include/llvm/Support/Allocator.h

   1 //===- Allocator.h - Simple memory allocation abstraction -------*- 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 /// \file
   9 ///
  10 /// This file defines the MallocAllocator and BumpPtrAllocator interfaces. Both
  11 /// of these conform to an LLVM "Allocator" concept which consists of an
  12 /// Allocate method accepting a size and alignment, and a Deallocate accepting
  13 /// a pointer and size. Further, the LLVM "Allocator" concept has overloads of
  14 /// Allocate and Deallocate for setting size and alignment based on the final
  15 /// type. These overloads are typically provided by a base class template \c
  16 /// AllocatorBase.
  17 ///
  18 //===----------------------------------------------------------------------===//
  19
  20 #ifndef LLVM_SUPPORT_ALLOCATOR_H
  21 #define LLVM_SUPPORT_ALLOCATOR_H
  22
  23 #include "llvm/ADT/Optional.h"
  24 #include "llvm/ADT/SmallVector.h"
  25 #include "llvm/Support/Compiler.h"
  26 #include "llvm/Support/ErrorHandling.h"
  27 #include "llvm/Support/MathExtras.h"
  28 #include "llvm/Support/MemAlloc.h"
  29 #include <algorithm>
  30 #include <cassert>
  31 #include <cstddef>
  32 #include <cstdint>
  33 #include <cstdlib>
  34 #include <iterator>
  35 #include <type_traits>
  36 #include <utility>
  37
  38 namespace llvm {
  39
  40 /// CRTP base class providing obvious overloads for the core \c
  41 /// Allocate() methods of LLVM-style allocators.
  42 ///
  43 /// This base class both documents the full public interface exposed by all
  44 /// LLVM-style allocators, and redirects all of the overloads to a single core
  45 /// set of methods which the derived class must define.
  46 template <typename DerivedT> class AllocatorBase {
  47 public:
  48   /// Allocate \a Size bytes of \a Alignment aligned memory. This method
  49   /// must be implemented by \c DerivedT.
  50   void *Allocate(size_t Size, size_t Alignment) {
  51 #ifdef __clang__
  52     static_assert(static_cast<void *(AllocatorBase::*)(size_t, size_t)>(
  53                       &AllocatorBase::Allocate) !=
  54                       static_cast<void *(DerivedT::*)(size_t, size_t)>(
  55                           &DerivedT::Allocate),
  56                   "Class derives from AllocatorBase without implementing the "
  57                   "core Allocate(size_t, size_t) overload!");
  58 #endif
  59     return static_cast<DerivedT *>(this)->Allocate(Size, Alignment);
  60   }
  61
  62   /// Deallocate \a Ptr to \a Size bytes of memory allocated by this
  63   /// allocator.
  64   void Deallocate(const void *Ptr, size_t Size) {
  65 #ifdef __clang__
  66     static_assert(static_cast<void (AllocatorBase::*)(const void *, size_t)>(
  67                       &AllocatorBase::Deallocate) !=
  68                       static_cast<void (DerivedT::*)(const void *, size_t)>(
  69                           &DerivedT::Deallocate),
  70                   "Class derives from AllocatorBase without implementing the "
  71                   "core Deallocate(void *) overload!");
  72 #endif
  73     return static_cast<DerivedT *>(this)->Deallocate(Ptr, Size);
  74   }
  75
  76   // The rest of these methods are helpers that redirect to one of the above
  77   // core methods.
  78
  79   /// Allocate space for a sequence of objects without constructing them.
  80   template <typename T> T *Allocate(size_t Num = 1) {
  81     return static_cast<T *>(Allocate(Num * sizeof(T), alignof(T)));
  82   }
  83
  84   /// Deallocate space for a sequence of objects without constructing them.
  85   template <typename T>
  86   typename std::enable_if<
  87       !std::is_same<typename std::remove_cv<T>::type, void>::value, void>::type
  88   Deallocate(T *Ptr, size_t Num = 1) {
  89     Deallocate(static_cast<const void *>(Ptr), Num * sizeof(T));
  90   }
  91 };
  92
  93 class MallocAllocator : public AllocatorBase<MallocAllocator> {
  94 public:
  95   void Reset() {}
  96
  97   LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t Size,
  98                                                 size_t /*Alignment*/) {
  99     return safe_malloc(Size);
 100   }
 101
 102   // Pull in base class overloads.
 103   using AllocatorBase<MallocAllocator>::Allocate;
 104
 105   void Deallocate(const void *Ptr, size_t /*Size*/) {
 106     free(const_cast<void *>(Ptr));
 107   }
 108
 109   // Pull in base class overloads.
 110   using AllocatorBase<MallocAllocator>::Deallocate;
 111
 112   void PrintStats() const {}
 113 };
 114
 115 namespace detail {
 116
 117 // We call out to an external function to actually print the message as the
 118 // printing code uses Allocator.h in its implementation.
 119 void printBumpPtrAllocatorStats(unsigned NumSlabs, size_t BytesAllocated,
 120                                 size_t TotalMemory);
 121
 122 } // end namespace detail
 123
 124 /// Allocate memory in an ever growing pool, as if by bump-pointer.
 125 ///
 126 /// This isn't strictly a bump-pointer allocator as it uses backing slabs of
 127 /// memory rather than relying on a boundless contiguous heap. However, it has
 128 /// bump-pointer semantics in that it is a monotonically growing pool of memory
 129 /// where every allocation is found by merely allocating the next N bytes in
 130 /// the slab, or the next N bytes in the next slab.
 131 ///
 132 /// Note that this also has a threshold for forcing allocations above a certain
 133 /// size into their own slab.
 134 ///
 135 /// The BumpPtrAllocatorImpl template defaults to using a MallocAllocator
 136 /// object, which wraps malloc, to allocate memory, but it can be changed to
 137 /// use a custom allocator.
 138 template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096,
 139           size_t SizeThreshold = SlabSize>
 140 class BumpPtrAllocatorImpl
 141     : public AllocatorBase<
 142           BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold>> {
 143 public:
 144   static_assert(SizeThreshold <= SlabSize,
 145                 "The SizeThreshold must be at most the SlabSize to ensure "
 146                 "that objects larger than a slab go into their own memory "
 147                 "allocation.");
 148
 149   BumpPtrAllocatorImpl() = default;
 150
 151   template <typename T>
 152   BumpPtrAllocatorImpl(T &&Allocator)
 153       : Allocator(std::forward<T &&>(Allocator)) {}
 154
 155   // Manually implement a move constructor as we must clear the old allocator's
 156   // slabs as a matter of correctness.
 157   BumpPtrAllocatorImpl(BumpPtrAllocatorImpl &&Old)
 158       : CurPtr(Old.CurPtr), End(Old.End), Slabs(std::move(Old.Slabs)),
 159         CustomSizedSlabs(std::move(Old.CustomSizedSlabs)),
 160         BytesAllocated(Old.BytesAllocated), RedZoneSize(Old.RedZoneSize),
 161         Allocator(std::move(Old.Allocator)) {
 162     Old.CurPtr = Old.End = nullptr;
 163     Old.BytesAllocated = 0;
 164     Old.Slabs.clear();
 165     Old.CustomSizedSlabs.clear();
 166   }
 167
 168   ~BumpPtrAllocatorImpl() {
 169     DeallocateSlabs(Slabs.begin(), Slabs.end());
 170     DeallocateCustomSizedSlabs();
 171   }
 172
 173   BumpPtrAllocatorImpl &operator=(BumpPtrAllocatorImpl &&RHS) {
 174     DeallocateSlabs(Slabs.begin(), Slabs.end());
 175     DeallocateCustomSizedSlabs();
 176
 177     CurPtr = RHS.CurPtr;
 178     End = RHS.End;
 179     BytesAllocated = RHS.BytesAllocated;
 180     RedZoneSize = RHS.RedZoneSize;
 181     Slabs = std::move(RHS.Slabs);
 182     CustomSizedSlabs = std::move(RHS.CustomSizedSlabs);
 183     Allocator = std::move(RHS.Allocator);
 184
 185     RHS.CurPtr = RHS.End = nullptr;
 186     RHS.BytesAllocated = 0;
 187     RHS.Slabs.clear();
 188     RHS.CustomSizedSlabs.clear();
 189     return *this;
 190   }
 191
 192   /// Deallocate all but the current slab and reset the current pointer
 193   /// to the beginning of it, freeing all memory allocated so far.
 194   void Reset() {
 195     // Deallocate all but the first slab, and deallocate all custom-sized slabs.
 196     DeallocateCustomSizedSlabs();
 197     CustomSizedSlabs.clear();
 198
 199     if (Slabs.empty())
 200       return;
 201
 202     // Reset the state.
 203     BytesAllocated = 0;
 204     CurPtr = (char *)Slabs.front();
 205     End = CurPtr + SlabSize;
 206
 207     __asan_poison_memory_region(*Slabs.begin(), computeSlabSize(0));
 208     DeallocateSlabs(std::next(Slabs.begin()), Slabs.end());
 209     Slabs.erase(std::next(Slabs.begin()), Slabs.end());
 210   }
 211
 212   /// Allocate space at the specified alignment.
 213   LLVM_ATTRIBUTE_RETURNS_NONNULL LLVM_ATTRIBUTE_RETURNS_NOALIAS void *
 214   Allocate(size_t Size, size_t Alignment) {
 215     assert(Alignment > 0 && "0-byte alignnment is not allowed. Use 1 instead.");
 216
 217     // Keep track of how many bytes we've allocated.
 218     BytesAllocated += Size;
 219
 220     size_t Adjustment = alignmentAdjustment(CurPtr, Alignment);
 221     assert(Adjustment + Size >= Size && "Adjustment + Size must not overflow");
 222
 223     size_t SizeToAllocate = Size;
 224 #if LLVM_ADDRESS_SANITIZER_BUILD
 225     // Add trailing bytes as a "red zone" under ASan.
 226     SizeToAllocate += RedZoneSize;
 227 #endif
 228
 229     // Check if we have enough space.
 230     if (Adjustment + SizeToAllocate <= size_t(End - CurPtr)) {
 231       char *AlignedPtr = CurPtr + Adjustment;
 232       CurPtr = AlignedPtr + SizeToAllocate;
 233       // Update the allocation point of this memory block in MemorySanitizer.
 234       // Without this, MemorySanitizer messages for values originated from here
 235       // will point to the allocation of the entire slab.
 236       __msan_allocated_memory(AlignedPtr, Size);
 237       // Similarly, tell ASan about this space.
 238       __asan_unpoison_memory_region(AlignedPtr, Size);
 239       return AlignedPtr;
 240     }
 241
 242     // If Size is really big, allocate a separate slab for it.
 243     size_t PaddedSize = SizeToAllocate + Alignment - 1;
 244     if (PaddedSize > SizeThreshold) {
 245       void *NewSlab = Allocator.Allocate(PaddedSize, 0);
 246       // We own the new slab and don't want anyone reading anyting other than
 247       // pieces returned from this method.  So poison the whole slab.
 248       __asan_poison_memory_region(NewSlab, PaddedSize);
 249       CustomSizedSlabs.push_back(std::make_pair(NewSlab, PaddedSize));
 250
 251       uintptr_t AlignedAddr = alignAddr(NewSlab, Alignment);
 252       assert(AlignedAddr + Size <= (uintptr_t)NewSlab + PaddedSize);
 253       char *AlignedPtr = (char*)AlignedAddr;
 254       __msan_allocated_memory(AlignedPtr, Size);
 255       __asan_unpoison_memory_region(AlignedPtr, Size);
 256       return AlignedPtr;
 257     }
 258
 259     // Otherwise, start a new slab and try again.
 260     StartNewSlab();
 261     uintptr_t AlignedAddr = alignAddr(CurPtr, Alignment);
 262     assert(AlignedAddr + SizeToAllocate <= (uintptr_t)End &&
 263            "Unable to allocate memory!");
 264     char *AlignedPtr = (char*)AlignedAddr;
 265     CurPtr = AlignedPtr + SizeToAllocate;
 266     __msan_allocated_memory(AlignedPtr, Size);
 267     __asan_unpoison_memory_region(AlignedPtr, Size);
 268     return AlignedPtr;
 269   }
 270
 271   // Pull in base class overloads.
 272   using AllocatorBase<BumpPtrAllocatorImpl>::Allocate;
 273
 274   // Bump pointer allocators are expected to never free their storage; and
 275   // clients expect pointers to remain valid for non-dereferencing uses even
 276   // after deallocation.
 277   void Deallocate(const void *Ptr, size_t Size) {
 278     __asan_poison_memory_region(Ptr, Size);
 279   }
 280
 281   // Pull in base class overloads.
 282   using AllocatorBase<BumpPtrAllocatorImpl>::Deallocate;
 283
 284   size_t GetNumSlabs() const { return Slabs.size() + CustomSizedSlabs.size(); }
 285
 286   /// \return An index uniquely and reproducibly identifying
 287   /// an input pointer \p Ptr in the given allocator.
 288   /// The returned value is negative iff the object is inside a custom-size
 289   /// slab.
 290   /// Returns an empty optional if the pointer is not found in the allocator.
 291   llvm::Optional<int64_t> identifyObject(const void *Ptr) {
 292     const char *P = static_cast<const char *>(Ptr);
 293     int64_t InSlabIdx = 0;
 294     for (size_t Idx = 0, E = Slabs.size(); Idx < E; Idx++) {
 295       const char *S = static_cast<const char *>(Slabs[Idx]);
 296       if (P >= S && P < S + computeSlabSize(Idx))
 297         return InSlabIdx + static_cast<int64_t>(P - S);
 298       InSlabIdx += static_cast<int64_t>(computeSlabSize(Idx));
 299     }
 300
 301     // Use negative index to denote custom sized slabs.
 302     int64_t InCustomSizedSlabIdx = -1;
 303     for (size_t Idx = 0, E = CustomSizedSlabs.size(); Idx < E; Idx++) {
 304       const char *S = static_cast<const char *>(CustomSizedSlabs[Idx].first);
 305       size_t Size = CustomSizedSlabs[Idx].second;
 306       if (P >= S && P < S + Size)
 307         return InCustomSizedSlabIdx - static_cast<int64_t>(P - S);
 308       InCustomSizedSlabIdx -= static_cast<int64_t>(Size);
 309     }
 310     return None;
 311   }
 312
 313   /// A wrapper around identifyObject that additionally asserts that
 314   /// the object is indeed within the allocator.
 315   /// \return An index uniquely and reproducibly identifying
 316   /// an input pointer \p Ptr in the given allocator.
 317   int64_t identifyKnownObject(const void *Ptr) {
 318     Optional<int64_t> Out = identifyObject(Ptr);
 319     assert(Out && "Wrong allocator used");
 320     return *Out;
 321   }
 322
 323   /// A wrapper around identifyKnownObject. Accepts type information
 324   /// about the object and produces a smaller identifier by relying on
 325   /// the alignment information. Note that sub-classes may have different
 326   /// alignment, so the most base class should be passed as template parameter
 327   /// in order to obtain correct results. For that reason automatic template
 328   /// parameter deduction is disabled.
 329   /// \return An index uniquely and reproducibly identifying
 330   /// an input pointer \p Ptr in the given allocator. This identifier is
 331   /// different from the ones produced by identifyObject and
 332   /// identifyAlignedObject.
 333   template <typename T>
 334   int64_t identifyKnownAlignedObject(const void *Ptr) {
 335     int64_t Out = identifyKnownObject(Ptr);
 336     assert(Out % alignof(T) == 0 && "Wrong alignment information");
 337     return Out / alignof(T);
 338   }
 339
 340   size_t getTotalMemory() const {
 341     size_t TotalMemory = 0;
 342     for (auto I = Slabs.begin(), E = Slabs.end(); I != E; ++I)
 343       TotalMemory += computeSlabSize(std::distance(Slabs.begin(), I));
 344     for (auto &PtrAndSize : CustomSizedSlabs)
 345       TotalMemory += PtrAndSize.second;
 346     return TotalMemory;
 347   }
 348
 349   size_t getBytesAllocated() const { return BytesAllocated; }
 350
 351   void setRedZoneSize(size_t NewSize) {
 352     RedZoneSize = NewSize;
 353   }
 354
 355   void PrintStats() const {
 356     detail::printBumpPtrAllocatorStats(Slabs.size(), BytesAllocated,
 357                                        getTotalMemory());
 358   }
 359
 360 private:
 361   /// The current pointer into the current slab.
 362   ///
 363   /// This points to the next free byte in the slab.
 364   char *CurPtr = nullptr;
 365
 366   /// The end of the current slab.
 367   char *End = nullptr;
 368
 369   /// The slabs allocated so far.
 370   SmallVector<void *, 4> Slabs;
 371
 372   /// Custom-sized slabs allocated for too-large allocation requests.
 373   SmallVector<std::pair<void *, size_t>, 0> CustomSizedSlabs;
 374
 375   /// How many bytes we've allocated.
 376   ///
 377   /// Used so that we can compute how much space was wasted.
 378   size_t BytesAllocated = 0;
 379
 380   /// The number of bytes to put between allocations when running under
 381   /// a sanitizer.
 382   size_t RedZoneSize = 1;
 383
 384   /// The allocator instance we use to get slabs of memory.
 385   AllocatorT Allocator;
 386
 387   static size_t computeSlabSize(unsigned SlabIdx) {
 388     // Scale the actual allocated slab size based on the number of slabs
 389     // allocated. Every 128 slabs allocated, we double the allocated size to
 390     // reduce allocation frequency, but saturate at multiplying the slab size by
 391     // 2^30.
 392     return SlabSize * ((size_t)1 << std::min<size_t>(30, SlabIdx / 128));
 393   }
 394
 395   /// Allocate a new slab and move the bump pointers over into the new
 396   /// slab, modifying CurPtr and End.
 397   void StartNewSlab() {
 398     size_t AllocatedSlabSize = computeSlabSize(Slabs.size());
 399
 400     void *NewSlab = Allocator.Allocate(AllocatedSlabSize, 0);
 401     // We own the new slab and don't want anyone reading anything other than
 402     // pieces returned from this method.  So poison the whole slab.
 403     __asan_poison_memory_region(NewSlab, AllocatedSlabSize);
 404
 405     Slabs.push_back(NewSlab);
 406     CurPtr = (char *)(NewSlab);
 407     End = ((char *)NewSlab) + AllocatedSlabSize;
 408   }
 409
 410   /// Deallocate a sequence of slabs.
 411   void DeallocateSlabs(SmallVectorImpl<void *>::iterator I,
 412                        SmallVectorImpl<void *>::iterator E) {
 413     for (; I != E; ++I) {
 414       size_t AllocatedSlabSize =
 415           computeSlabSize(std::distance(Slabs.begin(), I));
 416       Allocator.Deallocate(*I, AllocatedSlabSize);
 417     }
 418   }
 419
 420   /// Deallocate all memory for custom sized slabs.
 421   void DeallocateCustomSizedSlabs() {
 422     for (auto &PtrAndSize : CustomSizedSlabs) {
 423       void *Ptr = PtrAndSize.first;
 424       size_t Size = PtrAndSize.second;
 425       Allocator.Deallocate(Ptr, Size);
 426     }
 427   }
 428
 429   template <typename T> friend class SpecificBumpPtrAllocator;
 430 };
 431
 432 /// The standard BumpPtrAllocator which just uses the default template
 433 /// parameters.
 434 typedef BumpPtrAllocatorImpl<> BumpPtrAllocator;
 435
 436 /// A BumpPtrAllocator that allows only elements of a specific type to be
 437 /// allocated.
 438 ///
 439 /// This allows calling the destructor in DestroyAll() and when the allocator is
 440 /// destroyed.
 441 template <typename T> class SpecificBumpPtrAllocator {
 442   BumpPtrAllocator Allocator;
 443
 444 public:
 445   SpecificBumpPtrAllocator() {
 446     // Because SpecificBumpPtrAllocator walks the memory to call destructors,
 447     // it can't have red zones between allocations.
 448     Allocator.setRedZoneSize(0);
 449   }
 450   SpecificBumpPtrAllocator(SpecificBumpPtrAllocator &&Old)
 451       : Allocator(std::move(Old.Allocator)) {}
 452   ~SpecificBumpPtrAllocator() { DestroyAll(); }
 453
 454   SpecificBumpPtrAllocator &operator=(SpecificBumpPtrAllocator &&RHS) {
 455     Allocator = std::move(RHS.Allocator);
 456     return *this;
 457   }
 458
 459   /// Call the destructor of each allocated object and deallocate all but the
 460   /// current slab and reset the current pointer to the beginning of it, freeing
 461   /// all memory allocated so far.
 462   void DestroyAll() {
 463     auto DestroyElements = [](char *Begin, char *End) {
 464       assert(Begin == (char *)alignAddr(Begin, alignof(T)));
 465       for (char *Ptr = Begin; Ptr + sizeof(T) <= End; Ptr += sizeof(T))
 466         reinterpret_cast<T *>(Ptr)->~T();
 467     };
 468
 469     for (auto I = Allocator.Slabs.begin(), E = Allocator.Slabs.end(); I != E;
 470          ++I) {
 471       size_t AllocatedSlabSize = BumpPtrAllocator::computeSlabSize(
 472           std::distance(Allocator.Slabs.begin(), I));
 473       char *Begin = (char *)alignAddr(*I, alignof(T));
 474       char *End = *I == Allocator.Slabs.back() ? Allocator.CurPtr
 475                                                : (char *)*I + AllocatedSlabSize;
 476
 477       DestroyElements(Begin, End);
 478     }
 479
 480     for (auto &PtrAndSize : Allocator.CustomSizedSlabs) {
 481       void *Ptr = PtrAndSize.first;
 482       size_t Size = PtrAndSize.second;
 483       DestroyElements((char *)alignAddr(Ptr, alignof(T)), (char *)Ptr + Size);
 484     }
 485
 486     Allocator.Reset();
 487   }
 488
 489   /// Allocate space for an array of objects without constructing them.
 490   T *Allocate(size_t num = 1) { return Allocator.Allocate<T>(num); }
 491 };
 492
 493 } // end namespace llvm
 494
 495 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
 496 void *operator new(size_t Size,
 497                    llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize,
 498                                               SizeThreshold> &Allocator) {
 499   struct S {
 500     char c;
 501     union {
 502       double D;
 503       long double LD;
 504       long long L;
 505       void *P;
 506     } x;
 507   };
 508   return Allocator.Allocate(
 509       Size, std::min((size_t)llvm::NextPowerOf2(Size), offsetof(S, x)));
 510 }
 511
 512 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
 513 void operator delete(
 514     void *, llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold> &) {
 515 }
 516
 517 #endif // LLVM_SUPPORT_ALLOCATOR_H