- Add support for marking bits in the object header.

vm/raw_object.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "vm/assert.h"
 #include "vm/globals.h"
 #include "vm/snapshot.h"
@@ skipping 130 matching lines @@
 
   bool IsNewObject() const {
     uword addr = reinterpret_cast<uword>(this);
     return (addr & kNewObjectAlignmentOffset) == kNewObjectAlignmentOffset;
   }
   bool IsOldObject() const {
     uword addr = reinterpret_cast<uword>(this);
     return (addr & kNewObjectAlignmentOffset) == kOldObjectAlignmentOffset;
   }
 
+  // Support for GC marking bit.
+  bool IsMarked() const {
+    uword header_bits = reinterpret_cast<uword>(ptr()->class_);
+    uword mark_bits = header_bits & kMarkingMask;
+    ASSERT((mark_bits == kNotMarked) || (mark_bits == kMarked));
+    return mark_bits == kMarked;
+  }
+  void SetMarkBit() {
+    ASSERT(!IsMarked());
+    uword header_bits = reinterpret_cast<uword>(ptr()->class_);
+    ptr()->class_ = reinterpret_cast<RawClass*>(header_bits | kMarked);
+  }
+  void ClearMarkBit() {
+    ASSERT(IsMarked());
+    uword header_bits = reinterpret_cast<uword>(ptr()->class_);
+    ptr()->class_ = reinterpret_cast<RawClass*>(header_bits ^ kMarked);
+  }
+
   void Validate() const;
   intptr_t Size() const;
   intptr_t VisitPointers(ObjectPointerVisitor* visitor);
 
   static RawObject* FromAddr(uword addr) {
     // We expect the untagged address here.
     ASSERT((addr & kSmiTagMask) != kHeapObjectTag);
     return reinterpret_cast<RawObject*>(addr + kHeapObjectTag);
   }
 
   static uword ToAddr(RawObject* raw_obj) {
     return reinterpret_cast<uword>(raw_obj->ptr());
   }
 
  protected:
   RawClass* class_;
 
  private:
+  enum {
+    kMarkingMask = 3,
+    kNotMarked = 1,  // Tagged pointer.
+    kMarked = 3,  // Tagged pointer and forwarding bit set.
+  };
+
   RawObject* ptr() const {
     ASSERT(IsHeapObject());
     return reinterpret_cast<RawObject*>(
         reinterpret_cast<uword>(this) - kHeapObjectTag);
   }
 
   friend class Object;
   friend class Array;
   friend class SnapshotWriter;
   friend class SnapshotReader;
+  friend class MarkingVisitor;
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(RawObject);
 };
 
 
 class RawClass : public RawObject {
  public:
   enum ClassState {
     kAllocated,     // Initial state.
@@ skipping 638 matching lines @@
   intptr_t type_;  // Uninitialized, simple or complex.
   intptr_t flags_;  // Represents global/local, case insensitive, multiline.
 
   // Variable length data follows here.
   uint8_t data_[0];
 };
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_