--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/include/llvm/Support/UniqueLock.h	Mon Sep 08 22:06:00 2014 +0900
@@ -0,0 +1,67 @@
+//===-- Support/UniqueLock.h - Acquire/Release Mutex In Scope ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a guard for a block of code that ensures a Mutex is locked
+// upon construction and released upon destruction.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_UNIQUE_LOCK_H
+#define LLVM_SUPPORT_UNIQUE_LOCK_H
+
+#include "llvm/Support/Mutex.h"
+
+namespace llvm {
+  /// A pared-down imitation of std::unique_lock from C++11. Contrary to the
+  /// name, it's really more of a wrapper for a lock. It may or may not have
+  /// an associated mutex, which is guaranteed to be locked upon creation
+  /// and unlocked after destruction. unique_lock can also unlock the mutex
+  /// and re-lock it freely during its lifetime.
+  /// @brief Guard a section of code with a mutex.
+  template<typename MutexT>
+  class unique_lock {
+    MutexT *M;
+    bool locked;
+
+    unique_lock(const unique_lock &) LLVM_DELETED_FUNCTION;
+    void operator=(const unique_lock &) LLVM_DELETED_FUNCTION;
+  public:
+    unique_lock() : M(nullptr), locked(false) {}
+    explicit unique_lock(MutexT &m) : M(&m), locked(true) { M->lock(); }
+
+    void operator=(unique_lock &&o) {
+      if (owns_lock())
+        M->unlock();
+      M = o.M;
+      locked = o.locked;
+      o.M = nullptr;
+      o.locked = false;
+    }
+
+    ~unique_lock() { if (owns_lock()) M->unlock(); }
+
+    void lock() {
+      assert(!locked && "mutex already locked!");
+      assert(M && "no associated mutex!");
+      M->lock();
+      locked = true;
+    }
+
+    void unlock() {
+      assert(locked && "unlocking a mutex that isn't locked!");
+      assert(M && "no associated mutex!");
+      M->unlock();
+      locked = false;
+    }
+
+    bool owns_lock() { return locked; }
+  };
+}
+
+#endif // LLVM_SUPPORT_UNIQUE_LOCK_H