- Promote objects from new gen to old space if they survived a scavenge.

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 142 matching lines @@
     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;
+    return MarkBit::decode(ptr()->tags_);
   }
   void SetMarkBit() {
     ASSERT(!IsMarked());
-    uword header_bits = reinterpret_cast<uword>(ptr()->class_);
-    ptr()->class_ = reinterpret_cast<RawClass*>(header_bits | kMarked);
+    intptr_t tags = ptr()->tags_;
+    ptr()->tags_ = MarkBit::update(true, tags);
   }
   void ClearMarkBit() {
     ASSERT(IsMarked());
-    uword header_bits = reinterpret_cast<uword>(ptr()->class_);
-    ptr()->class_ = reinterpret_cast<RawClass*>(header_bits ^ kMarkBit);
+    intptr_t tags = ptr()->tags_;
+    ptr()->tags_ = MarkBit::update(false, tags);
   }
 
   // Support for object tags.
   bool IsCanonical() const {
     return CanonicalObjectTag::decode(ptr()->tags_);
   }
   void SetCanonical() {
     intptr_t tags = ptr()->tags_;
     ptr()->tags_ = CanonicalObjectTag::update(true, tags);
   }
@@ skipping 26 matching lines @@
   static bool IsCanonical(intptr_t value) {
     return CanonicalObjectTag::decode(value);
   }
 
  protected:
   RawClass* class_;
   intptr_t tags_;  // Various object tags (bits).
 
  private:
   enum {
-    kMarkingMask = 3,
-    kNotMarked = 1,  // Tagged pointer.
-    kMarked = 3,  // Tagged pointer and forwarding bit set.
-    kMarkBit = 2,
+    kMarkBit = 1,
+    kCanonicalBit = 2,
+    kFromSnapshotBit = 3,
   };
 
-  class CanonicalObjectTag : public BitField<bool, 2, 1> {
-  };
+  class MarkBit : public BitField<bool, kMarkBit, 1> {};
 
-  class CreatedFromSnapshotTag : public BitField<bool, 3, 1> {
-  };
+  class CanonicalObjectTag : public BitField<bool, kCanonicalBit, 1> {};
+
+  class CreatedFromSnapshotTag : public BitField<bool, kFromSnapshotBit, 1> {};
 
   RawObject* ptr() const {
     ASSERT(IsHeapObject());
     return reinterpret_cast<RawObject*>(
         reinterpret_cast<uword>(this) - kHeapObjectTag);
   }
 
   friend class Object;
   friend class Array;
   friend class SnapshotWriter;
@@ skipping 674 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_