1 files changed, 1350 insertions, 0 deletions

diff --git a/contrib/llvm-project/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp b/contrib/llvm-project/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
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index 000000000000..84c52f53ca5e
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+++ b/contrib/llvm-project/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
@@ -0,0 +1,1350 @@
+// SimpleSValBuilder.cpp - A basic SValBuilder -----------------------*- C++ -*-
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines SimpleSValBuilder, a basic implementation of SValBuilder.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/SubEngine.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/SValVisitor.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class SimpleSValBuilder : public SValBuilder {
+protected:
+  SVal dispatchCast(SVal val, QualType castTy) override;
+  SVal evalCastFromNonLoc(NonLoc val, QualType castTy) override;
+  SVal evalCastFromLoc(Loc val, QualType castTy) override;
+
+public:
+  SimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context,
+                    ProgramStateManager &stateMgr)
+                    : SValBuilder(alloc, context, stateMgr) {}
+  ~SimpleSValBuilder() override {}
+
+  SVal evalMinus(NonLoc val) override;
+  SVal evalComplement(NonLoc val) override;
+  SVal evalBinOpNN(ProgramStateRef state, BinaryOperator::Opcode op,
+                   NonLoc lhs, NonLoc rhs, QualType resultTy) override;
+  SVal evalBinOpLL(ProgramStateRef state, BinaryOperator::Opcode op,
+                   Loc lhs, Loc rhs, QualType resultTy) override;
+  SVal evalBinOpLN(ProgramStateRef state, BinaryOperator::Opcode op,
+                   Loc lhs, NonLoc rhs, QualType resultTy) override;
+
+  /// getKnownValue - evaluates a given SVal. If the SVal has only one possible
+  ///  (integer) value, that value is returned. Otherwise, returns NULL.
+  const llvm::APSInt *getKnownValue(ProgramStateRef state, SVal V) override;
+
+  /// Recursively descends into symbolic expressions and replaces symbols
+  /// with their known values (in the sense of the getKnownValue() method).
+  SVal simplifySVal(ProgramStateRef State, SVal V) override;
+
+  SVal MakeSymIntVal(const SymExpr *LHS, BinaryOperator::Opcode op,
+                     const llvm::APSInt &RHS, QualType resultTy);
+};
+} // end anonymous namespace
+
+SValBuilder *ento::createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc,
+                                           ASTContext &context,
+                                           ProgramStateManager &stateMgr) {
+  return new SimpleSValBuilder(alloc, context, stateMgr);
+}
+
+//===----------------------------------------------------------------------===//
+// Transfer function for Casts.
+//===----------------------------------------------------------------------===//
+
+SVal SimpleSValBuilder::dispatchCast(SVal Val, QualType CastTy) {
+  assert(Val.getAs<Loc>() || Val.getAs<NonLoc>());
+  return Val.getAs<Loc>() ? evalCastFromLoc(Val.castAs<Loc>(), CastTy)
+                           : evalCastFromNonLoc(Val.castAs<NonLoc>(), CastTy);
+}
+
+SVal SimpleSValBuilder::evalCastFromNonLoc(NonLoc val, QualType castTy) {
+  bool isLocType = Loc::isLocType(castTy);
+  if (val.getAs<nonloc::PointerToMember>())
+    return val;
+
+  if (Optional<nonloc::LocAsInteger> LI = val.getAs<nonloc::LocAsInteger>()) {
+    if (isLocType)
+      return LI->getLoc();
+    // FIXME: Correctly support promotions/truncations.
+    unsigned castSize = Context.getIntWidth(castTy);
+    if (castSize == LI->getNumBits())
+      return val;
+    return makeLocAsInteger(LI->getLoc(), castSize);
+  }
+
+  if (const SymExpr *se = val.getAsSymbolicExpression()) {
+    QualType T = Context.getCanonicalType(se->getType());
+    // If types are the same or both are integers, ignore the cast.
+    // 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 (haveSameType(T, castTy))
+      return val;
+
+    if (!isLocType)
+      return makeNonLoc(se, T, castTy);
+    return UnknownVal();
+  }
+
+  // If value is a non-integer constant, produce unknown.
+  if (!val.getAs<nonloc::ConcreteInt>())
+    return UnknownVal();
+
+  // Handle casts to a boolean type.
+  if (castTy->isBooleanType()) {
+    bool b = val.castAs<nonloc::ConcreteInt>().getValue().getBoolValue();
+    return makeTruthVal(b, castTy);
+  }
+
+  // Only handle casts from integers to integers - if val is an integer constant
+  // being cast to a non-integer type, produce unknown.
+  if (!isLocType && !castTy->isIntegralOrEnumerationType())
+    return UnknownVal();
+
+  llvm::APSInt i = val.castAs<nonloc::ConcreteInt>().getValue();
+  BasicVals.getAPSIntType(castTy).apply(i);
+
+  if (isLocType)
+    return makeIntLocVal(i);
+  else
+    return makeIntVal(i);
+}
+
+SVal SimpleSValBuilder::evalCastFromLoc(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();
+
+  // Casting a Loc to a bool will almost always be true,
+  // unless this is a weak function or a symbolic region.
+  if (castTy->isBooleanType()) {
+    switch (val.getSubKind()) {
+      case loc::MemRegionValKind: {
+        const MemRegion *R = val.castAs<loc::MemRegionVal>().getRegion();
+        if (const FunctionCodeRegion *FTR = dyn_cast<FunctionCodeRegion>(R))
+          if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(FTR->getDecl()))
+            if (FD->isWeak())
+              // FIXME: Currently we are using an extent symbol here,
+              // because there are no generic region address metadata
+              // symbols to use, only content metadata.
+              return nonloc::SymbolVal(SymMgr.getExtentSymbol(FTR));
+
+        if (const SymbolicRegion *SymR = R->getSymbolicBase())
+          return makeNonLoc(SymR->getSymbol(), BO_NE,
+                            BasicVals.getZeroWithPtrWidth(), castTy);
+
+        // FALL-THROUGH
+        LLVM_FALLTHROUGH;
+      }
+
+      case loc::GotoLabelKind:
+        // Labels and non-symbolic memory regions are always true.
+        return makeTruthVal(true, castTy);
+    }
+  }
+
+  if (castTy->isIntegralOrEnumerationType()) {
+    unsigned BitWidth = Context.getIntWidth(castTy);
+
+    if (!val.getAs<loc::ConcreteInt>())
+      return makeLocAsInteger(val, BitWidth);
+
+    llvm::APSInt i = val.castAs<loc::ConcreteInt>().getValue();
+    BasicVals.getAPSIntType(castTy).apply(i);
+    return makeIntVal(i);
+  }
+
+  // All other cases: return 'UnknownVal'.  This includes casting pointers
+  // to floats, which is probably badness it itself, but this is a good
+  // intermediate solution until we do something better.
+  return UnknownVal();
+}
+
+//===----------------------------------------------------------------------===//
+// Transfer function for unary operators.
+//===----------------------------------------------------------------------===//
+
+SVal SimpleSValBuilder::evalMinus(NonLoc val) {
+  switch (val.getSubKind()) {
+  case nonloc::ConcreteIntKind:
+    return val.castAs<nonloc::ConcreteInt>().evalMinus(*this);
+  default:
+    return UnknownVal();
+  }
+}
+
+SVal SimpleSValBuilder::evalComplement(NonLoc X) {
+  switch (X.getSubKind()) {
+  case nonloc::ConcreteIntKind:
+    return X.castAs<nonloc::ConcreteInt>().evalComplement(*this);
+  default:
+    return UnknownVal();
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// Transfer function for binary operators.
+//===----------------------------------------------------------------------===//
+
+SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS,
+                                    BinaryOperator::Opcode op,
+                                    const llvm::APSInt &RHS,
+                                    QualType resultTy) {
+  bool isIdempotent = false;
+
+  // Check for a few special cases with known reductions first.
+  switch (op) {
+  default:
+    // We can't reduce this case; just treat it normally.
+    break;
+  case BO_Mul:
+    // a*0 and a*1
+    if (RHS == 0)
+      return makeIntVal(0, resultTy);
+    else if (RHS == 1)
+      isIdempotent = true;
+    break;
+  case BO_Div:
+    // a/0 and a/1
+    if (RHS == 0)
+      // This is also handled elsewhere.
+      return UndefinedVal();
+    else if (RHS == 1)
+      isIdempotent = true;
+    break;
+  case BO_Rem:
+    // a%0 and a%1
+    if (RHS == 0)
+      // This is also handled elsewhere.
+      return UndefinedVal();
+    else if (RHS == 1)
+      return makeIntVal(0, resultTy);
+    break;
+  case BO_Add:
+  case BO_Sub:
+  case BO_Shl:
+  case BO_Shr:
+  case BO_Xor:
+    // a+0, a-0, a<<0, a>>0, a^0
+    if (RHS == 0)
+      isIdempotent = true;
+    break;
+  case BO_And:
+    // a&0 and a&(~0)
+    if (RHS == 0)
+      return makeIntVal(0, resultTy);
+    else if (RHS.isAllOnesValue())
+      isIdempotent = true;
+    break;
+  case BO_Or:
+    // a|0 and a|(~0)
+    if (RHS == 0)
+      isIdempotent = true;
+    else if (RHS.isAllOnesValue()) {
+      const llvm::APSInt &Result = BasicVals.Convert(resultTy, RHS);
+      return nonloc::ConcreteInt(Result);
+    }
+    break;
+  }
+
+  // Idempotent ops (like a*1) can still change the type of an expression.
+  // Wrap the LHS up in a NonLoc again and let evalCastFromNonLoc do the
+  // dirty work.
+  if (isIdempotent)
+      return evalCastFromNonLoc(nonloc::SymbolVal(LHS), resultTy);
+
+  // If we reach this point, the expression cannot be simplified.
+  // Make a SymbolVal for the entire expression, after converting the RHS.
+  const llvm::APSInt *ConvertedRHS = &RHS;
+  if (BinaryOperator::isComparisonOp(op)) {
+    // We're looking for a type big enough to compare the symbolic value
+    // with the given constant.
+    // FIXME: This is an approximation of Sema::UsualArithmeticConversions.
+    ASTContext &Ctx = getContext();
+    QualType SymbolType = LHS->getType();
+    uint64_t ValWidth = RHS.getBitWidth();
+    uint64_t TypeWidth = Ctx.getTypeSize(SymbolType);
+
+    if (ValWidth < TypeWidth) {
+      // If the value is too small, extend it.
+      ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
+    } else if (ValWidth == TypeWidth) {
+      // If the value is signed but the symbol is unsigned, do the comparison
+      // in unsigned space. [C99 6.3.1.8]
+      // (For the opposite case, the value is already unsigned.)
+      if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType())
+        ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
+    }
+  } else
+    ConvertedRHS = &BasicVals.Convert(resultTy, RHS);
+
+  return makeNonLoc(LHS, op, *ConvertedRHS, resultTy);
+}
+
+// See if Sym is known to be a relation Rel with Bound.
+static bool isInRelation(BinaryOperator::Opcode Rel, SymbolRef Sym,
+                         llvm::APSInt Bound, ProgramStateRef State) {
+  SValBuilder &SVB = State->getStateManager().getSValBuilder();
+  SVal Result =
+      SVB.evalBinOpNN(State, Rel, nonloc::SymbolVal(Sym),
+                      nonloc::ConcreteInt(Bound), SVB.getConditionType());
+  if (auto DV = Result.getAs<DefinedSVal>()) {
+    return !State->assume(*DV, false);
+  }
+  return false;
+}
+
+// See if Sym is known to be within [min/4, max/4], where min and max
+// are the bounds of the symbol's integral type. With such symbols,
+// some manipulations can be performed without the risk of overflow.
+// assume() doesn't cause infinite recursion because we should be dealing
+// with simpler symbols on every recursive call.
+static bool isWithinConstantOverflowBounds(SymbolRef Sym,
+                                           ProgramStateRef State) {
+  SValBuilder &SVB = State->getStateManager().getSValBuilder();
+  BasicValueFactory &BV = SVB.getBasicValueFactory();
+
+  QualType T = Sym->getType();
+  assert(T->isSignedIntegerOrEnumerationType() &&
+         "This only works with signed integers!");
+  APSIntType AT = BV.getAPSIntType(T);
+
+  llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max;
+  return isInRelation(BO_LE, Sym, Max, State) &&
+         isInRelation(BO_GE, Sym, Min, State);
+}
+
+// Same for the concrete integers: see if I is within [min/4, max/4].
+static bool isWithinConstantOverflowBounds(llvm::APSInt I) {
+  APSIntType AT(I);
+  assert(!AT.isUnsigned() &&
+         "This only works with signed integers!");
+
+  llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max;
+  return (I <= Max) && (I >= -Max);
+}
+
+static std::pair<SymbolRef, llvm::APSInt>
+decomposeSymbol(SymbolRef Sym, BasicValueFactory &BV) {
+  if (const auto *SymInt = dyn_cast<SymIntExpr>(Sym))
+    if (BinaryOperator::isAdditiveOp(SymInt->getOpcode()))
+      return std::make_pair(SymInt->getLHS(),
+                            (SymInt->getOpcode() == BO_Add) ?
+                            (SymInt->getRHS()) :
+                            (-SymInt->getRHS()));
+
+  // Fail to decompose: "reduce" the problem to the "$x + 0" case.
+  return std::make_pair(Sym, BV.getValue(0, Sym->getType()));
+}
+
+// Simplify "(LSym + LInt) Op (RSym + RInt)" assuming all values are of the
+// same signed integral type and no overflows occur (which should be checked
+// by the caller).
+static NonLoc doRearrangeUnchecked(ProgramStateRef State,
+                                   BinaryOperator::Opcode Op,
+                                   SymbolRef LSym, llvm::APSInt LInt,
+                                   SymbolRef RSym, llvm::APSInt RInt) {
+  SValBuilder &SVB = State->getStateManager().getSValBuilder();
+  BasicValueFactory &BV = SVB.getBasicValueFactory();
+  SymbolManager &SymMgr = SVB.getSymbolManager();
+
+  QualType SymTy = LSym->getType();
+  assert(SymTy == RSym->getType() &&
+         "Symbols are not of the same type!");
+  assert(APSIntType(LInt) == BV.getAPSIntType(SymTy) &&
+         "Integers are not of the same type as symbols!");
+  assert(APSIntType(RInt) == BV.getAPSIntType(SymTy) &&
+         "Integers are not of the same type as symbols!");
+
+  QualType ResultTy;
+  if (BinaryOperator::isComparisonOp(Op))
+    ResultTy = SVB.getConditionType();
+  else if (BinaryOperator::isAdditiveOp(Op))
+    ResultTy = SymTy;
+  else
+    llvm_unreachable("Operation not suitable for unchecked rearrangement!");
+
+  // FIXME: Can we use assume() without getting into an infinite recursion?
+  if (LSym == RSym)
+    return SVB.evalBinOpNN(State, Op, nonloc::ConcreteInt(LInt),
+                           nonloc::ConcreteInt(RInt), ResultTy)
+        .castAs<NonLoc>();
+
+  SymbolRef ResultSym = nullptr;
+  BinaryOperator::Opcode ResultOp;
+  llvm::APSInt ResultInt;
+  if (BinaryOperator::isComparisonOp(Op)) {
+    // Prefer comparing to a non-negative number.
+    // FIXME: Maybe it'd be better to have consistency in
+    // "$x - $y" vs. "$y - $x" because those are solver's keys.
+    if (LInt > RInt) {
+      ResultSym = SymMgr.getSymSymExpr(RSym, BO_Sub, LSym, SymTy);
+      ResultOp = BinaryOperator::reverseComparisonOp(Op);
+      ResultInt = LInt - RInt; // Opposite order!
+    } else {
+      ResultSym = SymMgr.getSymSymExpr(LSym, BO_Sub, RSym, SymTy);
+      ResultOp = Op;
+      ResultInt = RInt - LInt; // Opposite order!
+    }
+  } else {
+    ResultSym = SymMgr.getSymSymExpr(LSym, Op, RSym, SymTy);
+    ResultInt = (Op == BO_Add) ? (LInt + RInt) : (LInt - RInt);
+    ResultOp = BO_Add;
+    // Bring back the cosmetic difference.
+    if (ResultInt < 0) {
+      ResultInt = -ResultInt;
+      ResultOp = BO_Sub;
+    } else if (ResultInt == 0) {
+      // Shortcut: Simplify "$x + 0" to "$x".
+      return nonloc::SymbolVal(ResultSym);
+    }
+  }
+  const llvm::APSInt &PersistentResultInt = BV.getValue(ResultInt);
+  return nonloc::SymbolVal(
+      SymMgr.getSymIntExpr(ResultSym, ResultOp, PersistentResultInt, ResultTy));
+}
+
+// Rearrange if symbol type matches the result type and if the operator is a
+// comparison operator, both symbol and constant must be within constant
+// overflow bounds.
+static bool shouldRearrange(ProgramStateRef State, BinaryOperator::Opcode Op,
+                            SymbolRef Sym, llvm::APSInt Int, QualType Ty) {
+  return Sym->getType() == Ty &&
+    (!BinaryOperator::isComparisonOp(Op) ||
+     (isWithinConstantOverflowBounds(Sym, State) &&
+      isWithinConstantOverflowBounds(Int)));
+}
+
+static Optional<NonLoc> tryRearrange(ProgramStateRef State,
+                                     BinaryOperator::Opcode Op, NonLoc Lhs,
+                                     NonLoc Rhs, QualType ResultTy) {
+  ProgramStateManager &StateMgr = State->getStateManager();
+  SValBuilder &SVB = StateMgr.getSValBuilder();
+
+  // We expect everything to be of the same type - this type.
+  QualType SingleTy;
+
+  auto &Opts =
+    StateMgr.getOwningEngine().getAnalysisManager().getAnalyzerOptions();
+
+  // FIXME: After putting complexity threshold to the symbols we can always
+  //        rearrange additive operations but rearrange comparisons only if
+  //        option is set.
+  if(!Opts.ShouldAggressivelySimplifyBinaryOperation)
+    return None;
+
+  SymbolRef LSym = Lhs.getAsSymbol();
+  if (!LSym)
+    return None;
+
+  if (BinaryOperator::isComparisonOp(Op)) {
+    SingleTy = LSym->getType();
+    if (ResultTy != SVB.getConditionType())
+      return None;
+    // Initialize SingleTy later with a symbol's type.
+  } else if (BinaryOperator::isAdditiveOp(Op)) {
+    SingleTy = ResultTy;
+    if (LSym->getType() != SingleTy)
+      return None;
+  } else {
+    // Don't rearrange other operations.
+    return None;
+  }
+
+  assert(!SingleTy.isNull() && "We should have figured out the type by now!");
+
+  // Rearrange signed symbolic expressions only
+  if (!SingleTy->isSignedIntegerOrEnumerationType())
+    return None;
+
+  SymbolRef RSym = Rhs.getAsSymbol();
+  if (!RSym || RSym->getType() != SingleTy)
+    return None;
+
+  BasicValueFactory &BV = State->getBasicVals();
+  llvm::APSInt LInt, RInt;
+  std::tie(LSym, LInt) = decomposeSymbol(LSym, BV);
+  std::tie(RSym, RInt) = decomposeSymbol(RSym, BV);
+  if (!shouldRearrange(State, Op, LSym, LInt, SingleTy) ||
+      !shouldRearrange(State, Op, RSym, RInt, SingleTy))
+    return None;
+
+  // We know that no overflows can occur anymore.
+  return doRearrangeUnchecked(State, Op, LSym, LInt, RSym, RInt);
+}
+
+SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state,
+                                  BinaryOperator::Opcode op,
+                                  NonLoc lhs, NonLoc rhs,
+                                  QualType resultTy)  {
+  NonLoc InputLHS = lhs;
+  NonLoc InputRHS = rhs;
+
+  // Handle trivial case where left-side and right-side are the same.
+  if (lhs == rhs)
+    switch (op) {
+      default:
+        break;
+      case BO_EQ:
+      case BO_LE:
+      case BO_GE:
+        return makeTruthVal(true, resultTy);
+      case BO_LT:
+      case BO_GT:
+      case BO_NE:
+        return makeTruthVal(false, resultTy);
+      case BO_Xor:
+      case BO_Sub:
+        if (resultTy->isIntegralOrEnumerationType())
+          return makeIntVal(0, resultTy);
+        return evalCastFromNonLoc(makeIntVal(0, /*isUnsigned=*/false), resultTy);
+      case BO_Or:
+      case BO_And:
+        return evalCastFromNonLoc(lhs, resultTy);
+    }
+
+  while (1) {
+    switch (lhs.getSubKind()) {
+    default:
+      return makeSymExprValNN(op, lhs, rhs, resultTy);
+    case nonloc::PointerToMemberKind: {
+      assert(rhs.getSubKind() == nonloc::PointerToMemberKind &&
+             "Both SVals should have pointer-to-member-type");
+      auto LPTM = lhs.castAs<nonloc::PointerToMember>(),
+           RPTM = rhs.castAs<nonloc::PointerToMember>();
+      auto LPTMD = LPTM.getPTMData(), RPTMD = RPTM.getPTMData();
+      switch (op) {
+        case BO_EQ:
+          return makeTruthVal(LPTMD == RPTMD, resultTy);
+        case BO_NE:
+          return makeTruthVal(LPTMD != RPTMD, resultTy);
+        default:
+          return UnknownVal();
+      }
+    }
+    case nonloc::LocAsIntegerKind: {
+      Loc lhsL = lhs.castAs<nonloc::LocAsInteger>().getLoc();
+      switch (rhs.getSubKind()) {
+        case nonloc::LocAsIntegerKind:
+          // FIXME: at the moment the implementation
+          // of modeling "pointers as integers" is not complete.
+          if (!BinaryOperator::isComparisonOp(op))
+            return UnknownVal();
+          return evalBinOpLL(state, op, lhsL,
+                             rhs.castAs<nonloc::LocAsInteger>().getLoc(),
+                             resultTy);
+        case nonloc::ConcreteIntKind: {
+          // FIXME: at the moment the implementation
+          // of modeling "pointers as integers" is not complete.
+          if (!BinaryOperator::isComparisonOp(op))
+            return UnknownVal();
+          // Transform the integer into a location and compare.
+          // FIXME: This only makes sense for comparisons. If we want to, say,
+          // add 1 to a LocAsInteger, we'd better unpack the Loc and add to it,
+          // then pack it back into a LocAsInteger.
+          llvm::APSInt i = rhs.castAs<nonloc::ConcreteInt>().getValue();
+          // If the region has a symbolic base, pay attention to the type; it
+          // might be coming from a non-default address space. For non-symbolic
+          // regions it doesn't matter that much because such comparisons would
+          // most likely evaluate to concrete false anyway. FIXME: We might
+          // still need to handle the non-comparison case.
+          if (SymbolRef lSym = lhs.getAsLocSymbol(true))
+            BasicVals.getAPSIntType(lSym->getType()).apply(i);
+          else
+            BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i);
+          return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy);
+        }
+        default:
+          switch (op) {
+            case BO_EQ:
+              return makeTruthVal(false, resultTy);
+            case BO_NE:
+              return makeTruthVal(true, resultTy);
+            default:
+              // This case also handles pointer arithmetic.
+              return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
+          }
+      }
+    }
+    case nonloc::ConcreteIntKind: {
+      llvm::APSInt LHSValue = lhs.castAs<nonloc::ConcreteInt>().getValue();
+
+      // If we're dealing with two known constants, just perform the operation.
+      if (const llvm::APSInt *KnownRHSValue = getKnownValue(state, rhs)) {
+        llvm::APSInt RHSValue = *KnownRHSValue;
+        if (BinaryOperator::isComparisonOp(op)) {
+          // We're looking for a type big enough to compare the two values.
+          // FIXME: This is not correct. char + short will result in a promotion
+          // to int. Unfortunately we have lost types by this point.
+          APSIntType CompareType = std::max(APSIntType(LHSValue),
+                                            APSIntType(RHSValue));
+          CompareType.apply(LHSValue);
+          CompareType.apply(RHSValue);
+        } else if (!BinaryOperator::isShiftOp(op)) {
+          APSIntType IntType = BasicVals.getAPSIntType(resultTy);
+          IntType.apply(LHSValue);
+          IntType.apply(RHSValue);
+        }
+
+        const llvm::APSInt *Result =
+          BasicVals.evalAPSInt(op, LHSValue, RHSValue);
+        if (!Result)
+          return UndefinedVal();
+
+        return nonloc::ConcreteInt(*Result);
+      }
+
+      // 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).
+      // While we're at it, catch some special cases for non-commutative ops.
+      switch (op) {
+      case BO_LT:
+      case BO_GT:
+      case BO_LE:
+      case BO_GE:
+        op = BinaryOperator::reverseComparisonOp(op);
+        LLVM_FALLTHROUGH;
+      case BO_EQ:
+      case BO_NE:
+      case BO_Add:
+      case BO_Mul:
+      case BO_And:
+      case BO_Xor:
+      case BO_Or:
+        std::swap(lhs, rhs);
+        continue;
+      case BO_Shr:
+        // (~0)>>a
+        if (LHSValue.isAllOnesValue() && LHSValue.isSigned())
+          return evalCastFromNonLoc(lhs, resultTy);
+        LLVM_FALLTHROUGH;
+      case BO_Shl:
+        // 0<<a and 0>>a
+        if (LHSValue == 0)
+          return evalCastFromNonLoc(lhs, resultTy);
+        return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
+      default:
+        return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
+      }
+    }
+    case nonloc::SymbolValKind: {
+      // We only handle LHS as simple symbols or SymIntExprs.
+      SymbolRef Sym = lhs.castAs<nonloc::SymbolVal>().getSymbol();
+
+      // LHS is a symbolic expression.
+      if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) {
+
+        // Is this a logical not? (!x is represented as x == 0.)
+        if (op == BO_EQ && rhs.isZeroConstant()) {
+          // We know how to negate certain expressions. Simplify them here.
+
+          BinaryOperator::Opcode opc = symIntExpr->getOpcode();
+          switch (opc) {
+          default:
+            // We don't know how to negate this operation.
+            // Just handle it as if it were a normal comparison to 0.
+            break;
+          case BO_LAnd:
+          case BO_LOr:
+            llvm_unreachable("Logical operators handled by branching logic.");
+          case BO_Assign:
+          case BO_MulAssign:
+          case BO_DivAssign:
+          case BO_RemAssign:
+          case BO_AddAssign:
+          case BO_SubAssign:
+          case BO_ShlAssign:
+          case BO_ShrAssign:
+          case BO_AndAssign:
+          case BO_XorAssign:
+          case BO_OrAssign:
+          case BO_Comma:
+            llvm_unreachable("'=' and ',' operators handled by ExprEngine.");
+          case BO_PtrMemD:
+          case BO_PtrMemI:
+            llvm_unreachable("Pointer arithmetic not handled here.");
+          case BO_LT:
+          case BO_GT:
+          case BO_LE:
+          case BO_GE:
+          case BO_EQ:
+          case BO_NE:
+            assert(resultTy->isBooleanType() ||
+                   resultTy == getConditionType());
+            assert(symIntExpr->getType()->isBooleanType() ||
+                   getContext().hasSameUnqualifiedType(symIntExpr->getType(),
+                                                       getConditionType()));
+            // Negate the comparison and make a value.
+            opc = BinaryOperator::negateComparisonOp(opc);
+            return makeNonLoc(symIntExpr->getLHS(), opc,
+                symIntExpr->getRHS(), resultTy);
+          }
+        }
+
+        // For now, only handle expressions whose RHS is a constant.
+        if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) {
+          // If both the LHS and the current expression are additive,
+          // fold their constants and try again.
+          if (BinaryOperator::isAdditiveOp(op)) {
+            BinaryOperator::Opcode lop = symIntExpr->getOpcode();
+            if (BinaryOperator::isAdditiveOp(lop)) {
+              // Convert the two constants to a common type, then combine them.
+
+              // resultTy may not be the best type to convert to, but it's
+              // probably the best choice in expressions with mixed type
+              // (such as x+1U+2LL). The rules for implicit conversions should
+              // choose a reasonable type to preserve the expression, and will
+              // at least match how the value is going to be used.
+              APSIntType IntType = BasicVals.getAPSIntType(resultTy);
+              const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS());
+              const llvm::APSInt &second = IntType.convert(*RHSValue);
+
+              const llvm::APSInt *newRHS;
+              if (lop == op)
+                newRHS = BasicVals.evalAPSInt(BO_Add, first, second);
+              else
+                newRHS = BasicVals.evalAPSInt(BO_Sub, first, second);
+
+              assert(newRHS && "Invalid operation despite common type!");
+              rhs = nonloc::ConcreteInt(*newRHS);
+              lhs = nonloc::SymbolVal(symIntExpr->getLHS());
+              op = lop;
+              continue;
+            }
+          }
+
+          // Otherwise, make a SymIntExpr out of the expression.
+          return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy);
+        }
+      }
+
+      // Does the symbolic expression simplify to a constant?
+      // If so, "fold" the constant by setting 'lhs' to a ConcreteInt
+      // and try again.
+      SVal simplifiedLhs = simplifySVal(state, lhs);
+      if (simplifiedLhs != lhs)
+        if (auto simplifiedLhsAsNonLoc = simplifiedLhs.getAs<NonLoc>()) {
+          lhs = *simplifiedLhsAsNonLoc;
+          continue;
+        }
+
+      // Is the RHS a constant?
+      if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs))
+        return MakeSymIntVal(Sym, op, *RHSValue, resultTy);
+
+      if (Optional<NonLoc> V = tryRearrange(state, op, lhs, rhs, resultTy))
+        return *V;
+
+      // Give up -- this is not a symbolic expression we can handle.
+      return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
+    }
+    }
+  }
+}
+
+static SVal evalBinOpFieldRegionFieldRegion(const FieldRegion *LeftFR,
+                                            const FieldRegion *RightFR,
+                                            BinaryOperator::Opcode op,
+                                            QualType resultTy,
+                                            SimpleSValBuilder &SVB) {
+  // Only comparisons are meaningful here!
+  if (!BinaryOperator::isComparisonOp(op))
+    return UnknownVal();
+
+  // Next, see if the two FRs have the same super-region.
+  // FIXME: This doesn't handle casts yet, and simply stripping the casts
+  // doesn't help.
+  if (LeftFR->getSuperRegion() != RightFR->getSuperRegion())
+    return UnknownVal();
+
+  const FieldDecl *LeftFD = LeftFR->getDecl();
+  const FieldDecl *RightFD = RightFR->getDecl();
+  const RecordDecl *RD = LeftFD->getParent();
+
+  // Make sure the two FRs are from the same kind of record. Just in case!
+  // FIXME: This is probably where inheritance would be a problem.
+  if (RD != RightFD->getParent())
+    return UnknownVal();
+
+  // We know for sure that the two fields are not the same, since that
+  // would have given us the same SVal.
+  if (op == BO_EQ)
+    return SVB.makeTruthVal(false, resultTy);
+  if (op == BO_NE)
+    return SVB.makeTruthVal(true, resultTy);
+
+  // Iterate through the fields and see which one comes first.
+  // [C99 6.7.2.1.13] "Within a structure object, the non-bit-field
+  // members and the units in which bit-fields reside have addresses that
+  // increase in the order in which they are declared."
+  bool leftFirst = (op == BO_LT || op == BO_LE);
+  for (const auto *I : RD->fields()) {
+    if (I == LeftFD)
+      return SVB.makeTruthVal(leftFirst, resultTy);
+    if (I == RightFD)
+      return SVB.makeTruthVal(!leftFirst, resultTy);
+  }
+
+  llvm_unreachable("Fields not found in parent record's definition");
+}
+
+// FIXME: all this logic will change if/when we have MemRegion::getLocation().
+SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state,
+                                  BinaryOperator::Opcode op,
+                                  Loc lhs, Loc rhs,
+                                  QualType resultTy) {
+  // Only comparisons and subtractions are valid operations on two pointers.
+  // See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15].
+  // However, if a pointer is casted to an integer, evalBinOpNN may end up
+  // calling this function with another operation (PR7527). We don't attempt to
+  // model this for now, but it could be useful, particularly when the
+  // "location" is actually an integer value that's been passed through a void*.
+  if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub))
+    return UnknownVal();
+
+  // Special cases for when both sides are identical.
+  if (lhs == rhs) {
+    switch (op) {
+    default:
+      llvm_unreachable("Unimplemented operation for two identical values");
+    case BO_Sub:
+      return makeZeroVal(resultTy);
+    case BO_EQ:
+    case BO_LE:
+    case BO_GE:
+      return makeTruthVal(true, resultTy);
+    case BO_NE:
+    case BO_LT:
+    case BO_GT:
+      return makeTruthVal(false, resultTy);
+    }
+  }
+
+  switch (lhs.getSubKind()) {
+  default:
+    llvm_unreachable("Ordering not implemented for this Loc.");
+
+  case loc::GotoLabelKind:
+    // The only thing we know about labels is that they're non-null.
+    if (rhs.isZeroConstant()) {
+      switch (op) {
+      default:
+        break;
+      case BO_Sub:
+        return evalCastFromLoc(lhs, resultTy);
+      case BO_EQ:
+      case BO_LE:
+      case BO_LT:
+        return makeTruthVal(false, resultTy);
+      case BO_NE:
+      case BO_GT:
+      case BO_GE:
+        return makeTruthVal(true, resultTy);
+      }
+    }
+    // There may be two labels for the same location, and a function region may
+    // have the same address as a label at the start of the function (depending
+    // on the ABI).
+    // FIXME: we can probably do a comparison against other MemRegions, though.
+    // FIXME: is there a way to tell if two labels refer to the same location?
+    return UnknownVal();
+
+  case loc::ConcreteIntKind: {
+    // If one of the operands is a symbol and the other is a constant,
+    // build an expression for use by the constraint manager.
+    if (SymbolRef rSym = rhs.getAsLocSymbol()) {
+      // We can only build expressions with symbols on the left,
+      // so we need a reversible operator.
+      if (!BinaryOperator::isComparisonOp(op) || op == BO_Cmp)
+        return UnknownVal();
+
+      const llvm::APSInt &lVal = lhs.castAs<loc::ConcreteInt>().getValue();
+      op = BinaryOperator::reverseComparisonOp(op);
+      return makeNonLoc(rSym, op, lVal, resultTy);
+    }
+
+    // If both operands are constants, just perform the operation.
+    if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {
+      SVal ResultVal =
+          lhs.castAs<loc::ConcreteInt>().evalBinOp(BasicVals, op, *rInt);
+      if (Optional<NonLoc> Result = ResultVal.getAs<NonLoc>())
+        return evalCastFromNonLoc(*Result, resultTy);
+
+      assert(!ResultVal.getAs<Loc>() && "Loc-Loc ops should not produce Locs");
+      return UnknownVal();
+    }
+
+    // Special case comparisons against NULL.
+    // This must come after the test if the RHS is a symbol, which is used to
+    // build constraints. The address of any non-symbolic region is guaranteed
+    // to be non-NULL, as is any label.
+    assert(rhs.getAs<loc::MemRegionVal>() || rhs.getAs<loc::GotoLabel>());
+    if (lhs.isZeroConstant()) {
+      switch (op) {
+      default:
+        break;
+      case BO_EQ:
+      case BO_GT:
+      case BO_GE:
+        return makeTruthVal(false, resultTy);
+      case BO_NE:
+      case BO_LT:
+      case BO_LE:
+        return makeTruthVal(true, resultTy);
+      }
+    }
+
+    // Comparing an arbitrary integer to a region or label address is
+    // completely unknowable.
+    return UnknownVal();
+  }
+  case loc::MemRegionValKind: {
+    if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {
+      // If one of the operands is a symbol and the other is a constant,
+      // build an expression for use by the constraint manager.
+      if (SymbolRef lSym = lhs.getAsLocSymbol(true)) {
+        if (BinaryOperator::isComparisonOp(op))
+          return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy);
+        return UnknownVal();
+      }
+      // Special case comparisons to NULL.
+      // This must come after the test if the LHS is a symbol, which is used to
+      // build constraints. The address of any non-symbolic region is guaranteed
+      // to be non-NULL.
+      if (rInt->isZeroConstant()) {
+        if (op == BO_Sub)
+          return evalCastFromLoc(lhs, resultTy);
+
+        if (BinaryOperator::isComparisonOp(op)) {
+          QualType boolType = getContext().BoolTy;
+          NonLoc l = evalCastFromLoc(lhs, boolType).castAs<NonLoc>();
+          NonLoc r = makeTruthVal(false, boolType).castAs<NonLoc>();
+          return evalBinOpNN(state, op, l, r, resultTy);
+        }
+      }
+
+      // Comparing a region to an arbitrary integer is completely unknowable.
+      return UnknownVal();
+    }
+
+    // Get both values as regions, if possible.
+    const MemRegion *LeftMR = lhs.getAsRegion();
+    assert(LeftMR && "MemRegionValKind SVal doesn't have a region!");
+
+    const MemRegion *RightMR = rhs.getAsRegion();
+    if (!RightMR)
+      // The RHS is probably a label, which in theory could address a region.
+      // FIXME: we can probably make a more useful statement about non-code
+      // regions, though.
+      return UnknownVal();
+
+    const MemRegion *LeftBase = LeftMR->getBaseRegion();
+    const MemRegion *RightBase = RightMR->getBaseRegion();
+    const MemSpaceRegion *LeftMS = LeftBase->getMemorySpace();
+    const MemSpaceRegion *RightMS = RightBase->getMemorySpace();
+    const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion();
+
+    // If the two regions are from different known memory spaces they cannot be
+    // equal. Also, assume that no symbolic region (whose memory space is
+    // unknown) is on the stack.
+    if (LeftMS != RightMS &&
+        ((LeftMS != UnknownMS && RightMS != UnknownMS) ||
+         (isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) {
+      switch (op) {
+      default:
+        return UnknownVal();
+      case BO_EQ:
+        return makeTruthVal(false, resultTy);
+      case BO_NE:
+        return makeTruthVal(true, resultTy);
+      }
+    }
+
+    // If both values wrap regions, see if they're from different base regions.
+    // Note, heap base symbolic regions are assumed to not alias with
+    // each other; for example, we assume that malloc returns different address
+    // on each invocation.
+    // FIXME: ObjC object pointers always reside on the heap, but currently
+    // we treat their memory space as unknown, because symbolic pointers
+    // to ObjC objects may alias. There should be a way to construct
+    // possibly-aliasing heap-based regions. For instance, MacOSXApiChecker
+    // guesses memory space for ObjC object pointers manually instead of
+    // relying on us.
+    if (LeftBase != RightBase &&
+        ((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) ||
+         (isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){
+      switch (op) {
+      default:
+        return UnknownVal();
+      case BO_EQ:
+        return makeTruthVal(false, resultTy);
+      case BO_NE:
+        return makeTruthVal(true, resultTy);
+      }
+    }
+
+    // Handle special cases for when both regions are element regions.
+    const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR);
+    const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR);
+    if (RightER && LeftER) {
+      // Next, see if the two ERs have the same super-region and matching types.
+      // FIXME: This should do something useful even if the types don't match,
+      // though if both indexes are constant the RegionRawOffset path will
+      // give the correct answer.
+      if (LeftER->getSuperRegion() == RightER->getSuperRegion() &&
+          LeftER->getElementType() == RightER->getElementType()) {
+        // Get the left index and cast it to the correct type.
+        // If the index is unknown or undefined, bail out here.
+        SVal LeftIndexVal = LeftER->getIndex();
+        Optional<NonLoc> LeftIndex = LeftIndexVal.getAs<NonLoc>();
+        if (!LeftIndex)
+          return UnknownVal();
+        LeftIndexVal = evalCastFromNonLoc(*LeftIndex, ArrayIndexTy);
+        LeftIndex = LeftIndexVal.getAs<NonLoc>();
+        if (!LeftIndex)
+          return UnknownVal();
+
+        // Do the same for the right index.
+        SVal RightIndexVal = RightER->getIndex();
+        Optional<NonLoc> RightIndex = RightIndexVal.getAs<NonLoc>();
+        if (!RightIndex)
+          return UnknownVal();
+        RightIndexVal = evalCastFromNonLoc(*RightIndex, ArrayIndexTy);
+        RightIndex = RightIndexVal.getAs<NonLoc>();
+        if (!RightIndex)
+          return UnknownVal();
+
+        // Actually perform the operation.
+        // evalBinOpNN expects the two indexes to already be the right type.
+        return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy);
+      }
+    }
+
+    // Special handling of the FieldRegions, even with symbolic offsets.
+    const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR);
+    const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR);
+    if (RightFR && LeftFR) {
+      SVal R = evalBinOpFieldRegionFieldRegion(LeftFR, RightFR, op, resultTy,
+                                               *this);
+      if (!R.isUnknown())
+        return R;
+    }
+
+    // Compare the regions using the raw offsets.
+    RegionOffset LeftOffset = LeftMR->getAsOffset();
+    RegionOffset RightOffset = RightMR->getAsOffset();
+
+    if (LeftOffset.getRegion() != nullptr &&
+        LeftOffset.getRegion() == RightOffset.getRegion() &&
+        !LeftOffset.hasSymbolicOffset() && !RightOffset.hasSymbolicOffset()) {
+      int64_t left = LeftOffset.getOffset();
+      int64_t right = RightOffset.getOffset();
+
+      switch (op) {
+        default:
+          return UnknownVal();
+        case BO_LT:
+          return makeTruthVal(left < right, resultTy);
+        case BO_GT:
+          return makeTruthVal(left > right, resultTy);
+        case BO_LE:
+          return makeTruthVal(left <= right, resultTy);
+        case BO_GE:
+          return makeTruthVal(left >= right, resultTy);
+        case BO_EQ:
+          return makeTruthVal(left == right, resultTy);
+        case BO_NE:
+          return makeTruthVal(left != right, resultTy);
+      }
+    }
+
+    // At this point we're not going to get a good answer, but we can try
+    // conjuring an expression instead.
+    SymbolRef LHSSym = lhs.getAsLocSymbol();
+    SymbolRef RHSSym = rhs.getAsLocSymbol();
+    if (LHSSym && RHSSym)
+      return makeNonLoc(LHSSym, op, RHSSym, resultTy);
+
+    // If we get here, we have no way of comparing the regions.
+    return UnknownVal();
+  }
+  }
+}
+
+SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state,
+                                  BinaryOperator::Opcode op,
+                                  Loc lhs, NonLoc rhs, QualType resultTy) {
+  if (op >= BO_PtrMemD && op <= BO_PtrMemI) {
+    if (auto PTMSV = rhs.getAs<nonloc::PointerToMember>()) {
+      if (PTMSV->isNullMemberPointer())
+        return UndefinedVal();
+      if (const FieldDecl *FD = PTMSV->getDeclAs<FieldDecl>()) {
+        SVal Result = lhs;
+
+        for (const auto &I : *PTMSV)
+          Result = StateMgr.getStoreManager().evalDerivedToBase(
+              Result, I->getType(),I->isVirtual());
+        return state->getLValue(FD, Result);
+      }
+    }
+
+    return rhs;
+  }
+
+  assert(!BinaryOperator::isComparisonOp(op) &&
+         "arguments to comparison ops must be of the same type");
+
+  // Special case: rhs is a zero constant.
+  if (rhs.isZeroConstant())
+    return lhs;
+
+  // Perserve the null pointer so that it can be found by the DerefChecker.
+  if (lhs.isZeroConstant())
+    return lhs;
+
+  // We are dealing with pointer arithmetic.
+
+  // Handle pointer arithmetic on constant values.
+  if (Optional<nonloc::ConcreteInt> rhsInt = rhs.getAs<nonloc::ConcreteInt>()) {
+    if (Optional<loc::ConcreteInt> lhsInt = lhs.getAs<loc::ConcreteInt>()) {
+      const llvm::APSInt &leftI = lhsInt->getValue();
+      assert(leftI.isUnsigned());
+      llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true);
+
+      // Convert the bitwidth of rightI.  This should deal with overflow
+      // since we are dealing with concrete values.
+      rightI = rightI.extOrTrunc(leftI.getBitWidth());
+
+      // Offset the increment by the pointer size.
+      llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true);
+      QualType pointeeType = resultTy->getPointeeType();
+      Multiplicand = getContext().getTypeSizeInChars(pointeeType).getQuantity();
+      rightI *= Multiplicand;
+
+      // Compute the adjusted pointer.
+      switch (op) {
+        case BO_Add:
+          rightI = leftI + rightI;
+          break;
+        case BO_Sub:
+          rightI = leftI - rightI;
+          break;
+        default:
+          llvm_unreachable("Invalid pointer arithmetic operation");
+      }
+      return loc::ConcreteInt(getBasicValueFactory().getValue(rightI));
+    }
+  }
+
+  // Handle cases where 'lhs' is a region.
+  if (const MemRegion *region = lhs.getAsRegion()) {
+    rhs = convertToArrayIndex(rhs).castAs<NonLoc>();
+    SVal index = UnknownVal();
+    const SubRegion *superR = nullptr;
+    // We need to know the type of the pointer in order to add an integer to it.
+    // Depending on the type, different amount of bytes is added.
+    QualType elementType;
+
+    if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) {
+      assert(op == BO_Add || op == BO_Sub);
+      index = evalBinOpNN(state, op, elemReg->getIndex(), rhs,
+                          getArrayIndexType());
+      superR = cast<SubRegion>(elemReg->getSuperRegion());
+      elementType = elemReg->getElementType();
+    }
+    else if (isa<SubRegion>(region)) {
+      assert(op == BO_Add || op == BO_Sub);
+      index = (op == BO_Add) ? rhs : evalMinus(rhs);
+      superR = cast<SubRegion>(region);
+      // TODO: Is this actually reliable? Maybe improving our MemRegion
+      // hierarchy to provide typed regions for all non-void pointers would be
+      // better. For instance, we cannot extend this towards LocAsInteger
+      // operations, where result type of the expression is integer.
+      if (resultTy->isAnyPointerType())
+        elementType = resultTy->getPointeeType();
+    }
+
+    // Represent arithmetic on void pointers as arithmetic on char pointers.
+    // It is fine when a TypedValueRegion of char value type represents
+    // a void pointer. Note that arithmetic on void pointers is a GCC extension.
+    if (elementType->isVoidType())
+      elementType = getContext().CharTy;
+
+    if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) {
+      return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV,
+                                                       superR, getContext()));
+    }
+  }
+  return UnknownVal();
+}
+
+const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state,
+                                                   SVal V) {
+  V = simplifySVal(state, V);
+  if (V.isUnknownOrUndef())
+    return nullptr;
+
+  if (Optional<loc::ConcreteInt> X = V.getAs<loc::ConcreteInt>())
+    return &X->getValue();
+
+  if (Optional<nonloc::ConcreteInt> X = V.getAs<nonloc::ConcreteInt>())
+    return &X->getValue();
+
+  if (SymbolRef Sym = V.getAsSymbol())
+    return state->getConstraintManager().getSymVal(state, Sym);
+
+  // FIXME: Add support for SymExprs.
+  return nullptr;
+}
+
+SVal SimpleSValBuilder::simplifySVal(ProgramStateRef State, SVal V) {
+  // For now, this function tries to constant-fold symbols inside a
+  // nonloc::SymbolVal, and does nothing else. More simplifications should
+  // be possible, such as constant-folding an index in an ElementRegion.
+
+  class Simplifier : public FullSValVisitor<Simplifier, SVal> {
+    ProgramStateRef State;
+    SValBuilder &SVB;
+
+    // Cache results for the lifetime of the Simplifier. Results change every
+    // time new constraints are added to the program state, which is the whole
+    // point of simplifying, and for that very reason it's pointless to maintain
+    // the same cache for the duration of the whole analysis.
+    llvm::DenseMap<SymbolRef, SVal> Cached;
+
+    static bool isUnchanged(SymbolRef Sym, SVal Val) {
+      return Sym == Val.getAsSymbol();
+    }
+
+    SVal cache(SymbolRef Sym, SVal V) {
+      Cached[Sym] = V;
+      return V;
+    }
+
+    SVal skip(SymbolRef Sym) {
+      return cache(Sym, SVB.makeSymbolVal(Sym));
+    }
+
+  public:
+    Simplifier(ProgramStateRef State)
+        : State(State), SVB(State->getStateManager().getSValBuilder()) {}
+
+    SVal VisitSymbolData(const SymbolData *S) {
+      // No cache here.
+      if (const llvm::APSInt *I =
+              SVB.getKnownValue(State, SVB.makeSymbolVal(S)))
+        return Loc::isLocType(S->getType()) ? (SVal)SVB.makeIntLocVal(*I)
+                                            : (SVal)SVB.makeIntVal(*I);
+      return SVB.makeSymbolVal(S);
+    }
+
+    // TODO: Support SymbolCast. Support IntSymExpr when/if we actually
+    // start producing them.
+
+    SVal VisitSymIntExpr(const SymIntExpr *S) {
+      auto I = Cached.find(S);
+      if (I != Cached.end())
+        return I->second;
+
+      SVal LHS = Visit(S->getLHS());
+      if (isUnchanged(S->getLHS(), LHS))
+        return skip(S);
+
+      SVal RHS;
+      // By looking at the APSInt in the right-hand side of S, we cannot
+      // figure out if it should be treated as a Loc or as a NonLoc.
+      // So make our guess by recalling that we cannot multiply pointers
+      // or compare a pointer to an integer.
+      if (Loc::isLocType(S->getLHS()->getType()) &&
+          BinaryOperator::isComparisonOp(S->getOpcode())) {
+        // The usual conversion of $sym to &SymRegion{$sym}, as they have
+        // the same meaning for Loc-type symbols, but the latter form
+        // is preferred in SVal computations for being Loc itself.
+        if (SymbolRef Sym = LHS.getAsSymbol()) {
+          assert(Loc::isLocType(Sym->getType()));
+          LHS = SVB.makeLoc(Sym);
+        }
+        RHS = SVB.makeIntLocVal(S->getRHS());
+      } else {
+        RHS = SVB.makeIntVal(S->getRHS());
+      }
+
+      return cache(
+          S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType()));
+    }
+
+    SVal VisitSymSymExpr(const SymSymExpr *S) {
+      auto I = Cached.find(S);
+      if (I != Cached.end())
+        return I->second;
+
+      // For now don't try to simplify mixed Loc/NonLoc expressions
+      // because they often appear from LocAsInteger operations
+      // and we don't know how to combine a LocAsInteger
+      // with a concrete value.
+      if (Loc::isLocType(S->getLHS()->getType()) !=
+          Loc::isLocType(S->getRHS()->getType()))
+        return skip(S);
+
+      SVal LHS = Visit(S->getLHS());
+      SVal RHS = Visit(S->getRHS());
+      if (isUnchanged(S->getLHS(), LHS) && isUnchanged(S->getRHS(), RHS))
+        return skip(S);
+
+      return cache(
+          S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType()));
+    }
+
+    SVal VisitSymExpr(SymbolRef S) { return nonloc::SymbolVal(S); }
+
+    SVal VisitMemRegion(const MemRegion *R) { return loc::MemRegionVal(R); }
+
+    SVal VisitNonLocSymbolVal(nonloc::SymbolVal V) {
+      // Simplification is much more costly than computing complexity.
+      // For high complexity, it may be not worth it.
+      return Visit(V.getSymbol());
+    }
+
+    SVal VisitSVal(SVal V) { return V; }
+  };
+
+  // A crude way of preventing this function from calling itself from evalBinOp.
+  static bool isReentering = false;
+  if (isReentering)
+    return V;
+
+  isReentering = true;
+  SVal SimplifiedV = Simplifier(State).Visit(V);
+  isReentering = false;
+
+  return SimplifiedV;
+}