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