Make embedded maps in optimized code weak.

src/lithium.cc

Index: src/lithium.cc
diff --git a/src/lithium.cc b/src/lithium.cc
index eb2198d85480242d08f166f5c673046dcd156b69..478bf10e5ebb015153ccbcd1f12f65d3fc1b16bd 100644
--- a/src/lithium.cc
+++ b/src/lithium.cc
@@ -429,6 +429,7 @@ Handle<Code> LChunk::Codegen() {
     Handle<Code> code =
         CodeGenerator::MakeCodeEpilogue(&assembler, flags, info());
     generator.FinishCode(code);
+    RegisterDependentCodeForEmbeddedMaps(code);
     CodeGenerator::PrintCode(code, info());
     return code;
   }
@@ -436,4 +437,22 @@ Handle<Code> LChunk::Codegen() {
 }
 
 
+void LChunk::RegisterDependentCodeForEmbeddedMaps(Handle<Code> code) {
+  ZoneList<Handle<Map> > maps(1, zone());
+  int mode_mask = RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT);
+  for (RelocIterator it(*code, mode_mask); !it.done(); it.next()) {
+    RelocInfo::Mode mode = it.rinfo()->rmode();
+    if (mode == RelocInfo::EMBEDDED_OBJECT &&
+        it.rinfo()->target_object()->IsMap()) {
+      Handle<Map> map(Map::cast(it.rinfo()->target_object()));
+      if (map->CanTransition()) {
+        maps.Add(map, zone());
+      }
+    }
+  }
+  for (int i = 0; i < maps.length(); i++) {
+    maps.at(i)->AddDependentCode(code);
+  }
+}
+
 } }  // namespace v8::internal