================
@@ -202,53 +203,72 @@ class AnalysisImpl
     return getLoans(getState(P), OID);
   }
 
-  llvm::SmallVector<OriginID>
-  buildOriginFlowChain(ProgramPoint StartPoint, const OriginID StartOID,
-                       const LoanID TargetLoan) const {
+  llvm::SmallVector<OriginID> buildOriginFlowChain(ProgramPoint StartPoint,
+                                                   const OriginID StartOID,
+                                                   const LoanID TargetLoan,
+                                                   const CFG *Cfg) const {
     assert(getLoans(StartOID, StartPoint).contains(TargetLoan) &&
            "TargetLoan must be present in the StartOID at the StartPoint");
 
-    OriginID CurrOID = StartOID;
-    llvm::SmallVector<OriginID> OriginFlowChain;
-    llvm::ArrayRef<const Fact *> Facts = 
FactMgr.getBlockContaining(StartPoint);
-    const auto *StartIt = llvm::find(Facts, StartPoint);
-    assert(StartIt != Facts.end());
+    // Locate the CFG block containing the StartPoint
+    const CFGBlock *EndBlock = nullptr;
+    size_t BlockID = FactMgr.getBlockID(StartPoint);
+    for (const CFGBlock *Block : *Cfg)
+      if (Block->getBlockID() == BlockID) {
+        EndBlock = Block;
+        break;
+      }
 
-    for (const Fact *F :
-         llvm::reverse(llvm::make_range(Facts.begin(), StartIt))) {
-      if (const auto *IF = F->getAs<IssueFact>())
-        if (IF->getLoanID() == TargetLoan) {
-          assert(IF->getOriginID() == CurrOID);
-          return OriginFlowChain;
-        }
+    // Set up DFS traversal state
+    // SearchState tracks which block we're in and which origin we're tracing
+    // Each DFSNode maintains its own OriginFlowChain.
+    using SearchState = std::pair<const CFGBlock *, OriginID>;
+    struct DFSNode {
+      SearchState CurrState;
+      llvm::SmallVector<OriginID> OriginFlowChain;
+    };
+
+    llvm::SmallVector<DFSNode> PendingStates;
+    llvm::SmallSet<SearchState, 16> VistedStates;
+    PendingStates.push_back({{EndBlock, StartOID}, {}});
+
+    // DFS loop to trace loan backwards through CFG
+    while (!PendingStates.empty()) {
+      DFSNode CurrNode = PendingStates.pop_back_val();
+      auto [CurrBlock, CurrOID] = CurrNode.CurrState;
+
+      // Trace origins within the current block
+      const auto [BuildResult, Complete] =
+          buildOriginFlowChain(CurrBlock, CurrOID, TargetLoan);
+      if (!BuildResult.empty()) {
+        CurrNode.OriginFlowChain.append(BuildResult);
+        CurrOID = BuildResult.back();
+      }
 
-      const auto *OFF = F->getAs<OriginFlowFact>();
-      if (!OFF)
-        continue;
-      if (OFF->getDestOriginID() != CurrOID)
-        continue;
+      // If we found the IssueFact, we're done
+      if (Complete)
+        return CurrNode.OriginFlowChain;
 
-      const OriginID SrcOriginID = OFF->getSrcOriginID();
-      if (!getLoans(SrcOriginID, OFF).contains(TargetLoan))
-        continue;
-      OriginFlowChain.push_back(SrcOriginID);
-      CurrOID = SrcOriginID;
+      for (const CFGBlock *PredBlock : CurrBlock->preds()) {
+        SearchState NextState = {PredBlock, CurrOID};
+        if (getLoans(getOutState(PredBlock), CurrOID).contains(TargetLoan) &&
----------------
usx95 wrote:

nit: doc
`// Only explore predecessor blocks where the target loan is present in the 
current origin.`

https://github.com/llvm/llvm-project/pull/204592
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