1 //==- llvm/Support/Recycler.h - Recycling Allocator --------------*- C++ -*-==//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines the Recycler class template. See the doxygen comment for
10 // Recycler for more details.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #ifndef LLVM_SUPPORT_RECYCLER_H
15 #define LLVM_SUPPORT_RECYCLER_H
16
17 #include "llvm/ADT/ilist.h"
18 #include "llvm/Support/Allocator.h"
19 #include "llvm/Support/ErrorHandling.h"
20 #include <cassert>
21
22 namespace llvm {
23
24 /// PrintRecyclingAllocatorStats - Helper for RecyclingAllocator for
25 /// printing statistics.
26 ///
27 void PrintRecyclerStats(size_t Size, size_t Align, size_t FreeListSize);
28
29 /// Recycler - This class manages a linked-list of deallocated nodes
30 /// and facilitates reusing deallocated memory in place of allocating
31 /// new memory.
32 ///
33 template <class T, size_t Size = sizeof(T), size_t Align = alignof(T)>
34 class Recycler {
35 struct FreeNode {
36 FreeNode *Next;
37 };
38
39 /// List of nodes that have deleted contents and are not in active use.
40 FreeNode *FreeList = nullptr;
41
pop_val()42 FreeNode *pop_val() {
43 auto *Val = FreeList;
44 __asan_unpoison_memory_region(Val, Size);
45 FreeList = FreeList->Next;
46 __msan_allocated_memory(Val, Size);
47 return Val;
48 }
49
push(FreeNode * N)50 void push(FreeNode *N) {
51 N->Next = FreeList;
52 FreeList = N;
53 __asan_poison_memory_region(N, Size);
54 }
55
56 public:
~Recycler()57 ~Recycler() {
58 // If this fails, either the callee has lost track of some allocation,
59 // or the callee isn't tracking allocations and should just call
60 // clear() before deleting the Recycler.
61 assert(!FreeList && "Non-empty recycler deleted!");
62 }
63
64 /// clear - Release all the tracked allocations to the allocator. The
65 /// recycler must be free of any tracked allocations before being
66 /// deleted; calling clear is one way to ensure this.
67 template<class AllocatorType>
clear(AllocatorType & Allocator)68 void clear(AllocatorType &Allocator) {
69 while (FreeList) {
70 T *t = reinterpret_cast<T *>(pop_val());
71 Allocator.Deallocate(t);
72 }
73 }
74
75 /// Special case for BumpPtrAllocator which has an empty Deallocate()
76 /// function.
77 ///
78 /// There is no need to traverse the free list, pulling all the objects into
79 /// cache.
clear(BumpPtrAllocator &)80 void clear(BumpPtrAllocator &) { FreeList = nullptr; }
81
82 template<class SubClass, class AllocatorType>
Allocate(AllocatorType & Allocator)83 SubClass *Allocate(AllocatorType &Allocator) {
84 static_assert(alignof(SubClass) <= Align,
85 "Recycler allocation alignment is less than object align!");
86 static_assert(sizeof(SubClass) <= Size,
87 "Recycler allocation size is less than object size!");
88 return FreeList ? reinterpret_cast<SubClass *>(pop_val())
89 : static_cast<SubClass *>(Allocator.Allocate(Size, Align));
90 }
91
92 template<class AllocatorType>
Allocate(AllocatorType & Allocator)93 T *Allocate(AllocatorType &Allocator) {
94 return Allocate<T>(Allocator);
95 }
96
97 template<class SubClass, class AllocatorType>
Deallocate(AllocatorType &,SubClass * Element)98 void Deallocate(AllocatorType & /*Allocator*/, SubClass* Element) {
99 push(reinterpret_cast<FreeNode *>(Element));
100 }
101
102 void PrintStats();
103 };
104
105 template <class T, size_t Size, size_t Align>
PrintStats()106 void Recycler<T, Size, Align>::PrintStats() {
107 size_t S = 0;
108 for (auto *I = FreeList; I; I = I->Next)
109 ++S;
110 PrintRecyclerStats(Size, Align, S);
111 }
112
113 }
114
115 #endif
116