Fix free space repairing after deserialization.

src/heap/spaces.cc

 // Copyright 2011 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/spaces.h"
 
 #include <utility>
 
 #include "src/base/bits.h"
 #include "src/base/platform/platform.h"
@@ skipping 2816 matching lines @@
 }
 
 
 // After we have booted, we have created a map which represents free space
 // on the heap.  If there was already a free list then the elements on it
 // were created with the wrong FreeSpaceMap (normally NULL), so we need to
 // fix them.
 void PagedSpace::RepairFreeListsAfterDeserialization() {
   free_list_.RepairLists(heap());
   // Each page may have a small free space that is not tracked by a free list.
-  // Update the maps for those free space objects.
+  // Those free spaces still contain null as their map pointer.
+  // Overwrite them with new fillers.
   for (Page* page : *this) {
-    size_t size = page->wasted_memory();
-    if (size == 0) continue;
-    DCHECK_GE(static_cast<size_t>(Page::kPageSize), size);
-    Address address = page->OffsetToAddress(Page::kPageSize - size);
-    heap()->CreateFillerObjectAt(address, static_cast<int>(size),
-                                 ClearRecordedSlots::kNo);
+    int size = static_cast<int>(page->wasted_memory());
+    if (size == 0) {
+      // If there is no wasted memory then all free space is in the free list.
+      continue;
+    }
+    Address start = page->HighWaterMark();
+    Address end = page->area_end();
+    CHECK_EQ(size, static_cast<int>(end - start));
+    heap()->CreateFillerObjectAt(start, size, ClearRecordedSlots::kNo);
   }
 }
 
 HeapObject* PagedSpace::SweepAndRetryAllocation(int size_in_bytes) {
   MarkCompactCollector* collector = heap()->mark_compact_collector();
   if (collector->sweeping_in_progress()) {
     // Wait for the sweeper threads here and complete the sweeping phase.
     collector->EnsureSweepingCompleted();
 
     // After waiting for the sweeper threads, there may be new free-list
@@ skipping 439 matching lines @@
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %" V8PRIdPTR "\n", mark_size,
          MarkingState::Internal(this).live_bytes());
 }
 
 #endif  // DEBUG
 }  // namespace internal
 }  // namespace v8