[llvm] Reapply "[coro][CoroSplit] Use `llvm.lifetime.end` to compute putting objects on the frame vs the stack (#90265) (PR #91372)

[Nikita Popov via llvm-commits]

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@@ -204,6 +221,43 @@ bool llvm::isPotentiallyReachableFromMany(
   return false;
 }
 
+template <class T> class SingleEntrySet {
+public:
+  using iterator = T *;
+  using const_iterator = const T *;
+
+  SingleEntrySet(T Elem) : Elem(Elem) {}
+
+  bool contains(T Other) const { return Elem == Other; }
+
+  iterator begin() { return &Elem; }
+  iterator end() { return &Elem + 1; }
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nikic wrote:

I don't think the non-const methods are necessary.

https://github.com/llvm/llvm-project/pull/91372