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diff --git a/include/llvm/ADT/BitVector.h b/include/llvm/ADT/BitVector.h
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+++ b/include/llvm/ADT/BitVector.h
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+//===- llvm/ADT/BitVector.h - Bit vectors -----------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Evan Cheng and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the BitVector class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_BITVECTOR_H
+#define LLVM_ADT_BITVECTOR_H
+
+#include "llvm/Support/MathExtras.h"
+#include <algorithm>
+#include <cstdlib>
+#include <cassert>
+
+namespace llvm {
+
+class BitVector {
+  typedef unsigned long BitWord;
+
+  enum { BITWORD_SIZE = sizeof(BitWord) * 8 };
+
+  BitWord  *Bits;        // Actual bits. 
+  unsigned Size;         // Size of bitvector in bits.
+  unsigned Capacity;     // Size of allocated memory in BitWord.
+
+public:
+  // Encapsulation of a single bit.
+  class reference {
+    friend class BitVector;
+
+    BitWord *WordRef;
+    unsigned BitPos;
+
+    reference();  // Undefined
+
+  public:
+    reference(BitVector &b, unsigned Idx) {
+      WordRef = &b.Bits[Idx / BITWORD_SIZE];
+      BitPos = Idx % BITWORD_SIZE;
+    }
+
+    ~reference() {}
+
+    reference& operator=(bool t) {
+      if (t)
+        *WordRef |= 1L << BitPos;
+      else
+        *WordRef &= ~(1L << BitPos);
+      return *this;
+    }
+
+    operator bool() const {
+      return (*WordRef) & (1L << BitPos);
+    }
+  };
+
+
+  /// BitVector default ctor - Creates an empty bitvector.
+  BitVector() : Size(0), Capacity(0) {
+    Bits = NULL;
+  }
+
+  /// BitVector ctor - Creates a bitvector of specified number of bits. All
+  /// bits are initialized to the specified value.
+  explicit BitVector(unsigned s, bool t = false) : Size(s) {
+    Capacity = NumBitWords(s);
+    Bits = new BitWord[Capacity];
+    init_words(Bits, Capacity, t);
+    if (t)
+      clear_unused_bits();
+  }
+
+  /// BitVector copy ctor.
+  BitVector(const BitVector &RHS) : Size(RHS.size()) {
+    if (Size == 0) {
+      Bits = NULL;
+      Capacity = 0;
+      return;
+    }
+
+    Capacity = NumBitWords(RHS.size());
+    Bits = new BitWord[Capacity];
+    std::copy(RHS.Bits, &RHS.Bits[Capacity], Bits);
+  }
+  
+  ~BitVector() {
+    delete[] Bits;
+  }
+
+  /// size - Returns the number of bits in this bitvector.
+  unsigned size() const { return Size; }
+
+  /// count - Returns the number of bits which are set.
+  unsigned count() const {
+    unsigned NumBits = 0;
+    for (unsigned i = 0; i < NumBitWords(size()); ++i)
+      if (sizeof(BitWord) == 4)
+        NumBits += CountPopulation_32(Bits[i]);
+      else if (sizeof(BitWord) == 8)
+        NumBits += CountPopulation_64(Bits[i]);
+      else
+        assert(0 && "Unsupported!");
+    return NumBits;
+  }
+
+  /// any - Returns true if any bit is set.
+  bool any() const {
+    for (unsigned i = 0; i < NumBitWords(size()); ++i)
+      if (Bits[i] != 0)
+        return true;
+    return false;
+  }
+
+  /// none - Returns true if none of the bits are set.
+  bool none() const {
+    return !any();
+  }
+
+  /// find_first - Returns the index of the first set bit, -1 if none
+  /// of the bits are set.
+  int find_first() const {
+    for (unsigned i = 0; i < NumBitWords(size()); ++i)
+      if (Bits[i] != 0) {
+        if (sizeof(BitWord) == 4)
+          return i * BITWORD_SIZE + CountTrailingZeros_32(Bits[i]);
+        else if (sizeof(BitWord) == 8)
+          return i * BITWORD_SIZE + CountTrailingZeros_64(Bits[i]);
+        else
+          assert(0 && "Unsupported!");
+      }
+    return -1;
+  }
+
+  /// 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 {
+    ++Prev;
+    if (Prev >= Size)
+      return -1;
+
+    unsigned WordPos = Prev / BITWORD_SIZE;
+    unsigned BitPos = Prev % BITWORD_SIZE;
+    BitWord Copy = Bits[WordPos];
+    // Mask off previous bits.
+    Copy &= ~0L << BitPos;
+
+    if (Copy != 0) {
+      if (sizeof(BitWord) == 4)
+        return WordPos * BITWORD_SIZE + CountTrailingZeros_32(Copy);
+      else if (sizeof(BitWord) == 8)
+        return WordPos * BITWORD_SIZE + CountTrailingZeros_64(Copy);
+      else
+        assert(0 && "Unsupported!");
+    }
+
+    // Check subsequent words.
+    for (unsigned i = WordPos+1; i < NumBitWords(size()); ++i)
+      if (Bits[i] != 0) {
+        if (sizeof(BitWord) == 4)
+          return i * BITWORD_SIZE + CountTrailingZeros_32(Bits[i]);
+        else if (sizeof(BitWord) == 8)
+          return i * BITWORD_SIZE + CountTrailingZeros_64(Bits[i]);
+        else
+          assert(0 && "Unsupported!");
+      }
+    return -1;
+  }
+
+  /// clear - Clear all bits.
+  void clear() {
+    Size = 0;
+  }
+
+  /// resize - Grow or shrink the bitvector.
+  void resize(unsigned N, bool t = false) {
+    if (N > Capacity * BITWORD_SIZE) {
+      unsigned OldCapacity = Capacity;
+      grow(N);
+      init_words(&Bits[OldCapacity], (Capacity-OldCapacity), t);
+    }
+    
+    // If we previously had no size, initialize the low word
+    if (Size == 0)
+      for (unsigned i = 0; i < Capacity; ++i)
+        Bits[i] = 0 - (unsigned)t;
+    
+    Size = N;
+    clear_unused_bits();
+  }
+
+  void reserve(unsigned N) {
+    if (N > Capacity * BITWORD_SIZE)
+      grow(N);
+  }
+
+  // Set, reset, flip
+  BitVector &set() {
+    init_words(Bits, Capacity, true);
+    clear_unused_bits();
+    return *this;
+  }
+
+  BitVector &set(unsigned Idx) {
+    Bits[Idx / BITWORD_SIZE] |= 1L << (Idx % BITWORD_SIZE);
+    return *this;
+  }
+
+  BitVector &reset() {
+    init_words(Bits, Capacity, false);
+    return *this;
+  }
+
+  BitVector &reset(unsigned Idx) {
+    Bits[Idx / BITWORD_SIZE] &= ~(1L << (Idx % BITWORD_SIZE));
+    return *this;
+  }
+
+  BitVector &flip() {
+    for (unsigned i = 0; i < NumBitWords(size()); ++i)
+      Bits[i] = ~Bits[i];
+    clear_unused_bits();
+    return *this;
+  }
+
+  BitVector &flip(unsigned Idx) {
+    Bits[Idx / BITWORD_SIZE] ^= 1L << (Idx % BITWORD_SIZE);
+    return *this;
+  }
+
+  // No argument flip.
+  BitVector operator~() const {
+    return BitVector(*this).flip();
+  }
+
+  // Indexing.
+  reference operator[](unsigned Idx) {
+    return reference(*this, Idx);
+  }
+
+  bool operator[](unsigned Idx) const {
+    BitWord Mask = 1L << (Idx % BITWORD_SIZE);
+    return (Bits[Idx / BITWORD_SIZE] & Mask) != 0;
+  }
+
+  bool test(unsigned Idx) const {
+    return (*this)[Idx];
+  }
+
+  // Comparison operators.
+  bool operator==(const BitVector &RHS) const {
+    if (Size != RHS.Size)
+      return false;
+
+    for (unsigned i = 0; i < NumBitWords(size()); ++i)
+      if (Bits[i] != RHS.Bits[i])
+        return false;
+    return true;
+  }
+
+  bool operator!=(const BitVector &RHS) const {
+    return !(*this == RHS);
+  }
+
+  // Intersection, union, disjoint union.
+  BitVector operator&=(const BitVector &RHS) {
+    assert(Size == RHS.Size && "Illegal operation!");
+    for (unsigned i = 0; i < NumBitWords(size()); ++i)
+      Bits[i] &= RHS.Bits[i];
+    return *this;
+  }
+
+  BitVector operator|=(const BitVector &RHS) {
+    assert(Size == RHS.Size && "Illegal operation!");
+    for (unsigned i = 0; i < NumBitWords(size()); ++i)
+      Bits[i] |= RHS.Bits[i];
+    return *this;
+  }
+
+  BitVector operator^=(const BitVector &RHS) {
+    assert(Size == RHS.Size && "Illegal operation!");
+    for (unsigned i = 0; i < NumBitWords(size()); ++i)
+      Bits[i] ^= RHS.Bits[i];
+    return *this;
+  }
+  
+  // Assignment operator.
+  const BitVector &operator=(const BitVector &RHS) {
+    if (this == &RHS) return *this;
+
+    Size = RHS.size();
+    unsigned RHSWords = NumBitWords(Size);
+    if (Size <= Capacity * BITWORD_SIZE) {
+      std::copy(RHS.Bits, &RHS.Bits[RHSWords], Bits);
+      clear_unused_bits();
+      return *this;
+    }
+  
+    // Grow the bitvector to have enough elements.
+    Capacity = NumBitWords(Size);
+    BitWord *NewBits = new BitWord[Capacity];
+    std::copy(RHS.Bits, &RHS.Bits[RHSWords], NewBits);
+
+    // Destroy the old bits.
+    delete[] Bits;
+    Bits = NewBits;
+
+    return *this;
+  }
+
+private:
+  unsigned NumBitWords(unsigned S) const {
+    return (S + BITWORD_SIZE-1) / BITWORD_SIZE;
+  }
+
+  // Clear the unused top bits in the high word.
+  void clear_unused_bits() {
+    unsigned ExtraBits = Size % BITWORD_SIZE;
+    if (ExtraBits) {
+      unsigned index = Size / BITWORD_SIZE;
+      Bits[index] &= ~(~0L << ExtraBits);
+    }
+  }
+
+  void grow(unsigned NewSize) {
+    unsigned OldCapacity = Capacity;
+    Capacity = NumBitWords(NewSize);
+    BitWord *NewBits = new BitWord[Capacity];
+
+    // Copy the old bits over.
+    if (OldCapacity != 0)
+      std::copy(Bits, &Bits[OldCapacity], NewBits);
+
+    // Destroy the old bits.
+    delete[] Bits;
+    Bits = NewBits;
+  }
+
+  void init_words(BitWord *B, unsigned NumWords, bool t) {
+    memset(B, 0 - (int)t, NumWords*sizeof(BitWord));
+  } 
+};
+
+inline BitVector operator&(const BitVector &LHS, const BitVector &RHS) {
+  BitVector Result(LHS);
+  Result &= RHS;
+  return Result;
+}
+
+inline BitVector operator|(const BitVector &LHS, const BitVector &RHS) {
+  BitVector Result(LHS);
+  Result |= RHS;
+  return Result;
+}
+
+inline BitVector operator^(const BitVector &LHS, const BitVector &RHS) {
+  BitVector Result(LHS);
+  Result ^= RHS;
+  return Result;
+}
+ 
+} // End llvm namespace
+#endif