2 files changed, 39 insertions, 4 deletions

diff --git a/llvm/lib/Support/ManagedStatic.cpp b/llvm/lib/Support/ManagedStatic.cpp
index b8fb2841e52..b1feddc09ec 100644
--- a/llvm/lib/Support/ManagedStatic.cpp
+++ b/llvm/lib/Support/ManagedStatic.cpp
@@ -16,16 +16,23 @@
 #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;
+LLVM_DEFINE_ONCE_FLAG(mutex_init_flag);
 
-static sys::Mutex& getManagedStaticMutex() {
+static void initializeMutex() {
+  ManagedStaticMutex = new sys::Mutex();
+}
+
+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.
-  static sys::Mutex ManagedStaticMutex;
+  call_once(mutex_init_flag, initializeMutex);
   return ManagedStaticMutex;
 }
 
@@ -33,7 +40,7 @@ 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();
@@ -83,7 +90,7 @@ 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();
diff --git a/llvm/lib/Support/Threading.cpp b/llvm/lib/Support/Threading.cpp
index ca7f3f64aa3..a4e1e44261b 100644
--- a/llvm/lib/Support/Threading.cpp
+++ b/llvm/lib/Support/Threading.cpp
@@ -16,6 +16,7 @@
 #include "llvm/Config/config.h"
 #include "llvm/Support/Atomic.h"
 #include "llvm/Support/Mutex.h"
+#include "llvm/Support/thread.h"
 #include <cassert>
 
 using namespace llvm;
@@ -110,3 +111,30 @@ void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
 }
 
 #endif
+
+void llvm::call_once(once_flag &flag, void (*fptr)(void)) {
+#if LLVM_THREADING_USE_STD_CALL_ONCE
+  std::call_once(flag, fptr);
+#else
+  // For other platforms we use a generic (if brittle) version based on our
+  // atomics.
+  sys::cas_flag old_val = sys::CompareAndSwap(&flag, Wait, Uninitialized);
+  if (old_val == Uninitialized) {
+    fptr();
+    sys::MemoryFence();
+    TsanIgnoreWritesBegin();
+    TsanHappensBefore(&flag);
+    flag = Done;
+    TsanIgnoreWritesEnd();
+  } else {
+    // Wait until any thread doing the call has finished.
+    sys::cas_flag tmp = flag;
+    sys::MemoryFence();
+    while (tmp != Done) {
+      tmp = flag;
+      sys::MemoryFence();
+    }
+  }
+  TsanHappensAfter(&flag);
+#endif
+}