1//==- llvm/Support/Recycler.h - Recycling Allocator --------------*- C++ -*-==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines the Recycler class template.  See the doxygen comment for
11// Recycler for more details.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_SUPPORT_RECYCLER_H
16#define LLVM_SUPPORT_RECYCLER_H
17
18#include "llvm/ADT/ilist.h"
19#include "llvm/Support/AlignOf.h"
20#include "llvm/Support/Allocator.h"
21#include "llvm/Support/ErrorHandling.h"
22#include <cassert>
23
24namespace llvm {
25
26/// PrintRecyclingAllocatorStats - Helper for RecyclingAllocator for
27/// printing statistics.
28///
29void PrintRecyclerStats(size_t Size, size_t Align, size_t FreeListSize);
30
31/// Recycler - This class manages a linked-list of deallocated nodes
32/// and facilitates reusing deallocated memory in place of allocating
33/// new memory.
34///
35template<class T, size_t Size = sizeof(T), size_t Align = AlignOf<T>::Alignment>
36class Recycler {
37  struct FreeNode {
38    FreeNode *Next;
39  };
40
41  /// List of nodes that have deleted contents and are not in active use.
42  FreeNode *FreeList = nullptr;
43
44  FreeNode *pop_val() {
45    auto *Val = FreeList;
46    FreeList = FreeList->Next;
47    return Val;
48  }
49
50  void push(FreeNode *N) {
51    N->Next = FreeList;
52    FreeList = N;
53  }
54
55public:
56  ~Recycler() {
57    // If this fails, either the callee has lost track of some allocation,
58    // or the callee isn't tracking allocations and should just call
59    // clear() before deleting the Recycler.
60    assert(!FreeList && "Non-empty recycler deleted!");
61  }
62
63  /// clear - Release all the tracked allocations to the allocator. The
64  /// recycler must be free of any tracked allocations before being
65  /// deleted; calling clear is one way to ensure this.
66  template<class AllocatorType>
67  void clear(AllocatorType &Allocator) {
68    while (FreeList) {
69      T *t = reinterpret_cast<T *>(pop_val());
70      Allocator.Deallocate(t);
71    }
72  }
73
74  /// Special case for BumpPtrAllocator which has an empty Deallocate()
75  /// function.
76  ///
77  /// There is no need to traverse the free list, pulling all the objects into
78  /// cache.
79  void clear(BumpPtrAllocator &) { FreeList = nullptr; }
80
81  template<class SubClass, class AllocatorType>
82  SubClass *Allocate(AllocatorType &Allocator) {
83    static_assert(AlignOf<SubClass>::Alignment <= Align,
84                  "Recycler allocation alignment is less than object align!");
85    static_assert(sizeof(SubClass) <= Size,
86                  "Recycler allocation size is less than object size!");
87    return FreeList ? reinterpret_cast<SubClass *>(pop_val())
88                    : static_cast<SubClass *>(Allocator.Allocate(Size, Align));
89  }
90
91  template<class AllocatorType>
92  T *Allocate(AllocatorType &Allocator) {
93    return Allocate<T>(Allocator);
94  }
95
96  template<class SubClass, class AllocatorType>
97  void Deallocate(AllocatorType & /*Allocator*/, SubClass* Element) {
98    push(reinterpret_cast<FreeNode *>(Element));
99  }
100
101  void PrintStats();
102};
103
104template <class T, size_t Size, size_t Align>
105void Recycler<T, Size, Align>::PrintStats() {
106  size_t S = 0;
107  for (auto *I = FreeList; I; I = I->Next)
108    ++S;
109  PrintRecyclerStats(Size, Align, S);
110}
111
112}
113
114#endif
115