Use acquire/release stores and loads when reading and writing the parallel...

Use acquire/release stores and loads when reading and writing the parallel sweeping state of a page.

BUG=
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/214543008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20301 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/spaces.h

@@ -484,15 +484,15 @@ class MemoryChunk {
 
   ParallelSweepingState parallel_sweeping() {
     return static_cast<ParallelSweepingState>(
-        NoBarrier_Load(&parallel_sweeping_));
+        Acquire_Load(&parallel_sweeping_));
   }
 
   void set_parallel_sweeping(ParallelSweepingState state) {
-    NoBarrier_Store(&parallel_sweeping_, state);
+    Release_Store(&parallel_sweeping_, state);
   }
 
   bool TryParallelSweeping() {
-    return NoBarrier_CompareAndSwap(&parallel_sweeping_,
+    return Acquire_CompareAndSwap(&parallel_sweeping_,
                                   PARALLEL_SWEEPING_PENDING,
                                   PARALLEL_SWEEPING_IN_PROGRESS) ==
                                       PARALLEL_SWEEPING_PENDING;