- Remove kFreeBit, as it is not needed any longer

runtime/vm/scavenger.cc

 // 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.
 
 #include "vm/scavenger.h"
 
 #include <algorithm>
 #include <map>
 #include <utility>
 
 #include "vm/dart.h"
 #include "vm/dart_api_state.h"
 #include "vm/isolate.h"
 #include "vm/object.h"
 #include "vm/stack_frame.h"
 #include "vm/store_buffer.h"
 #include "vm/verifier.h"
 #include "vm/visitor.h"
 
 namespace dart {
 
-// Scavenger uses RawObject::kFreeBit to distinguish forwaded and non-forwarded
+// Scavenger uses RawObject::kMarkBit to distinguish forwaded and non-forwarded
 // objects because scavenger can never encounter free list element during

[Vyacheslav Egorov (Google), 2013/04/30 14:36:01]

this comment is out of date (mentions free lists and kFreeBit)

also note that forwarding bit must not intersect with bits of the forwarded
address which holds because objects are properly aligned.

[Ivan Posva, 2013/04/30 15:03:53]

Simplified comment.

 // evacuation and thus all objects scavenger encounters have
 // kFreeBit cleared.
 enum {
-  kForwardingMask = 1,
+  kForwardingMask = 1 << RawObject::kMarkBit,
   kNotForwarded = 0,
-  kForwarded = 1,
+  kForwarded = kForwardingMask,
 };
 
 
 static inline bool IsForwarding(uword header) {
   uword bits = header & kForwardingMask;
   ASSERT((bits == kNotForwarded) || (bits == kForwarded));
   return bits == kForwarded;
 }
 
 
@@ skipping 252 matching lines @@
 };
 
 
 Scavenger::Scavenger(Heap* heap, intptr_t max_capacity, uword object_alignment)
     : heap_(heap),
       object_alignment_(object_alignment),
       scavenging_(false) {
   // Verify assumptions about the first word in objects which the scavenger is
   // going to use for forwarding pointers.
   ASSERT(Object::tags_offset() == 0);
-  ASSERT(kForwardingMask == (1 << RawObject::kFreeBit));
 
   // Allocate the virtual memory for this scavenge heap.
   space_ = VirtualMemory::Reserve(max_capacity);
   if (space_ == NULL) {
     FATAL("Out of memory.\n");
   }
 
   // Allocate the entire space at the beginning.
   space_->Commit(false);
 
@@ skipping 361 matching lines @@
   PeerTable::iterator it = peer_table_.find(raw_obj);
   return (it == peer_table_.end()) ? NULL : it->second;
 }
 
 
 int64_t Scavenger::PeerCount() const {
   return static_cast<int64_t>(peer_table_.size());
 }
 
 }  // namespace dart