- Add a WeakTable to the VM. This is used to remember the

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"
+#include "vm/weak_table.h"
 
 namespace dart {
 
 // Scavenger uses RawObject::kMarkBit to distinguish forwaded and non-forwarded
 // objects. The kMarkBit does not intersect with the target address because of
 // object alignment.
 enum {
   kForwardingMask = 1 << RawObject::kMarkBit,
   kNotForwarded = 0,
   kForwarded = kForwardingMask,
@@ skipping 520 matching lines @@
       // Key is white.  Delay the weak property.
       visitor->DelayWeakProperty(raw_weak);
       return raw_weak->Size();
     }
   }
   // Key is gray or black.  Make the weak property black.
   return raw_weak->VisitPointers(visitor);
 }
 
 
-void Scavenger::ProcessPeerReferents() {
-  PeerTable prev;
-  std::swap(prev, peer_table_);
-  for (PeerTable::iterator it = prev.begin(); it != prev.end(); ++it) {
-    RawObject* raw_obj = it->first;
-    ASSERT(raw_obj->IsHeapObject());
-    uword raw_addr = RawObject::ToAddr(raw_obj);
-    uword header = *reinterpret_cast<uword*>(raw_addr);
-    if (IsForwarding(header)) {
-      // The object has survived.  Preserve its record.
-      uword new_addr = ForwardedAddr(header);
-      raw_obj = RawObject::FromAddr(new_addr);
-      heap_->SetPeer(raw_obj, it->second);
+void Scavenger::ProcessWeakTables() {
+  for (Heap::WeakSelector sel = static_cast<Heap::WeakSelector>(0);
+       sel < Heap::kNumWeakSelectors;
+       sel++) {
+    WeakTable* table = heap_->GetWeakTable(Heap::kNew, sel);
+    intptr_t size = table->size();
+    heap_->SetWeakTable(Heap::kNew, sel, WeakTable::NewFrom(table));
+    for (intptr_t i = 0; i < size; i++) {
+      if (table->IsValidEntryAt(i)) {
+        RawObject* raw_obj = table->ObjectAt(i);
+        ASSERT(raw_obj->IsHeapObject());
+        uword raw_addr = RawObject::ToAddr(raw_obj);
+        uword header = *reinterpret_cast<uword*>(raw_addr);

[siva, 2013/06/27 22:11:33]

how does this work for deleted entries (they are considered valid by
IsValidEntryAt(i) above but table->ObjectAt(i) would return 1

[Ivan Posva, 2013/06/27 23:59:12]

ditto.

+        if (IsForwarding(header)) {
+          // The object has survived.  Preserve its record.
+          uword new_addr = ForwardedAddr(header);
+          raw_obj = RawObject::FromAddr(new_addr);
+          heap_->SetWeakEntry(raw_obj, sel, table->ValueAt(i));
+        }
+      }
     }
   }
 }
 
 
 void Scavenger::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
   uword cur = FirstObjectStart();
   while (cur < top_) {
     RawObject* raw_obj = RawObject::FromAddr(cur);
     cur += raw_obj->VisitPointers(visitor);
@@ skipping 36 matching lines @@
   ScavengerVisitor visitor(isolate, this);
   Prologue(isolate, invoke_api_callbacks);
   IterateRoots(isolate, &visitor, !invoke_api_callbacks);
   int64_t start = OS::GetCurrentTimeMicros();
   ProcessToSpace(&visitor);
   int64_t middle = OS::GetCurrentTimeMicros();
   IterateWeakReferences(isolate, &visitor);
   ScavengerWeakVisitor weak_visitor(this);
   IterateWeakRoots(isolate, &weak_visitor, invoke_api_callbacks);
   visitor.Finalize();
-  ProcessPeerReferents();
+  ProcessWeakTables();
   int64_t end = OS::GetCurrentTimeMicros();
   heap_->RecordTime(kProcessToSpace, middle - start);
   heap_->RecordTime(kIterateWeaks, end - middle);
   Epilogue(isolate, invoke_api_callbacks);
 
   if (FLAG_verify_after_gc) {
     OS::PrintErr("Verifying after Scavenge...");
     heap_->Verify();
     OS::PrintErr(" done.\n");
   }
 
   // Done scavenging. Reset the marker.
   ASSERT(scavenging_);
   scavenging_ = false;
 }
 
 
 void Scavenger::WriteProtect(bool read_only) {
   space_->Protect(
       read_only ? VirtualMemory::kReadOnly : VirtualMemory::kReadWrite);
 }
 
 
-void Scavenger::SetPeer(RawObject* raw_obj, void* peer) {
-  if (peer == NULL) {
-    peer_table_.erase(raw_obj);
-  } else {
-    peer_table_[raw_obj] = peer;
-  }
-}
-
-
-void* Scavenger::GetPeer(RawObject* raw_obj) {
-  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