Recycler.h revision 314564 
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/Allocator.h"
20#include "llvm/Support/ErrorHandling.h"
21#include <cassert>
22
23namespace llvm {
24
25/// PrintRecyclingAllocatorStats - Helper for RecyclingAllocator for
26/// printing statistics.
27///
28void PrintRecyclerStats(size_t Size, size_t Align, size_t FreeListSize);
29
30/// Recycler - This class manages a linked-list of deallocated nodes
31/// and facilitates reusing deallocated memory in place of allocating
32/// new memory.
33///
34template <class T, size_t Size = sizeof(T), size_t Align = alignof(T)>
35class Recycler {
36  struct FreeNode {
37    FreeNode *Next;
38  };
39
40  /// List of nodes that have deleted contents and are not in active use.
41  FreeNode *FreeList = nullptr;
42
43  FreeNode *pop_val() {
44    auto *Val = FreeList;
45    FreeList = FreeList->Next;
46    return Val;
47  }
48
49  void push(FreeNode *N) {
50    N->Next = FreeList;
51    FreeList = N;
52  }
53
54public:
55  ~Recycler() {
56    // If this fails, either the callee has lost track of some allocation,
57    // or the callee isn't tracking allocations and should just call
58    // clear() before deleting the Recycler.
59    assert(!FreeList && "Non-empty recycler deleted!");
60  }
61
62  /// clear - Release all the tracked allocations to the allocator. The
63  /// recycler must be free of any tracked allocations before being
64  /// deleted; calling clear is one way to ensure this.
65  template<class AllocatorType>
66  void clear(AllocatorType &Allocator) {
67    while (FreeList) {
68      T *t = reinterpret_cast<T *>(pop_val());
69      Allocator.Deallocate(t);
70    }
71  }
72
73  /// Special case for BumpPtrAllocator which has an empty Deallocate()
74  /// function.
75  ///
76  /// There is no need to traverse the free list, pulling all the objects into
77  /// cache.
78  void clear(BumpPtrAllocator &) { FreeList = nullptr; }
79
80  template<class SubClass, class AllocatorType>
81  SubClass *Allocate(AllocatorType &Allocator) {
82    static_assert(alignof(SubClass) <= Align,
83                  "Recycler allocation alignment is less than object align!");
84    static_assert(sizeof(SubClass) <= Size,
85                  "Recycler allocation size is less than object size!");
86    return FreeList ? reinterpret_cast<SubClass *>(pop_val())
87                    : static_cast<SubClass *>(Allocator.Allocate(Size, Align));
88  }
89
90  template<class AllocatorType>
91  T *Allocate(AllocatorType &Allocator) {
92    return Allocate<T>(Allocator);
93  }
94
95  template<class SubClass, class AllocatorType>
96  void Deallocate(AllocatorType & /*Allocator*/, SubClass* Element) {
97    push(reinterpret_cast<FreeNode *>(Element));
98  }
99
100  void PrintStats();
101};
102
103template <class T, size_t Size, size_t Align>
104void Recycler<T, Size, Align>::PrintStats() {
105  size_t S = 0;
106  for (auto *I = FreeList; I; I = I->Next)
107    ++S;
108  PrintRecyclerStats(Size, Align, S);
109}
110
111}
112
113#endif
114