[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 d5b093e806ca03355eaa76ca7cf5bba252a92ad3 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] [LifetimeSafety] Add loan expiry analysis

---
 .../clang/Analysis/Analyses/LifetimeSafety.h  |  2 +
 clang/lib/Analysis/LifetimeSafety.cpp         | 64 +++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/clang/include/clang/Analysis/Analyses/LifetimeSafety.h b/clang/include/clang/Analysis/Analyses/LifetimeSafety.h
index f5ce23848448f..3d301941790df 100644
--- a/clang/include/clang/Analysis/Analyses/LifetimeSafety.h
+++ b/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.
@@ -96,6 +97,7 @@ 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
diff --git a/clang/lib/Analysis/LifetimeSafety.cpp b/clang/lib/Analysis/LifetimeSafety.cpp
index 22c724dbd6ed9..bbd944daffb75 100644
--- a/clang/lib/Analysis/LifetimeSafety.cpp
+++ b/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)`
@@ -872,6 +932,10 @@ 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,