text: //===-- CGValue.h - LLVM CodeGen wrappers for llvm::Value* ------*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // These classes implement wrappers around llvm::Value in order to
  // fully represent the range of values for C L- and R- values.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CLANG_LIB_CODEGEN_CGVALUE_H
  #define LLVM_CLANG_LIB_CODEGEN_CGVALUE_H
  
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/CharUnits.h"
  #include "clang/AST/Type.h"
  #include "llvm/IR/Value.h"
  
  namespace llvm {
    class Constant;
    class MDNode;
  }
  
  namespace clang {
  namespace CodeGen {
    class AggValueSlot;
    struct CGBitFieldInfo;
  
  /// RValue - This trivial value class is used to represent the result of an
  /// expression that is evaluated.  It can be one of three things: either a
  /// simple LLVM SSA value, a pair of SSA values for complex numbers, or the
  /// address of an aggregate value in memory.
  class RValue {
    enum Flavor { Scalar, Complex, Aggregate };
  
    // Stores first value and flavor.
    llvm::PointerIntPair<llvm::Value *, 2, Flavor> V1;
    // Stores second value and volatility.
    llvm::PointerIntPair<llvm::Value *, 1, bool> V2;
  
  public:
    bool isScalar() const { return V1.getInt() == Scalar; }
    bool isComplex() const { return V1.getInt() == Complex; }
    bool isAggregate() const { return V1.getInt() == Aggregate; }
  
    bool isVolatileQualified() const { return V2.getInt(); }
  
    /// getScalarVal() - Return the Value* of this scalar value.
    llvm::Value *getScalarVal() const {
      assert(isScalar() && "Not a scalar!");
      return V1.getPointer();
    }
  
    /// getComplexVal - Return the real/imag components of this complex value.
    ///
    std::pair<llvm::Value *, llvm::Value *> getComplexVal() const {
      return std::make_pair(V1.getPointer(), V2.getPointer());
    }
  
    /// getAggregateAddr() - Return the Value* of the address of the aggregate.
    llvm::Value *getAggregateAddr() const {
      assert(isAggregate() && "Not an aggregate!");
      return V1.getPointer();
    }
  
    static RValue get(llvm::Value *V) {
      RValue ER;
      ER.V1.setPointer(V);
      ER.V1.setInt(Scalar);
      ER.V2.setInt(false);
      return ER;
    }
    static RValue getComplex(llvm::Value *V1, llvm::Value *V2) {
      RValue ER;
      ER.V1.setPointer(V1);
      ER.V2.setPointer(V2);
      ER.V1.setInt(Complex);
      ER.V2.setInt(false);
      return ER;
    }
    static RValue getComplex(const std::pair<llvm::Value *, llvm::Value *> &C) {
      return getComplex(C.first, C.second);
    }
    // FIXME: Aggregate rvalues need to retain information about whether they are
    // volatile or not.  Remove default to find all places that probably get this
    // wrong.
    static RValue getAggregate(llvm::Value *V, bool Volatile = false) {
      RValue ER;
      ER.V1.setPointer(V);
      ER.V1.setInt(Aggregate);
      ER.V2.setInt(Volatile);
      return ER;
    }
  };
  
  /// Does an ARC strong l-value have precise lifetime?
  enum ARCPreciseLifetime_t {
    ARCImpreciseLifetime, ARCPreciseLifetime
  };
  
  /// LValue - This represents an lvalue references.  Because C/C++ allow
  /// bitfields, this is not a simple LLVM pointer, it may be a pointer plus a
  /// bitrange.
  class LValue {
    enum {
      Simple,       // This is a normal l-value, use getAddress().
      VectorElt,    // This is a vector element l-value (V[i]), use getVector*
      BitField,     // This is a bitfield l-value, use getBitfield*.
      ExtVectorElt, // This is an extended vector subset, use getExtVectorComp
      GlobalReg     // This is a register l-value, use getGlobalReg()
    } LVType;
  
    llvm::Value *V;
  
    union {
      // Index into a vector subscript: V[i]
      llvm::Value *VectorIdx;
  
      // ExtVector element subset: V.xyx
      llvm::Constant *VectorElts;
  
      // BitField start bit and size
      const CGBitFieldInfo *BitFieldInfo;
    };
  
    QualType Type;
  
    // 'const' is unused here
    Qualifiers Quals;
  
    // The alignment to use when accessing this lvalue.  (For vector elements,
    // this is the alignment of the whole vector.)
    int64_t Alignment;
  
    // objective-c's ivar
    bool Ivar:1;
  
    // objective-c's ivar is an array
    bool ObjIsArray:1;
  
    // LValue is non-gc'able for any reason, including being a parameter or local
    // variable.
    bool NonGC: 1;
  
    // Lvalue is a global reference of an objective-c object
    bool GlobalObjCRef : 1;
  
    // Lvalue is a thread local reference
    bool ThreadLocalRef : 1;
  
    // Lvalue has ARC imprecise lifetime.  We store this inverted to try
    // to make the default bitfield pattern all-zeroes.
    bool ImpreciseLifetime : 1;
  
    Expr *BaseIvarExp;
  
    /// Used by struct-path-aware TBAA.
    QualType TBAABaseType;
    /// Offset relative to the base type.
    uint64_t TBAAOffset;
  
    /// TBAAInfo - TBAA information to attach to dereferences of this LValue.
    llvm::MDNode *TBAAInfo;
  
  private:
    void Initialize(QualType Type, Qualifiers Quals,
                    CharUnits Alignment,
                    llvm::MDNode *TBAAInfo = nullptr) {
      this->Type = Type;
      this->Quals = Quals;
      this->Alignment = Alignment.getQuantity();
      assert(this->Alignment == Alignment.getQuantity() &&
             "Alignment exceeds allowed max!");
  
      // Initialize Objective-C flags.
      this->Ivar = this->ObjIsArray = this->NonGC = this->GlobalObjCRef = false;
      this->ImpreciseLifetime = false;
      this->ThreadLocalRef = false;
      this->BaseIvarExp = nullptr;
  
      // Initialize fields for TBAA.
      this->TBAABaseType = Type;
      this->TBAAOffset = 0;
      this->TBAAInfo = TBAAInfo;
    }
  
  public:
    bool isSimple() const { return LVType == Simple; }
    bool isVectorElt() const { return LVType == VectorElt; }
    bool isBitField() const { return LVType == BitField; }
    bool isExtVectorElt() const { return LVType == ExtVectorElt; }
    bool isGlobalReg() const { return LVType == GlobalReg; }
  
    bool isVolatileQualified() const { return Quals.hasVolatile(); }
    bool isRestrictQualified() const { return Quals.hasRestrict(); }
    unsigned getVRQualifiers() const {
      return Quals.getCVRQualifiers() & ~Qualifiers::Const;
    }
  
    QualType getType() const { return Type; }
  
    Qualifiers::ObjCLifetime getObjCLifetime() const {
      return Quals.getObjCLifetime();
    }
  
    bool isObjCIvar() const { return Ivar; }
    void setObjCIvar(bool Value) { Ivar = Value; }
  
    bool isObjCArray() const { return ObjIsArray; }
    void setObjCArray(bool Value) { ObjIsArray = Value; }
  
    bool isNonGC () const { return NonGC; }
    void setNonGC(bool Value) { NonGC = Value; }
  
    bool isGlobalObjCRef() const { return GlobalObjCRef; }
    void setGlobalObjCRef(bool Value) { GlobalObjCRef = Value; }
  
    bool isThreadLocalRef() const { return ThreadLocalRef; }
    void setThreadLocalRef(bool Value) { ThreadLocalRef = Value;}
  
    ARCPreciseLifetime_t isARCPreciseLifetime() const {
      return ARCPreciseLifetime_t(!ImpreciseLifetime);
    }
    void setARCPreciseLifetime(ARCPreciseLifetime_t value) {
      ImpreciseLifetime = (value == ARCImpreciseLifetime);
    }
  
    bool isObjCWeak() const {
      return Quals.getObjCGCAttr() == Qualifiers::Weak;
    }
    bool isObjCStrong() const {
      return Quals.getObjCGCAttr() == Qualifiers::Strong;
    }
  
    bool isVolatile() const {
      return Quals.hasVolatile();
    }
  
    Expr *getBaseIvarExp() const { return BaseIvarExp; }
    void setBaseIvarExp(Expr *V) { BaseIvarExp = V; }
  
    QualType getTBAABaseType() const { return TBAABaseType; }
    void setTBAABaseType(QualType T) { TBAABaseType = T; }
  
    uint64_t getTBAAOffset() const { return TBAAOffset; }
    void setTBAAOffset(uint64_t O) { TBAAOffset = O; }
  
    llvm::MDNode *getTBAAInfo() const { return TBAAInfo; }
    void setTBAAInfo(llvm::MDNode *N) { TBAAInfo = N; }
  
    const Qualifiers &getQuals() const { return Quals; }
    Qualifiers &getQuals() { return Quals; }
  
    unsigned getAddressSpace() const { return Quals.getAddressSpace(); }
  
    CharUnits getAlignment() const { return CharUnits::fromQuantity(Alignment); }
    void setAlignment(CharUnits A) { Alignment = A.getQuantity(); }
  
    // simple lvalue
    llvm::Value *getAddress() const { assert(isSimple()); return V; }
    void setAddress(llvm::Value *address) {
      assert(isSimple());
      V = address;
    }
  
    // vector elt lvalue
    llvm::Value *getVectorAddr() const { assert(isVectorElt()); return V; }
    llvm::Value *getVectorIdx() const { assert(isVectorElt()); return VectorIdx; }
  
    // extended vector elements.
    llvm::Value *getExtVectorAddr() const { assert(isExtVectorElt()); return V; }
    llvm::Constant *getExtVectorElts() const {
      assert(isExtVectorElt());
      return VectorElts;
    }
  
    // bitfield lvalue
    llvm::Value *getBitFieldAddr() const {
      assert(isBitField());
      return V;
    }
    const CGBitFieldInfo &getBitFieldInfo() const {
      assert(isBitField());
      return *BitFieldInfo;
    }
  
    // global register lvalue
    llvm::Value *getGlobalReg() const { assert(isGlobalReg()); return V; }
  
    static LValue MakeAddr(llvm::Value *address, QualType type,
                           CharUnits alignment, ASTContext &Context,
                           llvm::MDNode *TBAAInfo = nullptr) {
      Qualifiers qs = type.getQualifiers();
      qs.setObjCGCAttr(Context.getObjCGCAttrKind(type));
  
      LValue R;
      R.LVType = Simple;
      R.V = address;
      R.Initialize(type, qs, alignment, TBAAInfo);
      return R;
    }
  
    static LValue MakeVectorElt(llvm::Value *Vec, llvm::Value *Idx,
                                QualType type, CharUnits Alignment) {
      LValue R;
      R.LVType = VectorElt;
      R.V = Vec;
      R.VectorIdx = Idx;
      R.Initialize(type, type.getQualifiers(), Alignment);
      return R;
    }
  
    static LValue MakeExtVectorElt(llvm::Value *Vec, llvm::Constant *Elts,
                                   QualType type, CharUnits Alignment) {
      LValue R;
      R.LVType = ExtVectorElt;
      R.V = Vec;
      R.VectorElts = Elts;
      R.Initialize(type, type.getQualifiers(), Alignment);
      return R;
    }
  
    /// \brief Create a new object to represent a bit-field access.
    ///
    /// \param Addr - The base address of the bit-field sequence this
    /// bit-field refers to.
    /// \param Info - The information describing how to perform the bit-field
    /// access.
    static LValue MakeBitfield(llvm::Value *Addr,
                               const CGBitFieldInfo &Info,
                               QualType type, CharUnits Alignment) {
      LValue R;
      R.LVType = BitField;
      R.V = Addr;
      R.BitFieldInfo = &Info;
      R.Initialize(type, type.getQualifiers(), Alignment);
      return R;
    }
  
    static LValue MakeGlobalReg(llvm::Value *Reg,
                                QualType type,
                                CharUnits Alignment) {
      LValue R;
      R.LVType = GlobalReg;
      R.V = Reg;
      R.Initialize(type, type.getQualifiers(), Alignment);
      return R;
    }
  
    RValue asAggregateRValue() const {
      // FIMXE: Alignment
      return RValue::getAggregate(getAddress(), isVolatileQualified());
    }
  };
  
  /// An aggregate value slot.
  class AggValueSlot {
    /// The address.
    llvm::Value *Addr;
  
    // Qualifiers
    Qualifiers Quals;
  
    unsigned short Alignment;
  
    /// DestructedFlag - This is set to true if some external code is
    /// responsible for setting up a destructor for the slot.  Otherwise
    /// the code which constructs it should push the appropriate cleanup.
    bool DestructedFlag : 1;
  
    /// ObjCGCFlag - This is set to true if writing to the memory in the
    /// slot might require calling an appropriate Objective-C GC
    /// barrier.  The exact interaction here is unnecessarily mysterious.
    bool ObjCGCFlag : 1;
  
    /// ZeroedFlag - This is set to true if the memory in the slot is
    /// known to be zero before the assignment into it.  This means that
    /// zero fields don't need to be set.
    bool ZeroedFlag : 1;
  
    /// AliasedFlag - This is set to true if the slot might be aliased
    /// and it's not undefined behavior to access it through such an
    /// alias.  Note that it's always undefined behavior to access a C++
    /// object that's under construction through an alias derived from
    /// outside the construction process.
    ///
    /// This flag controls whether calls that produce the aggregate
    /// value may be evaluated directly into the slot, or whether they
    /// must be evaluated into an unaliased temporary and then memcpy'ed
    /// over.  Since it's invalid in general to memcpy a non-POD C++
    /// object, it's important that this flag never be set when
    /// evaluating an expression which constructs such an object.
    bool AliasedFlag : 1;
  
  public:
    enum IsAliased_t { IsNotAliased, IsAliased };
    enum IsDestructed_t { IsNotDestructed, IsDestructed };
    enum IsZeroed_t { IsNotZeroed, IsZeroed };
    enum NeedsGCBarriers_t { DoesNotNeedGCBarriers, NeedsGCBarriers };
  
    /// ignored - Returns an aggregate value slot indicating that the
    /// aggregate value is being ignored.
    static AggValueSlot ignored() {
      return forAddr(nullptr, CharUnits(), Qualifiers(), IsNotDestructed,
                     DoesNotNeedGCBarriers, IsNotAliased);
    }
  
    /// forAddr - Make a slot for an aggregate value.
    ///
    /// \param quals - The qualifiers that dictate how the slot should
    /// be initialied. Only 'volatile' and the Objective-C lifetime
    /// qualifiers matter.
    ///
    /// \param isDestructed - true if something else is responsible
    ///   for calling destructors on this object
    /// \param needsGC - true if the slot is potentially located
    ///   somewhere that ObjC GC calls should be emitted for
    static AggValueSlot forAddr(llvm::Value *addr, CharUnits align,
                                Qualifiers quals,
                                IsDestructed_t isDestructed,
                                NeedsGCBarriers_t needsGC,
                                IsAliased_t isAliased,
                                IsZeroed_t isZeroed = IsNotZeroed) {
      AggValueSlot AV;
      AV.Addr = addr;
      AV.Alignment = align.getQuantity();
      AV.Quals = quals;
      AV.DestructedFlag = isDestructed;
      AV.ObjCGCFlag = needsGC;
      AV.ZeroedFlag = isZeroed;
      AV.AliasedFlag = isAliased;
      return AV;
    }
  
    static AggValueSlot forLValue(const LValue &LV,
                                  IsDestructed_t isDestructed,
                                  NeedsGCBarriers_t needsGC,
                                  IsAliased_t isAliased,
                                  IsZeroed_t isZeroed = IsNotZeroed) {
      return forAddr(LV.getAddress(), LV.getAlignment(),
                     LV.getQuals(), isDestructed, needsGC, isAliased, isZeroed);
    }
  
    IsDestructed_t isExternallyDestructed() const {
      return IsDestructed_t(DestructedFlag);
    }
    void setExternallyDestructed(bool destructed = true) {
      DestructedFlag = destructed;
    }
  
    Qualifiers getQualifiers() const { return Quals; }
  
    bool isVolatile() const {
      return Quals.hasVolatile();
    }
  
    void setVolatile(bool flag) {
      Quals.setVolatile(flag);
    }
  
    Qualifiers::ObjCLifetime getObjCLifetime() const {
      return Quals.getObjCLifetime();
    }
  
    NeedsGCBarriers_t requiresGCollection() const {
      return NeedsGCBarriers_t(ObjCGCFlag);
    }
  
    llvm::Value *getAddr() const {
      return Addr;
    }
  
    bool isIgnored() const {
      return Addr == nullptr;
    }
  
    CharUnits getAlignment() const {
      return CharUnits::fromQuantity(Alignment);
    }
  
    IsAliased_t isPotentiallyAliased() const {
      return IsAliased_t(AliasedFlag);
    }
  
    // FIXME: Alignment?
    RValue asRValue() const {
      return RValue::getAggregate(getAddr(), isVolatile());
    }
  
    void setZeroed(bool V = true) { ZeroedFlag = V; }
    IsZeroed_t isZeroed() const {
      return IsZeroed_t(ZeroedFlag);
    }
  };
  
  }  // end namespace CodeGen
  }  // end namespace clang
  
  #endif
  