text: //===- llvm/ADT/PointerIntPair.h - Pair for pointer and int -----*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file defines the PointerIntPair class.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_ADT_POINTERINTPAIR_H
  #define LLVM_ADT_POINTERINTPAIR_H
  
  #include "llvm/Support/Compiler.h"
  #include "llvm/Support/PointerLikeTypeTraits.h"
  #include <cassert>
  #include <limits>
  
  namespace llvm {
  
  template<typename T>
  struct DenseMapInfo;
  
  /// PointerIntPair - This class implements a pair of a pointer and small
  /// integer.  It is designed to represent this in the space required by one
  /// pointer by bitmangling the integer into the low part of the pointer.  This
  /// can only be done for small integers: typically up to 3 bits, but it depends
  /// on the number of bits available according to PointerLikeTypeTraits for the
  /// type.
  ///
  /// Note that PointerIntPair always puts the IntVal part in the highest bits
  /// possible.  For example, PointerIntPair<void*, 1, bool> will put the bit for
  /// the bool into bit #2, not bit #0, which allows the low two bits to be used
  /// for something else.  For example, this allows:
  ///   PointerIntPair<PointerIntPair<void*, 1, bool>, 1, bool>
  /// ... and the two bools will land in different bits.
  ///
  template <typename PointerTy, unsigned IntBits, typename IntType=unsigned,
            typename PtrTraits = PointerLikeTypeTraits<PointerTy> >
  class PointerIntPair {
    intptr_t Value;
    static_assert(PtrTraits::NumLowBitsAvailable <
                  std::numeric_limits<uintptr_t>::digits,
                  "cannot use a pointer type that has all bits free");
    static_assert(IntBits <= PtrTraits::NumLowBitsAvailable,
                  "PointerIntPair with integer size too large for pointer");
    enum : uintptr_t {
      /// PointerBitMask - The bits that come from the pointer.
      PointerBitMask =
        ~(uintptr_t)(((intptr_t)1 << PtrTraits::NumLowBitsAvailable)-1),
  
      /// IntShift - The number of low bits that we reserve for other uses, and
      /// keep zero.
      IntShift = (uintptr_t)PtrTraits::NumLowBitsAvailable - IntBits,
  
      /// IntMask - This is the unshifted mask for valid bits of the int type.
      IntMask = (uintptr_t)(((intptr_t)1 << IntBits) - 1),
  
      // ShiftedIntMask - This is the bits for the integer shifted in place.
      ShiftedIntMask = (uintptr_t)(IntMask << IntShift)
    };
  
  public:
    PointerIntPair() : Value(0) {}
    PointerIntPair(PointerTy PtrVal, IntType IntVal) {
      setPointerAndInt(PtrVal, IntVal);
    }
    explicit PointerIntPair(PointerTy PtrVal) {
      initWithPointer(PtrVal);
    }
  
    PointerTy getPointer() const {
      return PtrTraits::getFromVoidPointer(
                           reinterpret_cast<void*>(Value & PointerBitMask));
    }
  
    IntType getInt() const {
      return (IntType)((Value >> IntShift) & IntMask);
    }
  
    void setPointer(PointerTy PtrVal) {
      intptr_t PtrWord
        = reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(PtrVal));
      assert((PtrWord & ~PointerBitMask) == 0 &&
             "Pointer is not sufficiently aligned");
      // Preserve all low bits, just update the pointer.
      Value = PtrWord | (Value & ~PointerBitMask);
    }
  
    void setInt(IntType IntVal) {
      intptr_t IntWord = static_cast<intptr_t>(IntVal);
      assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
  
      // Preserve all bits other than the ones we are updating.
      Value &= ~ShiftedIntMask;     // Remove integer field.
      Value |= IntWord << IntShift;  // Set new integer.
    }
  
    void initWithPointer(PointerTy PtrVal) {
      intptr_t PtrWord
        = reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(PtrVal));
      assert((PtrWord & ~PointerBitMask) == 0 &&
             "Pointer is not sufficiently aligned");
      Value = PtrWord;
    }
  
    void setPointerAndInt(PointerTy PtrVal, IntType IntVal) {
      intptr_t PtrWord
        = reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(PtrVal));
      assert((PtrWord & ~PointerBitMask) == 0 &&
             "Pointer is not sufficiently aligned");
      intptr_t IntWord = static_cast<intptr_t>(IntVal);
      assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
  
      Value = PtrWord | (IntWord << IntShift);
    }
  
    PointerTy const *getAddrOfPointer() const {
      return const_cast<PointerIntPair *>(this)->getAddrOfPointer();
    }
  
    PointerTy *getAddrOfPointer() {
      assert(Value == reinterpret_cast<intptr_t>(getPointer()) &&
             "Can only return the address if IntBits is cleared and "
             "PtrTraits doesn't change the pointer");
      return reinterpret_cast<PointerTy *>(&Value);
    }
  
    void *getOpaqueValue() const { return reinterpret_cast<void*>(Value); }
    void setFromOpaqueValue(void *Val) { Value = reinterpret_cast<intptr_t>(Val);}
  
    static PointerIntPair getFromOpaqueValue(void *V) {
      PointerIntPair P;
      P.setFromOpaqueValue(V);
      return P;
    }
  
    // Allow PointerIntPairs to be created from const void * if and only if the
    // pointer type could be created from a const void *.
    static PointerIntPair getFromOpaqueValue(const void *V) {
      (void)PtrTraits::getFromVoidPointer(V);
      return getFromOpaqueValue(const_cast<void *>(V));
    }
  
    bool operator==(const PointerIntPair &RHS) const {return Value == RHS.Value;}
    bool operator!=(const PointerIntPair &RHS) const {return Value != RHS.Value;}
    bool operator<(const PointerIntPair &RHS) const {return Value < RHS.Value;}
    bool operator>(const PointerIntPair &RHS) const {return Value > RHS.Value;}
    bool operator<=(const PointerIntPair &RHS) const {return Value <= RHS.Value;}
    bool operator>=(const PointerIntPair &RHS) const {return Value >= RHS.Value;}
  };
  
  template <typename T> struct isPodLike;
  template<typename PointerTy, unsigned IntBits, typename IntType>
  struct isPodLike<PointerIntPair<PointerTy, IntBits, IntType> > {
     static const bool value = true;
  };
  
  // Provide specialization of DenseMapInfo for PointerIntPair.
  template<typename PointerTy, unsigned IntBits, typename IntType>
  struct DenseMapInfo<PointerIntPair<PointerTy, IntBits, IntType> > {
    typedef PointerIntPair<PointerTy, IntBits, IntType> Ty;
    static Ty getEmptyKey() {
      uintptr_t Val = static_cast<uintptr_t>(-1);
      Val <<= PointerLikeTypeTraits<Ty>::NumLowBitsAvailable;
      return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
    }
    static Ty getTombstoneKey() {
      uintptr_t Val = static_cast<uintptr_t>(-2);
      Val <<= PointerLikeTypeTraits<PointerTy>::NumLowBitsAvailable;
      return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
    }
    static unsigned getHashValue(Ty V) {
      uintptr_t IV = reinterpret_cast<uintptr_t>(V.getOpaqueValue());
      return unsigned(IV) ^ unsigned(IV >> 9);
    }
    static bool isEqual(const Ty &LHS, const Ty &RHS) { return LHS == RHS; }
  };
  
  // Teach SmallPtrSet that PointerIntPair is "basically a pointer".
  template<typename PointerTy, unsigned IntBits, typename IntType,
           typename PtrTraits>
  class PointerLikeTypeTraits<PointerIntPair<PointerTy, IntBits, IntType,
                                             PtrTraits> > {
  public:
    static inline void *
    getAsVoidPointer(const PointerIntPair<PointerTy, IntBits, IntType> &P) {
      return P.getOpaqueValue();
    }
    static inline PointerIntPair<PointerTy, IntBits, IntType>
    getFromVoidPointer(void *P) {
      return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
    }
    static inline PointerIntPair<PointerTy, IntBits, IntType>
    getFromVoidPointer(const void *P) {
      return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
    }
    enum {
      NumLowBitsAvailable = PtrTraits::NumLowBitsAvailable - IntBits
    };
  };
  
  } // end namespace llvm
  #endif
  