xref: /netbsd-src/external/apache2/llvm/dist/llvm/include/llvm/Support/Allocator.h (revision 82d56013d7b633d116a93943de88e08335357a7c)
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/Optional.h"
21 #include "llvm/ADT/SmallVector.h"
22 #include "llvm/Support/Alignment.h"
23 #include "llvm/Support/AllocatorBase.h"
24 #include "llvm/Support/Compiler.h"
25 #include "llvm/Support/ErrorHandling.h"
26 #include "llvm/Support/MathExtras.h"
27 #include "llvm/Support/MemAlloc.h"
28 #include <algorithm>
29 #include <cassert>
30 #include <cstddef>
31 #include <cstdint>
32 #include <cstdlib>
33 #include <iterator>
34 #include <type_traits>
35 #include <utility>
36 
37 namespace llvm {
38 
39 namespace detail {
40 
41 // We call out to an external function to actually print the message as the
42 // printing code uses Allocator.h in its implementation.
43 void printBumpPtrAllocatorStats(unsigned NumSlabs, size_t BytesAllocated,
44                                 size_t TotalMemory);
45 
46 } // end namespace detail
47 
48 /// Allocate memory in an ever growing pool, as if by bump-pointer.
49 ///
50 /// This isn't strictly a bump-pointer allocator as it uses backing slabs of
51 /// memory rather than relying on a boundless contiguous heap. However, it has
52 /// bump-pointer semantics in that it is a monotonically growing pool of memory
53 /// where every allocation is found by merely allocating the next N bytes in
54 /// the slab, or the next N bytes in the next slab.
55 ///
56 /// Note that this also has a threshold for forcing allocations above a certain
57 /// size into their own slab.
58 ///
59 /// The BumpPtrAllocatorImpl template defaults to using a MallocAllocator
60 /// object, which wraps malloc, to allocate memory, but it can be changed to
61 /// use a custom allocator.
62 ///
63 /// The GrowthDelay specifies after how many allocated slabs the allocator
64 /// increases the size of the slabs.
65 template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096,
66           size_t SizeThreshold = SlabSize, size_t GrowthDelay = 128>
67 class BumpPtrAllocatorImpl
68     : public AllocatorBase<BumpPtrAllocatorImpl<AllocatorT, SlabSize,
69                                                 SizeThreshold, GrowthDelay>>,
70       private AllocatorT {
71 public:
72   static_assert(SizeThreshold <= SlabSize,
73                 "The SizeThreshold must be at most the SlabSize to ensure "
74                 "that objects larger than a slab go into their own memory "
75                 "allocation.");
76   static_assert(GrowthDelay > 0,
77                 "GrowthDelay must be at least 1 which already increases the"
78                 "slab size after each allocated slab.");
79 
80   BumpPtrAllocatorImpl() = default;
81 
82   template <typename T>
BumpPtrAllocatorImpl(T && Allocator)83   BumpPtrAllocatorImpl(T &&Allocator)
84       : AllocatorT(std::forward<T &&>(Allocator)) {}
85 
86   // Manually implement a move constructor as we must clear the old allocator's
87   // slabs as a matter of correctness.
BumpPtrAllocatorImpl(BumpPtrAllocatorImpl && Old)88   BumpPtrAllocatorImpl(BumpPtrAllocatorImpl &&Old)
89       : AllocatorT(static_cast<AllocatorT &&>(Old)), CurPtr(Old.CurPtr),
90         End(Old.End), Slabs(std::move(Old.Slabs)),
91         CustomSizedSlabs(std::move(Old.CustomSizedSlabs)),
92         BytesAllocated(Old.BytesAllocated), RedZoneSize(Old.RedZoneSize) {
93     Old.CurPtr = Old.End = nullptr;
94     Old.BytesAllocated = 0;
95     Old.Slabs.clear();
96     Old.CustomSizedSlabs.clear();
97   }
98 
~BumpPtrAllocatorImpl()99   ~BumpPtrAllocatorImpl() {
100     DeallocateSlabs(Slabs.begin(), Slabs.end());
101     DeallocateCustomSizedSlabs();
102   }
103 
104   BumpPtrAllocatorImpl &operator=(BumpPtrAllocatorImpl &&RHS) {
105     DeallocateSlabs(Slabs.begin(), Slabs.end());
106     DeallocateCustomSizedSlabs();
107 
108     CurPtr = RHS.CurPtr;
109     End = RHS.End;
110     BytesAllocated = RHS.BytesAllocated;
111     RedZoneSize = RHS.RedZoneSize;
112     Slabs = std::move(RHS.Slabs);
113     CustomSizedSlabs = std::move(RHS.CustomSizedSlabs);
114     AllocatorT::operator=(static_cast<AllocatorT &&>(RHS));
115 
116     RHS.CurPtr = RHS.End = nullptr;
117     RHS.BytesAllocated = 0;
118     RHS.Slabs.clear();
119     RHS.CustomSizedSlabs.clear();
120     return *this;
121   }
122 
123   /// Deallocate all but the current slab and reset the current pointer
124   /// to the beginning of it, freeing all memory allocated so far.
Reset()125   void Reset() {
126     // Deallocate all but the first slab, and deallocate all custom-sized slabs.
127     DeallocateCustomSizedSlabs();
128     CustomSizedSlabs.clear();
129 
130     if (Slabs.empty())
131       return;
132 
133     // Reset the state.
134     BytesAllocated = 0;
135     CurPtr = (char *)Slabs.front();
136     End = CurPtr + SlabSize;
137 
138     __asan_poison_memory_region(*Slabs.begin(), computeSlabSize(0));
139     DeallocateSlabs(std::next(Slabs.begin()), Slabs.end());
140     Slabs.erase(std::next(Slabs.begin()), Slabs.end());
141   }
142 
143   /// Allocate space at the specified alignment.
144   LLVM_ATTRIBUTE_RETURNS_NONNULL LLVM_ATTRIBUTE_RETURNS_NOALIAS void *
Allocate(size_t Size,Align Alignment)145   Allocate(size_t Size, Align Alignment) {
146     // Keep track of how many bytes we've allocated.
147     BytesAllocated += Size;
148 
149     size_t Adjustment = offsetToAlignedAddr(CurPtr, Alignment);
150     assert(Adjustment + Size >= Size && "Adjustment + Size must not overflow");
151 
152     size_t SizeToAllocate = Size;
153 #if LLVM_ADDRESS_SANITIZER_BUILD
154     // Add trailing bytes as a "red zone" under ASan.
155     SizeToAllocate += RedZoneSize;
156 #endif
157 
158     // Check if we have enough space.
159     if (Adjustment + SizeToAllocate <= size_t(End - CurPtr)) {
160       char *AlignedPtr = CurPtr + Adjustment;
161       CurPtr = AlignedPtr + SizeToAllocate;
162       // Update the allocation point of this memory block in MemorySanitizer.
163       // Without this, MemorySanitizer messages for values originated from here
164       // will point to the allocation of the entire slab.
165       __msan_allocated_memory(AlignedPtr, Size);
166       // Similarly, tell ASan about this space.
167       __asan_unpoison_memory_region(AlignedPtr, Size);
168       return AlignedPtr;
169     }
170 
171     // If Size is really big, allocate a separate slab for it.
172     size_t PaddedSize = SizeToAllocate + Alignment.value() - 1;
173     if (PaddedSize > SizeThreshold) {
174       void *NewSlab =
175           AllocatorT::Allocate(PaddedSize, alignof(std::max_align_t));
176       // We own the new slab and don't want anyone reading anyting other than
177       // pieces returned from this method.  So poison the whole slab.
178       __asan_poison_memory_region(NewSlab, PaddedSize);
179       CustomSizedSlabs.push_back(std::make_pair(NewSlab, PaddedSize));
180 
181       uintptr_t AlignedAddr = alignAddr(NewSlab, Alignment);
182       assert(AlignedAddr + Size <= (uintptr_t)NewSlab + PaddedSize);
183       char *AlignedPtr = (char*)AlignedAddr;
184       __msan_allocated_memory(AlignedPtr, Size);
185       __asan_unpoison_memory_region(AlignedPtr, Size);
186       return AlignedPtr;
187     }
188 
189     // Otherwise, start a new slab and try again.
190     StartNewSlab();
191     uintptr_t AlignedAddr = alignAddr(CurPtr, Alignment);
192     assert(AlignedAddr + SizeToAllocate <= (uintptr_t)End &&
193            "Unable to allocate memory!");
194     char *AlignedPtr = (char*)AlignedAddr;
195     CurPtr = AlignedPtr + SizeToAllocate;
196     __msan_allocated_memory(AlignedPtr, Size);
197     __asan_unpoison_memory_region(AlignedPtr, Size);
198     return AlignedPtr;
199   }
200 
201   inline LLVM_ATTRIBUTE_RETURNS_NONNULL LLVM_ATTRIBUTE_RETURNS_NOALIAS void *
Allocate(size_t Size,size_t Alignment)202   Allocate(size_t Size, size_t Alignment) {
203     assert(Alignment > 0 && "0-byte alignment is not allowed. Use 1 instead.");
204     return Allocate(Size, Align(Alignment));
205   }
206 
207   // Pull in base class overloads.
208   using AllocatorBase<BumpPtrAllocatorImpl>::Allocate;
209 
210   // Bump pointer allocators are expected to never free their storage; and
211   // clients expect pointers to remain valid for non-dereferencing uses even
212   // after deallocation.
Deallocate(const void * Ptr,size_t Size,size_t)213   void Deallocate(const void *Ptr, size_t Size, size_t /*Alignment*/) {
214     __asan_poison_memory_region(Ptr, Size);
215   }
216 
217   // Pull in base class overloads.
218   using AllocatorBase<BumpPtrAllocatorImpl>::Deallocate;
219 
GetNumSlabs()220   size_t GetNumSlabs() const { return Slabs.size() + CustomSizedSlabs.size(); }
221 
222   /// \return An index uniquely and reproducibly identifying
223   /// an input pointer \p Ptr in the given allocator.
224   /// The returned value is negative iff the object is inside a custom-size
225   /// slab.
226   /// Returns an empty optional if the pointer is not found in the allocator.
identifyObject(const void * Ptr)227   llvm::Optional<int64_t> identifyObject(const void *Ptr) {
228     const char *P = static_cast<const char *>(Ptr);
229     int64_t InSlabIdx = 0;
230     for (size_t Idx = 0, E = Slabs.size(); Idx < E; Idx++) {
231       const char *S = static_cast<const char *>(Slabs[Idx]);
232       if (P >= S && P < S + computeSlabSize(Idx))
233         return InSlabIdx + static_cast<int64_t>(P - S);
234       InSlabIdx += static_cast<int64_t>(computeSlabSize(Idx));
235     }
236 
237     // Use negative index to denote custom sized slabs.
238     int64_t InCustomSizedSlabIdx = -1;
239     for (size_t Idx = 0, E = CustomSizedSlabs.size(); Idx < E; Idx++) {
240       const char *S = static_cast<const char *>(CustomSizedSlabs[Idx].first);
241       size_t Size = CustomSizedSlabs[Idx].second;
242       if (P >= S && P < S + Size)
243         return InCustomSizedSlabIdx - static_cast<int64_t>(P - S);
244       InCustomSizedSlabIdx -= static_cast<int64_t>(Size);
245     }
246     return None;
247   }
248 
249   /// A wrapper around identifyObject that additionally asserts that
250   /// the object is indeed within the allocator.
251   /// \return An index uniquely and reproducibly identifying
252   /// an input pointer \p Ptr in the given allocator.
identifyKnownObject(const void * Ptr)253   int64_t identifyKnownObject(const void *Ptr) {
254     Optional<int64_t> Out = identifyObject(Ptr);
255     assert(Out && "Wrong allocator used");
256     return *Out;
257   }
258 
259   /// A wrapper around identifyKnownObject. Accepts type information
260   /// about the object and produces a smaller identifier by relying on
261   /// the alignment information. Note that sub-classes may have different
262   /// alignment, so the most base class should be passed as template parameter
263   /// in order to obtain correct results. For that reason automatic template
264   /// parameter deduction is disabled.
265   /// \return An index uniquely and reproducibly identifying
266   /// an input pointer \p Ptr in the given allocator. This identifier is
267   /// different from the ones produced by identifyObject and
268   /// identifyAlignedObject.
269   template <typename T>
identifyKnownAlignedObject(const void * Ptr)270   int64_t identifyKnownAlignedObject(const void *Ptr) {
271     int64_t Out = identifyKnownObject(Ptr);
272     assert(Out % alignof(T) == 0 && "Wrong alignment information");
273     return Out / alignof(T);
274   }
275 
getTotalMemory()276   size_t getTotalMemory() const {
277     size_t TotalMemory = 0;
278     for (auto I = Slabs.begin(), E = Slabs.end(); I != E; ++I)
279       TotalMemory += computeSlabSize(std::distance(Slabs.begin(), I));
280     for (auto &PtrAndSize : CustomSizedSlabs)
281       TotalMemory += PtrAndSize.second;
282     return TotalMemory;
283   }
284 
getBytesAllocated()285   size_t getBytesAllocated() const { return BytesAllocated; }
286 
setRedZoneSize(size_t NewSize)287   void setRedZoneSize(size_t NewSize) {
288     RedZoneSize = NewSize;
289   }
290 
PrintStats()291   void PrintStats() const {
292     detail::printBumpPtrAllocatorStats(Slabs.size(), BytesAllocated,
293                                        getTotalMemory());
294   }
295 
296 private:
297   /// The current pointer into the current slab.
298   ///
299   /// This points to the next free byte in the slab.
300   char *CurPtr = nullptr;
301 
302   /// The end of the current slab.
303   char *End = nullptr;
304 
305   /// The slabs allocated so far.
306   SmallVector<void *, 4> Slabs;
307 
308   /// Custom-sized slabs allocated for too-large allocation requests.
309   SmallVector<std::pair<void *, size_t>, 0> CustomSizedSlabs;
310 
311   /// How many bytes we've allocated.
312   ///
313   /// Used so that we can compute how much space was wasted.
314   size_t BytesAllocated = 0;
315 
316   /// The number of bytes to put between allocations when running under
317   /// a sanitizer.
318   size_t RedZoneSize = 1;
319 
computeSlabSize(unsigned SlabIdx)320   static size_t computeSlabSize(unsigned SlabIdx) {
321     // Scale the actual allocated slab size based on the number of slabs
322     // allocated. Every GrowthDelay slabs allocated, we double
323     // the allocated size to reduce allocation frequency, but saturate at
324     // multiplying the slab size by 2^30.
325     return SlabSize *
326            ((size_t)1 << std::min<size_t>(30, SlabIdx / GrowthDelay));
327   }
328 
329   /// Allocate a new slab and move the bump pointers over into the new
330   /// slab, modifying CurPtr and End.
StartNewSlab()331   void StartNewSlab() {
332     size_t AllocatedSlabSize = computeSlabSize(Slabs.size());
333 
334     void *NewSlab =
335         AllocatorT::Allocate(AllocatedSlabSize, alignof(std::max_align_t));
336     // We own the new slab and don't want anyone reading anything other than
337     // pieces returned from this method.  So poison the whole slab.
338     __asan_poison_memory_region(NewSlab, AllocatedSlabSize);
339 
340     Slabs.push_back(NewSlab);
341     CurPtr = (char *)(NewSlab);
342     End = ((char *)NewSlab) + AllocatedSlabSize;
343   }
344 
345   /// Deallocate a sequence of slabs.
DeallocateSlabs(SmallVectorImpl<void * >::iterator I,SmallVectorImpl<void * >::iterator E)346   void DeallocateSlabs(SmallVectorImpl<void *>::iterator I,
347                        SmallVectorImpl<void *>::iterator E) {
348     for (; I != E; ++I) {
349       size_t AllocatedSlabSize =
350           computeSlabSize(std::distance(Slabs.begin(), I));
351       AllocatorT::Deallocate(*I, AllocatedSlabSize, alignof(std::max_align_t));
352     }
353   }
354 
355   /// Deallocate all memory for custom sized slabs.
DeallocateCustomSizedSlabs()356   void DeallocateCustomSizedSlabs() {
357     for (auto &PtrAndSize : CustomSizedSlabs) {
358       void *Ptr = PtrAndSize.first;
359       size_t Size = PtrAndSize.second;
360       AllocatorT::Deallocate(Ptr, Size, alignof(std::max_align_t));
361     }
362   }
363 
364   template <typename T> friend class SpecificBumpPtrAllocator;
365 };
366 
367 /// The standard BumpPtrAllocator which just uses the default template
368 /// parameters.
369 typedef BumpPtrAllocatorImpl<> BumpPtrAllocator;
370 
371 /// A BumpPtrAllocator that allows only elements of a specific type to be
372 /// allocated.
373 ///
374 /// This allows calling the destructor in DestroyAll() and when the allocator is
375 /// destroyed.
376 template <typename T> class SpecificBumpPtrAllocator {
377   BumpPtrAllocator Allocator;
378 
379 public:
SpecificBumpPtrAllocator()380   SpecificBumpPtrAllocator() {
381     // Because SpecificBumpPtrAllocator walks the memory to call destructors,
382     // it can't have red zones between allocations.
383     Allocator.setRedZoneSize(0);
384   }
SpecificBumpPtrAllocator(SpecificBumpPtrAllocator && Old)385   SpecificBumpPtrAllocator(SpecificBumpPtrAllocator &&Old)
386       : Allocator(std::move(Old.Allocator)) {}
~SpecificBumpPtrAllocator()387   ~SpecificBumpPtrAllocator() { DestroyAll(); }
388 
389   SpecificBumpPtrAllocator &operator=(SpecificBumpPtrAllocator &&RHS) {
390     Allocator = std::move(RHS.Allocator);
391     return *this;
392   }
393 
394   /// Call the destructor of each allocated object and deallocate all but the
395   /// current slab and reset the current pointer to the beginning of it, freeing
396   /// all memory allocated so far.
DestroyAll()397   void DestroyAll() {
398     auto DestroyElements = [](char *Begin, char *End) {
399       assert(Begin == (char *)alignAddr(Begin, Align::Of<T>()));
400       for (char *Ptr = Begin; Ptr + sizeof(T) <= End; Ptr += sizeof(T))
401         reinterpret_cast<T *>(Ptr)->~T();
402     };
403 
404     for (auto I = Allocator.Slabs.begin(), E = Allocator.Slabs.end(); I != E;
405          ++I) {
406       size_t AllocatedSlabSize = BumpPtrAllocator::computeSlabSize(
407           std::distance(Allocator.Slabs.begin(), I));
408       char *Begin = (char *)alignAddr(*I, Align::Of<T>());
409       char *End = *I == Allocator.Slabs.back() ? Allocator.CurPtr
410                                                : (char *)*I + AllocatedSlabSize;
411 
412       DestroyElements(Begin, End);
413     }
414 
415     for (auto &PtrAndSize : Allocator.CustomSizedSlabs) {
416       void *Ptr = PtrAndSize.first;
417       size_t Size = PtrAndSize.second;
418       DestroyElements((char *)alignAddr(Ptr, Align::Of<T>()),
419                       (char *)Ptr + Size);
420     }
421 
422     Allocator.Reset();
423   }
424 
425   /// Allocate space for an array of objects without constructing them.
426   T *Allocate(size_t num = 1) { return Allocator.Allocate<T>(num); }
427 };
428 
429 } // end namespace llvm
430 
431 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold,
432           size_t GrowthDelay>
433 void *
new(size_t Size,llvm::BumpPtrAllocatorImpl<AllocatorT,SlabSize,SizeThreshold,GrowthDelay> & Allocator)434 operator new(size_t Size,
435              llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold,
436                                         GrowthDelay> &Allocator) {
437   return Allocator.Allocate(Size, std::min((size_t)llvm::NextPowerOf2(Size),
438                                            alignof(std::max_align_t)));
439 }
440 
441 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold,
442           size_t GrowthDelay>
delete(void *,llvm::BumpPtrAllocatorImpl<AllocatorT,SlabSize,SizeThreshold,GrowthDelay> &)443 void operator delete(void *,
444                      llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize,
445                                                 SizeThreshold, GrowthDelay> &) {
446 }
447 
448 #endif // LLVM_SUPPORT_ALLOCATOR_H
449