[clang] [analyzer] Fix false positive on `UnreachableCode` with CTU mode (PR #219225)

[Arseniy Zaostrovnykh via cfe-commits]

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@@ -161,6 +161,7 @@ bool CoreEngine::ExecuteWorkList(const StackFrame *SF, unsigned MaxSteps,
     return MaxSteps - Steps;
   };
   const unsigned STUSteps = ProcessWList(MaxSteps);
+  STUHadWorkRemaining = WList->hasWork();
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necto wrote:

Ideally, we would keep the remaining STU work at the end of the CTU work list, to continue STU exploration if CTU turns out fruitless. However, that would be a significantly more complex and risky change.

However, if it ever get's done, it is important to not forget about this shortcut. Would it make sense to move it right next to where the STU remaining work gets discarded (l.173)?

https://github.com/llvm/llvm-project/pull/219225