[llvm] [NFC][Coverage] Do not use recursion for GCOV propagateCounts. (PR #68455)

[via llvm-commits]

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@@ -366,24 +366,80 @@ GCOVBlock &GCOVFunction::getExitBlock() const {
 // outgoing edge counts by Kirchoff's circuit law. If the unmeasured arcs form a
 // spanning tree, the count for each unmeasured arc (GCOV_ARC_ON_TREE) can be
 // uniquely identified.
-uint64_t GCOVFunction::propagateCounts(const GCOVBlock &v, GCOVArc *pred) {
-  // If GCOV_ARC_ON_TREE edges do form a tree, visited is not needed; otherwise
-  // this prevents infinite recursion.
-  if (!visited.insert(&v).second)
-    return 0;
+uint64_t GCOVFunction::propagateCounts(const GCOVBlock &V, GCOVArc *Pred) {
+  struct StackElem {
+    const GCOVBlock &Block;
+    GCOVArc *Pred;
+    size_t PrevStackElemIdx;
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shen3qing1 wrote:

The pointer to Parent is not stable because we push back/remove the vector, which invalidate all reference/pointers.

https://github.com/llvm/llvm-project/pull/68455