[clang] [clang-tools-extra] [clang]: Propagate `*noreturn` attributes in `CFG` (PR #146355)

[Andrey Karlov via cfe-commits]

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@@ -6298,10 +6304,43 @@ static bool isImmediateSinkBlock(const CFGBlock *Blk) {
   // at least for now, but once we have better support for exceptions,
   // we'd need to carefully handle the case when the throw is being
   // immediately caught.
-  if (llvm::any_of(*Blk, [](const CFGElement &Elm) {
+  if (llvm::any_of(*Blk, [](const CFGElement &Elm) -> bool {
+        if (std::optional<CFGStmt> StmtElm = Elm.getAs<CFGStmt>())
+          return isa<CXXThrowExpr>(StmtElm->getStmt());
+        return false;
+      }))
+    return true;
+
+  auto HasNoReturnCall = [](const CallExpr *CE) {
+    if (!CE)
+      return false;
+
+    static thread_local llvm::SmallPtrSet<const FunctionDecl *, 32> InProgress;
+
+    auto *FD = CE->getDirectCallee();
+
+    if (!FD || InProgress.count(FD))
+      return false;
+
+    InProgress.insert(FD);
+    auto DoCleanup = llvm::make_scope_exit([&]() { InProgress.erase(FD); });
+
+    auto NoReturnFromCFG = [FD]() {
+      if (!FD->getBody())
+        return false;
+
+      auto CalleeCFG =
+          CFG::buildCFG(FD, FD->getBody(), &FD->getASTContext(), {});
+
+      return CalleeCFG && CalleeCFG->getEntry().isInevitablySinking();
+    };
+
+    return FD->isAnalyzerNoReturn() || NoReturnFromCFG();
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negativ wrote:

> What if we have redecls, does it matter which has the attribute, or do we always bind the attribute to the canonical decl?

Good catch! I'll fix my code to use the canonical decl.

https://github.com/llvm/llvm-project/pull/146355