Make embedded maps in optimized code weak.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 1d95a5c15271ab3d955e2cbd3f2b6ad1b270cc25..1937f5b90353ab09a48927a0c1e922dc5a2e87e6 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -9684,6 +9684,39 @@ void Map::ZapPrototypeTransitions() {
 }
 
 
+Handle<FixedArray> DependentCodes::Append(Handle<FixedArray> codes,
+                                          Handle<Code> value) {
+  int append_index = number_of_codes(*codes);
+  if (append_index > 0 && code(*codes, append_index - 1) == *value) {
+    // Do not append the code if it is already in the array.
+    // It is sufficient to just check only the last element because
+    // we process embedded maps of an optimized code in one batch.
+    return codes;
+  }
+  if (codes->length() < kCodesOffset + append_index + 1) {
+    Factory* factory = codes->GetIsolate()->factory();
+    int capacity = kCodesOffset + append_index + 1;
+    if (capacity > 5) capacity = capacity * 5 / 4;
+    Handle<FixedArray> new_codes = factory->NewFixedArray(capacity);
+    // The number of codes can change after GC.
+    append_index = number_of_codes(*codes);
+    set_number_of_codes(*new_codes, append_index + 1);
+    for (int i = 0; i < append_index; i++) {
+      set_code(*new_codes, i, code(*codes, i));
+      clear_code(*codes, i);
+    }
+    set_code(*new_codes, append_index, *value);
+    for (int i = append_index + 1; kCodesOffset + i < capacity; i++) {
+      clear_code(*new_codes, i);
+    }
+    return new_codes;
+  }
+  set_code(*codes, append_index, *value);
+  set_number_of_codes(*codes, append_index + 1);
+  return codes;
+}
+
+
 MaybeObject* JSReceiver::SetPrototype(Object* value,
                                       bool skip_hidden_prototypes) {
 #ifdef DEBUG