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
38namespace 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.
46template <typename DerivedT> class AllocatorBase {
47public:
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
93class MallocAllocator : public AllocatorBase<MallocAllocator> {
94public:
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
115namespace 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.
119void 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.
138template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096,
139 size_t SizeThreshold = SlabSize>
140class BumpPtrAllocatorImpl
141 : public AllocatorBase<
142 BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold>> {
143public:
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
360private:
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.
434typedef 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.
441template <typename T> class SpecificBumpPtrAllocator {
442 BumpPtrAllocator Allocator;
443
444public:
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
495template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
496void *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
512template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
513void operator delete(
514 void *, llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold> &) {
515}
516
517#endif // LLVM_SUPPORT_ALLOCATOR_H
518