LLVM 17.0.0git
Allocator.h
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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
25#include <algorithm>
26#include <cassert>
27#include <cstddef>
28#include <cstdint>
29#include <iterator>
30#include <optional>
31#include <utility>
32
33namespace llvm {
34
35namespace 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.
39void 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.
61template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096,
62 size_t SizeThreshold = SlabSize, size_t GrowthDelay = 128>
64 : public AllocatorBase<BumpPtrAllocatorImpl<AllocatorT, SlabSize,
65 SizeThreshold, GrowthDelay>>,
66 private detail::AllocatorHolder<AllocatorT> {
68
69public:
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
79
80 template <typename T>
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.
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
98 DeallocateSlabs(Slabs.begin(), Slabs.end());
99 DeallocateCustomSizedSlabs();
100 }
101
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).
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 (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.
173 return AlignedPtr;
174 }
175
176 // If Size is really big, allocate a separate slab for it.
177 size_t PaddedSize = SizeToAllocate + Alignment.value() - 1;
178 if (PaddedSize > SizeThreshold) {
179 void *NewSlab =
180 this->getAllocator().Allocate(PaddedSize, alignof(std::max_align_t));
181 // We own the new slab and don't want anyone reading anyting other than
182 // pieces returned from this method. So poison the whole slab.
183 __asan_poison_memory_region(NewSlab, PaddedSize);
184 CustomSizedSlabs.push_back(std::make_pair(NewSlab, PaddedSize));
185
186 uintptr_t AlignedAddr = alignAddr(NewSlab, Alignment);
187 assert(AlignedAddr + Size <= (uintptr_t)NewSlab + PaddedSize);
188 char *AlignedPtr = (char*)AlignedAddr;
189 __msan_allocated_memory(AlignedPtr, Size);
191 return AlignedPtr;
192 }
193
194 // Otherwise, start a new slab and try again.
195 StartNewSlab();
196 uintptr_t AlignedAddr = alignAddr(CurPtr, Alignment);
197 assert(AlignedAddr + SizeToAllocate <= (uintptr_t)End &&
198 "Unable to allocate memory!");
199 char *AlignedPtr = (char*)AlignedAddr;
200 CurPtr = AlignedPtr + SizeToAllocate;
201 __msan_allocated_memory(AlignedPtr, Size);
203 return AlignedPtr;
204 }
205
207 Allocate(size_t Size, size_t Alignment) {
208 assert(Alignment > 0 && "0-byte alignment is not allowed. Use 1 instead.");
209 return Allocate(Size, Align(Alignment));
210 }
211
212 // Pull in base class overloads.
214
215 // Bump pointer allocators are expected to never free their storage; and
216 // clients expect pointers to remain valid for non-dereferencing uses even
217 // after deallocation.
218 void Deallocate(const void *Ptr, size_t Size, size_t /*Alignment*/) {
220 }
221
222 // Pull in base class overloads.
224
225 size_t GetNumSlabs() const { return Slabs.size() + CustomSizedSlabs.size(); }
226
227 /// \return An index uniquely and reproducibly identifying
228 /// an input pointer \p Ptr in the given allocator.
229 /// The returned value is negative iff the object is inside a custom-size
230 /// slab.
231 /// Returns an empty optional if the pointer is not found in the allocator.
232 std::optional<int64_t> identifyObject(const void *Ptr) {
233 const char *P = static_cast<const char *>(Ptr);
234 int64_t InSlabIdx = 0;
235 for (size_t Idx = 0, E = Slabs.size(); Idx < E; Idx++) {
236 const char *S = static_cast<const char *>(Slabs[Idx]);
237 if (P >= S && P < S + computeSlabSize(Idx))
238 return InSlabIdx + static_cast<int64_t>(P - S);
239 InSlabIdx += static_cast<int64_t>(computeSlabSize(Idx));
240 }
241
242 // Use negative index to denote custom sized slabs.
243 int64_t InCustomSizedSlabIdx = -1;
244 for (size_t Idx = 0, E = CustomSizedSlabs.size(); Idx < E; Idx++) {
245 const char *S = static_cast<const char *>(CustomSizedSlabs[Idx].first);
246 size_t Size = CustomSizedSlabs[Idx].second;
247 if (P >= S && P < S + Size)
248 return InCustomSizedSlabIdx - static_cast<int64_t>(P - S);
249 InCustomSizedSlabIdx -= static_cast<int64_t>(Size);
250 }
251 return std::nullopt;
252 }
253
254 /// A wrapper around identifyObject that additionally asserts that
255 /// the object is indeed within the allocator.
256 /// \return An index uniquely and reproducibly identifying
257 /// an input pointer \p Ptr in the given allocator.
258 int64_t identifyKnownObject(const void *Ptr) {
259 std::optional<int64_t> Out = identifyObject(Ptr);
260 assert(Out && "Wrong allocator used");
261 return *Out;
262 }
263
264 /// A wrapper around identifyKnownObject. Accepts type information
265 /// about the object and produces a smaller identifier by relying on
266 /// the alignment information. Note that sub-classes may have different
267 /// alignment, so the most base class should be passed as template parameter
268 /// in order to obtain correct results. For that reason automatic template
269 /// parameter deduction is disabled.
270 /// \return An index uniquely and reproducibly identifying
271 /// an input pointer \p Ptr in the given allocator. This identifier is
272 /// different from the ones produced by identifyObject and
273 /// identifyAlignedObject.
274 template <typename T>
275 int64_t identifyKnownAlignedObject(const void *Ptr) {
276 int64_t Out = identifyKnownObject(Ptr);
277 assert(Out % alignof(T) == 0 && "Wrong alignment information");
278 return Out / alignof(T);
279 }
280
281 size_t getTotalMemory() const {
282 size_t TotalMemory = 0;
283 for (auto I = Slabs.begin(), E = Slabs.end(); I != E; ++I)
284 TotalMemory += computeSlabSize(std::distance(Slabs.begin(), I));
285 for (const auto &PtrAndSize : CustomSizedSlabs)
286 TotalMemory += PtrAndSize.second;
287 return TotalMemory;
288 }
289
290 size_t getBytesAllocated() const { return BytesAllocated; }
291
292 void setRedZoneSize(size_t NewSize) {
293 RedZoneSize = NewSize;
294 }
295
296 void PrintStats() const {
297 detail::printBumpPtrAllocatorStats(Slabs.size(), BytesAllocated,
299 }
300
301private:
302 /// The current pointer into the current slab.
303 ///
304 /// This points to the next free byte in the slab.
305 char *CurPtr = nullptr;
306
307 /// The end of the current slab.
308 char *End = nullptr;
309
310 /// The slabs allocated so far.
312
313 /// Custom-sized slabs allocated for too-large allocation requests.
314 SmallVector<std::pair<void *, size_t>, 0> CustomSizedSlabs;
315
316 /// How many bytes we've allocated.
317 ///
318 /// Used so that we can compute how much space was wasted.
319 size_t BytesAllocated = 0;
320
321 /// The number of bytes to put between allocations when running under
322 /// a sanitizer.
323 size_t RedZoneSize = 1;
324
325 static size_t computeSlabSize(unsigned SlabIdx) {
326 // Scale the actual allocated slab size based on the number of slabs
327 // allocated. Every GrowthDelay slabs allocated, we double
328 // the allocated size to reduce allocation frequency, but saturate at
329 // multiplying the slab size by 2^30.
330 return SlabSize *
331 ((size_t)1 << std::min<size_t>(30, SlabIdx / GrowthDelay));
332 }
333
334 /// Allocate a new slab and move the bump pointers over into the new
335 /// slab, modifying CurPtr and End.
336 void StartNewSlab() {
337 size_t AllocatedSlabSize = computeSlabSize(Slabs.size());
338
339 void *NewSlab = this->getAllocator().Allocate(AllocatedSlabSize,
340 alignof(std::max_align_t));
341 // We own the new slab and don't want anyone reading anything other than
342 // pieces returned from this method. So poison the whole slab.
343 __asan_poison_memory_region(NewSlab, AllocatedSlabSize);
344
345 Slabs.push_back(NewSlab);
346 CurPtr = (char *)(NewSlab);
347 End = ((char *)NewSlab) + AllocatedSlabSize;
348 }
349
350 /// Deallocate a sequence of slabs.
351 void DeallocateSlabs(SmallVectorImpl<void *>::iterator I,
352 SmallVectorImpl<void *>::iterator E) {
353 for (; I != E; ++I) {
354 size_t AllocatedSlabSize =
355 computeSlabSize(std::distance(Slabs.begin(), I));
356 this->getAllocator().Deallocate(*I, AllocatedSlabSize,
357 alignof(std::max_align_t));
358 }
359 }
360
361 /// Deallocate all memory for custom sized slabs.
362 void DeallocateCustomSizedSlabs() {
363 for (auto &PtrAndSize : CustomSizedSlabs) {
364 void *Ptr = PtrAndSize.first;
365 size_t Size = PtrAndSize.second;
366 this->getAllocator().Deallocate(Ptr, Size, alignof(std::max_align_t));
367 }
368 }
369
370 template <typename T> friend class SpecificBumpPtrAllocator;
371};
372
373/// The standard BumpPtrAllocator which just uses the default template
374/// parameters.
376
377/// A BumpPtrAllocator that allows only elements of a specific type to be
378/// allocated.
379///
380/// This allows calling the destructor in DestroyAll() and when the allocator is
381/// destroyed.
382template <typename T> class SpecificBumpPtrAllocator {
383 BumpPtrAllocator Allocator;
384
385public:
387 // Because SpecificBumpPtrAllocator walks the memory to call destructors,
388 // it can't have red zones between allocations.
389 Allocator.setRedZoneSize(0);
390 }
392 : Allocator(std::move(Old.Allocator)) {}
394
396 Allocator = std::move(RHS.Allocator);
397 return *this;
398 }
399
400 /// Call the destructor of each allocated object and deallocate all but the
401 /// current slab and reset the current pointer to the beginning of it, freeing
402 /// all memory allocated so far.
403 void DestroyAll() {
404 auto DestroyElements = [](char *Begin, char *End) {
405 assert(Begin == (char *)alignAddr(Begin, Align::Of<T>()));
406 for (char *Ptr = Begin; Ptr + sizeof(T) <= End; Ptr += sizeof(T))
407 reinterpret_cast<T *>(Ptr)->~T();
408 };
409
410 for (auto I = Allocator.Slabs.begin(), E = Allocator.Slabs.end(); I != E;
411 ++I) {
412 size_t AllocatedSlabSize = BumpPtrAllocator::computeSlabSize(
413 std::distance(Allocator.Slabs.begin(), I));
414 char *Begin = (char *)alignAddr(*I, Align::Of<T>());
415 char *End = *I == Allocator.Slabs.back() ? Allocator.CurPtr
416 : (char *)*I + AllocatedSlabSize;
417
418 DestroyElements(Begin, End);
419 }
420
421 for (auto &PtrAndSize : Allocator.CustomSizedSlabs) {
422 void *Ptr = PtrAndSize.first;
423 size_t Size = PtrAndSize.second;
424 DestroyElements((char *)alignAddr(Ptr, Align::Of<T>()),
425 (char *)Ptr + Size);
426 }
427
428 Allocator.Reset();
429 }
430
431 /// Allocate space for an array of objects without constructing them.
432 T *Allocate(size_t num = 1) { return Allocator.Allocate<T>(num); }
433};
434
435} // end namespace llvm
436
437template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold,
438 size_t GrowthDelay>
439void *
440operator new(size_t Size,
441 llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold,
442 GrowthDelay> &Allocator) {
443 return Allocator.Allocate(Size, std::min((size_t)llvm::NextPowerOf2(Size),
444 alignof(std::max_align_t)));
445}
446
447template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold,
448 size_t GrowthDelay>
449void operator delete(void *,
450 llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize,
451 SizeThreshold, GrowthDelay> &) {
452}
453
454#endif // LLVM_SUPPORT_ALLOCATOR_H
This file defines MallocAllocator.
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
#define __asan_poison_memory_region(p, size)
Definition: Compiler.h:422
#define __asan_unpoison_memory_region(p, size)
Definition: Compiler.h:423
#define LLVM_ATTRIBUTE_RETURNS_NONNULL
Definition: Compiler.h:247
#define __msan_allocated_memory(p, size)
Definition: Compiler.h:397
Returns the sub type a function will return at a given Idx Should correspond to the result type of an ExtractValue instruction executed with just that one unsigned Idx
uint64_t Size
#define I(x, y, z)
Definition: MD5.cpp:58
#define T
#define P(N)
Basic Register Allocator
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This file defines the SmallVector class.
Value * RHS
CRTP base class providing obvious overloads for the core Allocate() methods of LLVM-style allocators.
Definition: AllocatorBase.h:34
Allocate memory in an ever growing pool, as if by bump-pointer.
Definition: Allocator.h:66
size_t GetNumSlabs() const
Definition: Allocator.h:225
LLVM_ATTRIBUTE_RETURNS_NONNULL void * Allocate(size_t Size, size_t Alignment)
Definition: Allocator.h:207
void setRedZoneSize(size_t NewSize)
Definition: Allocator.h:292
std::optional< int64_t > identifyObject(const void *Ptr)
Definition: Allocator.h:232
LLVM_ATTRIBUTE_RETURNS_NONNULL void * Allocate(size_t Size, Align Alignment)
Allocate space at the specified alignment.
Definition: Allocator.h:148
BumpPtrAllocatorImpl(BumpPtrAllocatorImpl &&Old)
Definition: Allocator.h:86
int64_t identifyKnownAlignedObject(const void *Ptr)
A wrapper around identifyKnownObject.
Definition: Allocator.h:275
size_t getBytesAllocated() const
Definition: Allocator.h:290
void Reset()
Deallocate all but the current slab and reset the current pointer to the beginning of it,...
Definition: Allocator.h:123
void Deallocate(const void *Ptr, size_t Size, size_t)
Definition: Allocator.h:218
BumpPtrAllocatorImpl(T &&Allocator)
Definition: Allocator.h:81
size_t getTotalMemory() const
Definition: Allocator.h:281
BumpPtrAllocatorImpl & operator=(BumpPtrAllocatorImpl &&RHS)
Definition: Allocator.h:102
int64_t identifyKnownObject(const void *Ptr)
A wrapper around identifyObject that additionally asserts that the object is indeed within the alloca...
Definition: Allocator.h:258
bool empty() const
Definition: SmallVector.h:94
size_t size() const
Definition: SmallVector.h:91
iterator erase(const_iterator CI)
Definition: SmallVector.h:741
void push_back(const T &Elt)
Definition: SmallVector.h:416
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1200
A BumpPtrAllocator that allows only elements of a specific type to be allocated.
Definition: Allocator.h:382
SpecificBumpPtrAllocator(SpecificBumpPtrAllocator &&Old)
Definition: Allocator.h:391
T * Allocate(size_t num=1)
Allocate space for an array of objects without constructing them.
Definition: Allocator.h:432
void DestroyAll()
Call the destructor of each allocated object and deallocate all but the current slab and reset the cu...
Definition: Allocator.h:403
SpecificBumpPtrAllocator & operator=(SpecificBumpPtrAllocator &&RHS)
Definition: Allocator.h:395
void printBumpPtrAllocatorStats(unsigned NumSlabs, size_t BytesAllocated, size_t TotalMemory)
Definition: Allocator.cpp:20
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
uint64_t offsetToAlignedAddr(const void *Addr, Align Alignment)
Returns the necessary adjustment for aligning Addr to Alignment bytes, rounding up.
Definition: Alignment.h:203
BumpPtrAllocatorImpl BumpPtrAllocator
The standard BumpPtrAllocator which just uses the default template parameters.
Definition: Allocator.h:375
OutputIt move(R &&Range, OutputIt Out)
Provide wrappers to std::move which take ranges instead of having to pass begin/end explicitly.
Definition: STLExtras.h:1862
constexpr uint64_t NextPowerOf2(uint64_t A)
Returns the next power of two (in 64-bits) that is strictly greater than A.
Definition: MathExtras.h:437
uintptr_t alignAddr(const void *Addr, Align Alignment)
Aligns Addr to Alignment bytes, rounding up.
Definition: Alignment.h:187
Definition: BitVector.h:851
This struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:39
uint64_t value() const
This is a hole in the type system and should not be abused.
Definition: Alignment.h:85