diff --git a/clang/unittests/Analysis/FlowSensitive/CMakeLists.txt b/clang/unittests/Analysis/FlowSensitive/CMakeLists.txt
--- a/clang/unittests/Analysis/FlowSensitive/CMakeLists.txt
+++ b/clang/unittests/Analysis/FlowSensitive/CMakeLists.txt
@@ -12,12 +12,13 @@
   MapLatticeTest.cpp
   MatchSwitchTest.cpp
   MultiVarConstantPropagationTest.cpp
+  SignAnalysisTest.cpp
   SingleVarConstantPropagationTest.cpp
+  SolverTest.cpp
   TestingSupport.cpp
   TestingSupportTest.cpp
   TransferTest.cpp
   TypeErasedDataflowAnalysisTest.cpp
-  SolverTest.cpp
   UncheckedOptionalAccessModelTest.cpp
   ValueTest.cpp
   )
diff --git a/clang/unittests/Analysis/FlowSensitive/SignAnalysisTest.cpp b/clang/unittests/Analysis/FlowSensitive/SignAnalysisTest.cpp
new file mode 100644
--- /dev/null
+++ b/clang/unittests/Analysis/FlowSensitive/SignAnalysisTest.cpp
@@ -0,0 +1,982 @@
+//===- unittests/Analysis/FlowSensitive/SignAnalysisTest.cpp --===//
+//
+// 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 a simplistic version of Sign Analysis as a demo of a
+//  forward, monotonic dataflow analysis. The implementation uses 3 boolean
+//  values to represent the sign lattice (negative, zero, positive). In
+//  practice, 2 booleans would be enough, however, this approach has the
+//  advantage of clarity over the optimized solution.
+//
+//===----------------------------------------------------------------------===//
+
+#include "TestingSupport.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Analysis/FlowSensitive/CFGMatchSwitch.h"
+#include "clang/Analysis/FlowSensitive/DataflowAnalysis.h"
+#include "clang/Analysis/FlowSensitive/NoopLattice.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Testing/Support/Annotations.h"
+#include "llvm/Testing/Support/Error.h"
+#include "gtest/gtest.h"
+#include <memory>
+
+namespace {
+
+using namespace clang;
+using namespace dataflow;
+using namespace ast_matchers;
+using namespace test;
+using ::testing::UnorderedElementsAre;
+
+enum class Sign : int { Negative, Zero, Positive };
+
+Sign getSign(int64_t V) {
+  return V == 0 ? Sign::Zero : (V < 0 ? Sign::Negative : Sign::Positive);
+}
+
+using LatticeTransferState = TransferState<NoopLattice>;
+
+constexpr char kVar[] = "var";
+
+void initNegative(Value &Val, Environment &Env) {
+  Val.setProperty("neg", Env.getBoolLiteralValue(true));
+  Val.setProperty("zero", Env.getBoolLiteralValue(false));
+  Val.setProperty("pos", Env.getBoolLiteralValue(false));
+}
+void initPositive(Value &Val, Environment &Env) {
+  Val.setProperty("neg", Env.getBoolLiteralValue(false));
+  Val.setProperty("zero", Env.getBoolLiteralValue(false));
+  Val.setProperty("pos", Env.getBoolLiteralValue(true));
+}
+void initZero(Value &Val, Environment &Env) {
+  Val.setProperty("neg", Env.getBoolLiteralValue(false));
+  Val.setProperty("zero", Env.getBoolLiteralValue(true));
+  Val.setProperty("pos", Env.getBoolLiteralValue(false));
+}
+
+// The boolean properties that are associated to a Value. If a property is not
+// set then these are null pointers, otherwise, the pointed BoolValues are
+// owned by the Environment.
+struct SignProperties {
+  BoolValue *Neg, *Zero, *Pos;
+};
+void setSignProperties(Value &Val, const SignProperties &Ps) {
+  Val.setProperty("neg", *Ps.Neg);
+  Val.setProperty("zero", *Ps.Zero);
+  Val.setProperty("pos", *Ps.Pos);
+}
+SignProperties initUnknown(Value &Val, Environment &Env) {
+  SignProperties Ps{&Env.makeAtomicBoolValue(), &Env.makeAtomicBoolValue(),
+                    &Env.makeAtomicBoolValue()};
+  setSignProperties(Val, Ps);
+  return Ps;
+}
+SignProperties getSignProperties(const Value &Val, const Environment &Env) {
+  return {dyn_cast_or_null<BoolValue>(Val.getProperty("neg")),
+          dyn_cast_or_null<BoolValue>(Val.getProperty("zero")),
+          dyn_cast_or_null<BoolValue>(Val.getProperty("pos"))};
+}
+
+void transferUninitializedInt(const DeclStmt *D,
+                              const MatchFinder::MatchResult &M,
+                              LatticeTransferState &State) {
+  const auto *Var = M.Nodes.getNodeAs<clang::VarDecl>(kVar);
+  assert(Var != nullptr);
+  const StorageLocation *Loc =
+      State.Env.getStorageLocation(*Var, SkipPast::None);
+  Value *Val = State.Env.getValue(*Loc);
+  initUnknown(*Val, State.Env);
+}
+
+// Get the Value (1), the properties for the operand (2), and the properties
+// for the unary operator (3). The return value is a tuple of (1,2,3).
+//
+// The returned Value (1) is a nullptr, if there is no Value associated to the
+// operand of the unary operator, or if the properties are not set for that
+// operand.
+// Other than that, new sign properties are created for the Value of the
+// unary operator and a new Value is created for the unary operator itself if
+// it hadn't have any previously.
+std::tuple<Value *, SignProperties, SignProperties>
+getValueAndSignProperties(const UnaryOperator *UO,
+                          const MatchFinder::MatchResult &M,
+                          LatticeTransferState &State) {
+  // The DeclRefExpr refers to this variable in the operand.
+  const auto *OperandVar = M.Nodes.getNodeAs<clang::VarDecl>(kVar);
+  assert(OperandVar != nullptr);
+  const auto *OperandValue = State.Env.getValue(*OperandVar, SkipPast::None);
+  if (!OperandValue)
+    return {nullptr, {}, {}};
+
+  // Value of the unary op.
+  auto *UnaryOpValue = State.Env.getValue(*UO, SkipPast::None);
+  if (!UnaryOpValue) {
+    auto &Loc = State.Env.createStorageLocation(*UO);
+    State.Env.setStorageLocation(*UO, Loc);
+    UnaryOpValue = &State.Env.makeAtomicBoolValue();
+    State.Env.setValue(Loc, *UnaryOpValue);
+  }
+
+  // Properties for the operand (sub expression).
+  SignProperties OperandProps = getSignProperties(*OperandValue, State.Env);
+  if (OperandProps.Neg == nullptr)
+    return {nullptr, {}, {}};
+  // Properties for the operator expr itself.
+  SignProperties UnaryOpProps = initUnknown(*UnaryOpValue, State.Env);
+  return {UnaryOpValue, UnaryOpProps, OperandProps};
+}
+
+void transferBinary(const BinaryOperator *BO, const MatchFinder::MatchResult &M,
+                    LatticeTransferState &State) {
+  StorageLocation *Loc = State.Env.getStorageLocation(*BO, SkipPast::None);
+  if (!Loc) {
+    Loc = &State.Env.createStorageLocation(*BO);
+    State.Env.setStorageLocation(*BO, *Loc);
+  }
+  BoolValue *Comp = cast_or_null<BoolValue>(State.Env.getValue(*Loc));
+  if (!Comp) {
+    Comp = &State.Env.makeAtomicBoolValue();
+    State.Env.setValue(*Loc, *Comp);
+  }
+
+  // FIXME Use this as well:
+  // auto *NegatedComp = &State.Env.makeNot(*Comp);
+
+  auto *LHS = State.Env.getValue(*BO->getLHS(), SkipPast::None);
+  auto *RHS = State.Env.getValue(*BO->getRHS(), SkipPast::None);
+
+  if (!LHS || !RHS)
+    return;
+
+  SignProperties LHSProps = getSignProperties(*LHS, State.Env);
+  SignProperties RHSProps = getSignProperties(*RHS, State.Env);
+  if (LHSProps.Neg == nullptr || RHSProps.Neg == nullptr)
+    return;
+
+  switch (BO->getOpcode()) {
+  case BO_GT:
+    // pos > pos
+    State.Env.addToFlowCondition(State.Env.makeImplication(
+        *Comp, State.Env.makeImplication(*RHSProps.Pos, *LHSProps.Pos)));
+    // pos > zero
+    State.Env.addToFlowCondition(State.Env.makeImplication(
+        *Comp, State.Env.makeImplication(*RHSProps.Zero, *LHSProps.Pos)));
+    break;
+  case BO_LT:
+    // neg < neg
+    State.Env.addToFlowCondition(State.Env.makeImplication(
+        *Comp, State.Env.makeImplication(*RHSProps.Neg, *LHSProps.Neg)));
+    // neg < zero
+    State.Env.addToFlowCondition(State.Env.makeImplication(
+        *Comp, State.Env.makeImplication(*RHSProps.Zero, *LHSProps.Neg)));
+    break;
+  case BO_GE:
+    // pos >= pos
+    State.Env.addToFlowCondition(State.Env.makeImplication(
+        *Comp, State.Env.makeImplication(*RHSProps.Pos, *LHSProps.Pos)));
+    break;
+  case BO_LE:
+    // neg <= neg
+    State.Env.addToFlowCondition(State.Env.makeImplication(
+        *Comp, State.Env.makeImplication(*RHSProps.Neg, *LHSProps.Neg)));
+    break;
+  case BO_EQ:
+    State.Env.addToFlowCondition(State.Env.makeImplication(
+        *Comp, State.Env.makeImplication(*RHSProps.Neg, *LHSProps.Neg)));
+    State.Env.addToFlowCondition(State.Env.makeImplication(
+        *Comp, State.Env.makeImplication(*RHSProps.Zero, *LHSProps.Zero)));
+    State.Env.addToFlowCondition(State.Env.makeImplication(
+        *Comp, State.Env.makeImplication(*RHSProps.Pos, *LHSProps.Pos)));
+    break;
+  case BO_NE: // Noop.
+    break;
+  default:
+    llvm_unreachable("not implemented");
+  }
+}
+
+void transferUnaryMinus(const UnaryOperator *UO,
+                        const MatchFinder::MatchResult &M,
+                        LatticeTransferState &State) {
+  auto [UnaryOpValue, UnaryOpProps, OperandProps] =
+      getValueAndSignProperties(UO, M, State);
+  if (!UnaryOpValue)
+    return;
+
+  // a is pos ==> -a is neg
+  State.Env.addToFlowCondition(
+      State.Env.makeImplication(*OperandProps.Pos, *UnaryOpProps.Neg));
+  // a is neg ==> -a is pos
+  State.Env.addToFlowCondition(
+      State.Env.makeImplication(*OperandProps.Neg, *UnaryOpProps.Pos));
+  // a is zero ==> -a is zero
+  State.Env.addToFlowCondition(
+      State.Env.makeImplication(*OperandProps.Zero, *UnaryOpProps.Zero));
+}
+
+void transferUnaryNot(const UnaryOperator *UO,
+                      const MatchFinder::MatchResult &M,
+                      LatticeTransferState &State) {
+  auto [UnaryOpValue, UnaryOpProps, OperandProps] =
+      getValueAndSignProperties(UO, M, State);
+  if (!UnaryOpValue)
+    return;
+
+  // a is neg or pos ==> !a is zero
+  State.Env.addToFlowCondition(State.Env.makeImplication(
+      State.Env.makeOr(*OperandProps.Pos, *OperandProps.Neg),
+      *UnaryOpProps.Zero));
+
+  // FIXME Handle this logic universally, not just for unary not. But Where to
+  // put the generic handler, transferExpr maybe?
+  if (auto *UOBoolVal = dyn_cast<BoolValue>(UnaryOpValue)) {
+    // !a <==> a is zero
+    State.Env.addToFlowCondition(
+        State.Env.makeIff(*UOBoolVal, *OperandProps.Zero));
+    // !a <==> !a is not zero
+    State.Env.addToFlowCondition(
+        State.Env.makeIff(*UOBoolVal, State.Env.makeNot(*UnaryOpProps.Zero)));
+  }
+}
+
+void transferExpr(const Expr *E, const MatchFinder::MatchResult &M,
+                  LatticeTransferState &State) {
+  const ASTContext &Context = *M.Context;
+  StorageLocation *Loc = State.Env.getStorageLocation(*E, SkipPast::None);
+  if (!Loc) {
+    Loc = &State.Env.createStorageLocation(*E);
+    State.Env.setStorageLocation(*E, *Loc);
+  }
+  Value *Val = State.Env.getValue(*Loc);
+  if (!Val) {
+    Val = State.Env.createValue(Context.IntTy);
+    State.Env.setValue(*Loc, *Val);
+  }
+  // The sign symbolic values have been initialized already.
+  if (Val->getProperty("neg"))
+    return;
+
+  Expr::EvalResult R;
+  // An integer expression which we cannot evaluate.
+  if (!(E->EvaluateAsInt(R, Context) && R.Val.isInt())) {
+    initUnknown(*Val, State.Env);
+    return;
+  }
+
+  const Sign S = getSign(R.Val.getInt().getExtValue());
+  switch (S) {
+  case Sign::Negative:
+    initNegative(*Val, State.Env);
+    break;
+  case Sign::Zero:
+    initZero(*Val, State.Env);
+    break;
+  case Sign::Positive:
+    initPositive(*Val, State.Env);
+    break;
+  }
+}
+
+auto refToVar() { return declRefExpr(to(varDecl().bind(kVar))); }
+
+auto buildTransferMatchSwitch() {
+  // Note, the order of the cases is important, the most generic should be
+  // added last.
+  // FIXME Discover what happens if there are multiple matching ASTMatchers for
+  // one Stmt? All matching case's handler should be called and in what order?
+  return CFGMatchSwitchBuilder<LatticeTransferState>()
+      // a op b (comparison)
+      .CaseOfCFGStmt<BinaryOperator>(binaryOperator(isComparisonOperator()),
+                                     transferBinary)
+
+      // FIXME handle binop +,-,*,/
+
+      // -a
+      .CaseOfCFGStmt<UnaryOperator>(
+          unaryOperator(hasOperatorName("-"),
+                        hasUnaryOperand(hasDescendant(refToVar()))),
+          transferUnaryMinus)
+
+      // !a
+      .CaseOfCFGStmt<UnaryOperator>(
+          unaryOperator(hasOperatorName("!"),
+                        hasUnaryOperand(hasDescendant(refToVar()))),
+          transferUnaryNot)
+
+      // int a;
+      .CaseOfCFGStmt<DeclStmt>(declStmt(hasSingleDecl(varDecl(
+                                   decl().bind(kVar), hasType(isInteger()),
+                                   unless(hasInitializer(expr()))))),
+                               transferUninitializedInt)
+
+      // constexpr int
+      .CaseOfCFGStmt<Expr>(expr(hasType(isInteger())), transferExpr)
+
+      .Build();
+}
+
+class SignPropagationAnalysis
+    : public DataflowAnalysis<SignPropagationAnalysis, NoopLattice> {
+public:
+  SignPropagationAnalysis(ASTContext &Context)
+      : DataflowAnalysis<SignPropagationAnalysis, NoopLattice>(Context),
+        TransferMatchSwitch(buildTransferMatchSwitch()) {}
+
+  static NoopLattice initialElement() { return {}; }
+
+  void transfer(const CFGElement *Elt, NoopLattice &L, Environment &Env) {
+    LatticeTransferState State(L, Env);
+    TransferMatchSwitch(*Elt, getASTContext(), State);
+  }
+  bool merge(QualType Type, const Value &Val1, const Environment &Env1,
+             const Value &Val2, const Environment &Env2, Value &MergedVal,
+             Environment &MergedEnv) override;
+
+private:
+  CFGMatchSwitch<TransferState<NoopLattice>> TransferMatchSwitch;
+};
+
+// Copied from crubit.
+BoolValue &mergeBoolValues(BoolValue &Bool1, const Environment &Env1,
+                           BoolValue &Bool2, const Environment &Env2,
+                           Environment &MergedEnv) {
+  if (&Bool1 == &Bool2) {
+    return Bool1;
+  }
+
+  auto &MergedBool = MergedEnv.makeAtomicBoolValue();
+
+  // If `Bool1` and `Bool2` is constrained to the same true / false value,
+  // `MergedBool` can be constrained similarly without needing to consider the
+  // path taken - this simplifies the flow condition tracked in `MergedEnv`.
+  // Otherwise, information about which path was taken is used to associate
+  // `MergedBool` with `Bool1` and `Bool2`.
+  if (Env1.flowConditionImplies(Bool1) && Env2.flowConditionImplies(Bool2)) {
+    MergedEnv.addToFlowCondition(MergedBool);
+  } else if (Env1.flowConditionImplies(Env1.makeNot(Bool1)) &&
+             Env2.flowConditionImplies(Env2.makeNot(Bool2))) {
+    MergedEnv.addToFlowCondition(MergedEnv.makeNot(MergedBool));
+  }
+  return MergedBool;
+}
+
+bool SignPropagationAnalysis::merge(QualType Type, const Value &Val1,
+                                    const Environment &Env1, const Value &Val2,
+                                    const Environment &Env2, Value &MergedVal,
+                                    Environment &MergedEnv) {
+  if (!Type->isIntegerType())
+    return false;
+  SignProperties Ps1 = getSignProperties(Val1, Env1);
+  SignProperties Ps2 = getSignProperties(Val2, Env2);
+  if (!Ps1.Neg || !Ps2.Neg)
+    return false;
+  BoolValue &MergedNeg =
+      mergeBoolValues(*Ps1.Neg, Env1, *Ps2.Neg, Env2, MergedEnv);
+  BoolValue &MergedZero =
+      mergeBoolValues(*Ps1.Zero, Env1, *Ps2.Zero, Env2, MergedEnv);
+  BoolValue &MergedPos =
+      mergeBoolValues(*Ps1.Pos, Env1, *Ps2.Pos, Env2, MergedEnv);
+  setSignProperties(MergedVal,
+                    SignProperties{&MergedNeg, &MergedZero, &MergedPos});
+  return true;
+}
+
+template <typename Matcher>
+void runDataflow(llvm::StringRef Code, Matcher Match,
+                 LangStandard::Kind Std = LangStandard::lang_cxx17,
+                 llvm::StringRef TargetFun = "fun") {
+  using ast_matchers::hasName;
+  ASSERT_THAT_ERROR(
+      checkDataflow<SignPropagationAnalysis>(
+          AnalysisInputs<SignPropagationAnalysis>(
+              Code, hasName(TargetFun),
+              [](ASTContext &C, Environment &) {
+                return SignPropagationAnalysis(C);
+              })
+              .withASTBuildArgs(
+                  {"-fsyntax-only", "-fno-delayed-template-parsing",
+                   "-std=" +
+                       std::string(LangStandard::getLangStandardForKind(Std)
+                                       .getName())}),
+          /*VerifyResults=*/
+          [&Match](const llvm::StringMap<DataflowAnalysisState<NoopLattice>>
+                       &Results,
+                   const AnalysisOutputs &AO) { Match(Results, AO.ASTCtx); }),
+      llvm::Succeeded());
+}
+
+// FIXME add this to testing support.
+template <typename NodeType, typename MatcherType>
+const NodeType *findFirst(ASTContext &ASTCtx, const MatcherType &M) {
+  auto TargetNodes = match(M.bind("v"), ASTCtx);
+  assert(TargetNodes.size() == 1 && "Match must be unique");
+  auto *const Result = selectFirst<NodeType>("v", TargetNodes);
+  assert(Result != nullptr);
+  return Result;
+}
+
+template <typename Node>
+std::pair<testing::AssertionResult, Value *>
+getProperty(const Environment &Env, ASTContext &ASTCtx, const Node *N,
+            StringRef Property) {
+  if (!N)
+    return {testing::AssertionFailure() << "No node", nullptr};
+  const StorageLocation *Loc = Env.getStorageLocation(*N, SkipPast::None);
+  if (!isa_and_nonnull<ScalarStorageLocation>(Loc))
+    return {testing::AssertionFailure() << "No location", nullptr};
+  const Value *Val = Env.getValue(*Loc);
+  if (!Val)
+    return {testing::AssertionFailure() << "No value", nullptr};
+  auto *Prop = Val->getProperty(Property);
+  if (!isa_and_nonnull<BoolValue>(Prop))
+    return {testing::AssertionFailure() << "No property for " << Property,
+            nullptr};
+  return {testing::AssertionSuccess(), Prop};
+}
+
+// Test if the given property of the given node is implied by the flow
+// condition. If 'Implies' is false then check if it is not implied.
+template <typename Node>
+testing::AssertionResult isPropertyImplied(const Environment &Env,
+                                           ASTContext &ASTCtx, const Node *N,
+                                           StringRef Property, bool Implies) {
+  auto [Result, Prop] = getProperty(Env, ASTCtx, N, Property);
+  if (!Prop)
+    return Result;
+  auto *BVProp = cast<BoolValue>(Prop);
+  if (Env.flowConditionImplies(*BVProp) != Implies)
+    return testing::AssertionFailure()
+           << Property << " is " << (Implies ? "not" : "") << " implied"
+           << ", but should " << (Implies ? "" : "not ") << "be";
+  return testing::AssertionSuccess();
+}
+
+template <typename Node>
+testing::AssertionResult isNegative(const Node *N, ASTContext &ASTCtx,
+                                    const Environment &Env) {
+  testing::AssertionResult R = isPropertyImplied(Env, ASTCtx, N, "neg", true);
+  if (!R)
+    return R;
+  R = isPropertyImplied(Env, ASTCtx, N, "zero", false);
+  if (!R)
+    return R;
+  return isPropertyImplied(Env, ASTCtx, N, "pos", false);
+}
+template <typename Node>
+testing::AssertionResult isPositive(const Node *N, ASTContext &ASTCtx,
+                                    const Environment &Env) {
+  testing::AssertionResult R = isPropertyImplied(Env, ASTCtx, N, "pos", true);
+  if (!R)
+    return R;
+  R = isPropertyImplied(Env, ASTCtx, N, "zero", false);
+  if (!R)
+    return R;
+  return isPropertyImplied(Env, ASTCtx, N, "neg", false);
+}
+template <typename Node>
+testing::AssertionResult isZero(const Node *N, ASTContext &ASTCtx,
+                                const Environment &Env) {
+  testing::AssertionResult R = isPropertyImplied(Env, ASTCtx, N, "zero", true);
+  if (!R)
+    return R;
+  R = isPropertyImplied(Env, ASTCtx, N, "pos", false);
+  if (!R)
+    return R;
+  return isPropertyImplied(Env, ASTCtx, N, "neg", false);
+}
+template <typename Node>
+testing::AssertionResult isTop(const Node *N, ASTContext &ASTCtx,
+                               const Environment &Env) {
+  testing::AssertionResult R = isPropertyImplied(Env, ASTCtx, N, "zero", false);
+  if (!R)
+    return R;
+  R = isPropertyImplied(Env, ASTCtx, N, "pos", false);
+  if (!R)
+    return R;
+  return isPropertyImplied(Env, ASTCtx, N, "neg", false);
+}
+
+TEST(SignAnalysisTest, Init) {
+  std::string Code = R"(
+    int foo();
+    void fun() {
+      int a = -1;
+      int b = 0;
+      int c = 1;
+      int d;
+      int e = foo();
+      int f = c;
+      // [[p]]
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        // ASTCtx.getTranslationUnitDecl()->dump();
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p"));
+        const Environment &Env = getEnvironmentAtAnnotation(Results, "p");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+        const ValueDecl *B = findValueDecl(ASTCtx, "b");
+        const ValueDecl *C = findValueDecl(ASTCtx, "c");
+        const ValueDecl *D = findValueDecl(ASTCtx, "d");
+        const ValueDecl *E = findValueDecl(ASTCtx, "e");
+        const ValueDecl *F = findValueDecl(ASTCtx, "f");
+
+        EXPECT_TRUE(isNegative(A, ASTCtx, Env));
+        EXPECT_TRUE(isZero(B, ASTCtx, Env));
+        EXPECT_TRUE(isPositive(C, ASTCtx, Env));
+        EXPECT_TRUE(isTop(D, ASTCtx, Env));
+        EXPECT_TRUE(isTop(E, ASTCtx, Env));
+        EXPECT_TRUE(isPositive(F, ASTCtx, Env));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, UnaryMinus) {
+  std::string Code = R"(
+    void fun() {
+      int a = 1;
+      int b = -a;
+      // [[p]]
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p"));
+        const Environment &Env = getEnvironmentAtAnnotation(Results, "p");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+        const ValueDecl *B = findValueDecl(ASTCtx, "b");
+        EXPECT_TRUE(isPositive(A, ASTCtx, Env));
+        EXPECT_TRUE(isNegative(B, ASTCtx, Env));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, UnaryNot) {
+  std::string Code = R"(
+    void fun() {
+      int a = 2;
+      int b = !a;
+      // [[p]]
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p"));
+        const Environment &Env = getEnvironmentAtAnnotation(Results, "p");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+        const ValueDecl *B = findValueDecl(ASTCtx, "b");
+        EXPECT_TRUE(isPositive(A, ASTCtx, Env));
+        EXPECT_TRUE(isZero(B, ASTCtx, Env));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, UnaryNotInIf) {
+  std::string Code = R"(
+    int foo();
+    void fun() {
+      int a = foo();
+      if (!a) {
+        int b1;
+        int p_a = a;
+        int p_not_a = !a;
+        // [[p]]
+      } else {
+        int q_a = a;
+        int q_not_a = !a;
+        // [[q]]
+      }
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p", "q"));
+        const Environment &EnvP = getEnvironmentAtAnnotation(Results, "p");
+        const Environment &EnvQ = getEnvironmentAtAnnotation(Results, "q");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+        const ValueDecl *PA = findValueDecl(ASTCtx, "p_a");
+        const ValueDecl *PNA = findValueDecl(ASTCtx, "p_not_a");
+        const ValueDecl *QA = findValueDecl(ASTCtx, "q_a");
+        const ValueDecl *QNA = findValueDecl(ASTCtx, "q_not_a");
+
+        // p
+        EXPECT_TRUE(isZero(A, ASTCtx, EnvP));
+        EXPECT_TRUE(isZero(PA, ASTCtx, EnvP));
+        EXPECT_TRUE(isTop(PNA, ASTCtx, EnvP));
+
+        // q
+        EXPECT_TRUE(isTop(A, ASTCtx, EnvQ));
+        EXPECT_TRUE(isTop(QA, ASTCtx, EnvQ));
+        EXPECT_TRUE(isZero(QNA, ASTCtx, EnvQ));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, BinaryGT) {
+  std::string Code = R"(
+    int foo();
+    void fun() {
+      int a = foo();
+      int b = 1;
+      if (a > 1) {
+        (void)0;
+        // [[p]]
+      }
+      if (a > 0) {
+        (void)0;
+        // [[q]]
+      }
+      if (a > -1) {
+        (void)0;
+        // [[r]]
+      }
+      if (a > b) {
+        (void)0;
+        // [[s]]
+      }
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p", "q", "r", "s"));
+        const Environment &EnvP = getEnvironmentAtAnnotation(Results, "p");
+        const Environment &EnvQ = getEnvironmentAtAnnotation(Results, "q");
+        const Environment &EnvR = getEnvironmentAtAnnotation(Results, "r");
+        const Environment &EnvS = getEnvironmentAtAnnotation(Results, "s");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+
+        // p
+        EXPECT_TRUE(isPositive(A, ASTCtx, EnvP));
+        // q
+        EXPECT_TRUE(isPositive(A, ASTCtx, EnvQ));
+        // r
+        EXPECT_TRUE(isTop(A, ASTCtx, EnvR));
+        // s
+        EXPECT_TRUE(isPositive(A, ASTCtx, EnvS));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, BinaryLT) {
+  std::string Code = R"(
+    int foo();
+    void fun() {
+      int a = foo();
+      int b = -1;
+      if (a < -1) {
+        (void)0;
+        // [[p]]
+      }
+      if (a < 0) {
+        (void)0;
+        // [[q]]
+      }
+      if (a < 1) {
+        (void)0;
+        // [[r]]
+      }
+      if (a < b) {
+        (void)0;
+        // [[s]]
+      }
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p", "q", "r", "s"));
+        const Environment &EnvP = getEnvironmentAtAnnotation(Results, "p");
+        const Environment &EnvQ = getEnvironmentAtAnnotation(Results, "q");
+        const Environment &EnvR = getEnvironmentAtAnnotation(Results, "r");
+        const Environment &EnvS = getEnvironmentAtAnnotation(Results, "s");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+
+        // p
+        EXPECT_TRUE(isNegative(A, ASTCtx, EnvP));
+        // q
+        EXPECT_TRUE(isNegative(A, ASTCtx, EnvQ));
+        // r
+        EXPECT_TRUE(isTop(A, ASTCtx, EnvR));
+        // s
+        EXPECT_TRUE(isNegative(A, ASTCtx, EnvS));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, BinaryGE) {
+  std::string Code = R"(
+    int foo();
+    void fun() {
+      int a = foo();
+      int b = 1;
+      if (a >= 1) {
+        (void)0;
+        // [[p]]
+      }
+      if (a >= 0) {
+        (void)0;
+        // [[q]]
+      }
+      if (a >= -1) {
+        (void)0;
+        // [[r]]
+      }
+      if (a >= b) {
+        (void)0;
+        // [[s]]
+      }
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p", "q", "r", "s"));
+        const Environment &EnvP = getEnvironmentAtAnnotation(Results, "p");
+        const Environment &EnvQ = getEnvironmentAtAnnotation(Results, "q");
+        const Environment &EnvR = getEnvironmentAtAnnotation(Results, "r");
+        const Environment &EnvS = getEnvironmentAtAnnotation(Results, "s");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+
+        // p
+        EXPECT_TRUE(isPositive(A, ASTCtx, EnvP));
+        // q
+        EXPECT_TRUE(isTop(A, ASTCtx, EnvQ));
+        // r
+        EXPECT_TRUE(isTop(A, ASTCtx, EnvR));
+        // s
+        EXPECT_TRUE(isPositive(A, ASTCtx, EnvS));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, BinaryLE) {
+  std::string Code = R"(
+    int foo();
+    void fun() {
+      int a = foo();
+      int b = -1;
+      if (a <= -1) {
+        (void)0;
+        // [[p]]
+      }
+      if (a <= 0) {
+        (void)0;
+        // [[q]]
+      }
+      if (a <= 1) {
+        (void)0;
+        // [[r]]
+      }
+      if (a <= b) {
+        (void)0;
+        // [[s]]
+      }
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p", "q", "r", "s"));
+        const Environment &EnvP = getEnvironmentAtAnnotation(Results, "p");
+        const Environment &EnvQ = getEnvironmentAtAnnotation(Results, "q");
+        const Environment &EnvR = getEnvironmentAtAnnotation(Results, "r");
+        const Environment &EnvS = getEnvironmentAtAnnotation(Results, "s");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+
+        // p
+        EXPECT_TRUE(isNegative(A, ASTCtx, EnvP));
+        // q
+        EXPECT_TRUE(isTop(A, ASTCtx, EnvQ));
+        // r
+        EXPECT_TRUE(isTop(A, ASTCtx, EnvR));
+        // s
+        EXPECT_TRUE(isNegative(A, ASTCtx, EnvS));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, BinaryEQ) {
+  std::string Code = R"(
+    int foo();
+    void fun() {
+      int a = foo();
+      if (a == -1) {
+        (void)0;
+        // [[n]]
+      }
+      if (a == 0) {
+        (void)0;
+        // [[z]]
+      }
+      if (a == 1) {
+        (void)0;
+        // [[p]]
+      }
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("n", "z", "p"));
+        const Environment &EnvN = getEnvironmentAtAnnotation(Results, "n");
+        const Environment &EnvZ = getEnvironmentAtAnnotation(Results, "z");
+        const Environment &EnvP = getEnvironmentAtAnnotation(Results, "p");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+
+        // n
+        EXPECT_TRUE(isNegative(A, ASTCtx, EnvN));
+        // z
+        EXPECT_TRUE(isZero(A, ASTCtx, EnvZ));
+        // p
+        EXPECT_TRUE(isPositive(A, ASTCtx, EnvP));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, JoinToTop) {
+  std::string Code = R"(
+    int foo();
+    void fun(bool b) {
+      int a = foo();
+      if (b) {
+        a = -1;
+        (void)0;
+        // [[p]]
+      } else {
+        a = 1;
+        (void)0;
+        // [[q]]
+      }
+      (void)0;
+      // [[r]]
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p", "q", "r"));
+        const Environment &EnvP = getEnvironmentAtAnnotation(Results, "p");
+        const Environment &EnvQ = getEnvironmentAtAnnotation(Results, "q");
+        const Environment &EnvR = getEnvironmentAtAnnotation(Results, "r");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+
+        // p
+        EXPECT_TRUE(isNegative(A, ASTCtx, EnvP));
+        // q
+        EXPECT_TRUE(isPositive(A, ASTCtx, EnvQ));
+        // r
+        EXPECT_TRUE(isTop(A, ASTCtx, EnvR));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, JoinToNeg) {
+  std::string Code = R"(
+    int foo();
+    void fun() {
+      int a = foo();
+      if (a < 1) {
+        a = -1;
+        (void)0;
+        // [[p]]
+      } else {
+        a = -1;
+        (void)0;
+        // [[q]]
+      }
+      (void)0;
+      // [[r]]
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p", "q", "r"));
+        const Environment &EnvP = getEnvironmentAtAnnotation(Results, "p");
+        const Environment &EnvQ = getEnvironmentAtAnnotation(Results, "q");
+        const Environment &EnvR = getEnvironmentAtAnnotation(Results, "r");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+
+        // p
+        EXPECT_TRUE(isNegative(A, ASTCtx, EnvP));
+        // q
+        EXPECT_TRUE(isNegative(A, ASTCtx, EnvQ));
+        // r
+        EXPECT_TRUE(isNegative(A, ASTCtx, EnvR));
+      },
+      LangStandard::lang_cxx17);
+}
+
+TEST(SignAnalysisTest, NestedIfs) {
+  std::string Code = R"(
+    int foo();
+    void fun() {
+      int a = foo();
+      if (a >= 0) {
+        (void)0;
+        // [[p]]
+        if (a == 0) {
+          (void)0;
+          // [[q]]
+        }
+      }
+      (void)0;
+      // [[r]]
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p", "q", "r"));
+        const Environment &EnvP = getEnvironmentAtAnnotation(Results, "p");
+        const Environment &EnvQ = getEnvironmentAtAnnotation(Results, "q");
+        const Environment &EnvR = getEnvironmentAtAnnotation(Results, "r");
+
+        const ValueDecl *A = findValueDecl(ASTCtx, "a");
+
+        // p
+        EXPECT_TRUE(isTop(A, ASTCtx, EnvP));
+        // q
+        EXPECT_TRUE(isZero(A, ASTCtx, EnvQ));
+        // r
+        EXPECT_TRUE(isTop(A, ASTCtx, EnvR));
+      },
+      LangStandard::lang_cxx17);
+}
+
+} // namespace