| //==- llvm/Support/ArrayRecycler.h - Recycling of Arrays ---------*- C++ -*-==// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines the ArrayRecycler class template which can recycle small |
| // arrays allocated from one of the allocators in Allocator.h |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_SUPPORT_ARRAYRECYCLER_H |
| #define LLVM_SUPPORT_ARRAYRECYCLER_H |
| |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/Support/Allocator.h" |
| #include "llvm/Support/MathExtras.h" |
| |
| namespace llvm { |
| |
| /// Recycle small arrays allocated from a BumpPtrAllocator. |
| /// |
| /// Arrays are allocated in a small number of fixed sizes. For each supported |
| /// array size, the ArrayRecycler keeps a free list of available arrays. |
| /// |
| template <class T, size_t Align = alignof(T)> class ArrayRecycler { |
| // The free list for a given array size is a simple singly linked list. |
| // We can't use iplist or Recycler here since those classes can't be copied. |
| struct FreeList { |
| FreeList *Next; |
| }; |
| |
| static_assert(Align >= alignof(FreeList), "Object underaligned"); |
| static_assert(sizeof(T) >= sizeof(FreeList), "Objects are too small"); |
| |
| // Keep a free list for each array size. |
| SmallVector<FreeList*, 8> Bucket; |
| |
| // Remove an entry from the free list in Bucket[Idx] and return it. |
| // Return NULL if no entries are available. |
| T *pop(unsigned Idx) { |
| if (Idx >= Bucket.size()) |
| return nullptr; |
| FreeList *Entry = Bucket[Idx]; |
| if (!Entry) |
| return nullptr; |
| __asan_unpoison_memory_region(Entry, Capacity::get(Idx).getSize()); |
| Bucket[Idx] = Entry->Next; |
| __msan_allocated_memory(Entry, Capacity::get(Idx).getSize()); |
| return reinterpret_cast<T*>(Entry); |
| } |
| |
| // Add an entry to the free list at Bucket[Idx]. |
| void push(unsigned Idx, T *Ptr) { |
| assert(Ptr && "Cannot recycle NULL pointer"); |
| FreeList *Entry = reinterpret_cast<FreeList*>(Ptr); |
| if (Idx >= Bucket.size()) |
| Bucket.resize(size_t(Idx) + 1); |
| Entry->Next = Bucket[Idx]; |
| Bucket[Idx] = Entry; |
| __asan_poison_memory_region(Ptr, Capacity::get(Idx).getSize()); |
| } |
| |
| public: |
| /// The size of an allocated array is represented by a Capacity instance. |
| /// |
| /// This class is much smaller than a size_t, and it provides methods to work |
| /// with the set of legal array capacities. |
| class Capacity { |
| uint8_t Index; |
| explicit Capacity(uint8_t idx) : Index(idx) {} |
| |
| public: |
| Capacity() : Index(0) {} |
| |
| /// Get the capacity of an array that can hold at least N elements. |
| static Capacity get(size_t N) { |
| return Capacity(N ? Log2_64_Ceil(N) : 0); |
| } |
| |
| /// Get the number of elements in an array with this capacity. |
| size_t getSize() const { return size_t(1u) << Index; } |
| |
| /// Get the bucket number for this capacity. |
| unsigned getBucket() const { return Index; } |
| |
| /// Get the next larger capacity. Large capacities grow exponentially, so |
| /// this function can be used to reallocate incrementally growing vectors |
| /// in amortized linear time. |
| Capacity getNext() const { return Capacity(Index + 1); } |
| }; |
| |
| ~ArrayRecycler() { |
| // The client should always call clear() so recycled arrays can be returned |
| // to the allocator. |
| assert(Bucket.empty() && "Non-empty ArrayRecycler deleted!"); |
| } |
| |
| /// Release all the tracked allocations to the allocator. The recycler must |
| /// be free of any tracked allocations before being deleted. |
| template<class AllocatorType> |
| void clear(AllocatorType &Allocator) { |
| for (; !Bucket.empty(); Bucket.pop_back()) |
| while (T *Ptr = pop(Bucket.size() - 1)) |
| Allocator.Deallocate(Ptr); |
| } |
| |
| /// Special case for BumpPtrAllocator which has an empty Deallocate() |
| /// function. |
| /// |
| /// There is no need to traverse the free lists, pulling all the objects into |
| /// cache. |
| void clear(BumpPtrAllocator&) { |
| Bucket.clear(); |
| } |
| |
| /// Allocate an array of at least the requested capacity. |
| /// |
| /// Return an existing recycled array, or allocate one from Allocator if |
| /// none are available for recycling. |
| /// |
| template<class AllocatorType> |
| T *allocate(Capacity Cap, AllocatorType &Allocator) { |
| // Try to recycle an existing array. |
| if (T *Ptr = pop(Cap.getBucket())) |
| return Ptr; |
| // Nope, get more memory. |
| return static_cast<T*>(Allocator.Allocate(sizeof(T)*Cap.getSize(), Align)); |
| } |
| |
| /// Deallocate an array with the specified Capacity. |
| /// |
| /// Cap must be the same capacity that was given to allocate(). |
| /// |
| void deallocate(Capacity Cap, T *Ptr) { |
| push(Cap.getBucket(), Ptr); |
| } |
| }; |
| |
| } // end llvm namespace |
| |
| #endif |