Use SameValueZero for Map and Set

src/objects.h

 // 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include "allocation.h"
 #include "assert-scope.h"
 #include "builtins.h"
@@ skipping 1493 matching lines @@
   // Returns the permanent hash code associated with this object depending on
   // the actual object type. May create and store a hash code if needed and none
   // exists.
   static Handle<Smi> GetOrCreateHash(Isolate* isolate, Handle<Object> object);
 
   // Checks whether this object has the same value as the given one.  This
   // function is implemented according to ES5, section 9.12 and can be used
   // to implement the Harmony "egal" function.
   bool SameValue(Object* other);
 
+  // Checks whether this object has the same value as the given one.
+  // +0 and -0 are treated equal. Everything else is the same as SameValue.
+  // This function is implemented according to ES6, section 7.2.4 and is used
+  // by ES6 Map and Set.
+  bool SameValueZero(Object* other);
+
   // Tries to convert an object to an array index.  Returns true and sets
   // the output parameter if it succeeds.
   inline bool ToArrayIndex(uint32_t* index);
 
   // Returns true if this is a JSValue containing a string and the index is
   // < the length of the string.  Used to implement [] on strings.
   inline bool IsStringObjectWithCharacterAt(uint32_t index);
 
   DECLARE_VERIFIER(Object)
 #ifdef VERIFY_HEAP
@@ skipping 2611 matching lines @@
   static inline int EntryToValueIndex(int entry) {
     return EntryToIndex(entry) + 1;
   }
 };
 
 
 // OrderedHashTable is a HashTable with Object keys that preserves
 // insertion order. There are Map and Set interfaces (OrderedHashMap
 // and OrderedHashTable, below). It is meant to be used by JSMap/JSSet.
 //
-// Only Object* keys are supported, with Object::SameValue() used as the
+// Only Object* keys are supported, with Object::SameValueZero() used as the
 // equality operator and Object::GetHash() for the hash function.
 //
 // Based on the "Deterministic Hash Table" as described by Jason Orendorff at
 // https://wiki.mozilla.org/User:Jorend/Deterministic_hash_tables
 // Originally attributed to Tyler Close.
 //
 // Memory layout:
 //   [0]: bucket count
 //   [1]: element count
 //   [2]: deleted element count
@@ skipping 6954 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_