Implement aging of maps embedded in optimized code.

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index b929d8567f5c7463a35873db6674d0080c4d5009..e7e9165fc7527153806f8f4a01a08f217fb1be94 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -1960,6 +1960,8 @@ void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) {
 
   MarkWeakObjectToCodeTable();
 
+  heap()->IterateEmbeddedMapCache(visitor);
+
   // There may be overflowed objects in the heap.  Visit them now.
   while (marking_deque_.overflowed()) {
     RefillMarkingDeque();
@@ -2199,6 +2201,8 @@ void MarkCompactCollector::MarkLiveObjects() {
 
   ProcessTopOptimizedFrame(&root_visitor);
 
+  ProcessMarkingDeque();

[Hannes Payer (out of office), 2014/11/17 17:34:33]

Why?

+
   // The objects reachable from the roots are marked, yet unreachable
   // objects are unmarked.  Mark objects reachable due to host
   // application specific logic or through Harmony weak maps.
@@ -3533,6 +3537,10 @@ void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
     table->Rehash(heap_->isolate()->factory()->undefined_value());
   }
 
+  updating_visitor.VisitPointer(heap_->embedded_map_cache_address());
+  // No need to iterate the contents of the embedded map cache since

[Hannes Payer (out of office), 2014/11/17 17:34:33]

Please move the comment before
updating_visitor.VisitPointer(heap_->embedded_map_cache_address()); and say
something like "We just visit the embedded_map_cache slot here and update it if
needed.  No need to iterate the contents of the embedded map cache since maps do
not move."

+  // maps do not move.
+
   // Update pointers from external string table.
   heap_->UpdateReferencesInExternalStringTable(
       &UpdateReferenceInExternalStringTableEntry);