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