[clang] [LifetimeSafety] Add per-program-point lattice tracking (PR #149199)

[Gábor Horváth via cfe-commits]

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@@ -524,14 +531,20 @@ template <typename Derived, typename LatticeType, Direction Dir>
 class DataflowAnalysis {
 public:
   using Lattice = LatticeType;
-  using Base = DataflowAnalysis<Derived, LatticeType, Dir>;
+  using Base = DataflowAnalysis<Derived, Lattice, Dir>;
 
 private:
   const CFG &Cfg;
   AnalysisDeclContext &AC;
 
+  /// The dataflow state before a basic block is processed.
   llvm::DenseMap<const CFGBlock *, Lattice> InStates;
+  /// The dataflow state after a basic block is processed.
   llvm::DenseMap<const CFGBlock *, Lattice> OutStates;
+  /// The dataflow state at a Program Point.
+  /// In a forward analysis, this is the state after the Fact at that point has
+  /// been applied, while in a backward analysis, it is the state before.
+  llvm::DenseMap<ProgramPoint, Lattice> PerPointStates;
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Xazax-hun wrote:

Do you think all of the analyses need `PerPointStates`? E.g., what about the `ExpiredLoansAnalysis`? I wonder if we should have a boolean policy here. 

https://github.com/llvm/llvm-project/pull/149199