Allocator.h revision 360784
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 39namespace 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. 47template <typename DerivedT> class AllocatorBase { 48public: 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 94class MallocAllocator : public AllocatorBase<MallocAllocator> { 95public: 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 116namespace 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. 120void 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. 139template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096, 140 size_t SizeThreshold = SlabSize> 141class BumpPtrAllocatorImpl 142 : public AllocatorBase< 143 BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold>> { 144public: 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 alignment 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 365private: 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. 439typedef 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. 446template <typename T> class SpecificBumpPtrAllocator { 447 BumpPtrAllocator Allocator; 448 449public: 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 501template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold> 502void *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 518template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold> 519void operator delete( 520 void *, llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold> &) { 521} 522 523#endif // LLVM_SUPPORT_ALLOCATOR_H 524