[heap] Prepare Heap::CopyFixedArrayWithMap for black allocation

src/heap/heap.cc

 // 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.
 
 #include "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/scopeinfo.h"
 #include "src/base/bits.h"
@@ skipping 3804 matching lines @@
 }
 
 AllocationResult Heap::CopyFixedArrayWithMap(FixedArray* src, Map* map) {
   int len = src->length();
   HeapObject* obj = nullptr;
   {
     AllocationResult allocation = AllocateRawFixedArray(len, NOT_TENURED);
     if (!allocation.To(&obj)) return allocation;
   }
   obj->set_map_no_write_barrier(map);
-  if (InNewSpace(obj)) {
+
+  FixedArray* result = FixedArray::cast(obj);
+  DisallowHeapAllocation no_gc;
+  WriteBarrierMode mode = result->GetWriteBarrierMode(no_gc);
+
+  // Eliminate the write barrier if possible.
+  if (mode == SKIP_WRITE_BARRIER) {
     CopyBlock(obj->address() + kPointerSize, src->address() + kPointerSize,
               FixedArray::SizeFor(len) - kPointerSize);
     return obj;
   }
-  FixedArray* result = FixedArray::cast(obj);
+
+  // Slow case: Just copy the content one-by-one.
   result->set_length(len);
-
-  // Copy the content.
-  DisallowHeapAllocation no_gc;
-  WriteBarrierMode mode = result->GetWriteBarrierMode(no_gc);
   for (int i = 0; i < len; i++) result->set(i, src->get(i), mode);
   return result;
 }
 
 
 AllocationResult Heap::CopyFixedDoubleArrayWithMap(FixedDoubleArray* src,
                                                    Map* map) {
   int len = src->length();
   HeapObject* obj = nullptr;
   {
@@ skipping 2586 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8