[clang][dataflow] Intersect ExprToLoc when joining environments

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed-by: xazax.hun

Differential Revision: https://reviews.llvm.org/D117754

Author: sgatev

clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp

@@ -83,6 +83,11 @@ LatticeJoinEffect Environment::join(const Environment &Other) {
   if (DeclToLocSizeBefore != DeclToLoc.size())
     Effect = LatticeJoinEffect::Changed;
 
+  const unsigned ExprToLocSizeBefore = ExprToLoc.size();
+  ExprToLoc = intersectDenseMaps(ExprToLoc, Other.ExprToLoc);
+  if (ExprToLocSizeBefore != ExprToLoc.size())
+    Effect = LatticeJoinEffect::Changed;
+
   // FIXME: Add support for joining distinct values that are assigned to the
   // same storage locations in `LocToVal` and `Other.LocToVal`.
   const unsigned LocToValSizeBefore = LocToVal.size();

clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp

@@ -23,6 +23,7 @@
 #include "clang/Analysis/FlowSensitive/Transfer.h"
 #include "clang/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.h"
 #include "clang/Analysis/FlowSensitive/Value.h"
+#include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/Support/raw_ostream.h"

clang/unittests/Analysis/FlowSensitive/TransferTest.cpp

@@ -1828,4 +1828,41 @@ TEST_F(TransferTest, VarDeclInitAssignConditionalOperator) {
       });
 }
 
+TEST_F(TransferTest, VarDeclInDoWhile) {
+  std::string Code = R"(
+    void target(int *Foo) {
+      do {
+        int Bar = *Foo;
+      } while (true);
+      (void)0;
+      /*[[p]]*/
+    }
+  )";
+  runDataflow(Code,
+              [](llvm::ArrayRef<
+                     std::pair<std::string, DataflowAnalysisState<NoopLattice>>>
+                     Results,
+                 ASTContext &ASTCtx) {
+                ASSERT_THAT(Results, ElementsAre(Pair("p", _)));
+                const Environment &Env = Results[0].second.Env;
+
+                const ValueDecl *FooDecl = findValueDecl(ASTCtx, "Foo");
+                ASSERT_THAT(FooDecl, NotNull());
+
+                const ValueDecl *BarDecl = findValueDecl(ASTCtx, "Bar");
+                ASSERT_THAT(BarDecl, NotNull());
+
+                const auto *FooVal =
+                    cast<PointerValue>(Env.getValue(*FooDecl, SkipPast::None));
+                const auto *FooPointeeVal =
+                    cast<IntegerValue>(Env.getValue(FooVal->getPointeeLoc()));
+
+                const auto *BarVal = dyn_cast_or_null<IntegerValue>(
+                    Env.getValue(*BarDecl, SkipPast::None));
+                ASSERT_THAT(BarVal, NotNull());
+
+                EXPECT_EQ(BarVal, FooPointeeVal);
+              });
+}
+
 } // namespace