Revert r211066, 211067, 211068, 211069, 211070.

These were committed accidentally from the wrong branch before having
a review sign-off.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211072 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 46 insertions, 28 deletions

diff --git a/lib/Support/ManagedStatic.cpp b/lib/Support/ManagedStatic.cpp
index ced2b13b3a..6a1c2a545a 100644
--- a/lib/Support/ManagedStatic.cpp
+++ b/lib/Support/ManagedStatic.cpp
@@ -14,36 +14,17 @@
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Config/config.h"
 #include "llvm/Support/Atomic.h"
-#include "llvm/Support/MutexGuard.h"
 #include <cassert>
-#include <mutex>
 using namespace llvm;
 
 static const ManagedStaticBase *StaticList = nullptr;
 
-// ManagedStatics can get created during execution of static constructors.  As a
-// result, we cannot use a global static std::mutex object for the lock since it
-// may not have been constructed.  Instead, we do a call-once initialization of
-// a pointer to a mutex.  This also means that we must not "initialize" the
-// mutex with nullptr, otherwise it might get reset to nullptr after being
-// initialized by std::call_once.
-static std::once_flag MutexInitializationFlag;
-static std::recursive_mutex *ManagedStaticMutex;
-
-namespace {
-  void InitializeManagedStaticMutex() {
-    std::call_once(MutexInitializationFlag,
-        []() { ManagedStaticMutex = new std::recursive_mutex(); });
-  }
-}
-
 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
                                               void (*Deleter)(void*)) const {
   assert(Creator);
   if (llvm_is_multithreaded()) {
-    InitializeManagedStaticMutex();
+    llvm_acquire_global_lock();
 
-    std::lock_guard<std::recursive_mutex> Lock(*ManagedStaticMutex);
     if (!Ptr) {
       void* tmp = Creator();
 
@@ -62,6 +43,8 @@ void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
       Next = StaticList;
       StaticList = this;
     }
+
+    llvm_release_global_lock();
   } else {
     assert(!Ptr && !DeleterFn && !Next &&
            "Partially initialized ManagedStatic!?");
@@ -92,9 +75,8 @@ void ManagedStaticBase::destroy() const {
 
 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
 void llvm::llvm_shutdown() {
-  InitializeManagedStaticMutex();
-  std::lock_guard<std::recursive_mutex> Lock(*ManagedStaticMutex);
-
   while (StaticList)
     StaticList->destroy();
+
+  if (llvm_is_multithreaded()) llvm_stop_multithreaded();
 }
diff --git a/lib/Support/Threading.cpp b/lib/Support/Threading.cpp
index 838a71b789..1acfa79b11 100644
--- a/lib/Support/Threading.cpp
+++ b/lib/Support/Threading.cpp
@@ -7,8 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file implements helper functions for running LLVM in a multi-threaded
-// environment.
+// This file implements llvm_start_multithreaded() and friends.
 //
 //===----------------------------------------------------------------------===//
 
@@ -20,14 +19,50 @@
 
 using namespace llvm;
 
-bool llvm::llvm_is_multithreaded() {
+static bool multithreaded_mode = false;
+
+static sys::Mutex* global_lock = nullptr;
+
+bool llvm::llvm_start_multithreaded() {
 #if LLVM_ENABLE_THREADS != 0
+  assert(!multithreaded_mode && "Already multithreaded!");
+  multithreaded_mode = true;
+  global_lock = new sys::Mutex(true);
+
+  // We fence here to ensure that all initialization is complete BEFORE we
+  // return from llvm_start_multithreaded().
+  sys::MemoryFence();
   return true;
 #else
   return false;
 #endif
 }
 
+void llvm::llvm_stop_multithreaded() {
+#if LLVM_ENABLE_THREADS != 0
+  assert(multithreaded_mode && "Not currently multithreaded!");
+
+  // We fence here to insure that all threaded operations are complete BEFORE we
+  // return from llvm_stop_multithreaded().
+  sys::MemoryFence();
+
+  multithreaded_mode = false;
+  delete global_lock;
+#endif
+}
+
+bool llvm::llvm_is_multithreaded() {
+  return multithreaded_mode;
+}
+
+void llvm::llvm_acquire_global_lock() {
+  if (multithreaded_mode) global_lock->acquire();
+}
+
+void llvm::llvm_release_global_lock() {
+  if (multithreaded_mode) global_lock->release();
+}
+
 #if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)
 #include <pthread.h>
 
diff --git a/lib/Support/Timer.cpp b/lib/Support/Timer.cpp
index 7738283bad..61465ae5e8 100644
--- a/lib/Support/Timer.cpp
+++ b/lib/Support/Timer.cpp
@@ -18,7 +18,7 @@
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/ManagedStatic.h"
-#include "llvm/Support/MutexGuard.h"
+#include "llvm/Support/Mutex.h"
 #include "llvm/Support/Process.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
@@ -84,13 +84,14 @@ static TimerGroup *getDefaultTimerGroup() {
   sys::MemoryFence();
   if (tmp) return tmp;
   
-  sys::SmartScopedLock<true> Lock(*TimerLock);
+  llvm_acquire_global_lock();
   tmp = DefaultTimerGroup;
   if (!tmp) {
     tmp = new TimerGroup("Miscellaneous Ungrouped Timers");
     sys::MemoryFence();
     DefaultTimerGroup = tmp;
   }
+  llvm_release_global_lock();
 
   return tmp;
 }