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diff --git a/runtime/atomic.h b/runtime/atomic.h
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+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_SRC_ATOMIC_H_
+#define ART_SRC_ATOMIC_H_
+
+#include <stdint.h>
+
+#include "base/macros.h"
+
+namespace art {
+
+// NOTE: Two "quasiatomic" operations on the exact same memory address
+// are guaranteed to operate atomically with respect to each other,
+// but no guarantees are made about quasiatomic operations mixed with
+// non-quasiatomic operations on the same address, nor about
+// quasiatomic operations that are performed on partially-overlapping
+// memory.
+class QuasiAtomic {
+ public:
+  static void Startup();
+
+  static void Shutdown();
+
+  // Reads the 64-bit value at "addr" without tearing.
+  static int64_t Read64(volatile const int64_t* addr);
+
+  // Writes to the 64-bit value at "addr" without tearing.
+  static void Write64(volatile int64_t* addr, int64_t val);
+
+  // Atomically compare the value at "addr" to "old_value", if equal replace it with "new_value"
+  // and return true. Otherwise, don't swap, and return false.
+  static bool Cas64(int64_t old_value, int64_t new_value, volatile int64_t* addr);
+
+  // Does the architecture provide reasonable atomic long operations or do we fall back on mutexes?
+  static bool LongAtomicsUseMutexes();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(QuasiAtomic);
+};
+
+}  // namespace art
+
+#endif  // ART_SRC_ATOMIC_H_