Index: llvm/cmake/modules/AddLLVM.cmake
===================================================================
--- llvm/cmake/modules/AddLLVM.cmake
+++ llvm/cmake/modules/AddLLVM.cmake
@@ -687,7 +687,7 @@
     # it forces Xcode to properly link the static library.
     list(APPEND ALL_FILES "${LLVM_MAIN_SRC_DIR}/cmake/dummy.cpp")
   endif()
-  
+
   if( EXCLUDE_FROM_ALL )
     add_executable(${name} EXCLUDE_FROM_ALL ${ALL_FILES})
   else()
@@ -1112,7 +1112,13 @@
 # variables needed for the 'lit.site.cfg' files. This function bundles the
 # common variables that any Lit instance is likely to need, and custom
 # variables can be passed in.
-function(configure_lit_site_cfg input output)
+function(configure_lit_site_cfg site_in site_out)
+  cmake_parse_arguments(ARG "" "" "MAIN_CONFIG" ${ARGN})
+
+  if ("${ARG_MAIN_CONFIG}" STREQUAL "")
+    set(ARG_MAIN_CONFIG "${CMAKE_CURRENT_SOURCE_DIR}/lit.cfg")
+  endif()
+
   foreach(c ${LLVM_TARGETS_TO_BUILD})
     set(TARGETS_BUILT "${TARGETS_BUILT} ${c}")
   endforeach(c)
@@ -1158,7 +1164,7 @@
   set(HOST_CXX "${CMAKE_CXX_COMPILER} ${CMAKE_CXX_COMPILER_ARG1}")
   set(HOST_LDFLAGS "${CMAKE_EXE_LINKER_FLAGS}")
 
-  set(LIT_SITE_CFG_IN_HEADER  "## Autogenerated from ${input}\n## Do not edit!")
+  set(LIT_SITE_CFG_IN_HEADER  "## Autogenerated from ${site_in}\n## Do not edit!")
 
   # Override config_target_triple (and the env)
   if(LLVM_TARGET_TRIPLE_ENV)
@@ -1177,10 +1183,10 @@
      "import lit.llvm\n"
      "lit.llvm.initialize(lit_config, config)\n")
 
-  configure_file(${input} ${output} @ONLY)
-  get_filename_component(INPUT_DIR ${input} DIRECTORY)
-  if (EXISTS "${INPUT_DIR}/lit.cfg")
-    set(PYTHON_STATEMENT "map_config('${INPUT_DIR}/lit.cfg', '${output}')")
+  configure_file(${site_in} ${site_out} @ONLY)
+  get_filename_component(INPUT_DIR ${site_in} DIRECTORY)
+  if (EXISTS "${ARG_MAIN_CONFIG}")
+    set(PYTHON_STATEMENT "map_config('${ARG_MAIN_CONFIG}', '${site_out}')")
     get_property(LLVM_LIT_CONFIG_MAP GLOBAL PROPERTY LLVM_LIT_CONFIG_MAP)
     set(LLVM_LIT_CONFIG_MAP "${LLVM_LIT_CONFIG_MAP}\n${PYTHON_STATEMENT}")
     set_property(GLOBAL PROPERTY LLVM_LIT_CONFIG_MAP ${LLVM_LIT_CONFIG_MAP})
@@ -1365,7 +1371,7 @@
   # magic. First we grab one of the types, and a type-specific path. Then from
   # the type-specific path we find the last occurrence of the type in the path,
   # and replace it with CMAKE_CFG_INTDIR. This allows the build step to be type
-  # agnostic again. 
+  # agnostic again.
   if(NOT ARG_OUTPUT_DIR)
     # If you're not overriding the OUTPUT_DIR, we can make the link relative in
     # the same directory.
Index: llvm/test/CMakeLists.txt
===================================================================
--- llvm/test/CMakeLists.txt
+++ llvm/test/CMakeLists.txt
@@ -11,12 +11,16 @@
   BUILD_SHARED_LIBS)
 
 configure_lit_site_cfg(
-  ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in
-  ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg
+  ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.py.in
+  ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg.py
+  MAIN_CONFIG
+  ${CMAKE_CURRENT_SOURCE_DIR}/lit.cfg.py
   )
 configure_lit_site_cfg(
-  ${CMAKE_CURRENT_SOURCE_DIR}/Unit/lit.site.cfg.in
-  ${CMAKE_CURRENT_BINARY_DIR}/Unit/lit.site.cfg
+  ${CMAKE_CURRENT_SOURCE_DIR}/Unit/lit.site.cfg.py.in
+  ${CMAKE_CURRENT_BINARY_DIR}/Unit/lit.site.cfg.py
+  MAIN_CONFIG
+  ${CMAKE_CURRENT_SOURCE_DIR}/Unit/lit.cfg.py
   )
 
 # Don't include check-llvm into check-all without LLVM_BUILD_TOOLS.
@@ -148,15 +152,11 @@
 
 add_lit_testsuite(check-llvm "Running the LLVM regression tests"
   ${CMAKE_CURRENT_BINARY_DIR}
-  PARAMS llvm_site_config=${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg
-         llvm_unit_site_config=${CMAKE_CURRENT_BINARY_DIR}/Unit/lit.site.cfg
   DEPENDS ${LLVM_TEST_DEPENDS}
   )
 set_target_properties(check-llvm PROPERTIES FOLDER "Tests")
 
 add_lit_testsuites(LLVM ${CMAKE_CURRENT_SOURCE_DIR}
-  PARAMS llvm_site_config=${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg
-         llvm_unit_site_config=${CMAKE_CURRENT_BINARY_DIR}/Unit/lit.site.cfg
   DEPENDS ${LLVM_TEST_DEPENDS}
   )
 
Index: llvm/test/Unit/lit.site.cfg.py.in
===================================================================
--- llvm/test/Unit/lit.site.cfg.py.in
+++ llvm/test/Unit/lit.site.cfg.py.in
@@ -20,4 +20,4 @@
     lit_config.fatal("unable to find %r parameter, use '--param=%s=VALUE'" % (key,key))
 
 # Let the main config do the real work.
-lit_config.load_config(config, "@LLVM_SOURCE_DIR@/test/Unit/lit.cfg")
+lit_config.load_config(config, "@LLVM_SOURCE_DIR@/test/Unit/lit.cfg.py")
Index: llvm/test/lit.site.cfg.py.in
===================================================================
--- llvm/test/lit.site.cfg.py.in
+++ llvm/test/lit.site.cfg.py.in
@@ -55,4 +55,4 @@
 @LIT_SITE_CFG_IN_FOOTER@
 
 # Let the main config do the real work.
-lit_config.load_config(config, "@LLVM_SOURCE_DIR@/test/lit.cfg")
+lit_config.load_config(config, "@LLVM_SOURCE_DIR@/test/lit.cfg.py")
Index: llvm/utils/lit/lit/LitConfig.py
===================================================================
--- llvm/utils/lit/lit/LitConfig.py
+++ llvm/utils/lit/lit/LitConfig.py
@@ -43,9 +43,10 @@
 
         # Configuration files to look for when discovering test suites.
         self.config_prefix = config_prefix or 'lit'
-        self.config_name = '%s.cfg' % (self.config_prefix,)
-        self.site_config_name = '%s.site.cfg' % (self.config_prefix,)
-        self.local_config_name = '%s.local.cfg' % (self.config_prefix,)
+        self.suffixes = ['cfg.py', 'cfg']
+        self.config_names = ['%s.%s' % (self.config_prefix,x) for x in self.suffixes]
+        self.site_config_names = ['%s.site.%s' % (self.config_prefix,x) for x in self.suffixes]
+        self.local_config_names = ['%s.local.%s' % (self.config_prefix,x) for x in self.suffixes]
 
         self.numErrors = 0
         self.numWarnings = 0
Index: llvm/utils/lit/lit/discovery.py
===================================================================
--- llvm/utils/lit/lit/discovery.py
+++ llvm/utils/lit/lit/discovery.py
@@ -10,13 +10,18 @@
 from lit.TestingConfig import TestingConfig
 from lit import LitConfig, Test
 
+def chooseConfigFileFromDir(dir, config_names):
+    for name in config_names:
+        p = os.path.join(dir, name)
+        if os.path.exists(p):
+            return p
+    return None
+
 def dirContainsTestSuite(path, lit_config):
-    cfgpath = os.path.join(path, lit_config.site_config_name)
-    if os.path.exists(cfgpath):
-        return cfgpath
-    cfgpath = os.path.join(path, lit_config.config_name)
-    if os.path.exists(cfgpath):
-        return cfgpath
+    cfgpath = chooseConfigFileFromDir(path, lit_config.site_config_names)
+    if not cfgpath:
+        cfgpath = chooseConfigFileFromDir(path, lit_config.config_names)
+    return cfgpath
 
 def getTestSuite(item, litConfig, cache):
     """getTestSuite(item, litConfig, cache) -> (suite, relative_path)
@@ -92,10 +97,10 @@
 
         # Check if there is a local configuration file.
         source_path = ts.getSourcePath(path_in_suite)
-        cfgpath = os.path.join(source_path, litConfig.local_config_name)
+        cfgpath = chooseConfigFileFromDir(source_path, litConfig.local_config_names)
 
         # If not, just reuse the parent config.
-        if not os.path.exists(cfgpath):
+        if not cfgpath:
             return parent
 
         # Otherwise, copy the current config and load the local configuration