1 //===--- Allocator.h - Simple memory allocation abstraction -----*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 /// \file
10 ///
11 /// This file defines the MallocAllocator and BumpPtrAllocator interfaces. Both
12 /// of these conform to an LLVM "Allocator" concept which consists of an
13 /// Allocate method accepting a size and alignment, and a Deallocate accepting
14 /// a pointer and size. Further, the LLVM "Allocator" concept has overloads of
15 /// Allocate and Deallocate for setting size and alignment based on the final
16 /// type. These overloads are typically provided by a base class template \c
17 /// AllocatorBase.
18 ///
19 //===----------------------------------------------------------------------===//
20
21 #ifndef LLVM_SUPPORT_ALLOCATOR_H
22 #define LLVM_SUPPORT_ALLOCATOR_H
23
24 #include "llvm/ADT/SmallVector.h"
25 #include "llvm/Support/Compiler.h"
26 #include "llvm/Support/MathExtras.h"
27 #include <algorithm>
28 #include <cassert>
29 #include <cstddef>
30 #include <cstdint>
31 #include <cstdlib>
32 #include <iterator>
33 #include <type_traits>
34 #include <utility>
35
36 namespace llvm {
37
38 /// \brief CRTP base class providing obvious overloads for the core \c
39 /// Allocate() methods of LLVM-style allocators.
40 ///
41 /// This base class both documents the full public interface exposed by all
42 /// LLVM-style allocators, and redirects all of the overloads to a single core
43 /// set of methods which the derived class must define.
44 template <typename DerivedT> class AllocatorBase {
45 public:
46 /// \brief Allocate \a Size bytes of \a Alignment aligned memory. This method
47 /// must be implemented by \c DerivedT.
Allocate(size_t Size,size_t Alignment)48 void *Allocate(size_t Size, size_t Alignment) {
49 #ifdef __clang__
50 static_assert(static_cast<void *(AllocatorBase::*)(size_t, size_t)>(
51 &AllocatorBase::Allocate) !=
52 static_cast<void *(DerivedT::*)(size_t, size_t)>(
53 &DerivedT::Allocate),
54 "Class derives from AllocatorBase without implementing the "
55 "core Allocate(size_t, size_t) overload!");
56 #endif
57 return static_cast<DerivedT *>(this)->Allocate(Size, Alignment);
58 }
59
60 /// \brief Deallocate \a Ptr to \a Size bytes of memory allocated by this
61 /// allocator.
Deallocate(const void * Ptr,size_t Size)62 void Deallocate(const void *Ptr, size_t Size) {
63 #ifdef __clang__
64 static_assert(static_cast<void (AllocatorBase::*)(const void *, size_t)>(
65 &AllocatorBase::Deallocate) !=
66 static_cast<void (DerivedT::*)(const void *, size_t)>(
67 &DerivedT::Deallocate),
68 "Class derives from AllocatorBase without implementing the "
69 "core Deallocate(void *) overload!");
70 #endif
71 return static_cast<DerivedT *>(this)->Deallocate(Ptr, Size);
72 }
73
74 // The rest of these methods are helpers that redirect to one of the above
75 // core methods.
76
77 /// \brief Allocate space for a sequence of objects without constructing them.
78 template <typename T> T *Allocate(size_t Num = 1) {
79 return static_cast<T *>(Allocate(Num * sizeof(T), alignof(T)));
80 }
81
82 /// \brief Deallocate space for a sequence of objects without constructing them.
83 template <typename T>
84 typename std::enable_if<
85 !std::is_same<typename std::remove_cv<T>::type, void>::value, void>::type
86 Deallocate(T *Ptr, size_t Num = 1) {
87 Deallocate(static_cast<const void *>(Ptr), Num * sizeof(T));
88 }
89 };
90
91 class MallocAllocator : public AllocatorBase<MallocAllocator> {
92 public:
Reset()93 void Reset() {}
94
Allocate(size_t Size,size_t)95 LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t Size,
96 size_t /*Alignment*/) {
97 return malloc(Size);
98 }
99
100 // Pull in base class overloads.
101 using AllocatorBase<MallocAllocator>::Allocate;
102
Deallocate(const void * Ptr,size_t)103 void Deallocate(const void *Ptr, size_t /*Size*/) {
104 free(const_cast<void *>(Ptr));
105 }
106
107 // Pull in base class overloads.
108 using AllocatorBase<MallocAllocator>::Deallocate;
109
PrintStats()110 void PrintStats() const {}
111 };
112
113 namespace detail {
114
115 // We call out to an external function to actually print the message as the
116 // printing code uses Allocator.h in its implementation.
117 void printBumpPtrAllocatorStats(unsigned NumSlabs, size_t BytesAllocated,
118 size_t TotalMemory);
119
120 } // end namespace detail
121
122 /// \brief Allocate memory in an ever growing pool, as if by bump-pointer.
123 ///
124 /// This isn't strictly a bump-pointer allocator as it uses backing slabs of
125 /// memory rather than relying on a boundless contiguous heap. However, it has
126 /// bump-pointer semantics in that it is a monotonically growing pool of memory
127 /// where every allocation is found by merely allocating the next N bytes in
128 /// the slab, or the next N bytes in the next slab.
129 ///
130 /// Note that this also has a threshold for forcing allocations above a certain
131 /// size into their own slab.
132 ///
133 /// The BumpPtrAllocatorImpl template defaults to using a MallocAllocator
134 /// object, which wraps malloc, to allocate memory, but it can be changed to
135 /// use a custom allocator.
136 template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096,
137 size_t SizeThreshold = SlabSize>
138 class BumpPtrAllocatorImpl
139 : public AllocatorBase<
140 BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold>> {
141 public:
142 static_assert(SizeThreshold <= SlabSize,
143 "The SizeThreshold must be at most the SlabSize to ensure "
144 "that objects larger than a slab go into their own memory "
145 "allocation.");
146
BumpPtrAllocatorImpl()147 BumpPtrAllocatorImpl()
148 : CurPtr(nullptr), End(nullptr), BytesAllocated(0), Allocator() {}
149 template <typename T>
BumpPtrAllocatorImpl(T && Allocator)150 BumpPtrAllocatorImpl(T &&Allocator)
151 : CurPtr(nullptr), End(nullptr), BytesAllocated(0),
152 Allocator(std::forward<T &&>(Allocator)) {}
153
154 // Manually implement a move constructor as we must clear the old allocator's
155 // slabs as a matter of correctness.
BumpPtrAllocatorImpl(BumpPtrAllocatorImpl && Old)156 BumpPtrAllocatorImpl(BumpPtrAllocatorImpl &&Old)
157 : CurPtr(Old.CurPtr), End(Old.End), Slabs(std::move(Old.Slabs)),
158 CustomSizedSlabs(std::move(Old.CustomSizedSlabs)),
159 BytesAllocated(Old.BytesAllocated),
160 Allocator(std::move(Old.Allocator)) {
161 Old.CurPtr = Old.End = nullptr;
162 Old.BytesAllocated = 0;
163 Old.Slabs.clear();
164 Old.CustomSizedSlabs.clear();
165 }
166
~BumpPtrAllocatorImpl()167 ~BumpPtrAllocatorImpl() {
168 DeallocateSlabs(Slabs.begin(), Slabs.end());
169 DeallocateCustomSizedSlabs();
170 }
171
172 BumpPtrAllocatorImpl &operator=(BumpPtrAllocatorImpl &&RHS) {
173 DeallocateSlabs(Slabs.begin(), Slabs.end());
174 DeallocateCustomSizedSlabs();
175
176 CurPtr = RHS.CurPtr;
177 End = RHS.End;
178 BytesAllocated = RHS.BytesAllocated;
179 Slabs = std::move(RHS.Slabs);
180 CustomSizedSlabs = std::move(RHS.CustomSizedSlabs);
181 Allocator = std::move(RHS.Allocator);
182
183 RHS.CurPtr = RHS.End = nullptr;
184 RHS.BytesAllocated = 0;
185 RHS.Slabs.clear();
186 RHS.CustomSizedSlabs.clear();
187 return *this;
188 }
189
190 /// \brief Deallocate all but the current slab and reset the current pointer
191 /// to the beginning of it, freeing all memory allocated so far.
Reset()192 void Reset() {
193 // Deallocate all but the first slab, and deallocate all custom-sized slabs.
194 DeallocateCustomSizedSlabs();
195 CustomSizedSlabs.clear();
196
197 if (Slabs.empty())
198 return;
199
200 // Reset the state.
201 BytesAllocated = 0;
202 CurPtr = (char *)Slabs.front();
203 End = CurPtr + SlabSize;
204
205 __asan_poison_memory_region(*Slabs.begin(), computeSlabSize(0));
206 DeallocateSlabs(std::next(Slabs.begin()), Slabs.end());
207 Slabs.erase(std::next(Slabs.begin()), Slabs.end());
208 }
209
210 /// \brief Allocate space at the specified alignment.
211 LLVM_ATTRIBUTE_RETURNS_NONNULL LLVM_ATTRIBUTE_RETURNS_NOALIAS void *
Allocate(size_t Size,size_t Alignment)212 Allocate(size_t Size, size_t Alignment) {
213 assert(Alignment > 0 && "0-byte alignnment is not allowed. Use 1 instead.");
214
215 // Keep track of how many bytes we've allocated.
216 BytesAllocated += Size;
217
218 size_t Adjustment = alignmentAdjustment(CurPtr, Alignment);
219 assert(Adjustment + Size >= Size && "Adjustment + Size must not overflow");
220
221 // Check if we have enough space.
222 if (Adjustment + Size <= size_t(End - CurPtr)) {
223 char *AlignedPtr = CurPtr + Adjustment;
224 CurPtr = AlignedPtr + Size;
225 // Update the allocation point of this memory block in MemorySanitizer.
226 // Without this, MemorySanitizer messages for values originated from here
227 // will point to the allocation of the entire slab.
228 __msan_allocated_memory(AlignedPtr, Size);
229 // Similarly, tell ASan about this space.
230 __asan_unpoison_memory_region(AlignedPtr, Size);
231 return AlignedPtr;
232 }
233
234 // If Size is really big, allocate a separate slab for it.
235 size_t PaddedSize = Size + Alignment - 1;
236 if (PaddedSize > SizeThreshold) {
237 void *NewSlab = Allocator.Allocate(PaddedSize, 0);
238 // We own the new slab and don't want anyone reading anyting other than
239 // pieces returned from this method. So poison the whole slab.
240 __asan_poison_memory_region(NewSlab, PaddedSize);
241 CustomSizedSlabs.push_back(std::make_pair(NewSlab, PaddedSize));
242
243 uintptr_t AlignedAddr = alignAddr(NewSlab, Alignment);
244 assert(AlignedAddr + Size <= (uintptr_t)NewSlab + PaddedSize);
245 char *AlignedPtr = (char*)AlignedAddr;
246 __msan_allocated_memory(AlignedPtr, Size);
247 __asan_unpoison_memory_region(AlignedPtr, Size);
248 return AlignedPtr;
249 }
250
251 // Otherwise, start a new slab and try again.
252 StartNewSlab();
253 uintptr_t AlignedAddr = alignAddr(CurPtr, Alignment);
254 assert(AlignedAddr + Size <= (uintptr_t)End &&
255 "Unable to allocate memory!");
256 char *AlignedPtr = (char*)AlignedAddr;
257 CurPtr = AlignedPtr + Size;
258 __msan_allocated_memory(AlignedPtr, Size);
259 __asan_unpoison_memory_region(AlignedPtr, Size);
260 return AlignedPtr;
261 }
262
263 // Pull in base class overloads.
264 using AllocatorBase<BumpPtrAllocatorImpl>::Allocate;
265
Deallocate(const void * Ptr,size_t Size)266 void Deallocate(const void *Ptr, size_t Size) {
267 __asan_poison_memory_region(Ptr, Size);
268 }
269
270 // Pull in base class overloads.
271 using AllocatorBase<BumpPtrAllocatorImpl>::Deallocate;
272
GetNumSlabs()273 size_t GetNumSlabs() const { return Slabs.size() + CustomSizedSlabs.size(); }
274
getTotalMemory()275 size_t getTotalMemory() const {
276 size_t TotalMemory = 0;
277 for (auto I = Slabs.begin(), E = Slabs.end(); I != E; ++I)
278 TotalMemory += computeSlabSize(std::distance(Slabs.begin(), I));
279 for (auto &PtrAndSize : CustomSizedSlabs)
280 TotalMemory += PtrAndSize.second;
281 return TotalMemory;
282 }
283
getBytesAllocated()284 size_t getBytesAllocated() const { return BytesAllocated; }
285
PrintStats()286 void PrintStats() const {
287 detail::printBumpPtrAllocatorStats(Slabs.size(), BytesAllocated,
288 getTotalMemory());
289 }
290
291 private:
292 /// \brief The current pointer into the current slab.
293 ///
294 /// This points to the next free byte in the slab.
295 char *CurPtr;
296
297 /// \brief The end of the current slab.
298 char *End;
299
300 /// \brief The slabs allocated so far.
301 SmallVector<void *, 4> Slabs;
302
303 /// \brief Custom-sized slabs allocated for too-large allocation requests.
304 SmallVector<std::pair<void *, size_t>, 0> CustomSizedSlabs;
305
306 /// \brief How many bytes we've allocated.
307 ///
308 /// Used so that we can compute how much space was wasted.
309 size_t BytesAllocated;
310
311 /// \brief The allocator instance we use to get slabs of memory.
312 AllocatorT Allocator;
313
computeSlabSize(unsigned SlabIdx)314 static size_t computeSlabSize(unsigned SlabIdx) {
315 // Scale the actual allocated slab size based on the number of slabs
316 // allocated. Every 128 slabs allocated, we double the allocated size to
317 // reduce allocation frequency, but saturate at multiplying the slab size by
318 // 2^30.
319 return SlabSize * ((size_t)1 << std::min<size_t>(30, SlabIdx / 128));
320 }
321
322 /// \brief Allocate a new slab and move the bump pointers over into the new
323 /// slab, modifying CurPtr and End.
StartNewSlab()324 void StartNewSlab() {
325 size_t AllocatedSlabSize = computeSlabSize(Slabs.size());
326
327 void *NewSlab = Allocator.Allocate(AllocatedSlabSize, 0);
328 // We own the new slab and don't want anyone reading anything other than
329 // pieces returned from this method. So poison the whole slab.
330 __asan_poison_memory_region(NewSlab, AllocatedSlabSize);
331
332 Slabs.push_back(NewSlab);
333 CurPtr = (char *)(NewSlab);
334 End = ((char *)NewSlab) + AllocatedSlabSize;
335 }
336
337 /// \brief Deallocate a sequence of slabs.
DeallocateSlabs(SmallVectorImpl<void * >::iterator I,SmallVectorImpl<void * >::iterator E)338 void DeallocateSlabs(SmallVectorImpl<void *>::iterator I,
339 SmallVectorImpl<void *>::iterator E) {
340 for (; I != E; ++I) {
341 size_t AllocatedSlabSize =
342 computeSlabSize(std::distance(Slabs.begin(), I));
343 Allocator.Deallocate(*I, AllocatedSlabSize);
344 }
345 }
346
347 /// \brief Deallocate all memory for custom sized slabs.
DeallocateCustomSizedSlabs()348 void DeallocateCustomSizedSlabs() {
349 for (auto &PtrAndSize : CustomSizedSlabs) {
350 void *Ptr = PtrAndSize.first;
351 size_t Size = PtrAndSize.second;
352 Allocator.Deallocate(Ptr, Size);
353 }
354 }
355
356 template <typename T> friend class SpecificBumpPtrAllocator;
357 };
358
359 /// \brief The standard BumpPtrAllocator which just uses the default template
360 /// paramaters.
361 typedef BumpPtrAllocatorImpl<> BumpPtrAllocator;
362
363 /// \brief A BumpPtrAllocator that allows only elements of a specific type to be
364 /// allocated.
365 ///
366 /// This allows calling the destructor in DestroyAll() and when the allocator is
367 /// destroyed.
368 template <typename T> class SpecificBumpPtrAllocator {
369 BumpPtrAllocator Allocator;
370
371 public:
372 SpecificBumpPtrAllocator() = default;
SpecificBumpPtrAllocator(SpecificBumpPtrAllocator && Old)373 SpecificBumpPtrAllocator(SpecificBumpPtrAllocator &&Old)
374 : Allocator(std::move(Old.Allocator)) {}
~SpecificBumpPtrAllocator()375 ~SpecificBumpPtrAllocator() { DestroyAll(); }
376
377 SpecificBumpPtrAllocator &operator=(SpecificBumpPtrAllocator &&RHS) {
378 Allocator = std::move(RHS.Allocator);
379 return *this;
380 }
381
382 /// Call the destructor of each allocated object and deallocate all but the
383 /// current slab and reset the current pointer to the beginning of it, freeing
384 /// all memory allocated so far.
DestroyAll()385 void DestroyAll() {
386 auto DestroyElements = [](char *Begin, char *End) {
387 assert(Begin == (char *)alignAddr(Begin, alignof(T)));
388 for (char *Ptr = Begin; Ptr + sizeof(T) <= End; Ptr += sizeof(T))
389 reinterpret_cast<T *>(Ptr)->~T();
390 };
391
392 for (auto I = Allocator.Slabs.begin(), E = Allocator.Slabs.end(); I != E;
393 ++I) {
394 size_t AllocatedSlabSize = BumpPtrAllocator::computeSlabSize(
395 std::distance(Allocator.Slabs.begin(), I));
396 char *Begin = (char *)alignAddr(*I, alignof(T));
397 char *End = *I == Allocator.Slabs.back() ? Allocator.CurPtr
398 : (char *)*I + AllocatedSlabSize;
399
400 DestroyElements(Begin, End);
401 }
402
403 for (auto &PtrAndSize : Allocator.CustomSizedSlabs) {
404 void *Ptr = PtrAndSize.first;
405 size_t Size = PtrAndSize.second;
406 DestroyElements((char *)alignAddr(Ptr, alignof(T)), (char *)Ptr + Size);
407 }
408
409 Allocator.Reset();
410 }
411
412 /// \brief Allocate space for an array of objects without constructing them.
413 T *Allocate(size_t num = 1) { return Allocator.Allocate<T>(num); }
414 };
415
416 } // end namespace llvm
417
418 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
new(size_t Size,llvm::BumpPtrAllocatorImpl<AllocatorT,SlabSize,SizeThreshold> & Allocator)419 void *operator new(size_t Size,
420 llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize,
421 SizeThreshold> &Allocator) {
422 struct S {
423 char c;
424 union {
425 double D;
426 long double LD;
427 long long L;
428 void *P;
429 } x;
430 };
431 return Allocator.Allocate(
432 Size, std::min((size_t)llvm::NextPowerOf2(Size), offsetof(S, x)));
433 }
434
435 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
delete(void *,llvm::BumpPtrAllocatorImpl<AllocatorT,SlabSize,SizeThreshold> &)436 void operator delete(
437 void *, llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold> &) {
438 }
439
440 #endif // LLVM_SUPPORT_ALLOCATOR_H
441