//===- llvm/ADT/SmallPtrSet.h - 'Normally small' pointer set ----*- C++ -*-===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This file defines the SmallPtrSet class. See the doxygen comment for // SmallPtrSetImplBase for more details on the algorithm used. // //===----------------------------------------------------------------------===// #ifndef LLVM_ADT_SMALLPTRSET_H #define LLVM_ADT_SMALLPTRSET_H #include "llvm/ADT/EpochTracker.h" #include "llvm/Support/Compiler.h" #include "llvm/Support/ReverseIteration.h" #include "llvm/Support/type_traits.h" #include #include #include #include #include #include #include namespace llvm { /// SmallPtrSetImplBase - This is the common code shared among all the /// SmallPtrSet<>'s, which is almost everything. SmallPtrSet has two modes, one /// for small and one for large sets. /// /// Small sets use an array of pointers allocated in the SmallPtrSet object, /// which is treated as a simple array of pointers. When a pointer is added to /// the set, the array is scanned to see if the element already exists, if not /// the element is 'pushed back' onto the array. If we run out of space in the /// array, we grow into the 'large set' case. SmallSet should be used when the /// sets are often small. In this case, no memory allocation is used, and only /// light-weight and cache-efficient scanning is used. /// /// Large sets use a classic exponentially-probed hash table. Empty buckets are /// represented with an illegal pointer value (-1) to allow null pointers to be /// inserted. Tombstones are represented with another illegal pointer value /// (-2), to allow deletion. The hash table is resized when the table is 3/4 or /// more. When this happens, the table is doubled in size. /// class SmallPtrSetImplBase : public DebugEpochBase { friend class SmallPtrSetIteratorImpl; protected: /// SmallArray - Points to a fixed size set of buckets, used in 'small mode'. const void **SmallArray; /// CurArray - This is the current set of buckets. If equal to SmallArray, /// then the set is in 'small mode'. const void **CurArray; /// CurArraySize - The allocated size of CurArray, always a power of two. unsigned CurArraySize; /// Number of elements in CurArray that contain a value or are a tombstone. /// If small, all these elements are at the beginning of CurArray and the rest /// is uninitialized. unsigned NumNonEmpty; /// Number of tombstones in CurArray. unsigned NumTombstones; // Helpers to copy and move construct a SmallPtrSet. SmallPtrSetImplBase(const void **SmallStorage, const SmallPtrSetImplBase &that); SmallPtrSetImplBase(const void **SmallStorage, unsigned SmallSize, SmallPtrSetImplBase &&that); explicit SmallPtrSetImplBase(const void **SmallStorage, unsigned SmallSize) : SmallArray(SmallStorage), CurArray(SmallStorage), CurArraySize(SmallSize), NumNonEmpty(0), NumTombstones(0) { assert(SmallSize && (SmallSize & (SmallSize-1)) == 0 && "Initial size must be a power of two!"); } ~SmallPtrSetImplBase() { if (!isSmall()) free(CurArray); } public: using size_type = unsigned; SmallPtrSetImplBase &operator=(const SmallPtrSetImplBase &) = delete; LLVM_NODISCARD bool empty() const { return size() == 0; } size_type size() const { return NumNonEmpty - NumTombstones; } void clear() { incrementEpoch(); // If the capacity of the array is huge, and the # elements used is small, // shrink the array. if (!isSmall()) { if (size() * 4 < CurArraySize && CurArraySize > 32) return shrink_and_clear(); // Fill the array with empty markers. memset(CurArray, -1, CurArraySize * sizeof(void *)); } NumNonEmpty = 0; NumTombstones = 0; } protected: static void *getTombstoneMarker() { return reinterpret_cast(-2); } static void *getEmptyMarker() { // Note that -1 is chosen to make clear() efficiently implementable with // memset and because it's not a valid pointer value. return reinterpret_cast(-1); } const void **EndPointer() const { return isSmall() ? CurArray + NumNonEmpty : CurArray + CurArraySize; } /// insert_imp - This returns true if the pointer was new to the set, false if /// it was already in the set. This is hidden from the client so that the /// derived class can check that the right type of pointer is passed in. std::pair insert_imp(const void *Ptr) { if (isSmall()) { // Check to see if it is already in the set. const void **LastTombstone = nullptr; for (const void **APtr = SmallArray, **E = SmallArray + NumNonEmpty; APtr != E; ++APtr) { const void *Value = *APtr; if (Value == Ptr) return std::make_pair(APtr, false); if (Value == getTombstoneMarker()) LastTombstone = APtr; } // Did we find any tombstone marker? if (LastTombstone != nullptr) { *LastTombstone = Ptr; --NumTombstones; incrementEpoch(); return std::make_pair(LastTombstone, true); } // Nope, there isn't. If we stay small, just 'pushback' now. if (NumNonEmpty < CurArraySize) { SmallArray[NumNonEmpty++] = Ptr; incrementEpoch(); return std::make_pair(SmallArray + (NumNonEmpty - 1), true); } // Otherwise, hit the big set case, which will call grow. } return insert_imp_big(Ptr); } /// erase_imp - If the set contains the specified pointer, remove it and /// return true, otherwise return false. This is hidden from the client so /// that the derived class can check that the right type of pointer is passed /// in. bool erase_imp(const void * Ptr) { const void *const *P = find_imp(Ptr); if (P == EndPointer()) return false; const void **Loc = const_cast(P); assert(*Loc == Ptr && "broken find!"); *Loc = getTombstoneMarker(); NumTombstones++; return true; } /// Returns the raw pointer needed to construct an iterator. If element not /// found, this will be EndPointer. Otherwise, it will be a pointer to the /// slot which stores Ptr; const void *const * find_imp(const void * Ptr) const { if (isSmall()) { // Linear search for the item. for (const void *const *APtr = SmallArray, *const *E = SmallArray + NumNonEmpty; APtr != E; ++APtr) if (*APtr == Ptr) return APtr; return EndPointer(); } // Big set case. auto *Bucket = FindBucketFor(Ptr); if (*Bucket == Ptr) return Bucket; return EndPointer(); } private: bool isSmall() const { return CurArray == SmallArray; } std::pair insert_imp_big(const void *Ptr); const void * const *FindBucketFor(const void *Ptr) const; void shrink_and_clear(); /// Grow - Allocate a larger backing store for the buckets and move it over. void Grow(unsigned NewSize); protected: /// swap - Swaps the elements of two sets. /// Note: This method assumes that both sets have the same small size. void swap(SmallPtrSetImplBase &RHS); void CopyFrom(const SmallPtrSetImplBase &RHS); void MoveFrom(unsigned SmallSize, SmallPtrSetImplBase &&RHS); private: /// Code shared by MoveFrom() and move constructor. void MoveHelper(unsigned SmallSize, SmallPtrSetImplBase &&RHS); /// Code shared by CopyFrom() and copy constructor. void CopyHelper(const SmallPtrSetImplBase &RHS); }; /// SmallPtrSetIteratorImpl - This is the common base class shared between all /// instances of SmallPtrSetIterator. class SmallPtrSetIteratorImpl { protected: const void *const *Bucket; const void *const *End; public: explicit SmallPtrSetIteratorImpl(const void *const *BP, const void*const *E) : Bucket(BP), End(E) { if (shouldReverseIterate()) { RetreatIfNotValid(); return; } AdvanceIfNotValid(); } bool operator==(const SmallPtrSetIteratorImpl &RHS) const { return Bucket == RHS.Bucket; } bool operator!=(const SmallPtrSetIteratorImpl &RHS) const { return Bucket != RHS.Bucket; } protected: /// AdvanceIfNotValid - If the current bucket isn't valid, advance to a bucket /// that is. This is guaranteed to stop because the end() bucket is marked /// valid. void AdvanceIfNotValid() { assert(Bucket <= End); while (Bucket != End && (*Bucket == SmallPtrSetImplBase::getEmptyMarker() || *Bucket == SmallPtrSetImplBase::getTombstoneMarker())) ++Bucket; } void RetreatIfNotValid() { assert(Bucket >= End); while (Bucket != End && (Bucket[-1] == SmallPtrSetImplBase::getEmptyMarker() || Bucket[-1] == SmallPtrSetImplBase::getTombstoneMarker())) { --Bucket; } } }; /// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet. template class SmallPtrSetIterator : public SmallPtrSetIteratorImpl, DebugEpochBase::HandleBase { using PtrTraits = PointerLikeTypeTraits; public: using value_type = PtrTy; using reference = PtrTy; using pointer = PtrTy; using difference_type = std::ptrdiff_t; using iterator_category = std::forward_iterator_tag; explicit SmallPtrSetIterator(const void *const *BP, const void *const *E, const DebugEpochBase &Epoch) : SmallPtrSetIteratorImpl(BP, E), DebugEpochBase::HandleBase(&Epoch) {} // Most methods provided by baseclass. const PtrTy operator*() const { assert(isHandleInSync() && "invalid iterator access!"); if (shouldReverseIterate()) { assert(Bucket > End); return PtrTraits::getFromVoidPointer(const_cast(Bucket[-1])); } assert(Bucket < End); return PtrTraits::getFromVoidPointer(const_cast(*Bucket)); } inline SmallPtrSetIterator& operator++() { // Preincrement assert(isHandleInSync() && "invalid iterator access!"); if (shouldReverseIterate()) { --Bucket; RetreatIfNotValid(); return *this; } ++Bucket; AdvanceIfNotValid(); return *this; } SmallPtrSetIterator operator++(int) { // Postincrement SmallPtrSetIterator tmp = *this; ++*this; return tmp; } }; /// RoundUpToPowerOfTwo - This is a helper template that rounds N up to the next /// power of two (which means N itself if N is already a power of two). template struct RoundUpToPowerOfTwo; /// RoundUpToPowerOfTwoH - If N is not a power of two, increase it. This is a /// helper template used to implement RoundUpToPowerOfTwo. template struct RoundUpToPowerOfTwoH { enum { Val = N }; }; template struct RoundUpToPowerOfTwoH { enum { // We could just use NextVal = N+1, but this converges faster. N|(N-1) sets // the right-most zero bits to one all at once, e.g. 0b0011000 -> 0b0011111. Val = RoundUpToPowerOfTwo<(N|(N-1)) + 1>::Val }; }; template struct RoundUpToPowerOfTwo { enum { Val = RoundUpToPowerOfTwoH::Val }; }; /// A templated base class for \c SmallPtrSet which provides the /// typesafe interface that is common across all small sizes. /// /// This is particularly useful for passing around between interface boundaries /// to avoid encoding a particular small size in the interface boundary. template class SmallPtrSetImpl : public SmallPtrSetImplBase { using ConstPtrType = typename add_const_past_pointer::type; using PtrTraits = PointerLikeTypeTraits; using ConstPtrTraits = PointerLikeTypeTraits; protected: // Constructors that forward to the base. SmallPtrSetImpl(const void **SmallStorage, const SmallPtrSetImpl &that) : SmallPtrSetImplBase(SmallStorage, that) {} SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize, SmallPtrSetImpl &&that) : SmallPtrSetImplBase(SmallStorage, SmallSize, std::move(that)) {} explicit SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize) : SmallPtrSetImplBase(SmallStorage, SmallSize) {} public: using iterator = SmallPtrSetIterator; using const_iterator = SmallPtrSetIterator; using key_type = ConstPtrType; using value_type = PtrType; SmallPtrSetImpl(const SmallPtrSetImpl &) = delete; /// Inserts Ptr if and only if there is no element in the container equal to /// Ptr. The bool component of the returned pair is true if and only if the /// insertion takes place, and the iterator component of the pair points to /// the element equal to Ptr. std::pair insert(PtrType Ptr) { auto p = insert_imp(PtrTraits::getAsVoidPointer(Ptr)); return std::make_pair(makeIterator(p.first), p.second); } /// erase - If the set contains the specified pointer, remove it and return /// true, otherwise return false. bool erase(PtrType Ptr) { return erase_imp(PtrTraits::getAsVoidPointer(Ptr)); } /// count - Return 1 if the specified pointer is in the set, 0 otherwise. size_type count(ConstPtrType Ptr) const { return find(Ptr) != end() ? 1 : 0; } iterator find(ConstPtrType Ptr) const { return makeIterator(find_imp(ConstPtrTraits::getAsVoidPointer(Ptr))); } template void insert(IterT I, IterT E) { for (; I != E; ++I) insert(*I); } void insert(std::initializer_list IL) { insert(IL.begin(), IL.end()); } iterator begin() const { if (shouldReverseIterate()) return makeIterator(EndPointer() - 1); return makeIterator(CurArray); } iterator end() const { return makeIterator(EndPointer()); } private: /// Create an iterator that dereferences to same place as the given pointer. iterator makeIterator(const void *const *P) const { if (shouldReverseIterate()) return iterator(P == EndPointer() ? CurArray : P + 1, CurArray, *this); return iterator(P, EndPointer(), *this); } }; /// Equality comparison for SmallPtrSet. /// /// Iterates over elements of LHS confirming that each value from LHS is also in /// RHS, and that no additional values are in RHS. template bool operator==(const SmallPtrSetImpl &LHS, const SmallPtrSetImpl &RHS) { if (LHS.size() != RHS.size()) return false; for (const auto *KV : LHS) if (!RHS.count(KV)) return false; return true; } /// Inequality comparison for SmallPtrSet. /// /// Equivalent to !(LHS == RHS). template bool operator!=(const SmallPtrSetImpl &LHS, const SmallPtrSetImpl &RHS) { return !(LHS == RHS); } /// SmallPtrSet - This class implements a set which is optimized for holding /// SmallSize or less elements. This internally rounds up SmallSize to the next /// power of two if it is not already a power of two. See the comments above /// SmallPtrSetImplBase for details of the algorithm. template class SmallPtrSet : public SmallPtrSetImpl { // In small mode SmallPtrSet uses linear search for the elements, so it is // not a good idea to choose this value too high. You may consider using a // DenseSet<> instead if you expect many elements in the set. static_assert(SmallSize <= 32, "SmallSize should be small"); using BaseT = SmallPtrSetImpl; // Make sure that SmallSize is a power of two, round up if not. enum { SmallSizePowTwo = RoundUpToPowerOfTwo::Val }; /// SmallStorage - Fixed size storage used in 'small mode'. const void *SmallStorage[SmallSizePowTwo]; public: SmallPtrSet() : BaseT(SmallStorage, SmallSizePowTwo) {} SmallPtrSet(const SmallPtrSet &that) : BaseT(SmallStorage, that) {} SmallPtrSet(SmallPtrSet &&that) : BaseT(SmallStorage, SmallSizePowTwo, std::move(that)) {} template SmallPtrSet(It I, It E) : BaseT(SmallStorage, SmallSizePowTwo) { this->insert(I, E); } SmallPtrSet(std::initializer_list IL) : BaseT(SmallStorage, SmallSizePowTwo) { this->insert(IL.begin(), IL.end()); } SmallPtrSet & operator=(const SmallPtrSet &RHS) { if (&RHS != this) this->CopyFrom(RHS); return *this; } SmallPtrSet & operator=(SmallPtrSet &&RHS) { if (&RHS != this) this->MoveFrom(SmallSizePowTwo, std::move(RHS)); return *this; } SmallPtrSet & operator=(std::initializer_list IL) { this->clear(); this->insert(IL.begin(), IL.end()); return *this; } /// swap - Swaps the elements of two sets. void swap(SmallPtrSet &RHS) { SmallPtrSetImplBase::swap(RHS); } }; } // end namespace llvm namespace std { /// Implement std::swap in terms of SmallPtrSet swap. template inline void swap(llvm::SmallPtrSet &LHS, llvm::SmallPtrSet &RHS) { LHS.swap(RHS); } } // end namespace std #endif // LLVM_ADT_SMALLPTRSET_H