diff --git a/openmp/CMakeLists.txt b/openmp/CMakeLists.txt
--- a/openmp/CMakeLists.txt
+++ b/openmp/CMakeLists.txt
@@ -37,6 +37,35 @@
   set(OPENMP_TEST_CXX_COMPILER ${CMAKE_CXX_COMPILER} CACHE STRING
     "C++ compiler to use for testing OpenMP runtime libraries.")
   set(OPENMP_LLVM_TOOLS_DIR "" CACHE PATH "Path to LLVM tools for testing.")
+
+  if (NOT DEFINED LLVM_PATH)
+    set(LLVM_PATH ${CMAKE_CURRENT_LIST_DIR}/../llvm CACHE PATH "" FORCE)
+  endif()
+
+  if(NOT IS_DIRECTORY ${LLVM_PATH})
+    message(WARNING
+      "The provided LLVM_PATH (${LLVM_PATH}) is not a valid directory.")
+  endif()
+
+  set(LLVM_PATH ${LLVM_PATH} CACHE PATH "Path to LLVM source tree")
+  set(LLVM_MAIN_SRC_DIR ${LLVM_PATH})
+  set(LLVM_CMAKE_DIR "${LLVM_PATH}/cmake/modules")
+
+  set(LLVM_LIT_OUTPUT_DIR "${CMAKE_CURRENT_BINARY_DIR}/bin")
+
+  if (EXISTS "${LLVM_CMAKE_DIR}")
+    list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
+    find_package(Python3 REQUIRED COMPONENTS Interpreter)
+    include(AddLLVM)
+  endif()
+
+  set(DEFAULT_LIT_ARGS "-sv --show-unsupported --show-xfail")
+  if (MSVC OR XCODE)
+    set(DEFAULT_LIT_ARGS "${DEFAULT_LIT_ARGS} --no-progress-bar")
+  endif()
+  set(OPENMP_LIT_ARGS "${DEFAULT_LIT_ARGS}" CACHE STRING "Options for lit.")
+  set(LLVM_LIT_ARGS "${OPENMP_LIT_ARGS}")
+  separate_arguments(OPENMP_LIT_ARGS)
 else()
   set(OPENMP_ENABLE_WERROR ${LLVM_ENABLE_WERROR})
   # If building in tree, we honor the same install suffix LLVM uses.
@@ -120,3 +149,12 @@
 
 # Now that we have seen all testsuites, create the check-openmp target.
 construct_check_openmp_target()
+
+if (OPENMP_STANDALONE_BUILD AND EXISTS "${LLVM_MAIN_SRC_DIR}")
+  # Make sure the llvm-lit script is generated into the bin directory, and
+  # do it after adding all tests, since the generated script will only work
+  # correctly discovered tests against test locations from the source tree
+  # that have already been discovered.
+  add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/llvm-lit
+                   ${CMAKE_CURRENT_BINARY_DIR}/llvm-lit)
+endif()
diff --git a/openmp/cmake/OpenMPTesting.cmake b/openmp/cmake/OpenMPTesting.cmake
--- a/openmp/cmake/OpenMPTesting.cmake
+++ b/openmp/cmake/OpenMPTesting.cmake
@@ -13,15 +13,19 @@
   endif()
 
   # Find executables.
-  find_program(OPENMP_LLVM_LIT_EXECUTABLE
-    NAMES llvm-lit.py llvm-lit lit.py lit
-    PATHS ${OPENMP_LLVM_TOOLS_DIR})
-  if (NOT OPENMP_LLVM_LIT_EXECUTABLE)
-    message(STATUS "Cannot find llvm-lit.")
-    message(STATUS "Please put llvm-lit in your PATH, set OPENMP_LLVM_LIT_EXECUTABLE to its full path, or point OPENMP_LLVM_TOOLS_DIR to its directory.")
-    message(WARNING "The check targets will not be available!")
-    set(ENABLE_CHECK_TARGETS FALSE PARENT_SCOPE)
-    return()
+  # If we've got add_lit_testsuite, we've got the main llvm source directory,
+  # and will generate the llvm-lit script at the end.
+  if (NOT COMMAND add_lit_testsuite)
+    find_program(OPENMP_LLVM_LIT_EXECUTABLE
+      NAMES llvm-lit.py llvm-lit lit.py lit
+      PATHS ${OPENMP_LLVM_TOOLS_DIR})
+    if (NOT OPENMP_LLVM_LIT_EXECUTABLE)
+      message(STATUS "Cannot find llvm-lit.")
+      message(STATUS "Please put llvm-lit in your PATH, set OPENMP_LLVM_LIT_EXECUTABLE to its full path, or point OPENMP_LLVM_TOOLS_DIR to its directory.")
+      message(WARNING "The check targets will not be available!")
+      set(ENABLE_CHECK_TARGETS FALSE PARENT_SCOPE)
+      return()
+    endif()
   endif()
 
   find_program(OPENMP_FILECHECK_EXECUTABLE
@@ -49,14 +53,6 @@
 
 if (${OPENMP_STANDALONE_BUILD})
   find_standalone_test_dependencies()
-
-  # Set lit arguments.
-  set(DEFAULT_LIT_ARGS "-sv --show-unsupported --show-xfail")
-  if (MSVC OR XCODE)
-    set(DEFAULT_LIT_ARGS "${DEFAULT_LIT_ARGS} --no-progress-bar")
-  endif()
-  set(OPENMP_LIT_ARGS "${DEFAULT_LIT_ARGS}" CACHE STRING "Options for lit.")
-  separate_arguments(OPENMP_LIT_ARGS)
 else()
   if (NOT TARGET "FileCheck")
     message(STATUS "Cannot find 'FileCheck'.")
@@ -190,7 +186,7 @@
     set_property(GLOBAL APPEND PROPERTY OPENMP_LIT_DEPENDS ${ARG_DEPENDS})
   endif()
 
-  if (${OPENMP_STANDALONE_BUILD})
+  if (NOT COMMAND add_lit_testsuite)
     set(LIT_ARGS ${OPENMP_LIT_ARGS} ${ARG_ARGS})
     add_custom_target(${target}
       COMMAND ${PYTHON_EXECUTABLE} ${OPENMP_LLVM_LIT_EXECUTABLE} ${LIT_ARGS} ${ARG_UNPARSED_ARGUMENTS}
@@ -199,19 +195,23 @@
       USES_TERMINAL
     )
   else()
+    if (NOT OPENMP_STANDALONE_BUILD)
+      list(APPEND ARG_DEPENDS clang FileCheck not)
+    endif()
+
     if (ARG_EXCLUDE_FROM_CHECK_ALL)
       add_lit_testsuite(${target}
         ${comment}
         ${ARG_UNPARSED_ARGUMENTS}
         EXCLUDE_FROM_CHECK_ALL
-        DEPENDS clang FileCheck not ${ARG_DEPENDS}
+        DEPENDS ${ARG_DEPENDS}
         ARGS ${ARG_ARGS}
       )
     else()
       add_lit_testsuite(${target}
         ${comment}
         ${ARG_UNPARSED_ARGUMENTS}
-        DEPENDS clang FileCheck not ${ARG_DEPENDS}
+        DEPENDS ${ARG_DEPENDS}
         ARGS ${ARG_ARGS}
       )
     endif()
diff --git a/openmp/runtime/test/CMakeLists.txt b/openmp/runtime/test/CMakeLists.txt
--- a/openmp/runtime/test/CMakeLists.txt
+++ b/openmp/runtime/test/CMakeLists.txt
@@ -43,4 +43,10 @@
 
 # Configure the lit.site.cfg.in file
 set(AUTO_GEN_COMMENT "## Autogenerated by libomp configuration.\n# Do not edit!")
-configure_file(lit.site.cfg.in lit.site.cfg @ONLY)
+if (COMMAND configure_lit_site_cfg)
+  configure_lit_site_cfg("${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in" "${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg"
+      MAIN_CONFIG "${CMAKE_CURRENT_SOURCE_DIR}/lit.cfg")
+else()
+  # Building standalone, without the main llvm directory available.
+  configure_file(lit.site.cfg.in lit.site.cfg @ONLY)
+endif()