runtime/vm/heap/compactor.h

// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#ifndef RUNTIME_VM_HEAP_COMPACTOR_H_
#define RUNTIME_VM_HEAP_COMPACTOR_H_

#include "vm/allocation.h"
#include "vm/dart_api_state.h"
#include "vm/globals.h"
#include "vm/visitor.h"

namespace dart {

// Forward declarations.
class FreeList;
class Heap;
class HeapPage;
class RawObject;

// Implements a sliding compactor.
class GCCompactor : public ValueObject,
                    public HandleVisitor,
                    public ObjectPointerVisitor {
 public:
  GCCompactor(Thread* thread, Heap* heap)
      : HandleVisitor(thread),
        ObjectPointerVisitor(thread->isolate()),
        heap_(heap) {}
  ~GCCompactor() {}

  void Compact(HeapPage* pages, FreeList* freelist, Mutex* mutex);

 private:
  void SetupImagePageBoundaries();
  void ForwardStackPointers();
  void ForwardPointer(RawObject** ptr);
  void VisitPointers(RawObject** first, RawObject** last);
  void VisitHandle(uword addr);

  Heap* heap_;

  struct ImagePageRange {
    uword base;
    uword size;
  };
  // There are up to 6 images to consider:
  // {instructions, data} x {vm isolate, current isolate, shared}
  static const intptr_t kMaxImagePages = 6;
  ImagePageRange image_page_ranges_[kMaxImagePages];
};

}  // namespace dart

#endif  // RUNTIME_VM_HEAP_COMPACTOR_H_