[llvm] [LLVM] Add option to store Parent-pointer in ilist_node_base (PR #94224)

[Duncan P. N. Exon Smith via llvm-commits]

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@@ -42,6 +45,48 @@ template <> class ilist_node_base<true> {
   ilist_node_base *getPrev() const { return PrevAndSentinel.getPointer(); }
   ilist_node_base *getNext() const { return Next; }
 
+  void setNodeBaseParent(void) {}
+  inline void getNodeBaseParent() const {}
+
+  bool isSentinel() const { return PrevAndSentinel.getInt(); }
+  bool isKnownSentinel() const { return isSentinel(); }
+  void initializeSentinel() { PrevAndSentinel.setInt(true); }
+};
+
+template <class ParentPtrTy> class ilist_node_base<false, ParentPtrTy> {
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dexonsmith wrote:

Can this inherit from `<false, void>` to reduce code duplication? Or if that's confusing, extract a common base class for the previous/next logic?

https://github.com/llvm/llvm-project/pull/94224