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/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/// RecyclerStruct - Implementation detail for Recycler. This is a
31/// class that the recycler imposes on free'd memory to carve out
32/// next/prev pointers.
33struct RecyclerStruct {
34  RecyclerStruct *Prev, *Next;
35};
36
37template<>
38struct ilist_traits<RecyclerStruct> :
39    public ilist_default_traits<RecyclerStruct> {
40  static RecyclerStruct *getPrev(const RecyclerStruct *t) { return t->Prev; }
41  static RecyclerStruct *getNext(const RecyclerStruct *t) { return t->Next; }
42  static void setPrev(RecyclerStruct *t, RecyclerStruct *p) { t->Prev = p; }
43  static void setNext(RecyclerStruct *t, RecyclerStruct *n) { t->Next = n; }
44
45  mutable RecyclerStruct Sentinel;
46  RecyclerStruct *createSentinel() const {
47    return &Sentinel;
48  }
49  static void destroySentinel(RecyclerStruct *) {}
50
51  RecyclerStruct *provideInitialHead() const { return createSentinel(); }
52  RecyclerStruct *ensureHead(RecyclerStruct*) const { return createSentinel(); }
53  static void noteHead(RecyclerStruct*, RecyclerStruct*) {}
54
55  static void deleteNode(RecyclerStruct *) {
56    llvm_unreachable("Recycler's ilist_traits shouldn't see a deleteNode call!");
57  }
58};
59
60/// Recycler - This class manages a linked-list of deallocated nodes
61/// and facilitates reusing deallocated memory in place of allocating
62/// new memory.
63///
64template<class T, size_t Size = sizeof(T), size_t Align = AlignOf<T>::Alignment>
65class Recycler {
66  /// FreeList - Doubly-linked list of nodes that have deleted contents and
67  /// are not in active use.
68  ///
69  iplist<RecyclerStruct> FreeList;
70
71public:
72  ~Recycler() {
73    // If this fails, either the callee has lost track of some allocation,
74    // or the callee isn't tracking allocations and should just call
75    // clear() before deleting the Recycler.
76    assert(FreeList.empty() && "Non-empty recycler deleted!");
77  }
78
79  /// clear - Release all the tracked allocations to the allocator. The
80  /// recycler must be free of any tracked allocations before being
81  /// deleted; calling clear is one way to ensure this.
82  template<class AllocatorType>
83  void clear(AllocatorType &Allocator) {
84    while (!FreeList.empty()) {
85      T *t = reinterpret_cast<T *>(FreeList.remove(FreeList.begin()));
86      Allocator.Deallocate(t);
87    }
88  }
89
90  template<class SubClass, class AllocatorType>
91  SubClass *Allocate(AllocatorType &Allocator) {
92    assert(sizeof(SubClass) <= Size &&
93           "Recycler allocation size is less than object size!");
94    assert(AlignOf<SubClass>::Alignment <= Align &&
95           "Recycler allocation alignment is less than object alignment!");
96    return !FreeList.empty() ?
97           reinterpret_cast<SubClass *>(FreeList.remove(FreeList.begin())) :
98           static_cast<SubClass *>(Allocator.Allocate(Size, Align));
99  }
100
101  template<class AllocatorType>
102  T *Allocate(AllocatorType &Allocator) {
103    return Allocate<T>(Allocator);
104  }
105
106  template<class SubClass, class AllocatorType>
107  void Deallocate(AllocatorType & /*Allocator*/, SubClass* Element) {
108    FreeList.push_front(reinterpret_cast<RecyclerStruct *>(Element));
109  }
110
111  void PrintStats() {
112    PrintRecyclerStats(Size, Align, FreeList.size());
113  }
114};
115
116}
117
118#endif
119