llvm-project/llvm/include/Support/BitSetVector.h

271 lines
8.3 KiB
C++

//===-- BitVectorSet.h - A bit-vector representation of sets -----*- C++ -*--=//
//
// class BitVectorSet --
//
// An implementation of the bit-vector representation of sets.
// Unlike vector<bool>, this allows much more efficient parallel set
// operations on bits, by using the bitset template . The bitset template
// unfortunately can only represent sets with a size chosen at compile-time.
// We therefore use a vector of bitsets. The maxmimum size of our sets
// (i.e., the size of the universal set) can be chosen at creation time.
//
// The size of each Bitset is defined by the macro WORDSIZE.
//
// NOTE: The WORDSIZE macro should be made machine-dependent, in order to use
// 64-bit words or whatever gives most efficient Bitsets on each platform.
//
//
// External functions:
//
// bool Disjoint(const BitSetVector& set1, const BitSetVector& set2):
// Tests if two sets have an empty intersection.
// This is more efficient than !(set1 & set2).any().
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_BITVECTORSET_H
#define LLVM_SUPPORT_BITVECTORSET_H
#include <bitset>
#include <vector>
#include <functional>
#include <iostream>
#define WORDSIZE (32U)
class BitSetVector {
// Types used internal to the representation
typedef std::bitset<WORDSIZE> bitword;
typedef bitword::reference reference;
class iterator;
// Data used in the representation
std::vector<bitword> bitsetVec;
unsigned maxSize;
private:
// Utility functions for the representation
static unsigned NumWords(unsigned Size) { return (Size+WORDSIZE-1)/WORDSIZE;}
static unsigned LastWordSize(unsigned Size) { return Size % WORDSIZE; }
// Clear the unused bits in the last word.
// The unused bits are the high (WORDSIZE - LastWordSize()) bits
void ClearUnusedBits() {
unsigned long usedBits = (1U << LastWordSize(size())) - 1;
bitsetVec.back() &= bitword(usedBits);
}
const bitword& getWord(unsigned i) const { return bitsetVec[i]; }
bitword& getWord(unsigned i) { return bitsetVec[i]; }
friend bool Disjoint(const BitSetVector& set1,
const BitSetVector& set2);
BitSetVector(); // do not implement!
public:
///
/// Constructor: create a set of the maximum size maxSetSize.
/// The set is initialized to empty.
///
BitSetVector(unsigned maxSetSize)
: bitsetVec(NumWords(maxSetSize)), maxSize(maxSetSize) { }
/// size - Return the number of bits tracked by this bit vector...
unsigned size() const { return maxSize; }
///
/// Modifier methods: reset, set for entire set, operator[] for one element.
///
void reset() {
for (unsigned i=0, N = bitsetVec.size(); i < N; ++i)
bitsetVec[i].reset();
}
void set() {
for (unsigned i=0, N = bitsetVec.size(); i < N; ++i) // skip last word
bitsetVec[i].set();
ClearUnusedBits();
}
reference operator[](unsigned n) {
assert(n < size() && "BitSetVector: Bit number out of range");
unsigned ndiv = n / WORDSIZE, nmod = n % WORDSIZE;
return bitsetVec[ndiv][nmod];
}
iterator begin() { return iterator::begin(*this); }
iterator end() { return iterator::end(*this); }
///
/// Comparison operations: equal, not equal
///
bool operator == (const BitSetVector& set2) const {
assert(maxSize == set2.maxSize && "Illegal == comparison");
for (unsigned i = 0; i < bitsetVec.size(); ++i)
if (getWord(i) != set2.getWord(i))
return false;
return true;
}
bool operator != (const BitSetVector& set2) const {
return ! (*this == set2);
}
///
/// Set membership operations: single element, any, none, count
///
bool test(unsigned n) const {
assert(n < size() && "BitSetVector: Bit number out of range");
unsigned ndiv = n / WORDSIZE, nmod = n % WORDSIZE;
return bitsetVec[ndiv].test(nmod);
}
bool any() const {
for (unsigned i = 0; i < bitsetVec.size(); ++i)
if (bitsetVec[i].any())
return true;
return false;
}
bool none() const {
return ! any();
}
unsigned count() const {
unsigned n = 0;
for (unsigned i = 0; i < bitsetVec.size(); ++i)
n += bitsetVec[i].count();
return n;
}
bool all() const {
return (count() == size());
}
///
/// Set operations: intersection, union, disjoint union, complement.
///
BitSetVector operator& (const BitSetVector& set2) const {
assert(maxSize == set2.maxSize && "Illegal intersection");
BitSetVector result(maxSize);
for (unsigned i = 0; i < bitsetVec.size(); ++i)
result.getWord(i) = getWord(i) & set2.getWord(i);
return result;
}
BitSetVector operator| (const BitSetVector& set2) const {
assert(maxSize == set2.maxSize && "Illegal intersection");
BitSetVector result(maxSize);
for (unsigned i = 0; i < bitsetVec.size(); ++i)
result.getWord(i) = getWord(i) | set2.getWord(i);
return result;
}
BitSetVector operator^ (const BitSetVector& set2) const {
assert(maxSize == set2.maxSize && "Illegal intersection");
BitSetVector result(maxSize);
for (unsigned i = 0; i < bitsetVec.size(); ++i)
result.getWord(i) = getWord(i) ^ set2.getWord(i);
return result;
}
BitSetVector operator~ () const {
BitSetVector result(maxSize);
for (unsigned i = 0; i < bitsetVec.size(); ++i)
(result.getWord(i) = getWord(i)).flip();
result.ClearUnusedBits();
return result;
}
///
/// Printing and debugging support
///
void print(std::ostream &O) const;
void dump() const { print(std::cerr); }
public:
//
// An iterator to enumerate the bits in a BitSetVector.
// Eventually, this needs to inherit from bidirectional_iterator.
// But this iterator may not be as useful as I once thought and
// may just go away.
//
class iterator {
unsigned currentBit;
unsigned currentWord;
BitSetVector* bitvec;
iterator(unsigned B, unsigned W, BitSetVector& _bitvec)
: currentBit(B), currentWord(W), bitvec(&_bitvec) { }
public:
iterator(BitSetVector& _bitvec)
: currentBit(0), currentWord(0), bitvec(&_bitvec) { }
iterator(const iterator& I)
: currentBit(I.currentBit),currentWord(I.currentWord),bitvec(I.bitvec) { }
iterator& operator=(const iterator& I) {
currentWord == I.currentWord;
currentBit == I.currentBit;
bitvec = I.bitvec;
return *this;
}
// Increment and decrement operators (pre and post)
iterator& operator++() {
if (++currentBit == WORDSIZE)
{ currentBit = 0; if (currentWord < bitvec->maxSize) ++currentWord; }
return *this;
}
iterator& operator--() {
if (currentBit == 0) {
currentBit = WORDSIZE-1;
currentWord = (currentWord == 0)? bitvec->maxSize : --currentWord;
}
else
--currentBit;
return *this;
}
iterator operator++(int) { iterator copy(*this); ++*this; return copy; }
iterator operator--(int) { iterator copy(*this); --*this; return copy; }
// Dereferencing operators
reference operator*() {
assert(currentWord < bitvec->maxSize &&
"Dereferencing iterator past the end of a BitSetVector");
return bitvec->getWord(currentWord)[currentBit];
}
// Comparison operator
bool operator==(const iterator& I) {
return (I.bitvec == bitvec &&
I.currentWord == currentWord && I.currentBit == currentBit);
}
protected:
static iterator begin(BitSetVector& _bitvec) { return iterator(_bitvec); }
static iterator end(BitSetVector& _bitvec) { return iterator(0,
_bitvec.maxSize, _bitvec); }
friend class BitSetVector;
};
};
inline void BitSetVector::print(std::ostream& O) const
{
for (std::vector<bitword>::const_iterator
I=bitsetVec.begin(), E=bitsetVec.end(); I != E; ++I)
O << "<" << (*I) << ">" << (I+1 == E? "\n" : ", ");
}
inline std::ostream& operator<< (std::ostream& O, const BitSetVector& bset)
{
bset.print(O);
return O;
};
///
/// Optimized versions of fundamental comparison operations
///
inline bool Disjoint(const BitSetVector& set1,
const BitSetVector& set2)
{
assert(set1.size() == set2.size() && "Illegal intersection");
for (unsigned i = 0; i < set1.bitsetVec.size(); ++i)
if ((set1.getWord(i) & set2.getWord(i)).any())
return false;
return true;
}
#endif