Index: compiler-rt/trunk/cmake/config-ix.cmake
===================================================================
--- compiler-rt/trunk/cmake/config-ix.cmake
+++ compiler-rt/trunk/cmake/config-ix.cmake
@@ -27,7 +27,7 @@
 check_cxx_compiler_flag(-std=c++11           COMPILER_RT_HAS_STD_CXX11_FLAG)
 check_cxx_compiler_flag(-ftls-model=initial-exec COMPILER_RT_HAS_FTLS_MODEL_INITIAL_EXEC)
 check_cxx_compiler_flag(-fno-lto             COMPILER_RT_HAS_FNO_LTO_FLAG)
-check_cxx_compiler_flag(-msse3               COMPILER_RT_HAS_MSSE3_FLAG)
+check_cxx_compiler_flag("-Werror -msse3" COMPILER_RT_HAS_MSSE3_FLAG)
 check_cxx_compiler_flag(-std=c99             COMPILER_RT_HAS_STD_C99_FLAG)
 check_cxx_compiler_flag(--sysroot=.          COMPILER_RT_HAS_SYSROOT_FLAG)
 
@@ -574,14 +574,6 @@
   set(COMPILER_RT_HAS_UBSAN FALSE)
 endif()
 
-# -msse3 flag is not valid for Mips therefore clang gives a warning
-# message with -msse3. But check_c_compiler_flags() checks only for
-# compiler error messages. Therefore COMPILER_RT_HAS_MSSE3_FLAG turns out to be
-# true on Mips, so we make it false here.
-if("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "mips")
-  set(COMPILER_RT_HAS_MSSE3_FLAG FALSE)
-endif()
-
 if (COMPILER_RT_HAS_SANITIZER_COMMON AND SAFESTACK_SUPPORTED_ARCH AND
     OS_NAME MATCHES "Darwin|Linux|FreeBSD")
   set(COMPILER_RT_HAS_SAFESTACK TRUE)