Refactor UnionOfKeys into ElementsAccessor

src/elements.cc

Index: src/elements.cc
diff --git a/src/elements.cc b/src/elements.cc
index 45ab2d9aa8a30e9b1ef2f7dfed104e1c19633d2a..9cfcceec24cadeea63fd15c452cff71a3b08caf8 100644
--- a/src/elements.cc
+++ b/src/elements.cc
@@ -37,6 +37,20 @@ namespace internal {
 ElementsAccessor** ElementsAccessor::elements_accessors_;
 
 
+bool HasKey(FixedArray* array, Object* key) {
+  int len0 = array->length();
+  for (int i = 0; i < len0; i++) {
+    Object* element = array->get(i);
+    if (element->IsSmi() && element == key) return true;
+    if (element->IsString() &&
+        key->IsString() && String::cast(element)->Equals(String::cast(key))) {
+      return true;
+    }
+  }
+  return false;
+}
+
+
 // Base class for element handler implementations. Contains the
 // the common logic for objects with different ElementsKinds.
 // Subclasses must specialize method for which the element
@@ -73,6 +87,78 @@ class ElementsAccessorBase : public ElementsAccessor {
                               uint32_t index,
                               JSReceiver::DeleteMode mode) = 0;
 
+  virtual MaybeObject* AddJSArrayKeysToFixedArray(JSArray* other,
+                                                  FixedArray* keys) {
+    int len0 = keys->length();
+#ifdef DEBUG
+    if (FLAG_enable_slow_asserts) {
+      for (int i = 0; i < len0; i++) {
+        ASSERT(keys->get(i)->IsString() || keys->get(i)->IsNumber());
+      }
+    }
+#endif
+    int len1 = ElementsAccessorSubclass::GetCapacity(other);
+
+    // Optimize if 'other' is empty.
+    // We cannot optimize if 'this' is empty, as other may have holes
+    // or non keys.
+    if (len1 == 0) return keys;
+
+    // Compute how many elements are not in other.
+    int extra = 0;
+    for (int y = 0; y < len1; y++) {
+      Object* value;
+      MaybeObject* maybe_value =
+          ElementsAccessorSubclass::GetElementAtCapacityIndex(other, y);
+      if (!maybe_value->ToObject(&value)) return maybe_value;
+      if (!value->IsTheHole() && !HasKey(keys, value)) extra++;
+    }
+
+    if (extra == 0) return keys;
+
+    // Allocate the result
+    FixedArray* result;
+    MaybeObject* maybe_obj =
+        other->GetHeap()->AllocateFixedArray(len0 + extra);
+    if (!maybe_obj->To<FixedArray>(&result)) return maybe_obj;
+
+    // Fill in the content
+    {
+      AssertNoAllocation no_gc;
+      WriteBarrierMode mode = result->GetWriteBarrierMode(no_gc);
+      for (int i = 0; i < len0; i++) {
+        Object* e = keys->get(i);
+        ASSERT(e->IsString() || e->IsNumber());
+        result->set(i, e, mode);
+      }
+    }
+    // Fill in the extra keys.
+    int index = 0;
+    for (int y = 0; y < len1; y++) {
+      MaybeObject* maybe_value =
+          ElementsAccessorSubclass::GetElementAtCapacityIndex(other, y);
+      Object* value;
+      if (!maybe_value->ToObject(&value)) return maybe_value;
+      if (!value->IsTheHole() && !HasKey(keys, value)) {
+        ASSERT(value->IsString() || value->IsNumber());
+        result->set(len0 + index, value);
+        index++;
+      }
+    }
+    ASSERT(extra == index);
+    return result;
+  }
+
+  static uint32_t GetCapacity(JSObject* obj) {
+    return ElementsAccessorSubclass::GetBackingStore(obj)->length();
+  }
+
+  static MaybeObject* GetElementAtCapacityIndex(JSObject* obj, int index) {
+    BackingStoreClass* backing_store =
+        ElementsAccessorSubclass::GetBackingStore(obj);
+    return backing_store->get(index);
+  }
+
  protected:
   static BackingStoreClass* GetBackingStore(JSObject* obj) {
     return BackingStoreClass::cast(obj->elements());
@@ -325,6 +411,19 @@ class DictionaryElementsAccessor
                                       obj->element_dictionary(),
                                       index);
   }
+
+  static uint32_t GetCapacity(JSObject* obj) {
+    return obj->element_dictionary()->Capacity();
+  }
+
+  static MaybeObject* GetElementAtCapacityIndex(JSObject* obj, int index) {
+    NumberDictionary* dict = obj->element_dictionary();
+    if (dict->IsKey(dict->KeyAt(index))) {
+      return dict->ValueAt(index);
+    } else {
+      return obj->GetHeap()->the_hole_value();
+    }
+  }
 };
 
 
@@ -382,6 +481,18 @@ class NonStrictArgumentsElementsAccessor
     }
     return obj->GetHeap()->true_value();
   }
+
+  static uint32_t GetCapacity(JSObject* obj) {
+    // TODO(danno): Return max of parameter map length or backing store
+    // capacity.
+    return 0;
+  }
+
+  static MaybeObject* GetElementAtCapacityIndex(JSObject* obj, int index) {
+    // TODO(danno): Return either value from parameter map of backing
+    // store value at index.
+    return obj->GetHeap()->the_hole_value();
+  }
 };