llvm-6502/include/llvm/ADT/SmallPtrSet.h
Jeff Cohen ac58a16f85 Fix PR1329.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36016 91177308-0d34-0410-b5e6-96231b3b80d8
2007-04-14 21:50:21 +00:00

241 lines
7.7 KiB
C++

//===- 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.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_SMALLPTRSET_H
#define LLVM_ADT_SMALLPTRSET_H
#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 {
protected:
/// CurArray - This is the current set of buckets. If it points to
/// SmallArray, then the set is in 'small mode'.
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;
void *SmallArray[1]; // Must be last ivar.
// Helper to copy construct a SmallPtrSet.
SmallPtrSetImpl(const SmallPtrSetImpl& that);
public:
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;
clear();
}
~SmallPtrSetImpl() {
if (!isSmall())
delete[] CurArray;
}
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() {
// Fill the array with empty markers.
memset(CurArray, -1, CurArraySize*sizeof(void*));
NumElements = 0;
NumTombstones = 0;
}
/// insert - This returns true if the pointer was new to the set, false if it
/// was already in the set.
bool insert(void *Ptr);
template <typename IterT>
void insert(IterT I, IterT E) {
for (; I != E; ++I)
insert((void*)*I);
}
/// erase - If the set contains the specified pointer, remove it and return
/// true, otherwise return false.
bool erase(void *Ptr);
bool count(void *Ptr) const {
if (isSmall()) {
// Linear search for the item.
for (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;
}
private:
bool isSmall() const { return CurArray == &SmallArray[0]; }
unsigned Hash(void *Ptr) const {
return ((uintptr_t)Ptr >> 4) & (CurArraySize-1);
}
void * const *FindBucketFor(void *Ptr) const;
/// Grow - Allocate a larger backing store for the buckets and move it over.
void Grow();
};
/// SmallPtrSetIteratorImpl - This is the common base class shared between all
/// instances of SmallPtrSetIterator.
class SmallPtrSetIteratorImpl {
protected:
void *const *Bucket;
public:
SmallPtrSetIteratorImpl(void *const *BP) : Bucket(BP) {
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() {
while (*Bucket == SmallPtrSetImpl::getEmptyMarker() ||
*Bucket == SmallPtrSetImpl::getTombstoneMarker())
++Bucket;
}
};
/// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
template<typename PtrTy>
class SmallPtrSetIterator : public SmallPtrSetIteratorImpl {
public:
SmallPtrSetIterator(void *const *BP) : SmallPtrSetIteratorImpl(BP) {}
// Most methods provided by baseclass.
PtrTy operator*() const {
return static_cast<PtrTy>(*Bucket);
}
inline SmallPtrSetIterator& operator++() { // Preincrement
++Bucket;
AdvanceIfNotValid();
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];
public:
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);
}
typedef SmallPtrSetIterator<PtrType> iterator;
typedef SmallPtrSetIterator<PtrType> const_iterator;
inline iterator begin() const {
return iterator(CurArray);
}
inline iterator end() const {
return iterator(CurArray+CurArraySize);
}
};
}
#endif