[llvm] r219638 - Removing the static destructor from ManagedStatic.cpp by controlling the allocation and de-allocation of the mutex.

[Chris Bieneman]

Author: cbieneman
Date: Mon Oct 13 17:37:25 2014
New Revision: 219638

URL: http://llvm.org/viewvc/llvm-project?rev=219638&view=rev
Log:
Removing the static destructor from ManagedStatic.cpp by controlling the allocation and de-allocation of the mutex.

This patch adds a new llvm_call_once function which is used by the ManagedStatic implementation to safely initialize a global to avoid static construction and destruction.

Modified:
    llvm/trunk/include/llvm/Support/Threading.h
    llvm/trunk/lib/Support/ManagedStatic.cpp

Modified: llvm/trunk/include/llvm/Support/Threading.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Threading.h?rev=219638&r1=219637&r2=219638&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/Threading.h (original)
+++ llvm/trunk/include/llvm/Support/Threading.h Mon Oct 13 17:37:25 2014
@@ -15,6 +15,10 @@
 #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.
@@ -33,6 +37,20 @@ namespace llvm {
   /// the thread stack.
   void llvm_execute_on_thread(void (*UserFn)(void*), void *UserData,
                               unsigned RequestedStackSize = 0);
+
+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

Modified: llvm/trunk/lib/Support/ManagedStatic.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/ManagedStatic.cpp?rev=219638&r1=219637&r2=219638&view=diff
==============================================================================
--- llvm/trunk/lib/Support/ManagedStatic.cpp (original)
+++ llvm/trunk/lib/Support/ManagedStatic.cpp Mon Oct 13 17:37:25 2014
@@ -16,16 +16,22 @@
 #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 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;
+  llvm_call_once<initializeMutex>();
   return ManagedStaticMutex;
 }
 
@@ -33,7 +39,7 @@ void ManagedStaticBase::RegisterManagedS
                                               void (*Deleter)(void*)) const {
   assert(Creator);
   if (llvm_is_multithreaded()) {
-    MutexGuard Lock(getManagedStaticMutex());
+    MutexGuard Lock(*getManagedStaticMutex());
 
     if (!Ptr) {
       void* tmp = Creator();
@@ -83,8 +89,13 @@ 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();
+  }
 
-  while (StaticList)
-    StaticList->destroy();
+  delete ManagedStaticMutex;
+  ManagedStaticMutex = nullptr;
 }