[runtime/heap] Introduce CopyFixedArrayUpTo to match CopyFixedArrayAndGrow, copying to a smaller ar…

src/objects.cc

 // Copyright 2015 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.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 8512 matching lines @@
   for (int i = 0; i < len; i++) {
     Object* e = array->get(i);
     if (!(e->IsName() || e->IsNumber())) return false;
   }
   return true;
 }
 
 
 static Handle<FixedArray> ReduceFixedArrayTo(
     Handle<FixedArray> array, int length) {
-  DCHECK(array->length() >= length);
+  DCHECK_LE(length, array->length());
   if (array->length() == length) return array;
-
-  Handle<FixedArray> new_array =
-      array->GetIsolate()->factory()->NewFixedArray(length);
-  for (int i = 0; i < length; ++i) new_array->set(i, array->get(i));
-  return new_array;
+  return array->GetIsolate()->factory()->CopyFixedArrayUpTo(array, length);
 }
 
 bool Map::OnlyHasSimpleProperties() {
   // Wrapped string elements aren't explicitly stored in the elements backing
   // store, but are loaded indirectly from the underlying string.
   return !IsStringWrapperElementsKind(elements_kind()) &&
          !is_access_check_needed() && !has_named_interceptor() &&
          !has_indexed_interceptor() && !has_hidden_prototype() &&
          !is_dictionary_map();
 }
@@ skipping 11425 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8