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/Alignment.h"
  26 #include "llvm/Support/Compiler.h"
  27 #include "llvm/Support/ErrorHandling.h"
  28 #include "llvm/Support/MathExtras.h"
  29 #include "llvm/Support/MemAlloc.h"
  30 #include <algorithm>
  31 #include <cassert>
  32 #include <cstddef>
  33 #include <cstdint>
  34 #include <cstdlib>
  35 #include <iterator>
  36 #include <type_traits>
  37 #include <utility>
  38
  39 namespace llvm {
  40
  41 /// CRTP base class providing obvious overloads for the core \c
  42 /// Allocate() methods of LLVM-style allocators.
  43 ///
  44 /// This base class both documents the full public interface exposed by all
  45 /// LLVM-style allocators, and redirects all of the overloads to a single core
  46 /// set of methods which the derived class must define.
  47 template <typename DerivedT> class AllocatorBase {
  48 public:
  49   /// Allocate \a Size bytes of \a Alignment aligned memory. This method
  50   /// must be implemented by \c DerivedT.
  51   void *Allocate(size_t Size, size_t Alignment) {
  52 #ifdef __clang__
  53     static_assert(static_cast<void *(AllocatorBase::*)(size_t, size_t)>(
  54                       &AllocatorBase::Allocate) !=
  55                       static_cast<void *(DerivedT::*)(size_t, size_t)>(
  56                           &DerivedT::Allocate),
  57                   "Class derives from AllocatorBase without implementing the "
  58                   "core Allocate(size_t, size_t) overload!");
  59 #endif
  60     return static_cast<DerivedT *>(this)->Allocate(Size, Alignment);
  61   }
  62
  63   /// Deallocate \a Ptr to \a Size bytes of memory allocated by this
  64   /// allocator.
  65   void Deallocate(const void *Ptr, size_t Size) {
  66 #ifdef __clang__
  67     static_assert(static_cast<void (AllocatorBase::*)(const void *, size_t)>(
  68                       &AllocatorBase::Deallocate) !=
  69                       static_cast<void (DerivedT::*)(const void *, size_t)>(
  70                           &DerivedT::Deallocate),
  71                   "Class derives from AllocatorBase without implementing the "
  72                   "core Deallocate(void *) overload!");
  73 #endif
  74     return static_cast<DerivedT *>(this)->Deallocate(Ptr, Size);
  75   }
  76
  77   // The rest of these methods are helpers that redirect to one of the above
  78   // core methods.
  79
  80   /// Allocate space for a sequence of objects without constructing them.
  81   template <typename T> T *Allocate(size_t Num = 1) {
  82     return static_cast<T *>(Allocate(Num * sizeof(T), alignof(T)));
  83   }
  84
  85   /// Deallocate space for a sequence of objects without constructing them.
  86   template <typename T>
  87   typename std::enable_if<
  88       !std::is_same<typename std::remove_cv<T>::type, void>::value, void>::type
  89   Deallocate(T *Ptr, size_t Num = 1) {
  90     Deallocate(static_cast<const void *>(Ptr), Num * sizeof(T));
  91   }
  92 };
  93
  94 class MallocAllocator : public AllocatorBase<MallocAllocator> {
  95 public:
  96   void Reset() {}
  97
  98   LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t Size,
  99                                                 size_t /*Alignment*/) {
 100     return safe_malloc(Size);
 101   }
 102
 103   // Pull in base class overloads.
 104   using AllocatorBase<MallocAllocator>::Allocate;
 105
 106   void Deallocate(const void *Ptr, size_t /*Size*/) {
 107     free(const_cast<void *>(Ptr));
 108   }
 109
 110   // Pull in base class overloads.
 111   using AllocatorBase<MallocAllocator>::Deallocate;
 112
 113   void PrintStats() const {}
 114 };
 115
 116 namespace detail {
 117
 118 // We call out to an external function to actually print the message as the
 119 // printing code uses Allocator.h in its implementation.
 120 void printBumpPtrAllocatorStats(unsigned NumSlabs, size_t BytesAllocated,
 121                                 size_t TotalMemory);
 122
 123 } // end namespace detail
 124
 125 /// Allocate memory in an ever growing pool, as if by bump-pointer.
 126 ///
 127 /// This isn't strictly a bump-pointer allocator as it uses backing slabs of
 128 /// memory rather than relying on a boundless contiguous heap. However, it has
 129 /// bump-pointer semantics in that it is a monotonically growing pool of memory
 130 /// where every allocation is found by merely allocating the next N bytes in
 131 /// the slab, or the next N bytes in the next slab.
 132 ///
 133 /// Note that this also has a threshold for forcing allocations above a certain
 134 /// size into their own slab.
 135 ///
 136 /// The BumpPtrAllocatorImpl template defaults to using a MallocAllocator
 137 /// object, which wraps malloc, to allocate memory, but it can be changed to
 138 /// use a custom allocator.
 139 template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096,
 140           size_t SizeThreshold = SlabSize>
 141 class BumpPtrAllocatorImpl
 142     : public AllocatorBase<
 143           BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold>> {
 144 public:
 145   static_assert(SizeThreshold <= SlabSize,
 146                 "The SizeThreshold must be at most the SlabSize to ensure "
 147                 "that objects larger than a slab go into their own memory "
 148                 "allocation.");
 149
 150   BumpPtrAllocatorImpl() = default;
 151
 152   template <typename T>
 153   BumpPtrAllocatorImpl(T &&Allocator)
 154       : Allocator(std::forward<T &&>(Allocator)) {}
 155
 156   // Manually implement a move constructor as we must clear the old allocator's
 157   // slabs as a matter of correctness.
 158   BumpPtrAllocatorImpl(BumpPtrAllocatorImpl &&Old)
 159       : CurPtr(Old.CurPtr), End(Old.End), Slabs(std::move(Old.Slabs)),
 160         CustomSizedSlabs(std::move(Old.CustomSizedSlabs)),
 161         BytesAllocated(Old.BytesAllocated), RedZoneSize(Old.RedZoneSize),
 162         Allocator(std::move(Old.Allocator)) {
 163     Old.CurPtr = Old.End = nullptr;
 164     Old.BytesAllocated = 0;
 165     Old.Slabs.clear();
 166     Old.CustomSizedSlabs.clear();
 167   }
 168
 169   ~BumpPtrAllocatorImpl() {
 170     DeallocateSlabs(Slabs.begin(), Slabs.end());
 171     DeallocateCustomSizedSlabs();
 172   }
 173
 174   BumpPtrAllocatorImpl &operator=(BumpPtrAllocatorImpl &&RHS) {
 175     DeallocateSlabs(Slabs.begin(), Slabs.end());
 176     DeallocateCustomSizedSlabs();
 177
 178     CurPtr = RHS.CurPtr;
 179     End = RHS.End;
 180     BytesAllocated = RHS.BytesAllocated;
 181     RedZoneSize = RHS.RedZoneSize;
 182     Slabs = std::move(RHS.Slabs);
 183     CustomSizedSlabs = std::move(RHS.CustomSizedSlabs);
 184     Allocator = std::move(RHS.Allocator);
 185
 186     RHS.CurPtr = RHS.End = nullptr;
 187     RHS.BytesAllocated = 0;
 188     RHS.Slabs.clear();
 189     RHS.CustomSizedSlabs.clear();
 190     return *this;
 191   }
 192
 193   /// Deallocate all but the current slab and reset the current pointer
 194   /// to the beginning of it, freeing all memory allocated so far.
 195   void Reset() {
 196     // Deallocate all but the first slab, and deallocate all custom-sized slabs.
 197     DeallocateCustomSizedSlabs();
 198     CustomSizedSlabs.clear();
 199
 200     if (Slabs.empty())
 201       return;
 202
 203     // Reset the state.
 204     BytesAllocated = 0;
 205     CurPtr = (char *)Slabs.front();
 206     End = CurPtr + SlabSize;
 207
 208     __asan_poison_memory_region(*Slabs.begin(), computeSlabSize(0));
 209     DeallocateSlabs(std::next(Slabs.begin()), Slabs.end());
 210     Slabs.erase(std::next(Slabs.begin()), Slabs.end());
 211   }
 212
 213   /// Allocate space at the specified alignment.
 214   LLVM_ATTRIBUTE_RETURNS_NONNULL LLVM_ATTRIBUTE_RETURNS_NOALIAS void *
 215   Allocate(size_t Size, Align Alignment) {
 216     // Keep track of how many bytes we've allocated.
 217     BytesAllocated += Size;
 218
 219     size_t Adjustment = offsetToAlignedAddr(CurPtr, Alignment);
 220     assert(Adjustment + Size >= Size && "Adjustment + Size must not overflow");
 221
 222     size_t SizeToAllocate = Size;
 223 #if LLVM_ADDRESS_SANITIZER_BUILD
 224     // Add trailing bytes as a "red zone" under ASan.
 225     SizeToAllocate += RedZoneSize;
 226 #endif
 227
 228     // Check if we have enough space.
 229     if (Adjustment + SizeToAllocate <= size_t(End - CurPtr)) {
 230       char *AlignedPtr = CurPtr + Adjustment;
 231       CurPtr = AlignedPtr + SizeToAllocate;
 232       // Update the allocation point of this memory block in MemorySanitizer.
 233       // Without this, MemorySanitizer messages for values originated from here
 234       // will point to the allocation of the entire slab.
 235       __msan_allocated_memory(AlignedPtr, Size);
 236       // Similarly, tell ASan about this space.
 237       __asan_unpoison_memory_region(AlignedPtr, Size);
 238       return AlignedPtr;
 239     }
 240
 241     // If Size is really big, allocate a separate slab for it.
 242     size_t PaddedSize = SizeToAllocate + Alignment.value() - 1;
 243     if (PaddedSize > SizeThreshold) {
 244       void *NewSlab = Allocator.Allocate(PaddedSize, 0);
 245       // We own the new slab and don't want anyone reading anyting other than
 246       // pieces returned from this method.  So poison the whole slab.
 247       __asan_poison_memory_region(NewSlab, PaddedSize);
 248       CustomSizedSlabs.push_back(std::make_pair(NewSlab, PaddedSize));
 249
 250       uintptr_t AlignedAddr = alignAddr(NewSlab, Alignment);
 251       assert(AlignedAddr + Size <= (uintptr_t)NewSlab + PaddedSize);
 252       char *AlignedPtr = (char*)AlignedAddr;
 253       __msan_allocated_memory(AlignedPtr, Size);
 254       __asan_unpoison_memory_region(AlignedPtr, Size);
 255       return AlignedPtr;
 256     }
 257
 258     // Otherwise, start a new slab and try again.
 259     StartNewSlab();
 260     uintptr_t AlignedAddr = alignAddr(CurPtr, Alignment);
 261     assert(AlignedAddr + SizeToAllocate <= (uintptr_t)End &&
 262            "Unable to allocate memory!");
 263     char *AlignedPtr = (char*)AlignedAddr;
 264     CurPtr = AlignedPtr + SizeToAllocate;
 265     __msan_allocated_memory(AlignedPtr, Size);
 266     __asan_unpoison_memory_region(AlignedPtr, Size);
 267     return AlignedPtr;
 268   }
 269
 270   inline LLVM_ATTRIBUTE_RETURNS_NONNULL LLVM_ATTRIBUTE_RETURNS_NOALIAS void *
 271   Allocate(size_t Size, size_t Alignment) {
 272     assert(Alignment > 0 && "0-byte alignnment is not allowed. Use 1 instead.");
 273     return Allocate(Size, Align(Alignment));
 274   }
 275
 276   // Pull in base class overloads.
 277   using AllocatorBase<BumpPtrAllocatorImpl>::Allocate;
 278
 279   // Bump pointer allocators are expected to never free their storage; and
 280   // clients expect pointers to remain valid for non-dereferencing uses even
 281   // after deallocation.
 282   void Deallocate(const void *Ptr, size_t Size) {
 283     __asan_poison_memory_region(Ptr, Size);
 284   }
 285
 286   // Pull in base class overloads.
 287   using AllocatorBase<BumpPtrAllocatorImpl>::Deallocate;
 288
 289   size_t GetNumSlabs() const { return Slabs.size() + CustomSizedSlabs.size(); }
 290
 291   /// \return An index uniquely and reproducibly identifying
 292   /// an input pointer \p Ptr in the given allocator.
 293   /// The returned value is negative iff the object is inside a custom-size
 294   /// slab.
 295   /// Returns an empty optional if the pointer is not found in the allocator.
 296   llvm::Optional<int64_t> identifyObject(const void *Ptr) {
 297     const char *P = static_cast<const char *>(Ptr);
 298     int64_t InSlabIdx = 0;
 299     for (size_t Idx = 0, E = Slabs.size(); Idx < E; Idx++) {
 300       const char *S = static_cast<const char *>(Slabs[Idx]);
 301       if (P >= S && P < S + computeSlabSize(Idx))
 302         return InSlabIdx + static_cast<int64_t>(P - S);
 303       InSlabIdx += static_cast<int64_t>(computeSlabSize(Idx));
 304     }
 305
 306     // Use negative index to denote custom sized slabs.
 307     int64_t InCustomSizedSlabIdx = -1;
 308     for (size_t Idx = 0, E = CustomSizedSlabs.size(); Idx < E; Idx++) {
 309       const char *S = static_cast<const char *>(CustomSizedSlabs[Idx].first);
 310       size_t Size = CustomSizedSlabs[Idx].second;
 311       if (P >= S && P < S + Size)
 312         return InCustomSizedSlabIdx - static_cast<int64_t>(P - S);
 313       InCustomSizedSlabIdx -= static_cast<int64_t>(Size);
 314     }
 315     return None;
 316   }
 317
 318   /// A wrapper around identifyObject that additionally asserts that
 319   /// the object is indeed within the allocator.
 320   /// \return An index uniquely and reproducibly identifying
 321   /// an input pointer \p Ptr in the given allocator.
 322   int64_t identifyKnownObject(const void *Ptr) {
 323     Optional<int64_t> Out = identifyObject(Ptr);
 324     assert(Out && "Wrong allocator used");
 325     return *Out;
 326   }
 327
 328   /// A wrapper around identifyKnownObject. Accepts type information
 329   /// about the object and produces a smaller identifier by relying on
 330   /// the alignment information. Note that sub-classes may have different
 331   /// alignment, so the most base class should be passed as template parameter
 332   /// in order to obtain correct results. For that reason automatic template
 333   /// parameter deduction is disabled.
 334   /// \return An index uniquely and reproducibly identifying
 335   /// an input pointer \p Ptr in the given allocator. This identifier is
 336   /// different from the ones produced by identifyObject and
 337   /// identifyAlignedObject.
 338   template <typename T>
 339   int64_t identifyKnownAlignedObject(const void *Ptr) {
 340     int64_t Out = identifyKnownObject(Ptr);
 341     assert(Out % alignof(T) == 0 && "Wrong alignment information");
 342     return Out / alignof(T);
 343   }
 344
 345   size_t getTotalMemory() const {
 346     size_t TotalMemory = 0;
 347     for (auto I = Slabs.begin(), E = Slabs.end(); I != E; ++I)
 348       TotalMemory += computeSlabSize(std::distance(Slabs.begin(), I));
 349     for (auto &PtrAndSize : CustomSizedSlabs)
 350       TotalMemory += PtrAndSize.second;
 351     return TotalMemory;
 352   }
 353
 354   size_t getBytesAllocated() const { return BytesAllocated; }
 355
 356   void setRedZoneSize(size_t NewSize) {
 357     RedZoneSize = NewSize;
 358   }
 359
 360   void PrintStats() const {
 361     detail::printBumpPtrAllocatorStats(Slabs.size(), BytesAllocated,
 362                                        getTotalMemory());
 363   }
 364
 365 private:
 366   /// The current pointer into the current slab.
 367   ///
 368   /// This points to the next free byte in the slab.
 369   char *CurPtr = nullptr;
 370
 371   /// The end of the current slab.
 372   char *End = nullptr;
 373
 374   /// The slabs allocated so far.
 375   SmallVector<void *, 4> Slabs;
 376
 377   /// Custom-sized slabs allocated for too-large allocation requests.
 378   SmallVector<std::pair<void *, size_t>, 0> CustomSizedSlabs;
 379
 380   /// How many bytes we've allocated.
 381   ///
 382   /// Used so that we can compute how much space was wasted.
 383   size_t BytesAllocated = 0;
 384
 385   /// The number of bytes to put between allocations when running under
 386   /// a sanitizer.
 387   size_t RedZoneSize = 1;
 388
 389   /// The allocator instance we use to get slabs of memory.
 390   AllocatorT Allocator;
 391
 392   static size_t computeSlabSize(unsigned SlabIdx) {
 393     // Scale the actual allocated slab size based on the number of slabs
 394     // allocated. Every 128 slabs allocated, we double the allocated size to
 395     // reduce allocation frequency, but saturate at multiplying the slab size by
 396     // 2^30.
 397     return SlabSize * ((size_t)1 << std::min<size_t>(30, SlabIdx / 128));
 398   }
 399
 400   /// Allocate a new slab and move the bump pointers over into the new
 401   /// slab, modifying CurPtr and End.
 402   void StartNewSlab() {
 403     size_t AllocatedSlabSize = computeSlabSize(Slabs.size());
 404
 405     void *NewSlab = Allocator.Allocate(AllocatedSlabSize, 0);
 406     // We own the new slab and don't want anyone reading anything other than
 407     // pieces returned from this method.  So poison the whole slab.
 408     __asan_poison_memory_region(NewSlab, AllocatedSlabSize);
 409
 410     Slabs.push_back(NewSlab);
 411     CurPtr = (char *)(NewSlab);
 412     End = ((char *)NewSlab) + AllocatedSlabSize;
 413   }
 414
 415   /// Deallocate a sequence of slabs.
 416   void DeallocateSlabs(SmallVectorImpl<void *>::iterator I,
 417                        SmallVectorImpl<void *>::iterator E) {
 418     for (; I != E; ++I) {
 419       size_t AllocatedSlabSize =
 420           computeSlabSize(std::distance(Slabs.begin(), I));
 421       Allocator.Deallocate(*I, AllocatedSlabSize);
 422     }
 423   }
 424
 425   /// Deallocate all memory for custom sized slabs.
 426   void DeallocateCustomSizedSlabs() {
 427     for (auto &PtrAndSize : CustomSizedSlabs) {
 428       void *Ptr = PtrAndSize.first;
 429       size_t Size = PtrAndSize.second;
 430       Allocator.Deallocate(Ptr, Size);
 431     }
 432   }
 433
 434   template <typename T> friend class SpecificBumpPtrAllocator;
 435 };
 436
 437 /// The standard BumpPtrAllocator which just uses the default template
 438 /// parameters.
 439 typedef BumpPtrAllocatorImpl<> BumpPtrAllocator;
 440
 441 /// A BumpPtrAllocator that allows only elements of a specific type to be
 442 /// allocated.
 443 ///
 444 /// This allows calling the destructor in DestroyAll() and when the allocator is
 445 /// destroyed.
 446 template <typename T> class SpecificBumpPtrAllocator {
 447   BumpPtrAllocator Allocator;
 448
 449 public:
 450   SpecificBumpPtrAllocator() {
 451     // Because SpecificBumpPtrAllocator walks the memory to call destructors,
 452     // it can't have red zones between allocations.
 453     Allocator.setRedZoneSize(0);
 454   }
 455   SpecificBumpPtrAllocator(SpecificBumpPtrAllocator &&Old)
 456       : Allocator(std::move(Old.Allocator)) {}
 457   ~SpecificBumpPtrAllocator() { DestroyAll(); }
 458
 459   SpecificBumpPtrAllocator &operator=(SpecificBumpPtrAllocator &&RHS) {
 460     Allocator = std::move(RHS.Allocator);
 461     return *this;
 462   }
 463
 464   /// Call the destructor of each allocated object and deallocate all but the
 465   /// current slab and reset the current pointer to the beginning of it, freeing
 466   /// all memory allocated so far.
 467   void DestroyAll() {
 468     auto DestroyElements = [](char *Begin, char *End) {
 469       assert(Begin == (char *)alignAddr(Begin, Align::Of<T>()));
 470       for (char *Ptr = Begin; Ptr + sizeof(T) <= End; Ptr += sizeof(T))
 471         reinterpret_cast<T *>(Ptr)->~T();
 472     };
 473
 474     for (auto I = Allocator.Slabs.begin(), E = Allocator.Slabs.end(); I != E;
 475          ++I) {
 476       size_t AllocatedSlabSize = BumpPtrAllocator::computeSlabSize(
 477           std::distance(Allocator.Slabs.begin(), I));
 478       char *Begin = (char *)alignAddr(*I, Align::Of<T>());
 479       char *End = *I == Allocator.Slabs.back() ? Allocator.CurPtr
 480                                                : (char *)*I + AllocatedSlabSize;
 481
 482       DestroyElements(Begin, End);
 483     }
 484
 485     for (auto &PtrAndSize : Allocator.CustomSizedSlabs) {
 486       void *Ptr = PtrAndSize.first;
 487       size_t Size = PtrAndSize.second;
 488       DestroyElements((char *)alignAddr(Ptr, Align::Of<T>()),
 489                       (char *)Ptr + Size);
 490     }
 491
 492     Allocator.Reset();
 493   }
 494
 495   /// Allocate space for an array of objects without constructing them.
 496   T *Allocate(size_t num = 1) { return Allocator.Allocate<T>(num); }
 497 };
 498
 499 } // end namespace llvm
 500
 501 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
 502 void *operator new(size_t Size,
 503                    llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize,
 504                                               SizeThreshold> &Allocator) {
 505   struct S {
 506     char c;
 507     union {
 508       double D;
 509       long double LD;
 510       long long L;
 511       void *P;
 512     } x;
 513   };
 514   return Allocator.Allocate(
 515       Size, std::min((size_t)llvm::NextPowerOf2(Size), offsetof(S, x)));
 516 }
 517
 518 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
 519 void operator delete(
 520     void *, llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold> &) {
 521 }
 522
 523 #endif // LLVM_SUPPORT_ALLOCATOR_H