Scavenge watched objects by scavenging their watchers.

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>
 
@@ skipping 104 matching lines @@
       return;
     }
 
     // Read the header word of the object and determine if the object has
     // already been copied.
     uword header = *reinterpret_cast<uword*>(raw_addr);
     uword new_addr = 0;
     if (IsForwarding(header)) {
       // Get the new location of the object.
       new_addr = ForwardedAddr(header);
+    } else if (raw_obj->IsWatched()) {
+      // Forward the object by scavenging its watchers.
+      raw_obj->ClearWatchedBit();
+      std::pair<DelaySet::iterator, DelaySet::iterator> ret;
+      // Visit all elements with a key equal to raw_obj.
+      ret = delay_set_.equal_range(raw_obj);
+      for (DelaySet::iterator it = ret.first; it != ret.second; ++it) {
+        // Scavenge the delayed WeakProperty.  These objects have been
+        // forwarded but have not been scavenged because their key
+        // object was not known to be reachable.  Now that the key
+        // object is known to be reachable we can scavenge the key and
+        // value pointers.
+        it->second->VisitPointers(this);
+      }
+      delay_set_.erase(ret.first, ret.second);
+      // Reread the header word to get the new location of the object.
+      header = *reinterpret_cast<uword*>(raw_addr);
+      ASSERT(IsForwarding(header));
+      new_addr = ForwardedAddr(header);
     } else {
-      if (raw_obj->IsWatched()) {
-        std::pair<DelaySet::iterator, DelaySet::iterator> ret;
-        // Visit all elements with a key equal to raw_obj.
-        ret = delay_set_.equal_range(raw_obj);
-        for (DelaySet::iterator it = ret.first; it != ret.second; ++it) {
-          // Visit through the associated WeakProperty at this time.
-          it->second->VisitPointers(this);
-        }
-        delay_set_.erase(ret.first, ret.second);
-        raw_obj->ClearWatchedBit();
-      }
       intptr_t size = raw_obj->Size();
       // Check whether object should be promoted.
       if (scavenger_->survivor_end_ <= raw_addr) {
         // Not a survivor of a previous scavenge. Just copy the object into the
         // to space.
         new_addr = scavenger_->TryAllocate(size);
       } else {
         // TODO(iposva): Experiment with less aggressive promotion. For example
         // a coin toss determines if an object is promoted or whether it should
         // survive in this generation.
@@ skipping 480 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