Revert of Changed scavenge GC to collect unmodified references

src/global-handles.cc

Index: src/global-handles.cc
diff --git a/src/global-handles.cc b/src/global-handles.cc
index ebb2837730949224e01f9ef54e718d06b4c43bd0..650999f394c5cc7c2e5397afff53c74e3c186d20 100644
--- a/src/global-handles.cc
+++ b/src/global-handles.cc
@@ -64,11 +64,7 @@
     class_id_ = v8::HeapProfiler::kPersistentHandleNoClassId;
     index_ = 0;
     set_independent(false);
-    if (FLAG_scavenge_reclaim_unmodified_objects) {
-      set_unmodified(false);
-    } else {
-      set_partially_dependent(false);
-    }
+    set_partially_dependent(false);
     set_in_new_space_list(false);
     parameter_or_next_free_.next_free = NULL;
     weak_callback_ = NULL;
@@ -81,9 +77,6 @@
     set_state(FREE);
     set_weakness_type(NORMAL_WEAK);
     set_in_new_space_list(false);
-    if (FLAG_scavenge_reclaim_unmodified_objects) {
-      set_unmodified(false);
-    }
     parameter_or_next_free_.next_free = *first_free;
     *first_free = this;
   }
@@ -93,11 +86,7 @@
     object_ = object;
     class_id_ = v8::HeapProfiler::kPersistentHandleNoClassId;
     set_independent(false);
-    if (FLAG_scavenge_reclaim_unmodified_objects) {
-      set_unmodified(false);
-    } else {
-      set_partially_dependent(false);
-    }
+    set_partially_dependent(false);
     set_state(NORMAL);
     parameter_or_next_free_.parameter = NULL;
     weak_callback_ = NULL;
@@ -117,11 +106,7 @@
     object_ = reinterpret_cast<Object*>(kGlobalHandleZapValue);
     class_id_ = v8::HeapProfiler::kPersistentHandleNoClassId;
     set_independent(false);
-    if (FLAG_scavenge_reclaim_unmodified_objects) {
-      set_unmodified(false);
-    } else {
-      set_partially_dependent(false);
-    }
+    set_partially_dependent(false);
     weak_callback_ = NULL;
     DecreaseBlockUses();
   }
@@ -155,21 +140,10 @@
   }
 
   bool is_partially_dependent() {
-    CHECK(!FLAG_scavenge_reclaim_unmodified_objects);
     return IsPartiallyDependent::decode(flags_);
   }
   void set_partially_dependent(bool v) {
-    CHECK(!FLAG_scavenge_reclaim_unmodified_objects);
     flags_ = IsPartiallyDependent::update(flags_, v);
-  }
-
-  bool is_unmodified() {
-    CHECK(FLAG_scavenge_reclaim_unmodified_objects);
-    return IsUnmodified::decode(flags_);
-  }
-  void set_unmodified(bool v) {
-    CHECK(FLAG_scavenge_reclaim_unmodified_objects);
-    flags_ = IsUnmodified::update(flags_, v);
   }
 
   bool is_in_new_space_list() {
@@ -375,8 +349,6 @@
   // in_new_space_list) and a State.
   class NodeState : public BitField<State, 0, 3> {};
   class IsIndependent : public BitField<bool, 3, 1> {};
-  // The following two fields are mutually exclusive
-  class IsUnmodified : public BitField<bool, 4, 1> {};
   class IsPartiallyDependent : public BitField<bool, 4, 1> {};
   class IsInNewSpaceList : public BitField<bool, 5, 1> {};
   class NodeWeaknessType : public BitField<WeaknessType, 6, 2> {};
@@ -674,18 +646,10 @@
 void GlobalHandles::IterateNewSpaceStrongAndDependentRoots(ObjectVisitor* v) {
   for (int i = 0; i < new_space_nodes_.length(); ++i) {
     Node* node = new_space_nodes_[i];
-    if (FLAG_scavenge_reclaim_unmodified_objects) {
-      if (node->IsStrongRetainer() ||
-          (node->IsWeakRetainer() && !node->is_independent() &&
-           !node->is_unmodified())) {
+    if (node->IsStrongRetainer() ||
+        (node->IsWeakRetainer() && !node->is_independent() &&
+         !node->is_partially_dependent())) {
         v->VisitPointer(node->location());
-      }
-    } else {
-      if (node->IsStrongRetainer() ||
-          (node->IsWeakRetainer() && !node->is_independent() &&
-           !node->is_partially_dependent())) {
-        v->VisitPointer(node->location());
-      }
     }
   }
 }
@@ -723,49 +687,6 @@
 }
 
 
-void GlobalHandles::IdentifyWeakUnmodifiedObjects(
-    WeakSlotCallback is_unmodified) {
-  for (int i = 0; i < new_space_nodes_.length(); ++i) {
-    Node* node = new_space_nodes_[i];
-    if (node->IsWeak() && is_unmodified(node->location())) {
-      node->set_unmodified(true);
-    }
-  }
-}
-
-
-void GlobalHandles::MarkNewSpaceWeakUnmodifiedObjectsPending(
-    WeakSlotCallbackWithHeap is_unscavenged) {
-  for (int i = 0; i < new_space_nodes_.length(); ++i) {
-    Node* node = new_space_nodes_[i];
-    DCHECK(node->is_in_new_space_list());
-    if ((node->is_independent() || node->is_unmodified()) && node->IsWeak() &&
-        is_unscavenged(isolate_->heap(), node->location())) {
-      node->MarkPending();
-    }
-  }
-}
-
-
-void GlobalHandles::IterateNewSpaceWeakUnmodifiedRoots(ObjectVisitor* v) {
-  for (int i = 0; i < new_space_nodes_.length(); ++i) {
-    Node* node = new_space_nodes_[i];
-    DCHECK(node->is_in_new_space_list());
-    if ((node->is_independent() || node->is_unmodified()) &&
-        node->IsWeakRetainer()) {
-      // Pending weak phantom handles die immediately. Everything else survives.
-      if (node->state() == Node::PENDING &&
-          node->weakness_type() != NORMAL_WEAK) {
-        node->CollectPhantomCallbackData(isolate(),
-                                         &pending_phantom_callbacks_);
-      } else {
-        v->VisitPointer(node->location());
-      }
-    }
-  }
-}
-
-
 bool GlobalHandles::IterateObjectGroups(ObjectVisitor* v,
                                         WeakSlotCallbackWithHeap can_skip) {
   ComputeObjectGroupsAndImplicitReferences();
@@ -836,22 +757,13 @@
       // the freed_nodes.
       continue;
     }
-    // Skip dependent or unmodified handles. Their weak callbacks might expect
-    // to be
+    // Skip dependent handles. Their weak callbacks might expect to be
     // called between two global garbage collection callbacks which
     // are not called for minor collections.
-    if (FLAG_scavenge_reclaim_unmodified_objects) {
-      if (!node->is_independent() && !node->is_unmodified()) {
-        continue;
-      }
-      node->set_unmodified(false);
-    } else {
-      if (!node->is_independent() && !node->is_partially_dependent()) {
-        continue;
-      }
-      node->clear_partially_dependent();
-    }
-
+    if (!node->is_independent() && !node->is_partially_dependent()) {
+      continue;
+    }
+    node->clear_partially_dependent();
     if (node->PostGarbageCollectionProcessing(isolate_)) {
       if (initial_post_gc_processing_count != post_gc_processing_count_) {
         // Weak callback triggered another GC and another round of
@@ -878,11 +790,7 @@
       // the freed_nodes.
       continue;
     }
-    if (FLAG_scavenge_reclaim_unmodified_objects) {
-      it.node()->set_unmodified(false);
-    } else {
-      it.node()->clear_partially_dependent();
-    }
+    it.node()->clear_partially_dependent();
     if (it.node()->PostGarbageCollectionProcessing(isolate_)) {
       if (initial_post_gc_processing_count != post_gc_processing_count_) {
         // See the comment above.