[Mlir-commits] [mlir] [MLIR][LLVM] Support Recursive DITypes (PR #80251)

[Tobias Gysi]

================
@@ -247,12 +244,43 @@ DINodeAttr DebugImporter::translate(llvm::DINode *node) {
   if (DINodeAttr attr = nodeToAttr.lookup(node))
     return attr;
 
-  // Return nullptr if a cyclic dependency is detected since the same node is
-  // being traversed twice. This check avoids infinite recursion if the debug
-  // metadata contains cycles.
-  if (!translationStack.insert(node))
-    return nullptr;
-  auto guard = llvm::make_scope_exit([&]() { translationStack.pop_back(); });
+  // If the node type is capable of being recursive, check if it's seen before.
+  auto recSelfCtor = getRecSelfConstructor(node);
+  if (recSelfCtor) {
+    // If a cyclic dependency is detected since the same node is being traversed
+    // twice, emit a recursive self type, and mark the duplicate node on the
+    // translationStack so it can emit a recursive decl type.
+    auto [iter, inserted] = translationStack.try_emplace(node, nullptr);
+    if (!inserted) {
+      // The original node may have already been assigned a recursive ID from
+      // a different self-reference. Use that if possible.
+      DistinctAttr recId = iter->second;
+      if (!recId) {
+        recId = DistinctAttr::create(UnitAttr::get(context));
+        iter->second = recId;
+      }
+      unboundRecursiveSelfRefs.back().insert(recId);
+
+      return cast<DINodeAttr>(recSelfCtor(recId));
----------------
gysit wrote:

```suggestion
      unboundRecursiveSelfRefs.back().insert(recId);
      return cast<DINodeAttr>(recSelfCtor(recId));
```
ultra nit:

https://github.com/llvm/llvm-project/pull/80251