llvm/Support/Recycler.h

0001 //==- llvm/Support/Recycler.h - Recycling Allocator --------------*- C++ -*-==//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008 //
0009 // This file defines the Recycler class template.  See the doxygen comment for
0010 // Recycler for more details.
0011 //
0012 //===----------------------------------------------------------------------===//
0013
0014 #ifndef LLVM_SUPPORT_RECYCLER_H
0015 #define LLVM_SUPPORT_RECYCLER_H
0016
0017 #include "llvm/ADT/ilist.h"
0018 #include "llvm/Support/Allocator.h"
0019 #include "llvm/Support/ErrorHandling.h"
0020 #include <cassert>
0021
0022 namespace llvm {
0023
0024 /// PrintRecyclingAllocatorStats - Helper for RecyclingAllocator for
0025 /// printing statistics.
0026 ///
0027 void PrintRecyclerStats(size_t Size, size_t Align, size_t FreeListSize);
0028
0029 /// Recycler - This class manages a linked-list of deallocated nodes
0030 /// and facilitates reusing deallocated memory in place of allocating
0031 /// new memory.
0032 ///
0033 template <class T, size_t Size = sizeof(T), size_t Align = alignof(T)>
0034 class Recycler {
0035   struct FreeNode {
0036     FreeNode *Next;
0037   };
0038
0039   /// List of nodes that have deleted contents and are not in active use.
0040   FreeNode *FreeList = nullptr;
0041
0042   FreeNode *pop_val() {
0043     auto *Val = FreeList;
0044     __asan_unpoison_memory_region(Val, Size);
0045     FreeList = FreeList->Next;
0046     __msan_allocated_memory(Val, Size);
0047     return Val;
0048   }
0049
0050   void push(FreeNode *N) {
0051     N->Next = FreeList;
0052     FreeList = N;
0053     __asan_poison_memory_region(N, Size);
0054   }
0055
0056 public:
0057   ~Recycler() {
0058     // If this fails, either the callee has lost track of some allocation,
0059     // or the callee isn't tracking allocations and should just call
0060     // clear() before deleting the Recycler.
0061     assert(!FreeList && "Non-empty recycler deleted!");
0062   }
0063   Recycler(const Recycler &) = delete;
0064   Recycler(Recycler &&Other)
0065       : FreeList(std::exchange(Other.FreeList, nullptr)) {}
0066   Recycler() = default;
0067
0068   /// clear - Release all the tracked allocations to the allocator. The
0069   /// recycler must be free of any tracked allocations before being
0070   /// deleted; calling clear is one way to ensure this.
0071   template<class AllocatorType>
0072   void clear(AllocatorType &Allocator) {
0073     while (FreeList) {
0074       T *t = reinterpret_cast<T *>(pop_val());
0075       Allocator.Deallocate(t, Size, Align);
0076     }
0077   }
0078
0079   /// Special case for BumpPtrAllocator which has an empty Deallocate()
0080   /// function.
0081   ///
0082   /// There is no need to traverse the free list, pulling all the objects into
0083   /// cache.
0084   void clear(BumpPtrAllocator &) { FreeList = nullptr; }
0085
0086   template<class SubClass, class AllocatorType>
0087   SubClass *Allocate(AllocatorType &Allocator) {
0088     static_assert(alignof(SubClass) <= Align,
0089                   "Recycler allocation alignment is less than object align!");
0090     static_assert(sizeof(SubClass) <= Size,
0091                   "Recycler allocation size is less than object size!");
0092     static_assert(Size >= sizeof(FreeNode) &&
0093                   "Recycler allocation size must be at least sizeof(FreeNode)");
0094     return FreeList ? reinterpret_cast<SubClass *>(pop_val())
0095                     : static_cast<SubClass *>(Allocator.Allocate(Size, Align));
0096   }
0097
0098   template<class AllocatorType>
0099   T *Allocate(AllocatorType &Allocator) {
0100     return Allocate<T>(Allocator);
0101   }
0102
0103   template<class SubClass, class AllocatorType>
0104   void Deallocate(AllocatorType & /*Allocator*/, SubClass* Element) {
0105     push(reinterpret_cast<FreeNode *>(Element));
0106   }
0107
0108   void PrintStats();
0109 };
0110
0111 template <class T, size_t Size, size_t Align>
0112 void Recycler<T, Size, Align>::PrintStats() {
0113   size_t S = 0;
0114   for (auto *I = FreeList; I; I = I->Next)
0115     ++S;
0116   PrintRecyclerStats(Size, Align, S);
0117 }
0118
0119 }
0120
0121 #endif