Fix atomicops internal implementation using GCC intrinsics.

base/atomicops_internals_gcc.h

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file is an internal atomic implementation, include base/atomicops.h
 // instead. This file is for platforms that use GCC intrinsics rather than
 // platform-specific assembly code for atomic operations.
 
 #ifndef BASE_ATOMICOPS_INTERNALS_GCC_H_
 #define BASE_ATOMICOPS_INTERNALS_GCC_H_
 
 namespace base {
 namespace subtle {
 
 inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
                                          Atomic32 old_value,
                                          Atomic32 new_value) {
   Atomic32 prev_value;
   do {
-    prev_value = __sync_val_compare_and_swap(ptr, old_value, new_value);
-  } while (prev_value != old_value);
-  return old_value;
+    if (__sync_bool_compare_and_swap(ptr, old_value, new_value))
+      return old_value;
+    prev_value = *ptr;
+  } while (prev_value == old_value);
+  return prev_value;
 }
 
 inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
                                          Atomic32 new_value) {
   Atomic32 old_value;
   do {
     old_value = *ptr;
   } while (!__sync_bool_compare_and_swap(ptr, old_value, new_value));
   return old_value;
 }
@@ skipping 62 matching lines @@
 inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
   MemoryBarrier();
   return *ptr;
 }
 
 }  // namespace base::subtle
 }  // namespace base
 
 #endif  // BASE_ATOMICOPS_INTERNALS_GCC_H_