Separating transitions from descriptors.

src/transitions.cc

+// Copyright 2012 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+
+#include "objects.h"
+#include "transitions-inl.h"
+#include "utils.h"
+
+namespace v8 {
+namespace internal {
+
+
+MaybeObject* TransitionArray::Allocate(int number_of_transitions) {
+  Heap* heap = Isolate::Current()->heap();
+  // Use FixedArray to not use DescriptorArray::cast on incomplete object.
+  FixedArray* array;
+  { MaybeObject* maybe_array =
+        heap->AllocateFixedArray(ToKeyIndex(number_of_transitions));
+    if (!maybe_array->To(&array)) return maybe_array;
+  }
+
+  array->set(kElementsTransitionIndex, Smi::FromInt(0));
+  return array;
+}
+
+
+void TransitionArray::CopyFrom(TransitionArray* origin,
+                               int origin_transition,
+                               int target_transition,
+                               const WhitenessWitness& witness) {
+  this->Set(target_transition,
+            origin->GetKey(origin_transition),
+            origin->GetValue(origin_transition),
+            witness);
+}
+
+
+static bool InsertionPointFound(String* key1, String* key2) {
+  return key1->Hash() > key2->Hash();
+}
+
+
+MaybeObject* TransitionArray::NewWith(String* name, Object* value) {
+  TransitionArray* result;
+
+  { MaybeObject* maybe_array;
+    maybe_array = TransitionArray::Allocate(1);
+    if (!maybe_array->To(&result)) return maybe_array;
+  }
+
+  FixedArray::WhitenessWitness witness(result);
+
+  result->Set(0, name, value, witness);
+  return result;
+}
+
+
+MaybeObject* TransitionArray::CopyInsert(String* name, Object* value) {
+  TransitionArray* result;
+
+  int number_of_transitions = this->number_of_transitions();
+  int new_size = number_of_transitions;
+
+  int insertion_index = this->Search(name);
+  if (insertion_index == kNotFound) ++new_size;
+
+  { MaybeObject* maybe_array;
+    maybe_array = TransitionArray::Allocate(new_size);
+    if (!maybe_array->To(&result)) return maybe_array;
+  }
+
+  if (HasElementsTransition()) {
+    result->set_elements_transition(elements_transition());
+  }
+
+  FixedArray::WhitenessWitness witness(result);
+
+  if (insertion_index != kNotFound) {
+    for (int i = 0; i < number_of_transitions; ++i) {
+      if (i != insertion_index) result->CopyFrom(this, i, i, witness);
+    }
+    result->Set(insertion_index, name, value, witness);
+    return result;
+  }
+
+  insertion_index = 0;
+  for (; insertion_index < number_of_transitions; ++insertion_index) {
+    if (InsertionPointFound(GetKey(insertion_index), name)) break;
+    result->CopyFrom(this, insertion_index, insertion_index, witness);
+  }
+
+  result->Set(insertion_index, name, value, witness);
+
+  for (; insertion_index < number_of_transitions; ++insertion_index) {
+    result->CopyFrom(this, insertion_index, insertion_index + 1, witness);
+  }
+
+  return result;
+}
+
+
+} }  // namespace v8::internal