[clang] [NFC][LifetimeSafety]: Track assignment history within a single CFGBlock (PR #196075)

[Utkarsh Saxena via cfe-commits]

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@@ -0,0 +1,40 @@
+//===- AssignmentQuery.cpp - C++ Lifetime Safety Checker --------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements trackAssignmentHistory.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/Analyses/LifetimeSafety/AssignmentQuery.h"
+
+namespace clang::lifetimes::internal {
+void trackAssignmentHistory(
+    const FactManager &FactMgr, const LoanPropagationAnalysis &LoanPropagation,
+    llvm::SmallVectorImpl<AssignmentUnit> &AssignmentList,
+    const CFGBlock *StartBlock, OriginID StartOID, const LoanID &EndLoanID) {
+  const auto TryInsertPropagationChain = [&](const OriginFlowFact *OFF) {
+    if (OFF->getDestOriginID() == StartOID &&
+        LoanPropagation.getLoans(OFF->getSrcOriginID(), OFF)
+            .contains(EndLoanID)) {
+      const OriginID SrcOriginID = OFF->getSrcOriginID();
+      AssignmentList.push_back(FactMgr.getOriginMgr().getOrigin(SrcOriginID));
+      StartOID = SrcOriginID;
+    }
+  };
+
+  llvm::ArrayRef<const Fact *> Facts = FactMgr.getFacts(StartBlock);
+  for (const Fact *F : llvm::reverse(Facts)) {
+    if (const auto *OFF = F->getAs<OriginFlowFact>()) {
+      TryInsertPropagationChain(OFF);
+    } else if (const auto *IF = F->getAs<IssueFact>()) {
----------------
usx95 wrote:

Let us reduce the nesting here by making this the first condition allowing early return.

After that you can have

```cpp
const auto *OFF = F->getAs<OriginFlowFact>()
if (!OFF) continue;
// ... insert into the chain
```



https://github.com/llvm/llvm-project/pull/196075