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//===- llvm/ADT/SmallPtrSet.h - 'Normally small' pointer set ----*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file was developed by Chris Lattner and 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
// SmallPtrSetImpl for more details on the algorithm used.
#include <cassert>
#include <cstring>
#include "llvm/Support/DataTypes.h"
namespace llvm {
/// SmallPtrSetImpl - 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 SmallPtrSetImpl {
/// CurArray - This is the current set of buckets. If it points to
/// SmallArray, then the set is in 'small mode'.
const void **CurArray;
/// CurArraySize - The allocated size of CurArray, always a power of two.
/// Note that CurArray points to an array that has CurArraySize+1 elements in
/// it, so that the end iterator actually points to valid memory.
unsigned CurArraySize;
// If small, this is # elts allocated consequtively
unsigned NumElements;
unsigned NumTombstones;
const void *SmallArray[1]; // Must be last ivar.
// Helper to copy construct a SmallPtrSet.
SmallPtrSetImpl(const SmallPtrSetImpl& that);
SmallPtrSetImpl(unsigned SmallSize) {
assert(SmallSize && (SmallSize & (SmallSize-1)) == 0 &&
"Initial size must be a power of two!");
CurArray = &SmallArray[0];
CurArraySize = SmallSize;
// The end pointer, always valid, is set to a valid element to help the
// iterator.
CurArray[SmallSize] = 0;
bool empty() const { return size() == 0; }
unsigned size() const { return NumElements; }
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);
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;
/// 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[0]; }
unsigned Hash(const void *Ptr) const {
return ((uintptr_t)Ptr >> 4) & (CurArraySize-1);
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();
void operator=(const SmallPtrSetImpl &RHS); // DO NOT IMPLEMENT.
void CopyFrom(const SmallPtrSetImpl &RHS);
/// SmallPtrSetIteratorImpl - This is the common base class shared between all
/// instances of SmallPtrSetIterator.
class SmallPtrSetIteratorImpl {
const void *const *Bucket;
SmallPtrSetIteratorImpl(const void *const *BP) : Bucket(BP) {
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() {
while (*Bucket == SmallPtrSetImpl::getEmptyMarker() ||
*Bucket == SmallPtrSetImpl::getTombstoneMarker())
/// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
template<typename PtrTy>
class SmallPtrSetIterator : public SmallPtrSetIteratorImpl {
SmallPtrSetIterator(const void *const *BP) : SmallPtrSetIteratorImpl(BP) {}
// Most methods provided by baseclass.
const PtrTy operator*() const {
return static_cast<const PtrTy>(const_cast<void*>(*Bucket));
inline SmallPtrSetIterator& operator++() { // Preincrement
return *this;
SmallPtrSetIterator operator++(int) { // Postincrement
SmallPtrSetIterator tmp = *this; ++*this; return tmp;
/// NextPowerOfTwo - This is a helper template that rounds N up to the next
/// power of two.
template<unsigned N>
struct NextPowerOfTwo;
/// NextPowerOfTwoH - If N is not a power of two, increase it. This is a helper
/// template used to implement NextPowerOfTwo.
template<unsigned N, bool isPowerTwo>
struct NextPowerOfTwoH {
enum { Val = N };
template<unsigned N>
struct NextPowerOfTwoH<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 = NextPowerOfTwo<(N|(N-1)) + 1>::Val
template<unsigned N>
struct NextPowerOfTwo {
enum { Val = NextPowerOfTwoH<N, (N&(N-1)) == 0>::Val };
/// SmallPtrSet - This class implements a set which is optimizer 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
/// SmallPtrSetImpl for details of the algorithm.
template<class PtrType, unsigned SmallSize>
class SmallPtrSet : public SmallPtrSetImpl {
// Make sure that SmallSize is a power of two, round up if not.
enum { SmallSizePowTwo = NextPowerOfTwo<SmallSize>::Val };
void *SmallArray[SmallSizePowTwo];
SmallPtrSet() : SmallPtrSetImpl(NextPowerOfTwo<SmallSizePowTwo>::Val) {}
SmallPtrSet(const SmallPtrSet &that) : SmallPtrSetImpl(that) {}
template<typename It>
SmallPtrSet(It I, It E)
: SmallPtrSetImpl(NextPowerOfTwo<SmallSizePowTwo>::Val) {
insert(I, E);
/// 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(Ptr); }
/// erase - If the set contains the specified pointer, remove it and return
/// true, otherwise return false.
bool erase(PtrType Ptr) { return erase_imp(Ptr); }
/// count - Return true if the specified pointer is in the set.
bool count(PtrType Ptr) const { return count_imp(Ptr); }
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);
inline iterator end() const {
return iterator(CurArray+CurArraySize);
// Allow assignment from any smallptrset with the same element type even if it
// doesn't have the same smallsize.
const SmallPtrSet<PtrType, SmallSize>&
operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) {
return *this;