 llvm_extension_lower_tail)
-    string(CONCAT llvm_extension_project ${llvm_extension_upper_first} ${llvm_extension_lower_tail})
-
-    if(LLVM_${llvm_extension_upper}_LINK_INTO_TOOLS)
-      file(APPEND "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "HANDLE_EXTENSION(${llvm_extension_project})\n")
-
-      get_property(llvm_plugin_targets GLOBAL PROPERTY LLVM_PLUGIN_TARGETS)
-      foreach(llvm_plugin_target ${llvm_plugin_targets})
-        set_property(TARGET ${llvm_plugin_target} APPEND PROPERTY LINK_LIBRARIES ${llvm_extension})
-        set_property(TARGET ${llvm_plugin_target} APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${llvm_extension})
-      endforeach()
-    else()
-      add_llvm_library(${llvm_extension_lower} MODULE obj.${llvm_extension_lower})
-    endif()
+  cmake_parse_arguments(ARG
+      "GEN_CONFIG" "" ""
+    ${ARGN})
 
+  if(ARG_GEN_CONFIG)
+      get_property(LLVM_STATIC_EXTENSIONS GLOBAL PROPERTY LLVM_STATIC_EXTENSIONS)
+  else()
+      include(LLVMConfigExtensions)
+  endif()
+
+  # Add static plugins to each plugin target.
+  foreach(llvm_extension ${LLVM_STATIC_EXTENSIONS})
+    get_property(llvm_plugin_targets GLOBAL PROPERTY LLVM_PLUGIN_TARGETS)
+    foreach(llvm_plugin_target ${llvm_plugin_targets})
+      set_property(TARGET ${llvm_plugin_target} APPEND PROPERTY LINK_LIBRARIES ${llvm_extension})
+      set_property(TARGET ${llvm_plugin_target} APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${llvm_extension})
+    endforeach()
   endforeach()
-  file(APPEND "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "#undef HANDLE_EXTENSION\n")
 
-  # only replace if there's an actual change
-  execute_process(COMMAND ${CMAKE_COMMAND} -E copy_if_different
-    "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp"
-    "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def")
-  file(REMOVE "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp")
+  # Eventually generate the extension header, and store config to a cmake file
+  # for usage in third-party configuration.
+  if(ARG_GEN_CONFIG)
+      set(LLVM_INSTALL_PACKAGE_DIR lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm)
+      set(llvm_cmake_builddir "${LLVM_BINARY_DIR}/${LLVM_INSTALL_PACKAGE_DIR}")
+      file(WRITE
+          "${llvm_cmake_builddir}/LLVMConfigExtensions.cmake"
+          "set(LLVM_STATIC_EXTENSIONS ${LLVM_STATIC_EXTENSIONS})")
+      install(FILES
+          ${llvm_cmake_builddir}/LLVMConfigExtensions.cmake
+          DESTINATION ${LLVM_INSTALL_PACKAGE_DIR}
+          COMPONENT cmake-exports)
+
+      file(WRITE "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "//extension handlers\n")
+      foreach(llvm_extension ${LLVM_STATIC_EXTENSIONS})
+        file(APPEND "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "HANDLE_EXTENSION(${llvm_extension})\n")
+      endforeach()
+      file(APPEND "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "#undef HANDLE_EXTENSION\n")
+
+      # only replace if there's an actual change
+      execute_process(COMMAND ${CMAKE_COMMAND} -E copy_if_different
+        "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp"
+        "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def")
+      file(REMOVE "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp")
+  endif()
 endfunction()
 
 function(export_executable_symbols target)
diff --git a/llvm/cmake/modules/CMakeLists.txt b/llvm/cmake/modules/CMakeLists.txt
index 9cf22b436fa..af757d6199a 100644
--- llvm/cmake/modules/CMakeLists.txt
+++ llvm/cmake/modules/CMakeLists.txt
@@ -136,6 +136,7 @@ if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
     FILES_MATCHING PATTERN *.cmake
     PATTERN .svn EXCLUDE
     PATTERN LLVMConfig.cmake EXCLUDE
+    PATTERN LLVMConfigExtensions.cmake EXCLUDE
     PATTERN LLVMConfigVersion.cmake EXCLUDE
     PATTERN LLVM-Config.cmake EXCLUDE
     PATTERN GetHostTriple.cmake EXCLUDE)