Reduce unnecessary read barriers in GC

Removed read barrier from IsUnprocessed, DequeuePendingReference,
EnqueueReference, and a few other places.

Hard to tell if GC time goes down.

EAAC:
Before GC slow path count: 254857
After GC slow path count: 1005

Bug: 30162165
Bug: 12687968

Test: test-art-host, volantis boot with CC

Change-Id: Ic2add3a9b1e1d7561b0b167f2218b10f8dbff76c

1 files changed, 3 insertions, 2 deletions

diff --git a/runtime/mirror/reference.h b/runtime/mirror/reference.h
index 3baa12e40b..e8ad5fa1c8 100644
--- a/runtime/mirror/reference.h
+++ b/runtime/mirror/reference.h
@@ -76,8 +76,9 @@ class MANAGED Reference : public Object {
     SetFieldObjectVolatile<kTransactionActive>(ReferentOffset(), nullptr);
   }
 
+  template <ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
   Reference* GetPendingNext() SHARED_REQUIRES(Locks::mutator_lock_) {
-    return GetFieldObject<Reference>(PendingNextOffset());
+    return GetFieldObject<Reference, kDefaultVerifyFlags, kReadBarrierOption>(PendingNextOffset());
   }
 
   void SetPendingNext(Reference* pending_next)
@@ -102,7 +103,7 @@ class MANAGED Reference : public Object {
   // removed from the list after having determined the reference is not ready
   // to be enqueued on a java ReferenceQueue.
   bool IsUnprocessed() SHARED_REQUIRES(Locks::mutator_lock_) {
-    return GetPendingNext() == nullptr;
+    return GetPendingNext<kWithoutReadBarrier>() == nullptr;
   }
 
   template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>