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348 lines
12 KiB
C++
348 lines
12 KiB
C++
//===- llvm/ADT/SmallPtrSet.h - 'Normally small' pointer set ----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the SmallPtrSet class. See the doxygen comment for
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// SmallPtrSetImplBase for more details on the algorithm used.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_SMALLPTRSET_H
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#define LLVM_ADT_SMALLPTRSET_H
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/DataTypes.h"
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#include "llvm/Support/PointerLikeTypeTraits.h"
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#include <cassert>
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#include <cstddef>
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#include <cstring>
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#include <iterator>
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#include <utility>
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namespace llvm {
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class SmallPtrSetIteratorImpl;
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/// SmallPtrSetImplBase - This is the common code shared among all the
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/// SmallPtrSet<>'s, which is almost everything. SmallPtrSet has two modes, one
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/// for small and one for large sets.
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///
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/// Small sets use an array of pointers allocated in the SmallPtrSet object,
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/// which is treated as a simple array of pointers. When a pointer is added to
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/// the set, the array is scanned to see if the element already exists, if not
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/// the element is 'pushed back' onto the array. If we run out of space in the
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/// array, we grow into the 'large set' case. SmallSet should be used when the
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/// sets are often small. In this case, no memory allocation is used, and only
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/// light-weight and cache-efficient scanning is used.
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///
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/// Large sets use a classic exponentially-probed hash table. Empty buckets are
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/// represented with an illegal pointer value (-1) to allow null pointers to be
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/// inserted. Tombstones are represented with another illegal pointer value
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/// (-2), to allow deletion. The hash table is resized when the table is 3/4 or
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/// more. When this happens, the table is doubled in size.
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///
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class SmallPtrSetImplBase {
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friend class SmallPtrSetIteratorImpl;
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protected:
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/// SmallArray - Points to a fixed size set of buckets, used in 'small mode'.
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const void **SmallArray;
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/// CurArray - This is the current set of buckets. If equal to SmallArray,
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/// then the set is in 'small mode'.
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const void **CurArray;
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/// CurArraySize - The allocated size of CurArray, always a power of two.
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unsigned CurArraySize;
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// If small, this is # elts allocated consecutively
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unsigned NumElements;
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unsigned NumTombstones;
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// Helpers to copy and move construct a SmallPtrSet.
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SmallPtrSetImplBase(const void **SmallStorage, const SmallPtrSetImplBase &that);
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SmallPtrSetImplBase(const void **SmallStorage, unsigned SmallSize,
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SmallPtrSetImplBase &&that);
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explicit SmallPtrSetImplBase(const void **SmallStorage, unsigned SmallSize) :
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SmallArray(SmallStorage), CurArray(SmallStorage), CurArraySize(SmallSize) {
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assert(SmallSize && (SmallSize & (SmallSize-1)) == 0 &&
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"Initial size must be a power of two!");
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clear();
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}
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~SmallPtrSetImplBase();
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public:
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typedef unsigned size_type;
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bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const { return size() == 0; }
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size_type size() const { return NumElements; }
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void clear() {
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// If the capacity of the array is huge, and the # elements used is small,
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// shrink the array.
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if (!isSmall() && NumElements*4 < CurArraySize && CurArraySize > 32)
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return shrink_and_clear();
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// Fill the array with empty markers.
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memset(CurArray, -1, CurArraySize*sizeof(void*));
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NumElements = 0;
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NumTombstones = 0;
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}
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protected:
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static void *getTombstoneMarker() { return reinterpret_cast<void*>(-2); }
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static void *getEmptyMarker() {
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// Note that -1 is chosen to make clear() efficiently implementable with
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// memset and because it's not a valid pointer value.
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return reinterpret_cast<void*>(-1);
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}
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/// insert_imp - This returns true if the pointer was new to the set, false if
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/// it was already in the set. This is hidden from the client so that the
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/// derived class can check that the right type of pointer is passed in.
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std::pair<const void *const *, bool> insert_imp(const void *Ptr);
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/// erase_imp - If the set contains the specified pointer, remove it and
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/// return true, otherwise return false. This is hidden from the client so
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/// that the derived class can check that the right type of pointer is passed
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/// in.
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bool erase_imp(const void * Ptr);
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bool count_imp(const void * Ptr) const {
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if (isSmall()) {
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// Linear search for the item.
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for (const void *const *APtr = SmallArray,
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*const *E = SmallArray+NumElements; APtr != E; ++APtr)
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if (*APtr == Ptr)
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return true;
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return false;
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}
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// Big set case.
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return *FindBucketFor(Ptr) == Ptr;
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}
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private:
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bool isSmall() const { return CurArray == SmallArray; }
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const void * const *FindBucketFor(const void *Ptr) const;
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void shrink_and_clear();
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/// Grow - Allocate a larger backing store for the buckets and move it over.
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void Grow(unsigned NewSize);
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void operator=(const SmallPtrSetImplBase &RHS) = delete;
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protected:
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/// swap - Swaps the elements of two sets.
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/// Note: This method assumes that both sets have the same small size.
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void swap(SmallPtrSetImplBase &RHS);
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void CopyFrom(const SmallPtrSetImplBase &RHS);
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void MoveFrom(unsigned SmallSize, SmallPtrSetImplBase &&RHS);
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};
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/// SmallPtrSetIteratorImpl - This is the common base class shared between all
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/// instances of SmallPtrSetIterator.
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class SmallPtrSetIteratorImpl {
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protected:
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const void *const *Bucket;
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const void *const *End;
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public:
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explicit SmallPtrSetIteratorImpl(const void *const *BP, const void*const *E)
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: Bucket(BP), End(E) {
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AdvanceIfNotValid();
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}
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bool operator==(const SmallPtrSetIteratorImpl &RHS) const {
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return Bucket == RHS.Bucket;
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}
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bool operator!=(const SmallPtrSetIteratorImpl &RHS) const {
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return Bucket != RHS.Bucket;
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}
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protected:
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/// AdvanceIfNotValid - If the current bucket isn't valid, advance to a bucket
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/// that is. This is guaranteed to stop because the end() bucket is marked
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/// valid.
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void AdvanceIfNotValid() {
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assert(Bucket <= End);
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while (Bucket != End &&
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(*Bucket == SmallPtrSetImplBase::getEmptyMarker() ||
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*Bucket == SmallPtrSetImplBase::getTombstoneMarker()))
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++Bucket;
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}
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};
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/// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
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template<typename PtrTy>
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class SmallPtrSetIterator : public SmallPtrSetIteratorImpl {
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typedef PointerLikeTypeTraits<PtrTy> PtrTraits;
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public:
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typedef PtrTy value_type;
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typedef PtrTy reference;
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typedef PtrTy pointer;
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typedef std::ptrdiff_t difference_type;
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typedef std::forward_iterator_tag iterator_category;
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explicit SmallPtrSetIterator(const void *const *BP, const void *const *E)
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: SmallPtrSetIteratorImpl(BP, E) {}
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// Most methods provided by baseclass.
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const PtrTy operator*() const {
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assert(Bucket < End);
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return PtrTraits::getFromVoidPointer(const_cast<void*>(*Bucket));
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}
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inline SmallPtrSetIterator& operator++() { // Preincrement
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++Bucket;
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AdvanceIfNotValid();
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return *this;
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}
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SmallPtrSetIterator operator++(int) { // Postincrement
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SmallPtrSetIterator tmp = *this; ++*this; return tmp;
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}
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};
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/// RoundUpToPowerOfTwo - This is a helper template that rounds N up to the next
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/// power of two (which means N itself if N is already a power of two).
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template<unsigned N>
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struct RoundUpToPowerOfTwo;
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/// RoundUpToPowerOfTwoH - If N is not a power of two, increase it. This is a
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/// helper template used to implement RoundUpToPowerOfTwo.
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template<unsigned N, bool isPowerTwo>
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struct RoundUpToPowerOfTwoH {
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enum { Val = N };
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};
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template<unsigned N>
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struct RoundUpToPowerOfTwoH<N, false> {
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enum {
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// We could just use NextVal = N+1, but this converges faster. N|(N-1) sets
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// the right-most zero bits to one all at once, e.g. 0b0011000 -> 0b0011111.
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Val = RoundUpToPowerOfTwo<(N|(N-1)) + 1>::Val
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};
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};
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template<unsigned N>
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struct RoundUpToPowerOfTwo {
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enum { Val = RoundUpToPowerOfTwoH<N, (N&(N-1)) == 0>::Val };
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};
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/// \brief A templated base class for \c SmallPtrSet which provides the
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/// typesafe interface that is common across all small sizes.
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///
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/// This is particularly useful for passing around between interface boundaries
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/// to avoid encoding a particular small size in the interface boundary.
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template <typename PtrType>
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class SmallPtrSetImpl : public SmallPtrSetImplBase {
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typedef PointerLikeTypeTraits<PtrType> PtrTraits;
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SmallPtrSetImpl(const SmallPtrSetImpl&) = delete;
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protected:
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// Constructors that forward to the base.
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SmallPtrSetImpl(const void **SmallStorage, const SmallPtrSetImpl &that)
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: SmallPtrSetImplBase(SmallStorage, that) {}
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SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize,
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SmallPtrSetImpl &&that)
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: SmallPtrSetImplBase(SmallStorage, SmallSize, std::move(that)) {}
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explicit SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize)
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: SmallPtrSetImplBase(SmallStorage, SmallSize) {}
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public:
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typedef SmallPtrSetIterator<PtrType> iterator;
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typedef SmallPtrSetIterator<PtrType> const_iterator;
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/// Inserts Ptr if and only if there is no element in the container equal to
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/// Ptr. The bool component of the returned pair is true if and only if the
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/// insertion takes place, and the iterator component of the pair points to
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/// the element equal to Ptr.
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std::pair<iterator, bool> insert(PtrType Ptr) {
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auto p = insert_imp(PtrTraits::getAsVoidPointer(Ptr));
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return std::make_pair(iterator(p.first, CurArray + CurArraySize), p.second);
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}
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/// erase - If the set contains the specified pointer, remove it and return
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/// true, otherwise return false.
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bool erase(PtrType Ptr) {
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return erase_imp(PtrTraits::getAsVoidPointer(Ptr));
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}
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/// count - Return 1 if the specified pointer is in the set, 0 otherwise.
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size_type count(PtrType Ptr) const {
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return count_imp(PtrTraits::getAsVoidPointer(Ptr)) ? 1 : 0;
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}
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template <typename IterT>
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void insert(IterT I, IterT E) {
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for (; I != E; ++I)
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insert(*I);
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}
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inline iterator begin() const {
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return iterator(CurArray, CurArray+CurArraySize);
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}
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inline iterator end() const {
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return iterator(CurArray+CurArraySize, CurArray+CurArraySize);
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}
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};
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/// SmallPtrSet - This class implements a set which is optimized for holding
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/// SmallSize or less elements. This internally rounds up SmallSize to the next
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/// power of two if it is not already a power of two. See the comments above
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/// SmallPtrSetImplBase for details of the algorithm.
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template<class PtrType, unsigned SmallSize>
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class SmallPtrSet : public SmallPtrSetImpl<PtrType> {
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typedef SmallPtrSetImpl<PtrType> BaseT;
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// Make sure that SmallSize is a power of two, round up if not.
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enum { SmallSizePowTwo = RoundUpToPowerOfTwo<SmallSize>::Val };
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/// SmallStorage - Fixed size storage used in 'small mode'.
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const void *SmallStorage[SmallSizePowTwo];
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public:
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SmallPtrSet() : BaseT(SmallStorage, SmallSizePowTwo) {}
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SmallPtrSet(const SmallPtrSet &that) : BaseT(SmallStorage, that) {}
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SmallPtrSet(SmallPtrSet &&that)
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: BaseT(SmallStorage, SmallSizePowTwo, std::move(that)) {}
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template<typename It>
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SmallPtrSet(It I, It E) : BaseT(SmallStorage, SmallSizePowTwo) {
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this->insert(I, E);
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}
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SmallPtrSet<PtrType, SmallSize> &
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operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) {
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if (&RHS != this)
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this->CopyFrom(RHS);
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return *this;
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}
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SmallPtrSet<PtrType, SmallSize>&
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operator=(SmallPtrSet<PtrType, SmallSize> &&RHS) {
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if (&RHS != this)
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this->MoveFrom(SmallSizePowTwo, std::move(RHS));
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return *this;
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}
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/// swap - Swaps the elements of two sets.
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void swap(SmallPtrSet<PtrType, SmallSize> &RHS) {
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SmallPtrSetImplBase::swap(RHS);
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}
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};
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}
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namespace std {
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/// Implement std::swap in terms of SmallPtrSet swap.
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template<class T, unsigned N>
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inline void swap(llvm::SmallPtrSet<T, N> &LHS, llvm::SmallPtrSet<T, N> &RHS) {
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LHS.swap(RHS);
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}
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}
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#endif
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