third_party/llvm-subzero/include/llvm/Support/Allocator.h - SwiftShader - Git at Google

 //===--- Allocator.h - Simple memory allocation abstraction -----*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 /// \file
 ///
 /// This file defines the MallocAllocator and BumpPtrAllocator interfaces. Both
 /// of these conform to an LLVM "Allocator" concept which consists of an
 /// Allocate method accepting a size and alignment, and a Deallocate accepting
 /// a pointer and size. Further, the LLVM "Allocator" concept has overloads of
 /// Allocate and Deallocate for setting size and alignment based on the final
 /// type. These overloads are typically provided by a base class template \c
 /// AllocatorBase.
 ///
 //===----------------------------------------------------------------------===//

 #ifndef LLVM_SUPPORT_ALLOCATOR_H
 #define LLVM_SUPPORT_ALLOCATOR_H

 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/MathExtras.h"
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
 #include <cstdlib>
 #include <iterator>
 #include <type_traits>
 #include <utility>

 namespace llvm {

 /// \brief CRTP base class providing obvious overloads for the core \c
 /// Allocate() methods of LLVM-style allocators.
 ///
 /// This base class both documents the full public interface exposed by all
 /// LLVM-style allocators, and redirects all of the overloads to a single core
 /// set of methods which the derived class must define.
 template <typename DerivedT> class AllocatorBase {
 public:
   /// \brief Allocate \a Size bytes of \a Alignment aligned memory. This method
   /// must be implemented by \c DerivedT.
   void *Allocate(size_t Size, size_t Alignment) {
 #ifdef __clang__
     static_assert(static_cast<void *(AllocatorBase::*)(size_t, size_t)>(
                       &AllocatorBase::Allocate) !=
                       static_cast<void *(DerivedT::*)(size_t, size_t)>(
                           &DerivedT::Allocate),
                   "Class derives from AllocatorBase without implementing the "
                   "core Allocate(size_t, size_t) overload!");
 #endif
     return static_cast<DerivedT *>(this)->Allocate(Size, Alignment);
   }

   /// \brief Deallocate \a Ptr to \a Size bytes of memory allocated by this
   /// allocator.
   void Deallocate(const void *Ptr, size_t Size) {
 #ifdef __clang__
     static_assert(static_cast<void (AllocatorBase::*)(const void *, size_t)>(
                       &AllocatorBase::Deallocate) !=
                       static_cast<void (DerivedT::*)(const void *, size_t)>(
                           &DerivedT::Deallocate),
                   "Class derives from AllocatorBase without implementing the "
                   "core Deallocate(void *) overload!");
 #endif
     return static_cast<DerivedT *>(this)->Deallocate(Ptr, Size);
   }

   // The rest of these methods are helpers that redirect to one of the above
   // core methods.

   /// \brief Allocate space for a sequence of objects without constructing them.
   template <typename T> T *Allocate(size_t Num = 1) {
     return static_cast<T *>(Allocate(Num * sizeof(T), alignof(T)));
   }

   /// \brief Deallocate space for a sequence of objects without constructing them.
   template <typename T>
   typename std::enable_if<
       !std::is_same<typename std::remove_cv<T>::type, void>::value, void>::type
   Deallocate(T *Ptr, size_t Num = 1) {
     Deallocate(static_cast<const void *>(Ptr), Num * sizeof(T));
   }
 };

 class MallocAllocator : public AllocatorBase<MallocAllocator> {
 public:
   void Reset() {}

   LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t Size,
                                                 size_t /*Alignment*/) {
     return malloc(Size);
   }

   // Pull in base class overloads.
   using AllocatorBase<MallocAllocator>::Allocate;

   void Deallocate(const void *Ptr, size_t /*Size*/) {
     free(const_cast<void *>(Ptr));
   }

   // Pull in base class overloads.
   using AllocatorBase<MallocAllocator>::Deallocate;

   void PrintStats() const {}
 };

 namespace detail {

 // We call out to an external function to actually print the message as the
 // printing code uses Allocator.h in its implementation.
 void printBumpPtrAllocatorStats(unsigned NumSlabs, size_t BytesAllocated,
                                 size_t TotalMemory);

 } // end namespace detail

 /// \brief Allocate memory in an ever growing pool, as if by bump-pointer.
 ///
 /// This isn't strictly a bump-pointer allocator as it uses backing slabs of
 /// memory rather than relying on a boundless contiguous heap. However, it has
 /// bump-pointer semantics in that it is a monotonically growing pool of memory
 /// where every allocation is found by merely allocating the next N bytes in
 /// the slab, or the next N bytes in the next slab.
 ///
 /// Note that this also has a threshold for forcing allocations above a certain
 /// size into their own slab.
 ///
 /// The BumpPtrAllocatorImpl template defaults to using a MallocAllocator
 /// object, which wraps malloc, to allocate memory, but it can be changed to
 /// use a custom allocator.
 template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096,
           size_t SizeThreshold = SlabSize>
 class BumpPtrAllocatorImpl
     : public AllocatorBase<
           BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold>> {
 public:
   static_assert(SizeThreshold <= SlabSize,
                 "The SizeThreshold must be at most the SlabSize to ensure "
                 "that objects larger than a slab go into their own memory "
                 "allocation.");

   BumpPtrAllocatorImpl()
       : CurPtr(nullptr), End(nullptr), BytesAllocated(0), Allocator() {}
   template <typename T>
   BumpPtrAllocatorImpl(T &&Allocator)
       : CurPtr(nullptr), End(nullptr), BytesAllocated(0),
         Allocator(std::forward<T &&>(Allocator)) {}

   // Manually implement a move constructor as we must clear the old allocator's
   // slabs as a matter of correctness.
   BumpPtrAllocatorImpl(BumpPtrAllocatorImpl &&Old)
       : CurPtr(Old.CurPtr), End(Old.End), Slabs(std::move(Old.Slabs)),
         CustomSizedSlabs(std::move(Old.CustomSizedSlabs)),
         BytesAllocated(Old.BytesAllocated),
         Allocator(std::move(Old.Allocator)) {
     Old.CurPtr = Old.End = nullptr;
     Old.BytesAllocated = 0;
     Old.Slabs.clear();
     Old.CustomSizedSlabs.clear();
   }

   ~BumpPtrAllocatorImpl() {
     DeallocateSlabs(Slabs.begin(), Slabs.end());
     DeallocateCustomSizedSlabs();
   }

   BumpPtrAllocatorImpl &operator=(BumpPtrAllocatorImpl &&RHS) {
     DeallocateSlabs(Slabs.begin(), Slabs.end());
     DeallocateCustomSizedSlabs();

     CurPtr = RHS.CurPtr;
     End = RHS.End;
     BytesAllocated = RHS.BytesAllocated;
     Slabs = std::move(RHS.Slabs);
     CustomSizedSlabs = std::move(RHS.CustomSizedSlabs);
     Allocator = std::move(RHS.Allocator);

     RHS.CurPtr = RHS.End = nullptr;
     RHS.BytesAllocated = 0;
     RHS.Slabs.clear();
     RHS.CustomSizedSlabs.clear();
     return *this;
   }

   /// \brief Deallocate all but the current slab and reset the current pointer
   /// to the beginning of it, freeing all memory allocated so far.
   void Reset() {
     // Deallocate all but the first slab, and deallocate all custom-sized slabs.
     DeallocateCustomSizedSlabs();
     CustomSizedSlabs.clear();

     if (Slabs.empty())
       return;

     // Reset the state.
     BytesAllocated = 0;
     CurPtr = (char *)Slabs.front();
     End = CurPtr + SlabSize;

     __asan_poison_memory_region(*Slabs.begin(), computeSlabSize(0));
     DeallocateSlabs(std::next(Slabs.begin()), Slabs.end());
     Slabs.erase(std::next(Slabs.begin()), Slabs.end());
   }

   /// \brief Allocate space at the specified alignment.
   LLVM_ATTRIBUTE_RETURNS_NONNULL LLVM_ATTRIBUTE_RETURNS_NOALIAS void *
   Allocate(size_t Size, size_t Alignment) {
     assert(Alignment > 0 && "0-byte alignnment is not allowed. Use 1 instead.");

     // Keep track of how many bytes we've allocated.
     BytesAllocated += Size;

     size_t Adjustment = alignmentAdjustment(CurPtr, Alignment);
     assert(Adjustment + Size >= Size && "Adjustment + Size must not overflow");

     // Check if we have enough space.
     if (Adjustment + Size <= size_t(End - CurPtr)) {
       char *AlignedPtr = CurPtr + Adjustment;
       CurPtr = AlignedPtr + Size;
       // Update the allocation point of this memory block in MemorySanitizer.
       // Without this, MemorySanitizer messages for values originated from here
       // will point to the allocation of the entire slab.
       __msan_allocated_memory(AlignedPtr, Size);
       // Similarly, tell ASan about this space.
       __asan_unpoison_memory_region(AlignedPtr, Size);
       return AlignedPtr;
     }

     // If Size is really big, allocate a separate slab for it.
     size_t PaddedSize = Size + Alignment - 1;
     if (PaddedSize > SizeThreshold) {
       void *NewSlab = Allocator.Allocate(PaddedSize, 0);
       // We own the new slab and don't want anyone reading anyting other than
       // pieces returned from this method.  So poison the whole slab.
       __asan_poison_memory_region(NewSlab, PaddedSize);
       CustomSizedSlabs.push_back(std::make_pair(NewSlab, PaddedSize));

       uintptr_t AlignedAddr = alignAddr(NewSlab, Alignment);
       assert(AlignedAddr + Size <= (uintptr_t)NewSlab + PaddedSize);
       char *AlignedPtr = (char*)AlignedAddr;
       __msan_allocated_memory(AlignedPtr, Size);
       __asan_unpoison_memory_region(AlignedPtr, Size);
       return AlignedPtr;
     }

     // Otherwise, start a new slab and try again.
     StartNewSlab();
     uintptr_t AlignedAddr = alignAddr(CurPtr, Alignment);
     assert(AlignedAddr + Size <= (uintptr_t)End &&
            "Unable to allocate memory!");
     char *AlignedPtr = (char*)AlignedAddr;
     CurPtr = AlignedPtr + Size;
     __msan_allocated_memory(AlignedPtr, Size);
     __asan_unpoison_memory_region(AlignedPtr, Size);
     return AlignedPtr;
   }

   // Pull in base class overloads.
   using AllocatorBase<BumpPtrAllocatorImpl>::Allocate;

   void Deallocate(const void *Ptr, size_t Size) {
     __asan_poison_memory_region(Ptr, Size);
   }

   // Pull in base class overloads.
   using AllocatorBase<BumpPtrAllocatorImpl>::Deallocate;

   size_t GetNumSlabs() const { return Slabs.size() + CustomSizedSlabs.size(); }

   size_t getTotalMemory() const {
     size_t TotalMemory = 0;
     for (auto I = Slabs.begin(), E = Slabs.end(); I != E; ++I)
       TotalMemory += computeSlabSize(std::distance(Slabs.begin(), I));
     for (auto &PtrAndSize : CustomSizedSlabs)
       TotalMemory += PtrAndSize.second;
     return TotalMemory;
   }

   size_t getBytesAllocated() const { return BytesAllocated; }

   void PrintStats() const {
     detail::printBumpPtrAllocatorStats(Slabs.size(), BytesAllocated,
                                        getTotalMemory());
   }

 private:
   /// \brief The current pointer into the current slab.
   ///
   /// This points to the next free byte in the slab.
   char *CurPtr;

   /// \brief The end of the current slab.
   char *End;

   /// \brief The slabs allocated so far.
   SmallVector<void *, 4> Slabs;

   /// \brief Custom-sized slabs allocated for too-large allocation requests.
   SmallVector<std::pair<void *, size_t>, 0> CustomSizedSlabs;

   /// \brief How many bytes we've allocated.
   ///
   /// Used so that we can compute how much space was wasted.
   size_t BytesAllocated;

   /// \brief The allocator instance we use to get slabs of memory.
   AllocatorT Allocator;

   static size_t computeSlabSize(unsigned SlabIdx) {
     // Scale the actual allocated slab size based on the number of slabs
     // allocated. Every 128 slabs allocated, we double the allocated size to
     // reduce allocation frequency, but saturate at multiplying the slab size by
     // 2^30.
     return SlabSize * ((size_t)1 << std::min<size_t>(30, SlabIdx / 128));
   }

   /// \brief Allocate a new slab and move the bump pointers over into the new
   /// slab, modifying CurPtr and End.
   void StartNewSlab() {
     size_t AllocatedSlabSize = computeSlabSize(Slabs.size());

     void *NewSlab = Allocator.Allocate(AllocatedSlabSize, 0);
     // We own the new slab and don't want anyone reading anything other than
     // pieces returned from this method.  So poison the whole slab.
     __asan_poison_memory_region(NewSlab, AllocatedSlabSize);

     Slabs.push_back(NewSlab);
     CurPtr = (char *)(NewSlab);
     End = ((char *)NewSlab) + AllocatedSlabSize;
   }

   /// \brief Deallocate a sequence of slabs.
   void DeallocateSlabs(SmallVectorImpl<void *>::iterator I,
                        SmallVectorImpl<void *>::iterator E) {
     for (; I != E; ++I) {
       size_t AllocatedSlabSize =
           computeSlabSize(std::distance(Slabs.begin(), I));
       Allocator.Deallocate(*I, AllocatedSlabSize);
     }
   }

   /// \brief Deallocate all memory for custom sized slabs.
   void DeallocateCustomSizedSlabs() {
     for (auto &PtrAndSize : CustomSizedSlabs) {
       void *Ptr = PtrAndSize.first;
       size_t Size = PtrAndSize.second;
       Allocator.Deallocate(Ptr, Size);
     }
   }

   template <typename T> friend class SpecificBumpPtrAllocator;
 };

 /// \brief The standard BumpPtrAllocator which just uses the default template
 /// paramaters.
 typedef BumpPtrAllocatorImpl<> BumpPtrAllocator;

 /// \brief A BumpPtrAllocator that allows only elements of a specific type to be
 /// allocated.
 ///
 /// This allows calling the destructor in DestroyAll() and when the allocator is
 /// destroyed.
 template <typename T> class SpecificBumpPtrAllocator {
   BumpPtrAllocator Allocator;

 public:
   SpecificBumpPtrAllocator() = default;
   SpecificBumpPtrAllocator(SpecificBumpPtrAllocator &&Old)
       : Allocator(std::move(Old.Allocator)) {}
   ~SpecificBumpPtrAllocator() { DestroyAll(); }

   SpecificBumpPtrAllocator &operator=(SpecificBumpPtrAllocator &&RHS) {
     Allocator = std::move(RHS.Allocator);
     return *this;
   }

   /// Call the destructor of each allocated object and deallocate all but the
   /// current slab and reset the current pointer to the beginning of it, freeing
   /// all memory allocated so far.
   void DestroyAll() {
     auto DestroyElements = [](char *Begin, char *End) {
       assert(Begin == (char *)alignAddr(Begin, alignof(T)));
       for (char *Ptr = Begin; Ptr + sizeof(T) <= End; Ptr += sizeof(T))
         reinterpret_cast<T *>(Ptr)->~T();
     };

     for (auto I = Allocator.Slabs.begin(), E = Allocator.Slabs.end(); I != E;
          ++I) {
       size_t AllocatedSlabSize = BumpPtrAllocator::computeSlabSize(
           std::distance(Allocator.Slabs.begin(), I));
       char *Begin = (char *)alignAddr(*I, alignof(T));
       char *End = *I == Allocator.Slabs.back() ? Allocator.CurPtr
                                                : (char *)*I + AllocatedSlabSize;

       DestroyElements(Begin, End);
     }

     for (auto &PtrAndSize : Allocator.CustomSizedSlabs) {
       void *Ptr = PtrAndSize.first;
       size_t Size = PtrAndSize.second;
       DestroyElements((char *)alignAddr(Ptr, alignof(T)), (char *)Ptr + Size);
     }

     Allocator.Reset();
   }

   /// \brief Allocate space for an array of objects without constructing them.
   T *Allocate(size_t num = 1) { return Allocator.Allocate<T>(num); }
 };

 } // end namespace llvm

 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
 void *operator new(size_t Size,
                    llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize,
                                               SizeThreshold> &Allocator) {
   struct S {
     char c;
     union {
       double D;
       long double LD;
       long long L;
       void *P;
     } x;
   };
   return Allocator.Allocate(
       Size, std::min((size_t)llvm::NextPowerOf2(Size), offsetof(S, x)));
 }

 template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
 void operator delete(
     void *, llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold> &) {
 }

 #endif // LLVM_SUPPORT_ALLOCATOR_H
	//===--- Allocator.h - Simple memory allocation abstraction ------ C++ --===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	/// \file
	///
	/// This file defines the MallocAllocator and BumpPtrAllocator interfaces. Both
	/// of these conform to an LLVM "Allocator" concept which consists of an
	/// Allocate method accepting a size and alignment, and a Deallocate accepting
	/// a pointer and size. Further, the LLVM "Allocator" concept has overloads of
	/// Allocate and Deallocate for setting size and alignment based on the final
	/// type. These overloads are typically provided by a base class template \c
	/// AllocatorBase.
	///
	//===----------------------------------------------------------------------===//

	#ifndef LLVM_SUPPORT_ALLOCATOR_H
	#define LLVM_SUPPORT_ALLOCATOR_H

	#include "llvm/ADT/SmallVector.h"
	#include "llvm/Support/Compiler.h"
	#include "llvm/Support/MathExtras.h"
	#include <algorithm>
	#include <cassert>
	#include <cstddef>
	#include <cstdint>
	#include <cstdlib>
	#include <iterator>
	#include <type_traits>
	#include <utility>

	namespace llvm {

	/// \brief CRTP base class providing obvious overloads for the core \c
	/// Allocate() methods of LLVM-style allocators.
	///
	/// This base class both documents the full public interface exposed by all
	/// LLVM-style allocators, and redirects all of the overloads to a single core
	/// set of methods which the derived class must define.
	template <typename DerivedT> class AllocatorBase {
	public:
	/// \brief Allocate \a Size bytes of \a Alignment aligned memory. This method
	/// must be implemented by \c DerivedT.
	void *Allocate(size_t Size, size_t Alignment) {
	#ifdef __clang__
	static_assert(static_cast<void (AllocatorBase::)(size_t, size_t)>(
	&AllocatorBase::Allocate) !=
	static_cast<void (DerivedT::)(size_t, size_t)>(
	&DerivedT::Allocate),
	"Class derives from AllocatorBase without implementing the "
	"core Allocate(size_t, size_t) overload!");
	#endif
	return static_cast<DerivedT *>(this)->Allocate(Size, Alignment);
	}

	/// \brief Deallocate \a Ptr to \a Size bytes of memory allocated by this
	/// allocator.
	void Deallocate(const void *Ptr, size_t Size) {
	#ifdef __clang__
	static_assert(static_cast<void (AllocatorBase::)(const void , size_t)>(
	&AllocatorBase::Deallocate) !=
	static_cast<void (DerivedT::)(const void , size_t)>(
	&DerivedT::Deallocate),
	"Class derives from AllocatorBase without implementing the "
	"core Deallocate(void *) overload!");
	#endif
	return static_cast<DerivedT *>(this)->Deallocate(Ptr, Size);
	}

	// The rest of these methods are helpers that redirect to one of the above
	// core methods.

	/// \brief Allocate space for a sequence of objects without constructing them.
	template <typename T> T *Allocate(size_t Num = 1) {
	return static_cast<T >(Allocate(Num sizeof(T), alignof(T)));
	}

	/// \brief Deallocate space for a sequence of objects without constructing them.
	template <typename T>
	typename std::enable_if<
	!std::is_same<typename std::remove_cv<T>::type, void>::value, void>::type
	Deallocate(T *Ptr, size_t Num = 1) {
	Deallocate(static_cast<const void >(Ptr), Num sizeof(T));
	}
	};

	class MallocAllocator : public AllocatorBase<MallocAllocator> {
	public:
	void Reset() {}

	LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t Size,
	size_t /Alignment/) {
	return malloc(Size);
	}

	// Pull in base class overloads.
	using AllocatorBase<MallocAllocator>::Allocate;

	void Deallocate(const void Ptr, size_t /Size*/) {
	free(const_cast<void *>(Ptr));
	}

	// Pull in base class overloads.
	using AllocatorBase<MallocAllocator>::Deallocate;

	void PrintStats() const {}
	};

	namespace detail {

	// We call out to an external function to actually print the message as the
	// printing code uses Allocator.h in its implementation.
	void printBumpPtrAllocatorStats(unsigned NumSlabs, size_t BytesAllocated,
	size_t TotalMemory);

	} // end namespace detail

	/// \brief Allocate memory in an ever growing pool, as if by bump-pointer.
	///
	/// This isn't strictly a bump-pointer allocator as it uses backing slabs of
	/// memory rather than relying on a boundless contiguous heap. However, it has
	/// bump-pointer semantics in that it is a monotonically growing pool of memory
	/// where every allocation is found by merely allocating the next N bytes in
	/// the slab, or the next N bytes in the next slab.
	///
	/// Note that this also has a threshold for forcing allocations above a certain
	/// size into their own slab.
	///
	/// The BumpPtrAllocatorImpl template defaults to using a MallocAllocator
	/// object, which wraps malloc, to allocate memory, but it can be changed to
	/// use a custom allocator.
	template <typename AllocatorT = MallocAllocator, size_t SlabSize = 4096,
	size_t SizeThreshold = SlabSize>
	class BumpPtrAllocatorImpl
	: public AllocatorBase<
	BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold>> {
	public:
	static_assert(SizeThreshold <= SlabSize,
	"The SizeThreshold must be at most the SlabSize to ensure "
	"that objects larger than a slab go into their own memory "
	"allocation.");

	BumpPtrAllocatorImpl()
	: CurPtr(nullptr), End(nullptr), BytesAllocated(0), Allocator() {}
	template <typename T>
	BumpPtrAllocatorImpl(T &&Allocator)
	: CurPtr(nullptr), End(nullptr), BytesAllocated(0),
	Allocator(std::forward<T &&>(Allocator)) {}

	// Manually implement a move constructor as we must clear the old allocator's
	// slabs as a matter of correctness.
	BumpPtrAllocatorImpl(BumpPtrAllocatorImpl &&Old)
	: CurPtr(Old.CurPtr), End(Old.End), Slabs(std::move(Old.Slabs)),
	CustomSizedSlabs(std::move(Old.CustomSizedSlabs)),
	BytesAllocated(Old.BytesAllocated),
	Allocator(std::move(Old.Allocator)) {
	Old.CurPtr = Old.End = nullptr;
	Old.BytesAllocated = 0;
	Old.Slabs.clear();
	Old.CustomSizedSlabs.clear();
	}

	~BumpPtrAllocatorImpl() {
	DeallocateSlabs(Slabs.begin(), Slabs.end());
	DeallocateCustomSizedSlabs();
	}

	BumpPtrAllocatorImpl &operator=(BumpPtrAllocatorImpl &&RHS) {
	DeallocateSlabs(Slabs.begin(), Slabs.end());
	DeallocateCustomSizedSlabs();

	CurPtr = RHS.CurPtr;
	End = RHS.End;
	BytesAllocated = RHS.BytesAllocated;
	Slabs = std::move(RHS.Slabs);
	CustomSizedSlabs = std::move(RHS.CustomSizedSlabs);
	Allocator = std::move(RHS.Allocator);

	RHS.CurPtr = RHS.End = nullptr;
	RHS.BytesAllocated = 0;
	RHS.Slabs.clear();
	RHS.CustomSizedSlabs.clear();
	return *this;
	}

	/// \brief Deallocate all but the current slab and reset the current pointer
	/// to the beginning of it, freeing all memory allocated so far.
	void Reset() {
	// Deallocate all but the first slab, and deallocate all custom-sized slabs.
	DeallocateCustomSizedSlabs();
	CustomSizedSlabs.clear();

	if (Slabs.empty())
	return;

	// Reset the state.
	BytesAllocated = 0;
	CurPtr = (char *)Slabs.front();
	End = CurPtr + SlabSize;

	__asan_poison_memory_region(*Slabs.begin(), computeSlabSize(0));
	DeallocateSlabs(std::next(Slabs.begin()), Slabs.end());
	Slabs.erase(std::next(Slabs.begin()), Slabs.end());
	}

	/// \brief Allocate space at the specified alignment.
	LLVM_ATTRIBUTE_RETURNS_NONNULL LLVM_ATTRIBUTE_RETURNS_NOALIAS void *
	Allocate(size_t Size, size_t Alignment) {
	assert(Alignment > 0 && "0-byte alignnment is not allowed. Use 1 instead.");

	// Keep track of how many bytes we've allocated.
	BytesAllocated += Size;

	size_t Adjustment = alignmentAdjustment(CurPtr, Alignment);
	assert(Adjustment + Size >= Size && "Adjustment + Size must not overflow");

	// Check if we have enough space.
	if (Adjustment + Size <= size_t(End - CurPtr)) {
	char *AlignedPtr = CurPtr + Adjustment;
	CurPtr = AlignedPtr + Size;
	// Update the allocation point of this memory block in MemorySanitizer.
	// Without this, MemorySanitizer messages for values originated from here
	// will point to the allocation of the entire slab.
	__msan_allocated_memory(AlignedPtr, Size);
	// Similarly, tell ASan about this space.
	__asan_unpoison_memory_region(AlignedPtr, Size);
	return AlignedPtr;
	}

	// If Size is really big, allocate a separate slab for it.
	size_t PaddedSize = Size + Alignment - 1;
	if (PaddedSize > SizeThreshold) {
	void *NewSlab = Allocator.Allocate(PaddedSize, 0);
	// We own the new slab and don't want anyone reading anyting other than
	// pieces returned from this method. So poison the whole slab.
	__asan_poison_memory_region(NewSlab, PaddedSize);
	CustomSizedSlabs.push_back(std::make_pair(NewSlab, PaddedSize));

	uintptr_t AlignedAddr = alignAddr(NewSlab, Alignment);
	assert(AlignedAddr + Size <= (uintptr_t)NewSlab + PaddedSize);
	char AlignedPtr = (char)AlignedAddr;
	__msan_allocated_memory(AlignedPtr, Size);
	__asan_unpoison_memory_region(AlignedPtr, Size);
	return AlignedPtr;
	}

	// Otherwise, start a new slab and try again.
	StartNewSlab();
	uintptr_t AlignedAddr = alignAddr(CurPtr, Alignment);
	assert(AlignedAddr + Size <= (uintptr_t)End &&
	"Unable to allocate memory!");
	char AlignedPtr = (char)AlignedAddr;
	CurPtr = AlignedPtr + Size;
	__msan_allocated_memory(AlignedPtr, Size);
	__asan_unpoison_memory_region(AlignedPtr, Size);
	return AlignedPtr;
	}

	// Pull in base class overloads.
	using AllocatorBase<BumpPtrAllocatorImpl>::Allocate;

	void Deallocate(const void *Ptr, size_t Size) {
	__asan_poison_memory_region(Ptr, Size);
	}

	// Pull in base class overloads.
	using AllocatorBase<BumpPtrAllocatorImpl>::Deallocate;

	size_t GetNumSlabs() const { return Slabs.size() + CustomSizedSlabs.size(); }

	size_t getTotalMemory() const {
	size_t TotalMemory = 0;
	for (auto I = Slabs.begin(), E = Slabs.end(); I != E; ++I)
	TotalMemory += computeSlabSize(std::distance(Slabs.begin(), I));
	for (auto &PtrAndSize : CustomSizedSlabs)
	TotalMemory += PtrAndSize.second;
	return TotalMemory;
	}

	size_t getBytesAllocated() const { return BytesAllocated; }

	void PrintStats() const {
	detail::printBumpPtrAllocatorStats(Slabs.size(), BytesAllocated,
	getTotalMemory());
	}

	private:
	/// \brief The current pointer into the current slab.
	///
	/// This points to the next free byte in the slab.
	char *CurPtr;

	/// \brief The end of the current slab.
	char *End;

	/// \brief The slabs allocated so far.
	SmallVector<void *, 4> Slabs;

	/// \brief Custom-sized slabs allocated for too-large allocation requests.
	SmallVector<std::pair<void *, size_t>, 0> CustomSizedSlabs;

	/// \brief How many bytes we've allocated.
	///
	/// Used so that we can compute how much space was wasted.
	size_t BytesAllocated;

	/// \brief The allocator instance we use to get slabs of memory.
	AllocatorT Allocator;

	static size_t computeSlabSize(unsigned SlabIdx) {
	// Scale the actual allocated slab size based on the number of slabs
	// allocated. Every 128 slabs allocated, we double the allocated size to
	// reduce allocation frequency, but saturate at multiplying the slab size by
	// 2^30.
	return SlabSize * ((size_t)1 << std::min<size_t>(30, SlabIdx / 128));
	}

	/// \brief Allocate a new slab and move the bump pointers over into the new
	/// slab, modifying CurPtr and End.
	void StartNewSlab() {
	size_t AllocatedSlabSize = computeSlabSize(Slabs.size());

	void *NewSlab = Allocator.Allocate(AllocatedSlabSize, 0);
	// We own the new slab and don't want anyone reading anything other than
	// pieces returned from this method. So poison the whole slab.
	__asan_poison_memory_region(NewSlab, AllocatedSlabSize);

	Slabs.push_back(NewSlab);
	CurPtr = (char *)(NewSlab);
	End = ((char *)NewSlab) + AllocatedSlabSize;
	}

	/// \brief Deallocate a sequence of slabs.
	void DeallocateSlabs(SmallVectorImpl<void *>::iterator I,
	SmallVectorImpl<void *>::iterator E) {
	for (; I != E; ++I) {
	size_t AllocatedSlabSize =
	computeSlabSize(std::distance(Slabs.begin(), I));
	Allocator.Deallocate(*I, AllocatedSlabSize);
	}
	}

	/// \brief Deallocate all memory for custom sized slabs.
	void DeallocateCustomSizedSlabs() {
	for (auto &PtrAndSize : CustomSizedSlabs) {
	void *Ptr = PtrAndSize.first;
	size_t Size = PtrAndSize.second;
	Allocator.Deallocate(Ptr, Size);
	}
	}

	template <typename T> friend class SpecificBumpPtrAllocator;
	};

	/// \brief The standard BumpPtrAllocator which just uses the default template
	/// paramaters.
	typedef BumpPtrAllocatorImpl<> BumpPtrAllocator;

	/// \brief A BumpPtrAllocator that allows only elements of a specific type to be
	/// allocated.
	///
	/// This allows calling the destructor in DestroyAll() and when the allocator is
	/// destroyed.
	template <typename T> class SpecificBumpPtrAllocator {
	BumpPtrAllocator Allocator;

	public:
	SpecificBumpPtrAllocator() = default;
	SpecificBumpPtrAllocator(SpecificBumpPtrAllocator &&Old)
	: Allocator(std::move(Old.Allocator)) {}
	~SpecificBumpPtrAllocator() { DestroyAll(); }

	SpecificBumpPtrAllocator &operator=(SpecificBumpPtrAllocator &&RHS) {
	Allocator = std::move(RHS.Allocator);
	return *this;
	}

	/// Call the destructor of each allocated object and deallocate all but the
	/// current slab and reset the current pointer to the beginning of it, freeing
	/// all memory allocated so far.
	void DestroyAll() {
	auto DestroyElements = [](char Begin, char End) {
	assert(Begin == (char *)alignAddr(Begin, alignof(T)));
	for (char *Ptr = Begin; Ptr + sizeof(T) <= End; Ptr += sizeof(T))
	reinterpret_cast<T *>(Ptr)->~T();
	};

	for (auto I = Allocator.Slabs.begin(), E = Allocator.Slabs.end(); I != E;
	++I) {
	size_t AllocatedSlabSize = BumpPtrAllocator::computeSlabSize(
	std::distance(Allocator.Slabs.begin(), I));
	char Begin = (char )alignAddr(*I, alignof(T));
	char End = I == Allocator.Slabs.back() ? Allocator.CurPtr
	: (char )I + AllocatedSlabSize;

	DestroyElements(Begin, End);
	}

	for (auto &PtrAndSize : Allocator.CustomSizedSlabs) {
	void *Ptr = PtrAndSize.first;
	size_t Size = PtrAndSize.second;
	DestroyElements((char )alignAddr(Ptr, alignof(T)), (char )Ptr + Size);
	}

	Allocator.Reset();
	}

	/// \brief Allocate space for an array of objects without constructing them.
	T *Allocate(size_t num = 1) { return Allocator.Allocate<T>(num); }
	};

	} // end namespace llvm

	template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
	void *operator new(size_t Size,
	llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize,
	SizeThreshold> &Allocator) {
	struct S {
	char c;
	union {
	double D;
	long double LD;
	long long L;
	void *P;
	} x;
	};
	return Allocator.Allocate(
	Size, std::min((size_t)llvm::NextPowerOf2(Size), offsetof(S, x)));
	}

	template <typename AllocatorT, size_t SlabSize, size_t SizeThreshold>
	void operator delete(
	void *, llvm::BumpPtrAllocatorImpl<AllocatorT, SlabSize, SizeThreshold> &) {
	}

	#endif // LLVM_SUPPORT_ALLOCATOR_H