[heap] Remove NewSpace::set_top and the corresponding hack

src/objects.cc

 // Copyright 2013 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 9910 matching lines @@
     new_size = SeqTwoByteString::SizeFor(new_length);
   }
 
   int delta = old_size - new_size;
 
   Address start_of_string = string->address();
   DCHECK_OBJECT_ALIGNED(start_of_string);
   DCHECK_OBJECT_ALIGNED(start_of_string + new_size);
 
   Heap* heap = string->GetHeap();
-  NewSpace* newspace = heap->new_space();
-  if (newspace->Contains(start_of_string) &&
-      newspace->top() == start_of_string + old_size) {
-    // Last allocated object in new space.  Simply lower allocation top.
-    newspace->set_top(start_of_string + new_size);
-  } else {
-    // Sizes are pointer size aligned, so that we can use filler objects
-    // that are a multiple of pointer size.
-    heap->CreateFillerObjectAt(start_of_string + new_size, delta);
-  }
+  // Sizes are pointer size aligned, so that we can use filler objects
+  // that are a multiple of pointer size.
+  heap->CreateFillerObjectAt(start_of_string + new_size, delta);
   heap->AdjustLiveBytes(*string, -delta, Heap::CONCURRENT_TO_SWEEPER);
 
   // We are storing the new length using release store after creating a filler
   // for the left-over space to avoid races with the sweeper thread.
   string->synchronized_set_length(new_length);
 
   if (new_length == 0) return heap->isolate()->factory()->empty_string();
   return string;
 }
 
@@ skipping 6850 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