https://github.com/usx95 updated
https://github.com/llvm/llvm-project/pull/148976
>From 9834dbd9e095cad2bcafbeef763ff21bf223b26e Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <u...@google.com>
Date: Tue, 15 Jul 2025 22:19:48 +0000
Subject: [PATCH] add-liveness-finally
---
clang/lib/Analysis/LifetimeSafety.cpp | 78 +++++++++++++++++++++++++++
1 file changed, 78 insertions(+)
diff --git a/clang/lib/Analysis/LifetimeSafety.cpp
b/clang/lib/Analysis/LifetimeSafety.cpp
index 3a492b2e6707d..e12f4aaf1c4b0 100644
--- a/clang/lib/Analysis/LifetimeSafety.cpp
+++ b/clang/lib/Analysis/LifetimeSafety.cpp
@@ -675,12 +675,14 @@ join(llvm::ImmutableMap<K, V> A, llvm::ImmutableMap<K, V>
B,
// TODO(opt): Consider using a bitset to represent the set of loans.
using LoanSet = llvm::ImmutableSet<LoanID>;
using OriginLoanMap = llvm::ImmutableMap<OriginID, LoanSet>;
+using OriginSet = llvm::ImmutableSet<OriginID>;
/// An object to hold the factories for immutable collections, ensuring
/// that all created states share the same underlying memory management.
struct LifetimeFactory {
OriginLoanMap::Factory OriginMapFactory;
LoanSet::Factory LoanSetFactory;
+ OriginSet::Factory OriginSetFactory;
/// Creates a singleton set containing only the given loan ID.
LoanSet createLoanSet(LoanID LID) {
@@ -777,6 +779,78 @@ class LoanPropagationAnalysis
}
};
+// ========================================================================= //
+// Live Origins Analysis
+// ========================================================================= //
+
+/// The dataflow lattice for origin liveness analysis.
+/// It tracks the set of origins that are live at a given program point.
+struct LivenessLattice {
+ OriginSet LiveOrigins;
+
+ LivenessLattice() : LiveOrigins(nullptr) {};
+ explicit LivenessLattice(OriginSet S) : LiveOrigins(S) {}
+
+ bool operator==(const LivenessLattice &Other) const {
+ return LiveOrigins == Other.LiveOrigins;
+ }
+ bool operator!=(const LivenessLattice &Other) const {
+ return !(*this == Other);
+ }
+
+ void dump(llvm::raw_ostream &OS) const {
+ OS << "LivenessLattice State:\n";
+ if (LiveOrigins.isEmpty())
+ OS << " <empty>\n";
+ for (const OriginID &OID : LiveOrigins)
+ OS << " Origin " << OID << " is live\n";
+ }
+};
+
+/// The analysis that tracks which origins are live. This is a backward
+/// analysis.
+class LiveOriginAnalysis
+ : public DataflowAnalysis<LiveOriginAnalysis, LivenessLattice,
+ Direction::Backward> {
+
+ OriginSet::Factory &SetFactory;
+
+public:
+ LiveOriginAnalysis(const CFG &C, AnalysisDeclContext &AC, FactManager &F,
+ OriginSet::Factory &SF)
+ : DataflowAnalysis(C, AC, F), SetFactory(SF) {}
+
+ using DataflowAnalysis<LiveOriginAnalysis, Lattice,
+ Direction::Backward>::transfer;
+
+ StringRef getAnalysisName() const { return "LiveOrigins"; }
+
+ Lattice getInitialState() { return Lattice(SetFactory.getEmptySet()); }
+
+ /// Merges two lattices by taking the union of the live origin sets.
+ Lattice join(Lattice L1, Lattice L2) const {
+ return Lattice(utils::join(L1.LiveOrigins, L2.LiveOrigins, SetFactory));
+ }
+
+ /// An assignment `p = q` kills the liveness of `p` and generates liveness
+ /// for `q`.
+ Lattice transfer(Lattice In, const AssignOriginFact &F) {
+ OriginSet S = SetFactory.remove(In.LiveOrigins, F.getDestOriginID());
+ S = SetFactory.add(S, F.getSrcOriginID());
+ return Lattice(S);
+ }
+
+ /// Issuing a new loan to an origin kills its liveness.
+ Lattice transfer(Lattice In, const IssueFact &F) {
+ return Lattice(SetFactory.remove(In.LiveOrigins, F.getOriginID()));
+ }
+
+ /// A return statement generates liveness for the returned origin.
+ Lattice transfer(Lattice In, const ReturnOfOriginFact &F) {
+ return Lattice(SetFactory.add(In.LiveOrigins, F.getReturnedOriginID()));
+ }
+};
+
// ========================================================================= //
// Expired Loans Analysis
// ========================================================================= //
@@ -872,5 +946,9 @@ void runLifetimeSafetyAnalysis(const DeclContext &DC, const
CFG &Cfg,
ExpiredLoansAnalysis ExpiredLoans(Cfg, AC, FactMgr, Factory);
ExpiredLoans.run();
DEBUG_WITH_TYPE("LifetimeExpiredLoans", ExpiredLoans.dump());
+
+ LiveOriginAnalysis Liveness(Cfg, AC, FactMgr, Factory.OriginSetFactory);
+ Liveness.run();
+ DEBUG_WITH_TYPE("LifetimeLiveOrigins", Liveness.dump());
}
} // namespace clang
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