include/llvm/Support/Recycler.h

   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
  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
  50   void push(FreeNode *N) {
  51     N->Next = FreeList;
  52     FreeList = N;
  53     __asan_poison_memory_region(N, Size);
  54   }
  55
  56 public:
  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>
  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.
  80   void clear(BumpPtrAllocator &) { FreeList = nullptr; }
  81
  82   template<class SubClass, class AllocatorType>
  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>
  93   T *Allocate(AllocatorType &Allocator) {
  94     return Allocate<T>(Allocator);
  95   }
  96
  97   template<class SubClass, class AllocatorType>
  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>
 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