Index: test/builtins/CMakeLists.txt
===================================================================
--- test/builtins/CMakeLists.txt
+++ test/builtins/CMakeLists.txt
@@ -9,6 +9,23 @@
   ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg
 )
 
+#Unit tests.
+
+include(builtin-config-ix)
+
+foreach(arch ${BUILTIN_SUPPORTED_ARCH})
+  set(BUILTINS_TEST_TARGET_ARCH ${arch})
+  string(TOLOWER "-${arch}-${OS_NAME}" BUILTINS_TEST_CONFIG_SUFFIX)
+  get_test_cc_for_arch(${arch} BUILTINS_TEST_TARGET_CC BUILTINS_TEST_TARGET_CFLAGS)
+  string(TOUPPER ${arch} ARCH_UPPER_CASE)
+  set(CONFIG_NAME ${ARCH_UPPER_CASE}${OS_NAME}Config)
+  configure_lit_site_cfg(
+    ${CMAKE_CURRENT_SOURCE_DIR}/Unit/lit.site.cfg.in
+    ${CMAKE_CURRENT_BINARY_DIR}/Unit/${CONFIG_NAME}/lit.site.cfg
+    )
+  list(APPEND BUILTINS_TESTSUITES ${CMAKE_CURRENT_BINARY_DIR}/Unit/${CONFIG_NAME})
+endforeach()
+
 add_lit_testsuite(check-builtins "Running the Builtins tests"
   ${BUILTINS_TESTSUITES}
   DEPENDS ${BUILTINS_TEST_DEPS})
Index: test/builtins/Unit/lit.cfg
===================================================================
--- /dev/null
+++ test/builtins/Unit/lit.cfg
@@ -0,0 +1,80 @@
+# -*- Python -*-
+
+import os
+import platform
+
+import lit.formats
+
+def get_required_attr(config, attr_name):
+  attr_value = getattr(config, attr_name, None)
+  if attr_value == None:
+    lit_config.fatal(
+      "No attribute %r in test configuration! You may need to run "
+      "tests from your build directory or add this attribute "
+      "to lit.site.cfg " % attr_name)
+  return attr_value
+
+# Setup config name.
+config.name = 'Builtins' + config.name_suffix
+
+# Platform-specific default Builtins_OPTIONS for lit tests.
+default_builtins_opts = ''
+
+# Setup source root.
+config.test_source_root = os.path.dirname(__file__)
+
+# Path to the static library
+base_lib = os.path.join(config.compiler_rt_libdir, "libclang_rt.builtins-%s.a "
+    % config.target_arch)
+
+builtins_source_dir = os.path.join(
+  get_required_attr(config, "compiler_rt_src_root"), "lib", "builtins")
+builtins_lit_source_dir = get_required_attr(config, "builtins_lit_source_dir")
+
+extra_link_flags = ["-nodefaultlibs"]
+config.substitutions.append( ("%librt ", base_lib + ' -lc -lm ') )
+
+target_cflags = [get_required_attr(config, "target_cflags")]
+target_cflags += ['-fno-builtin', '-I', builtins_source_dir]
+target_cflags += extra_link_flags
+target_cxxflags = config.cxx_mode_flags + target_cflags
+clang_builtins_static_cflags = ([""] +
+                            config.debug_info_flags + target_cflags)
+clang_builtins_static_cxxflags = config.cxx_mode_flags + \
+                                 clang_builtins_static_cflags
+
+clang_builtins_cflags = clang_builtins_static_cflags
+clang_builtins_cxxflags = clang_builtins_static_cxxflags
+
+
+config.available_features.add('not-android')
+clang_wrapper = ""
+
+def build_invocation(compile_flags):
+  return " " + " ".join([clang_wrapper, config.clang] + compile_flags) + " "
+
+
+target_arch = config.target_arch
+if (target_arch == "arm"):
+  target_arch = "armv7"
+
+config.substitutions.append( ("%clang ", build_invocation(target_cflags)) )
+config.substitutions.append( ("%clangxx ", build_invocation(target_cxxflags)) )
+config.substitutions.append( ("%clang_builtins ", \
+                              build_invocation(clang_builtins_cflags)))
+config.substitutions.append( ("%clangxx_builtins ", \
+                              build_invocation(clang_builtins_cxxflags)))
+
+# FIXME: move the call_apsr.s into call_apsr.h as inline-asm.
+# some ARM tests needs call_apsr.s
+call_apsr_source = os.path.join(builtins_lit_source_dir, 'arm', 'call_apsr.S')
+march_flag = '-march=' + target_arch
+call_apsr_flags = ['-c', march_flag, call_apsr_source]
+config.substitutions.append( ("%arm_call_apsr ", \
+                              build_invocation(call_apsr_flags)) )
+
+# Default test suffixes.
+config.suffixes = ['.c', '.cc', '.cpp']
+
+if not config.emulator:
+  config.available_features.add('native-run')
Index: test/builtins/Unit/lit.site.cfg.in
===================================================================
--- /dev/null
+++ test/builtins/Unit/lit.site.cfg.in
@@ -0,0 +1,12 @@
+@LIT_SITE_CFG_IN_HEADER@
+
+config.name_suffix = "@BUILTINS_TEST_CONFIG_SUFFIX@"
+config.builtins_lit_source_dir = "@BUILTINS_LIT_SOURCE_DIR@/Unit"
+config.target_cflags = "@BUILTINS_TEST_TARGET_CFLAGS@"
+config.target_arch = "@BUILTINS_TEST_TARGET_ARCH@"
+
+# Load common config for all compiler-rt lit tests.
+lit_config.load_config(config, "@COMPILER_RT_BINARY_DIR@/test/lit.common.configured")
+
+# Load tool-specific config that would do the real work.
+lit_config.load_config(config, "@BUILTINS_LIT_SOURCE_DIR@/Unit/lit.cfg")