[clang] [LifetimeSafety] Introduce a liveness-based lifetime policy (PR #159991)

[Utkarsh Saxena via cfe-commits]

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@@ -1087,11 +1073,19 @@ class LoanPropagationAnalysis
   /// Merges two lattices by taking the union of loans for each origin.
   // TODO(opt): Keep the state small by removing origins which become dead.
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usx95 wrote:

No. This is a separate garbage-collection optimisation which can be implemented using liveness but is not implemented yet. 

https://github.com/llvm/llvm-project/pull/159991