[heap] Add compaction space.

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 "src/base/bits.h"
 #include "src/base/platform/platform.h"
 #include "src/full-codegen/full-codegen.h"
 #include "src/heap/mark-compact.h"
@@ skipping 985 matching lines @@
   PageIterator iterator(this);
   while (iterator.has_next()) {
     heap()->isolate()->memory_allocator()->Free(iterator.next());
   }
   anchor_.set_next_page(&anchor_);
   anchor_.set_prev_page(&anchor_);
   accounting_stats_.Clear();
 }
 
 
+void PagedSpace::MergeCompactionSpace(CompactionSpace* other) {
+  // Unmerged fields:
+  //   area_size_
+  //   allocation_info_
+  //   emergency_memory_
+  //   end_of_unswept_pages_
+  //   unswept_free_bytes_
+  //   anchor_
+
+  // It only makes sense to merge compatible spaces.
+  DCHECK(identity() == other->identity());
+
+  // Destroy the linear allocation space of {other}. This is needed to (a) not
+  // waste the memory and (b) keep the rest of the chunk in an iterable state
+  // (filler is needed).
+  int linear_size = static_cast<int>(other->limit() - other->top());
+  other->Free(other->top(), linear_size);
+
+  // Move over the free list.
+  free_list_.Concatenate(other->free_list());
+
+  // Update and clear accounting statistics.
+  accounting_stats_.Merge(other->accounting_stats_);
+  other->accounting_stats_.Clear();
+
+  // Move over pages.
+  PageIterator it(other);
+  Page* p = nullptr;
+  while (it.has_next()) {
+    p = it.next();
+    p->set_owner(this);
+    p->InsertAfter(anchor_.prev_page());
+  }
+}
+
+
 size_t PagedSpace::CommittedPhysicalMemory() {
   if (!base::VirtualMemory::HasLazyCommits()) return CommittedMemory();
   MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
   size_t size = 0;
   PageIterator it(this);
   while (it.has_next()) {
     size += it.next()->CommittedPhysicalMemory();
   }
   return size;
 }
@@ skipping 2133 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 }  // namespace internal
 }  // namespace v8