[llvm-branch-commits] [clang] [LifetimeSafety] Add loan expiry analysis (PR #148712)

[Utkarsh Saxena via llvm-branch-commits]

https://github.com/usx95 updated https://github.com/llvm/llvm-project/pull/148712

>From a9cb32152b8ba94a6a93c7923cce1abac43c9022 Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <usx at google.com>
Date: Mon, 14 Jul 2025 19:32:35 +0000
Subject: [PATCH 1/2] users/usx95/lifetime-safety-add-loan-expiry


>From a50b00e1b5394dacd635fd1da3aef83eb54348e5 Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <usx at google.com>
Date: Mon, 14 Jul 2025 19:37:49 +0000
Subject: [PATCH 2/2] [LifetimeSafety] Add loan expiry analysis

---
 clang/lib/Analysis/LifetimeSafety.cpp | 62 +++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/clang/lib/Analysis/LifetimeSafety.cpp b/clang/lib/Analysis/LifetimeSafety.cpp
index 99bd7bc36faf5..1ac8f42318b8d 100644
--- a/clang/lib/Analysis/LifetimeSafety.cpp
+++ b/clang/lib/Analysis/LifetimeSafety.cpp
@@ -747,6 +747,65 @@ class LoanPropagationAnalysis
   }
 };
 
+// ========================================================================= //
+//                         Expired Loans Analysis
+// ========================================================================= //
+
+/// The lattice for tracking expired loans. It is a set of loan IDs.
+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";
+  }
+};
+
+class ExpiredLoansAnalysis
+    : public DataflowAnalysis<ExpiredLoansAnalysis, ExpiredLattice> {
+
+  LoanSet::Factory &SetFactory;
+
+public:
+  ExpiredLoansAnalysis(const CFG &C, AnalysisDeclContext &AC, FactManager &F,
+                       LoanSet::Factory &SF)
+      : DataflowAnalysis(C, AC, F), SetFactory(SF) {}
+
+  using DataflowAnalysis<ExpiredLoansAnalysis, Lattice>::transfer;
+
+  const char *getAnalysisName() const { return "ExpiredLoans"; }
+
+  Lattice getInitialState() { return Lattice(SetFactory.getEmptySet()); }
+
+  Lattice join(Lattice L1, Lattice L2) const {
+    LoanSet JoinedSet = L1.Expired;
+    for (LoanID LID : L2.Expired)
+      JoinedSet = SetFactory.add(JoinedSet, LID);
+    return Lattice(JoinedSet);
+  }
+
+  Lattice transfer(Lattice In, const ExpireFact &F) {
+    return Lattice(SetFactory.add(In.Expired, F.getLoanID()));
+  }
+
+  Lattice transfer(Lattice In, const IssueFact &F) {
+    return Lattice(SetFactory.remove(In.Expired, F.getLoanID()));
+  }
+};
+
 // ========================================================================= //
 //  TODO: 
 // - Modifying loan propagation to answer `LoanSet getLoans(Origin O, Point P)`
@@ -779,5 +838,8 @@ void runLifetimeSafetyAnalysis(const DeclContext &DC, const CFG &Cfg,
   LoanPropagationAnalysis LoanPropagation(Cfg, AC, FactMgr, LifetimeFact);
   LoanPropagation.run();
   DEBUG_WITH_TYPE("LifetimeLoanPropagation", LoanPropagation.dump());
+
+  ExpiredLoansAnalysis ExpiredAnalysis(Cfg, AC, FactMgr,
+                                       LifetimeFact.LoanSetFact);
 }
 } // namespace clang