lib/AST/ExprConstant.cpp - platform/external/clang - Gitiles

 //===--- ExprConstant.cpp - Expression Constant Evaluator -----------------===//
 //
 //                     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 Expr constant evaluator.
 //
 //===----------------------------------------------------------------------===//

 #include "clang/AST/APValue.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/Basic/TargetInfo.h"
 #include "llvm/Support/Compiler.h"
 using namespace clang;
 using llvm::APSInt;

 #define USE_NEW_EVALUATOR 0

 static bool CalcFakeICEVal(const Expr *Expr,
                            llvm::APSInt &Result,
                            ASTContext &Context) {
   // Calculate the value of an expression that has a calculatable
   // value, but isn't an ICE. Currently, this only supports
   // a very narrow set of extensions, but it can be expanded if needed.
   if (const ParenExpr *PE = dyn_cast<ParenExpr>(Expr))
     return CalcFakeICEVal(PE->getSubExpr(), Result, Context);

   if (const CastExpr *CE = dyn_cast<CastExpr>(Expr)) {
     QualType CETy = CE->getType();
     if ((CETy->isIntegralType() && !CETy->isBooleanType()) ||
         CETy->isPointerType()) {
       if (CalcFakeICEVal(CE->getSubExpr(), Result, Context)) {
         Result.extOrTrunc(Context.getTypeSize(CETy));
         // FIXME: This assumes pointers are signed.
         Result.setIsSigned(CETy->isSignedIntegerType() ||
                            CETy->isPointerType());
         return true;
       }
     }
   }

   if (Expr->getType()->isIntegralType())
     return Expr->isIntegerConstantExpr(Result, Context);

   return false;
 }

 static bool EvaluatePointer(const Expr *E, APValue &Result, ASTContext &Ctx);
 static bool EvaluateInteger(const Expr *E, APSInt  &Result, ASTContext &Ctx);


 //===----------------------------------------------------------------------===//
 // Pointer Evaluation
 //===----------------------------------------------------------------------===//

 namespace {
 class VISIBILITY_HIDDEN PointerExprEvaluator
   : public StmtVisitor<PointerExprEvaluator, APValue> {
   ASTContext &Ctx;
 public:

   PointerExprEvaluator(ASTContext &ctx) : Ctx(ctx) {}

   APValue VisitStmt(Stmt *S) {
     // FIXME: Remove this when we support more expressions.
     printf("Unhandled pointer statement\n");
     S->dump();
     return APValue();
   }

   APValue VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }

   APValue VisitBinaryOperator(const BinaryOperator *E);
   APValue VisitCastExpr(const CastExpr* E);
 };
 } // end anonymous namespace

 static bool EvaluatePointer(const Expr* E, APValue& Result, ASTContext &Ctx) {
   if (!E->getType()->isPointerType())
     return false;
   Result = PointerExprEvaluator(Ctx).Visit(const_cast<Expr*>(E));
   return Result.isLValue();
 }

 APValue PointerExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
   if (E->getOpcode() != BinaryOperator::Add &&
       E->getOpcode() != BinaryOperator::Sub)
     return APValue();

   const Expr *PExp = E->getLHS();
   const Expr *IExp = E->getRHS();
   if (IExp->getType()->isPointerType())
     std::swap(PExp, IExp);

   APValue ResultLValue;
   if (!EvaluatePointer(PExp, ResultLValue, Ctx))
     return APValue();

   llvm::APSInt AdditionalOffset(32);
   if (!EvaluateInteger(IExp, AdditionalOffset, Ctx))
     return APValue();

   uint64_t Offset = ResultLValue.getLValueOffset();
   if (E->getOpcode() == BinaryOperator::Add)
     Offset += AdditionalOffset.getZExtValue();
   else
     Offset -= AdditionalOffset.getZExtValue();

   return APValue(ResultLValue.getLValueBase(), Offset);
 }


 APValue PointerExprEvaluator::VisitCastExpr(const CastExpr* E) {
   const Expr* SubExpr = E->getSubExpr();

    // Check for pointer->pointer cast
   if (SubExpr->getType()->isPointerType()) {
     APValue Result;
     if (EvaluatePointer(SubExpr, Result, Ctx))
       return Result;
     return APValue();
   }

   if (SubExpr->getType()->isArithmeticType()) {
     llvm::APSInt Result(32);
     if (EvaluateInteger(SubExpr, Result, Ctx)) {
       Result.extOrTrunc(static_cast<uint32_t>(Ctx.getTypeSize(E->getType())));
       return APValue(0, Result.getZExtValue());
     }
   }

   assert(0 && "Unhandled cast");
   return APValue();
 }


 //===----------------------------------------------------------------------===//
 // Integer Evaluation
 //===----------------------------------------------------------------------===//

 namespace {
 class VISIBILITY_HIDDEN IntExprEvaluator
   : public StmtVisitor<IntExprEvaluator, bool> {
   ASTContext &Ctx;
   APSInt &Result;
 public:
   IntExprEvaluator(ASTContext &ctx, APSInt &result) : Ctx(ctx), Result(result){}

   unsigned getIntTypeSizeInBits(QualType T) const {
     return (unsigned)Ctx.getTypeSize(T);
   }

   //===--------------------------------------------------------------------===//
   //                            Visitor Methods
   //===--------------------------------------------------------------------===//

   bool VisitStmt(Stmt *S) {
     // FIXME: Remove this when we support more expressions.
     printf("unhandled int expression");
     S->dump();
     return false;
   }

   bool VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }

   bool VisitBinaryOperator(const BinaryOperator *E);

   bool VisitUnaryOperator(const UnaryOperator *E);

   bool VisitCastExpr(const CastExpr* E) {
     return HandleCast(E->getSubExpr(), E->getType());
   }
   bool VisitImplicitCastExpr(const ImplicitCastExpr* E) {
     return HandleCast(E->getSubExpr(), E->getType());
   }
   bool VisitSizeOfAlignOfTypeExpr(const SizeOfAlignOfTypeExpr *E) {
     return EvaluateSizeAlignOf(E->isSizeOf(),E->getArgumentType(),E->getType());
   }

   bool VisitIntegerLiteral(const IntegerLiteral *E) {
     Result = E->getValue();
     return true;
   }
 private:
   bool HandleCast(const Expr* SubExpr, QualType DestType);
   bool EvaluateSizeAlignOf(bool isSizeOf, QualType SrcTy, QualType DstTy);
 };
 } // end anonymous namespace

 static bool EvaluateInteger(const Expr* E, APSInt &Result, ASTContext &Ctx) {
   return IntExprEvaluator(Ctx, Result).Visit(const_cast<Expr*>(E));
 }


 bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
   // The LHS of a constant expr is always evaluated and needed.
   llvm::APSInt RHS(32);
   if (!Visit(E->getLHS()) || !EvaluateInteger(E->getRHS(), RHS, Ctx))
     return false;

   switch (E->getOpcode()) {
   default: return false;
   case BinaryOperator::Mul: Result *= RHS; break;
   case BinaryOperator::Add: Result += RHS; break;
   case BinaryOperator::Sub: Result -= RHS; break;
   case BinaryOperator::And: Result &= RHS; break;
   case BinaryOperator::Xor: Result ^= RHS; break;
   case BinaryOperator::Or:  Result |= RHS; break;
   case BinaryOperator::Div:
     if (RHS == 0) return false;
     Result /= RHS;
     break;
   case BinaryOperator::Rem:
     if (RHS == 0) return false;
     Result %= RHS;
     break;
   case BinaryOperator::Shl:
     Result <<= (unsigned)RHS.getLimitedValue(Result.getBitWidth()-1);
     break;
   case BinaryOperator::Shr:
     Result >>= (unsigned)RHS.getLimitedValue(Result.getBitWidth()-1);
     break;

   case BinaryOperator::LT:
     Result = Result < RHS;
     Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
     break;
   case BinaryOperator::GT:
     Result = Result > RHS;
     Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
     break;
   case BinaryOperator::LE:
     Result = Result <= RHS;
     Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
     break;
   case BinaryOperator::GE:
     Result = Result >= RHS;
     Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
     break;
   case BinaryOperator::EQ:
     Result = Result == RHS;
     Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
     break;
   case BinaryOperator::NE:
     Result = Result != RHS;
     Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
     break;

   case BinaryOperator::Comma:
     // C99 6.6p3: "shall not contain assignment, ..., or comma operators,
     // *except* when they are contained within a subexpression that is not
     // evaluated".  Note that Assignment can never happen due to constraints
     // on the LHS subexpr, so we don't need to check it here.
     // FIXME: Need to come up with an efficient way to deal with the C99
     // rules on evaluation while still evaluating this.  Maybe a
     // "evaluated comma" out parameter?
     return false;
   }

   Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
   return true;
 }

 /// EvaluateSizeAlignOf - Evaluate sizeof(SrcTy) or alignof(SrcTy) with a result
 /// as a DstTy type.
 bool IntExprEvaluator::EvaluateSizeAlignOf(bool isSizeOf, QualType SrcTy,
                                            QualType DstTy) {
   // Return the result in the right width.
   Result.zextOrTrunc(getIntTypeSizeInBits(DstTy));
   Result.setIsUnsigned(DstTy->isUnsignedIntegerType());

   // sizeof(void) and __alignof__(void) = 1 as a gcc extension.
   if (SrcTy->isVoidType())
     Result = 1;

   // sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
   if (!SrcTy->isConstantSizeType()) {
     // FIXME: Should we attempt to evaluate this?
     return false;
   }

   // GCC extension: sizeof(function) = 1.
   if (SrcTy->isFunctionType()) {
     // FIXME: AlignOf shouldn't be unconditionally 4!
     Result = isSizeOf ? 1 : 4;
     return true;
   }

   // Get information about the size or align.
   unsigned CharSize = Ctx.Target.getCharWidth();
   if (isSizeOf)
     Result = getIntTypeSizeInBits(SrcTy) / CharSize;
   else
     Result = Ctx.getTypeAlign(SrcTy) / CharSize;
   return true;
 }

 bool IntExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
   if (E->isOffsetOfOp()) {
     Result = E->evaluateOffsetOf(Ctx);
     Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
     return true;
   }

   if (E->isSizeOfAlignOfOp())
     return EvaluateSizeAlignOf(E->getOpcode() == UnaryOperator::SizeOf,
                                E->getSubExpr()->getType(), E->getType());

   // Get the operand value.
   if (!EvaluateInteger(E->getSubExpr(), Result, Ctx))
     return false;

   switch (E->getOpcode()) {
     // Address, indirect, pre/post inc/dec, etc are not valid constant exprs.
     // See C99 6.6p3.
   default:
     return false;
   case UnaryOperator::LNot: {
     bool Val = Result == 0;
     Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
     Result = Val;
     break;
   }
   case UnaryOperator::Extension:
   case UnaryOperator::Plus:
     // The result is always just the subexpr
     break;
   case UnaryOperator::Minus:
     Result = -Result;
     break;
   case UnaryOperator::Not:
     Result = ~Result;
     break;
   }

   Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
   return true;
 }

 bool IntExprEvaluator::HandleCast(const Expr* SubExpr, QualType DestType) {
   unsigned DestWidth = getIntTypeSizeInBits(DestType);

   // Handle simple integer->integer casts.
   if (SubExpr->getType()->isIntegerType()) {
     if (!EvaluateInteger(SubExpr, Result, Ctx))
       return false;

     // Figure out if this is a truncate, extend or noop cast.
     // If the input is signed, do a sign extend, noop, or truncate.
     if (DestType->isBooleanType()) {
       // Conversion to bool compares against zero.
       Result = Result != 0;
       Result.zextOrTrunc(DestWidth);
     } else
       Result.extOrTrunc(DestWidth);
   } else if (SubExpr->getType()->isPointerType()) {
     APValue LV;
     if (!EvaluatePointer(SubExpr, LV, Ctx))
       return false;
     if (LV.getLValueBase())
       return false;

     Result.extOrTrunc(DestWidth);
     Result = LV.getLValueOffset();
   } else {
     assert(0 && "Unhandled cast!");
   }

   Result.setIsUnsigned(DestType->isUnsignedIntegerType());
   return true;
 }

 //===----------------------------------------------------------------------===//
 // Top level TryEvaluate.
 //===----------------------------------------------------------------------===//

 bool Expr::tryEvaluate(APValue &Result, ASTContext &Ctx) const {
   llvm::APSInt sInt(32);
 #if USE_NEW_EVALUATOR
   if (getType()->isIntegerType()) {
     if (EvaluateInteger(this, sInt, Ctx)) {
       Result = APValue(sInt);
       return true;
     }
   } else
     return false;

 #else
   if (CalcFakeICEVal(this, sInt, Ctx)) {
     Result = APValue(sInt);
     return true;
   }
 #endif

   return false;
 }
	//===--- ExprConstant.cpp - Expression Constant Evaluator -----------------===//
	//
	// 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 Expr constant evaluator.
	//
	//===----------------------------------------------------------------------===//

	#include "clang/AST/APValue.h"
	#include "clang/AST/ASTContext.h"
	#include "clang/AST/Expr.h"
	#include "clang/AST/StmtVisitor.h"
	#include "clang/Basic/TargetInfo.h"
	#include "llvm/Support/Compiler.h"
	using namespace clang;
	using llvm::APSInt;

	#define USE_NEW_EVALUATOR 0

	static bool CalcFakeICEVal(const Expr *Expr,
	llvm::APSInt &Result,
	ASTContext &Context) {
	// Calculate the value of an expression that has a calculatable
	// value, but isn't an ICE. Currently, this only supports
	// a very narrow set of extensions, but it can be expanded if needed.
	if (const ParenExpr *PE = dyn_cast<ParenExpr>(Expr))
	return CalcFakeICEVal(PE->getSubExpr(), Result, Context);

	if (const CastExpr *CE = dyn_cast<CastExpr>(Expr)) {
	QualType CETy = CE->getType();
	if ((CETy->isIntegralType() && !CETy->isBooleanType()) \|\|
	CETy->isPointerType()) {
	if (CalcFakeICEVal(CE->getSubExpr(), Result, Context)) {
	Result.extOrTrunc(Context.getTypeSize(CETy));
	// FIXME: This assumes pointers are signed.
	Result.setIsSigned(CETy->isSignedIntegerType() \|\|
	CETy->isPointerType());
	return true;
	}
	}
	}

	if (Expr->getType()->isIntegralType())
	return Expr->isIntegerConstantExpr(Result, Context);

	return false;
	}

	static bool EvaluatePointer(const Expr *E, APValue &Result, ASTContext &Ctx);
	static bool EvaluateInteger(const Expr *E, APSInt &Result, ASTContext &Ctx);


	//===----------------------------------------------------------------------===//
	// Pointer Evaluation
	//===----------------------------------------------------------------------===//

	namespace {
	class VISIBILITY_HIDDEN PointerExprEvaluator
	: public StmtVisitor<PointerExprEvaluator, APValue> {
	ASTContext &Ctx;
	public:

	PointerExprEvaluator(ASTContext &ctx) : Ctx(ctx) {}

	APValue VisitStmt(Stmt *S) {
	// FIXME: Remove this when we support more expressions.
	printf("Unhandled pointer statement\n");
	S->dump();
	return APValue();
	}

	APValue VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }

	APValue VisitBinaryOperator(const BinaryOperator *E);
	APValue VisitCastExpr(const CastExpr* E);
	};
	} // end anonymous namespace

	static bool EvaluatePointer(const Expr* E, APValue& Result, ASTContext &Ctx) {
	if (!E->getType()->isPointerType())
	return false;
	Result = PointerExprEvaluator(Ctx).Visit(const_cast<Expr*>(E));
	return Result.isLValue();
	}

	APValue PointerExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
	if (E->getOpcode() != BinaryOperator::Add &&
	E->getOpcode() != BinaryOperator::Sub)
	return APValue();

	const Expr *PExp = E->getLHS();
	const Expr *IExp = E->getRHS();
	if (IExp->getType()->isPointerType())
	std::swap(PExp, IExp);

	APValue ResultLValue;
	if (!EvaluatePointer(PExp, ResultLValue, Ctx))
	return APValue();

	llvm::APSInt AdditionalOffset(32);
	if (!EvaluateInteger(IExp, AdditionalOffset, Ctx))
	return APValue();

	uint64_t Offset = ResultLValue.getLValueOffset();
	if (E->getOpcode() == BinaryOperator::Add)
	Offset += AdditionalOffset.getZExtValue();
	else
	Offset -= AdditionalOffset.getZExtValue();

	return APValue(ResultLValue.getLValueBase(), Offset);
	}


	APValue PointerExprEvaluator::VisitCastExpr(const CastExpr* E) {
	const Expr* SubExpr = E->getSubExpr();

	// Check for pointer->pointer cast
	if (SubExpr->getType()->isPointerType()) {
	APValue Result;
	if (EvaluatePointer(SubExpr, Result, Ctx))
	return Result;
	return APValue();
	}

	if (SubExpr->getType()->isArithmeticType()) {
	llvm::APSInt Result(32);
	if (EvaluateInteger(SubExpr, Result, Ctx)) {
	Result.extOrTrunc(static_cast<uint32_t>(Ctx.getTypeSize(E->getType())));
	return APValue(0, Result.getZExtValue());
	}
	}

	assert(0 && "Unhandled cast");
	return APValue();
	}


	//===----------------------------------------------------------------------===//
	// Integer Evaluation
	//===----------------------------------------------------------------------===//

	namespace {
	class VISIBILITY_HIDDEN IntExprEvaluator
	: public StmtVisitor<IntExprEvaluator, bool> {
	ASTContext &Ctx;
	APSInt &Result;
	public:
	IntExprEvaluator(ASTContext &ctx, APSInt &result) : Ctx(ctx), Result(result){}

	unsigned getIntTypeSizeInBits(QualType T) const {
	return (unsigned)Ctx.getTypeSize(T);
	}

	//===--------------------------------------------------------------------===//
	// Visitor Methods
	//===--------------------------------------------------------------------===//

	bool VisitStmt(Stmt *S) {
	// FIXME: Remove this when we support more expressions.
	printf("unhandled int expression");
	S->dump();
	return false;
	}

	bool VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }

	bool VisitBinaryOperator(const BinaryOperator *E);

	bool VisitUnaryOperator(const UnaryOperator *E);

	bool VisitCastExpr(const CastExpr* E) {
	return HandleCast(E->getSubExpr(), E->getType());
	}
	bool VisitImplicitCastExpr(const ImplicitCastExpr* E) {
	return HandleCast(E->getSubExpr(), E->getType());
	}
	bool VisitSizeOfAlignOfTypeExpr(const SizeOfAlignOfTypeExpr *E) {
	return EvaluateSizeAlignOf(E->isSizeOf(),E->getArgumentType(),E->getType());
	}

	bool VisitIntegerLiteral(const IntegerLiteral *E) {
	Result = E->getValue();
	return true;
	}
	private:
	bool HandleCast(const Expr* SubExpr, QualType DestType);
	bool EvaluateSizeAlignOf(bool isSizeOf, QualType SrcTy, QualType DstTy);
	};
	} // end anonymous namespace

	static bool EvaluateInteger(const Expr* E, APSInt &Result, ASTContext &Ctx) {
	return IntExprEvaluator(Ctx, Result).Visit(const_cast<Expr*>(E));
	}


	bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
	// The LHS of a constant expr is always evaluated and needed.
	llvm::APSInt RHS(32);
	if (!Visit(E->getLHS()) \|\| !EvaluateInteger(E->getRHS(), RHS, Ctx))
	return false;

	switch (E->getOpcode()) {
	default: return false;
	case BinaryOperator::Mul: Result *= RHS; break;
	case BinaryOperator::Add: Result += RHS; break;
	case BinaryOperator::Sub: Result -= RHS; break;
	case BinaryOperator::And: Result &= RHS; break;
	case BinaryOperator::Xor: Result ^= RHS; break;
	case BinaryOperator::Or: Result \|= RHS; break;
	case BinaryOperator::Div:
	if (RHS == 0) return false;
	Result /= RHS;
	break;
	case BinaryOperator::Rem:
	if (RHS == 0) return false;
	Result %= RHS;
	break;
	case BinaryOperator::Shl:
	Result <<= (unsigned)RHS.getLimitedValue(Result.getBitWidth()-1);
	break;
	case BinaryOperator::Shr:
	Result >>= (unsigned)RHS.getLimitedValue(Result.getBitWidth()-1);
	break;

	case BinaryOperator::LT:
	Result = Result < RHS;
	Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
	break;
	case BinaryOperator::GT:
	Result = Result > RHS;
	Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
	break;
	case BinaryOperator::LE:
	Result = Result <= RHS;
	Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
	break;
	case BinaryOperator::GE:
	Result = Result >= RHS;
	Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
	break;
	case BinaryOperator::EQ:
	Result = Result == RHS;
	Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
	break;
	case BinaryOperator::NE:
	Result = Result != RHS;
	Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
	break;

	case BinaryOperator::Comma:
	// C99 6.6p3: "shall not contain assignment, ..., or comma operators,
	// except when they are contained within a subexpression that is not
	// evaluated". Note that Assignment can never happen due to constraints
	// on the LHS subexpr, so we don't need to check it here.
	// FIXME: Need to come up with an efficient way to deal with the C99
	// rules on evaluation while still evaluating this. Maybe a
	// "evaluated comma" out parameter?
	return false;
	}

	Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
	return true;
	}

	/// EvaluateSizeAlignOf - Evaluate sizeof(SrcTy) or alignof(SrcTy) with a result
	/// as a DstTy type.
	bool IntExprEvaluator::EvaluateSizeAlignOf(bool isSizeOf, QualType SrcTy,
	QualType DstTy) {
	// Return the result in the right width.
	Result.zextOrTrunc(getIntTypeSizeInBits(DstTy));
	Result.setIsUnsigned(DstTy->isUnsignedIntegerType());

	// sizeof(void) and __alignof__(void) = 1 as a gcc extension.
	if (SrcTy->isVoidType())
	Result = 1;

	// sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
	if (!SrcTy->isConstantSizeType()) {
	// FIXME: Should we attempt to evaluate this?
	return false;
	}

	// GCC extension: sizeof(function) = 1.
	if (SrcTy->isFunctionType()) {
	// FIXME: AlignOf shouldn't be unconditionally 4!
	Result = isSizeOf ? 1 : 4;
	return true;
	}

	// Get information about the size or align.
	unsigned CharSize = Ctx.Target.getCharWidth();
	if (isSizeOf)
	Result = getIntTypeSizeInBits(SrcTy) / CharSize;
	else
	Result = Ctx.getTypeAlign(SrcTy) / CharSize;
	return true;
	}

	bool IntExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
	if (E->isOffsetOfOp()) {
	Result = E->evaluateOffsetOf(Ctx);
	Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
	return true;
	}

	if (E->isSizeOfAlignOfOp())
	return EvaluateSizeAlignOf(E->getOpcode() == UnaryOperator::SizeOf,
	E->getSubExpr()->getType(), E->getType());

	// Get the operand value.
	if (!EvaluateInteger(E->getSubExpr(), Result, Ctx))
	return false;

	switch (E->getOpcode()) {
	// Address, indirect, pre/post inc/dec, etc are not valid constant exprs.
	// See C99 6.6p3.
	default:
	return false;
	case UnaryOperator::LNot: {
	bool Val = Result == 0;
	Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
	Result = Val;
	break;
	}
	case UnaryOperator::Extension:
	case UnaryOperator::Plus:
	// The result is always just the subexpr
	break;
	case UnaryOperator::Minus:
	Result = -Result;
	break;
	case UnaryOperator::Not:
	Result = ~Result;
	break;
	}

	Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
	return true;
	}

	bool IntExprEvaluator::HandleCast(const Expr* SubExpr, QualType DestType) {
	unsigned DestWidth = getIntTypeSizeInBits(DestType);

	// Handle simple integer->integer casts.
	if (SubExpr->getType()->isIntegerType()) {
	if (!EvaluateInteger(SubExpr, Result, Ctx))
	return false;

	// Figure out if this is a truncate, extend or noop cast.
	// If the input is signed, do a sign extend, noop, or truncate.
	if (DestType->isBooleanType()) {
	// Conversion to bool compares against zero.
	Result = Result != 0;
	Result.zextOrTrunc(DestWidth);
	} else
	Result.extOrTrunc(DestWidth);
	} else if (SubExpr->getType()->isPointerType()) {
	APValue LV;
	if (!EvaluatePointer(SubExpr, LV, Ctx))
	return false;
	if (LV.getLValueBase())
	return false;

	Result.extOrTrunc(DestWidth);
	Result = LV.getLValueOffset();
	} else {
	assert(0 && "Unhandled cast!");
	}

	Result.setIsUnsigned(DestType->isUnsignedIntegerType());
	return true;
	}

	//===----------------------------------------------------------------------===//
	// Top level TryEvaluate.
	//===----------------------------------------------------------------------===//

	bool Expr::tryEvaluate(APValue &Result, ASTContext &Ctx) const {
	llvm::APSInt sInt(32);
	#if USE_NEW_EVALUATOR
	if (getType()->isIntegerType()) {
	if (EvaluateInteger(this, sInt, Ctx)) {
	Result = APValue(sInt);
	return true;
	}
	} else
	return false;

	#else
	if (CalcFakeICEVal(this, sInt, Ctx)) {
	Result = APValue(sInt);
	return true;
	}
	#endif

	return false;
	}