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462 lines
12 KiB
C++
462 lines
12 KiB
C++
//===- llvm/ADT/SmallBitVector.h - 'Normally small' bit vectors -*- 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 implements the SmallBitVector class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_SMALLBITVECTOR_H
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#define LLVM_ADT_SMALLBITVECTOR_H
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#include "llvm/ADT/BitVector.h"
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#include "llvm/Support/MathExtras.h"
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#include <cassert>
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namespace llvm {
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/// SmallBitVector - This is a 'bitvector' (really, a variable-sized bit array),
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/// optimized for the case when the array is small. It contains one
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/// pointer-sized field, which is directly used as a plain collection of bits
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/// when possible, or as a pointer to a larger heap-allocated array when
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/// necessary. This allows normal "small" cases to be fast without losing
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/// generality for large inputs.
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///
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class SmallBitVector {
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// TODO: In "large" mode, a pointer to a BitVector is used, leading to an
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// unnecessary level of indirection. It would be more efficient to use a
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// pointer to memory containing size, allocation size, and the array of bits.
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uintptr_t X;
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enum {
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// The number of bits in this class.
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NumBaseBits = sizeof(uintptr_t) * CHAR_BIT,
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// One bit is used to discriminate between small and large mode. The
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// remaining bits are used for the small-mode representation.
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SmallNumRawBits = NumBaseBits - 1,
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// A few more bits are used to store the size of the bit set in small mode.
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// Theoretically this is a ceil-log2. These bits are encoded in the most
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// significant bits of the raw bits.
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SmallNumSizeBits = (NumBaseBits == 32 ? 5 :
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NumBaseBits == 64 ? 6 :
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SmallNumRawBits),
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// The remaining bits are used to store the actual set in small mode.
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SmallNumDataBits = SmallNumRawBits - SmallNumSizeBits
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};
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public:
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// Encapsulation of a single bit.
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class reference {
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SmallBitVector &TheVector;
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unsigned BitPos;
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public:
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reference(SmallBitVector &b, unsigned Idx) : TheVector(b), BitPos(Idx) {}
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reference& operator=(reference t) {
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*this = bool(t);
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return *this;
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}
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reference& operator=(bool t) {
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if (t)
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TheVector.set(BitPos);
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else
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TheVector.reset(BitPos);
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return *this;
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}
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operator bool() const {
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return const_cast<const SmallBitVector &>(TheVector).operator[](BitPos);
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}
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};
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private:
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bool isSmall() const {
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return X & uintptr_t(1);
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}
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BitVector *getPointer() const {
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assert(!isSmall());
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return reinterpret_cast<BitVector *>(X);
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}
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void switchToSmall(uintptr_t NewSmallBits, size_t NewSize) {
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X = 1;
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setSmallSize(NewSize);
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setSmallBits(NewSmallBits);
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}
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void switchToLarge(BitVector *BV) {
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X = reinterpret_cast<uintptr_t>(BV);
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assert(!isSmall() && "Tried to use an unaligned pointer");
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}
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// Return all the bits used for the "small" representation; this includes
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// bits for the size as well as the element bits.
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uintptr_t getSmallRawBits() const {
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assert(isSmall());
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return X >> 1;
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}
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void setSmallRawBits(uintptr_t NewRawBits) {
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assert(isSmall());
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X = (NewRawBits << 1) | uintptr_t(1);
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}
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// Return the size.
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size_t getSmallSize() const {
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return getSmallRawBits() >> SmallNumDataBits;
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}
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void setSmallSize(size_t Size) {
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setSmallRawBits(getSmallBits() | (Size << SmallNumDataBits));
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}
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// Return the element bits.
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uintptr_t getSmallBits() const {
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return getSmallRawBits() & ~(~uintptr_t(0) << getSmallSize());
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}
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void setSmallBits(uintptr_t NewBits) {
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setSmallRawBits((NewBits & ~(~uintptr_t(0) << getSmallSize())) |
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(getSmallSize() << SmallNumDataBits));
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}
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public:
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/// SmallBitVector default ctor - Creates an empty bitvector.
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SmallBitVector() : X(1) {}
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/// SmallBitVector ctor - Creates a bitvector of specified number of bits. All
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/// bits are initialized to the specified value.
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explicit SmallBitVector(unsigned s, bool t = false) {
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if (s <= SmallNumDataBits)
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switchToSmall(t ? ~uintptr_t(0) : 0, s);
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else
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switchToLarge(new BitVector(s, t));
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}
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/// SmallBitVector copy ctor.
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SmallBitVector(const SmallBitVector &RHS) {
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if (RHS.isSmall())
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X = RHS.X;
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else
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switchToLarge(new BitVector(*RHS.getPointer()));
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}
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~SmallBitVector() {
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if (!isSmall())
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delete getPointer();
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}
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/// empty - Tests whether there are no bits in this bitvector.
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bool empty() const {
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return isSmall() ? getSmallSize() == 0 : getPointer()->empty();
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}
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/// size - Returns the number of bits in this bitvector.
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size_t size() const {
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return isSmall() ? getSmallSize() : getPointer()->size();
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}
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/// count - Returns the number of bits which are set.
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unsigned count() const {
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if (isSmall()) {
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uintptr_t Bits = getSmallBits();
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if (sizeof(uintptr_t) * CHAR_BIT == 32)
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return CountPopulation_32(Bits);
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if (sizeof(uintptr_t) * CHAR_BIT == 64)
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return CountPopulation_64(Bits);
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assert(0 && "Unsupported!");
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}
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return getPointer()->count();
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}
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/// any - Returns true if any bit is set.
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bool any() const {
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if (isSmall())
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return getSmallBits() != 0;
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return getPointer()->any();
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}
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/// all - Returns true if all bits are set.
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bool all() const {
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if (isSmall())
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return getSmallBits() == (uintptr_t(1) << getSmallSize()) - 1;
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return getPointer()->all();
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}
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/// none - Returns true if none of the bits are set.
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bool none() const {
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if (isSmall())
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return getSmallBits() == 0;
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return getPointer()->none();
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}
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/// find_first - Returns the index of the first set bit, -1 if none
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/// of the bits are set.
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int find_first() const {
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if (isSmall()) {
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uintptr_t Bits = getSmallBits();
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if (Bits == 0)
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return -1;
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if (sizeof(uintptr_t) * CHAR_BIT == 32)
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return CountTrailingZeros_32(Bits);
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if (sizeof(uintptr_t) * CHAR_BIT == 64)
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return CountTrailingZeros_64(Bits);
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assert(0 && "Unsupported!");
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}
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return getPointer()->find_first();
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}
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/// find_next - Returns the index of the next set bit following the
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/// "Prev" bit. Returns -1 if the next set bit is not found.
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int find_next(unsigned Prev) const {
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if (isSmall()) {
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uintptr_t Bits = getSmallBits();
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// Mask off previous bits.
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Bits &= ~uintptr_t(0) << (Prev + 1);
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if (Bits == 0 || Prev + 1 >= getSmallSize())
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return -1;
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if (sizeof(uintptr_t) * CHAR_BIT == 32)
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return CountTrailingZeros_32(Bits);
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if (sizeof(uintptr_t) * CHAR_BIT == 64)
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return CountTrailingZeros_64(Bits);
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assert(0 && "Unsupported!");
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}
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return getPointer()->find_next(Prev);
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}
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/// clear - Clear all bits.
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void clear() {
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if (!isSmall())
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delete getPointer();
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switchToSmall(0, 0);
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}
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/// resize - Grow or shrink the bitvector.
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void resize(unsigned N, bool t = false) {
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if (!isSmall()) {
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getPointer()->resize(N, t);
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} else if (SmallNumDataBits >= N) {
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uintptr_t NewBits = t ? ~uintptr_t(0) << getSmallSize() : 0;
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setSmallSize(N);
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setSmallBits(NewBits | getSmallBits());
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} else {
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BitVector *BV = new BitVector(N, t);
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uintptr_t OldBits = getSmallBits();
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for (size_t i = 0, e = getSmallSize(); i != e; ++i)
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(*BV)[i] = (OldBits >> i) & 1;
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switchToLarge(BV);
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}
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}
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void reserve(unsigned N) {
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if (isSmall()) {
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if (N > SmallNumDataBits) {
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uintptr_t OldBits = getSmallRawBits();
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size_t SmallSize = getSmallSize();
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BitVector *BV = new BitVector(SmallSize);
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for (size_t i = 0; i < SmallSize; ++i)
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if ((OldBits >> i) & 1)
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BV->set(i);
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BV->reserve(N);
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switchToLarge(BV);
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}
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} else {
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getPointer()->reserve(N);
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}
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}
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// Set, reset, flip
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SmallBitVector &set() {
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if (isSmall())
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setSmallBits(~uintptr_t(0));
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else
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getPointer()->set();
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return *this;
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}
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SmallBitVector &set(unsigned Idx) {
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if (isSmall())
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setSmallBits(getSmallBits() | (uintptr_t(1) << Idx));
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else
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getPointer()->set(Idx);
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return *this;
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}
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SmallBitVector &reset() {
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if (isSmall())
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setSmallBits(0);
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else
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getPointer()->reset();
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return *this;
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}
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SmallBitVector &reset(unsigned Idx) {
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if (isSmall())
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setSmallBits(getSmallBits() & ~(uintptr_t(1) << Idx));
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else
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getPointer()->reset(Idx);
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return *this;
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}
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SmallBitVector &flip() {
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if (isSmall())
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setSmallBits(~getSmallBits());
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else
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getPointer()->flip();
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return *this;
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}
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SmallBitVector &flip(unsigned Idx) {
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if (isSmall())
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setSmallBits(getSmallBits() ^ (uintptr_t(1) << Idx));
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else
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getPointer()->flip(Idx);
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return *this;
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}
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// No argument flip.
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SmallBitVector operator~() const {
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return SmallBitVector(*this).flip();
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}
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// Indexing.
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reference operator[](unsigned Idx) {
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assert(Idx < size() && "Out-of-bounds Bit access.");
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return reference(*this, Idx);
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}
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bool operator[](unsigned Idx) const {
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assert(Idx < size() && "Out-of-bounds Bit access.");
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if (isSmall())
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return ((getSmallBits() >> Idx) & 1) != 0;
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return getPointer()->operator[](Idx);
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}
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bool test(unsigned Idx) const {
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return (*this)[Idx];
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}
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// Comparison operators.
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bool operator==(const SmallBitVector &RHS) const {
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if (size() != RHS.size())
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return false;
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if (isSmall())
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return getSmallBits() == RHS.getSmallBits();
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else
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return *getPointer() == *RHS.getPointer();
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}
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bool operator!=(const SmallBitVector &RHS) const {
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return !(*this == RHS);
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}
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// Intersection, union, disjoint union.
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SmallBitVector &operator&=(const SmallBitVector &RHS) {
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resize(std::max(size(), RHS.size()));
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if (isSmall())
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setSmallBits(getSmallBits() & RHS.getSmallBits());
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else if (!RHS.isSmall())
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getPointer()->operator&=(*RHS.getPointer());
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else {
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SmallBitVector Copy = RHS;
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Copy.resize(size());
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getPointer()->operator&=(*Copy.getPointer());
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}
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return *this;
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}
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SmallBitVector &operator|=(const SmallBitVector &RHS) {
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resize(std::max(size(), RHS.size()));
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if (isSmall())
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setSmallBits(getSmallBits() | RHS.getSmallBits());
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else if (!RHS.isSmall())
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getPointer()->operator|=(*RHS.getPointer());
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else {
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SmallBitVector Copy = RHS;
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Copy.resize(size());
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getPointer()->operator|=(*Copy.getPointer());
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}
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return *this;
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}
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SmallBitVector &operator^=(const SmallBitVector &RHS) {
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resize(std::max(size(), RHS.size()));
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if (isSmall())
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setSmallBits(getSmallBits() ^ RHS.getSmallBits());
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else if (!RHS.isSmall())
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getPointer()->operator^=(*RHS.getPointer());
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else {
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SmallBitVector Copy = RHS;
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Copy.resize(size());
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getPointer()->operator^=(*Copy.getPointer());
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}
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return *this;
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}
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// Assignment operator.
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const SmallBitVector &operator=(const SmallBitVector &RHS) {
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if (isSmall()) {
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if (RHS.isSmall())
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X = RHS.X;
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else
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switchToLarge(new BitVector(*RHS.getPointer()));
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} else {
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if (!RHS.isSmall())
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*getPointer() = *RHS.getPointer();
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else {
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delete getPointer();
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X = RHS.X;
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}
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}
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return *this;
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}
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void swap(SmallBitVector &RHS) {
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std::swap(X, RHS.X);
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}
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};
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inline SmallBitVector
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operator&(const SmallBitVector &LHS, const SmallBitVector &RHS) {
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SmallBitVector Result(LHS);
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Result &= RHS;
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return Result;
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}
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inline SmallBitVector
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operator|(const SmallBitVector &LHS, const SmallBitVector &RHS) {
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SmallBitVector Result(LHS);
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Result |= RHS;
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return Result;
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}
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inline SmallBitVector
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operator^(const SmallBitVector &LHS, const SmallBitVector &RHS) {
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SmallBitVector Result(LHS);
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Result ^= RHS;
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return Result;
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}
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} // End llvm namespace
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namespace std {
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/// Implement std::swap in terms of BitVector swap.
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inline void
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swap(llvm::SmallBitVector &LHS, llvm::SmallBitVector &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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