Improve memory usage of receiver type feedback.

src/small-pointer-list.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 26 matching lines @@
 
 // SmallPointerList is a list optimized for storing no or just a
 // single value. When more values are given it falls back to ZoneList.
 //
 // The interface tries to be as close to List from list.h as possible.
 template <typename T>
 class SmallPointerList {
  public:
   SmallPointerList() : data_(kEmptyTag) {}
 
+  explicit SmallPointerList(int capacity) : data_(kEmptyTag) {
+    Reserve(capacity);
+  }
+
+  void Reserve(int capacity) {
+    if (capacity < 2) return;
+    if ((data_ & kTagMask) == kListTag) {
+      if (list()->capacity() >= capacity) return;
+      int old_length = list()->length();
+      list()->AddBlock(NULL, capacity - list()->capacity());
+      list()->Rewind(old_length);
+      return;
+    }
+    PointerList* list = new PointerList(capacity);
+    if ((data_ & kTagMask) == kSingletonTag) {
+      list->Add(single_value());
+    }
+    ASSERT(IsAligned(reinterpret_cast<intptr_t>(list), kPointerAlignment));
+    data_ = reinterpret_cast<intptr_t>(list) | kListTag;
+  }
+
+  void Clear() {
+    data_ = kEmptyTag;
+  }
+
   bool is_empty() const { return length() == 0; }
 
   int length() const {
     if ((data_ & kTagMask) == kEmptyTag) return 0;
     if ((data_ & kTagMask) == kSingletonTag) return 1;
     return list()->length();
   }
 
   void Add(T* pointer) {
     ASSERT(IsAligned(reinterpret_cast<intptr_t>(pointer), kPointerAlignment));
@@ skipping 97 matching lines @@
   }
 
   intptr_t data_;
 
   DISALLOW_COPY_AND_ASSIGN(SmallPointerList);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SMALL_POINTER_LIST_H_