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 <cassert>
21
22namespace llvm {
23
24/// PrintRecyclingAllocatorStats - Helper for RecyclingAllocator for
25/// printing statistics.
26///
27void PrintRecyclerStats(size_t Size, size_t Align, size_t FreeListSize);
28
29/// RecyclerStruct - Implementation detail for Recycler. This is a
30/// class that the recycler imposes on free'd memory to carve out
31/// next/prev pointers.
32struct RecyclerStruct {
33  RecyclerStruct *Prev, *Next;
34};
35
36template<>
37struct ilist_traits<RecyclerStruct> :
38    public ilist_default_traits<RecyclerStruct> {
39  static RecyclerStruct *getPrev(const RecyclerStruct *t) { return t->Prev; }
40  static RecyclerStruct *getNext(const RecyclerStruct *t) { return t->Next; }
41  static void setPrev(RecyclerStruct *t, RecyclerStruct *p) { t->Prev = p; }
42  static void setNext(RecyclerStruct *t, RecyclerStruct *n) { t->Next = n; }
43
44  mutable RecyclerStruct Sentinel;
45  RecyclerStruct *createSentinel() const {
46    return &Sentinel;
47  }
48  static void destroySentinel(RecyclerStruct *) {}
49
50  RecyclerStruct *provideInitialHead() const { return createSentinel(); }
51  RecyclerStruct *ensureHead(RecyclerStruct*) const { return createSentinel(); }
52  static void noteHead(RecyclerStruct*, RecyclerStruct*) {}
53
54  static void deleteNode(RecyclerStruct *) {
55    assert(0 && "Recycler's ilist_traits shouldn't see a deleteNode call!");
56  }
57};
58
59/// Recycler - This class manages a linked-list of deallocated nodes
60/// and facilitates reusing deallocated memory in place of allocating
61/// new memory.
62///
63template<class T, size_t Size = sizeof(T), size_t Align = AlignOf<T>::Alignment>
64class Recycler {
65  /// FreeList - Doubly-linked list of nodes that have deleted contents and
66  /// are not in active use.
67  ///
68  iplist<RecyclerStruct> FreeList;
69
70public:
71  ~Recycler() {
72    // If this fails, either the callee has lost track of some allocation,
73    // or the callee isn't tracking allocations and should just call
74    // clear() before deleting the Recycler.
75    assert(FreeList.empty() && "Non-empty recycler deleted!");
76  }
77
78  /// clear - Release all the tracked allocations to the allocator. The
79  /// recycler must be free of any tracked allocations before being
80  /// deleted; calling clear is one way to ensure this.
81  template<class AllocatorType>
82  void clear(AllocatorType &Allocator) {
83    while (!FreeList.empty()) {
84      T *t = reinterpret_cast<T *>(FreeList.remove(FreeList.begin()));
85      Allocator.Deallocate(t);
86    }
87  }
88
89  template<class SubClass, class AllocatorType>
90  SubClass *Allocate(AllocatorType &Allocator) {
91    assert(sizeof(SubClass) <= Size &&
92           "Recycler allocation size is less than object size!");
93    assert(AlignOf<SubClass>::Alignment <= Align &&
94           "Recycler allocation alignment is less than object alignment!");
95    return !FreeList.empty() ?
96           reinterpret_cast<SubClass *>(FreeList.remove(FreeList.begin())) :
97           static_cast<SubClass *>(Allocator.Allocate(Size, Align));
98  }
99
100  template<class AllocatorType>
101  T *Allocate(AllocatorType &Allocator) {
102    return Allocate<T>(Allocator);
103  }
104
105  template<class SubClass, class AllocatorType>
106  void Deallocate(AllocatorType & /*Allocator*/, SubClass* Element) {
107    FreeList.push_front(reinterpret_cast<RecyclerStruct *>(Element));
108  }
109
110  void PrintStats() {
111    PrintRecyclerStats(Size, Align, FreeList.size());
112  }
113};
114
115}
116
117#endif
118