diff --git a/include/llvm/Support/Threading.h b/include/llvm/Support/Threading.h
index cc9727031fd..7e8758407c7 100644
--- a/include/llvm/Support/Threading.h
+++ b/include/llvm/Support/Threading.h
@@ -15,10 +15,6 @@
 #ifndef LLVM_SUPPORT_THREADING_H
 #define LLVM_SUPPORT_THREADING_H
 
-#if !defined(__MINGW__)
-#include <mutex>
-#endif
-
 namespace llvm {
   /// Returns true if LLVM is compiled with support for multi-threading, and
   /// false otherwise.
@@ -37,33 +33,6 @@ namespace llvm {
   /// the thread stack.
   void llvm_execute_on_thread(void (*UserFn)(void*), void *UserData,
                               unsigned RequestedStackSize = 0);
-
-/// \brief Execute the function specified as a template parameter once.
-///
-/// Calls \p UserFn once ever. The call uniqueness is based on the address of
-/// the function passed in via the template arguement. This means no matter how
-/// many times you call llvm_call_once<foo>() in the same or different
-/// locations, foo will only be called once.
-///
-/// Typical usage:
-/// \code
-///   void foo() {...};
-///   ...
-///   llvm_call_once<foo>();
-/// \endcode
-///
-/// \tparam UserFn Function to call once.
-template <void (*UserFn)(void)> void llvm_call_once() {
-#if !defined(__MINGW__)
-  static std::once_flag flag;
-  std::call_once(flag, UserFn);
-#else
-  struct InitOnceWrapper {
-    InitOnceWrapper() { UserFn(); }
-  };
-  static InitOnceWrapper InitOnceVar;
-#endif
-}
 }
 
 #endif
diff --git a/lib/Support/ManagedStatic.cpp b/lib/Support/ManagedStatic.cpp
index fbcce598b21..b8fb2841e52 100644
--- a/lib/Support/ManagedStatic.cpp
+++ b/lib/Support/ManagedStatic.cpp
@@ -16,22 +16,16 @@
 #include "llvm/Support/Atomic.h"
 #include "llvm/Support/Mutex.h"
 #include "llvm/Support/MutexGuard.h"
-#include "llvm/Support/Threading.h"
 #include <cassert>
 using namespace llvm;
 
 static const ManagedStaticBase *StaticList = nullptr;
-static sys::Mutex *ManagedStaticMutex = nullptr;
 
-static void initializeMutex() {
-  ManagedStaticMutex = new sys::Mutex();
-}
-
-static sys::Mutex* getManagedStaticMutex() {
+static sys::Mutex& getManagedStaticMutex() {
   // We need to use a function local static here, since this can get called
   // during a static constructor and we need to guarantee that it's initialized
   // correctly.
-  llvm_call_once<initializeMutex>();
+  static sys::Mutex ManagedStaticMutex;
   return ManagedStaticMutex;
 }
 
@@ -39,7 +33,7 @@ void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
                                               void (*Deleter)(void*)) const {
   assert(Creator);
   if (llvm_is_multithreaded()) {
-    MutexGuard Lock(*getManagedStaticMutex());
+    MutexGuard Lock(getManagedStaticMutex());
 
     if (!Ptr) {
       void* tmp = Creator();
@@ -89,13 +83,8 @@ void ManagedStaticBase::destroy() const {
 
 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
 void llvm::llvm_shutdown() {
-  {
-    MutexGuard Lock(*getManagedStaticMutex());
+  MutexGuard Lock(getManagedStaticMutex());
 
-    while (StaticList)
-      StaticList->destroy();
-  }
-
-  delete ManagedStaticMutex;
-  ManagedStaticMutex = nullptr;
+  while (StaticList)
+    StaticList->destroy();
 }