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    __asan_unpoison_memory_region(Val, Size);
46    FreeList = FreeList->Next;
47    __msan_allocated_memory(Val, Size);
48    return Val;
49  }
50
51  void push(FreeNode *N) {
52    N->Next = FreeList;
53    FreeList = N;
54    __asan_poison_memory_region(N, Size);
55  }
56
57public:
58  ~Recycler() {
59    // If this fails, either the callee has lost track of some allocation,
60    // or the callee isn't tracking allocations and should just call
61    // clear() before deleting the Recycler.
62    assert(!FreeList && "Non-empty recycler deleted!");
63  }
64
65  /// clear - Release all the tracked allocations to the allocator. The
66  /// recycler must be free of any tracked allocations before being
67  /// deleted; calling clear is one way to ensure this.
68  template<class AllocatorType>
69  void clear(AllocatorType &Allocator) {
70    while (FreeList) {
71      T *t = reinterpret_cast<T *>(pop_val());
72      Allocator.Deallocate(t);
73    }
74  }
75
76  /// Special case for BumpPtrAllocator which has an empty Deallocate()
77  /// function.
78  ///
79  /// There is no need to traverse the free list, pulling all the objects into
80  /// cache.
81  void clear(BumpPtrAllocator &) { FreeList = nullptr; }
82
83  template<class SubClass, class AllocatorType>
84  SubClass *Allocate(AllocatorType &Allocator) {
85    static_assert(alignof(SubClass) <= Align,
86                  "Recycler allocation alignment is less than object align!");
87    static_assert(sizeof(SubClass) <= Size,
88                  "Recycler allocation size is less than object size!");
89    return FreeList ? reinterpret_cast<SubClass *>(pop_val())
90                    : static_cast<SubClass *>(Allocator.Allocate(Size, Align));
91  }
92
93  template<class AllocatorType>
94  T *Allocate(AllocatorType &Allocator) {
95    return Allocate<T>(Allocator);
96  }
97
98  template<class SubClass, class AllocatorType>
99  void Deallocate(AllocatorType & /*Allocator*/, SubClass* Element) {
100    push(reinterpret_cast<FreeNode *>(Element));
101  }
102
103  void PrintStats();
104};
105
106template <class T, size_t Size, size_t Align>
107void Recycler<T, Size, Align>::PrintStats() {
108  size_t S = 0;
109  for (auto *I = FreeList; I; I = I->Next)
110    ++S;
111  PrintRecyclerStats(Size, Align, S);
112}
113
114}
115
116#endif
117