Address some post-commit review comments on r217261

llvm-svn: 217276
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: afe6794bc2ee35880e970e7e9fcde6c2ad72b51b
diff --git a/src/memory.cpp b/src/memory.cpp
index 31e823c..c56d031 100644
--- a/src/memory.cpp
+++ b/src/memory.cpp
@@ -121,7 +121,7 @@
 
 #endif  // _LIBCPP_NO_RTTI
 
-#if __has_feature(cxx_atomic) && !_LIBCPP_HAS_NO_THREADS
+#if __has_feature(cxx_atomic) && !defined(_LIBCPP_HAS_NO_THREADS)
 
 static const std::size_t __sp_mut_count = 16;
 static pthread_mutex_t mut_back_imp[__sp_mut_count] =