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Allocator.h
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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"
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 
38 namespace 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.
46 template <typename DerivedT> class AllocatorBase {
47 public:
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)>(
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)>(
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 
93 class MallocAllocator : public AllocatorBase<MallocAllocator> {
94 public:
95  void Reset() {}
96 
98  size_t /*Alignment*/) {
99  return safe_malloc(Size);
100  }
101 
102  // Pull in base class overloads.
104 
105  void Deallocate(const void *Ptr, size_t /*Size*/) {
106  free(const_cast<void *>(Ptr));
107  }
108 
109  // Pull in base class overloads.
111 
112  void PrintStats() const {}
113 };
114 
115 namespace 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.
119 void 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.
138 template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096,
139  size_t SizeThreshold = SlabSize>
141  : public AllocatorBase<
142  BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold>> {
143 public:
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>
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.
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 
169  DeallocateSlabs(Slabs.begin(), Slabs.end());
170  DeallocateCustomSizedSlabs();
171  }
172 
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.
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.
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.
283 
284  size_t GetNumSlabs() const { return Slabs.size() + CustomSizedSlabs.size(); }
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 (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.
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  /// The allocator instance we use to get slabs of memory.
331  AllocatorT Allocator;
332 
333  static size_t computeSlabSize(unsigned SlabIdx) {
334  // Scale the actual allocated slab size based on the number of slabs
335  // allocated. Every 128 slabs allocated, we double the allocated size to
336  // reduce allocation frequency, but saturate at multiplying the slab size by
337  // 2^30.
338  return SlabSize * ((size_t)1 << std::min<size_t>(30, SlabIdx / 128));
339  }
340 
341  /// Allocate a new slab and move the bump pointers over into the new
342  /// slab, modifying CurPtr and End.
343  void StartNewSlab() {
344  size_t AllocatedSlabSize = computeSlabSize(Slabs.size());
345 
346  void *NewSlab = Allocator.Allocate(AllocatedSlabSize, 0);
347  // We own the new slab and don't want anyone reading anything other than
348  // pieces returned from this method. So poison the whole slab.
349  __asan_poison_memory_region(NewSlab, AllocatedSlabSize);
350 
351  Slabs.push_back(NewSlab);
352  CurPtr = (char *)(NewSlab);
353  End = ((char *)NewSlab) + AllocatedSlabSize;
354  }
355 
356  /// Deallocate a sequence of slabs.
357  void DeallocateSlabs(SmallVectorImpl<void *>::iterator I,
359  for (; I != E; ++I) {
360  size_t AllocatedSlabSize =
361  computeSlabSize(std::distance(Slabs.begin(), I));
362  Allocator.Deallocate(*I, AllocatedSlabSize);
363  }
364  }
365 
366  /// Deallocate all memory for custom sized slabs.
367  void DeallocateCustomSizedSlabs() {
368  for (auto &PtrAndSize : CustomSizedSlabs) {
369  void *Ptr = PtrAndSize.first;
370  size_t Size = PtrAndSize.second;
371  Allocator.Deallocate(Ptr, Size);
372  }
373  }
374 
375  template <typename T> friend class SpecificBumpPtrAllocator;
376 };
377 
378 /// The standard BumpPtrAllocator which just uses the default template
379 /// parameters.
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:
392  // Because SpecificBumpPtrAllocator walks the memory to call destructors,
393  // it can't have red zones between allocations.
394  Allocator.setRedZoneSize(0);
395  }
397  : Allocator(std::move(Old.Allocator)) {}
398  ~SpecificBumpPtrAllocator() { DestroyAll(); }
399 
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, alignof(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, alignof(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, alignof(T)), (char *)Ptr + Size);
430  }
431 
432  Allocator.Reset();
433  }
434 
435  /// Allocate space for an array of objects without constructing them.
436  T *Allocate(size_t num = 1) { return Allocator.Allocate<T>(num); }
437 };
438 
439 } // end namespace llvm
440 
441 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
442 void *operator new(size_t Size,
443  llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize,
444  SizeThreshold> &Allocator) {
445  struct S {
446  char c;
447  union {
448  double D;
449  long double LD;
450  long long L;
451  void *P;
452  } x;
453  };
454  return Allocator.Allocate(
455  Size, std::min((size_t)llvm::NextPowerOf2(Size), offsetof(S, x)));
456 }
457 
458 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
459 void operator delete(
461 }
462 
463 #endif // LLVM_SUPPORT_ALLOCATOR_H
void push_back(const T &Elt)
Definition: SmallVector.h:213
#define LLVM_ATTRIBUTE_RETURNS_NOALIAS
LLVM_ATTRIBUTE_RETURNS_NOALIAS Used to mark a function as returning a pointer that does not alias any...
Definition: Compiler.h:227
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:137
void Deallocate(const void *Ptr, size_t Size)
Deallocate Ptr to Size bytes of memory allocated by this allocator.
Definition: Allocator.h:64
void printBumpPtrAllocatorStats(unsigned NumSlabs, size_t BytesAllocated, size_t TotalMemory)
Definition: Allocator.cpp:21
void * Allocate(size_t Size, size_t Alignment)
Allocate Size bytes of Alignment aligned memory.
Definition: Allocator.h:50
#define __asan_unpoison_memory_region(p, size)
Definition: Compiler.h:391
void PrintStats() const
Definition: Allocator.h:112
Definition: BitVector.h:921
void Reset()
Deallocate all but the current slab and reset the current pointer to the beginning of it...
Definition: Allocator.h:194
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:42
BumpPtrAllocatorImpl & operator=(BumpPtrAllocatorImpl &&RHS)
Definition: Allocator.h:173
This file defines counterparts of C library allocation functions defined in the namespace &#39;std&#39;...
void Deallocate(const void *Ptr, size_t Size)
Definition: Allocator.h:277
#define T
void DestroyAll()
Call the destructor of each allocated object and deallocate all but the current slab and reset the cu...
Definition: Allocator.h:408
size_t getBytesAllocated() const
Definition: Allocator.h:295
BumpPtrAllocatorImpl BumpPtrAllocator
The standard BumpPtrAllocator which just uses the default template parameters.
Definition: Allocator.h:380
#define LLVM_ATTRIBUTE_RETURNS_NONNULL
Definition: Compiler.h:217
#define P(N)
Allocate memory in an ever growing pool, as if by bump-pointer.
Definition: Allocator.h:140
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
size_t alignmentAdjustment(const void *Ptr, size_t Alignment)
Returns the necessary adjustment for aligning Ptr to Alignment bytes, rounding up.
Definition: MathExtras.h:634
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator begin()
Definition: SmallVector.h:117
LLVM_ATTRIBUTE_RETURNS_NONNULL LLVM_ATTRIBUTE_RETURNS_NOALIAS void * Allocate(size_t Size, size_t Alignment)
Allocate space at the specified alignment.
Definition: Allocator.h:214
#define offsetof(TYPE, MEMBER)
void Deallocate(const void *Ptr, size_t)
Definition: Allocator.h:105
T * Allocate(size_t num=1)
Allocate space for an array of objects without constructing them.
Definition: Allocator.h:436
void setRedZoneSize(size_t NewSize)
Definition: Allocator.h:297
uint64_t NextPowerOf2(uint64_t A)
Returns the next power of two (in 64-bits) that is strictly greater than A.
Definition: MathExtras.h:640
SpecificBumpPtrAllocator & operator=(SpecificBumpPtrAllocator &&RHS)
Definition: Allocator.h:400
Basic Register Allocator
LLVM_ATTRIBUTE_RETURNS_NONNULL void * safe_malloc(size_t Sz)
Definition: MemAlloc.h:26
SpecificBumpPtrAllocator(SpecificBumpPtrAllocator &&Old)
Definition: Allocator.h:396
static GCRegistry::Add< StatepointGC > D("statepoint-example", "an example strategy for statepoint")
A BumpPtrAllocator that allows only elements of a specific type to be allocated.
Definition: Allocator.h:387
size_t GetNumSlabs() const
Definition: Allocator.h:284
uintptr_t alignAddr(const void *Addr, size_t Alignment)
Aligns Addr to Alignment bytes, rounding up.
Definition: MathExtras.h:623
LLVM_ATTRIBUTE_RETURNS_NONNULL void * Allocate(size_t Size, size_t)
Definition: Allocator.h:97
T * Allocate(size_t Num=1)
Allocate space for a sequence of objects without constructing them.
Definition: Allocator.h:80
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:121
#define I(x, y, z)
Definition: MD5.cpp:58
std::enable_if< !std::is_same< typename std::remove_cv< T >::type, void >::value, void >::type Deallocate(T *Ptr, size_t Num=1)
Deallocate space for a sequence of objects without constructing them.
Definition: Allocator.h:88
size_t getTotalMemory() const
Definition: Allocator.h:286
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
constexpr char Size[]
Key for Kernel::Arg::Metadata::mSize.
#define __msan_allocated_memory(p, size)
Definition: Compiler.h:379
BumpPtrAllocatorImpl(T &&Allocator)
Definition: Allocator.h:152
BumpPtrAllocatorImpl(BumpPtrAllocatorImpl &&Old)
Definition: Allocator.h:157
#define __asan_poison_memory_region(p, size)
Definition: Compiler.h:390
CRTP base class providing obvious overloads for the core Allocate() methods of LLVM-style allocators...
Definition: Allocator.h:46