Enable weak embedded maps in optimized code.

src/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
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@@ skipping 2037 matching lines @@
   string_table->IteratePrefix(&marker);
   ProcessMarkingDeque();
 }
 
 
 void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) {
   // Mark the heap roots including global variables, stack variables,
   // etc., and all objects reachable from them.
   heap()->IterateStrongRoots(visitor, VISIT_ONLY_STRONG);
 
+  // If the call-site of the top optimized code was not prepared for
+  // deoptimization, then treat the maps in the code as strong pointers,
+  // otherwise a map can die and deoptimize the code.

[Michael Starzinger, 2013/07/02 14:20:54]

Can we move this into MarkCompactCollector::MarkLiveObjects? It is not actually
part of the root-set, it is just a requirement from the mark-compact collector
(e.g. similar to PrepareForCodeFlushing).

[ulan, 2013/07/02 14:45:41]

Done.

+  StackFrame* frame = isolate()->TopOptimizedFrame();
+  if (frame) {
+    Code* code = frame->LookupCode();
+    if (!code->CanDeoptAt(frame->pc())) {
+      code->CodeIterateBody(visitor);
+    }
+  }
+
   // Handle the string table specially.
   MarkStringTable();
 
   // There may be overflowed objects in the heap.  Visit them now.
   while (marking_deque_.overflowed()) {
     RefillMarkingDeque();
     EmptyMarkingDeque();
   }
 }
 
@@ skipping 2249 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal