lib/CodeGen/CGValue.h

//===-- 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 CLANG_CODEGEN_CGVALUE_H
#define CLANG_CODEGEN_CGVALUE_H

#include "clang/AST/Type.h"

namespace llvm {
  class Constant;
  class Value;
}

namespace clang {
  class ObjCPropertyRefExpr;

namespace CodeGen {

/// 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 {
  llvm::Value *V1, *V2;
  // TODO: Encode this into the low bit of pointer for more efficient
  // return-by-value.
  enum { Scalar, Complex, Aggregate } Flavor;
  
  // FIXME: Aggregate rvalues need to retain information about whether they are
  // volatile or not.
public:
  
  bool isScalar() const { return Flavor == Scalar; }
  bool isComplex() const { return Flavor == Complex; }
  bool isAggregate() const { return Flavor == Aggregate; }
  
  /// getScalar() - Return the Value* of this scalar value.
  llvm::Value *getScalarVal() const {
    assert(isScalar() && "Not a scalar!");
    return V1;
  }

  /// getComplexVal - Return the real/imag components of this complex value.
  ///
  std::pair<llvm::Value *, llvm::Value *> getComplexVal() const {
    return std::pair<llvm::Value *, llvm::Value *>(V1, V2);
  }
  
  /// getAggregateAddr() - Return the Value* of the address of the aggregate.
  llvm::Value *getAggregateAddr() const {
    assert(isAggregate() && "Not an aggregate!");
    return V1;
  }
  
  static RValue get(llvm::Value *V) {
    RValue ER;
    ER.V1 = V;
    ER.Flavor = Scalar;
    return ER;
  }
  static RValue getComplex(llvm::Value *V1, llvm::Value *V2) {
    RValue ER;
    ER.V1 = V1;
    ER.V2 = V2;
    ER.Flavor = Complex;
    return ER;
  }
  static RValue getComplex(const std::pair<llvm::Value *, llvm::Value *> &C) {
    RValue ER;
    ER.V1 = C.first;
    ER.V2 = C.second;
    ER.Flavor = Complex;
    return ER;
  }
  static RValue getAggregate(llvm::Value *V) {
    RValue ER;
    ER.V1 = V;
    ER.Flavor = Aggregate;
    return ER;
  }
};


/// 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 {
  // FIXME: alignment?
  
  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
    PropertyRef   // This is an Objective-C property reference, use
                  // getPropertyRefExpr
  } LVType;

  enum ObjCType {
    None = 0,	// object with no gc attribute.
    Weak,	// __weak object expression
    Strong      // __strong object expression
  };
  
  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
    struct {
      unsigned short StartBit;
      unsigned short Size;
      bool IsSigned;
    } BitfieldData;

    // Obj-C property reference expression
    const ObjCPropertyRefExpr *PropertyRefExpr;
  };

  bool Volatile:1;
  // FIXME: set but never used, what effect should it have?
  bool Restrict:1;

  // objective-c's gc attributes
  unsigned ObjCType : 2;  

private:
  static void SetQualifiers(unsigned Qualifiers, LValue& R) {
    R.Volatile = (Qualifiers&QualType::Volatile)!=0;
    R.Restrict = (Qualifiers&QualType::Restrict)!=0;
    // FIXME: Convenient place to set objc flags to 0. This
    // should really be done in a user-defined constructor instead.
    R.ObjCType = None;
  }
  
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 isPropertyRef() const { return LVType == PropertyRef; }

  bool isVolatileQualified() const { return Volatile; }
  bool isRestrictQualified() const { return Restrict; }
  
  bool isObjCWeak() const { return ObjCType == Weak; }
  bool isObjCStrong() const { return ObjCType == Strong; }
  
  static void SetObjCType(unsigned WeakVal, unsigned StrongVal, LValue& R) {
    if (WeakVal)
      R.ObjCType = Weak;
    else if (StrongVal)
      R.ObjCType = Strong;
  }
  
  // simple lvalue
  llvm::Value *getAddress() const { assert(isSimple()); return V; }
  // 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; }
  unsigned short getBitfieldStartBit() const {
    assert(isBitfield());
    return BitfieldData.StartBit;
  }
  unsigned short getBitfieldSize() const {
    assert(isBitfield());
    return BitfieldData.Size;
  }
  bool isBitfieldSigned() const {
    assert(isBitfield());
    return BitfieldData.IsSigned;
  }
  // property ref lvalue
  const ObjCPropertyRefExpr *getPropertyRefExpr() const {
    assert(isPropertyRef());
    return PropertyRefExpr;
  }

  static LValue MakeAddr(llvm::Value *V, unsigned Qualifiers) {
    LValue R;
    R.LVType = Simple;
    R.V = V;
    SetQualifiers(Qualifiers,R);
    return R;
  }
  
  static LValue MakeVectorElt(llvm::Value *Vec, llvm::Value *Idx,
                              unsigned Qualifiers) {
    LValue R;
    R.LVType = VectorElt;
    R.V = Vec;
    R.VectorIdx = Idx;
    SetQualifiers(Qualifiers,R);
    return R;
  }
  
  static LValue MakeExtVectorElt(llvm::Value *Vec, llvm::Constant *Elts,
                                 unsigned Qualifiers) {
    LValue R;
    R.LVType = ExtVectorElt;
    R.V = Vec;
    R.VectorElts = Elts;
    SetQualifiers(Qualifiers,R);
    return R;
  }

  static LValue MakeBitfield(llvm::Value *V, unsigned short StartBit,
                             unsigned short Size, bool IsSigned,
                             unsigned Qualifiers) {
    LValue R;
    R.LVType = BitField;
    R.V = V;
    R.BitfieldData.StartBit = StartBit;
    R.BitfieldData.Size = Size;
    R.BitfieldData.IsSigned = IsSigned;
    SetQualifiers(Qualifiers,R);
    return R;
  }

  // FIXME: It is probably bad that we aren't emitting the target when
  // we build the lvalue. However, this complicates the code a bit,
  // and I haven't figured out how to make it go wrong yet.
  static LValue MakePropertyRef(const ObjCPropertyRefExpr *E,
                                unsigned Qualifiers) {
    LValue R;
    R.LVType = PropertyRef;
    R.PropertyRefExpr = E;
    SetQualifiers(Qualifiers,R);
    return R;
  }
};

}  // end namespace CodeGen
}  // end namespace clang

#endif