[llvm] [FuncAttrs] Relax norecurse attribute inference (PR #139943)

[Usha Gupta via llvm-commits]

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@@ -2059,8 +2059,49 @@ static void inferAttrsFromFunctionBodies(const SCCNodeSet &SCCNodes,
   AI.run(SCCNodes, Changed);
 }
 
+/// Returns true if N or any function it (transitively) calls makes a call
+/// to an unknown external function: either an indirect call or a declaration
+/// without the NoCallback attribute.
+static bool callsUnknownExternal(LazyCallGraph::Node *N) {
+  std::deque<LazyCallGraph::Node *> Worklist;
+  DenseSet<LazyCallGraph::Node *> Visited;
+  Worklist.push_back(N);
+  Visited.insert(N);
+
+  while (!Worklist.empty()) {
+    auto *Cur = Worklist.front();
+    Worklist.pop_front();
+
+    Function &F = Cur->getFunction();
+    for (auto &BB : F) {
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usha1830 wrote:

I have removed this helper now and updated my fix approach to check if the address of this function is taken. If the address is not taken, we can presume that the external function deeper in call stack could not reach back the current function.

https://github.com/llvm/llvm-project/pull/139943