[heap] Do not allow left trimming on new space pages that need to be swept.

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 3065 matching lines @@
 bool Heap::CanMoveObjectStart(HeapObject* object) {
   if (!FLAG_move_object_start) return false;
 
   // Sampling heap profiler may have a reference to the object.
   if (isolate()->heap_profiler()->is_sampling_allocations()) return false;
 
   Address address = object->address();
 
   if (lo_space()->Contains(object)) return false;
 
-  Page* page = Page::FromAddress(address);
-  // We can move the object start if:
-  // (1) the object is not in old space,
-  // (2) the page of the object was already swept,
-  // (3) the page was already concurrently swept. This case is an optimization
-  // for concurrent sweeping. The WasSwept predicate for concurrently swept
-  // pages is set after sweeping all pages.
-  return !InOldSpace(object) || page->SweepingDone();
+  // We can move the object start if the page was already swept.
+  return Page::FromAddress(address)->SweepingDone();
 }
 
 
 void Heap::AdjustLiveBytes(HeapObject* object, int by, InvocationMode mode) {
   // As long as the inspected object is black and we are currently not iterating
   // the heap using HeapIterator, we can update the live byte count. We cannot
   // update while using HeapIterator because the iterator is temporarily
   // marking the whole object graph, without updating live bytes.
   if (lo_space()->Contains(object)) {
     lo_space()->AdjustLiveBytes(by);
@@ skipping 3334 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8