src/llvm/include/llvm/Support/Allocator.h

   1 //===--- Allocator.h - Simple memory allocation abstraction -----*- 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 /// \file
  10 ///
  11 /// This file defines the MallocAllocator and BumpPtrAllocator interfaces. Both
  12 /// of these conform to an LLVM "Allocator" concept which consists of an
  13 /// Allocate method accepting a size and alignment, and a Deallocate accepting
  14 /// a pointer and size. Further, the LLVM "Allocator" concept has overloads of
  15 /// Allocate and Deallocate for setting size and alignment based on the final
  16 /// type. These overloads are typically provided by a base class template \c
  17 /// AllocatorBase.
  18 ///
  19 //===----------------------------------------------------------------------===//
  20
  21 #ifndef LLVM_SUPPORT_ALLOCATOR_H
  22 #define LLVM_SUPPORT_ALLOCATOR_H
  23
  24 #include "llvm/ADT/SmallVector.h"
  25 #include "llvm/Support/AlignOf.h"
  26 #include "llvm/Support/DataTypes.h"
  27 #include "llvm/Support/MathExtras.h"
  28 #include "llvm/Support/Memory.h"
  29 #include <algorithm>
  30 #include <cassert>
  31 #include <cstddef>
  32 #include <cstdlib>
  33
  34 namespace llvm {
  35
  36 /// \brief CRTP base class providing obvious overloads for the core \c
  37 /// Allocate() methods of LLVM-style allocators.
  38 ///
  39 /// This base class both documents the full public interface exposed by all
  40 /// LLVM-style allocators, and redirects all of the overloads to a single core
  41 /// set of methods which the derived class must define.
  42 template <typename DerivedT> class AllocatorBase {
  43 public:
  44   /// \brief Allocate \a Size bytes of \a Alignment aligned memory. This method
  45   /// must be implemented by \c DerivedT.
  46   void *Allocate(size_t Size, size_t Alignment) {
  47 #ifdef __clang__
  48     static_assert(static_cast<void *(AllocatorBase::*)(size_t, size_t)>(
  49                       &AllocatorBase::Allocate) !=
  50                       static_cast<void *(DerivedT::*)(size_t, size_t)>(
  51                           &DerivedT::Allocate),
  52                   "Class derives from AllocatorBase without implementing the "
  53                   "core Allocate(size_t, size_t) overload!");
  54 #endif
  55     return static_cast<DerivedT *>(this)->Allocate(Size, Alignment);
  56   }
  57
  58   /// \brief Deallocate \a Ptr to \a Size bytes of memory allocated by this
  59   /// allocator.
  60   void Deallocate(const void *Ptr, size_t Size) {
  61 #ifdef __clang__
  62     static_assert(static_cast<void (AllocatorBase::*)(const void *, size_t)>(
  63                       &AllocatorBase::Deallocate) !=
  64                       static_cast<void (DerivedT::*)(const void *, size_t)>(
  65                           &DerivedT::Deallocate),
  66                   "Class derives from AllocatorBase without implementing the "
  67                   "core Deallocate(void *) overload!");
  68 #endif
  69     return static_cast<DerivedT *>(this)->Deallocate(Ptr, Size);
  70   }
  71
  72   // The rest of these methods are helpers that redirect to one of the above
  73   // core methods.
  74
  75   /// \brief Allocate space for a sequence of objects without constructing them.
  76   template <typename T> T *Allocate(size_t Num = 1) {
  77     return static_cast<T *>(Allocate(Num * sizeof(T), AlignOf<T>::Alignment));
  78   }
  79
  80   /// \brief Deallocate space for a sequence of objects without constructing them.
  81   template <typename T>
  82   typename std::enable_if<
  83       !std::is_same<typename std::remove_cv<T>::type, void>::value, void>::type
  84   Deallocate(T *Ptr, size_t Num = 1) {
  85     Deallocate(static_cast<const void *>(Ptr), Num * sizeof(T));
  86   }
  87 };
  88
  89 class MallocAllocator : public AllocatorBase<MallocAllocator> {
  90 public:
  91   void Reset() {}
  92
  93   LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t Size,
  94                                                 size_t /*Alignment*/) {
  95     return malloc(Size);
  96   }
  97
  98   // Pull in base class overloads.
  99   using AllocatorBase<MallocAllocator>::Allocate;
 100
 101   void Deallocate(const void *Ptr, size_t /*Size*/) {
 102     free(const_cast<void *>(Ptr));
 103   }
 104
 105   // Pull in base class overloads.
 106   using AllocatorBase<MallocAllocator>::Deallocate;
 107
 108   void PrintStats() const {}
 109 };
 110
 111 namespace detail {
 112
 113 // We call out to an external function to actually print the message as the
 114 // printing code uses Allocator.h in its implementation.
 115 void printBumpPtrAllocatorStats(unsigned NumSlabs, size_t BytesAllocated,
 116                                 size_t TotalMemory);
 117 } // End namespace detail.
 118
 119 /// \brief Allocate memory in an ever growing pool, as if by bump-pointer.
 120 ///
 121 /// This isn't strictly a bump-pointer allocator as it uses backing slabs of
 122 /// memory rather than relying on boundless contiguous heap. However, it has
 123 /// bump-pointer semantics in that is a monotonically growing pool of memory
 124 /// where every allocation is found by merely allocating the next N bytes in
 125 /// the slab, or the next N bytes in the next slab.
 126 ///
 127 /// Note that this also has a threshold for forcing allocations above a certain
 128 /// size into their own slab.
 129 ///
 130 /// The BumpPtrAllocatorImpl template defaults to using a MallocAllocator
 131 /// object, which wraps malloc, to allocate memory, but it can be changed to
 132 /// use a custom allocator.
 133 template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096,
 134           size_t SizeThreshold = SlabSize>
 135 class BumpPtrAllocatorImpl
 136     : public AllocatorBase<
 137           BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold>> {
 138 public:
 139   static_assert(SizeThreshold <= SlabSize,
 140                 "The SizeThreshold must be at most the SlabSize to ensure "
 141                 "that objects larger than a slab go into their own memory "
 142                 "allocation.");
 143
 144   BumpPtrAllocatorImpl()
 145       : CurPtr(nullptr), End(nullptr), BytesAllocated(0), Allocator() {}
 146   template <typename T>
 147   BumpPtrAllocatorImpl(T &&Allocator)
 148       : CurPtr(nullptr), End(nullptr), BytesAllocated(0),
 149         Allocator(std::forward<T &&>(Allocator)) {}
 150
 151   // Manually implement a move constructor as we must clear the old allocators
 152   // slabs as a matter of correctness.
 153   BumpPtrAllocatorImpl(BumpPtrAllocatorImpl &&Old)
 154       : CurPtr(Old.CurPtr), End(Old.End), Slabs(std::move(Old.Slabs)),
 155         CustomSizedSlabs(std::move(Old.CustomSizedSlabs)),
 156         BytesAllocated(Old.BytesAllocated),
 157         Allocator(std::move(Old.Allocator)) {
 158     Old.CurPtr = Old.End = nullptr;
 159     Old.BytesAllocated = 0;
 160     Old.Slabs.clear();
 161     Old.CustomSizedSlabs.clear();
 162   }
 163
 164   ~BumpPtrAllocatorImpl() {
 165     DeallocateSlabs(Slabs.begin(), Slabs.end());
 166     DeallocateCustomSizedSlabs();
 167   }
 168
 169   BumpPtrAllocatorImpl &operator=(BumpPtrAllocatorImpl &&RHS) {
 170     DeallocateSlabs(Slabs.begin(), Slabs.end());
 171     DeallocateCustomSizedSlabs();
 172
 173     CurPtr = RHS.CurPtr;
 174     End = RHS.End;
 175     BytesAllocated = RHS.BytesAllocated;
 176     Slabs = std::move(RHS.Slabs);
 177     CustomSizedSlabs = std::move(RHS.CustomSizedSlabs);
 178     Allocator = std::move(RHS.Allocator);
 179
 180     RHS.CurPtr = RHS.End = nullptr;
 181     RHS.BytesAllocated = 0;
 182     RHS.Slabs.clear();
 183     RHS.CustomSizedSlabs.clear();
 184     return *this;
 185   }
 186
 187   /// \brief Deallocate all but the current slab and reset the current pointer
 188   /// to the beginning of it, freeing all memory allocated so far.
 189   void Reset() {
 190     if (Slabs.empty())
 191       return;
 192
 193     // Reset the state.
 194     BytesAllocated = 0;
 195     CurPtr = (char *)Slabs.front();
 196     End = CurPtr + SlabSize;
 197
 198     // Deallocate all but the first slab, and all custome sized slabs.
 199     DeallocateSlabs(std::next(Slabs.begin()), Slabs.end());
 200     Slabs.erase(std::next(Slabs.begin()), Slabs.end());
 201     DeallocateCustomSizedSlabs();
 202     CustomSizedSlabs.clear();
 203   }
 204
 205   /// \brief Allocate space at the specified alignment.
 206   LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t Size, size_t Alignment) {
 207     assert(Alignment > 0 && "0-byte alignnment is not allowed. Use 1 instead.");
 208
 209     // Keep track of how many bytes we've allocated.
 210     BytesAllocated += Size;
 211
 212     size_t Adjustment = alignmentAdjustment(CurPtr, Alignment);
 213     assert(Adjustment + Size >= Size && "Adjustment + Size must not overflow");
 214
 215     // Check if we have enough space.
 216     if (Adjustment + Size <= size_t(End - CurPtr)) {
 217       char *AlignedPtr = CurPtr + Adjustment;
 218       CurPtr = AlignedPtr + Size;
 219       // Update the allocation point of this memory block in MemorySanitizer.
 220       // Without this, MemorySanitizer messages for values originated from here
 221       // will point to the allocation of the entire slab.
 222       __msan_allocated_memory(AlignedPtr, Size);
 223       return AlignedPtr;
 224     }
 225
 226     // If Size is really big, allocate a separate slab for it.
 227     size_t PaddedSize = Size + Alignment - 1;
 228     if (PaddedSize > SizeThreshold) {
 229       void *NewSlab = Allocator.Allocate(PaddedSize, 0);
 230       CustomSizedSlabs.push_back(std::make_pair(NewSlab, PaddedSize));
 231
 232       uintptr_t AlignedAddr = alignAddr(NewSlab, Alignment);
 233       assert(AlignedAddr + Size <= (uintptr_t)NewSlab + PaddedSize);
 234       char *AlignedPtr = (char*)AlignedAddr;
 235       __msan_allocated_memory(AlignedPtr, Size);
 236       return AlignedPtr;
 237     }
 238
 239     // Otherwise, start a new slab and try again.
 240     StartNewSlab();
 241     uintptr_t AlignedAddr = alignAddr(CurPtr, Alignment);
 242     assert(AlignedAddr + Size <= (uintptr_t)End &&
 243            "Unable to allocate memory!");
 244     char *AlignedPtr = (char*)AlignedAddr;
 245     CurPtr = AlignedPtr + Size;
 246     __msan_allocated_memory(AlignedPtr, Size);
 247     return AlignedPtr;
 248   }
 249
 250   // Pull in base class overloads.
 251   using AllocatorBase<BumpPtrAllocatorImpl>::Allocate;
 252
 253   void Deallocate(const void * /*Ptr*/, size_t /*Size*/) {}
 254
 255   // Pull in base class overloads.
 256   using AllocatorBase<BumpPtrAllocatorImpl>::Deallocate;
 257
 258   size_t GetNumSlabs() const { return Slabs.size() + CustomSizedSlabs.size(); }
 259
 260   size_t getTotalMemory() const {
 261     size_t TotalMemory = 0;
 262     for (auto I = Slabs.begin(), E = Slabs.end(); I != E; ++I)
 263       TotalMemory += computeSlabSize(std::distance(Slabs.begin(), I));
 264     for (auto &PtrAndSize : CustomSizedSlabs)
 265       TotalMemory += PtrAndSize.second;
 266     return TotalMemory;
 267   }
 268
 269   void PrintStats() const {
 270     detail::printBumpPtrAllocatorStats(Slabs.size(), BytesAllocated,
 271                                        getTotalMemory());
 272   }
 273
 274 private:
 275   /// \brief The current pointer into the current slab.
 276   ///
 277   /// This points to the next free byte in the slab.
 278   char *CurPtr;
 279
 280   /// \brief The end of the current slab.
 281   char *End;
 282
 283   /// \brief The slabs allocated so far.
 284   SmallVector<void *, 4> Slabs;
 285
 286   /// \brief Custom-sized slabs allocated for too-large allocation requests.
 287   SmallVector<std::pair<void *, size_t>, 0> CustomSizedSlabs;
 288
 289   /// \brief How many bytes we've allocated.
 290   ///
 291   /// Used so that we can compute how much space was wasted.
 292   size_t BytesAllocated;
 293
 294   /// \brief The allocator instance we use to get slabs of memory.
 295   AllocatorT Allocator;
 296
 297   static size_t computeSlabSize(unsigned SlabIdx) {
 298     // Scale the actual allocated slab size based on the number of slabs
 299     // allocated. Every 128 slabs allocated, we double the allocated size to
 300     // reduce allocation frequency, but saturate at multiplying the slab size by
 301     // 2^30.
 302     return SlabSize * ((size_t)1 << std::min<size_t>(30, SlabIdx / 128));
 303   }
 304
 305   /// \brief Allocate a new slab and move the bump pointers over into the new
 306   /// slab, modifying CurPtr and End.
 307   void StartNewSlab() {
 308     size_t AllocatedSlabSize = computeSlabSize(Slabs.size());
 309
 310     void *NewSlab = Allocator.Allocate(AllocatedSlabSize, 0);
 311     Slabs.push_back(NewSlab);
 312     CurPtr = (char *)(NewSlab);
 313     End = ((char *)NewSlab) + AllocatedSlabSize;
 314   }
 315
 316   /// \brief Deallocate a sequence of slabs.
 317   void DeallocateSlabs(SmallVectorImpl<void *>::iterator I,
 318                        SmallVectorImpl<void *>::iterator E) {
 319     for (; I != E; ++I) {
 320       size_t AllocatedSlabSize =
 321           computeSlabSize(std::distance(Slabs.begin(), I));
 322 #ifndef NDEBUG
 323       // Poison the memory so stale pointers crash sooner.  Note we must
 324       // preserve the Size and NextPtr fields at the beginning.
 325       if (AllocatedSlabSize != 0) {
 326         sys::Memory::setRangeWritable(*I, AllocatedSlabSize);
 327         memset(*I, 0xCD, AllocatedSlabSize);
 328       }
 329 #endif
 330       Allocator.Deallocate(*I, AllocatedSlabSize);
 331     }
 332   }
 333
 334   /// \brief Deallocate all memory for custom sized slabs.
 335   void DeallocateCustomSizedSlabs() {
 336     for (auto &PtrAndSize : CustomSizedSlabs) {
 337       void *Ptr = PtrAndSize.first;
 338       size_t Size = PtrAndSize.second;
 339 #ifndef NDEBUG
 340       // Poison the memory so stale pointers crash sooner.  Note we must
 341       // preserve the Size and NextPtr fields at the beginning.
 342       sys::Memory::setRangeWritable(Ptr, Size);
 343       memset(Ptr, 0xCD, Size);
 344 #endif
 345       Allocator.Deallocate(Ptr, Size);
 346     }
 347   }
 348
 349   template <typename T> friend class SpecificBumpPtrAllocator;
 350 };
 351
 352 /// \brief The standard BumpPtrAllocator which just uses the default template
 353 /// paramaters.
 354 typedef BumpPtrAllocatorImpl<> BumpPtrAllocator;
 355
 356 /// \brief A BumpPtrAllocator that allows only elements of a specific type to be
 357 /// allocated.
 358 ///
 359 /// This allows calling the destructor in DestroyAll() and when the allocator is
 360 /// destroyed.
 361 template <typename T> class SpecificBumpPtrAllocator {
 362   BumpPtrAllocator Allocator;
 363
 364 public:
 365   SpecificBumpPtrAllocator() : Allocator() {}
 366   SpecificBumpPtrAllocator(SpecificBumpPtrAllocator &&Old)
 367       : Allocator(std::move(Old.Allocator)) {}
 368   ~SpecificBumpPtrAllocator() { DestroyAll(); }
 369
 370   SpecificBumpPtrAllocator &operator=(SpecificBumpPtrAllocator &&RHS) {
 371     Allocator = std::move(RHS.Allocator);
 372     return *this;
 373   }
 374
 375   /// Call the destructor of each allocated object and deallocate all but the
 376   /// current slab and reset the current pointer to the beginning of it, freeing
 377   /// all memory allocated so far.
 378   void DestroyAll() {
 379     auto DestroyElements = [](char *Begin, char *End) {
 380       assert(Begin == (char*)alignAddr(Begin, alignOf<T>()));
 381       for (char *Ptr = Begin; Ptr + sizeof(T) <= End; Ptr += sizeof(T))
 382         reinterpret_cast<T *>(Ptr)->~T();
 383     };
 384
 385     for (auto I = Allocator.Slabs.begin(), E = Allocator.Slabs.end(); I != E;
 386          ++I) {
 387       size_t AllocatedSlabSize = BumpPtrAllocator::computeSlabSize(
 388           std::distance(Allocator.Slabs.begin(), I));
 389       char *Begin = (char*)alignAddr(*I, alignOf<T>());
 390       char *End = *I == Allocator.Slabs.back() ? Allocator.CurPtr
 391                                                : (char *)*I + AllocatedSlabSize;
 392
 393       DestroyElements(Begin, End);
 394     }
 395
 396     for (auto &PtrAndSize : Allocator.CustomSizedSlabs) {
 397       void *Ptr = PtrAndSize.first;
 398       size_t Size = PtrAndSize.second;
 399       DestroyElements((char*)alignAddr(Ptr, alignOf<T>()), (char *)Ptr + Size);
 400     }
 401
 402     Allocator.Reset();
 403   }
 404
 405   /// \brief Allocate space for an array of objects without constructing them.
 406   T *Allocate(size_t num = 1) { return Allocator.Allocate<T>(num); }
 407 };
 408
 409 }  // end namespace llvm
 410
 411 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
 412 void *operator new(size_t Size,
 413                    llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize,
 414                                               SizeThreshold> &Allocator) {
 415   struct S {
 416     char c;
 417     union {
 418       double D;
 419       long double LD;
 420       long long L;
 421       void *P;
 422     } x;
 423   };
 424   return Allocator.Allocate(
 425       Size, std::min((size_t)llvm::NextPowerOf2(Size), offsetof(S, x)));
 426 }
 427
 428 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
 429 void operator delete(
 430     void *, llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold> &) {
 431 }
 432
 433 #endif // LLVM_SUPPORT_ALLOCATOR_H