[LifetimeSafety] Add loan expiry analysis

Author: usx95

clang/include/clang/Analysis/Analyses/LifetimeSafety.h

@@ -33,6 +33,7 @@ namespace internal {
 class Fact;
 class FactManager;
 class LoanPropagationAnalysis;
+class ExpiredLoansAnalysis;
 struct LifetimeFactory;
 
 /// A generic, type-safe wrapper for an ID, distinguished by its `Tag` type.
@@ -81,6 +82,9 @@ class LifetimeSafetyAnalysis {
   /// Returns the set of loans an origin holds at a specific program point.
   LoanSet getLoansAtPoint(OriginID OID, ProgramPoint PP) const;
 
+  /// Returns the set of loans that have expired at a specific program point.
+  LoanSet getExpiredLoansAtPoint(ProgramPoint PP) const;
+
   /// Finds the OriginID for a given declaration.
   /// Returns a null optional if not found.
   std::optional<OriginID> getOriginIDForDecl(const ValueDecl *D) const;
@@ -105,6 +109,7 @@ class LifetimeSafetyAnalysis {
   std::unique_ptr<LifetimeFactory> Factory;
   std::unique_ptr<FactManager> FactMgr;
   std::unique_ptr<LoanPropagationAnalysis> LoanPropagation;
+  std::unique_ptr<ExpiredLoansAnalysis> ExpiredLoans;
 };
 } // namespace internal
 } // namespace clang::lifetimes

clang/lib/Analysis/LifetimeSafety.cpp

@@ -23,6 +23,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/TimeProfiler.h"
 #include <cstdint>
+#include <memory>
 
 namespace clang::lifetimes {
 namespace internal {
@@ -832,6 +833,65 @@ class LoanPropagationAnalysis
   }
 };
 
+// ========================================================================= //
+//                         Expired Loans Analysis
+// ========================================================================= //
+
+/// The dataflow lattice for tracking the set of expired loans.
+struct ExpiredLattice {
+  LoanSet Expired;
+
+  ExpiredLattice() : Expired(nullptr) {};
+  explicit ExpiredLattice(LoanSet S) : Expired(S) {}
+
+  bool operator==(const ExpiredLattice &Other) const {
+    return Expired == Other.Expired;
+  }
+  bool operator!=(const ExpiredLattice &Other) const {
+    return !(*this == Other);
+  }
+
+  void dump(llvm::raw_ostream &OS) const {
+    OS << "ExpiredLattice State:\n";
+    if (Expired.isEmpty())
+      OS << "  <empty>\n";
+    for (const LoanID &LID : Expired)
+      OS << "  Loan " << LID << " is expired\n";
+  }
+};
+
+/// The analysis that tracks which loans have expired.
+class ExpiredLoansAnalysis
+    : public DataflowAnalysis<ExpiredLoansAnalysis, ExpiredLattice,
+                              Direction::Forward> {
+
+  LoanSet::Factory &Factory;
+
+public:
+  ExpiredLoansAnalysis(const CFG &C, AnalysisDeclContext &AC, FactManager &F,
+                       LifetimeFactory &Factory)
+      : DataflowAnalysis(C, AC, F), Factory(Factory.LoanSetFactory) {}
+
+  using Base::transfer;
+
+  StringRef getAnalysisName() const { return "ExpiredLoans"; }
+
+  Lattice getInitialState() { return Lattice(Factory.getEmptySet()); }
+
+  /// Merges two lattices by taking the union of the expired loan sets.
+  Lattice join(Lattice L1, Lattice L2) const {
+    return Lattice(utils::join(L1.Expired, L2.Expired, Factory));
+  }
+
+  Lattice transfer(Lattice In, const ExpireFact &F) {
+    return Lattice(Factory.add(In.Expired, F.getLoanID()));
+  }
+
+  Lattice transfer(Lattice In, const IssueFact &F) {
+    return Lattice(Factory.remove(In.Expired, F.getLoanID()));
+  }
+};
+
 // ========================================================================= //
 //  TODO:
 // - Modify loan expiry analysis to answer `bool isExpired(Loan L, Point P)`
@@ -873,6 +933,10 @@ void LifetimeSafetyAnalysis::run() {
   LoanPropagation =
       std::make_unique<LoanPropagationAnalysis>(Cfg, AC, *FactMgr, *Factory);
   LoanPropagation->run();
+
+  ExpiredLoans =
+      std::make_unique<ExpiredLoansAnalysis>(Cfg, AC, *FactMgr, *Factory);
+  ExpiredLoans->run();
 }
 
 LoanSet LifetimeSafetyAnalysis::getLoansAtPoint(OriginID OID,
@@ -881,6 +945,11 @@ LoanSet LifetimeSafetyAnalysis::getLoansAtPoint(OriginID OID,
   return LoanPropagation->getLoans(OID, PP);
 }
 
+LoanSet LifetimeSafetyAnalysis::getExpiredLoansAtPoint(ProgramPoint PP) const {
+  assert(ExpiredLoans && "ExpiredLoansAnalysis has not been run.");
+  return ExpiredLoans->getState(PP).Expired;
+}
+
 std::optional<OriginID>
 LifetimeSafetyAnalysis::getOriginIDForDecl(const ValueDecl *D) const {
   assert(FactMgr && "FactManager not initialized");