[clang][dataflow] Support range-for loops in fixpoint algorithm.

[ymandel]

Summary

Adds support for recognizing range-for loops in the main algorithm for computing
the model fixpoint.

[ymandel]

fix test

[mboehme]

clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp

114

Making this purely a comment might risk getting it attached to the wrong method.

Consider adding an empty VisitCXXForRangeStmt(), which would make the "do nothing" behavior explicit in code?

clang/unittests/Analysis/FlowSensitive/TypeErasedDataflowAnalysisTest.cpp

1631

Is this check (and the (void)0 with the [[after_loop] annotation) actually needed?

IIUC, the condition we want to test is that the analysis converges. The fact that it produces a Results entry for [[after_loop]] is really more a check of the testing infrastructure rather than the analysis itself?

[ymandel]

address review comments

clang/unittests/Analysis/FlowSensitive/TypeErasedDataflowAnalysisTest.cpp

1631

Correct. I thought it would be useful to include some expectations, but those are really quite independent, so I've removed them. We could go further and call runAnalysis instead of runDataflow, but I prefer the latter for consistency (in terms of build args and the like) with the other tests in this suite.

[ymandel]

clang-format

clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp

 #include <optional>
 #include <system_error>
 #include <utility>
 #include <vector>
 
 #include "clang/AST/ASTDumper.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/OperationKinds.h"
+#include "clang/AST/StmtCXX.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/Analysis/Analyses/PostOrderCFGView.h"
 #include "clang/Analysis/CFG.h"
 #include "clang/Analysis/FlowSensitive/DataflowEnvironment.h"
 #include "clang/Analysis/FlowSensitive/DataflowLattice.h"
 #include "clang/Analysis/FlowSensitive/DataflowWorklist.h"
 #include "clang/Analysis/FlowSensitive/RecordOps.h"
 #include "clang/Analysis/FlowSensitive/Transfer.h"

 }
 
 static bool isLoopHead(const CFGBlock &B) {
   if (const auto *T = B.getTerminatorStmt())
     switch (T->getStmtClass()) {
       case Stmt::WhileStmtClass:
       case Stmt::DoStmtClass:
       case Stmt::ForStmtClass:
+      case Stmt::CXXForRangeStmtClass:
         return true;
       default:
         return false;
     }
 
   return false;
 }
 
public:
 
   TerminatorVisitorRetTy VisitForStmt(const ForStmt *S) {
     auto *Cond = S->getCond();
     if (Cond != nullptr)
       return extendFlowCondition(*Cond);
     return {nullptr, false};
   }
 
+  TerminatorVisitorRetTy VisitCXXForRangeStmt(const CXXForRangeStmt *) {
+    // Don't do anything special for CXXForRangeStmt, because the condition
+    // (being implicitly generated) isn't visible from the loop body.
+    return {nullptr, false};
+  }
+
   TerminatorVisitorRetTy VisitBinaryOperator(const BinaryOperator *S) {
     assert(S->getOpcode() == BO_LAnd || S->getOpcode() == BO_LOr);
     auto *LHS = S->getLHS();
     assert(LHS != nullptr);
     return extendFlowCondition(*LHS);
   }
 
   TerminatorVisitorRetTy

clang/unittests/Analysis/FlowSensitive/TypeErasedDataflowAnalysisTest.cpp

runDataflow(
 
         Value *FooVal2 = GetFooValue(Env2);
         ASSERT_THAT(FooVal2, NotNull());
         EXPECT_TRUE(isa<TopBoolValue>(FooVal2))
             << debugString(FooVal2->getKind());
 
       });
 }
+
+TEST_F(TopTest, ForRangeStmtConverges) {
+  std::string Code = R"(
+    void target(bool Foo) {
+      int Ints[10];
+      bool B = false;
+      for (int I : Ints)
+        B = true;
+    }
+  )";
+  runDataflow(Code,
+              [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &,
+                 const AnalysisOutputs &) {
+                // No additional expectations. We're only checking that the
+                // analysis converged.
+              });
+}
 } // namespace