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

[Utkarsh Saxena via llvm-branch-commits]

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@@ -778,6 +778,65 @@ 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
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usx95 wrote:

Yes. We do expect this to be significantly cheaper than the other analyses and have a tight bound (proportional to both the #loans and the max nesting).

Deferring to a later PR to add some asserts along with strict bounds makes sense to me.

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