Retain maps embedded in optimized code for several garbage collections.

src/lithium.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/lithium.h"
 
 #include "src/v8.h"
 
 #include "src/scopes.h"
 #include "src/serialize.h"
@@ skipping 430 matching lines @@
         Handle<Map> map(Map::cast(it.rinfo()->target_object()));
         maps.Add(map, zone());
       } else {
         Handle<HeapObject> object(
             HeapObject::cast(it.rinfo()->target_object()));
         objects.Add(object, zone());
       }
     }
   }
   for (int i = 0; i < maps.length(); i++) {
+    if (maps.at(i)->dependent_code()->number_of_entries(
+            DependentCode::kWeakCodeGroup) == 0) {
+      isolate()->heap()->AddRetainedMap(maps.at(i));
+    }
     Map::AddDependentCode(maps.at(i), DependentCode::kWeakCodeGroup, code);
   }
   for (int i = 0; i < objects.length(); i++) {
     AddWeakObjectToCodeDependency(isolate(), objects.at(i), code);
   }
   if (FLAG_enable_ool_constant_pool) {
     code->constant_pool()->set_weak_object_state(
         ConstantPoolArray::WEAK_OBJECTS_IN_OPTIMIZED_CODE);
   }
   code->set_can_have_weak_objects(true);
@@ skipping 256 matching lines @@
 
 
 LPhase::~LPhase() {
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceLithium(name(), chunk_);
   }
 }
 
 
 } }  // namespace v8::internal