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/// RecyclerStruct - Implementation detail for Recycler. This is a
32/// class that the recycler imposes on free'd memory to carve out
33/// next/prev pointers.
34struct RecyclerStruct {
35  RecyclerStruct *Prev, *Next;
36};
37
38template<>
39struct ilist_traits<RecyclerStruct> :
40    public ilist_default_traits<RecyclerStruct> {
41  static RecyclerStruct *getPrev(const RecyclerStruct *t) { return t->Prev; }
42  static RecyclerStruct *getNext(const RecyclerStruct *t) { return t->Next; }
43  static void setPrev(RecyclerStruct *t, RecyclerStruct *p) { t->Prev = p; }
44  static void setNext(RecyclerStruct *t, RecyclerStruct *n) { t->Next = n; }
45
46  mutable RecyclerStruct Sentinel;
47  RecyclerStruct *createSentinel() const {
48    return &Sentinel;
49  }
50  static void destroySentinel(RecyclerStruct *) {}
51
52  RecyclerStruct *provideInitialHead() const { return createSentinel(); }
53  RecyclerStruct *ensureHead(RecyclerStruct*) const { return createSentinel(); }
54  static void noteHead(RecyclerStruct*, RecyclerStruct*) {}
55
56  static void deleteNode(RecyclerStruct *) {
57    llvm_unreachable("Recycler's ilist_traits shouldn't see a deleteNode call!");
58  }
59};
60
61/// Recycler - This class manages a linked-list of deallocated nodes
62/// and facilitates reusing deallocated memory in place of allocating
63/// new memory.
64///
65template<class T, size_t Size = sizeof(T), size_t Align = AlignOf<T>::Alignment>
66class Recycler {
67  /// FreeList - Doubly-linked list of nodes that have deleted contents and
68  /// are not in active use.
69  ///
70  iplist<RecyclerStruct> FreeList;
71
72public:
73  ~Recycler() {
74    // If this fails, either the callee has lost track of some allocation,
75    // or the callee isn't tracking allocations and should just call
76    // clear() before deleting the Recycler.
77    assert(FreeList.empty() && "Non-empty recycler deleted!");
78  }
79
80  /// clear - Release all the tracked allocations to the allocator. The
81  /// recycler must be free of any tracked allocations before being
82  /// deleted; calling clear is one way to ensure this.
83  template<class AllocatorType>
84  void clear(AllocatorType &Allocator) {
85    while (!FreeList.empty()) {
86      T *t = reinterpret_cast<T *>(FreeList.remove(FreeList.begin()));
87      Allocator.Deallocate(t);
88    }
89  }
90
91  /// Special case for BumpPtrAllocator which has an empty Deallocate()
92  /// function.
93  ///
94  /// There is no need to traverse the free list, pulling all the objects into
95  /// cache.
96  void clear(BumpPtrAllocator&) {
97    FreeList.clearAndLeakNodesUnsafely();
98  }
99
100  template<class SubClass, class AllocatorType>
101  SubClass *Allocate(AllocatorType &Allocator) {
102    static_assert(AlignOf<SubClass>::Alignment <= Align,
103                  "Recycler allocation alignment is less than object align!");
104    static_assert(sizeof(SubClass) <= Size,
105                  "Recycler allocation size is less than object size!");
106    return !FreeList.empty() ?
107           reinterpret_cast<SubClass *>(FreeList.remove(FreeList.begin())) :
108           static_cast<SubClass *>(Allocator.Allocate(Size, Align));
109  }
110
111  template<class AllocatorType>
112  T *Allocate(AllocatorType &Allocator) {
113    return Allocate<T>(Allocator);
114  }
115
116  template<class SubClass, class AllocatorType>
117  void Deallocate(AllocatorType & /*Allocator*/, SubClass* Element) {
118    FreeList.push_front(reinterpret_cast<RecyclerStruct *>(Element));
119  }
120
121  void PrintStats() {
122    PrintRecyclerStats(Size, Align, FreeList.size());
123  }
124};
125
126}
127
128#endif
129