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diff --git a/lib/Checker/SimpleSValuator.cpp b/lib/Checker/SimpleSValuator.cpp
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+// SimpleSValuator.cpp - A basic SValuator ------------------------*- 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 SimpleSValuator, a basic implementation of SValuator.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Checker/PathSensitive/SValuator.h"
+#include "clang/Checker/PathSensitive/GRState.h"
+
+using namespace clang;
+
+namespace {
+class SimpleSValuator : public SValuator {
+protected:
+  virtual SVal EvalCastNL(NonLoc val, QualType castTy);
+  virtual SVal EvalCastL(Loc val, QualType castTy);
+
+public:
+  SimpleSValuator(ValueManager &valMgr) : SValuator(valMgr) {}
+  virtual ~SimpleSValuator() {}
+
+  virtual SVal EvalMinus(NonLoc val);
+  virtual SVal EvalComplement(NonLoc val);
+  virtual SVal EvalBinOpNN(const GRState *state, BinaryOperator::Opcode op,
+                           NonLoc lhs, NonLoc rhs, QualType resultTy);
+  virtual SVal EvalBinOpLL(BinaryOperator::Opcode op, Loc lhs, Loc rhs,
+                           QualType resultTy);
+  virtual SVal EvalBinOpLN(const GRState *state, BinaryOperator::Opcode op,
+                           Loc lhs, NonLoc rhs, QualType resultTy);
+};
+} // end anonymous namespace
+
+SValuator *clang::CreateSimpleSValuator(ValueManager &valMgr) {
+  return new SimpleSValuator(valMgr);
+}
+
+//===----------------------------------------------------------------------===//
+// Transfer function for Casts.
+//===----------------------------------------------------------------------===//
+
+SVal SimpleSValuator::EvalCastNL(NonLoc val, QualType castTy) {
+
+  bool isLocType = Loc::IsLocType(castTy);
+
+  if (nonloc::LocAsInteger *LI = dyn_cast<nonloc::LocAsInteger>(&val)) {
+    if (isLocType)
+      return LI->getLoc();
+
+    // FIXME: Correctly support promotions/truncations.
+    ASTContext &Ctx = ValMgr.getContext();
+    unsigned castSize = Ctx.getTypeSize(castTy);
+    if (castSize == LI->getNumBits())
+      return val;
+
+    return ValMgr.makeLocAsInteger(LI->getLoc(), castSize);
+  }
+
+  if (const SymExpr *se = val.getAsSymbolicExpression()) {
+    ASTContext &Ctx = ValMgr.getContext();
+    QualType T = Ctx.getCanonicalType(se->getType(Ctx));
+    if (T == Ctx.getCanonicalType(castTy))
+      return val;
+    
+    // FIXME: Remove this hack when we support symbolic truncation/extension.
+    // HACK: If both castTy and T are integers, ignore the cast.  This is
+    // not a permanent solution.  Eventually we want to precisely handle
+    // extension/truncation of symbolic integers.  This prevents us from losing
+    // precision when we assign 'x = y' and 'y' is symbolic and x and y are
+    // different integer types.
+    if (T->isIntegerType() && castTy->isIntegerType())
+      return val;
+
+    return UnknownVal();
+  }
+
+  if (!isa<nonloc::ConcreteInt>(val))
+    return UnknownVal();
+
+  // Only handle casts from integers to integers.
+  if (!isLocType && !castTy->isIntegerType())
+    return UnknownVal();
+
+  llvm::APSInt i = cast<nonloc::ConcreteInt>(val).getValue();
+  i.setIsUnsigned(castTy->isUnsignedIntegerType() || Loc::IsLocType(castTy));
+  i.extOrTrunc(ValMgr.getContext().getTypeSize(castTy));
+
+  if (isLocType)
+    return ValMgr.makeIntLocVal(i);
+  else
+    return ValMgr.makeIntVal(i);
+}
+
+SVal SimpleSValuator::EvalCastL(Loc val, QualType castTy) {
+
+  // Casts from pointers -> pointers, just return the lval.
+  //
+  // Casts from pointers -> references, just return the lval.  These
+  //   can be introduced by the frontend for corner cases, e.g
+  //   casting from va_list* to __builtin_va_list&.
+  //
+  if (Loc::IsLocType(castTy) || castTy->isReferenceType())
+    return val;
+
+  // FIXME: Handle transparent unions where a value can be "transparently"
+  //  lifted into a union type.
+  if (castTy->isUnionType())
+    return UnknownVal();
+
+  assert(castTy->isIntegerType());
+  unsigned BitWidth = ValMgr.getContext().getTypeSize(castTy);
+
+  if (!isa<loc::ConcreteInt>(val))
+    return ValMgr.makeLocAsInteger(val, BitWidth);
+
+  llvm::APSInt i = cast<loc::ConcreteInt>(val).getValue();
+  i.setIsUnsigned(castTy->isUnsignedIntegerType() || Loc::IsLocType(castTy));
+  i.extOrTrunc(BitWidth);
+  return ValMgr.makeIntVal(i);
+}
+
+//===----------------------------------------------------------------------===//
+// Transfer function for unary operators.
+//===----------------------------------------------------------------------===//
+
+SVal SimpleSValuator::EvalMinus(NonLoc val) {
+  switch (val.getSubKind()) {
+  case nonloc::ConcreteIntKind:
+    return cast<nonloc::ConcreteInt>(val).evalMinus(ValMgr);
+  default:
+    return UnknownVal();
+  }
+}
+
+SVal SimpleSValuator::EvalComplement(NonLoc X) {
+  switch (X.getSubKind()) {
+  case nonloc::ConcreteIntKind:
+    return cast<nonloc::ConcreteInt>(X).evalComplement(ValMgr);
+  default:
+    return UnknownVal();
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// Transfer function for binary operators.
+//===----------------------------------------------------------------------===//
+
+static BinaryOperator::Opcode NegateComparison(BinaryOperator::Opcode op) {
+  switch (op) {
+  default:
+    assert(false && "Invalid opcode.");
+  case BinaryOperator::LT: return BinaryOperator::GE;
+  case BinaryOperator::GT: return BinaryOperator::LE;
+  case BinaryOperator::LE: return BinaryOperator::GT;
+  case BinaryOperator::GE: return BinaryOperator::LT;
+  case BinaryOperator::EQ: return BinaryOperator::NE;
+  case BinaryOperator::NE: return BinaryOperator::EQ;
+  }
+}
+
+// Equality operators for Locs.
+// FIXME: All this logic will be revamped when we have MemRegion::getLocation()
+// implemented.
+
+static SVal EvalEquality(ValueManager &ValMgr, Loc lhs, Loc rhs, bool isEqual,
+                         QualType resultTy) {
+
+  switch (lhs.getSubKind()) {
+    default:
+      assert(false && "EQ/NE not implemented for this Loc.");
+      return UnknownVal();
+
+    case loc::ConcreteIntKind: {
+      if (SymbolRef rSym = rhs.getAsSymbol())
+        return ValMgr.makeNonLoc(rSym,
+                                 isEqual ? BinaryOperator::EQ
+                                 : BinaryOperator::NE,
+                                 cast<loc::ConcreteInt>(lhs).getValue(),
+                                 resultTy);
+      break;
+    }
+    case loc::MemRegionKind: {
+      if (SymbolRef lSym = lhs.getAsLocSymbol()) {
+        if (isa<loc::ConcreteInt>(rhs)) {
+          return ValMgr.makeNonLoc(lSym,
+                                   isEqual ? BinaryOperator::EQ
+                                   : BinaryOperator::NE,
+                                   cast<loc::ConcreteInt>(rhs).getValue(),
+                                   resultTy);
+        }
+      }
+      break;
+    }
+
+    case loc::GotoLabelKind:
+      break;
+  }
+
+  return ValMgr.makeTruthVal(isEqual ? lhs == rhs : lhs != rhs, resultTy);
+}
+
+SVal SimpleSValuator::EvalBinOpNN(const GRState *state,
+                                  BinaryOperator::Opcode op,
+                                  NonLoc lhs, NonLoc rhs,
+                                  QualType resultTy)  {
+  // Handle trivial case where left-side and right-side are the same.
+  if (lhs == rhs)
+    switch (op) {
+      default:
+        break;
+      case BinaryOperator::EQ:
+      case BinaryOperator::LE:
+      case BinaryOperator::GE:
+        return ValMgr.makeTruthVal(true, resultTy);
+      case BinaryOperator::LT:
+      case BinaryOperator::GT:
+      case BinaryOperator::NE:
+        return ValMgr.makeTruthVal(false, resultTy);
+    }
+
+  while (1) {
+    switch (lhs.getSubKind()) {
+    default:
+      return UnknownVal();
+    case nonloc::LocAsIntegerKind: {
+      Loc lhsL = cast<nonloc::LocAsInteger>(lhs).getLoc();
+      switch (rhs.getSubKind()) {
+        case nonloc::LocAsIntegerKind:
+          return EvalBinOpLL(op, lhsL, cast<nonloc::LocAsInteger>(rhs).getLoc(),
+                             resultTy);
+        case nonloc::ConcreteIntKind: {
+          // Transform the integer into a location and compare.
+          ASTContext& Ctx = ValMgr.getContext();
+          llvm::APSInt i = cast<nonloc::ConcreteInt>(rhs).getValue();
+          i.setIsUnsigned(true);
+          i.extOrTrunc(Ctx.getTypeSize(Ctx.VoidPtrTy));
+          return EvalBinOpLL(op, lhsL, ValMgr.makeLoc(i), resultTy);
+        }
+        default:
+          switch (op) {
+            case BinaryOperator::EQ:
+              return ValMgr.makeTruthVal(false, resultTy);
+            case BinaryOperator::NE:
+              return ValMgr.makeTruthVal(true, resultTy);
+            default:
+              // This case also handles pointer arithmetic.
+              return UnknownVal();
+          }
+      }
+    }
+    case nonloc::SymExprValKind: {
+      // Logical not?
+      if (!(op == BinaryOperator::EQ && rhs.isZeroConstant()))
+        return UnknownVal();
+
+      const SymExpr *symExpr =
+        cast<nonloc::SymExprVal>(lhs).getSymbolicExpression();
+
+      // Only handle ($sym op constant) for now.
+      if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(symExpr)) {
+        BinaryOperator::Opcode opc = symIntExpr->getOpcode();
+        switch (opc) {
+          case BinaryOperator::LAnd:
+          case BinaryOperator::LOr:
+            assert(false && "Logical operators handled by branching logic.");
+            return UnknownVal();
+          case BinaryOperator::Assign:
+          case BinaryOperator::MulAssign:
+          case BinaryOperator::DivAssign:
+          case BinaryOperator::RemAssign:
+          case BinaryOperator::AddAssign:
+          case BinaryOperator::SubAssign:
+          case BinaryOperator::ShlAssign:
+          case BinaryOperator::ShrAssign:
+          case BinaryOperator::AndAssign:
+          case BinaryOperator::XorAssign:
+          case BinaryOperator::OrAssign:
+          case BinaryOperator::Comma:
+            assert(false && "'=' and ',' operators handled by GRExprEngine.");
+            return UnknownVal();
+          case BinaryOperator::PtrMemD:
+          case BinaryOperator::PtrMemI:
+            assert(false && "Pointer arithmetic not handled here.");
+            return UnknownVal();
+          case BinaryOperator::Mul:
+          case BinaryOperator::Div:
+          case BinaryOperator::Rem:
+          case BinaryOperator::Add:
+          case BinaryOperator::Sub:
+          case BinaryOperator::Shl:
+          case BinaryOperator::Shr:
+          case BinaryOperator::And:
+          case BinaryOperator::Xor:
+          case BinaryOperator::Or:
+            // Not handled yet.
+            return UnknownVal();
+          case BinaryOperator::LT:
+          case BinaryOperator::GT:
+          case BinaryOperator::LE:
+          case BinaryOperator::GE:
+          case BinaryOperator::EQ:
+          case BinaryOperator::NE:
+            opc = NegateComparison(opc);
+            assert(symIntExpr->getType(ValMgr.getContext()) == resultTy);
+            return ValMgr.makeNonLoc(symIntExpr->getLHS(), opc,
+                                     symIntExpr->getRHS(), resultTy);
+        }
+      }
+    }
+    case nonloc::ConcreteIntKind: {
+      if (isa<nonloc::ConcreteInt>(rhs)) {
+        const nonloc::ConcreteInt& lhsInt = cast<nonloc::ConcreteInt>(lhs);
+        return lhsInt.evalBinOp(ValMgr, op, cast<nonloc::ConcreteInt>(rhs));
+      }
+      else {
+        // Swap the left and right sides and flip the operator if doing so
+        // allows us to better reason about the expression (this is a form
+        // of expression canonicalization).
+        NonLoc tmp = rhs;
+        rhs = lhs;
+        lhs = tmp;
+
+        switch (op) {
+          case BinaryOperator::LT: op = BinaryOperator::GT; continue;
+          case BinaryOperator::GT: op = BinaryOperator::LT; continue;
+          case BinaryOperator::LE: op = BinaryOperator::GE; continue;
+          case BinaryOperator::GE: op = BinaryOperator::LE; continue;
+          case BinaryOperator::EQ:
+          case BinaryOperator::NE:
+          case BinaryOperator::Add:
+          case BinaryOperator::Mul:
+            continue;
+          default:
+            return UnknownVal();
+        }
+      }
+    }
+    case nonloc::SymbolValKind: {
+      nonloc::SymbolVal *slhs = cast<nonloc::SymbolVal>(&lhs);
+      SymbolRef Sym = slhs->getSymbol();
+      
+      // Does the symbol simplify to a constant?  If so, "fold" the constant
+      // by setting 'lhs' to a ConcreteInt and try again.
+      if (Sym->getType(ValMgr.getContext())->isIntegerType())
+        if (const llvm::APSInt *Constant = state->getSymVal(Sym)) {
+          // The symbol evaluates to a constant. If necessary, promote the
+          // folded constant (LHS) to the result type.
+          BasicValueFactory &BVF = ValMgr.getBasicValueFactory();
+          const llvm::APSInt &lhs_I = BVF.Convert(resultTy, *Constant);
+          lhs = nonloc::ConcreteInt(lhs_I);
+          
+          // Also promote the RHS (if necessary).
+
+          // For shifts, it necessary promote the RHS to the result type.
+          if (BinaryOperator::isShiftOp(op))
+            continue;
+          
+          // Other operators: do an implicit conversion.  This shouldn't be
+          // necessary once we support truncation/extension of symbolic values.
+          if (nonloc::ConcreteInt *rhs_I = dyn_cast<nonloc::ConcreteInt>(&rhs)){
+            rhs = nonloc::ConcreteInt(BVF.Convert(resultTy, rhs_I->getValue()));
+          }
+          
+          continue;
+        }
+      
+      if (isa<nonloc::ConcreteInt>(rhs)) {
+        return ValMgr.makeNonLoc(slhs->getSymbol(), op,
+                                 cast<nonloc::ConcreteInt>(rhs).getValue(),
+                                 resultTy);
+      }
+
+      return UnknownVal();
+    }
+    }
+  }
+}
+
+SVal SimpleSValuator::EvalBinOpLL(BinaryOperator::Opcode op, Loc lhs, Loc rhs,
+                                  QualType resultTy) {
+  switch (op) {
+    default:
+      return UnknownVal();
+    case BinaryOperator::EQ:
+    case BinaryOperator::NE:
+      return EvalEquality(ValMgr, lhs, rhs, op == BinaryOperator::EQ, resultTy);
+    case BinaryOperator::LT:
+    case BinaryOperator::GT:
+      // FIXME: Generalize.  For now, just handle the trivial case where
+      //  the two locations are identical.
+      if (lhs == rhs)
+        return ValMgr.makeTruthVal(false, resultTy);
+      return UnknownVal();
+  }
+}
+
+SVal SimpleSValuator::EvalBinOpLN(const GRState *state,
+                                  BinaryOperator::Opcode op,
+                                  Loc lhs, NonLoc rhs, QualType resultTy) {
+  // Special case: 'rhs' is an integer that has the same width as a pointer and
+  // we are using the integer location in a comparison.  Normally this cannot be
+  // triggered, but transfer functions like those for OSCommpareAndSwapBarrier32
+  // can generate comparisons that trigger this code.
+  // FIXME: Are all locations guaranteed to have pointer width?
+  if (BinaryOperator::isEqualityOp(op)) {
+    if (nonloc::ConcreteInt *rhsInt = dyn_cast<nonloc::ConcreteInt>(&rhs)) {
+      const llvm::APSInt *x = &rhsInt->getValue();
+      ASTContext &ctx = ValMgr.getContext();
+      if (ctx.getTypeSize(ctx.VoidPtrTy) == x->getBitWidth()) {
+        // Convert the signedness of the integer (if necessary).
+        if (x->isSigned())
+          x = &ValMgr.getBasicValueFactory().getValue(*x, true);
+
+        return EvalBinOpLL(op, lhs, loc::ConcreteInt(*x), resultTy);
+      }
+    }
+  }
+
+  // Delegate pointer arithmetic to the StoreManager.
+  return state->getStateManager().getStoreManager().EvalBinOp(op, lhs,
+                                                              rhs, resultTy);
+}