blob: 74f3fd43cec4cbd1ecfdce82410d4905b9570da7 [file] [log] [blame]
//===- llvm/ADT/SmallPtrSet.h - 'Normally small' pointer set ----*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file defines the SmallPtrSet class. See the doxygen comment for
// SmallPtrSetImplBase for more details on the algorithm used.
#include "llvm/Support/Compiler.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/PointerLikeTypeTraits.h"
#include <cassert>
#include <cstddef>
#include <cstring>
#include <iterator>
namespace llvm {
class SmallPtrSetIteratorImpl;
/// 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 {
friend class SmallPtrSetIteratorImpl;
/// 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;
// If small, this is # elts allocated consecutively
unsigned NumElements;
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) {
assert(SmallSize && (SmallSize & (SmallSize-1)) == 0 &&
"Initial size must be a power of two!");
typedef unsigned size_type;
bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const { return size() == 0; }
size_type size() const { return NumElements; }
void clear() {
// If the capacity of the array is huge, and the # elements used is small,
// shrink the array.
if (!isSmall() && NumElements*4 < CurArraySize && CurArraySize > 32)
return shrink_and_clear();
// Fill the array with empty markers.
memset(CurArray, -1, CurArraySize*sizeof(void*));
NumElements = 0;
NumTombstones = 0;
static void *getTombstoneMarker() { return reinterpret_cast<void*>(-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<void*>(-1);
/// 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.
bool insert_imp(const void * 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);
bool count_imp(const void * Ptr) const {
if (isSmall()) {
// Linear search for the item.
for (const void *const *APtr = SmallArray,
*const *E = SmallArray+NumElements; APtr != E; ++APtr)
if (*APtr == Ptr)
return true;
return false;
// Big set case.
return *FindBucketFor(Ptr) == Ptr;
bool isSmall() const { return CurArray == SmallArray; }
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);
void operator=(const SmallPtrSetImplBase &RHS) LLVM_DELETED_FUNCTION;
/// 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);
/// SmallPtrSetIteratorImpl - This is the common base class shared between all
/// instances of SmallPtrSetIterator.
class SmallPtrSetIteratorImpl {
const void *const *Bucket;
const void *const *End;
explicit SmallPtrSetIteratorImpl(const void *const *BP, const void*const *E)
: Bucket(BP), End(E) {
bool operator==(const SmallPtrSetIteratorImpl &RHS) const {
return Bucket == RHS.Bucket;
bool operator!=(const SmallPtrSetIteratorImpl &RHS) const {
return Bucket != RHS.Bucket;
/// 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()))
/// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
template<typename PtrTy>
class SmallPtrSetIterator : public SmallPtrSetIteratorImpl {
typedef PointerLikeTypeTraits<PtrTy> PtrTraits;
typedef PtrTy value_type;
typedef PtrTy reference;
typedef PtrTy pointer;
typedef std::ptrdiff_t difference_type;
typedef std::forward_iterator_tag iterator_category;
explicit SmallPtrSetIterator(const void *const *BP, const void *const *E)
: SmallPtrSetIteratorImpl(BP, E) {}
// Most methods provided by baseclass.
const PtrTy operator*() const {
assert(Bucket < End);
return PtrTraits::getFromVoidPointer(const_cast<void*>(*Bucket));
inline SmallPtrSetIterator& operator++() { // Preincrement
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<unsigned N>
struct RoundUpToPowerOfTwo;
/// RoundUpToPowerOfTwoH - If N is not a power of two, increase it. This is a
/// helper template used to implement RoundUpToPowerOfTwo.
template<unsigned N, bool isPowerTwo>
struct RoundUpToPowerOfTwoH {
enum { Val = N };
template<unsigned N>
struct RoundUpToPowerOfTwoH<N, false> {
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<unsigned N>
struct RoundUpToPowerOfTwo {
enum { Val = RoundUpToPowerOfTwoH<N, (N&(N-1)) == 0>::Val };
/// \brief 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 <typename PtrType>
class SmallPtrSetImpl : public SmallPtrSetImplBase {
typedef PointerLikeTypeTraits<PtrType> PtrTraits;
// 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) {}
/// insert - This returns true if the pointer was new to the set, false if it
/// was already in the set.
bool insert(PtrType Ptr) {
return insert_imp(PtrTraits::getAsVoidPointer(Ptr));
/// 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(PtrType Ptr) const {
return count_imp(PtrTraits::getAsVoidPointer(Ptr)) ? 1 : 0;
template <typename IterT>
void insert(IterT I, IterT E) {
for (; I != E; ++I)
typedef SmallPtrSetIterator<PtrType> iterator;
typedef SmallPtrSetIterator<PtrType> const_iterator;
inline iterator begin() const {
return iterator(CurArray, CurArray+CurArraySize);
inline iterator end() const {
return iterator(CurArray+CurArraySize, CurArray+CurArraySize);
/// 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 PtrType, unsigned SmallSize>
class SmallPtrSet : public SmallPtrSetImpl<PtrType> {
typedef SmallPtrSetImpl<PtrType> BaseT;
// Make sure that SmallSize is a power of two, round up if not.
enum { SmallSizePowTwo = RoundUpToPowerOfTwo<SmallSize>::Val };
/// SmallStorage - Fixed size storage used in 'small mode'.
const void *SmallStorage[SmallSizePowTwo];
SmallPtrSet() : BaseT(SmallStorage, SmallSizePowTwo) {}
SmallPtrSet(const SmallPtrSet &that) : BaseT(SmallStorage, that) {}
SmallPtrSet(SmallPtrSet &&that)
: BaseT(SmallStorage, SmallSizePowTwo, std::move(that)) {}
template<typename It>
SmallPtrSet(It I, It E) : BaseT(SmallStorage, SmallSizePowTwo) {
this->insert(I, E);
SmallPtrSet<PtrType, SmallSize> &
operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) {
if (&RHS != this)
return *this;
SmallPtrSet<PtrType, SmallSize>&
operator=(SmallPtrSet<PtrType, SmallSize> &&RHS) {
if (&RHS != this)
this->MoveFrom(SmallSizePowTwo, std::move(RHS));
return *this;
/// swap - Swaps the elements of two sets.
void swap(SmallPtrSet<PtrType, SmallSize> &RHS) {
namespace std {
/// Implement std::swap in terms of SmallPtrSet swap.
template<class T, unsigned N>
inline void swap(llvm::SmallPtrSet<T, N> &LHS, llvm::SmallPtrSet<T, N> &RHS) {