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
25class BumpPtrAllocator;
26
27/// PrintRecyclingAllocatorStats - Helper for RecyclingAllocator for
28/// printing statistics.
29///
30void PrintRecyclerStats(size_t Size, size_t Align, size_t FreeListSize);
31
32/// RecyclerStruct - Implementation detail for Recycler. This is a
33/// class that the recycler imposes on free'd memory to carve out
34/// next/prev pointers.
35struct RecyclerStruct {
36  RecyclerStruct *Prev, *Next;
37};
38
39template<>
40struct ilist_traits<RecyclerStruct> :
41    public ilist_default_traits<RecyclerStruct> {
42  static RecyclerStruct *getPrev(const RecyclerStruct *t) { return t->Prev; }
43  static RecyclerStruct *getNext(const RecyclerStruct *t) { return t->Next; }
44  static void setPrev(RecyclerStruct *t, RecyclerStruct *p) { t->Prev = p; }
45  static void setNext(RecyclerStruct *t, RecyclerStruct *n) { t->Next = n; }
46
47  mutable RecyclerStruct Sentinel;
48  RecyclerStruct *createSentinel() const {
49    return &Sentinel;
50  }
51  static void destroySentinel(RecyclerStruct *) {}
52
53  RecyclerStruct *provideInitialHead() const { return createSentinel(); }
54  RecyclerStruct *ensureHead(RecyclerStruct*) const { return createSentinel(); }
55  static void noteHead(RecyclerStruct*, RecyclerStruct*) {}
56
57  static void deleteNode(RecyclerStruct *) {
58    llvm_unreachable("Recycler's ilist_traits shouldn't see a deleteNode call!");
59  }
60};
61
62/// Recycler - This class manages a linked-list of deallocated nodes
63/// and facilitates reusing deallocated memory in place of allocating
64/// new memory.
65///
66template<class T, size_t Size = sizeof(T), size_t Align = AlignOf<T>::Alignment>
67class Recycler {
68  /// FreeList - Doubly-linked list of nodes that have deleted contents and
69  /// are not in active use.
70  ///
71  iplist<RecyclerStruct> FreeList;
72
73public:
74  ~Recycler() {
75    // If this fails, either the callee has lost track of some allocation,
76    // or the callee isn't tracking allocations and should just call
77    // clear() before deleting the Recycler.
78    assert(FreeList.empty() && "Non-empty recycler deleted!");
79  }
80
81  /// clear - Release all the tracked allocations to the allocator. The
82  /// recycler must be free of any tracked allocations before being
83  /// deleted; calling clear is one way to ensure this.
84  template<class AllocatorType>
85  void clear(AllocatorType &Allocator) {
86    while (!FreeList.empty()) {
87      T *t = reinterpret_cast<T *>(FreeList.remove(FreeList.begin()));
88      Allocator.Deallocate(t);
89    }
90  }
91
92  /// Special case for BumpPtrAllocator which has an empty Deallocate()
93  /// function.
94  ///
95  /// There is no need to traverse the free list, pulling all the objects into
96  /// cache.
97  void clear(BumpPtrAllocator&) {
98    FreeList.clearAndLeakNodesUnsafely();
99  }
100
101  template<class SubClass, class AllocatorType>
102  SubClass *Allocate(AllocatorType &Allocator) {
103    assert(sizeof(SubClass) <= Size &&
104           "Recycler allocation size is less than object size!");
105    assert(AlignOf<SubClass>::Alignment <= Align &&
106           "Recycler allocation alignment is less than object alignment!");
107    return !FreeList.empty() ?
108           reinterpret_cast<SubClass *>(FreeList.remove(FreeList.begin())) :
109           static_cast<SubClass *>(Allocator.Allocate(Size, Align));
110  }
111
112  template<class AllocatorType>
113  T *Allocate(AllocatorType &Allocator) {
114    return Allocate<T>(Allocator);
115  }
116
117  template<class SubClass, class AllocatorType>
118  void Deallocate(AllocatorType & /*Allocator*/, SubClass* Element) {
119    FreeList.push_front(reinterpret_cast<RecyclerStruct *>(Element));
120  }
121
122  void PrintStats() {
123    PrintRecyclerStats(Size, Align, FreeList.size());
124  }
125};
126
127}
128
129#endif
130