virtual_memory_compressed.h

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// Copyright (c) 2021, 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_VIRTUAL_MEMORY_COMPRESSED_H_
#define RUNTIME_VM_VIRTUAL_MEMORY_COMPRESSED_H_
 
#include "vm/globals.h"
#include "vm/heap/page.h"
#include "vm/memory_region.h"
 
namespace dart {
 
#if defined(DART_COMPRESSED_POINTERS)
static constexpr intptr_t kCompressedHeapSize = 4 * GB;
static constexpr intptr_t kCompressedHeapAlignment = 4 * GB;
static constexpr intptr_t kCompressedPageSize = kPageSize;
static constexpr intptr_t kCompressedHeapNumPages =
    kCompressedHeapSize / kPageSize;
static constexpr intptr_t kCompressedHeapBitmapSize =
    kCompressedHeapNumPages / 8;
 
#if !defined(DART_HOST_OS_FUCHSIA)
#define DART_COMPRESSED_HEAP
#endif  // !defined(DART_HOST_OS_FUCHSIA)
#endif  // defined(DART_COMPRESSED_POINTERS)
 
#if defined(DART_COMPRESSED_HEAP)
 
// Utilities for allocating memory within a contiguous region of memory, for use
// with compressed pointers.
class VirtualMemoryCompressedHeap : public AllStatic {
 public:
  // Initializes the compressed heap. The callee must allocate a region of
  // kCompressedHeapSize bytes, aligned to kCompressedHeapSize.
  static void Init(void* compressed_heap_region, size_t size);
 
  // Cleans up the compressed heap. The callee is responsible for freeing the
  // region's memory.
  static void Cleanup();
 
  // Allocates a segment of the compressed heap with the given size. Returns a
  // heap memory region if a large enough free segment can't be found.
  static MemoryRegion Allocate(intptr_t size, intptr_t alignment);
 
  // Frees a segment.
  static void Free(void* address, intptr_t size);
 
  // Returns whether the address is within the compressed heap.
  static bool Contains(void* address);
 
  // Returns a pointer to the compressed heap region.
  static void* GetRegion();
 
 private:
  static bool IsPageUsed(uword page_id);
  static void SetPageUsed(uword page_id);
  static void ClearPageUsed(uword page_id);
 
  static uword base_;
  static uword size_;
  static uint8_t* pages_;
  static uword minimum_free_page_id_;
  static Mutex* mutex_;
};
 
#endif  // defined(DART_COMPRESSED_HEAP)
 
}  // namespace dart
 
#endif  // RUNTIME_VM_VIRTUAL_MEMORY_COMPRESSED_H_