Simple BlinkGC heap compaction.

third_party/WebKit/Source/platform/heap/InlinedGlobalMarkingVisitor.h

 // Copyright 2014 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.
 
 #ifndef InlinedGlobalMarkingVisitor_h
 #define InlinedGlobalMarkingVisitor_h
 
 #include "platform/heap/MarkingVisitorImpl.h"
 
 namespace blink {
 
 class InlinedGlobalMarkingVisitor final
     : public VisitorHelper<InlinedGlobalMarkingVisitor>,
       public MarkingVisitorImpl<InlinedGlobalMarkingVisitor> {
  public:
   friend class VisitorHelper<InlinedGlobalMarkingVisitor>;
   using Helper = VisitorHelper<InlinedGlobalMarkingVisitor>;
   friend class MarkingVisitorImpl<InlinedGlobalMarkingVisitor>;
   using Impl = MarkingVisitorImpl<InlinedGlobalMarkingVisitor>;
 
-  explicit InlinedGlobalMarkingVisitor(ThreadState* state)
-      : VisitorHelper(state) {}
+  InlinedGlobalMarkingVisitor(ThreadState* state,
+                              Visitor::MarkingMode markingMode)
+      : VisitorHelper(state), m_markingMode(markingMode) {}
 
   // Hack to unify interface to visitor->trace().
   // Without this hack, we need to use visitor.trace() for
   // trace(InlinedGlobalMarkingVisitor) and visitor->trace() for
   // trace(Visitor*).
   InlinedGlobalMarkingVisitor* operator->() { return this; }
 
   using Impl::mark;
   using Impl::ensureMarked;
   using Impl::registerDelayedMarkNoTracing;
@@ skipping 14 matching lines @@
   }
 
  protected:
   // Methods to be called from MarkingVisitorImpl.
 
   inline bool shouldMarkObject(const void*) const {
     // As this is global marking visitor, we need to mark all objects.
     return true;
   }
 
-  inline Visitor::MarkingMode getMarkingMode() const {
-    return Visitor::GlobalMarking;
-  }
+  inline Visitor::MarkingMode getMarkingMode() const { return m_markingMode; }
 
  private:
   static InlinedGlobalMarkingVisitor fromHelper(Helper* helper) {
     return *static_cast<InlinedGlobalMarkingVisitor*>(helper);
   }
+
+  const Visitor::MarkingMode m_markingMode;

[haraken, 2016/12/02 12:43:20]

Would you help me understand why you need to add this member whereas Visitor
already has m_markingMode?

[sof, 2016/12/04 14:55:38]

InlinedGlobalMarkingVisitor isn't a Visitor, and the marking mode is needed to
correctly implement MarkingVisitorImpl::registerMoving*().

[haraken, 2016/12/09 07:25:54]

Maybe can we move m_markingMode to VisitorHelper? Then we won't need to
duplicate m_markingMode in two classes.

[sof, 2016/12/09 21:44:03]

Possibly, but it's a more complex than that given that we also need to
accommodate MarkingVisitor<Mode> const-Mode visitors. I've added a TODO.

 };
 
 inline void GarbageCollectedMixin::trace(InlinedGlobalMarkingVisitor) {}
 
 }  // namespace blink
 
 #endif